The femoral arterial system consists of the common femoral artery (CFA), superficial femoral artery (SFA), deep femoral artery (DFA), as well as the medial femoral circumflex artery (MFCA) and lateral femoral circumflex artery (LFCA) as two primary side branches. According to the common view of human anatomy, the DFA typically originates from the posterior or lateral aspect of the CFA approximately 2 to 5 cm below the inguinal ligament [1, 2]. The CFA continues as the SFA beyond the point of origin of the DFA. Initially, the DFA courses slightly laterally to the SFA, passing over the iliacus muscle, before taking a descending route with a gentle medial and posterior curve. This path places it over the pectineus and posterolateral to the SFA, with the accompanying deep femoral vein situated between the two arteries. At approximately the apex of the femoral triangle, the DFA passes behind the superficial femoral vein, and shortly thereafter, it courses deep to the adductor longus muscle along the medial side of the femur. Ultimately, the DFA concludes its course by giving rise to a small branch that perforates the adductor magnus muscle (i.e., fourth perforating branch).

It is known that DFA is liable to variations in its origin, course, and branches. These variations and their prevalence have been documented by frontier anatomists including Srb [3], Quain and Maclise [4], and Adachi [5], and revisited by many others to this date. The DFA arises from CFA at a variable height below the inguinal ligament, often around 5 cm below it (in 56% of cases reported by Srb) [3]. Srb [3] further noted that with an independent origin of the MFCA from the femoral artery, the origin of the DFA shifts downwards. The absence of DFA or its origin from external iliac artery is extremely rare [6, 7]. The trunk of DFA may course entirely dorsal (in 41% of cases reported by Adachi), medial or mediodorsal (in 12% of cases reported by Adachi) to the SFA [5]. The MFCA and/or whole or part of LFCA may independently arise from the SFA (in 66% of cases reported by Adachi), rather than originating from DFA. The perforating branches of DFA may vary in number and size. The DFA itself may be overdeveloped where its fourth perforating branch possesses a substantial caliber or, conversely, it may be underdeveloped and shortened, potentially lacking some of its distal perforating branches.

One “peculiar and striking” variation involves DFA or MFCA crossing superficially over the femoral vein within the oval fossa of the subinguinal region (below the inguinal ligament). This peculiar configuration has been described by Adachi as being a “great anatomical rarity” [5]. In a systematic study of 795 lower extremities, Adachi reported encountering 26 such variations, representing a prevalence of 0.5%. He additionally documented two special cases that featured an exceptionally unique arrangement of vessels within the oval fossa (Fig. 1). In this report, the authors present a case of a variant DFA that traversed superficially over the femoral vein within the subinguinal region. To the best of the authors’ knowledge, this case represents the second reported instance of such a DFA variation, with the first being Adachi’s special case, where a malpositioned DFA gave rise to the inferior epigastric and obturator arteries, in addition to the MFCA.

Figure 1. Adachi’s special case, illustrating a deep femoral artery (DFA) that crosses over the common femoral vein. The DFA is the medial division of the common femoral artery, shortly below the inguinal ligament. Note the origin of the inferior epigastric, obturator, and medial femoral circumflex arteries from the DFA. Adapted from Adachi ([The arterial system of the Japanese 2]; 1928. p. 111-96), with permission [5].

The variations were observed during the routine dissection of a male cadaver. The left CFA bifurcated into two equal-sized branches approximately 2 cm below the inguinal ligament (Fig. 2). The lateral branch descended into the adductor canal and represented the SFA in its usual course. The medial branch was identified as the left DFA since it terminated in perforating branches that traversed the adductor magnus muscle. The variant DFA originated from the medial side of the CFA and initially followed an oblique course from the lateral to the medial side, traversing anterior to the femoral vein above the saphenofemoral junction, where the saphenous vein joins the femoral vein. The inferior epigastric and obturator arteries originated from a common stem within the pre-venous segment of the DFA. Subsequently, the DFA assumed a spiral trajectory, wrapping itself around the medial aspect of the femoral vein while descending slightly lateralward and posteriorly before ultimately positioning itself behind the vein. The DFA was overdeveloped, with its terminal portion (the fourth perforating branch) exhibiting a substantial caliber, which penetrated the adductor magnus muscle at the lower third of the thigh, above the adductor hiatus (Fig. 3). Meanwhile, the MFCA arose from the medial aspect of the DFA as the latter curved around the medial side of the femoral vein. The external pudendal artery branched from the segment of the DFA located medially to the femoral vein. The LFCA had an independent origin from the SFA, distal to the point of origin of the DFA. No significant arterial variations were observed in the right femoral arterial system.

Figure 2. Anterior view of the left thigh. CFA, common femoral artery; CFV, common femoral vein; M, medial; I, inferior; L, lateral; S, superior.

Figure 3. Medial view of the left thigh. CFA, common femoral artery; CFV, common femoral vein; L, lateral; S, superior; M, medial; I, inferior.

