Radiographic assessment of knee alignment after total knee arthroplasty

Standard anteroposterior standing radiographs (14 X 17-inch cassettes) and full-limb radiographs (51-inch) from a randomized group of 50 patients undergoing total knee arthroplasty between January 1985 and June 1986 were analyzed. The mean tibiofemoral angle on short films was 5.8 degrees valgus, compared with 7.2 degrees valgus on full-limb films. This 1.4 degrees discrepancy had a standard deviation of 2.2 degrees, emphasizing the measurement variability in any individual case. The distance from the knee center to the mechanical axis related linearly to the tibiofemoral angle. Twenty-six percent (13 of 50) of knee arthroplasties failed to achieve satisfactory postoperative alignment of 4-10 degrees valgus in this study.