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.
D
B
E
A
C

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
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

Obturator
Internus
Gemelli
Piriformis
And so what inserts here?
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.

Cut gluteus medius muscle
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.