Case 50: Is Your Hand Pain Hypothenar Hammer Syndrome?

Case 50: Is Your Hand Pain Hypothenar Hammer Syndrome?

Patient Presentation & History

A 48-year-old right-hand dominant male presented to the orthopedic trauma clinic with a 6-month history of progressive left hand pain, cold intolerance, numbness, and episodic digital pallor and cyanosis primarily affecting the ring and small fingers. He reported an insidious onset with worsening of symptoms over the past three months. The pain was described as a dull ache in the hypothenar eminence, radiating distally into the digits, exacerbated by gripping activities and cold exposure. He also noted a subjective sensation of "weakness" in the hand, particularly with fine motor tasks, although he denied specific motor deficits.

His occupational history is significant: he has been a carpenter for 25 years, frequently using his left hand as an improvised hammer or striking surface for nails and chisels, particularly the hypothenar region. He also enjoys cycling, often holding handlebars for extended periods. There was no history of acute traumatic injury to the hand.

Demographics:
* Age: 48
* Sex: Male
* Dominant Hand: Right
* Affected Hand: Left

Comorbidities:
* Well-controlled hypertension on a single oral antihypertensive.
* Hyperlipidemia, managed with statin therapy.
* No history of diabetes, autoimmune disease, or other known vasculitis.
* Non-smoker, occasional alcohol use.
* No history of prior hand surgery or significant trauma.

The patient initially attributed his symptoms to "overuse" or "arthritis" and attempted self-management with over-the-counter analgesics and rest, with minimal relief. The increasing frequency and severity of digital ischemic episodes prompted his presentation.

Clinical Examination

General Inspection:
* Left hand showed mild hypothenar fullness and erythema compared to the contralateral side.
* Trophic changes were noted in the distal phalanges of the left ring and small fingers, including subtle nail ridging and dry, slightly atrophic skin.
* Intermittent pallor and cyanosis observed in the fingertips of the ring and small fingers, particularly when the hand was dependent or exposed to room temperature.
* No gross deformities, open wounds, or obvious muscle atrophy was apparent.

Palpation:
* Tenderness was elicited directly over the hypothenar eminence, specifically overlying Guyon's canal, with a focal point just proximal to the hook of the hamate.
* A subtle, pulsatile, yet slightly firm mass was palpable in this region, which was tender to direct pressure.
* Peripheral pulses: Radial pulse was strong and equal bilaterally. Ulnar pulse was diminished on the left side compared to the right, and occasionally non-palpable with mild digital pressure.
* Temperature of the affected digits (ring and small fingers) was perceptibly cooler than the corresponding fingers on the right hand or other fingers on the left hand.
* Allen's test: Performed bilaterally.
* Right hand: Radial and ulnar arteries patent; good collateral flow (reperfusion time < 5 seconds).
* Left hand: Radial artery occlusion and release showed normal reperfusion. Ulnar artery occlusion and release resulted in significantly delayed reperfusion (> 15 seconds) or absent reperfusion in the ring and small fingers, confirming compromised ulnar artery flow and inadequate collateral circulation from the radial artery to the ulnar digits.

Range of Motion (ROM):
* Active and passive ROM of the wrist, thumb, and digits were full and symmetrical compared to the contralateral limb, though sustained gripping caused discomfort in the hypothenar region.
* No crepitus or instability detected.

Neurological Assessment:
* Sensory:
* Two-point discrimination (2PD) was impaired in the ulnar half of the ring finger (10mm, normal <6mm) and the entire small finger (9mm, normal <6mm) on the left hand.
* Light touch and pinprick sensation were diminished in the same distribution, consistent with sensory deficit in the ulnar nerve distribution.
* No sensory deficits noted in the median or radial nerve distributions.
* Motor:
* Gross motor strength of intrinsic hand muscles was assessed. Mild weakness (4/5 MRC scale) was noted in the intrinsic muscles supplied by the ulnar nerve (e.g., adductor pollicis, interossei, abductor digiti minimi) on the left hand compared to the right.
* Specifically, grip strength was subjectively weaker, and pinch strength (key pinch, tip pinch) was mildly reduced.
* No obvious clawing of the fingers or Froment's sign was present.
* Special Tests:
* Tinel's sign over Guyon's canal was positive, eliciting paresthesia into the small finger.
* Phalen's and reverse Phalen's tests were negative.
* Finkelstein's test was negative.

