Review Question - QID 219946

The patient sustained a hook of hamate fracture complicated by ulnar artery aneurysm at the level of Guyon's canal, resulting in hypothenar hammer syndrome that has been surgically addressed with aneurysmal resection and reverse interposition vein grafting. Graft failure and symptom recurrence at 6 months is most likely due to intimal hyperplasia (Answer 3).

Hypothenar hammer syndrome represents post-traumatic digital ischemia from thrombosis of the ulnar artery at Guyon's canal. Patients often present with pain over the hypothenar eminence and ring finger, with paresthesia along the ulnar-most two digits, cold intolerance, and mottling and blanching indicative of ischemia. Treatment involves excision of the involved segment of the ulnar artery with interpositional vein grafting. Studies in the vascular literature have shown that the patency rates of a vein graft diminish from 98% immediately after surgery to less than 88% within the first month secondary to thrombosis, making this the most common mode of clinical failure in the acute period. An additional 30 to 50% of grafts then fail in months 1 to 18 after surgery, with this period representing the most biologically active period, making the secondary cause of failure intimal hyperplasia due to the migration and proliferation of vascular smooth muscle cells at the site of the anastomosis.

Hui-Chou et al. reviewed the current options for the treatment of hypothenar hammer syndrome. The authors note that the clinical signs and symptoms include a palpable mass, distal digital embolization to long, ring, or small fingers, pain, cyanosis, pallor, coolness, and recurrent episodes of vasospasm. They conclude that arteriography with contrast remains the gold standard for diagnosis and evaluation, with surgical management including resection of the abnormal segment with ligation of the vessel with or without reconstruction with venous or arterial grafts.

Owens et al. reviewed the adaptive changes in autogenous vein grafts for arterial reconstruction. The authors noted that the incidence of bypass graft stenosis and graft failure remains substantial, and wholesale improvements in patency are lacking. They concluded that stenosis arises not only from over exuberant intimal hyperplasia but also due to insufficient adaptation or remodeling of the vein to the arterial environment.

Endress et al. reviewed the long-term results of vascular reconstruction for hypothenar hammer syndrome. The authors used color flow ultrasound to determine the patency of 18 vein graft reconstructions of the ulnar artery at the wrist in 16 patients and found that, 14 grafts (78%) were occluded at a mean of 118 months postoperatively. They concluded, however, that despite a high percentage of occlusion, overall, patients remained satisfied with low functional disability and all would recommend surgical reconstruction at a mean follow-up of 9.8 years.

Figure A is a carpal tunnel view radiograph demonstrating a hook of hamate fracture. Figure B is an angiogram showing an ulnar artery aneurysm at the level of Guyon's canal. Figure C is an intraoperative surgical photograph showing ulnar artery aneurysmal resection, which is followed by arterial reconstruction using reversed interpositional vein grafting.

Incorrect Answers:
Answer 1: Though this is theoretically possible, it is not the primary mode of failure of interpositional vein grafting at 6 months.
Answer 2: Vein graft resorption is not a common mode of failure of interpositional vein grafting.
Answer 4: Recurrence is much less likely than thrombosis in the acute period or intimal hyperplasia in the subacute-chronic period.
Answer 5: Thrombosis of the vein graft is the most common cause of failure in the acute period.