Estimation of Joint Incongruence in Dysplastic Canine Elbows Before and After Dynamic Proximal Ulnar Osteotomy

Abstract

To characterize joint incongruence in dysplastic canine elbows before and after dynamic proximal ulnar osteotomy (DPUO). Clinical, prospective study. Dogs (n = 10; 12 elbows) with ≥ 2 mm radioulnar incongruence (RUI), FCP, and/or OCD. Computed tomography in a nonload bearing position was used to generate in silico 3D models of the elbow joint before DPUO, and this was repeated after DPUO union (median 3 months postoperatively). On these models, RUI, humeroradial and humeroulnar subchondral joint space width (SJSW) as well as alignment of the proximal ulnar segment were investigated. RUI at the medial coronoid process (MCP) decreased (P = .001), while it increased at the lateral coronoid process (P = .0005), and remained unchanged at the level of the trochlear ridge (P = .25). SJSW at the MCP increased (P = .001), changing from focal joint space collapse preoperatively to a more homogeneous pattern of moderate SJSW at follow-up. The proximal ulnar segment rotated in all 3 planes with caudal tipping at the level of the osteotomy and varus deformity, while no axial translation could be noted. DPUO results in reduction of RUI and amelioration of focal contact area at the MCP. This effect is the result of a complex three-dimensional rotation of the proximal ulnar segment, rather than axial shift.