Preoperative planning for implant sizes can help ensure proper implants are available as well as improve surgical efficiencies. The purpose of this study is to determine if patient gender and height can accurately predict the femoral size of the Oxford® knee.
3986 knees (2085 female and 1901 males) that underwent a medial unicondylar knee arthroplasty (UKA) with the Oxford® mobile bearing knee (Zimmer Biomet, Warsaw, Indiana) were reviewed. Patient gender and height were compared to operative reports of the implanted femoral component. The relationship of height and femur size was then compared to create a prediction table for implant size.
Females mean height was 64" (range, 48 to 78") and males mean height was 70" (range, 58 to 79"). In male patients, large implants were used in the majority of cases (76.6%). In female patients, small implants were used in the majority of cases (64.3%). Based on the relationship of height and femur size, two groups were created for each gender. In males: ≤66" = medium and ≥67" = large. In females: ≤64" = small and ≥65" = medium. Using these cutoffs, the correct implant would be chosen in 78.7% of cases (82.1% in males and 75.6% in females). Extra-small and extra-large sizes were used at the extremes of height in each gender, but never more commonly than small, medium, or large at any height.
Patient gender and height can accurately predict femoral size of the Oxford® knee in the majority of cases. Our findings validate the original report of this method.