Describe the 3 articulations of the elbow joint
1. Humero-ulnar joint between the trochlea of the humerus and the trochlear notch of the ulnar or elbow proper.
2. Humero-radial joint between the capitulum of the humerus and the radial head
3. The proximal radio-ulnar joint between the edge of the head of the radius and the radial notch of the ulna.
All 3 are synovial joints and surrounded by a capsule that is attached near the margins of the articular surfaces and defining a single joint capsule.
The elbow is a hinge type synovial joint. At full extension, the ulna makes an angle of 170 with the humerus.
Note: the forearm is angled further away from the trunk in females.
What are the muscles producing the hinge movement of the elbow joint?
Major flexors: biceps brachii, brachialis and brachioradialis
Major extensor: triceps brachii
Describe the capsule surrounding the elbow joint
Relatively weak anteriorly and posteriorly
Strengthen by COLLATERAL LIGAMENTS medially and laterally.
The elbow and proximal radio ulnar joint share a capsule (both enveloped within the same capsule).
Synovial membrane lines the fibrous capsule and humerus enclosed by the capsule.
What are the 3 major ligaments associated with this joint?
Describe the ulnar collateral ligament
Triangular between the medial epicondyle and the coronoid process and olecranon of the ulna.
3 bands: Anterior (strongest, tough, cordlike)
Posterior (spreads out into can shape)
Oblique (slender, deepens the socket for trochlea - runs in the trochlea notch of the ulna)
Describe the radial collateral ligament
Broad fan like shape
Blends with annular ligament - continuous which helps prevent disruption of the Humero-radial joint.
Attaches between the lateral epicondyle of the humerus and the annular ligament of the radius below
It keeps the head of the radius and the capitulum in close association.
Describe the annular ligament
Ligamentous ring just beneath the head of the radius
Attach to the ulna anterior and posterior to its radial notch,
Allows complete freedom of the movement of the elbow joint because the ligamentous collar/ring supports the joint from underneath (inferior, beneath the head of the radius)
Maintains its contact with the radial notch on the ulna.
Describe the bursae around the elbow
Number of bursae around the elbow but only 2 have major importance: Subcutaneous olecranon bursa lies in the subcutaneous connective tissue overlying the olecranon. Repeated pressure in this area can cause inflammation (student's/miner's elbow) Subtendinous bursa lies between the triceps tendon and the olecranon and can become inflamed due to friction such as can occur in some assembly line jobs. Although not common, the feature of this injury is that it is most severe during flexion of the forearm. In addition to these, a bursa between the triceps tendon and the radius may become inflamed in persons who make repeated pronation/supination movements.
Describe the neurovascular supply of elbow
Hilton's Law: the nerve supplying s joint also supplies both the muscles that move the joint and the skin covering the articular insertion of those muscles (radial and ulnar) Arterial anastomoses, formed by collateral arteries and recurrent branches of ulnar, radial and interrosseus arteries give a prominent, rich blood supply with lots of redundancy.
Describe the radioulnar joints
Distal radio-ulnar joint is a pivot joint in which the distal end of the radius moves around the distal end of the ulnar. The articular disc use main structure affording joint integrity - it separates cavity of distal radioulnar joint from wrist cavity. The proximal radio-ulnar joint is also a pivot joint. In addition, the interosseous membrane forms a fibrous joint (does not show up on x-Ray) between the radius and ulna. Attached from the radius above to the ulna below this membrane keeps the bones together during movements of pronation and supination, and also prevents anterior displacement of the radius when a force is applied to the outstretched hand. Fibres run inferio-medially which allows some distribution of force from radius (which receives most of the force when you fall) to ulna. The aim is to prevent fracture of the radius but sometimes force is too great.
What does pronation and supination exactly involve?
Movement at the elbow and forearm joints; head of radius pivots on the capitulum (ball and socket joint). During supination: bones are parallel During pronation: bones cross as head of radius pivots on capitulum.
Describe the Distal Radioulnar Joint in Pronation/Supination
Articular disc ensures joint integrity is maintained - allows a little bit of twisting to allow the bones to cross each other. Sacciform recess superior extension of synovial capsule allows twisting of the capsule.