Imaging & Diagnostics

Plain Radiographs (X-ray):
* Left Hand (PA, Oblique, Lateral views): Revealed no acute fractures, dislocations, or significant degenerative changes. Bony architecture appeared normal. No evidence of calcification within vascular structures. This was primarily to rule out bony causes of compression or pathology.

Duplex Ultrasound (DUS) with Doppler Flow Study:
* Indications: High suspicion of arterial pathology given the history of repetitive trauma, focal tenderness, diminished ulnar pulse, positive Allen's test, and digital ischemic symptoms.
* Findings:
* Demonstrated a fusiform aneurysm of the ulnar artery within Guyon's canal, measuring approximately 5mm in diameter, with evidence of intraluminal thrombus formation.
* Distal to the aneurysm, there was significant post-stenotic turbulent flow and a segment of complete occlusion of the ulnar artery, extending approximately 2cm.
* Doppler studies confirmed absent flow in the ulnar artery distal to the occlusion, and severely dampened flow proximally.
* The common digital arteries to the ring and small fingers showed markedly reduced and monophasic flow, consistent with severe distal ischemia.
* The radial artery demonstrated normal caliber and triphasic flow, supplying the superficial palmar arch via robust communicating branches, but insufficient to compensate for the ulnar artery compromise in the ulnar digits.
* No obvious external compression of the ulnar nerve by the aneurysm was definitively visualized, though the surrounding tissues appeared edematous.

Computed Tomography Angiography (CTA):
* Indications: To precisely delineate the extent of the ulnar artery pathology, assess the full length of the vessel and its branches, evaluate collateral circulation, and provide a 3D anatomical map for surgical planning.
* Findings:
* Confirmed the presence of a 5x7mm saccular aneurysm originating from the ulnar artery within Guyon's canal, immediately proximal to the origin of the superficial palmar arch.
* Significant intraluminal thrombus was noted within the aneurysm and extending into the distal ulnar artery for approximately 2.5cm, leading to complete occlusion.
* Microaneurysms and occlusive changes were also identified in the proper digital arteries of the ring and small fingers, distal to the main ulnar artery occlusion, suggesting embolization from the primary lesion.
* The superficial palmar arch was partially patent, receiving flow primarily from the radial artery via the radial-superficial arch connection, but flow to the ulnar digits was severely impaired.
* Collateral circulation from the radial artery via the deep palmar arch appeared relatively robust, but its contribution to the superficial arch and ulnar digits was insufficient.
* No bony abnormalities or extrinsic compression from surrounding soft tissues were identified other than the mass effect of the aneurysm itself.

Magnetic Resonance Imaging (MRI):
* Indications: Primarily to assess for potential ulnar nerve compression or involvement, soft tissue pathology, and to evaluate the extent of ischemic changes in intrinsic muscles or other hand structures.
* Findings:
* Showed a well-circumscribed lesion consistent with an aneurysm within Guyon's canal, with signal characteristics suggestive of intraluminal thrombus.
* Edema and mild signal changes were noted in the surrounding soft tissues, particularly adjacent to the ulnar nerve.
* The ulnar nerve itself appeared mildly compressed and displayed increased signal intensity on T2-weighted images proximal to the aneurysm, suggesting demyelination or irritation, but no definite nerve transection or severe structural damage.
* No significant muscle atrophy or other diffuse ischemic changes were evident in the intrinsic muscles beyond what might be attributed to chronic nerve irritation.

