[Uncemented knee prosthesis. Results apropos of 58 cases with a minimum of 5-year follow-up].

PURPOSE OF THE STUDY

The aim of this study was to evaluate, after at least 5 year's follow-up, the results of 64 PCA (TM) cementless total knee prostheses.

MATERIAL

From 1984 to 1988, 13 male and 45 female patients (a total of 64 prostheses including 6 bilateral) received PCA Primary prostheses. Both femoral and tibial components were implanted without cement. Mean age of patients was 68.9 years (range: 35-81); mean patient height was 164.41 cm and mean weight 76.74 Kg. The most frequent pathology was gonarthrosis: 43 cases of medial gonarthrosis and 15 of lateral gonarthrosis. There were 4 cases of rheumatoid arthritis and two post-traumatic degenerative arthritis. 52 knees were free of any previous surgical procedure. Of the 64 prostheses and the 58 patients: 6 died and 2 were lost to follow-up; 56 knees were reviewed. The longest follow-up is 9 years for an average of 6.8 years.

METHODS

Prosthetic review included clinical evaluation (Hungerford score based on 100 points, ISK rate based on 200 points) and complete radiological evaluation enabling the postoperative position of the implants to be examined. Radiolucencies were examined according to Ewald. X-ray study of polyethylene wear was performed based on the distance between the prosthetic condyle to the height of the metal tibial plateau. All patients were operated on by the same surgeon using the same procedure, and the same postoperative outcome.

RESULTS

There were no local postoperative complications or any early reoperations. PHlebitis occurred in 12 per cent of cases. With the exception of 8 patients who were reoperated due to mechanical complications, the Hungerford score raised from 37.5 preoperatively to 88.3 postoperatively. The results of 43 of the 48 patients were rated good or excellent. The 200 point score rating gave 91 per cent of good and excellent results for knee examination, and 69 per cent of good and excellent results for knee function. Mean flexion angle was 107.8 degrees mean pain scored 45/50. Radiologically 75 per cent of operated patients had postoperative varus or valgus in the range 0-5 degrees as against 24 per cent preoperatively. The study of edge defects revealed the absence of any radiological abnormality on the femoral lateral projection in 85 per cent of cases, and the absence of abnormality on the tibial anteroposterior and lateral projections in more than 60 per cent of cases. X-ray study of polyethylene wear was conducted on 49 cases: polyethylene wear was observed radiologically in 1 of 4 cases. There was no correlation between polyethylene wear and polyethylene thickness, postoperative axes, body weight or clinical results. 8 patients had to be reoperated due to mechanical complications: 2 because of a tilting tibial plateau (due to a technical fault), 4 because of polyethylene wear and 2 because of patellar loosening (uncemented metal-back patellar implant).

DISCUSSION

The implantation of femoral and tibial components of cementless PCA Primary fitted seems very satisfactory. With longer follow-up, we noted no tibial or femoral osteolysis signs such as those described by Engh, Peters or Berry in the USA. Stability of mid term radiographical results was commonly observed throughout our study. Only 5 very slight lateral displacements were noted: 3 cases of secondary LCP insufficiency with tibial posterior subluxation; in 2 cases the cause was R.A.

CONCLUSION

The implantation of uncemented PCA Primary prosthesis caused non complications with respect to the femur. Regarding the tibia, only two reoperations were required because of tibial fixation failure due to a technical fault. The use of a hybrid prosthesis is not required. The microbeads used in PCA are effective but current availability of other materials promoting better bone growth (such as hydroxyapatite, titanium mesh) allows safe implantation of uncemented prostheses. PCA Primary polyethylene wear seems to develop steadily. This is why it should be replaced by the less