Week 2 - fractures and dislocations Flashcards
Define a fracture. (LO1)
“A fracture is described as a disruption in the continuity of all or part of the cortex of the bone.”
What are the different types of fractures relating to cause? (LO1)
- traumatic (acute)
- insufficiency
- stress
- avulsion
How do traumatic fractures occur? (LO1)
Generally the result of a sudden incident/impact that results in damage to the bone, e.g. sport or road traffic accidents.
How do insufficiency fractures occur? (LO1)
Result from a normal load on an “insufficient” bone, e.g. osteoporosis.
How do stress fractures occur? (LO1)
Due to a reasonable action repeated excessively resulting in abnormal stress on the bone, e.g. excessive marching in army personnel.
How do avulsion fractures occur? (LO1)
Result from a trauma to a ligament or tendon and usually occur in young athletic people.
What is the standard way to confirm a clinical diagnosis of a suspected fracture? (LO1)
X-ray
Some fractures may not be visible on an X-ray (particularly stress fractures), what are some indirect signs of a possible fracture? (LO1)
- The disappearance of normal fat stripes and fascial planes.
- Joint effusions.
- Periosteal reactions.
- New periosteal bone formation (faint white addition at the fracture site on x-ray).
What are the rules associated with taking an x-ray? (LO1)
- A minimum of 2 planes of view is necessary, 4 for scaphoid fracture.
- If multiple injuries are suspected or trauma has occurred, the field of view should be expanded in order to accommodate these.
Why do fractures become more visible with time before healing? (LO1)
Osteoclasts resorp the dead bone at the edge of the fracture site making the gap wider.
Which parts of the body would you not x-ray? (LO1)
- Ribs - make a clinical diagnosis, an x-ray won’t help you.
- Nose - mostly cartilage so won’t be able to see much.
- Coccyx - some point forwards, downwards, backwards, you might just be able to see the fracture.
N.B. if there is pain at the end of expiration (suspected pneumothorax), then x-ray of ribs is warranted.
What is meant by lucent lines on a fracture x-ray? (LO1)
A dark line indicating the fracture.
What do the different colours on an x-ray indicate? (LO1)
Black = air Dark grey = fat Light grey = water White = bone White stripe = epidermis
What is the rule regarding ring fractures? (LO1)
A rigid ring must break in at least 2 places so if you find one fracture, find another.
e.g. pelvis
What is the rule regarding paired bone fractures? (LO1)
If only one bone in paired bones is fractured, x-ray the joint above and below as there must be a dislocation/ligament disruption.
e. g. tibia/fibula
e. g. facial bones: maxilla, zygomatic, lacrimal, nasal (would take an additional x-ray of the neck in this case)
e. g. radius/ulna
What are the different categories to describe a fracture clinically? (LO1)
- Position.
- Path of fracture line.
- Simple or comminuted.
- Joint involvement.
- Closed or open (compound).
How would we further subcategorise the position of a fracture? (LO1)
- Angulation.
- Displacement.
- Distraction.
- Impaction.
- Rotation.
- Foreshortening.
How would we describe the angulation of a fracture? (LO1)
The degree of the angle, e.g. 45 degrees, followed by:
- Valgus - fracture ends of the bone pointing medially.
- Varus - fracture ends of the bone pointing laterally.
- Posterior - fracture ends of the bone pointing posteriorly.
- Anterior - fracture ends of the bone pointing anteriorly.
How would we describe the displacement of the bone as a result of the fracture? (LO1)
- Laterally displaced - away from the plane of the body.
- Medially displaced - towards the plane of the body.
Describe what is meant by distracted and impacted fractures. (LO1)
Distracted: two ends of the bone (from the fracture site), have been pulled away from each other.
Impacted: two ends of the bone have been crushed together at the fracture site.
Describe what is meant by rotation with regards to a fracture? (LO1)
- Medially rotated = the mobile fragment of bone is internally rotated.
- Laterally rotated = the mobile fragment of bone is externally rotated.
Describe what is meant by foreshortening of the bone in a fracture? (LO1)
This is when the bone fragments are completely misaligned, with one of the fragments moving so the ends of the two fragments overlap, visibly shortening the bone.
What are the four different paths of a fracture line? (LO1)
- Transverse (most stable) - horizontal line through the shaft.
- Oblique - diagonally through the shaft.
- Spiral - spiralling through the shaft.
- Longitudinal (least stable) - vertical along the axis of the bone.
If a fracture results in more than 2 fragments of bone, what is it referred to as? (LO1)
Comminuted fracture.
What are the types of joint involvement in a fracture and how could they impact the patient long-term? (LO1)
- Dislocation - adjoining bones no longer touching each other.
- Subluxation - minor/incomplete dislocation where joint surfaces still touch but are not in normal relation to each other.
Joint involvement can mean damage to the cartilage leading to premature osteoarthritis later in life.
Describe what is meant by open (compound) and closed fractures? (LO1)
If the skin is unbroken, it is a closed fracture.
If a piece of bone is in contact with air, it’s a compound fracture (open).
What is a Colles fracture? (LO1)
A fracture of the distal radius resulting in a posterior displacement of the radius and obvious deformity.
What are the different types of fractures in children? (LO1)
- Plastic.
- Torus.
- Greenstick.
- Growth plate fractures.
- Non-accidental injury.
What is a Greenstick fracture? (LO1)
Children’s bones have a degree of elasticity but when bent too far, one side (the side being stretched) may crack slightly, causing a Greenstick fracture.
What is a Torus (buckle) fracture? (LO1)
“An incomplete fracture of the shaft of a long bone that is characterised by the bulging of the cortex.”
As children’s bones have a degree of elasticity, instead of a crack on the side being stretched (Greenstick), the opposite side pushes out some of the bone, creating a bulge.
What is a plastic (bowing) fracture? (LO1)
As children’s bones have a degree of elasticity, when a longitudinal force is applied. If the force is low and subsequently released, the bone will return to its normal position.
If the force is greater than the mechanical strength of the bone, the bone undergoes plastic deformation and when the force is released, the bone remains in this bowed position.
Although no fractures are visible radiographically, microscopic fractures occur on the concave border of the bowed bone.
What are the different types of growth plate fractures? (LO1)
We use the Salter-Harris classification for this: S - slipped (type I) - best case A - above (type II) L - lower (type III) T - through (type IV) R - ruined (type V) - worse case
Describe what is meant by a Salter-Harris type I fracture (slipped). (LO1)
Horizontal along and through the growth plate, not involving bone.
Describe what is meant by a Salter-Harris type II fracture (above). (LO1)
Through the growth plate and metaphysis (most common).
