Observational Study to Evaluate the Effect of Epidural Steroid Injection on Bone Mineral Density and Bone Turnover Markers

Background: Epidural steroid injection (ESI) is widely used to manage low back pain. ESIs are commonly performed to treat pain accompanying intervertebral disc prolapse, spinal stenosis, facet joint pathologies, and other degenerative spinal pathologies. Corticosteroids for musculoskeletal conditions, regardless of the route of administration, can reduce bone mineral density (BMD) and increase the risk of fracture. With paraspinal administration of steroids, the severity of risk is enhanced as the steroid is being deposited in close proximity to bone. BMD and molecular markers of bone metabolism are the standard methods to assess the effect of any insult on bone strength and bone metabolism. Carboxy terminal crosslinked telopeptides of type 1 collagen (sCTX) and serum Procollagen Type I N-terminal propeptide (P1NP) are the reference markers of bone resorption and formation, respectively. Objective: We conducted this study to determine the effect of ESI on BMD and bone turnover markers. Study Design: This was a prospective observational cohort study, involving a cohort of 264 patients between the ages of 40 to 60 years who were advised to undergo ESI at L3-4 or L4-5 by their pain physician. Setting: Research was conducted at a tertiary care teaching hospital pain clinic in collaboration with the department of orthopaedics and radiodiagnosis. Methods: Serum CTX-1, P1NP, and pre-ESI BMD of the spine, femur neck, and dual femur were evaluated at baseline; these same parameters were serially evaluated post ESI on follow-ups at 1, 3, and 6 months. Additional follow-up at 10 days post ESI was called for evaluation of bone turnover markers (BTMs). A paired t test was used to analyze changes in BMD and BTMs vs baseline within the group. Cumulative incidence and relative risk of moderate to markedly low BMD were calculated using standard formulas. Any fractures sustained during follow-ups were also evaluated thoroughly and quantified separately. A P value less than .05 was considered statistically significant. Results: The proportion of pre-ESI moderately to markedly low BMD was 10.22% in the study population. There was a statistically significant increase in serum CTX 10 days post ESI which persisted at the one-month and 3-month follow-ups. There was no significant change in serum P1NP level post ESI after 7 days and at the one-month follow-up. The mean value of serum P1NP was, however, significantly higher at the 3-month follow-up. Statistical comparison of the mean BMD value at the spine and femur neck revealed statistically significant decline 3 months post ESI. There was no significant impact of ESI on the total femur BMD. The cumulative incidence of moderately low to markedly low BMD over a period of 6 months in the study population was 45 out of 223, i.e., 20.17%. Limitations: The study's primary limitations included its high dropout rate, a larger reference range for BTMs, making them a less specific tool for comparison, and the absence of a control group. ESI has a negative impact on the BMD of the hip and spine. Reduced BMD should be considered as a potential side effect of ESI.