Soft-Tissue Defects After Total Knee Arthroplasty: Management and Reconstruction

Daniel A. Osei, MD, MSc; Kelsey A. Rebehn, MD; Martin I. Boyer, MD, MS

Disclosures

J Am Acad Orthop Surg. 2016;24(11):769-779. 

In This Article

Management Options

In patients with wound healing complications after TKA, the goal of soft-tissue reconstruction is to ensure definitive coverage of the prosthesis with thin, pliable, and durable tissue to facilitate joint function. An understanding of the arterial anatomy around the knee is crucial for appropriate planning. Perfusion of the skin surrounding the knee follows the angiosome concept, in which regions of skin and soft tissue are perfused by specific, longitudinally oriented source vessels.[21] These perforator vessels originate deep to the fascia and have direct cutaneous, musculocutaneous, and septocutaneous branches.

Adjacent angiosomes are linked by so-called choke vessels, or intravascular anastomoses, which play an important role in perfusing the tissue around joints.[21] This linkage allows for collateral blood supply to the soft tissue in the event of a wound healing complication. Because few muscles cross the knee joint, the soft tissues around the knee are supplied mostly by extramuscular vascular anastomoses among the genicular vessels.[21] This peripatellar anastomotic ring is composed of the medial superior, medial inferior, lateral superior, lateral inferior, and descending genicular arteries and the anterior tibial recurrent artery.[22] The medial-sided vessels provide a more dominant contribution, which should be taken into account during soft-tissue management. In patients with prior incisions and wound healing complications, perfusion to the soft tissue overlying the prosthesis may be compromised.

When planning reconstruction of soft-tissue defects, including defects occurring after TKA, the surgeon should consider the principle of the reconstructive ladder. This concept dictates that the simplest method of achieving wound closure (eg, primary closure) should be chosen when possible. However, the simplest method of closure with the most readily available tissue for reconstruction may not be optimal. Therefore, strict adherence to the principle of the reconstructive ladder is not advisable. Rather, the more modern "reconstructive elevator" principle is better suited to address wound defects after TKA. This concept allows ascension from the simplest to the most complex techniques, based on the specific characteristics of the wound and the soft-tissue coverage needed. It facilitates a comprehensive approach to treatment that focuses on early closure of the defect with stable soft-tissue coverage over the prosthesis while allowing for any future procedures the patient may require at the site of the wound.

Primary Closure and Healing by Secondary Intent

Primary closure is an option for the management of wounds with minimal necrosis or tissue loss if tension-free repair is possible after adequate débridement to healthy tissue. Primary closure is not advisable if the edges of the wound are not readily approximated or if closure would place skin flaps under tension. Wound healing by secondary intent occurs when the wound is allowed to granulate progressively from the edges with supportive dressing changes. This method is generally reserved for the management of small wounds over muscle or fascia that are not amenable to other treatment modalities because of the patient's medical status. In most TKA patients, because of the increased risk of deep or periprosthetic infections associated with prolonged wound drainage, waiting for granulation of tissue to fill substantial defects is not advisable.

Negative-pressure Wound Therapy

Negative-pressure wound therapy (NPWT), originally developed to address chronic wounds refractory to nonsurgical management, has been explored more recently for the management of tissue defects associated with orthopaedic trauma and arthroplasty.[23,24] NPWT provides a negative-pressure environment that continually removes fluid from the wound and provides constant, equal pressure across the entire exposed surface to promote epithelial migration from the edges toward the center of the wound. Immediate contraindications to the use of NPWT for the management of a wound after TKA include the need for placement of the NPWT device over necrotic tissue with eschar, exposed vessels, or exposed nerves.[24] In other patients, NPWT remains an option for wound management after TKA and may be of value as a temporary measure for use before definitive management. However, it should not be used to delay definitive management or to manage wounds likely to require a prolonged time to heal. Prolonged NPWT is associated with increased rates of continual drainage and periprosthetic infection in addition to the previously mentioned risks associated with delayed wound coverage.[24]