Describe what is meant by a Salter-Harris type III fracture (lower). (LO1)
Through the growth plate and epiphysis.
Describe what is meant by Salter-Harris type IV fracture (through). (LO1)
Throught the metaphysis, growth plate and the epiphysis.
Describe what is meant by Salter-Harris type V fracture (ruined). (LO1)
Crush injury of the epiphyseal growth plate (worse prognosis).
Bonus question: why is a metaphyseal corner fracture a sign of abuse? (LO1)
The only way to obtain this fracture is to grab a child by the arm and swing them around your head.
How do pathological fractures occur? (LO1)
This is due to focally abnormal bone.
E.g. myeloma eating away at bone.
E.g. metastatic cancer.
What are the two examples of fracture mimics? (LO1)
- Unfused epiphyseal growth plate.
- Unfused apophysis (ossification centre where the tendon inserts).
What are the factors determining fracture healing? (LO1)
- age
- fracture site
- position of fracture fragments (e.g. comminuted).
- blood supply to fracture site.
- immobilisation of the fracture.
- other conditions, e.g. osteoporosis.
How does healing of a fracture take place? (LO1)
- The osteoclasts will remove damaged bone which may result in widening of the fracture line.
- Endosteal healing in stable fractures will result in the obliteration of the fracture line after several weeks.
- In less stable fractures, periosteal healing results in the formation of a callus manifesting as a white mass around the fracture site.
What are the types of complications which can occur during healing of a fracture? (LO1)
- Delayed union.
- Malunion.
- Nonunion.
- Damage to blood supply or nerves.
- Damage to surrounding tissues.
What is meant by delayed union? (LO1)
When the fracture does not heal in the expected time.
Usually with further immobilisation, the fracture will heal.
What is meant by malunion? (LO1)
When the fracture heals in a manner that is unacceptable.
This could be cosmetically or mechanically.
What is meant by nonunion? (LO1)
When it is determined that a fracture will never heal on its own.
This can present as sclerotic fracture margins (thickening of the bone). Pseudoarthritis (lack of bone fusion) may occur along with a synovial lining (connective tissue).
What must happen if it’s suspected that a fracture could be compromising blood supply? (LO1)
The fracture must be reduced before any imaging is done to preserve function and prevent long term damage.
Define compartment syndrome. (LO2)
Increased pressure within an osteofascial compartment leading to compromised perfusion of the tissue. If left untreated, necrosis can occur within hours.
Describe acute and chronic compartment syndrome. (LO2)
Acute compartment syndrome is a medical emergency, usually caused by trauma, i.e. broken leg.
Chronic/exertion compartment syndrome is caused by intensive repetitive exercise and usually pain is alleviated when exercise stops and the limb rests.
Describe the epidemiology of compartment syndrome. (LO2)
- Most cases occur after a trauma.
- 75% of acute cases are associated with fractures.
- Tibial shaft fracture is the most common cause of acute cases, associated with 1-10% of incidence rates.
- Soft tissue injuries is the second most common cause of acute cases.
- Other causes include: burns, vascular injuries, crush injuries, drug overdoses, thrombosis, infections, penetrating trauma, improperly placed casts or splints, poor positioning during surgery, etc.
Describe the presentation of compartment syndrome. (LO2)
- Tense or “wood-like” feeling of the compartment.
- Pain is severe and out of proportion to the injury.
- Initially pain may be burning sensation or deep ache.
- Paraesthesia, hypoaesthesia or poorly localised deep muscular pain may also be present.
- Late findings: the 5 Ps
- Pain
- Pulselessness
- Paraesthesia
- Paralysis
- Pallor
Describe the investigations for compartment syndrome. (LO2)
- Skin: look for lesions, swelling or colour change.
- Palpate: the compartment, note temperature, tension, tenderness.
- Check pulses.
- Weber two-point discrimination test for sensation - evaluate how finely innervated the skin is.
- Evaluate motor function of the affected limb.
- Radiographs if fracture is suspected.
- Manometer to measure intracompartmental pressure if uncertain (does this by measuring resistance to saline solution when injected into the compartment).
- Slit catheter place within compartment, pressure measured with arterial line transducer (continuous monitoring and more accurate).
- Normal pressure 0-8mmHg.
- Pressure >30mmHg = compartment syndrome.
- Delta pressure (perfusion pressure) = diastolic pressure - measured intracompartmental pressure.
- Ultrasound with Doppler to look for occlusion or thrombus.
- Blood cound and coagulation (pre-operative).
- Creatinine phosphokinase (CPK) levels show muscle breakdown from from ischaemia, damage, or rhabdomyolysis.
- If rhabdomyolysis, do renal function tests, urin myoglobin and urinalysis (full chemistry panel).
Describe the management for compartment syndrome. (LO2)
- Fasciotomy.
- Immediate surgical consult.
- Provide supplemental oxygen.
- Relieve pressure - remove any restrictive casts, dressings or bandages.
- Keep extremity at the level of the heart to prevent hypo-perfusion.
- Prevent hypotension and provide blood pressure support in patients with hypotension.
Define dislocation. (LO3)
Absence of articulation between two bones.
What are the most common dislocations? (LO3)
- Anterior glenohumeral dislocations.
- Acromioclavicular subluxations and dislocations.
- Hip dislocations.
- Knee dislocations.
- Ankle sprains.
What are key questions to ask in a trauma history? (LO3)
Use the AMPLE mnemonic: A - allergies M - medications P - past medical history L - last meal E - events
Fully medical history if time allows.
In what direction does the shoulder commonly dislocate and what complications could this present? (LO3)
Anterior - this moves the humeral head towards the axilla and might damage the neurovascular bundle running there.
Shoulder dislocations are more common in men and may require surgery if recurrent.
List the key things that need to be considered alongside a shoulder dislocation. (LO3)
The nerves and vascular supply.
- Assess for nerves because the humeral head (shoulder dislocation) can move to the area of the nerves during a dislocation.
- Assess for the motor and sensory function of the medial nerve.
List the key finding when examining a patient susceptible to recurrent shoulder dislocations. (LO3)
Patients with recurrent shoulder dislocations will have joint instability - on certain movements, the patient will experience the sensation when they are about to dislocate the joint.
When this happens, they will stop the examination or move their arm away.
What does the median nerve innervate? (LO3)
The median nerve innervates the palm of the hand (thumb, index, middle and half of the ring finger) and the adductor pollicis brevis.
How do we test median nerve function? (LO3)
Place the hand with the palm facing up. The thumb must also be facing up. Push down on the thumb and if the patient is able to resist it, the median nerve is functioning normally.
What does the radial nerve innervate? (LO3)
The radial nerve innervates the posterior aspect of the arm, from the upper arm all the way down to the back of the hand and fingers. It also innervates the extensor muscles in the forearm.
