Comparative experience with intramedullary and extramedullary alignment in total knee arthroplasty.

A comparative analysis of intramedullary and extramedullary alignment was performed in 72 consecutive total knee arthroplasties, using the Moreland Knee Instrument System adapted for the Synatomic knee (DePuy). Six measurements were made from full-length anteroposterior radiographs taken 3 months after operation. Thirty-five of 40 (87.5%) of the intramedullary aligned patients had correct alignment (defined as 4 degrees-10 degrees of femoral component valgus). Using the same criterion, 22 of 32 (68.8%) of the extramedullary aligned patients were correctly aligned. The difference between intramedullary and extramedullary alignment was statistically significant at P less than .1. A correct tibiofemoral angle was achieved in 88% of the intramedullary aligned patients, compared to 73% of the extramedullary aligned patients.