Whole-spine CT predictors of lumbar surgery in patients with ossification of the posterior longitudinal ligament.

PURPOSE: Patients with ossification of the posterior longitudinal ligament (OPLL) may require lumbar surgery due to ossified lesions and degenerative changes. However, risk stratification for lumbar intervention remains underexplored. We aimed to identify predictors of lumbar surgery in patients with OPLL.

METHODS: We retrospectively analyzed 178 OPLL patients who underwent whole-spine computed tomography (CT) (2007-2023). Patients were classified according to whether they underwent lumbar surgery. CT obtained prior to lumbar surgery or during conservative follow-up was reviewed. Imaging parameters, including ossification distribution and degenerative changes, were compared between groups and analyzed using multivariable logistic regression to identify independent predictors.

RESULTS: Lumbar surgery was performed in 70 (39.3%) patients. The surgery group exhibited higher body mass index and greater prevalence of thoracolumbar ankylosis, thoracic and lumbar OPLL, lumbar ossification of the ligamentum flavum (OLF), and intervertebral disc (IVD) gas. Multivariable analysis identified lumbar OLF (OR, 6.49; 95% CI, 2.60-16.25) and lumbar IVD gas (OR, 5.75; 95% CI, 2.37-13.97) as independent risk factors. Coexisting OPLL and OLF at the same level was associated with younger surgical age and greater neurological severity.

CONCLUSIONS: Using whole-spine CT, we demonstrated that patients requiring lumbar surgery frequently exhibited a diffuse whole-spine ossification phenotype, characterized by thoracolumbar OPLL and ankylosis. Lumbar OLF and IVD gas were identified as independent risk factors; notably, lumbar OLF reflects this generalized ossification tendency, whereas disc gas indicates mechanical stress and degeneration. These findings support whole-spine CT-based risk stratification and longitudinal monitoring in patients with OPLL.