Posterior Thigh Flap Pedicled on the Cutaneous Vessels Arising From the Popliteo-posterior Intermediate Artery: A Report of 5 Cases

Surgical repair of soft tissue defects of the knee and leg remains challenging. Using a case study approach, the anatomy of the popliteo-posterior intermediate cutaneous artery was examined, and a reverse island flap method was developed and implemented. After obtaining informed consent, 5 patients (1 woman, 4 men, age range 31 to 57 years) underwent the experimental use of a reverse island flap with a posterior thigh flap pedicled on the cutaneous vessels arising from the popliteo-posterior intermediate artery to repair soft-tissue defects of the knee and leg.The defects were caused by burned skin below the knee (n = 1), progressive skin necrosis in the knee after fracture surgery (n = 2), and skin infections associated with diabetes mellitus (n = 2). Skin defect sizes ranged from 15 cm x 5 cm to 30 cm x 12 cm. These large defects did not heal spontaneously; wound duration ranged from 1 week to 1 year, and all patients had refused defect repair with free flaps. Patients received posterior thigh flaps pedicled on the popliteo-posterior intermediate artery with areas ranging from 17 cm x 6 cm to 25 cm x 12 cm. All patients were treated with antibiotics and local dressings (iodoform and alcohol) changed daily post surgery, and blood supply was monitored by assessing the texture and color of the flap and venous regurgitation (ie, vein drainage disturbance). Four (4) of the five flaps survived completely. In 1 patient, partial survival of the flap, which had a good blood supply despite a venous circulation disorder, occurred: in this case, complete survival was achieved after treatment with a retrograde fascial flap and skin grafting. The appearance and texture of all flaps were satisfactory (ie, patients underwent only 1 operation, healing time was approximately 2 weeks, flap quality was close to normal skin, the donor site closed directly, and the shape and function of the knee and leg recovered well). No donor site abnormality was observed, and no postsurgical infection occurred. More research is needed, but the use of a reverse island flap with a posterior thigh flap pedicled on the cutaneous vessels arising from the popliteo-posterior intermediate artery may be a feasible option to repair soft tissue defects of the knee and leg. 

Skin defects of the knee and leg are not common in the authors’ clinical practice where it has been observed that in patients who have undergone surgical knee reconstruction, soft tissue necrosis around the knee can rapidly lead to deep infection at the arthroplasty site, requiring prosthesis replacement or, in extreme cases, amputation. 

Currently, numerous surgical approaches utilize flaps for reconstruction in cases of lower limb soft tissue necrosis. A case study by Ries and Bozic¹ found a medial gastrocnemius transposition flap effectively covered distal defects over the tibial tubercle or patellar tendon in 11 patients with skin necrosis. Some case studies have recommended the use of anterolateral thigh flaps.^2-4 Chen et al² reported the use of an anterolateral thigh perforator flap achieved a satisfactory outcome in a 46-year-old man with a defect around the knee; Wang et al³ found reverse anterolateral adipofascial thigh flaps survived well and covered defects of the knee and proximal calf in 5 patients; and Yildirim et al⁴ reported anterolateral thigh flaps achieved good clinical outcomes in 8 patients with post-burn flexion contractures of the knee. Case reports of local muscle flaps such as medial gastrocnemius, distal sartorius, vastus lateralis medialis, and gracilis flaps also have been used for the repair of large defects in the knee and leg.^5-9 Jepegnanam et al⁵ reported the use of gastrocnemius flaps resulted in excellent or good outcomes in 8 patients with high-velocity, open-knee injuries. Busfield et al⁶ found extended medial gastrocnemius rotational flaps allowed effective reconstruction of chronic knee extensor mechanism deficiencies in 9 patients with and without total knee arthroplasty. Clavert et al⁷ noted the distal sartorius flap was effective for the treatment of a long-term, nonhealing wound below the tibial tubercle. In approximately 9 out of 13 patients, Larson et al⁸ reported reconstruction with vastus lateralis muscle flaps after Girdlestone arthroplasty for ulcers or chronic wounds affecting the hip joint resulted in satisfactory healing, with no need for further operative intervention. Tiengo et al⁹ reported distally based, secondary pedicle gracilis flaps allowed effective reconstruction of large soft-tissue, total-knee defects in 3 patients.

