The psoas major and iliacus arise within the ab- domen and fuse with each other as they enter the thigh, posterior to the inguinal ligament [Fig. 13.14], the femoral nerve, and the lateral part of the femoral sheath. They are separated poster- iorly from the capsule of the hip joint by a bursa which may communicate with the joint cavity.
The muscles pass inferior to the neck of the femur and are inserted into the lesser trochanter (psoas) and the surface of the femur below it (iliacus).
CLINICAL APPLICATION 13.1 Femoral hernia In the erect position, the weight of the abdominal con-
tents presses down on the inguinal region. The femoral ring forms a point of weakness and may allow the en- try of a loop of intestine or other abdominal contents into the femoral canal. Such protrusion of abdominal contents into the thigh constitutes a femoral hernia. As the femoral ring is limited anteriorly by the inguinal liga- ment, any event which stretches the inguinal ligament enlarges the femoral ring. This could happen as a result of repeated pregnancies that weaken the abdominal muscles. Any other condition which chronically raises the intra-abdominal pressure, e.g. repeated coughing or straining, will also predispose to the development of such a hernia. Femoral hernias are more common in women.
When a loop of intestine enters the femoral ring, it car- ries the peritoneum covering of the abdominal opening of the canal in front of it. The peritoneum forms a her- nial sac which descends in the femoral canal and bulges forwards through the cribriform fascia into the superfi- cial fascia of the thigh. If the sac continues to enlarge, it expands superolaterally in the superficial fascia, so that
the entire hernia becomes U-shaped. This course of the hernia should be kept in mind when external pressure is applied in an attempt to return the hernial sac and its contents to the abdomen. The sac should first be pushed down and medially towards the saphenous opening, then through the cribriform fascia, and only then should an attempt be made to return it through the distended femoral canal.
As the hernial sac expands in the subcutaneous tis- sue, the margins of the femoral ring may constrict the neck of the sac. This tends to obstruct the passage of intestinal contents in the loop of gut and occlude the blood vessels to it. This could lead to strangulation of the hernia, possibly resulting in gangrene and rupture.
Surgical reduction of an obstructed or strangulated hernia commonly requires division of the lacunar lig- ament. Care should be taken in dividing the lacunar ligament, as an abnormal obturator artery may lie on it. When present, this abnormal artery arises from the inferior epigastric artery, instead of the internal iliac ar- tery, and commonly crosses the abdominal aspect of the lacunar ligament.
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Medial side of the thigh
CLINICAL APPLICATION 13.2 Deep tendon reflexes The patellar tendon reflex is a deep tendon reflex rou-
tinely done to test L. 3 and L. 4 segments of the spinal cord. The patient sits at the edge of the examination ta- ble, with his legs hanging freely. The physician strikes the patellar tendon sharply with a reflex hammer. This causes the leg to extend at the knee. Mostly, the response is evaluated visually by watching for the extension of the knee. The contraction of the quadriceps muscle can be evaluated by palpation as well.
The impact of the reflex hammer stretches the patel- lar tendon. This triggers sensory nerves that innervate the quadriceps to send information from the tendon to the spinal cord—segments L. 3 and L. 4. In the spinal cord, small internuncial neurons are activated which, in turn, stimulate the motor neurons supplying the quadriceps.
This leads to contraction of the quadriceps and extension of the knee
Some important points about the deep tendon re- flexes are:
1. Sensory fibres relaying the stimulus to the spinal cord form the afferent limb of the reflex arc (see the black somatic efferent fibre in Fig. 1.5).
2. The motor fibres supplying the quadriceps form the ef- ferent limb (see the blue somatic afferent fibre in Fig. 1.5).
3. Deep tendon reflexes are withdrawal reflexes involv- ing the spinal cord (no involvement from the higher centres).
4. Both afferent and efferent nerves have to be intact for the reflex action to occur.
5. Abnormal reflexes include reflexes that are lost, dimin- ished, or heightened (of increased power and/or speed).
6. Responses are graded using standard criteria.
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Dissection 14.1 looks at the cutaneous nerves in the gluteal region.
