Flow-Through Lateral Arm Flap With Vein Grafting for Repairing Circumferential Thumb Soft-Tissue and Segmental Vascular Defects

Abstract

Background:

Circumferential soft-tissue loss of the thumb and vascular defects are among the most challenging problems in microsurgical reconstruction.

Methods:

We present the case of a 15-year-old male patient who sustained a thermal crush injury to the thumb, resulting in complete circumferential loss of skin and soft tissue with segmental defects of both the proper digital arteries and veins. After thorough debridement, reconstruction was performed with a free lateral arm flap based on the radial collateral artery. The flap was designed in a flow-through configuration: its proximal pedicle was anastomosed to the superficial branch of the radial artery, and its distal end to the remnant of the dorsal digital artery, thereby bridging the arterial defect while perfusing the flap. Because the venae comitantes were too small for venous repair, a Y-shaped vein graft was harvested from the forearm to reestablish distal outflow.

Results:

The flap and the thumb pulp survived completely, with satisfactory contour. At 1-year follow-up, flap sensory recovery was confirmed, and 2-point discrimination of the thumb pulp was 3 mm. The thumb achieved functional key pinch and contralateral-matched grip strength, despite mild interphalangeal joint limitation (20-degree flexion).

Conclusions:

This case highlights both the potential and the limitations of flow-through lateral arm flap in digital reconstruction and underscores the importance of tailoring flap selection and vascular strategies to the unique challenges posed by circumferential thumb defects.

Takeaways

Question: Can lateral arm flaps serve as an effective option for repairing circumferential soft-tissue defects associated with segmental vascular loss in the thumb?

Findings: We successfully reconstructed a thumb with such defects—caused by a thermal crush injury—using a flow-through lateral arm flap combined with vein grafting. The flap and the thumb pulp survived completely, with satisfactory contour.

Meaning: A flow-through lateral arm flap can be used to successfully repair circumferential soft-tissue and segmental vascular defects of the thumb or digits, but additional vein grafting is required to bridge venous defects.

INTRODUCTION

The thumb is fundamental to hand function, providing stability, opposition, and fine motor control essential for daily activities. Trauma to the thumb can therefore result in profound disability, particularly when it involves circumferential loss of skin and soft tissue.¹ Such wounds expose underlying bone, tendons, or ligaments and are among the most complex defects encountered in reconstructive microsurgery. When vascular structures are also disrupted, the challenge becomes even greater. Segmental loss of the proper digital arteries and associated veins jeopardizes distal perfusion and venous return. In these situations, timely revascularization is mandatory to prevent ischemia, congestion, and eventual necrosis of the digit.²

In such dual challenges, perforator flaps incorporating a flow-through pedicle have been proposed as a solution for reconstructing simultaneous soft-tissue integrity and main vessel integrity.^3,4 Among the various flap options for thumb and finger reconstruction, the free lateral arm flap, typically based on perforators of the radial collateral artery, has been widely used in hand reconstruction due to its thin, pliable texture; favorable color match; and consistent vascular anatomy.⁵

Here, we present an unusual case of a thumb injury caused by thermal crush trauma, resulting in complete circumferential loss of skin, soft tissue, and neurovascular structures, including both proper digital arteries and veins. Reconstruction was achieved with a free lateral arm flap designed in a flow-through configuration, supplemented with vein grafting to restore venous outflow. This case highlights both the potential and the limitations of flow-through flap design in digital reconstruction and underscores the importance of tailoring flap selection and vascular strategies to the unique challenges posed by circumferential thumb defects.

CASE PRESENTATION

A 15-year-old male patient presented 6 hours after sustaining a thermal crush injury to the right thumb. The injury occurred when his thumb was trapped for approximately 1 minute in a high-temperature annular machine component operating at 200–300°C, resulting in combined thermal and mechanical trauma. Clinical examination revealed total necrosis of all the soft tissue at the proximal phalanx. The distal phalanx appeared pale with absent capillary refill.

SURGICAL PROCEDURE: DEBRIDEMENT

After thorough debridement, a circumferential soft-tissue defect of the proximal phalanx was evident, accompanied by extensive vascular injury, including loss of the radial and ulnar proper digital arteries, the dorsal digital artery, and the associated veins. In the distal phalanx, a remnant of the ulnar proper digital artery (PDA) and 2 small dorsal digital veins (DDVs) were preserved (Fig. 1). The structural integrity of both the ulnar and radial proper digital nerves of the thumb was preserved despite the injury. Accordingly, the native digital nerves were retained during surgical debridement (Fig. 1).

Fig. 1.

The view of the wound. Circumferential soft-tissue and vascular defects on the thumb were present immediately after radical debridement. The continuity of the thumb proper digital nerves (ulnar and radial sides) was preserved.

