Introduction. Precise knowledge of the Femoral Head (FH) arterial supply is critical to avoid FH avascular necrosis following open and arthroscopic intra-capsular surgical procedures about the hip. The Medial Femoral Circumflex Artery (MFCA) provides the primary FH vascular contribution. Distribution of vascular foramina at the Femoral Head-Neck Junction (FHNJ) has been reported previously using an imaginary clock face. However, no quantitative information exists on the precise Capsular Insertion (CI) and intra-capsular course of the MFCA Terminal Branches (TBs) supplying the FH. This study seeks to determine the precise anatomic location of the MFCA's TBs supplying the FH, in order to help avoid iatrogenic vascular damage during surgical intervention. Methods. In 14 fresh-frozen cadaveric hips (9 left and 5 right), we cannulated the MFCA and injected a polyurethane compound. Using a posterior approach, careful dissection of the MFCA allowed us to identify and document the extra- and intra-capsular course of the TBs penetrating the FHNJ and supplying the FH. An H-type capsulotomy provided joint access while preserving the intracapsular Retinaculum of Weitbrecht (RW), followed by circumferential capsulotomy at the acetabular margin exposing the FH. The dome of the FH was osteotomized 5 mm proximal to the Articular Border (AB) providing a flat surface for our 360° scale. Right-side equivalents were used for data processing. Results. Gross dissection revealed a constant single branch arising from the transverse MFCA penetrating the capsule at the level of the anterior-inferior neck at 177° (range 167–187°), then courses within the medial RW obliquely (elevated from the neck) to the posterior-inferior FHNJ (Figure 1). This vessel was found to have an average of 5 TBs (range 3–9) penetrating the inferior FHNJ 4 mm (range 1–7 mm) from the AB at 204° (range 145–244°; 14% . 10. /. 69. anterior; 86% . 59. /. 69. posterior). In 79% (. 11. /. 14. ) of specimens, an average of 1.5 branches (range 1–3) arising from the ascending MFCA entered the Femoral Capsular Attachment (FCA) at 244° (range 216–269°), running subsynovial through the neck, and terminating in 2 TBs (range 1–3) penetrating the inferior-posterior FHNJ 5 mm (range 3–9) from the AB at 254° (range 207–281°). The deep branch of the MFCA penetrated the FCA at 327° (range 310–335°) providing an average of 6 TBs (range 4–9) running subsynovial and within the lateral RW, finally penetrating the superior FHNJ 6 mm (range 4–9) from the AB at 339° (range 286–25°; 20%. 15/74. anterior; 80%. 59/74. posterior). Discussion and Conclusion. This study demonstrates that TBs of the MFCA penetrate the joint through the mid-substance of the capsule (from the transverse MFCA) or the FCA (from the ascending or deep MFCA). Once intra-capsular, these vessels course subsynovial or within the RW and terminate at the posterior FHNJ superiorly (from the deep MFCA) and inferiorly (from the ascending and transverse MFCA). Any surgical hip intervention should preserve the posterior FCA, and lateral and medial RW in order to preserve the FH vascular supply. These results illustrate a vascular danger zone that should be respected during surgery and can be easily interpreted with the commonly used clock face

This study investigates and defines the topographic anatomy of the medial femoral circumflex artery (MFCA) terminal branches supplying the femoral head (FH). Gross dissection of 14 fresh–frozen cadaveric hips was undertaken to determine the extra and intracapsular course of the MFCA’s terminal branches. A constant branch arising from the transverse MFCA (inferior retinacular artery; IRA) penetrates the capsule at the level of the anteroinferior neck, then courses obliquely within the fibrous prolongation of the capsule wall (inferior retinacula of Weitbrecht), elevated from the neck, to the posteroinferior femoral head–neck junction. This vessel has a mean of five (three to nine) terminal branches, of which the majority penetrate posteriorly. Branches from the ascending MFCA entered the femoral capsular attachment posteriorly, running deep to the synovium, through the neck, and terminating in two branches. The deep MFCA penetrates the posterosuperior femoral capsular. Once intracapsular, it divides into a mean of six (four to nine) terminal branches running deep to the synovium, within the superior retinacula of Weitbrecht of which 80% are posterior. Our study defines the exact anatomical location of the vessels, arising from the MFCA and supplying the FH. The IRA is in an elevated position from the femoral neck and may be protected from injury during fracture of the femoral neck. We present vascular ‘danger zones’ that may help avoid iatrogenic vascular injury during surgical interventions about the hip.

Cite this article: Bone Joint J 2015;97-B:1204–13.