Injury and Healing (extra-recap) Flashcards
Session plan:
How do bones break?
Mechanisms of Bone Fracture
Trauma – High vs. Low energy
Left-high energy trauma
Right-falling from standing height causing low energy fracture
What’s the difference between a stress fracture a pathological fracture and an insufficiency fracture?
If we take the example of our poor elderly lady, it may be that she fell over. But not only was there energy transfer from the fall, but the bone itself, particularly of her hip, may have been either thin and weak. And this is known as an insufficiency fracture.
The bone is insufficiently strong because of a pathology, that’s different to a stress fracture, which is what these army recruits may get when they’re carrying 30, 40 kilos for 30 or 40 miles running like this. There are very big repetitive stresses that is put on bones, which are very strong. But because there’s a cyclical load, they can get stress fractures.
Stress – Abnormal Stresses of normal bone
So just to clarify. Stress fractures are overuse fractures where an abnormal stress is exerted on normal bone and is cyclical loading of this bone from the abnormal stress leads to weakening or little micro fractures in the bone, and those cracks can propagate to become a stress fracture. Now, they can also occur as a combination of abnormal stresses, but with some underlying abnormality in the bone, either from disordered eating, so we see this in people with anorexia who have poor nutrition but are also running very hard in order to lose weight. But other causes of abnormal bone include osteoporosis. And for whatever hormonal causes, amenorroea.
Pathological or insufficiency – Normal stresses on abnormal Bone: local or general
We’ve talked about the combination of stress and this insufficiency fracture. But you can get pure insufficiency fractures, and insufficiency or pathological fractures are where normal stresses are exerted on bone that has an underlying abnormality. Now, that underlying abnormality can either be local, in one bone, or general in almost all the bones of the skeleton.
An example of a local pathological fracture could be osteomyelitis of the tibia that leads to a fracture of the tibia where the infection is localised to the tibial shaft.
An example of a generalised pathological insufficiency fracture is osteoporosis, where almost all the skeleton has. a loss of bone density, this leads to weakening of the bone.
There are some congenital causes as well of generalised bone weakness. One example of this is osteogenesis imperfecta. And a generalised demineralisation of bone occurs in vitamin D deficiency.
Insufficiency 1 :Osteopenia & Osteoporosis
So if we look at an insufficiency fracture that’s the most common in the Western world is osteopenia or osteoporosis. And this is defined as loss of bone density. And it is actually bone density that’s statistically defined as two and a half standard deviations away from the normal bone density, as measured by DEXA scan.
Osteoporosis can also be localised or generalised. It can be primary or secondary. So primary osteoporosis is related to age ,otherwise known as senile osteoporosis. But you can get secondary osteoporosis due to hormonal problems such as hypogonadism, glucocorticoid excess or alcoholism. They can occur at any age and in any sex.
All of these osteoporotic fractures are associated with insufficiency, fractures, and they’re also known as fragility fractures. In general, a fall from a standing height shouldn’t cause a fracture, but it does in people with osteoporosis.
Insufficiency 2 :Vitamin D Deficiency
Before physis closure – rickets
After physis closure – osteomalacia
Another example of bone insufficiency that can lead to fracture is with vitamin D deficiency. I regard vitamin D very much as a hormone rather than a vitamin because it’s so important in calcium metabolism. It helps calcium absorption in the gut, but also helps the osteoblasts of the bone secrete bone mineral matrix. And so if you have a deficiency of vitamin D, you have demineralisation of bone. This leads to soft bone and can predispose to fractures.
In a child this is known as rickets. And you can see in this picture here, these tibiae are very bowed. And this person who is now an adult, must have suffered from rickets as a child to have such bowed tibiae. In adults low vitamin D is known as osteomalacia. So all of these can lead to an insufficiency fracture.
