Radiograph-Negative Lateral Ankle Injuries in Children: Occult Growth Plate Fracture or Sprain?
An 7-year-old girl presents to your Emergency Department (ED) with an ankle inversion injury from while performing gymnastics. Plain films of her ankle show no fracture. It has been a long-held presumption that skeletally immature children with fracture-negative radiographs should be immobilized with a cast given the concern for an occult Salter-Harris 1 fracture. “Children do not get sprains” is a common teaching point. But a recent 2016 JAMA Pediatrics article challenges that premise in a prospective cohort study of 135 pediatric patients.1 Can these injuries be managed more like a sprain, utilizing a removable ankle brace?
The main objective of the study was to determine the incidence of true Salter-Harris 1 fracture of the distal fibula (SH1DF) in children ages 5-12 years using magnetic resonance imaging (MRI). Additionally the authors sought to compare the functional recovery of all patients with lateral ankle injuries (regardless of whether sprain or fracture) when treated similarly at discharge.
Children were included in the study if they were 5-12 years old, had an isolated lateral ankle injury, and clinically presumed to have SH1DF.
- Injuries occurred over 3 days ago
- Pre-existing musculoskeletal disorder or coagulopathy
- Developmental delay
- Ankle fracture in the past 3 months
- Families with a language barrier
Patient care timeline:
- T=0 days: In the initial ED visit, a functional assessment tool was filled out by families, the modified performance Activities Scale for Kids (ASKp), as a baseline of their functional status before the injury. All enrolled patients were treated with a removable air-stirrup brace and instructed to return to activities as tolerated.
- T= 1 week: Patients underwent MRI.
- T=1 month: Families again completed the ASKp and had follow-up with an orthopedic surgeon.
- T=3 months: Families received a phone follow-up.
MRIs were reviewed by 3 pediatric radiologists, who were all blinded to the study findings. They categorized the injuries in:
- Avulsion fracture
- Bone contusion
- Ligamentous injury
- The primary outcome was the number of MRI-confirmed SH1DF.
- Secondary outcome measures included the number of other injuries diagnosed on MRI (ligamentous injuries, avulsion fractures, or bone contusions), physical functioning as determined by the ASKp, and those who had full, painless weight-bearing capability and a return to normal activities at least “almost all the time”.
135 children underwent MRI. This study had great follow-up in that 129 of those patients were seen at the 1-month follow-up, and 128 patients were seen at the 3-month follow-up. Of these 135 children, the following diagnoses were made:
- SH1DF – 4
- Ligamentous injury – 108
- Avulsion fractures – 38
- Bony contusions – 107
- There was some overlap because some patients had multiple injuries (i.e., some patients had both ligamentous injury and fracture on MRI).
- Baseline mean score for all patients = 92.3%
- Mean score at 1 month follow-up = 83.4%
Full painless weight bearing ability
- At 1 month follow-up = 72.1%
- At 3 month follow-up = 96.1%
Return to normal activities “almost all the time”
- At 1 month follow-up = 68.8%
- At 3 month follow-up = 96.9%
Subgroup analysis: When they split the children into two groups, those with fracture on MRI and those without, there was no significant difference in the above measurements between the two groups.
This study totes a multidisciplinary author group including pediatric emergency medicine physicians, radiologists, and orthopedic surgeons, all of whom play a role in the management of patients with these types of injuries. The authors report that the incidence of MRI-confirmed SH1DF is actually quite low and of the children with lateral ankle injuries in this study, nearly all of them reached full recovery within 3 months when treated with the same interventions regardless of fracture presence. They propose that with these results, practitioners can pursue a less-conservative approach to managing these patients and thus potentially avoid unnecessary interventions.
The authors did not investigate long-term outcomes of growth arrest in these patients, which is a concern for patients with presumed growth plate injuries. The fibula is not a weight-bearing bone and thus the clinical significance of growth arrest may not be fully apparent in the short term period. Thus, these results may not be applicable to other Salter-Harris 1 fractures.
Take home message
This study seems to serve as practice-changing evidence in emergency medicine. Children with lateral ankle injuries, open growth plates, and no fracture seen on x-ray, can be treated with a removable air-stirrup ankle brace for comfort and instructed to return to activity as tolerated. These patients can follow-up initially with their general pediatrician as opposed to an orthopedist.
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