Revision knee arthroplasty. The limits of press fit medullary fixation.

Nonlinked (nonhinged) but constrained knee prostheses have been used with some success, usually by fully cementing narrow fixed stems in the medullary canal. Modular press fit stems augment fixation and limit cement to the cut bone surface. Forty-four revision knee arthroplasties were followed prospectively for 2 to 6 years. Thirty-one were reconstructed with posterior stabilized implants and 13 required constrained (condylar) articulations. Of these 13, 2 have been revised for loosening and another has radiographic evidence of impending loosening. All 3 were in patients who had reimplantations after a 2-stage protocol for infection, and none failed sooner than 3 years after surgery. No evidence of recurrent sepsis was observed. The press fit technique with limited cement use may not provide adequate fixation for the constrained condylar implant, especially when bone quality is poor.