Reliability and Validity of Hand Dynamometer Trunk Muscle Strength Measurements in Patients With AIS

Adolescent idiopathic scoliosis (AIS) is a three-dimensional complex deformity of the spine characterized by lateral deviation of 10 degrees or more in the frontal plane, rotation in the transverse plane and hypokyphosis in the sagittal plane. It has been reported that in the presence of scoliosis, there is a change in muscle strength of people compared to their healthy peers due to the deterioration of their postural balance. There are many studies in the literature that evaluate the muscle strength of cases diagnosed with scoliosis with objective devices. Among these objective devices, reliability studies on hand dynamometry devices, which are easy to use, portable and cheaper than other devices, have been conducted for different populations. However, no reliability study of the handheld dynamometer device in patients with AIS has been found in the literature. Therefore, the aim of our study is to study the intra-rater and inter-rater reliability and validity of the trunk flexion, extension and lateral flexion muscle strengths of the hand dynamometer device in cases with AIS, which are known to have changes in muscle strength compared to their peers as a result of the change in spinal alignment. After obtaining the demographic information of the cases that meet the inclusion criteria within the scope of the study, the isometric muscle strength of the trunk flexor, extensor and right-left lateral flexor muscles will be evaluated by two different evaluators using a Lafayette hand dynamometer. To avoid systematic error, each participant will perform the isometric handheld dynamometer protocol in a random testing order. In order to determine interobserver reliability, on the first day of the test, the same hand dynamometer protocol will be applied to each participant by two different evaluators, after a 1-hour rest to prevent fatigue. To determine intraobserver reliability and compliance, participants will be re-evaluated by the same researchers at the same protocol,