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Medicine year 2 semester 2 > Case 24- Head injury and bone > Flashcards

Case 24- Head injury and bone Flashcards

1
Q

Evaluating a patient with a head injury

A 
ABCDE approach
• A - Airway with cervical spine control
• B - Breathing
• C - Circulation with haemorrhage control
• D - Disability 
• E - Exposure and environment
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2
Q

Difficulties in the initial assessment of a spinal injury

A
  • Confused/uncooperative
  • Under alcohol influence
  • Past spinal problems
  • Neurological problems
  • Significant distracting injuries
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3
Q

Destination after spinal injury

A
  • Usually major trauma centre (MTC)
  • Some circumstances- trauma unit for urgent treatment
  • If spinal cord injury is suspected, direct to MTC irrespective of time
  • If only a spinal column injury, can be taken to local trauma unit
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4
Q

Cervical spine injury- Canadian C spine rule

A

Applicable in alert and stable trauma patients:
• High- >65 yrs, dangerous mechanism, paraesthesia in upper/lower limbs
• Low- delayed onset neck pain, comfortable in sitting position, low energy injury, ambulatory
• No- Able to actively rotate their neck 45 degrees to left/right and one of the low risk factors

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5
Q

Full inline spinal immobilisation

A

Used if there are high risk factors or if there are low risk factors in the cervical spine with restriction of neck rotation

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6
Q

Thoracic or lumbosacral injury

A
  • > 65 yrs
  • High energy mechanism
  • Prev spinal problems
  • Abnormal neurology
  • Bony midline tenderness
  • Pain on mobilisation
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7
Q

Impact of trauma on the spinal cord

A
  • Bony- fractures/dislocation
  • Intervertebral discs
  • Neurological
  • Ligaments/muscles
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8
Q

Cauda equina syndrome

A
  • Vertebral fracture/subluxation
  • Disc herniation- L5/S1 and L4/5
  • Other causes- Neoplasm, infection, iatrogenic, inflammatory arthropathy
  • Symptoms= lower motor neuron lesion, severe back pain, sexual dysfunction
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9
Q

Effects of Cauda equina syndrome

A
  • Reduced perianal sensation
  • Absence of anal tone
  • Absence of bulbocavernous reflex
  • Reduced lower limb sensation/power
  • Bladder or bowel dysfunction
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10
Q

Intervertebral discs

A
  • Allows spinal motion
  • Provides stability
  • Responsible for 25% of vertebral height
  • Inner nucleus pulposus, outer annulus fibrosus
  • Avascular
  • Nerve fibres supply only the superficial fibers of annulus
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11
Q

Disc prolapse

A
  • Degenerative/traumatic
  • Depends on level of prolapse
  • Location- central or peripheral
  • UMN signs below the prolapse
  • LMN signs at the level of the prolapse
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12
Q

Bone

A
  • Functions in movement, support, protection (thoracic Cage protects the heart), mineral storage (calcium)
  • Derived from mesenchyme (embryonic connective tissue), where woven bone comes from
  • Type of connective tissue (cells surrounded by fibres and ground substance, ECM)
  • Mineralised matrix containing crystals of hydroxyapatite Ca10(PO4)6(OH)2, which gives it its hard structure
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13
Q

Anatomy of the bone

A
  • Dense outer cortex of mature compact cortical bone
  • Inner cavity meshwork of trabecular/spongy bone with spaces between which are occupied by marrow
  • Covered externally with two layers of periosteum. Periosteum allows muscles and tendons to attach to the bone
  • Outer layer – contains collagen, blood vessels
  • Inner layer – osteoprogenitor cells which differentiate into different bone subtypes
  • Covered internally with endosteum- contains Osteoprogenitor cells, reticular fibres (type of collagen). Lines the Medullary cavity
  • At each end of the bone you have articular (hyaline) cartilage which articulates with other bones
  • The head and neck of the bone at each end are the Epiphysis. The shaft of the bone is the Diaphysis. The Epiphysis are important for the growth of long bone
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13
Q