Insufficiency 3: congenital
Osteogenesis Imperfecta
Another form of insufficiency can be congenital and osteogenesis imperfecta is a deficiency of type one collagen being produced normally. And it has several types, some of which are autosomal dominant, and some of which are autosomal recessive. And you can see in the picture here, the patients can present with blue sclera of the eye, lens dislocation and short stature. And it’s really the lack of normal collagen that leads to insufficient osteoid production and this will lead to bone weakening and insufficiency or pathological fractures.
Insufficiency 4: Pagets Disease
A metabolic disturbance of bone turnover is Paget’s disease, and this is where you can have either increased or decreased osteoblastic activity or increased or decreased osteoclastic activity. But in any case, the bone turnover is disturbed, and this leads to bone deformity, as well as pathological fractures. And these patients can, in chronic cases, develop osteosarcoma or cancer of the bone.
Pathological (insufficiency?) :Malignancy
Now, you’ll notice that I’ve used pathological and insufficiency as terms almost interchangeably which is correct. In general though, we talk about pathological fractures in the context of cancer or infection. But you could argue that these are also insufficiency, fractures.
So let’s move on to bone cancer. Bone cancer can be either primary or secondary. Secondary is where you have metastatic bone tumours from other tissues. And these are the five most common tissues on the left prostate, breast, kidney, thyroid and lung. Now, the metastases that these produce in bone can either lead to increased bone production, which occurs in the case of prostate cancer. Or in terms of bone resorption or bone destruction, which is known as osteolytic lesions. And that could be kidney, thyroid or lung cancer.
Bone cancers can also be primary, i.e., arising from the bones themselves, and they can arise from osteoblastic tissue, or osteosarcoma. They can arise from chondral tissue, which is chondrosarcoma. And there are some other forms of primary bone cancer as well. So all of these can lead to pathological fractures.
HOW DO WE DESCRIBE FRACTURES?
Fracture Patterns
Are the Soft Tissues Intact?
- Yes – Closed
- No – Open
Is the break complete?
- Yes – How many pieces?
- 2 – simple
- >2 – comminuted
- No – Greenstick
Are the bony ends aligned?
- Yes – Displaced
- No - Displaced
Fractures can be described either in terms of whether the soft tissue over the fracture is disturbed, particularly the skin. So if the skin if the bone is poking out through the skin or has poked out through the skin and gone back in again. That’s known as an open fracture. If the bone has never poked out through the skin which is intact, that’s known as a closed fracture.
The bone fragments may either be bent in the case of greenstick fractures and they occur in children. They may just be two fragments with a fracture of between, which is a simple fracture. Or they could be in many fragments which used to be known as a comminuted fracture, but is now known as a multi fragmentary fracture?
And the bone fragments themselves could have moved apart a lot or not very much at all. This is called as displaced in the case of moved apart a lot or undisplaced if they’ve hardly moved.
On the left here, you can see in the child that the bones are bent and here, this cortex is actually intact and the bone is just bent. Both the radius and the ulna, and, you know, this is a child because there’s a growing physis here. So this is a greenstick fracture of the forearm in the child.
This is a right tibia with a fibula here. And this is a transverse fracture of the tibia, which is just left in 2 pieces. So this is a simple fracture.
And this is a fracture of the left femur. And you can see many pieces. One there. Another one here. Another one here. Another one here. So this is known as a multi fragmentary or comminuted fracture.
How do fractures heal?: General principles of tissue healing
Well, you may get questions which say how do tissues heal. And this is a very broad scheme which you can use to answer those questions.
All tissues heal initially with bleeding. And this leads to inflammation. Eventually, new tissue forms. And then you get remodelling.
So initially you have blood and blood products. Then you have inflammatory cells, which can include neutrophils and macrophages. And depending on the type of tissue you have, you can either have fibroblasts in the case of collagen tissues such as ligaments or tendons. Osteoblasts, in the case of bones and chondroplasts, also in the case of bones. And eventually the remodelling phase involves cells that turn over the tissues, either macrophages, osteoblasts or osteoclasts all working together to help remodel the bone or the soft tissue.
