Clinical and Radiographic Features of Subtypes of Acute Proximal Junctional Failures Following Correction Surgery for Degenerative Sagittal Imbalance

OBJECTIVE: To identify clinical and radiographic features of subtypes of acute proximal junctional failures (PJFs) following correction surgery for degenerative sagittal imbalance. METHODS: The study included 157 patients with mean age 68.0 +/- 6.3 years who underwent correction surgery for degenerative sagittal imbalance. Acute PJFs were categorized into 4 subtypes: fracture at uppermost instrumented vertebra (UIV), fracture at vertebra just proximal to UIV (UIV+1), fixation failure at UIV, and junctional subluxation. Demographic, clinical, and radiographic data were analyzed retrospectively. RESULTS: There were 18 patients with acute PJFs. PJF group had significantly lower T-score (-3.3 +/- 1.1 vs. -1.9 +/- 1.5) on bone densitometry and lower body mass index (BMI) (23.0 +/- 3.9 kg/m(2) vs. 25.6 +/- 3.7 kg/m(2)) than non-PJF group. Radiographic parameters exhibited no significant differences. UIV fracture, UIV+1 fracture, UIV fixation failure, and junctional subluxation were observed in 5, 6, 4, and 3 patients. Fixation failure developed the earliest (median 1.3 months), followed by UIV fracture (1.5 months). UIV fracture occurred earlier than UIV+1 fracture (36 months). Patients with UIV or UIV+1 fracture had significantly lower T-scores than others. Although BMI and T-score were significant risk factors for all PJFs (P = 0.043 and P = 0.021, respectively), different risk factors for each subtype of PJFs were identified on separate risk factor analysis. CONCLUSIONS: Patients with acute PJFs had lower T-score and BMI. Each subtype of PJFs had different clinical and radiographic features. Although BMI and T-score were associated with all PJFs, each subtype may have different risk factors. Identifying risk factors for each subtype of acute PJFs may help avoid it.