Anatomy of the bone

A
  • Dense outer cortex of mature compact cortical bone
  • Inner cavity meshwork of trabecular/spongy bone with spaces between which are occupied by marrow
  • Covered externally with two layers of periosteum. Periosteum allows muscles and tendons to attach to the bone
  • Outer layer – contains collagen, blood vessels
  • Inner layer – osteoprogenitor cells which differentiate into different bone subtypes
  • Covered internally with endosteum- contains Osteoprogenitor cells, reticular fibres (type of collagen). Lines the Medullary cavity
  • At each end of the bone you have articular (hyaline) cartilage which articulates with other bones
  • The head and neck of the bone at each end are the Epiphysis. The shaft of the bone is the Diaphysis. The Epiphysis are important for the growth of long bone
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14
Q

Two phases of bone development

A 
Woven bone (immature)
Lamellar bone (mature)
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15
Q

Woven bone

A
  • Immature, irregular, collagen fibrils within the ECM
  • Laid bone first during bone formation
  • Irregular arrangement of collagen fibrils with spaces in between
  • Persists in adults in a few sites- tooth sockets/cranial suture. May be formed in fracture repair and will then mature to form the Lamellar bone
  • Contain osteoblasts which are immature bone cells, as they mature they become osteocytes which are trapped in the mineralised matrix
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16
Q

The two types of mature bone

A

Compact and trabecular (spongy)

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17
Q

Compact bone

A

Formed in the outer cortex of the long bone, tightly compacted layers. The bone is arranged in Haversian systems (osteons) which are circular rings of lamellae, 3D structures which run in cylinders. Can have surrounding lamellae outside the Haversian systems

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18
Q

Trabecular bone

A

Contains spaces, found towards the centre of the bone. Bone marrow is found between the spaces

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19
Q

Lamellar bone

A
  • Mature, arranged in layers (Lamellae), compact or trabecular
  • Lamella- means plate like
  • Compact structure
  • Both compact and trabecular bone types are mature lamella bones
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20
Q

Haversian system (osteon)

A
  • Cylindrical subunits
  • Contains holes which are known as Haversian canals which are surrounded by rings of Lamellae
  • Arranged around a central canal
  • Surrounded circumferentially by lamellae
  • Cement line- boundary around each haversian system
  • Interstitial lamellae- outside the cement line and osteons
  • Canaliculi are microscopic canals connecting lacunae, linking the osteocytes together
  • Osteocytes are trapped in the bone matrix in the Lacunae. The osteocytes are surrounded by a mineralised matrix
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21
Q

Structure of the Haversian system/osteon

A
  • Outer circumferential lamellae- outside the cement line
  • Interstitial lamellae- outside the cement line, between two adjacent osteons
  • Periosteum- lines the outside surface, contains Sharpey fibres
  • Compact bone, blood vessels
  • Sharpey’s fibres (connect)- connects the periosteum to tendons
  • Haversian canals
  • Volkmann’s canals (perpendicular)- contains blood vessels
  • Endosteum- contains Osteroprogenitor cells, lines the inner surface
  • Inner circumferential lamellae- plates of mature, compact bone
  • Cement line
  • Collagen fibres in alternate helical orientations
  • Lacunae- along each lamellae, spaces in which the osteocytes are found. The canaliculi are channels between the osteocytes
22
Q

Macroscopic structure of the Haversian structure

A

• A typical long bone (e.g. femur) has:
• A dense outer cortex of compact cortical bone
• An inner cavity meshwork of trabecular/spongy bone with spaces between occupied by marrow
The diaphysis is the shaft of the bone

23
Q

Long bone structure

A

Long bones have proximal and distal epiphyses at the peripheries of the bones. These portions of the bone are initially separate and fuse together during life. These regions are coated in articular cartilage.
Between the epiphysis and diaphysis is the metaphysis which contains the growth plate. Once skeletal maturity has occurred the growth plate closes and final bone length is achieved.

24
Q

Periosteum and endosteum

A

There is an outer periosteum which contains two periosteal layers.
Beneath the perisosteum is the lamellar bone consisting of a layer of cortical (compact bone) and trabecular (spongy) bone.
An inner lining of endosteum which forms the boundary of the central medullary cavity.
There are small openings called nutrient foramina in all bones where the nutrient artery pierces the periosteum and enters the bone.

