Risk Factor Analysis for Proximal Junctional Kyphosis After Adult Spinal Deformity Surgery: A New Simple Scoring System to Identify High-Risk Patients.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: Develop a simple scoring system to estimate proximal junctional kyphosis (PJK) risk. METHODS: A total of 417 adult spinal deformity (ASD) patients (80% females, 57.8 years) with 2-year follow-up were included. PJK was defined as a >10° kyphotic angle between the upper-most instrumented vertebra (UIV) and the vertebrae 2 levels above the UIV (UIV+2). Based on a previous literature review, the following point score was attributed to parameters likely to impact PJK development: age >55 years (1 point), fusion to S1/ilium (1 point), UIV in the upper thoracic spine (UIV-UT: 1 point), UIV in the lower thoracic region (UIV-LT: 2 points), flattening of the thoracic kyphosis (TK) relative to the lumbar lordosis (LL; ie, ▵LL - ▵TK) greater than 10° (1 point). RESULTS: At 2 years, the overall PJK rate was 43%. The odds ratios for each risk factor were the following: age >55 years (2.52), fusion to S1/ilium (5.17), UIV-UT (6.63), UIV-LT (8.24), and ▵LL - ▵TK >10° (1.59). Analysis by risk factor revealed a significant impact on PJK (no PJK vs PJK): age >55 years (28% vs 51%, P < .001), LIV S1/ilium (16.3% vs 51.4%, P < .001), UIV in lower thoracic spine (12.0% vs 38.7% vs 52.9%, P < .001), and a >10° surgical reduction in TK relative to LL increase (40.0% vs 51.5%, P < .001). The PJK rate by point score was as follows: 1 = 17%, 2 = 29%, 3 = 40%, 4 = 53%, and 5 = 69%. CONCLUSION: A pragmatic scoring system was developed that is tied to the increasing risk of PJK. These findings are helpful for surgical planning and preoperative counseling.

Duke Scholars

Author Christopher Ignatius Shaffrey Orthopaedic Surgery