Purpose: A high C7 slope induces C2–C7 lordosis to compensate for cervical sagittal balance adjustments. A muscle-preserving selective laminectomy (SL) can maintain this compensation postoperatively. This study evaluated the effect of an extremely high C7 slope on C2–C7 lordotic compensation following SL. Methods: This study enrolled 151 cervical compressive myelopathy patients who underwent SL. Lateral cervical spine radiographs were taken before surgery and during final follow-up. Patients were divided into extremely high C7 slope (≥ 30°) (EH) and non-high C7 slope (< 30°) (NH) groups and the influence of a high C7 slope on radiological and surgical outcomes was examined. Results: Mean age was higher in group EH (p < 0.001). Preoperatively, patients in group EH had a larger C2–C7 sagittal vertical axis (SVA) (p = 0.001) and greater cervical lordosis (p < 0.001). Although C2–C7 SVA increased after surgery, mean C2–C7 angle of group EH decreased. Mismatches between C7 slope and C2–C7 angle increased for group EH postoperatively (p = 0.015). Postoperative Japanese Orthopedic Association (JOA) score and recovery rate (RR) were slightly lower in group EH (p = 0.001 and p = 0.006, respectively). Multiple linear regression analyses revealed that extremely high C7 slope, not age, affected the RR of JOA score (p = 0.006). Conclusions: Patients in group EH were older and had highly compensated cervical sagittal alignment preoperatively. They demonstrated postoperative cervical sagittal balance mismatch increases and slightly worse functional recovery. An extremely high C7 slope limited compensatory cervical lordosis following SL. Graphical abstract: These slides can be retrieved under Electronic Supplementary Material.[Figure not available: see fulltext.].
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