Injection Treatment for Lower Back Pain in Older Adults with Lumbar Spinal Stenosis: A Dissertation

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. With an aging population, the proportion of people over the age of 65 is expected to reach 20% by the year 2030. Because of this increase in older adults, lumbar spinal stenosis (LSS) associated with arthritic changes will also likely increase. In older adults, lower back pain is most often caused by degenerative lumbar spinal stenosis. Stenosis is the narrowing ofthe spinal canal, causing pressure on the nerve roots and is frequently treated surgically. Lumbar spinal stenosis is one of the most common reasons for back surgery in patients 65 years and older 2. However, risks associated with surgery increase with age 3-5 and older patients may choose non-surgical treatment for their lower back pain, including injection treatment. Injection treatment, usually consisting of anti-inflammatory medications and analgesics, has improved since the mid-1990\u27s when fluoroscopic guidance was developed. Information about injection treatment for lower back pain is limited, especially in the older population. An extensive review of published literature regarding injection treatment revealed a paucity of information about older adults diagnosed with lumbar spinal stenosis. In this study, three aims were designed to gain more information about the effectiveness of injection treatment in older patients with lumbar spinal stenosis. In the first (retrospective) study, information about receipt of second injections and time between injections was collected to examine injection usage. In the second and third (prospective) studies, information about pain relief and functional return following injection treatment was collected to examine the effectiveness of injection treatment in patients age 60 and older diagnosed with lumbar spinal stenosis. To our knowledge, such results have not been repolted for this population in the literature. Objective:Injection treatment is a commonly used non-surgical procedure to alleviate lower back pain in older adults. However, older patients do not have enough information about how long pain relief will last after treatment or the amount of pain relief and functional return they will experience. These studies focused on three topics: 1) usage of injection treatment; 2) effectiveness of injection treatment on pain relief; 3) effectiveness of injection treatment on functional return. In addition, the variations of the effectiveness were examined by selected patient attributes. Methods:In a retrospective study, medical records of patients aged 60 years or older from a high volume dedicated spine center at the University of Massachusetts Memorial Hospital were retrospectively reviewed. This study included those diagnosed with degenerative LSS, who had not received an injection for lower back pain within six months, and whom were treated between June I, 2006 and May 31, 2007. In two prospective studies, patients scheduled for lumbar injection treatment between January 1 and June 30, 2008 were selected from the University of Massachusetts Memorial Hospital Spine Center. 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 three months post injection. The Physical Component Score (PCS) of the SF-36 questionnaire and the Oswestry Disability Index (ODI) were used to measure function at baseline and at one and three months post injection. Variations in longitudinal changes in 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. Results: In the retrospective cohort, the mean age of the cohort was 68, 64% were female, 59% were married, with a mean Body Mass index of 32 kg/m2. Of 92 eligible patients, 57% returned for a second injection within six months of the first. The mean number of months between injections was 4.8 for all patients, ranging from 1 to 22 months. When patient characteristics were examined, the only variable that showed a statistically significant difference was age. Patients aged 70 years and older were found to be 67% less likely to return for a second injection when compared to patients age 60-69 (OR=0.33 (0.12 - 0.94)p In the prospective cohort, information was collected on 62 patients. Mean Pain scores improved significantly from baseline to one month (14.1 points), and from baseline to three 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\u3e50), was associated with greater reduction in pain over three months when compared to lower emotional health (MCS Conclusion: Patients over age 70 do not return for repeat injection as frequently as patients age 60-69. In addition, each year a patient ages over age 60, they are 10% less likely to return for a repeat injection. Lower back pain in older adults with LSS is clinically significantly alleviated after injection treatment. In addition, injection treatment for LSS is associated with return of lost function needed for daily living activities in older adults. Pain relief and functional return varies by patient personal and clinical characteristics. Higher emotional health was associated with more pain relief and more functional return experienced over three months following injection treatment. Additional information is needed about why older patients do not return for second injections at the same rate as younger patients and how emotional health affects response to injection treatment in older adults