Variability of Distal Femoral Valgus Resection Angle in Patients with End-stage Osteoarthritis and Genu Varum Deformity: Radiographic Study in an Ethnic Asian Population.

Background: When performing a total knee arthroplasty, most surgeons use the intramedullary alignment guide with a fixed distal femoral valgus resection angle. In this study, we assessed the variability of the distal femoral valgus resection angle in ethnic Asian patients by reviewing our arthroplasty database. Methods: Between January 2004 and December 2012, the patients with end-stage osteoarthritis with genu varum deformity who underwent total knee arthroplasty were enrolled in this retrospective review. Clinical and radiographic data were collected and analyzed. Results: Nine hundred and fifty-two knees met the inclusion criteria. Three hundred and four (31.9%) knees had a distal femoral valgus resection angle value outside the range of 5 degrees 2 degrees (range, 4 degrees-14 degrees). There were significant differences in the mean distal femoral valgus resection angle between males and females (p < 0.001) and between non-bowed femur and bowed femur (p < 0.001) cohorts. With regard to the correlation coefficients between the distal femoral valgus resection angle and the usual radiographic measurements, only the coronal femoral bowing angle demonstrated a good correlation (r = 0.72). Conclusions: 32% of Asian patients present with a distal femoral valgus resection angle that is outside the range of 5 degrees 2 degrees. Taking a long-leg weight-bearing split scanogram may provide information that allows the surgeon to determine the true distal femoral valgus resection angle and adjust the cut accordingly. Level of Evidence: Therapeutic level III.