Venous mapping with Color Doppler Ultrasound (CD-US) sheds light on both the diagnosis and preferred treatment option for superficial venous insufficiency. However, due to anatomical variations, the course of the small saphenous vein (SSV) or the localization of the saphenopopliteal junction (SPJ) may not be adequately identified in 22% of patients, even after preoperative CD-US assessment. Subsequently, SPJ ligation was technically successful in only 59% of patients, with no exhibition of superficial venous residual flow [1]. When deciding on the optimal treatment for SSV incompetence, it is crucial to clearly identify not only the severity of insufficiency and affected vessel segments but also the variations in the SSV through preoperative evaluation. This approach is essential for understanding the underlying mechanisms and minimizing the risk of recurrence [2-4]. To elucidate the association between the variation in the termination of SSV and SSV incompetence, we decided to conduct a study by comparing variation data among patients with isolated SSV incompetence and those with isolated great saphenous vein (GSV) incompetence. Additionally, symptomatic patients were treated in accordance with the latest clinical practice guideline [5].

This prospective, observational study was conducted in a cardiovascular surgery department from December 2014 to June 2015. The study included patients with either isolated SSV incompetence or isolated GSV incompetence. A demographic profile questionnaire was submitted by patients who wanted to participate in this study. Patients presenting with both SSV and GSV incompetence, deep venous insufficiency, a history of venous thrombosis and/or thrombophlebitis, postphlebitic syndrome with venous ulcer, peripheral arterial disease, or congenital vascular malformations were excluded. The Institutional Ethical Committee of Istanbul Haydarpasa Numune Training and Research Hospital approved the study, and written informed consent was obtained from all participants. (IRB approval number and date: HNEAH-KAEK 2014/99 – 24.11.2014)

All patients underwent evaluation of the drainage location of the SSV using CD-US, performed by the same radiologist. In the CD-US examination, persistent retrograde flow beyond 0.5 second during the Valsalva maneuver was considered as pathological reflux. Subsequently, patients were categorized into two groups based on their incompetent veins: those with isolated SSV incompetence (study group) and those with isolated GSV incompetence (control group).

In 1926, Kosinski [6] initially classified SSV variations using an anatomical approach. This classification system was later modified using CD-US in 2004 by Aguinaldo de Oliveira et al. [7], introducing the following types of classifications. Type 1a is defined by SSV termination into the popliteal vein in the popliteal fossa, above the popliteal skin crease almost the level of lateral femoral epicondyle. In Type 1b, SSV divides into two branches: one draining into the popliteal vein in the popliteal fossa, and the other draining into the GSV. In Type 2a, SSV terminates completely into the posterior deep veins of the thigh. Type 2b involves the division of the SSV into two branches at the level of the popliteal fossa: one draining into the GSV and the other into the posterior deep veins of the thigh. Type 2c is defined by direct termination of the SSV into the GSV above the popliteal fossa. In Type 3a, SSV terminates into the GSV below the popliteal fossa and popliteal crease, while Type 3b terminates into the gastrocnemius veins. The illustration of the modified Kosinski classification system with drawings on photographs is presented in Fig. 1. Type 1 variation is the typical termination of SSV draining into popliteal vein in popliteal fossa. Type 2 and 3 variation was defined as atypical termination of SSV. Our data were analyzed using this modified Kosinski classification system. Data on variations of SPJ and termination of SSV were collected and compared between two groups.

Figure 1. The illustration of the modified Kosinski classification system with drawings on photographs. GSV: great saphenous vein, SSV: small saphenous vein.

For each group of patients, the preferred treatment option was selected based on their anatomical variations, ultrasound findings, and symptoms. Conservative treatments, including compression stockings and medical therapy, were preferred for patients deemed inappropriate for endovenous intervention or surgery, or for those who opted against undergoing surgery.

