[Reoperation after failure of unicompartmental knee prosthesis. Therapeutic strategy and results based on 40 cases]

Forty revisions for failure of unicompartmental knee prostheses were assessed. Twenty-eight women and twelve men (mean age: 67 years) were reoperated. Failure of an medial single-compartment prosthesis was involved in 35 cases, of a lateral prosthesis in 5 cases. The initial prostheses had been cemented in 19 cases and uncemented in 21 cases. Preoperative functional conditions were assessed by Hungerford's functional score and a 200-points score. The radiological study before revision showed 35 cases of varus distortion; in 12 of these, the varus distortion exceeded 10 degrees. Rather than studying the causes for failure of the single-compartment prosthesis, it seemed more useful to try to define the adequate reoperation procedure strategy and analyze its results. Our procedure aimed at solving the following difficulties: surgical approach: the same incision as in the initial operation was performed, the primary prosthesis was removed and a two-stage treatment was justified in cases of infection, metallosis involved complete removal of debris, the problem of bone-recutting and, chiefly, the problem of residual bone defect requiring bone-graft. Bone-recutting was performed with the tibial and femoral elements of the primary prosthesis still in place and using the ancillary equipment of the new prosthesis. Bone defects involved the femur as often (14 cases) as the tibia (12 cases); tibial bone defects occurred more frequently with cemented prostheses (9 cases) than with uncemented prostheses (3 cases). Femoral graft being relatively easier to perform one of the two major difficulties in our strategy was the achievement of a tibial graft.(ABSTRACT TRUNCATED AT 250 WORDS)