Anatomy Made Easy “MSS” ‫ الى‬12 ‫هذا الملف يشمل تفريغ المحاضرة‬ 13 ‫صفحة‬

part (elbow)

Done By :AWN Academic Team

ELBOW JOINT Synovial Hinge Joint Articulation 

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Trochlea(me dially) and capitulum(la terally, which acts with the head of the radius) Trochlear notch of ulna and the head of radius below which form the U/L shape.

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Elbow joint is the Synovial Hinge Joint that occurs between the lower extremity of the humerus and the upper extremity of both forearm bones; radius and ulna.

ELBOW JOINT 

The articular surfaces are covered with articular (hyaline) cartilage.

the joint articular surfaces are found in: 

The capitulum and trochlea of the humerus "above".

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The head of the radius "below" **notice that:  the head of the radius and the radial notch on ulna are covered with hyaline cartilage  Also,there is an “annular” ligament that covers the head of radius and goes to the radial notch on ulna to help in pronation and supination by this “radio-ulnar” joint.

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Trochlear notch "below“, that is between the two processes of the upper extremity of the ulna. **Note that :  this hyaline cartilage is similar to any hyaline cartilage in other parts of the body.

CAPSULE Anteriorly: attached  Above  To the humerus along the upper margins of the coronoid and radial fossae and to the front of the medial and lateral epicondyles (epicondyles are not parts of the capsule).  Below  To the margin of the coronoid process of the ulna and to the annular ligament, which surrounds the head of the radius.

CAPSULE Posteriorly: attached  Above  To the margins of the olecranon fossa of the humerus.  Below  To the upper margin and sides of the olecranon process of the ulna and to the anular ligament. (the olecranon is not a part)

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Note from posterior view the articuler surfaces of ulna, humerus and the head of radius.

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You can notice that the medial and lateral epicondyles are not parts of the capsule, because they form attachments for muscles

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the capsule is very tough and tight laterally and it is loose anteriorly and posteriorly, and that will allow the flexion and extension to occur. And there are certain things which are found within the cubital fossa and within this joint that prevent the hyper flexion of this bone.

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the capsule is loose posteriorly and it will permit the complete extension the hyper extension is prevented by : the olecranon process + the capsule + biceps tendon (insertion) + biceptel aponurosis (a band at the insertion of the biceps brachii that goes to the ulna, it covers and enforce the anterior aspect of the capsule of this joint.). If you let your hand and the forearm extend onto the arm and you feel your joint posteriorly, you will be able to notice that there is an amount of fat and skin, and the skin has the capsule attached to it.

The posterior of the capsule is less stretched than the anterior.  The anterior is wider that gives flexibility to the joint anteriorly but limits the flexibility posteriorly. 

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the articular cartilage is attached to the border of olecranon fossa

LIGAMENTS Lateral (Radial Collateral) Ligament Triangular in shape:  Apex  Attached to the lateral epicondyle of humerus  Base  Attached to the upper margin of annular ligament. 

LIGAMENTS Medial (Ulnar Collateral Ligament)  Anterior (medial) strong cord-like band:  Between medial epicondyle and the coronoid process of ulna  Posterior (lateral) weaker fan-like band:  Between medial epicondyle and the olecranon process of ulna  Transverse band:  Passes between the anterior and posterior bands and it will hold and cover most of the capsule that is around the olecranon fossa of the ulna.

SYNOVIAL MEMBRANE 

This lines the capsule and covers fatty pads in the floors of the coronoid, radial, and olecranon fossae.

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Is continuous below with synovial membrane of the superior radio-ulnar joint

Synovial Membrane 

It is a membrane that follows the entire capsule and covers most of joint, leaving it sterile and it doesn’t allow any thing to go in there. It exactly follows the inner aspect of the capsule (anteriorly and posteriorly), except that in the posterior -where the capsule is loose- this will form a bag.

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the posterior fat pad is bigger and has more specific role than the anterior one.

