Young bone is different from mature bone – so kids’ bones break and heal differently. Orthopedic surgeon Ravinder Brar, MD, MPH, offers a refresher on the remodeling process and elucidates the widely used Salter-Harris classification system for fractures involving the physis, illustrating each type with case X-ray images. Learn keys to ensuring good outcomes, including the window for surgery.
um um lavender bra are part of the orthopedic department. And I work in um both Oakland and walnut Creek. Um And I'm excited to see fractures and that's why I'm talking to you today about five ceo physiology growth and fracture classification. Um I have no relevant financial disclosures. And the 1st 1st point of today is that Children are just not small adults. There's differences in their skeleton. Um And that is the radio lucent growth cartilage or the Fyssas. And sometimes you can't see a fracture very clearly in the bone but you can infer injury because there's widening of the growth plate. Um The difference between adults and Children as well is that they have a thicker perry Osti um uh And it's stronger. And this can sometimes help in a reduction or sometimes they can be inter posed in a fracture site which that makes it more difficult to obtain a reduction. The nice thing about kids as well. Um Is there skeleton allows them with that curiosity um to develop callous more quickly. Um Compared to adults continuing with the differences in bone, young bone is more porous or less dense. Um They have version canals and they occupy a greater portion of the bone. Um And that can limit the extension of the fracture line. They can also tolerate a greater degree of deformation than adult phone and that's why you can have Boeing. Um Instead of a fracture compact, adult bone fails intention and more porous. Young bone allows for failure and compression and that's what we refer to as buckle fractures. Um Buckle fractures and tourist fractures are the same. Uh They happen in the metamorphosis because that's where the bone is the most poorest. You can see this also in non ambulatory Children who don't bear weight. And so they have more porous bones. So they may sustain buckle fractures like in their distal femur. Um And they called it a tourist because of the bottom of the architectural column continuing on this. Um As I mentioned earlier, bones in Children cambo rather than break and have that plastic deformation. The compressive force uh does result in a tourist or buckle fracture as seen in this X ray. Um A green stick fracture is when there is a force to one side of the bone and it only breaks one cortex and thats failure intention there the other fails in compression. And then here's an example in very young Children. Neither cortex may break and that's that plastic deformation. You can see that here To further illustrate that or those types of fractures. Um this is just another diagram showing the ones involving a crisis buckle fractures. Green six in the plastic deformation continuing on a description of the periodicity omits the virus sheet that covers the bone. It has a lot of blood supply to it. It's thick and it's strong. Um And we often use it to aid in the reduction, as I said before. It's metabolically active, which allows for the more callous formation and more rapid healing and more remodeling potential. But the fight ISIS is a difference maker. Um And many childhood fractures involve the Fyssas. Uh It's involved in 20 to 25% of all skeletal injuries and it can disrupt um the growth of the bone. It's the injury or the fracture through the Fyssas that when it starts to heal um it can put bone there instead of cartilage. And so if there is uh bone across a portion of it um that can lead to angular growth or angular deformity. Um If the entire Fyssas is disturbed, that can cause a deformity or a difference in length injury um nearer but not a thief, ISIS can actually stimulate the bone to grow more. Another difference between Children and adults is that um ligaments are stronger than bone um in kids. And so you're more likely to have um an avulsion of a ligament rather than a terror. And a good way to think about that is with a CLS. Adults and skeletal immature teenagers are more likely um to have an A. C. L. Tear. Whereas Children are more likely to have or skills immature, Children are more likely to have a tibial spine avulsion. Um This is another depiction of the ligaments being stronger than the Fyssas. And this is why kids are more likely to have a distal fibula her uh fracture um at the level of the Fyssas rather than an ankle sprain where they tear a ligament and it's just that the ligaments are stronger than the crisis itself. Another way to think about this is the medial epic condo. The weakest point um Is the insertion um or the origin of the muscle at that growth plate or the attraction of pith Asus. Um And the media lab a condo is the site of origin of the common flexor muscles of the forearm and they may be engulfed by a severe valdas force of the elbow. Um Since attraction epic assist does not contribute to longitudinal both of the grown. I'm sorry, a growth of the bone. It is uh there's no