34th Annual Scientific Meeting proceedings

Introduction
Post-traumatic radioulnar synostosis is usually associated with decreased antebrachial pronation and supination angles. This motion is especially important in cats. The aim of this feline cadaveric study was to evaluate, if radioulnar synostosis decreases pronation and supination angles and if these reductions differ depending on the position of the synostosis on the radial diaphysis.

Materials and Methods
Fifty-four cadaveric feline thoracic limbs were mounted on a custom-built jig with the elbow and carpus flexed at a 90° angle. Radiographs of the forelimbs were performed to exclude any orthopedic disease prior to the mechanical tests. Radioulnar synostosis was imitated with a 2 mm cortical screw through the radius into the ulna in the proximal (Group-P; n=54), middle (Group-M; n=52), and distal (Group-D; n=53) radial diaphysis. The angles of pronation and supination were recorded after applying manually a two-finger tight rotational force to the metacarpus. Rotational tests were performed without a screw (Group-N) and with a screw in each position. 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 significantly between Group-N (129.5 ± 15.9°) and all groups with imitated radioulnar synostosis (p < .0001). Mean angles of rotation did not differ between the groups with imitated radioulnar synostosis. (Group-P: 35.6 ± 12.3°; Group-M: 37.0 ± 16.0°; Group-D: 39.9 ± 15.3°).

Discussion/Conclusion
Radioulnar synostosis significantly decreases antebrachial rotation, regardless of location.