KEY WORDS
Distal major pedicle - muscle flap - sartorius
INTRODUCTION
Reconstruction of soft-tissue loss around the knee and popliteal region is a difficult
task.[[1]] The reconstructive options are either local fasciocutaneous flaps[[2]
[3]
[4]] or muscle flaps especially gastrocnemius,[[5]
[6]
[7]
[8]] which is a major muscle flap available for local cover and the microvascular-free
flap.[[9]
[10]] The sartorius muscle provides an alternative for muscle flap in this region. Sartorius
has all the qualities of an ideal donor for flap.[[11]] It is dispensable highly vascular, long muscle. According to Mathes and Nahai,
it is classified as class IV muscle[[11]] with segmental blood supply. Various studies have shown that 80%–90% of muscle
can survive with a single vascular pedicle; either on the proximal or distal.[[12]
[13]
[14]] It is apparent that larger the diameter of the pedicle, the greater is the chance
that it supplies the majority of the muscle. Use of sartorius as proximally based
flap for coverage of exposed femoral vessels is well known.[[15]] Hence, in this study, we analyse the pedicle diameter to identify the largest diameter
pedicle in distal one-third of the thigh, its location and also the arc of rotation
of the distally based muscle flap with this pedicle as the pivot point when used in
clinical application.
METHODS
Ten Cadavers were selected which had no external scars or previous surgery marks.
All were embalmed cadavers only. In all cadavers, bilateral femoral vessels exposed
by small incisions and similarly popliteal vessels were exposed and ligated. About
15–20 ml of the liquid dyed silicone was injected into the femoral vessels and allowed
to run down. Slight head-up (20–30° head-up) was maintained to provide additional
benefit of gravity. After about 6 hours (duration for hardening of silicone), the
dissection was done. The sartorius muscle was exposed with a longitudinal incision
from anterior superior iliac spine (ASIS) to knee joint line. Under operating loupe
magnification, the vascular pedicles of sartorius were identified (as silicone dyes
the vessels red it in easier). The muscle was divided into the upper, middle and lower
one-third. In the lower one-third, the visibly largest pedicle was identified and
termed as distal major pedicle. Its location from ASIS was determined. Then, the diameter
of the arterial part of the pedicle was measured at the site of origin from the superficial
femoral artery. Since the liquid silicone injected hardens, measurement of the diameter
becomes easier as vessels were filled with hard silicone. After identification of
the pedicle the muscle was detached from origin and all pedicles proximal to the identified
Pedicle were cut. Then, muscle was rotated with distal major pedicle as pivot point
to know the distal reach of muscle. In clinical cases, the pedicles distal to the
identified distal major pedicle were kept intact to reinforce the vascularity of the
muscle. However, the arc of rotation was measured with the identified distal major
pedicle as pivot point.
RESULTS
Out of the 10 cadavers analysed, 6 were male and 4 were female. The mean location
of the distal major pedicle was at 35.25 cm from ASIS and range was between 30.4 cm
to 38.3 cm [[Picture. 1]]. There was no significant variation between right and left limbs in individual
cadaver (range 0.2–1.6 cm). No dexterity was maintained to opine that one side has
pedicle higher or lower than the other side. The mean diameter of the arterial component
of distal major pedicle was 1.54 mm[[Table. 1]]. The range was 1.4–1.8 mm. In cadavers, the Arc of rotation was not measured. However,
in clinical cases, the distal reach of the muscle, with distal major pedicle, was
till the infrapatellar region.
