Injection Treatment and Back Pain Associated with Degenerative Lumbar Spinal Stenosis in Older Adults

Background: Lower back pain is one of the most common health-related complaints in theadult population. Thirty percent of Americans 65 years and older reported symptoms of lowerback pain in 2004 (NCHS, 2006). Injection treatment is a commonly used non-surgical procedureto alleviate lower back pain in older adults. However, the effectiveness of injection treatment,particularly in older adults, has not been well documented.Objective: This study quantified the effectiveness of injection treatment on pain relief amongadults 60 years and over who were diagnosed with degenerative lumbar spinal stenosis, a commoncause of lower back pain in older adults. The variations of the effectiveness were examined byselected patient attributes.Study Design: Prospective, non-randomized, observational human study.Setting: Single institution spine clinic.Methods: Patients scheduled for lumbar injection treatment between January 1 and July 1,2008 were prospectively selected from the study spine clinic. Selection criteria included patientsage 60 and over, diagnosed with degenerative lumbar spinal stenosis and no previous lumbarinjection within 6 months or lumbar surgery within 2 years. The pain sub-score of the SF-36questionnaire was used to measure pain at baseline and at one and 3 months post injection.Variations in longitudinal changes in pain scores by patient characteristics were analyzed in bothunadjusted (univariate) analyses using one-way analysis of variance (ANOVA), and adjusted(multiple regression) analyses using linear mixed effects models.Limitations: This study is limited by its sample size and observational design.Results: Of 62 patients receiving epidural steroid injections, the mean Pain score at baselinewas 27.4 (SD =1 3.6), 41.7 (SD = 22.0) at one month and 35.8 (SD = 19.0) at 3 months. MeanPain scores improved significantly from baseline to one month (14.1 points), and from baselineto 3 months (8.3 points). Post injection changes in pain scores varied by body mass index (BMI)and baseline emotional health. Based on a linear mixed effects model analysis, higher baselineemotional health, as measured by the SF-36 Mental Component Score (MCS≥50), was associatedwith greater reduction in pain over 3 months when compared to lower emotional health (MCS<50). In patients with higher emotional health, pain scores improved by 14.1 (P < .05: 95% CI6.9, 21.3). Patients who were obese also showed significant improvement in pain scores over 3months compared to non-obese patients. In obese patients, pain scores increased by 7.9 (P <.05;95% CI:1.0, 14.8) points.Conclusion: Lower back pain in older adults with degenerative lumbar spinal stenosis might beclinically significantly alleviated after injection treatment. Pain relief varies by a patient’s personaland clinical characteristics. Healthier emotional status and obesity appears to be associated withmore pain relief experienced over 3 months following injection.Key words: Degenerative lumbar spinal stenosis, low back pain, older adults, epidural steroidinjection, MRI, SF-36, Pain sub-score.