Untreated Osteoporosis in Lumbar Fusion Surgery Patients: Prevalence, Risk-factors and Effect on Bone Metabolism.

Study Design: Secondary analysis of a prospective single-center study.

Objective: To analyze the prevalence and risk factors for untreated osteoporosis in patients undergoing lumbar spinal fusion surgery (LFS) and its impact on bone mineral density (BMD) and bone turnover markers.

Background: Osteoporosis is a risk factor for mechanical complications in LFS, which can be mitigated by antiosteoporotic treatment. However, there's limited research on factors leading to untreated osteoporosis before LFS and its impact on preoperative bone status.

Methods: A secondary analysis of a prospective study enrolling adults undergoing LFS for degenerative conditions (2014-2024) with preoperative quantitative CT osteoporosis screening was performed. Demographic data and medical history were analyzed for prevalence and risk factors of untreated osteoporosis, while BMD, vitamin D, PTH levels, and bone turnover markers were assessed for the effects of lacking treatment.

Results: A total of 445 patients (48% female, median age 64) were included, of which 137 patients (31%) had osteoporosis. Of these, 66 (48%) were untreated and 71 (52%) were treated, with 40 (56%) receiving pharmacological and 31 (44%) non-pharmacologic treatment including vitamin D supplementation and lifestyle modifications. Of the untreated patients, 55 (80%) were identified by preoperative screening. 71% of osteoporotic men versus 35% of osteoporotic women were untreated (P<0.001). Multivariable logistic regression confirmed male sex as an significant contributing factor (OR 4.3, 95% CI 1.9-10.1, P<0.001) for untreated osteoporosis. Treated osteoporotic patients had higher BMD (P<0.001), higher VitD levels P=0.023) and lower levels of bone resorption parameters (P=0.004) than untreated patients.

Conclusion: Untreated osteoporosis is common before LFS, especially in men, with the untreated having lower BMD and higher bone resorption marker levels than treated patients. Identification of osteoporotic cases and subsequent osteological optimization could potentially reduce the risks of adjacent fractures or screw loosening.