Undetected low bone mineral density in patients undergoing lumbar fusion surgery-prevalence and risk factors.

BACKGROUND

Sufficient bone quality is a prerequisite for low complication rates and satisfactory outcomes in lumbar fusion surgery (LFS). Low bone mineral density (BMD), including osteoporosis and osteopenia, is linked to adverse postoperative outcomes. Despite reports of a high prevalence of undiagnosed osteoporosis, it is uncertain which risk factors should guide preoperative BMD screening in LFS.

METHODS

This secondary cross-sectional analysis of a prospective institutional database at an academic spine center included adult patients undergoing LFS for degenerative conditions between 2014 and 2023. Opportunistic quantitative CT (qCT) at the L1/2 level was performed before surgery, and demographic and medical history data were extracted. Descriptive and comparative statistics, univariable and multivariable logistic regression were performed to determine risk factors for present and undiagnosed osteoporosis.

RESULTS

Of the 675 patients screened, 578 (54% female) were included after excluding those with preoperative lumbar CT scans not suitable for qCT. The median age was 65 years (IQR 58-72), and the median BMI of 28.9 kg/m (IQR 25.2-32.9). Osteoporosis was identified in 182 patients (31%), with 114 previously diagnosed and 68 newly detected via preoperative qCT. Undiagnosed osteoporosis was found in 12% of all patients and 37% of those with osteoporosis. Osteopenia was present in 199 patients (34%), leading to an overall impaired bone quality prevalence of 66%. Multivariable analysis revealed that age and female sex were independent risk factors for osteoporosis, while undiagnosed cases were more common in males, patients with higher BMI, and older individuals.

CONCLUSIONS

This study found a high prevalence of abnormal BMD in LFS patients, with a significant proportion of undiagnosed osteoporosis. While osteoporosis was more common in females, male patients with osteoporosis were more frequently undiagnosed. Spine surgeons must remain vigilant about metabolic bone disease in LFS patients to ensure preoperative optimization and prevent complications.