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What is a Growth Plate Injury in Kids?

layers of the growth plate resting zone proliferative zone zone of hypertrophy zone of calcification

An injury to the growth plate is a major concern for most parents.  But before we can talk about how growth plates can be injured, its important to understand the basics of how growth plates work. 

"Long bones" are the bones  that make up our arms (humerus, radius, and ulna) and legs (femur, tibia, fibula). We get taller during childhood because these long bones contain growth plates that cause them to become longer over time.  The growth plate itself is a very thin stripe located at the ends of each long bone.  There are a few layers within this thin stripe .  Think of these layers as stations along a conveyer belt, and the whole growth plate as a factory for making new bone.  

The first layer (Layer 1) is called the Resting Zone, it is made of cartilage cells that are waiting around ready to start making bone.  This is interesting because it means that all of our bone starts out as cartilage an is converted into bone (to use the factory analogy: our bone is processed cartilage).  When the cells in the Resting Zone get the signal to start making bone, the cells start multiplying, and this is Layer 2 (Proliferative Zone).  All of these cells are pushing the ends of the bone (called the epiphysis) outward, causing growth.  Now we have lots of cartilage cells moving down the conveyer belt, and the next step in becoming new bone is to fatten up (called Layer 3, the Hypertrophic Zone).  As these cells become bigger they become bossy, and start changing the surrounding environment by ordering lots of calcium (this is Layer 4: the Zone of Provisional Calcification).  Thus the area surrounding these cells becomes calcified, which is more like bone, but we don't have normal bone yet.   The environment becomes so calcified that the cells die off, leaving empty houses.  These houses become filled by the bone cells (osteoblasts), which rearrange the calcium environment, to make it officially bone (this is Layer 5: the Ossification Zone).

The problem with growth plates is that most of the layers we talked about are made of cartilage cells.  Cartilage is weaker than bone, and therefore the growth plate is a weak link.  In kids, its not uncommon for a break in the bone to involve the growth plate.  Therefore a growth plate injury is a common injury in kids when they break a bone in their arm or leg.  Now lets see how we diagnose and treat these growth plate injuries.  

Diagnosing a Growth Plate Injury in Kids:

Doctors are suspicious for a growth plate injury when a kid comes in reporting twisting or falling onto their arm or leg, and are now unable to use the affected extremity.  Doctors are first looking for a broken bone, and then they can determine whether the break involves a growth plate. The injured arm or leg is usually very painful to touch and swollen.

A doctor will order basic x-rays, which are the best way to diagnose a broken bone, and to determine whether the break enters a growth plate.  Its uncommon to need a CAT scan .  MRIs arent required because x-rays give doctors a great view of the injured bone, and they can plan their treatment with x-rays alone.

On x-ray, the growth plate is a big black line at the end of the bone and it almost looks like a fracture line (the growth plate is black because its made of cartilage and therefore its doesnt appear white like normal bone).

There are different break patterns that involve the growth plate, and they are described by the Salter-Harris Classification (see picture).  A type 4 injury, the most severe injury, occurs when the break starts within the bone, travels through the growth plate, and then exits out the end of the bone. A type 3 injury occurs when the break starts within the growth plate and then exits out the end of the bone.  A type 2 injury occurs when the break starts within the bone and then travels out through the growth plate.

 A type 1 injury occurs when the bone itself isnt broken, but rather the growth plate gets squished or slightly separated.  This injury is sometimes very difficult to diagnose because there is only a slight change in the appearance of the growth plate (its slightly wide), and doctors will often order an x-ray of the uninjured arm or leg to compare the two sides.  Once the diagnosis is made, doctors can decide on treatment.  

growth plate injury salter-harris classification

Treating a Growth Plate Injury in Kids:

A growth plate injury is considered a type of broken bone, and so treatment is similar to treating a break.  If the break goes through the growth plate, but nothing gets separated (moved out of position), then a cast is applied to the injured arm or leg to protect it while it heals.  If the break goes through the growth plate, and the bone separates, its important to restore the normal alignment of the bone and growth plate as quickly as possible (this is sometimes referred to as "setting the bone").  This is a procedure performed by an experienced orthopedic surgeon and it usually requires the child to be sedated.  Once the bone is realigned, its treated the same as any other break, and its put in a cast to protect the injured arm or leg.

Overall growth plate injuries are treated like any other type of broken bone.  There is the risk that injury will cause the growth plate to stop working, and we discuss that in the next section.    

What is the long term outcome?  

Sometimes the injury to a growth plate is severe and it stops that growth plate from working.  This is referred to as "Premature Closure" of the growth plate.  It occurs because the body responds to a broken bone by filling in the crack with new bone, but around the growth plate, it may accidentally form a bridge of new bone across all the layers of the growth plate, thus fusing the end of the bone and preventing any further elongation. This can be problematic because the bone on the other arm or leg will continue to grow, causing a limb-length difference (one leg can be slightly shorter than the other leg if the tibia growth plate fuses after a break).  

The good news is that "premature closure" is uncommon after a growth plate injury, but it does occur (roughly 10-15% of cases overall).  The risk of this occurring depends on a few factors. The most important factor is the severity of injury.  A high-speed car accident or major trauma carries a much higher risk for premature closure (up to 85% of cases) compared to a break that occurs while a child is playing sports or running around (only about 5-10% of cases).  The injuries that cause significant separation in the bone have a higher risk of closure, and this ties in with severity of initial injury.  High energy injuries, like a motor-vehicle collision, cause more separation than a simple fall.  Additionally, the fracture pattern (remember Salter-Harris Classification) also helps predict risk for premature closure, in part because it describes the severity of injury. A Type 1 fracture, which is the least severe injury, almost never has growth arrest, while a Type 4 injury, which is usually caused by a major trauma, goes on to growth arrest more commonly.  

The next question is how to treat a growth arrest once it occurs.  

Unfortunately, once a growth plate shuts down, its very challenging to re-start.  The decision about what to do next depends on how much more growth was expected for that bone.  If the growth plate closes in a 17 year old kid, it might not matter too much because the kid is going to stop growing in only a few months, and therefore the injured bone may lose only a few milimeters of length (which is not obvious to the kid or to other people).  Also some growth plates are more active than others.  ts look at the arm bone (humerus) for example.  The growth plate at the top of the humerus (near the shoulder) contributes 80% of the growth, while the growth plate at the bottom of the humerus (near the elbow) only contributes 20%. Therefore, closure of the top growth plate may be a bigger deal because its preventing a lot of future growth, while closure of the lower growth plate may not matter in an older child because its not doing too much anyway.  Therefore, treatment of a closed growth plate depends a lot on timing.  

However, lets say the growth plate closes in a kid with a lot of growing left.  The most important thing to avoid is asymmetry.  We dont want the healthy bone on the uninjured arm or leg to keep on growing because it will lead to limb-length differences.  Because its challenging to re-open growth plates, the answer in such cases is to use surgery to stop the bone in the uninjured arm or leg from growing.  






1. Aitken AP. Fractures of the epiphysis. Clin Orthop. 1965;41:19-23. see full article.

2.  Salter RB, Harris WR. Injuries involving the epiphyseal plate. J Bone Joint Surg (Am). 1963;45:587-622. see full article

3. Spiegel PG, Cooperman DR, Laros GS. Epiphyseal fractures of the distal ends of the tibia and fibula. A retrospective study of two hundred and thirty-seven cases in children. JBJS 1978;60:1046. see full article

4. Leary JT, Bowe JA et al. Physeal fractures of the distal tibia: predictive factors of premature physeal closure and growth arrest. JPO 2009; 29(4); 356-61. see full article.