Module 9 The Extremities

The Wrist

includes the distal radius and ulna, 8 carpal bones and the proximal portions of the 5 metacarpals.

The Elbow

is a complex joint with 3 articulations involving the humerus, radius and ulna. The humeroulnar articulation consists of the trochlea of the humerus and the trochlear notch of the ulna. This hinge-type joint permits flexion and extension. The humeroradial articulation occurs where the capitulum of the humerus meets the head of the radius. This unstable joint allows for hinge-like flexion and extension, as well as rotation and pivoting. The proximal radioulnar articulation includes the head of the radius and the sigmoid notch of the ulna. This joint allows the radial head to rotate during supination and pronation of the forearm. The relationship of the elbow's bony structures varies over the range of motion. The bones are in their most stable position with the elbow in about 90 degrees flexion and midway between supination and pronation. The entire elbow joint is surrounded by a synovium-lined joint capsule. The fibrous capsule encloses the anterior and posterior fat pads, which are extrasynovial and intracapsular.

Teres Minor

is a flat muscle that acts in opposition to the subscapularis. It originates from the posterior superior border of the scapula and inserts on the lower aspect of the greater tubercle of the humerus.

Subscapularis

is a flat muscle that forms the anterior aspect of the rotator cuff. It originates from the subscapular fossa on the anterior aspect of the scapula. The subscapularis inserts on the lesser tuberosity of the humerus.

Trapezius

is a large, flat muscle that covers the upper back and shoulders and suspends the shoulder complex from the base of the skull.

Clavicle

is a linear bone that runs horizontally in the coronal plane. It articulates medially with the sternum to form the sternoclavicular joint and laterally with the acromion to form the acromioclavicular joint.

Ultrasonography of the Joints

is a noninvasive way to evaluate joints that is faster than MR and unlike CT and radiography does not involve exposure to ionizing radiation. Ultrasound usage is mostly confined to evaluating the integrity of ligaments and other muscular structures of the joint. It also can be used to detect pathology such as synovial proliferation, hematomas and abscess formation.

Supraspinatus

is a portion of the rotator cuff that lies draped over the superior aspect of the humeral head. It originates from the supraspinatus fossa of the scapula and inserts on the upper aspect of the greater tubercle of the humerus.

Scapula

is a triangular-shaped flat bone on the posterior aspect of the shoulder girdle. Scapular landmarks include the scapular spine, acromion process, coracoid process and glenoid fossa. The glenoid fossa is a shallow, oval-shaped recess in the scapula that articulates with the humeral head to form the glenohumeral joint. A fibrocartilaginous ring called the labrum surrounds the rim of the glenoid, making the cavity deeper and broader so that the humeral head can fit more securely into the socket.

The Ankle

is made up of 3 bones: the tibia, the fibula and the talus. The malleoli of these bones are located medially and laterally. The medial malleolus is a bony outgrowth of the distal tibia; the lateral malleolus projects from the distal fibula. The malleoli articulate with the medial and lateral portions of the talus and are responsible in part for stabilizing the ankle.

Humerus

is the long bone of the upper arm. Proximally, the head of the humerus articulates with the glenoid fossa, a depression in the scapula. Distally, the humerus forms a hinge joint with the ulna. Important landmarks of the humerus include the greater tubercle, lesser tubercle, bicipital groove, anatomic neck and surgical neck.

Glenohumeral Joint

is the main shoulder joint. It is a complex, unstable synovial joint capable of a wide range of motion and is formed where the hemispherical portion of the humeral head fits into the glenoid fossa. Like other major joints, the glenohumeral joint is enclosed by a fibrous capsule that connects the humerus to the glenoid. The ligaments of the joint capsule provide the main source of stability for the shoulder to prevent dislocation. The articulating portions of the humeral head and the glenoid fossa are protected by articular cartilage. Articular cartilage has a rubbery, slippery surface that absorbs shock and makes motion easier. In addition to the joint capsule, the glenohumeral joint is stabilized superiorly by the coracoacromial arch and posteriorly by the infraspinatus tendon, teres minor tendon, posterior labrum and inferior glenohumeral ligament. Anteriorly, it is supported by the subscapularis tendon, anterior labrum and the superior, middle and inferior glenohumeral ligaments.

Ligamentum Teres

is the sole intracapsular ligament. It is a triangular-shaped ligament that attaches to the fovea capitis femoris of the femoral head. The other 2 points of attachment are each side of the acetabular notch. The ligamentum teres limits adduction of the hip.

Deltoid

is the strongest muscle of the shoulder. It forms a cap over the humeral head, producing the outer, rounded contour of the shoulder. The deltoid is divided into 3 parts, each with a different origin.

