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Can Normal Knee Kinematics Be Restored with Unicompartmental Knee Replacement?

¹ Orthopaedic Research Laboratories, Scripps Clinic Center for Orthopaedic Research and Education, 11025 North Torrey Pines Road, Suite 140, La Jolla, CA 92037. E-mail address for D.D. D'Lima: ddlima{at}scripps.edu

Investigation performed at the Orthopaedic Research Laboratories, Scripps Clinic Center for Orthopaedic Research and Education, La Jolla, California

In support of their research or preparation of this manuscript, one or more of the authors received grants or outside funding from DePuy, a Johnson and Johnson company, and from Alfred A. Smith and Susan Smith D. Richardson. None of the authors received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.

Methods: Six human cadaver knees were tested before implantation, after implantation with a bicruciate-retaining unicompartmental knee prosthesis, and after implantation with a posterior cruciate-retaining tricompartmental knee prosthesis. The unicompartmental prosthesis was initially implanted, and it was then revised to a total condylar knee replacement. The knee kinematics were measured with use of an electromagnetic tracking device while the knee was put through dynamic simulated stair-climbing under peak flexion moments of approximately 40 N-m. Quadriceps tension was also measured for all three conditions.

Results: No significant differences in tibial axial rotation were noted between the intact and unicompartmental conditions. However, tricompartmental replacement significantly affected tibial axial rotation (p = 0.001). Femoral rollback was not significantly affected by either unicompartmental or tricompartmental arthroplasty. Quadriceps tension was also similar among all three conditions.

Conclusions: In this in vitro cadaver study, the tricompartmental replacement significantly changed knee kinematics while the unicompartmental replacement preserved normal knee kinematics.

Clinical Relevance: The results of this in vitro biomechanical cadaver study suggest that the unicompartmental design has the potential to restore (or preserve) normal kinematic function better than tricompartmental implants. Restoration of normal knee function may benefit patient rehabilitation, extensor function, implant survival, and wear.

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