INTRODUCTION TO UPPER EXTREMITY VASCULAR PATHOLOGY
Ischemic conditions of the hand and digits represent a formidable challenge in operative orthopaedics and hand surgery. While the upper extremity is endowed with a robust and highly redundant collateral circulation, localized vascular insults—specifically aneurysms, thrombosis, and embolisms within the radial, ulnar, and digital arteries—can precipitate profound ischemia. Left untreated, these pathologies can progress to debilitating pain, ulceration, and irreversible tissue necrosis.
Arterial occlusive ischemia in the upper extremity is frequently multifactorial. It is commonly associated with direct blunt or penetrating trauma, iatrogenic injury from arterial cannulation or angiography, and systemic vasculopathies including atherosclerosis, fibromuscular dysplasia, and various collagen vascular diseases. Mastery of the vascular anatomy, precise diagnostic algorithms, and advanced microsurgical reconstructive techniques are mandatory for the practicing hand surgeon to salvage function and prevent amputation.
SURGICAL ANATOMY AND HEMODYNAMICS
A profound understanding of the palmar arterial arches is the cornerstone of surgical decision-making in hand ischemia. The vascular supply to the hand is characterized by a complex anastomotic network primarily fed by the radial and ulnar arteries.
The Superficial and Deep Palmar Arches
Through the continuation of the radial artery into the hand as the deep palmar arch, and the ulnar artery as the superficial palmar arch, circulation is usually sufficient to maintain digital viability despite significant proximal disease or injury.
- The Superficial Palmar Arch: Primarily formed by the ulnar artery, it anastomoses with the superficial palmar branch of the radial artery. Anatomical studies demonstrate that the superficial arch is complete in approximately 80% of hands and incomplete in 20%.
- The Deep Palmar Arch: Primarily formed by the radial artery, it anastomoses with the deep palmar branch of the ulnar artery. The deep arch is highly reliable, being complete in approximately 98% of hands.
Arterial Dominance
Hemodynamic dominance varies significantly among individuals, which directly impacts the clinical presentation of arterial occlusions:
* Radial Dominance: The radial artery provides the majority of blood flow to three or more digits in 57% of hands.
* Ulnar Dominance: The ulnar artery provides the primary flow to three or more digits in nearly 22% of hands.
* Co-Dominance: Equal flow contribution from both the radial and ulnar arteries is observed in approximately 22% of hands.
Surgical Warning: Never assume a co-dominant vascular supply. The 20% incidence of an incomplete superficial palmar arch means that indiscriminate ligation of a traumatized ulnar or radial artery without prior confirmation of collateral flow can result in catastrophic digital ischemia.
PATHOPHYSIOLOGY AND ETIOLOGY
Arterial Aneurysms
Aneurysms in the hand and wrist may have atherosclerotic, mycotic, metabolic, or congenital origins; however, the vast majority encountered by the orthopaedic surgeon are traumatic in etiology.
* True Aneurysms: Involve dilation of all three layers of the arterial wall (intima, media, adventitia). These are typically the result of repetitive blunt trauma, which causes degradation of the elastic lamina and media.
* False Aneurysms (Pseudoaneurysms): Consist of a contained hematoma communicating with the arterial lumen, lacking a true epithelialized wall. These almost exclusively result from penetrating trauma (e.g., knife wounds, glass lacerations) or iatrogenic instrumentation.
Arterial Thrombosis
Arterial thrombosis in the wrist, palm, and fingers is frequently related to occupational or recreational trauma.
* Hypothenar Hammer Syndrome (HHS): The ulnar artery is the vessel most commonly affected by trauma-related thrombosis. As the ulnar artery exits Guyon's canal, it lies relatively unprotected over the hook of the hamate. Repeated forceful impacts—such as using the hypothenar eminence as a hammer—cause intimal injury, vasospasm, and subsequent thrombosis.
* Iatrogenic Thrombosis: Arterial cannulation in the forearm (e.g., radial artery lines for hemodynamic monitoring) is a leading cause of iatrogenic thrombosis, necessitating careful post-procedural vascular assessment.
Arterial Embolism
Emboli in the upper extremity typically originate from proximal sources. Cardiac emboli (e.g., from atrial fibrillation or valvular vegetations) or microemboli shedding from a proximal subclavian or ulnar artery aneurysm can lodge in the digital arteries, causing sudden, painful ischemia.