How do we test radial nerve function? (LO3)
Ask the patient to extend the wrist and fingers while you push against them. If the patient is able to resist it, the radial nerve is functioning normally.
What does the axillary nerve innervate? (LO3)
The axillary nerve innervates the deltoid muscle and provides sensation over the shoulder.
How do we test axillary nerve function? (LO3)
Ask the patient to abduct their arm from the shoulder joint. If they can lift it up past 90 degrees, axillary nerve is functioning normally.
What does the ulnar nerve innervate? (LO3)
The ulnar nerve innervates the pinky finger and the medial half of the ring finger. It also innervates some muscles in the flexor compartment of the forearm (flexor capri ulnaris and part of the flexor digitorum profundus).
How do we test ulnar nerve function? (LO3)
Ask patient to flex their wrist while you provide an opposing force. If they are able to resist, the ulnar nerve is functioning normally.
Alternately, ask the patient to adduct their pinky.
How do you confirm a diagnosis of a fracture/dislocation? (LO3)
X-ray can identify the main issue.
CT/MRI can identify the underlying cause and associated soft tissue injuries.
List the 4 key principles of fracture management. (LO3 + LO5)
Follow the 4 Rs:
Resuscitate - life-saving treatment if the patient is dying.
Reduce - put bone back in its anatomical position (closed vs open).
Retain - maintain bone in the reduced position - with sling/cast/plates, etc.
Rehabilitation - movement to aid recovery and reduce future risk of osteoarthritis.
Describe the pharmacological management of a fracture. (LO3)
- Analgesia.
- If pain is severe, might require opioids, e.g. morphine.
- If pathological fracture, treat the underlying condition, e.g. for osteoporosis - calcium and vitamin D, bisphosphonates and glucosamine.
Why is it important to assess neurovascular status when dealing with a fracture? (LO3)
Bony injuries can damage the surrounding structures, e.g. nerves and blood vessels. This can have long-term effects if not managed promptly. This also helps determine the severity of fractures and further management.
List the 2 most common wrist fractures? (LO3)
Colle’s fracture - outwards
Smiths fracture - inwards
Colle’s fracture occurs during a fall on outstretched hand (FOOSH).
How long do wrist fractures need to be in a cast (LO3)
4-6 weeks
What type of fracture is associated with dangling? (LO3)
Distal humerus fracture, sometimes along with damage to the olecranon.
It’s important to note that the ulnar nerve runs near this area and may be damaged.
Which way does the hip most commonly dislocate? (LO3)
Posteriorly, which can affect the sciatic nerve.
What are the clinical findings in a hip fracture? (LO3)
The leg is shortened and externally rotated.
What type of hip fracture can cause avascular necrosis of the femoral head? (LO3)
Intracapsular/sub-capital
Which way does the knee most commonly dislocate? (LO3)
Laterally - the patella slides sideways after impact injuries. These can spontaneously reduce when the knee straightens.
How is a muscle sprain managed? (LO3)
Use the RICE mnemonic: R - rest I - ice C - compression E - elevation
What is the movement that causes ankle sprains. (LO3)
Excessive inversion or eversion of the ankle.
How can we check for sufficient blood supply in the limbs? (LO3)
In a normal limb:
- Capillary refill is <2 seconds.
- Pulses present and normal.
- No cyanosis.
Capillary refill - squeeze the tip of the finger and let go. Refill time is how long it takes for the tip to turn oink again from blood re-entering.
Describe the 3 different levels of energy that can cause injury to a joint. (LO3)
- Low energy - ankle sprain.
- High energy - accident during collision sports.
- Extreme energy - road traffic accidents.
List the 5 different types of imaging used to image bone. (LO4)
- Plain x-rays.
- Magnetic resonance imaging (MRI).
- Ultrasonography.
- Computed tomography (CT).
- Nuclear medicine.
Briefly describe x-rays. (LO4)
X-rays produce images that show structural changes and help to monitor bone and joint diseases.
List some advantages of using X-rays to image bone. (LO4)
- Useful for osteoarthritis.
- They are non-invasive.
- Can be used for guidance whilst inserting catheters.
- Can also show up issues that weren’t the initial reason for the imaging.
- Can be used on a wide range of people.
List some disadvantages of using X-rays to image bone. (LO4)
- Some features of osteoarthritis such as erosions only show up with time so can’t be seen on an initial x-ray.
- Poor images of soft tissues.
- The radiation can be harmful.
- There’s a limit to the number of x-rays you can have in a given period of time due to radiation.
Briefly describe magnetic resonance imaging (MRI). (LO4)
MRIs use strong magnetic field gradients and radio waves to generate images of the organs in the body.
List some advantages of using MRIs. (LO4)
- There is enough good soft tissue discrimination to show tumours, inflammation and degeneration.
List some disadvantages of using MRIs. (LO4)
- Expensive.
- The patient may feel claustrophobic.
- The loud noise may make the patient uncomfortable.
Briefly describe ultrasonography. (LO4)
Ultrasonography uses high-frequency sound-waves in order to image internal bodily structures.
List some advantages of using ultrasonography. (LO4)
- Cheap.
- No ionising radiation.
- Good for superficial anatomy.
- Good for investigation into small joint synovitis and erosions.
List some disadvantages of using ultrasonography. (LO4)
- Lower resolution when looking at deeper parts of the body.
- Don’t show structure inside the joint.
Briefly describe computed tomography (CT). (LO4)
CT uses x-rays and a computer to image inside the body.
List some advantages of using CTs. (LO4)
- Can be used when an MRI scan isn’t possible.
- It’s non-invasive.
- It can image bone, soft tissue and blood vessels all at the same time.
List some disadvantages of using CTs. (LO4)
- It requires patients to hold their breath which some can’t manage.
- Uses radiation.
Briefly describe nuclear medicine (imaging). (LO4)
Nuclear medicine is an imaging method that shows bone metastases (cancer) by using small amounts of radiation.
List some advantages of using nuclear medicine for imaging. (LO4)
- Cheap.
- Very helpful in diagnosing cancer.
List some disadvantages of using nuclear medicine for imaging. (LO4)
- Uses radiation.
- It is sensitive.
- It isn’t very specific.
Describe the basic epidemiology of fractures. (LO5)
- Fractures mainly occur due to trauma.
- The incidence of fractures in the US is 21 per 1000.
- More common in men.
- Femoral shaft fractures are more common in young men and women over 65.
List the most common fractures. (LO5)
- Tibial fractures.
- Femoral shaft fractures.
- Distal radius fractures.
- Humeral shaft fractures.
List the common underlying conditions for fractures. (LO5)
- Osteoporosis.
