Outcome of posterior decompression with instrumented fusion surgery for K-line (−) cervical ossification of the longitudinal ligament

• Patients with K-line (−) ossification of the posterior longitudinal ligament (OPLL) may have a poor surgical prognosis.
• We report on surgical outcomes of posterior decompression and instrumented fusion (PDF) for patients with K-line (−) OPLL.
• Patients with PDF for K-line (−) OPLL showed moderate neurological recovery.

We investigated the outcome of posterior decompression and instrumented fusion (PDF) surgery for patients with K-line (−) ossification of the posterior longitudinal ligament (OPLL) of the cervical spine, who may have a poor surgical prognosis. We retrospectively analyzed the outcome of a series of 27 patients who underwent PDF without correction of cervical alignment for K-line (−) OPLL and were followed-up for at least 1 year after surgery. We had performed double-door laminoplasty followed by posterior instrumented fusion without excessive correction of cervical spine alignment. The preoperative Japanese Orthopedic Association (JOA) score for cervical myelopathy was 8.0 points and postoperative JOA score was 11.9 points on average. The mean JOA score recovery rate was 43.6%. The average C2–C7 angle was 2.2° preoperatively and 3.1° postoperatively. The average maximum occupation ratio of OPLL was 56.7%. In conclusion, PDF without correcting cervical alignment for patients with K-line (−) OPLL showed moderate neurological recovery, which was acceptable considering K-line (−) predicts poor surgical outcomes. Thus, PDF is a surgical option for such patients with OPLL.