Anatomical variation types of the deep femoral vein and its tributaries

Abstract

Background

The deep femoral vein generally has individual differences in origin, course, tributary, caliber, and quantity. However, systematic research on deep femoral vein variations remains insufficient. Given this, this study used anatomical observation to reveal the types and ratios of variations in the deep femoral vein and its tributaries.

Methods

This study selected 63 gross specimens of intact lower extremities and dissected their 126 lower limbs layer by layer to explore variations in the deep femoral vein and its tributaries.

Results

A total of 15 lower limbs exhibit variations in the deep femoral vein and its tributaries, of which 93% were unilateral. No correlation was found between the mutations and gender. They can be generally classified into three types: variations in the small saphenous vein branch of the deep femoral vein (7.14%), variations in the popliteal vein branch of the deep femoral vein (3.96%), and multiple deep femoral vein variations (0.79%).

Conclusions

Variations in the deep femoral vein and its tributaries are not rare and can achieve a variation rate of 11.9%. Moreover, 93% of the variations involve tributaries of the deep femoral vein, among which 60% occur in the small saphenous vein branch, and approximately 30% are related to the popliteal vein branch. The variation diversity can lay a theoretical foundation for clinical diagnosis and treatment.

Article Highlights.

• •Type of Research: Anatomical basic research
• •Key Findings: Anatomical examination of 63 cadavers, including 126 lower limbs, revealed variations in the femoral deep vein and its tributaries in 15 cases, with a variation rate of 11.9%, which could be classified into three types.
• •Take Home Message: Variations in the deep femoral vein and its tributaries exhibit diversity and can form communications with the popliteal vein and small saphenous vein. These variations may substitute for lower limb venous circulation function, providing anatomical references for the clinical diagnosis and treatment of deep vein thrombosis.

The deep femoral vein and its tributaries has numerous and complicated anatomy variant types. The mutated deep femoral vein communicates with multiple veins and has a thickened caliber, which may induce venous blood backstreaming and sedimentation and promote the risk of deep vein thrombosis metastasis. Moreover, it is prone to misdiagnosis and missed diagnosis during imaging examinations. Therefore, recognizing the anatomical structure of the deep femoral vein and its tributaries is of guiding significance for the diagnosis and treatment of deep vein thrombosis.

The deep femoral vein is an essential component of the deep venous system of the lower extremities, which originates from the deep vastus lateralis, runs along the deep femoral artery, and eventually merges into the femoral vein.¹ However, the origin, course, tributary, and caliber of the deep femoral vein usually undergo anatomical variations,^2,3 enabling blood to flow back in diverse ways. There are numerous case reports on deep femoral vein variations.4, 5, 6, 7 However, systematic research on the deep femoral vein is inadequate. Therefore, this study systematically probed into the types and ratios of variations in the deep femoral vein and its tributaries through anatomical observation.

Methods

Experimental material

This study dissected 63 gross specimens with complete lower limb structures, including 42 males and 21 females, 35 to 93 years old, with an average age of 64 years. The specimens were provided by the Anatomy Teaching and Research Department of Chengdu Medical College and voluntarily donated by the donors and their families from the southwestern region of China with informed consent.

Experimental methods

Sixty-three cadaver specimens with structurally intact lower limbs were selected and fixed with 10% formalin. The deep veins of the thigh and their tributaries were exposed by layer-by-layer dissection and underwent observation regarding their origin, course, adjacency, and point of entry. Then, a vernier caliper (accuracy of 0.05 mm) was used to measure the flattened diameter of the veins. The measurement data were expressed as mean ± range. The gender of the specimens was recorded, and the types and ratios of variations were documented with photographs.

Data processing

Statistical analysis was performed using SPSS 21.0 software. A χ² test was conducted to examine the relationship between gender and the number of variations. A P value of <.05 was considered statistically significant. Different types of variations were visualized using GraphPad Prism 8 and Adobe Illustrator software.