- Chronic renal failure.
- Advanced age.
- Diabetes.
List the protective factors against fractures. (LO5)
- High BMI.
- Black ethnicity.
Describe the presentation of non-pathological fractures. (LO5)
- Pain.
- Swelling.
- Impaired range of movement.
- Neurovascular complications (in some cases).
- Deformities (in some cases).
Symptoms are more useful for diagnosing closed fractures which may not necessarily be visible.
Briefly describe the presentation of pathological fractures (LO5).
- Sudden onset pain.
- Swelling.
- Bruising.
- Reduced movement.
Describe the investigations for fractures. (LO5)
- Take a full and thorough history.
- Examination of the affected region as well as joint above and below. This is where you check for neurovascular complications.
- Basic observations - open fractures?
- Blood tests - FBC, U+E, calcium, phosphate and any specific blood tests for suspected underlying causes.
- X-ray - do they need surgery?
- Ultrasound - if vascular injury is suspected.
- For all fractures, maintain a high suspicion index for compartment syndrome.
List some of the complications of fractures. (LO5)
- Infection - of the wound or bone.
- Acute compartment syndrome.
- Venous thromboembolism - chronic inflammation is prothrombotic.
- Fat embolism syndrome.
- Malunion.
- Delayed union.
- Non-union.
- Complex regional pain syndrome.
- Avascular necrosis.
- Adhesive capsulitis.
Describe the prognosis of fractures. (LO5)
Average recovery can take 6-8 weeks, however certain factors can delay it:
- NSAIDs.
- SAIDs.
- Smoking.
- Anything that reduces the inflammatory response.
Certain fractures can take longer to heal such as neck of femur: 12-24 weeks.
List the four different shapes of bone in the skeletal system. (LO6)
- Long bone - e.g. femur.
- Short bone - e.g. carpals.
- Flat bone - e.g. ribs.
- Irregular bone - e.g. vertebrae.
List the 3 main regions of the long bone. (LO6)
- Diaphysis - the shaft and main portion of the bone.
- Epiphysis - the two ends of the bone.
- Metaphysis (mature bone) - the regions where the diaphysis and epiphysis join.
In a maturing bone, what would you see where the metaphysis should be? (LO6)
The epiphyseal growth plate.
List the three sections of the internal structure of a long bone. (LO6)
- Articular cartilage.
- Periosteum.
- Medullary cavity.
- Endosteum.
Describe the articular cartilage in bones. (LO6)
The articular cartilage is a layer of hyaline cartilage covering the epiphyses of bone to prevent friction during movement.
Describe the periosteum of bone. (LO6)
This is the connective tissue surround the bone in the regions where there is no articular cartilage.
The periosteum contains osteogenic precursor cells which thicken the bone. It protects the bone and assists in fracture repair.
Tendons and ligaments can also attach to this.
Describe the medullary cavity of bone. (LO6)
Also known as the marrow cavity.
This resides inside the diaphysis and contains bone marrow.
Describe the two types of bone marrow. (LO6)
When you’re born, all of your marrow is red, but becomes yellow as you grow dur to a decrease in erythropoietin - a substance that stimulates blood cell production.
Red marrow - produces both red and white blood cells and platelets (haematopoietic tissue).
Yellow marrow - contains adipose and connective tissue and only produces some white blood cells.
Describe the endosteum of the bone. (LO6)
Just like the periosteum, the endosteum is a membrane. However, the endosteum lines the inner side of the diaphysis. It lines the medullary cavity. This also contains osteoblasts. It’s the site of new bone formation as it contains osteogenic precursor cells (which will become osteoblasts).
List the two types of bone in terms of structure. (LO6)
- Compact/cortical bone.
- Cancellous/spongy/trabecular bone.
Describe compact bone. (LO6)
- High proportion of bone and fewer spaces.
- Consists of collagen impregnated with inorganic calcium salts.
- Typically found in the epiphyses of long bones.
- Made to resist the weight put on it by regular movement.
Describe trabecular bone. (LO6)
- Low proportion of bone and more spaces.
- Composed of network of rods and plates called trabeculae.
- The spaces between trabeculae are filled with red or yellow bone marrow.
- Typically found in the diaphysis of long bones.
Describe the bone matrix. (LO6)
- Forms the majority of bone mass.
- Has an organic and inorganic component.
- Organic component mainly comprises of collagen.
- Inorganic component mainly comprises of mineral salts.
What are the key components of bone matrix? (LO6)
- Type 1 collagen.
- Bone proteoglycan.
- Non-collagenous proteins such as osteocalcins and osteonectins.
- Hydroxyapatite (complex calcium phosphate salt).
In what 2 distinct patterns can collagen be deposited into the bone matrix? (LO6)
- Woven bone - an immature form with random fibre orientation created during rapid growth and fracture repair.
- Lamellar bone - successive layers of collagen fibres with a distinct orientation.
List the cells found within the bone. (LO6)
- Osteoblasts.
- Osteoclasts.
- Osteocytes.
- Lining cells.
Describe the function of osteoblasts. (LO6)
- Carry out bone formation.
- Synthesis of the bone matrix.
- Priming for mineralisation.
Structurally these are plump cuboidal cells with abundant organelles for protein synthesis and secretion.
They form an epithelioid layer on the bone surface.
Describe the function of osteoclasts. (LO6)
- Carry out bone resorption.
These are multinucleate cells and appear to have a ruffled border and clear zone.
Describe the function of osteocytes. (LO6)
These are osteoblasts trapped within the bone matrix.
- Play a role in calcium homeostasis.
- Balance osteoblast vs. osteoclasts activity.
Structurally, they have canaliculi which have junctions with other osteocytes and the blood supply.
Describe the function of lining cells. (LO6)
These are osteoblasts which have completed synthesis of bone. They are inactive cells which can be reactivated.
- Reactivated in bone remodelling and work with osteocytes to regulate calcium homeostasis.
Describe how bone is maintained throughout life. (LO6)
- It’s a balance between bone remodelling by the osteoblasts and bone resorption by the osteoclasts.
- The adult skeleton is constantly undergoing a cycle of resorption and formation.
- The main process of remodelling seeks to reform the bone rather than the creation of new bone.
- The creation of new bone, which would increase bone mass is called modelling.
How long does resorption of cortical bone take? (LO6)
30 days.
How long does resorption of trabecular bone take. (LO6)
40 days.
How long does remodelling of cortical bone take? (LO6)
90 days.
How long does remodelling of trabecular bone take? (LO6)
140 days.
List the four key stages of remodelling. (LO6)
- Activation.
- Resorption.
- Reversal.
- Formation.
