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Intrinsic constraint of unlinked total elbow replacements--the ulnotrochlear joint
S Kamineni1, S W O'Driscoll, M Urban
1Orthopedic Biomechanics Laboratory, Mayo Clinic, 200 First Street S.W., Rochester, MN 55905, USA.
The Journal of Bone and Joint Surgery. American Volume
|September 6, 2005
Summary
This study compared the intrinsic constraints of unlinked total elbow replacement implants to the natural human elbow joint. The Souter-Strathclyde and Kudo implants most closely mimicked normal elbow biomechanics.
Area of Science:
- Orthopedic Surgery
- Biomechanical Engineering
- Biomaterials Science
Background:
- Numerous unlinked total elbow replacement designs with varying articular geometries exist, indicating a lack of consensus on optimal design.
- The intrinsic constraint of the implant's articular design is crucial for joint stability.
- A comparison between the intrinsic constraints of unlinked implants and the normal ulnotrochlear joint is needed.
Purpose of the Study:
- To compare the intrinsic constraints of five unlinked total elbow replacement designs with the native human ulnotrochlear joint.
- To evaluate how different implant designs affect elbow joint stability under varying loads.
- To identify which implant designs most closely replicate the biomechanical behavior of a healthy elbow.
Main Methods:
- Testing of twelve cadaveric ulnotrochlear joints using a custom multi-axis materials testing machine.
- Application of compressive loads (10-100 N) while moving joints in valgus and varus directions at 90° flexion.
- Measurement of torques, forces, and angular/axial displacements for five unlinked elbow replacement components (Ewald, Kudo, Pritchard ERS, Sorbie-Questor, Souter-Strathclyde) and native joints.
Main Results:
- Peak torque and constraint ratio increased with compressive load for both implants and native joints.
- In valgus: Souter-Strathclyde showed highest peak torque and constraint ratio; Sorbie-Questor had lowest peak torque; Ewald had lowest constraint ratio.
- In varus: Kudo showed highest peak torque and constraint ratio; Ewald had lowest peak torque and constraint ratio.
Conclusions:
- The constraint ratio effectively characterizes elbow joint behavior and allows comparison with implants.
- The Souter-Strathclyde and Kudo prostheses demonstrated biomechanical behavior closest to the human elbow.
- Implants mimicking human elbow appearance do not consistently replicate normal function; further research into elbow form and function is essential for improving prostheses.