Review of the influence of anaemia on the effect of total hip arthroplasty, and the prognosis of patients: recent advances and future directions.

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Learn more: PMC Disclaimer | PMC Copyright Notice Ann Med . 2026 Apr 10;58(1):2650919. doi: 10.1080/07853890.2026.2650919 Search in PMC Search in PubMed View in NLM Catalog Add to search Review of the influence of anaemia on the effect of total hip arthroplasty, and the prognosis of patients: recent advances and future directions Zhang Chen Zhang Chen 1 Department of Orthopaedics, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China Investigation, Project administration, Writing – original draft, Writing – review & editing Find articles by Zhang Chen 1, ✉ Author information Article notes Copyright and License information 1 Department of Orthopaedics, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China ✉ CONTACT Zhang Chen [email protected] Department of Orthopaedics, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100730, China. Roles Zhang Chen : Investigation, Project administration, Writing – original draft, Writing – review & editing Received 2025 Dec 5; Accepted 2026 Mar 21; Collection date 2026. © 2026 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial License ( http://creativecommons.org/licenses/by-nc/4.0/ ), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. The terms on which this article has been published allow the posting of the Accepted Manuscript in a repository by the author(s) or with their consent. PMC Copyright notice PMCID: PMC13072687  PMID: 41958436 Abstract Background This review examines the impact of preoperative anaemia on outcomes following total hip arthroplasty (THA) and the importance of managing it, given rising surgical volumes and the need to optimize patient care and prevent complications. Discussion Preoperative anaemia in THA patients is consistently linked to negative outcomes, such as increased blood loss, higher transfusion rates, longer hospital stays, and a higher risk of complications, according to key results. A holistic approach that includes identifying the underlying cause, making any necessary corrections, and using blood-conservation strategies is necessary for effective management. Nonetheless, there is a crucial conflict in the literature: while anaemia is often characterized as a modifiable risk factor, there remains a lack of high-quality data demonstrating that preoperative correction improves key clinical outcomes, such as functional recovery, implant survival, or mortality. It is uncertain whether anaemia is a direct cause or primarily a marker of underlying patient fragility and comorbidity, as most available data are observational. Conclusion For patients receiving THA, preoperative anaemia is a reliable and substantial predictor of unfavourable outcomes. For patient optimization and risk stratification, systematic identification before surgery is crucial. However, unless significant randomized controlled trials demonstrate that correction results in better patient-centred outcomes, the classification of anaemia as a modifiable risk factor should be approached with caution. To improve treatment for this group, it is essential to address existing evidence gaps and implementation issues. Keywords: Total hip arthroplasty, anaemia, preoperative anaemia, patient blood management, treatment outcome GRAPHICAL ABSTRACT Open in a new tab 1. Introduction Total hip arthroplasty (THA) is a highly effective and safe procedure for end-stage hip osteoarthritis, renowned for successfully alleviating pain and restoring mobility, to the point that it has been termed the ‘operation of the century’. Its utilization is projected to grow substantially, with estimates in the United States indicating a 284% increase by 2040 compared to 2014 [ 1 , 2 ]. Despite its high success rate and 10-year implant survival rates of up to 96%, challenges remain; up to 7% of patients report dissatisfaction, often due to persistent pain or mechanical issues [ 1–4 ]. A range of risk factors, including surgical technique, implant selection and patient-specific characteristics such as age and comorbidities, influences patient outcomes. Common complications include infection, dislocation and thromboembolic events. Among these, postoperative anaemia, a frequent consequence of surgical blood loss, poses a significant risk, particularly for elderly patients, as it increases morbidity and the need for allogeneic blood transfusion [ 3–5 ]. Although transfusions are an efficient way to increase blood volume, there are risks associated with them, such as infection, allergic responses and a higher chance of death. Thus, methods to reduce blood loss, including the administration of tranexamic acid (TXA), have emerged as a key component of safe perioperative care in major orthopaedic surgery [ 5 , 6 ]. Anaemia is a significant global public health concern, affecting an estimated 1.92 billion people, approximately 24% of the global population [ 7–9 ]. However, its prevalence is not uniform; it varies significantly across demographic groups and geographical regions. The prevalence of anaemia is disproportionately high in women, children under five and populations in low-income countries, particularly in sub-Saharan Africa and South Asia [ 10 , 11 ]. This condition can lead to symptoms such as weakness, fatigue and cognitive impairment, ultimately affecting quality of life and work productivity. In the surgical context, preoperative anaemia is of particular concern as it is linked to higher morbidity, mortality and an increased likelihood of requiring allogeneic blood transfusions [ 12–14 ]. Blood loss, anaemia and allogeneic blood transfusions are critical considerations in major orthopaedic surgery, and their effective management is central to Patient Blood Management (PBM) programs. In a study evaluating hospital compliance with PBM guidelines for THA, researchers found that adherence to blood management protocols was suboptimal and varied considerably across centres. The study validated composite measures for assessing hospital PBM performance, suggesting that such quality indicators can be valuable tools for monitoring practice and comparing healthcare organizations [ 15 ]. These results highlight the crucial role of evidence-based, standardized procedures in improving patient outcomes after major joint arthroplasty, including THA. Studies have shown that up to 44% of hospitalized patients awaiting joint replacement and 87% of patients after surgery suffer from preoperative anaemia, which is especially common in the elderly population having joint arthroplasty [ 6 , 16 ]. Patients with concomitant conditions, including anaemia and increasing frailty, are more likely to present for THA as the population ages. After THA surgery, even mild cases of preoperative anaemia might raise the risk of complications, need blood transfusions, and cause a delayed recovery [ 17 , 18 ]. In this narrative review, we examine the impact of preoperative anaemia on outcomes following THA. Additionally, we explore current obstacles and potential future directions for improving patient care in this group, and we examine the significance of preventing and treating anaemia in patients undergoing THA before surgery. This narrative review aims to provide a comprehensive overview of preoperative anaemia in THA. We conducted an exploratory search of PubMed, Scopus and Google Scholar for articles published from 2011 to 2025, utilizing combinations of keywords such as ‘total hip arthroplasty’, ‘THA’, ‘anaemia’, ‘preoperative anaemia’, ‘iron deficiency’, ‘patient blood management’ and ‘treatment outcomes’. Given the narrative nature of the work, no formal systematic review methodology was employed; instead, we emphasized meta-analyses, systematic reviews, randomized controlled trials, and large cohort studies to substantiate key points, supplemented by additional references as deemed necessary. The selection of studies is based on the authors’ assessment of relevance and quality, rather than predefined inclusion criteria, which constitutes a limitation of this review. 2. Overview of total hip arthroplasty and its clinical significance THA is a common and highly successful surgical procedure that helps patients with end-stage hip disease regain function and reduce discomfort. Although symptomatic osteoarthritis is the most common indication for THA, the operation is also often used to treat inflammatory arthropathies such as rheumatoid arthritis, avascular necrosis of the femoral head, and femoral neck fractures [ 19 ]. THA has undergone significant development over recent decades and is now one of the most successful and frequently performed orthopaedic interventions. In the United States, nearly 7 million hip and knee replacements have been performed to date, and the number of arthroplasties continues to increase annually, a trend that is expected to persist in the coming years [ 20 , 21 ]. THA consistently improves function and significantly reduces discomfort in individuals with hip osteoarthritis. These results are useful for understanding patient selection and outcomes, even though they are often obtained from retrospective analyses, which may be prone to recall and selection bias and may not accurately reflect the complex, multifactorial decision-making process involving patient preferences and surgeon judgement [ 22 ]. According to studies, the lack of osteophytes, advanced age, and fast joint space narrowing are all important predictors of THA. Additionally, studies show that cementless, proximally porous-coated stems are a good alternative for elderly patients; however, ongoing evaluation is required to determine their long-term effectiveness in older, more active populations that may be more susceptible to periprosthetic fractures [ 22 ]. Muscle strength recovery is a crucial part of postoperative rehabilitation after THA, as it directly impacts functional outcomes and quality of life. One of the main factors influencing recovery after THA is hip joint muscle strength, which controls walking movements, balance and daily activities, including short-distance walking [ 23 ]. Loss of muscular strength may result from the surgical operation itself or from the underlying problem that required THA. By delaying or reducing the completeness of healing, such a decrease may prolong negative long-term impairment or lead to patient discontent. Inadequate muscular strength may also prolong the healing process after surgery, leading to abnormal gait patterns and decreased mobility [ 23 ]. THA is cost-effective and significantly increases quality-adjusted life years in several economic evaluations [ 22 , 24 ]. These economic models, however, may not apply across different healthcare systems and price structures because they are sensitive to underlying assumptions, such as implant lifetime and reoperation rates. Furthermore, a range of options for patient needs, comorbidities and rehabilitation adherence may not be considered in a ‘one-size-fits-all’ rehabilitation plan. To effectively advise postoperative therapy, it is important to thoroughly evaluate each patient’s individual features, as the referenced research often lacks information on the optimal type, intensity and duration of rehabilitation [ 22 , 24 ]. 