Fracture Healing
Step 1: Bleeding/Haematoma – prostaglandins/cytokines released; growth factors increase local blood flow – Periosteal supply takes over
Step 2: Granulation Tissue/connective tissue/Fibrous tissue laid down / Soft Callus
Step3: Once fracture is bridged with soft callus- hard callus is formed ( laying down of Osteoid/ bone)
Step4 : Bone is remodelled via endochondral ossification lamellar bone in its place.
So when we apply this principle to fracture healing, the initial phase is where you have bleeding in between the bone ends, and this is known as haematoma. Those blood products release cytokines. They bring cells to the fracture site and have those cells produce granulation tissue and new vessels form. So in one and two here, that’s your inflammatory phase.
Then you have the repair or proliferation phase where you have Chondroblasts or Osteoblasts secreting new bone tissue, and I’ll come back to which one’s which. But initially you get soft callus, which is type two collagen, which is primarily cartilage type collagen. And this is then converted to a hard callus, which is type one collagen, which is more like bone.
And after this repair phase, you have a remodelling phase where callus response to activity and the forces applied to it, and functional demands and growth affect the way that this bone then grows out. And that remodelling phase involves osteoblasts and osteoclasts, and there is a law that says that bone grows and remodels (both in terms of fracture and in terms of children’s growing bone), in response to the forces that are placed upon it.
Bone healing
Inflammatory phase (duration: hours–days): Broken bones result in torn blood vessels and the formation of a blood clot or haematoma. The inflammatory reaction results in the release of cytokines, growth factors and prostaglandins, all of which are important in healing. The fracture haematoma becomes organised and is then infiltrated by fibrovascular tissue, which forms a matrix for bone formation and primary callus. Reparative phase (duration: days-weeks): A thick mass of callus forms around the bone ends, from the fracture haematoma. Bone-forming cells are recruited from several sources to form new bone, which can be seen on radiographs within 7-10 days after injury (Figure 9). Soft callus is organised and remodelled into hard callus over several weeks. Soft callus is plastic and can easily deform or bend if the fracture is not adequately supported. Hard callus is weaker than normal bone but is better able to withstand external forces and equates to the stage of "clinical union", i.e. the fracture is not tender to palpation or with movement.
Remodelling phase (duration: months-years): This is the longest phase and may last for several years. During remodelling, the healed fracture and surrounding callus responds to activity, external forces, functional demands and growth. Bone (external callus) which is no longer needed is removed and the fracture site is smoothed and sculpted until it looks much more normal on an x-ray (Figure 9). The epiphyses gradually realign and residual angulation may be slowly corrected, in accordance with the rules of remodelling, outlined above.
Now, when we talk about bones healing, they can heal in two different ways. And you have two different ways displayed here. This is a fibula fracture and you can hardly see the fracture it’s just here because it’s been reduced and fixed with a plate. The fracture ends are almost touching. They’re very close together. And you get something called intramembranous healing here.
If you go back to our introduction to a MSK slides intramembranous healing was where you had a mesenchymal stem cell that went straight to a bone cell or osteoblast and you get a straight formation of woven bone in this case, and this happens when you have a very stable fracture and the ends are almost completely back together again from the fixation.
If you contrast that with this, this is an intramedullary nail. And this fracture has kind of been reduced, but it’s not perfect. And this then leads to a secondary type of bone healing, which is known as Endochondral Healing. And here, again, if you refer to your MSK lecture’s, the endochondral bone healing, the mesenchymal stem cell will go to a chondral precursor and the chondral precursor will then produce bone cells. And here, this kind of secondary bone healing results in more callus than the primary bone healing you can see in the fibula here.
Fracture Healing Times
So here’s another type of secondary bone healing occurring, this is in a three year old child here, the humerus is fractured. You can see the fracture ends are quite far moved apart. But amazingly, these children have the most incredible healing potential. And you can see over a matter of days how callus is formed and how that calluses, then joins the bones and over a few months, you can virtually detect no fracture whatsoever. And here’s a good example of a secondary bone healing using callus with the inflammatory phase initially, you can’t see that on the x rays, but you can imagine the bleeding and the inflammation occurring. Then you get the repair and proliferative phase with callus formation. And then in these last two pictures, the callus is remodelling.
