Long-Term Follow-Up Evaluation of Surgery for Ossification of the Posterior Longitudinal Ligament

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Abstract

Study Design.

We compared anterior and posterior surgery for cervical myelopathy resulting from ossification of the posterior longitudinal ligament. Surgical techniques, based on shape and distribution of ossification of the posterior longitudinal ligament, were divided into four technical phases.

Objectives.

Long-term follow-up data on anterior and posterior surgery were analyzed to establish guidelines for surgical treatment.

Summary of Background Data.

Comparison of anterior and posterior surgery is difficult because surgical techniques, ossification of the posterior longitudinal ligament shape classifications, and surgical criteria varied. No reports have accurately assessed spinal changes over a 10-year follow-up period.

Methods.

Fifty patients received anterior surgery and 65 received posterior surgery between 1968 and 1993. Assessment after surgery was based on the recovery rate using the scoring system of the Japanese Orthopaedic Association. Spinal changes in the anterior group were assessed radiographically.

Results.

Recovery and final results improved with phase after anterior, but not posterior, surgery. Neurologic deterioration after initial recovery was lower for the anterior group. One third of patients in the anterior group followed for more than 7 years exhibited neurologic deterioration, with most showing these changes within 10 years. Worsening was attributed to insufficient removal of lateral, superior, or inferior, or inferior ossification of the posterior longitudinal ligament, reossification at the excision site, kyphotic malalignment, growth of ossification at upper cervical levels, or untreated complicated hypertrophy of the posterior longitudinal ligament. Many patients showed a good outcome after surgery. Accurate alignment and long-range fusion improved results. If the cord was compressed in a canal narrowed to under 3 mm, anterior surgery was considered “too risky.”

Conclusions.

Complete extirpation of ossification of the posterior longitudinal ligament as confirmed by ultrasonography during surgery and long-range fusion with fibular grafts is advocated in the management of ossification of the posterior longitudinal ligament.

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