Describe the activation stage
of remodelling. (LO6)
The resting bone surface is relabelled into a remodelling surface. This leads to attraction and recruitment of osteoclasts. The osteoclasts fuse into multinuclear osteoclasts.
Describe the resorption stage of remodelling. (LO6)
This occurs when osteoclasts destroy the bone matrix. This releases calcium into the bloodstream. The osteoclasts disband and migrate away where they are apoptosed.
Describe the reversal stage of remodelling. (LO6)
Osteoblasts are recruited to the bone surface.
Describe the formation stage of remodelling. (LO6)
Osteoblasts use organic and inorganic components to replace the bone with osteoid (unmineralised bone matrix) which provides the basic structure before mineralisation of the matrix with calcium salts.
Describe RANK-L and its function. (LO6)
- RANK ligand (RANK-L) is a molecule which stimulates osteoclasts formation, survival and function.
- The expression of RANK-L is tightly regulated by osteoblasts and other immune cells, e.g. T cells.
- RANK-L increases bone resorption.
Describe OPG and its function. (LO6)
- Osteoprotegerin is a molecule which opposes the action of RANK-L.
- It prevents osteoclasts activation by binding RANK-L and preventing its action.
Many disease processes increase the RANK-L:OPG ratio leading to bone resorption and weakness. This can manifest as weakened bones which leads to pathological fractures and other sequelae.
List some healthcare associated infections (HCAIs) and how they come about. (LO7)
- Indwelling catheters, poor hygiene: MRSA.
- Antibiotic resistance, proton pump inhibitors, poor hygiene: C. difficile.
- Urinary catheters: ESBL (extended spectrum beta lactamase).
- Surgical site infections: gram negative bacteria, anaerobes, group A Streptococcus, MRSA (methicillin resistant Staphylococcus aureus).
How do we prevent healthcare associated infections (HCAIs)? (LO7)
- Infection control in healthcare (PPE).
- Vaccination.
- Post-exposure prophylaxis.
- Surveillance - infection control information passed onto the government.
- Outbreak investigations.
- Standardisation.
- ANTT - antiseptic non-touch technique.
List some reasons we need to prevent healthcare associated infections (HCAIs)? (LO7)
- to reduce morbidity and mortality which may result in sepsis.
- to reduce length of stay.
- to reduce economic burden.
- to reduce risk of surgical procedure.
- patients with HCAIs are 7x more likely to die as inpatients.
List some factors associated with infection. (LO7)
- The microorganism.
- The host.
- The environment.
- Treatment: previous and current - will affect the flora.
How would we prevent the transmission of air-borne diseases? (LO7)
- Place the infected patient in source isolation.
- Protect the vulnerable patients by use of filtered air, negative pressure.
Examples: Tuberculosis.
How would we prevent the transmission of direct contact diseases? (LO7)
- Place the infected patient in source isolation.
- Aseptic technique, hand hygiene, etc.
Examples: MRSA, Vancomycin-resistant enterococci, Clostridium difficile, Norovirus.
What is specifically used in operating theatres to prevent infections? (LO7)
Laminar air flow system.
Describe the difference between colonisation and infection. (LO7)
Colonisation is when microorganisms exist in the body but don’t invade.
Infection is when they begin to invade and cause detectable damage.
List the different routes of delivery of antibiotics. (LO7)
- Oral (needs time).
- Intravenous (injection or infusion - very fast).
- Intramuscular.
- Local.
List the different levels of contamination of a wound. (LO7)
- Clean
- Clean/contaminated.
- Dirty.
Any of these could be in an operating theatre and they would be prone to different infections.
Define pain. (LO8)
An unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage.
Describe acute pain. (LO8)
Acute pain promotes protective mechanisms and is caused by noxious stimuli and tissue damage. Acute pain tends to stop when the tissue has healed and is only short-lived. Chronic pain is the persisting pain after the tissue has healed.
Describe chronic pain. (LO8)
Chronic pain can sometimes have no known cause such as migraines and does not seem to have any function.
Which pathway is pain transmitted through? (LO8)
Pain is part of the somatosensory system of the CNS. It’s transmitted through the anterolateral pathway, also known as the spinothalamic tract.
Define nociception. (LO8)
Nociception is the neural process of encoding noxious stimuli, usually leading to the sensation of pain.
List some noxious stimuli. (LO8)
- Mechanical (high intensity).
- Chemical (exogenous or endogenous).
- Thermal (>45°C, <5°C).
Describe nociceptors and their function. (LO8)
- Nociceptors are primary afferent neurones with a pseudounipolar and free nerve ending morphology.
- They encode noxious stimuli into electrophysiological neural signals in the form of action potentials - a process known as transduction.
What happens when a stimulus becomes large enough? (LO8)
When a stimulus is large enough to reach the threshold:
- It causes depolarisation of the nociceptor cells of the neuron and an electrical signal is sent to afferent nerve fibres (Aδ, Aβ, C).
- The primary afferent fibres carry the input into the dorsal horn of the spinal cord, where they synapse with secondary neurones.
- The first synapse in the pain pathway is always in the dorsal horn of the spinal cord.
- The dorsal horn is arranged in laminae.
Where do each of the types of fibres synapse in the dorsal horn? (LO8)
Laminae 1: most Aδ fibres.
Laminae 2: most C fibres.
Laminae 5: most Aβ fibres.
Laminae 5 is also where the converging stimuli go and where direct Aδ and C fibre inputs from the dorsal horn pathway go.
List the three central pathways ascending to the brain. (LO8)
- Spinothalamic.
- Spinoreticular.
- Spinomesencephalic.
Describe the pathway of the secondary neurons from the dorsal horn. (LO8)
The secondary neurons can take 1 of 3 central pathways ascending to the brain.
The secondary neurons cross to the other side of the spinal cord and ascend contra-laterally.
Describe the spinothalamic pathway of secondary neurones. (LO8)
In the spinothalamic pathway, the secondary neurone goes through the brain stem to the thalamus. Here it can synapse with a third neurone and gets taken from the thalamus to the somatosensory cortex.
What are the two forms of initial pain and how do they differ? (LO8)
- First pain.
- Second pain.
- They both reach the brain at different rates due to different fibres carrying the input and the rate at which the fibre conducts action potentials.
Describe what you feel before first pain when you stub your toe. (LO8)
- When you stub your toe, prior to the pain you feel an “ouch!”.
- This is the Aβ fibres being stimulated by low threshold mechanoreceptors.
Describe the first pain of stubbing your toe. (LO8)
- First pain is a fast, prickling pain.
- Carried by Aδ fibres and enters the CNS faster.
- Aδ fibres undertake saltatory conduction as they are thicker in diamater and myelinated.
