L38. Joints of the Upper Limb 2: Elbow and Radioulnar Flashcards
What are the two major types of joints in the distal upper limb?
The Hinge joint (The elbow joint proper) Pivot joints (proximal radioulnar joint)
What is the major purpose of the proximal radioulnar joint?
Permits the pronation and supination movements
What are the parts of the distal humerus and the radial and ulna bones that make up the elbow?
What is the main movement of the elbow joint?
Main movement is flexion and extension
What is the relationship of the ulnar and the radius bones in terms of medial and lateral?
The ulnar bone is medial bone of the forearm while the radius is the lateral bone
What is the trend of the support of hinge joints in terms of ligaments?
Hinge joints (especially in the forearm) are supported by colateral ligaments on either sides of them. This limits their side to side movement (supports the sagittal movement).
Muscles of the forearm originate from the colateral ligaments of the medial and lateral epichondyl. What is the difference between the medial and lateral superficial muscles?
Superficial muscles off the medial epichondyl of the humerus are FLEXOR muscles
Superficial muscles originating off the lateral epichodyl of the humerus are EXTENSOR muscles.
There are various stages of epiphyses development. What is the last one to fuse generally and what is important to note in terms of radiological diagnosis?
The last one to fuse is the medial epichondyl.
Important to note that opacities in radiographs of young children do not show fractures but rather epipheyses.
What is the elbow complex?
The elbow joint and the proximal radioulnar joint SHARE THE SAME JOINT COMPLEX AND CAPSULE.
Both joints share the one synovial cavity: the elbow joint capsule descends and incorporates and encapulates the radioulnar joint.
Describe what the elbow joint capsule includes
It rises about the various fossa of the humerus and descends down to include the neck of the radius as well as down to the proximal ulnar
The elbow joint complex capsule is reinforced by ligaments. What are the two major collateral ligaments?
How does the capsule interact with the annular?
The medial (ulnar) collateral ligament off the medial epichondyl
The lateral (radial) collateral ligament off the lateral epichondyl of the humerus
The capsule blends laterally with the annular ligament
Describe the difference in attachments of the medial vs. the radial colateral ligaments off the epichondyls of the humerus
The medial colateral ligament attaches to the coronoid process of the ulnar
The lateral colateral ligament does NOT attach to bone (boney insertion would limit the movement)
The lateral colateral ligament attaches to the ANNULAR LIGAMENT.
Describe the location and function of the annular ligament
The annular ligament encircles the head of the radius (it forms a circle around the radius)
It serves as insertion for the lateral colateral ligament
The annular forms a socket in the ulna as well
Describe the differences in movement of the ulna vs. radial bones in supination and pronation of the forearm
In supination and pronation of the forarm the radius rotates while the ULNAR STAYS RELATIVELY STABLE AND UNMOVING.
The radius rotates around the ulnar
Are there intracapsular fat pads in the fossae of the bones in the elbow joint?
Is there a bursa? Is it in communication with the joint?
Yes
These is an olecranon bursa but it is not in communication with the joint
What is the difference between the alignment of the:
- Medial epichondyl
- Olecranon of the ulnar
- Lateral epichondyl
in flexion vs. extension?
In extension all of these landmarks are horizontally in line with one another
In flexion, an isoceles triangle is formed between the three points (the tip being the olecranon)
Describe the stability of the elbow joint
in what position is there maximum stability?
The elbow joint is very stable (especially in contrast with the shoulder joint).
The parts of the joint match one another very well (no mismatch of processes to fossa) which is further supported by the deep fossa and the fat pads.
Maximum stability is in the extension position because the ligaments are taught around the joint on either side of it.
In extension of the forarm, there is a natural “VALGUS ANGULATION” or “carrying angle” what does this mean?
What happens in “CUBITUS VALGUS”?
In extension (disappear in flexion) there is a normal angle between the straight line of the humerus and the forearm of about 15 degrees.
Cubitus valgus is when there is an increase in the angle made between them leading to tension on the medial structures (like the medial colateral ligament and the ulnar nerve)
What important vascular structure lies beneath the radial head?
There is a bifurcation of the brachial artery
What are the two radioulnar joints?
Describe the type of joint that these are
Superior (proximal) radioulnar joint which lies within the joint complex
The inferior radioulnar joint which forms part of the wrist
Both are synovial joints and are pivot
What is the major movement of the radioulnar joints?
Supination and pronation of the forearm
The radius swings around the ulnar which is held in position by the annular ligament
What is important to note about the annular ligament in children?
The annular ligament is looser in children thus disloaction of the head of the radious is more likely
What is the fibrous membrane between the shafts of the radius and the ulnar bones?
Describe the fibres
What are the two functions of the membrane?
The interosseous membrane
The fibres pass inferiorly and medially
The two functions are:
- Transmit forces from the radius to the ulnar
- Provide sites of attachement for the deep flexor and extensor muscles (not the superior ones from the epichondyls)
Describe the inferior radioulnar joint
The ulnar notch (on the medial aspect of the radius) and the head of the ulna join together with a TRIANGULAR FIBROCARTILAGINOUS COMPLEX DISC.
What is the difference between the styloid process of the ulna and the styloid process of the radius? [2 major differences]
- The styloid process of the radius descends further down than the process of the ulnar bone
- The styloid process of the radius also articulates at the wrist joint while the ulnar does not because the triangular fibrocartilaginous disc of the inferior radioulnarjoint is between them
Describe the interosseus membrane in terms of its
- Strength
- Parts
- ‘Ring” principle
- It is a very strong membrane of fibres
- It has a proximal quadrate ligament (small vestigal origin) and a larger part
- The ‘ring’ principle states that because the forces of the bones are intimatlely joined by this membrane, fracture at one site are commonly associated with fractures at the other.
What kind of joint is the distal radioulnar joint?
What happens with age of the joint?
A synovial joint
With age, the disc becomes increasingly perforated and degenerates as a result (wrist pathology)
Describe the supinator and pronator muscles of the forearm
The PROTONATOR TERES muscle is the large power generator and is superficial arising from he medial empichondyl and inserts into the greater lateral curvature of the radius
THe PROTONATOR QADRATUS muscle is a positioning pronator at the distal end of the forarm surrounding both the radius and ulnar bones
The SUPINATOR and BICEPS BRACHII are the supinator muscles of the forearm
What is the bursa in the elbow joint and what pathology can occur with it?
The olecranon bursa between the olecranon and the skin.
Olecranon bursitis and pulled elbow can occur by force onto the bursa (students elbow) or an upwards pull on extended arm can pull radial head out of the annular ligament
What are the two types of fractures/dislocationst that commonly occur in the elbow joint?
- Supracondylar
- Coranoid
What is the most common direction of fracture/dislocation of the elbow?
What is endangered in this case?
Posterior
The coranoid process can fracture the trochlear head (directon of force going posteriorly) and the remainder of the shaft can be displaced posterior to the articular surfaces.
The brachial artery and bifurcation can suffer traction (stretch) leading to decreased lumen diameter or ischemic damage
Epichondyles are traction epiphyses and are susceptible to traction injury (muscle pull can tear off part of bone)
What kind of structures are susceptible to damage in these cases?
Ulnar nerve is susceptible to injury in fracture of the medial epichondyl
Lateral epichondylitis - tendinitis of the wrist extensor muscles
