K-line (-) in the Neck-Flexed Position in Patients With Ossification of the Posterior Longitudinal Ligament Is a Risk Factor for Poor Clinical Outcome After Cervical Laminoplasty.

Abstract

Retrospective study comparing postoperative clinical outcomes after cervical laminoplasty between K-line (-) ossification of the posterior longitudinal ligament (OPLL) and K-line (+) OPLL in the neck-flexed position. To investigate postoperative outcomes using Japanese Orthopedic Association (JOA) scores, and grip-and-release (GR) and foot-tap (FT) test scores after laminoplasty in patients with K-line (-) OPLL in the neck-flexed position. Cervical laminoplasty has been reported to lead to poor outcomes in K-line (-) OPLL and good outcomes in K-line (+) OPLL. The cervical spine, however, continues moving in the extension and flexion direction after laminoplasty. Patients with cervical myelopathy were divided into K-line (+) and (-) in the neck-flexed position. We compared postoperative outcomes after cervical laminoplasty using recovery rate, as assessed by the JOA score and degree of improvement in the six JOA score items, and performance, as assessed by GR and (FT) tests, between patients with K-line (+) OPLL (n = 18) and K-line (-) OPLL (n = 23) in the neck-flexed position. Recovery rate of JOA score (23.8%) of patients in the K-line (-) group was significantly lower (P = 0.028) than that (46.3%) of K-line (+) group in the neck-flexed position. In the K-line (+) group, significant improvements were seen in all JOA-score items except bladder function; however, in the K-line (-) group, improvements were seen only in upper- and the lower-extremity sensory functions. In the K-line (+) group, mean GR and FT tests significantly improved, but in the K-line (-) group, only mean FT test significantly improved. The K-line (-) OPLL in the neck-flexed position is a risk factor for poor clinical outcome after cervical laminoplasty. 4.