Natural history of the ossification of cervical posterior longitudinal ligament: a three dimensional analysis.

Purpose: Three-dimensional (3D) imaging using computed tomography (CT) has made it possible to accurately evaluate ossification of the posterior longitudinal ligament (OPLL). Recently, we developed a novel technique to measure ossification volume using the 3D analysis. The purpose of this study was to investigate the natural course of OPLL and the risk factors for volume progression.

Methods: Forty-one patients (22 males and 19 females) diagnosed with cervical OPLL who had been non-surgically treated were included in this study. We evaluated clinical examination, radiological findings, and the volume of ossified lesions during at least 1-year intervals. Furthermore, we performed risk factor analysis for OPLL volume progression.

Results: The mean ossification volume was 2047.4 ± 1437.3 mm in the first examination and 2201.0 ± 1524.1 mm in the final examination, indicating a significant increase during the follow-up period (p < 0.001). The mean annual rate of lesion increase was 4.1 ± 2.7%. Univariate regression analysis demonstrated significant relationships between the annual rate of lesion increase and age (β = -0.48; p = 0.001), body weight (BW) (β = 0.36; p = 0.02), and body mass index (BMI) (β = 0.35; p = 0.03). Furthermore, age was the only significant predictor of OPLL progression (R = 0.23; p = 0.001) in multivariate liner regression analysis.

Conclusions: Younger age, higher BW, and higher BMI are predictors of OPLL progression. Younger age is the most significant predictor in non-surgically treated patients.