CLINICAL PRESENTATION AND EVALUATION
Symptoms of hand ischemia include severe pain, claudication with activity, sensory changes, skin discoloration, ulceration, and frank necrosis. These symptoms are characteristically aggravated by smoking, physical activity, and cold exposure.
Physical Examination
A meticulous physical examination is diagnostic in many cases. Findings include:
* Digital pallor or cyanosis.
* Skin ulceration or necrosis distal to the occlusion.
* Sensory deficits (and occasionally motor changes) in the distribution of the affected nerves, particularly the ulnar nerve in Guyon's canal due to compression from an ulnar artery aneurysm.
* Coolness to palpation.
* Tenderness over an aneurysmal or thrombotic mass.
* A palpable thrill or pulsatile mass (indicative of an aneurysm).
The Allen Test
The Allen test is the fundamental clinical tool for assessing the patency of the palmar arches.
1. The patient is asked to tightly clench their fist to exsanguinate the hand.
2. The examiner applies firm occlusive pressure to both the radial and ulnar arteries at the wrist.
3. The patient opens their hand (which should appear blanched).
4. Pressure is released from one artery, and the time taken for the hand to flush pink is recorded.
5. A normal capillary refill time is less than 7 seconds. A delay indicates an incomplete arch or proximal occlusion.
Clinical Pearl: Because of severe vasospasm in the distal vessels, traumatic thrombosis can easily be confused with vasospastic disorders such as Raynaud's disease. A thorough occupational history and unilateral presentation strongly favor a traumatic etiology.
Diagnostic Imaging
When clinical examination suggests vascular compromise, advanced imaging is required to map the lesion and plan surgical intervention.
* Non-Invasive Modalities: Doppler flow assessment, ultrasonography (Duplex), pulse volume recordings (PVR), segmental arterial measurement, and skin temperature measurement. A digital-brachial index (DBI) is highly useful; a DBI > 0.7 generally indicates adequate perfusion.
* Advanced Imaging: Magnetic Resonance Angiography (MRA) and Computed Tomography Angiography (CTA) provide excellent non-invasive mapping.
* Contrast Angiography: Remains the gold standard. It provides definitive, high-resolution information regarding the location and extent of the principal lesion, the status of the collateral circulation, and the presence of distal microemboli.
SURGICAL INDICATIONS AND DECISION MAKING
The primary decision in the surgical management of hand aneurysms and thrombosis is whether to perform excision alone (ligation) or excision with arterial reconstruction.
Preoperative and intraoperative evaluations of the palmar vascular arch anatomy and the quality of distal circulation dictate this decision.
* Indications for Excision Alone: If the palmar arterial arch is complete and distal circulation is robust—determined by a brisk pink distal skin color after tourniquet release, or by pulse volume recordings demonstrating a digital-brachial index of > 0.7—repair or reconstruction is usually unnecessary. The diseased segment can be safely ligated and resected.
* Indications for Reconstruction: Conversely, if the palmar arterial arch is incomplete, or if distal circulation is inadequate following temporary clamping of the diseased segment, the artery must be reconstructed. This is typically achieved using a reversed segmental interposition vein graft.
OPERATIVE TECHNIQUES
1. Preoperative Preparation and Positioning
- Anesthesia: General anesthesia or a regional brachial plexus block is utilized. Regional anesthesia is often preferred as it provides a sympathectomy effect, reducing vasospasm and maximizing vasodilation.
- Positioning: The patient is positioned supine with the affected arm extended on a radiolucent hand table.
- Equipment: A pneumatic tourniquet is applied to the proximal arm. Operating loupes (3.5x to 4.5x magnification) or an operating microscope are essential for microsurgical anastomosis.
2. Surgical Approach to the Ulnar Artery (Guyon's Canal)
For hypothenar hammer syndrome or ulnar artery aneurysms:
1. Incision: A zigzag or Brunner-type incision is made over the volar-ulnar aspect of the wrist, extending from the distal forearm, across the wrist crease, and into the hypothenar eminence.
2. Dissection: The antebrachial fascia is incised. The ulnar nerve and artery are identified proximal to the wrist crease.
3. Guyon's Canal Release: The volar carpal ligament is meticulously divided to unroof Guyon's canal. The ulnar artery is mobilized, and the ulnar nerve (and its superficial and deep branches) is carefully protected with vessel loops.
4. Lesion Identification: The thrombosed segment or aneurysm is identified. Proximal and distal vascular control is obtained using atraumatic microvascular clamps.
