How are you all doing? I feel a little embarrassed! I mean, you know it has been a while since we have started talking to each other but I never asked about you. Sometimes I SHOULD ask about you, about your life. Especially after covid has locked us as birds in a cage. So, since covid has been contained a little, are you going outside?
Do you want to explore the world or do you want to play outdoors? You may be thinking of playing outside, with friends, jumping, falling, injuring yourself? You might be even thinking that getting wounded was not so bad, or maybe getting fractured or playing like crazy despite of the pain and later realising of a tumor growing inside your bone? Wait! Wait! Wait! What? Who thinks that? Well, personally I do. But not in the way depicted here. Its just that, sometimes I found myself curious about some bone tumors. And not just that, I remembered I was preparing myself for possible gout disease which well… later turned out to be just an ingrown toenail in my big toe. Hmm… stupid me. How can I think ingrown toenail to be gout?
Well, this is exactly we will found out in some next blogs. This time around we will discuss:
- Bone structure
- Fractures and its types
- Fibrous dysplasia
Let us begin!
We all are used to hearing from our childhood, about the bone count that adults have 206 bones which is less than at the birth time i.e. around 300 soft bones.
Now, 1st we should know that bone is a specialised connective tissue(Q#1) just like blood and cartilage and it contains variety of elements suspended in matrix. So, what are those elements and matrix. We are getting just right into it.
Main components of bone:
Osteoblasts- These cells are uninucleated that actually are the new bone forming cells.
- They appear at developing bone surface in a simple layer manner.
- These cells work in organised manner, this organisation is called osteon.
- Osteoblasts initially forms osteoid i.e. new bone which is composed of collagen with other proteins.
- Osteoid mineralises to form bone (see pathological condition or P#1).
- As I have discussed couple of times in my previous blogs that bone is a mesenchymal tissue. Therefore, osteoblasts are actually derived from mesenchymal stem cells.
P#1. Osteomalacia: A disease in which the mineralisation is impaired causing bone to be weak and soft. In children, there is a similar condition found knows as by rickets where children are affected with poor growth and height.
Symptoms: Pain in bones or joints making hard to walk; muscle cramps, muscle weakens or pain especially after activity or exercise; risk of fracture especially there where bones support heavy weight like hip or lower spine.
Causes: Vitamin D deficiency.
Treatment: Or prevention, can be done by Vitamin D or Calcium supplements. Takes months to be treated.
Osteocytes- Also uninucleated cells.
- After the osteoblasts secretes their material, they now bathe in the matrix of bone itself, in metabolically inactive form.
- These are present in spaces of matrix called lacunae.
- Their role is now to maintain the bone and mineral homeostasis i.e. uniform internal environment. They do this via providing signals of bone formation or resorption. This is called remodelling.
Osteoclasts- Multinucleated cells.
- Cells of resorption i.e. dissolving or releasing of minerals (Calcium) from bone into blood.
- Essential for bone structure along with osteocytes or osteoblasts (see PC#2).
PC#2. Osteoporosis: Causes osteoporosis if osteoclast is more active than osteoblasts. More likely to cause if induced by Parathyroid hormone (PTH) i.e. hormone of parathyroid gland to increase serum Calcium level.
Symptoms: Most people are asymptomatic. If symptoms are present, decreases height over time and increases risk of fracture.
Treatment: Vitamine D supplements or Calcium rich food for prevention. Drugs like bisphosphonates are drug of choice as they slow down osteoclast’s activity. They do so by binding with hydroxyapatite(A#1) on bone surfaces.
A#1. Hydroxyapatite: It is a crystal found in the matrix of bone that provides strength and rigidity to bone.
Matrix: The major portion of bone is made up of matrix which provides it rigidity and strength.
- Composed of both organic (1/3 of matrix) and inorganic (2/3) substances.
- Organic matter contains collagen fibres and ground substance.
- Type I collagen is most predominant one secreted by osteoblasts.
- Inorganic matter consist mostly calcium phosphate, an inorganic salt, which is present as hydroxylapatite crystals which hardens the bone and makes it rigid.
- It is also known by osteoid.
Q#1. What is a connective tissue?
