Resistance to lateral luxation of two canine total elbow replacement systems under variable mechanical loads.

Objective: To measure the loads required to induce lateral luxation of the Iowa State University (ISU) elbow implant, a modified elbow implant, and the normal canine elbow with the ligaments and joint capsule removed.

Study Design: Mechanical testing on cadaveric specimens

Sample Population: Twelve thoracic limbs were harvested from adult, medium sized dogs that had been euthanatized for reasons unrelated to the study.

Methods: The torque needed for luxation was identified on potted cadaver elbows under variable axial load and compared to ISU implants and modified implants. Shear force needed to induce medial and lateral luxation were collected for the 2-implant designs at 10, 109, 209, and 342 N of axial load based on. Shear force needed to induce lateral luxation were collected for the normal elbows (with and without an anconeal process) at 10 N of axial load.

Results: The modified implant had 5× higher torque at luxation than the ISU implant and cadavers elbows for both internal and external rotation. Luxation during shear testing was significantly higher in cadaver elbows when compared to either implant but the modified implant was 4-7× more resistant then the ISU implant.

Conclusion: The modified total elbow replacement implant may reduce lateral luxation in vivo by increased resistance to shear and torsional forces.