Bone injury, fracture healing and bone regeneration Flashcards
what does osteoinductive mean?
a material that induces the differentiation of stem cells into osteoblasts. you want to implant this into your site and see if it induces bone
what does osteoconductive mean?
Material conducts bone formation over the surface of the implant.
what does osteointegration mean?
should only be used to describe the appearance of the interfaceand simply implies bone growth up to the surface of the implant.
what does bone bonding mean?
Direct chemical link between implant and bone
what demographic is normally affected by bone cancers?
children
what does a joint implant need to have ?
if it is going into a chilled then it needs to have a sliding region that allows it to increase in size as the patient grows
how does the survival rate of implants relative to age>
- the longer you have the distal femoral replacement, the more likely you are to have to have it replaced due to aseptic loosening- at 10 years after implant there s a 68% survivorship
what are generally used to treat bone cancers?
implants such as distal femora replacement
are old implants osteointegrated?
no the implant normally becomes loose
how can telemetry be used to help implant design?
- it allows the force put on the implants to be measured- the forces and moments that occur as you walk on an implant
what did telemmetry tell us about the way in which load was being transferred over time?
load becomes distributed more towards the tip of the stem as the implant becomes loose.- to the shaft
what happens at the interface of fold implants over time?
- a fibrous tissue occurs between the implant and the bone and doesn’t become osteointegrated. This results in a change in load over time.
how did they seek to promote osteointegration with the implants in order to prevent damaging load changes? what happened as a result ?
- they engineered a porous collar to the end of the implant with the hope that bone would integrate into it. But this didn’t work- became encapsulated by fibrous tissue and the fiction was not stabilised
due to the act the porous collar did not promote oseointegration, what did they use instead?
they used a hydroxyapatite covered implant (applied by spray) this is the mineral component of bone. They found that bone grew into his prosthesis
how did putting a hydroxyapetite coating on the implant improve the survivorship of implants against aseptic loosening?
it was improved for the ten year period to 88%, from 68%. If you subdivide this into those that got oseointegration at the shoulder of the implant - 98% of these cases survive but when you dont it is reduced. This shows that oseintegration at the shoulder is very important
why is oseointegration at the shoulder so important?
you prevent the load moving to the shaft of the implant and you load the bound in a more physiological manner. the stem of the bone is protected from being over loaded.
how can mesenchymal stem cells be used in bone cancer treatment generally?
take these cells and implant them with the implant in the hope that they promote osteointegration at the implant interface
how does mesenchymal stem cells turn into oteocytes?
- run 2 an OS X for pre osteoblast, then b-catenin for and osteoblast and then an osteocyte if it becomes trapped.
how can you mark mesenchymal stem cells?
- see if they express STRO-1, see if they will become bones when applied to osteogenic supplements. See if they produce rnx-2 and AP
how did they measure wether mesenchymal stem cells were affected by chemotherapy?
they exposed rats to chemotherapy and not the controls- they then broke a bone and fixated them. They then had 3 different groups t look at the repair: osteotomy only, osteotomy with just fibrin glue and then osteotomy with MSC and fibrin glue they show that MSCs could be maintained in fibrin glue)
what does chemotherapy do, how can this be treated, how was this shown?
It reduces bone formation- which is bad because if you are treating someone with bone cancer you want high bone formation because you want to promote regrowth. But when you add mesenchymal stem cells in a glue to a fracture- you find that bone formation increases to the same levels as those without chemotherapy
how can MScs be applied to implants?
a spray- they checked that they could be sprayed and remain viable first.
what did they find when they spray MSCs?
there is an initial reduction in viability and then it increases
describe the experiment used to investigate whether a spray of MSC onto an implant can improve osteointegration.
they sprayed it onto surface of the implant and they used an animal model which was a tibial replacement in the sheep- they looked at a group with stem cells and some without and as early as 2 months you could see differences in the amount of bone formation. - the found that the more cells you integrate the better the response. These cells were all autogenic cells.
what is the problem with using the autogenic MSC spray into implant approach? how can this be circumvented?
you are taking cells from a cancer patient so you may be spraying back on cancerous cells. You can use the same model but with allogenic cells and also with cells that have been differentiated down the osteogenic lineage.
what were the results of trying to circumvent the problem with using autologous cells within the spray MSC approach?
- you use cells that are allogenic and some cells that have been differentiated down the osteogenic line
- you find that the allogenic cells in this system didn’t work. bu t when you use autogenic stem cells tat have been differentiated partially down the osteogenic pathway then you get a better response.
- it is thought that the allogenic cells caused some kind of immune response/ infammatory which caused bone resorption.
how can you use autogenic stem cells for implantation?
if you aren’t using cells from a cancer patient
