Epidural steroid injections in the treatment of lumbar spinal stenosis efficacy and predictability of successful response.

OBJECTIVE

The purpose of this study was to determine response to interlaminar epidural steroid injections in the treatment of lumbar spinal stenosis as measured using self-reported activity level and measured walking ability. The results were correlated through demographic data, magnetic resonance imaging (MRI) characteristics, and electrodiagnostic (EDX) results.

DESIGN

Subjects with a history of painful ambulation and lumbar spinal stenosis confirmed by MRI (N = 17) underwent a detailed history, physical examination, EDX, completed the Swiss Spinal Stenosis Questionnaire (SSSQ), and performed a 6-Minute Walk Test (SMWT). All subjects received between one and three epidural steroid injections, depending on clinical response. The SSSQ and the SMWT were repeated approximately 6 wks after completion of the last injection. EDX was performed using previously published techniques. MRIs were reviewed and classified according to type, severity, and canal diameter.

RESULTS

The subjects' initial performance on the SMWT was significantly worse than predicted normative data, accounting for age, sex, and measurements of height and weight. After completion of the treatment protocol, there was a significant improvement as measured by changes in SMWT (ΔSMWT; P = 0. 023) and SSSQ (ΔSMWT; P = 0.0003). ΔSMWT and ΔSSSQ only weakly correlated (r = 0.57). Body mass index, MRI, and EDX criteria were not predictive of ΔSMWT or ΔSSSQ. Younger subjects trended toward greater improvement than older subjects (ΔSMWT, -4.7 m/yr, P = 0.07, SSSQΔ P = 0.08). When adjusting for body mass index and sex, there was a significantly less improvement in walking distance with increasing age (ΔSMWT, -7.4 m/yr, P = 0.007). When adjusting for age and body mass index, women enjoyed a more robust treatment effect than did men (ΔSMWT, +106.9 m, P = 0.03).

CONCLUSIONS

Epidural steroid injections is an effective treatment for improving ambulation and functional limitations caused by lumbar spinal stenosis. Relative youth and female sex are associated with a more favorable response. Body mass index, EDX abnormal findings, and MRI severity are not predictive.