Picture 1: Cadaver study showing all pedicles along with distal major pedicle at 32.2 cm
Table 1
Cadaver anatomical characteristics
|
Cadaver sex
|
Cadaver number
|
Distance of distal major pedicle from ASIS (cm)
|
Diameter of distal major pedicle (mm)
|
|
* ASIS: Anterior superior iliac spine
|
|
Female
|
1 right
|
34.9
|
|
|
1 left
|
35.4
|
1.4
|
|
Male
|
2 right
|
36.2
|
|
|
2 left
|
37
|
1.5
|
|
Male
|
3 right
|
35
|
|
|
3 left
|
35.5
|
1.7
|
|
Male
|
4 right
|
38.3
|
|
|
4 left
|
38
|
1.7
|
|
Female
|
5 right
|
30.6
|
|
|
5 left
|
30.4
|
1.4
|
|
Male
|
6 right
|
32.2*
|
|
|
6 left
|
32.8
|
1.4
|
|
Male
|
7 right
|
36.5
|
|
|
7 left
|
38.1
|
1.6
|
|
Female
|
8 right
|
34.9
|
|
|
8 left
|
35.3
|
1.6
|
|
Female
|
9 right
|
34.8
|
|
|
9 left
|
33.3
|
1.4
|
|
Male
|
10 right
|
38.1
|
|
|
10 left
|
37.8
|
1.7
|
|
6 male, 4 female
|
Average
|
35.25
|
1.54
|
Clinical cases
In four clinical cases where this flap was used, the arc of rotation was 95°, 110°,
125°. One of the cases where flap was used to cover the tibial plateau, distal end
of the muscle necrosed [[Table 2]].
Table 2
Clinical cases indicating pedicle location and arc of rotation
|
Indication
|
Pedicle distance from ASIS (cm)
|
Arc of rotation (°)
|
Flap outcome
|
|
ASIS: Anterior superior iliac spine
|
|
Chronic non healing ulcer knee)
|
35.8
|
110
|
Healthy
|
|
Post-traumatic lateral knee defect
|
34
|
95
|
Healthy
|
|
Exposed suprapatellar tendon
|
36.2
|
125
|
Healthy
|
|
Exposed tibial plateau
|
36.4
|
155
|
Necrosed distal end
|
Case 1
The patient had post-traumatic fracture of the lower one-third of femur with wound
on the lateral aspect of knee [[Picture 2]]. Fracture was fixed with ring external fixator and wound closed primarily. However,
the sutures gaped and there was necrosis of the skin. Finally, ulcer of about 4 cm
× 4 cm remained, but it was bone deep with discharging sinus. The sinus was plugged
with inferiorly based sartorius muscle flap and skin grafting. Ulcer healed and also
the discharge from the bone reduced and bony union occurred within 4 weeks [[Picture. 3] shows the arc of rotation].
Picture 2: Nonhealing ulcer over lateral knee with Comminuted fracture femur, covered with sartorius
flap and skin graft
Picture 3: Diagram showing the arc of rotation measurement
Case 2
Post-traumatic wound over the knee with exposed suprapatellar tendon. Inferiorly based
sartorius flap done to cover the tendon and joint region. Arc of rotation, in this
case, was 125° [[Picture4a. 4b. 4c]].
Picture 4: (a) Post-traumatic defect over knee exposing suprapatellar tendon. (b) Sartorius
muscle based on distal pedicle placed before in setting. (c) After wound healing
Case 3
The patient had chronic ulcer over the lateral knee region. This was previously operated
case for post-traumatic ulcer with skin graft. The patient had ulcer following skin
graft break down which failed to heel for 2 years. After malignancy was ruled out,
inferiorly based sartorius muscle flap was done to cover the defect following excision
of chronic ulcer.
Case 4
The patient had post-electrical burn necrosis of the skin over the tibial plateau.
Since it was the area of contact, the gastrocnemius was unsuitable because of partial
necrosis. Therefore, inferiorly based sartorius flap was used (arc of rotation was
155°). However, the distal end necrosed. Probably, extensive rotation stretched the
pedicle causing ischaemia. Later, the wound was covered with cross leg flap.
DISCUSSION
The efficiency of gastrocnemius flap to cover the knee region is proved beyond doubt.
However, in injuries of knee region, the vascularity of Gastrocnemius muscle may be
affected and it may be unsuitable.[[1]] Distally based sartorius muscle flap is an effective alternative in such situation.
Sartorius is one of muscles having multiple pedicles. It is also described that each
of the pedicles supply roughly the same amount of muscle and they commented that generally
such muscles are of less useful in reconstruction than the single or double pedicled
muscles.[[16]] The phenomenon of delay is well known to increase the vascularity in adjacent arteriosome.
