Bone Healing & Wound Management Flashcards
Remind yourself of the difference between woven (primary) and lamellar (secondary bone)
- Woven (primary)= appears in embryonic development and fracture repair. Laid down rapidly. Consists of osteoid (unmineralised ECM) with collagen fibres arranged randomly. Temporary structure to be replaced by mature lamellar bone
- Lamellar (secondary) bone= bone of adult skeleton. Consists of highly o_rganised sheets of mineralised osteoid_. Can be divided into two subtypes: compact & spongey
For spongy bone, discuss:
- Where it is found
- Structure
- Properties
- Why we need spongey bone
- Interior of most bones- deep to compact bone
- Bony matrix of fine columns which crosslink to form trabeculae.
- Light, pourous bone
- Why we need it:
- If all bone was compact skeleton would be too heavy
- Spaces between trabeculae filled with bone marrrow
For compact bone, discuss:
- Where it is found
- Structure
- Outer shell of bone
- Lamellae organised into concentric circles which surround a verical Haversian canal (transmits neurovascular and lymphatic vessels). The entire structure is called an osteon (it is the functional unit of bone). Haversian canals are connected by horizontal Volkmann’s canals (these contain small vessels that join the arteries of the Haversian canals and also transmit blood vessels to periosteum). Osteocytes are located between laemllae within cavities called lacunae. Lacunae are interconnected by tunnels called cannaliculi.
Briefly remind yourself of the process of endochondral ossification
Hyaline cartialge replaced by osteoblasts secreting osteoid- responsible for long bone development.
- Initial cartiage model
- Collar of periosteal boen appears in shaft
- Central cartilage calcifies. Nutrient artery penetrates supplying bone and depositing osteogenic cells. Primary ossification centre formed.
- Medulla becomes cancellous bone.
- Cartilage forms epiphyseal growth plates. Epihpyses form secondary ossification centres
- Epiphyses ossify and growth plates continue to move apart lengthening bone
- Epiphyseal growth plates replaced by bone Hyaline cartilage persists at ends
Briefly remind yourself of intra-membranous ossification
Bone formed from clusters of mesenchymal stem cells- forms flat bones.
- Mesenchymal stem cells aggregate to form tight cluster
- Differentiate into osteoblasts
- Osteoblasts lay down osteoid
- Osteoid mineralises to form bone tissue & spicules
- Spicules join to form trabeculae
- Superficial trabeculae replaced by compact bone
Describe the stages of fracture healing (4/5)
-
Haematoma formation:
- Blood vessels in bone break so haematoma form
- Bones at fracture edge die as no blood supply
-
Inflammatory reaction:
- Inflammatory cells appear in haematoma
- These can help remove dead bone
-
Soft callus formation:
- Cell population changes to osteoblasts & osteoclats
- Dead bone is removed
- New blood vessels appear
- Woven bone appears
-
Hard callus formation/consolidation
- Woven bone replaced by lamellar bone
- Fracture has united
-
Remodelling
- Cancellous bone at edges remodelled into compact bone
- Osteoclats resorb any bulging bone
What is meant by primary and secondary bone union?
- Primary bone union: occurs in fractures treated operatively with internal fixation. Inflammatory response is much reduced and bones heal by direct union end to end. Osteoclasts remove dead bone at edges of fracture and osteoblasts fill the cutting cones (made by osteoclasts) with new bone. No callus formation.
- Secondary bone union: occurs in pts reated with plaster. Normal fracture healing process.
Explain how fracture healing is influenced by:
- Plaster
- External fixation
- IM nails
- Screws & plates
Healing by callus ensures mechanical sterngth whilst the bone end heals. With internal fixation the absence of callus means there is a long period during which the bone depends entirely upon the metal implant for its integrity. In addition, the implant diverts stress away from the bone which may then become osteoporotic and not fully recover once metal is removed.
- Plaster= secondary bone union
- External fixation:
- IM nails:
- Screws & plates:
State some factors that contribute to non and mal-union
- Smoking
- Increasing age
- Infection
- Poor nutrition
- Inadequete mobilisation
- Large displacement of bone ends
- Disturbances of ossification e.g. metabolic bone disease, osteoporosis, tumour
- Severe local trauma, bone loss, soft tissue interposition
- Site of fracture e.g. scaphoid, distal 1/3 tibia, talar fractures
What are bone morphogenetic proteins (BMPS)?
What is bone grafting?
BMPS= growth factors that stimulate bone growth naturally in the human body. BMPs can be implanted into sections of bone that need to repair
Bone grafting is a surgical procedure that uses transplanted bone to repair and rebuild diseased or damaged bones. Relies on BMPS from
Discuss the NICe guidance in relation to the use of USS in fracture healing
“The evidence for low-intensity pulsed ultrasound to promote healing of delayed-union and non-union fractures raises no major safety concerns. The current evidence on efficacy is inadequate in quality. Therefore, this procedure should only be used with special arrangements for clinical governance, consent and audit or research.”
“The procedure should be used with other treatments for delayed-union and non-union fractures”
What is meant by the following:
- Malunion
- Delayed union
- Non-union
- Malunion= bone not healed correctly
- Delayed union= failure of union to occur in 1.5 times the nomral time for fracture union
- Non-union= failure of union to occur within 2 times the normal time to fracture union
*NOTE: can expect open fractures to take 2x the normal times
Roughly how long does it take to see visible callus formation on x-ray?
2-3 weeks
Roughly how long does it take for fracture healing in:
- Upper limb
- Lower limb
- Tibia fractures
*
- Upper limb: 6-8 weeks
- Lower limb: 12-16 weeks
- Tibia fractures: 24 weeks
What chemoprophylaxis is used in joint replacements, include:
- Drug(s) used
- When they are started
- How long continued for