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There are fat pads between synovial membrane and the capsule to prevent erosion and friction, and this is useful when putting you elbow on the table :3

RELATIONS Bursae around the elbow joint: 1- Subcutaneous olecranon bursa: between the lateral (collateral) ligament and the insertion as well as between the origin of these extensor muscles and the bones. This bursa prevents the extensor muscle form friction over the posterior aspect of the ulna; * because the ulna is bigger posteriorly, so that it needs more potential.

2- Subtendinous olecranon bursa  which is a continuation , and it is between the origin of the extensors

Relations of the elbow Joint 

Anterior:  Brachialis and biceps brachii ( they both provide protection to the capsule anteriorly)  Tendon of Biceps

 Median nerve  Brachial artery 

Posterior:  Triceps muscle  Small bursa intervening Triceps muscle and the subcutaneous fat and the bursa will hold the friction and enforce the loose capsule posteriorly even though the muscle insertion is tough, but still we have this olecranon bursa that prevent the friction between the tendon of the insertion of the triceps and the posterior olecranon surface

Lateral: Common extensor tendon The supinator Medial: Ulnar nerve The clinical aspect of the ulnar nerve is very important, for palpatation; you go into the lateral aspect and the groove there,immediately under the medial epicondyle. E.g : as when we hit our hand and feel electricity goes into the forearm and hand. **The radial nerve is the most dangerous and exposable part of the brachial plexus and it is the only thing that is weak in the elbow joint.

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The presence of the Brachialis enforces the joint laterally, where the biceps brachii enforces the capsule anteriorly and prevents the hyper flexion.

MOVEMENTS  Flexion

Is limited by the anterior surfaces of the forearm and arm coming into contact.  Extension Is limited by the tension of the anterior ligament and the brachialis muscle which prevents the hyper extension.  The

joint is supplied branches from the:

Median Ulnar Musculocutaneous

by

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The flexion is made by → the brachialis and biceps brachii

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The extension is made by → the triceps brachii

CARRYING ANGLE  Angle

 Between the long axis of the extended forearm and the long axis of the arm  Opens  Laterally  About  170 degrees in male and 167 degrees in females  Disappears  When the elbow joint is flexed

1650-1700

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This carrying angle is very important in radiology by measuring it.

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Some people have larger carrying angle which is abnormal situation and it might be deformity.

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Holding a child from his hands upward is totally wrong, because that will increase the angle and what will happen is that the dislocation of the radius help more because it is laterally more open , so the dislocation of the head of the radius that occurs at that level will allow the angle to be bigger, and you will see the hand of the child after he was injured goes with the carrying angle which is widely opened in the lateral aspect.

ARTICULATIONS  The

elbow joint is stable because of the:  Wrench-shaped articular surface of the olecranon and the pulley-shaped trochlea of the humerus  Strong medial and lateral ligaments.  Elbow dislocations are common & most are posterior.  Posterior dislocation usually follows falling on the outstretched hand.  Posterior dislocations of the joint are common in children because the parts of the bones that stabilize the joint are incompletely developed.

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Elbow dislocations are common & most are posterior because the anterior aspect of the joint is having the coronoid process that might slip posteriorly and the olecranon can be fractured, and when it is fractured the dislocation occurs posteriorly.

ELBOW JOINT  Avulsion

of the epiphysis of the medial epicondyle is also common in childhood

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In bones, there is a line which is the Epiphyseal plate (in the metaphysis) → it is a line that connects between the epiphysis and the diaphysis

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This Epiphyseal plate is a layer of hyaline cartilage that provides elongation of the bone, and will disapperar after age of 17

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When there is a fracture in the bone, you have to look for the epiphysial line, because this line extends from the upper part of the lateral epiphysis to the upper part of the medial epiphysis. So when the bone is broken; it will be broken at the weakest part which is in the Epiphyseal line. So the breakage of the lower end of the humerus occurs at the level of the epiphysis.

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The lower fracture will happen at the level of the epicondyle lateral and medial and in the lower of the Epiphyseal line that is weak at this part and there is no bony structures.