What are the implications of the left small saphenous vein (SSV) terminating into the popliteal vein?

Normal Anatomical Variant with Clinical Significance

The left small saphenous vein (SSV) terminating directly into the popliteal vein represents a normal anatomical variant that occurs in approximately 54-70% of the population and is considered the classic "Type A" or "normal" termination pattern 1. This configuration is clinically significant primarily in the context of venous insufficiency treatment and surgical planning.

Anatomical Context

The SSV-popliteal vein junction (saphenopopliteal junction or SPJ) typically occurs within 100 mm above the lateral femoral epicondyle in approximately 70% of cases 2. This direct termination pattern is the most common configuration, though significant anatomical variation exists 1, 2.

Key Anatomical Relationships

• The popliteal vein lies superficial to the popliteal artery in the popliteal fossa, with both vessels positioned superficial to bony structures 3
• The common peroneal nerve runs in close proximity to the SPJ, with mean distances of 16.7 mm in normal terminations and 23.3 mm in low terminations 2
• The SSV typically forms from the confluence of dorsal foot veins and ascends in the posterior leg compartment 4

Clinical Implications

For Venous Insufficiency and Varicose Veins

Direct SSV termination into the popliteal vein creates a potential pathway for foam sclerotherapy complications, though deep vein thrombosis (DVT) remains rare at 0.6% 5. When treating SSV reflux:

• Patients with direct SSV-popliteal connections should undergo duplex ultrasound examination 1-2 weeks post-sclerotherapy to detect asymptomatic popliteal vein extension 5
• Extension of sclerosis into the popliteal vein occurs exclusively when the SSV connects directly to the popliteal vein 5
• Medial gastrocnemius vein thrombosis risk increases when perforators are present (p = 0.02) 5

For Surgical Planning

The small saphenous vein serves as an alternative autogenous conduit for lower extremity bypass when the great saphenous vein is unavailable or inadequate 3. Key considerations include:

• Preoperative vein mapping using duplex ultrasound should assess SSV patency, diameter (ideally ≥3 mm), length, branching patterns, and presence of thrombosis 3
• SSV grafts demonstrate durable patency in single-center studies for femoral-popliteal and infrapopliteal bypass 3
• The autologous saphenous vein (great or small) remains the conduit of choice for infrainguinal bypass with superior outcomes compared to prosthetic grafts 3

Surgical Risk Considerations

The proximity of the common peroneal nerve to the SPJ creates significant risk during surgical exploration, particularly when the junction is located above the lateral femoral epicondyle 2. The risk increases with:

• High SPJ terminations (>100 mm above lateral femoral epicondyle) where nerve-junction distance decreases 2
• Failure to identify the exact SPJ location preoperatively 2
• Variable anatomy in 30% of cases where termination differs from the classic pattern 1, 2

Diagnostic Approach

Duplex ultrasound remains the first-line imaging method for characterizing SSV anatomy and termination patterns 3. The examination should:

• Image the popliteal fossa with the patient prone or in lateral decubitus position with 10-30 degrees knee flexion 3
• Apply gel from 12 cm superior to 5 cm inferior to the popliteal crease 3
• Document the exact SPJ location relative to anatomical landmarks (lateral femoral epicondyle, fibula head) 2
• Assess for anatomical variants including cranial extensions, gastrocnemius vein connections, and perforators 5, 1

Common Pitfalls

• Assuming all SSVs terminate in the popliteal vein—approximately 17-30% have variant terminations including continuation into the thigh or termination via perforators 1, 6
• Failing to identify the SPJ during ultrasound examination due to anatomical variation, which may require imaging to 7 cm below the popliteal crease 3
• Inadequate preoperative mapping before using SSV as a bypass conduit, risking intraoperative discovery of unsuitable vein 3
• Not recognizing the increased surgical risk when the SPJ is located high in the popliteal fossa near the common peroneal nerve 2