Reconstruction of Finger Soft Tissue Defects With a Thinned Free Anterolateral Thigh Flap

Background

Reconstructing complex soft tissue defects of the finger requires both functional and aesthetic aspects. There are many free tissue transfers as suitable options for digital resurfacing. The anterolateral thigh (ALT) flap is not the first choice for reconstruction of this area because it has the disadvantage that the subcutaneous tissue is too thick; however, its use as a thinned form has yet to be described much. This study presents the flap thinning technique in the small-sized ALT flap for the finger soft tissue defect.

Method

From May 2009 to March 2018, 10 patients with complete circumferential or semicircumcision defects in the fingers underwent reconstructive procedures that included thinned ALT flap transfer. Finger soft tissue damage due to contusion trauma includes loss of skin and exposure of the bone and tendon. The flap is thinned in 2 different ways: peripheral thinning and total microsurgical thinning, which is selected based on the perforator vessel structure of the flap.

Result

The ALT flap sizes, averaging 4–9 cm wide and 6–12 cm long, were thinned to 4–7 mm. One perforator was included in the flaps with a pedicle length average of 6.1 cm. The flaps survived entirely in all patients except one with a 30% area in the distal part of the thinned ALT flap that became necrotic because of venous occlusion. Donor sites were closed primarily for all patients. No patients required secondary flap defatting.

Conclusions

The small thinned ALT perforator flap can be an excellent option for full circumferential or semicircumferential soft tissue defects of the finger. Follow-up showed this as an excellent alternative for finger reconstruction in terms of aesthetic appearance and functional outcome.

Finger injuries, especially soft tissue defects, are common in hand emergencies, which can occur in isolation or the context of hand injuries, often due to causes such as occupational accidents, traffic accidents, and domestic violations.^1–4 The defects are of various positions, such as fingertip, palm, or dorsum, with different types like partial or total degloving injuries.⁵ For minor defects, local skin flaps, perforator-based flaps, and axial pattern flaps are used because of the simplicity of the technique, the similarity in skin quality, and good recovery. These nonmicrosurgical operations provide adequate soft-tissue coverage but have several limitations.^6,7 Free tissue transfer is a valuable reconstructive option. Significant digital soft tissue defects indicate more complex regional or free flaps. Different kinds of such flaps have been reported, and the main factor in choosing these flaps is surgeon preference and technical expertise.^8–10 Since Song et al¹¹ discovered the anterolateral thigh (ALT) flap, this has become a material for reconstructing many body parts, including the hand. The ALT-free flap for reconstructing hand defects with the advantages of large dimensions and long pedicles.^12–14 However, this flap has received little attention because its thickness is unsuitable for covering finger defects and deglove digital injuries. The thinning technique has overcome these disadvantages. Thinned ALT flap has met the requirement for recovering both function and aesthetics in hand defects.^15–18 We apply thinned, small-sized ALT flaps to cover full circumferential or semicircumferential soft tissue defects of the finger digits. Evaluating how to thin for each type of finger injury enhances the effectiveness of covering soft finger defects.

PATIENTS AND METHODS

From May 2009 to March–January 2018, a total of 10 patients with full-circumferential or semicircumferential defects in the fingers underwent reconstructive procedures that included thinned ALT flap transfer. One female and 9 male patients were included. The patient's age was an average of 25.4 years old (ranging from 19 to 35 years). The mechanisms of injury were traffic accidents (6/10) and occupational accidents (4/10). Two flaps were used for the treatment after traumatic limb amputation, 5 flaps for covering full-circumferential defects, and 3 flaps were for palmar semicircumferential injury. The defect site was the thumb in 5 patients, others 3 defects at the index, one in the ring, and the last one in the middle finger. Details related to these patients are provided in Table 1.

TABLE 1.

