Improved fit by asymmetric tibial prosthesis for total knee arthroplasty

The adequacy of the fit of the prosthesis to the tibia is an important variable in the outcome of total knee arthroplasty. A good fit covers the cancellous bone of both condyles, involves the denser bone of the tibial shell, but does not overhang beyond the bone at any point. In this research, an anatomically shaped tibial prosthetic base plate was developed from tibial measurements. A series of five template sizes, chosen to fit our patient database, was then evaluated for fit in the operating room by one surgeon. The assessment included bone exposure and the overhang of the prosthesis beyond the bone perimeter. The measurements of overhang or bone exposure were analysed. A commercial prosthesis was used as a control. An asymmetrical tibial plate conformed well to the anatomical shape of the resected upper tibia resulting in very little exposed bone and very few cases of overhang. The absence of such overhang provides better function in the surrounding stabilizing soft tissues, and so permits recovery of the maximum range of motion post-operatively.