A new study demonstrates the connection between femoroacetabular impingement of the cam type and anteversion of the femoral neck. The study set out to assess the relationship between anteversion of the femoral neck and the alpha angle in an osteological collection of human femora. The University of Iowa–Stanford bone collection was used in order to address the aims of the research. Axial photographs of the proximal femora were used to measure the alpha angle and the anteversion of the femoral neck, the precise measurements were made with dedicated software, and the correlation between the alpha angle and femoral anteversion was made using statistical models.
A total of 1321 cadaveric femora from 721 cadaveric specimens were used. The mean alpha angle of all the femora was 47.8 ± 10.9° and the mean anteversion of the femoral neck was 8.53 ± 8.09°. In all, 191 of the 1321 femora showed cam-type morphology. Of the 721 cadaveric specimens, 600 had both femora available for a side-to-side comparison. The mean anteversion of the femoral neck in combination with cam-type morphology was statistically higher than in the femora without cam morphology, and the statistical analysis showed that an increased alpha angle was significantly associated with increased anteversion of the femoral neck.
The authors concluded that there is a positive correlation between the alpha angle and increased anteversion of the femoral neck. They commented that femoroacetabular impingement syndrome and cam morphology are more complex than the simple descriptions of cam and pincer morphology. Cam-type morphology in combination with increased anteversion of the femoral neck may allow normal or near-normal hip mechanics without impingement, and this may partly explain the high rates of asymptomatic patients with cam-type morphology in the general population. These findings show the pressing need for further research on this subject.
Source: “Arthroscopy”, August 2021