COMPLETING THE PICTURE: A COMPREHENSIVE QUANTITATIVE ANALYSIS OF THE FEMORAL HEAD AND FEMORAL NECK BLOOD SUPPLY

Introduction The vascular anatomy of the femoral head and neck has been previously reported, with the primary blood supply attributed to the deep branch of the Medial Femoral Circumflex Artery (MFCA). This understanding has led to development of improved techniques for surgical hip dislocation for multiple intra-capsular hip procedures including Hip Resurfacing Arthroplasty (HRA). However, there is a lack of information in the literature on quantitative analysis of the contributions of the Lateral Femoral Circumflex Artery (LFCA) to femoral head and neck. Additionally, there is a lack of detailed descriptions in the literature of the anatomic course of the LFCA from its origin to its terminal branches. Materials & Methods Twelve fresh-frozen human pelvic cadaveric specimens were studied (mean age 54.3 years, range 28–69). One hip per specimen was randomly assigned as the experimental hip, with the contralateral used as a control. Bilateral vascular dissection was performed to cannulate the MFCA and LFCA. Specimens were assigned as either LFCA-experimental or MFCA-experimental. All specimens underwent a validated quantitative-MRI protocol: 2mm slice thickness with pre- and post- MRI contrast sequences (Gd-DTPA diluted with saline at 3:1). In the LFCA-experimental group 15ml of MRI contrast solution was injected into the LFCA cannula. In the MFCA-experimental group 15ml of contrast solution was injected into the MFCA cannula. On the control hip contrast solution was injected into both MFCA and LFCA cannulas, 15ml each (30ml total for the control hip). Following MRI, the MFCA and LFCA were injected with polyurethane compound mixed with barium sulfate (barium sulfate only present in either MFCA or LFCA on each hip). Once polymerization had occurred, hips underwent thin-slice CT scan to document the extra- and intra-capsular course of the LFCA and MFCA. Gross dissection was performed to visually assess all intra-capsular branches of both the MFCA and LFCA and assess for extravasation. Quantitative-MRI analysis was performed based on Region of Interest (ROI) assessment. Femoral heads were osteotomized at the level of the largest diameter proximal to the articular margin and perpendicular to the femoral neck, for placement of a 360° scale. Measurements using the 360° scale were recorded. For data processing, we used right-side equivalents and integrated our 360° data into the more commonly used imaginary clock face. Results Quantitative analysis of contributions of the MFCA and LFCA are detailed (Table 1). Thin slice CT scan graphical analysis of the LFCA provided (Figure 1). Topographic 360° scale (and imaginary clock face) results are also detailed in a diagram (Figure 2). Discussion This study provides the first comparative results for quantitative assessment of arterial contributions from both the MFCA and LFCA for the femoral head and neck. The MFCA is the dominant vessel for both the femoral head and neck, supplying 82% of the femoral head and 67% of the femoral neck. The LFCA plays its largest role in the inferoanterior femoral neck (with a 48% arterial contribution). This finding highlights the importance of protecting the LFCA in addition to the MFCA during intra-capsular hip procedures including Hip Resurfacing Arthroplasty.