dissection of the gluteal region. skin incisions 1.make a median vertical cut from the lower lumbar...
TRANSCRIPT
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.
AB
C
D
E
Superior cluneal nerves
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.
Middle cluneal nervesInferior cluneal
nerves
Gluteus maximus
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.
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.)
Iliotibial tract
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.
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
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 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.
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.
Piriform
is
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.
Pirifo
rmis
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.
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.
Ischial spine
Sacrospinous ligament
Sacrotuberous ligament
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.
Pudendal nerve
Sacrotuberous ligament
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
Quadratus femoris muscle
So, the obturator internus and the superior and
inferior gemelli occupy the space between the piriformis and the
quadratus femoris muscles.
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.
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.
Quadratus femoris inserts on the
trochanteric crest of the femur
Piriformis
Obturator Internus
Gemelli
And so what inserts here?
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.
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…
… 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.
Cut gluteus medius muscle