Skin Grafts

Split-thickness skin grafts are a useful tool in the management of small defects that lack deep extension or evidence of infection. Skin grafts require a well-vascularized recipient site to oxygenate the grafted tissue. Both muscle and fascia are usually favorable recipient sites for graft survival. The role of skin grafts in the management of knee wounds is limited because skin grafts do not adequately eliminate dead space and because they limit future surgical procedures through the wound bed. Furthermore, split-thickness skin grafts have an associated risk of contracture inversely related to depth of the skin graft. Therefore, grafting across joint surfaces has the potential to limit long-term range of motion and negate some of the benefits of joint arthroplasty.

Flaps

Flaps can be classified according to the type of tissue to be transferred (eg, fasciocutaneous, muscle), the pattern of blood supply to the flap (eg, random, axial), the spatial relationship of the flap and the recipient site (eg, local, regional, distant), and the mechanism of transfer (eg, free, rotational, transposition). Flap selection for soft-tissue reconstruction after TKA is guided by the three-dimensional shape of the tissue defect and the location of the defect (Figure 1). Knowledge of the locations from which donor tissue can be harvested is important in determining the best option for wound coverage.

Figure 1.

AP (A) and lateral (B) illustrations depicting standard flap donor sites for soft-tissue reconstruction of the knee after total knee arthroplasty. Asterisks indicate distally based flaps.

Local Flaps. Muscular and Musculocutaneous Local Flaps: Local muscular flaps are widely considered to be the workhorse flaps for coverage of soft-tissue defects surrounding the knee and have been discussed extensively in the literature.[17,19,25] Muscle provides a well-vascularized flap with substantial bulk for elimination of dead space. Furthermore, muscular flaps may be advantageous in the management of periprosthetic infection because increased collagen deposition and greater inhibition and elimination of bacterial growth have been observed in chronically infected wounds covered by musculocutaneous flaps compared with those covered by fasciocutaneous flaps.[26] These flaps can be especially useful in patients in whom additional surgical procedures on the knee are planned and have been associated with excellent outcomes in complex cases of infection or prosthetic exposure.[17,19]

For local coverage, the medial gastrocnemius muscle is most commonly used because of its reliability and ease of harvest. The medial head of the gastrocnemius is supplied by the medial sural artery and can be rotated to cover soft-tissue defects of the medial, anterior, and upper knee. The medial gastrocnemius flap ranges from 5 to 9 cm in width and from 13 to 20 cm in length. It is commonly used to cover wounds between 3 and 7 cm in width and with surface areas between 33 and 49 cm2.[17,27] The flap can be easily rotated to cover medial and distal defects in the area of the tibial tubercle or patellar tendon. The arc of rotation can be further extended by 20% to 50% or 5 to 8 cm with dissection of the muscle origin and the pes anserinus[19,25,27] (Figure 2). Division or excision of the superficial and deep fascia can extend the width and length of the muscle. This method may allow for coverage of a larger wound and facilitates healing of a skin graft to the underlying muscle (Figure 3). The lateral gastrocnemius muscle can be used to cover both lateral and anterior knee defects. Because of its smaller size (5 × 12 cm, on average) and obstructed anterior rotation caused by the fibula, the lateral gastrocnemius has a lesser arc of motion than the medial gastrocnemius and is used less frequently for coverage of a soft-tissue defect about the knee.[17] In addition, careful dissection and decompression of the common peroneal nerve may be necessary; passage of the muscle deep to the nerve can prevent iatrogenic nerve compression (Figure 4). For the management of a larger wound centered over the patella and tibial tubercle, both the medial and lateral gastrocnemius muscles can be elevated and used for coverage of the wound.

Figure 2.

