Conformity and Polyethylene Damage in Total Knee Replacement Tibial Tray

Thomas P. Andriacchi, Ph.D., Raghu N. Natarajan, Ph.D.

Internal Document From Department of Orthopaedic Surgery, Rush-Presbyterian-St. Luke's Medical Center, Chicago, Illinois

Abstract: The purpose of this paper is to examine the mechanical factors associated with contact stresses and their relationship to the type of failure modes seen in total joint arthroplasty.

Although polyethylene debris has been reported in both hip and knee replacements, greater concern has been raised over the potential risk in the knee because of the less-conforming nature of the articulation.

In total knee replacement, complications associated with polyethylene wear debris are now recognized as one of the primary limitations to the longevity of the implant. These complications include foreign body reactions such as endosteal bone resorption which can lead to implant loosening.

One significant source of polyethylene wear debris is mechanical failure of the polyethylene component. However, mechanical failure is not necessary for the generation of this debris. In fact, it is possible for polyethylene debris to be generated without a complete mechanical failure of the polyethylene component.

Clearly, a better understanding of the factors leading to the generation of polyethylene debris in total joint replacements would help in the evaluation of current designs and provide insight for improving prosthesis designs. It will allow developers to focus on reducing the complications associated with polyethylene debris.

Wear Patterns on Tibial Plateaus From Varus and Valgus Osteoarthritic Knees

Melinda K. Harman, M.S., West Palm Beach, Florida; George D. Markovich, M.D., Portsmouth, Virginia; Scott A. Banks, Ph.D., West Palm Beach, Florida; and W. Andrew Hodge, M.D., West Palm Beach, Florida

Clinical Orthopedics and Related Research, Number 352, pp 149-158, July 1998

Abstract: The size and location of articular cartilage wear was assessed on 106 varus and 37 valgus osteoarthritic tibial plateaus resected during total knee arthroplasty. Anterior cruciate ligament integrity was assessed intraoperatively, and calibrated digital images were used to measure the wear patterns. Complete anterior cruciate ligament deficiency was seen in 25% of the varus and 24% of the valgus knees. Wear patterns on anterior cruciate ligament intact and attenuated varus tibial plateaus occurred in the middle to anterior aspect of the medial plateau. Anterior cruciate ligament deficient varus plateaus had significantly larger wear areas located more posterior on the medial plateau. In contrast, anterior cruciate ligament intact and deficient valgus tibial plateaus had wear located posterior to the center of the lateral plateau. Anterior cruciate ligament integrity is a discrete feature of advanced osteoarthritis that strongly influences the articular wear patterns. The anterior cruciate ligament deficient wear pattens show a wear mechanism that is consistent with the posterior femoral subluxation and posterior tibiofemoral contact observed after acute anterior cruciate ligament ligament rupture. These observations provide insight into the altered knee mechanics that exist in osteoarthritic knees and the resulting mechanical factors that contribute to degenerative changes.

Use of the Single Medial/Lateral Radius Design in Cemented Total Knee Arthroplasty: Clinical and Radiographic Results at 5-Year Follow-up

Lawrence G. Morawa, Charles W. Carpenter, Kamlesh S. Desai, Douglas R. Kerr, and Michael G. McClure, Michigan and New York

Seminars in Arthroplasty, Volume 7, Number 3 (July), 1996, pp 276-284

Abstract: A retrospective analysis was conducted on 88 cemented cruciate-sparing primary total knee arthroplasties with a mean follow-up of 5.6 years (range 3.9 to 7.1 years). At the latest follow-up, the mean Hospital for Special Surgery Knee Score was 86.5. Radiolucent lines greater than or equal to one mm in width were present in only two (2.4%) of the femoral views, five (6%) of the tibial anteroposterior views, and two (2.4%) of the tibial medial/lateral views. Osteolysis was not observed in any of the radiographic views. There were two revisions; one because of an early deep joint infection and one patellar component because of a traumatic postoperative patella fracture. These clinical and radiographic findings suggest that devices with a single medial/lateral radius design (increased femorotibial contact) may minimize the potential for the generation of polyethylene wear debris in total knee arthroplasty.

Maximizing Conformity Without Excessive Rotational Constraint in TKA

Z. Fishkin, L. Serpe, M.A. Kester, Allendale, New Jersey, O.M. Mahoney, Athens, Georgia, and T.P. Schmalzried, Los Angeles, California

45th Annual Meeting, Orthopaedic Research Society, February 1-4, 1999, Anaheim, California

Abstract: Traditionally, knee implant designers have advocated dual-radius condylar coronal geometry with highly conforming "tibial troughs" as a means of maximizing contact area. However, these designs may lead to high rotational constraint and incrased shear stresses during physiologic application of torque. The purpose of this study was to compare contact area and rotational constraint in a highly curved, dual-radius design versus a design incorporating a single mediolateral radius. It is hypothesized that a single mediolateral radius design may provide equivalent conformity, but without excessive constraint.