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Anatomic variation study of small saphenous vein termination using color Doppler ultrasound *

(Portuguese PDF version)

Aguinaldo de Oliveira,¹ Enrique Antonio Vidal,¹
Graciliano José França,¹ Jeferson Toregiani,² Jorge R. Ribas Timi,³ Ricardo César Rocha Moreira⁴

1. MD, Serviço de Eco-Doppler Vascular, Clínica de Ecodoppler Colorido and Hospital Nossa Senhora das Graças, Curitiba, PR, Brazil.
2. Resident physician, Serviço de Cirurgia Vascular Prof. Dr. Elias Abrão, Hospital Nossa Senhora das Graças, Curitiba, PR, Brazil.
3. MD, Serviço de Cirurgia Vascular Prof. Dr. Elias Abrão, Hospital Nossa Senhora das Graças, Curitiba, PR, Brazil.
4. Chief of Serviço de Cirurgia Vascular Prof. Dr. Elias Abrão, Hospital Nossa Senhora das Graças, Curitiba, PR, Brazil.

* This work was performed at Clínica de Ecodoppler Colorido, Curitiba, PR, Brazil.

Correspondence:
Aguinaldo de Oliveira
Rua Elvira Harkot Ramina, 82/502
CEP 81200-620 - Curitiba, PR
Brazil
Phone: + 55 (41) 342.6860
Fax: + 55 (41) 342.6311
E-mail: aguinaldo@onda.com.br

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ABSTRACT

Objective: To study the different modes of terminations of the small saphenous vein, using color Doppler ultrasound, based on Kosinski classification.

Patients and method: A total of 1,000 lower limbs were studied in 500 patients (400 women and 100 men) with mean age of 49.3 ± 16.6 years. The anatomic variations of the small saphenous vein termination were registered in a protocol specifically developed for the study. The several modes of terminations were divided into three main types, according to Kosinski classification: Type I, when the termination was in the popliteal vein. This type had two subtypes: (a) termination exclusively in the popliteal vein; and (b) in both the popliteal vein and the greater saphenous vein. Type II, with termination in thigh veins, with three subtypes: (a) deep veins of the thigh; (b) in both the deep veins of the thigh and the greater saphenous vein; and (c): in the greater saphenous vein. Type III, with termination in leg veins, with two subtypes: (a) in the greater saphenous vein below the knee; and (b) in deep leg veins (gastrocnemius veins). The distances of the termination from the popliteal skin crease were also registered.

Results: Type I termination was found in 528 limbs (52.8%), with subtype I(a) found in 431 limbs (43.1%) and subtype I(b) in 97 limbs (9.7%). Type II termination was found in 444 limbs (44.4%), with subtype II(a) found in 286 limbs (28.6%), subtype II(b) in 102 limbs (10.2%) and subtype II(c) in 56 limbs (5.6%). Type III was found in 28 limbs (2.8%), with subtype III(a) found in 20 limbs (2%) and subtype III(b) in eight limbs (0.8%).

Conclusion: The small saphenous vein presents anatomical variations in its termination. It often terminates in thigh veins (97.2%), communicating with the popliteal vein in half of the cases (52.8%). It seldom terminates in leg veins (2.8%).

Key-words: saphenous vein, color Doppler ultrasonography.
Palavras-chave: veia safena, ultra-sonografia Doppler em cores.

J Vasc Br 2004;3(3):223-30

The small saphenous vein has been the object of many studies, specially its anatomical features: considerable variations in its trajectory and, most of all, its termination, which may contribute to recurrent varicose veins in this territory. This is due to the fact that the embryological formation of the small saphenous vein is much more precocious and even more complex than that of the greater saphenous vein.^1-5 Until recent years, all information about the small saphenous vein and its termination were obtained through post mortem dissections or surgical or phlebographic findings.^4,6,7 Giacomini, in 1893, and Kosinski, in 1926, were the first researchers to provide detailed information - obtained through corpse dissections - about the small saphenous vein termination. Subsequently, with the advent of phlebography, and later on, with the use of color Doppler ultrasound, new studies confirmed the previous results reported by Giacomini and Kosinski.⁴

In Brazil, the first anatomic study approaching the termination of the small saphenous vein was performed by professor Alcino Lázaro da Silva,^8,9 in 1965, followed by another study conducted by professor Emil Burihan.¹⁰ Both studies confirmed significant anatomic variations of the termination.

