Introduction
Digital nerve injury is a common condition that may result in persistent sensory impairment and functional limitation of the hand, depending on the severity and type of nerve injury [1,2]. In the finger, the digital nerve and artery lie in close proximity within a neurovascular bundle. Traumatic finger injuries frequently result in simultaneous damage to both structures [3]. These combined injuries often lead to compromised local circulation.
Conventional non-vascularized nerve grafts are dependent on secondary revascularization from the surrounding tissue. Revascularization may be delayed or insufficient in ischemic or scarred recipient beds, resulting in unpredictable functional outcomes [4]. This is particularly relevant in cases of severe trauma or burn injuries associated with fibrosis and prior reconstruction procedures.
Vascularized nerve grafting was introduced to overcome these limitations by providing an intrinsic blood supply to the graft, thereby preserving Schwann cell viability and the endoneurial microenvironment essential for axonal regeneration [5]. Subsequent experimental and clinical studies demonstrated more reliable nerve regeneration with vascularized nerve grafts than conventional grafts, particularly in compromised recipient beds [6-8].
Although vascularized nerve grafting is not generally indicated for finger reconstruction, the anatomical characteristics of the finger and the pathological changes associated with complex trauma warrant careful consideration. We report a case of finger sensory reconstruction using a vascularized second toe digital nerve graft in a patient with combined digital nerve and artery injury following burn trauma. The patient provided written informed consent for the publication and use of his images.
Case
A 26-year-old man presented with persistent sensory impairment of the right middle finger following an electrical burn injury on the voloradial aspect of the middle phalanx. Split-thickness skin grafting had been performed approximately 1 month after the initial injury at another institution for wound coverage. Re-presentation 1 month later demonstrated skin graft coverage over the voloradial aspect of the middle phalanx with no active wound (Fig. 1). Though the initial wound had been successfully healed, the patient continued to experience sensory dullness extending to the radial side of the fingertip, accompanied by occasional tingling sensations. Intraoperative exploration revealed fibrotic degeneration of the digital nerve and accompanying digital artery (Fig. 2A). The fibrotic segment was debrided, leaving a nerve defect of approximately 2.3 cm. Given the history of electrical burn injury and prior skin grafting, a fibrotic and poorly vascularized recipient bed was suspected, and reconstruction using a vascularized nerve graft was planned.
A vascularized digital nerve graft was harvested from the second toe, which was selected because of its close anatomical similarity to the finger digital nerve in terms of diameter and fascicular organization, thereby facilitating precise microsurgical coaptation. The graft was harvested as a neurovascular bundle from the left second toe, including the medial digital nerve and its accompanying digital artery (Fig. 2B and C). Microvascular anastomosis was performed to restore arterial inflow to the graft, including anastomosis of the accompanying digital artery, followed by tension-free epineural nerve coaptation using standard microsurgical techniques (Fig. 2D). Adequate perfusion of the transferred digital artery was confirmed intraoperatively, indicating satisfactory vascular inflow to the neurovascular bundle and, consequently, to the transferred nerve. After harvesting, the donor site of the left second toe was closed directly.
Sensory recovery progressed gradually after surgery. The patient initially experienced intermittent tingling sensations, which gradually improved after 6 months. Static two-point discrimination, measured at the radial side of the fingertip, demonstrated progressive improvement, measuring 11 mm at 6 months, 9 mm at 12 months, and 6 mm at 2 years. Overall finger sensation improved during follow-up. However, mild sensory dullness persisted at the skin-grafted area of the middle phalanx, whereas sensory recovery at the fingertip was more favorable. At the donor site, the wound healed without complications, including no evidence of skin necrosis or dehiscence. Mild pain at the donor site subsided within the first postoperative week. At the time of discharge on postoperative day 18, no gait disturbance was observed. Mild sensory dullness along the medial border of the donor toe was noted at the final follow-up.
Fig. 1
Initial presentation after electrical burn injury managed at another institute. Preoperative photographs of the right middle finger following burn injury and prior split-thickness skin grafting. Persistent sensory impairment was noted despite adequate soft-tissue coverage. (A) Anteroposterior view. (B) Lateral view.