25
Q

Woven bone summary

A
  • Newly calcified, immature bone that has an irregular arrangement of collagen fibres.
  • Forms during bone formation in foetal development
  • Also forms during bone healing where it is subsequently remodelled into lamellar bone.
  • It persists in adults in certain regions e.g. the cranial sutures of the skull, tooth sockets.
  • It has a higher cell content but a lower mineral content as compared to lamellar bone.
  • It is formed more rapidly, but is also weaker, than lamellar bone.
26
Q

Lamellar bone summary

A
  • Lamellar bone contains lamellae of calcified bony matrix which form structures called osteons.
  • The lamellae are layers of collagen fibres arranged in concentric rings around a centrally placed canal.
  • This canal is called the Haversian canal and contains blood vessels, nerves and lymphatics.
  • Osteoblasts aid in mineralised bone formation. As the bony matrix is laid down osteoblasts become trapped within bone. Once they are trapped in the lacunae they become relatively inactive and are termed osteocytes.
  • The canaliculi form an interconnecting network between the lacunae and contain the dendritic processes of the osteocytes.
27
Q

Lamellae

A
  • Each lamella consists of deposited mineralised bone matrix. The collagen fibres within a lamella are arranged in parallel sheets. Adjacent lamellae have collagen fibers that alternate approximately 90 degrees. This organisation confers great strength to the lamellar bone.
  • The boundary of each osteon is called the cement line.
  • The lamellae between osteons are called interstitial lamellae
28
Q

Types of Lamellar bone (Cortical and trabecular)

A
  • Cortical and trabecular bone are lamellar bone but have distinct gross morphological features.
  • Cortical (compact) bone is a dense layer of bone that contributes to 80% of total bone mass. It is found deep to the outer two layers of periosteum.
  • Compact bone is delineated from the periosteum by the outer circumferential lamellae.
  • Trabecular (spongy) bone is found deep to the cortical layer and consists of bony spicules called trabeculae which serve to keep bones light whilst maintaining their structural integrity.
  • Compact bone is delineated from trabecular bone by the inner circumferential lamellae.
  • Lining the internal surface of the bone is the endosteum.
  • Within the compact bone are the osteons with the alternating orientation of collagen fibers.
  • Blood vessels, nerves and lymphatics enter from the periosteum in Volksmann’s canals which are arranged perpendicular to the Haversian canals
29
Q

Regions of bone

A
  • Long bones have proximal and distal epiphyses at the peripheries of the bones. These portions of the bone are initially separate and fuse together during life. These regions are coated in articular cartilage.
  • The diaphysis is the shaft of the bone. Between the epiphysis and diaphysis is the metaphysis which contains the growth plate. Once skeletal maturity has occurred the growth plate closes and final bone length is achieved.
30
Q

Layers of bone from external to internal

A
  • There is an outer periosteum which contains two periosteal layers
  • Beneath the periosteum is the lamellar bone consisting of a layer of cortical (compact bone) and trabecular (spongy) bone
  • An inner lining of the endosteum which forms the boundary of the central medullary cavity
31
Q

Blood supply to the bone

A

There are small openings called the nutrient foramina in all the bones where the nutrient artery pierces the periosteum and enters the bone

32
Q

Features and location of woven bone

A

Features- newly calcified bone, irregular collagen and cellular arrangement
Location- newly developing bone i.e. in foetal development. Callus in fracture repair

33
Q

Features and location of Lamellar bone

A

Features- remodelled from woven bones, Osteons

Location- adult bone

34
Q

Features and location of cortical bone

A

Forms 80% of lamellar bone, a dense arrangement of osteons

Location- located external to the trabecular bone

35
Q

Features and location of Trabecular bone

A

Forms 20% of lamellar bone. Spicules of bone coated in endosteum
Located internal to the cortical bone

36
Q

What does the Lamella consist of

A

Each lamella consists of deposited mineralised bone matrix. The canaliculi form an interconnecting network between the lacunae and contain the dendritic processes of the osteocytes.

37
Q

What does the Lamella consist of

A

Each lamella consists of deposited mineralised bone matrix. The canaliculi form an interconnecting network between the lacunae and contain the dendritic processes of the osteocytes.