Distinguish between dislocation and subluxation
Dislocation: complete loss of contact of the joint surfaces
Subluxation: partial dislocation of a joint, so that the bone ends are misaligned but still in contact (e.g. Some contact between radius and ulna but radius and capitulum have lost touch)
Describe the facilitation of supination and pronation function:
Head of radius and capitulum of humerus
Sacciform recesses (extensions of the synovial membrane on neck of radium and at distal radius and ulna (superiorly from articular disc))
Describe the wrist joint
Radiocarpal joint: Condyloid type of synovial joint formed between the distal end of the radius, and the scaphoid, lunate and triquetrum (proximal carpal bones).
Ulnar makes no contribution to the wrist joint.
Stabilised by collateral palmar and dorsal ligaments
Describe the ligaments associated with the wrist joint
Radial collateral ligament extends between the radial styloid process and the scaphoid and triquetrum.
Ulnar collateral ligament attaches to the ulnar styloid process and the triquetrum and pisiform.
Palmar ulna-carpal ligament connects the ulnar styloid process to the lunate and triquetrum.
Palmar radio carpal ligament connects the radius to the scaphoid, lunate and triquetrum.
This ensures the hand follows the radius during supination.
The dorsal radio carpal ligament connects the radius with the scaphoid, lunate and triquetrum. This ensures the hand follows radius during pronation
Why is abduction of the wrist limited?
By the radial styloid process
What happens in 40% of Colle's fractures?
Avulsion of the ulnar styloid process
What are the function of joints?
Allow growth (epiphyseal growth plates at ends of long bones near joints in children)
In the young, what could fractures of the distal radius result in?
Fractures of the distal radius may extend through the distal epiphyseal plate.
During healing there may be mal-alignment of the epiphyseal plate and radial growth may be impaired.
When taking a history, what should you consider?
Mechanism of injury
If UL injury, dominant hand
Occupation (fractures are rarely lethal - need to consider more about impairment of function)
Social circumstances (e.g. can they get about at home, care plan etc)
Relevant previous medical history (IHD/COPD/Diabetes/AF/heart valves/Rheumatoid Arthritis)/Previous injuries/Joint replacement/malignancy(+metastasis?)/Previous DVT
Drug history - anti-clotting agents; steroids/insulin
What are three principles to keep in mind during examination?
What are some possible examination findings?
Puncture or skin wounds: puncture wounds indicate bone could have gone through the skin and then gone back inside
Joint fluids e.g. Effusion in the knee could be caused by a ligament injury causing a bleed into the knee. Lots of effusion indicates a severe injury.
Painful anatomical sites
Crepitus - crunching sound
Range of movement
Pulses difficult to feel - assess neurovascular status, check for nerves and distal pulses
What are some common associations?
Distal radius injury (Colles) - Median nerve
Distal 1/3rd humerus - Radial nerve
Shoulder dislocation - Axillary nerve
Hip (or THR) dislocation - Sciatic nerve
Knee dislocation - Popliteal Artery, Common Peroneal Nerve
What investigations do you need to consider ordering?
X-Rays: 2 shots at 90 degrees to each other (AP and LATERAL views) otherwise you might miss a fracture
Aspiration: a bleed indicates a serious injury
What is the Polo Mint Analogy?
Some bones are paired e.g. Pelvis, radius and ulna, tibia and fibula
It is very hard to fracture one side of the bone alone so always assess both bones.
What is the rule of 2's?
2 joints (above and below)
2 views (for X-Rays)
Define a Fracture
It is a soft tissue injury with an underlying break in the bony cortex.
Includes damage to nerve and vascular structures
What are the possible causes of a Fracture?
Stress (from continuous low level repetitive injury - usually causes a small bone fracture, common in marathon runners and soldiers. Very subtle evidence - callous formation. Stress fractures always heal but painful initially)
Insufficiency (osteoporosis/osteopenia - bone marrow density is lower than normal)
What does fracture stability determine?
Type of fractue healing.
Mechanical stability governs the mechanical strain.
Primary healing (no callus formation): depends on stability of the bone ends to allow the cells to enter and stem cells to different to form a callus)