Minimum 5-year Follow-up Results for Occipitocervical Fusion Using the Screw-Rod System in Craniocervical Instability

Study Design: Retrospective clinical study. Objective: To evaluate the clinical outcome of patients who had undergone occipitocervical (OC) fusion using pedicle screws and rods over a minimum 5-year follow-up. Summary of Background Data: Few studies have evaluated occipitocervical (OC) fusion using pedicle screws and rods for long-term follow-up. Methods: Twenty-seven consecutive patients treated underwent posterior OC fusion using pedicle screws and rods over a minimum 5-year follow-up. The Modified McCormick scale to grade a patient's functional status and the Japanese Orthopaedic Association (JOA) scoring system were used to evaluate preoperative and postoperative neurological function. We assessed fusion by both direct and indirect evidence; bony trabeculae at the graft-recipient interface on lateral cervical radiographs and sagittal computed tomography reconstruction was considered direct evidence of union. Results: The mean follow-up period was 7.2 years (5-14 y). JOA scores were 8.1 +/- 3.8 before surgery and 11.7 +/- 3.7 at the final follow-up. The recovery rate calculated from the JOA scores was 42.0 +/- 30.0%. Functional status did improve at least 1 grade according to the modified McCormick scale in 18 patients (66.7%). There was no deterioration at the final follow-up. There were postoperative implant-related complications in 8 patients (29.6%): loosening of pedicle screws in 2, rod breakage in 2, plate breakage in 1, screw breakage in 1, pullout of pedicle screws in 1, and wiring induced myelopathy in 1 patient. The average duration between surgery and implant failure was 31.2 months (12-60 mo) except for 2. Conclusions: Sufficient bone grafting, proper decortication of the bone bed, using thicker and high stiffness rods, and ultra-high molecular weight polyethylene tape as a fixation or reinforcement of implant may help prevent implant failure.