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° ±2° (range, 4°-14°). 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° ±2°. 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.