Ossification of the posterior longitudinal ligament of the spine (OPLL) is recognized as a common disorder among Japanese and throughout Asia. Estimates of its prevalence are in the range of 1. 9%-4.3%. Although its etiology is thought to involve a multiplicity of factors, epidemiological and family studies strongly implicate genetic susceptibility in the pathogenesis of OPLL. In this study we report an identification of a predisposing locus for OPLL, on chromosome 6p, close to the HLA complex. The evidence for this localization is provided by a genetic-linkage study of 91 affected sib pairs from 53 Japanese families. In this sib-pair study, D6S276, a marker lying close to the HLA complex, gives evidence for strongly significant linkage (P = .000006) to the OPLL locus. A candidate gene in the region, that for collagen 11A2, was analyzed for the presence of molecular variants in affected probands. Of 19 distinct variants identified, 4 showed strong statistical associations with OPLL (highest P = .0004). These observations of linkage and association, taken together, show that a genetic locus for OPLL lies close to the HLA region, on chromosome 6p.
Study DesignThis was a prospective study with an average 11-year follow-up review. Clinical and radiographic changes in Object. The goal of this study was to clarify the pathogenesis of myelopathy in patients with ossification of the posterior longitudinal ligament (OPLL) based on the relationship between static compression factors and dynamic factors.Methods. There was a total of 247 patients, including 167 patients who were conservatively followed for a mean of 11 years and 2 months and 80 patients who had myelopathy at initial consultation and underwent surgery. The changes in clinical symptoms associated with OPLL in the cervical spine were examined periodically.During the natural course of OPLL in the cervical spine, 37 (22%) of 167 patients developed or suffered aggravated spinal symptoms. All of the patients with a space available for the spinal cord (SAC) less than 6 mm suffered myelopathy, whereas the patients with an SAC diameter of 14 mm or greater did not. No correlation was found between the presence or absence of myelopathy in patients whose SAC diameter ranged from 6 mm to less than 14 mm. In patients with myelopathy whose minimal SAC diameter ranged from 6 mm to less than 14 mm, the range of motion of the cervical spine was significantly greater.Conclusions. These results indicate that pathological compression by the ossified ligament above a certain critical point may be the most significant factor in inducing myelopathy, whereas below that point dynamic factors may be largely involved in inducing myelopathy. KEY WORDS • ossification of the posterior longitudinal ligament • myelopathy • spinal cordA J. Neurosurg: Spine / Volume 96 / March, 2002 Abbreviations used in this paper: OPLL = ossification of the posterior longitudinal ligament; ROM = range of motion; SAC = space available for the spinal cord.
Psychologic tests may be useful and provide a means of modifying brace therapy tailored to the psychologic conditions of individual patients.
Genetic factors predispose toward the development of OPLL.
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