Should we resurface the patella in total knee replacement? Experience with the Nex Gen prothesis.

Patellar resurfacing is a controversial issue in primary total knee replacement. So, we took advantage of a large study to try and answer this question. An open prospective multicentric study was conducted about the outcome of the Nex Gen Total Knee prosthesis with clinical and radiological follow-up at regular intervals (1, 2 and 5 years). The data were centrally collected and analyzed by independent observers. A total of whole 5,915 cases were included (487 in the French group); incidences of patello-femoral pain were observed in both French and international groups and compared between cases with or without resurfaced patellae. Only osteoarthritic cases were selected for this particular study. Statistical analysis was performed using a Pearson's Chi-square test with a 95% confidence interval. The frequency of preoperative pain was significantly higher in the French group; 85.1% versus 66.6% (p<0.05). No patello-femoral pain appeared in preoperatively painless patients in the French group. The frequency of lateral patellar release was similar in both groups. 35.7% of the patellae were resurfaced in the international group versus 98.8% in the French one. At 2 years, patello-femoral pain was observed in 6.3% of cases in the former group versus 0.7% in the latter one. The risk of having patello-femoral pain was 9.45 times higher in the international group. When considering resurfaced cases in both groups the risk of having anterior knee pain was not significantly different (p=0.35). In the French group, one case out of nine (11.1%) with patello-femoral pain had not been resurfaced, while 129 cases out of 151 (85.4%) had not had a resurfacing in the international group. This emphasizes the effect of patellar implant on pain. Although patello-femoral pain is multifactorial, this analysis tool is powerful in getting rid of the "center effect " (cf Swedish register). Even if a longer follow-up for confirmation is needed, our data favor patellar resurfacing with this type of implant in spite of the fact that the trochlear design was considered as anatomical.