Anatomic compatibility of femoral intramedullary implants: a cadaveric study

The purpose of this study was to describe the morphology of the proximal and diaphysis of femur, distribution of neck version, neck-shaft angles, and radius of anterior curvature in a Turkish population to compare with that of femoral intramedullary implants.

Using 84 cadaveric femora, three-dimensional (3D) modeling was performed with a light scanner, data were transferred to Solidworks 2013 software (Solidworks, Waltham, MA, USA) to determine the variability in the femoral length (FL), neck version, neck-shaft angle (NSA), and anterior bow. Three independent observers' measurements were tested with a reliability analysis and then evaluated using Cronbach's alpha value, after which they were compared with the neck-shaft angles, and the radii of curvature (RAC) of intramedullary femoral nails, as stated on the official manufacturer websites.

Mean FL, femoral neck anteversion (FNA), and NSA had ranges of 346.1-454.1 mm, -11.3-40.4°, and 105.9-149.0°, respectively, and RAC was between 1.0 and 1.2 m. The correlation coefficient and 95% confidence intervals (CI) were 0.89 (CI 0.849-0.928), 0.86 (CI 0.799-0.904), and 0.85 (95% CI 0.785-0.898) for FL, FNA, and NSA, respectively. FNA was <10° in 32 femora (37.6%) and >14° 38 (44.7%). NSA was between 130° and 135° in 40 femora (47.1%), and RAC ranged from 0.5 to 1.5 m in 76 femora (91.6%), <1 m in 38 (45.8%), and >1.5 m in 7 (8.4%).

FNA and NSA show a wide distribution, mostly out of the range of intramedullary implants. There is a need for implants that are compatible with a range of NSAs and versions, so that they are suitable for use with a variety of morphologies.