Biomechanical comparison of semirigid junctional fixation techniques to prevent proximal junctional failure after thoracolumbar adult spinal deformity correction

Abstract BACKGROUND CONTEXT Adult spinal deformity patients treated operatively by long-segment instrumented fusion are prone to develop proximal junctional kyphosis (PJK) and failure (PJF). A gradual transition in range of motion (ROM) at the end instrumentation may reduce incidence PJK PJF, however, previously evaluated techniques have not directly been compared. PURPOSE To determine biomechanical characteristics five different posterior achieve semirigid fixation, or “topping-off,” between rigid pedicle screw fixation (PSF) uninstrumented spine. STUDY DESIGN Biomechanical cadaveric study. METHODS Seven fresh-frozen human spine segments (T8–L3) were subjected ex vivo pure moment loading flexion-extension, lateral bending axial rotation up 5 Nm. The native condition, three-level PSF (T11–L2), with supplemental transverse process hooks T10 (TPH), two sublaminar taping (knotted clamped) as one- (T10) two-level (T9, T10) ROM neutral zone (NZ) normalized condition. linearity zones over three four was determined through linear regression analysis. RESULTS All achieved a significantly reduced T10-T11 flexion-extension relative Additionally, both (CT2, KT2) had T9-T10. One-level clamped tape (CT1) lower NZ compared one-level knotted (KT1) T10-T11. Linear analysis showed highest correlation vertebral level for TPH lowest CT2. CONCLUSIONS studied levels thus provide more than screws. achieves most vertebrae, whereas KT2 that vertebrae. In contrast, CT2 effectively is technique shift upper level. Clamped reduces greatly, maintain physiologic NZ. Clinical validation ultimately required translate biomechanics various into clinical goal reducing failure. CLINICAL SIGNIFICANCE direct comparison multiple aim after thoracolumbar surgery provides basis upon which studies could be designed. Furthermore, data provided this study can used further analyze effects using finite element models better predict their post-operative effectiveness.