OBJECTIVECombining K-line (the connecting line of the midpoint of C₂ and C₇ spinal canal on the cervical lateral X-ray film) to analyze the relationship between cervical range of motion of patients with ossification of posterior longitudinal ligament (OPLL) and surgical prognosis.

METHODSA total 42 patients with ossification of cervical posterior longitudinal ligament underwent cervical posterior single open-door laminoplasty between April 2014 and March 2017 were retrospectively ananyzed. The patients were dividing into K-line (+) group and K-line (-) group according to the position realationship of OPLL and K-line. The lesion of ossification of the posterior longitudinal ligament was not over than the K-line known as K-line (+). Conversely, the lesion of ossification of the posterior longitudinal ligament crossing the K-line was called K-line (-). Preoperative and postoperative 3 months JOA scores were observed, and postoperative 3 months JOA improvement rate were computed to assess patient's neurological function recovery. Preoperation and postoperative 3 months, OPLL occupation ratio (OOR), cervical lordotic angles (CLA) and cervical lordotic value (CLV) were measured respectively. The realationship between postoperative neurologic functional recovery in patients of CLV>0 group and CLV<=0 group was evaluated in different K-line subgroups.

RESULTSFor the patients in K (+) group and K (-) group, preoperative CLA were (14.7±9.6)° and (-6.4±9.5)°(<0.05) respectively, postoperative at 3 months CLA were (14.0±8.0)° and (-1.4±10.4)°(<0.05) respectively; preoperative JOA scores were 10.9±3.2 and 11.2±2.5 (>0.05) respectively, postoperative at 3 months JOA scores were 14.2±1.8 and 12.6±2.2 (<0.05) respectively, and postoperative at 3 months JOA score improvement rate were (54.7±17.6)% and (25.5±15.7)%(<0.05) respectively. In the K-line (+) group, there were 29 patients in CLV>0 group at 3 months after operation, with improvement rate of (52.3±17.2)%, and 4 patients in CLV<=0 group, with improvement rate of (72.2±7.8)%. The improvement rate of the patients in CLV<=0 group was significantly better than that of the patients in CLV>0 group (<0.05).

CONCLUSIONSNo matter whether the ossification of cervical posterior longitudinal ligament was classified as K-line (+) or K-line (-), the cervical posterior single open-door laminoplasty can improve the neurological symptoms of patients, especially the patients in the K-line(+) group with better prognosis. The patinets in K-line(+) group, when postoperative at 3 months CLV>0, their improvement rate was lower than that of the patients with postoperative at 3 months CLV<=0.