Impact of K-Line (-) in the Neck-Flexion Position on Patient-reported Outcomes After Cervical Laminoplasty For Patients With Ossification of the Posterior Longitudinal Ligament.

Abstract

This study was a post hoc analysis of prospective data. The objective of this study was to investigate whether K-line (-) in the neck-flexion position [f-K-line (-)] affects patient-reported outcome measures after cervical laminoplasty for patients with ossification of the posterior longitudinal ligament (OPLL). The f-K-line was recently proposed as a predictor of poor outcomes after laminoplasty for patients with OPLL. However, its impact on patient-reported outcome measures remains to be elucidated. We analyzed prospectively collected data from 68 patients with cervical myelopathy due to OPLL who underwent double-door laminoplasty between 2008 and 2015. Patients were categorized into f-K-line (-) and f-K-line (+) groups on a baseline neck-flexion radiograph. Outcome measures included the Japanese Orthopaedic Association score, EuroQol 5-Dimensional Questionnaire, the Japanese Orthopaedic Association Cervical Myelopathy Evaluation Questionnaire, and 11-point Numerical Rating Scale for pain. The degree of satisfaction with the outcome was assessed at the 2-year follow-up using a 7-point Numerical Rating Scale. Of the 68 patients, 22 (32%) and 46 (68%) were grouped into the f-K-line (-) and f-K-line (+) groups, respectively. The 2 groups showed no significant difference in baseline functions. The f-K-line (-) group showed a significantly lower recovery rate of the Japanese Orthopaedic Association score and a significantly lower gain in EuroQol 5-Dimensional Questionnaire score than compared with the f-K-line (+) group at the 2-year follow-up. Among the 5 domains of the Japanese Orthopaedic Association Cervical Myelopathy Evaluation Questionnaire, cervical function, and upper extremity function were significantly lower in the f-K-line (-) group than in the f-K-line (+) group. Patients in the f-K-line (-) group also reported a significantly higher pain intensity in the upper and lower extremities and a significantly lower degree of satisfaction compared with those in the f-K-line (+) group. The f-K-line (-) was significantly associated with poorer functional recovery, higher pain intensity in the extremities, and lower patient satisfaction after cervical laminoplasty for patients with OPLL.