Reliability of the hip-to-ankle radiograph in determining the knee and implant alignment after total knee arthroplasty.

Hip-to-ankle radiographs have been used to evaluate lower limb alignment before and after total knee arthroplasty. However, earlier studies have inappropriately used correlation to assess the reproducibility of the radiographs. We determined the reliability of the hip-to-ankle radiograph using the Bland-Altman analysis. Two consecutive hip-to-ankle radiographs were obtained in 52 patients (52 knees) after total knee arthroplasty. There was an excellent agreement between mechanical axis angles, tibiofemoral angles, and femoral and tibial component alignment in the two radiographs. There was also an excellent agreement between all intra and interobserver analyses. The hip-to-ankle radiograph appears to be a reliable and reproducible means for determining the alignment of the knee in the coronal plane after total knee arthroplasty. In routine follow-up, the short anteroposterior knee radiograph may provide sufficient information. However, only the hip-to-ankle radiograph provides accurate information on the weightbearing mechanical axis in patients with suspected lower limb malalignment.