4.4 Peripheral Vascular Examination
Key Takeaways
- Normal capillary refill returns color within about 2 seconds; delayed refill suggests peripheral arterial insufficiency.
- The Allen test assesses collateral circulation between the radial and ulnar arteries through the palmar arch before relying on either vessel alone.
- Vascular claudication is relieved by simply standing still, while neurogenic claudication from spinal stenosis is relieved by sitting or spinal flexion.
- Diminished or absent distal pulses support a vascular cause of leg pain, while neurogenic claudication typically preserves normal pulses.
- Homan's sign has poor sensitivity and specificity for DVT; unexplained unilateral swelling and calf tenderness warrant referral for vascular imaging rather than manual care.
Why the Peripheral Vascular Exam Matters
Limb pain, numbness, and fatigue are common presenting complaints in a chiropractic setting, and Part III expects candidates to recognize when a complaint that looks neuromusculoskeletal on the surface is actually vascular in origin and requires referral rather than manual care. The peripheral vascular exam — pulse palpation, capillary refill, the Allen test, and claudication history — is the standard screening toolkit for that discrimination.
Pulse Palpation and Grading
Pulses are palpated bilaterally and compared for symmetry, rate, rhythm, and amplitude at standard sites:
| Site | Location |
|---|---|
| Carotid | Anterior to the sternocleidomastoid, at the level of the thyroid cartilage (palpate one side at a time, gently, to avoid provoking a vasovagal or baroreceptor response) |
| Brachial | Medial aspect of the antecubital fossa |
| Radial | Anterolateral wrist, lateral to the flexor carpi radialis tendon |
| Femoral | Below the inguinal ligament, midway between the ASIS and pubic symphysis |
| Popliteal | Deep in the popliteal fossa; best felt with the knee slightly flexed |
| Posterior tibial | Posterior to the medial malleolus |
| Dorsalis pedis | Dorsum of the foot, lateral to the extensor hallucis longus tendon |
Pulses are typically graded on a 0-4+ scale: 0 = absent, 1+ = markedly diminished, 2+ = normal, 3+ = full/increased, and 4+ = bounding. A diminished or absent pulse distal to a suspected occlusion is a core finding of peripheral arterial disease (PAD), and asymmetric pulses between limbs are more diagnostically meaningful than a single, isolated reading.
Capillary Refill Test
The capillary refill test evaluates peripheral perfusion at the microvascular level. The examiner compresses a fingertip or nail bed until it blanches, then releases and times the return of normal color. A refill time of about 2 seconds or less is normal; a delayed refill suggests reduced peripheral perfusion, which can reflect peripheral arterial insufficiency, shock, or dehydration, though the test is also confounded by ambient temperature and hypothermia, which slow refill even in healthy vasculature. Capillary refill is a fast bedside adjunct to pulse palpation, not a replacement for it.
The Allen Test
The Allen test evaluates the adequacy of collateral blood flow between the radial and ulnar arteries through the palmar arch of the hand, most classically performed before procedures that rely on radial artery patency, and also useful when a patient reports hand ischemic symptoms. Procedure:
- The examiner occludes both the radial and ulnar arteries at the wrist with firm digital pressure.
- The patient clenches and opens the fist several times to exsanguinate (drain blood from) the hand, then holds it open.
- The examiner releases pressure over one artery, for example the ulnar, while keeping the other occluded.
- Color should return to the entire hand within about 5-7 seconds if collateral flow through the palmar arch is adequate.
- The test is then repeated, releasing the other artery.
A delayed or incomplete return of color (a positive/abnormal Allen test) indicates inadequate collateral circulation through the palmar arch from the artery that was released, meaning that vessel cannot be safely relied upon alone to perfuse the hand.
Vascular Claudication vs. Neurogenic Claudication
Both peripheral arterial disease and lumbar spinal stenosis can produce leg pain that appears with walking, but the underlying mechanism, and therefore the pattern, differs sharply — a distinction the exam tests directly:
| Feature | Vascular (True) Claudication | Neurogenic Claudication (Pseudoclaudication) |
|---|---|---|
| Underlying cause | Arterial insufficiency (atherosclerosis/PAD) | Lumbar spinal stenosis compressing the cauda equina/nerve roots |
| Typical pain location | Calf (most common), or thigh/buttock depending on the level of occlusion | Bilateral buttock, thigh, and/or leg, often vaguely localized |
| Aggravated by | A fairly consistent walking distance; worse walking uphill (greater muscular oxygen demand) | Walking downhill, standing upright, or any lumbar extension posture |
| Relieved by | Simply standing still (rest); no position change required | Sitting down or bending forward (lumbar flexion), which enlarges the spinal canal |
| Distal pulses | Diminished or absent | Normal |
| Skin/trophic changes | Hair loss, shiny skin, pallor on elevation, dependent rubor | None |
| Response to stationary cycling | Still provokes pain (exertion-dependent regardless of trunk position) | Often tolerated well in a flexed position, since flexion, not exertion alone, relieves the symptoms |
The single most efficient discriminator to remember is posture-dependence: vascular claudication cares about how far and how hard the patient walks, while neurogenic claudication cares about what posture the spine is in.
Signs of Deep Vein Thrombosis (DVT)
Deep vein thrombosis is a vascular emergency that can mimic calf strain or mechanical leg pain, making recognition essential before applying any manual therapy to the limb. Classic findings include unilateral calf swelling (commonly defined as a calf circumference difference of 3 cm or more compared with the other leg), warmth, erythema, tenderness along the deep venous tract, and pitting edema.
Homan's sign (passive dorsiflexion of the ankle with the knee extended, said to be positive if it provokes calf pain) is still commonly taught, but candidates should know it has poor sensitivity and specificity and is no longer recommended as a reliable standalone diagnostic maneuver; some clinicians avoid it altogether out of a longstanding, though not strongly evidenced, concern about mechanically dislodging a thrombus. Modern practice instead uses validated clinical prediction tools, such as the Wells criteria, to stratify pretest probability, combined with D-dimer testing and compression ultrasound for confirmation. The exam-relevant takeaway is behavioral: any real suspicion of DVT is an immediate referral, not a differential to work through with orthopedic testing or a trial of conservative care.
Integrating the Vascular Screen
The peripheral vascular exam exists on Part III primarily as a safety filter: it identifies the subset of limb complaints that are not appropriate for chiropractic management alone. A patient with normal, symmetric pulses, brisk capillary refill, and posture-independent leg pain that varies with walking distance is more likely to have a musculoskeletal or vascular claudication picture worth further orthopedic and vascular workup, while unilateral swelling with unremarkable pulses and refill but calf tenderness and warmth should raise DVT concern immediately, ahead of any mechanical explanation.
During capillary refill testing, color should normally return to a blanched nail bed or fingertip within approximately:
What is the primary purpose of the Allen test?
A patient's leg pain is relieved by sitting down and bending forward, but is reliably reproduced after walking downhill or standing upright, with distal pulses that remain normal. This presentation is most consistent with: