Outcomes of Coverage of Soft Tissue Defects in the Thumb with a “Kite Flap”

Abstract

Deep soft tissue injuries and defects in the digits such as pulp amputation and degloving injuries are relatively frequent in hand surgical practice. Injuries around the thumb constitute a specific subtype, because their fitting requires the use of techniques that are different from standard. Many different surgical options have been described for the treatment of these serious lesions, depending on site and size of the defect, as well as on bone exposition. The “kite flap” is one of the most popular and frequently used. Results of the treatment of 14 of the 22 patients whose defects in the thumb were fitted with the kite flap are presented. The flaps healed in all patients. At the mean follow-up of 3 years all patients declared satisfaction with the result of surgery. Most of them had slightly limited mobility of the operated thumbs but with no significant translation to the function of the hands, which was very good. The results of this study show that the kite flap is useful in reconstruction of soft tissue defects around the thumb, which are difficult to cover by more conventional techniques

Zusammenfassung

Weichteildefekte an den Fingern wie Fingerkuppenamputationen kommen sehr häufig vor, wobei Defekte am Daumen eine besondere Herausforderung sind. Von den verschiedenen Behandlungsoptionen ist der „Kite-Flap“ eine der am häufigsten verwendeten. Die Ergebnisse der Defektdeckung am Daumen mittels eines „Kite-Flaps“ von 14 von 22 Patienten werden berichtet. Alle Lappen heilten ein. Drei Jahre postoperativ waren alle Patienten mit dem Ergebnis zufrieden. Bei den meisten fand sich eine leichte Bewegungseinschränkung des operierten Daumens, ohne dass dies jedoch die Funktion der Hand beeinträchtigte. Insgesamt hat sich der „Kite-Flap“ zur Defektdeckung am Daumen bewährt.

Key words

Thumb soft tissue defect - „Kite-flap“

Schlüsselwörter

Weichteildefekte am Daumen - „Kite-Flap“

Introduction

Deep soft tissue injuries and defects in the digits such as pulp amputation and degloving injuries are relatively frequent in hand surgical practice. Injuries around the thumb constitute a specific subtype, because their fitting requires the use of techniques that are different from standard. Moreover, reconstruction of the thumb is highly desirable, as its defects severely hinder hand function if not treated correctly. Many different surgical options have been described for the treatment of these serious lesions, depending on site and size of the defect, as well as on bone exposition. The first dorsal metacarpal artery flap (the “kite flap”, the “Foucher flap”) is one of those frequently used in salvage of the injured thumb integrity. The term “Foucher flap” comes from the name of French surgeon, Guy Foucher, who first performed and described this technique in 1979 year [1]. It is however frequently named a “kite flap”, owing to its appearance which resembles a kite (children’s toy). The kite flap has a relatively long pedicle which contains axial vessels (providing its main vascularity), namely, the first dorsal metacarpal artery and vein (FDMA). This artery is one of the dorsal branches of the radial artery. The flap itself is a rectangle of skin which is harvested from the dorsal side of the proximal phalanx of the index finger. Principal indications for the use of this technique include coverage of the defects in the thumb, predominantly in the proximal phalanx and around the interphalangeal (IP) joint [2] [3]. Microsurgical skills are required to harvest this flap, and technically the procedure is moderately demanding.

The objective of this study was an assessment of long-term outcomes of the coverage of soft tissue defects within the thumb with a kite flap.

Materials and methods

In the years 2010–2020, a total of 22 patients – 21 men and 1 woman, at a mean age of 28 years (range 18–45) presenting at the author’s institution with traumatic soft tissue defects in the thumb were operated on using the “kite flap”. The most common wounds were caused by a circular saw – 15 cases (68%) and most of them were work-related accidents. The defects were localised on the dorsal side of the thumb – in 11 cases, on the palmar side – in 8 cases and on the lateral side of the thumb – in 3 patients. In 15 cases the main defect was located in the proximal phalanx and in 7 the distal phalanx. One patient presenting with the proximal phalanx wound, sustained a simultaneous injury of the flexor pollicis longus tendon; in this case, primary repair of the tendon was performed first, followed by coverage of the defect with the flap. All procedures were performed under brachial plexus block anaesthesia and with the use of a tourniquet. Operations were done immediately after injury in 13 patients, whereas with 2–7 days delay in nine.

Fig. 1 Skin incisions to prepare a kite flap. Note the defect on the dorsum of the thumb.

Fig. 2 Harvesting of the flap from the dorsal side of the index finger.

Fig. 3 Picture demonstrating the length of the pedicle.

Fig. 4 Transposition of the flap to the defect in the thumb.

Fig. 5 Kite flap transposed to the thumb. Note good vascularity of the flap.

Fig. 6 Final view after completing surgery.

• Surgical technique

  • Preparation of the pedicle of the flap. A lazy S or zig-zag incision is made on the dorsal side of the metacarpus, parallel to the radial border of the second metacarpal, where the axial vessels should be present ([Fig. 1]).

  • Next, a rectangle of the skin and subcutaneous tissue is harvested in the dorsal side of the proximal phalanx on the index finger ([Fig. 2]). It is advisable to include a small part of the extensor hood with the flap, this is meant to prevent injuries to the vascular connection between the skin island and the vascular pedicle.

  • In the space under the skin, a fascial strip containing the first dorsal metacarpal artery and vein (the pedicle of the flap) is prepared. The axial vessels are relatively thin and are visible only under magnification ([Fig. 3]).

  • A careful cauterization at the radio-dorsal side of the metacarpo-phalangeal joint is required, with particular attention to the pedicle. Next the tourniquet is deflated and the vascularity of the flap is checked.

  • Once bleeding from the flap is good, the flap is transposed to the thumb. An additional incision can be made to place the pedicle or, alternatively, the pedicle can be pulled under a skin bridge. It is recommended to keep this tunnel under the skin loose, so as to lessen any compressive effects on the vascular pedicle ([Figs. 4], [5]).

  • The donor site on the index finger is then covered with a full-thickness skin graft, taken from the forearm.

  • The flap is then sutured to the skin of the thumb ([Fig. 6]).

• Further care

  The patients were released home 2–3 days postoperative, after ensuring good vascularity of the flap. [Figs. 7] and [8] show kite flaps in the course of healing. In the older post-op protocol, the patients had to take one dose of low-weighted heparin for 10 days, as an antithrombotic therapy. In the current protocol, the use of acetylsalicylic acid is recommended in prophylactic dose (150 mg/day) for 7 days. Wound healing was supervised in out-patient clinics, usually in the patients’ place of living.

• Assessment protocol

  Long-term outcomes were assessed at a mean of 3 years post-surgery (range 2–6) in the form of a phone interview. The investigators asked about:

  • Pain at the operation site (in the thumb and the index finger) experienced when the patient uses the hand. The patients were asked to rate the pain using a numerical ranking scale (NRS, range 0 – no pain, 10 – maximum pain).

  • Active range of motion (AROM) of the thumb in categorical manner (full or limited AROM)

  • Function of the hand in daily living activities and at work (full or limited function)

  • Function of the hand was also assessed with a quickDASH (Disability of the Arm, Shoulder and Hand) questionnaire (range 0 – full function to 100 – no function).

Fig. 7 Kite flap in the course of healing.

Fig. 8 Kite flap in the course of healing.

The follow-up assessment was performed in 14 patients (64% of the group), who responded to the phone call. The results of these measurements are the subject of this analysis.

Results

Post-operative course

Post-operative course was uneventful in 17 patients (77%) in whom operative wounds healed by primary intention and the skin graft at the donor site in the index finger healed completely. In five patients 23%) wound healing was complicated by means of marginal necrosis of the flap in two, and incomplete healing of the skin graft in another two patients. There was also one case of infection of the operative wound. All these complications were successfully treated conservatively.

Long-term outcomes

Long term outcomes were assessed at a mean of 3 years after the operation in 14 patients. They are shown in [Table 1]. Most patients had no pain in the operated hand, neither during daily life activities nor at manual work. Four patients experienced pain while making a strong grip with engagement of the affected thumb, and in one of these patients the pain was scored 6 in the NRS scale. Only 3 patients had a full active range of motion of the thumb, whereas 14 had a slight deficit, predominantly regarding extension of the thumb. The patient who underwent flexor tendon repair had decreased flexion and extension and rated his AROM as 50% of the healthy thumb. Four patients had a slight reduction in extension of the index finger from which the kite flap was harvested (donor site morbidity). Eleven patients considered function of the operated hand normal, whereas three felt some functional impairment. The mean quickDASH questionnaire score was 4.7, a point which indicates full function (dexterity) of the operated hand. One patient who underwent flexor tendon repair had greater dysfunction associated with reduced thumb mobility and pain at strong grip, and scored his quickDASH as 26 (mild dysfunction). During the interview, all patients declared satisfaction with the result of surgery and having an almost normal thumb.

Table 1 Results of measurements of postoperative variables in the study group.

Variable	Mean	Range
Pain (NRS)	1,4	0–6
quickDASH score	4,7	0–26
Variable	Full (number of patients)	Limited (number of patients)
Thumb ROM	3	11
Index finger ROM	10	4
Hand function	11	3
Overall satisfaction	14	0

After obtaining review of this study, we re-assessed 11 patients who responded our call. The following additional information was obtained. Three of 11 patients, all with defects at the dorsal side of the thumb, declared full sensation on the repaired area. In contrast, 8 patients had diminished (at least protective) sensation at the transferred skin. All patients declared correct warm/cold perception. All re-assessed patients declared that they felt the thumb as thumb.

Discussion

The idea and anatomical grounds for the island flap from the dorsal side of the index finger was elaborated by Gaul in 1954. Several years later, Holevich noticed that the dorsal branches of the radial artery, supplying the skin in the proximal phalanx of the index finger arise from the main trunk of the artery at the level of 2^nd carpo-metacarpal joint. These anatomical considerations allowed preparation of a relatively long pedicle of the flap and its transposition to the thumb [4]. Foucher and Brown first employed this technique for coverage of soft tissue defects in 11 thumbs and in one case for recovery of sensation in a replanted thumb, achieving healing of the flaps and good clinical outcomes in all cases [1]. Early and Millner reported 2 anatomical patterns of the FDMA course. In the most common type A (90% of cases), the artery was found superficially, in the dorsal retinaculum, whereas in the rarer type B it passed deeper, along the 1^st dorsal interosseous muscle. The authors noticed that preparation of the pedicle of the flap with a wide fascial strip allows safe harvesting of vessels, and identification of the course pattern of the FDMA is not necessary [5].

Literature review

There are several reports in the literature presenting outcomes of surgery with the use of kite flaps. Molski and Pisarek reported use of this flap in reconstruction of soft tissue defects and recovery of sensation in the thumbs of 8 patients. In 6 cases satisfactory sensation was achieved, with 2 point discrimination (2 PD) of 6–8 mm. In two cases, however, the operation failed in terms of total and partial necrosis of the flaps [6]. In his later works Molski reported successful reconstructions of combined bone and soft tissue defects in the thumbs using modified kite flaps, containing also, aside from the skin, a vascularized bone fragment [7]. This author reported outcomes of the treatment of 13 patients with post-traumatic defects in the thumb. In 5 cases bone fragments were transferred together with the skin to fill the bone defect, in 2 cases the dorsal digital nerve was harvested with the flap and coapted with the digital nerve of the thumb. All flaps survived and long-term outcomes were satisfactory with 2 PD in the pulp of the thumbs of 8–10 mm [8].

Williams et al., used the kite flap for coverage of soft tissue defects in 8 thumbs. All flaps healed uneventfully and all patients returned to their original jobs. The authors found that the sensation in the recovered thumb was the same as in the healthy thumb in only 3 cases, but in the other 5 was deprecated or only protective [9].

In an earlier work from the authors’ institution, the results of reconstruction of soft tissue defects in 3 patients who suffered from severe injuries to the thumb are presented. The patients were followed-up at 1–2 years after operation. All flaps healed uneventfully and defects were covered in all patients without terminalisation of the thumb. Functional results were satisfactory in 2 of the patients, but the other one had decreased total grip and pinch strengths. In the other patient a limited range of motion occurred in MCP joint of the index finger from which the flap was harvested. Sensation was satisfactory in all patients with 2 PD of 10 mm [10].

In a more recent study, Zhang et al., reported the use of a modified kite flap for the reconstruction of thumb pulp defects with nerve repair to improve thumb pulp sensation. They used the radial branch of the second dorsal digital nerve which was harvested with the flap and coapted to one of the proper digital nerves of the thumb. Results of the treatment of 42 patients were presented. At final follow-up at a mean of 2 years, a mean 2 point-discrimination of 8 mm was noted on all flaps. In the patients without nerve repair the mean 2 PD was 12 mm at final follow-up (difference stat. sign.) [11].

Adani et al. reported results of the treatment of 24 patients with dorsal thumb soft tissue defects using four different surgical techniques. In 9 of these patients with defects between the MCP joint and the nail, reconstruction was performed with the kite flap. The donor site was covered in all cases by a split-thickness skin graft. The extensor pollicis longus tendon was reconstructed in 2 cases using a strip harvested from the palmaris longus tendon. Flap survival was obtained in all cases. The authors conclude that the kite flap still represents a feasible solution for medium-size thumb defects with an intact nail [12].

