Fracture Biology Flashcards
What is shown by numbers 1-6?
1 → epiphysis - has a complex geometry and carries the joint surface
2 → metaphysis -transition from the thick cortical bone to the thinner cortex of trabecular. Acts as a shock absorber + has larger surface area in order to carry the joint from the epiphysis
3 → diphysis - growing area of the bone. Calcified in adults but stays open in children so
bone keeps growing
4 - hyaline cartilage (type 2)
5 - compact/layered bone - more spongy
6 - spongy/trabecular bone
What is shown by numbers 7-13
7 - epiphyseal line
8- red bone marrow, at the ends of the bone
9 - yellow bone marrow, at the central area
10 - Medullary cavity - higher fat content, but esentially it is the central tubular structure of the diphysis
11 - periosteum - lining of bone surface
12 - endosteum - lining of internal bone surface
13- nutrient artery
Where are most of the haemopetic actions in adults?
note that most of the haemopoietic actions in adulthood are actually in the flat bones rather than long bones
Describe the structure of bone
Well packed in the cortical area.
Compact bone is organised into osteons/Haverisan systems
Osteons are a series of concentric rings of bone, with a few cells resting there and in central blood vessel
The rings are arranged densely packed next to each other to form the cortical bone itself
Relatively acellular - have canaliculi - blood vessels that sit there and allow nutrients to pass through the bones and communication between the different bone regions.
What is periosteum and what functions does it have?
Periosteum is the surface lining of the bone. Functions:
Provide an anchor point for tendons and ligaments, where they can join onto the bone
Ligaments - bone to bone (BBL), prevents excessive movement. Tendons - muscle to bone (BMT). When a muscle contracts, it exerts a force to induce mvt
Periosteum’s deeper cellular layer, has pluripotent scs, used for healing - in children, it is used in the growth and width of cell growth
What is the endosteum?
Endosteum - similar in structure to periosteum, has cells waiting to work on the internal lining of the bone. Also brings up blood supply to the internal lining.
Describe bones at the cellular level
Increased osteoclastic activity leads to increase in osteoblastic activity and vice versa.
Primarily done through RANK-L (signalling molecule)
What type of collagen is found in bone?
Collagen is in triple helix formation
Bone is type 1 collagen - these fibres are lined up typically in the orientations to resist the stresses within the bone.
Type 2 - cartilage at the end of the bone.
What is the organic and inorganic component of bone?
Organic material: cells and collagen fibres
Inorganic material: crystal and mineral components, the calcium phosphate of bone. Mineral part called hydroxyapatite or calcium phosphate mineral - that’s deposited onto the collagen fibrils and organised in a hierarchical fashion within the bony structure to form bone.
Both organic and inorganic are intrinsically linked together
The process of mineralising collagen is that final nudge towards deposition of bone itself in a bone healing cascade
What is important to note when talking about bone at different macroscopic levels?
When we talk about bones macroscopically (at a bigger level - so trabecular vs cortical) - it’s the SAME bone. The collagen is the same, the hydroxyapatite is the same, its just organised differently at a macroscopic level.
How is bone organised based on its specific function?
Organised internally - to reduce stresses on the bone or to resist loads and stresses that the bone experiences on a daily basis.
Typically in bones that are used for bending, the compression side (concave side) will be thicker - the tension side (convex side) will be thinner
eg in femur, posterior is much thicker than anterior surface
What are the 5 stages of fracture healing?
What 4 steps happen when you break bone?
1 - bleeding. Vascular endothelial damage: that might be through the tiny vessels within the bone itself, the vessels lining on the periosteum
2 - triggers initial signalling molecules to be released. E.g. vascular endothelial derived growth factor.
3 - haematoma aggregates + form clot
4 - platelets give out signalling molecules e.g. platelet derived growth factor + insulin like growth factor = helps form clot.
2 reasons why we cannot just produce bony matrix?
bone is expensive to make - cellular differentiation of osteoblasts uses up a LOT of ATP and energy
type of tissue formed in bone gap is dependent on amount of movement occurring in the gap
naturally, when you have just broken a bone, there is a lot of movement in that gap and its too much to allow differentiation into Obs and the formation of bony matrix
Describe what happens during the beginning of the inflammatory phase of a fracture
Inflammatory phase: localised macrophage activity to remove debris
Pluripotent scs differentiate into fibroblasts (first line differentiation- not need much ATP to make tissue) - this then makes fibrocartilage which lessens the mvt in the gap between the broken bones+ makes the gap a bit stickier
What do we mean when we say heal?
What are the priorities in fracture management?
What is an open/compound fracture and hwo would you manage it?
How is the managemnt of this different to other areas of medicine?
Open fracture - skin opened and the skeleton is exposed to the outside world. You would manage this using the A system:
Unlike other organs, open fracture bone is avascular, stripped of periosteum and loss of soft tissue - antibiotic penetration into the bone is not good. Also, bacteria can hide in bone forming a biofilm.
The management of fractions include reduce hold and rehabilitate. Describe hold
What is the difference betwween internal and external fixation?
Internal fixation - plate and screws sits to one side of the bone. The intramedullary nail goes down the medullary canal of the bone
External fixation - circular/complex, with lots of wires and pins. Sometimes if soft tissue is compromised: dont put plates and screws deep inside because of all the bacterial colonisation that can occur
The footprint of an external fixator on the bone is much less. So it allows us to keep the majority of the hardware outside of the skin and reduces the infection risk.
