Contact Mechanics and Three-Dimensional Alignment of Normal Dog Elbows

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 degrees, 135 degrees, and 155 degrees elbow flexion, with the antebrachium in a neutral position, in 28 degrees supination, and in 16 degrees 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 (1.83.2 mm) closer to the apex of the medial coronoid process in pronation and 2.0 mm (1.82.2 mm) farther away in supination. The radial head and medial coronoid process rotated 5.4 degrees and 1.9 degrees internally during pronation and 7.2 degrees and 1.2 degrees externally during supination. Conclusions Contact mechanics and 3D alignment of normal dog elbows varied significantly at different elbow poses.