Differences in Femoral Medullary Canal Dimensions in the USA and East Asian Populations

With emerging technologies and improved operative techniques, cementless total hip arthroplasty is becoming more popular and showing better results. The femoral prosthesis and intramedullary nail should precisely fit in the medullary canal to prevent micromotion and loosening. Most of the femoral prosthesis and nail designs are made from the data obtained from Caucasian femur and may not press fit if used in Asian populations. This study compares the femoral medullary canal diameter in American and Oriental populations at different bony levels. A total of 245 dry femora were collected which included 47 from United States, 77 from China, 44 from Japan, 50 from Korea and 27 from Taiwan, and plan radiographs were taken. Radiographs were digitized to measure the medullary canal width at 20% (lesser trochanter; LT), 35% (supra-isthmus; SI), 50% (mid-isthmus; MI), 65% and 80% of the total femur length. The results revealed significant differences in the medullary canal width between the US and East Asian Oriental populations. The medullary canal in the US population was significantly larger at the LT, SI, MI, and 65% but significantly smaller at 80% of the femoral shaft length compared to the East Asian populations. Among the East Asian populations, significant differences were obse4rved between the Chinese and Taiwanese populations as well as the Japanese and Taiwanese populations. The Taiwanese population had the smallest femoral medullary canal size among the east Asian populations. We conclude that there are significant differences in the femoral medullary width between the American and East Asian populations. These results will be useful for surgeons operating on the proximal or distal femur.