Wound Management

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• The soft tissues about the knee are relatively unforgiving, and problems that occur with wound healing can quickly result in potentially disabling, long-term complications.

• A comprehensive understanding of the systemic, anatomic, and iatrogenic variables that may be associated with wound problems after knee arthroplasty will help identify patients at risk. Once they are identified, management can be optimized throughout the perioperative period.

• Important preoperative considerations include medical optimization, planning of appropriate skin incisions, and use of prophylactic soft tissue procedures such as tissue expanders or soft tissue flaps.

• Intraoperatively, knee arthroplasty that is performed efficiently with minimal soft tissue trauma in a technically rigorous manner will likely improve early wound healing.

• Postoperatively, if wound ischemia, hematoma, or drainage occurs, early immobilization followed by appropriate surgical intervention within the first week should be considered.

• It is critical to distinguish between primary wound problems that are not associated with deep periprosthetic infections and secondary wound problems that result from underlying deep infection. Therefore, early deep aspiration should be considered. In the presence of deep periprosthetic infection, the primary principle is appropriate treatment of the deep infection followed by salvage soft tissue procedures.

• In cases of primary wound complications, failure to aggressively address the problem places the patient at risk for development of secondary deep periprosthetic infection. Once infection occurs, the treatment strategy must change and is likely to be associated with worse results.

Introduction

In distinction to the hip, the soft tissue envelope about the knee can be unforgiving; furthermore, wound complications can rapidly and permanently compromise the success of any knee procedure. Whereas the general challenges posed by the temperamental nature of the periarticular soft tissues about the knee are understood, few concrete guidelines exist to minimize complications. Rather, only general principles can be outlined. These concepts are largely based on anecdotal evidence and case series rather than prospective, randomized trials.

Prior work has documented a large number of factors that may contribute to wound healing problems after surgery. These include systemic factors, local factors about the knee, and iatrogenic factors. Systemic factors associated with delayed wound healing include increased patient age, malnutrition, obesity, diabetes, immune system problems, smoking, medication effects, and peripheral vascular disease. Local factors include the presence of prior incisions, patella baja, and restricted range of motion (ROM). Iatrogenic factors include placement of the skin incision, how the soft tissues are handled during the operation, and how persistent wound drainage is managed postoperatively. In order to assess and manage as many variables as possible in an effective manner, it is important to develop a strategy that focuses on the three distinct time periods of an operation: preoperative, intraoperative, and postoperative.

Preoperative medical evaluation and optimization of underlying systemic conditions is critical. Tight control of diabetes, reversal of malnutrition, and smoking cessation are important for optimal wound healing. Evaluation of the soft tissues about the knee should also be performed by the operating surgeon. Presence of prior incisions, adherent or damaged skin, and evidence of peripheral vascular disease should be noted; if significant concerns exist, consultation with a plastic surgeon can help to determine whether soft tissue expanders or prophylactic soft tissue flaps are necessary. Furthermore, if pulses in the ipsilateral foot cannot be palpated, vascular surgery consultation should be considered to determine whether a revascularization procedure is required before knee surgery. The ROM of the knee should be determined, because a stiff knee can be associated with exposure difficulties and noncompliant periarticular soft tissues. Finally, radiographs should be examined to identify hardware requiring removal or significant patella baja that may require exposure steps beyond the standard surgical approach. Once all of the required assessments have been performed, the operating surgeon can consider each issue and formulate a plan regarding whether a prior incision will be used or a new incision made, whether prophylactic soft tissue procedures should be considered, and what type of additional exposure maneuvers may be required.

Intraoperatively, factors that may contribute to development of skin ischemia and increased wound problems include patient hypothermia, poor placement of the skin incision, failure to create full-thickness subcutaneous soft tissue flaps, use of a tourniquet, increased mechanical trauma to the skin and subcutaneous tissues, use of a lateral peripatellar release, and failure to use a deep drain. Without doubt, total knee arthroplasty (TKA) performed efficiently, with minimal soft tissue trauma and with attention to optimizing component positioning, has the best chance of facilitating uncomplicated wound healing.

Despite diligent preoperative assessment and optimization and prudent intraoperative handling of the soft tissues and care of the patient, wound problems still occur postoperatively in some patients. Skin ischemia and wound drainage are two early problems that should be identified rapidly and aggressively managed. Wound problems or hematoma significant enough to require reoperation have been reported to occur in about 0.5% of patients undergoing TKA ; in addition, persistent wound drainage occurs in 1% to 3% of cases. If either of these issues is present on postoperative day 2 or 3, early intervention may reduce the need for reoperation, although there are no data to directly support this assertion.

After TKA, skin oxygenation declines early in the postoperative period, improves beginning at about 48 hours, and recovers toward baseline by 10 to 14 days ; furthermore, tissue oxygenation has been directly correlated with the rate of collagen deposition. Therefore, marginal skin may benefit from any measure that minimizes this early decline in oxygenation until the rebound effect occurs. Although anemia was once thought to be an important factor in tissue oxygenation, it appears that the oxygen requirements to stimulate rapid wound healing are met by blood with a wide range of hemoglobin content; therefore, as long as perfusion and oxygenation of the blood are adequate, anemia does not seem to be a significant concern. Other factors can reduce tissue perfusion and oxygenation, including peripheral vascular disease, significant pulmonary disease, poor cardiac output, hypothermia, volume depletion, and peripheral vasoconstriction; each of these may adversely affect wound healing and should be optimized in the postoperative period.

Other studies indirectly support early intervention when wound healing is suboptimal. Skin oxygenation has been proved to decline with knee flexion, especially beyond 40 degrees ; therefore, in the presence of early skin ischemia, physical therapy and continuous passive motion, if used, should be stopped. In addition to promoting early wound healing, immobilization may also diminish postoperative wound drainage. However, significant drainage beyond 5 to 7 days postoperatively, especially if bloody, should be treated with early exploration, hematoma evacuation, and reclosure of any dehiscence of the arthrotomy that is identified. Early wound complications and the development of hematoma that requires reoperation have been shown to be associated with an increased risk of infection and the need for subsequent soft tissue procedures. However, it is not known whether this is caused by intervention that was initiated too late (i.e., after irreversible skin ischemia or bacterial seeding occurred). Importantly, one small study demonstrated that when wound drainage persists after TKA, early intervention to evacuate a hematoma, followed by reclosure, can be associated with successful outcomes.

When one is presented with suboptimal wound healing, drainage or hematoma, the prime directive is to intervene aggressively to avoid secondary deep periprosthetic infection. Therefore, although no absolute directives exist and nonsurgical care may be the optimal intervention in certain cases, when early wound breakdown occurs or drainage persists beyond the first 2 or 3 days, definitive surgical intervention should be considered within the first week after TKA.

Indications and Contraindications

In this section, five scenarios relating to soft tissue and wound management about the knee are reviewed; indications and contraindications for specific treatment strategies are outlined.