These fractures are confined to the physis and usually result from a shearing or avulsion force that parallels the growth plate. Type I fractures occur most often in children less than 5 years old but are relatively uncommon, representing around 6 % of all growth plate injuries. In infancy, they usually occur in the proximal humerus, distal humerus, and proximal femur, resulting from birth trauma or non-accidental trauma [6]. In older children, Type I fractures are most common in the distal radius, proximal humerus, and proximal femur. “Little Leaguer’s shoulder,” a Type I fracture of the proximal humerus, occurs around age 10–12 in throwing athletes. Slipped capital femoral epiphysis (SCFE), also a Type I fracture, occurs around puberty, usually without specific antecedent trauma. Most Type I injuries have an excellent prognosis [6], but SCFE may be complicated by avascular necrosis of the femoral head, since the artery supplying the epiphysis courses along the physis and may be injured at epiphyseal separation.

The classic but relatively uncommon radiographic finding is displacement of the epiphysis without an osseous fracture. This may be seen in infants with traumatic separation of the distal humerus, which usually results in posteromedial displacement of the distal fragment [19] (Fig. 17.16) (see Chap. 8). However, in many cases the fracture reduces spontaneously after the initial slip, and radiological diagnosis may be difficult. Findings that suggest a Type I fracture include slight widening of the growth plate or poor definition of the metaphyseal margin adjacent to the growth plate, due to slight angulation. Very small, thin bone fragments may be seen along the physis, due to fracture propagation from the hypertrophic zone into the zone of provisional calcification [6] (Fig. 17.17). In infants whose epiphysis has not yet ossified, a slipped epiphysis may mimic a dislocation. Ultrasound may confirm a Type I fracture by showing malalignment between the metaphysis and cartilaginous epiphysis (Fig. 17.18). MRI may be used to assess for occult Type I injury, particularly in regions where growth plate damage could cause significant growth arrest, such as the knee. Water-sensitive sequences typically show a wide, hyperintense physis, with adjacent marrow and soft tissue edema (Fig. 17.19). Follow-up radiographs in 7–10 days may show periosteal new bone formation in the adjacent metaphysis, due to healing.

Type II fractures extend along the growth plate into the metaphysis and usually result from a shearing or avulsive force. They are the most common physeal injury, representing 75 % of growth plate fractures. Type II injuries are rare in infancy and usually occur in children older than age 10. The distal radius is most often affected, accounting for up to 50 % of Type II fractures [6]. Other common sites include the distal tibia, distal fibula, and phalanges. Growth usually continues undisturbed or with minimal shortening, as the germinal matrix is often preserved. However, Type II fractures at the knee, especially at the distal femur, have a guarded prognosis, as the force required to produce these injuries may crush the germinal cells [6]. Distal femoral growth plate fractures are usually caused by severe force, such as high-speed motor vehicle collisions, but these fractures also have an increased incidence in adolescents playing contact sports.

Type III fractures extend both vertically and obliquely through the epiphysis to the articular surface, and horizontally through the physis, resulting in separation of a portion of the epiphysis. They represent 8 % of growth plate fractures and most commonly occur during adolescence. These fractures usually result from vertical shearing force, and fragments are typically at most minimally displaced [6]. The prognosis is generally good, provided the fracture is not significantly displaced and the epiphyseal blood supply is intact. However, if a displaced fracture is incompletely reduced, bone bridging and/or articular incongruity may result. The most common locations for these fractures are the distal tibia, proximal tibia, distal femur, and phalanges [6].

These fractures usually result from a vertical compression or shearing force that extends through the metaphysis, epiphysis, and intervening physis. They represent 10 % of growth plate fractures and most commonly occur at the distal humerus (lateral condyle), distal tibia, and distal radius [20]. Because these fractures are intra-articular, they must be reduced to near-anatomic alignment to prevent long-term complications such as joint deformity, accelerated osteoarthritis, or bone bridge formation. Such complications are most likely at the elbow, knee, and ankle.

The triplane fracture is a Type IV injury of the distal tibia, occurring at the end of puberty, as the physis is fusing (see Chap. 16). Usually a result of eversion injury, it may result from a fall [25]. This fracture consists of a coronal fracture through the posterior metaphysis, a transverse fracture along the lateral physis and a sagittal fracture through the anterior epiphysis. This complex pattern is related to asymmetric fusion of the distal tibial growth plate, which begins medially at a physeal undulation, “Kump’s bump” [26]. Radiographs typically show widening of the lateral physis, with the epiphyseal fracture evident on the frontal or oblique view and the metaphyseal fracture evident on the lateral view (Fig. 17.31). CT with multiplanar reformats is indicated for presurgical assessment (Fig. 17.32). Since these fractures occur near skeletal maturity, limb shortening is uncommon; the prognosis is largely determined by the integrity of the tibial plafond [12, 20].

These injuries represent only 1 % of growth plate fractures and result from severe axial loading with physeal compression or crush injury. This damages the vascular supply and germinal cells of the physis, and subsequent growth arrest is therefore common and the prognosis poor [6]. Type V fractures are most common in the distal femur, proximal tibia, and distal tibia and may also coexist with other types of complex growth plate injuries [12]. Radiographic diagnosis is difficult and often made retrospectively, when premature physeal fusion is observed. Type V injuries may be suspected after significant axial loading injury of the knee or ankle, especially if associated with adjacent fractures. MRI can establish the diagnosis immediately after injury, if hemorrhage or hematoma is identified within the growth plate [6].

This injury is very rare and damages the perichondrial ring. It frequently involves a lawn mower or farm machinery and is often associated with a compound or open fracture. With healing, a bone bridge forms, connecting the epiphysis to the metaphysis and leading to angular deformity. The distal femur and distal tibia are common locations. Radiographs may demonstrate a small, sliver-like fragment at the lateral margin of the epiphysis [6].