Transcript Gluteal region

DISSECTION OF THE GLUTEAL REGION
SKIN INCISIONS
1. Make a median vertical
cut from the lower lumbar
region to the approximate
level of the coccyx (A to
B).
2. Cut from point A laterally
over the iliac crest. (A to
C)
3. Cut from proximal medial
aspect of the thigh to the
lateral part of the thigh.
(D to E)
4. Cut from B to D.
B
A
D
C
E
Once the skin and fascia has been removed from the gluteal region, you should
see some cutaneous nerves, the superior, middle inferior cluneal (or clunial) [L.,
clunes = buttocks] nerves. These nerves are responsible for providing the
sensation to the buttocks or gluteal region as far as the greater trochanter.
Superior cluneal
nerves
Inferior cluneal
nerves
Middle cluneal
nerves
Once you have observed the cluneal nerves, clean the gluteal region so that it
looks something like this figure. Note that the gluteus maximus covers the
other gluteal muscles except for a small portion of the gluteus medius muscle.
Gluteus maximus
Above the superior border of the gluteus
maximus,identify some of the gluteus medius muscle..
(Only a small amount of the gluteus medius muscle can
be seen at this time.)
Most fibers of the gluteus maximus muscle end in the iliotibial tract that
ultimately inserts into the lateral condyle of the tibia. A few of the deeper
and more inferior fibers insert on the gluteal tuberosity of the femur.
Iliotibial tract
At the inferior border of the gluteus maximus muscle,identify the posterior
femoral cutaneous nerve. This nerve is best identified on the superficial aspect
of the hamstring muscles. It provides branches to the skin on the posterior
aspect of the thigh.
Starting at the inferior border of the gluteus maximus muscle, cut along the
medial border of the muscle and detach it from the posterior surfaces of the
ilium, sacrum, coccyx, and sacrotuberous ligament.
After the muscle is freed from these medial attachments, reflect it laterally.
Note that it inserts distally into the femur and iliotibial tract.
Upon performing this reflection, the
gluteus medius muscle should appear
obvious to you.
Note the insertion of the gluteus
medius muscle on the greater
trochanter of the femur.
Some other
smaller muscles
are also
considered to be
part of this
gluteal region:
1. the piriformis
muscle
2. the obturator
internus muscle
3. the superior
and inferior
gemelli muscles
AND
4. the quadratus
femoris muscle
These muscles
primarily function
as external, or
lateral, rotators
of the femur.
These muscles take an interesting course as they travel from their origins to
their insertions.
For example, the piriformis muscle extends from the anterior surface of the
sacrum to the superior border of the greater trochanter of the femur. In
other words, this muscle originates within the true pelvis, but then exits this
region via the greater sciatic foramen.
The obturator internus muscle travels from the inner surface of the obturator
membrane to the greater trochanter via the lesser sciatic foramen.
Identify the piriformis muscle as it passes through the greater sciatic
foramen.
This muscle serves as an important landmark for the identification of other
structures in the gluteal region.
Piriformis muscle
During the reflection of the gluteus maximus
muscle, identify the superior gluteal vessels
and inferior gluteal nerves and vessels relative
to the piriformis muscle.
Inferior gluteal
artery, vein, and
nerve
The superior gluteal
artery and vein
emerge from the
greater sciatic
foramen above the
superior border of
the piriformis
muscle.
Hopefully, you have not overlooked the sciatic nerve.
Though not typical, it is possible that this nerve may have
already divided into its two terminal divisions in the gluteal
region – tibial and common fibular.
At this point in your dissection, you may also now observe the trochanteric
bursa which overlies the greater trochanter of the femur. One of the primary
functions of this bursa is to cushion and protect the gluteus maximus muscle
from excessive friction and wear as it moves over the greater trochanter.
trochanteric bursa
greater trochanter
of the femur
Now, to view the pudendal
nerve and internal pudendal
vessels, retract the
sacrotuberous ligament (held
by the retractor) near its
attachment to the sacrum.
Sacrotuberous
ligament
Ischial spine
Sacrospinous
ligament
The pudendal nerve and internal pudendal vessels pass posterior to the
ischial spine between the sacrospinous ligament and the sacrotuberous
ligament, before then supplying structures within the perineum.
Sacrospinous
ligament
The pudendal nerve and internal pudendal vessels pass posterior to the
ischial spine between the sacrospinous ligament and the sacrotuberous
ligament, before then supplying structures within the perineum.
Sacrotuberous
ligament
Pudendal nerve
So, a pudendal nerve block involves introducing an anesthetic agent into the
pudendal nerve to decrease the sensation of the perineum, such as during
childbirth.
Internal
pudendal vein
Internal
pudendal
artery
So, at this point you should have noted that the
structures that pass through the greater sciatic
foramen to the gluteal region at the inferior
border of piriformis muscle are the:
1. inferior gluteal nerve, artery and vein
2. sciatic nerve
3. posterior femoral cutaneous nerve
4. pudendal nerve and internal pudendal vessels
Now, let’s take a look
at some of those deep
muscles of the gluteal
region that we
referred to in an
earlier slide.
Obturator internus muscle
– this muscle leaves the
pelvis via the lesser
sciatic foramen before it
then attaches onto the
medial aspect of the
greater trochanter
Superior gemellus muscle – superior
to the obturator internus muscle
Inferior gemellus muscle – inferior
to the obturator internus muscle
So, the obturator internus and
the superior and inferior gemelli
occupy the space between the
piriformis and the quadratus
femoris muscles.
Quadratus femoris muscle
Piriformis
Obturator
Internus
And so what inserts here?
Gemelli
Quadratus femoris
inserts on the
trochanteric crest
of the femur
It must be a muscle
that functions as a
hip external rotator
and/or abductor. And
we are viewing the
posterior femur. It
must be the insertion
site of the gluteus
medius muscle.
Since these muscles primarily
function as external, or lateral,
rotators of the femur, it makes
sense that they would insert in the
region of the greater trochanter.
Now, you are going to
reflect the gluteus
medius muscle, but
BEFORE you do this,
again identify the
superior gluteal artery
and vein which should
be located at the
medial border of this
muscle. These
structures pass in the
plane between gluteus
medius and gluteus
minimus muscles.
Cut the gluteus medius muscle near its
insertion and reflect it.
You should now be able to see the
underlying gluteus minimus muscle…
Cut gluteus
medius muscle
… and the superior gluteal nerve
which is accompanied by deep
branches of the superior gluteal
vessels.
This nerve supplies the gluteus
medius, gluteus minimus,and
tensor fasciae latae muscles.