Surgery was performed on symptomatic patients with severe venous insufficiency, as defined by the CEAP [8] (C=clinical manifestations, E=etiology, A=anatomic distribution, P=pathophysiology) clinical stage C2-3, which includes cases where the diameter of GSV was >5 mm, the diameter of SSV was >4 mm, or reflux flow was measured beyond 2 seconds during Valsalva maneuver. GSV stripping or endovenous laser ablation (EVLA) was performed for patients with isolated GSV incompetence. In cases of SSV insufficiency, EVLA was avoided due to its anatomical proximity to the sural nerve. For patients with Type 2 or 3 variation, surgical procedure of SSV ligation and division at the termination point were performed. Phlebectomy was conducted to eliminate additional varicose veins. Following surgery or transcatheter intervention, all patients were advised to use elastic bandages and elevate the operated limbs for one week. Hospitalization typically lasted around 24 hours, with patients mobilized on the first day after surgery. A follow-up examination was scheduled one week and one month post-surgery.

1. Statistical analyses

Normally distributed continuous data were presented as a mean±standard deviation (SD) together with its ranges in brackets and nominal variables were presented as counts and/or percentages. The normality of data distribution was tested using the Kolmogorov Smirnov test and the homogeneity of variations was assessed by Levene’s Test. For statistical comparison of group data, the Student’s t-test was used for normally distributed continuous variables and the Mann-Whitney U-test was used for non-normally distributed continuous variables. The Pearson chi-squared test and Fisher’s exact test were used for statistical comparison of inter-group data. A p-value of <0.05 was considered statistically significant. The SPSS statistical program for Windows, version 16 (SPSS, Inc., Chicago, IL, USA) was used to conduct data analysis.

A total of 133 symptomatic patients with either isolated SSV incompetence or isolated GSV incompetence were evaluated using CD-US to elucidate lower extremity venous anatomy, and to determine the location and severity of insufficiency. The mean age was 33±17 years, with males comprising 84% (n=111) of the participants. Forty-seven patients were diagnosed with isolated SSV incompetence, and 86 patients with isolated GSV incompetence.

Isolated GSV incompetence was more common in male patients than in female patients (p=0.011). When analyzing the demographic data including risk factors for venous insufficiency and symptoms reported by patients, no statistically significant differences were observed between the two groups. Venous insufficiency was more common in the right lower extremities than in the left. However, there was no statistically significant difference between the type of venous insufficiency and the left or right side of the affected leg. Demographic data were summarized in Table 1.

Table 1 . Demographic data.

Variables	Isolated SSV incompetence (n=47)	Isolated GSV incompetence (n=86)	p-value
Male; n (%)	34 (72)	77 (90)	0.01*
Age; mean±SD	34.9±19.0	31.2±15.9	0.64
BMI (kg/m2); mean±SD	24.9±4.5	25.4±3.9	0.7
Obesite (BMI>30); n (%)	6 (13)	13 (15)	0.71
History of smoking; n (%)	23 (49)	53 (62)	0.15
Family history of venous disease; n (%)	24 (51)	44 (51)	0.99
Right lower extremity venous insufficiency; n (%)	25 (53)	52 (61)	0.41
Primary symptoms; n (%)
Pain	33 (70)	59 (69)	0.85
Varicose vein	11 (23)	21 (24)	0.9
Edema	31 (66)	57 (66)	0.97
Hyperpigmentation	3 (6)	4 (5)	0.67
Flushing	24 (51)	54 (63)	0.19
Venous ulcer	0 (0)	0 (0)

BMI: body mass index, GSV: great saphenous vein, kg: kilogram, m2: square meter, SD: standart deviation, SSV: small saphenous vein. *Statistically significant p-values (p<0.05) are displayed by asterisk..

