Effect of external rotational humeral osteotomy on the contact mechanics of the canine elbow joint

Abstract

OBJECTIVE:
To evaluate the effect of 15° external rotational humeral osteotomy (ERHO) on canine elbow joint contact mechanics.
STUDY DESIGN:
Ex vivo biomechanical study.
SAMPLE POPULATION:
Unpaired cadaveric canine thoracic limbs (n = 8)
METHODS:
Digital pressure sensors placed in a subchondral osteotomy distal to the elbow joint were used to measure contact area, peak and mean contact pressure, peak pressure location, center of pressure, and total force in the subchondral bone of the radius and the ulna. Measurements were taken in the following sequence: (i) neutral and (ii) after 15° external rotation. The distal aspect of the humerus was externally rotated by a middiaphyseal osteotomy and stabilized with an internal fixator. Data were normalized and analyzed using paired t-tests; P ≤ .05 was considered significant.
RESULTS:
Peak pressure location and center of pressure shifted 37.5 ± 15.9% and 21.5 ± 6.8% laterally after ERHO (P < .001 for both). Both were situated over the subchondral bone of the ulna in neutral position and over the radius after rotation in all 8 specimens (P < .001). Pressure measured in the ulnar part of the osteotomy was reduced from 58.7 ± 9.1% to 27.1% after ERHO (P < .001). Contact area, peak and mean contact pressure, and total force did not vary significantly between conditions.
CONCLUSION:
ERHO shifts the peak pressure location and the center of pressure laterally, toward the radial head and reduced the pressure acting on the ulna. The lateral shift of peak pressure may be beneficial in dogs with medial compartment disease.