Perthes Test: Purpose, Procedure, Interpretation, and Limitations

What is the Perthes Test Used For?

The Perthes test is a clinical maneuver primarily used to assess the patency (openness) of the deep venous system in the lower extremities, particularly when investigating chronic venous insufficiency or varicose veins. It helps clinicians determine if the deep veins are obstructed, which can impact blood flow dynamics.

Introduction to the Perthes Test

The Perthes test is a classical bedside examination, a component of the physical assessment for individuals presenting with venous leg issues. While modern imaging techniques like Duplex ultrasound have largely supplanted its routine use for definitive diagnosis, understanding the Perthes test provides valuable insight into the physiology of venous return and remains a foundational concept in vascular assessment. It is a practical application of biomechanical principles related to the muscle pump mechanism.

Purpose of the Perthes Test

The primary purpose of the Perthes test is to evaluate the patency of the deep venous system in the leg. Specifically, it aims to differentiate between:

• Deep Venous Obstruction: To determine if there is a blockage in the deep veins (e.g., due to a past deep vein thrombosis, DVT, or external compression).
• Competent Deep Veins: To confirm that the deep veins are clear and capable of handling venous return.

It helps to understand the underlying cause of superficial venous distension or chronic leg swelling, guiding further diagnostic steps and treatment strategies.

Anatomy and Physiology Behind the Test

To comprehend the Perthes test, a basic understanding of lower limb venous anatomy and physiology is crucial:

• Superficial Veins: These veins (e.g., great saphenous vein, small saphenous vein) lie just beneath the skin. They collect blood from the skin and subcutaneous tissues.
• Deep Veins: These veins (e.g., femoral vein, popliteal vein, tibial veins) run alongside arteries, deep within the muscle compartments. They carry the majority of venous blood return from the leg.
• Perforating Veins: These short veins connect the superficial venous system to the deep venous system, piercing through the deep fascia. They contain valves that normally ensure unidirectional flow from superficial to deep veins.
• Calf Muscle Pump: The contraction and relaxation of calf muscles (gastrocnemius and soleus) act as a pump. During contraction, muscles compress deep veins, pushing blood proximally towards the heart. During relaxation, valves prevent backflow, and blood is drawn from the superficial system into the deep system via perforators.

The Perthes test leverages the calf muscle pump mechanism. If the deep veins are patent, the muscle pump efficiently propels blood from the superficial system (which is temporarily isolated by a tourniquet) into the deep system and then proximally. If the deep veins are obstructed, this pathway is blocked, leading to a visible change in the superficial veins.

How the Test is Performed

The Perthes test typically involves the following steps:

1. Patient Positioning: The patient lies supine (on their back) with the affected leg elevated to approximately 45-60 degrees for a few minutes. This allows gravity to assist in emptying the superficial veins of blood.
2. Tourniquet Application: Once the superficial veins appear collapsed or maximally emptied, a tourniquet (or a blood pressure cuff inflated to just above venous pressure, typically 60-80 mmHg) is applied around the thigh, just below the knee. The tourniquet should be tight enough to occlude superficial venous flow but not arterial flow.
3. Ambulation/Exercise: The patient is then asked to stand and perform repetitive ankle dorsiflexion and plantarflexion (like marching in place) or walk for 5 to 10 minutes. This activates the calf muscle pump.
4. Observation: The superficial veins are carefully observed during and immediately after the exercise.

Interpreting the Results

The interpretation of the Perthes test depends on the changes observed in the superficial veins:

• Normal (Patent Deep Veins):
  • Observation: The superficial veins either remain collapsed or significantly diminish in size.
  • Interpretation: This indicates that the deep venous system is patent and competent. The calf muscle pump is effectively pushing blood from the superficial veins (via the perforators) into the deep system, which then transports it proximally past the tourniquet.
• Positive Perthes Test (Deep Vein Obstruction):
  • Observation: The superficial veins become more distended, engorged, or prominent during the exercise. The patient may also report pain or a feeling of fullness in the leg.
  • Interpretation: This is a positive Perthes test, suggesting an obstruction within the deep venous system. With the deep veins blocked, the muscle pump cannot effectively move blood from the superficial system proximally. The blood gets trapped and backs up, causing the superficial veins to swell further.

Clinical Significance and Limitations

• Clinical Significance: A positive Perthes test strongly suggests deep venous obstruction, which could be a sequela of a previous DVT or a rare congenital anomaly. This finding would necessitate further investigation, typically with Duplex ultrasound, to confirm the diagnosis and identify the exact location and nature of the obstruction. It helps in planning management for chronic venous insufficiency and decision-making regarding surgical interventions for varicose veins (e.g., stripping superficial veins in the presence of deep vein obstruction could worsen leg swelling).
• Limitations:
  • Subjectivity: The interpretation can be subjective, relying on visual assessment of venous distension.
  • Specificity/Sensitivity: The test is not highly specific or sensitive compared to modern diagnostic imaging. It may not detect partial obstructions or distinguish between different types of venous pathology with precision.
  • Inability to pinpoint location: It indicates an obstruction but doesn't specify its exact location or extent.
  • Replacement by Imaging: Duplex ultrasound is now the gold standard for evaluating venous patency and competence, offering real-time visualization of blood flow, thrombi, and valvular function.

Despite its limitations, the Perthes test remains a valuable historical and educational tool, illustrating the fundamental mechanics of venous return in the lower limbs.

Who Performs This Test?

The Perthes test is typically performed by healthcare professionals involved in vascular assessment, including:

• Physicians: General practitioners, vascular surgeons, dermatologists, and internal medicine specialists.
• Nurses: Especially those specializing in wound care or vascular assessment.
• Physical Therapists: As part of a comprehensive lower extremity examination.

Conclusion

The Perthes test is a classic clinical maneuver designed to evaluate the patency of the deep venous system in the lower leg. By observing the changes in superficial veins during calf muscle pump activation while superficial flow is occluded, clinicians can infer whether the deep veins are clear or obstructed. While largely superseded by advanced imaging, its understanding remains fundamental for anyone studying vascular physiology or assessing patients with venous disorders, providing a tangible link between anatomical structures and physiological function.