The Posterior Cruciate Ligament in Total Knee Arthroplasty

Joel I. Sorger, M.D., Doug Federle, M.S., Patrick G. Kirk, M.D., Edward Grood, Ph.D., James Cochran, Ph.D., and Martin Levy, Ph.D., Cincinnati, Ohio

Abstract: The purpose of this study was to answer 2 questions: Does the posterior cruciate ligament (PCL) produce femoral rollback in a single-design, cruciate-sparing total knee arthroplasty (TKA)? Does the PCL prevent posterior tibial displacement when it is retained after a single-design, cruciate-sparing TKA? Knee kinematics and limits of motion were measured with the knees in the following states: (1) intact knee, (2) anterior cruciate-deficient knee, (3) PCL-retaining total knee of a single design (TKA), (4) PCL-retaining TKA with PCL cut, and (5) PCL-substituting TKA. Femoral rollback was then calculated from the above data. The results showed that the PCL was able to prevent posterior translation and maintain femoral rollback when it was preserved during TKA. Therefore, the PCL can be functional after TKA, in a single-design, cruciate-sparing TKA. When the PCL was cut, significant changes in knee kinematics were observed.

The Effect of Conformity, Thickness, and Material on Stresses in Ultra-High Molecular Weight Components for Total Joint Replacement

By D.L Bartel, Ph.D., New York, New York, V.L. Bicknell, M.S., Ithaca, New York, and T.M. Wright, Ph.D, New York, N.Y.

The Journal of Bone and Joint Surgery, Volume 68-A, Number 7, September 1986, pp 1041-1051

Abstract: Debris resulting from damage to the surface of polyethylene components of total joint replacements has previously been show to contribute to long-term problems such as loosening and infection. Surface damage has been associated with fatigue processes due to stresses arising from contact between the metal and polyethylene components in these prostheses. In the present study, we used elasticity and finite-element solutions to determine these stresses for total hip replacements with head diameters of twenty-two and twenty-eight millimeters and for a condylar total knee replacement. We also examined the effect on these stresses of using carbon-fiber-reinforced polyethylene instead of plain polyethylene.

This study provides important guidelines for making choices between contemporary total hip and knee replacements. For example, when a choice is possible, the knee replacement that is most conforming in the medial-lateral direction should be chosen to minimize the risk of surface damage. Similarly, the risk of surface damage in total hip replacements should be less when a twenty-eight-millimeter head is used instead of a twenty-two-millimeter head. Whenever possible, the thickness of the polyethylene layer in tibial components for knee replacements should be at least eight to ten millimeters. Carbon-fiber-reinforced polyethylene should not be used for articulating components in total joint replacements.