Thinned ALT Flap Patient's Characteristics

Pt	Age Sex	Etiology	Defect	Flap Size, cm	Before Thinning, mm	After Thinning, mm	Size Pedicle, cm	Flap Survival
1	22/M	Crush	L thumb	9 × 12	24	4	5	Complete
2	21/M	Crush	L thumb	10 × 10	20	4	7	Partial Necrosis
3	19/M	Crush	R thumb	7 × 12	20	9	7	Complete
4	23/M	Machinery	R index finger	5 × 8	12	7	7	Complete
5	30/F	Machinery	L thumb	6 × 9	22	9	7	Complete
6	32/M	Crush	L index finger	7 × 13	12	5	9	Complete
7	22/M	Machinery	R thumb	4 × 7	15	6	8	Complete
8	25/M	Crush	R middle finger	4 × 6	14	7	6	Complete
9	35/M	Crush	L index finger	4 × 7	12	7	5	Complete
10	25/M	Machinery	L ring finger	4 × 8	21	4	6	Complete

F, Female; L, left; M, male; R, right.

Operation Technique

All the flaps were harvested in a similar manner. The location of the perforators was mapped using a Doppler probe. A longitudinal skin incision is made on the medial side of the flap. Dissection to the subfascial plane until the descending branch of the lateral circumflex femoral artery and its perforators were identified. Dissection of the descending branch was performed, and the perforators were freely dissected retrograde to their origin. The fasciocutaneous flaps with the independent perforators were elevated based on the size of the skin defect.

Two different techniques can do the thinning procedure. With semicircumferential degloved defects, the thinning starts at the periphery and retains a fascia island with adipose tissue around the perforator entry. The flap was then microdissected and thinned up to 4–5 mm. In the completely degloved finger, the flap was thinned entirely and retained only 1 cm of the fascia around the perforating artery (Fig. 1). After thinning, the flap was elevated, and its pedicle was clipped from the descending branch of the lateral circumflex femoral artery. Finally, it was transferred to the recipient site for reconstruction. The anastomosis was performed with the radial artery, dorsal branch of the radial artery, or the proper palmar digital arteries by end-to-end or end-to-side methods. The donor site can be closed primarily. Postoperatively, the flap was monitored frequently by its color, refill, and by handed-held Doppler. When there is suspected occlusion, revision surgery is required. The patient's results are shown in Figures 2–5.

FIGURE 1.

The technique of thinning ALT flap. A, With a partial degloved injury, flap was microdissected at the periphery site. Preserved the fascia island around perforator entry. The thinned site was used to cover the tip and sides of the defect. B, With the complete degloving finger, flap was thinned entirely to cover the whole digit.

FIGURE 2.

A 22-year-old male patient, occupational accident. A, A partial degloving injury at the distal digit of the right thumb. B, A 4 × 7-cm ALT flap was harvested and thinned at the periphery site. C and D, 8 months postoperatively.

FIGURE 5.

A 25-year-old male patient after an occupational accident. A, Complete degloving of the ring finger in the left hand. B, An ALT flap size of 4 × 8 cm was raised and thinned to 4 mm. C and D, 18 months postoperatively.

FIGURE 3.

A 32-year-old male patient was involved in a traffic accident. A. A completely degloved at the left index finger, lost the distal digit. B, The ALT flap size 7 × 13 cm was thinned to 7 mm. C and D, Results after 4 months.

FIGURE 4.

A 25-year-old male patient had a car accident. A, Semicircumferential degloved in the right middle finger. B, A 4 × 6-cm ALT flap was raised and thinned to 7 mm entirely. C and D, Follow-up after 12 months.

RESULTS

The skin flap size ranged from 6–12 cm in length and 4–10 cm in width. The flap area was 58.9 ± 31.6 cm² (24–108 cm²). The original flaps thickness of 12–24 mm (average, 17.2 ± 4.4 mm). The flap's pedicle length ranged from 5 to 9 cm (mean, 6.1 ± 1.8 cm). After thinning, the flap thickness was reduced to 4–9 mm (6.2 ± 1.8 mm). In 7 cases of complete degloving injury in the thumb, index, and ring finger, the entire flap was thinned to 4–9 mm by microdissection. There were 3 cases of semicircumferential degloving, in which the flap was partially thinned in the peripheral site. There were 5 flaps in which anastomosis was performed end-to-end at the proper palmar digital artery. Three cases were anastomosed end-to-end with the dorsal branch of the radial artery, and 2 others were end-to-side with the radial artery. The donor site was closed primarily. One patient had a complication: vascular occlusion in a complete thumb degloving injury. The revision procedure was performed at the 12th hour after flap insertion. Reperfusion was achieved, and only the minor margin of 3-cm skin flap necrosis. In the remaining cases, no complications were observed. After 4–36 months (mean, 12 months) of follow-up, the flaps were well vascularized, including reliable soft tissue and pleasing contour in the original defects. No patients required secondary flap defatting, and no donor site complications were reported. Patients with semicircumferential degloving injury did not experience any difficulty in daily activities. The rehabilitation therapy was started 6 weeks postoperatively. Patients with a total degloved injury still have some limitations in the flexion of the fingers. In thumb degloving cases, the power and precision grips are still preserved, and the patient can perform finger opposition. However, the interphalangeal flexion only improved to two thirds of the normal range. All the patients were satisfied with the appearance of the reconstruction.