Posterior Ankle Muscle Group

made up of 6 muscles. The gastrocnemius muscle originates from the posterior borders of the medial and lateral femoral condyles and extends inferiorly before inserting on the posterior surface of the calcaneus via the largest tendon in the body, the Achilles tendon. The gastrocnemius is responsible for plantar flexion of the ankle. The soleus and plantaris muscles also assist in plantar flexion of the ankle. The plantaris muscle is absent in a small percentage of the human population. The tibialis posterior aids in plantar flexion of the ankle and inversion of the foot. The flexor digitorum longus is responsible for flexion of the second through fifth toes, plantar flexion of the ankle and inversion of the foot. Finally, the flexor hallicus longus muscle is responsible for flexion of the first digit, plantar flexion of the ankle and inversion of the foot. The medial muscle group includes the tendons of the posterior tibialis, flexor hallucis longus and flexor digitorum longus muscles. These tendons cross in the area of the medial malleolus en route to their insertion points on the foot. this animation to see the posterior and medial muscle groups of the ankle that we just discussed.

Quadriceps Femoris Muscle Group

makes up the majority of the anterior thigh. The group consists of 4 muscles sharing an insertion point on the tibial tuberosity via the patellar ligament. The rectus femoris is responsible for the flexion of the hip and extension of the knee. The vastus lateralis, vastus intermedius and vastus medialis act to extend the knee.

Teres Major

originates from the inferior third of the dorsal lateral border of the scapula and inserts on the medial wall of the bicipital groove. The teres major acts to medially rotate and adduct the arm.

Major Bursae of the Shoulder

A bursa is a synovial sac filled with fluid that helps cushion the joint and alleviate friction. There are 3 major bursae in the shoulder: the subacromial-subdeltoid, the subcoracoid and the infraspinatus. The subacromial-subdeltoid bursa overlies the rotator cuff on the undersurface of the acromion. In its normal state, this bursa should have only a trace amount of fluid. The subcoracoid bursa lies between the tendon of the subscapularis and the short head of the biceps and coracobrachialis tendons. Although the subcoracoid bursa can communicate with the subacromial-subdeltoid bursa, it does not normally communicate with the joint.

Shoulder Muscles

A group of 4 intrinsic muscles surround the humeral head and constitute the rotator cuff: the subscapularis, supraspinatus, infraspinatus and teres minor. These muscles help raise the arm and rotate it in many directions. The tendons of the rotator cuff form a continuous sheath that attaches to the humerus.

Pronator Teres and Pronator Quadratus

As their names suggest, the pronator teres and the pronator quadratus muscles are involved in pronation. Supination is accomplished by the biceps brachii and supinator muscles. The supinator muscle originates from the lateral epicondyle of the humerus as well as the supinator crest of the ulna. It inserts on the lateral aspect of the proximal diaphysis of the radius and acts to supinate the forearm.

Bony Structures of the Wrist

From radius to ulna, the proximal carpal row includes the scaphoid, the lunate, the triquetrum and the pisiform. The distal carpal row comprises the trapezium, the trapezoid, the capitate and the hamate.

The Proximal Femur

Important landmarks of the femur include the femoral head, greater trochanter and lesser trochanter. The ball-shaped femoral head is the most superior portion of the bone. The fovea capitis femoris is the attachment point for the ligamentum teres. The neck of the femur extends inferolaterally from the femoral head and connects the femoral head to the longitudinally oriented femoral shaft. Two bony processes arise from the base of the femoral neck: the greater trochanter and the lesser trochanter. The greater trochanter arises from the lateral border of the femoral neck and extends slightly superiorly, laterally and posteriorly. The greater trochanter serves as the attachment point for tendons of some of the large muscles of the pelvis. The lesser trochanter arises from the medial border of the base of the femoral neck and extends slightly posteriorly and also serves as the attachment point for tendons.

Ulna and Radius

Its proximal landmarks include the olecranon and coronoid processes and the trochlear notch. The olecranon process is a hook-shaped projection that makes up the bony tip of the elbow. Its anterior surface forms the trochlear notch, a roughly hemi-cylindrical groove that holds the trochlea of the humerus. This articulation is located on the posterior aspect of the elbow with the trochlear notch directed anteriorly. The coronoid process is a triangular-shaped protuberance that extends from the anterior aspect of the proximal ulna and forms an extension of the distal wall of the trochlear notch. This structure provides increased stability for the elbow joint when the elbow is in full extension. The radius is located laterally within the forearm. The radial head is the proximal epiphysis of the radius bone. It is covered with articular cartilage and is shaped roughly like the head of a hammer. The radial head contains a bowl-shaped depression known as the fovea into which the capitulum of the humerus can articulate and rotate. The neck of the radius is a narrowing of the proximal radius just beyond the radial head and proximal to the radial tuberosity. The radial tuberosity is a ridge-like protuberance from the ulnar aspect of the proximal radius just distal to the radial neck.

Sartorius

Known as the longest muscle in the body, it originates from the anterior superior iliac spine and extends inferiorly and medially across the anterior thigh until it reaches the medial knee area. The sartorius plays a role in flexing, adducting, abducting and laterally rotating the hip, as well as flexing the knee.

