Experimental osteoarthritis induced by selective myectomy and tendotomy.

A new model of osteoarthritis has been developed that utilizes an extraarticular surgical technique to alter gait and weight-bearing capabilities in the hind limbs of experimental animals. Guinea pigs, averaging 650 gm in weight, were subjected to unilateral resection of a segment of the gluteal muscles at the sacral origin, to section of the infrapatellar ligament, or to both procedures. Progressive changes consistent with osteoarthritis developed over 10-24 weeks as judged by gross, radiologic, and microscopic findings. In addition, an increase in mean cartilage water content and 35SO4(-2) incorporation into proteoglycans by 10 and 14 weeks, respectively, were consistent with the chemical changes observed in early osteoarthritis. Abnormalities developed not only in the operated hind limb, but in the contralateral, unoperated hind limb at a slightly later time. Thus, this animal model provided the opportunity to evaluate a mild gait abnormality and other biomechanical influences on the evolution of osteoarthritis which is uninfluenced by any intraarticular joint trauma.

Classic gout in Hageman factor (Factor XII) deficiency.

A 62-year-old man with a typical history of gout was admitted to the hospital with left-sided hemiplegia. His serum uric acid level was 10.3 mg/dL, his partial thromboplastin time was 198 s, and his Hageman factor (factor XII) coagulant activity and antigen were less than 1% of normal. Aspiration of synovial fluid from his inflamed knee disclosed urate crystals and abundant leukocytes but an absence of Hageman factor antigen. The presence of acute gouty arthritis in a patient with Hageman trait challenges the role of Hageman factor in the pathogenesis of gouty arthropathy.