However, posterior and superior thigh flaps are pedicled on the medial popliteal, lateral popliteal, or popliteo-posterior intermediate artery, and thus have a wide pedicle that restricts flap rotation. Therefore, these flaps have limited utility for the treatment of skin defects in the anterior knee and leg. For patients who have undergone amputation, free flaps or anterior or posterior thigh flaps are required to repair the large skin defects of the stump. For poorly vascularized patients who are not transplanted with free flaps, anterior or posterior thigh flaps are the only choice to repair skin defects. In addition, anterior thigh flaps cannot cover large skin defects in the posterior popliteal fossa.^10,11 Thus, a novel flap is needed to provide an alternative method for the coverage of large skin defects on the knee and leg.

In 2006, the authors noted during resection of popliteal cysts that the cutaneous artery arising from the popliteo-posterior intermediate artery was large; subsequently, the authors hypothesized a posterior thigh flap pedicled on the cutaneous vessels would be suitable for the repair of soft-tissue defects of the knee and leg. Ten (10) cadavers were used to characterize the anatomy of the popliteo-posterior intermediate cutaneous artery, and a reverse island flap method was developed. Utilizing a case study approach, the anatomy was examined and the procedure subsequently was implemented in 5 patients. 

Anatomy. Ten (10) cadavers were used to confirm the anatomy of the popliteo-posterior intermediate cutaneous artery. The cadavers were donated by family members, and their use was approved by the Ethics Committee of First Hospital of Jilin University, China. The popliteo-posterior intermediate cutaneous arteries were evident in all 10 cadavers in this series. Seven (7) of the 10 arteries originated directly from the popliteal artery and 3 arose from its muscular branches, which terminate at the semimembranosus muscle (see Figure 1). Using vernier and micrometer calipers (Wollschlaeger, Germany), all measurements were recorded and standard deviation (SD) calculated (see Tables 1 and 2). Artery origins were located a mean of 28.50 ± 4.92 mm proximal to the midpoint between the medial and lateral femoral condyles. The average outer diameter of the branches at the origin site was 1.72 ± 0.12 mm. In 3 cases, a muscular branch supplying the semimembranosus extended medially from the artery 22.06 ± 3.77 mm distal to the origin. The average outer diameter and length of the muscular branches were 0.56 ± 0.05 mm and 17.42 ± 5.20 mm, respectively. 

The popliteo-posterior intermediate cutaneous artery passed between the medial and lateral gastrocnemius heads and penetrated the deep fascia 33.36 ± 5.39 mm distal to the origin. The average outer diameter of the branch at this point was 1.35 ± 0.12 mm. The artery then divided into descending and ascending branches. The descending artery accompanied the small saphenous vein and sural nerve along the posterior midline of the leg with no obvious branch. The average outer diameters of the descending artery were 0.59 ± 0.12 mm at the origin and 0.27 ± 0.12 mm at the terminus, and its average length was 161.58 ± 9.67 mm. The ascending artery passed along the intermuscular space between the semimembranosus, semitendinosus, and biceps femoris; it had 18 to 25 branches and a length >5.6 cm. Its average outer diameters were 0.95 ± 0.16 mm at the origin and 0.46 ± 0.15 mm at the branching point. The branches extended medially and laterally toward the back of the thigh, forming anastomoses with one another. The ascending artery anastomosed with the descending branch of the third perforating artery of the deep femoral artery 110.84 ± 9.18 mm proximal to the midpoint between the medial and lateral femoral condyles. The average outer diameter of the ascending artery at the anastomosis point was 0.84 ± 0.12 mm (see Figure 2). 

Clinical study. A reverse island flap with a posterior thigh flap pedicled on the cutaneous vessels arising from the popliteo-posterior intermediate artery was designed to repair soft-tissue defects of the knee and leg in 5 patients (1 woman, 4 men, ages 31 to 57 [mean 42] years) (see Figure 3). These patients were selected because the defects were caused by amputation, located in the posterior fossa, or were the result of poor vascularization due to diabetes mellitus, making the defect more difficult to treat. The defects were caused by scalded skin below the knee (n = 1), progressive skin necrosis in the knee after fracture surgery (n = 2), and skin infections associated with diabetes mellitus (n = 2). Skin defect sizes ranged from 15 cm x 5 cm to 30 cm x 12 cm, and flap areas ranged from 17 cm x 6 cm to 25 cm x 12 cm (see Table 3). The use of the reverse island flap was most suitable to repair the skin defects in these cases, based on anatomical characteristics and improved chances, in the authors’ experience, of surgical success. 

