Salter-Harris I fractures are limited to young children, whose physes are still smooth; these fractures, along with Salter-Harris II fractures, are the most common distal tibia fractures in children (see Chap. 17 for further discussion of the Salter-Harris and Ogden classification systems). Salter-Harris II fractures tend to occur after age 10. Older children, who have an undulating or partly fused physis, are prone to more complex Salter-Harris fractures. Focal physeal fusion or undulation may alter fracture force propagation. Fractures propagate along the path of least resistance; therefore, the open physis is usually first to fail, rather than the metaphyseal or epiphyseal bone. Similarly, fractures are more likely to propagate along an open, smooth physis than along an undulating physis. Physeal fracture propagation will usually terminate at sites of undulation, such as Kump bump, or at sites where there is already bony physeal fusion. These areas resist transmission of force more than the open, smooth physis.

The juvenile Tillaux and triplane fractures are affected by the contour of the distal tibial physis (Box 16.1). Both of these fractures usually occur when the foot is in supination and subject to external rotational forces [4], usually during a fall. They are most common between ages 12 and 15, especially during the approximately 18-month transitional period when the distal tibial physis begins closure [5, 6].

The Salter-Harris III juvenile Tillaux fracture occurs in early adolescence and is most common in girls. The force initially propagates along the anterolateral smooth distal tibial physis. However, physeal fracture propagation stops at Kump bump, where the force deviates vertically into the epiphyseal bone anterolateral to Kump bump [6]. The older the child, the more lateral the epiphyseal fracture line, since more of the physis is fused. The anterior tibiofibular ligament inserts into the epiphyseal fragment, and therefore some degree of separation of the fracture fragments is common.

Triplane fractures are Salter-Harris IV fractures; the degree of physeal undulation and fusion affects propagation of this fracture and the resultant number of bone fragments. As a general rule, there is a sagittal component in the epiphysis, an axial component through the physis, and a coronal component in the metaphysis [5]. The distal fibula is fractured in about 50 % of cases.

Distal fibular physeal fractures have been described with any mechanism of injury. Tibial fractures accompany approximately 25 % of fibular fractures [7], so if there is a fibular fracture the tibia should be closely examined.

Periosteal avulsion fractures about the ankle may occur at the medial or lateral collateral ligament insertion sites (Fig. 16.2). These are frequently seen in skeletally immature children, in whom the periosteum where ligaments attach is less resilient than are ligaments and tendons [8]. Maisonneuve fractures result from pronation/external rotation of the ankle and consist of the combination of proximal tibial/tibiofibular injury and ligamentous injury at the medial ankle.

The objective of treatment of ankle physeal fractures is to avoid premature physeal fusion by minimizing the degree of physeal injury and displacement. If the epiphysis is involved, incongruity at the articular surface may lead to early osteoarthritis if left untreated. Therefore, the threshold for operative intervention is relatively low for epiphyseal fractures. In addition, Salter-Harris fractures may lead to physeal bars, especially those that are higher grade. When physeal bars are eccentrically located in the tibia, varus or valgus deformity of the ankle may result, whereas central physeal bars may lead to restricted growth without angular deformity [7].

Operative reduction is indicated for juvenile Tillaux and triplane fractures when the gap between fragments exceeds 2 mm [4]. If the gap is less than or equal to 2 mm, the fracture may be treated conservatively with 4 weeks of non-weight bearing with a long leg cast followed by 4 weeks of relative non-weight bearing in a boot [9]. Maisonneuve fractures are considered unstable and require operative reduction.

Computed tomography (CT) is helpful for comprehensive delineation of the fracture pattern, particularly if operative reduction is planned. CT allows more accurate measurement of fracture displacement, assessment of articular surface congruity as well as location and extent of physeal involvement, and determination of the number and location of fracture fragments.

Salter-Harris I and II distal tibial and fibular fractures are the most common ankle fractures. It is important to search for a metaphyseal fragment or small flake (the so-called Thurston Holland fragment) in order to differentiate between a Salter-Harris I and a subtle Salter-Harris II. The degree of displacement and extent of physeal widening determine operative versus nonoperative management. Isolated Salter-Harris I and II fractures at the level of the distal fibular physis are not uncommon (Fig. 16.3).

It can be difficult to identify Salter-Harris I fractures of the distal fibula (or elsewhere). Isolated soft tissue swelling centered at the level of the open physis should be considered a Salter-Harris I fracture until proven otherwise (Fig. 16.3). However, in children younger than 10, the cartilaginous epiphysis of the medial or lateral malleolus may be confused with soft tissue swelling. If there is any question, comparison views of the asymptomatic distal fibula may help assess for physeal widening on the affected side.

The juvenile Tillaux fracture subgroup of distal tibial Salter-Harris III fractures has a vertical epiphyseal fracture line that is usually anterolateral to Kump bump (see Fig. 16.1) [9]. The older the child, the more lateral this vertical epiphyseal fracture line tends to be. The distal tibial epiphyseal fragment may rotate anterolaterally due to traction from the anterior syndesmosis (or tibiofibular ligament) at the level of the tibial plafond (Fig. 16.4). Although the anterolateral physis is fractured, it does not always appear widened.

The triplane subgroup of Salter-Harris IV fractures of the distal tibia must have at least three orthogonal fracture planes. These fractures can be divided into two-, three-, and even four-part fractures. Each category has several subtypes, which creates a confusing classification system [5]. Rather than trying to label these fractures according to their type and subtype, it is useful to define and describe the fracture components and extent of displacement. The two-part fracture is most common, followed by the three-part [11]. The classic two-part triplane fracture consists of a sagittal fracture plane through the tibial epiphysis, an axial fracture plane through the physis, and a coronal fracture plane through the metaphysis (Fig. 16.5). The posterolateral epiphyseal fracture fragment usually moves with the distal fibula, whereas the distal tibial epiphysis between the medial malleolus and Kump bump (or the anteromedially fused physis) follows the rest of the tibia. In younger patients, a three-part medial triplane fracture may have an axial fracture plane that extends through the anteromedial physis where Kump bump will develop. Once Kump bump appears, the medial fracture fragment in a three-part triplane fracture may include the medial epiphysis as well as Kump bump (Fig. 16.6).

Additional fractures about the ankle include avulsion fractures related to the lateral collateral ligament, syndesmosis (anterior or posterior tibiofibular ligament) (see Fig. 16.4), and peroneal sheath. Lateral and medial avulsion fractures usually appear as sharply defined flecks of bone along the tibia or talus (see Fig. 16.2); these should not be confused with the normal fragmentary ossification pattern of the malleoli or accessory ossicles such as the os subfibulare, which are corticated and round or ovoid in shape.

The Maisonneuve fracture has several components (Box 16.2). There is a medial malleolar fracture or deltoid ligament injury (Fig. 16.7), along with injury to the syndesmosis and interosseous tibiofibular ligament, which results in widening of the medial tibiotalar joint. In addition, there is a proximal fibular fracture or proximal tibiofibular dislocation. Therefore, if the medial tibiotalar joint is widened or there is a medial malleolar fracture on ankle radiographs, radiographs of the upper tibia and fibula near the knee are recommended to evaluate for a concomitant proximal fibular fracture or proximal tibiofibular dislocation.