The Combination of Moberg Flap with V-Y Advancement and Reverse Adipofascial Cross Finger Flap for Coverage of Degloving Injury of the Thumb-Case Report

We report a case of 22 years old male patient who is a worker in a factory and sustained degloving injury of his left thumb in a machine while working. There was loss of the pulp of the thumb extending circumferentially to the dorsal aspect with loss of the skin of the terminal phalanx and part of the proximal phalanx. The nail and germinal matrix were lost with exposure of the bone and extensor pollicis longus tendon insertion. The thumb was totally covered with a combination of two flaps: Moberg flap with V-Y advancement was used to cover most of the volar surface of the thumb and reverse adipofascial cross finger flap from the adjacent index finger was used to cover the dorsal surface and the tip of the thumb. The reverse adipofascial cross finger flap was covered with split thickness skin graft. Three weeks later this flap was divided and the thumb was mobilized freely. The patient had a full range of movement of the thumb and index finger with few settings of physiotherapy postoperatively. We recommend combining both of these flaps to reconstruct degloving injury of the thumb as they provide near adjacent tissue of similar texture, preserve sensation at the volar aspect of the thumb and also avoid the complications of the distant flaps.


Introduction
The thumb is responsible for about 40% of the function of the hand. Preserving techniques are described to reconstruct degloving injuries of the thumb. This article will discuss the procedure we used to reconstruct a degloving injury of the thumb using a combination of two flaps; one from the volar aspect of the thumb itself and another one from the adjacent index finger to preserve its length with durable flaps and preserve sensation at its volar aspect.

Case Report
A twenty two years old worker in a factory presented to the Emergency Department with circumferential degloving injury of his left thumb while working on a machine. There was loss of skin, subcutaneous fat, the whole nail and the nailbed and the tip of the head of the bone of the terminal phalanx ( Figure 1). The bone of the terminal phalanx was totally exposed with exposure of the extensor tendon on the interphalangeal joint dorsally. The interphalangeal joint was covered with skin volarly with no exposure of the flexor pollicis longus tendon insertion.
There was no skin at the dorsal aspect of the interphalangeal joint and the distal part of the proximal phalanx dorsally. The patient did not bring the degloved part with him as it was crushed in the machine.

Operative Procedure
The patient was taken to the operation theatre on the same day and under the effect of general anaesthesia and with the use of arm tourniquet, wound de-

Discussion
The Moberg flap was first described in 1964 to cover defects at the pulp of the thumb by advancing the volar skin distally. It was used also with success in other fingers [1].
The Moberg flap involves making two bilateral incisions dorsal to the neurovascular bundles. The flap is raised over the paratenon including both the neurovascular bundles and advanced distally to cover the raw area at the tip of the thumb with the interphalangeal joint kept in flexion position. This can result in inability to extend the interphalangeal joint of the thumb fully post operatively [2]. To avoid this, different techniques were prescribed to provide more advancement of the flap without the need to keep the interphalangeal joint in flexion position. One of these techniques was prescribed by Jindal et al. in the form of "Z" plasty modification at the base of the flap [3]. Another technique to avoid flexion of the interphalangeal joint is to incorporate "V" at the base of the flap and the proximal defect is closed in a "V-Y" fashion [4]. In our case, we used the "V-Y" advancement technique to move the flap distally without flexing the interphalangeal joint of the thumb.
In a study done by Baumeister et al. on 36 patients, eighty three percent of the cases had the defects covered with the flap without additional iatrogenic shortening of the thumb [5]. In our case, the flap was advanced distally as much as possible but could not cover the whole distal phalanx volarly till the tip of the thumb. The bone was not shortened, as each millimeter of the thumb counts, but its tip was covered with the distal part of a reverse cross finger adipofascial flap from the dorsal aspect of the adjacent index finger. This flap was used also to cover the rest of the raw area at the dorsal aspect of the thumb.
Anatomic studies showed that this flap is based on constant dorsal branches of the palmar digital arteries in the proximal phalanx, which anastomose with the vascular system of the dorsal skin. The flap is drained by small vena concomitants that follow the arterial branches [6].
We Adipofascial flaps can also be used as turnover flaps from the same digit to cover defects of the digit distally. This homodigital flap can be used with success to cover the dorsal aspects of the middle [9] and terminal [10] phalanges of the fingers and also to cover raw areas at the dorsal aspect of the thumb [11]. It is a one stage procedure and does not involve other fingers than the one injured and when compared with the de-epithelialized cross finger flap it showed better results [12]. In our case we could not use this flap as the injury was circumferential

Conclusions
The Moberg flap preserves the touch sensation at the volar aspect of the thumb replacing its pulp with the same type of tissue. Incorporation of V-Y advancement fashion at its base avoids flexion deformity of the thumb. The reverse adipofascial cross finger flap is a simple and rapid procedure. It is an excellent option because of its thinness, good pliability and minimal donor site deformity.
Combining both flaps together can avoid the need for distant flaps leaving the shoulder and hand entirely free and avoiding bulky disfigured insensate flaps.

Conflicts of Interest
The authors declare no conflicts of interest regarding the publication of this paper.

Ethical Approval
The procedures performed in this study involving human participant were in

Informed Consent
Additional informed consent was obtained from the participant for whom identifying information is included in this article.