Elbow

Question 1

How many degrees of freedom does the Elbow have and how many joints?

Answer 1

1 degree of freedom with 1 hinge diarthrosis joint.

Question 2

Physiologically what are the function

Answer 2

Flexion-extension:involving the true elbow

Pronation-Supination (axial rotation): involving the superior radio-ulnar joint

Question 3

Joint Structure:

number of articular surfaces

Answer 3

2
The Trochleae
The Capitulum

Question 4

The Trochleae

Answer 4

pulley-shaped with a central groove lying in a sagittal plane and bounded by two convex lips.

Question 5

The Capitulum

Answer 5

a spherical surface lying lateral to the trochlea.

not a complete sphere but a hemisphere

Question 6

Immediately above the articular surfaces two concavities are present

Answer 6

Anteriorly, the coronoid fossa, which receives the coronoid process of the ulna during flexion.

Posteriorly, the olecranon fossa which receives the olecranon process during extension position.

Question 7

Purpose of the concavities Immediately above the articular surfaces

Answer 7

increase the range of flexion and extension at the elbow by delaying the moment of impact of the coronoid and olecranon processes on the shaft of the humerus.

They also allow the trochlear notch of the ulna, which has a range of movement of 180°, to glide over the trochlear for an appreciable distance on either side of the neutral position.

Question 8

The proximal ends of the two bones of the forearm

Two surfaces corresponding to those of the humerus

Answer 8

• The cupped proximal surface of the head of the radius

* The trochlear notch of the ulna

Question 9

The cupped proximal surface of the head of the radius:

Answer 9

• Concavity corresponding to the convexity of the capitulum humeri
• It is bounded by a rim which articulates with the capitulo-trochlear groove.

Question 10

The trochlear notch of the ulna:

Answer 10

• It articulates with the trochlea and has the corresponding shape.
• It consists of a longitudinal rounded ridge extending from the olecranon process superiorly, to the coronoid process anteriorly and inferiorly.
• On either side of this ridge, which corresponds to the trochlear groove, is a concave surface corresponding to the lips of the trochlea.
• The articular surface is shaped like one unit of a corrugated iron sheet, formed by a ridge and two gutters.

Question 11

The articular relations of the head of the radius in extreme positions:

Answer 11

• In full extension only the anterior half of the proximal surface of the radial head articulates with the
capitulum.

• In full flexion the rim of the radial head reaches beyond the capitulum and enters the radial fossa, which is much less deep than the coronoid fossa.

Question 12

The distal end of the humerus

Answer 12

It bulges anteriorly at an angle of 45° to the shaft so that the trochlea lies in front of the axis of the shaft.

Question 13

The proximal end of the ulna

Answer 13

The trochlear notch of the ulna projects anteriorly and superiorly at an angle of 45° to the ulnar shaft and so lies in front of the axis of the ulna.

Question 14

Basic Tendon & Ligaments

Answer 14

There are both lateral and medial ligaments. The function of these ligaments is to keep the articular surfaces in apposition. They act as two stays located on either side of the joint.

Question 15

The medial ligament consists of three parts

Answer 15

• The anterior fibres, some of which strengthen the annular ligament.
• The intermediate fibres, being the most powerful.
• The posterior fibres or the ligament of Bardinet, strengthened by the transverse fibres of Cooper’s liga-ment.

Question 16

The lateral ligament also consists of three parts:

Answer 16

• The anteriorfibres, which strengthen the annular ligament posteriorly.
• The intermediate fibres, which strengthen the annular ligament posteriorly.
• The posterior fibres

Question 17

The capsule

Answer 17

It is strengthened anteriorly by the anterior ligament and the oblique anterior ligament.
Posteriorly by the fibres of the posterior ligament, which run transversely across the humerus and obliquely from humerus to olecranon.

Question 18

Flexor muscles of the elbow

Answer 18

There are three primary flexor muscles: 
•	Brachialis
•	Brachio-radialis
•	Biceps brachii
Accessory flexor muscles:
•	Extensor carpi radialis longus 
•	Pronator teres

The flexor muscles work at their best advantage when the elbow is flexed at 90°

Question 19

Brachialis

Answer 19

From: the anterior aspect of the lower half of the humerus

To: the tuberosity of the ulna.

Function:Flexor of the elbow.

Question 20

Brachio-radialis

Answer 20

From: the lateral supracondylar ridge of the humerus

To: the styloid process of the radius

Function: Flexor of the elbow, Supinator only in extreme pronation, Pronator in extreme supination

flexion angle of maximum efficiency lies between 100°and 110

Question 21

Biceps brachii

Answer 21

Long head from: the supraglenoid tubercle
Short head from: the coracoid process

Both to: the radial tuberosity

Function: Main flexor of the elbow, Supinator, Keeps the articular surfaces of the shoulder in apposition.

flexion angle of maximum efficiency lies between 80°and 90°

Question 22

Extensor muscles of the elbow:

Answer 22

Primary exensor muscles: Triceps brachii

Accessory extensor muscle: Anconeus

Question 23

Triceps brachii

Answer 23

• The medial head arises from the entire posterior surface of the humerus below the level of the spiral groove for the radial nerve.
• The lateral head arises chiefly from the lateral border of the humerus above the spiral groove.
• The long head arises from the infraglenoid tubercle of the scapula.
• The three separate fleshy heads converging on to a common tendon which is inserted into the olecranon process.

