Reconstruction of a knee defect in a morbidly obese patient with a pedicled reverse anterolateral thigh flap

Abstract

The anterolateral thigh (ALT) flap is widely used in the reconstruction of a variety of soft tissue defects. Descriptions of patients with severe obesity in the literature are scarce. We report a case where a reverse pedicled fasciocutaneous ALT flap was successfully used for resurfacing of a knee defect measuring 12×6 cm in a patient with a body mass index (BMI) of 47.3. The flap was supercharged to the greater saphenous vein to optimise flap survival. Reconstruction of the soft tissue of the knee was achieved as planned. There were no flap or donor site complications.

Background

Soft tissue reconstruction following knee trauma is complex. Limited local tissue and exposed bone and ligaments often necessitate free tissue transfer. Microvascular reconstruction may be challenging due to pre-existing scarring and lack of reliable recipient vessels in the zone of injury.^1–3 The result is often poor wound healing and prolonged recovery. Long-lasting microsurgical procedures are poorly tolerated by morbidly obese patients.

Thus, a single-stage operative approach followed by early mobilisation is preferred and may provide favourable outcomes.⁴ Pedicled flaps originating from the thigh, such as the reverse vastus lateralis muscle or the reverse anterolateral thigh (ALT) flaps, can be used for coverage of the knee. These options provide reliable donor tissue in close proximity to the defect, reducing surgical trauma and the risk of complications as well as operative time, compared with a free flap.^5–7

Previous studies have described persistent marginal necrosis of the distally based ALT (dbALT) flap, likely due to the large flap size relative to its vascular supply.^{8 9} In obese patients, the risk of flap necrosis and donor site complications is significantly increased.^{10 11} To enhance the reliability of the dbALT flap and to avoid reverse venous blood flow, venous supercharging has been suggested.^{1 5 10}

Few studies have focused on the clinical application of this flap for regional reconstruction,^{7 12–14} particularly in obese patients. In this case report, we illustrate a single-stage surgical technique using a supercharged dbALT flap to resurface a large, traumatic knee defect, allowing for early mobilisation in a morbidly obese patient.

Case presentation

A man in his 30s incurred a traumatic rupture of his right quadriceps muscle when falling down the stairs. Initially, the defect was treated at the department of orthopaedic surgery with direct suture. The postoperative course was complicated by infection and wound dehiscence. Subsequent multiple revision surgeries left the patient with a knee defect with intra-articular involvement measuring 12×6 cm (figure 1). The body mass index (BMI) of the patient was 47.3. There were no other risk factors or comorbidities.

Figure 1.

Right knee defect with exposed quadriceps tendon.

Investigations

MRI revealed a 3.5 cm diastasis between the quadriceps muscle and the patella. Initial attempts of repairing the quadriceps tendon using anchor sutures had been unsuccessful. Further reconstruction was deemed likely to fail, partially due to the considerable BMI of the patient. Closure of the extensive tissue defect therefore became the main focus. Preoperative evaluation assessed the supercharged dbALT flap to be a suitable option. Considered alternatives were a gastrocnemius flap or a free flap, such as a latissimus dorsi flap or an ALT flap.

Treatment

Markings for the ALT flap were drawn as a line between the anterior superior iliac spine and the lateral edge of the patella, corresponding to the intermuscular septum between the rectus femoris and the vastus lateralis muscles. The midpoint of the line was marked. Cutaneous perforators, from the descending branch of the lateral circumflex femoral artery (dLCFA), were identified by colour Doppler ultrasound and mapped. The flap was designed to incorporate the selected perforators.

The flap was raised with the patient in supine position. The perforators were localised and dissected to the dLCFA (figure 2). The branch was dissected distally through a lengthy intramuscular course, until an adequate pivot point was reached approximately 10 cm proximal to the patella (figure 3). After confirming distal perfusion using indocyanine green imaging (HyperEye Medical System, HEMS), the dLCFA was divided proximally. The flap was transposed to the defect through a subcutaneous tunnel.

Figure 2.

Harvested anterolateral thigh flap with perforators.

Figure 3.

Assessment of pedicle length.

The greater saphenous vein (GSV) was identified, dissected and divided so that it could reach the flap. The GSV was anastomosed to the dominant vena comitante using a 2.5 mm Unilink/3M coupler, optimising the venous outflow from the flap. The donor site was closed using Vicryl 3–0 and Ethilon 3–0 sutures in the skin (figure 4). Prophylactic antibiotics were administered peroperatively (1.5 g cefuroxime), and maintained 2 weeks postsurgery (1 g dicloxacillin, 4 times per day). The total surgical time was 4 hour 59 min.

