The anatomical basis of the modified volar advancement flap for fingertip reconstruction.

Somes C Guha, Stephen M. Milner and Amitabha Chanda

Keywords: modified volar advancement flap, neurovascular bundle; cross sectional study.

Abstract

Composite digital-end tissue loss in industry and the kitchen is labeled as a "minor" injury. There are no published data to estimate the social and industrial work-hour losses, and other implications accurately; but by all accounts, there is a disproportionate loss in time, money and aesthetic appearance. At present, the standard of care for such injury is with skin graft or skin flaps by a number of techniques. They are sensate or insensate, local or distant, and often involve complex finger immobilization. Some are also technically challenging. Yet no procedure is widely acceptable that restores both optimal functionality and cosmetic outcome rapidly. We advanced this volar advancement flap (VAF) concept modifying upon the technique described by Moberg1 (1964) and Snow2 (1967). However, unlike them, we used one neurovascular bundle with our VAF. It is safe, simple to do, and reproducible. It may be used in any digit and multiple digits at a time for most types of composite tip loss. It restores a sensate, durable, cosmetically acceptable fingertip with minimal loss of digital length, skill and work-hours. Also, this avoids dorsal skin necrosis, loss of sensation, and joint stiffness as seen with cross finger flap and in other VAF techniques.

We present the anatomical study showing the basis of the concept and tested the VAF in a tertiary hospital based, cross-sectional, consecutive case study series. A larger series of prospective study is recommended.

Introduction

Amputation of the fingertip is often viewed as a relatively minor injury. Nevertheless, it can cause considerable loss of skilled hand function as well as loss of aesthetic appeal. When bone is exposed, the use of skin grafts is not feasible and numerous ingenious methods have been described to advance skin locally or from adjacent digits.3 Although management of these injuries is controversial, it is generally agreed that the preservation and restoration of length, sensibility and range of motion of an injured digit is important to regain optimum function of the entire hand.

In 1964, Moberg1 described his classical volar advancement flap (VAF) where he applied these principles to resurface the tip of the thumb. His VAF, which includes both neurovascular bundles (NVB), preserves available length and maximum sensation.

In 1967, Snow3 first published his series of eight digits where he applied the VAF concept of Moberg1 to all digits. Though he documented excellent application of the flap, there was a significantly high incidence of blistering and necrosis of the dorsal skin proximal to the nail bed. Beasley4, Keim et al5 documented similar complications in his book on hand injury. This is attributed to the removal of the dominant blood supply of the finger distally following VAF transfer. This contrasts with the situation in the thumb, in which the distal dorsal skin has a dual blood supply. Additional branches from the radial artery reinforce the volar vessels of the thumb dorsally.6,7,8,9,10

In any finger, the risk of vascular compromise of the distal dorsal skin and nail apparatus has rendered the VAF relatively unsuitable for reconstruction of its tip after amputation. Preservation of proper sensation to the fingertip is critical to the optimal function of any skilled hand.

The anatomical basis of our modification is to raise an axial pattern VAF based on only one NVB. The other NVB is left in situ to maintain blood and sensory supply to the dorsal skin and nail bed.

Materials and Methods

The Anatomic study

This study was carried out in the Department of Anatomy, Louisiana State University Health Sciences center at Shreveport, LA. The preparation of the cadaver specimen followed the standard embalming technique described by Sanan11 with minor modifications. The embalming of the cadaver hand and forearm composite were done with formalin and alcohol. The radial and ulnar arteries, cephalic and basilic veins were dissected in the forearm. They were canulated and washed thoroughly to clear out all the blood products from the large and small vessels. Once the efflux is very clear, colored Microfil dye (Flowtech Inc ®, Carver, MA) was injected. Red dye was injected into the arteries and blue dye was injected into the veins. During injection, light pressure was applied to avoid rupture of the vessels and extravasations of the dye. After injection, the specimen was wrapped in wet towel and kept so for 24 hours. This period will allow solidification of the dye within the vessels. Following this, the specimen is kept in an aqueous solution of pHA, GX and Di-SAN (The Champion Company Inc ®, Springfield, OH) and refrigerated.

The quality of dorsal skin blood supply is demonstrated. The distal dorsal blood supply in any digit is fair in comparison to that of the thumb as demonstrated in slides as composite figures here. Cormack6 has also reported a similar observation.

A common variant of fingertip loss is created (left case, Figure One).

Figure One Fingers shown after 24 hours of Microfil dye injection. The quality of dorsal skin blood supply is demonstrated. Note the pointers showing the quality of distal dorsal blood supply. The blood supply to thumb is much better than that of the digits. A common defect is illustrated in the left-hand case. Right-hand case depicts the midaxial incision line on right index finger in relation to the radial volar neurovascular bundle in double lines.

The VAF for respective digits were raised. The NVBs lie a few mm volar to the midaxial line, which connects the ends of the joint skin creases. The incision on the side of the primary NVB, which stays with the volar flap, is made along this midaxial line whereas the incision on the other side is made 2 mm volar to the midaxial line. The VAF is raised superficial to the flexor tendon sheath and flexor tendon pulleys, leaving some tissue around the NVBs for protection (Figure Two).

