THE USE OF THE PERCENTAGE CHANGE IN OSWESTRY DISABILITY INDEX SCORE AS AN OUTCOME MEASURE IN LUMBAR SPINAL SURGERY

Study Design. A retrospective analysis of the change in the Oswestry L ow Back Pain Disability Questionnaire in a heterogeneous group of 144 operatively managed patients was undertaken to examine the change in d isability index as an outcome measure. Objectives. To establish the pe rcent change in disability index as an outcome measure able to identif y risk factors for poor results in lumbar spinal surgery. Methods. Epi demiologic, diagnostic, and surgical variables were examined as risk f actors using step-wise multiple linear regression analysis at both fol low-up times (6 months and 2 years), with percent change in disability index used as the outcome measure. Results. At 6-months follow-up, pr evious surgery, female gender, workers' compensation, a lower initial disability index score, increasing age, and spinal fusion alone as an operative procedure were independently and significantly negatively co rrelated with outcome. Further analysis revealed that for patients wit h spinal canal stenosis, the magnitude of the initial disability index did not correlate with outcome, whereas patients with low back pain o r a prolapsed intervertebral disc fared better if they had high initia l disability scores. Data at 2-years follow-up were less adequate. How ever, previous surgery on the spine and low initial disability score w ere significant negative predictors of outcome at 6-month and 2-year f ollow-up. Conclusions. The findings indicate that the absolute value a nd change in these scores after surgery vary from patient to patient, but that their percentage change is likely to be the best marker of ou tcome when such subjective scoring systems are used.