Describe the secondary pain of stubbing your toe. (LO8)
- Second pain lingers and feels more like a burning pain.
- This takes a long time to reach the brain (up to 1 second).
- C fibres have much slower conduction velocity due to only being slightly myelinated.
What else apart from fibres can affect the speed of pain perception? (LO8)
- Rate of neurotransmitter diffusion at synapses in the dorsal horn.
- Glutamate is one of the fast neurotransmitters released from central terminals of the axon.
- Substance P has a slower transmission rate as it is a peptide which diffuses slower so causes slower depolarisation.
How do neurotransmitters affect first and second pain? (LO8)
- For first pain, glutamate transmits the signal quickly.
- When a harder stimulus is applied, more action potentials are generated and substance P can also be released.
- Substance P is shown to cause a larger perception of pain.
- Substance P has a slower transmission rate as it is a peptide which diffuses slower so causes slower depolarisation - pain will linger.
What are the most common receptors in the detection of noxious stimuli? (LO8)
A superfamily of receptors called Transient Receptor Potential channels (TRP). Each subclass has different abilities for detecting noxious stimuli.
Name the stimulants for different TRP channels in the detection of noxious stimuli? (LO8)
- TRPV1 - activated by capsaicin.
- TRPM8 - activated by menthol.
What happens when a TRP channel is stimulated? (LO8)
- Stimulation of TRP channels leads to neurogenic inflammation and transduction of an action potential (AP).
- This causes the release of other neuro-chemical factors which leads to nociception.
- From this, the sensation of pain can arise.
What is the general process when a stimulus is applied? (LO8)
- A particular stimulus activates ion channels.
- Action potential is generated if the input is large enough to reach the threshold.
- Nociceptors respond to different stimuli depending on the types of ion channels they contain. They are usually polymodal.
Which neurones are involved with noxious heat modality? Which TRPs could be activated? (LO8)
- Aδ + C fibres.
- TRPV1 (capsaicin).
Which neurones are involved with noxious mechanical modality? Which TRPs could be activated? (LO8)
- Aδ + C fibres.
- TRPA1, TRPV4, Piezo.
Which neurones are involved with noxious chemical modality? Which TRPs could be activated? (LO8)
- Aδ + C fibres.
- ASIC, TRPA1, TRPV1.
Which neurones are involved with noxious cold modality? Which TRPs could be activated? (LO8)
- C fibres.
- TRPM8 (menthol), TRPA1.
What is referred pain? (LO8)
- Sensations of pain at a site other than the injured tissue.
- When nociceptive afferents activate interneurones, it may lead to referred pain.
- E.g. during a heart attack, people experience pain in their left arm rather than the heart. This is because the visceral and active afferents converge at the same neurone in the spinal cord.
List the main factors in a joint that contribute to stability of the joint. (LO9)
- Articular surface shape (congruence).
- Cartilaginous structures.
- Ligaments.
- Tendons.
- Muscle.
List some features of the hip joint that provide stability. (LO9)
- The acetabulum.
- Intracapsular ligaments.
- Extracapsular ligaments.
Describe how the acetabulum provides stability at the hip joint. (LO9)
Deep joint socket. Encompassed by the acetabular labrum (horseshoe-shaped fibrocartilaginous ring) that:
- Increases the depth of the joint.
- Gives a larger articular surface.
- Provides vacuum seal by maintaining negative pressure.
The shape of the acetabulum allows for it to encapsulate almost the entire head of the femur.
Describe how the intracapsular ligaments provide stability at the hip joint. (LO9)
- Only one ligament of the head of femur:
- Ligamentum Teres.
- It runs from the acetabular fossa to the fovea of the femur.
List the three extracapsular ligaments of the hip joint. (LO9)
3 main ligaments:
- Iliofemoral ligament.
- Pubofemoral ligament.
- Ischiofemoral ligament.
Describe the iliofemoral ligament in the hip. (LO9)
Y-shaped ligament that connects the pelvis to the femoral head at the front of the joint.
Helps in limiting over-extension of the hip.
Describe the pubofemoral ligament in the hip. (LO9)
Triangular shaped ligament that extends between the upper portion of the pubis and the iliofemoral ligament.
It attaches the pubis to the femoral head.
Describe the ischiofemoral ligament in the hip. (LO9)
A group of strong fibres that arise from the ischium behind the acetabulum and merge with the fibres of the joint capsule.
List some conditions caused by an unstable hip joint. (LO9)
- Congenital Hip Dysplasia - shallow acetabulum due to failed development in utero.
- Acquired Hip Dysplasia - femoral head tears through the interior, posterior joint capsule, uncommon, result of trauma, usually occurs posteriorly (90%),
List the features of a knee joint that maintain stability. (LO9)
- Two menisci.
- Joint capsule.
- Intracapsular ligaments.
- Extracapsular ligaments.
Describe how the two menisci provide stability at the knee joint. (LO9)
- Concave shape.
- Sit between the femoral condyles and tibial plateau.
- Provide congruence.
Describe how the joint capsule provides stability at the knee joint. (LO9)
- Fibrous layer surrounding the joint.
- Reinforced by tendons of surrounding muscles, e.g. iliotibial tract, semimembranosus.
List the intracapsular ligaments of the knee joint. (LO9)
- Anterior cruciate ligament (ACL).
- Posterior cruciate ligament (PCL).
- Transverse ligament of the knee.
- Coronary ligaments.
Describe how the intracapsular ligaments provide stability at the knee joint. (LO9)
- Anterior cruciate ligament prevents anterior displacement of the tibia on the femur.
- Posterior cruciate ligament prevents posterior displacement of the tibia.
- ACL and PCL both prevent hyperextension and hyperflexion of the joint.
- Coronary and transverse ligaments hold the menisci in place during movement and limit knee rotation.
Describe how the extracapsular ligaments provide stability at the knee joint. (LO9)
- Medial and lateral collateral ligaments prevent translation of the femur on the tibia and maintain congruency.
Briefly describe the general stability of a knee joint. (LO9)
- Hinge joint.
- Poor congruence between articulating surfaces due to shape of femoral condyles and the flatness of the tibial plateau.
- Most stable in extension.
Briefly describe the general stability of an anatomical ankle joint. (LO9)
- Hinge-type synovial joint.
- Malleolus of the tibia and fibula create a grip around the talus bone and help stability.
List the features of an anatomical ankle joint that maintain stability. (LO9)
- Lateral ligaments of the ankle (lateral collateral ligament complex).
- Anterior talo-fibular ligament (ATFL).
- Posterior talo-fibular ligament (PTFL).
- Calcaneo-fibular ligament (CFL). - Medial ligaments of the ankle (much stronger than lateral side).
