5 degrees to 6 degrees of distal femoral cut for uncomplicated primary total knee arthroplasty: is it safe?

The angle formed between the anatomical axis and mechanical axis of the femur determines the angle of resection of distal femur in total knee arthroplasty. The objective of this study was to analyse the safety of the routine practice of selecting 5-6 degrees of valgus for distal femoral cut during uncomplicated primary total knee arthroplasty. A retrospective study was undertaken involving a review of pre-operative CT scout films of osteoarthritic knees in 83 consecutive patients (44 males and 39 females; mean age 70 years) who presented for total knee arthroplasty. The anatomical and mechanical axis of femur were plotted on CT scout films and the angle between the two femoral axes were measured. Mean femoral axes angle was 5.4 degrees (range 3.3-7.6 degrees, SD 0.9 degrees). Estimated 95% confidence interval of the mean for the population was 5.2-5.6 degrees. There were no significant differences for age, gender or laterality of the limb. The routine practice of selecting 5 degrees to 6 degrees of the distal femoral cut for an uncomplicated primary total knee arthroplasty is safe.