Growth & Repair Flashcards
Describe the parts of a long bone?
Diaphysis - Shaft
Metaphysis - Flare at the end of the shaft before epiphysis, contains growth plate
Epiphysis - Joint-end of the bone, after the epiphyseal plate
Medullary Cavity - Inside diaphysis, full of marrow
Whats the structural difference between cortical and cancellous bone?
Cortical is made of cylindrical osteons of concentric lamenae. They contain central canals of veins/arteries.
Spongy Bone contains marrow
What is the geographical difference between compact and spongy bone?
Cortical bone is found in the diaphysis of long bones
Trabecular is found in the metaphysis & growth plate of long bones
What is the functional difference between cortical and cancellous bone?
Compact resists bending & torsion
Cancellous resists compression
What are the stages of fracture repair?
1) Inflammation
2) Soft Callus
3) Hard Callus
4) Bone Remodelling
How might we intervene in stage 1 of fracture repair?
Inflammation
- NSAIDS for inflammation (there is debate as to whether they help the pain more or delay healing more)
- Plate Concentrates to improve healing e.g. Platelet derived growth factor (PDGF), Insulin derived gf (IGF) & Vascular endothelial gf (VEGF)
What is the soft callus stage of fracture repair?
The inflammation/swelling goes down
Cartilage and fibrous tissue start to unite the bony fragments.
It gives back some stability but angulation ca still occur
What interventions are possible for stage 2 of fracture healing?
- Cartilage replacement with DMB (Demineralised Bone Matrix)
- Bone Graft
- Bone substitutes
Describe the types of bone graft?
Autogenous Cancellous Bone Graft (Autograft) - Gold standard. Is both osteoconductive and inductive.
Allograft - Osteoconductive but not inductive and risks transmission of disease
What happens during the 3rd stage of fracture repair?
Cartilage forms into woven bone
What happens during the 4th stage of fracture repair?
Woven bone forms into lamellar bone and the medullary canal is reconstituted
How is strain involved in fracture repair?
Mechanical strain induces tissue differentiation so if strain is too low you don’t grow fresh bone
If its too much then the healing process is interrupted
Describe the structure of a peripheral nerve?
In what 2 ways can nerves become acutely injured?
Axon sheathed in endoneurium
Axons grouped into fascicles sheathed in perineurium
Fascicles grouped into a nerve sheathed in epineurium
Nerve injuries can either be through compression or through trauma
In what situations might a peripheral nerve become entrapped?
Median nerve during carpal tunnel syndrome
Spinal root during intervertebral disc prolapse (i.e. sciatica)
Digital nerve in 2/3rd web spaces of foot during morton’s Neuroma
What are the different types of nerve trauma?
Direct (blow or laceration) vs indirect (Avulsion vs traction)
What is neurapraxia?
a temporary loss of motor/sensory function due to:
- Stretch/bruise –> Local ischaemia & Demyelination
Prognosis for neurapraxia?
Reversible, symptoms usually last 6-8wks
What is axonotmesis?
Damage to a nerve axon but not the sheath
Stretch/crush/direct blow leads to wallerian degeneration
Whats the prognosis for axonotmesis?
Fair but worse than neurapraxia
Usually good but not full sensory recovery and less motor recovery
Whats is Neurotmesis?
Completely divided axon and sheath due to laceration or avulsion