The Shape and Size of the Frmoral Canal in the Korean for Press Fit Femoral Stem

Ahn, Jin Hwan; Bae, Dae Kyung; Yoo, Myung Chul; Kim, Ki Tack; Ryu, Kyung Nam; Kim, Yong Jae; Yoo, Jin Wha

Abstract

It is very important to obtain a reliable geometric data of the femoral canal for designing femoral component in total hip arthroplasty. So authors estimated the shape and measured the size of the proximal femoral canal by using 3 dimensional images obtained from computerized tomographic data of 60 korean normal adult cadaveric femora. EXTRACT II PROGRAM VERSION 2.5 BY CORNELL UNIVERSITY at the SUN 3 WORK STATION was used for this study. The averge femoral length was 416.0±25.2mm ranging from 358.6mm to 465. 1 mm. The average femoral anteversion angle was 20.5±9.1°ranging from 2° to 36.5°. The average neck-shaft angle was 127.8±5.7°, ranging from 115.5° to 139.0°. The average length of femoral offset was 37.5±5.2mm. The average length of transverse diameter measured at the center of lesser trochanter was 29.4+3.5mm and measured at 20mm above the lesser trochanter was 47.3±4.6mm. The isthmic position was located at 109.4±13.1mm belew the center of the lesser trochanter and the average transverse diameter at the isthmic position was 12.1±2.1mm in mediolateral direction and 14.4±2.4mm in anteroposterior direction. The average of canal flare index which indicates the shape of proximal femoral canal, was 3.8±0.7; Stove-pipe shape was 8.4% normal shape was 70.0% and Champagne-flute shape was 21.6%. The press-fit hip stem design(PFC) had much more improved stem-canal contact on total and priority regions. And the other four devices had better fit proximally than distally and viceversa(proximal-distal mismatch). The improvement of fit can be achieved by considering the proximal-distal geometry of the femur more carefully and by diversifying the stem design which adapts to the anatomical variation of femur.