DISCUSSION

Traumatic hand injuries can be found in fingers, metacarpal region, and wrist, in which finger injuries are the most common diagnosis, accounting for approximately 39%–62% according to different studies.^1–4 Injuries from trauma to the finger soft tissue are diverse, from fingertip defect, partial defect, and semicircumferential to the most severe, full-circumferential degloving. Traumatic soft tissue defects of the finger can be combined with the exposure of the joints, bones, or tendons, and usually happen emergently. This circumstance needs to be covered entirely with the flap to optimize both functional and aesthetic outcomes and to ensure early rehabilitation for restoring hand function.^6,7 Traditionally, local, regional, and pedicle flaps are used for digital resurfacing. These choices cover small to moderate digital defects, such as homodigital, heterodigital, cross-finger flap, thenar flap, and hypothenar flap. Still, these flaps have several limitations of flap size and can compromise the function of an otherwise noninjured finger.^19–24 Some distal flaps, such as reverse radial forearm flap or posterior interosseous artery flap, cross-arm flap, and pedicled abdominal flap, offer a reconstructive alternative but still have some drawbacks. The clinical manifestations of complete degloving or semicircumferential injuries differ from the blast and the pure crush mechanism, as the soft tissue envelope is disproportionately injured. The injuries may result in extensive tissue loss, disfigurement, and significant functional impairment. When soft tissue coverage is achieved early, the finger's functional length and range of motion may be preserved and maximized with fewer subsequent procedures.

The alternative options to this approach require a free flap. Free flap is recommended when the defect is too large for coverage with local or pedicle flaps in patients with injuries exhibiting more than two thirds of the digital pulp extending proximally to the distal interphalangeal joint. The free flap can meet the requirements in the primary goal for hand reconstruction: ensure that the fingers regain normal or near-normal motion, preserve the length of the finger injured, complete in one-stage procedure to prevent adjacent joint contracture, and minimize the aesthetic distortion. Hypothenar free flap, venous flap, temporoparietal fascial flap, lateral arm flap, free posterior interosseous flap, toe plantar flap, and innervated radial artery superficial palmar branch flap does the same for fingertip, volar, or degloving defects.^5–10 Although free flaps are technically more demanding, they offer a favorable cosmetic result and acceptable donor site morbidity.^25–34

The ALT perforator flap is an excellent material for the development of reconstructing different parts of the body. The ALT has a long-standing heritage as a workhorse-free flap. The skin of the ALT is pliable and soft, various in size, and can be combined with other components like fascia, adipose tissue, and even muscle. For these reasons, many surgeons now use this flap instead of previous ones for extremities, head, and neck reconstruction.^{12–14,16,35,36} The ALT flap has previously been described with fascia lata to provide a gliding surface.^37,38 In addition, ALT-free flap combined with other free flaps like dorsal pedal artery and groin flap for extensive soft tissue defects involving the hands and multiple digits has been reported.^39,40 The main advantages of the ALT flap are the smooth, soft texture of the skin, the long flap pedicle, and one or more perforators that can vascularize it. However, it still has some pitfalls, like the thickness of the subcutaneous, especially in women. The average ALT flap thickness is from 2 to 4 cm, which is very difficult to cover the digital soft tissue defect. In the finger defect, the requirements are a thin and pliable skin that allows digital flexion and gliding of the underlying tendons. Additional liposuction may enhance aesthetic results, but excessive debulking can further impair mobility and perfusion. In 2001, Kimura et al^15–17 introduced the thinning technique in ALT flap; it can be done in 2 different ways: primary thinning or microdissected procedure, and the result can be thinned down to 3–4 mm. The thinned ALT free flap is valuable and reliable. It has been proved in the reconstructive procedures for coverage of various defects in the body. The reports of Rajacic et al,³⁵ Adani et al,¹⁸ or Viviano et al³⁶ mainly focus on thinned ALT flaps covering the arm and hand. It was consensus that ALT flaps can tolerate defatting at the time of flap inset if they are designed for minor, thin defects, such as those of the dorsal hand.^18,35,36

