Proximal junctional kyphosis in adolescent idiopathic scoliosis after 3 different types of posterior segmental spinal instrumentation and fusions : Incidence and risk factor analysis of 410 cases

Retrospective study. Determine proximal junctional kyphosis (PJK) prevalence and analyze risk factors associated with PJK in adolescent idiopathic scoliosis (AIS) patients following 3 different posterior segmental spinal instrumentation and fusion surgeries. No comparison study exists on proximal junctional AIS changes following 3 different segmental posterior spinal instrumentation and fusion surgeries at 2 years postoperative. A clinical/radiographic assessment was conducted in 410 consecutive AIS patients (average age = 14.7, range = 10.6-20) (men/women = 73/337) treated with instrumented segmental posterior spinal fusion with 2-year follow-up. Revision and anterior cases were not included. Standing long-cassette radiographic measurements were analyzed including various sagittal/coronal parameters for preoperative, early postoperative, and 2-year follow-up. Abnormal PJK was defined by proximal junction sagittal Cobb angles between the lower endplate of the uppermost instrumented vertebra and the upper endplate of 2 supradjacent vertebrae >or=+10 degrees and at least 10 degrees greater than the preoperative measurement at 2 years postoperative. PJK prevalence defined at 2 years postoperative was 27% (111 of 410 patients). Statistically significant factors: larger preoperative thoracic kyphosis angle (T5-T12 >40 degrees vs. T5-T12 10 degrees -40 degrees vs. T5-T12 5 degrees vs. 5 degrees decrease-5 degrees increase vs. increase >5 degrees ; P < 0.0001), thoracoplasty versus no thoracoplasty (P = 0.001), and men versus women (P = 0.007). Instrumentation types (hook-only vs. proximal hook, distal pedicle screw vs. pedicle screw P = 0.058), number of fused vertebrae >12 versus 12>or= (P = 0.12), the uppermost instrumented vertebra among T2, T3, T4, T5 (P = 0.75). There were no significant differences in Scoliosis Research Society Patient Questionnaire-24 outcome-scores (PJK total score = 97.0, self-image subscales = 21.3 vs. non-PJK group = 95.3, 21.0) (P = 0.34 total score, P = 0.54 self-image subscale). Two-year postoperative PJK prevalence in AIS following 3 different posterior segmental spinal instrumentation and fusion surgeries was 27%. A larger preoperative thoracic kyphosis angle, greater immediate postoperative thoracic kyphosis angle decrease, thoracoplasty, and male sex correlated significantly with PJK. There were no significant differences in S