Salter-Harris fractures (physeal fractures) refer to fractures through a growth plate (physis) and are therefore specifically applied to bone fractures in children. The classification system used to grade fractures according to the involvement of the physis, metaphysis, and epiphysis is important as it has implications for both prognosis and treatment.
Most of these injuries occur during the time of a child's growth spurt when physes are the weakest. Active pediatric patients are the most likely to encounter injuries involving the growth plate as the ligaments and joint capsules surrounding the growth plate tend to be much stronger and more stable. They are thereby able to sustain greater external loads to the joint, relative to the growth plate itself.
Physeal injuries are common among children and comprise 15% to 30% of all bony injuries. Harris-Salter fractures are described exclusively in children and do not occur in the well-developed bones of adults.
In general, upper extremity injuries are more common than lower-extremity injuries.
Of the five most common Salter-Harris fracture types, type II is the most common (75%) followed by types III (10%), IV (10%), type I (5%), and lastly, type V which is very rare.
Males are more likely to be affected because they have an increased tendency to engage in high-risk activities. Girls are affected at a younger age (11 to 12 years) than boys (12 to 14 years).
Most long bones in the body contain at least two growth plates, a hyaline cartilage plate located between the epiphysis and metaphysis near both ends of a long bone. Once a child or adolescent completes his or her growth spurt, the plate will eventually ossify and form an epiphyseal line.
In the physis, four zones are described from the epiphysis toward the metaphysis: (1) resting cells, (2) proliferating cells, (3) hypertrophic/maturing cells, and (4) provisional calcification.
The zone of hypertrophic/maturing cells is involved when fractures occur. In the event of a fracture, the blood supply which enters the bone through the epiphysis may become compromised.
Physeal fractures tend to occur through the zone of provisional calcification. They may even cross several zones depending on the type of injury or the external force that is applied (e.g., shear vs. compression vs. tension forces).
The physis or growth plate is a weak part of cartilage present in the developing bone. The physis closes in children at varying ages.
The most common presentation of a Salter-Harris fracture is localized joint pain following a traumatic event (e.g., collision, crush injury, or fall). The patient may present with swelling around the joint in addition to focal (or point) tenderness over the physis. If the injury occurs in the upper extremity, the patient may complain of reduced (or limited) range of motion. If the injury involves a lower extremity, the patient may be unable to bear weight on the affected side. It is important to note that symptoms may mimic ligamentous injury, and there potentially may be findings on ligamentous laxity tests. Therefore, one must be cautious to avoid misdiagnosing symptoms as related to joint tissues alone.
Salter-Harris classification includes types I through V, with the higher numbers indicating a higher risk for growth abnormalities.
Salter I (Slipped)
The fracture line extends “through the physis” or within the growth plate. Type I fractures are due to the longitudinal force applied through the physis and split the epiphysis from the metaphysis. Beware that a normal radiograph cannot exclude a physis injury in a symptomatic pediatric patient. A radiograph may be normal due to lack of bony involvement, and mild to moderate soft tissue swelling may be noted. Look for the widening of the physis or displacement of the epiphysis, which may suggest a fracture. Diagnosis is based on clinical findings such as the presence of focal tenderness or a swelling surrounding the growth plate. An example is Slipped Capital Femoral Epiphysis (SCFE).
Salter II (Above)
A “fracture of the physis, extending to the metaphysis” away from the joint space. Type II fractures are the most common and occur when a piece of the metaphysis remains attached to the epiphysis.
A corner sign means the small corner of metaphysis may be visible as corner sign which is also called Thurston-Holland fragment. Beware that these involve the metaphysis. Be careful in using the terms proximal and distal to describe the extension, because the position of the physis is relative to the metaphysis and is not fixed.
If the proximal end of the bone is involved, the physis is proximal to the metaphysis, so this extends distally from the physis into the metaphysis. If it involves the distal end of the bone, the physis is distal to the metaphysis, so the this extends proximally from the physis into the metaphysis.
Salter III (Lower)
It is an intra-articular fracture extending from the physis (growth plate) into the epiphysis (toward the joint space). If the fracture extends the complete length of the physis, this type of fracture may form two epiphyseal segments. Since epiphysis is involved, damage to the articular cartilage can occur. An example is a Tillaux fracture of the ankle which is a fracture of the anterolateral aspect of the growth plate and epiphysis.
Salter IV (Through/Transverse)
This is also an intra-articular fracture, in which the fracture passes through the epiphysis, physis, and metaphysis. As this fracture involves the epiphysis, the articular cartilage may be damaged. An example is a Triplane fracture at the ankle which has the following three components:
Types III and IV fractures each carry a risk for growth retardation, altered joint mechanics, and functional impairment. They therefore both require urgent orthopedic evaluation.
Salter V (Rammed/Ruined)
This fracture type is due to a crush or compression injury of the growth plate. Beware that it can be radiographically occult, and thus the radiograph may appear normal. One should consider the possibility of type V in a symptomatic child with a normal radiograph in an appropriate setting.
In this type of fracture, the force is transmitted through the epiphysis and physis, potentially resulting in disruption of the germinal matrix, hypertrophic region, and vascular supply. Though Harris-Salter V fractures are very rare, they may be seen in cases of electric shock, frostbite, and irradiation. These typically result in a poor prognosis in so far as this fracture pattern tends to result in severe injury, involving bone growth arrest.
Though many acute Salter-Harris fractures may not initially be visible on a plain radiograph, there may be evidence of physeal widening, in other words, a potential clue to the presence of displacement. Two views, anteroposterior and lateral, may be necessary to delineate the fracture type properly; in addition to comparing the injured extremity with the opposite, unaffected extremity.
Computerized tomography (CT) scan with multiplanar reconstruction can be obtained if it is necessary to determine the exact orientation of severely comminuted epiphyseal or metaphyseal fractures. This may be helpful to define the exact measurements of fracture diastasis which is important when an articular cartilage is involved, for example in weight-bearing zones).
MRI Scan may show the following findings:
Ultrasound may be useful in infants as cartilage has not ossified in young infants.
Harris- Salter I and II fractures can be treated with closed reduction and casting or splinting. The reduction should be performed carefully to avoid damage to or grating of the physis on any metaphyseal bone fragments.
Harris-Salter III and IV fractures usually require open reduction and an internal fixation (avoiding crossing the physis).
Beware that Salter V fracture diagnosis may be delayed unless there is a high degree of clinical suspicion. Often the diagnosis is not made at the initial presentation. An emergent orthopedic consultation should be obtained if the fracture is recognized in the emergency department. As these fractures involve the germinal matrix, they have a potential for growth arrest.
In all cases, a reexamination is necessary for seven to ten days to monitor and maintain proper reduction and healing and determine whether any complications, such as growth arrest, will occur. If clinically indicated, an additional follow-up radiograph at six months and 12 months may be obtained to reassess for any growth arrest.
Early closure or fusion of the physis leads to growth disturbances such as deformity and limb length discrepancies. Fractures of the distal tibia and distal femur are usually involved when complications occur.
Angular deformities may be present when the closure of only a part of the plate occurs.
Entrapment of periosteum within the fracture may occur and can prevent complete reduction of the fracture. MRI can identify this.