"A Free thenar flap – A case report"
© Garg et al; licensee BioMed Central Ltd. 2007
Received: 02 January 2007
Accepted: 12 March 2007
Published: 12 March 2007
We present a case report of a free thenar flap surgery done for a volar right hand middle finger, distal and middle phalanx degloving injury. A free thenar flap is a fasciocutaneous sensate flap supplied by a constant branch of the superficial radial artery and its variable nerve supply. It has a distinct advantage of low donor site morbidity, better cosmesis and texture of the flap. No immobilization is required postop. The donor site can be closed primiarily.
Numerous local or regional flaps have been used to cover medium to small size volar soft tissue defects of the digit. Large volar defects over the digit have presented a therapeutic challenge to the reconstructive hand surgeon. Free flaps from the feet or toes have been used to provide satisfactory coverage of these large defects, however donor site morbidity is unavoidable and the patient's acceptance is questionable.
We would like to report an alternative method to resurface a large volar defect of the finger utilizing a free thenar flap.
A primary debridment was done on the day of injury, because the wound was contaminated with grease and grit in the emergency operation theatre. The exposed tendon and bone was covered with a collagen dressing.
When the wound was inspected on day 3, it was found to be healthy and a flap was planned to cover the exposed tissues.
We have had a lot of experience with cross finger flaps and free flaps from the toe and foot. However, they have been associated with lack of patient compliance, morbidity to the donor areas and immobilization in the case of cross finger flaps. Therefore, we planned to do a free thenar flap, based on the superficial branch of the radial artery. We had carried out cadaver dissections and found the vascular supply consistently associated with this fasciocutaneous flap. This fasciocutaneous flap would have a texture similar to the pulp tissue. The other main advantage of the free thenar flap would be its sensory supply by either of the nerves (palmar cutaneous branch of median nerve, lateral antebrachial cutaneous nerve or branch of superficial radial nerve).
months after the injury, the patient is satisfied with the flap. He is happy about the texture of the flap which matched the other fingers
Free thenar flap was first used by Kamei  in 1993 and later by Tamai  in 1996. They used it successfully on seven patients. An anatomical study of the flap was done in 1997 by Pilz and Omokawa .
The flap is based on the superficial branch of the radial artery. This artery was seen to be constantly present in all the cadaver dissections  that were done. It branches out from the radial artery 2.5 cm proximal to the scaphoid tubercle with a pedicle length of 2 cm. The average diameter of the vessel ranges from 0.8–1.4 mm. It supplies a constant skin area of 3 × 4 cm. In addition to being a fasiocutaneous flap, it is a sensory flap (supplied by the palmar cutaneous branch of median nerve, lateral ante brachial cutaneous nerve or branch of superficial radial nerve) with a texture that closely matches the pulp tissue. If the width of the flap is less than 2 cm, the donor site can be closed primarily.
We advocate this flap as it is a fasciocutaneous sensate flap, locally available from the same injured hand, thereby decreasing donor site morbidity and a preferred flap by patients in comparison with cross finger flaps or flaps from the toe or foot. The flap has adequate subcutaneous tissue to give it the texture of pulp and also the genotypic appearance of the lost cover. It has a constant vascular pedicle (superficial branch of the radial artery). The donor site of the flap (thenar eminence) can be closed primarily, if the size is less then 2 cms, with minimal scarring. No postoperative immobilization is required unlike cross finger flaps.
Like other free flaps, this thenar free flap also has some risk of failure of flap due to loss of circulation postoperatively. The patient may also complain of pain at the site of detachment of the donor nerve, if the nerve was not carefully dissected and buried, due to neuroma formation. It can sometimes be very tedious to identify the nerve in the flap.
We started this project by reviewing the literature, dissecting cadavers and checking the consistency of the neurovascular pedicle. Our first case was successful and we intend to use this flap to cover medium to large digital soft tissue defects when conventional means are not feasible.
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