Establishing Minimal Important Change After Percutaneous Vertebroplasty for Osteoporotic Vertebral Compression Fractures

STUDY DESIGN: Observational longitudinal cohort study. OBJECTIVE: The aim of this study was to establish the minimal important change (MIC) for patients with osteoporotic vertebral compression fractures (OVCFs) treated with percutaneous vertebroplasty (PVP). SUMMARY OF BACKGROUND DATA: MIC thresholds have been established for several surgically treated spine diseases but not for OVCFs after PVP. This lack of relevant MIC thresholds for OVCFs has led to the use of threshold values derived from non-specific low back pain cohorts that may not accurately represent the experience of patients with OVCFs treated with PVP. METHODS: Five hundred and four patients with OVCFs reported their health status before and after PVP using Visual Analog Scale (VAS) for back pain, the Oswestry Disability Index (ODI) and the EuroQOL-5D (EQ-5D). Net change, percent change and follow up scores were calculated for each patient reported outcome measure. An anchor-based receiver operating characteristic curve analysis was used to develop MIC thresholds using the Health Transition Item of the Short Form 36 as the anchor. RESULTS: The following MIC thresholds were optimized for their ability to discriminate improved from unchanged patients: VAS for back pain: 30.5 mm net change, 39% change, follow up score less than 44.5; ODI 17.5 net change, 35% change, follow up score less than 33.5; EQ-5D: 0.4 net change, follow up score less than 0.70. VAS and ODI thresholds outperformed EQ-5D, where discrimination was poor. CONCLUSION: VAS back pain and ODI had a greater ability to discriminate between improved and unchanged patients compared to EQ-5D. Patients with OVCF undergoing vertebroplasty require larger change scores of back pain and disability to experience improvement than other spinal surgery populations.