2.1. Factors affecting outcomes after total hip arthroplasty Despite the high success rate of THA, 15-30% of patients experience suboptimal outcomes [ 25 ]. To properly address this, a comprehensive strategy is needed to identify those at risk and understand the variables affecting rehabilitation. Developing focused therapies requires identifying the critical elements that indicate poorer recovery, ranging from surgical technique to patient-specific factors. The long-term success of THA is influenced by both implant-specific biomechanics and the patient’s preoperative physiological state. While the Collum Femoris Preserving stem offers biomechanical advantages, its performance may be compromised by specific risk factors for aseptic loosening, including substantial varus or valgus malalignment, femoral neck resorption and steroid use [ 26 ]. The patient’s physical condition is equally critical. Severe sarcopenia, characterized by low muscle mass and strength, has been identified as a powerful independent predictor of delayed functional recovery and worse patient-reported outcomes at 6 months post-THA [ 27 ]. These results highlight the need for both careful surgical technique and implant placement to achieve mechanical stability, as well as thorough preoperative assessment and improvement of the patient’s musculoskeletal health, to maximize THA outcomes. Blood loss and subsequent anaemia significantly impact recovery after THA. Surgical factors, including implant fixation method and drain use, can influence perioperative blood loss. The use of drains in joint arthroplasty has been associated with higher rates of blood loss and transfusion requirements without offering clear long-term therapeutic advantages [ 28 ] ( Figure 1 ). Surgeons have to carefully weigh these risks, especially when treating patients who already have anaemia or who are at high risk of suffering significant blood loss. Figure 1. Open in a new tab Several factors influence the results of THA. Gender, age, body mass index (BMI), prosthesis material, and risk factors are nonsurgical considerations. Surgical considerations include anaesthesia, surgical risks, and recovery time [ 134 ]. Preoperative patient characteristics substantially influence outcomes. Severe sarcopenia is associated with delayed recovery, while psychological factors such as low resilience and pain catastrophizing predict worse functional outcomes [ 29 , 30 ]. Male sex and younger age increase the risk of revision for infection and aseptic loosening. Longer operative times and lower surgeon volume are linked to higher revision rates. Surgical choices, including implant selection and cemented versus uncemented fixation, significantly affect outcomes. Current trends suggest that uncemented prostheses may carry a higher risk of revision in certain populations [ 31 ]. From preoperative optimization to postoperative rehabilitation and long-term monitoring, maximizing outcomes requires an integrated strategy that accounts for the patient’s physical and emotional state at every step [ 31 ]. Although useful, the data on the variables influencing THA results have significant limitations that need to be taken into account. Registry data and retrospective research, which can only show associations rather than establish causality, account for a large portion of our existing knowledge. It is challenging to determine whether conditions like sarcopenia or low psychological resilience actually result in inferior outcomes or whether they are only a reflection of a patient profile that predisposes to a later recovery because of these research designs. Additionally, little is known about how patient features and surgical choices interact. In contrast to healthy people, further research is required to determine whether patients with preoperative anaemia or low nutritional conditions might benefit from other implant options or fixation procedures. Prospective cohort studies with thorough adjustment for confounders and standardized outcome measures should be given priority in future research. To determine whether preoperative optimization of controllable factors (muscle strength, psychological resilience and nutritional status) directly enhances functional recovery and patient-reported outcomes after THA, RCTs are required. Personalized treatment plans and more effective resource allocation would also be made possible by the creation and validation of integrated risk-prediction algorithms that incorporate surgical, perioperative and patient-specific factors. To understand how early postoperative variables, such as anaemia and blood loss, affect implant survival and functional outcomes over decades rather than months, longer-term follow-up studies are crucial. 3. Mechanisms and contributing factors of anaemia in surgical patients Iron deficiency is a leading cause of anaemia, particularly in adolescent females. Other causes include infections, bleeding and nutritional inadequacies. Direct influences include behaviour, nutrition and sleep. Indirect factors encompass knowledge, age, socioeconomic status and healthcare access [ 32 ]. Clinically, anaemia is defined as reduced erythrocyte mass that impairs tissue oxygenation. In surgical patients, the clinical presentation depends on age, sex, rapidity of onset, preoperative haemoglobin (Hb) and physiological reserve [ 33 ]. Major causes in surgical patients include iron deficiency, anaemia of chronic illness and perioperative blood loss [ 34 , 35 ]. These conditions increase the risk of complications and may prolong the hospital stay. Effective management requires minimizing blood loss and optimizing red blood cell (RBC) production [ 35 ]. Due to its high prevalence and significant impact on adults’ health and well-being, anaemia is a serious public health concern. It may cause symptoms including weakness, fatigue, palpitations, tachycardia, shortness of breath and cognitive impairment. Anaemia may also lead to higher healthcare costs and reduced work productivity in adults. The disruption of normal tissue oxygenation, a key consequence of anaemia, is a primary factor contributing to the burden of several illnesses globally and is associated with decreased exercise tolerance and diminished quality of life. Hb levels are typically measured as part of a complete blood count (CBC) and anaemia status is determined according to established World Health Organization (WHO) criteria [ 11 ]. Iron is essential for erythropoiesis and cellular health. The body requires approximately 25 mg of iron daily, obtained from erythrocyte breakdown, macrophage recycling, stores and intestinal absorption [ 36 ]. Iron deficiency anaemia (IDA) is characterized by a serum ferritin level below 15 μg/L and a Hb level below 120 g/L. It is prevalent in pregnant women, infants and populations in low-income countries [ 36 ]. Pernicious anaemia (PA) is the most common cause of vitamin B12 deficiency worldwide. It develops insidiously and may be missed without CBC testing. Early diagnosis is crucial, as some neurologic sequelae may become irreversible despite treatment [ 37 ]. Preoperative anaemia is linked to worse postoperative outcomes regardless of the need for transfusions, indicating that decreased oxygen-carrying capacity has direct physiological effects rather than those that are only mediated by transfusion exposure. Improved Hb concentrations, reduced need for allogeneic blood transfusions, and better clinical outcomes have been associated with structured preoperative anaemia management [ 38 ]. In elderly surgical patients, anaemia is directly related to higher rates of complications and is regarded as a significant risk factor in both the preoperative and postoperative phases. Low Hb levels are linked to pulmonary and cardiovascular complications, which negatively impact postoperative survival. Beyond immediate surgical consequences, anaemia is associated with cognitive impairment, frailty syndrome and functional decline in older adults. The elderly population is particularly susceptible to inflammation-related anaemia, which disrupts iron metabolism, impairs wound healing and increases the risk of infection [ 39 ]. These factors make early diagnosis of anaemia in older surgical patients and comprehensive haematologic examination during the preoperative period crucial steps in lowering postoperative morbidity [ 39 ]. The physiological response to surgical stress encompasses the metabolic and hormonal changes that occur following tissue injury. This response classically proceeds through three phases: the initial ‘ebb phase’, a hypodynamic period in the first hours after trauma characterized by homeostatic efforts; the subsequent ‘flow phase’, a hyperdynamic and hypercatabolic state; and finally the ‘recovery phase’ [ 40 ]. The inflammatory response after surgery may cause anaemia to develop or worsen through several mechanisms. Inflammatory cytokines suppress erythropoiesis, alter iron metabolism and blunt the normal physiological response to anaemia. Specifically, inflammation upregulates hepcidin production, which traps iron within macrophages and hepatocytes, reducing iron availability for erythropoiesis. Simultaneously, circulating erythropoietin (EPO) levels are relatively decreased and bone marrow responsiveness to EPO is diminished [ 41 ] ( Figure 2 ). Surgical patients with comorbidities or postoperative difficulties often exhibit the typical pattern of anaemia of inflammation, also known as anaemia of chronic illness, which is caused by these inflammatory alterations. Figure 2. Open in a new tab Anaemia in surgical patients is a prevalent and complex problem that often results from a confluence of preoperative, intraoperative, and postoperative variables. Blood loss after surgery and the ensuing inflammatory reactions may worsen preoperative anaemia, which is often caused by iron deficiency and chronic inflammation. Iatrogenic factors also have a role, such as excessive blood draws [ 33 , 135 ]. Pharmacologic approaches to treating inflammation-induced anaemia have been studied. EPO medication reduced the need for blood transfusions by approximately 31% in critically ill patients, according to a meta-analysis of 12 RCTs, although it did not substantially lower mortality [ 41 ]. Although further research is needed to determine its precise involvement in inflammation-driven anaemia, intravenous (IV) iron supplementation has also been shown to lower the need for transfusions in a variety of surgical patients. There is currently little data on the use of corticosteroids for sepsis-associated anaemia and no trials have been found in the postoperative surgical group [ 41 ]. Careful thought must be given to how applicable these results are to patients having elective THA. Although everyone experiences inflammation after surgery, the intensity and duration of this reaction vary widely. The best ways to treat inflammation-related anaemia in the THA population, including the potential applications of IV iron, EPO and combination therapies within comprehensive PBM regimens, require further investigation. In conclusion, numerous limitations persist despite a thorough understanding of the fundamental mechanisms underlying anaemia. These include diagnostic challenges in surgical patients, a preponderance of associative data over interventional evidence, and a lack of customized treatment plans for specific surgical subgroups, particularly the elderly and those with sepsis [ 35 , 39 , 41 ]. Future research must emphasize well-designed RCTs over correlational studies to establish the impact of targeted anaemic treatment techniques on clinically meaningful outcomes, such as functional recovery, morbidity, and mortality. The proactive management of anaemia presents different challenges in elective versus emergency surgery, though transfusion-sparing techniques are gaining popularity across both settings. For elective surgical patients, the available evidence supports implementing PBM programs in accordance with established standards, such as those proposed by the network for the advancement of PBM, haemostasis and thrombosis [ 33 , 42–44 ]. In the emergency setting, some studies suggest a role for IV iron, possibly supplemented with EPO, for anaemic patients; however, a significant evidence gap prevents definitive conclusions. A large-scale RCT is urgently needed to thoroughly assess the impact of these interventions on clinical outcomes in emergency surgery. To develop a uniform, evidence-based strategy, such research must evaluate cost-effectiveness and identify the optimal balance between the benefits of preoperative anaemia management and the need for prompt surgical intervention [ 33 , 42–44 ]. Studies of critically ill or medically unwell populations, rather than individuals undergoing elective THA, provide the majority of our knowledge about the development of anaemia in surgical patients. This is significant because a patient undergoing hip replacement surgery may have different causes of low Hb than a patient suffering from sepsis. For instance, we are still unsure of the extent of preoperative anaemia in TH, whether a patient has a basic iron deficiency or inflammation from a chronic illness, or how these various conditions may respond to therapy. Most of the research currently available is observational, demonstrating associations rather than cause-and-effect relationships. Among the significant unresolved issues are: What impact does the body’s inflammatory reaction to surgery have on anaemic individuals’ iron handling? Does a patient’s response to EPO or iron supplementation alter with age or frailty? Would greater recovery and fewer transfusions result from treating anaemia according to its unique cause? To determine whether treating the underlying cause of anaemia improves outcomes important to patients, such as recovery time and avoidance of blood transfusions, future studies should first identify the most common anaemia patterns in THA patients. 