[Mid-term behavior of the bone fixation in non-cemented Miller-Galante 1 total knee arthroplasty].

PURPOSE OF THE STUDY: This retrospective work was conducted to analyze the quality of the bone-implant interface at mid-term in 45 cases treated with a non-cemented Miller-Galante 1 total knee arthroplasty.
MATERIAL AND METHODS: All the protheses reviewed were implanted without cement. A patellar implant was cemented in 31.1 p. 100 of the cases. Female sex predominated in this series (77.5 p. 100) and the mean age at operation was 67 +/- 6 years. Pre- and postoperative assessment was based on the HSS score. Mean follow-up was 8.3 years (range 7-11 years). We used the method advocated by the International Knee Society to analyze lucent lines on tibial and femoral implants. Non-parametric tests were used for the statistical analysis with a significance level set at 5 p. 100.
RESULTS: The mean HSS score rose from 55 +/- 12 preoperatively to 80 +/- 13 postoperatively, with 62.2 p. 100 good or excellent results at last follow-up. One re-operation was required for aseptic loosening. The femoral implant presented a lucent line in 24.4 p. 100 of the cases at the first follow-up examination only. The tibial implant presented an anterior lucent line at the second follow-up examination then a medial line at the last follow-up in 22.2 p. 100 and 26.6 p. 100 of the cases respectively. Presence of a lucent line (tibial or femoral) on at least one view was significantly correlated with activity (p=0.01) and tibial slope (p=0.0087). DISCUSSION: The disappearance of the lucent lines seen on the femoral component at the second follow-up examination was the expression of its secondary integration. Inversely, we observed an evolution in the lines observed on the tibia. This was probably the result of posterolateral impaction and anteromedial ascension micromovements of the tibial component. An excessive tibial slope was statistically related to development of lucent lines. It increased tibial translation on weight bearing and probably induced an abnormal alteration of the polyethylene. We did not observe any case of massive osteolysis of the tibial metaphysis as described in the literature for non-cemented knee arthroplasties. The screws of the Miller-Galante 1 prosthesis do not protrude from the tibial implant (which would risk generating polyethylene debris) and the pieces used (screws and implants) are all made of the same metal.
CONCLUSION: The quality of primary fixation of the non-cemented Miller-Galante 1 tibial implant was not totally satisfactory at mid-term. Inversely, simple impaction of the femoral component was sufficient to ensure stable positioning.