- Deltoid ligament.
Describe how the anterior talo-fibular ligament (ATFL) provides stability at the ankle joint. (LO9)
- Runs anteriorly from the lateral malleolus to the talus.
- Weakest so most frequently injured.
- Resists torsion and inversion in a ~flexed ankle~.
Describe how the posterior talo-fibular ligament (PTFL) provides stability at the ankle joint. (LO9)
- Runs posteriorly from the lateral malleolus to the posterior aspect of the talus.
Describe how the calcaneo-fibular ligament (CFL) provides stability at the ankle joint. (LO9)
- Runs from the lateral malleolus to the lateral aspect of the calcaneus, between the ATFL and the PTFL.
- Resists torsion and inversion in an ~extended~ ankle.
Describe how the deltoid ligament provides stability at the ankle joint. (LO9)
- Consists of 4 ligaments forming a triangle.
- Connects tibia to navicular, calcaneus and talus bones.
- Stabilises ankle during eversion and prevents subluxation by restricting talus from shifting into valgus position or translating antero-laterally or rotating externally.
Briefly describe the general stability of a subtalar joint. (LO9)
- Plane, synovial joint.
- Fibrous layer of joint capsule attached to margins of articular surface.
- Main movements are inversion and eversion.
- Talar dome: upper portion of talus where articular cartilage for the tibiotalar joint is located.
List the features of a subtalar joint that maintain stability. (LO9)
- Medial, lateral, posterior talocalcaneal ligament - support the capsule.
- Interosseous talocalcaneal ligament - binds the bones together.
Briefly describe the general stability of a talocalcaneonavicular joint. (LO9)
- Ball and socket - talonavicular portion.
- Synovial.
- Head of the talus articulates with calcaneus and navicular bones.
- The joint capsule incompletely encloses the joint (dorsal and proximal aspects).
- Proximal aspect is better developed, known as the ‘true’ joint capsule and forms the strong talocalcaneal interosseous ligament.
List the features of a talocalcaneonavicular joint that maintain stability. (LO9)
3 ligaments supporting the joint:
- Plantar calcaneonavicular (aka ‘spring’) ligament - supports head of the talus.
- Dorsal talonavicular ligament.
- Bifurcate ligament - Y-shaped structure running from calcaneus and divides into the calcaneocuboid and calcaneonavicular part.
List the biomedical aspects of a consultation as opposed to biopsychosocial. (LO10)
- Disease-centred.
- Treatment decided by doctor.
- Biology is only factor.
- Aim is eradicating disease.
- Reductionist (one aspect) and inflexible.
- Monofactual.
- One person team (doctor).
- Disease.
- Fact focused: no ICE used.
1. What are the symptoms?
2. Duration of symptoms.
3. Investigations, e.g. tests.
4. Diagnosis.
5. Treatment.
List the biopsychosocial aspects of a consultation as opposed to biomedical. (LO10)
- Patient-centred.
- Open conversation about options for treatment.
- Biology, psychology and social history all important.
- Aim is chosen with patient’s wishes and best interests.
- Holistic and fluid.
- Multifactorial.
- Multi-disciplinary team (MDT).
- Illness.
- Facts as well as patient: use ICE.
1. What are the symptoms? - with history of when they occur.
2. Duration of symptoms - recurring, sudden, due to an event?
3. Investigations, e.g. tests - with informed consent of patient.
4. Diagnosis - full explanation, in language patient understands.
5. Treatment - a plan, options, support and continued support, if another issue arises, patient is consulted with dynamic history.
In a biopsychosocial model of consultation, how would you obtain the facts with the patient in mind? (LO11)
- What are the symptoms? - with history of when they occur.
- Duration of symptoms - recurring, sudden, due to an event?
- Investigations, e.g. tests - with informed consent of patient.
- Diagnosis - full explanation, in language patient understands.
- Treatment - a plan, options, support and continued support, if another issue arises, patient is consulted with dynamic history.
Ideas, concerns, expectations!!
What are the 7 principles of decision-making and consent? (LO11)
- All patients have the right to be involved in decisions about their treatment.
- Decision-making is an ongoing process focused on meaningful dialogue.
- All patients have the right to be listened to and be given information they need and time and support they need to understand it.
- Find out what matters to the patients so can share relevant information about benefits and harms of options.
- You must start from the presumption that all adult patients have capacity to make decisions.
- Choice of treatment for patients lacking capacity must be of overall benefit to them, consult with those close to them.
- Patients whose rights to consent are affected by law should be supported to be involved in the decision-making process and exercise choice if possible.
Describe capacity in adults. (LO11)
- Legally adult >18 years.
Adult with capacity:
- Can refuse medical treatment.
- Has right to make unwise decisions.
Adult without capacity:
- Should be treated in their best interests.
- People involved with patients should be consulted about their wishes and relevant values and beliefs.
- These discussions must be limited and disclosures in the best interest of the patient.
Which legislation supports the information we have on capacitous adults’ rights? (LO11)
The Mental Capacity Act 2005.
This act defines adults as those over 16 years of age.
Describe capacity in 16 and 17 year olds. (LO11)
- Defined as adults for the purposes of healthcare.
- Confidentiality MUST be maintained.
- Can consent to treatment.
- Cannot refuse beneficial treatment.
- Presumed competent for the purposes of consent to medical treatment.
Describe how Gillick competence works. (LO11)
- Rights of the child to have confidential advice and treatment is more important than any right of the parent.
- <16s, if capacitous, can consent to treatment.
- Guidance has come from contraception and sexual health cases.
Describe capacity in children. (LO11)
- Parents can give proxy consent on behalf of minor.
- Parents are under legal duty to act in minor’s best interests.
- If doctors and parents cannot agree, a court may be needed.
- If child does not have Gillick competence, they are still owed a duty of confidentiality. Although this is not usually needed as their parents are probably involved in decisions due to their lack of ability to give consent anyways.
Describe consent in non-emergency situations. (LO11)
Patients need relevant information to be shared in a way they understand and retain:
- Share it in place and time where they are most likely to understand and retain it.
- Anticipate whether they find it distressing - be considerate.
- Accommodate patient’s wishes to record the discussion.
- Accommodate patient’s wishes if they would like someone else to be involved (relative, carer).
- Use an interpreter/translation service.
- Share in a format they prefer - written, audio, translated, pictures, media, or methods.
- Give them time and support to consider it.
Describe consent in emergency situations. (LO11)
- Decisions made quickly so less time to apply guidance.
- Principles remain the same.
Describe consent in emergency situations with a conscious patient. (LO11)
Presume they have capacity and seek consent.
Describe consent in emergency situations with an unconscious patient. (LO11)
- Provide treatment that is immediately necessary to save their life or prevent serious deterioration.