Illustrations depicting dissection of the medial gastrocnemius muscle and a small portion of the Achilles tendon away from the triceps surae complex. The muscle can be released up to its proximal blood supply to facilitate anterior rotation (arrows). Depending on the length and size of the muscle, the flap can be used for coverage of wounds as proximal as the superior pole of the patella or the distal quadriceps.

Figure 3.

Intraoperative photographs demonstrating gastrocnemius flap coverage after revision total knee arthroplasty. The overlying fascia (A) is excised (B) to facilitate healing of a split-thickness skin graft (not pictured).

Figure 4.

Intraoperative photograph depicting dissection before elevation of a lateral gastrocnemius flap. The common peroneal nerve is seen proximally (star). Decompression of the nerve as it passes around the fibular neck (F) into the peroneus longus interval (P) allows for passage of the lateral gastrocnemius deep to the nerve and into the recipient site on the anterior knee (blue arrows), which can prevent iatrogenic compression of the nerve.

In patients with larger or more proximal defects involving the anterior portion of the knee with deficiencies of the skin, anterior capsule, and quadriceps tendon, a gastrocnemius flap alone may be of insufficient size to provide coverage.[17,19,28] These composite defects affecting the extensor mechanism can be managed with local transfer of the vastus lateralis muscle, in conjunction with the vastus medialis muscle and/or gastrocnemius muscle if necessary.[28–30] The distally based vastus lateralis flap is based on the reverse flow in the anastomoses between the descending branch of the lateral circumflex femoral artery (LCFA) and the lateral superior genicular artery. The vastus lateralis muscle flap is 7 to 11 cm × 9 to 14 cm in size and can be used to cover defects of approximately 6 × 9 cm along the anterior proximal knee.[30]

Another locoregional muscle option for coverage of proximal and/or lateral knee wounds is the distally based pedicled gracilis flap, which is based on minor pedicles from the superficial femoral or popliteal artery that pass between the sartorius and adductor longus muscles[31] (Figure 5). This flap carries a high risk of partial flap loss and is reserved for use in scenarios in which a pedicled gastrocnemius flap would be inadequate and when the patient is not a suitable candidate for a free flap.[31]

Figure 5.

Illustration depicting a distally based gracilis flap, which can be useful for coverage of proximal wounds after total knee arthroplasty or as additional proximal coverage if a gastrocnemius flap is insufficient for wound coverage. The vascularity of the flap is based on intact flow at the distal extent of the muscle. The dominant arterial supply is ligated along with the branch of the obturator nerve that innervates the muscle.

Fasciocutaneous and Perforator Local Flaps: Fasciocutaneous flaps consist of skin, subcutaneous tissue, and underlying fascia. The vascular supply is derived from perforating arteries originating from longitudinally oriented source arteries that initially course under the deep fascia or in the intermuscular septum between adjacent muscles. These arteries provide multidirectional perforator vessels at the level of the deep fascia that form fascial plexuses, which perfuse the skin through a confluence of multiple vascular anastomoses at the subfascial, suprafascial, subcutaneous, and subdermal levels.[32] Fasciocutaneous flaps are helpful in reconstructing soft-tissue defects around the knee because they are thin, pliable, and easy to contour to the shape of the defect. Because arterial perforators radiate in a stellate, multidirectional pattern throughout the fascial plexus, distally based flaps can be used (Figure 6). Historically, fasciocutaneous flaps have been used to manage incisional necrosis after TKA in patients without underlying infection or an exposed prosthesis. Flaps that are based proximally, along the axially oriented pattern of blood supply, preserve cutaneous innervation and have been advocated for coverage of areas of skin necrosis.[17,32] Similarly, the use of unilateral or bilateral local fasciocutaneous flaps in a V-Y pattern allows soft-tissue advancement for closure of wounds 2 to 4 cm × 5 to 12 cm in size.[33]

Figure 6.