38
Q

Cortical (compact) bone

A

A dense layer of bone that contributes to 80% of total bone mass. It is found deep to the outer two layers of the periosteum, compact bone is delineated from the periosteum by the outer circumferential lamellae

39
Q

Trabecular (spongy) bone

A

Found deep to the cortical layer and consists of bony spicules called trabeculae which serve to keep bones light whilst maintaining their structural integrity. Compact bone is delineated from trabecular bone by the inner circumferential lamellae. Lining the internal surface of the bone is the endosteum

40
Q

What tissue type is bone

A

Bone is a type of connective tissue, the cells are osteocytes surrounded by an extracellular matrix. Contains osteoid collagen in the ECM, which lines up into a structural configuration. The extracellular matrix is mineralised gives it its hardness

41
Q

Bone mineralisation

A
  • Osteoblasts secrete osteoid collagen
  • Vesicles deposit hydroxyapatite, which is the mineral part of the matrix
  • The hydroxyapatite crystalises to form the minerals of the bone
  • Osteoid + hydroxyapatite + proteoglycans + proteins= Mineralisation
42
Q

Mineralised bone matrix

A
  • Inorganic and organic components
  • Organic: osteoid collagen fibres, proteins and proteoglycans
  • Inorganic: hydroxyapatite and other molecules
43
Q

Organic components of the bone matrix

A
  • Collagen type I fibres
  • Proteoglycans- Chondroitin sulfate, Keratan sulfate
  • Other proteins- Osteopontin, Osteocalcin
44
Q

Osteopontin and Osteocalcin

A
  • Bone matrix proteins
  • Osteocalcin is unique to bone and is secreted by osteoblasts
  • Osteocalcin binds to hydroxyapatite crystals
  • Osteocalcin binds osteoblasts to bone matrix
45
Q

Inorganic components of the bone matrix- Hydroxypaptite

A
  • Almost identical to calcium phosphate found in geological deposits
  • Hydroxypapatite forms rod like crystals approx. 40nm x 3nm
  • Crystals attach along the length of the osteoid collagen fibres which forms the bone mineralisation matrix
46
Q

Mineralisation (calcification) of bone

A
  • Occurs in matrix vesicles which release Hydroxyapatite
  • Hydroxyapatite growth and seeding depends on Ca/PO4 concentration
  • Bone only forms where crystal nuclei can form
  • Normal tissue contains factors (e.g. pyrophosphates) which prevent formation of crystal nuclei
47
Q

Calcium homeostasis

A
  • Calcium ions are important in the body
  • Bone is a store of calcium
  • Calcium can be mobilised from the bone to maintain levels in the body
48
Q

Hypocalcaemia

A
  • Low blood calcium levels
  • Caused by low vitamin D or PTH
  • Can be treated with vitamin D supplements
49
Q

Hypocalcaemia

A
  • Low blood calcium levels
  • Caused by low vitamin D or PTH
  • Can be treated with vitamin D supplements
50
Q

Bone mineralisation

A

• Osteoblasts secrete osteoid collagen
• Vesicles deposit hydroxyapatite
• Osteoid + hydroxypapatite + proteoglycans + protein= mineralisation
Requires formation of the bone matrix and then its subsequent mineralisation. The failure of mineralisation may result in osteomalaci

51
Q

Bone matrix

A

Results in a bone matrix called osteoid (approx. 90% of collagen type 1 fibres)
• Bone is a type of connective tissue
• Osteoblasts are one of the cell types in bone and are essential for bone formation. They are responsible for the secretion of bone extracellular matrix which is called osteoid.
• Bone matrix consists primarily of type I collagen (90%).
• The remaining portion consists of ground substance proteoglycans and proteins that aid in subsequent mineralisation e.g. ostecalcin and osteonectin.

52
Q

Bone mineralisation

A
  • Results in a mineralised bone matrix= osteoid + hydroxyapatite + proteoglycans + proteins
  • After the bone matrix has been synthesised then mineralisation occurs. This process involves the addition of hydroxyapatite [Ca10(PO4)6(OH)2] to the collagenous osteoid.
53
Q

The process of bone mineralisation

A
  1. Osteoblasts release vesicles which become interspersed among the collagen fibres of the osteoid.
  2. Osteocalcin aids in binding calcium (Ca2+).
  3. Enzymatic activity of alkaline phosphatase and other enzymes raises the local concentration of phosphate (PO43-).
  4. The calcium and phosphate form hydroxyapatite [Ca10(PO4)6(OH)2] which is deposited around the vesicles.
  5. As more hydroxyapatite is deposited the regions of mineralised osteoid eventually coalesce.

Medicine year 2 semester 2 (47 decks)

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