Effects of lumbar degeneration on the global and regional bone mineral density in osteoporotic patients requiring lumbar interbody fusion for degenerative lumbar diseases.

Abstract

Lumbar disc degeneration (LDD) and osteoporosis are common diseases coexisting in elderly population. LDD significantly affects the distribution of bone mineral density (BMD), misleading preoperative BMD evaluation. In this study, effects of LDD on global and regional BMD were evaluated through multiple techniques. 77 patients with lumbar degenerative diseases and osteoporosis were retrospectively included. BMD was measured using lumbar T-score, trabecular Hounsfield units (HU) value and endplate volumetric BMD (EP-vBMD). The average BMD of lumbar intervertebral disc was calculated. Modified Pfirrmann grading (mPG), total endplate score (TEPS) and modic change (MC) was used to evaluate LDD. The influence factors of BMD were analyzed. This cohort included 24 men and 53 women with an average age of 67.7 ± 5.6 years. From L1/2 to L4/5, the T-score and EP-vBMD significantly increased(P < 0.001), while for trabecular HU value, higher BMD was found in L1/2 and L4/5(P < 0.001). Higher mPG and TEPS were found in lower lumbar (P < 0.001). Significantly positive correlations between LDD gradings and T-score or EP-vBMD were demonstrated, while there was only a very weak correlation between mPG and HU value (β = 0.097, P = 0.004). When evaluating different lumbar levels separately, no correlation between trabecular HU value and LDD was demonstrated. LDD significantly affects endplate BMD and lumbar T-score. Among different methods, EP-vBMD is closely related to regional degeneration, and trabecular HU value is most sensitive to age-related systemic BMD status. Integrating both global and regional BMD measurements is recommended to enhance the accuracy of BMD evaluation in patients with LDD.