Photographs depicting the use of a fasciocutaneous rotational flap. A, Clinical photograph depicting a superficial infection and wound drainage after total knee arthroplasty in a 52-year-old woman. An attempt to irrigate, débride, and revise the primary closure was unsuccessful. B, Intraoperative photograph depicting markings on the patient's skin to indicate the planned incisions for a distally based peninsular-type fasciocutaneous perforator flap based on the cutaneous branch of the descending genicular artery. C, Intraoperative photograph depicting the patient's knee after the flap was elevated and transposed to close the midline knee wound. D, Postoperative clinical photograph obtained at 10 weeks depicting the patient's knee. In many patients, the donor site can be closed, but in this patient, the flap was too large to allow for tension-free closure. Therefore, a small split-thickness skin graft (arrow) was used to close the donor site.

The use of perforator-based flaps has revolutionized the reconstruction of complex lower extremity wounds, including soft-tissue defects around the knee. Each clinically relevant perforator vessel supplies a so-called perforasome, or vascular territory of three-dimensional tissue. These territories are linked to adjacent territories both directly (through large vessels that communicate directly between perforators) and indirectly (in the form of recurrent flow through the subdermal plexus).[34] Pedicled perforator flaps can be customized to the defect, minimize donor site morbidity, and allow coverage with tissue similar to that of the recipient site in adherence to the "like with like" principle of tissue replacement.

The perforator concept is extended in the use of propeller flaps, in which a local island of tissue is axially rotated 90° to 180° after dissection has been performed along the length of the pedicle. The design of these flaps and the orientation of the skin paddle take advantage of the axial direction of the linking vessels. A handheld Doppler ultrasonographic device is routinely used to locate perforators before the flap is harvested. Thigh perforator flaps have been increasingly used for coverage of large composite defects surrounding the knee. For the management of suprapatellar anterior or lateral defects, the distally based or reverse-flow anterolateral thigh (ALT) flap or the lateral supragenicular perforator flap can be used. The distal ALT flap is based on constant skin perfusion through retrograde blood flow between the descending branch of the LCFA and the lateral superior genicular artery and/or the deep femoral artery.[35] The pivot point is 3 to 10 cm proximal to the superolateral patella, and the dominant perforator, which is commonly found in the mid thigh, is mobilized to its origin from the descending branch to yield a pedicle of 15 to 28 cm in length.[35,36] A cuff of vastus lateralis muscle can be included to protect the pedicle, and flaps up to 10 × 16 cm in size can be used to cover wound defects ranging from 6 to 10 cm × 8 to 16 cm on the proximal anterior or lateral knee.[35,36] The lateral supragenicular perforator flap is based on the lateral supragenicular perforator, which arises from the superior lateral genicular artery within 5 cm lateral and 7 cm proximal to the superolateral patella.[37] The width of this flap is typically limited to 4 to 6 cm to allow primary closure of the donor site, whereas the length can be up to 18 cm.[38]

The distally based anteromedial thigh flap is useful for covering proximal anterior or medial knee wounds. This flap is based on a supragenicular perforator from the saphenous branch of the descending genicular artery that commonly emerges from the anterior margin of the sartorius muscle within 3 cm of the adductor tubercle.[39] Flaps of 6 to 10 cm × 15 to 32 cm have been harvested to cover large tissue defects of 6 to 10 cm × 15 to 27 cm.[39] Disadvantages of distally based or reverse-flow flaps are the increased risk of venous congestion and flap tip necrosis, the technical difficulty of perforator dissection, and the need to perform skin grafting at the donor site if primary closure is not possible.[25] Proximally based perforator flaps based on the medial sural artery can be used to cover medial and distal knee defects with the advantage of less donor site morbidity than would result from the use of a gastrocnemius muscle flap. This flap can be 3 to 7 cm × 3 to 16 cm in size, have a rotation arc of 8 to 12 cm, and can be reliably harvested on the basis of a perforator located 8 cm distal to the popliteal crease on a line connecting the midpoint of the crease to the midpoint of the medial malleolus.[40]

