A 65-year-old man presented with complaints of wound drainage, pain, and infection of his left knee replacement lasting 2 years. He had undergone a primary knee replacement 3 years before presentation. One year after knee replacement, he underwent a polyethylene exchange because of instability. This was complicated by an acute postoperative deep periprosthetic infection. He was treated with débridement and 6 weeks of antibiotics, but the infection persisted. He developed recurrent sinus tracts and underwent three further débridements before presentation to our institution.
On examination, range of motion of the left knee was 10 to 95 degrees. It was stable to varus and valgus stress. There were several fluctuant bullae over the medial pes anserine area of the knee ( Fig. 37.1 ). Radiographs revealed a cemented mobile-bearing total knee arthroplasty with evidence of tibial loosening ( Fig. 37.2 ). Aspiration revealed a white blood cell count of 46,000/μL with a differential of 96% neutrophils; cultures from the aspirate grew Staphylococcus epidermidis .
Removal of the knee prosthesis with insertion of an articulating, antibiotic-impregnated cement spacer was performed with a medial gastrocnemius muscle flap performed during the same anesthesia ( Fig. 37.3 ).
Uncomplicated wound healing is critical for success in total knee arthroplasty (TKA). Patients at risk for wound problems should be identified preoperatively, and treatment should be optimized. If multiple prior incisions or adherent subcutaneous tissues are identified (especially with a history of healing problems), prophylactic soft tissue transfer should be considered.
Prophylactic soft tissue transfer appears to be associated with better range of motion and lower risk of infection after TKA compared with salvage flaps. Therefore, aggressive prophylactic intervention should be encouraged in patients judged to be at high risk for wound healing problems with a hostile soft tissue environment.
Delayed surgical intervention for wound problems that occur after TKA may allow secondary deep periprosthetic infection to occur. Therefore, early definitive intervention is recommended.
In the presence of deep periprosthetic infection, deep débridement or placement of an antibiotic-impregnated spacer is required at the time of salvage soft tissue transfer.
Fasciocutaneous perforator flaps are associated with better cosmesis and have lower donor site morbidity than muscle flaps. They represent an excellent option for prophylactic soft tissue transfer.
In the salvage setting, especially in the presence of infection, local rotational muscle flaps or free muscle flaps are a better choice.
The medial gastrocnemius muscle flap remains an excellent choice for salvage of wound problems that occur in the postoperative setting.
If a wound problem extends proximal to the tibial tubercle and patellar tendon, or in the presence of a very large area of skin necrosis about the knee, a free muscle flap is the best choice.
Distally based anterolateral thigh perforator flaps are not a good choice in patients with prior knee replacement, because the inflow via the superior lateral genicular artery may have been compromised.
Successful outcomes after total knee arthroplasty (TKA) depend on rapid and uncomplicated wound healing. Problems in achieving this milestone may result, at a minimum, in delayed rehabilitation and in other cases may contribute to failure of the TKA. Whereas up to 20% of patients experience some type of wound problem, the rate of serious problems that require reoperation is less than 0.5%. Factors that may be associated with poor wound healing were reviewed in Chapter 36 . Even if all efforts are made before, during, and after the TKA to reduce the risk of soft tissue problems, situations will occasionally occur that require additional soft tissue procedures.
Whether these circumstances arise intraoperatively or postoperatively, soft tissue transfer procedures that are performed either concomitant with the TKA or days to weeks later are considered salvage procedures. In distinction, soft tissue transfers that are performed weeks to months before the knee surgery are considered prophylactic procedures. Recent work has suggested that these prophylactic procedures are associated with better results, most likely because of a reduction in the risk of infection, the provision of a pliable soft tissue envelope, and minimal impact on rehabilitation after the knee surgery. When a flap that was transferred prophylactically is mobilized at the time of TKA, postoperative range of motion (ROM) and physical therapy may need no or only minimal changes compared with standard rehabilitation protocols. On the other hand, when a salvage flap is required, prolonged periods of bed rest or immobilization may be needed and can seriously affect the functional results of the TKA. In this chapter, soft tissue transfers that may be used either prophylactically or in the salvage setting are reviewed.
Indications and Contraindications
Prophylactic soft tissue transfer may be required in patients with substantial risk factors for wound healing problems. In particular, patients with multiple prior longitudinal incisions about the knee, failed prior soft tissue expansion, or adherent or poor subcutaneous tissues around the knee resulting from prior simple skin grafts onto fascia, radiation treatment, or burns may be at increased risk of wound healing problems. In these cases, options for prophylactic soft tissue transfer include rotational or free fasciocutaneous perforator flaps, such as the anterolateral (ATL) thigh flap; local rotational muscle flaps (with or without the skin and subcutaneous tissue), such as the medial gastrocnemius flap; and free muscle flaps, such as a latissimus dorsi or rectus abdominis muscle flap (with or without the skin and subcutaneous tissues). In general, local rotational fasciocutaneous perforator flaps are best used in the presence of smaller areas of skin involvement without infection, whereas local rotational muscle flaps and free flaps are better suited for larger areas of involvement.
There are no absolute indications to guide the orthopedic surgeon about when a prophylactic procedure should be used; instead, this decision is based on an educated assessment of all the risk factors that are present, including systemic conditions that may further complicate the wound healing potential. Some patients who undergo prophylactic soft tissue procedures might have been able to heal adequately after TKA without them, but considering the potentially devastating complications that can occur if wound problems develop, some degree of overutilization of preemptive soft tissue procedures seems preferable. Fasciocutaneous perforator flaps are particularly well suited for use in the prophylactic setting. The advantages of these perforator flaps in comparison to local muscle flaps include minimal functional deficits (because no muscle is transposed) and better cosmetic results at the recipient site (because they tend to be less bulky and can be easier to revise from a cosmetic standpoint).
