The Crossover Composite Filet of Hand Flap and Heterotopic Thumb Replantation

Abstract

Sir: The extremity filet flap offers ideal tissue with limited donor-site morbidity. After nonreplantable traumatic upper extremity amputation, preservation of length can be crucial for proper fitting of a prosthesis, and the filet flap has served in this capacity.1-3 In an effort to maintain a prehensile hand, heterotopic digital replantation is also often used. We present a unique scenario in which a crossover composite filet of hand flap was used for coverage of an extensive contralateral hand wound combined with a heterotopic thumb replantation. A 46-year-old woman presented following jumping in front of a subway train with traumatic amputation of her right upper extremity at the proximal humeral level, traumatic amputation of her left thumb, and severe degloving of her left hand (Fig. 1). Secondary to delayed presentation and extensive elbow injury, replantation of the right upper extremity was not attempted. Instead, an extended filet of hand flap was designed to include both the palmer and dorsal surfaces of the hand and the thumb (Fig. 2). The extensor pollicis longus and flexor pollicis longus were identified and harvested at their musculotendinous junction. The thumb was disarticulated at the basal joint. The thumb sensory nerves, radial sensory nerve, dorsal ulnar sensory nerve, radial artery, and multiple veins were included within the flap. All similar structures were prepared on the left hand.Fig. 1: Preoperative image of the left hand degloving injury and thumb avulsion injury.Fig. 2: Composite filet of hand and thumb flap. EPL, extensor pollicis longus; FPL, flexor pollicis longus; APL, abductor pollicis longus; EPB, extensor pollicis brevis.Secondary to ischemia time, the revascularization (one artery end-to-side, and two veins) was completed first. The recipient-site metacarpal stump was smoothed and a matching amount of metacarpal base was removed from the flap. Fixation was completed with Kirschner wires. The tendons and all nerves were repaired and the skin was closed over the defect. There was 100 percent flap survival. Three additional operations were required for further débridement and limited skin grafting of the native left hand. At 9 months, the patient had a viable left hand and thumb (Fig. 3). She has limited thumb sensation, but this may continue to improve. She has minimal thumb interphalangeal or metacarpophalangeal joint motion but has a functional post. She has range of motion in abduction and adduction of 45 and 15 degrees, respectively. She is able to use her left hand for normal daily activities, including writing.Fig. 3: Nine months after left thumb and hand reconstruction using the crossover composite filet of hand and thumb flap.The classic filet flap involves harvest of an axial pattern flap from a nonsalvageable extremity allowing wound coverage without increased donor-site morbidity.2 We present a variant of this typical flap with harvest of a crossover composite filet of hand and thumb flap. Crossover flaps have been used in both bilateral lower extremity4 and upper extremity amputations.5 In this case, an alternative option would have involved a temporizing procedure followed by multiple microvascular procedures. Our approach offered several advantages, including an immediate reconstruction allowing early rehabilitation and a superb reconstruction without donor-site morbidity. Other reconstructive options would have involved sacrificing another digit either on the hand or the foot. We were able to provide a reconstruction with very similar tissue, allowing preservation of function in an otherwise severely debilitating injury. DISCLOSURE The authors have no financial interest to declare in relation to the content of this article. Nicholas T. Haddock, M.D. Hospital of the University of Pennsylvania Philadelphia, Pa. David A. Ehrlich, M.D. Jamie P. Levine, M.D. Pierre B. Saadeh, M.D. New York University Langone Medical Center Institute of Reconstructive Plastic Surgery New York, N.Y.