growth disturbance and this doesn't cause um deformity it reduced properly. Say with this screw there should be a bony union through the physio plate. If it isn't then um a child can have a fibrous union. The difference between growth and development growth just an increase in physical size of a body or an organ. Whereas developments maturation when it comes to normal growth, um Long bone growth. This is just the types of like bone formation is. Nd control. Flat bone isn't remember this, we can do distraction osteogenesis with lengthening and that's an intra member nous and fracture healing is a combination um of Andy control and intra member nous and that all depends on inter fragmentary strain. Um And that's the amount of motion between the fracture fragments, Fracture healing occurs in three phases. The first phase is it the inflammatory phase? And that's acute inflammation in hematoma formation. The second one is a reparative phase. And that's when we see the callous formation, it's a weaker structure and you see um more volume to the amount of callous that's there. And that affords temporary stabilization. With that disorganized, callous then you have remodeling and that occurs over months to years. Um And that provisional callous that you saw on the reparative stage is res orbed a new bone is deposited along the lines of stress in this bone is more rigid and strong, and the idea behind this has to do with the diameter. So callous formation at the perry osteo surface significantly increases the stiffness and strength of the healing bone, and that fracture stiffness is proportional to the amount of mineralized tissue at the fracture site and that increases with time. So initially you have this fracture hematoma um that provides a limited stability at the fracture site, it makes it wider and you have a lot of motion there. Um and so once the inner fragmentary strain is less than 100 um graduation tissue like bridges the gap of the fracture. And that stiffens up the fracture and reduces the inter fragmentary strainer motion. And that allows callus formation that's robust now you can appreciate um with this wider diameter. Um And that with that stiffens up the fracture site further and the increased cross sectional diameter of the soft callous um lowers the inter fragmentary strain. So then that soft callous becomes mineralized which is a hard callous. And I'm sorry this is so so much. Um And then it's the cycle of progressively stiffer tissue um and reduced strain with the remodeling. Um So that you have like They're strange going from 100% to less than 2%. And that's when you have the cortical bone formation. So that's why you can see on sequential x rays that first the callous will be robust and then as the bone remodels and heels um it looks more and more uh like the bone did prior to the fracture. Mhm. Remodeling potential is fantastic. It's it's why Children's skeletons are so forgiving. Um And you don't need an an atomic reduction for a good outcome in kids. Growth provides um like a lot more remodeling than you've ever seen an adult. And so and violation. And displacement can remodel but rotation cannot. And so what happens is you have like this and related fracture. And on the site Harold do here on the site of the con cavity, you have asymmetric bone deposition. So your body will put more of the bone here and resort more of the bone here until it straightens up. And so what it's trying to do if you have this angular ation um is get these uh physio plates to be perpendicular to the longitudinal axis of the bone. By putting bone here and resolving it here and once this plate is now perpendicular to the to the launch to access of the bone, it resumes the the symmetrical growth. Uh And so that's what's really nice about kids forgiving skeletons. You can see this on this X ray where you have more bone deposition on the con cavity and more resort option um on the convexity and some of the magic of bone healing. Then you can appreciate in this remodeling just over a three month period Of this risk fracture and a five year old girl. And it's just kind of amazing that the body wants to write it like this. And it all has to do with the physics. Um of that Fyssas, here's another example of a five year old boy with the distal radius Salter to fracture that was not reduced. And you can see the amazing remodeling over eight months. So the factors that affect remodeling potential, the most important is the years of growth remaining. Uh in general we say um that girls on average uh stopped growing by age 14 or two years after their first period. And boys on average at age 16, the position where the fracture is in the bone also affects remodeling potential. The closer the fracture is to the spices, the higher or the more remodeling potential that exists the faisal status. So the fracture um and how it affects the prices can affect your modeling potential. Just because if that if ISIS is too injured to recover, then you won't get much remodeling. And then where in the fracture. So I said, you know, it matters um if it's closer to the bone or I'm sorry, closer to the Fyssas are farther away, but then also