Triplane or triplanar fractures are of the distal tibia only occurring in adolescents. As the physiological closure of the physeal plate begins medially, the lateral (open) physis is prone to this type of fracture. Most authors regard it as a type 4 Salter-Harris fracture.
It comprises of:
a vertical fracture through the epiphysis
a horizontal fracture through the physis
an oblique fracture through the metaphysis
As physeal closure has to begin at one end, triplane fractures have occasionally been reported in other sites too, e.g. distal radius 2, proximal tibia 4, distal femur 5.
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Epidemiology
In adolescents with closing epiphyseal plate(s) they are the most common ankle joint fractures - along with Tillaux fractures.
Clinical presentation
Symptoms comprise of pain and inability to weightbear. Possible signs include swelling, localized/referred pain, and/or deformity of the ankle.
Pathology
Mechanism
External rotation and supination is the main mechanism of injury in lateral triplane fractures. The uncommon medial variation usually occurs with an adduction force 9.
Radiographic features
Plain radiograph
Standard ankle series suggested; AP, lateral and mortise (best view to define displacement). Due to the aforementioned characteristics, the fracture typically resembles:
Salter-Harris 3 fracture on AP
Salter-Harris 2 fracture on lateral
Small dislocations and the vertical fracture itself are frequently overlooked, and CT is advised if there is concern.
CT
The imaging modality of choice, permitting identification of;
fracture pattern and articular congruity
fragment number and orientation/relationship
For the same reasons, CT aids in treatment planning as well 6.
MRI
May be used to reveal associated ligamentous injuries, osteochondral fractures and chondral fractures 7.
Treatment and prognosis
Treatment options comprise of surgery (e.g. open reduction and internal fixation (ORIF)) or conservative management (e.g. long leg cast immobilization). Physeal arrest may occur in 7% to 21% of cases, rarely leading to angular deformity. The significance of preserving the physis is questionable given the limited remaining growth potential, but patients with greater than 2 years of growth remaining should be followed.
History and etymology
The distinctive term for this fracture was coined by L Marmor in 1970 stemming from it lying in the frontal, lateral, and transverse planes 8.
Differential diagnosis
Tillaux fracture: lacks a metaphyseal fracture
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