Spine Journal - 2026-07-01 - Journal Article
Lumbar ossification of the posterior longitudinal ligament as a distinct phenotype of diffuse spinal ligament ossification.
Koike Y, Endo T, Fujita R, Yamada K, Kanayama M, Sudo H, Kadoya K, Xue H, Terkawi MA, Ukeba D, Ohnishi T, Fukada S, Sodeyama Y, Suzuki R, Ishii M, Iwasaki N
Topics
Key Takeaway
Lumbar OPLL patients had significantly higher BMI (median 27.5 vs 26.0 kg/m², p=.003) and independently higher whole-spine ossification index scores (regression coefficient 0.448, 95% CI 0.162–0.735) compared to non-lumbar OPLL patients, supporting L-OPLL as a distinct diffuse ossification phenotype.
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Summary
This cross-sectional study with replication cohort asked whether L-OPLL represents a distinct phenotype within the OPLL spectrum by comparing clinical and whole-spine CT ossification indices between L-OPLL and non-L-OPLL patients. L-OPLL patients had higher BMI, greater thoracic OPLL and OLF indices, and independently higher total OS index on multivariate regression. Replication in 75 asymptomatic population-screened individuals confirmed the association between L-OPLL, obesity, and diffuse ligament ossification.
Key Limitation
The study population is exclusively Japanese, where OPLL prevalence is 10–20× higher than Western populations, making the phenotypic proportions and BMI thresholds non-transferable to most surgical practices outside East Asia.
Original Abstract
BACKGROUND CONTEXT
Lumbar ossification of the posterior longitudinal ligament (L-OPLL) has been underrecognized and remains poorly characterized clinically. We hypothesized that L-OPLL constitutes a distinct phenotype within the broader OPLL spectrum, sharing features of obesity and diffuse spinal ligament ossification.
PURPOSE
To evaluate the clinical and radiographic features of L-OPLL and assess their relationship with diffuse spinal ligament ossification and obesity-related factors.
STUDY DESIGN
Cross-sectional study with a replication cohort.
PATIENT SAMPLE
A total of 186 patients with OPLL were diagnosed using whole-spine computed tomography (CT) at a regional spine center in Japan (2007-2024). Additionally, 75 asymptomatic individuals with OPLL from a population-based health screening cohort comprised the replication cohort.
OUTCOME MEASURES
Patient background, including BMI, was assessed. Spinal ligament ossification was evaluated using whole-spine computed tomography. The severity of ossification was scored for 4 ligaments-OPLL, ossification of the anterior longitudinal ligament (OALL), ossification of the ligamentum flavum (OLF), and ossification of the supra/interspinous ligament (OSIL)-and summed to define the ossification index (OS index). Regional scores from the cervical, thoracic, and lumbar spine were combined to calculate the total index.
METHODS
In the primary analysis, patients were classified into L-OPLL and non-L-OPLL groups, and their clinical and radiographic features were compared. Multiple linear regression analysis was used to assess the independent association between L-OPLL and OS index. In the secondary analysis, patients were classified into three groups: localized cervical OPLL (C-OPLL), thoracic OPLL (T-OPLL), and L-OPLL groups, and comparisons were made between the localized C-OPLL group and the T- and L-OPLL groups.
RESULTS
The L-OPLL group had a significantly higher BMI (median 27.5 vs 26.0 kg/m², p=.003) and greater prevalence of obesity than the non-L-OPLL group, along with significantly elevated thoracic OPLL and OLF indices. Multiple linear regression analysis confirmed that L-OPLL was independently associated with a higher OS index (regression coefficient: 0.448, 95% confidence interval: 0.162 to 0.735, p=.002). The L-OPLL group also exhibited significantly higher BMI and OS index than the localized C-OPLL group, primarily driven by increased thoracic and lumbar OPLL and OLF. The replication cohort results were consistent with an association between L-OPLL, obesity, and diffuse ligament ossification.
CONCLUSIONS
L-OPLL is rarely an isolated lumbar lesion; instead, it commonly coexists with extensive spinal ligament ossification and marked obesity. Its distinct clinical and radiographic features support classification as a separate entity within the broader OPLL spectrum.