Early stabilization of the uncemented Symax hip stem in a 2-year RSA study.

Background and purpose - The uncemented Symax hip stem has shown early proximal ingrowth as result of the BONIT-hydroxyapatite (HA) coating and the distal DOTIZE surface treatment. We evaluated 2-year postoperative radiostereometric analysis (RSA) migration of the Symax hip stem in THA patients. We also investigated the correlation between migration at 4 weeks and clinical outcomes after 2 years.Patients and methods - Patients in a 2-year clinical follow-up single-centre RSA randomized controlled trial were randomized to 2 different cup designs. All 45 patients received a Symax hip stem. RSA migration patterns of the Symax hip stem is presented here as a single cohort. RSA examinations were performed postoperatively, but before weight-bearing, and subsequently after 1, 3, 6, 12, and 24 months. Clinical outcomes and radiographic evaluations were assessed 3, 6, 12, and 24 months postoperatively.Results - During the first 4 weeks, the Symax hip stem subsided, rotated into retroversion, and translated posteriorly, after which the migration ceased and the prosthesis stabilized. All clinical outcomes improved from preoperatively to 2 years. There was no clinically or statistically significant correlation between subsidence and retroversion at 4 weeks and clinical outcomes after 2 years.Interpretation - RSA evaluation of the uncemented Symax hip stem confirms that the design principles and coating properties lead to early stabilization of the stem, as early as 4 weeks postoperatively. There was no correlation between subsidence and retroversion at 4 weeks and clinical outcomes after 2 years. Based on the predictive potential of the RSA technique, we anticipate excellent long-term survival of this hip stem.

Brachygnathia superior and degenerative joint disease: a new lethal syndrome in Angus calves.

Brachygnathia superior and generalized diarthrodial degenerative joint disease were seen in 17 related, purebred Angus calves ranging in age from 2 days to 4 months. Craniometrical studies revealed decreased maxillary and palatine bone lengths and increased cranial, skull, and facial indices. Radiological evaluation of major appendicular joints demonstrated lipping of the joint margins with osteophyte formation, sclerosis of subchondral bone, and narrowing of joint spaces. Synovial fluid evaluation indicated joint degeneration but no etiologic agent. Rheumatoid factor analysis of plasma was negative. Grossly, all major appendicular joints were defective including the atlanto-occipital articulation. Lesions ranged from loss of surface luster to erosions and deep ulcers with eburnation of the subchondral bone and secondary proliferative synovitis. Histological changes were degeneration of the articular cartilage matrix, chondrocyte necrosis, flaking and fibrillation, chondrone formation, erosions and ulcers of the articular cartilage with subchondral bone sclerosis, vascular invasion with fibrosis, and chronic, nonsuppurative, proliferative synovitis. Growth plates had defective chondrocyte proliferation and hypertrophy with aberrant ossification of calcified cartilaginous matrix. Histochemical analysis of cartilage and bone failed to incriminate which component was defective, glycosaminoglycan or collagen, but indicated different distribution or absence of one or the other. Genealogic studies revealed a genetic basis for the new defect.