ABSTRACT
STUDY DESIGN: Reliability/external validation study. OBJECTIVE: Investigate inter- and intrarater reliability of the Hart-International Spine Study Group (ISSG) Proximal Junctional Failure Severity Scale (PJFSS) and its correlation with operative revision in patients with proximal junctional failure (PJF). SUMMARY OF BACKGROUND DATA: The Hart-ISSG PJFSS is a validated classification system for PJF. Reliability of the PJFSS has not been assessed. METHODS: Sixteen detailed clinical scenarios were assessed using the ISSG PJFSS classification in six categories: neurologic status, axial pain, instrumentation issue, proximal kyphotic angle, level of upper instrumented vertebrae (UIV), and severity of UIV/UIV+1 fracture. Eleven spine surgeons evaluated each case in all six categories during two different assessments, and provided recommendations regarding operative revision or observation for each case. Inter- and intrarater reliability were calculated based on intraclass correlation coefficients. RESULTS: All intraclass correlation coefficients demonstrated "almost perfect"' (0.817-0.988) inter-rater agreement for both assessments, except UIV/UIV+1 fracture severity during the second assessment, which demonstrated "substantial" agreement' (0.692). Five of six categories had "almost perfect" mean intrarater reliability (0.805-0.981), while "instrumentation issue" demonstrated "substantial" mean agreement (0.757). Inter-rater reliability for recommendation of surgical intervention was "almost perfect" during both assessments (0.911 and 0.922, respectively). Mean PJFSS scores between the two assessments were significantly higher for cases recommended for operative revision (8.43â±â0.90) versus cases recommended for observation (Pâ<â0.0001). CONCLUSION: The ISSG PJFSS is a reliable and repeatable classification system for assessing patients with PJF. Higher PJFSS scales correlate with recommendation for operative revision, extending prior external validation of the PJFSS. LEVEL OF EVIDENCE: 3.