Results

In this study, 126 lower limbs were dissected. A total of 15 cases of deep femoral vein and its tributaries variations were found, including 12 in males and 3 in females. Except for one case involving a variation in number, all others variations were found in the tributaries of the deep femoral vein. The variation types can be categorized into three major groups: variations in the small saphenous vein branch of the deep femoral vein, variations in the popliteal vein branch of the deep femoral vein, and multiple deep femoral vein variations (Fig 1). The total variation rate is 11.9%, of which 93% is unilateral. The association between mutation and gender has not been found (χ² = 1.362; df = 1; P = .243).

Fig 1.

The proportion of each type of deep femoral vein variation. Except for type 3 involving a variation in number, all others are variations in the tributaries of the deep femoral vein. Type 1: Variations in the small saphenous vein branch of the deep femoral vein. Type 1a: The main trunk of the small saphenous vein continues as the deep femoral vein. Type 1b: The communicating branch of the small saphenous vein extends to form the deep femoral vein. Type 2: Variations in the popliteal vein branch of the deep femoral vein. Type 2a: The branch of the popliteal vein extends to form the deep femoral vein. Type 2b: The communicating branch of the popliteal vein extends to form the deep femoral vein. Type 3: Multiple deep femoral vein variations.

Type 1: Variations in the small saphenous vein branch of the deep femoral vein

This type of variation is the most common, with nine cases in total, accounting for a variation rate of 7.14%. The normal small saphenous vein originates from the dorsal vein arch of the foot and flows into the popliteal vein at the inferior cornu of the popliteal fossa. Instead of fully draining into the popliteal vein, the mutated small saphenous vein runs cranial and merges into the deep femoral vein.

Type 1a: The main trunk of the small saphenous vein continues as the deep femoral vein

A total of five cases belong to this variation, with a variation rate of 3.97%. The mutated small saphenous vein does not inject into the popliteal vein at the popliteal fossa and only has tiny communicating branches with the popliteal vein. It passes through the deep fascia at the upper one-third of the posterior thigh and eventually completely extends to form the deep femoral vein. The average caliber of the mutated vein is 4.25 ± 0.65 mm, approximatelyt twice that of the normal small saphenous vein (Fig 2).

Fig 2.

Type 1a: The main trunk of the small saphenous vein continues as the deep femoral vein. (A) Physical diagram. (B) Pattern diagram. 1: The small saphenous vein branch of the deep femoral vein. 2: Popliteal vein. 3: Subsartorial canal. 4: Small saphenous vein.

Type 1b: The communicating branch of the small saphenous vein extends to form the deep femoral vein

This variation includes four cases and has a variation rate of 3.17%. The small saphenous vein penetrates the deep fascia and injects into the popliteal vein. In addition, a communicating branch is located at the inferior cornu of the popliteal fossa. It has a relatively small caliber of 1.50 ± 1.20 mm at the beginning, an obviously varicose middle section, and an average caliber of 3.45 ± 0.55 mm. The mutated vein lays on the superficial surface of the tibial nerve, ascends along the sciatic nerve, turns to the deep surface at the upper corner of the popliteal fossa, and finally connects with the deep femoral vein at the upper one-third of the posterior thigh (Fig 3).

Fig 3.

Type 1b: The communicating branch of the small saphenous vein extends to form the deep femoral vein. (A) Physical diagram. (B) Pattern diagram. 1: The small saphenous vein branch of the deep femoral vein. 2: Popliteal vein. 3: Subsartorial canal. 4: Small saphenous vein.

Type 2: Variations in the popliteal vein branch of the deep femoral vein

There are five cases of this type, accounting for a variation rate of 3.96%. The normal popliteal vein is formed by the confluence of the anterior tibial vein and the posterior tibial vein. It ascends along the popliteal artery in the deep surface of the popliteal fossa and extends directly to form the femoral vein without communication with the deep femoral vein during its ascent. The mutated popliteal vein does not enter the adductor tendon hiatus and continues to flow upward into the deep femoral vein.