None of our patients in either group exhibited Type 3 variation. The prevalence of Type 1 variation (typical termination) was higher in patients with SSV incompetence compared to those with isolated GSV incompetence (41/47, 87% vs. 54/86, 63%). Although small saphenous vein incompetence was less common in patients with type 2 variation in the termination of the small saphenous vein (16% vs. 43%), the difference was not statistically significant (p=0.055). Additionally, the subgroup analyses of variations categorized with modified Kosinski classification revealed that there was no statistically significant difference between two groups. The data of variations for both groups were presented in Table 2.

Table 2 . Subgroup analysis of both groups based on variations in small saphenous vein termination.

Variations of SSV termination	All patients (n=133)	Isolated SSV incompetence (n=47)	Isolated GSV incompetence (n=86)	p-value
Type 1A; n (%)	59 (44)	26 (55)	33 (38)	0.06
Type 1B; n (%)	36 (27)	15 (32)	21 (24)	0.35
Type 2A; n (%)	12 (9)	2 (4)	10 (12)	0.16
Type 2B; n (%)	17 (13)	2 (4)	15 (17)	0.03*
Type 2C; n (%)	9 (7)	2 (4)	7 (8)	0.39
Type 3A and 3B; n (%)	0 (0)	0 (0)	0 (0)	NA

GSV: great saphenous vein, SSV: small saphenous vein..

*Statistically significant p-values (p<0.05) are displayed by asterisk..

In patients with isolated SSV incompetence, 11 patients (23%, 11/47) underwent a operation for SSV incompetence. The remaining 36 patients received conservative treatment including the use of compression stockings and medical therapy and were followed-up regularly. In patients with isolated GSV incompetence, 21 patients (24%, 21/86) received catheter interventions or underwent surgery to address GSV incompetence. Outpatient follow-up care, including medical treatment was provided to the remaining 65 patients. Surgical techniques for each group were summarized in Table 3.

Table 3 . Surgical procedures for each group.

	Stripping	High ligation and division	Phlebectomy	Perforator vein ligation	EVLA	Overall
Isolated SSV incompetence (n=47)	5	3	2	1	0	11
Isolated GSV incompetence (n=86)	17	0	2	0	2	21

EVLA: endovenous lase ablation, GSV: great saphenous vein, SSV: small saphenous vein..

The postoperative follow-up time was one month. The patients who underwent a surgical or catheter-based intervention in both groups experienced no major complications such as deep venous thrombosis, early recurrence, or neurologic deficit within one month following intervention. However, two patients among those with isolated GSV incompetence reported hypaesthesia on the medial side of their ankles following the GSV stripping procedure.

Considering the variability in embryological development, venous structures may have different origins, courses, and endings. Awareness of these anatomical variations is crucial when determining surgical strategies, as these variations can lead to postoperative complications or recurrence [9]. The variations in localization of junction and termination contribute to a higher rate of recurrent insufficiency for the SPJ, reaching 30%, compared to 7% for the sapheno-femoral junction [10]. The variations may also affect adjacent venous structures, such as the impact of SSV incompetence on GSV incompetence through an incompetent intersaphenous vein [11,12]. To understand more about therapeutic management, we conducted a comparative analysis of variations of SSV in patients with isolated SSV incompetence and isolated GSV incompetence, and subsequently to evaluate the association between the anatomic variance of SSV and SSV incompetence was aimed.

In our study, we compared patients with isolated SSV incompetence to those with isolated GSV incompetence. Our epidemiological committee defined the control group as patients with isolated GSV incompetence instead of a healthy population. This decision was made to prevent an escalation in health costs. Our outcomes are more specifically similar to the findings of Creton [13]. In their study, they observed that Type 1 variation was higher in patients with SSV incompetence than in healthy group (80% vs. 63%). In our study, these rates were 87% and 63%, respectively. They also reported that Type 2 variation was higher in the healthy group, similar as our findings. Therefore, we believe that describing the patients with isolated GSV incompetence as the control group would not affect our results.