SURGICAL PROCEDURE: RECONSTRUCTION

The surgical goal was to reconstruct both the soft-tissue defect and vascularization to the distal phalanx using a flow-through design. To address the defect (10 × 5 cm), its dimensions and configuration were first assessed with precision. Based on these measurements, a large free lateral arm flap (10 × 5.5 cm) was elevated in accordance with the standard operative technique. The perforator, which originated from the radial collateral artery, was localized using Doppler ultrasonography, and a pinch test was performed to determine the maximal harvestable skin while still permitting primary donor-site closure. Guided by these steps, the shape of the flap was designed to conform closely to the soft-tissue defect (Fig. 2). (See figure, Supplemental Digital Content 1, which displays the reconstruction immediately after surgery. The flap is shown on the ulnar palmar aspect of the thumb, with its proximal and distal ends juxtaposed to resurface the defect, https://links.lww.com/PRSGO/E734.)

Fig. 2.

Flap elevation. A, Design of the flap on the donor site. B, the flap after harvest. ILBCN, inferior lateral brachial cutaneous nerve; RCA, radial collateral artery.

Attention was then directed to the vascular pedicle: it was carefully dissected from the perforator (3 cm) level to the trunk segment (10 cm in total) of the radial collateral artery together with its venae comitantes, thereby allowing the later formation of a flow-through design (Fig. 2). Following this, the distal end of the radial collateral artery was ligated, and the flap with its vascular pedicle was harvested in its entirety. Finally, the donor site on the right upper arm was closed primarily.

The flap was wrapped circumferentially around the proximal phalanx, providing coverage for the exposed bone and ligament structures. Under microscopy, the distal end of the flap’s radial collateral artery was anastomosed to the remnant of the ulnar PDA, whereas the proximal end was connected to the deep branch of the radial artery (DRA). This established a flow-through configuration, enabling the pedicle to function as an interpositional arterial graft that bridged the arterial defect and permitted the DRA to perfuse both the flap and the distal phalanx.

Venous outflow of the flap was secured by anastomosing its 2 venae comitantes of the radial collateral artery to the venae comitantes of the DRA, thereby ensuring adequate drainage and preventing venous congestion. However, when attempting to use the flap’s venae comitantes to bridge the venous defect of the distal thumb, a significant caliber mismatch was encountered with the 2 small venous stumps (2 DDVs)—the diameter of the flap’s venae comitantes was too small (<0.3 mm), rendering direct reconstruction impossible. To overcome this, a 7-cm Y-shaped vein graft was harvested from the forearm. The 2 distal limbs of the vein graft were anastomosed to the tiny venous remnants (2 DDVs) in the distal phalanx, whereas the proximal limb was connected to a subcutaneous vein near the radial artery, thus reestablishing sufficient venous outflow from the distal thumb.

To allow better sensory recovery, an inferior lateral brachial cutaneous nerve was harvested with the flap and was then coapted to a branch of the superficial radial nerve (See figure, Supplemental Digital Content 2, which displays flap coverage of the thumb and neurovascular coaptations. Points a, b, c, d, e, f, and g refer to the arterial or venous anastomosis sites. For instance, points a, b, and c represent anastomosis between DRA [and its venae comitantes] and the proximal end of flap pedicles, and point e refers to the arterial anastomosis between the ulnar PDA remnant and the distal end of the radial collateral artery. Red refers to arteries, blue vessels refer to veins, and yellow refers to nerves. A vein graft was harvested from the forearm to create stable drainage for the distal phalanx, https://links.lww.com/PRSGO/E735).

Postoperatively, the right arm/hand was routinely elevated, and mannitol (20%, 100 mL once daily for 3 d) was administered to mitigate tissue edema. A protocol for intermittent suture release was in place should constriction from edema have occurred.

OUTCOME

Postoperatively, blood perfusion to the distal thumb was restored, and the flap demonstrated reliable circulation (Supplemental Digital Content 2, https://links.lww.com/PRSGO/E735). At 1-year follow-up, the flap contour was satisfactory, thumb function was preserved, and the donor site healed uneventfully with only a linear scar. The flap demonstrated recovered sensory function, including light touch, pain, and temperature perception. Two-point discrimination at the fingertip measured 3 mm, nearly comparable to the contralateral side. Full range of motion was present at the thumb MCP joint, whereas interphalangeal joint motion was restricted to approximately 20 degrees of flexion. Key pinch function was present, and grip strength of the reconstructed hand was comparable to that of the unaffected side. (See figure, Supplemental Digital Content 3, which displays 1-y postoperative appearance of the reconstructed thumb versus the contralateral thumb, https://links.lww.com/PRSGO/E736.)

