The Relationship of the Canine Femoral Head to the Femoral Neck: An Anatomic Study with Relevance for Hip Arthroplasty Implant Design and Implantation

Objectives: (1) To evaluate a novel method for characterizing the relationship of the canine femoral head to the femoral neck and (2) to determine whether the femoral head is symmetrically positioned upon the femoral neck. Study Design: Cadaveric study. Sample Population: Cadaveric dog femurs (16 dogs, 32 femurs) Methods: Femurs were photographed in frontal and sagittal planes simultaneously using 2 cameras positioned orthogonally. Ten measurements were made by 2 independent observers and agreement assessed by calculating intraclass correlation coefficients (ICC). Repeatability in specimen positioning was assessed by repositioning and imaging a single femur 10 times. Results: ICC values exceeded 0.6 for 8 of the 10 different measurements made. Mean +/- SD femoral head offset ratios in the frontal and sagittal planes were 0.14 +/- 0.08 and 2.66 +/- 1.16. The mean specimen positioning error (+/- SD) for the single specimen that was repositioned 10 times was 0.93 degrees +/- 1.92 degrees and 2.39 degrees +/- 1.13 degrees in the frontal and sagittal planes, respectively. Conclusions: Correlations between observers were moderately strong or strong for 8 of 10 measurements. Specimen positioning was repeatable. The offset ratios indicate that dogs have a substantial cranial and ventral offset of the femoral head from the femoral neck.