Nerve Conduction Studies (NCS) and Electromyography (EMG):
* Indications: To objectively quantify ulnar nerve function and rule out other causes of neuropathy, as the clinical picture involved both vascular and neurological symptoms.
* Findings:
* Nerve Conduction Studies: Demonstrated mildly reduced sensory nerve action potential (SNAP) amplitudes and prolonged sensory latencies of the ulnar nerve to the small finger, confirming a mild ulnar neuropathy at the wrist. Motor nerve conduction velocities across the wrist were borderline slow but within normal limits.
* Electromyography: Showed sparse positive sharp waves and fibrillation potentials in the abductor digiti minimi and first dorsal interosseous muscles, indicating mild chronic denervation, consistent with a mild to moderate ulnar neuropathy.
* Conclusion: Findings suggested a mild ulnar neuropathy at the wrist, likely secondary to external compression or irritation from the adjacent vascular pathology, rather than a primary severe ulnar nerve entrapment syndrome.

Templating / Pre-operative Planning:
* Based on CTA findings, the segment of ulnar artery pathology (aneurysm and thrombotic occlusion) measured approximately 3-4 cm.
* Pre-operative discussion considered the need for interposition vein grafting versus simple ligation. Given the patient's symptomatic digital ischemia and the length of the occluded segment, an interposition graft was deemed the preferred approach to restore distal arterial flow and optimize digital perfusion.
* Potential harvest sites for autogenous vein graft (e.g., ipsilateral forearm vein, contralateral arm/leg vein) were identified.
* The operative plan included careful dissection of Guyon's canal, resection of the pathological ulnar artery segment, reconstruction with an autogenous vein graft, and concomitant ulnar nerve neurolysis.

Differential Diagnosis

The patient's presentation with hand pain, digital ischemia, and neurological symptoms in the ulnar distribution necessitates a thorough differential diagnosis. The key is to distinguish primary vascular pathologies from nerve entrapments, systemic conditions, or local musculoskeletal issues.

Surgical Decision Making & Classification

The decision to proceed with surgical intervention was based on several critical factors:
1. Persistent and Worsening Digital Ischemia: The patient's symptoms of cold intolerance, intermittent pallor/cyanosis, and trophic changes were progressive and indicative of critical arterial insufficiency to the ulnar two digits. Conservative management (activity modification, antiplatelet therapy) had failed to alleviate these symptoms.
2. Symptomatic Ulnar Artery Aneurysm with Thrombus: The presence of a palpable, tender, pulsatile mass, confirmed by DUS and CTA to be an ulnar artery aneurysm with significant intraluminal thrombus, presented a clear risk of further distal embolization and complete digital necrosis. Aneurysms within Guyon's canal are particularly prone to thrombosis and embolization due to their anatomical vulnerability and the potential for repeated trauma.
3. Compromised Ulnar Nerve Function: While mild, the objective evidence of ulnar neuropathy on NCS/EMG and clinical examination suggested that the aneurysm was contributing to nerve irritation or compression within the confined space of Guyon's canal. Addressing the vascular pathology was anticipated to relieve this neural component.
4. Inadequate Collateral Circulation: The positive Allen's test and CTA findings confirmed insufficient collateral flow from the radial artery to adequately perfuse the ulnar digits in the absence of a patent ulnar artery. Simple ligation of the ulnar artery without reconstruction would risk further exacerbating the digital ischemia.

Surgical Classification for Hypothenar Hammer Syndrome (HHS):
While there isn't a universally accepted formal surgical classification system like those for fractures, HHS can be categorized based on the specific arterial pathology observed, which directly influences surgical planning:

• Type I: Ulnar Artery Thrombosis without Aneurysm: Occlusion of the ulnar artery, often with distal emboli, but no significant dilation of the vessel wall.
• Type II: Ulnar Artery Aneurysm with or without Thrombosis: Aneurysmal dilation of the ulnar artery, which may contain intraluminal thrombus, and may or may not be associated with distal embolization. This was the patient's presentation.
• Type III: Intimal Hyperplasia/Fibrosis: Chronic repetitive trauma can lead to intimal damage and subsequent thickening without overt aneurysm or complete thrombosis, causing stenosis and reduced flow.
• Type IV: Multiple Lesions/Extensive Disease: More widespread involvement of the ulnar artery or its branches, potentially including multiple microaneurysms or occlusions distally, indicative of chronic and severe disease.

