Part 5 of 6 Anatomy Flashcards
List the 3 most common facial fractures.
- Mandibular
- Orbital
- Zygomatic
(Just know these bones, no need to learn this in detail!)
Usually intracranial injuries are also implicated.
In clinical mangement, treatment of the fracture is usually delayed as sinus fractures means that the airway is actually obstructed so ABC must be done before any further considerations.
What are LeFort fractures?
List and describe the different types.
LeFort Fractures
Types of facial fractures involving the maxillary bone and surrounding structures
LeFort Type #1 (15%)
- Palate separated from maxilla
LeFort Type #2 (10-12%)
- Maxilla separated from face
LeFort Type #3 (10-12%)
- Craniofacial dysjunction
(See F422 - LeFort fractures classification)
List and describe the mechanisms of brain injury.
1. Open/ Penetrating Injuries
- Bullets
- Weapons
- Fractures
2. Closed Head Injuries
- 2 major mechanisms:
o Blow on stationery head – acceleration
o Sudden stopping of moving head (Fall/MVA) – deceleration
3. Damaging forces during acceleration and deceleration.
· Sheer forces: naligned forces pushing one part of a body in one direction, and another part the body in the opposite direction
· Axial transfer of force, i.e. the direct effect of force on the brain, aka the ‘linear force’
· Invariable associated with some rotational forces
o If a head is hit, it generally rotates – causing additional injury inside the head
o Head generally rotates in a slightly oblique manner on the point of articulation on top of the spine as it is hit
o A major cause of injury in boxers and MVA
4. Collision with anatomical structures
- Flat bones/irregular bony surfaces, e.g. Base, petrous bone, edge of the sphenoid
- Flat dura/ free sharp dural edges, e.g. Tentorium, falx
- Tearing of blood vessels running between skull / Dura and brain → Common in old people/alcoholics?
5. Pressure changes in cranial cavity
· Site of impact – momentary invagination = positive pressure
· Diametrically opposed side of skull bulges out momentarily = negative pressure (more severe damage)
Explain what ‘coup’ and ‘contrecoup’ injuries are with relation to the skull.
- Skull and brain movements are not simultaneous
- Hence, during MVA:
- Sudden deceleration of skull - brain momentum continues forward, coup injury
- Head then snaps back and the now backward momentum of the brain causes contrecoup injury
(See F423 - Coup-contrecoup injury)
Describe which vessels might be implicated in intracranial haemorrhages.
(See F424 - Intracranial haemorrhage and associated vasculature)
List the types of intracranial haemorrhages which exist and their main causes.
- Epidural/extradural (EDH)
- Subdural (SDH)
- Subarachnoid (SAH)
- Intracerebral
Generally 1-4 can all be caused by trauma, but 3 and 4 are more commonly due to CVA.
More details on exact causes of these different haemorrhages can be found here:
(See F425 - Intracranial haemorrhage types and mechanisms)
Be able to draw the coronal anatomy of these 3 cranial haemorrhages:
- Extradural/epidural
- Subdural/ dural border
- Subarachnoid
See F426 - Coronal anatomy of intracranial haemorrhages.
Differentiate between different intracranial haemorrhages in a CT scan.
How do you tell the age of a bleed in a CT scan?
CT Scans of Intracranial Haemorrhages
(See F427 - CT scans of intracranial haemorrhages)
Ageing a CT of Haemorrhage
- Acute = appear hyperdense due to globin protein (bright white)
- Chronic = appear isodense - harder to see
Explain why an acute subdural haemorrhage’s presentation may differ in a child compared to an adult.
- Symptoms based on accumulation of blood between dura mater and arachnoid mater
- Cerebral atrophy in older patients - larger space for bleeding before clinically significant increase in pressure in brain, compared to children
Describe the main types of brain herniations which can occur and list the structures which would be affected.
(See F428 - Brain herniation types and affected structures)
What is Kernohan’s phenomenon? (Kernohan’s notch?)
Kernohan’s notch is a cerebral peduncle indentation associated with some forms of transtentorial herniation (uncal herniation). It is a secondary condition caused by a primary injury on the opposite hemisphere of the brain.
(See F429 - Kernohan’s phenomenon)
What is papilloedema? Explain the mechanism.
- Raised intracranial pressure (ICP) –> compression of optic nerve –> compression of vein inside nerve –> impeding of venous return –> more pressure on neurons –> obstruction of axoplasmic flow (normal movement of cellular contents in neuron cell bodies) –> oedema of nerve –> optic disc oedema (the raised disc on the retina at the point of entry of the optic nerve, lacking visual receptors and so creating a blind spot)
Px is almost always bilateral.
See an image of what optic oedema looks like here through an opthalmoscope: F430 - Optic oedema, opthalmoscope view.
CN VI (Abducens n.) is commonly involved in head injuries. Explain why.
