Anatomical basis for distal sartorius muscle flap for reconstructive surgery below the knee. Anatomical study and case report

Anatomical study 

Material and methods 

Fifteen healthy embalmed lower limbs (i.e. no previous scars from the iliac crest down to the foot) from 15 different cadavers, obtained from cadaver donations sent to the Institute of Normal Anatomy of the Faculty of Medicine of Strasbourg were studied.

There were eight females and seven males, chosen at random (six right and nine left lower limbs). The anatomical specimens were injected with 10% formalin through the femoral artery. One of the specimens was injected with a red ink latex solution after catheterisation of the femoral artery.

Each sartorius muscle was carefully dissected from its tibial insertion to the anterior and superior iliac spine. To locate all the pedicles that can be used for any reconstruction surgery, we divided each muscle into three equal parts: superior, middle and inferior. For each pedicle we measured its position from the distal part of the muscle (in cm), the length of the artery corresponding to the arc of rotation (in cm) and the diameter of the artery (in mm). The presence of a nerve associated to the artery was also noted (Fig. 1).

View Large Image Download to PowerPoint

Figure 1 Dissection of a distal pedicle. The presence of a nerve associated to an artery was noted in each dissection. A, artery; N, nerve.

Results 

Muscle dimensions 

All the data on the specimens are reported in Table 1. Mean muscle length was 52.2cm (range 50 to 54.5cm; SD 1.48). These measurements are comparable to those published,6, 8, 9 thus we can compare the measurement of the pedicles to those already published.

Table 1. General data of the anatomical specimens

	No.	Sex	Side	Length (cm)
	1	M	G	53.00
	2	M	D	51.00
	3	M	G	52.50
	4	M	G	53.50
	5	M	G	54.50
	6	F	D	51.00
	7	F	D	53.50
	8	F	G	50.00
	9	F	G	50.50
	10	F	G	52.00
	11	M	D	53.50
	12	M	G	52.20
	13	F	G	54.00
	14	F	D	50.10
	15	F	D	51.10
	Mean			52.16
	SD			1.48

SD, standard deviation.

Vascular pedicles 

For each third of muscle there was at least one vascular pedicle, often two pedicles, and occasionally three. For the proximal third of the muscle, three specimens had three pedicles and 13 specimens had two pedicles. For the middle and distal third of the muscle 10 specimens had two pedicles for the mid-part of the muscle and 12 specimens had two pedicles for the distal third of the muscle. All the details regarding the position of these pedicles relative to the pes anserinus, their length and diameter are reported in Table 2.

Table 2. Position of pedicles relative to the pes anserinus, their length and diameter

			First pedicle	Second pedicle	Third pedicle
	Proximal 1/3	Position (cm)	37.47	32.19	29.25
		Length (cm)	3.15	4.39	1.85
		Diameter (mm)	1.87	1.72	1.25
	Mean 1/3	Position (cm)	26.56	20.2	XXX
		Length (cm)	3.15	3.3	XXX
		Diameter (mm)	2.1	2	XXX
	Distal 1/3	Position (cm)	10.34	7.13	XXX
		Length (cm)	5.64	3.9	XXX
		Diameter (mm)	2.1	1.57	XXX

First row: number of the specimen; second row: position of the first pedicle, length of the pedicle and diameter of the artery; third row: position of the second pedicle, length of the pedicle and diameter of the artery.

From the data recorded for the inferior third of the muscle there was a mean of 1.7 pedicles, with a mean diameter of 2.1mm and a mean mobile length of 5.6cm. These pedicles arose directly from the superficial femoral artery at the level of the adductor hiatus or from the saphenous artery or at least from the descending genicular artery. After entering the muscle from its deep surface each artery splits into two or more longitudinal vessels (Fig. 2). Each of them is connected to the surrounding vessels; it creates an anastomotic network with perpendicular connections along the muscle belly. At the level of the pes anserinus, there was also an anastomotic network within the tendon and at its surface (Fig. 3). These vessels were connected to those arising from the muscle.

View Large Image Download to PowerPoint

Figure 2 Intramuscular arterial network. There is a longitudinal distribution of each artery.

View Large Image Download to PowerPoint

Figure 3 Retrograde arterial supply through the pes anserinus.

