Effects of simulated radioulnar synostosis on supination and pronation in cats. A cadaveric study.

Abstract

OBJECTIVE: To evaluate the effect of an induced synostosis with a screw on pronation and supination in cats. STUDY DESIGN: Ex vivo biomechanical study. SAMPLE POPULATION: A total of 58 feline forelimbs. METHODS: A total of 58 cadaveric feline thoracic limbs were mounted on a custom-built jig with the elbow and carpus flexed at a 90&#xb0; angle. To exclude any orthopedic disease, radiographs of the forelimbs were performed prior to the mechanical tests. Radioulnar synostosis was imitated with a 2&#x2009;mm cortical screw through the radius into the ulna in the proximal (Group P; n&#x2009;=&#x2009;54), middle (Group M; n&#x2009;=&#x2009;52), and distal (Group D; n&#x2009;=&#x2009;53) radial diaphysis. The angles of pronation and supination were recorded after manually applying a two-finger tight rotational force to the metacarpus. Rotational tests were performed without a screw (Group N) and with a screw in each of the aforementioned positions. Pairwise comparisons between the groups were performed based on their angles of rotation with a paired t-test with the Benjamini-Hochberg procedure and a mixed model ANOVA. RESULTS: Mean angles of rotation decreased between Group N (129.5&#x2009;&#xb1;&#x2009;15.9&#xb0;) and all groups with imitated radioulnar synostosis to a mean angle of 37.5&#x2009;&#xb1;&#x2009;14.5&#xb0; (p&#x2009;<&#x2009;.0001). Mean angles of rotation did not differ between the groups with imitated radioulnar synostosis. CONCLUSION: Induced radioulnar synostosis decreases antebrachial rotation by more than two-thirds, regardless of location. CLINICAL SIGNIFICANCE: Implants fixating the radius to the ulna should be avoided in cats, regardless where they are located along the radial diaphysis.