T1 slope (T1S) has emerged as a predictor of kyphotic alignment change after laminoplasty. Although it was reported that patients with cervical ossification of the posterior longitudinal ligament (OPLL) and higher T1S had more pronounced lordotic curvature before surgery and higher loss of cervical lordosis after surgery, few studies have attempted to correlate these findings with clinical outcomes. We aimed to investigate the relationship of T1S with loss of cervical lordosis and surgical outcomes after laminoplasty for cervical OPLL.
35 consecutive patients (26 men and 9 women) with cervical OPLL who underwent double-door laminoplasty were followed for more than 12 months. Radiological and clinical measurements were performed to analyze the following parameters: pre and postoperative C2-C7 Cobb lordotic angle (LA), preoperative C2-C7 range of motion (ROM), loss of cervical lordosis, percentage of change in postoperative kyphosis, pre and postoperative C2-C7 sagittal vertical axis (SVA), change in C2-C7 SVA and occupying ratio of the OPLL, Japanese Orthopedic Association (JOA) score recovery rate, preoperative MRI grade.
Patients were divided into 2 groups according to preoperative T1 slope, with the cutoff value being the average preoperative T1 slope. Preoperative C2-C7 Cobb LA (P=0.007) and loss of cervical lordosis (P=0.034) differed between the two groups. Preoperative C2-C7 Cobb LA (R=0.50, P=0.002) and loss of cervical lordosis (R=0.36, P=0.036) were significantly correlated to preoperative T1S. Multivariate linear regression analysis showed that the preoperative T1S was not related to JOA score recovery rate and the preoperative MRI grade (OR=-9.985, P=0.015) was only related to JOA score recovery rate.
Although the degree of alignment compromise is correlated with the preoperative T1S, clinical outcomes demonstrate overall improvement after cervical laminoplasty with cervical OPLL, regardless of preoperative T1S.