4. Preoperative anaemia and its impact on THA outcomes IDA is among the most prevalent medical conditions seen in individuals after primary THA. Sequeira and colleagues [ 45 ] described hospital resource consumption and early postoperative problems in patients with preoperative IDA undergoing THA using a large retrospective database. When 98,681 patients with preoperative IDA were compared to 386,724 non-anaemic controls, the research discovered that IDA was linked to noticeably higher rates of unfavourable outcomes [ 45 ]. The 30-day readmission and ED visit rates were considerably higher in those with IDA. Individuals with IDA were also more likely to have revision surgery, dislocation, periprosthetic fracture and periprosthetic joint infection (PJI) within a year after surgery. Indicating a disproportionate financial burden, IDA was associated with a higher incidence of 90-day medical complications, higher hospital costs and poorer reimbursement [ 45 ]. These results highlight the significance of detecting and treating IDA during preoperative optimization. Recent studies have shown that preoperative anaemia, which is most typically described by Hb levels, is a major predictor of unfavourable outcomes after THA. Transfusion thresholds are the levels of Hb and haematocrit (HCT) at which transfusion therapy should start. The goal of the liberal transfusion strategy is to keep Hb levels between 100 and 120 g/L, with a transfusion threshold of 100 g/L [ 18 , 46 , 47 ]. Because they are derived from whole blood, Hb and HCT both rely on plasma volume. The HCT is approximately 3 times the Hb value (HCT = 3 × Hb), indicating a clear and consistent relationship between the two. Hb and HCT levels will appear higher than they would be if the patient were normovolemic; if the patient is extremely dehydrated, they will appear lower than their normal levels; and if they are fluid overloaded, they will appear higher than their normal levels. Independent radionuclide examination of the plasma and RBCs (using 51Cr and 131I, respectively) is required to determine the actual RBC mass [ 18 , 46 , 47 ]. Preoperative anaemia, typically defined by Hb levels, is a major predictor of unfavourable outcomes after THA. One study using HCT values to evaluate preoperative anaemic status found that even mild anaemia significantly increased the risk for sepsis, wound infection, urinary tract infection, renal complications and respiratory difficulties compared to normal HCT. Moderate and severe anaemia were associated with higher rates of non-home discharge, unplanned readmissions and perioperative blood transfusions [ 18 ]. A meta-analysis of 18 studies including 424,158 patients identified several risk factors for perioperative blood transfusion in THA: increased intraoperative bleeding, increased postoperative drainage, preoperative anaemia, age > 80 years, female sex and American Society of Anaesthesiologists (ASA) class ≥3. Low BMI (≤18.5) was also a significant predictor [ 48 ]. Although primary THA is highly effective for end-stage hip osteoarthritis, if the initial operation is unsuccessful, revision THA (rTHA) may be necessary. Compared with primary operations, rTHA is asso­ciated with higher risks, including higher infection rates, longer operating times, greater blood loss and longer hospital stays. Therefore, improving perioperative optimization requires understanding the demographics, comorbidity profiles and outcomes of patients undergoing initial and rTHA [ 49 , 50 ]. A large epidemiological registry study using data from the National Inpatient Sample investigated these factors by comparing patients who underwent primary THA and rTHA between 2006 and 2014 [ 49 ]. The study found that overall complication rates were 27.32% for primary THA and 39.46% for rTHA. Notably, postoperative anaemia was the most frequent complication in both groups, occurring in 25.20% of primary THA patients and 35.69% of rTHA patients. Common comorbidities included chronic pulmonary disease and hypertension. The most frequent indications for rTHA were dislocation or instability (21.85%), mechanical loosening (19.74%), infection (15.10%) and other mechanical problems (17.38%). During the study period, the volume of primary THA procedures increased by 69.50%, while rTHA procedures increased by 28.50% [ 49 ]. These results demonstrate the significant prevalence of postoperative anaemia in both original and revision total hip arthroplasties. The greater complexity and blood loss connected with revision surgery are probably the reasons for the higher anaemia incidence in rTHA patients. Strategies to prevent and treat postoperative anaemia, such as intraoperative blood conservation, preoperative optimization and judicious administration of iron and erythropoiesis-stimulating drugs, require ongoing study given the increasing number of primary and revision surgeries. Jørgensen and colleagues conducted a prospective cohort study to examine the relationship between postoperative outcomes and non-anaemic iron deficiency in patients receiving fast-track hip or knee arthroplasty [ 51 ]. The research included 3,919 individuals without iron deficiency who had primary unilateral hip or knee replacements and 964 patients with iron deficiency (defined as transferrin saturation ≤20% with normal Hb). Days Alive and out of Hospital at 30 days (DAH30) and 90 (DAH90) postoperatively served as the main outcome measure. The range of results varied significantly, but the median DAH30 was 29.0 days in both groups. The difference in median DAH30 and DAH90 across groups was insignificant (−0.00 days for both time periods) after controlling for confounding factors. Other postoperative outcomes, such as complications, readmissions, or length of stay (LOS), did not correlate significantly with iron deficiency [ 51 ]. The effect of non-anaemic iron deficiency on days alive and out of the hospital was statistically significant owing to the large sample size; nonetheless, the authors determined that the absolute difference was clinically negligible. They proposed that frequent postoperative outcomes in fast-track hip and knee arthroplasty are unlikely to be improved by addressing preoperative iron deficiency in the absence of anaemia [ 51 ]. These results have significant ramifications for preoperative optimization strategies in THA. They contend that individuals with overt anaemia or other modifiable risk factors may benefit more from therapeutic services, whereas iron deficiency without anaemia may not require frequent repair. To determine whether these results apply to larger THA populations outside fast-track settings, further investigation is necessary. A prospective database study of Enhanced Recovery After Surgery (ERAS) THA patients found that those with IDA (Hb ≤130 g/L and transferrin saturation ≤20%) were older, more likely to live alone, use walking aids and receive home care than non-anaemic patients [ 52 ]. While the median LOS was 1 day in both groups, 11.6% of IDA patients had a LOS >2 days, compared with 5.4% of non-anaemic patients. Readmission rates were also higher in the IDA group: 6.5% versus 4.1% at 30 days and 13.4% versus 5.4% at 90 days. The authors noted that the substantial burden of patient-related risk factors may limit the ability of IDA correction alone to improve outcomes, highlighting challenges for trial design [ 52 ]. A meta-analysis reported that preoperative anaemia affects approximately 22% of patients awaiting joint replacement. Compared to non-anaemic patients, anaemic patients had a four-fold higher risk of mortality, significantly higher rates of surgical site infection and transfusion, longer hospital stays and higher readmission rates. Proposed mechanisms include impaired tissue oxygenation and a hypercoagulable state, both of which increase the risk of infection and thromboembolism [ 16 ]. Despite consistent associations between preoperative anaemia and adverse outcomes, a fundamental tension remains. Extensive observational data link anaemia to increased readmissions, periprosthetic infections, dislocations and higher costs. However, it remains uncertain whether anaemia is a direct, modifiable cause of poor outcomes or merely a marker of underlying patient frailty and comorbidity. This evidence gap, the inability of observational data to demonstrate causation, means that while preoperative screening is clearly warranted, the effectiveness of routine anaemia correction has not been established [ 16 , 53 , 54 ]. Although there is a wealth of research about preoperative anaemia in THA patients, the strength of therapeutic advice is diminished by several methodological limitations. The vast majority of research is observational, using retrospective cohorts or registry data that show regular correlations but cannot prove causation. These studies are vulnerable to selection bias, indication-based confounding, and insufficient control for critical factors such as inflammatory load, nutritional status and frailty. Consequently, it is still unknown whether anaemia is a primary indicator of underlying patient susceptibility or if it causes negative outcomes on its own. Transfusion reduction has been the main emphasis of the few available interventional trials, with little attention paid to patient-centred outcomes, including functional recovery, quality of life and implant longevity. Regarding the best Hb thresholds for intervention, the relative efficacy of oral versus IV iron across various patient phenotypes, the role of erythropoiesis-stimulating agents (ESAs) in combination protocols, and the cost-effectiveness of different management approaches across healthcare settings, there are still significant evidence gaps. To determine whether preoperative anaemia treatment targeted to specific underlying causes enhances clinically significant outcomes beyond transfusion avoidance, future research should prioritize well-powered RCTs. Longer follow-up periods, standardized outcome measures and strict adjustment for confounders should all be included in these studies. Furthermore, before clinical deployment, external validation and prospective testing are necessary for integrating machine learning (ML) algorithms into individualized risk assessment. Lastly, to support comparative effectiveness research and meta-analysis, the discipline would benefit from standardized criteria for anaemia severity and response to therapy. 