Effects of Transverse Process Hook Fixation for Preventing Proximal Junctional Kyphosis/Failure in Adult Spinal Deformity Surgery: A Multiple Regression Analysis Adjusting for Confounding Factors

Study design: Retrospective study. Objectives: To investigate the effects of transverse process hook (TPH) at the uppermost instrumented vertebra (UIV) + 1 on the prevention of proximal junctional kyphosis/failure (PJK/F) following adult spinal deformity (ASD) surgery. Methods: We included patients who underwent fusion of the lower thoracic spine (T8–T11) to the sacrum for ASD. The patients were divided into the non-TPH and TPH groups. PJK and PJF were defined as proximal junctional angle >20° and any cases requiring revision surgery. Multiple regression analysis was performed, including surgical techniques (non-use of TPH vs TPH) and confounding variables. Results: Altogether, 153 patients were included in the study (women, 91.5%; mean age, 69.2 years; total levels fused, 8.5). The non-TPH and TPH groups comprised 88 and 65 patients. Unadjusted bivariate analysis showed that the TPH did not significantly affect the risk of PJK and PJF. However, multiple regression analysis revealed that the non-use of TPH was associated with an increased risk of developing PJK and PJF (odds ratio [OR] = 3.079, P = 0.029 for PJK; OR = 6.363, P = 0.049 for PJF). In patients who underwent TPH fixation, confounder-adjusted regression analysis showed that two-level TPH fixation did not further decrease the risk of PJK/F. Conclusions: The preventive effect of TPH against PJK/F development was not significant in the unadjusted bivariate analysis. However, multiple regression analysis adjusted for the confounding factors demonstrated that TPH fixation at the UIV +1 significantly decreased the risk of PJK and PJF.