Type 2a: The branch of the popliteal vein extends to form the deep femoral vein

This type includes four cases, with a variation rate of 3.17%. The anterior tibial vein and the tibial-peroneal trunk converge at the inferior angle of the popliteal fossa to form the main trunk of the popliteal vein, with a caliber at the confluence of 7.00 ± 0.15 mm. As for this type of variant, the main trunk of the popliteal vein bifurcates into two veins in the middle of the popliteal fossa. The caliber at the beginning of the normal branch of the popliteal vein is 4.00 ± 0.20 mm, whereas that at the beginning of the variant branch of the popliteal vein is 6.85 ± 0.15 mm. Two popliteal veins ascend along the two sides of the popliteal artery in the popliteal fossa, with small communicating branches between them. The normal branch passes through the adductor hiatus and extends to form the femoral vein; instead of entering the adductor canal, the variant branch passes through the deep fascia in the middle of the femur and merges into the deep femoral vein (Fig 4).

Fig 4.

Type 2a: The branch of the popliteal vein extends to form the deep femoral vein. (A) Physical diagram. (B) Pattern diagram. 1: The popliteal vein branch of the deep femoral vein. 2: Popliteal vein. 3: Subsartorial canal. 4: Small saphenous vein.

Type 2b: The communicating branch of the popliteal vein extends to form the deep femoral vein

There is only one case of this type, with a variation rate of 0.79%. The popliteal vein in this type has a variant communicating branch below the adductor tendinous opening. The average diameter of the popliteal vein is 10.00 mm. The variant communicating branch has an initial caliber of 3.40 mm. It travels upward along the deep surface of the semimembranosus muscle and the biceps femoris muscle and enters the branches of the deep femoral vein below the quadratus femoris muscle (Fig 5).

Fig 5.

Type 2b: The communicating branch of the popliteal vein extends to form the deep femoral vein. (A) Physical diagram. (B) Pattern diagram. 1: The popliteal vein branch of the deep femoral vein. 2: Popliteal vein. 3: Subsartorial canal.

Type 3: Multiple deep femoral vein variations

One case belongs to this type, and the variation rate is 0.79%. In this type, two deep femoral veins exist in the anterior thigh region, with calibers of 4.81 mm and 2.50 mm, respectively. They both originate from the deep medial muscle group of the thigh and ultimately drain into the femoral vein accompanied by the deep femoral artery (Fig 6).

Fig 6.

Type 3: Multiple deep femoral vein variations. (A) Physical diagram. (B) Pattern diagram. 1: Multiple deep femoral vein. 2: Femoral vein. 5: Great saphenous vein.

Discussion

In the exploration of lower limb vascular variations, vascular variations are diverse and common.⁸ The variation incidence of veins is much higher than that of arteries, and most venous variations are unilateral⁸ and have no significant correlation with age or gender.⁹ Among venous variations, venous quantity variation is dominant.^8,10 In this kind of variation, the most common is multiple femoral veins; multiple deep femoral veins are infrequent.¹⁰

Although anatomical and position variations in lower limb veins occur relatively infrequently, they can have a significant impact on clinical practice.¹¹ Massive studies focused on femoral vein variation. Previous large studies focused on femoral vein variation. Uhl et al³ reported a variation rate of 12% in the femoral vein. This study found through dissection that the variation rate of the deep femoral vein and its tributaries was 11.9%. It implies that variations in the deep femoral vein and its tributaries are not rare.

Most research on the variability rate of lower limb veins adopted ultrasound scanning and lacked unified inclusion standards when selecting samples. Patients with recessive deep vein thrombosis were not wholly excluded.^3,8, 9, 10^,12 Moreover, owing to resolution limitations and tiny variant blood vessels, the possible deviation of variation rate always exists in anatomical findings.^3,12 Therefore, traditional anatomical methods can provide sufficient theoretical support for statistical variability. Deep femoral vein variations have been mentioned in systematic variation reports or case reports of other veins, such as the small saphenous vein and femoral vein.^3,9,13 However, systematic research on the deep femoral vein is inadequate.

According to the literature on variations related to the deep femoral vein and popliteal vein, the variant deep femoral vein originates from the posterior femoral thigh and popliteal fossa and communicates intimately with the lower end of the femoral vein,¹⁴ the popliteal vein,⁴ and the posterior tibial vein.⁷ This results in the replacement of partial femoral vein function by the deep femoral vein. Among the five related variants in this study, three cases exhibit variant deep femoral vein thickening, even greater than the portal femoral vein. The enlargement of the mutated veins leads to an increase in the total cross-sectional area of the veins and a relative drop in blood flow velocity.¹⁵ Studies have reported the general absence of the popliteal vein valve,¹⁶ which enhances the occurrence of blood reflux and pooling, burdens venous return in lower extremities, and potentially induces varicosity.¹⁷ Owing to the similar courses, when one of the two veins develops deep vein thrombosis, the thickened variant deep femoral vein may be mistaken for the femoral vein during ultrasound examination, leading to missed diagnosis and misdiagnosis.¹⁸

The small saphenous vein usually communicates with the superficial veins of the lower extremities, among which the most common one is the great saphenous vein.¹⁹ There are few reports on the variation of communications between the small saphenous vein and the deep veins of the lower extremities.^8,13 This study discovered that the variation related to the deep femoral vein and the small saphenous vein had the highest incidence, accounting for 60% of the total variation. Moreover, compared with the caliber of the small saphenous vein in contralateral normal limbs, that of the mutated vein was generally thickened, suggesting that the deep femoral vein may have the functional reflux of superficial venous blood. When the lower end of the femoral vein occurs thrombosis, normally, reflux obstruction of the small saphenous vein will lead to positive symptoms of calf varicose veins.¹⁹ However, if the deep femoral vein and its tributaries mutates, the blood of the small saphenous vein can flow back through the deep femoral vein, presenting a false-negative result and delaying indentification of the condition. When the small saphenous vein communicates with the popliteal vein and deep femoral vein simultaneously, if high ligation and stripping of the small saphenous vein are conducted, the ligation of the blood vessels will be incomplete, causing the thrombus to transfer upward through the mutated deep femoral vein and the easy recurrence of varicose veins in the lower extremities.^20,21

Although there are several variations in the deep femoral veins and its tributaries, they are essentially the presence of a variant vein in the middle of the posterior femur, which does not penetrate the adductor canal hiatus but runs upward until it extends to form the deep femoral vein. Some reports^17,22 referred to this variant deep femoral vein as the axial vein. Based on their speculation, in the early stage of development, the sciatic nerve induces the femoral vein to start parallel to the axial vein, and the axial vein occurs atresia and forms the deep femoral vein in the later stage. Nevertheless, the specific cause of deep femoral vein variations is still under debate.

It has been substantiated that, among patients with deep vein thrombosis, a considerable proportion (55%) exhibit abnormal sizes in the deep femoral vein, possibly as a compensatory mechanism.¹⁷ Therefore, investigating the deep femoral vein and its tributaries variations through gross anatomy can render a theoretical basis to probe the etiologies of deep vein thrombosis. Furthermore, during the detection of deep vein thrombosis in the lower extremities, clinical doctors should carefully scan all venous segments and avert the ignorance of possible deep femoral vein variations.

Conclusions

The deep femoral vein and its tributaries variations are not rare and can achieve a variation rate of 11.9%. Moreover, 93% of the variations involve tributaries of the deep femoral vein, among which 60% occur in the small saphenous vein branch, and approximately 30% are related to the popliteal vein branch. The diversity of the variations can provide sufficient theoretical support for clinical diagnosis and treatment.

Author Contributions

Conception and design: YT, MY, QS, LY

Analysis and interpretation: YT, MY, LY

Data collection: YT, MY, QS

Writing the article: YT, MY, QS, LY

Critical revision of the article: YT, QS, LY

Final approval of the article: YT, MY, QS, LY

Statistical analysis: YT, MY, QS, LY

Obtained funding: LY

Overall responsibility: LY

YT and MY contributed equally to this article and share co-first authorship.

ST, MY, and QS contributed equally to this article and share co-senior authorship.

Funding

This project was sponsored by the 2023 Provincial College Student Innovation and Entrepreneurship Training Program of Chengdu Medical College (S202313705090); Supported by the Key Laboratory of Development and Regeneration of Sichuan Province (sys16-006).

Disclosures

None.