There was no evidence of Type 3 variation in our study, similar to the findings in a study conducted by Anbumani et al. [14] involving 50 lower limbs from 25 cadavers. This is likely attributed to the insufficient number of patients in our study. Previous studies with a larger patient sample size have reported 1%–3% Type 3 variation in healthy population [7,15-17] and 0%–26% [18,19] in patients with SSV incompetence.

Patients with isolated SSV incompetence are more likely to have a typical SSV termination, wherein the SSV drains into the popliteal vein in the popliteal fossa. In patients with a typical SSV termination (Type 1 variation), the procedure of high ligation and division of SSV at SPJ was more effective than patients with an atypical SSV termination (Type 2 or 3 variation). Another advantage for the patients with Type 1 variation is the low risk of recurrence due to the incomplete ligation of SSV in the popliteal fossa. Performing an inadequate duplex evaluation before SSV surgery in a patient with SSV incompetence might lead to more complications. However, we did not compare our groups based on complication and recurrence due to short-term follow-up. On the other hand, Type 2 variation, particularly Type 2b, was more common in patients with isolated GSV incompetence. For instance, if a SSV otograft is required as an alternative graft during coronary bypass or peripheral arterial surgery in a patient with isolated GSV incompetence, the high prevelance of atypical termination of SSV should be considered to obtain a graft of optimal length.

The drainage point of gastrocnemius veins below the knee also guides the decision-making process on SSV surgery. The gastrocnemius veins are usually drained into the popliteal veins, sometimes into the tibial veins. They rarely use SSV to be drained into the popliteal vein [20]. Preoperative recognition of these different types of variation helps to prevent not only recurrence, but also the risk of deep venous thrombosis after SSV surgery. In our study, we found that the gastrocnemius veins directly drained into the popliteal veins in all patients. Consequently, no venous thrombosis was identified in any of the patients during the first month after surgery.

Surgery for SSV incompetence has been reported to be more challenging, with a higher complication rate and recurrence rate compared to surgery for GSV incompetence [18]. The primary causes of postoperative recurrence of varicose veins in the popliteal fossa include unrecognized terminal duplication, failure to obliterate the SPJ at the correct location (persistent SSV stump), the simultaneous involvement of the SSV and GSV in the popliteal vein, and the presence of an incompetent perforator or a bulky incompetent twin vein in the popliteal fossa. In these situations, stripping should be preferred over ligature [21].

The risk of neurological damage, particularly to the sural and common peroneal nerves, can reach up to 20% after SSV surgery and up to 5% after EVLA of the SSV [9]. Performing ligation and division of the SPJ above the lateral femoral epicondyle incurs increased risk of CPN injury (2%), not only because of the close association between the SPJ and CPN but also because of their variability [22]. Preoperative evaluation of the SSV closeness of those anatomical structures decreases the rate of neurological complications [20]. Regarding to this concern, we abstained from performing EVLA for SSV incompetence and stripped only the upper 1/3 part of the SSV. No neurological complications were observed in patients underwent SSV surgery.

One limitation of our study is that we did not incorporate the types of treatment methods based on SSV variation type into our analyses.

Based on our experience, it is crucial for an experienced radiologist to identify any anatomical proximity and variations before surgery to ensure effective treatment and prevent complications. To obtain more reliable and definitive findings, further studies with long-term follow-up should involve a larger number of patients.

The current findings emphasize the clinical necessity of a routine and comprehensive preoperative evaluation of the SSV using CD-US. A proper knowledge about the anatomy of the SSV regarding to location of termination, connection with other veins and its proximity to peripheral nerves, is essential for ensuring a safe and successful intervention. The risk of postoperative recurrence may increase in the absence of ultrasonographic mapping, especially in Type 2 and Type 3 variations. Although the results of our study suggest that anatomical variations of the SSV do not impact the prediction of SSV incompetence, we believe that taking SSV variations into account will directly influence postoperative success.

The authors declare no conflicts of interest.

No financial support was received for the research, authorship, and/or publication of this article.