| Discussion: |
This fracture represents a typical toddler's fracture described by Dunbar in 1964 as a subtle, non-displaced oblique fracture of the distal tibia in children, 9 months to 3 years of age. The child usually presents with an acute onset of limp or refusal to bear weight on one leg. An unsteady toddler may have fallen with a twist, or the child may have gotten his/her foot caught and fallen, twisting it while trying to free his/her foot. Many times the fall is unwitnessed and parents are unsure of what happened. This inability to give a history may prompt a clinician to suspect child abuse. Children at this age are also unable or unwilling to give a history or localize pain. Also, they are at times, uncooperative with a physical exam. In small children presenting with very mild or no history of trauma, the clinician should keep in mind possible non-accidental injury. However, the diagnosis of child abuse can bring about serious consequences for the suspected perpetrator, the family and the child. Thus, clinicians must be very careful when evaluating cases of possible child abuse and not arrive at a conclusion too quickly. We must be aware of the various conditions that can be mistaken for abuse and obtain an accurate history and do a thorough physical examination, as well as do the necessary studies to arrive at the correct conclusion.
Clinical signs of a toddler's fracture can be subtle with non-specific physical findings of local injury. Radiologic signs can also be subtle, as in our case. There have been cases in which initial radiographs were negative with fractures diagnosed only on follow-up studies. The fracture may only be seen on the internal oblique view of the lower leg. If all views are normal and one still suspects a toddler's fracture, a nuclear bone scan should be considered.
In describing the toddler's fracture in 1987, Alexander et. al. stated that while spiral fractures can suggest child abuse, spiral fractures of the mid and lower tibia have no such implication. In contrast, Tenenbein et. al. described cases in which patients presented with midshaft tibial fractures rather than distal tibial fractures. These patients were initially treated as innocent toddler's fractures, then later presented as cases of child maltreatment. Thus, Tenenbein concludes that fractures of the midshaft of the tibia may indicate abuse, while distal tibial fractures may be less suspicious. Spiral or oblique fractures of the tibia are particularly common in young children because of the susceptibility, during their rapid linear growth, to bony injury from minimal trauma. Twisting or rotational force through the tibia, while the ankle and foot are fixed, is the mechanism which would produce this typical injury. Tenenbein goes on to describe that different locations for accidental and inflicted fractures may also be explained by this mechanism. Typically, non-accidental injury would occur with the abuser holding the distal portion of the leg, twisting it, maximizing the force more proximally, localized to the midshaft of the tibia. If the foot is fixed, the force is maximized more distally, as seen in accidental injury. Mellick and Reesor reviewed cases of tibial fractures, and they state that isolated spiral tibial fractures of children are much more commonly accidental. In their radiological review of patients with isolated tibial fractures, they observed no differences between fractures judged as due to child abuse and those which were accidental. Their retrospective review over 5 years looked at 205 children categorized as child abuse. Orthopedic injuries were seen in 36 children and of these, 33 charts were reviewed and three had isolated tibial fractures. They also go on to describe the CAST (Childhood Accidental Spiral Tibial) fracture, which is an isolated spiral tibial fracture that is not obscure radiologically. This fracture often begins more proximally at the midshaft rather than the distal tibia. The approximate age range is described as 2 years to 6 years. Although overlapping with the age range of the toddler's fracture, the CAST fracture occurs commonly in older children. They consider the toddler's fracture as a subset of the more common CAST fracture. Thus, one can see that in the case of an isolated spiral fracture of the tibia in a child, the characteristics of the fracture are not sufficient enough to confirm or dismiss the possibility of child maltreatment. Accidental fractures in general are more likely to be isolated (except in major multiple trauma). Patients will present promptly after injury with a history that fits the fracture pattern. On the other hand, fractures in a child resulting from child abuse may be multiple and at various stages of healing. Inflicted skeletal trauma may involve any part of the skeleton. The presentation is often delayed with an often unclear history or a minor injury that does not fit the fracture pattern. For example, a femur fracture in a preambulatory child should raise the suspicion of non-accidental trauma. Fractures specific for abuse include metaphyseal-epiphyseal fractures, known as bucket handle or chip fractures because of their radiologic appearance. Fractures of the thoracic cage (rib fractures, sternum), scapula, spine (spinous process, vertebral body) are also specific for abuse. Highly suggestive fractures are multiple fractures, those of the hands and feet, and complex skull fractures. Especially important in addition to history is the association of non skeletal injury (intracranial, visceral). All children less than two years old suspected of abuse should have a complete skeletal survey or bone scan. Those less than a year may not show fractures until a repeat skeletal survey is done after 2 weeks. Bone scans can reveal occult fractures within hours of injury and can be helpful in detecting posterior rib fractures in infants. Although more sensitive than X-rays, bone scans are less specific. There are multiple conditions conditions that cause fractures which are mistaken for child abuse. Osteogenesis Imperfecta (OI) is a group of heritable conditions in which abnormal collagen formation results in osteoporosis and increased susceptibility to fractures. OI Types II and III (the most severe forms), are diagnosed at delivery. Children have extreme osteoporosis and are born with multiple fractures and deformities and have blue sclerae. Milder involvement is seen in children with OI Types I and IV, although those with fractures show cortical thinning on X-ray. They have mild short stature with lower extremity bowing and dentinogenesis imperfecta. Blue sclerae, lax ligaments and a family history of hearing impairment are seen in most patients with OI Type I, the most common type. Skull radiographs may reveal wormian bones. Although the mechanism fits the fracture pattern, there is less force than usual. The greatest difficulty in diagnosing OI, is in OI Type IV. Osteopenia may not be apparent in a child presenting with a fracture as they may not have blue sclerae or abnormal teeth. Because of frequent fractures and easy bruising, the concerns of abuse may arise in children with OI. Metaphyseal fractures resembling injuries of abuse can occur, although spiral or transverse fractures are most common. Multiple cases of OI have been mistaken for abuse, although one must realize that OI is less common than child abuse. Cases where child abuse occurs in children with OI have also been reported. If one suspects OI, a punch biopsy of skin for analysis of collagen synthesis should be done. Demineralization from disuse seen in children with cerebral palsy and severe neuromuscular disease can also lead to cortical thinning making these patients vulnerable to fractures, thus mistaken for abuse. Bone cysts may occur near the metaphyseal ends of long bones causing cortical thinning. Similar pathologic fractures may occur at sites of osteomyelitis or in portions of bone replaced by tumor. Other conditions that may produce fractures mistaken for abuse include congenital syphilis, Vitamin D deficiency rickets, copper deficiency, Menke's kinky hair syndrome, scurvy (Vitamin C deficiency), hypervitaminosis A and leukemia. Thus, in addition to the toddler's fracture seen in our patient, there are multiple conditions that produce fractures in children that can be mistaken for abuse. Although one must consider abuse as a possible diagnosis in suspicious fractures, especially with an unclear cause, we must also be very thorough in our history-taking and examination, as well as obtain the appropriate studies. We must be familiar with the type of fractures specific for abuse and be able to consider other conditions that may lead to fractures. This careful consideration can help avoid serious long term consequences for everyone involved.