The color Doppler ultrasound is a non-invasive method that offers some advantages such as easy repetition and great accuracy in detecting the termination of the small saphenous vein at the saphenopopliteal junction. However, when compared to intra-operative and phlebographic findings, the color Doppler is an examiner dependent method.^1,2,11 The color Doppler ultrasound has been used as a routine procedure to map the venous system of lower limbs in the pre-operative of varicose veins.

Many anatomic and phlebographic studies may be performed with the use of the color Doppler ultrasound. The Kosinski¹² classification is usually employed as a reference for the modes of termination of the small saphenous vein. This study aims at studying the different modes of termination of the small saphenous vein in 1,000 lower limbs, with the use of color Doppler ultrasound and based on Kosinski classification.

PATIENTS AND METHODS

Patients

Between February and October 2001, 1,671 patients underwent venous color Doppler ultrasound evaluation of lower limbs. Out of these patients, 500 individuals, who agreed to take part, were included in the study and had the termination of their small saphenous vein assessed, totalizing a number of 1,000 lower limbs. The patients were from both sexes and aged over 18 years. Patients with previous surgical history of the small saphenous vein and those who did not agree to take part in the study were excluded.

The work received the approval of the Research Ethics Committee of Hospital de Clínicas da Universidade Federal do Paraná, Brazil, under the number CEP-HC n. 032EXT. 0142001-05.

Methods

All exams were conducted by the same examiner with the use of a System Five, General Electric Diasonics Ultrasound with linear transducers and frequencies that varied from 5 to 10 MHz.

The patients were placed on a suitable bed in right or left lateral decubitus position. Patients with termination extending to the grater saphenous vein were placed in dorsal decubitus position.

The small saphenous vein arises at the junction of the dorsal digital vein of the fifth digit (little toe) with the dorsal venous arch, passes along the lateral side of the foot with the sural nerve and ascends along the lateral side of the tendon calcaneus (Achilles tendon).On the posterior side of the leg, the small saphenous vein passes on the deep fascia, between the two heads of the gastrocnemius muscle, to the popliteal fossa, and, usually, terminates in the popliteal vein.¹³

The small saphenous vein was, then, visualized on the lateral malleolus and its trajectory followed until it reached the popliteal fossa. On the popliteal fossa, the termination of the small saphenous vein was studied in more detail, in longitudinal and transversal planes.

The distance of its termination was measured with a 30 cm ruler, both in the thigh and in the leg, in relation to the popliteal crease. When the small saphenous vein presented more than one branch on the popliteal fossa, the branch with larger caliber was chosen to be followed. Based on Kosinski classification, the data was registered in a protocol that was specifically designed for the study.

The different modes of termination of the small saphenous were classified as follows:

• Type I - termination in the popliteal vein. This type has two subtypes: (a) termination exclusively in the popliteal vein, or (b) divided into two branches, one to the popliteal vein and the other to the greater saphenous vein;
  
• Type II - termination in thigh veins or in deep veins (femoral vein/veins of the posterior aspect of the thigh) and/or in the greater saphenous vein. This type has three subdivisions: (a) deep veins of the thigh, (b) both the deep veins of the thigh and the greater saphenous vein, and (c) directly in the greater saphenous vein;
  
• Type III, termination in leg veins, without reaching the popliteal region. This type has two subtypes: (a) termination in the greater saphenous vein of the; or (b) in the gastrocnemius veins.

The data presented in this study was analyzed using a parametric test (Student's t-test) and a non-parametric test (Mann-Whitney test) to compare two proportions. The minimum level of significance (significance probability) adopted was 5% (0.005).

RESULTS

Among the 500 patients who participated in this study, 400 were female (80%) and 100 were males (20%); the mean age was 49.3 (±16.6) years, ranging from 18 to 89 years.