Relative contraindications to prophylactic transfer include active soft tissue infection about the knee and deep periprosthetic infection. In these cases, removal of implants or débridement in the setting of acute infection with a simultaneous soft tissue procedure should be considered. Another relative contraindication to the use of soft tissue transfers is an elderly patient with medical comorbidities such as advanced chronic obstructive pulmonary disease, coronary artery disease, or severe cardiac valve stenosis that could contribute to a high risk for perioperative complications during the long operations. Absolute contraindications for prophylactic free muscle flaps include advanced peripheral vascular disease or prior damage to the arterial inflow to the lower leg, where there is no potential for reconstruction of the vessels. In some circumstances, a vascular surgery consultation with Doppler ultrasound imaging or a computed tomographic (CT) angiogram of the legs should be obtained to help define what vascular reconstructive options exist. Another absolute contraindication is multiple prior failed rotational muscle flaps, or free flaps where no viable soft tissue transfer options remain, especially when the soft tissue defect is large.
In the salvage setting, local rotational fasciocutaneous flaps may be used, but in our experience they may not provide adequate coverage; furthermore, use of fasciocutaneous perforator flaps in the setting of deep periprosthetic infection is controversial. In these circumstances, the medial gastrocnemius muscle flap remains the primary means of restoring adequate soft tissue coverage, especially if the wound breakdown occurs over the proximal medial tibia. In some circumstances, the lateral gastrocnemius is also an excellent option. If the medial gastrocnemius has been used previously, or if the compromised soft tissue extends proximally above the level of the tibial tubercle or over the patellar tendon, a free muscle flap or alternative should be considered. Therefore, in most salvage settings we encounter, either medial gastrocnemius muscle flaps or free muscle flaps are most commonly used for gaining adequate soft tissue coverage about the knee.
Relative and absolute contraindications for salvage soft tissue transfers include the same concerns as for prophylactic flaps. However additional contraindications may exist. In the complex clinical settings in which salvage flaps are often required, patients may have numerous associated life-threatening medical comorbidities such as sepsis or hemodynamic instability. In these circumstances, even when the soft tissue defect is ultimately reconstructable, a decision must sometimes be made whether local débridement followed by delayed reconstruction or immediate life-saving amputation is the best choice.
A hand-held Doppler ultrasound unit is used intraoperatively to identify perforating vessels during harvesting of a fasciocutaneous perforator flap.
Standard microvascular equipment, including an operating microscope, is required when performing free flap transfers.
A dermatome is useful for harvesting a split-thickness skin graft used to cover a muscle flap. A split-thickness skin graft can be passed through a 1 : 1.5 mesher to increase the surface area covered (or small perforations can be made for improved drainage).
Standard flat soft tissue drains are placed under the flaps intraoperatively; care must be taken to avoid contact with the vascular pedicle.
The general vascular anatomy of the skin and subcutaneous tissue about the knee is described in Chapter 36 . When considering the use of rotational or free fasciocutaneous perforator thigh flaps, it is particularly important to understand the role of perforating musculocutaneous and septocutaneous arterial inflow. One of the most commonly used fasciocutaneous perforator flaps about the knee is the ATL thigh flap. The vascular inflow to this flap is consistent, via large-caliber perforators from the descending branch of the lateral femoral circumflex artery. In about 90% of cases, the dominant perforator is a musculocutaneous perforator, whereas in the remainder a septocutaneous perforator is encountered. Detailed anatomy of this pedicle was previously described by Spyriounis. Recipient arteries commonly used for free flaps about the knee include the superficial femoral artery and the saphenous artery; use of the anterior and posterior tibial arteries, the superior medial genicular artery, or the descending branch of the lateral circumflex femoral has also been described. Although the popliteal artery is useful as a recipient vessel for soft tissue transfer to the posterior knee, it is not recommended for transfers about the anterior knee. The vascular inflow to a medial gastrocnemius flap is the medial sural artery, which is the first branch of the popliteal artery.
Examination and Imaging
Patients with a history of peripheral vascular disease should undergo vascular evaluation with CT angiography to determine whether the vessels for local rotational muscle flaps are available or whether the source vessels for perforator flaps have been compromised. Also, if free flaps are being considered, adequate flow through a distal recipient vessel should be verified; potential recipient arteries include the superficial femoral artery, the anterior tibial artery, and the popliteal artery. In patients with a prior TKA in whom the superior lateral genicular artery may have been transected or damaged (especially after lateral patella release), distally based ATL thigh flaps are a poor choice. If this flap is considered, preoperative CT angiography should be considered to evaluate the distal source vessel.
Hand-held Doppler ultrasound imaging is used intraoperatively to identify the perforator vessels when harvesting a fasciocutaneous perforator flap; in complex cases, Duplex ultrasound or CT angiography can be helpful for mapping vessels preoperatively.
Three types of procedures are described that provide excellent options for prophylactic and salvage soft tissue coverage about the knee.
Anterolateral Fasciocutaneous Perforator Thigh Flap
Fasciocutaneous perforator thigh flaps are an excellent option for soft tissue coverage about the knee, especially in the prophylactic setting in which there is no evidence of deep infection. The technique is as follows :
The patient is placed in the supine position.
The recipient site is adequately débrided of all necrotic and devascularized skin and subcutaneous tissue ( Fig. 37.4 , A).