Novel Pedicle Screws Used for Corrective Surgery in Spinal Deformity

There are still a large number of severe spinal deformity cases which would keep progressing without treatment. These patients not only have severe appearance deformity, but also suffer from cardiopulmonary compression, reduced abdominal volume, and even spinal cord injury. It is crucial to provide safe and effective surgical intervention for these patients. The corrective surgery with 3-column osteotomy is reported to be an effective surgical strategy for severe spinal deformity. However, due to the great corrective stress on the rods, there is an increased number of patients requiring revision surgery due to rod fracture (3.7%-15%). In patients with 3-column osteotomy, the osteotomy area and the upper and lower adjacent segments are mostly stress-concentrated areas, and the rod is prone to fatigue fracture. Therefore, it is necessary to reinforce the osteotomy area and adjacent segments to reduce the risk of rod fracture. Our previous study found the risk of rod fracture could be reduced by using satellite rods with duet connectors or dominos. However, in the traditional satellite rod technology, the connection of the main rod and the satellite rod rely on the traditional single slot screw and duet connectors. The two are separated and not a whole in the mechanical structure. The stability of the fixation is relatively insufficient, and stil deserves room for improvement. Based on the traditional duet connectors, we further invent a novel dual-headed pedicle screw, which is an combination of traditional single slot screw and duet connector. Compared with the traditional duet connector, the novel dual-headed pedicle screw theoretically has stronger stability between the main rod and satellite rod, due to its integration of screw and connector. Hence, the purpose of this study is to verify the strong stability of the novel dual-headed screw by biomechanical study in cadavers performed with long spinal fusion (T12-pelvis) with L3 pedicle subtraction osteotomy (PSO).