Microvascular Free Flaps. Microvascular free tissue transfer consists of raising a donor flap from a site distant to the defect, isolating the vascular pedicle of the flap, and transferring the flap to a suitable recipient vascular pedicle by performing vascular anastomoses to restore blood flow. Free flap reconstruction has substantial utility in the salvage of complex knee wounds with large composite tissue defects, infection, and/or prosthesis exposure. Free flaps can be used when no suitable local options are present. Selection of the flap is based on assessment of the characteristics of the recipient site, the dimensions of the wound, associated morbidity of the donor site, the extent of the vascular pedicle, and the available recipient vessels around the knee. Microvascular tissue transfer requires considerable surgical expertise and is integral in the armamentarium of the reconstructive surgeon. Free flap reconstruction of knee defects can be complicated by vascular compromise, which may require further exploration in up to 20% of patients.[41] A variety of recipient vessels can be used, and selection of appropriate recipient vessels is critical to success. Ideally, recipient vessels are well matched in diameter with the donor pedicle, are easily dissected, allow tension-free vascular anastomosis without kinking of the pedicle, and are located outside the zone of injury. The popliteal, geniculate, sural, deep femoral and superficial femoral arteries, and the descending branch of the LCFA have all been used, with the choice of artery depending on the location of the knee defect.[42] Most recently, the descending genicular artery has emerged as a primary recipient option in the management of most knee defects because of its consistent location, the ease of dissection, the excellent size match for end-to-end anastomosis with most free flap donor pedicles, and the ability to avoid intraoperative position changes.[43]

Muscular and Musculocutaneous Free Flaps: The most common muscles used for free flap transfer to the knee are the latissimus dorsi and rectus abdominis muscles. In infected wounds with an exposed prosthesis, free muscle transfer augments the blood supply to the wound and improves the local immunologic environment. Muscular flaps also offer the ability to eliminate dead space. The latissimus dorsi free flap and the rectus abdominis free flap have both been used for coverage of soft-tissue defects with excellent limb salvage rates (>90%) in infected knees with an exposed prosthesis after TKA.[16,18] The latissimus dorsi free flap can be harvested with a muscle dimension of 20 × 35 cm and with an overlying elliptic skin paddle of 9 × 25 cm that allows primary closure of the donor site. It is raised on a vascular pedicle containing the thoracodorsal artery, which allows for a length of 7 to 12 cm.[18,44] The latissimus dorsi flap has a high rate of donor site complications, including wound dehiscence, seroma, and functional morbidity limiting overhead arm motion. The rectus abdominis muscle can be harvested with a transverse or vertical skin paddle. It is typically supplied by the deep inferior epigastric artery or the superior epigastric artery; however, when it is harvested as a free flap, the deep inferior epigastric artery is most commonly used. The flap can be 10 × 30 cm with a pedicle length of 5 to 7 cm.[18,25] Because abdominal wall strength can be diminished after harvest of the rectus abdominis muscle, these flaps are not considered first-line treatment options.

Fasciocutaneous and Perforator Free Flaps: Muscles used in free tissue transfers are denervated during flap harvest, which can result in atrophy and fibrosis. To address these limitations and the donor site morbidity associated with muscle harvest, some authors have advocated the use of free adipocutaneous or fasciocutaneous flaps based on isolated perforators.[16] The free ALT perforator flap is the most commonly used fasciocutaneous free flap for reconstruction of defects surrounding the knee. The pedicle of the ALT flap includes the descending branch of the LCFA. A chimeric flap incorporating vastus lateralis muscle or tensor fascia lata can be used if increased bulk is necessary to eliminate dead space.[45] Compared with free myocutaneous flaps, fasciocutaneous or perforator free flaps offer the advantages of reduced donor site morbidity and improved contouring of the flap to the dimensions of the defect. Furthermore, perforator dissection increases the length of the pedicle, increasing the surgeon's options in the choice of recipient vessel.

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