Based on our patient's diagnostic findings (fusiform aneurysm with intraluminal thrombus and distal occlusion/emboli), he was classified as Type II Hypothenar Hammer Syndrome . Given the ongoing critical ischemia and risk of further embolic events, operative intervention with arterial reconstruction was deemed necessary and prioritized over conservative measures.

Surgical Technique / Intervention

Procedure: Resection of Left Ulnar Artery Aneurysm and Thrombosis with Interposition Vein Graft and Ulnar Nerve Neurolysis.

1. Patient Positioning:
* Supine on the operating table.
* The left upper extremity was positioned on a hand table, abducted to 90 degrees, with the elbow extended and the forearm supinated.
* A tourniquet was applied to the proximal arm but not inflated initially.
* Full antiseptic preparation and draping of the hand, forearm, and ipsilateral groin (for potential vein graft harvest if forearm veins were inadequate).

2. Approach and Incision:
* A curvilinear incision was made along the ulnar border of the hypothenar eminence, starting approximately 1cm proximal to the pisiform bone and extending distally towards the base of the small finger, curvilinear to follow the distal palmar crease. This approach provides excellent exposure to Guyon's canal.
* Careful incision through the skin and subcutaneous tissue, identifying and protecting sensory branches of the ulnar nerve.
* The palmaris brevis muscle was divided or retracted.

3. Exposure of Guyon's Canal and Neurovascular Structures:
* The transverse carpal ligament's superficial portion, forming the roof of Guyon's canal, was incised longitudinally. This decompressed the contents of the canal.
* The ulnar nerve was identified first, typically lying radial and slightly deep to the ulnar artery. The common trunk of the ulnar nerve was carefully dissected and traced distally into its motor and sensory branches.
* The ulnar artery was then identified. Proximally, it appeared relatively normal. Distally, within Guyon's canal, the fusiform aneurysm was clearly visible, appearing distended and firm due to the intraluminal thrombus.
* The ulnar nerve was found to be in close proximity to the aneurysm, displaying mild flattening and inflammatory changes. Neurolysis of the ulnar nerve was performed, carefully freeing it from the surrounding compressed and inflamed tissues and from the aneurysm.

4. Vascular Control and Resection:
* The ulnar artery was circumferentially dissected both proximal and distal to the aneurysm and thrombotic occlusion.
* Vascular control was obtained by placing vessel loops proximally and distally around the ulnar artery and its branches, including the superficial palmar arch communication.
* Systemic heparinization was administered (e.g., 5000 units IV) to prevent further thrombus formation during clamping.
* Microvascular clamps were applied to isolate the pathological segment.
* The thrombosed aneurysmal segment of the ulnar artery, along with the adjacent occluded segment, was meticulously resected. The resected segment measured approximately 3.5 cm.
* The harvested proximal and distal ends of the ulnar artery were gently irrigated with heparinized saline to ensure no residual thrombus and to check for back-bleeding from collateral vessels.

5. Vein Graft Harvest (Autogenous):
* Concurrently, a suitable segment of autogenous vein was harvested. Given the ipsilateral forearm veins (e.g., cephalic or basilic vein branches) were of appropriate caliber and length, a 4 cm segment was harvested.
* The vein segment was reversed to ensure proper valve orientation (to prevent distal obstruction) and gently distended with heparinized saline to check for leaks and confirm patency.

6. Arterial Reconstruction:
* The reversed vein graft was positioned to bridge the defect created by the arterial resection.
* Proximal Anastomosis: The proximal end of the vein graft was meticulously anastomosed to the healthy proximal ulnar artery using 9-0 or 10-0 monofilament non-absorbable sutures (e.g., nylon) in an interrupted or running fashion under microscopic magnification.
* Distal Anastomosis: Similarly, the distal end of the vein graft was anastomosed to the healthy distal ulnar artery (or superficial palmar arch if primary ulnar artery was non-reconstructible distally), also using microvascular techniques.
* Care was taken to ensure precise alignment, tension-free anastomoses, and avoidance of kinking or twisting of the graft.
* After completing both anastomoses, the distal clamp was released first, followed by the proximal clamp, allowing for controlled reperfusion. Any leaks were meticulously repaired.
* Pulsatile flow through the graft was visually confirmed, and Doppler flow was used to confirm patency and assess the quality of flow distally.