Insulin was used to control blood glucose concentration (<8 mmol/L) before surgery in patients with diabetes. In all patients, the most sensitive antibiotic was selected preoperatively based on the results of bacterial culture and drug sensitivity testing of wound secretions. Surgery was performed after antibiotic use had reduced wound secretion and fresh granulation tissue had formed. Antibiotics were continued for 1 week postoperatively. 

This study was approved by the Ethics Committee of Jilin University. The patients agreed to this surgical approach and provided written informed consent. The experimental protocol was established according to the ethical guidelines of the Helsinki Declaration and was approved by the Ethics Committee of First Hospital of Jilin University, China.

Surgical procedure. Under epidural anesthesia, each patient was placed in a lateral position. The flap was harvested from the back of the thigh according to defect size and shape. The flap axis was marked along the midline of the posterior aspect of the thigh, crossing the midpoint between the medial and lateral femoral condyles. The rotation point was located on the flap axis 3 cm above this midpoint. 

An incision was made from the medial edge of the flap to expose the subcutaneous and deep fascia. The deep fascia then was elevated, and the flap was dissected between the deep fascia and the muscle. Dissection continued until the midline of the posterior aspect of the thigh (the flap axis) was reached. The third perforating artery of the deep femoral artery was identified 11 cm proximal to the midpoint between the medial and lateral femoral condyles, and its proximal end, which penetrated the deep fascia, was cut and ligated. The lateral edge of the flap then was incised. The free flap was elevated from the proximal end toward the popliteal fossae, and the flap was dissected to the rotation point without exposing the vascular pedicle. The flap was rotated over the skin defect area and sutured in layers. Donor site defects involving <10 cm skin were sutured directly, and larger defects (>10 cm skin) were repaired by full-thickness skin grafts from contralateral inguinal regions. Inguinal region defects were sutured directly 10 days after skin grafting. All surgeries were performed by the same surgeons/authors; one handled all general postsurgical care. The incisions were topically treated with iodophor and alcohol daily, and patients received prophylactic oral antibiotics. Because none of the patients showed signs of infection, cultures were not taken.

Outcomes. All the patients experienced satisfactory outcomes: 1) they underwent a single operation and a short treatment period, taking 14 days to heal; 2) skin flap quality was close to normal skin; 3) the donor site closed directly, and seemed less traumatic than other type flaps; and 4) the shape  and function of the knee and leg recovered well.

Case 1. Mr. K, an otherwise healthy 57-year-old patient, had undergone amputation of the right lower leg and developed cutaneous necrosis of 2 months’ duration. After surgical repair of the defect using the flap, blood circulation was determined to be good based on consideration of flap texture and color of the flap and venous regurgitation (ie, vein drainage disturbance). Mr. K was treated with orally administered cefuroxime (2.0 g) twice a day for 1 week. The incision received routine postsurgical topical treatment consisting of iodophor and alcohol daily. The sutures were removed after 14 days. The donor site was not primarily closed and healed after full-thickness skin grafting. During the 1-month follow-up period, the texture and color of the flap were normal, and the length of the knee was maintained for artificial limb installation (see Figure 4). 

Case 2. Ms. L is an obese 37-year-old woman (body mass index 33 kg/m²) with type 2 diabetes who developed scar contraction in the right popliteal fossa at the site of a deep second-degree burn sustained when she was 14 years old. Insulin was used to control the blood glucose concentration (<8 mmol/L) before surgery. After surgical repair of the defect using the flap, blood circulation (determined by flap texture and color and venous regurgitation) was good, but a venous circulation disorder developed on postoperative day 1 in a 7-cm x 3-cm area of the flap pinnacle. The flap was dark purple and swollen, and a line of demarcation between the normal flap and flap tip was noted. The affected skin was necrotic but was reactivated after treatment with a retrograde fascial flap with superagenual cutaneous artery pedicles and skin grafting. Ms. L was treated with orally administered cefathiamidine (2.0 g twice a day for 1 week). The incision was treated topically with iodophor and alcohol daily. Three (3) weeks postoperatively, flap texture and color were normal (see Figure 5). The donor site was closed primarily. 