Several features of the abducens nerve make it more susceptible to head injuries:
- Long course through the subarachnoid space
- Acute angle
- Closeness to sphenoid bone where it can get compressed betwen the bone and brain stem or stretched due to brainstem movements.
(See F431 - Abducens nerve and injury susceptibility)
Compare the locations of the quadrangular and triangular spaces.
Describe the borders of each of these spaces and the structures which run through them.
Spaces and Teres Major
- Quadrangular space - above teres major
- Triangular space - below teres major
Quadrangular Space
Borders
- Medial: long head triceps
- Lateral: humeral shaft
- Superior: teres minor
- Inferior: teres major
Contents
- Axillary nerve - passes thorugh space on its way to innervate deltoid, teres minor and give sensory sensation to lateral aspect of arm, etc.
- Posterior humeral circumflex artery
Triangular Space
Borders
- Inferior: Teres major
- Lateral: Long head triceps
- Superior: Lower border of teres minor
- Contents*
- Scapular circumflex artery
Triangular Interval (Don’t Mistake this for Triangular Space)
Borders
- Superior: Teres major
- Lateral: lateral head of triceps or humreus
- Medial: Long head of triceps
Contents
- Profunda brachii artery
- Radial nerve
See F454 - Quadrangular space, triangular space, triangular int.
Explain the presentation of a clavicular fracture, the causes and what other exams you would perform.
Presentation of Clavicle Fracture
- Most common site of fracture is the distal 1/3 of the clavicle - weakest point of the clavicle
- Proximal fragment of clavicle - displaced upwards
- SCM pulls it upwards.
- Distal fragment of clavicle - displaced downards
- Weight of upper limb and latissimus dorsi pull distal end down
- Trapezius pulls distal end up
- Net effect: pulled down
- Brusing of skin sometimes present
Causes
- Falling onto outstretched hand (FOOSH)
- Fall on shoulder
Further Examination
- Other fractures
- Neurovascular damage - should be done in every fracture case. In this case, ulnar nerve damage common. Consider also: brachial plexus, distal perfusion.
- Pneumothorax
F455 - Clavicular fracture
Be able to recognise the structures in a middle and distal x-section of the arm.
See F456 - Structures in middle and distal x-section of arm.
Explain the mechanism of an elbow joint dislocation and further examination.
Dislocation of Elbow
- Humero-radio-ulnar joint affected, usually proximal dislocation common, compared to distal dislocation in shoulder
Mechanism
- Fall on outstretched hand (FOOSH), most common dislocation in children due to smaller coronoid process, the normal function of which is to resist ulnar displacement
- Radius and ulnar dislocate posteriorly
See F457 - Elbow humero-radio-ulnar dislocation.
Further Examination
- Check for neurovascular damage around the elbow.
See F458 - Neurovascular structures of the elbow.
What are ossification centres? Explain their clinical significance with regard to elbow injuries in falls.
Primary Ossification Centres
- Areas which ossify and form bone from cartilage
- Bone formed from these centres replaces most of the cartilage in the main body of the bone model
- Primary ossification centres appear before birth and ossify the diaphyses
Secondary Ossification Centres
- Areas which continue to ossify after birth, affecting epiphyseal growth
Elbow Secondary Ossification Centres
- 6 secondary ossification centres in elbow - CRITOE and age (yr) of appearance
- C - capitulum, 1
- R - radial head, 3
- I - inner medial epicondyle, 5
- T - trochlear, 7
- O - olecranon, 9
- E - external epicondyle, 11
- Hence in an elbow injury, you can tell from age of patient which centres should be present and may be missing or moved due to the fracture
See F459 - Secondary ossification centres of elbow
- In the figure, the X-ray shows the humerus of a 10yr old patient with swollen elbow after a fall
- The patient should have all centres up to O, however, can’t see I, athough R is present. (T is harder to spot).
- I has been displaced below.
Explain the 3 radiological featurs used in diagnosis of a posterior dislocation of the elbow.
- Radiocapitellar line: should pass through middle of capitulum in healthy elbow
- Anterior humeral line: should pass through middle 1/3 capitulum in healty elbow
- Fat pad shadows should not be present in a healthy elbow –> indicative of supracondylar fracture
See F460 - Radiological features of posterior elbow dislocation.
Explain why a fat pad shadow might show up on an X-ray of someone with a posterior elbow dislocation.
Fat pad shadow is indicative of supracondylar fracture.
Supracondylar Fracture
- Thin bone above the condyles near joint cavity
- Posterior fat pad is normally found within the olecranon fossa
- Hyperextension of elbow and supracondylar fracture is one way the fat pads can break out of the normal olecranon fossa and shift.
- Haemarthrosis may also be present
See F461 - Supracondylar fracture and fat pad shift.