In muscle flaps, it is the intramuscular anastomosis between the two pedicles which
determines the viability of the muscle. The phenomenon of delay to increase the amount
of muscle supplied by individual pedicle was studied by Buckland et al.[[17]
[18]] and Callegari et al.[[19]] Hong et al.[[1]] JP used this delay phenomenon to increase both muscle and myocutaneous flap over
the sartorius muscle to cover these difficult wounds around the knee joint. This was
in contrast to the belief that a single arterial pedicle is small to supply entire
sartorius muscle.[[16]] Various anatomical studies done by Kaiser et al.[[20]] and Habermeyer et al.[[12]] concluded that majority (80%–90%) of sartorius muscle can be harvested based on
either proximal or distal pedicle alone. The use of proximally based muscle flap on
single major pedicle has been already proved clinically.[[12]] Its use for coverage of exposed femoral vessels or after infection of groin with
prosthetic vessels has been published.[[13]
[21]
[22]
[23]
[24]
[25]
[26]
[27]] However, its use as distally based flap needs to be explored.
The vascular supply of the sartorius muscle has been well-defined. For the purpose
of vascular anatomy, we divide the muscle into equal parts (Proximal, Middle and Distal
one-thirds). The proximal of one-third receives supply (pedicles) from circumflex
femoral and superficial femoral, middle one-third by superficial femoral vessels and
distal one-third by superficial femoral as well as descending genicular artery branches.[[28]] We aimed our study for the distal one-third pedicles which arise from superficial
femoral as the major pedicle (defined as the largest outer diameter after liquid silicone
injection). It is obvious that greater the diameter, greater will be its contribution
to muscle survival.
Location
In our study, the distal major pedicle was located at 35.25 cm from ASIS. The location
of the similar pedicle was between 33.6 and 43.2 cm in a study done by Mojallal et al.[[14]] Clavert et al. studied the location of distal major pedicle from the pes anserinus (i.e., from
the sartorius insertion site). He identified similar pedicle at 10 cm from the sartorious
insertion.[[29]] The study group had mean muscle length of 52.16 cm. Considering this muscle length,
the distal major pedicle was positioned at 42.16 cm from ASIS in this study group.
Compared to our study group where it was positioned at 35.5 cm, the pedicle in that
study group was positioned far caudal. Since the study was done in France, the cadaver
built and muscle length definitely had bearing on the position of pedicle. Shorter
stature in the South Indian community where our study was contemplated influenced
the position of the distal major pedicle. In each limb position of the pedicle (distal
major) differed from the other limb. The position varied by 0.2–1.6 cm i.e., average
distance varied by 0.7 cm which was less significant.
The diameter
The mean diameter of the arterial component of distal major pedicle was 1.54 mm. The
other studies also show similar findings, diameter. In a study by Ali Mojjalal average
diameter was 1.97 ± 0.2 mm. Clavert P et al.[[29]] showed that diameter of largest pedicle in distal 1/3rd was 2.1 mm. Compared to these studies in our study the diameter was less. The reason
for this can only be the physical characteristics of the muscle which is influenced
by the physical stature of the individual.
Arc of rotation
Since sartorius is a long muscle, when based on distal one-third pedicles, it covered
up to knee and tibial plateau. It rotated more than 110° with distal major pedicle
as pivot point. If more distal smaller pedicles were cut and muscle was propelled
on the single major distal pedicle, then it would have rotated more. But when clinically
distally based sartorius flap was used we always preserved the distal minor pedicles
to supplement the blood supply. Other studies also showed similar results.[[30]] Buckland et al.[[17]] suggested that inferiorly based muscle reached almost mid tibial region. In one
of our cases, where sartorius was used to cover the exposed tibial plateau, (i.e.,
rotating muscle at 155°) even with distal pedicles intact, the working end necrosed.
Other three cases where sartorius rotated for coverage of knee defects (i.e., arch
of rotation 110°/125°/95°) had no untoward results. Hence, it can be inferred that
up to knee region this muscle based on distal pedicle can be safely arced.
CONCLUSION
Sartorius is known for its segmental blood supply. Our cadaver study shows that it
has a sizeable vascular pedicle in the distal one-third (located around 35 cm from
ASIS). Based on this distal major pedicle supplemented with the other minor pedicles,
whole of the muscle can be harvested as inferiorly based muscle flap. This flap reached
up to the infrapatellar region (arced up to 130°) safely. More clinical application
of this flap can further authenticate the present cadaver study.
Financial support and sponsorship
Nil.
