EBM Lecture Handout #6: Salter Harris 1 Injuries

The traditional teaching about Salter-Harris 1 injuries goes something like this: Because the injury is directly to the growth plate, these injuries will be invisible on x-ray. In children, ligaments are stronger than bone, so if there is pain near a growth plate, we should assume that it is an injury to the bone not the ligament. Therefore, we should cast (or splint) all children with tenderness near the growth plate, regardless of x-ray findings. This myth is based on a few misunderstandings, which are outlined below. 

History: What is a Salter-Harris 1 fracture?

Salter RB and Harris WR. Injuries Involving the Epiphyseal Plate. J Bone Joint Surg Am. 1963;45(3):587-622.

This is the original description of Salter-Harris (epiphyseal plate) injuries by Drs. Salter and Harris. In a type one injury, “there is complete separation of the epiphysis from the metaphysis without any bone fracture”. These injuries needed to be reduced. The classic example of a type 1 injury is a SCFE (slipped capital femoral epiphysis).

The fact that Salter-Harris 1 injuries are displaced seems to be recognized by a number of sources, but it certainly is not what I was taught in medical school and residency. For example, the radiologists at radiopaedia.org define a type 1 fracture as “slipped”: http://radiopaedia.org/articles/salter-harris-fractures

Another hint that we have completely misunderstood the definition of a Salter-Harris 1 injuries is the prevalence at which they are supposed to occur:

• Salter Harris 1: 6%
• Salter Harris 2: 75%
• Salter Harris 3: 8%
• Salter Harris 4: 10%
• Salter Harris 5: <1%

This means that for every 1 Salter-Harris 1 fracture you see, you should see more than 15 Salter-Harris 2-5s. Does that fit your current practice? It certainly did not fit mine. This means we have seen a huge indication creep when it comes to pediatric casting.

Bottom line: We have misunderstood the definition of a Salter-Harris type 1 injury. These injuries are complete separations of the epiphysis from the metaphysis that will usually require a reduction. When you think Salter-Harris 1, don’t think sprained ankle, think slipped capital femoral epiphysis (SCFE). 

Are childrens’ ligaments stronger than their bone?

This is one of those ideas that never made any sense to me. I am sure we have all heard that in children ligaments are stronger than bones. Therefore, you never diagnose a pediatric patient with a sprain. But I have seen thousands of kids with sprained ankles, and must have sprained my own ankle a hundred times growing up. What gives?

The evidence:

Boutis K, Narayanan UG, Dong FF, et al. Magnetic resonance imaging of clinically suspected Salter-Harris I fracture of the distal fibula. Injury. 2010;41:(8)852-6. PMID: 20494352

This is a prospective cohort of 18 pediatric patients, who had trouble ambulating and maximal tenderness at distal fibular growth plates. None of the 18 children had fractures. They all had sprains or boney contusions.

Boutis K, Plint A, Stimec J. Radiograph-Negative Lateral Ankle Injuries in Children: Occult Growth Plate Fracture or Sprain? JAMA pediatrics. 170(1):e154114. 2016. PMID: 26747077

This is a larger prospective cohort of 140 children between 5 and 12 years of age with clinically suspected Salter Harris 1 fractures of the ankle. They were all treated with a removable splint. Then all of the children had an MRI at one week. Of the 140 children, 108 had ligamentous injuries on MRI.  Another 27 had isolated bone contusions. Only 4 children (3.0%, 95% CI 0.1-5.9%) actually has Salter Harris 1 fractures, and only 2 of those had any evidence of growth plate injury. And even more important, at 1 month follow up, there was no difference in function between those with MRI confirmed fracture and those without.

Bottom line: Children do get sprains. The idea that ligament is stronger than bone is a myth. The incidence of true growth plate injuries is very low, and even those that occur are of questionable clinical relevance. 

However, to be clear, there may be significant growth plate injuries that are not displaced at the time of assessment, and will have negative x-rays. However, it seems like these will be clinically obvious:

Simpson WC, Fardon DF. Obscure distal femoral epiphyseal injury. South Med J. 1976;69:(10)1338-40. PMID: 982113

This is a case series of 3 children with distal femoral injuries. The injuries and swelling were so significant that, despite negative x-rays, they took them all to the operating room and, under general anesthesia, performed varus and valgus stress views, which identified complete separation of the epiphyseal plate. All three had good outcomes.

Are Salter-Harris 1 fractures clinically important?

