Femoral and tibial subchondral surface morphology has been extensively studied to aid in anatomically correct total knee arthroplasty (TKA) implant design. Emphasis has been placed on shape variations in individual bones, and person-to-person variability in joint conformity has been overlooked. The purpose of this study is to 1) determine individual variability in key measures of tibiofemoral joint conformity, and 2) determine whether variability differs by sex or race.
Laser-scanner-generated surface models of tibiofemoral joints were obtained from 165 archival skeletons (at death: age 28.8±7.6years; 85 African-American, 80 Caucasian, 86 men, 79 women). Ratios and correlations were determined among related femoral and tibial subchondral surface areas (SA), alignment, curvatures, and linear dimensions between opposing surfaces with stratification by race and sex.
Anterior-posterior length (R=0.80, p<0.001) and medial-lateral width (R=0.93, p<0.001) were the only linear measures that were highly correlated between the femur and tibia. Tibial and femoral surface areas were correlated among Caucasian men only (R=0.58, p<0.001; R<0.20), with a wide range of surface area ratios regardless of sex or race (SA ratio total sample: 2.32±0.39, range 1.36 to 3.62).
There is high individual variability in tibiofemoral joint conformity at the subchondral surface, and for some measures this variability is sex-or-race specific. Key measures of joint conformity including surface area, curvature, width, and depth covary weakly or not at all, and a wide range of TKA component sizes and shapes would be required to accurately replicate native joint conformity in most people.