which vices it is and that's because each vices um contributes differently um to the growth of the bone. So when it comes to the femur Here, distal femur has more remodeling potential because that Fyssas contributes 70% of the growth, whereas approximate one contributes 30% of the growth. So we'll be more forgiving when it comes to fracture reduction in the distal femur than we would be um at the hip. And that's the same. That's the opposite when it comes to the humorous where are approximately humorous has 80% of its growth from there. And then the distal humerus is only 20%. So um we want things. to look better closer to the distal humerus and we accept a lot more regulation or displacement in the proximal humerus. So I thought this story and this is one in in one of our Ortho textbooks, like the story of the Fyssas um from rang Children's fractures. Uh I thought this was a cool story. So it's formally known as conjugal cartilage or the area of the bone um that joins our congregates to the adjacent bone. And John Hunter confirmed its importance to bone growth in the 1700s. And so he was having dinner with a friend um and he's a british surgical scientists. Um It was a pork dinner and he noted slightly um colored transverse lines at the end of the young pigs bone and the pig had eaten contaminated food um which had like die in it for cloth and that selectively deposited in the in the growing pigs Fyssas. And so john Hunter suspected that this is the area where the bones grow longitudinal. So he conducted experiments um And so he put two pins in a Diouf Asus and over time he saw no change in the distance between the two pins. Um But they were further away from that area of cartilage or that like transverse line that he had seen in the paper. Um And then you put another in a in a different um experience. He put a pin in the Diouf Asus and one of the epithet sis. And over time he saw the distance between the two pins change. And so as the pins moved apart, he confirmed um that this is where the bones grow longer. Yeah, more on the history. Um These experiments demonstrated the force it takes to separate the epic Asus from the metamorphosis because uh it's firmly connected externally by the periodicity um and internally by the mammary processes And James Wilson. Um in 1820 showed that a longitudinal force of £550 was required to detach the epithet Asus from the metamorphosis. But um if you were to divide the curiosity, um First it only took £119. So um that shows the strength of a Perea's of the perry Osem and a child and a child's um Perry awesome is much thicker. Um Then uh than in adults curiosity. Um If I see all anatomy, this is getting into the basic science. Um we won't go too deep into the weeds here, but there are four zones um The resting or sorry, the reserves owned jump or also known as the germinal or resting zone. That's the one that's closest to the epithet sis. Um It has the highest matrix of cell ratio. Then you have your proliferated zone. And that's where the condo sites get organized into columns in your hypertrophic zone, that's where the contra sites mature and they get bigger. And then you have your zone of provisional calcification. The most common region for facial fractures um is through the zone and provisional classification which has a sub zone of the zone of hypertrophy, or which is a sub zone of the zone of hypertrophy. And the reason it happens here, it's a transition point between calcified and non calcified, extra cellular matrix proteins, so that makes it weaker than the surrounding um structures and more susceptible to injury. And the crisis is encircled by fibra cartilaginous tissue and that includes the groove of rambla and the ring of Lacroix. Um There are different collagen types uh and proteins found at the different levels. And then now to talk about the fractures that involve the Fyssas. So in 1963 to Canadian Ortho pods published a 36 page article in the Journal of Bone and joint surgery and classified um growth plate fractures. And this is what we refer to all the time as a psalter Harris Classification. And it's salter Harris refers to the last names of these two Canadian orthopedic surgeons. Um and so we'll go into it through each of these uh individually. Um but I thought that was a nice graphic to describe it. So, Assaulter One is where the fractures through the Fyssas. Only Assault or two is where it's through the Fyssas and then it exits the metamorphosis. So away from the joint and you see this little triangle here, Assaulters Three affects the articular surface because it's through the epic Asus and the Fyssas, Assaulter Harris for fracture is through all of these. Assaulter five is a crush injury. So this is what you probably see um or you hear people talking about, especially with the with x rays when they classify it. Um so it's a nice way to communicate so that we all use the same language and we know what each other is talking about. So a psalter Harris, one fracture extends directly directly through the growth plate and it results from the separation of the epic assist from them as a thesis without evidence of bony fracture. On the X ray we