Soft Tissue Coverage for Extensor Tendon Reconstruction

Chapter 35 Soft Tissue Coverage for Extensor Tendon Reconstruction



Michel Saint-Cyr, MDFRCS(C)



Outline




A myriad of options exist for soft tissue reconstruction and coverage of exposed extensor tendons. This can range from simple skin grafting with or without turnover adipofascial flaps to free flaps in more complex cases. Principles of proper patient and wound evaluation, radical débridement, early coverage, and rehabilitation are paramount to maximize function. Transfer of intrinsic flap (i.e., flap from the injured the hand) should be considered first to cover local and small area soft tissue defect. Local or regional flap such as radial or ulnar forearm flap, dorsal interosseous artery flap, or lateral arm flap may be considered to cover the defect in the dorsum of the hand. Anterior thigh flap or other vascularized distant flaps should be considered if the defects are extensive and located over the dorsum of the hand or forearm. Thorough débridement is required before embarking on complicated reconstructive procedures, and postoperative motion of the hand and wrist is important to prevent joint stiffness and tendon adhesions. Despite increased technical requirements and length of operation, free flap reconstruction often results in fewer postoperative complications due to better vascularization, which is important when early postoperative mobilization or adjuvant therapy is required.


Often, extensor tendon exposure, lacerations, or tendon loss will require coverage with well-vascularized tissue to promote proper tendon healing and early mobilization. Adequate coverage also helps minimize any subsequent scarring, in an environment that is already prone to significant adhesions and contracture formation. Therefore, it behooves the reconstructive hand surgeon to provide well-vascularized tissue with either an intrinsic, locoregional, or distant free flap to provide stable soft tissue coverage. The dorsal skin of the hand has many qualities that allow flexion and extension of the digits. The increased skin laxity, pliability, and thinness also make the dorsum of the hand an excellent donor site for local flaps applicable to extensor tendon coverage. Flap selection will ultimately be dictated by the size and location of the defect, donor site availability, and recipient tissue characteristics.


Goals of this chapter will be to outline initial evaluation and management principles in the presence of exposed extensor tendons of the upper extremity following injury. Principles of flap selection and use will be discussed to provide stable coverage and expedite rehabilitation and maximize function.



Evaluation and Treatment


As with any upper extremity–mutilating hand injury, ruling out other severe systemic injuries is paramount. Before embarking in a complex reconstruction, the patient needs to be stabilized and all other life-threatening injuries need to be addressed and resolved. Patient-specific factors such as overall general health condition, associated comorbidities, profession, socioeconomic status, age, and compliance to therapy need to be considered when selecting the type of reconstruction. There are also wound-specific factors such as defect size as well as mechanism of injury, such as crush, penetrating versus blunt trauma, amputation, etc. All wound factors need to be considered as well as the zone of injury and availability of local or distant tissue for flap coverage.



Wound Débridement


Early radical débridement, of all nonviable tissue under tourniquet, control is pivotal prior to any attempt at locoregional or free flap soft tissue reconstruction. The critical step involves débridement of all marginally and questionably viable tissue to convert a contaminated wound into a clean wound and thus minimize risks of subsequent infection. This also allows a clear evaluation of all injured and missing structures. Early aggressive débridement should be performed over traditional serial débridement whenever possible. Serial débridement can delay final wound closure and make assessment of tissue viability difficult, and trigger a cascade of additional tissue loss from desiccation due to prolonged dressing changes. Early débridement and reconstruction also help to achieve the ultimate goal of early mobilization and return to function, which is critical in the upper extremity.


The general assessment is done, ideally, in the operating room under tourniquet control. The upper extremity is exsanguinated and a tourniquet is elevated and used to provide a blood-free field, so as to better expose and identify potentially devitalized tissue. All devitalized tissue is then débrided and the wound is extirpated very much like a tumor from the periphery towards the center and within well-defined natural tissue planes. The wound bed is resected entirely thus converting it from a contaminated to a noncontaminated wound. Following wound débridement, and once the extensor tendons have been either grafted or repaired, healthy coverage can be provided with either an intrinsic, locoregional, or free flap, as needed. A major prerequisite is adequate wound débridement to minimize any risk of infection, wound breakdown, and flap loss. Any initial wound that cannot be débrided thoroughly is best débrided serially after 24 or 48 hours. A negative pressure dressing can be applied temporarily using a white sponge over exposed extensor tendons so as to minimize any risk of desiccation. Note that negative pressure therapy should be used sparingly and only as a temporizing measure prior to definitive closure, which should be performed ideally within the first week. The upper extremity is very sensitive to the timing of reconstruction, and any prolonged immobilization will have a definite negative impact on final range of motion due to progressive stiffness, joint contracture, and swelling. Early coverage allows patients to enter an aggressive rehabilitation program to maximize their range of motion.