Figure 4.

Final closure following transposition of the flap to the recipient site and anastomosis of a commitant flap vein to the greater saphenous vein.

Outcome and follow-up

Although the extensor mechanism of the knee was not restored, the patient was successfully mobilised with the knee in extended position, 1 week postoperatively. He was discharged 2 weeks following surgery, with complete flap survival and no complications or delay in donor site healing. The results were satisfactory 3 months postoperatively (figure 5). Nonetheless, the patient is currently awaiting knee fusion surgery, due to persistent synovial leakage.

Figure 5.

Three months postoperative view of distally based anterolateral thigh flap.

Discussion

The ALT flap is a feasible choice for reconstruction of soft tissue defects in the lower extremity, either as a pedicled or a free flap. Although numerous reports have described the versatility of this flap for free tissue transfer, there has been little focus on its potential for regional reconstruction as a pedicled flap.^15–19 We report an example of successful resurfacing of a substantial knee defect using a dbALT flap with venous anastomosis to the GSV in a morbidly obese patient.

Since it was first described by Song et al in 1984, and later popularised by Koshima et al in 1993 and Wei et al in 2002, the ALT flap has become a workhorse in reconstructive microsurgery.^20–22 Advantages include great versatility in soft tissue design, excellent pedicle length, a superior vascular supply, the relative ease of dissection and minimal donor site morbidity compared with other microsurgical alternatives.¹⁸ When a larger flap is needed, the entire lateral thigh may be included by conjoining the flap with the tensor fascia lata or anteromedial thigh flap.¹⁶

Although the possibility of using a free latissimus dorsi flap was considered in our patient, this would have required intraoperative repositioning, prolonging surgical time, as well as compromise of the muscle function in the donor site.²³ We also considered the gastrocnemius flap; however, it was deemed too small for coverage of the defect.

We chose the ALT flap, which is reliable for skin paddles of up to 30 cm in length, 20 cm in width and 480 cm² in size.^{15 17 18} The flap is associated with low donor site morbidity and in most cases can be closed directly.^{18 24} Furthermore, a two-team surgical approach is applicable, minimising operative time and surgical morbidity.

The pedicled ALT flap seems favourable compared with a free flap, due to reduced surgical time, and it is possible to conduct the procedure without changing the position of the patient.^{1 7} Venous outflow in a reverse ALT flap relies on small interconnections to bypass the functional valves. A potential complication is venous congestion leading to oedema and tissue necrosis. This is often the case with the dbALT flap due to the size of the harvested tissue.

In order to enhance the reliability of the dbALT flap, it should ideally rely on antegrade drainage, which can be achieved by anastomosing a commitant vein to the GSV.^{1 23} Suggested alternatives include surgical delay, expansion of a subcutaneous tunnel and insertion of a venous catheter to intermittently relieve venous engorgement.¹ However, these solutions are time consuming and thus unattractive when dealing with obese patients, who by default have elevated complication rates.

Although venous supercharging does require some additional surgical time, the procedure is simple and less time consuming compared with the arterial and venous anastomosis in a free flap. Identifying the recipient vessels in a free ALT flap to cover a potential knee defect, that is, the anterior or posterior tibial artery or the peroneal artery, is challenging and thus associated with increased morbidity.

Conclusion

The dbALT flap with anastomosis of the commitant vein to the GSV, to ensure antegrade drainage, may be a valid option for reconstruction of large soft tissue defects in the knee in morbidly obese patients. In the presented case, the flap was used for successful coverage of a large soft tissue defect of the knee in a morbidly obese patient.

Patient’s perspective.

I was at work when I fell down the stairs and felt a massive snap from my knee. I immediately knew something was wrong. I was able to sit down, however I could not extend or use my knee. I called an ambulance and was initially treated by suturing of the defect. Unfortunately, there were continuous problems post-surgery, and they were not able to reestablish the function of my knee.

The wound got increasingly worse and after repeated treatments they decided to close it with a tissue flap from my upper leg. I was grateful that they were able to close the defect, however, due to further issues with my knee I am currently awaiting additional surgery to stiffen my knee joint. It has been a frustrating process, but hopefully the upcoming surgery will be successful and I will be able to keep my leg.

Learning points.

• The supercharged distally based anterolateral thigh flap can be used for large soft tissue defects in the knee.

• Anastomosis between a commitant flap vein and the greater saphenous vein is recommended to ensure flap survival.

• The pedicled anterolateral thigh flap is a feasible choice for reconstruction of soft tissue defects in the lower extremity in the morbidly obese patient.

Ethics statements

Patient consent for publication

Consent obtained directly from patient(s).