Case 3. Mr. M, 31 years old and otherwise healthy, developed a skin infection and necrosis on the right lower limb 10 days after a traffic accident. After surgical repair of the defect using the flap, blood circulation was good. Mr. M was treated with orally administered cefathiamidine (2.0 g) twice a day for 1 week. The incision was topically treated with iodophor and alcohol daily. The sutures were removed after 14 days. During the 1-month follow-up period, the texture and color of the flap were normal (see Figure 6). The donor site was primarily closed. 

Case 4. Mr. N, a 46-year-old patient with type 2 diabetes, had skin necrosis of 40 days’ duration on the lower leg. Insulin was used to normalize the blood glucose concentration before surgery. After surgical repair of the defect using the flap, good blood circulation was observed. Mr. N was treated with orally administered cefuroxime for 1 week. The incision was topically treated with iodophor and alcohol daily. The sutures were removed after 14 days. The texture and color of the flap were normal postoperatively. The donor site was closed primarily.

Case 5. Otherwise healthy 40-year-old Mr. O developed skin necrosis 1 week after a traffic accident. After surgical repair of the defect using the flap, blood circulation was good. Mr. O was treated with orally administered cefuroxime (2.0 g) twice a day for 1 week. The incision was topically treated with iodophor and alcohol daily. The sutures were removed after 14 days. The texture and color of the flap were normal postoperatively. The donor site was closed primarily.

This study describes the use of a reverse island flap with a posterior thigh flap pedicled on the cutaneous vessels arising from the popliteo-posterior intermediate artery. Because this flap is not a main artery flap, harvesting does not affect the blood supply of the thigh. In addition, cutaneous vessels arising from the popliteo-posterior intermediate artery are readily separated and rotated. This flap is sufficiently large to cover the entire knee and the middle and upper sections of the leg (see Figure 3). Overall, this type of operation is able to protect the arteries; in the authors’ experience, use of this surgical method to repair soft-tissue defects of the knee and leg arising from various causes, including chronic ulcers and sinuses, is feasible and safe. No postoperative infection occurred in any patient, possibly attributed to the prophylactic use of antibiotics.

To reduce the possibility of flap necrosis, damage to the blood vessel was carefully avoided by not exposing the pedicle excessively during separation. The pedicle also should not be rotated >180˚ or placed under excessive traction. If the donor site defect cannot be directly sutured, the flap should be free to avoid compression of the pedicle. In addition, the anatomic study showed the blood supply of the popliteo-posterior intermediate cutaneous arteries in the thigh extends 25 cm proximal of the popliteal crease and 5.5 cm lateral of the vascular axis. The largest flap created in this study was 30 cm x 12 cm, and no necrosis was observed. Thus, transplanted tissues should survive when a smaller area is involved. The authors’ preliminary anatomic study of cadavers showed the average pedicle length was 250.03 ± 9.24 mm, with no necrosis. Thus, flaps with pedicle lengths <250 mm should survive. In case 2, only partial flap survival was achieved due to poor venous circulation, possibly due to compression of the pedicle by thick fat tissue in this obese patient. Necrosis developed in the flap due to poor venous return. Thus, care should be taken to avoid pedicle compression in obese patients.

Barret et al¹² recommended the use of skin autografting, Z-plasties, and flaps to repair defects in the skin and subcutaneous tissues. The authors reached a conclusion based on personal experience that flaps should be considered for the reconstruction of defects that involve tissues underlying subcutaneous tissues; suitable flaps include direct cutaneous, musculocutaneous, perforator-based, expanded, and free flaps (microvascular tissue transfer). Flap selection is based on individual patients’ conditions. In case 2 described here, the removal of scar tissue from the popliteal fossa created large soft-tissue defects. Z-plasty was not suitable for the repair of these defects due to the poor elasticity of the surrounding skin; also, Z-plasty could not improve knee joint function in this patient. The use of a reverse island flap with a posterior thigh flap pedicled on the popliteo-posterior intermediate artery achieved a satisfactory outcome in this obese patient with post-burn scar contraction.