4.1. Surgical complications and hemodynamic considerations in anaemic THA patients Perioperative blood loss in THA extends beyond visible intraoperative bleeding. Hidden blood loss (HBL) refers to blood lost into tissues or retained in joints postoperatively and contributes significantly to postoperative anaemia. A study of patients undergoing primary THA via the posterior approach measured a mean HBL of 700.39 ± 368.59 mL. Multivariate analysis identified preoperative Hb as a protective factor against HBL, while higher BMI, longer surgery time and greater Hb loss were significant risk factors (ChiCTR2100053888) [ 55 ]. These results emphasize how crucial it is to take HBL into account while maximizing perioperative care, especially for patients with high BMI, lengthy surgery times, or low preoperative Hb. Although sometimes necessary, perioperative blood transfusions carry inherent risks, including immunomodulatory effects, allergic reactions and infection. Because anaemic patients are more likely to need transfusions and are therefore more vulnerable to these consequences, these concerns are especially pertinent in the setting of preoperative anaemia. Therefore, reducing the need for transfusions by using efficient blood management techniques is a key objective in THA [ 56–58 ]. A before-and-after observational cohort study evaluated the implementation of an institution-specific perioperative PBM program for patients undergoing primary THA [ 59 ]. The study included 100 patients in the initial observation period and 108 patients following PBM implementation. The PBM protocol included elimination of routine preoperative low-molecular-weight heparin prophylaxis, intraoperative use of TXA and enhanced postoperative monitoring. Following implementation, the perioperative blood transfusion rate decreased significantly, despite an increase in the proportion of posttraumatic THA procedures performed. Patients who still required transfusions had lower preoperative Hb levels (129 vs. 147 g/L), higher ASA scores and higher rates of postoperative hypotension, oliguria and infections compared to those who did not require transfusion [ 59 ]. The researchers concluded that, especially in environments with limited funding for comprehensive blood management, even a partial, institution-specific PBM program may successfully lower transfusion rates and improve outcomes [ 59 ]. These results highlight the importance of including anaemia diagnosis and treatment in more comprehensive PBM plans for THA patients. A study comparing blood loss by fixation technique in THA for femoral neck fractures found no significant differences between cemented, hybrid and uncemented approaches. Mean perioperative blood loss ranged from 1087 to 1117 mL across groups. The researchers concluded that the fixation method should not be selected solely based on blood loss [ 60 ]. ERAS protocols incorporate multiple strategies relevant to anaemia management. In a study of 52 THA patients treated with an ERAS protocol, all received TXA, and only 17.3% required blood transfusion. Mean time to mobilization was 7.98 h, mean hospital stay was 13.18 days and no major early complications occurred [ 61 ]. In anaemic THA patients, anaesthetic control is essential to achieving optimal results. Maintaining oxygen supply, reducing blood loss and controlling hemodynamic instability are among the objectives. Reduced blood loss and better pain management are two potential benefits of regional anaesthesia over general anaesthesia [ 62–65 ]. Safe results depend on careful intraoperative monitoring, proper postoperative care and preoperative optimization [ 63 ]. Advanced PBM requires a paradigm change from reflexive transfusion. Implementing transdisciplinary PBM programs, creating evidence-based transfusion thresholds and creating dynamic indicators of tissue hypoxia are among the top goals [ 63 , 66 , 67 ]. Current evidence on managing anaemic THA patients is limited by small observational studies, short follow-up and bundled interventions that obscure the effects of individual components. Critical gaps include a lack of high-quality RCTs to determine optimal transfusion thresholds, insufficient data on long-term functional outcomes and cost-effectiveness, and poor mechanistic understanding of how anaemia drives complications such as HBL. Future research should prioritize standardized outcome measures and investigate pathophysiological mechanisms to develop targeted, evidence-based protocols that improve patient-centred outcomes [ 55 , 59–61 , 65 ]. There are significant limits to the available data on perioperative blood control in anaemic THA patients. Due to their small size, single-center design and observational nature, most studies are biased and have limited generalizability. In PBM research, bundled therapies make it challenging to identify the precise elements that contribute to benefits. It is unclear if anaemic populations react differently to normal therapy since studies on concealed blood loss and fixation procedures seldom look at results explicitly in these groups. There are still important gaps: no high-quality randomized trials have established the optimal transfusion thresholds for anaemic THA patients; little information exists on long-term functional recovery beyond short-term transfusion metrics; and it is unclear how cost-effective various PBM strategies are across contexts. Future studies should focus on multicentre randomized trials that are powered for patient-centred outcomes, such as complications and functional recovery. To determine which patients benefit most from specific therapies, trials should stratify by anaemia severity. To understand how anaemia leads to consequences, including infection and occult blood loss, mechanistic research is required. Finally, individualized perioperative treatment may be enabled by proven risk prediction systems that account for patient characteristics and preoperative Hb. 4.2. Anaemia-related adverse events after THA Several factors increase venous thromboembolism (VTE) risk after THA, including female sex, age over 70 years, hypertension, BMI ≥25, prolonged operative time, cemented prosthesis use and prior VTE history [ 68 ]. Evidence from orthopaedic trauma populations provides indirect support for the relationship between preoperative anaemia and thrombotic risk. A study of 1,049 patients with femoral and pelvic fractures found that anaemic patients had a 50-57% higher risk of developing deep vein thrombosis (DVT) compared to non-anaemic patients, with an Hb threshold of 125 g/L identified for predicting DVT risk [ 69 ]. Although trauma populations are the source of these results, THA patients may also be affected by suggested processes such as altered blood flow dynamics, endothelial dysfunction and coagulation pathway activation. However, the baseline inflammatory state and immobility of trauma patients vary significantly from those of elective THA candidates; care should be used when extrapolating these findings. In elderly anaemic patients undergoing THA, a study identified independent predictors of preoperative DVT, including HCT, albumin (ALB), prothrombin time (PT), fibrin degradation products and lymphocyte-monocyte ratio (LMR). A nomogram incorporating these factors achieved excellent predictive accuracy (Area Under the Curve (AUC) 0.929) and may aid clinical decision-making [ 70 ]. Longer hospital stays and preoperative anaemia were identified as independent risk factors for preoperative DVT in an older patient cohort with hip fractures [ 71 ]. According to a different large study of patients having total joint arthroplasty (TJA), preoperative anaemia raised the risk of DVT by 1.82 to 8.26 times, depending on its severity. The largest risk was associated with severe anaemia. As anaemia severity worsened, the risk of transfusion increased 3.52- to 61.37-fold (ChiCRT2100054844) [ 72 ]. Although further research is required to fully understand this association, preoperative statin usage has been linked to a lower 90-day VTE risk after THA [ 73 ]. After THA, PJI is a serious complication. Obesity, malnutrition, smoking, hyperglycaemia and preoperative anaemia are among the known modifiable risk factors [ 74 , 75 ]. Before surgery, optimizing these variables may lower the chance of infection. Preoperative anaemia (HCT ≤ 32.1%) and Staphylococcus aureus ( S. aureus ) infection were independent predictors of treatment failure in a study examining open debridement and polyethylene exchange (ODPE) for acute PJI. Because anaemia fosters a permissive environment for chronic infection, success rates were 97.1% when neither risk factor was present, compared with 73.6% overall [ 76 ]. There is a dose-response association between the severity of anaemia and unfavourable outcomes. Severe anaemia raises the risk of DVT by more than 8 times and transfusion by more than 60 times, whereas moderate anaemia (Hb 100–120 g/L) increases the risk of revision by around 3.5 times [ 70 , 72 , 76 , 77 ] ( Table 1 ). Disparate definitions of anaemia, differences between elective and trauma groups, and uneven correction for variables including inflammatory state and nutritional inadequacy are the main causes of significant variability between studies. Table 1. Summarizing the key findings from the articles on anaemia-related adverse events after THA surgery. Anaemia-related adverse events after THA Key findings Clinical implications Ref After THA, several variables may raise the risk of VTE, such as age, female sex, BMI ≥25, hypertension, prolonged operation, cemented prosthesis, and a history of VTE. Although it is not a risk factor for VTE, anaemia may occur after THA. It may result from problems after surgery or from blood loss during the procedure. Compression stockings and anticoagulants are preventive interventions essential for controlling the risk of VTE after THA. To identify the most effective preventive measures, a comprehensive evaluation of each individual’s risk factors is necessary. [ 68 ] Preoperative DVT in anemic patients undergoing THA is predicted by a greater LMR and lower levels of ALB, PT, Fibrinogen Degradation Products (FDP), and HCT. In anemic THA patients, a higher risk of preoperative DVT is independently linked to low HCT, low ALB, extended PT, raised FDP, and a high LMR. An AUC of 0.929 indicates that a nomogram that considers these parameters has significant predictive power for DVT. To reduce the dangers of both preoperative and postoperative anaemia, perioperative blood control techniques are essential. Clinicians can identify high-risk patients and provide the appropriate therapies by using a nomogram to predict postoperative anaemia. [ 70 ] Two separate risk factors for DVT in hip fractures include preoperative anaemia and extended hospitalization. According to studies, individuals with hip fractures who have even minor preoperative anaemia are more likely to have postoperative problems, such as DVT. There seems to be a correlation between the risk of DVT and the degree of anaemia. In hip fracture surgery, identifying and treating preoperative anaemia is essential to improving patient outcomes and lowering the risk of DVT. [ 71 ] There is an increased risk of DVT and blood transfusion after THA in patients who had anaemia before the procedure. Patients with preoperative anaemia had a 1.82 to 8.26 times greater risk of having DVT and a 3.52 to 61.37 times higher risk of needing a blood transfusion. Preoperative DVT screening should be performed before THA in patients with moderate to severe preoperative anaemia, according to the study. [ 72 ] The incidence of VTE in the ninety-day postoperative period may be decreased by taking statins before THA. However, the incidence of pulmonary embolism, DVT, ER visits, and reoperations did not differ significantly between the statin and non-statin groups, according to the study. Even though VTE rates have decreased due to advanced surgical techniques, it is still a significant issue after THA. To possibly reduce this risk, high-risk individuals