HYPOTHENAR HAMMER SYNDROME (ULNAR ARTERY THROMBOSIS)

Dr. Von Rosen was the first to describe “ulnar artery thrombosis,” in 1934, and his management strategy was to resect the patient’s involved segment. Dr. Conn applied the term “hypothenar hammer syndrome” (HHS) in 1970 to specify the condition as arising among those who use the ulnar side of the hand as a striking tool, or hammer. Hypothenar hammer syndrome typically results in the formation of an isolated thrombus among otherwise healthy vessels. Therefore, conservative treatment or bypass of the thrombosed vessels is possible in hypothenar hammer syndrome .

Pathophysiology

Hypothenar hammer syndrome  is caused by trauma to the ulnar artery: the intravascular injury may be diffuse (eg, resulting from intra-arterial injection) or localized (eg, repetitive compression or blunt force). When the trauma is repetitive, aneurysm with or without thrombosis and occlusion of the ulnar artery may result. It is hypothesized that thrombosis related to intra-arterial injection results from endothelial injury and subsequent platelet activation as well as the presence of particulate debris in the injected solution. These circumstances cause distal vasomotor disturbances and varying degrees of vascular insufficiency. Moreover, emboli from the thrombus may occlude digital vessels, worsening perfusion deficits. An associated aneurysm may also occur. These are urgent conditions, requiring prompt diagnosis and treatment (“time is tissue”).

Related Anatomy

• Blood supplying the hand originates from the radial and ulnar arteries.
• On the medial aspect of the wrist, the ulnar artery enters the hand through Guyon’s canal and supplies the superficial volar arch. The ulnar artery joins the dorsal portion of the radial artery to form the deep palmar arch, and may join the volar portion of the radial artery (35% of patients) to form a complete superficial palmar arch.
• The vulnerable position of the superficial branch of the ulnar artery puts it at risk of compression against the hook of hamate.

Incidence and Related Conditions

• Considered rare; precise incidence unknown because either ulnar artery occlusion is asymptomatic or individuals do not present for evaluation
• Possibly more common than believed, hypothenar hammer syndrome has been reported in mountain bikers, tennis players, golfers, and a variety of other athletes and in a drummer
• Hypothenar hammer syndrome is an uncommon cause of digital ischemia, which occurs in <2% of 1300 patients with hand ischemia

Differential Diagnosis

• Autoimmune disease
• Buerger’s disease
• Guyon’s canal syndrome
• Hand-arm vibration syndrome
• Raynaud’s phenomenon

The patient’s occupation may be manual labor involving the use of impact or vibratory tools. If not, then the individual may be engaged in activity involving repetitive hand and wrist trauma (eg, mountain biking, tennis). The patient may describe an accident involving blunt trauma to the hand. The patient will complain that the affected area is numb, cold, and white, and there may be decreased sensation. Only one hand will be affected (asymmetric condition).  The patient may complain of a lump with a pulse on the ulnar palm of the hand.

• Thrombolysis in upper extremity: complication rates up to 75%
  • Bleeding at access site or remotely
  • Fever, skin necrosis, contrast allergy, nephropathy
  • Hematoma, compartment syndrome
• Surgical revascularization: continued pain; plus standard risks such as infection, nerve injury and thrombosis of the vascular anastomosis
• In one study, vein graft occlusion rate was 78% after 10 years’ follow-up

• Thrombolysis: clinical and angiographic improvement in 50–80% of patients
• Surgical revascularization: relatively high success rates but limited indications
• Reconstruction by repairing ulnar artery ends: excellent results in 89% and patency incidence of 50%
  • Using interposition grafts: good to excellent results, and patency 84–100%
• Surgical reconstruction in general: most patients satisfied and have low functional disability

• Hypothenar hammer syndrome is a traumatic injury (diffuse or localized) caused by compression of the ulnar artery (“hammered”) against the hook of hamate
• Arterial insufficiency in hypothenar hammer syndrome is an urgent condition requiring urgent treatment, but usually the issue is an isolated thrombus, which may be managed conservatively or with bypass and grafting
• Hook of hamate fracture, suggested by tenderness over the hook of the hamate and evident on X-ray (carpal tunnel view or CT)
• Hypothenar muscle wasting (ie, abductor digiti minimi, flexor digiti minimi, and opponens digiti minimi) can accompany hypothenar hammer syndrome.
• Weakened grip and pinch strength, compared to opposite side
• Diagnosis can be aided by digital-brachial indices (DBI) for evaluation of chronic arterial insufficiency of fingers or hand
• Diagnosis can be aided by digital subtraction angiography: excellent resolution, and thrombolysis or thrombectomy can be performed concomitantly

New Articles

1. Endress RD, Johnson CH, Bishop AT, Shin AY. Hypothenar hammer syndrome: long-term results of vascular reconstruction. J Hand Surg Am 2015;40(4):660-5. PMID: 25746144
2. Iannuzzi NP, Higgins JP. Acute arterial thrombosis of the hand. J Hand Surg Am 2015;40(10):2099-106. PMID: 26408378

Reviews

1. Chen S-H, Tsai T-M. Ulnar tunnel syndrome. J Hand Surg Am 2014;39(3):571-9. PMID: 24559635
2. Monacelli G, Rizzo MI, Spagnoli AM, et al. Ulnar artery thrombosis and nerve entrapment at Guyon’s canal: our diagnostic and therapeutic algorithm. in vivo 2010;24:779-82. PMID: 20952749

Classics

1. Paaby H, Stadil F. Thrombosis of the ulnar artery. Acta Orthop Scandinav 1968;39:336-45. PMID: 5730310
2. Millender LH, Nalebuff EA, Kasdon E. Aneurysms and thromboses of the ulnar artery in the hand. Arch Surg 1972;105(5):686-90. PMID: 5081542

Retrospective Chart Analysis

1. Troum SJ, Waldo III FE, Sapp J. Ulnar artery thrombosis: a 6-year experience. J South Orthop Assoc 2001;10(3). PMID: 12132826