The study about the termination of the small saphenous vein showed Type I predominance in 52.8% (subtype a: 43.1%, and b: 9.7%) of cases. Type II was found in 44.4% (subtype a: 28.6%, b: 10.2%, and c: 5.6%), and Type III in 2.8% (subtype a: 2%, and b: 0.8%).

The analysis between genders did not show significant difference, with predominance of Type I in males and females. In males, Type I was found in 59% (subtype a: 50%, and b: 9%); Type II in 40% (subtype a: 26.5%, b: 7%, and c: 6.5%); and Type III in 1% (subtype a: 1%, and b: 0%).

In females, Type I was found in 51.3% (subtype a: 41.4%, and b: 9.9%); Type II in 45.5% (subtype a: 29.1%, b: 11%, and c: 5.4%); and Type III in 3.2% (subtype a: 2.2%, and b: 1%).

With respect to the popliteal crease, the distances of the termination and its intervals were also registered in the protocol, being homogeneous in the left and right lower limbs. Figures 1 to 7 shows this data in a more didactic manner.

Figure 1 - Type I, subtype a (43.1%). Termination exclusively in the popliteal vein, between 0 and 9 cm, mean of 2.7 ± 1.4 cm above the popliteal crease (PC).

Figure 2 - Type I, subtype b (9.7%). Termination into two branches: one branch to the popliteal vein (¹), between 0 and 10 cm, mean of 2.8 ± 1.9 cm above the popliteal crease, and the other to the greater saphenous vein (²), between 14 and 34 cm, mean of 24.5 ± 3.8 cm above the popliteal crease (PC).

Figure 3 - Type II, subtype a (28.6%). Termination in the deep veins of the thigh, between 6 and 21 cm, mean of 11.8 ± 1.9 cm above the popliteal crease (PC).

Figure 4 - Type II, subtype b (10.2%). Termination into two branches: one branch to the deep veins of the thigh (¹), between 5 and 15 cm, mean of 10.1 ± 1.8 cm above the popliteal crease, and the other branch to the greater saphenous vein (²), between 14 and 32 cm, mean of 24.1 ± 3.8 cm above the popliteal crease (PC).

Figure 5 - Type II, subtype c (5.6%). Termination into the grater saphenous vein, between 18 and 32 cm, mean of 25.5 ± 3.2 cm below the popliteal crease (PC).

Figure 6 - Type III, subtype a (2%). Termination into the greater saphenous vein, between 0 and 13 cm, mean of 2.5 ± 3.5 cm below the popliteal crease (PC).

Figure 7 - Type III, subtype b (0.8%). Termination into gastrocnemius veins, between 1 and 12 cm, mean of 6.4 ± 4.6 cm below the popliteal crease (PC).

This study was bilaterally performed, which allowed the authors to analyze the concordance among the terminations found in the lower limbs. The similarity of the findings in the lower limbs, that is, the concordance index was 59.5% for type and 37.4% for subtype. A double termination of the small saphenous vein was observed in four lower limbs (0.4%) as follows: in deep vein of the thigh and both in deep vein of the thigh and greater saphenous vein; in popliteal vein and in deep vein of the thigh, and both terminated in the popliteal vein in the other two lower limbs. Some slight variations were observed throughout the study, but they were related to the three types based on Kosinski classification.¹²

DISCUSSION

There is no consensus in the literature about the termination of the small saphenous vein. It seems that this fact is due to the embryonary formation of this vein, which is rather complex and much more precocious than that of the greater saphenous vein.^1-5,11 According to Fitzgerald,¹⁴ in the embryonary phase, the cervical and lumbar intersegmental arteries and veins extend freely into the sprouts of the respective limbs, making them permeable through anastomosing capillary nets. The preferential channels materialize; a single axial artery develops from the nucleus of the corresponding limb and blood returns to the cardinal system through a pre-axial vein (cephalic and grater saphenous) that lies along the cranial edge of the limb, and through a post-axial vein (basilic, small saphenous) that lies along the caudal edge. In the beginning of embryonary life, the marginal fibular vein (predecessor of the small saphenous vein) joins the posterior cardinal vein and, in a later stage, joins the ischiatic vein. After pelvis rotation, the external iliac vein becomes more important and joins the marginal fibular vein. When the lower limb begins to develop, the greater saphenous system is favored in relation to the small saphenous system, but the contact with these systems is established by the medial accessory vein. Multiple variations occur in consequence of the anastomosis, which may close or remain open.^3,12,15