may think about starting statins before surgery. [ 73 ] An infection with S. aureus might worsen anaemia after THA. S. aureus infection and preoperative anaemia (Hb ≤32.1%) are independent risk factors for ODPE failure in individuals undergoing THA. When both risk factors are present, the ODPE success rate falls to 73.6%. In particular, the failure rate was 48.3% for patients infected with S. aureus and 11.6% for those not infected. Improving patient outcomes requires optimizing Hb levels before surgery and detecting and treating S. aureus infections after surgery. [ 76 ] Several modifiable risk factors may increase the risk of PJI after THA. In particular, PJIs and surgery site infections are predisposed to by anaemia, obesity, malnutrition, smoking, and hyperglycemia. One frequent bacterium that may cause these illnesses is S. aureus. Multidisciplinary intervention, including patient education, counseling, and follow-up, is necessary for patients who exhibit one or more of these risk factors. For high-risk TJA patients, preoperative patient optimization may improve surgical results and patient care while dramatically lowering the risk of PJI and SSI. [ 75 ] Open in a new tab Anaemia is linked to negative consequences through several mechanisms. Through reduced blood viscosity, altered flow dynamics that promote venous stasis, and tissue hypoxia that leads to endothelial dysfunction and the production of procoagulant factors, anaemia causes a prothrombotic state in VTE [ 70 , 72 ]. Compromised tissue oxygenation in PJI hinders wound healing by reducing collagen synthesis and impairing neutrophil activity and lymphocyte proliferation [ 76 , 77 ]. Further research is necessary to rule out hormonal implications on erythropoiesis and immunological function, as shown by the finding that anaemia raises PJI and revision risk higher in men than in women [ 73 , 76 , 77 ]. Retrospective designs, variable anaemia classifications, and inadequate control for confounding comorbidities limit current evidence. Future research should prioritize randomized trials to determine whether preoperative anaemia correction reduces the risk of VTE, PJI and revision. Mechanistic studies are needed to clarify how anaemia drives these complications. Finally, validated risk-stratification tools incorporating anaemia severity with other clinical parameters could enable personalized prevention strategies [ 77–79 ]. Although the evidence connecting preoperative anaemia to post-THA problems is consistent, it has significant limitations. Instead of following patients forward in controlled trials, almost all the research now available looks backward at what happened to them. This implies that although we may confidently claim that anaemia is linked to poor outcomes, we cannot declare that it is the cause of them. Even the finest statistical adjustments may not fully clarify whether poor outcomes are due to the patient’s overall susceptibility or to low Hb levels. Anaemic patients are often older, frailer and sicker overall. The fact that various studies define anaemia further complicates the situation. HCT is used in place of Hb by some, according to procedure-specific standards by others, and according to WHO requirements by others. It is challenging to compare results or effectively pool data because of this variability. Studies also differ greatly in the confounders they consider; many fail to include dietary inadequacies, inflammatory conditions, or frailty measures, which may account for a large portion of the reported association. Important questions are still unresolved. Would treating anaemia before surgery really lower the chance of joint infections or blood clots? Although we don’t have any randomized studies to support it, the dose-response connection indicates that it may. Why does anaemia seem to make males more susceptible to infection than women? Is this an immunological difference, a hormonal consequence, or just a small-numbers artifact? In what precise ways does low Hb foster an environment conducive to the formation of clots and infections? Though they make biological sense, the suggested mechanisms, impaired oxygenation, endothelial dysfunction, and altered blood flow, have not been thoroughly investigated in THA patients in particular. Randomized studies are needed to determine whether treating anaemia at its root causes genuinely improves patient outcomes that matter to them, such as returning to their regular activities, avoiding reoperation, and avoiding hospitalization. These studies must be large enough to detect variations in complications and transfusion rates. In the particular setting of joint replacement, mechanistic research using contemporary biomarkers may provide light on the role anaemia plays in thrombosis and infection. Finally, surgeons may be able to determine which patients need more aggressive optimization before surgery using simple, useful risk algorithms that combine anaemia severity with other patient features. Until then, we should be honest about what the research does and does not establish and treat anaemia as a serious warning indication, a red flag that needs to be addressed. 4.3. Impact of preoperative anaemia on long-term mobility and patient-reported outcomes after THA Preoperative anaemia is associated with increased morbidity and mortality after TJA, including higher rates of sepsis, readmissions, and wound, cardiac, pulmonary and renal complications. However, significant heterogeneity across meta-analyses warrants caution in interpretation. Large-scale, multicentre RCTs are needed to determine whether anaemia correction reduces complication rates [ 80 ]. Research on hip fracture populations provides additional insights into the relationship between anaemia and outcomes, though these findings must be interpreted separately from elective THA. A descriptive epidemiology study examined perioperative anaemia in patients with hip fractures and evaluated correlations between Hb levels and clinical outcomes [ 81 ]. Among the study population, 40.4% had anaemia at admission, 45.6% immediately before surgery, 93.0% at the postoperative nadir and 84.6% at discharge (anaemia defined as Hb <120 g/L). The mean postoperative Hb decrease was 2.8 ± 1.6 g/L. After multivariate adjustment for prefracture health status and transfusion usage, higher admission Hb levels were associated with shorter hospital stays, reduced mortality and fewer readmissions. Higher postoperative Hb levels correlated with shorter LOS and lower readmission rates, but not with mortality or functional mobility scores [ 81 ]. These results from individuals with hip fractures highlight the importance of preoperative Hb adjustment. Hip fracture patients, on the other hand, are quite different from elective THA candidates; they are usually older, more fragile and have fewer options for preoperative optimization when undergoing nonelective surgery. Higher Hb is probably associated with better outcomes across all groups, although the extent of the benefit and the best ways to control it may vary. Despite the typically positive long-term prognosis of the operation itself, the more favourable baseline state of elective THA patients provides a greater opportunity for thorough preoperative anaemia diagnosis and correction, which remains a crucial aim. Research in hip fracture populations offers additional insights into the complex relationship between anaemia and outcomes, though caution is needed when extrapolating to elective THA. One study examining mortality prediction in hip fracture patients found that the prognostic significance of anaemia depends critically on when Hb is measured. Risk factors for admission anaemia included age, female sex, ASA score and intertrochanteric fracture. In contrast, postoperative anaemia was most strongly associated with surgical procedure type, operative duration, blood transfusion, intraoperative blood loss and drain output [ 82 ]. Cox proportional-hazards regression revealed that admission anaemia was associated with increased all-cause mortality, but this risk did not persist for postoperative or discharge anaemia after adjustment for confounders. The investigators concluded that therapeutic interventions can significantly influence postoperative and discharge anaemia status, and that admission anaemia, rather than later measurements, should be used to predict mortality in hip fracture patients [ 82 ]. These results highlight a crucial factor in THA research: the timing of Hb testing. The idea that anaemia’s prognostic relevance may change depending on when it is evaluated probably applies to all surgical populations, even though hip fracture patients differ from elective THA candidates in significant aspects, such as baseline health state, surgical urgency and inflammatory profile. Future research in THA should carefully examine whether preoperative, postoperative, or discharge Hb levels best predict clinically important outcomes. There is little data on whether postoperative anaemia hinders functional recovery after THA. Two weeks after discharge, the association between postoperative anaemia and recovery was investigated in a study of patients undergoing fast-track THA. Only 6% of the variation in recovery was explained by Hb levels, suggesting a weak relationship between Hb and performance on the 6-minute walk test. Hb and other mobility or quality-of-life metrics did not correlate. The authors concluded that early functional recovery after fast-track THA is not significantly affected by moderate postoperative anaemia [ 83 ]. A multidisciplinary preoperative anaemia program was shown to improve Hb on the day of surgery, decrease the need for transfusions, shorten hospital and intensive care unit stays, and reduce overall complications in patients undergoing cardiovascular surgery. Additionally, the program resulted in a 69% reduction in blood procurement costs [ 84 ]. These results suggest the potential benefits of systematic anaemia control, even if they are not unique to THA. Instead of focusing solely on short-term benefits, future research should emphasize RCTs to determine whether preoperative anaemia correction leads to long-term improvements in mobility, quality of life, and patient satisfaction. Longer follow-up periods should be used in studies to evaluate functional outcomes beyond the immediate postoperative period [ 81 , 82 , 85 ]. Instead of focusing solely on short-term advantages, future research should emphasize RCTs to determine whether preoperative anaemia correction results in long-term improvements in mobility, quality of life, and patient satisfaction. Longer follow-up periods should be used in studies to evaluate functional outcomes beyond the immediate postoperative period [ 81 , 82 , 85 ]. Surprisingly little, and mostly indirect, evidence exists that preoperative anaemia is associated with long-term functional outcomes after THA. Due to variations in baseline health and surgical urgency, the majority of studies use hip fracture populations rather than elective THA patients, which limits their relevance. Few studies specifically examine patient-centred outcomes, such as mobility recovery, quality of life, or happiness, after discharge; instead, most research on THA patients focuses on short-term outcomes, such as hospital stay and transfusion rates. The limited information available indicates that Hb levels account for only part of the variation in functional recovery, suggesting that other factors – such as muscular strength, diet and psychological state – probably have a greater impact. There are still important gaps: no prospective trials monitor functional recovery outside the first several weeks after surgery; it’s unclear whether correcting preoperative anaemia enhances significant long-term results; and confounding variables like sarcopenia and frailty are seldom sufficiently addressed. Longitudinal studies with prolonged follow-up that measure patient-reported outcomes and performance-based mobility are necessary for future study. Functional recovery and quality of life, rather than only transfusion reduction, should be the main objectives of randomized studies. Clinicians should treat anaemia as a significant risk factor until such data is available, but they should also be aware that treating it may not ensure better functional results. 