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