Gluteal+Region+and+Posterior+Thigh+-+Lecture+Notes

=**Objectives**=toc

Gluteal Region and Posterior Thigh

=**Lecture Notes**=

[|Lecture 1]



**Lecture 1**
Gluteal region extends from the iliac crest to the transverse gluteal crease/fold. The dermis of the skin at the gluteal fold is adherent to the deep fascia. Cleft between the two buttocks are the natal cleft, which separates the right and left gluteal regions on the midline.

Obturator foramen, closed by the obturator membrane and covered by obturator externis and internis. The acetabulum receives the head of the femur.

Hip bone composed of the ileum, ischium and pubis. The fusion of the bones are completed by the mid 20’s.

Femur has a head that fits into the acetabulum. The neck connects the head to the shaft. The distal end is expanded by medial and lateral condyle where it meets the knee. At the proximal limb of the shaft, is the greater trochanter anteriorly, and the lesser trochanter posteriorly.

Distance of the head of the 2 femurs are usually greater in the female because of the greater width of the female hips. Distally, the femurs angle medially when in anatomical position. This angle is called the angle of inclination, and is caused by the angle between the head and the neck and is usually between 115-140 degrees. These dimensions vary with sex, age, individual and can change. Greater than 140 degrees (example: 160 degrees) is called coxa valgus or bow-legged situaton; less than 115 degrees (example: 90 degrees) is called coxa varus. The oscoxa is a synonym for the hip, hence “coxa” meaning regarding the hip; do not confused with genu valgus and varus (knee).

The intertrochanter line is a line of bone that runs between anteriorly between the greater and lesser trochanter. Posteriorly, there is another line of bone called the intertrochanter crest. There is a roughened area on the posterior side called the gluteal tuberocity. Additionally, there is a linear ridge on the posterior side called the linea aspera, which splits into the two supracondylar ridges as it approaches the distal end. The linea aspera and the supracondylar are attachments of the intramuscular septae. The two supercondylar ridges created a triangular region called the popliteal surface.

Dermatomes of the posterior and gluteal region are S1 and S2, and S5 laterally. The posterior cutaneous nerve of the thigh innervates the S1 and S2 dermatomes and has the widest cutaneous innervation of the skin in the body.

Posterior thigh has many small veins and nerves in the superficial fascia but no major nerves/veins.

The deep fasica of the thigh and gluteal region is called the fascia lata. The deep fasia has a thickened part of laterally running fascia called the iliotibial tract/band. Attaches the crest of the ileum and runs through the medial thigh, crossing the knee joint, attaching to the tibula. The major part (3/4) of the gluteus maximus insert into the iliotibial tract to affect the hip joint. From the ASIS, the tensor fascia lata muscle attaches to the iliotibial tract, putting tension on the iliotibial tract on the fascia lata. The tensor fascia lata is actually embedded in the iliotibial tract. Because it crosses the knee joint, the tensor fascia lata helps maintain stability during full knee extension.

Gluteus maximus attaches from the ileum, sacrum, sacral tuberous ligament. The fibers pass laterally. Upper 3/4 insert into the iliotibial tract. The lower 1/4 attaches to the posterior femur at the gluteal tuberocity at the proximal part of the femur. Gluteus maximus does not take origin from all of the iliac surface; there is a portion of the ileum that is not covered by gluteus maximus. That is still covered by fascia lata, exposing the gluteus medius muscle and its fascia. This is important for gluteal injections -- aim for the carefree region high near the crest of the ileum because there are not large nerves or vessels in that area (the sciatic nerve is in the gluteus maximus).

The hip can extend, flex, abduct, adduct, lateral and medial rotation. Gluteus maximus only used for powerful hip extension (rising from seated positon, climbing stairs, running but //not// walking on a flat surface).

Most of gluteus medius is usually covered by gluteus maximus. The gluteus medius originates at the ileum, descending and attaching to the greater trochanter of the femur. Gluteus minimus is the third and deepest muscles and completely buried by gluteus medius. Gluteus minimus originates at the ileum and attaches at the greater trochanter just like gluteus medius.

Gluteus medius and minimus are important for abduction of the hip joints when the limb is not bearing weight. These muscles are essential for normal walking and abduction is not part of a normal gait. When the weight is shifted to one side of the lower limb and begins to bear weight, on the weight bearing side, gluteus medius and minimus contract, fixing the hip and tip the hip slightly; this shifts the hip on the non-weight bearing side upwards, freeing the non-weight bearing limb to swing freely. If gluteus medius and minimus are paralyzed, the pelvis cannot shift so the leg would drag on the floor; to compensate, the leg is swung out to the side to avoid dragging the leg. Trendalenburg sign is the inability to shift/stabilize the pelvis on one side due to paralysis of gluteus medius and minimus (if you ask the patient to stand on one leg, they can’t stabilize and will fall).