A report by Sharabi et al⁴¹ reviewed 11 articles, 88 ALT flaps were reported, and vascular complication was seen at 12.5%. With a free flap, the size beyond 150 cm² had a significantly increased compromise rate. There is no recommended thin flap when its size is greater than 150 cm².⁴¹ A systematic review by Agostini et al⁴² of 34 articles related to thinned ALT showed that the breakdown of vascular-related complications after flap thinning is 13.4% (in which the upper limbs take 14.6%). The incidence of partial flap necrosis of even the entire ALT flap loss is not a subject for surgeons to perform thinning techniques. Although there was consensus that thinning procedure should only be done with small flaps, there needed to be a specification on when it is possible to thin the ALT and to what extent it is safe to do so. Koshima et al⁴³ and Kimura et al⁴⁴ also introduced a mini ALT flap and used thinning technique for covering hand defects. For this reason, thinned ALT flaps still require special attention to reconstructing finger defects.

We thinned small ALT flaps in 2 ways depending on the flap type. The flap's perforator structure is an essential factor for thinning. We only selected flaps with perforating vessels that originate from the descending branch, which the perforator usually runs perpendicular through the fascia. The perforator originating from the transverse branch, or the one that runs parallel with the fascia, is not a candidate for the procedure. The vessel occlusion case was the one with a perforator running oblique to the skin paddle. In our experience, this perforator type has a higher chance of flap complications. For the defects in the finger pulp, we retained most of the fascia and fatty tissue around the pedicle and only thinned in the peripheral. The preservation of the fat layer is critical because it helps reconstruct the pulp's cortical part. On the contrary, peripheral thinning will create smooth margins around the digit, giving the finger a small and natural appearance. Peripheral pruning also adequately reduces the bulk of flap to match the tissue thickness of the finger closely. For complete finger degloving injuries, the requirement is that a flap is thin enough to cover the entire digits. The flaps for this type of injury are usually larger than for the partial circumferential degloving. We proceeded with the microdissection thinning and kept the fascia approximately 1 cm around the perforator; the entire flap was thinned to 3–5 mm. It was then wrapped around the damaged finger. If the flap was left 6- to 7-mm thick, it was likely to be ischemic at the distal end due to the tightening suture. One flap in our study, which was used to cover the total degloved thumb injury, has occlusion in the first 12 hours due to the tightened suture. The reanastomosis was good, but necrosis of the distal end of the flap was unavoidable. We found that the flap thickness is thin enough, and the suture is not too tight to be a decisive factor for the flap's survival. These simplify the flap insertion and greatly improve the final flap contour, reducing the need for secondary thinning procedures. All of our patients are satisfied with the result, especially patients with semicircumferential degloving injuries who can return to normal daily activities. In the case of the total deglove mechanism, there was some limitation in flexion; the patient still can move the finger but cannot advance to the full range of motion. However, the aesthetic result was incredible. There are still some pitfalls of this flap in hand reconstruction, because the most critical thing is sensation recovery. This must be considered when choosing the appropriate flap for a minor defect. In our study, every case has quite a large defect, more than a local flap can provide, so our flap choice is still suitable.

CONCLUSIONS

The thinned, small-sized ALT perforator flap can be an alternative option for full circumferential or semicircumferential soft tissue defects of the finger. In our experience, the ALT flap, which has a more perpendicular perforator to the skin, is more reliable for thinning procedures. The follow-up showed that this was an excellent alternative for finger reconstruction in terms of aesthetic appearance and functional outcome.