Morphological Measurement of Supracondylar Femur Based on Digital Technology in Chinese Han Population

Relatively few studies have reported on the morphology of the supracondylar femur, which is a fundamental factor affecting prosthetic reconstruction. The objectives of the present study were to measure the morphological parameters of the supracondylar femur, to classify the supracondylar femur, and to provide theoretical guidance for the development of distal femoral prostheses.

The study consisted of 82 patients of Han Chinese nationality in North China. There were 57 men and 25 women included in the study, with an average age of 50.9 years (range, 18-87 years). Effective CT data should include a range of more than 10 cm for the distal femur. CT data for the right distal supracondylar femurs was obtained from DICOM files. Results for the cancellous bone and marrow cavity were retained, and information for the cortical bone was erased to obtain information of the lumen. Measurements of the intracortical cavity have not been reported previously. Lumen models were reconstructed with Mimics 17.0 software. The surfaces of the lumen models were smoothed with Geomagic studio 12.0 software. Using the Solidworks 2014 software, we established a 3-D coordinate system, where variables of the lumen were examined. Correlations between the various measurements were calculated.

The supracondylar region of the femur was divided into five levels, and the length, breadth, height, and angle values were measured at each level. There were strong correlations between the length indexes (transverse diameter [EF], medial anteroposterior diameter [AC], middle anteroposterior diameter [GH], and lateral anteroposterior diameter [BD]) and the volume index (V). There were also strong correlations among the length indicators (EF, AC, GH, and BD) in each layer. Angle γ was correlated with the lateral anteroposterior diameter (BD) at L2-L6 layers (r = -0.383, -0.385, -0.296, -0.258, -0.24; all P < 0.05) and with the height index (h) at L4-L6 layers (r = -0.244, -0.385, -0.506; all P < 0.05). The most representative parameters were the medial anteroposterior diameter (AC₂ R₂ = 0.865; AC₆ R₂ = 0.932), the coronal width ratio, and the sagittal width ratio with volume. The analysis found that the lumen shape of flower-top hat accounted for 81% at most.

The supracondylar femur has an asymmetrical structural area. The coronal plane is dominated by a flowerpot-like morphology, and the sagittal plane is narrowest in the lateral 1/3 and resembles a top-hat-like morphology. Our results provide theoretical guidance for developing distal femoral prostheses and for their clinical application.