[A unicompartment knee prosthesis: the effect of the positioning of the tibial plate on the functional results].

The authors analyse the results of 51 unicompartmental knee prostheses with 1 to 12 years follow-up (mean follow-up: 5 years). The results were evaluated using the scoring system of the "Knee Group" of the SO.B.C.O.T. (Société Belge de Chirurgie Orthopédique et de Traumatologie). This analysis demonstrates that the quality of the results depends on implant positioning. The authors suggest positioning the tibial implant parallel with the healthy plateau and slightly distal, i.e. to position the tibial implant perpendicular to the epiphyseal axis and not to the mechanical axis, as is systematically done with the usual tibial cutting guides. When this ideal positioning was respected, 77.5% of the patients had a score above 90 points (out of a possible maximum of 100 points) and 12.5% had a score between 75 and 89 points. When this condition was not respected, none of the knees obtained more than 75 points. The difference was statistically significant (p = 0.0001).