Abstract
An anatomical cementless stem sometimes does not fit the femur of Japanese osteoarthritis (OA) patients due to deformity of the proximal femoral canal.
In order to develop a new stem, we performed morphological analysis of 36 normal femora and 113 OA femora by using a computer aided design system and a three-dimensional canal fill ratio of anatomical stem was calculated.
Thirty-six normal femora and 113 OA femora were reconstructed from 3D-CT data by using a computer aided design system. We analyzed each femur, and it became clear that there are 3 types of proximal femur in Japanese OA patients. In typeI, the configuration is the same as normal (42%). In typeII, the medial cortex is more steep (29%). In typeIII, the posterior cortex inclines anterior (26%). We chose 5 femora of the same size from each of the three types, and applied the anatomical stem of the most suitable size to each femur in the computer, we then calculated a three-dimensional canal fill ratio of the anatomical stem in the proximal portion of femoral canal.
The mean canal fill ratio was 76.4% in typeI, 60.0% in typeII, and 57.2% in typeIII. The canal fill ratio in typeI was significantly higher than the other types.
It is thought that to fill the proximal femoral canal with cementless stem is important to stabilize the stem and can lead to a good result. The anatomical stem fitted for the typeI, but did not fit for typeII and III, so we must consider developing a more suitable stem for typeII and typeIII.
The abstracts were prepared by Nico Verdonschot. Correspondence should be addressed to him at Orthopaedic Research Laboratory, University Medical Centre, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
