|
 The gracilis
muscle is long and thin, tapering from its widest point superiorly to a
tendinous insertion on the medial knee inferiorly.
It acts as a thigh adductor and a flexor of the knee joint, but causes no
significant donor functional loss. The medial thigh scar is slightly posterior
to the midline and relatively inconspicuous. The consistent vascular
anatomy and relative ease of dissection make this muscle an excellent choice for
small wounds, when a long vascular leash is not required. It can also be
use as a functional muscle, to reconstruct upper extremity,
lower extremity or facial muscular function.
Anatomy
The gracilis takes origin with a tendinous
aponeurosis on the ichiopubic ramus and inserts distilly on the medial tibia at
the adductor tubercle. The muscle lies on the adductor magnus along most
of its course, near the adductor longus superiorly and the sartorius inferiorly.
The saphenous vein lies just superficial and anterior to it at its distal
aspect. The muscle is innervated by the anterior branch of
the obturator nerve, itself a branch of the lumbar plexus. It enters the muscle slightly more superiorly than the
uppermost vascular pedicle. A long leash of six to seven centimeters can usually
be dissected free. The nerve can also be dissected intraneurally under
magnification, to split the muscle into smaller anterior and posterior segments.
This allows the muscle to be thinned in cases of facial reanimation where bulk
is avoided. It can also lend itself to functional reconstruction where
splitting the muscle can enable it to motor separate functions.
Vascular Anatomy
The gracilis is a type II muscle flap [Mathes and
Nahai, 1981], i.e. it has a single dominant and secondary minor vascular
pedicles. The primary pedicle is located anterior and superiorly about eight to ten
centimeters below the bony origin. The pedicle arises from the profunda femoral vessels in most cases, running between the adductor longus and
magnus muscles and then entering the undersurface of the gracilis. The
artery is small in comparison to most muscle flaps, with an external diameter of
less than 1 millimeter in pediatric patients, and ranging from 1 to 2 millimeters in the adult. It has two venae comitans,
often smaller than the artery, although occasionally one is larger.
Surgical Dissection
The patient is placed in the supine position and
the entire lower extremity is prepped and draped and positioned with the leg in
abduction and the knee flexed. A bundle of surgical towels are often used
to support the knee in this position. If a lower extremity reconstruction is
bein performed, the contralateral gracilis is usually used to allow a two team
approach and enable the reconstruction team to use a tourniquet if needed. The muscle location is marked on an axis
from the ischiopubic ramus to the medial condoyle of the knee.
The flap markings appear quite posterior to the
untrained eye. The incision is made proximally and the muscle is easily
identified at the base of the wound after the subcutaneous fat and muscular fascia
are divided. On the anterior border of the muscle the vascular pedicle and
nerve can be identified 8 to 10 cm below the ischipubic ramus entering the deep
surface of the gracilis. Early identification of the pedicle enables the
dissection to proceed more simply.
If muscle length is needed, or tendon is needed for
extremity muscle reconstruction, then a distal counter-incision is performed to
identify and dissect free the tendinous insertion. Alternatively, both
incision can be united to form a single large exposure.
The distal and proximal exposures are used to
surround the muscle and ligate the accessory pedicles. A penrose drain
around the tendon or proximal muscle (not pictured) aids in muscle elevation and
counter-traction.
The tendinous aponeurosis is proximally transected
while protecting the pedicle and nerve, and the appropriate length of nerve is
dissected free if functional muscle reconstruction is being performed, or if the
motor nerve is to be coapted to a sensory muscle. The distal tendon is
transected and the muscle is delivered into the proximal incision. The
fascial attachments of the adductor longus to the adductor magnus are freed
superior and inferior to the pedicle and the adductor longus is retracted away
from the magnus. This opens an areolar plane superficial to the pedicle
allowing the dissection to proceed superficial then lateral and then deep. The
pedicle in then freed meticulously. There are numerous small branches
running laterally and deep from the pedicle, and these must be approached with
great care. A major branch from the pedicle tends to run the to adductor
longus muscle, near the proximal most extent of dissection.
When the flap vessels are divided and the muscle is
transplanted, the wound is repaired with some deep buried sutures and the skin
is then approximated. A single suction drain and a light pressure wrapping
usually suffice to prevent seroma formation.
Post-Operative Care
The drain is pulled when
there is minimal serous output and after any anticoagulants are stopped. Patient
ambulation can begin as soon as is indicated with regard to the reconstruction.
|
