Does Preoperative T1 Slope Affect Radiological and Functional Outcomes After Cervical Laminoplasty?

Study Design. Retrospective comparative study. Objective. To analyze changes in the clinical and radiological factors related to cervical sagittal balance, relative to preoperative T1 slope, in patients with cervical myelopathy after laminoplasty (LP). Summary of Background Data. T1 slope is an important factor that should be considered before LP. However, until now, there have been no studies on how preoperative T1 slope affects the sagittal balance of cervical spine and various functional outcomes after LP. Methods. Seventy-six patients with cervical myelopathy (M: F ratio = 50:26; mean age = 64.7 +/- 9.1 yr) underwent a cervical LP and were followed for more than 2 years. Radiological measurements were performed to analyze the following parameters: (1) C2-C7 sagittal vertical axis; (2) T1 slope; (3) C2-C7 lordosis; and (4) thoracic kyphosis. The visual analogue scale, Japanese Orthopedic Association, neck disability index, and 36-Item Short-Form Health Survey were also investigated. Patients were divided into 2 groups according to preoperative T1 slope, with the cutoff value being the median preoperative T1 slope. Changes in clinical and radiological parameters were compared between the preoperative evaluation and final visit. Results. Overall, C2-C7 sagittal vertical axis increased from 21.2 to 24.5 mm (P = 0.004) and C2-C7 lordosis decreased from 13.9 degrees to 10.3 degrees (P = 0.007) postoperatively. The T1 slope did not show any postoperative differences. Preoperative C2-C7 lordosis was larger in the high-T1 group (19.1 degrees) than in the low-T1 group (9.0 degrees). However, postoperative changes in C2-C7 sagittal vertical axis and C2-C7 lordosis did not show any between-group differences. Clinical outcomes (except neck pain) demonstrated overall improvement in both groups. Comparing changes in both groups showed no differences in neck pain, arm pain, neck disability index, or 36-Item Short-Form Health Survey physical component score between groups. Conclusion. Cervical sagittal balance is compromised after cervical LP. However, the degree of aggravation does not correlate with the preoperative T1 slope. Most clinical parameters demonstrate overall improvement regardless of preoperative T1 slope.