Can K-Line Predict the Clinical Outcome of Anterior Controllable Antedisplacement and Fusion Surgery for Cervical Myelopathy Caused by Multisegmental Ossification of the Posterior Longitudinal Ligament?

Abstract

To analyze the correlation between the K-line-based classification of patients with ossification of the posterior longitudinal ligament (OPLL) and their outcome after anterior controllable antedisplacement and fusion (ACAF) surgery. A series of 24 patients with multisegmental OPLL were enrolled. All patients underwent ACAF surgery. First, the patients were classified into 2 groups according to their K-line classification. Then, we separated the patients into subgroups according to their OPLL thickness. The Japanese Orthopaedic Association scores before and 6 months after surgery were studied, and the recovery rate (RR) was calculated. The preoperative and postoperative radiologic parameters were also investigated. Clinical and radiographic assessments showed no significant correlation between the K-line-based classification of patients with OPLL and their outcome of ACAF surgery (P > 0.05). When the OPLL was ≤6 mm thick, K-line-based classification groups had a similar change of occupation ratio and RR (P > 0.05). However, when the OPLL was >6 mm thick, the mean RR was 61.8% ± 14.0% in the K-line (+) group and 78.3% ± 9.7% in the K-line (-) group (P < 0.05), and the mean was 16.0% ± 4.2% in the K-line (+) group and 28.0% ± 7.1% in the K-line (-) group (P < 0.05). This study shows that K-line can predict the clinical outcome of ACAF surgery for multisegmental OPLL in a different way from posterior decompression surgery. When the OPLL was thin, the outcome was satisfactory and there was no correlation with K-line-based classification of patients with OPLL. When the OPLL was >6 mm thick, the K-line (-) group patients had a better outcome than did K-line (+) group patients.