Question 24

The efficiency of the triceps varies according to the state of flexion of the elbow:

Answer 24

• In full extension: the centrifugal component tends to dislocate the ulna posteriorly and the more powerful tangential component, which is the only active force in extension.
• In slightly flexed to 20° to 30° : the centrifugal component becomes zero and the effective tangential component is the same as the muscular pull. Hence in this position the triceps is maximally efficient.
• In full flexion: the triceps tendon is reflected on the superior surface of the olecranon process as on a pulley and this tends to make up for its loss of efficiency. Moreover, its fibres are maximally stretched and so its force of contraction is maximal; this further compensates for its loss of efficiency

Question 25

The efficiency of the long head of the triceps and of the whole muscle also depends on the position of the shoulder because it is a biarticular muscle.

Answer 25

- The distance between its origin and insertion is greater when the shoulder is flexed at 90° than when the arm hangs down vertically. - Therefore the triceps is more powerful when the shoulder is in flexion. - The triceps is also at its most powerful when the elbow and shoulder are simultaneously extended

Question 26

The reference position

Answer 26

It is defined as the position achieved when the axes of the arm and forearm are in a straight line

Question 27

The extension

Answer 27

* It is the movement of the forearm posteriorly. * Since the position of reference corresponds to complete extension the range of extension of the elbow is zero by definition. * Except in subjects in whom great laxity of the ligaments allows hyperextension of 5° to 10°.

Question 28

The flexion:

Answer 28

* It is movement of the forearm anteriorly with approximation of the forearm to the anterior aspect of the arm. * Active flexion: range of 145° . * Passive flexion: range of 160°.

Question 29

Limitations of flexion and extension: | Extension is checked by three factors:

Answer 29

1. The impact of the olecranon process on the olecranon fossa 2. The tension of the anterior ligament of the joint 3. The resistance of the flexor muscles (biceps, brachialis, supinator) Limitation of flexion depends upon whether flexion is active or passive.

Question 30

Limitations of flexion and extension: | Passive flexion:

Answer 30

- The relaxed muscles can be flattened against each other allowing flexion to reach be-yond 145° - The impact of the head of the radius against the radial fossa and of the coronoid process against the coronoid fossa - The tension of the posterior capsular ligament - The tension developed passively in the triceps - Flexion can then reach 160°

Question 31

Coaptation during flexion:

Answer 31

- When the elbow is flexed to 90° the ulna is perfectly stable, because the trochlear notch is surrounded by the powerful musculo-tendinous insertions of the triceps and the brachialis. - which secure coaptation of the joint surfaces. - The radius is liable to proximal and anterior dislocation under the action of the biceps. - This dislocation is prevented solely by the annular ligament.

Question 32

Resistance to longitudinal traction:

Answer 32

- Ligaments: medial and lateral ligaments - Muscular: triceps, biceps, brachialis, brachioradialis and the muscles arising from the lateral and medial epicondyles. - During full extension the tip of the olecranon hooks over the trochlea in the olecranon fossa, thus imparting some mechanical resistance to the elbow joint in its long axis. - The only anatomic structure preventing "descent" of the radius relative to the ulna is the interosseous membrane.

Question 33

Limitations of flexion and extension: | Active flexion:

Answer 33

Active flexion: The first and foremost limiting factor is the apposition of the anterior muscles of the arm and forearm, hardened by contraction, which prevents active flexion beyond 145.

Question 34

Rotation (pronation-supination)

Answer 34

is the movement of the foreann about its longitudinal axis It involves two joints, which are mechanically linked: - the superior radio-ulnar (SRU) joint, which anatomically belongs to the elbow - the inferior radio-ulnar (IRU) joint, which is anatomically separate from the wrist

Question 35

In supination :

Answer 35

The radius and the ulna lie side by side with the ulna on the medial side, their axes are parallel

Question 36

In pronation:

Answer 36

The radius and the ulna are no longer parallel but cross each other, the radius is lateral to the ulna proximally and medial to it distally

Question 37

The superior radio-ulnar joint:

Answer 37

A trochoid with cylindrical surfaces and one degree of freedom: rotation about the axis of the two cylinders in contact. It consists of the following two cylindrical surfaces: the head of the radius, and the fibro-osseous ring.

Question 38

A fibro-osseous ring

Answer 38

Corresponds to the distal component of the ball-bearing system It consists of the following: - the radial notch of the ulna - covered by articular cartilage, concave antero-posteriorly and separated by a blunt ridge from the trochlear notch. - the annular ligament - consists of a strong fibrous band attached by its ends to the anterior and posterior margins of the radial notch of the ulna and lined internally by cartilage continuous with that lining the radial notch. - it serves as a ligament, by surrounding the head of the radius and binding it to the radial notch, and also as an articular surface in contact with the head of the radius - The quadrate ligament: - It consists of a fibrous band attached to the inferior border of the radial notch and to the neck of the radius - Its two borders are strengthened by the fibres of the upper border of the anular ligament. - It acts to reinforce the inferior aspect of the capsule.