Advantages. In the authors’ experience, this flap has several advantages. First, a local random-pattern skin flap has indistinct perfusion and is limited in size. The random-pattern skin flap aspect ratio is 2:1; if it is greater than the proportion, necrosis occurs. Defect repair using a cross-leg flap requires a long period of immobilization (eg, for 1 month post surgery) and several operative stages. Although a free flap can cover a defect successfully in a single-stage operation, the operating time is long and this procedure can be technically difficult due to the presence of deep recipient vessels.³ Because the popliteo-posterior intermediate cutaneous artery is located in the intermuscular space in the popliteal fossa and passes along the intermuscular septum, in patients with trauma on the back of the leg, the artery is readily separated and rotated.

This is first study of this surgical procedure to repair anterior soft-tissue defects of the knee and lower leg; the approach was found to be simple, safe, and reliable and shows great potential for clinical application. Also, the flap is supplied by the popliteo-posterior artery, which is located in the posterior compartment of the thigh and does not affect the normal anatomical structure. The medial gastrocnemius flap is most effective for coverage of distal defects over the tibial tubercle or patellar tendon,¹ but the removal of this flap thins the leg. In addition, the gastrocnemious flap can be used to repair large skin defects on the knee because the harvest area is large and located close to the knee. The anterolateral thigh flap is very large and thin, but the difficulty of perforator dissection and vascular anatomical variability constitute major disadvantages for their use.⁴ Finally, wounds with areas of <10 cm can close with no further treatment after the secondary skin graft.

Disadvantages. Use of the popliteo-posterior intermediate artery flap also is associated with several disadvantages. The distally based vastus lateralis muscle flap is too bulky to cover a knee defect, and donor site morbidity is a consideration.¹⁰ Fat is abundant in this region, especially in women, resulting in a thick flap that may cause venous circulatory disorders. For this reason, in the authors’ experience a secondary surgery is commonly required for skin transplantation and in case 2 was due to: 1) poor quality of the blood vessel due to a primary disease, such as diabetes (patients with rheumatoid arthritis, diabetes, or peripheral vascular disease have increased risks of wound healing complications¹¹); 2) poor local soft-tissue conditions because of bruising; and/or 3) poor refluence of the vein due to the large flap size.

This study has several limitations. First, the sample was small (N = 5). Further studies with larger samples are required to confirm the efficacy and safety of this method and to confer a better understanding of when such surgery would be indicated. Second, this was a single-center study and the method has not been used in other centers. Some factors, such as the source of the patient, operation skills, and economic conditions may be center-specific and not generalizable to other facilities. Third, the hemodynamics of the flap’s blood supply have not been studied. A hemodynamic study should be performed to confirm the blood supply to the flap, thereby facilitating its accurate removal. Fourth, a long-term view of this surgical technique and prognoses is warranted.

This report is the first description of the use of the posterior thigh flap pedicled on the cutaneous vessels arising from the popliteo-posterior intermediate artery for the reconstruction of knee and proximal calf defects. In the authors’ experience, the advantages of this novel approach include the ability to repair large soft-tissue defects in this region and that it is a relatively easy surgical procedure. This approach seems to be most suitable for soft-tissue defects measuring <30 cm x 12 cm after amputation or in the posterior fossa in nonobese patients. Additional studies involving this surgical approach in more diverse populations and with long-term follow up are warranted. 

This work was supported, in part, by the State Plan for Technology Research and Development of Jilin Province (no. 201101045).  

Dr. Sun is associate chief physician; Dr. Gong is chief physician; Dr. Song is visiting staff; Dr. Cui is associate chief physician; Dr. Yu is visiting staff; and Dr. Liu and Dr. Lu are chief physicians, Department of Hand Surgery, First Hospital of Jilin University, Jilin, China.

Please address correspondence to: Lai-Jin Lu, MD, PhD, Department of Hand Surgery, First Hospital of Jilin University, Xin Min Avenue 1008, Changchun 130021, Jilin, China; email: kjkliubin@126.com.