An Evaluation of the Load Bearing Capability of the Cancellous Proximal Tibia with Special Interest in the Design of Knee Implants

J.A. Johnson, W.H. Krug, D. Nahon, J.E. Miller, A.M. Ahmed, Montreal, Canada

29th Annual ORS, Anaheim, California, March 8-10, 1983

Abstract: In total knee arthroplasty, load is transmitted via the implant to the cancellous cortical system of the upper tibia. The capacity of this bone to sustain load is important to the long term survival of the reconstructed knee and failure of cancellous bone leads to subsidence of the implant.

It is the purpose of this study to measure the relative stiffness of cancellous bone in a highly detailed and discriminating fashion in the proximal tibia. The study emphasizes: 1) measurements in increments of about 5mm so that between 50 and 60 measurements are made across the cut surface of each tibia and repeated at various levels below the articular surface and 2) measurements are made at each site with the bone specimen "in situ" to retain the natural constraints provided by the surrounding bone.

Mechanical Consequences of Press-fitting or Cementing Keel Under Cemented Tibial Tray

M.A. Kester, Ph.D., Allendale, New Jersey, M.P. Kvitnitsky, M.S., Allendale, New Jersey, J.E. Dalton, M.S., New Orleans, Louisiana, S.D. Cook, Ph.D., New Orleans, Louisiana, and M.T. Manley, Ph.D., Allendale, New Jersey

Howmedica Osteonics Corporation, Literature Number LTSK7, 1994

Abstract: While most surgeons routinely cement under the tibial tray, it is often difficult to adequately pressurize the cement within the intramedullary canal and removal of this cement is difficult if revision is required. With improved keel designs, the question of whether to cement the keel has arisen. This question becomes increasingly important when the surgeon is faced with good quality bone.

The objective of this study is to compare the stability characteristics of a cemented tray under offset loads with either a press-fit or cemented keel within cadaveric specimens. Secondly, the effect of bone quality on tibial tray stability is addressed.