Background: Lower back pain is one of the most common health-related complaints in the adult population. Thirty percent of Americans 65 years and older reported symptoms of lower back pain in 2004 (NCHS, 2006). Injection treatment is a commonly used non-surgical procedure to 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 among adults 60 years and over who were diagnosed with degenerative lumbar spinal stenosis, a common cause of lower back pain in older adults. The variations of the effectiveness were examined by selected 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 patients age 60 and over, diagnosed with degenerative lumbar spinal stenosis and no previous lumbar injection within 6 months or lumbar surgery within 2 years. The pain sub-score of the SF-36 questionnaire 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 both unadjusted (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 baseline was 27.4 (SD =13.6), 41.7 (SD = 22.0) at one month and 35.8 (SD = 19.0) at 3 months. Mean Pain scores improved significantly from baseline to one month (14.1 points), and from baseline to 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 baseline emotional health, as measured by the SF-36 Mental Component Score (MCS >/= 50), was associated with greater reduction in pain over 3 months when compared to lower emotional health (MCS), was associated with 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% CI 6.9, 21.3). Patients who were obese also showed significant improvement in pain scores over 3 months 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 be clinically significantly alleviated after injection treatment. Pain relief varies by a patients personal and clinical characteristics. Healthier emotional status and obesity appears to be associated with more pain relief experienced over 3 months following injection.