Soft Tissue Issues: Exposure and Coverage

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CHAPTER SYNOPSIS

This chapter considers operative planning and reconstructions with associated soft tissue concerns. Multiple techniques are presented, including incision selection, soft tissue expansion, and both local and free flap coverage about the knee.

IMPORTANT POINTS:

1

Appropriate preoperative planning
2

Indications for specific techniques
3

Surgical applications
4

Postoperative protocols

CLINICAL/SURGICAL PEARLS:

1

Identify the knee at risk.
2

Recognize and treat comorbid conditions.
3

Obtain relevant consultations with experts in soft tissue and microvascular surgery.
4

Select the appropriate management plan.
5

Generally, when multiple parallel incisions exist, use the most lateral.
6

Sham incisions are reserved for very select cases but can give some indication as to wound healing potential.
7

A low threshold for the use of soft tissue expansion techniques should be maintained.
8

Recognize postoperative soft tissue concerns.
9

Well-vascularized soft tissue coverage is essential following knee reconstruction and can usually be achieved with a gastrocnemius flap.
10

Free flaps are effective tools for soft tissue coverage when a large or proximal defect exists.

CLINICAL/SURGICAL PITFALLS:

1

Failure to recognize and address soft tissue concerns preoperatively.
2

The use of simple incision management techniques when a more complex approach is necessary.
3

Sham incisions offer only an indication of healing potential and do not guarantee that soft tissue healing will proceed following reconstruction.
4

Soft tissue expansion techniques require a healthy plane for dissection and expansion and cannot be applied to areas of previous irradiation or skin graft application directly over tendon or bone.
5

Delayed management of postoperative soft tissue complications and draining wounds.
6

Not recognizing a potential deep infection at the time of soft tissue coverage.
7

Wound closure under tension frequently results in breakdown and is better treated with prophylactic coverage.
8

Attempting to cover proximal defects with rotational gastrocnemius flaps can lead to tension on the flap and necrosis.
9

Failure to obtain early appropriate consultation for soft tissue management.

VIDEO AVAILABLE:

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HISTORY/INTRODUCTION/SCOPE OF THE PROBLEM

Soft tissue considerations in total knee arthroplasty (TKA) must always be at the forefront when considering operative management. The knee area consists of a thin overlying soft tissue envelope that must be protective, well vascularized, and supple enough to allow for the large degrees of stretch and sheer required for a functional range of motion. The failure to address soft tissue concerns appropriately and preemptively can result not only in the failure of the reconstruction but also in deep infection, a nonfunctioning extremity, amputation, and/or a potentially life-threatening problem.

Historically, problems have occurred when surgeons have failed to recognize the significance of a soft tissue concern about the knee. Complications arise at multiple stages in the reconstructive pathway: preoperatively, particularly in the multiply operated extremity; postoperatively, when soft tissue breakdown occurs following reconstruction; and following infection, predominantly in chronic cases with soft tissue breakdown and sinus tract formation.

Although most TKAs can be performed with standard protocols, an understanding of when to apply specific soft tissue management principles is required. Cases requiring advanced management will likely continue to rise for a number of reasons. The first is that more patients, having had previous open surgeries including meniscectomies, tibial plateau fractures, osteotomies, ligament reconstructions, and other procedures about the knee, are now beginning to require TKAs. Secondly, as rates of TKA continue to rise, so do the number of cases requiring revision for septic and aseptic causes. Finally, the patient population has changed, as TKAs are performed at an earlier age and also on patients with multiple comorbidities.

CLASSIFICATION SYSTEM

Soft tissue management options can be broadly categorized into prearthroplasty and postarthroplasty techniques. Prearthroplasty techniques include incision choice and management, sham incisions, soft tissue expansion, and prophylactic flap coverage. Postarthroplasty techniques include local wound management techniques, irrigation and debridement (I&D) with primary closure, split-thickness skin grafting with and without vacuum assisted closure (VAC) sponge application, local fasciocutaneous flaps, muscle and myocutaneous flaps, and free flap applications.

INDICATIONS/CONTRAINDICATIONS

Soft tissue management issues cover a wide range of clinical presentations, but the goals and principles remain the same: to obtain a healthy, well-vascularized, mobile soft tissue sleeve about the knee. Based on the specific clinical presentation, an individualized plan is made, which attempts to incorporate the least complex management plan that will obtain healthy coverage for the knee area.

Prearthroplasty

When a clinician is faced with a preoperative knee in which the local soft tissues have been previously manipulated or compromised, examination must be preceded by a detailed medical and surgical history, particularly about the knee in question. Surgical diagnoses, timing of surgery, wound healing, and complications are all noted. A copy of all previous operative reports is helpful. Local and systemic concerns include vascular compromise, obesity, malnutrition, local radiation or burns, prolonged steroid or NSAID use, immunocompromised patients, smoking, and diabetes, as these all affect wound healing.

