Incidence, risk factors, and natural course of proximal junctional kyphosis: Surgical outcomes review of adult idiopathic scoliosis. minimum 5 years of follow-up

STUDY DESIGN. A retrospective case series of surgically treated patients with adult scoliosis. OBJECTIVE. The purpose of this study was to evaluate the incidence, risk factors, and natural course of proximal junctional kyphosis (PJK) in a long-term follow-up of patients with adult idiopathic scoliosis undergoing long instrumented spinal fusion. SUMMARY OF BACKGROUND DATA. Although recent reports have showed the prevalence, clinical outcomes, and the possible risk factors of PJK, quite a few reports have showed long-term follow-up outcome. MATERIALS AND METHODS. This is a retrospective review of the charts and radiographs of 76 consecutive patients with adult scoliosis treated with long instrumented spinal fusion. Radiographical measurements and demographic data were reviewed on preoperation, immediate postoperation, 2 years postoperation, 5 years postoperation, and at follow-up. Postoperative Scoliosis Research Society scores and Oswestry Disability Index were also evaluated. Means were compared with Student t test. A P value of less than 0.05 with 95% confidence interval was considered significant. RESULTS. The mean age was 48.8 years (range, 23-75 yr) and the average follow-up was 7.3 years (range, 5-14 yr). PJK has been identified in 17 patients. The Scoliosis Research Society and Oswestry Disability Index did not demonstrate significant differences between PJK group and non-PJK group; 2 patients had additional surgeries performed for local pain. Seventy-six percent of PJK has been identified within 3 months after surgery. Despite the fact that 53% of total degree of PJK was progressed within 3 months after surgery, PJK continuously progressed to the final follow-up. Pre-existing low bone mineral density, posterior spinal fusion (PSF), fusion to sacrum, inappropriate global spine alignment, and greater sagittal vertical axis change were identified as significant risk factors for PJK (P = 0.04, P < 0.001, P = 0.02, P < 0.0001, and P = 0.01). CONCLUSION. In a long-term review of minimum 5 years, 76% of PJK occurred within 3 months after surgery. Pre-existing low bone mineral density, PSF, fusion to the sacrum, inappropriate global spine alignment, and greater sagittal vertical axis change were significant risk factors for PJK. Careful long-term follow-up should be done for a patient with PJK.