The distal fibula epiphysis starts ossifying during the second year of life and closes 12–24 months later than the distal tibial physis. The distal tibial physis grows 4 mm a year and account for 40 % of the leg longitudinal growth.

Stability is a very important concept in the management of ankle fractures. Ligaments play a major role in ankle fracture stability. In practice most surgeons base their decisions on clinical assessment and plain x-rays to assess ankle fracture stability. Although this may be adequate in most cases where the features of instability are obvious, this is not the case in all fractures leading to some patients undergoing unnecessary surgery. In children, this is even more complicated due to the presence of the physis which poses diagnostic and therapeutic challenges to the treating surgeons.

Stress tests, CT scan and MRI scan have been used to aid decision making.

Several classifications have been proposed to help understand the nature of ankle fractures, inform treatment choices and predict future outcomes. Most of these have been based on morphological description and their predictive values for instability and better treatment choice have been questioned [2, 3]. However, to understand the published evidence better, basic knowledge of these classifications is valuable.

In adult practice, there are two common classifications in use: Weber and Lauge-Hanson classification.

Weber classified ankle fractures according to the relation of the fibular fracture to the syndesmosis into: type A (below the syndesmosis), type B (at the level the syndesmosis) and type C (above the syndesmosis). Weber classification was subsequently adopted and incorporated in the AO ankle classification which was expanded into two sub-layers as shown in Table 22.1.

Lauge-Hansen [4] classified ankle fractures according to the position of the foot at the time of impact (supinated or pronated) and the direction of the force applied to the ankle (adduction, abduction or external rotation). A pronated foot will result in tight deltoid ligament and lax lateral ligamentous complex and vice versa for a supinated foot. Lauge-Hansen indicated that these two elements (the position of the foot and the direction of the force) determine the order in which ankle stabilising structures fail, and that these structures fail in a predictable order (Table 22.2). Several biomechanical studies failed to reproduce the work and classification of Lauge-Hansen [5, 6]). Moreover, findings from MRI studies of displaced ankle fracture did not have the patterns of ligament and bony injury predicted by their apparent Lauge-Hansen type [1, 2, 7].

Salter and Harris introduced a classification system which carries their name based on the relationship of fracture lines to the growth plate [8, 9]. The classification is relatively simple and easily remembered and has been relatively successful in predicting future growth disturbance although the latter has been contested [10]. (Fig. 22.2 )

Dias and Tachdjian [11] modified the Lauge-Hansen classification to include the Salter-Harris classification so that it can applied to children ankle fractures. Subsequently four other types of fractures were added, namely the Tillaux, triplane, axial compression, and miscellaneous physeal fractures [12].

Tillaux fracture and triplane fractures have been added to the classification. The juvenile Tillaux fractures (to differentiate it from adult similar avulsion fracture) are SH-III fractures involving the anterolateral aspect of the distal tibia plafond which is not fused to the metaphysis yet (Fig. 22.3). These fractures are caused by external rotation forces and can be reduced by internally rotating the foot [13].

The triplane fracture was described by Lynn in 1972 [14]. As the name implies these fractures occur in three different planes: coronal, transverse, and sagittal. On the AP radiographs the fracture appears as a SH-III (like Tillaux fracture) whilst on the lateral view it appears as a SH-II (also called two-part triplane fracture) or SH-IV (also called three-part triplane fracture). Four-part triplane was also described in the literatures [15, 16] (see Figs. 46.1 and 46.2 in Chap. 46).

The prognostic value of these classifications has been debated. Leary [10] retrospectively reviewed 124 children after physeal fractures of the distal end of the tibia. They defined premature physeal closure (PPC) as radiographic evidence of physeal closure as compared to the uninjured side in this patient population. Fifteen fractures (12.1 %) were complicated by PPC, 67 % of the PPC observed occurred in SH-II fractures, followed by 13 % in SH-III, 13 % in SH-IV, and 7 % in triplane fractures. They did not observe any physeal arrest in the SH-I or Tillaux fractures. They were able to demonstrate statistically significant correlations between mechanism of injury and PPC and between the amount of initial fracture displacement and the rate of PPC. For each millimetre of initial displacement, there was a relative risk of 1.15 (P < 0.01).

In another study of 49 children with physeal fractures of the distal tibia or fibula or both, the Salter-Harris classification system could not significantly predict the growth pattern [17] (Fig. 22.2).

Spiegel et al. [18] followed 184 distal tibia and/or fibula, fractures for an average of 28 months after injury using the Salter-Harris classification. They differentiated three groups according to their risk for shortening of the leg, angular deformity of the bone, or incongruity of the joint. The low-risk group consisted of 89 patients, 6.7 % of whom had complications; this group included all type I and type II fibula fractures, all type I tibia fractures, type III and type IV tibia fractures with less than 2 mm of displacement, and epiphyseal avulsion injuries. The high-risk group consisted of 28 patients, 32 % of whom had complications; this group included type III and type IV tibia fractures with 2 mm or more of displacement, juvenile Tillaux fractures (Fig. 22.3 ), triplane fractures, and comminuted tibial epiphyseal fractures (type V). The unpredictable group was made up of 66 patients, 16.7 % of whom had complications; only type II tibia fractures were included. The incidence and types of complications were correlated with the type of fracture (Salter-Harris classification), the severity of displacement or comminution, and the adequacy of reduction.

de Sanctis et al. [19]) reviewed 158 ankle fractures; 132 were treated conservatively and 26 patients underwent surgical treatment. Fibular fractures of the malleolus without epiphyseal separation or dislocation (68 patients) were excluded. Of the 158 patients, 113 (70 %) were available for an average 6-year follow-up. They compared the degree of epiphyseal separation or dislocation, the Carothers-Crenshaw classification (a classification based on the mechanism of trauma) with the Salter-Harris classification (which is based on anatomical-radiographic criteria). They reported that fractures more likely to result in permanent damage to the physis are those caused by a traumatic adduction-supination mechanism that can produce SH-III, IV, and V fractures of the distal part of the tibia; they also reported that the combination of compression and adduction may cause a SH- V injury with type III and IV fractures. However, type V lesions are often diagnosed late. In 11 of their 12 poor results, 6 were caused by adduction-supination injuries and 5 were compressive injuries.

In a large retrospective study of 376 children with distal tibial physeal injury, Schurz et al. [20] reported the outcomes after various types of Salter-Harris fractures (Table 22.3).

Vahvanen and Aalto [21] studied 310 children treated for ankle fractures. They were classified according to the classifications of Ashhurst-Bromer-Weber, Lauge-Hansen, and Salter-Harris. They found that grouping of the fractures according to Lauge-Hansen and Ashurst-Bromer-Weber classifications suited to adults was largely unsuccessful. Epiphyseal fractures were easily classified according to Salter-Harris. They proposed that ankle fractures in children can be roughly divided into avulsion and epiphyseal fractures. Adequately reduced avulsion fractures can be expected to heal well; epiphyseal fractures, however, may cause late complications.