Contact Mechanics and Three‐Dimensional Alignment of Normal Dog Elbows

Abstract

OBJECTIVE: To evaluate the effects of antebrachial rotation at 3 elbow flexion angles on contact mechanics and 3-dimensional (3D) alignment of normal dog elbows. STUDY DESIGN: Ex vivo biomechanical study. ANIMALS: Unpaired thoracic limbs from 18 dogs (mean ± SD weight, 27 ± 4 kg). METHODS: With the limb under 200 N axial load, digital pressure sensors measured contact area (CA), mean contact pressure (MCP), peak contact pressure (PCP), and PCP location in the medial and lateral elbow compartments, and 3D static poses of the elbow were obtained. Each specimen was tested at 115°, 135°, and 155° elbow flexion, with the antebrachium in a neutral position, in 28° supination, and in 16° pronation. Repeated measure ANOVAs with post-hoc Bonferroni (P ≤ .0167) were performed. RESULTS: Both pronation and supination decreased CA by 16% and 8% and increased PCP by 5% and 10% in the medial and lateral compartments, respectively. PCP location moved 2.3 mm (1.8-3.2 mm) closer to the apex of the medial coronoid process in pronation and 2.0 mm (1.8-2.2 mm) farther away in supination. The radial head and medial coronoid process rotated 5.4° and 1.9° internally during pronation and 7.2° and 1.2° externally during supination. CONCLUSIONS: Contact mechanics and 3D alignment of normal dog elbows varied significantly at different elbow poses.