Sean is 13 years old. He was playing basketball but when he jumped to score a basket he landed awkwardly on his ankle, twisting and externally rotating it. He immediately fell to the floor on the court and couldn’t weight bear on it. The swelling and bruising increased and he attended his local emergency department where he was told that he had a triplane ankle fracture.
Although triplane ankle fractures account for only 5-15% of overall paediatric ankle fractures, along with Tillaux fractures, they are the most common ankle fractures in adolescents. This type of fracture represents a unique spectrum of injury that does not fit neatly into the Salter-Harris classification of physeal injury. They occur before complete closure of the distal tibial physis (hence why they occur in adolescents whose epiphyseal plates are closing) and are classically seen in 10-17 year olds. They are slightly more common in males.
Adolescents with triplane fractures will usually present to the emergency department with a very painful and swollen ankle after a twisting force to the leg during athletic or recreational activities. They are usually very reluctant or unable to weightbear.
There will often be swelling and bruising with focal or referred pain at the affected ankle. There may be deformity of the ankle. It is important also to examine skin integrity and the presence of neurologic defects or vascular injuries. Don’t forget to palpate the full length of the fibula to evaluate for a proximal fracture as well as along the foot to evaluate for injuries such as a fracture to the base of the 5th metatarsal.
AP and lateral ankle xrays will help evaluated the fracture type. Addition of a mortise view, performed with the leg internally rotated approximately 15 degrees to allow better assessment of the articular space, should be included to assess the amount of displacement if this can’t be fully appreciated on the AP view (although in some countries the AP view is a mortise view).
The triplane fracture on x-ray looks like a Salter-Harris II or III depending on whether this is a medial or lateral triplane fracture. The fracture is in all three planes, classically looking like a Mercedes sign on CT.
It may be classified as in 2, 3 or 4 parts.
It is important not to miss fibular fractures which are seen in 50% of triplane fractures. Typically this is a spiral fracture pattern located proximal to the physis in children nearing skeletal maturity.
CT scans are not routinely performed in the emergency department but may be organized by the orthopaedic team. Small dislocations and the vertical component of the fracture are not infrequently overlooked. CT is therefore often organized to fully delineate fracture pattern and to assess the degree of intra-articular congruity.
In the ED, as with any injury, ensure you prescribe adequate analgesia and provide assistance with non-weight bearing status, such as a wheelchair or crutches depending on the ability of the child. Placement in a boot or cast for comfort prior to definitive treatment by the orthopaedic team is appropriate.
Once the diagnosis is made, ongoing care depends on the degree of displacement. Orthopaedic review for consideration of conservative management versus operative management is important as these fractures will often need CT imaging to ensure adequate delineation of fracture pattern.
Fractures with minimal displacement (<2mm), particularly if they are 2 part triplane fractures, can often be managed with closed reduction and casting. If the fracture is in 3 or 4 parts, closed reduction is difficult to achieve.
Post reduction, place in a long leg/above knee cast for 3-4 weeks to control the rotational component of the injury, followed by a further 2-4 weeks in a short leg cast or walking boot to initiate ankle range of movement.
Any triplane fracture with >2mm displacement or that is in 3 or 4 parts is likely to require ORIF (Open Reduction, Internal Fixation). Intra-articular reduction to within 2 mm is required for optimal treatment of these unique paediatric ankle fractures.
Complications and Risks
- Growth Arrest:
The main concern in an adolescent with a triplane fracture is growth arrest. This occurs in between 7-21% of triplane injuries. This is often insignificant but does mean that patients with more than 2 years of growth remaining must be closely followed up.
- Ankle Pain and Degeneration:
Rare but increased risk with articular step greater than >2mm.
As with all things orthopaedic, the debate continues: should these fractures be managed operatively or conservatively? Though still in preliminary research stages, recent evidence suggests that non-operative treatment of triplane fractures may have comparable clinical and radiographic results to operative treatment. Discussion with the orthopaedic team is advised prior to discharge given the different management options.
Things not to miss!
Don’t forget to examine the rest of the child’s lower limb when they present with a painful swollen ankle as there may be an associated accompanying fracture. Ensure that you examine and especially palpate both the foot and the entire length of the fibula. With rotational forces, proximal spiral fibula fractures and base of 5th metatarsal fractures are relatively common with triplane fractures. Carefully check and document neurovascular status as nerve injury can occasionally be associated with spiral fibular fractures.
Sean was found to have a 2 part nondisplaced Triplane Fracture and was placed in an above-knee cast and followed up at his local orthopaedic outpatient clinic. He had interval x-rays which showed good healing and no evidence of displacement. After 4 weeks he was switched to a walking boot to encourage early ankle mobilization for another 2 weeks. He is looking forward to next year’s basketball season already!
Schnetzler, Kent A et al 2008 ‘The Pediatric Triplane Ankle Fracture’ The Journal of the American Academy of Orthopaedic Surgeons 15(12):738-47
Hyman et al, MSK Key https://musculoskeletalkey.com/transitional-ankle-fractures-juvenile-tillaux-and-triplane-fractures/ Accessed at 09/02/20
Beaty JH, Kasser JR. Rockwood and Wilkins’ Fractures in Children. 6th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2006:1105
Min Ryu, Seung et al 2017 ‘Is an operation always needed for pediatric triplane fractures?’ Journal of Pediatric Orthopaedics B 27(5):1 · November 2017