These numerous modes of termination of the small saphenous vein may contribute to recurrent varicose veins in the post-operative of this territory. The incidence of recurrence may vary from 14 to 44%, but it may reach up to 61% of cases due to the residual stump or small saphenous. The numerous variations of termination of the small saphenous vein alone is responsible for 10% of cases of post-operative recurrence.¹⁶,¹⁷

The introduction of the color Doppler imaging into the angiology has caused great impact on how varicose treatment is conducted. The color Doppler has the advantage of being a non-invasive method with relative low cost and provides a detailed study of the venous function and anatomy, allowing, therefore, a better pre-operative planning.¹⁸

Vidal & Oliveira¹⁹ report that in an inquiry conduct in 1997, during the Brazilian Congress of Angiology and Vascular Surgery, 74% of the interviewed required color Doppler examination in the pre-operative of varicose veins. Nowadays, this method is practically a routine procedure, as it can be observed in vascular laboratories, where pre-operative venous mapping of lower limbs represents nearly 70% of exam requests. One example is the laboratory where this research was performed. A literature review showed that Kosinski classification¹² was used as a reference for the designing of protocols in the majority of the studies on this subject.

The results obtained in this study are, in general, in conformity with previous results reported in the literature. Like in the majority of other studies, Type I (in the popliteal vein) was predominant, with 52.8%; Type II (in veins of the thigh) accounts for 44% whereas Type II (in veins of the leg) represents 2.8% of cases.

Table 1 shows some studies, similar to the present study, which employed Kosinski classification¹² for the assessment of the small saphenous vein termination. Some authors, according to their own interpretation of the data, suggest modifications in the types of termination.

Table 1 - Study of the small saphenous vein termination by color Doppler ultrasound compared to Kosinski's anatomic study

Authors	Number of limbs	Type I %	Type II %	Type III %	Type A %	Type IV %
Kosinski, 1926	124	57.3	33	9.7	-	-
Vasdeskis, 1989	64	60	30	10	-	-
Engel, 1991	62	78	15.4	6.6	-	-
Engel, 1994	104	52.4	46.6	1	63.2	-
Labrapoulos, 1997	383	60.8	19.3	15.4	-	4.5
Presente estudo, 2001	1.000	52.8	44.4	2.8	-	-

These types were created by the authors themselves and may be explained as follows: Type A - the small saphenous vein drains into the upper third of thigh or buttock, with or without connection with the popliteal vein, cited by Engel et al.;³ Type III and Type IV, proposed by Labropoulos et al.,⁴ means, respectively, the presence of Giacomini's vein and drainage into the gastrocnemius veins.

Engelhorn et al.²⁰ presented a classification for superficial venous insufficiency, on the basis of color Doppler findings, in 500 lower limbs. The authors found, during reflux research, the small saphenous vein terminating in the popliteal crease in 11% of cases, up to 4 cm in 34.6%; between 4 and 10 cm (communication with the deep venous system) in 42.4% of cases; over 10 cm in 8.6%, and communicating with the greater saphenous vein in the proximal aspect of the leg and thigh in 3.4% of cases. In the present study, the saphenopopliteal junction was located between 0 and 10 cm above the popliteal crease, and in the majority of cases (94.5%) it was located within the first 5 cm. When the termination occurred in deep veins of the thigh, the distance found varied from 6 to 21 cm, with a mean distance of 11.8% (being 70.1% of cases 10 cm above the popliteal crease). The distance varied from 14 to 34 cm for the greater saphenous vein, with a mean distance of 24.5 cm. The termination of veins in the leg, below the popliteal crease, was between 0 and 13 cm, with a mean distance of 2.5 cm in the greater saphenous vein, and 1 to 12 cm, with a mean distance of 6.4 cm, in gastrocnemius veins. In 43.1% of cases, the termination occurred exclusively in the popliteal vein. For Engel et al.,³ this mode of termination occurred in 35.6% of cases. Vasdeskis et al.² and Labropoulous et al.⁴ reported that, in 60% of cases, the small saphenous vein connects to the popliteal vein.