Fig. 2
Intraoperative findings and vascularized nerve graft reconstruction. (A) Fibrotic degeneration of the digital nerve with a poorly vascularized surrounding recipient bed. (B) Harvesting of a vascularized digital nerve graft from the medial digital neurovascular bundle of the left second toe. (C) Harvested vascularized second toe digital nerve graft with its vascular pedicle. (D) Microvascular anastomosis and tension-free nerve coaptation performed for reconstruction.
Discussion
Digital nerve reconstruction in the setting of concomitant arterial injury remains particularly challenging because the problem is not limited to loss of neural continuity alone. The proper digital nerve receives its vascular support through small branches arising from the accompanying digital artery [3]. Therefore, when a digital nerve injury is associated with arterial injury, the regenerative environment may be compromised not only by structural discontinuity of the nerve but also by loss of the vascular support required for axonal regeneration. This limitation is particularly critical in compromised beds such as burn injury or fibrosis, where secondary revascularization may be delayed or insufficient [4].
Vascularized nerve grafts provide an intrinsic blood supply to the graft, preserving microcirculation and the endoneurial microenvironment essential for axonal regeneration, without relying on revascularization from the surrounding tissue [5-8]. This principle is especially relevant in the present case, in which the recipient site had been altered by electrical burn injury, subsequent fibrosis, and prior split-thickness skin grafting. From this standpoint, one important advantage of the present procedure was the transfer of a healthy vascularized donor nerve into a scarred recipient bed. Because the graft was harvested together with its accompanying arterial inflow, the transferred nerve was vascularized independently of the surrounding scarred tissue.
Previous reports have shown that vascularized nerve grafts can provide meaningful sensory recovery in finger digits. In particular, free vascularized nerve grafts harvested from the dorsum of the foot have been reported to restore sensibility in anesthetic scarred digits, with average static two-point discrimination of 9.5 mm [8]. In addition, finger sensory reconstruction using a more local digital nerve donor has been reported to produce better sensory recovery than conventional sural nerve grafting, suggesting that donor selection may influence the quality of postoperative sensibility [9]. These findings support the view that, in digital nerve reconstruction, both vascularity of the graft and anatomical suitability of the donor should be considered.
The second toe was selected as the donor site based on both anatomical and clinical considerations. In our previous experience with sensate second toe pulp-free flap reconstruction, second toe tissue proved to be a reliable option for digital reconstruction, with favorable reconstructive applicability and acceptable donor-site morbidity [10]. On the basis of that experience, the second toe digital nerve and accompanying artery were considered well suited to the recipient proper digital neurovascular bundle. Because the toe donor nerve is itself a digital nerve, it was regarded as more anatomically compatible with the recipient nerve than more general sensory donors. This similarity was considered advantageous for precise nerve coaptation and vascular anastomosis. In addition, donor-site morbidity of the second toe has been reported to be generally limited and well tolerated in daily activities [11]. For this reason, the second toe was considered an appropriate and practical donor source in the present patient.
The postoperative course also provides several clinically meaningful observations. Sensory recovery at the radial fingertip improved progressively during follow-up, and tingling sensation gradually subsided after 6 months postoperatively. These findings suggest that meaningful sensory recovery can be achieved even in a compromised recipient bed when a healthy vascularized donor nerve is transferred. Although mild dullness persisted over the skin-grafted area of the middle phalanx, overall finger sensation improved during follow-up. This residual deficit may reflect the fact that reconstruction of nerve continuity does not completely reverse the sensory consequences of severe local tissue damage, particularly in areas affected by electrical burn injury, fibrosis, and altered soft-tissue quality. Nevertheless, the progressive improvement in fingertip sensibility indicates that the reconstruction was functionally beneficial.
The present case has limitations. It represents a single clinical observation, and direct comparison with conventional non-vascularized nerve grafting or other donor nerves is not possible. In addition, although fingertip sensation improved favorably, no meaningful sensory improvement was observed over the skin-grafted area of the middle phalanx. Despite these limitations, this case remains meaningful because it demonstrates the feasibility of using a vascularized second toe digital neurovascular bundle for reconstruction of a finger with combined digital nerve and arterial injury in a scarred, previously grafted burn bed.
In conclusion, vascularized second toe digital nerve grafting may represent a useful reconstructive option in selected patients with complex digital injuries associated with vascular compromise, fibrosis, and poor local tissue quality. Its potential value lies not only in the use of a vascularized graft in a compromised bed, but also in donor selection based on anatomical suitability and acceptable donor-site morbidity.
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