A#1. Connective tissue is just a tissue that supports and provides protection to various other tissues and organs. Most suitable example here is blood as it connects different parts of body by supporting them with oxygen, nutrients, hormones etc. Also it has same origin as that of any other connective tissue like bone, tendon, loose and dense connective tissue i.e. mesenchymal or mesodermal origin.
Bone has mainly 2 layers:
Compact bone: Or the cortical bone.
- It is the outer solid, dense layer where matrix is hard and filled with only tiny lacunae for osteocytes.
- It is covered by periosteum, a thin connective tissue layer that envelopes bone everywhere and leaves bone only at regions of joint which is covered by articular cartilage.
Spongy bone: Or the Cancellous/trabecular bone.
- The inner layer of the bone which is less dense, highly vascularised and porous, thus soft, to store red bone marrow.
- Red bone marrow is that portion of bone where blood cells are born.
- Red bone marrow is made up of myeloid tissue which contains hematopoietic stem cells.
- In a child, bone marrow is primarily red which gets diminished with the age as it gets replaced with yellow bone marrow i.e. marrow containing fat.
- Located in long and flat bones like ribs, shoulder blade, skull and at epiphyses (enlarged end) of long bones(A#2) like femur
A#2. Long bones: These are weight bearing bones i.e. femur of leg, humerus of arm. These are hard as mostly made of compact bones with little marrow.
Short bones: These are made up of thin layer of compact bone. Their role is to support the skeleton system by giving stability. They have no role in movement like long bones. Eg- carpals of hand, tarsals in ankle and yes even patella is a short bone.
There are 3 more types of bones. Lets go through them in brief manner.
Flat bones: Thin bones that includes bones of skull, sternum.
Sesamoid bones: Small bones within tendon whose role is to support tendon by reducing stress on it. Eg- patella.
Irregular bones: Thin compact bones with irregular dimensions. Prime eg- vertebrae.
A#3. Endosteum: It is internal lining of the bone/osteon that covers medullary cavity (space where bone marrow is stored) of all long bones.
Now, lets get onto fractures.
A fracture, is simply, a discontinuity in the bone. It can either be complete or incomplete.
Before going deep into its types, 1st let us know about some general information.
Symptoms: Pain, pretty straightforward to think. Inability to move the affected part, swelling can also be seen, in severe conditions or pain, faintness can also occur.
Causes: Everything, whether living or non-living, has some stress resiliency. Means, each object could withstand some limited force applied to it, and if that force exceeds the limit of that object, then what happens? Simple, it breaks.
Similarly, whenever a force or injury is more than the bone’s ability to hold, it cracks up or breaks apart. Especially if the person is old, as the bone gets weaker and brittle with aging. Why? Because bones get less and less denser with age making them fragile and easy to break.
Now its types.
Types: There are lots of fracture types. Some of them are mentioned here.
- Greenstick fracture: Imagine a fresh twig that is bend and gets torn up a little at one site
- Incomplete fracture along the width of bone.
- Caused by bending stress.
- Bone on tension side fails.
- Compression side remains intact.
- Common among children under age 10.
- Torus/buckle fracture:
- Caused by axial force i.e. force along the longitudinal axis of bone.
- Wrist bones are commonly affected during an outstretched hand.
- Cortex buckles on i.e. compresses on fracture side.
- Bone on tension side remains intact (vs greenstick).
- Complete fracture:
- As the name says, bone is completely separated into 2 pieces.
- Further classified into oblique (oblique across the bone), transverse (straight along the bone thereby breaking bone the across), comminuted (more than 2 pieces are shattered).
- Hairline fracture:
- Just with the name, a thin partial fracture.
- Caused by stress, hence also called stress fracture.
- Athletes are mostly seen as after increasing intensity of their activity, load on the legs are increased.
- Avulsion fracture:
- Part of bone drives away apart from the original bone.
- Caused by tendon or ligament pulling attached to that part.
- Often seen in joints like ankle, hip or elbow.
- Children or adult athletes.
- Pathological fracture:
- Fracture occurs due to some underlying conditions like osteoporosis, osteomalcia, osteosarcoma etc.
