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The Influence of an Anterior-Posterior Gliding Mobile Bearing on Range of Motion After Total Knee ArthroplastyA Prospective, Randomized, Double-Blinded Study
Christian Aigner, MD1; Reinhard Windhager, MD1; Michael Pechmann, MD1; Peter Rehak, PhD1; Klaus Engeleke, MD2
1 Department of Orthopaedic Surgery (C.A., R.W., M.P.) and Division of Biomedical Engineering and Computing (P.R.), University of Graz Medical School, Auenbruggerplatz 5, 8036 Graz, Austria. E-mail address for C. Aigner: christian.aigner@uni-graz.at
2 Orthopaedic Hospital Frohnleiten, Hauptplatz 3-5, 8130 Frohnleiten, Austria
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The authors did not receive grants or outside funding in support of their research or preparation of this manuscript. They did not receive 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.
Investigation performed at the University of Graz Medical School, Graz, Austria

The Journal of Bone and Joint Surgery, Incorporated
J Bone Joint Surg Am, 2004 Oct 01;86(10):2257-2262
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Background: Range of motion is a crucial measure of outcome after total knee arthroplasty. In order for maximum flexion to occur, the femur must progressively shift posteriorly on the tibia, a movement that is known as femoral rollback. Mobile bearings with free anterior-posterior translation could improve knee flexion by allowing such motion. The purpose of the present study was to determine the influence of an anterior-posterior gliding mobile bearing on the postoperative range of knee motion in patients with an intact posterior cruciate ligament.

Methods: We performed a prospective, randomized clinical trial of fifty consecutive total knee arthroplasties that were performed with use of the LCS-Universal prosthesis. Participants were randomized to receive either a deep-dish rotating platform or a mobile bearing that allowed additional anterior-posterior translation, the latter of which requires an intact posterior cruciate ligament. The ranges of motion of the knees were assessed to detect a 15° difference in the active non-weight-bearing range of motion with a power (1 — ß) of 20% and with the level of significance (a) set at 0.05. The translation of the mobile bearing was measured with use of a standardized ultrasound technique and was correlated with maximum knee flexion. The participants and the assessor were blinded throughout the study.

Results: At the time of the one-year follow-up evaluation, forty-eight knees were available for an intention-to-treat analysis. The mean active non-weight-bearing range of motion at one year was 113° (95% confidence interval, 108° to 118°) in the twenty-six knees that had received a rotating platform and 111° (95% confidence interval, 115° to 125°) in the twenty-two knees that had received an anterior-posterior gliding bearing (p = 0.57). In the latter group, a continuous rollback occurred in two knees. There was no significant correlation between knee flexion and anterior-posterior translation (r2 = 0.015).

Conclusions: The use of a mobile bearing that allowed free anterior-posterior translation did not regularly restore femoral rollback and did not improve range of motion after total knee arthroplasty compared with the findings seen in association with the use of a rotating platform.

Level of Evidence: Therapeutic study, Level I-1b (randomized controlled trial [no significant difference but narrow confidence intervals]). See Instructions to Authors for a complete description of levels of evidence.

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    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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