5. Advances in anaemia management in THA All patients having surgery with anticipated moderate to large blood loss (>500 mL) should have preoperative anaemia screening, according to international expert standards [ 35 , 86 ]. A specific aetiological diagnosis should guide treatment. When possible, non-urgent surgical procedures should be postponed to allow for the detection and treatment of iron deficiency and anaemia. To lower the risk of transfusion, the preoperative Hb concentration in both sexes should be more than 130 g/L [ 35 ]. Absolute iron deficiency is diagnosed when serum ferritin levels are less than 30 μg/L. Ferritin <100 μg/L indicates functional iron insufficiency when inflammation is present (C-reactive Protein >5 mg/L) or transferrin saturation is less than 20% [ 35 ]. For patients with iron insufficiency scheduled for surgery 6–8 weeks after diagnosis, oral iron supplements are suitable. Doses of 40–60 mg per day or 80–100 mg every other day are typical [ 35 ]. Oral iron is readily accessible and reasonably priced, and it may increase preoperative Hb by 6–7 g/L. However, around 17% of patients experience gastrointestinal (GI) adverse effects, and hepcidin-mediated inhibition reduces absorption in inflammatory conditions [ 87–90 ]. When oral iron is ineffective or poorly tolerated, or when surgery is planned within 6 weeks of diagnosis, IV iron is recommended [ 35 ]. With a mean difference of 7.8 g/L, IV iron elevates Hb more quickly than oral iron, and its efficacy peaks between 2 and 4 weeks [ 91 , 92 ]. Modern formulations of IV iron are safe but more expensive than oral iron; patient selection is crucial [ 91 , 92 ]. One potential strategy to treat anaemia and reduce the need for blood transfusions after THA is IV iron supplementation. A study examining the effects and safety of IV iron supplementation in patients undergoing THA found that IV iron supplementation significantly reduced blood transfusion rates compared with no supplementation when clinical symptoms guided transfusion decisions. However, no significant difference in Hb levels was observed between the first and seventh postoperative days. At 2 to 6 weeks postoperatively, IV iron supplementation substantially reduced Hb loss compared with no supplementation. Safety profiles were similar between groups, with only 0.5% of the treatment group experiencing adverse effects [ 93 ]. Subgroup analysis revealed that high-risk patients benefitted more from high-dose iron supplementation, demonstrating accelerated Hb recovery compared to those receiving low-dose iron. The study concluded that perioperative IV iron supplementation is safe and effective in reducing transfusions and Hb decline after THA, with high-dose regimens offering particular advantage for high-risk patients [ 93 ]. According to these results, IV iron should be part of comprehensive PBM regimens for THA patients, especially those diagnosed with iron deficiency or at higher risk of transfusion. In anaemic individuals, ESAs, such as EPO, efficiently increase Hb levels. Preoperative EPO improved outcomes and reduced the risk of allogeneic transfusion (RR 0.829) when used for preoperative optimization, according to a comprehensive evaluation of 8 studies involving 1,450 patients [ 94 ]. High-dose ESA regimens may lower transfusion rates from 44.9% to 11.4% and raise Hb by around 19.5 g/L [ 87–90 ] ESAs do have significant drawbacks, too, including their high cost, the need for sufficient iron reserves to sustain rapid erythropoiesis, and worries about thrombotic risk. Patients with chronic disease-related anaemia, those who reject transfusions, and those who have religious objections to blood products benefit from them the most [ 87–90 ] Combining IV iron sucrose with recombinant human EPO resulted in a non-significant 2.9 g/L decrease in Hb drop in 138 TJA patients, according to a retrospective study. The authors noted that variables that cause surgical blood loss could offset the advantages of short-term haematinic treatment. Thus, short-term postoperative protocols might be less successful than preoperative optimization [ 95 ]. Although vitamin B12 and folate deficiencies are rare in anaemic surgical patients, they should be treated promptly once identified. Special consideration should be given to patients who have already had gastric bypass surgery [ 96 , 97 ]. In a retrospective study of 1,442 THA patients, none of those who received EPO and had preoperative Hb levels below 120 g/L required transfusion within the first week. Optimizing preoperative Hb to> 120 g/L may not be required for patients undergoing traditional THA with low blood loss, according to the authors [ 98 ]. Risk prediction is strongly influenced by the definition of anaemia used for preoperative screening. According to one study, compared with other classifications, the WHO criteria identified the greatest proportion of patients in need of perioperative transfusion, with commensurate variations in expected complication rates [ 99 ]. Multimodal perioperative anaemia therapy in THA, including universal Hb and iron screening, is supported by current data. IV iron is recommended for shorter timeframes, inflammatory conditions, or oral intolerance, but oral iron works best when 6–8 weeks are available before surgery. Although erythropoiesis-stimulating drugs significantly raise Hb levels, they must be used with caution when choosing patients. Significant restrictions still exist, though: most trials lack sufficient power to assess clinical outcomes beyond transfusion reduction; there is a lack of recognized best practices for IV iron and ESA timing, dosage and patient selection; and different definitions of anaemia make it difficult to conduct comparative studies. There is a need for patient-centred, standardized outcome measures [ 99 ]. 5.1. Machine learning and artificial intelligence Recent developments in artificial intelligence (AI) and ML have enabled new methods for risk prediction and individualized treatment. ML algorithms may outperform traditional prediction models in analyzing complex datasets with nonlinear interactions [ 100–102 ]. According to one study, an AI program that uses pulse oximeter waveforms to calculate the Compensatory Reserve Index was able to predict transfusion needs after major orthopaedic surgery with more accuracy than traditional vital signs. Validation in a variety of groups is necessary, however, since the ideal CRI levels are yet unclear [ 100 ]. Using readily available clinical data, a Ridge Classifier ML model estimated the likelihood of perioperative blood transfusion in patients undergoing hip surgery with high predictive accuracy (AUC = 0.85). The most significant predictor was preoperative Hb, followed by operation type, ASA status, ALB, fibrinogen and operative length. By elucidating the contributions of individual variables, Shapley Additive exPlanations (SHAP) (a method to explain machine learning model predictions) analysis improved interpretability. However, generalizability must be confirmed, as this is a single-center, retrospective study [ 103 ]. Prospective studies assessing whether integrating ML-based risk prediction into clinical decision support systems results in quantifiable improvements in patient outcomes, transfusion rates and cost-effectiveness should follow external validation across a variety of THA cohorts. Another research questioned the standard gender-specific Hb criterion by using ML to determine a universal threshold of less than 148 g/L, which is much higher than previous cut-offs, as predictive of prolonged hospitalization or readmission after fast-track arthroplasty. Although further research is required, this suggests that the existing criteria for anaemia may be overly lenient for surgical groups [ 104 ]. AUCs of 0.887 internally and 0.834 externally were attained by a Random Forest model that forecasted intraoperative transfusion in hip fracture surgery. Hypoproteinemia, advanced age, preoperative anaemia, prolonged surgical duration, and internal fixation technique were important predictors [ 105 ]. With intraoperative blood loss, hypertension and postoperative drainage volume appearing as significant predictors, another ML model for transfusion prediction in older TJA patients attained an AUC >0.90 [ 102 ]. Logistic regression (AUC 0.98) performed better than more sophisticated ML algorithms in a multicentre study, creating a dynamic prediction model for transfusion after THA for femoral neck fractures, demonstrating that cutting-edge techniques do not always outperform conventional ones. Although the high AUC raises concerns about potential overfitting, a web-based calculator was developed for clinical use [ 106 ]. For the prediction and optimization of anaemia risk, ML and AI models are moving from theoretical instruments to real-world applications. Preventive referrals are now possible because algorithms can identify high-risk individuals by scanning electronic health information months before surgery. Faster and more precise differential detection of anaemia causes may be made possible by AI-driven diagnostic tools that analyze peripheral blood smears and biomarker panels [ 105 , 107 ] But there are still significant challenges. Concerns about algorithmic bias and generalizability are raised when multi-institutional data is absent during model training. The ‘black box’ status of certain models might limit physician adoption and confidence. Obstacles include high implementation costs and the need for a strong digital infrastructure, especially in environments with limited resources [ 105 , 107 ]. The creation of explainable AI (XAI), the conduct of multi-center, prospective studies to confirm effectiveness, and cost-effectiveness evaluations to support deployment across various healthcare settings should be the top priorities for future development [ 105 , 107 ] ( Table 2 ). Table 2. Evidence-based management methods for anaemia in THA surgery. Management method Key findings Optimal timing and dosing Advantages Limitations Ref Universal Screening To optimize and intervene with at-risk patients, they must be identified 4–8 weeks before surgery. 4–8 weeks before surgery Hb <130 g/L for both sexes Early risk stratification, Cost-effective (≈£1 per test), enables targeted therapy. Needs a well-coordinated care plan. If anaemia is found, surgery may be postponed. [ 35 , 39 , 41 , 104 , 123 ] Oral Iron Therapy Preoperatively, it elevates ferritin by 52–80 μg/L, decreases EPO usage by 60%, and increases Hb by 6–7 g/L. 6–8 weeks preoperatively 40–60 mg daily or 80–100 mg alternate days Low cost, Easy administration, Wide availability 17% GI side effects. Poor absorption in inflammation requires a long preparation time [ 35 , 97 , 98 ] IV Iron Reduces transfusions by 30-50%, reaches its maximal effectiveness at 2–4 weeks, and provides greater efficacy compared to dietary iron (a 7.8 g/L difference). <6 weeks preoperatively or postoperatively High-dose for severe anaemia Eliminates problems with GI absorption; acts quickly; useful in inflammatory conditions Higher cost, Transient benefit, Limited functional outcome data [ 91 , 92 ] ESAs Reduces transfusion rates from 45% to 11%, increases Hb by 19.5 g/L (high-dose), with RR 0.829 for allogeneic transfusion. 