THE EFFICACY OF INTRAMEDULLARY FEMORAL ALIGNMENT IN TOTAL KNEE REPLACEMENT

The angle formed between the femoral anatomic axis and the femoral pro sthesis was measured on radiographs of 201 total knee arthroplasties. The radiographs were taken on a 51 inch x 14 inch cassette and had to have satisfactory centering and minimal rotation to be included. All t otal knee arthroplasties had intramedullary femoral alignment. The mea n femoral component angle (relative to the femoral anatomic axis) was 6.1 degrees valgus, with a standard deviation of 2 degrees and a range from 2 degrees to 12 degrees valgus. Seventeen knees (8.5%) had a fem oral component angle that was less than or equal to 2 degrees valgus o r greater than or equal to 10 degrees valgus. In 4 knees, medial femor al bowing of the distal third of the femoral shaft caused an excessive valgus cut. In 7 knees, a capacious femoral canal was present that po tentially allowed for divergence of the relatively undersized guide ro d in the canal. Overall, 8.5% of cuts were believed to be less than id eal. Preoperative radiographs of the entire femur should identify pati ents in whom errors are more likely and allow for templating the amoun t of distal femoral bone to be resected. Extra caution is needed in bo wed femora and in capacious femoral canals.