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

Abstract

ObjectiveTo evaluate the effect of an induced synostosis with a screw on pronation and supination in cats.Study designEx vivo biomechanical study.Sample populationA total of 58 feline forelimbs.MethodsA total of 58 cadaveric feline thoracic limbs were mounted on a custom‐built jig with the elbow and carpus flexed at a 90° angle. To exclude any orthopedic disease, radiographs of the forelimbs were performed 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 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.ResultsMean angles of rotation decreased between Group N (129.5 ± 15.9°) and all groups with imitated radioulnar synostosis to a mean angle of 37.5 ± 14.5° (p < .0001). Mean angles of rotation did not differ between the groups with imitated radioulnar synostosis.ConclusionInduced radioulnar synostosis decreases antebrachial rotation by more than two‐thirds, regardless of location.Clinical significanceImplants fixating the radius to the ulna should be avoided in cats, regardless where they are located along the radial diaphysis.