Now bones can heal at different rates and in general, upper limbs heal quicker than lower limbs and hands heal quicker than feet. And you have a list there of the typical healing times. But I have to say that these healing times vary according to age, biology and comorbidities of the patient. So you have to be very careful to say a bone is healed or not healed. For example, with the tibia at 10 weeks, it may take a lot longer.
Introduction to Fracture Management
General principle:
Here are the main principles. You’ve got to bring the fractures back together again. That’s known as reduction. You’ve got to hold those ends in the right position. That’s known as holding the fracture with metal or no metal. And then once the bones of healed, you still have a very stiff limb that may be painful, weak and you then need to rehabilitate that limb.
Reduction
How to reduce fractures? Well, in general, you can just pull on them, and that’s known as closed reduction.
You can apply traction, eye of skin or skeletal, or you can reduce the fracture by making a cut in the skin, going down to the fracture site and putting the bones back together.
Reduction
https://www.youtube.com/watch?v=EhJ7kpurKnk
So here you have closed reduction. This is a typical dinner fork deformity. This is in the old days this was known as a colle’s fracture. The radius is dorsally tilted or angulated. And you can see that this is like a dinner fork.
And if you click on this YouTube link, you’ll see how these fractures are generally managed by closed manipulation. As I said, it’s not part of your core knowledge, but it’s a good way of showing you closed reduction with manipulation.
Reduction
Now, another way to reduce a fracture is that you wrap a whole bandage around it and around that bandage, you can hang a weight. This weight will bring the limb into alignment and the fracture ends ideally into a better position. So this is known as skin traction.
Or what you can do is put a pin right through the tibia here. So this femur, for example, is fractured. You put a pin through the tibia and you can put a much bigger weight because the pin is in the tibia, and you can apply more force to the tibia than you can to the skin. And this is known as skeletal traction. And not only can you use these forms of traction to reduce the bones, you can actually keep the weights on for a number of weeks or months, as we used to do 30 or 40 years ago. And you could hold the fractures in the same way.
Hold
So, again, holding can be closed or open with plaster, traction or fixation.
Fixation
So the exciting things about holding fractures is to use metal to fix them, and that’s what we do as surgeons. But you have to decide very carefully when you need to use metal or when you can use close reduction or fixation. So. You can internally fix the fracture with metal under the skin, and that can be outside the medulla or inside the medulla, or you can have pins sticking out to the skin that’s known as external fixation, and these pins can be monoplanar or multiplanar.
Try and guess which of these methods of fixation are applied to that previous decision tree.
Fibreglass type plaster-much more lightweight way of holding the fracture.
Here you can see a plate and screws on the surface of the radius bone. So this is extra medullary internal fixation. This is internal because it’s under the skin. And this is extra medullary internal fixation.
If you contrast that with these nails that are going straight through the canal. This is the medullary canal of the radius and the ulna. So this is intramedullary internal fixation.
And you can see in the bottom two pictures here, you have metal that’s coming out of the skin. So this is external fixation. And this is metal in one plane. So that’s monoplanar external fixation.
And this is metal in a cage in lots of different circular planes, which is multiplanar external fixation.
Rehabilitate
Once fractures have healed, you need to allow the limb to rehabilitate. And that doesn’t just mean physiotherapy, it means using the limb. And patients may need pain relief or to retrain their limb with the physiotherapy exercises. It means moving the limb. It means strengthening the muscles around the limb. And in the case of the lower limb it means weight bearing.
Summary of fracture management:
So how do we decide which way we manage fractures? Well, first of all, you have to decide where is the fracture? Have the bones moved apart? Is that fracture potentially stable or unstable? Is it at a joint surface? Are the soft tissues okay? What are the other illnesses the patients may be suffering that may put them at risk if they have an operation? And what does the patient think about it? Or do they want an operation or not want an operation?