7. Closure:
* The tourniquet was deflated, and hemostasis was meticulously achieved.
* The ulnar nerve was inspected again to ensure it lay freely within Guyon's canal after decompression.
* The palmaris brevis was reapproximated, and subcutaneous tissues were closed with fine absorbable sutures.
* The skin was closed with non-absorbable sutures.
* A bulky, non-constrictive dressing was applied, followed by a volar plaster splint immobilizing the wrist in a neutral position to protect the graft and surgical site.

Post-Operative Protocol & Rehabilitation

Immediate Post-Operative Period (Day 0-7):
* Monitoring: Continuous monitoring of digital perfusion (color, temperature, capillary refill) of the left ring and small fingers is paramount. Doppler auscultation of the graft site and distal arterial flow performed hourly initially, then every 4 hours. Any signs of compromise (pallor, cyanosis, delayed capillary refill, cold digits, loss of Doppler signal) warrant immediate re-exploration.
* Positioning: Hand elevated above heart level to minimize swelling.
* Anticoagulation/Antiplatelet Therapy: Systemic heparinization maintained for 24-48 hours, followed by transition to oral antiplatelet therapy (e.g., Aspirin 81-325mg daily) for at least 3-6 months. In some cases, dual antiplatelet therapy or a short course of oral anticoagulation (e.g., Warfarin or NOAC) may be considered depending on surgeon preference and patient risk factors.
* Pain Management: Multimodal analgesia including opioids, NSAIDs (if no contraindications), and paracetamol.
* Splinting: Volar plaster splint maintained for 1-2 weeks, keeping the wrist in a neutral position to protect the anastomoses and prevent excessive tension.
* Wound Care: Daily wound checks for signs of infection.

Early Rehabilitation (Week 1-6):
* Splint Removal & Sutures Out: At 10-14 days, the splint is removed, and sutures are taken out.
* Initiation of Gentle Range of Motion: Under guidance from a hand therapist, active and passive range of motion exercises for the wrist and digits are initiated.
* Wrist: Gentle flexion/extension, radial/ulnar deviation.
* Digits: Full flexion and extension of MCP, PIP, and DIP joints.
* Intrinsic Exercises: Gentle re-education of intrinsic muscles.
* Edema Management: Compression gloves, elevation, and gentle massage.
* Sensory Re-education: If ulnar nerve symptoms persist, sensory re-education techniques (e.g., textures, vibration) are started.
* Scar Management: Desensitization and massage initiated once the wound is well-healed.
* Activity Restrictions: No heavy lifting, gripping, or direct trauma to the hypothenar area. Avoidance of positions that may compromise arterial flow.

Intermediate Rehabilitation (Week 6-12):
* Strengthening: Gradual progression of strengthening exercises for grip, pinch, and intrinsic muscles. Light resistance exercises introduced.
* Functional Activities: Incorporate functional tasks that mimic daily activities, progressively increasing complexity.
* Continued Nerve Glides: For persistent ulnar nerve symptoms.
* Cold Intolerance Management: Advice on warm clothing, avoiding cold exposure, potentially topical vasodilators (under medical supervision) if severe.
* Return to Work/Sport: Gradual return to light duties, avoiding activities that put direct pressure or repetitive stress on the hypothenar eminence. Modifications to work tools or cycling gloves may be advised.

Long-Term Follow-up (Beyond 3 Months):
* Vascular Surveillance: Periodic duplex ultrasound at 3, 6, and 12 months post-operatively, then annually, to monitor graft patency and ensure no recurrence of arterial pathology.
* Neurological Recovery: Ongoing assessment of ulnar nerve function. Nerve recovery can be slow and may continue for 12-18 months.
* Functional Assessment: Evaluate hand function, grip strength, and pain levels.
* Patient Education: Reinforce avoidance of repetitive trauma to the hypothenar region, which was the underlying cause of HHS. Counseling on ergonomic modifications for work and hobbies.
* Antiplatelet Therapy: Duration is determined by the vascular surgeon based on the individual's risk factors and graft patency.

