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What happens when you break a bone? - Gurpreet Baht and Natalie Pang
What happens when you break a bone? - Gurpreet Baht and Natalie Pang
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0:06
Roughly 50% of people will break a bone at some point in their lives.
0:10
But whether the cause is as mundane as a slip on the ice
0:13
or as dramatic as a tightrope-walking accident,
0:17
broken bones tend to heal the same way.
0:20
The human body's 200 plus bones come in many shapes and sizes,
0:25
referred to by medical professionals as short bones, long bones, flat bones,
0:31
and the catch-all category of irregular bones.
0:34
Despite their differences,
0:36
bones generally have a rigid structure composed of a protein matrix
0:40
that’s dotted with bone cells
0:42
and reinforced with minerals containing calcium.
0:45
Inside these stiff exteriors is spongy marrow,
0:49
containing stem cells that can divide and differentiate
0:51
into specialized cell types.
0:54
Bones are also penetrated by blood vessels and nerves,
0:57
which relay the searing pain signal associated with the break.
1:01
Since these nerves are encased in hard tissue they’re very difficult to study,
1:06
so we still don't know exactly why broken bones hurt so much.
1:11
But we do know that long bones are the most likely to break
1:14
since they often take the brunt of the impact from a fall.
1:17
Whether an accident causes a clean break or a splintering crack,
1:20
any kind of fracture makes the blood vessels inside the bone rupture,
1:24
causing internal bleeding and inflammation.
1:27
This signals the body to start the first step of the healing process:
1:31
the inflammatory phase.
1:33
For the next week, the body floods the injury site with immune cells
1:37
which remove damaged tissue
1:39
and help prepare the site for healthy new tissue to grow.
1:42
The cells also release signaling molecules that recruit stem cells to the area.
1:47
As they arrive, these stem cells differentiate into chondrocytes.
1:51
These cells use the clotted blood at the break site
1:53
as a scaffold to build callus made of cartilage.
1:57
Cartilage can grow very quickly, making it a useful temporary patch.
2:01
But it’s much weaker than bone, so over the following weeks,
2:04
some of the chondrocytes and stem cells develop
2:07
into special bone-building cells called osteoblasts
2:10
that can create a stronger bony callus.
2:13
Once the bony callus is complete, the remodeling phase can begin.
2:18
Over the next few months,
2:19
another type of cell eats away at the bony callus
2:22
as osteoblasts lay down new bone tissue.
2:25
This phase is where most of the bone healing happens,
2:28
restoring the injury site to its previous shape.
2:31
But the healing timeline varies widely depending on a patient's diet,
2:35
how much rest they’re getting, and how messy the break is.
2:38
A clean break generally heals the fastest,
2:41
and doctors use casts and splints to keep bones aligned as they heal.
2:45
But if the bone has been splintered into tiny fragments
2:48
and significantly displaced,
2:49
surgery may be required to put those pieces back in place.
2:53
And if a bone does heal while misaligned,
2:56
a surgeon would need to refracture it, realign it,
2:59
and then use pins, plates, or screws to hold the bone together.
3:03
When the remodelling phase is over,
3:05
there may be a slight bump at the fracture site,
3:07
but this typically resolves over time,
3:10
leaving the bone just as strong as it was before.
3:13
Naturally, the strength of our bones varies from person to person.
3:17
And older populations are more likely to break their bones in the first place,
3:21
since bone density tends to decrease with age.
3:24
Researchers are still investigating why this happens,
3:27
but fortunately, we already know the best way to keep bones strong.
3:30
Even when they aren’t healing, bones are constantly remodeling—
3:34
adjusting their density and strength
3:36
to the amount of force they’re typically under.
3:38
So exercises like walking, running, and weightlifting
3:41
all stimulate your bones to grow denser.
3:44
Just make sure whatever activity you're doing is relatively safe,
3:47
because there’s nothing humorous about a broken humerus.