Physical examination begins with a standard musculoskeletal examination focused on the knee. Local inspection includes a careful examination of the soft tissue envelope. Previous incisions, status of the skin and underling tissues, and vascular perfusion are important to document.

Following a complete history, and depending on patient local and systemic factors, an appropriate management plan is formed. Consultation regarding medical optimization and early plastic surgery consultation for soft tissue management are of benefit for these complex cases.

Particular care must be taken with intraoperative soft tissue management in these settings. Adequate exposure without undue stress or retraction on wound and skin margins must be achieved. In most cases, this involves a longer standard length incision, rather than newer mini-exposures.

Skin Incisions

Previous skin incisions about the knee present a concern regarding both the planned approach and the healing potential of the skin and underlying tissues. A balance exists between the use of an old nonmidline incision and the ability to appropriately expose the knee without undermining extensive subcutaneous flaps. When it is thought that adequate exposure and healing can occur, a modified skin incision may be required, rather than more advanced techniques.

As mentioned, a complete history relating to the timing, incision used, procedure performed, and any wound healing concerns related to previous surgery must be obtained.

An understanding of the local anatomy and blood supply is necessary. Terminal branches of the peripatellar anastomotic ring of arteries are responsible for the majority of the blood supply to the anterior skin and subcutaneous tissues ( Fig. 16-1 ). This occurs through a subdermal plexus supplied by arterioles in the subcutaneous fascia. Thus, flap formation in the anterior knee must be limited and remain deep to the subcutaneous fascia.

A midline skin incision remains the optimal approach when possible, as this decreases the dimensions of the lateral skin flap where oxygen tension is lower. A previous longitudinal incision can be used, and some degree of modification can be performed to incorporate paramedian skin incisions ( Fig. 16-2 ). If multiple incisions exist, generally choose the most lateral incision, as the predominant blood supply is medial. Transverse skin incisions such as those from previous patellar surgery or high tibial osteotomy can safely be crossed at a right angle. Some short oblique incisions such as those from previous meniscectomies can be ignored, although care must be taken when they are longer and approach or cross the midline, as the narrow point of intersection with a new longitudinal incision can leave this area at risk. When the angle between old and proposed new incisions is less than 60 degrees, alternative techniques are indicated.

During the subsequent reconstruction, care should be taken to preserve the superolateral geniculate artery when performing a lateral release, as this vessel is important in lateral wound edge viability.

Postoperative management is routine for most cases where a modification to the standard longitudinal midline incision is used ( Fig. 16-3 ). In cases where a larger full-thickness flap or a tight closure exist, continuous passive motion (CPM) use may be held or limited to less than 40 degrees, and early range of motion is limited, as greater degrees of flexion diminish viability of the lateral wound edge. Elevation, compression, and the use of a drain can decrease subcutaneous fluid accumulation and pressure on the skin closure. Due to the increased risks associated with bleeding, an alternative to low-molecular-weight heparin (LMWH) can be used for deep venous thrombosis prophylaxis in these cases. Frequent clinical examination during the postoperative course is important to identify any healing problems as small areas of skin necrosis may lead to an underestimation of deep fascia and muscle ischemia or necrosis.

Pitfalls in simple incision management often requiring more advanced management include cases with previous soft tissue damage as a result of local radiation, trauma, burns, or previous surgery with soft tissue loss and/or flap coverage. Be aware of a thin, broad incision that is densely adherent to the underlying fascia, with little or no intervening subcutaneous tissue, as a safe plane for subcutaneous dissection may not exist.

Sham Incision

A sham incision involves incising the skin, subcutaneous tissue, and undermining flaps, along the planned approach, followed by closure and observation for wound healing. Two benefits to this protocol exist. The first is that the local healing ability is assessed. The second is that the incision disrupts local blood supply, thus creating a delay phenomenon. A delay phenomenon refers to the local changes in soft tissue healing and increased blood flow that occurs after an incision is made. An interval of week is necessary to assess wound healing and to allow for the delay phenomenon.

Limited applications exist for this technique. A sham incision is indicated when it is likely that healing will occur without more advanced methods. The disadvantage is that two procedures are required and that there is a risk that the incision does not heal, thus requiring further prearthroplasty management.

At 1 to 3 weeks before the planned arthroplasty, the patient is taken to the operating theatre and placed supine. A tourniquet is applied, and the extremity is prepared and draped in a sterile fashion. The planned TKA incision is marked, and this is incised through the subcutaneous layer to the level of the deep fascia. Flaps corresponding to those planned for the upcoming surgery are raised in a full-thickness manner. Hemostasis is obtained and the incision is irrigated and closed. A subcutaneous drain can be placed at the surgeon’s discretion. A sterile soft dressing is applied.

