[Association of lumbar canal stenosis and ankylosing vertebral hyperostosis. Results of a multicenter study].

The authors report data collected in a study of the association of narrow lumbar canal and vertebral hyperostosis. Five centres (Montpellier, Toulouse, Lille, Lyons and Paris) participated in this cooperative study which was both retrospective and prospective. Grid case forms were sent to homogenise the date provided. Two hundred and sixty nine cases of symptomatic lumbar canal stenosis were collected; 89 (33 per cent) had hyperostosis. Hyperostosis was definite in 74 cases and probable in 15 other cases. Certain radiological and/or CT scan morphological factors seen frequently in the hyperostosis patients group led us to undertake a second study in 2 of the 5 centres (Montpellier and Toulouse) in order to identify their specificity. Twenty eight items were adopted and studied by 3 different evaluators (2 rheumatologists and one radiologist) in the X-ray films and CT scan documents of 100 patients with acquired lumbar canal stenosis with or without hyperostosis (46 and 54 cases respectively). The most discriminative appearances, which we suggest as diagnostic criteria of narrow lumbar canal with hyperostosis concern anterior and/or posterolateral marginal somatic bone proliferations on the non-articular surfaces of the posterior apophyses and ossifications of the posterior joint capsule and of the ligaments (ligamentum flavum--posterior longitudinal ligament--supraspinous ligament). Four of these 6 criteria are necessary to make the diagnosis of lumbar stenosis with hyperostosis. The radiological and CT scan appearances of lumbar hyperostosis appear to differ from ordinary degenerative changes of osteoarthrosis and hyperostosis may be held responsible for compression of the dural cul-de-sac.