Soft Tissue Injury: how do ligaments/tendons tear?
This is David Beckham injuring his Achilles tendon. And you can see a very nice surface anatomy of the Achilles tendon in this walker. Here is the calf muscle, which consists of the gastrocnemius and soleus muscles. And there is the conjoint Achilles tendon inserting into the calcaneus bone. So when this tendon tears, it can usually tear in the mid substance here. So there’s David Beckham injuring his Achilles tendon.
Tendinopathy
And the Achilles may have had some inflammation.
Often sportsmen do have either inflammation of the tendon, which is tendinitis, or thickening of the tendon tissue, which is tendinosis.
And this in itself can lead to weakening of the tendon and tendon rupture.
Ligament injury classifications
Now, if a tendon or ligament is torn, there are different grades of tear. So you can have a normal ligament, a ligament that is very slightly stretched with very small microtears, bigger tears, but only a partial tear of the ligament, or a complete tear. So these are the different grades of ligament or tendon tear.
And you can see here, this is actually my ankle. Quite a while ago and I had a great to almost a grade three tear of my lateral ligament of the ankle. And that’s why you get this kind of bleeding and bruising, because the ligament is so badly torn that it’s bled quite a lot, and eventually, the blood is led to bruising under the skin.
How can we treat tendon or ligament tears?
Well, it’s a bit like bone. You can immobilise so that the tendon ends don’t move and hopefully rely on that process of haematoma formation, inflammation, proliferation and remodelling. Or you can bring the ends together in a much more sure way, but with surgical repair and suture the tendons. So David Beckham underwent a tendon repair a bit like this with a suture across his Achilles tendon. But you can do the same in the knee, either suture the tendon or you can put them in a brace.
If you want a nice video of a achilles repair surgery, again, not core knowledge, but just a really good example of how we repair Achilles tendons. There’s the YouTube link.
Immobilization vs. Mobilization: A Fine Line
So when do we repair and when do we mobilise? Well, it’s quite a complex discussion, and the immobilisation sounds, in principle, like the best thing to do, you want the chance to be together so that they can heal. But the problem with immobilisation, is that in general, it leads to more scar tissue and slightly less, blood Infiltration into the tissue. But if you suture the tendon, you can generally mobilise a little bit quicker, and that means that the ligament scars are wider and stronger and more elastic. And also, you have better vascularity or blood supply to the healing tissue.
So it’s, again, quite a complex discussion as to whether to repair, a tendon or ligament or whether to allow it to heal. And that can also depend on the blood supply of that ligament as well as the patient factors, including whether patients are elderly, whether they’re diabetic, whether immunosuppressed. All of these factors come into play when considering whether to fix a fracture with surgery or to mobilise.
How to do ligaments heal?
Tissue repair timeline
So how once you’ve immobilised, how do the ligaments heal? Well, we’ll go back to our principles of inflammation, proliferation and tissue remodelling. Inflammation takes hours to days, proliferation takes days to weeks, and remodelling takes months or even years.
Now, this is quite a complex site, but really the big take home messages are to think about the inflammatory cells in particularly the neutrophils and the macrophages. Think about what produces new tissue and that’s usually blast cells. In the case of collagen, it’s going to be fibroblasts. In the case of bone it’s going to be your osteoblasts. And think about remodelling, which occurs by both absorbing tissue and producing tissue. And that way you can work out the cells that are involved in inflammation, proliferation and remodelling.
Factors affecting tissue healing
Here are the factors that determine whether we’re going to heal on our own or whether we need to do surgery. It depends on the mechanical environment-Is it a very unstable tissue or bone? So what are the movements and forces around the disturbed tissue? And then the biological environment? What’s the blood supply? What’s the immune function of the patient? Is infection present? And is the patient well nourished?
Session review
