Validation of the Oswestry Disability Index in Adult Spinal Deformity

Abstract

Study Design. Retrospective cohort Objective. To examine the validity of the ODI in ASD patients treated with surgery. Summary of Background Data. The ODI is a patient-reported outcome measure (PROM) of low back pain and disability. While nearly ubiquitous in adult spinal deformity (ASD) research, the measure has not been validated in this patient population. Methods. A registry of ASD patients was queried for baseline and 1-year PROM data, including the ODI, the SRS-22r, and the Patient Reported Outcomes Measurement Information System – Pain Interference (PI), and -Physical Function(PF) computer adaptive tests (CAT). Internal reliability was assessed with Cronbach’s alpha, where values≥0.7 are considered reliable. Validity was assessed with Spearman correlation coefficients calculated for the ODI against validated PROMIS-Pain Interference and -Physical Function and legacy measures SRS-Pain, SRS-Activity. Responsiveness to change was measured with the adjusted effect size (aES). Results. 325 patients were enrolled, with 208 completing baseline and one-year PROMs. The majority (149, 72%) were female and white (193, 93%), median Charlson Comorbidity Index 0 (IQR 0-2). The majority of cases included sagittal plane deformity (mean T1PA 24.2° (13.9). Cronbach’s alpha showed excellent internal reliability (Baseline=0.89, 1yr=0.90). ODI was valid, with strong correlations between PROMIS-PI, -PF, SRS-Pain, and SRS-Activity at baseline and one-year follow-up. All measures were responsive to change, with the ODI showing greater responsiveness than PROMIS-PI, PROMIS-PF and SRS-Activity. Conclusions. The ODI is a valid measure of disability as measured by pain and function in patients with ASD. It is responsive to change in a manner not different from validated PROMIS-CAT or the SRS-22r legacy measure. It is multidimensional, however, as it assesses both pain and function simultaneously. It does not measure disability related to Self-Image and may not account for all disease-related disability in ASD patients.