2–4 weeks preoperatively Requires iron co-administration Robust induction of erythropoiesis, Effective in chronic disease-related anaemia; an alternative for those refusing transfusion. Thrombotic risk concerns, High cost, requires careful monitoring [ 87–90 ] Combination Therapy (ESA + IV Iron) Shows improvement over monotherapy by optimizing Hb levels quickly and comprehensively. Individualized based on severity Preoperative optimization preferred Addresses multiple pathways Maximize hematinic response, Suitable for complex cases Highest cost, Complex monitoring, Limited cost-effectiveness data [ 95 , 97 ] TXA Saves money by preventing further blood loss (30–40%) without raising the risk of VTEs. Intraoperative ± postoperative 20 mg/kg pre-incision ± repeat dose Excellent safety profile, Low cost, Reduces HBL Contraindicated in thrombosis history, Multiple dosing regimens [ 95 , 136 ] Restrictive Transfusion Strategy Results with Hb levels of 70–80 g/L are comparable to those of the liberal approach, and transfusion problems are reduced. Postoperative monitoring Hb 70–80 g/L threshold in stable patients Reduces transfusion risks, Cost-saving, Evidence-based Requires careful patient selection. May not suit cardiovascular patients [ 18 , 46 , 47 , 79 , 95 ] ML Prediction Obtains an AUC for transfusion risk of 0.85–0.98, identifies high-risk individuals efficiently, and enables individualized refinement. Preoperative risk assessment Real-time decision support High predictive accuracy, Multi-variable analysis, Dynamic risk stratification Single-center validation, mostly, ‘Black box’ limitations, Implementation costs [ 100 , 102 , 105 , 107 ] Open in a new tab The data supporting preoperative anaemia therapy in THA remain limited, despite decades of investigation. Instead of outcomes that really matter to patients, such as functional recovery, quality of life, and significant complications, the majority of studies concentrate on surrogate endpoints like Hb levels and transfusion rates. Because trials are tiny, diverse and underpowered, it is challenging to make definitive judgments about what works best. Inconsistencies abound in the literature. Comparisons are almost impossible since various studies use different definitions of anaemia, iron formulations, dose regimens and treatment durations. We are still unable to confidently answer fundamental clinical questions: Which individuals really need IV iron instead of oral iron? How long should therapy last before surgery? Does a healthy patient with a simple iron deficit benefit from fixing anaemia as much as a frail patient with chronic inflammation? Although advances in ML promise individualized risk prediction, most models are unvalidated, retrospective and single-center. We don’t know whether they apply to a wide range of people or whether following their recommendations actually leads to better results. Concerns about overfitting and generalizability arise from the small number of externally tested models. Large, multicentre randomized studies that are powered for patient-centred goals, functional recovery, quality of life, infection and implant survival must be given top priority in future research. To determine who benefits most, trials should stratify patients by anaemia severity and origin. There is an urgent need for standardized definitions and outcome measurements so that research can be meaningfully compared. Prospective implementation studies and external evaluation must precede clinical deployment of AI technologies. Clinicians must accept that a large portion of our work is based on insufficient data until that time. 6. Anaemia as a heterogeneous condition: aetiology and implications for THA In patients undergoing THA, anaemia is not a single disease entity but rather a clinical presentation of several underlying degenerative processes, each of which has unique consequences for prognosis, diagnosis and therapy. IDA, affecting 33–41% of anaemic THA patients, is the most prevalent and easily treated variant. It is characterized by either absolute iron deficiency (ferritin <30 μg/L) or functional iron deficiency (ferritin 30–100 μg/L with transferrin saturation <20%) [ 52 , 108 ]. In patients who have more than 6 weeks to wait before surgery, oral iron (40–60 mg daily) is suitable; however, up to seventeen percent of patients experience gastrointestinal side effects from this method. In contrast, intravenous iron increases haemoglobin levels more quickly (mean difference of 7.8 g/L compared with oral) and reduces the need for transfusions; high-dose regimens are especially beneficial for patients at high risk of complications [ 35 , 93 , 109 , 110 ]. On the other hand, normocytic anaemia, ferritin levels of 100 μg/L or higher, transferrin saturation levels below 20%, and elevated C-reactive protein and other inflammatory markers are typical symptoms of anaemia of chronic disease (ACD) or inflammation, which is caused by hepcidin-mediated iron sequestration, blunted erythropoietin responses, and direct cytokine suppression of erythropoiesis [ 111 ]. Because intravenous iron may only generate partial responses unless underlying inflammation is addressed, and oral iron is ineffective due to hepcidin blockade, ACD is especially relevant in THA populations with inflammatory arthritis, obesity, chronic kidney disease, or fragility, and presents greater therapeutic challenges [ 111 , 112 ]. The systemic inflammatory response following THA significantly alters iron markers, with CRP peaking at a median of 162 mg/L on postoperative day 2. As a result, unadjusted iron indices significantly overdiagnose iron deficiency by 40–50%; adjusting for inflammation using CRP and albumin provides a more accurate assessment of true iron status and may improve patient selection for therapy [ 113 ]. Elderly, weak individuals often have combined anaemia, which is iron deficiency on top of inflammation and requires both IV iron and treatment of inflammatory diseases [ 52 ]. Deficits in vitamin B12 and folate are less prevalent but easily treated; post-bariatric surgery patients should receive particular attention, as they require monitoring and supplementation for the rest of their lives [ 114 ]. Up to 30% of anaemic elderly patients have unexplained anaemia, which is probably a sign of physiologic ageing and vulnerability rather than a modifiable risk factor. Therefore, comprehensive geriatric assessment and thorough evaluation to rule out occult pathology are more important than aggressive correction alone [ 115 ]. This aetiologic framework has significant clinical implications: unexplained anaemia in frail elders should be treated as a risk marker requiring thorough perioperative optimization rather than expecting haemoglobin normalization to normalize outcomes; isolated iron deficiency in otherwise healthy patients is most likely to benefit from correction (primarily for transfusion reduction, though impact on patient-centred outcomes remains uncertain); and ACD may partially improve but requires concurrent inflammation management [ 52 , 113 , 115 ]. To go beyond a ‘one-size-fits-all’ approach to fully tailored patient treatment, recognizing anaemia heterogeneity enables aetiology-directed therapy, prevents unnecessary procedures, and ensures that preoperative screening addresses the underlying issues anaemia indicates. 7. Preoperative anaemia as a modifiable risk factor: evidence, limitations and clinical implications Many people agree that preoperative anaemia is a modifiable risk factor. Is there proof that changing it leads to better results? Much less sure. A deeper look at this conflict is necessary. Numerous observational studies and registry analyses have demonstrated a clear link between preoperative anaemia and worse postoperative outcomes. Compared to their non-anaemic counterparts, patients with preoperative anaemia who have THA routinely exhibit higher rates of allogeneic blood transfusion, longer hospital stays, higher 30-day readmission rates, and higher rates of morbidity and death [ 12–14 , 18 , 33 , 42–44 , 46 , 47 , 52 ]. As a result, anaemia is often presented as a target for preoperative optimization – a theoretically changeable condition that might reduce these risks if fixed. However, this paradigm is complicated by several significant drawbacks. Confounding by indication and patient characteristics must be taken into account first. Preoperative anaemia rarely develops spontaneously. It commonly coexists with underlying frailty, dietary deficiencies, chronic renal disease, inflammatory illnesses, or concealed cancer, and it may also be a sign of these conditions. These conditions independently predict poor surgical outcomes. Even with multivariable adjustment, observational studies cannot completely separate the impact of the factors that cause anaemia from the direct effects of anaemia. Therefore, it’s still unclear how much anaemia is a cause of the condition or only a sign of underlying patient susceptibility [ 16 , 51 , 53 , 54 ]. Second, there is a significant lack of data for anaemia repair. Although erythropoiesis-stimulating medications and iron replacement therapy successfully increase Hb levels, there are very few RCTs demonstrating that correcting preoperative anaemia improves patient outcomes beyond reducing the need for transfusions. Preoperative IV iron reduced the need for transfusions in major abdominal surgery in the PREVENTT study, but it did not affect mortality or duration of stay [ 116–118 ]. Transfusion has been the main focus of orthopaedic surgical studies, with variable results regarding complications, functional recovery and patient-reported outcomes. A 2021 meta-analysis of randomized trials in hip and knee arthroplasty concluded that while IV iron reduces transfusion requirements, evidence for improvement in morbidity, mortality, or recovery remains insufficient [ 87–90 , 119 , 120 ]. Third, it is crucial to distinguish between association and causality. The logical progression – anaemia leads to negative consequences, thus treating anaemia enhances results – presupposes a direct causal link. Other theories, however, are worth taking into account: (1) anaemia might act as a mediator on the causal pathway between comorbidity burden and poor outcomes; (2) the relationship might be reciprocal, with inflammation playing a role in both anaemia and poor surgical recovery; and (3) the observed associations might be explained by unmeasured confounders (such as functional status or nutritional reserve). Causal conclusions remain tentative in the absence of strong randomized data [ 45 , 121 , 122 ]. Fourth, there are important ramifications for clinical practice and research. Designating anaemia as ‘modifiable’ has therapeutic significance; it affects patient expectations, resource allocation and preoperative evaluation. Thus, a more nuanced framing is necessary. Preoperative anaemia should be considered a potentially controllable factor in reducing the need for transfusions, as well as a significant risk indicator that warrants research into its underlying aetiology. In the absence of addressing the broader context of patient optimization, practitioners should be cautious about assuming that Hb normalization alone would significantly change complication rates or functional outcomes [ 51 , 82 ]. The conflict between observational relationships and little interventional data does not diminish the clinical significance of preoperative anaemia. Instead, it demands clarity about what the data really demonstrates. Anaemia is an essential component of thorough perioperative care, a useful clinical indicator, and a valid objective for lowering transfusion exposure. It is still unclear, however, whether fixing it on its own improves hard outcomes for THA patients, such as implant survival, significant complications, functional recovery and death. RCTs with enough power to assess these patient-centred objectives must be given top priority in future studies. Whether anaemia directly causes bad outcomes or just reflects underlying patient fragility remains a fundamental issue, despite strong links between preoperative anaemia and unfavourable outcomes. This difference has serious