Cementless fixation of prosthetic components in total arthroplasty of the knee and hip.

An appropriately designed implant can be fixed without cement to accurately prepared bone surfaces so as to give results comparable with those of cemented fixation in the short term. The unchanging appearance of the roentgenograms suggests that these results may be maintained in the long term. If these conclusions are valid, polymethylmethacrylate (PMMA) may be thought of as an optional alternative in joint arthroplasty. Thus, theoretically, inert materials, e.g., carbon, can be directly interfaced with the skeleton. Since the authors have achieved interlock with viable bone without relying on bony ingrowth, these materials need not be porous. It is strongly suspected (but as yet unsupported by data) that adequate fixation can be obtained without relying even on the authors' relatively unsophisticated finned peg, provided that (1) the overall shape of the implant achieves interlock on the gross scale, with acceptably low shear stresses at the interface; and (2) the surgical technique achieves a correctly positioned implant applied to accurately cut bone surfaces. However, if for any reason accurate bone cuts can not be achieved, the authors advocate use of PMMA as a valuable fixation agent.