In vitro determination of contact areas in the normal elbow joint of dogs

Objective-To evaluate areas of articular contact of the proximal portions o f the radius and ulna in normal elbow joints of dogs and the effects of axi al load on size and location of these areas. Sample Population-Forelimbs obtained from cadavers of 5 adult mixed-breed d ogs. Procedure-After forelimbs were removed, liquid-phase polymethyl methacrylat e was applied to articular surfaces of the elbow joint, and limbs were axia lly loaded. Articular regions void of casting material were stained with wa ter-soluble paint. Relative articular contact areas were determined by comp uter-assisted image analyses of stained specimens. Repeatability of the tec hnique was evaluated by analyses of casts from bilateral forelimbs of 1 cad aver. Incremental axial loads were applied to left forelimbs from 4 cadaver s to determine effects of load on articular contact. Results-Specific areas of articular contact were identified on the radius, the craniolateral aspect of the anconeus, and the medial coronoid process. The medial coronoid and radial contact areas were continuous across the rad ioulnar articulation. There was no articular contact of the medial aspect o f the anconeus with the central trochlear notch. Coefficients of variation of contact areas between repeated tests and between contralateral limbs was < 20%. Significant overall effects of axial load on contact area or locati on were not identified. Conclusions-Three distinct contact areas were evident in the elbow joint of dogs. Two ulnar contact areas were detected, suggesting there may be physi ologic incongruity of the humeroulnar joint. There was no evidence of surfa ce incongruity between the medial edge of the radial head and the lateral e dge of the medial coronoid process.