Figure Two. The VAF for the Index is raised. The NVBs lie a few mm volar to the midaxial line, which connects the ends of the joint skin creases. The primary NVB stays with the volar flap. Note the VAF is raised superficial to the flexor tendon sheath and flexor tendon pulleys, leaving some tissue around the NVBs for protection.

The finger is flexed and VAF is advanced to the tip like a bowstring to cover the defect; flap is sutured down with unequal bites along the edges of the incision lines as described by Snow2.

The Clinical Experience

Fourteen patients (13 men and one woman) entered the study, which examined sixteen digits (one thumb and fifteen fingers). Most of the patients were migrant workers from the Indian subcontinent and the neighboring Arab countries. All were injured at work. Details of the fingertip injuries are described in Table One and Two.

There was significant loss of pulp tissue in all cases. Six patients had intact nail and nail beds, five had partial amputation of nail and nail bed, and one had guillotine amputation proximal to the nail. One patient had lost three fingertips just distal to the insertions of the flexor digitorum profunda, leaving the distal interphallangeal joint preserved (Figure Three).

Only pulp tip is lost; VAF raised and fashioned for dog-ear correction
Figure Three A defect is created at the tip of the finger without the loss of bone or nail. The VAF is raised, advanced, and set onto the tip by cupping the flap and flexing the finger. Unequal sutures along the edges set down the flap.

VAF: raised, cupped, and advanced to set in by flexing the digit for pulp reconstruction
Figure Four A defect is created at the tip of the finger without the loss of bone or nail. The VAF is raised, advanced, and set onto the tip by cupping the flap and flexing the finger. Unequal sutures along the edges set down the flap.

One patient had loss of pulp, and part of the nail and nail bed of the right thumb.

Operative technique

Most operations were carried out under tourniquet and general anesthesia, and some were done with digital ring block. The flap was designed and raised as described in the anatomic study above. At the end of the procedure, the finger remained flexed (Figure Three). The patient is encouraged to actively use the finger as much as tolerated and as soon as possible.

Figure Five A defect is created more proximally at the middle of the distal phalanx, distal to the insertion of the Flexor digitorum profunda tendon of the index finger with partial loss of bone and nail. VAF is raised, advanced, and set onto the tip as in slide No. three and four, by cupping the flap and flexing the finger. Unequal sutures along the edges set down the flap. We have done this procedure on three fingers simultaneously. After procedure, the finger adopts the functional position, held without splints and movement is encouraged as soon as tolerated.

Results

The outcome of treatments is documented in the Table Two. The follow up period ranged from 14-70 weeks. All patients were able to return to their jobs within three - six weeks, without change of previous duties. Sensation across the suture line was near completely restored to the full finger in three to six months with normal two-points discrimination. No further follow up was possible as the patients were migrant workers who decided to travel back home.

Discussion

This was a tertiary hospital based, cross-sectional and consecutive case study series. The patients were migrant workers or homemakers in a rapidly developing industrial society. People, who acquired gadgets with rotary blades, were often unfamiliar with the modern machines and the appropriate safety practices.

Every consideration was given to maximize the re-establishment of skilled function of the hand and enable the patient to return to his present occupation as soon as possible. The restored cosmetic appearance was an additional advantage. Irrespective of the dominance of hand, age, sex, race or specific anatomy of the digits, the operation proved to be universally successful. In general, Caucasians tend to have little natural hyperextension at the interphallangeal and metacarpophalangeal joints compared to people of Afro-Asian origin resulting in a greater likelihood of long-term flexion deformity with prolonged immobilization. This complication was largely eliminated by early and aggressive use of the hand and no such deformity occurred.

The various skilled grips of the hand as in writing, painting or in a power grip mandated the selection of the neurovascular bundle (NVB), radial or ulnar, to be used with the VAF. This modified VAF flap proved successful to optimally resurface all fingertips with composite tissue loss without significant deformity or dorsal skin necrosis. We have also used this technique in cases of traumatic amputations through middle or proximal phalanges preventing further loss of bony length whilst providing sensate and quality skin cover.

Our technique lends itself for use in all digits in most situations of composite tip loss. We managed to restore a sensate, durable, cosmetically acceptable finger with minimal loss of length. It also allows enables a more rapid return to work. The dorsal skin necrosis was prevented which we believe was due to inclusion of a NVB in situ with the skeletonized finger. This eliminated the need for complex immobilization, loss of sensation and joint stiffness as seen in cross finger or other insensitive skin flap usage. Also, as Snow2 has demonstrated, this VAF may be applied if more than one fingertip needs to be reconstructed simultaneously as their blood supply is independent at the fingers.

We feel this is a welcome addition to the armamentarium of hand surgeons.

References:

Bibliography:

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Acknowledgements:

ML Sharma, MS FRCS, Consultant Plastic and Reconstructive Surgeon, 9 Nilgiri Apartments, Alakananda, New Delhi, India-19.
Michael B. Harper, MD, Professor and Residency Program Director, Department of Family Medicine, Louisiana Health Science Center at Shreveport and Arthur Fort, MD, Professor and Chairman, Department of Family Medicine, Louisiana Health Science Center at Shreveport.
John H. Haynes. Jr., MD, Program Director, Rural Residency Program, Vivian/Shreveport, LA 71082.