DISCUSSION

The selection of an appropriate flap for reconstructing extensive thumb defects necessitates a comprehensive evaluation of multiple factors, including defect dimensions, tissue characteristics, donor-site morbidity, and functional requirements. In the present case, various alternative flaps were considered; however, the lateral arm flap was ultimately determined to be the most suitable option. Large flaps such as the deep inferior epigastric perforator flap or the anterolateral thigh flap provide ample tissue; however, their inherent thickness and subcutaneous bulk often compromise contour and restrict thumb mobility and fine function, guaranteeing extra thinning techniques.¹ In addition, the caliber of their perforators is poorly matched to the proper digital arteries or DDVs of the phalanx, excluding the possibility of simultaneous vascular reconstruction. Alternatively, the superficial circumflex iliac artery perforator flap offers thinner tissue for thumb reconstruction⁶; however, its perforator anatomy is less reliable, making it a less predictable choice.

Forearm-based flaps, typically perfused by the posterior interosseous artery, offer the advantages of thinness and pliability. When designed as a reverse pedicled flap, they eliminate the need for microvascular anastomosis and are commonly used in hand resurfacing procedures. However, this approach presents several substantial limitations in digital reconstruction. The pivot point is located approximately 2 cm proximal to the distal radioulnar joint, providing an inadequate rotational arc to reach the thumb tip and creating excessive tension on the vascular pedicle. Furthermore, this pedicled reverse radial forearm flap results in an extensive scar with considerable cosmetic implications. And the maximum harvestable dimensions of these flaps are also limited, rarely exceeding 5 cm in width or 10 cm in length, which restricts their utility for larger or circumferential thumb defects.⁷ The venous flow-through flap was excluded from consideration due to concerns regarding its unpredictable survival in large defects, significant caliber mismatch between the delicate distal arterial stump and the flap’s venous pedicle, and potential complications including poor color match and venous congestion.⁸

Overall, the lateral arm flap exhibits relatively thin and supple skin and subcutaneous tissue, avoiding the bulkiness typically associated with thigh or abdominal flaps. The donor site can be closed primarily even after harvesting a sizable flap, offering both versatility and favorable aesthetic outcomes. A unique advantage of this flap over alternatives—such as the radial forearm, superficial circumflex iliac artery perforator, deep inferior epigastric perforator, and anterolateral thigh flaps—is its reliable incorporation of the inferior lateral brachial cutaneous nerve. This consistent neural inclusion permits direct coaptation, which significantly improves the potential for sensory restoration in the flap and thereby facilitates a more functional thumb reconstruction.⁹ Furthermore, the flap’s vascular pedicle, based on the radial collateral artery, demonstrates consistent anatomy and a well-matched caliber for flow-through reconstruction.

However, our case underscored the added complexity of applying the concept of a flow-through flap to the thumb, where the vessels are much smaller and both the arterial and venous systems were completely absent. The radial collateral artery offered an almost ideal arterial match—approximately 1.0 mm proximally and 0.4 mm distally, closely corresponding to the radial artery branch and the proper digital arteries—making it an excellent choice for arterial bridging. However, its venae comitantes were too small to serve as venous outflow conduits, necessitating additional vein grafting. This limitation illustrates that although the flow-through flap design can be highly effective for digital arterial reconstruction, reliable venous restoration often remains the major obstacle in thumb salvage.

In real-world reconstruction, the circumferential inset of a flap also presents a well-recognized challenge, primarily the risk of postoperative edema–induced vascular compression. Our strategy to mitigate this risk was multifaceted. First, designing the flap 0.5 cm wider than the defect was a proactive measure to create a “buffer zone,” directly countering the effects of swelling and preventing dangerous constrictive tension. Second, the construction of 2 venous anastomoses was critical for enhancing outflow, addressing the edema at its physiological source. These intraoperative measures were complemented by postoperative protocols—limb elevation and mannitol administration—to further control tissue swelling. This comprehensive approach, from flap design to postoperative care, ensured a safe closure without vascular complications.

In summary, when addressing circumferential thumb defects complicated by arterial and venous loss, the flow-through lateral arm flap based on the radial collateral artery perforator is an optimal reconstructive choice, combining adequate size, favorable thickness, stable vascular anatomy, and the potential for sensory recovery.

DISCLOSURES

The authors have no financial interest to declare in relation to the content of this article. This work was supported by the Natural Science Foundation of Hunan Province (grant nos. 2023JJ40967, 2023JJ30951).

PATIENT CONSENT

Written informed consent was obtained from the individual(s) for the publication of any potentially identifiable images or data included in this article.

ETHICAL APPROVAL

The studies involving patients were reviewed and approved by Xiangya Hospital. The protocol was in accordance with the ethical standards of the Declaration of Helsinki (1975) and its subsequent revisions.