The bone structure is divided into 3 parts mainly i.e. epiphysis, metaphysic and diaphysis. While going through their description, keep in mind the image of a femur bone which is narrow, long and broad on its both ends.
Epiphysis: The dilated end part of the bone. This is filled with spongy bone means red bone marrow.
Metaphysis: The junction of epiphysis and diaphysis. In here, the epiphyseal plate or growth plate is present which provides height. The halt at this plate’s growth results into stopping of gaining height which occurs around age of 20 years.
Diaphysis: The centre portion of the shaft which contains medullary cavity that is filled with yellow bone marrow.
Now, I would like to tell you about a condition which I myself have been diagnosed and the reason I chose to become a doctor. That condition is fibrous dysplasia. I will try to describe it with my experience.
- It is a rare bone disorder where bone tissue gets replaced by fibrous ( another connective) tissue.
- As you can think, this makes bone weaker and prone to fracture.
- It may occur in any bone but commonly occurs in facial or skull bones, ribs, pelvis, arm or thigh bone. I, myself, had… sorry have this condition in my right femur.
- It usually occurs in diaphysis of the bone. I have this near to my hip joint thus making my leg vulnerable to complete fracture that would make it separated from the rest of the upper body.
- It is diagnosed mostly in early childhood. I had found it when I was 6 years old. Whenever I used to play, I was good at sports though, I found out that I was having dull mild pain whenever I was running or jumping. I was mischievous so I used to ignore it earlier but the pain gradually increased into a moderate one. It made me and my family concerned. Then we had X-ray which was unclear or faulty i.e. showing no threat so we found out later then we should have. In the X-ray we found out about the hole (lesion) in the bone.
- Like I said, mild to moderate pain as the fibrous tissue expands more and more and compresses nerve.
- Waddling walk. Person drops their hip slightly on the affected side thereby rocking side to side while walking to compensate the weakness of the hip girdle.
- Prone to fracture.
- Bone deformity like curving of leg bones. If we ever meet you will find that both of my legs are curved in the manner that they are making a perfect circle. No, just kidding. I am glad that I don’t have this complication.
- Causes: It is caused by idiopathic mutation of GNAS1 gene present at chromosome 20 that creates a protein guanine nucleotide-binding protein (G protein). This now, this protein has huge variety of roles like from regulation of metabolic exchange to control cell transcription and secretion.
- Why I said the mutation is idiopathic because the mutation occurs during embryogenesis where fetal cells are dividing. Therefore, parents are unaffected while the child is affected. Moreover, not all cells carry mutated gene. As the disease is not inherited, the disease remains only to the one person and not in their children.
- Now, the osteoblasts with the mutated gene will form irregular bone tissue.
- This usually happens at a single site ,like me, but sometimes multiple lesions could be found on multiple bones.
- Treatment: There is no cure. Only thing that could be done is preventing the risk of fractures. I did it by stopping all my running, sports, play etc. Honestly, this was hard as I could not just stop myself from playing. I remembered of breaking this forbidden law a few of the times by taking part in race, kicking football but later founding myself with the sudden pain and waddling.
- Prevention also includes taking Calcium supplements to increase bone strength.
- Surgery like Curettage. In this, the fibrous tissue is replaced with bone graft that either may be a part of bone from another place of same or different donor. For me, I had a graft where a piece of bone was taken out from my tibia. This iscalled autogenous bone graft where I was my own donor.
Yes this is the reason that I am pursuing a doctor’s carrier. I have realized the value of the doctors. It is just like that saying which goes like this-
“A doctor may not change the whole world, but he can change the whole world for someone.”
This phrase completely suits on me as now I am being a doctor and will be treating thousands of patients in my life time and returning the favour that once was bestowed on me. Sorry if this blog got a little personal or you got bored from it.
Lastly I would say one more thing about me as an update of the disease. The disease itself gets stopped as the person’s bone growth stops. Which exactly happened with me. As I am now 24 years old while writing this blog, the lesion has stopped growing. However, there may have been another reason but just like I said this would be the last thing about me in this blog.
Next time, I will be covering another topic.
Hope you have liked it. Please comment below if you have something to say or ask.