- If more than one option, choose one least restrictive of patient’s rights and freedoms, including future choices.
- Provide ongoing care for as long as they lack capacity.
- If they regain capacity, explain the situation to them, what has been done and why when they are recovered enough to understand.
- Discuss further options for any ongoing treatment.
Describe the process of endochondral ossification. (LO12)
- Hyaline cartilage developed and used as template for bone formation.
- Cells within cartilage template begin to differentiate into osteoblasts because of new blood vessels supplying nutrients. The periosteum and primary ossification centre in the middle of the diaphysis form, which acts as a start point for osteoblasts to lay done bone.
- Chondrocytes (cartilage-producing cells) begin to enlarge causing the matrix to calcify - this calcified matrix is then impermeable to nutrients and causes cell death. This cell death means that a central clearing forms in place of dead cells and healthy chondrocytes cause elongation.
- Periosteal bud contains blood vessels and delivers osteogenic cells which allows osteoclasts to degrad cartilage whilst osteoblasts lay down spongy bone.
- As the primary ossification centre continues to enlarge, osteoclasts break down the newly formed spongy bone, forming the medullary cavity. Whilst this happens, cartilaginous growth appears in the epiphyses, resulting in development of the secondary ossification centre (which usually only happens at birth).
- Cartilage is now only present on bone surface and at the epiphyseal growth plates.
Briefly describe skeletal development in utero and state the two types. (LO12)
- Begins 2 months in utero.
- Can be intramembranous ossification (development of flat bones, e.g. cranial and facial).
- Can be endochondral ossification (development of axial skeleton or limbs).
Describe childhood and adolescent bone growth. (LO12)
Bones continue to grow in length throughout childhood and adolescent years:
- Lengthening of the bone throughout our childhood at the epiphyseal plate (area made up of chondrocytes continue to actively make cartilage in the direction of the diaphysis).
- Osteoblasts continuously make bone to replace the cartilage made by chondrocytes until eventually there is no more cartilage to replace and the epiphyseal line forms between the epiphysis and diaphysis.
Describe the process of fracture repair. (LO12)
- When the fracture occurs, blood vessels around the fracture site rupture - leads to formation of haematoma.
- The haematoma fills the fracture, providing a fibrin mesh that seals the fracture site and creates a scaffold.
- Inflammatory cells rush to the scaffold and degranulating cells produce platelet-derived growth factors (as well as others) that activate the osteoprogenitor cells within the periosteum, medullary cavity and surrounding soft tissue - leads to formation of soft, uncalcified callus over the fracture site by the end of week 1.
- By the end of week 2, osteoprogenitor cells have begun to deposit woven bone which then forms a bony callus.
- As the callus matures and is subjected to weightbearing forces, resorption begins to take place and this allows the remodelling process to begin around week 3.
- Remodelling reduces the size of the callus until the shape of the bone is re-established as lamellar bone.
- The healing process is marked as complete at the restoration of the medullary cavity.
List the types of bone tumours. (LO12)
- Cartilage-forming tumours - tumours derived from cartilage.
- Bone-forming tumours - tumours derived from bone.
- Tumours of unknown origin.
List the types of cartilage-forming tumours (tumour derived from cartilage). (LO12)
- Osteochondroma.
- Chondroma.
- Chondrosarcoma.
Easy way to remember: cartilage is laid down by chondrocytes so cartilage-forming tumours have “chondro-“ in the name.
Describe the features of osteochondroma. (LO12)
- Benign.
- Usually occurs in the metaphysis of long bones.
- Occurs in 10-30 year olds.
- Forms as bony excrescence (protrusion) with a cartilage cap.
Describe the features of chondroma. (LO12)
- Benign.
- Commonly occurs in the small bones of hands and feet.
- Common in 30-50 year olds.
Describe the features of chondrosarcoma. (LO12)
- Malignant.
- Commonly occurs in pelvis and shoulder.
- Common in in 40-60 year olds.
- Extends from medulla through the cortex in soft tissue.
- Chondrocytes with increased cellularity and atypia.
- sarcoma always means ~malignant~ tumour of the bone, muscle or connective tissue.
- atypia = cells that are abnormal.
List the types of bone-forming tumours (tumour derived from bone). (LO12)
- Osteoid osteoma.
- Osteoblastoma.
- Osteosarcoma.
Easy way to remember: cartilage is laid down by chondrocytes so cartilage-forming tumours have “chondro-“ in the name.
Describe the features of osteoid osteoma. (LO12)
- Benign.
- Commonly occurs in the metaphysis of long bones.
- Common in 10-20 year olds.
Describe the features of osteoblastoma. (LO12)
- Benign.
- Commonly occurs in the vertebral column.
- Common in 10-20 year olds.
Trick to remember:
Blastoma means over-proliferated blasts (immature cells).
Describe the features of osteosarcoma. (LO12)
- Malignant.
- Commonly occurs in the metaphysis of the distal femur or proximal tibia.
- Common in 10-20 year olds.
List the types of tumours of unknown origin. (LO12)
- Giant cell tumour.
- Aneurysmal bone cyst.
- Ewing sarcoma.
Describe the features of giant cell tumours. (LO12)
- Benign.
- Commonly occurs in the epiphysis of long bones.
- Common in 20-40 year olds.
Describe the features of aneurysmal bone cysts. (LO12)
- Benign.
- Commonly occurs in the proximal tibia, distal femur and vertebra.
- Common in 10-20 year olds.
Describe the features of Ewing sarcoma. (LO12)
- Malignant.
- Commonly occurs in the diaphysis of long bones.
- Common in 10-20 year olds.
Describe the process of bone remodelling. (LO12)
- Osteoblasts sense microcracks and produce RANK-L.
- RANK-L induces monocytes to fuse together and form multinucleated osteoclasts. RANK-L also helps them mature into activates osteoclasts and start resorbing bone.
- Osteoclasts resorp bone by secreting lysosomal enzymes which digest collagen and drill pits (called Howship’s lacunae) into the bone surface. They also start to secrete hydrochloric acid which dissolves hydroxyapatite into soluble calcium and phosphate ions which are released into the blood.
- As the bone is dissolving, it scatters osteoclasts into the blood stream and these waste products are phagocytosed by osteoclasts.
- Osteoblasts secrete osteoprotegerin which binds to RANK-L and slows down activation of osteoclasts in order to control the rate of resorption.
- Once osteoclasts have finished, they apoptose and the osteoblasts secrete osteoid seam, a substrate mainly made of collagen. The osteoid seam begins to fill in the lacunae, trapping osteoblasts in the new bone. This leaves them to form osteocytes and the remodelling is complete.
