30 Perfusion Problems
30.1 Patient History Leading to the Specific Problem
A 53-year-old man previously sustained a crush injury to his dominant right hand, resulting in soft-tissue lacerations to the zone 2 region of his right index finger. After initial repair of his flexor digitorum profundus (FDP) of the index finger, he developed severe tendon adhesions that necessitated tenolysis shortly after. Unfortunately, he developed a secondary FDP rupture during mobilization at home later. This was treated with a tendon graft procedure, followed by an A3 pulley reconstruction. After several months of rehabilitation, the range of motion (ROM) at his proximal interphalangeal joint (PIPJ) remained poor with a flexion contracture (▶Fig. 30.1a). A decision was made to surgically release the dense scarring over the PIPJ as part of a flexion contracture release. After surgical excision of scar tissue and adhesions, a 3 to 4 cm × 2 cm soft-tissue defect was formed over his zone 2 right index finger (▶Fig. 30.1b).
30.2 Anatomic Description of the Patient’s Current Status
The zone 2 region of a finger was affectionately known as “no man’s land” by hand surgeons. This is due to the numerous structures contained within the section of the finger directly over the PIPJ. The decussation of the flexor digitorum superficialis (FDS) and passing of the FDP occur at this region, along with bilateral neurovascular bundles and a thick fibrous structure known as the volar plate. All these structures contribute to its bulky contents that make soft-tissue coverage over this region particularly tricky.
The complex nature of this case comes from multiple previous soft-tissue repair procedures along with tendon grafting and pulley reconstruction. As a result, tendon adhesion and dense fibrosis occur, necessitating surgical release. Flexion contracture release requires excision of all fibrotic scar tissue in order to adequately straighten the joint, allowing for smooth tendon excursion. The result is a full-thickness defect with exposure of vital structures including the radial and ulna neurovascular bundles.
30.3 Recommended Solution to the Problem
Reconstructive options should take the above into consideration to provide adequate coverage that should ideally also contain supple tissue to avoid recurrence of adhesions and contracture. Local flaps, homo- or heterodigital in this case, were unlikely to provide the soft-tissue quality or quantity required for adequate coverage. A free medialis pedis flap may be considered in reconstructing such a defect, but it will create new donor site wounds on the foot. A thin, pliable free flap would be most suited for this case and we chose to use a free venous flap harvested from the ipsilateral forearm.
Conventional venous flaps are notorious for their unreliable perfusion. We utilize a technique of “shunt restriction” and apply them to venous flaps, which increases their reliability and perfusion to the whole flap.
30.3.1 Recommended Solution to the Problem
• Adequate soft-tissue coverage is required over zone 2 finger defects.
• A venous flap fulfills the requirements needed in this case—thin, pliable, and adequate in size, often similar in thickness to soft tissue over a finger.
Fig. 30.1 (a) Fixed flexion contracture of the right index finger over his proximal interphalangeal joint (PIPJ). (b) Intraoperative photograph following release of the fixed flexion contracture and dense scarring of soft tissue impairing PIPJ movement. A resulting soft-tissue defect over the zone 2 region is seen.
• There is minimal size mismatch between distal forearm veins and the digital arteries and veins.
• Donor site can be kept to the ipsilateral forearm with minimal donor site morbidity.
• Reliability of venous flaps can be enhanced using a technique known as “shunt restriction.”
30.4 Technique
Venous flaps are designed conveniently in the forearm of the patient. They most likely can be closed primarily with minimal donor site morbidity. Careful planning of the venous pattern can be done preoperatively with the aid of near-infrared scanners.
An afferent vein refers to the vein that carries blood entering the flap, whereas an efferent vein refers to the veins that carry blood away from the flap. An efferent vein and an afferent vein to the flap have to be established and, if needed, an added efferent vein can be anastomosed. In order to prevent arteriovenous (AV) shunting of blood within the venous flap, “shunt restriction” using a hemoclip within the flap should be performed (▶Fig. 30.2). AV shunting results in bypass of arterial blood directly through the flap without perfusion of the flap. When a buildup of blood occurs within the flap, it cannot drain through the efferent end of the flap due to the high intravascular pressure resulting from the AV shunting of blood. When “shunt restriction” is applied, the distal 50% or so of the venous network collapses initially. Arterialized blood from the afferent end enters the flap and is forced through the flap tissue. When buildup of blood occurs, pressure within the flap forces blood to flow through the low-pressure valveless venules within the venous network and exits the flap via the efferent vein after tissue perfusion.