Once the wound has been properly débrided, the tourniquet is released and all nonbleeding and nonviable tissue is reexcised. Wound edges are inspected for bright red bleeding, and the wound is irrigated with a bulb syringe only. Pulse lavage is not used and can lead to extensor tendon friability and additional soft tissue trauma. Therefore, we only use triple antibiotic saline with bulb irrigation.


Choice of extensor tendon coverage, working from distal to proximal, will be based on the level of injury as well as the availability of nontraumatized soft tissue in the proximity of the wound. Clearly, replacing like with like is the ideal condition. All defects that are replaced with local tissue of similar color, texture, pliability, and sensation will provide a better outcome than non loco-regional flaps. The resulting defect, following radical débridement, will also be much larger than the initial wound size. Knowing that stable soft tissue coverage can be provided regardless of defect size should be impetus for providing aggressive initial débridement. This not only serves to expedite reconstruction but also helps minimize any risk of infection due to the presence of residual necrotic tissue (Figure 35-1).


image

Figure 35-1 Dorsal hand soft tissue defect following first-stage radical débridement, under tourniquet control. This wound was clean enough to be covered.



Timing of Reconstruction


Reconstruction should be attempted as early as possible once adequate débridement is achieved. Advantages of early reconstruction include primary wound closure, coverage of vital structures, shorter hospitalization course, avoidance of multiple procedures and multiple painful dressing changes, and early rehabilitation and mobilization. An absolute indication for immediate primary reconstruction includes exposure of reconstructed or native arteries and veins. Contraindications for immediate reconstruction include an unstable patient that cannot tolerate a prolonged operative procedure, and patients in whom amputation and prosthesis would provide a better functional result than reconstruction.


If delayed reconstruction is selected or necessary, then all joints must be actively or passively mobilized to maintain motion. Prolonged use of negative pressure wound therapy dressings in the hand without passive and active mobilization is to be condemned as this can lead to severe stiffness and fibrosis.



Soft Tissue Coverage and Reconstruction



Intrinsic Flaps


Clearly, if paratenon is available over the exposed extensor tendon, a simple form of coverage can involve either a split- or full-thickness skin graft, which is harvested from the either the forearm, the hypothenar region or groin. Note that skin grafts harvested further from the defect will be less cosmetically matched compared to more local skin graft options. Skin grafts harvested from the hand or from the forearm would provide better skin match compared to more distant skin grafts such as the proximal forearm, or groin.



Turnover and Distally Based Adipofascial Flap


If the exposed extensor tendon is devoid of paratenon, then a skin graft is not an option. A simple form of reconstruction can include a turnover adipofascial flap, which can be used to cover small-to-moderate sized defects. These are then covered with a split-thickness skin graft. Adipofascial flaps can be very useful for resurfacing small exposed extensor tendon defects in the digits as well as the dorsum of the hand. These can flaps can be based off of small perforators from the dorsal metacarpal arteries when covering defects in the hand or dorsal digital branches when covering dorsal digital defects. These can be wide based and are simply turned over under elevated skin flaps and skin grafted to provide well-vascularized coverage over the exposed extensor tendons. Turnover adipofascial flaps need to be widely based to maximize perforator incorporation into the flap, as well as subcutaneous veins. When covering digital defects, the flap is distally based and incorporates a maximal amount of arterial perforators and subcutaneous veins for venous outflow. Closure of the skin flaps that have been elevated should not be performed under any tension, so as to minimize any risk of venous congestion of the adipofascial turnover flap. These flaps are simple to elevate, provide quick and easy coverage options for small defects with exposed tendons, and offer minimal morbidity to the donor site.



