The review question was clear. The authors searched only one database and limited the review to published studies reported in English which increased the likelihood that some relevant studies were omitted, and that language or publication biases were introduced. The quality of the studies was not reported which made it difficult to determine the reliability of the data. Attempts were made to reduce reviewer bias in the study selection and data extraction processes.
It may not have been appropriate to combine studies with different study types (clinical, radiological, case report) and different follow-up periods, conservative management strategies and severities of myelopathy (mild, moderate, severe). One study conducted in Japan included most of the patient population (74.8%) and the result may not be completely applicable to all patients with ossification of the posterior longitudinal ligament, which the authors acknowledged. A number of the studies were retrospective in design and the authors acknowledged limitations associated with these.
The authors' conclusions appeared to reflect the results of the review. The reliability of the conclusions was uncertain due to the lack of quality assessment, variation in studies and one study contributing most of the data to the analysis.