Effects of Epidural Steroid Injections on Bone Mineral Density and Bone Turnover Markers in Patients Taking Anti-Osteoporotic Medications

Background: Glucocorticoids adversely affect bone mineral density (BMD) and increase the risk of fracture. Yet, the cause-and-effect relationship between epidural steroid injection (ESI) and BMD has not been thoroughly investigated, and available results are inconsistent. This is probably a consequence of differences in the dose of steroids and follow-up duration. Objective: This study aimed to evaluate changes in BMD and the risk of fracture according to duration of the follow-up and amount of steroids used for ESI. Setting: Department of Orthopedic Surgery at Seoul Metropolitan Government Seoul National University (SMG-SNU) Boramae Medical Center, Korea. Methods: We retrospectively reviewed the medical records of postmenopausal patients who underwent dual-energy x-ray absorptiometry (DEXA) at least 3 times in 5 years. Patients were divided into 2 groups. Group 1 consisted of 73 patients who received ESI, whereas Group 2 consisted of 294 patients who did not receive ESI. All patients took anti-osteoporotic medications. BMD measurements were performed in 4 different regions, and levels of bone turnover markers (BTMs) were measured. In Group 1, BMD and BTMs levels were measured before the last ESI and 1 and 2 years after. A sub-analysis was conducted in Group 1 to compare BMD values in sub-groups with different doses of steroids. Results: In Group 1, the absolute values of BMD of the spine were decreased at the 1-year follow-up, but by the 2-year follow-up they recovered and approached the values in Group 2. In Group 2, BMD increased both at the 1-and 2-year follow-ups. There was an increase in occurrence of osteoporosis during the first year after ESI, but the prevalence of osteoporosis declined remarkably during the second year. The levels of BTMs increased at the 1-year followup and decreased at the 2-year follow-up in Group 1. Higher cumulative doses of steroids induced greater decreases in BMD. However, the changes in spine BMD in the sub-analysis were insignificant. Limitations: This was a retrospective study. Additionally, administration of anti-osteoporotic medication might have prevented accurate evaluation of the effects of ESI. Conclusions: ESI adversely affects BMD in postmenopausal women, especially that of the spine, and the adverse effects increase with the dose of steroids. Gradual reduction of the effect of steroids one year after the cessation of ESI resulted in recovery of BMD to a level similar to that in the control group.