Humerus

Landmarks for the distal humerus include the medial and lateral epicondyles, olecranon fossa, trochlea and capitulum. The medial epicondyle is located on the ulnar aspect of the humerus and serves as an attachment point for the common flexor tendon that flexes the wrist. The lateral epicondyle is located on the radial aspect of the humerus and provides an attachment site for the common extensor tendon that extends the wrist. The olecranon fossa is a shallow, bowl-shaped area that allows the olecranon process of the ulna to pivot anteriorly without impacting the humerus during elbow extension. It also stabilizes the elbow from medial or lateral translocation of the ulna and humerus. The capitulum is the radial aspect of the humeral epiphysis that articulates with the radial head. The trochlea is the semicylindrical ulnar aspect of the distal humeral epiphysis that articulates with the proximal ulna in the trochlear notch. Both the capitulum and trochlea are covered with articular cartilage.

Muscles of the Elbow

Muscles involved in flexion of the elbow include the brachialis, biceps brachii, pronator teres and brachioradialis muscles. The brachioradialis muscle originates from the lateral supracondylar ridge of the humerus and inserts on the lateral aspect of the distal radius. The triceps and anconeus muscles provide elbow extension. The triceps muscle is the largest muscle in the upper arm and originates from multiple attachments in the shoulder and proximal humerus. It inserts on the olecranon process.

Veins of the Elbow

The 2 important veins at the level of the elbow are the cephalic and the basilic veins. The cephalic vein lies on the lateral aspect of the biceps while the basilic vein lies medial to the biceps.

Arteries of the Elbow

The brachial artery is the continuation of the axillary artery and is the main source of blood supply to the arm. Located in the cubital fossa, the artery runs with the median nerve medial to the biceps tendon

Vessels of the Leg

The deoxygenated blood of the lower extremities is returned via the common femoral vein. The common femoral vein receives blood from the greater saphenous, popliteal and deep femoral veins. The greater saphenous vein is the longest vein in the body and receives deoxygenated blood from many lower extremity vessels as it extends superiorly to meet the common femoral vein.

Cartilage and Ligaments of the Knee

The knee has 3 groups of major ligaments: the cruciate, collateral and patellar ligaments. The cruciate ligaments provide anterior and posterior stability for the knee. The collateral ligaments stabilize the medial and lateral sides of the knee. ©2014 ASRT. All rights reserved. Sectional Anatomy Essentials: Module 9

Lateral Ankle Muscle Group

The lateral muscle group is made up of 2 main muscles. The peroneus longus and the peroneus brevis are both responsible for plantar flexion of the ankle and eversion of the foot.

Anterior Ankle Muscle Group

The tibialis anterior is responsible for dorsiflexion of the ankle and inversion of the foot. The extensor hallucis longus muscle is involved in dorsiflexion of the ankle and extension of the first digit. The extensor digitorum longus muscle aids in dorsiflexion of the ankle, eversion of the foot and extension of the second through fourth digits. Finally, the peroneous tertius muscle is responsible for dorsiflexion of the ankle and eversion of the foot.

Nerves of the Shoulder

The upper extremity is innervated by the brachial plexus, which is formed in the posterior triangle of the neck from the anterior rami of the fifth through eighth cervical nerves and the first thoracic spinal nerve. The brachial plexus is divided into 5 roots, 3 trunks, 6 divisions and 3 cords, which are successively smaller and more specific units.

Latissimus Dorsi

This flat triangular muscle is located over the lower thorax and extending into the lumbar region. It originates from the posterior aspect of the iliac crest, the lower 3 or 4 ribs and the spinous processes of T6 through T12, where it runs deep to the trapezius.

Acromioclavicular Joint

This synovial-lined joint is enclosed by a joint capsule and protected by articular cartilage. The coracoclavicular ligaments attach the clavicle to the scapula at the coracoid process.

Nerves of the Elbow

are the radial, median and ulnar. The radial nerve arises from the posterior cord of the brachial plexus and innervates the triceps, anconeus, brachioradialis. The median nerve originates from the medial and lateral cords of the brachial plexus. It innervates the pronator teres muscle, pronator quadratus muscles and portions of the flexor compartment on the anterior aspect of the forearm. The ulnar nerve arises from the medial cord of the brachial plexus and provides articular branches to the elbow joint.

The Acetabulum

bilateral concave cavities. Each is formed by the 3 bones of the pelvis: the ischium, the ilium and the pubis. The ischium makes up a little more than two-fifths of the acetabulum and forms the superior border of the structure. The ilium makes up a little less than two-fifths of the acetabulum and creates the posterior border and part of the middle. The pubis makes up about one-fifth of the acetabulum and forms the anterior border and a portion of the middle.

The Knee

consists of the distal femur, the proximal tibia and the patella.

The Carpal Tunnel

contains the flexor digitorum profundus, flexor digitorum superficialis, flexor pollicis longus and median nerve. It is bounded dorsally by the carpal bones, volarly by the flexor retinaculum, medially by the hook of the hamate and pisiform, laterally by the scaphoid and trapezium, proximally by the radiocarpal joint and distally by the bases of the metacarpal bones. The surrounding structures form a restricted space that can sometimes impinge on the median nerve and become clinically significant.