Group of six small muscles that laterally rotate the hip joint: piriformus, superior gemellus, inferior gemellus, obturator internus tendon, obturator externus, and quadratus femoris. The keystone muscle is the piriformus, attaching to the pelvic side of the sacrum and the greater trochanter. The superior gluteal artery goes the gluteal region superor to the piriformus. The superior gluteal nerve innerves gluteus medius and minimus, and tensor fascia lata. The inferior gluteal nerve and vessels comes out inferior to the piriformus. Gluteus maximus is innervated by only the inferior gluteal nerve. Most of the gluteal maximus muscle blood supplies form the inferior gluteal artery (some form superior gluteal artery). The sciatic nerve and pudendal nerve are also inferior to piriformis, exiting the greater sciatic foramen. The posterior cutaneous nerve runs parallel with the sciatic nerve and comes out of the greater sciatic foramen.

Inferior to piriformus is the superior gemellus muscle originating from the ischial spine to the greater trochanter. There is an inferior gemellus muscle also originating on the ischial tuberocity and inserting to the greater trochanter. The superior and inferior gemellus muscles are superior and inferior to the tendon of obturator internus; most of the muscle body of the obturator internus is facing the pelvis, lining the inside of the obturator membrane. Very commonly, the superior and inferior gemellus will attach to the obturator internus and then all attach to the greater trochanter

The obturator internus tendon comes through the lesser sciatic foramen, attaching to the greater trochanter. The piriformus goes through the greater sciatic formation.

Quadratus femoris is attached to the ischial tuberocity and inserts to the intertrochanteric crest. Behind the quadratus femoris, the obturator externus is on the external surface of the obturator membrane, out in the lower limb, and attaches to the greater trocantor of the femur.

Nerve supply are small nerves from the sacral plexus except for obturator externis (name of nerves are all “nerve to…”). Obturator externis is innervated by the obturator nerve (L2-4) as it goes down towards the medial thigh. Blood supply are from the inferior gluteal arteries.

Thigh is like the arm in that there are compartment of muscles separated by deep fascia. The lateral fasica is thicker (fascia lata). The deep fascia separate the thigh into an anterior (extensor), posterior (flexor), and medial (adductor) compartments. The actions of these muscles refer to the hip joint.

Anterior and medial compartment have a major artery, vein, and nerve. However, there is no large major vessels in the posterior compartment, other than the sciatic nerve.

Proximal part of posterior thigh muscles covered by gluteus maximus. Gluteus maximus draps over the ischiotuberocity. When seated, the gluteus maximus rises, exposing the ischiotuberocity and making it subcutanoues.

The muscles of the posterior compartment of the thigh mostly originate from the ischial tuberocity (except one) and are collectively known as the hamstring muscles.

Removing gluteus maximus, the ischiotuberocity is exposed, and the common origin for most of the hamstring muscles are exposed. As the hamstring muscles go distally, one goes laterally, while the rest stay medial. The long head of the biceps femoris attaches to ischiotuberocity, descends the length of the posterior thigh, passing laterally to the knee joint and attaches to the fibula. The other two muscles of the hamstring group are called the semimembranosis, and semitendonosis muscles and stay medially and cross medially, inserting to the tibia. They are typically wrapped around each other. The tendon of the semimembranosis is flat and membranous; the tendon of the semitendonosis is cord-like.

Long head of biceps femoris, semimembranosis, and semitendonosis cross the hip and knee joint; The action on the knee joint is flexion; the action on the hip is extension during walking on a flat surface.

The sciatic nerve is really the tibial nerve and common fibular nerve wrapped together in a common CT sheath. About 12-15%, there is no sciatic nerve.

The short head of the biceps femoris is distally, taking the origin off the linea aspinea off the shaft of the femur to unite with the long head, inserting on the fibula. Short head of the biceps femoris is //not// a hamstring muscle. To qualify as a hamstring, it must have origin from the ischiotuberocity and the be innerated by the tibial nerve portion of the sciatic nerve. The short head of the bisceps is innervated by the common fibular nerve portion of the sciatic nerve.

As the sciatic nerve descends to the posterior thigh, it gives off branches to the hamstring. Once it reaches the popliteal surface, it bifercates into the common fibular nerve (lateral across the knee joint) and the tibial (medial) nerve.

Hamstring muscles demonstrate how a muscle cannot act efficently at the same time; the range is less and strength is less if you extend your hip and then try to flex the knee or vice versa. This is because the hamstring muscle has already contracted and can’t contract much more. This is called active insufficiency. It is also difficult to do a high kick (flex hip), and keep the knee fully extended – this is passive insufficency. That is, it can’t stretch enough to allow maximum movement and is more likely related with the connective tissue restricting the movement of the muscle.

Blood supply to the posterior compartment comes from branches of the deep artery of the thigh (profunda femoris) which actually lies in the medial compartment.