The sagittal curvature of femoral shaft in young Chinese
Rong-Sen Yang1, Chen-Yu Lung3, Chao-Chang A. Chen4, Sheng-Mou Hou1, Cheng-Kung Cheng2
1Orthopedics, College of Medicine, National Taiwan University, Taipei, Taiwan; 2Institute of Biomedical Engineering, National Yang-Ming
University, Taipei, Taiwan; 3Institute of Rehabilitation Science and Technology, National Yang-Ming University, Taipei, Taiwan; 4Department of
Medical Engineering, National Taiwan Univ. of Science and Technology, Taipei, Taiwan
Int roduct ion: Many studies have fully investigated the geometry of
the proximal and distal extremities of human femur to design a proper
prostheses for total hip arthroplasty (THA) or total knee arthroplasty
(TKA). However, little focus has been placed on the geometry of midthird region of the femur which is used not only for the fixation of the
revision prostheses of THA or TKA but also of the tumor prostheses.
Most revision THA prostheses or limb salvage surgery used middle onethird of the femur to fix the prostheses. With the limb salvage surgery of
femur, the proximal 1/3 or distal 1/3 femoral bone was resected, then
reconstructed with a long segment fixed with an intramedullary stem in
the middle. A mismatched bowing angle between femur and prosthesis
stem may raise local stress and bone remodelling. In our eight years experience of limb salvage surgery, it is usually to see on the radiograph that
the tip of a intramedullary stem abutted the cortex of the femur.
Therefore, this study aimed to investigate the sagittal curvature of femur
of Chinese tumor patients for a proper implant design in the future.
Mater ials and Methods: Twenty lateral radiographs of the femur of
young chinese were digitized by a manual digital plate. The radii of
femoral curvature were calculated using the coordinates of three middle
points of proximal, middle or distal one-third (Sectional method).
Furthermore, the coordinates of the middle points of 10 equal sections
were used to sketch a curve with EXCEL, divided into equal one-third
(Global method). Ten points on each one-third were used to calculate the
curvature radii using nonlinear regression methods. Oneway ANOVA
was used to compare the means of radii of curvature (significance set as
p< 0.05)
Results: By the method 1, the results showed that the average radii of
curvature of the proximal, middle and distal one-third of the femur were
1571 mm (range 196~10,000 mm, SD 2309 mm), 1277 mm (range
659~1969 mm, SD 429 mm) and 1749 mm (range 248~7534 mm, SD
2055 mm), respectively (Table 2). The radii of all three sections showed
no significant difference (p > 0.05).
The average radii of curvature of the proximal, middle and distal onethird of the femur by method 2 were 5607 mm (range 846-10,000 mm,
SD 4155 mm), 1480 mm (range 751-2695 mm, SD 548 mm) and 1910
mm (range 439-10,000 mm, SD 2218 mm), respectively. The proximal
one-third of the femora was significantly less bowed than those of the
middle one-third and distal one-third (p<0.05).These radii were not significantly different (p> 0.05).
Discussion: Most of the oncology patients were quite young and had
mass bone resection during the surgery. For the limb salvage surgery, the
oncology prostheses were fixed with bone by insertion a curved stem and
cement. Therefore, whether the curvature of stem can fit with the bone is
quite important to the stress distribution of implant and cement and long
term fixation of the prostheses. In this study, the resection length ranged
from 75mm to 250mm that accounted for 17% to 59% of the total length
of femur. Therefore, the middle one-third of the femur became the most
important area to fix the implant. The curvature of the middle part of the
method calculated with two different methods were quite similar to each
other which was around 1200-1500 mm.
The mean and SD of curvature radii by Sectional method were divergent as in other studies. The Global method was more consistent in the
curvature radii of three sections. The radii of middle section by both
methods were similar. This data may be adopted in the designing of the
stem in the oncological prosthesis.
Ref erences: 1. Gilbert BM. Am J Phys Anthropol 1976; 45:601-4
2.
Tang WM, et J Orthop Res 2005; 23: 41-45
3.
Egol KA, et J Orthop Trauma 2004 18(7):410-15
4.
Harper MC, et CLin Orthop 1987; 220:155-61
5.
Bruns W, et Am J Phys Anthropol 2002; 119:224-30
Acknowledgements: This study was supported by the grant of
NSC92-2622-B-002-007, Taiwan, ROC.
Curvature of the femur in three sections, Unit: MM
Schematic picture of the saggital bowing curve in proximal, middle and distal onethird of the femur
Poster No. 490 • 6th Combined Meeting of the Orthopaedic Research Societies