Pearls & Pitfalls (Crucial for FRCS/Board Exams)

Pearls:

1. High Index of Suspicion: Always consider HHS in a male patient with a history of repetitive blunt trauma to the hypothenar eminence presenting with unilateral hand pain, cold intolerance, digital ischemia, and/or ulnar nerve symptoms. It's often misdiagnosed as primary ulnar nerve entrapment or Raynaud's phenomenon.
2. Thorough History is Key: Detail the patient's occupation, hobbies, and any activities involving the hand as a hammer or repetitive gripping.
3. The Allen's Test is Critical: A positive or delayed reperfusion Allen's test for the ulnar artery is a strong indicator of ulnar artery compromise. Perform it meticulously.
4. Duplex Ultrasound (DUS) as First-Line Imaging: Non-invasive, readily available, and excellent for initial screening of ulnar artery pathology (aneurysm, thrombosis, stenosis, flow dynamics). Can guide further investigations.
5. CTA/MRA for Pre-operative Planning: Provides a detailed 3D roadmap of the arterial anatomy, collateral circulation, and extent of disease, crucial for surgical decision-making regarding resection length and reconstruction strategy. DSA (Digital Subtraction Angiography) remains the gold standard for dynamic assessment and can be therapeutic.
6. Ulnar Nerve Involvement: While primarily a vascular disorder, secondary ulnar nerve compression or irritation is common due to the confined space of Guyon's canal. Be prepared for neurolysis.
7. Autogenous Vein Graft Preferred: For arterial reconstruction, an autogenous vein graft (e.g., forearm cephalic/basilic, great saphenous) is generally preferred over synthetic grafts due to superior patency rates in small-diameter vessels. Ensure proper length and reversal of valves.
8. Microvascular Technique: Meticulous microvascular technique is paramount for successful arterial reconstruction. Operating microscope, fine instruments, and high-quality sutures are essential.
9. Post-operative Anticoagulation/Antiplatelets: Essential for maintaining graft patency and preventing re-thrombosis. The specific regimen should be tailored and often involves collaboration with vascular specialists.
10. Rehabilitation Focus: Early, gentle range of motion, edema control, and scar management are critical. Patient education on activity modification and ergonomic changes is vital to prevent recurrence.

Pitfalls:

1. Misdiagnosis: Missing HHS and attributing symptoms solely to ulnar nerve entrapment or systemic vasculitis can lead to inappropriate treatment and worsening ischemia.
2. Inadequate Vascular Workup: Proceeding to surgery for "Guyon's canal syndrome" without proper vascular imaging can lead to unexpected vascular findings, requiring aborting the initial plan or performing an inadequate intervention.
3. Ignoring Collateral Circulation: Simple ligation of the ulnar artery without ensuring adequate collateral flow via the radial artery or assessing the risk to distal perfusion can result in severe, irreversible digital ischemia or necrosis. The Allen's test and angiography are crucial.
4. Technical Errors in Anastomosis: Kinking, twisting, tension, or imperfect anastomosis can lead to immediate graft thrombosis or early failure. Requires specialized microvascular skills.
5. Incomplete Resection: Leaving behind diseased arterial segments or a source of distal emboli can lead to recurrence of symptoms.
6. Post-operative Hematoma/Compression: Accumulation of blood within the confined Guyon's canal post-operatively can compress the vein graft or ulnar nerve, leading to graft failure or persistent neuropathy. Careful hemostasis and a non-constrictive dressing are vital.
7. Inadequate Anticoagulation: Insufficient or poorly monitored antiplatelet/anticoagulation therapy can result in graft thrombosis.
8. Failure to Address the Cause: If the patient returns to the same activities that caused the repetitive trauma without modification, recurrence is highly probable, despite successful surgery.
9. Unrecognized Systemic Disease: In rare cases, HHS-like symptoms can be part of a broader systemic vasculitis or hypercoagulable state. If the history or clinical picture suggests this, a broader medical workup is indicated.
10. Delayed Presentation: Patients often present late after conservative measures have failed, potentially leading to more extensive and irreversible digital ischemic changes or nerve damage. Early diagnosis and intervention offer the best outcomes.