Qualitative evidence from a systematic review of prognostic predictors for surgical outcomes following cervical ossification of the posterior longitudinal ligament

Ossification of the posterior longitudinal ligament (OPLL) is a pathological ectopic ossification of this ligament that usually occurs in the cervical spine. For patients with cervical OPLL and neurological symptoms, surgical intervention is necessary but not always effective. Various prognostic factors influence the surgical outcome. The results of studies identifying these prognostic predictors are often inconclusive or contradictory. These predictors have not been well identified or summarized. The present study was designed to identify the prognostic predictors for the surgical outcome of cervical OPLL based on the available evidence in the literature. Non-interventional studies were searched in Medline, Embase, Science Direct, OVID and the Cochrane library. Forty-two observational studies involving 2791 patients were included. The quality of the included studies was assessed with a modified quality assessment tool, which was originally designed for use with observational studies. The effects of the studies were combined with the study quality score using a model of best-evidence synthesis. There was strong evidence for five predictors: (i) age, (ii) duration of symptoms, (iii) pre-operative neurological score, (iv) transverse area of the spinal cord, and (v) intramedullary high signal intensity on the T2-weighted MRI. We also identified eight predictors with moderate supporting evidence, seven with limited evidence, four with conflicting evidence and four predictors without supporting evidence. While there is no conclusive evidence regarding the surgical outcomes following cervical OPLL, these data provide evidence to guide the clinician in choosing an optimal therapeutic strategy for patients with cervical OPLL. Further research is necessary to fully evaluate the effects of the predictors described in this study. (c) 2012 Elsevier Ltd. All rights reserved.