Following surgery, the patient is encouraged to keep the extremity elevated at rest. If a drain is used, it is removed on the first postoperative day. Two days following the sham incision, the dressing is removed and the incision is examined. Close follow-up is required to assess the healing response. Appropriate healing and no further benefit to the delay phenomenon has been shown in other areas using this technique after 1 week. Following a successful sham procedure, arthroplasty can be performed at 1 to 3 weeks. A sham incision failing to heal requires further soft tissue management before the definitive reconstruction procedure.

One other pitfall to this technique is that the sham incision is an indicator that the incision is likely to heal, and not a guarantee. Prolonged use of a tourniquet, soft tissue retraction, and manipulation all means that the tissues are subjected to increased forces at the time of reconstruction. Due to these concerns, we have limited indications for the application of a sham incision and routinely use soft tissue expansion techniques when potential for healing problems exists.

Soft Tissue Expansion

Soft tissue expansion techniques are indicated when insufficient or inadequate soft tissue coverage is present for successful wound healing. Multiple, crossing, or combined incisions; previous skin graft or flap application; significant angular and/or rotational deformities; and procedures requiring expanded soft tissue coverage (e.g., extensor mechanism allograft) may be treated with expansion techniques. Eight to 10 weeks must be allocated for soft tissue expansion, depending on the magnitude of the planned expansion.

The patient is placed in a supine position on the operating table. Prophylactic antibiotics are given. A tourniquet is applied, but not inflated. The entire lower extremity is prepped and draped in a similar sterile fashion to the planned reconstructive procedure. All previous incisions are marked, and a planned incision line for the reconstructive procedure is drawn on the knee.

A mix of dilute local anesthetic is prepared and infiltrated subcutaneously in the area of the planned expansion ( Fig. 16-4 ) until the subcutaneous tissue and skin blanches, typically allowing 250 to 300 mL to be injected. A Tuohy needle, with a blunt tip and an opening at 90 degrees to the long axis of the shaft, is used. Fluid opens the plane ahead of the advancing blunt tip needle.

Insertion of the expanders is performed though a 2- to 4-cm incision at the superior aspect of the planned incision for later reconstruction. This access incision must not fall into the area of expansion. A subcutaneous pocket is created using blunt and scissor dissection in the areolar plane between the subcutaneous fat and the musculotendinous and patellar layer. Multiple length tenotomy scissors are useful for dissection. A dilute antibiotic solution is then used to irrigate the pocket followed by sustained pressure over the area to achieve hemostasis. In rare cases, a scope or fiberoptic retractor and insulated forceps are necessary to localize and cauterise bleeders, thus achieving a dry plane.

Rectangular expanders up to 350 mL in volume are then inserted. The amount of expanded tissue produced is proportional to the projection of the expander. Typically, two expanders are placed at right angles to each other. One to four expanders can be used, depending on the size of the extremity, ability of the soft tissues to accommodate the expanders, and the size of the soft tissue flap required. Avoid folds or creases in the expanders as this can cause increased local pressure on the soft tissues, particularly in the subcutaneous plane. The injection ports are secured on either side of the insertion site, superior to the expanders, decreasing the pressure on the ports during upright stance. Expanders are then inflated until all of the dead space is taken up. The knee is wrapped in a bulky dressing and Ace wrap, placed in a knee immobilizer, and elevated on pillows.

The patient is admitted overnight for observation. A knee immobilizer is worn for the first week and no expansion is performed during this period. The patient is allowed to weight bear as tolerated but is encouraged to keep the extremity elevated at rest throughout the expansion process.

Gradual expansion is begun 1 week later, at a rate of 10% of the expander volume per week. Two factors limit the rate of expansion: the capillary refill in the overlying skin should not exceed 5 seconds, and the patient must be able to comfortably tolerate the rate of expansion. Range of motion is not restricted during the expansion process.

At the time of surgery, the soft tissue envelope and previously planned incision line are reassessed ( Fig. 16-5 ). The soft tissue expanders are easily removed from the subcutaneous pocket. Care is taken not to violate the reflected margins of the pocket, as these are important in blood supply to the soft tissue flaps. Any lateral dissection must be made in a full-thickness, subperiosteal manner.

At the completion of the surgery, and following the closure of the arthrotomy, the soft tissue envelope is reexamined ( Fig. 16-6 ). In most cases, the skin can be closed primarily, but broad incisions and small intervening skin planes between parallel incisions may be excised.