Case report 

In 1982 a 46-year-old woman was admitted to another institution with right knee pain. Plain X-rays showed an osteolytic tumour of the tibial epiphysis. The initial diagnosis was a giant cell tumour and at that time a curretage and bone graft was performed. In fact histological investigations revealed periosteal fibrosarcoma. Therefore chemotherapy (six cycles) and radiotherapy (55Gy) were given. One year later, following a fracture of the proximal tibial epiphysis, a knee fusion was performed. There was no local tumoral recurrence. Postoperatively there was delayed healing of the incision and a medial gastrocnemius flap was required. Six years later, after a fall, the patient presented with a fracture at the arthrodesis level. External fixation with an osseous graft was performed. The non-healing of the fracture due to the previous radiotherapy required a proximal dynamic intramedullary nail, associated with a fibular osteotomy. There was no local recurrence and no problem of cutaneous healing. However, one year later there was still no consolidation of the fracture and fatigue failure of the nail occurred. A new plain nail was therefore implanted after reaming of the tibia. Postoperatively the situation improved with healing of the incisions and consolidation of the fracture. In 1998 a necrotic area appeared under the tibial tuberosity. This progressed due to a failure of the former gastrocnemius flap. Local treatment failed and there was a lesion 4cm in diameter. In 2001 we decided to perform a new local flap: a pedicled twist rotation distal sartorius flap. Preoperatively an angiography showed that the vascularisation of the lowest part of the sartorius muscle was satisfactory.

Procedure 

The muscle was dissected from its mid-portion. Arterial pedicles were dissected along the entire length of muscle. The muscle was cut 13cm above the pes anserinus and only the inferior main pedicle located 8cm from the distal insertion of the muscle was preserved. The skin between the pes anserinus and the lesion was excised. The muscle was turned in a flip-flap fashion. A split-thickness skin graft was also performed at the end of the surgery. Postoperative management included mobilisation with full weight bearing immediately. There was no morbidity from sartorius muscle harvest (Fig. 4).

View Large Image Download to PowerPoint

Figure 4 (A) Preoperative view of the flap. (B) Result after 1 month of follow up.

Discussion 

The sartorius muscle has a rich blood supply. Salmon et al.10 found in their study that 30% of the upper pedicles arise from the deep femoral artery and 25% from the superficial femoral artery. The remaining pedicles come from the circumflex arteries or from arterial branches of the femoral artery to the quadriceps femori muscle. For the middle third of the sartorius, arteries arise from the superficial femoral artery. Tang et al.6 found that the distal part of the muscle is vascularised by different branches arising from the saphenous artery or the descending genicular artery, and there are between three and eight branches arising in the deep part of the sartorius.

Mathes and Nahai11 have classified the sartorius muscle as a type 4 because it has six to 10 segmental pedicles arising from the superficial femoral artery. Cormack et al.12 have observed that all these pedicles also give some fasciocutaneous branches at 21 to 30cm from the articular space. These branches are anastomosed together. Tang et al.6 have suggested that retrograde vascularisation from the pes anserinus might be able to vascularise the distal part of the muscle, because of the numerous anastomoses between the saphenous artery and the descending genicular artery (both arise from the superficial femoral artery).

In keeping with the findings of Yang et al.13 we have found that the sartorius is vascularised by four to seven different pedicles. The distal arteries arise from the superficial femoral artery at the level of the adductor hiatus or from the saphenous artery or the descending genicular artery. These branches enter the muscle and then give some branches for the fasciocutaneous network. The mean diameter of these pedicles is 1.1mm for Tang et al.,6 1.8mm for Yang et al.13 and 2mm in our study. The mean length of artery that can be mobilised was 5.6cm. Theses results are comparable to those previously published.6, 10, 11, 12, 13, 14, 15, 16 Moreover we have noted that there was always a nerve associated to one of the distal pedicles. For Mathes et al.11, 17 the segmental vascularisation of the sartorius limits its rotation-transfer capacity because a division in more than three pedicles might lead to a distal necrosis of the muscle after its transposition. However, on the basis of 40 dissections, Kaiser et al.18 postulate that the sartorius muscle can be easily used as a proximal or distal flap for coverage of the abdominal wall, the groin, the hip, the gluteal area and the knee above the joint space. Habermeyer et al.19 state that even the proximal pedicle can irrigate the entire muscle with its intramuscular longitudinal collateral and anastomoses.

Indications for coverage with a sartorius muscle flap have already been published.1, 2, 3, 4 Initially this flap was described for coverage of exposed femoral vessels20 or after infection of the groin with prosthetic vessels.21, 22, 23, 24, 25, 26, 27, 28 We have found few anatomical studies about the feasibility of that flap for coverage of a defect below the knee level,5, 7, 29, 30, 31 and only one cohort of patients presenting with this type of wound defect which was treated with this flap.6

In conclusion, this anatomical study confirms that the sartorius is richly vascularised. We want to highlight that sartorius muscle can also be used for coverage of the upper part of the leg that cannot be covered by a gastrocnemius flap as well as for coverage of the groin and the thigh. The limitations of this study do not allow us to reach a conclusion regarding the feasibility of a combined myocutaneous flap. In the future, selective catheterisations will be required to analyse the cutaneous area supplied by each pedicle.