Proximal junctional kyphosis in adult spinal deformity following long instrumented posterior spinal fusion: Incidence, outcomes, and risk factor analysis

Study Design. To analyze patient outcomes and risk factors associated with proximal junctional kyphosis (PJK) in adults undergoing long posterior spinal fusion. Objectives. To determine the incidence of PJK and its effect on patient outcomes and to identify any risk factors associated with developing PJK. Summary of Background Data. The incidence of PJK and its affect on outcomes in adult deformity patients is unknown. No study has concentrated on outcomes of patients with PJK. Risk factors for developing PJK are unknown. Methods. Radiographic data on 81 consecutive adult deformity patients with minimum 2-year follow-up (average 5.3 years, range 2-16 years) treated with long instrumented segmental posterior spinal fusion was collected. Preoperative diagnosis was adult scoliosis, sagittal imbalance or both. Radiographic measurements analyzed included the sagittal Cobb angle at the proximal junction on preoperative, early postoperative, and final follow-up standing long cassette radiographs. Additional measurements used for analysis included the C7-Sacrum sagittal plumb and the T5-T12 sagittal Cobb. Postoperative SRS-24 scores were available on 73 patients. Results. Incidence of PJK as defined was 26%. Patients with PJK did not have lower outcomes scores. PJK did not produce a more positive sagittal C7 plumb. PJK was more common at T3 in the upper thoracic spine. Conclusions. Incidence of proximal junctional kyphosis was high, but SRS-24 scores were not significantly affected in patients with PJK. The sagittal C7 plumb was not significantly more positive in PJK patients. No patient, radiographic, or instrumentation variables were identified as risk factors for developing PJK.