Reverse Cross-Finger Flap


Extensor tendon exposure in zones 1 through 4 can be covered with reverse cross-finger flaps. The reverse cross-finger flap, first described by Pakiam in 1978, is an excellent local flap for soft tissue coverage of exposed extensor tendons in the dorsal digit. Its vascular supply is provided by the dorsal digital branches of the digital arteries, as well as small subcutaneous veins and venae comitantes from the dorsal digital branches. Subcutaneous veins from the cross-finger flap can also be used as venous flow through veins for replants to bridge both recipient and donor veins. The reverse cross-finger flap is then covered with either a split- or full-thickness skin graft for definitive coverage. The flap is elevated as follows: The adjacent donor digit is used for a cross-finger flap. The mid-axial skin incision is made proximal to the defect, and the skin flap is elevated just above the subcutaneous tissue in a direction that is opposite the side of the defect. The adipofascial flap is then harvested down through paratenon in the opposite direction of the elevation of the overlying skin flap. This is taken from mid-axial line to mid-axial line. Care is taken to not damage any of the dorsal branches of the digital artery when harvesting this flap. The flap is then turned over to cover the adjacent digit dorsal defect and provide good coverage for the exposed extensor tendon. The cross-finger adipofascial flap is covered with a split-thickness skin graft and the donor site is closed primarily with its hinged skin flap. The hand is immobilized for 2 to 3 weeks, preferably 3 weeks, and the division and inset of the flap is performed after 2 to 3 weeks, with revisions to the donor or recipient site as needed. The patient is splinted in a position of function for 3 weeks to minimize any contractures. In compliant patients, the patient can begin light active range of motion after the surgery but needs to be very compliant (Figure 35-2).


image

Figure 35-2 Step-by-step description of a reverse cross-finger flap elevation. Either a thin split-thickness or full-thickness skin graft can be used to cover the wound.



Metacarpal Artery Island Flaps


The dorsal aspect of the hand represents an invaluable and expendable donor site for dorsal digital coverage of exposed extensor tendons. A sound knowledge of the vascular anatomy of the hand and digits’ dorsal skin has led to many innovative flap designs for this area. This knowledge is an important prerequisite for the safe application of these flaps. The blood supply to the dorsal skin of the hand and digits is provided by (1) the dorsal metacarpal arteries, which vascularize the proximal portion of the hand and (2) the dorsal perforating metacarpal arterial branches from the deep palmar arch, which supply the distal hand and proximal phalanx. These two major arterial systems form the basis for direct and reverse dorsal metacarpal artery (DMA) flaps.



First Dorsal Metacarpal Artery Flap


The first dorsal metacarpal artery flap (FDMA flap, i.e., kite flap), described by Foucher and Braun,1 provides two major applications in hand reconstruction: (1) dorsal hand wound coverage and (2) thumb reconstruction.


In Foucher’s anatomical study of 30 injected cadaveric hands, the FDMA originated from the radial artery in 28 of 30 specimens and from the dorsalis superficialis antebrachialis artery in 2 of 30 cases. From there, it courses distal to the extensor pollicis longus tendon, and proximal to the radial artery’s entry between both heads of the first dorsal interosseous (DIO) muscle. The FDMA travels parallel to the dorsal surface of the second metacarpal, and superficial to the first DIO muscle fascia, with some fibers occasionally covering the vessel. The FDMA then continues distally and anastomoses at the level of the metacarpal neck with dorsal perforating branches from the palmar metacarpal arteries of the deep palmar arch. These perforator branches form the basis of the reverse flow FDMA island flap. They anastomose with three different arterial systems: (1) distally with the dorsal branches of the proper palmar digital arteries, (2) proximally with branches of the DMA, and (3) laterally with adjacent DMA perforating branches (Figure 35-3).


image

Figure 35-3 A, Dorsal tissue defect of left thumb with exposed phalanges and loss of extensor pollicis longus tendon. B, Harvest of a 3.0 × 5.5-cm flap based on the dorsal metacarpal artery with a skin island kept over the pedicle to avoid tunneling the flap and compression to the flap and vascular compromise. C,

Related posts:

Gene Therapy for Tendon Healing Default ThumbnailCurrent Status and Future Primary Repair of the Flexor Pollicis Longus Tendon Molecular Biology of Tendon Healing Outcomes of Flexor Tendon Repairs and Methods of Evaluation Customizing Flexor Rehabilitation Based on Zone or Type of Injury

Stay updated, free articles. Join our Telegram channel
Tags:
Mar 5, 2016 | Posted by in Hand surgery | Comments Off on Soft Tissue Coverage for Extensor Tendon Reconstruction

Full access? Get Clinical Tree
Get Clinical Tree app for offline access