Traumatic Ulnar Artery Aneurysm and the Hypothenar Hammer Syndrome
Hypothenar hammer syndrome (HHS) is a rare clinical entity with a symptom complex attributable to an ulnar artery aneurysm. These aneurysms are uncommon and have been linked with traumatic injuries to the hand. Although most commonly seen in workers who use the hypothenar eminence of their hands repetitively as a hammer, both acute penetrating and blunt traumas have been documented as sources of ulnar artery aneurysms. In this case report, we present a patient who presented with digital ischemia from a subsequently diagnosed ulnar artery aneurysm the day after moving large boulders with his hands.
A 45-year-old, non-smoking, previously healthy male presented with a three-day history of cyanotic, painful, and cold right fourth and fifth digits after a day of manual labor. He denied antecedent trauma or crush injuries to the digits. Conservative treatment of cold compresses and analgesia failed to resolve his symptoms, and the patient presented to the emergency department the following day. Incidentally, the patient was discovered to be in new onset, asymptomatic, atrial fibrillation. Physical examination of the right upper extremity revealed a readily palpable radial pulse, bounding ulnar pulse, and markedly diminished 4th and 5th digital pressures. An Allen’s test was consistent with a patent palmar arch with markedly diminished ulnar antegrade fill. An arteriogram demonstrated a normal caliber proximal ulnar artery with sluggish antegrade filling and complete obstruction of the distal artery (Figure 1). Catheter-directed thrombolysis with 4 mg of tPA (Activase; Genentech, San Francisco, California) was aborted after minimal resolution of the ulnar artery occlusion and the patient was then scheduled for surgical treatment. In light of the newly discovered dysrhythmia, an echocardiogram was also performed and revealed no evidence of mural thrombus that would account for a potential embolic source.
Intraoperatively, a longitudinal wrist incision extending to the middle of the palm, directly over the ulnar artery, was performed. A 6 mm ulnar artery aneurysm with extensive thrombus was discovered, and a cephalic vein interposition graft with resection of the ulnar artery aneurysm was performed (Figures 2 and 3). Completion duplex ultrasonography confirmed excellent triphasic signals at completion of the surgery. The patient was discharged on post-operative day 2 with resolution of his ischemia and pain. At 8-month follow up, the graft remained patent and the patient remained asymptomatic.
True aneurysms of the ulnar artery, first reported in 1934 by Van Rosen, continue to be the most reported site of arterial aneurysms of the upper extremity. Most commonly, they occur in the superficial portion of the artery overlying the hamate bone at the hypothenar eminence. In this area, the artery is only covered by skin, subcutaneous tissue, fibers of the palmaris brevis muscle, and a fibrous lamina derived from the superficial aspect of the transverse carpal retinaculum. Repetitive blunt trauma of the artery against the hook of the hamate can lead to aneurysmal degeneration, formation of intraluminal thrombus, and subsequent embolization to digital arteries. A history of repetitive trauma to this region prompted Conn et al1 to name this condition hypothenar hammer syndrome (HHS).
Hypothenar hammer syndrome has frequently been reported in athletes who use their hand for catching and striking objects, as well as in manual laborers whose hands are subjected to repetitive trauma.2–5 Usually seen in men, this syndrome manifests with a wide variety of symptoms related to the degree of vascular compromise. While thrombosis of the ulnar artery aneurysm may lead to occlusion, chronic digital embolization is a more common presentation.6 Affected individuals complain primarily of symptoms related to vascular insufficiency, including ulceration, cold intolerance, numbness, coolness, cyanosis, paresthesia, and sometimes, a hypothenar mass. Finger discoloration or pain, however, is the predominant symptom.6 The differential diagnosis of a patient presenting with this symptom complex can be broadly divided into vascular or neurogenic causes and can almost always be elucidated based on a focused history and physical examination alone. Potential vascular etiologies include Buerger’s disease, autoimmune diseases, ulnar artery anomalies, vasculitis, and Raynaud’s phenomenon. Potential neurogenic causes include ulnar tunnel syndrome, carpal tunnel syndrome, thoracic outlet syndrome, lower trunk brachial plexopathy, and C8/T1 radiculopathy. One author routinely recommends a wide battery of tests, including complete blood count, erythrocyte sedimentation rate, multichemistry panel, antinuclear antibody, serum protein electrophoresis, rheumatoid factor, cold agglutinin assay, and hepatitis serology.7 Ultimately, diagnosis can be confirmed with multiple modalities, although angiography remains the “gold standard.” Angiography cannot only establish the diagnosis, but can also aid in developing an interventional surgical strategy.4,8 Some have recommended interrogation of both upper extremities for precise definition of baseline anatomy.6 With continued technologic improvements, the role of computed tomographic angiography (CT-A) and endovascular therapy in the diagnosis and treatment of this rare disease entity remains to be determined.
The rare incidence of this entity has made the optimal choice for definitive management difficult to identify. Recommended treatments for HHS range from observation and risk-factor management to surgical intervention. Unfortunately, even among surgical options, various methods of treatment have been endorsed, such as cervical sympathectomy, ulnar artery ligation, thrombolysis, and thrombectomy. Common surgical approaches to this disease revolve around 1) excluding the aneurysm via excision and replacement with an interposition conduit; 2) ligation with bypass of the involved segment; or 3) primary repair.8-16
If the decision to proceed with an interposition graft is made, the surgeon faces even more controversy, as a wide range of veins and arteries have been used for conduits. Making the decision more difficult has been the reliable long-term patency rates of all of these conduits8,11,14-16 (Table 2). For instance, in arterial interposition grafts, the thoracodorsal artery, descending branch of the lateral femoral circumflex artery, and right inferior epigastric artery, among others, have been described for use in bridging the ulnar artery defect.
Some authors report the purported size match and handling characteristics when considering arteries for reconstruction. Still others have preferred different methods of revascularization. De Monaco et al11 reported their series of direct repair of the ulnar artery after resection of the aneurysm and end-to-end anastomosis. This repair can be performed when the resected arterial segment is less than 2 cm long and the distal superficial palmar arch is intact. The results of various studies with different grafts are listed in Table 1. At our institution, resection of the diseased ulnar artery segment with revascularization via an upper extremity venous bypass remains the mainstay of definitive therapy.
As evidenced from the various surgical approaches described, there is no consensus for the optimal solution for treatment of hypothenar hammer syndrome. Similarly, unlike patients undergoing lower extremity bypass, there are no evidence-based recommendations on graft surveillance for these patients. For our patient, he underwent an immediate post-operative duplex to establish baseline parameters followed by an 8-month post-operative duplex, which was normal. We feel it is prudent to obtain at least one duplex, so that if future complications arise from the procedure, there can be a basis for comparison. Fortunately, long-term patency, regardless of the conduit or method of surgical revascularization, is excellent. The decision should account for the surgeon’s experience and preference, as well as the patient’s overall comorbidities. Current series are limited by the rare incidence of this syndrome and most publications are isolated case series. In light of the data presented, we support the use of reverse vein interposition with either saphenous or cephalic veins.