can see on this X ray is that there's widening of the Fyssas that's consistent with injury. The thing we most often see is in clinic I mentioned earlier is the type one or the psalter Harris, one fracture of the distal fibula. Um This is of the distal tibia, but I thought it was a good example of showing the widening. Um this is these are the x rays of a 12 year old who sustained a skateboarding injury to the knee and on the day of injury presented to an urgent care. And what you can see here is that there is no obvious fracture that one might call. But if they took x rays of both needs for good comparison. And if you look on the lateral um there is a difference and it's very subtle. Um But you can see that there is a little more widening of the fais is here interior early on the left compared to the right. Um And so based on his exam, it's you know uh to look for those like really subtle signs. Uh Unfortunately it was told there was no fracture. He was given an immobilizer um and crutches and told to partially weight there. Uh So when he presented to our clinic, he had grossed displacement two weeks after injury through the Fyssas of the psalter. One. Um One of the things that matters too is like the anatomy of the Fyssas. Um And if you get Growth arrest at your distal femur and we knew that it's 70% of your growth and you're more likely to have um a leg length discrepancy. So that's what we're concerned about in this injury. This is a psalter Harris to fracture, as I mentioned before, it goes through the Fyssas and then exits out the metamorphosis away from the articular surface. And you usually can appreciate a triangle fragment there. You can see it here as well with the star over it. Sorry, I was pointing at the wrong screen, so there's a triangle. And then here is the triangle as well with the star over it. Sometimes people call that the thurston holland fragment and you expect the periodicity um to be torn at the convexity. Um and then to have it intact on the con cavity where the metaphor seal or that triangle fragment in. And so knowing that um can help with reduction. Since the curiosity um can hinge and aid in the reduction. The type two of the salto here is to fracture is the most common fracture that we see um When it comes to growth plate fractures, the psalter Harris type three fracture. Um They extend through the Fyssas and then exit out the Epp. If Asus. Uh So this is an intra articular fracture. Most common I would think of as a tallow fracture or this what's depicted here in the ankle. Um Because it involves a joint surface. Yeah an atomic reduction is paramount. Um And so what we care about most is restoration of this and getting it lined up nicely. Um there are less common than type two. Uh And in addition to worrying about growth arrest um Then you worry about post traumatic arthritis as you go up the levels of um. Salter Harris fractures. You have an increased risk of growth arrest, so no one is less likely. Um Whereas if we get to a four you're more likely to have um growth arrest. So Salter Harris type for fracture just spans the metamorphosis, yep. If Asus sorry the metamorphosis, the crisis and the epiphany sis you can see it here as well. Yeah the easiest way to think about this is um a lateral condo fracture. We see those a lot and it involves this triangular piece here. You can see it going through the Fyssas. Um And then you have your fifth epiphany shell fragment. Um We often do open reduction uh for cutaneous pinning for these here we want to realign the articular surface first. Um and then also do our best to realign the growth plate to kind of to help prevent any bony bridging across the plate, which might then cause premature growth arrest. Um If you have to cross the Fyssas, we choose smooth K wires uh to limit the damage two subsequent growth And then the type five fracture is uncommon and it results from severe crushing force. It happens in the ankle or knee. Um It's the worst prognosis for premature faisal arrest. Um And this type of comprehensive, comprehensive this type of compressive damage to the faces can also occur as a stress injury. Um and can be seen in gym nous or other athletes with repetitive loading um Like say, on their extended risk or on their um approximate radius that you can see here. So we have a lot of respect for the faces. It helps us with our reductions, it helps us with the remodeling. Um But sometimes our fracture uh dictates our need to put hardware across the Fyssas. If we're going to do that, we put in k wires or Steinman pins, we make them smooth because threads can otherwise damage it. Um When it comes to reductions, you do want to do a reduction if it involves a Fyssas within 5 to 7 days of injury, because if ISIS heels pretty rapidly, and if you wait outside that window, then you're potentially doing a second hit to the Fyssas, which can cause more injury to potential growth in the future. Um And what you see in this image is uh distal femur fracture after a child fell out of a window. Um and so we're able to do retrograde smooth pins, uh to control that fragment, and he is healed nicely. So, thank you for your attention today.