Proximal junctional kyphosis in adult spinal deformity after segmental posterior spinal instrumentation and fusion - Minimum five-year follow-up

Study Design. A retrospective study. Objective. To analyze time-dependent change of, prevalence of, and risk factors for proximal junctional kyphosis (PJK) in adult spinal deformity after long (>= 5 vertebrae) segmental posterior spinal instrumented fusion with a minimum 5-year postoperative follow-up. Summary of Background Data. No study has focused on time-dependent long-term proximal junctional change in adult spinal deformity after segmental posterior spinal instrumented fusion with minimum 5-year follow-up. Methods. Clinical and radiographic data of 161 (140 women/21 men) adult spinal deformity patients with minimum 5-year follow-up (average 7.8 years, range 5-19.8 years) treated with long posterior spinal instrumentation and fusion were analyzed. Radiographic measurements included sagittal Cobb angle at the proximal junction on preoperative, 8-weeks postoperation, 2-year postoperation, and ultimate follow-up (>= 5 years). Postoperative SRS outcome scores were also evaluated. Results. The prevalence of PJK at 7.8 years postoperation was 39% (62/161 patients). The PJK group (n = 62) demonstrated a significant increase in proximal junctional angle at 8 weeks (59%), between 2 years postoperation and ultimate postoperation (35%), and in thoracic kyphosis (T5-T12) at ultimate follow-up (P = 0.001). However, the sagittal vertical axis change at ultimate follow-up did not correlate with PJK (P = 0.53). Older age at surgery > 55 years (vs. <= 55 years) and combined anterior and posterior spinal fusion ( vs. posterior only) demonstrated significantly higher PJK prevalence (P = 0.001, 0.041, respectively). The SRS outcome scores did not demonstrate significant differences with the exception of the self-image domain when PJK exceeded 20 degrees. Conclusion. The prevalence of PJK at 7.8 years postoperation was 39%. PJK progressed significantly within 8 weeks postoperation (59%) and between 2 years postoperation and ultimate follow-up (35%). Older age at surgery (vs. <= 55 years) and combined anterior and posterior spinal fusion were identified as risk factors for developing PJK. The SRS outcome instrument was not adversely affected by PJK, except when PJK exceeded 20 degrees.