Superficial fascia
This is dense and contains a lot of fat, especially at the upper and lower margins of the gluteus maximus.
Cutaneous nerves
These reach the gluteal region from all four direc- tions—above, below, laterally, and medially.
1. From above: the lateral cutaneous branches of the subcostal (T. 12) and iliohypogastric (L. 1) nerves pass downwards, anterior and posterior to the tubercle of the iliac crest. They supply the skin down to the level of the greater trochanter.
2. From below: branches of the posterior cutane- ous nerve of the thigh curve over the lower border of the gluteus maximus to the posteroinfe- rior part of the gluteal region.
3. From the lateral side: the posterior branch of the lateral cutaneous nerve of the thigh (L. 2, 3) supplies the anteroinferior part.
4. From the medial side: cutaneous branches of the dorsal rami of L. 1–3, S. 1–3 and the perforat- ing cutaneous nerve (S. 2, 3 ventral rami) sup- ply the medial and intermediate part. The lumbar nerves are long and descend obliquely across the region almost to the gluteal fold. The sacral branch- es are short. The perforating cutaneous nerve
Surface anatomy
The gluteal region is bound by the iliac crest su- periorly, the gluteal fold of the round buttock inferiorly, a line joining the anterior superior iliac spine to the front of the greater trochanter later- ally, and the natal cleft between the buttocks medially [Fig. 14.1]. The horizontal gluteal fold is due to adherence of the skin to the deep fascia over the gluteus maximus, the large buttock muscle [Fig. 14.2]. Deep to the lower part of this muscle is the ischial tuberosity [Fig. 14.1]. This can be felt by pressing your fingers upwards into the medial part of the gluteal fold but is most easily identified as the rounded bony mass on which you sit.
The natal cleft begins near the third sacral spine.
The lower part of the sacrum and the coccyx are in its floor. Palpate your own sacrum and coccyx.
The coccyx can be identified by its relative mo- bility. Between the lower part of the sacrum and the ischial tuberosity, a deep resistance can be felt through the posterior part of the gluteus maximus.
This is the sacrotuberous ligament. It holds the lower part of the sacrum and prevents the upper part from being pushed down by the weight of the body.
Trace your iliac crest forwards to the anterior superior iliac spine and backwards to the poste- rior superior iliac spine. The posterior superior iliac spine lies in a skin dimple at the level of the second sacral spine. The posterior surface of the sacrum lies between the right and left posterior su- perior iliac spines.
CHAPTER 14
The gluteal region
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The gluteal region
pierces the sacrotuberous ligament and the gluteus maximus midway between the coccyx and the ischial tuberosity [Fig. 14.2].
Deep fascia
The deep fascia is thick over the anterior border of the gluteus maximus where the iliotibial tract splits to enclose the muscle. Everywhere else, the fascia is thin over the muscle and thick deep to it.
Dissection 14.2 looks at the gluteus maximus.
Mastoid process Clavicle
3 2
1 4
5 Acromion
Inferior angle of scapula
Medial epicondyle Head of radius Posterior superior iliac spine
Greater trochanter Styloid process of ulna Styloid process of radius
6
7 Head of fibula
Medial malleolus Lateral malleolus
Medial condyle of femur Ischial tuberosity Coccyx Spine of 4th lumbar vertebra
Olecranon 12th rib 7th rib
Spine of 3rd thoracic vertebra
Spine of 7th cervical vertebra
Spine of 2nd cervical vertebra External occipital protuberance
Fig. 14.1 Landmarks and incisions.
DISSECTION 14.1 Skin reflection and cutaneous nerves-1
Objective
I. To reflect the skin and identify the cutaneous nerves.
Instructions
1. Make skin incisions 5 and 6 [Fig. 14.1]. Reflect the flap of skin and superficial fascia laterally.
2. Attempt to find the cutaneous nerves of the glu- teal region. They are difficult to find because of the density of the superficial fascia, but it is usu- ally possible to identify the branches of the lumbar nerves [Fig. 14.2].
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Structures deep to the gluteus maximus