Observer reliability in the arthroscopic classification of osteoarthritis of the knee.

We studied 19 videotaped knee arthroscopies in 19 patients with mild to moderate osteoarthritis (OA) of the knee in order to compare the intraobserver and interobserver reliability and the patterns of disagreement between four orthopaedic surgeons. The classifications of OA of Collins, Outerbridge and the French Society of Arthroscopy were used. Intraobserver and interobserver agreements using kappa measures were 0.42 to 0.66 and 0.43 to 0.49, respectively. Only 6% to 8% of paired intraobserver classifications differed by more than one category. Observer-specific disagreement was evident both within and between observers. A small, but significant, occasional variation was also seen. Although reliability may improve by an analysis of disagreement, it appears that the arthroscopic grading of early osteoarthritic lesions is inexact.

Adverse reaction to metal release from a modular metal-on-polyethylene hip prosthesis.

A 70-year-old man with an uncemented metal-on-polyethylene total hip prosthesis underwent revision arthroplasty 33 months later because of pain, swelling and recurrent dislocation. There appeared to be corrosion and metal release from the prosthetic head, resulting in pseudotumour formation and severe local soft-tissue destruction. The corrosion occurred at the junction between the titanium-molybdenum-zirconium-iron taper and the cobalt-chrome-molybdenum head, but the mechanism was unproven.

Effect of load on articular cartilage matrix and the development of guinea-pig osteoarthritis.

OBJECTIVE: To study the biochemical changes in the early development of primary guinea-pig knee osteoarthritis (OA) and its dependence on load. METHODS: Load distribution was modified with below-knee amputation or femur valgus osteotomy in 9-month-old guinea-pigs. Soft tissue sham operated animals served as controls. The composition of uncalcified and calcified articular cartilage at the medial and lateral tibial condyle was studied by analysing small and large proteoglycans (PG) by gel electrophoresis and sulfation pattern with high-performance liquid chromatography. Collagen concentration was also determined. RESULTS: The articular surfaces with a presumed higher load after surgery had a slight, but consistent, higher water content. Decreased load-on the ipsilateral medial condyle after femur osteotomy, and on the ipsilateral medial and lateral condyles following tibia amputation-was associated with an increased concentration of PGs, while this concentration decreased in condyles with increased load. Collagen concentration followed a similar pattern in the osteotomy group. In the amputated animals collagen concentration went down in all condyles, regardless of change of load. The aggregability and proportion of large and small PGs, the concentration of hyaluronan and the sulfation pattern of chondroitin sulfate was not affected by load. No consistent changes in PG, collagen or HA concentration, HA aggregability or sulfation pattern were seen in the calcified cartilage. CONCLUSIONS: Primary guinea-pig knee OA is a reproducible model similar to human OA. It develops slowly and biochemical changes seem to appear before the morphological lesions become evident. The biochemical events are affected by load redistribution and correlate closely to morphological changes. These changes eventually result in a cartilage devoid in aggrecan, as also has been demonstrated in advanced human OA. All of this makes primary guinea-pig OA a suitable model for studying early OA changes.