Is the Ossification of the Posterior Longitudinal Ligament a Positive Factor for the Fusion after Posterior Cervical Fusion and Decompression?

Objective: Multilevel posterior cervical fusion (PCF) and decompression surgery is a viable treatment option for multilevel ossification of posterior longitudinal ligament (OPLL) and spondylotic myelopathy. Since OPLL is known to affect bone formation, this study aimed to examine the effect of OPLL on the incidence of pseudarthrosis following PCF in a cohort study. Methods: We conducted a retrospective cohort study of patients with PCF and laminectomy at our institution. This study included patients who underwent C3 to C6 posterior fusion surgery involving lateral mass screw fixation without anterior surgery for OPLL or spondylotic myelopathy. Fusion status was evaluated 1 year postoperatively with computed tomography. Bone mineral density (BMD) and sagittal parameters were also evaluated as potential contributing factors to the fusion rate.Results: Eighty patients were included. Pseudarthrosis was observed in 22.5% (n=18) of patients. Pseudarthrosis incidence was lower in patients with OPLL (spondylosis vs. OPLL, 33.3% vs. 12.2%; p=0.003), and a higher BMD T-score (pseudarthrosis vs. fusion, -1.9 ± 0.7 vs. -0.6 ± 1.3; p<0.01), a larger preoperative range of motion (ROM) (26.7 ± 13.3 vs. 17.6 ± 10.9; p=0.01), and a greater preoperative-to-postoperative decrease in cervical lordosis (-8.1 ± 7.9 vs. -2.7 ± 7.9; p<0.01). Pseudarthrosis was associated with worsening neck pain after surgery. Conclusion: The absence of OPLL, lower BMD, larger preoperative ROM, and a greater decrease in postoperative cervical lordosis were identified as risk factors for pseudarthrosis after multiple PCF.