Kite flaps were also used for recovery of sensibility in injured thumbs [1]. Tränkle et al., reported results of the treatment of 33 patients with tissue defects in the thumbs. These authors focused on assessment of sensation in the affected thumbs. Static 2-PD over the flap area averaged 10.8 mm, compared to 8.2 mm over the dorsal aspect of the contralateral index finger. Results of the filament testing showed no difference to normal skin or only diminished light touch in 76% of the patients [13]. Zhao et al., reported results of the treatment of 151 patients who had soft tissue defects of the digits. One of the subgroup comprised the patients with defects in the thumbs, treated with the dual-innervated or traditional kite flaps either. The results showed significant difference between dual-innervated and traditional kite flaps in static 2-PD, pain and overall patients’ satisfaction, favouring the former technique. Double nerve repairs presented better discriminatory sensation over the flap, less pain in the injured digit and higher patients’ satisfaction than single nerve repair [14] .

Huart et al., presented an anatomical study of the kite flap in conventional surgery versus robotic surgery. These authors found this flap feasible in robotic surgery, however, the time in performing this procedure by robot was significantly longer than compared with manual work [15].

The results of this study show that the kite flap is useful in the reconstruction of soft tissue defects around the thumb, which are difficult to cover by more conventional techniques. The authors believe that all skilled hand surgeons should be familiar with this procedure and that this article will be useful for trainees in this surgical discipline.

• References

• 1 Foucher G, Braun JB. A new island flap transfer from the dorsum of the index to the thumb. Plast Reconstr Surg 1979; 63: 344-349
• 2 Couceiro J, de Prado M, Menendez G. et al. The first dorsal metacarpal artery flap family: a review. Surg J (N Y) 2018; 4: e215-e219
• 3 Marin-Braun F, Merle M, Foucher G. The kite flap. Ann Chir Main 1988; 7: 147-150
• 4 Holevich J. A new method of restoring sensibility to the thumb. J Bone Joint Surg Br 1963; 45: 496-502
• 5 Early MJ, Millner RH. Dorsal metacarpal flaps. Br J Plast Surg 1987; 40: 333-341
• 6 Molski M, Pisarek W. Functional reconstruction of the palmar surface of the thumb usng the neurovascular flap from the index. Acta Chir Plast 1989; 31: 150-155
• 7 Molski M, Molski K. Neurovascular skin-bone combined flap from dorsal side of the index finger – a new method of reconstruction of peripheral part of the thumb (English abstract). Chir Narz Ruchu Ortop Pol 2002; 67: 625-631
• 8 Molski M. Use of the neurovascular flap from dorsal side of the index finger in reconstructions of complex, multi-tissue defects in the thumb (English abstract). Chir Narz Ruchu Ortop Pol 2003; 68: 115-119
• 9 Williams RL, Nanchahal J, Sykes PJ. et al. The provision of innervated skin cover for the injured thumb using dorsal metacarpal artery island flap. J Hand Surg Br 1995; 20: 231-236
• 10 Żyluk A, Walszek I, Puchalski P. Use of 1st dorsal metacarpal artery for reconstruction of soft tissue defects in the thumb (English abstract). Chir Narz Ruchu Ortop Pol 2005; 70: 17-20
• 11 Zhang X, Shao X, Ren C. et al. Reconstruction of thumb pulp defects using a modified kite flap. J Hand Surg Am 2011; 36: 1597-1603
• 12 Adani R, Mugnai R, Petrella G. Reconstruction of traumatic dorsal loss of the thumb: four different surgical approaches. Hand (N Y) 2019; 14: 223-229
• 13 Tränkle M, Germann G, Heitmann C. et al. Neurokutaner Insellappen nach Foucher. Weichteildeckung und Rekonstruktion der Sensibilität am Daumen. Chirurg 2004; 75: 996-1002
• 14 Zhao G, Wang B, Zhang W. et al. Sensory reconstruction in different regions of the digits: A review of 151 cases. Injury 2016; 47: 2269-2275
• 15 Huart A, Facca S, Lebailly F. et al. Are pedicled flaps feasible in robotic surgery? Report of an anatomical study of the kite flap in conventional surgery versus robotic surgery. Surg Innov 2012; 19: 89-92

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Eingereicht: 02. März 2022

Angenommen: 23. Mai 2022

Artikel online veröffentlicht:
19. Juli 2022