The prevalence of proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) in patients undergoing circumferential minimally invasive surgical (cMIS) correction for adult spinal deformity: long-term 2- to 13-year follow-up

OBJECTIVES: This aim of this study is to evaluate the prevalence of PJK and PJF in patients who underwent circumferential minimally invasive surgery (cMIS) for ASD. METHODS: A prospective database of patients who underwent cMIS correction of ASD from November 2006 to July 2018 was queried. PJK was defined as angle > 10° and at least 10° greater than the baseline when measuring UIV to UIV + 2. PJF was defined as any type of symptomatic PJK which required surgery. Pre-op, latest and delta SVA and PI-LL mismatch were compared between patients with PJK and without. Only patients instrumented at 4 or more levels with full length 36″ films and a minimum 2-year follow-up were included. RESULTS: A total of 184 patients met inclusion criteria for this study. Mean follow-up time was 85.2 months (24–158.9 months, SD 39.1). Mean age was 66 years (22–85 years). The mean number of operated levels was 6.9 levels (4–16 levels, SD 2.8). A total of 21 patients (10.8%) met PJK criteria. Only 10 (4.9%) were symptomatic (PJF) and underwent revision surgery. The other 11 patients remained asymptomatic. Comparing PJK to non-PJK patients, there was no statistically significant difference in the post-op SVA, delta SVA, post-op PI/LL and delta PI/LL between the two groups. CONCLUSION: Our study would suggest that in the appropriately selected and well-optimized patient, CMIS deformity correction is associated with a low prevalence of PJK and PJF.