Posterior radial head dislocation without ulnar fracture

Posterior radial head dislocation without an ulnar fracture in an adult is a rare injury. The pathology is often unrecognized initially. The patient’s resultant elbow motion becomes severely compromised. Prompt diagnosis and reduction of the dislocation yield excellent results. A review of the biomechanical studies of the elbow ligaments enables us to propose a pathophysiological model of this injury, and a case report and review of the literature are presented. © 1990 Raven Press, Ltd., New York

MR scanning of the acutely injured knee: Sensitive, but is it cost effective?

Although magnetic resonance (MR) imaging has been established as an accurate diagnostic modality for knee pathology, the cost-effectiveness of this test is not known. In this investigation, we formulated a mathematical equation to assess cost-effectiveness and then used this formula to evaluate the use of knee MR as a diagnostic modality in acute knee injuries. We analyzed 105 consecutive MR scans performed at an imaging center with a diverse referral base, and identified 63 patients who had had symptoms for less than 6 months. Based on average regional medical costs, we calculated that diagnostic arthroscopy is more cost-effective than MR if 78% of the scanned patients eventually undergo arthroscopy. In our study population, 87% had arthroscopy after the MR scan. Therefore, in this patient cohort representing a diverse orthopedic community, arthroscopy alone would have been more costeffective. Careful analysis in this type of cost-benefit framework would be beneficial and may lead to the establishment of objective criteria by which MR can be used in the most cost-effective manner. © 1990

Retinyl acetate–induced arthritis in C3H‐A\u3csup\u3evy\u3c/sup\u3e mice

Severely impaired musculoskeletal mobility in C3H‐Avy mice was noted during a pharmacologic trial evaluating the antitumorigenic properties of retinyl acetate (RAc). To determine the etiology of this impairment, we studied 103 female C3H‐Avy mice that were fed RAc in daily doses of 75–300 μg or placebo and were killed after 3–16 months. Whole‐body radiographs and histologic sections of the hindlimbs were scored for presence and severity of arthritis. C3H‐Avy mice treated with RAc in any dose had a significantly higher incidence of arthritis than placebo‐treated mice. Histologic evidence of enthesopathic disease closely paralleled the radiographic changes and ranged from small enthesophytes at tendinous and capsular insertions to complete periarticular bony bridging. Articular cartilage was not grossly affected. The incidence and severity of arthritis were significantly correlated with the total dose of RAc administered. The bony metaplasia induced by RAc was similar to the pathologic changes caused by other retinoids. This model may be useful for studying the pathogenesis of periarticular bone formation in diffuse idiopathic skeletal hyperostosis and related syndromes. Copyright © 1989 American College of Rheumatolog