Introduction
Traumatic hand injuries pose significant challenges for reconstructive surgeons. Complications associated with traumatic hand injuries, such as fractures, underlying joint exposure and tendon or neurovascular injuries, along with insufficient coverage, poor cosmesis and long-term functional limitations, often prohibit the use of simpler reconstructive techniques in complex hand trauma.
Three main pedicled forearm flaps have been described for larger hand defects: the radial forearm flap,1 ulnar forearm flap2 and posterior interosseous flap3,4 based on the radial artery, ulnar artery and posterior interosseous artery, respectively. The radial forearm flap is associated with significant donor site morbidity, including poor skin graft healing over the flexor tendons, injury to the radial nerve or its branches resulting in paraesthesia or cold intolerance, fracture of the radius if bone is harvested with the flap, wrist stiffness, reduced grip and pinch strength, poor cosmesis and compromised vascularity of the hand.5–14 Harvest of an ulnar artery flap requires sacrifice of a major artery. While this may not cause ischaemia of the forearm and hand, alternatives that preserve the ulnar artery are preferable. The posterior interosseous flap has marked vascular variability and discontinuity, making the flap less reliable. The first dorsal metacarpal artery flap offers another locoregional reconstructive option in hand injuries. However, the major disadvantage of this flap is the requirement of a full thickness skin graft over the exposed index finger extensor tendon, which may impact function and cause ungainly scarring.
Herein, we report the use of a free ulnar artery perforator (FUAP) flap in a patient with a complex soft-tissue injury of the thumb and perform a literature review investigating other reported cases of the FUAP flap in hand injuries.
Case
The patient was a 20-year-old, right hand dominant, male bricklayer who was transferred to our centre with flexor tenosynovitis of the left thumb secondary to a suspected insect bite. His medical history was significant for a bicuspid aortic valve and gastro-oesophageal reflux disease. He was a polysubstance drug user and an active smoker. Intravenous cefazolin was commenced on arrival and the patient taken to theatre for debridement. His antibiotic regimen was subsequently changed to clindamycin, given the growth of methicillin-resistant Staphylococcus aureus (MRSA) from intraoperative specimens. The patient had a repeat debridement five days after the index operation. The originally planned full-thickness skin graft was unable to be performed due to extensor pollicis tendon exposure (Figure 1A). An FUAP flap was chosen for wound coverage.
The ulnar artery perforators were surface marked using thermal and colour Doppler imaging. The operation was performed under general anaesthesia. A radial incision was made through fascia to identify the ulnar artery perforators (Figure 1B–C). The flap was measured according to the size of the defect (Figure 1D). The flap was islanded and the vessels were ligated under microscopy (Figure 1E). The flap was raised on a 2–3 cm pedicle to the ulnar artery (Figure 1F). The thumb radial digital artery did not have a reliable blood flow, therefore an end-to-side vein graft was used to anastomose the ulnar perforator to the radial artery. Venous anastomosis was performed via the venae comitantes. The flap was well contoured to the recipient site (Figure 1G). The donor site was closed primarily (Figure 1H).
Postoperatively, the patient was commenced on aspirin and a heparin infusion, and the hand was kept elevated and warmed with a Bair Hugger. Hand therapy was commenced on postoperative day two and a resting thermoplastic splint fashioned for support. The patient’s postoperative course was complicated by a haematoma, which required evacuation in theatre on postoperative day two. The remainder of his stay in hospital, which lasted a total of 18 days, was unremarkable. Three weeks following surgery, the patient had full extension of the interphalangeal joint and approximately 50 per cent flexion. The patient was last followed-up 4.5 years after his procedure and had full function of the thumb, having successfully returned to work. He reported persistent hypersensitivity of the thumb to cold and pain, however this did not affect his quality of life.
Two further FUAP flaps were performed on male patients (aged 36 and 38) with traumatic skin loss and extensor pollicis longus tenson exposure as a result of motor vehicle trauma. Both underwent uncomplicated flap reconstruction. The princeps pollicis artery was used for the arterial anastomosis and a cutaneous vein. Both patients reported good active range of motion subjectively in the thumb on discharge but were lost to follow-up.
Literature review
A literature search was conducted in PubMed since its inception without language restrictions using the following search terms: ‘free ulnar artery perforator flap’ and (‘hand*’ or ‘finger*’ or ‘digit*’) and ‘trauma*’. We identified seven studies that met the inclusion criteria (Table 1).15–21 Most studies were based in China (n = 5). The number of patients ranged from five to 75 with a mean age between 30 and 39. Only one study19 explicitly reported associated injuries. In this study, 40 per cent of patients had an underlying fracture, approximately half experienced tendon injuries, and 60 per cent had arterial and nerve injuries. Mean operative time ranged from 120 to 187 minutes. Three studies reported the procedure being done under regional anaesthesia for all cases.15,18,19 Primary closure at the donor site was achieved in all patients in three studies15,16,21 and ranged between 40 and 87.5 per cent in the remainder. Complete flap loss was not reported by any study. One case of partial flap necrosis was reported by Jihui and colleagues16 and Zheng and colleagues.19 Donor site complications included mild scar formation (n = 1 case), numbness over the medial wrist (n = 1 case), and partial necrosis of the skin graft to the donor site (n = 3 cases). Cold intolerance was the main complication reported at the recipient site (n = 6 cases). Between 25 and 40 per cent of patients required a debulking procedure in two studies.17,18 Only one study21 reported time to return to work of 13 weeks. Another study reported on return to presurgical occupation or activities of daily living and in that study all patients returned to premorbid function.18
Discussion
Free ulnar artery perforator flaps can be useful in the reconstruction of complex traumatic hand injuries with good long-term functional outcomes and acceptable donor site morbidity. To our knowledge, this is the first reported case of the use of a FUAP flap for hand injury in Australia.
The FUAP flap preserves the ulnar artery and has a number of benefits compared to the radial forearm flap, including:
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less obtrusive and hirsute donor site
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lower incidence of sensory deficits and cold intolerance
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preserved grip and pinch strength
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if a skin graft is required to close the donor site, it is applied over muscle bellies rather than exposed tendons.
The ulnar artery perforator has a diameter similar to the proximal proper digital artery and the flap contains both the accompanying vein and subcutaneous superficial veins that can improve flap survival. This anatomic feature reduces the technical complexity of anastomosing the vessels between the flap and the recipient site. The flap also contains the forearm medial cutaneous nerve or the dorsal branch of the ulnar nerve, which favours sensory recovery when used as a sensate flap. Furthermore, it allows for the use of the vascularised partial flexor carpi ulnaris tendon as part of the flap to repair tendon defects.
The FUAP flap procedure has relatively few complications and is tolerated well by patients. Complete flap loss has not been reported in the literature and only two cases of partial flap loss have been described.16,19 Hypersensitivity/cold intolerance at the recipient site is the main side effect of the procedure, being reported in six cases. Our patient reported similar symptoms at 4.5 years, although this did not affect his overall hand function or quality of life. Despite these inconveniences, patient satisfaction in studies that report this outcome is relatively high.17,18
Conclusion
Findings from our case report and narrative synthesis suggest that FUAP flaps are a feasible and useful reconstruction option for complex defects of the hand. The flap has minimal donor and recipient site morbidity and limited data to date suggest acceptable functional outcomes.
Patient consent
Patients/guardians have given informed consent to the publication of images and/or data.
Conflict of interest
The authors have no conflicts of interest to disclose.
Funding declaration
The authors received no financial support for the research, authorship and/or publication of this article.
Revised: June 28, 2024 AEST