The reported DFA variant exhibits several distinctive features: (1) it originated as the medial trunk of a premature bifurcation of the CFA; (2) it gave rise to the inferior epigastric, obturator, and external pudendal arteries and MFCA; (3) it followed an unusual course, passing anterior to the femoral vein above the saphenofemoral junction, then adopting a spiral trajectory, wrapping around the medial aspect of the femoral vein; and (4) it displayed overdevelopment, with its terminal portion (the fourth perforating branch) possessing a substantial caliber. This unique vascular configuration in the subinguinal region raises concerns about the potential for arterial injury during femoral vein cannulation.

The observation of a substantial femoral arterial branch passing anterior to the femoral vein is a rare occurrence [5]. This branch could manifest as the MFCA, medial deep circumflex trunk, or DFA (Fig. 4). The first recorded instance dates back to 1809 when Burns [8] described a case where the MFCA originated from the CFA slightly below the inguinal ligament and traversed the front of the common sheath of the great vein, and the lymphatics. Burns [8] speculated that had a (femoral) hernia occurred in this region, “the forepart of the sac must have been crossed by this artery, which during the performance of the operation would have been exposed to danger”. Cruveilhier [9] mentioned cases in which the CFA prematurely bifurcated into two equal and parallel trunks: the external trunk constituting the DFA, and the medial trunk, which constituted the SFA, overlaid the femoral vein. Adachi [5] noted the medial deep circumflex trunk, MFCA or DFA crossing anterior to the femoral vein in 3.3% of extremities from Japanese cadavers in contrast to the 0.5% reported in extremities from European cadavers by Quain and Maclise [4] and Srb [3]. Sahin and Bilgiç [10] examined 100 lower extremities from newborn cadavers and noted a DFA passing anterior to the femoral vein below the saphenofemoral junction in only one extremity (1%). Chitra reported a case in which the CFA trifurcated into three branches: LFCA, SFA, and DFA 1 cm below the inguinal ligament [11]. In this instance, the MFCA sprung from the origin of DFA and both arteries passed in front of the femoral vein.

Figure 4. Quain’s depiction of a medial femoral circumflex artery (MFCA) crossing over the common femoral vein. Note the origin of the inferior epigastric and obturator arteries from the convex side of the MFCA. Adapted from Quain and Maclise (The anatomy of the arteries of the human body: and its applications to pathology and operative surgery with a series of lithographic drawings; 1844) [4].

In the early stages of development, the sciatic artery forms the main artery of the lower extremity [12, 13]. De Vriese [14] noted the arteria nervi femoralis, a very small artery situated on the extensor side of the thigh in a 10 mm embryo. Small arteries in the anterior regions of the pelvis and thigh combine to form vascular networks known as the rete pelvicum and rete femorale. The sciatic artery establishes anastomoses with the rete femorale. Throughout development, certain arterial channels undergo regression while others enlarge, contributing to the formation of the definitive arterial anatomy [15]. Senior [13] observed that the formation of the femoral artery is preceded by the presence of a well-defined plexus of capillaries in 11 to 12 mm embryos. This plexus is proximally connected to the femoral branches of the external iliac artery and distally to the ramus communicans superius originating from the sciatic artery. He posited that this plexus arises through the coalescence of two subsidiary plexuses, potentially of unequal size, which extend from the arterial branches at either end of the ventral thigh. The recurrent branch of the sciatic artery establishes a connection between the dorsal and ventral arteries of the embryonic limb. Senior proposed that while the distal part of the adult femoral artery derives from the recurrent branch of the axial artery, the proximal portion is either formed through the coalescence of two femoral channels connecting the external iliac artery to the femoral plexus or by the persistence of one of these channels and the disappearance of the other. Senior’s framework provides valuable insight into understanding the diverse variations observed in the femoral arterial system. The selective regression or persistence of elements within the femoral plexus of capillaries can give rise to variations in the femoral arterial system. For instance, if a portion of the plexus persists anterior to the femoral vein below the inguinal ligament, it could lead to the DFA crossing over the femoral vein.

The dissection was carried out at Nova Southeastern University College of Allopathic Medicine (NSU MD) Anatomy lab. The cadaveric donor was obtained by the Anatomical Board of the State of Florida, having granted consent to the Board for use in anatomical education and research. The authors sincerely thank those who donated their bodies to science so that anatomical research could be performed. Results from such research can potentially increase mankind’s overall knowledge that can then improve patient care. Therefore, these donors and their families deserve our highest gratitude.

Conceptualization: MMS, MTDL. Data acquisition: MMS, MTDL, GBS. Data analysis or interpretation: MMS, MTDL, JS, SP, TT, GBS. Drafting of the manuscript: MMS, MTDL, JS, SP, TT, GBS. Critical revision of the manuscript: MMS, MTDL, JS, SP, TT, GBS. Approval of the final version of the manuscript: all authors.

No potential conflict of interest relevant to this article was reported.

None.