consequences for the field of medicine. Based on the clinical context and the origin of the anaemia, Table 3 offers a useful strategy for navigating this ambiguity. Anaemia serves as both a warning sign and a risk factor. Correction probably improves outcomes (causal) in otherwise healthy people with reversible iron deficiency. Anaemia is a warning indicator of underlying fragility in fragile patients with inflammation-driven anaemia; thus, treatment alone isn’t enough; the patients need thorough optimization before surgery (marker). Haemoglobin increase without clinical recovery indicates that anaemia was mainly a sign of persisting underlying danger, as inferred from the response to therapy. Table 3. Anaemia in THA, causal factor or marker of frailty? Patient profile Primary role of anaemia Recommended management Predicted benefit from correction Ref Isolated iron deficiency, otherwise healthy patient Direct contributor Make vigorous corrections with oral and intravenous iron; then, following optimization, continue with surgery. Reduction in transfusions is probable; functional recovery is likely to have improved; nevertheless, patient-centred outcomes are unknown owing to a lack of trial data. [ 52 , 93 , 108 , 109 ] ACD in inflammatory arthritis Mixed contributor and indicator Optimal disease-modifying treatment, intravenous iron (which bypasses hepcidin), and, in extreme cases, ESA. An increase in hemoglobin is likely, but the practical effect is uncertain because inflammation can hinder wound healing and recovery on its own. [ 111 , 113 ] Combined anaemia in the frail elderly with multiple comorbidities Primarily an indicator Full geriatric evaluation; dietary assistance; treat iron deficiency if it exists; but, establish reasonable goals. Despite an increase in hemoglobin, functional results may not return to normal; thus, multi-domain perioperative optimization should be prioritized. [ 37 , 51 , 108 ] Unexplained anaemia after a thorough negative evaluation Uncertain Exercise caution and do further investigations before elective surgery (occult cancer?). If TSAT is low, you may want to explore a trial of iron. Close postoperative surveillance was necessary due to unknown factors. [ 37 , 111 ] Anaemia persists despite adequate treatment Indicator of irreversible vulnerability Pay attention to changeable risk factors; implement stringent transfusion limits (70–80 g/L); and improve postoperative care. Anticipate a sustained increase in risk; control it with improved recovery measures. [ 16 , 40 , 52 , 137 ] Incidental mild anaemia in active, well-nourished older adult Minimal significance Quick assessment; if no reason is identified, go forward with surgery; refrain from over-treatment. Reassurance is appropriate as it is unlikely to have a major influence on outcomes. [ 138 , 139 ] Open in a new tab 8. Future directions Significant blood loss from THA may result in anaemia and the need for allogeneic blood transfusions. Longer hospital stays, higher morbidity, cardiovascular issues and slower recovery are all linked to these [ 123 , 124 ]. PBM programs are crucial for addressing these issues. Haematologists, anaesthesiologists, and surgeons should collaborate in a multidisciplinary, multimodal, evidence-based PBM [ 124 ]. Three stages should be included in standardized procedures for the treatment of anaemia in THA: intraoperative blood conservation, postoperative monitoring and support, and preoperative identification and correction [ 123 , 125–127 ]. Anaemia screening should be performed 4–8 weeks before THA in all patients [ 12 , 128 , 129 ]. Early screening is very cost-effective, as full blood counts, which identify people at risk of transfusion, cost only £1 per test [ 130 ]. If anaemia is found, further testing should identify the underlying reason, which may be chronic illness, iron deficiency, inflammation, or a lack of vitamin B12 or folate [ 123 , 125–127 ]. Treatment needs to focus on the particular cause. When surgery is 6 to 8 weeks away, oral iron is suitable. For shorter timescales, inflammatory conditions, or oral iron resistance, IV iron is recommended [ 12 , 128 , 129 ]. After dietary deficiencies are addressed, erythropoiesis-stimulating medications may be used to treat persistent anaemia, especially in patients who refuse transfusions or have ACD [ 123 , 125–127 ]. To reduce the risk of bleeding, anticoagulant drugs may need to be adjusted [ 123 , 125–127 ]. The most popular and cost-effective nonsurgical treatment for minimizing blood loss during THA is TXA, which should be routinely administered [ 123 , 131 ]. Routine drain usage is not supported by evidence [ 123 ]. Although further study is required, neuraxial anaesthesia and mini-incision posterior techniques may lessen blood loss [ 123 ]. Other treatments, such as topical haemostatic medications, cell salvage and acute normovolemic hemodilution, are expensive and lack solid evidence [ 123 , 131 ]. Anaemia after surgery is prevalent and has to be treated early. For stable patients, restrictive transfusion limits (70–80 g/L) are suitable [ 132 ]. In some situations, IV iron may help with recovery [ 91 , 92 ]. In complicated circumstances, targeted transfusions may be guided by viscoelastic testing [ 132 ]. ML and AI are becoming increasingly powerful tools for risk assessment and individualized treatment. Early intervention is now possible thanks to algorithms that can detect high-risk patients months before surgery by analysing electronic health data [ 105 , 107 ]. The accuracy of ML algorithms in forecasting transfusion danger has shown promise. Using preoperative Hb, ASA status, fibrinogen, ALB, operation length and procedure type, a Ridge Classifier obtained an AUC of 0.85. For hip fracture surgery, a Random Forest model produced an internal AUC of 0.887 and an exterior AUC of 0.834 [ 105 , 107 ]. Another research challenged conventional gender-specific cut-offs by determining a universal Hb threshold of less than 148 g/L for predicting prolonged hospitalization or readmission after fast-track arthroplasty [ 104 ]. Chatbots with AI capabilities, such as ChatGPT, can answer frequently asked questions regarding THA and provide patients with precise, easily accessible preoperative education [ 133 ]. Preoperative planning, implant placement and surgical precision are all being enhanced by robotic-assisted surgery and AI-powered diagnostic technologies [ 21 ]. But there are still major challenges. The majority of AI models are retrospective and single-center, raising questions about algorithmic bias and generalizability. The ‘black box’ nature of complex models undermines physician confidence. Barriers include infrastructure needs and implementation costs, especially in settings with limited resources. Cost-effectiveness analysis, multi-center prospective validation and XAI must be given top priority in future research [ 105 , 107 ]. Critical evidentiary gaps still exist despite advancements. Transfusion rates and Hb levels are the main focus of most studies, which are underpowered for patient-centred outcomes [ 12 , 105 , 107 , 128 , 129 ]. There is still a lack of clarity regarding the optimal timing, dosage and patient selection for IV iron and ESA treatment [ 93 ]. Research on comparative efficacy is hampered by the fact that different studies define anaemia differently [ 93 ]. Large pragmatic RCTs that are powered for patient-centred outcomes, such as functional recovery, quality of life, major complications and implant survival, should be the top priority for future research. These studies need to categorize patients by anaemia cause and severity to determine which subgroups benefit most from specific treatments. Standardized definitions and outcome measures of anaemia are desperately needed in the field to facilitate cross-study comparisons and relevant meta-analyses. Resource allocation requires cost-effectiveness evaluations of various PBM techniques in a range of healthcare environments. Furthermore, before clinical deployment, multi-center prospective validation is necessary for ML and AI prediction systems. Lastly, to investigate how to incorporate successful therapies into standard clinical practice, implementation science research is required. Personalized, interdisciplinary treatment is the way of the future for managing anaemia in THA patients. Effective PBM is based on aetiology-directed therapy, regular use of TXA, universal screening 4–8 weeks before surgery, and stringent transfusion thresholds [ 12 , 123 , 128 , 129 ]. Although they require thorough evaluation before widespread use, these technologies hold promise for future improvement [ 105 , 107 ]. Beyond reducing the need for transfusions, the ultimate objective is to demonstrate that optimal anaemia treatment enhances what patients value most: a quicker recovery, improved function and fewer long-term problems [ 12 , 105 , 107 , 128 , 129 ]. The present emphasis on reducing transfusions must give way to a more comprehensive approach to preoperative anaemia control in THA. Functional recovery, quality of life, infection rates and implant survival are patient-centred outcomes that should be prioritized in future research. This will require larger, more extensive studies than those conducted so far. Going beyond ‘one-size-fits-all’ methods is a crucial change. There are many causes of anaemia, including dietary deficiencies, inflammation-induced suppression and complete iron deficiency. To determine which therapies are most effective for different patients, future studies must stratify patients by these pathways. Although it needs thorough external validation and prospective testing, ML offers promise for risk prediction. In addition to identifying danger, algorithms must show that acting on their predictions improves results. Clinical adoption and confidence will depend on XAI. Most significantly, rather than being left to individual doctors, anaemia therapy must become standardized and incorporated into standard perioperative procedures. Antibiotic prophylaxis should be as automatic as screening, diagnosis and therapy. Patient-centred trials, aetiology-driven therapy, validated technology and integrated care systems are necessary for the future. Whether the field can meet this challenge is the question. 9. Conclusion The future of THA centres on less invasive procedures, improved materials and greater customization of care. Significant blood loss remains a concern in THA, and patients with preoperative anaemia or substantial intraoperative blood loss frequently require perioperative transfusions. Anaemia, defined as a deficiency of RBCs or Hb, is associated with longer hospital stays, increased surgical complications and a higher risk of transfusion. Optimizing patient outcomes, therefore, requires systematic management of anaemia before surgery. Preoperative anaemia is a significant concern in THA that may increase the risk of complications and blood transfusions. While some blood loss during and after surgery is expected, anaemia can exacerbate its impact and must be carefully managed. Future priorities for improving outcomes include enhanced preoperative screening, targeted therapy based on underlying aetiology and innovative methods to reduce blood loss and transfusion requirements. Creative strategies should focus on early and precise anaemia identification, individualized treatment plans, improved patient education and greater patient involvement in decision-making. Further research is necessary to understand the impact of anaemia on outcomes after rTHA fully and to develop optimal, evidence-based treatment protocols for anaemic patients undergoing primary and revision procedures. Acknowledgments Thanks to the Graduate School of Peking Union Medical College. Z.C., Writing – original draft, reviewed and edited, correspondence authors. All authors read and approved the final manuscript. 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