This is a difficult question to answer, because there seem to be two very different definitions of Salter-Harris 1 floating around out there. Unfortunately, when authors discuss a patient with a “Salter-Harris 1 fracture” there is often no way of knowing if they are referring to a displaced injury requiring reduction, or the non-displaced bone that just happens to hurt near the growth plate. There are a number of case reports of poor functional outcomes and growth disturbances after a Salter-Harris 1 injury. However, in all cases it sounds like there was probably displacement or a very significant injury. The most quoted paper is:

Basener CJ, Mehlman CT, DiPasquale TG. Growth disturbance after distal femoral growth plate fractures in children: a meta-analysis. J Orthop Trauma. 2009;23:(9)663-7. PMID: 19897989

This is a systematic review of including 16 papers, totaling 564 fractures. Salter Harris 1 injuries are said to have a 36% rate of growth disturbance. Unfortunately, there is no indication anywhere as to whether these Salter-Harris 1 injuries were displaced or not.

Bottom line: There is no case report I could find that shows a non-displaced Salter-Harris 1 injury having a poor outcome. However, because of the mixed definition, this literature is very difficult to decipher.

Should we immobilize Salter-Harris 1 fractures?

Boutis K, Willan AR, Babyn P, Narayanan UG, Alman B, Schuh S. A randomized, controlled trial of a removable brace versus casting in children with low-risk ankle fractures. Pediatrics. 2007;119:(6)e1256-63. PMID: 17545357

This is a RCT of 104 children with distal fibula fractures. There was a mix of type 2s and non-displaced “type 1s”. Two thirds of the Salter Harris 1 group had no x-ray changes. (For the mathematicians out there, that means ⅓ did have x-ray changes). They were randomized to a removable brace versus a cast. All were instructed to stay non-weight bearing for 5 days. At one month, functional outcomes were identical. The brace allowed earlier return to activities. The cast required more unscheduled appointments. Patients preferred the brace greatly.

Gleeson AP, Stuart MJ, Wilson B, Phillips B. Ultrasound assessment and conservative management of inversion injuries of the ankle in children: plaster of Paris versus Tubigrip. J Bone Joint Surg Br. 1996;78:(3)484-7. PMID: 8636192

This is a RCT of 45 children with concerning exam for fracture, but negative x-ray (almost 60% had an ultrasound that revealed signs of a boney injury). They were randomized to tube bandage and crutches or full cast. There were no differences in functional outcomes. The children treated with a bandage returned to activity about 1 week earlier than those with a cast.

Franz T, Jandali AR, Jung FJ, Leclère FM, von Wartburg U, Hug U. Functional-conservative treatment of extra-articular physeal fractures of the proximal phalanges in children and adolescents. Eur J Pediatr Surg. 2013;23:(4)317-21. PMID: 23444070

• This is a prospective observation of 13 pediatric patients with proximal phalanx salter 1 and 2 fractures. They were all given removable splints, and they all had good functional outcomes.

Bottom line: These studies include children with more severe injuries than normally get lumped into the Salter-Harris 1 bucket: they had x-ray changes, or they had Salter-Harris 2 fractures. Despite these more severe injuries, there was no benefit seen with casting. One major issue with these studies is that the majority of children diagnosed with Salter Harris 1 injuries might just be sprains, which clearly would not benefit from casting. Furterhmore, these are small studies so we cannot rule out rare instances where a cast might help.

What do I do?

My take is that we have completely misinterpreted the original literature on this topic and are calling injuries “Salter-Harris 1s” that Salter and Harris would not have included in their classification. However, even if these injuries don’t have a formal name, there is still the possibility of a bad outcomes. Currently there is limited literature on the outcomes of these injuries if we don’t immobilize them.

First, any orthopedic injury that I am really concerned about (because of the mechanism or the amount of pain and swelling) will get splinted and followed up with ortho, no matter what the x-ray reveals.

For the average kids with some ankle or wrist pain over a growth plate, I tell parents:

“I don’t see any break on the x-ray. Here on the x-ray is a line – that is the growth plate, or where the bones are growing. Technically, it would be possible to break right through that line, and it would be invisible to me. In the past, we would just put all children into casts, and that is still what many other doctors would do today. However, there are definitely downsides to being in a cast. If you want the cast, I am happy to put it on, but I would suggest controlling the pain with medications like tylenol, applying ice, and using a removable splint if that seems to make it more comfortable. However, if there is still a lot of pain or trouble using the (arm/leg) in 2 days please come back and we can check you again.”

You can find more evidence base topic reviews here.