3. Surgical Approach to the Radial Artery
For radial artery aneurysms or thrombosis:
1. Incision: A longitudinal or curvilinear incision is made over the volar-radial aspect of the distal forearm, extending toward the anatomic snuffbox if necessary.
2. Dissection: The fascia between the brachioradialis and flexor carpi radialis is incised. The superficial branch of the radial nerve is identified and protected.
3. Mobilization: The radial artery is dissected free from its venae comitantes. Proximal and distal control is achieved.
4. Resection and Intraoperative Assessment
- Systemic heparinization (e.g., 3,000 to 5,000 units IV) is administered prior to clamping, unless contraindicated.
- The diseased arterial segment is clamped proximally and distally.
- The aneurysm or thrombosed segment is excised entirely. It is critical to resect back to healthy, normal-appearing intima to prevent anastomotic failure.
- The Intraoperative Tourniquet Test: The proximal clamp is left in place, and the tourniquet is deflated. If the distal stump exhibits brisk back-bleeding and the digits remain pink, collateral flow is adequate. If back-bleeding is sluggish or absent, reconstruction is mandatory.
5. Arterial Reconstruction with Reversed Vein Graft
When reconstruction is indicated, an interposition vein graft is the gold standard.
1. Graft Harvest: A suitable superficial vein is harvested. The volar forearm veins (e.g., cephalic vein branches) are preferred for size-matching to the radial or ulnar arteries. Alternatively, the saphenous vein from the lower extremity can be used.
2. Preparation: The vein graft is gently dilated with heparinized saline. Crucially, the vein must be reversed so that its venous valves do not impede arterial blood flow.
3. Anastomosis: Under operating microscope magnification, the reversed vein graft is interposed into the arterial defect.
4. Suturing: End-to-end anastomoses are performed using 8-0 or 9-0 non-absorbable monofilament sutures (e.g., nylon). A triangulation technique or simple interrupted sutures are utilized to ensure a patent, leak-free anastomosis without stricture.
5. Reperfusion: The clamps are removed (distal first, then proximal). The anastomoses are inspected for leaks, and adventitial bands causing kinking are excised. Papaverine or warm lidocaine may be applied topically to alleviate vasospasm.
Surgical Pitfall: Failure to resect the artery back to healthy intima is the most common cause of acute graft thrombosis. Intimal hyperplasia or residual microscopic thrombus will rapidly occlude the microsurgical anastomosis.
POSTOPERATIVE PROTOCOL AND REHABILITATION
Postoperative management is critical to maintaining graft patency and ensuring optimal functional recovery.
Medical Management
- Anticoagulation: Depending on the surgeon's preference and the quality of the anastomosis, patients may be maintained on a continuous intravenous Heparin infusion or Dextran-40 for 3 to 5 days postoperatively.
- Antiplatelet Therapy: Aspirin (81 mg to 325 mg daily) is typically initiated immediately and continued for 3 to 6 months to prevent platelet aggregation at the anastomotic sites.
- Vasodilators: Calcium channel blockers (e.g., Nifedipine) may be prescribed to mitigate postoperative vasospasm, particularly in patients with a history of smoking or cold intolerance.
Monitoring and Rehabilitation
- Monitoring: The digits are monitored hourly for the first 24-48 hours using clinical observation (color, capillary refill, turgor) and surface Doppler probes.
- Immobilization: The wrist is immobilized in a bulky, non-compressive dressing and a volar splint in neutral position to prevent tension on the vascular anastomoses.
- Therapy: Gentle, supervised active range of motion of the digits is encouraged early to prevent tendon adhesions, while wrist motion is restricted for 2 to 3 weeks until the arterial repair has stabilized.
COMPLICATIONS
Despite meticulous technique, complications can arise:
1. Graft Thrombosis: The most devastating complication, usually occurring within the first 72 hours. It requires immediate re-exploration, thrombectomy, and potentially revision of the anastomosis.
2. Ischemic Contracture: Delayed or inadequate treatment can lead to intrinsic muscle necrosis and subsequent Volkmann-type ischemic contractures of the hand.
3. Nerve Injury: Iatrogenic injury to the ulnar or radial nerves during dissection can result in painful neuromas or permanent sensory/motor deficits.
4. Cold Intolerance: Even with successful revascularization, patients frequently experience long-term cold intolerance and must be counseled to avoid smoking and extreme temperatures.