It is important to emphasize one aspect: perhaps the major difficulty in determining level and type of termination is related to its occurrence in deep veins of the thigh. There is a consensus in the literature, confirmed in this work, that the higher the distance in relation to the popliteal crease, the higher the technical difficulty to determine the actual place of termination. Sucrue et al.¹ report 94% of accuracy when the termination of the small saphenous vein occurred in the popliteal fossa. However, when the termination occurred 5 cm away from the popliteal crease, this level of accuracy decreased to 30%. Vasdeskis et al.² report 96% of accuracy for the color Doppler ultrasound, with the saphenopopliteal junction up to 2 cm; 94% up to 5 cm; and 30% higher than 5 cm, when compared to phlebographic findings. Engel et al.¹¹ established a level of accuracy of 93% when the saphenopopliteal junction occurred up to 1 cm above the popliteal crease, when compared to intraoperative findings.

Reviewing various anatomical series in the literature, Creton e Kolher, cited by Garrido⁷, concluded that reflux is less likely to occur in high junctions, perhaps because of the obliquity of the junction or because of the protection exercised by the thigh muscles, in opposition to what occurs in the popliteal fossa, or because the junctions are multiple in some cases. However, according to these authors, the explanation for reflux is hemodynamic, not anatomical.

Since the exams of this study were all bilaterally performed, it was possible to establish a similarity among the limbs studied. When types were compared, 59.4% presented the same termination. When subtypes were compared, 37.4% of limbs presented similarity. The similarity was not considered in the literature, for the study was performed in both lower limbs only in few cases. The only report found in the literature was from a studied conducted in lower limbs by Labropoulos et al.,⁴ who observed 79% of similarity for the variable type.

Other variations were also found during data collection and they were included in the classification adopted; however there are two variations which deserve to be reported: Type I (a), that is, termination exclusively in the popliteal vein, observed in 43% of patients, presented a tributary vein - with a smaller caliber - progressing towards the posterior aspect of the thigh in 23.2% of cases. This vein may correspond to Meyer's posterior femoral cutaneous vein or Hyrtl's femoro-popliteal vein, cited by Kosinsky.¹² Images that suggest the duplicity of the termination of the small saphenous vein were found in four cases, corresponding to 0.4% of cases. Each branch was studied separately. Labropoulos et al.,²¹ in their study on the impact of the isolated incompetence of the small saphenous vein on the symptoms of chronic venous disease, report an incidence of 2.2% of duplicity (specially in the trajectory) in 2,254 lower limbs.

The small saphenous vein may extend itself along the posterior thigh. Georgiev²² states that the femoro-popliteal vein should be considered as a specific anatomic entity - a subfascial extension of the small saphenous vein - that lies over the sulcus between the semitendineous and biceps muscles. It should be distinguished as an extension of the small saphenous vein into the thigh, in two ways: the Giacomini's vein, and the high termination in the thigh. The term Giacomini should be reserved to oblique intersaphenous anastomosis, which may connect the small saphenous vein or the femoro-popliteal vein to the greater saphenous vein. For the small saphenous vein, its high termination extends between 5 and 10 cm above the popliteal. Different from the femoro-popliteal vein that runs superficially just below the fascia, the high termination of the small saphenous vein curves deeper towards the posterior musculature of the thigh.

The higher number of lower limbs of female patients, presented in this study in the proportion of 4:1, reflects the reality of clinics of vascular echography, where there is a predominance of this exam in female patients for evaluation of venous insufficiency in the lower limbs. Type I was predominant in both sexes, without significant difference, being 59 and 51.3%, respectively. In the literature, it was also observed the predominance of female patients, with results highly similar to those presented in this study. Regardless of gender, there is a predominance of the termination of the small saphenous vein in the popliteal vein, either exclusively, in cases of single termination, or in cases of multiple termination, where the major branch communicates with the popliteal vein.

CONCLUSION

The small saphenous vein presents anatomical variations in its termination. It often terminates in thigh veins (97.2%), communicating with the popliteal vein in, approximately, half of the cases (52.8%). It seldom terminates in leg veins (2.8%).

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