Radiologic and Clinical Importance of Lamina Hinge Fractures After Open-Door Cervical Laminoplasty: A Propensity Score-Matched Study.

STUDY DESIGN: A propensity score-matched retrospective cohort study. OBJECTIVE: To evaluate the clinical and radiologic significance of hinge fractures in a consecutively enrolled, relatively large cohort of patients. SUMMARY OF BACKGROUND DATA: Although a few studies have investigated the clinical outcomes of laminoplasty hinge fractures, no well-designed investigation involving a large consecutive patient cohort has evaluated their clinical and radiologic outcomes. METHODS: Patients who underwent laminoplasty and were followed for at least 2 years were included. Hinge fractures were assessed using immediate and 1-year postoperative computed tomography (CT). Patients with immediate postoperative hinge fractures were classified into the HF (+) group. The hinge without fracture [HF (-)] group was established using a 1:2 propensity score matching. The radiologic and clinical outcomes were compared between the groups preoperatively and at 6 months and 2 years postoperatively. RESULTS: Among 204 patients, 40 (19.6%) were included in the HF (+) group. Through 1:2 propensity score matching, 80 patients were assigned to the HF (-) group. Compared with the HF (-) group, the HF (+) group included a higher proportion of male patients and demonstrated larger preoperative C2 sagittal vertical axes (SVA). In addition, the HF (+) group exhibited lower C2-C7 lordosis, larger C2 SVA, and greater C2-C7 flexion capacity at 2 years postoperatively. Neck pain visual analog scale score was higher in the HF (+) group at 6 months, but no differences were noted at 2 years postoperatively. Of 49 fractures in the HF (+) group, 40 (81.6%) achieved union, as assessed on 1-year postoperative CT. CONCLUSIONS: Hinge fractures following laminoplasty occurred primarily in male patients and in those with larger preoperative C2 SVA. These patients exhibited a relatively kyphotic change postoperatively and experienced early postoperative neck pain. Our findings suggest that particular attention should be paid to avoid laminar hinge fractures during laminoplasty. LEVEL OF EVIDENCE: Level III.