Does T1 slope minus cervical lordosis mismatch affect surgical outcomes of cervical laminoplasty in the absence of preoperative severe kyphosis?

BACKGROUND: The impact of the T1 slope minus cervical lordosis (T1S-CL) on surgical outcomes in patients with degenerative cervical myelopathy undergoing laminoplasty (LP) remain uncertain. METHODS: One hundred patients who underwent cervical LP were retrospectively reviewed. Radiographic measurements included C2–C7 lordosis (CL), T1 slope (T1S), and C2–C7 sagittal vertical axis (SVA). Additionally, pain numeric rating scale, neck disability index (NDI), 12-Item Short-Form Health Survey, Euro QOL 5 dimensions (EQ5D), and Japanese Orthopedic Association score were investigated. According to past reports, T1S–CL > 20° was defined as mismatched. Then, based on T1S-CL mismatching, patients were divided into 2 groups. RESULTS: This research understudied 67 males and 33 females with a mean age of 67 y. Preoperatively, only eight patients showed a T1S-CL mismatch. While the C2–7 Cobb angles did not change significantly after surgery, the T1 slope (T1S) angle increased, increasing the T1S-CL as a result. As we compared the clinical outcomes based on the preoperative T1S-CL mismatching, there were no significant differences between the two groups. On the other hand, the number of patients in the mismatched group increased to 21 patients postoperatively. As we compared clinical outcomes based on the postoperative T1S-CL mismatching, the postoperative NDI score and preop/postop EQ5D score were significantly worse in the mismatch group. CONCLUSIONS: Although cervical LP showed inferior outcomes in patients with postoperative T1S-CL mismatch even in the absence of severe preoperative kyphosis (> 10°), preoperative T1S-CL mismatch was not adversely prognostic.