Anytime valgus instability is present in an adolescent, a distal femoral physeal fracture should be considered. This injury may not be suspected because ligament injuries are the most common result of lateral knee trauma. This type of injury may also be suspicious because fractures to the physeal are very rare.
Early detection of distal femoral physeal fractures is imprtant because this physis accounts for 70 percent of the femurŐs longitudinal growth and 40 percent or the lower apendageŐs. Fractures of the distal femoral physis have been proven to result in a signignificant circumstanceof limb-length discrepancy and angular deformity, either of which may be more severe than predicted by the initial Salter-Harris classification. It should be recognized, however, that although distal femoral physeal fractures are more frequent in adolescents than in younger children, complications in adolescents are less common because growth plate closure is forthcoming. Beside age, factors that affect growth deformity following distal femoral fractures are initial displacement of the fracture and the ability to maintain and anatomic reduction.
The placement of ligamentous attachments around the distal femoral physis make it vulnerable to injuryThe posterior capsule, medial collateral ligament, and cruciat ligaments all attach to the distal femoral epiphysis, leaving the physis fully exposed to valgus loads applied to the extended knee. In distinction, the MCL attaches at a site distal to the proximal tibial metaphysis, making the proximal tibial physis less vulnerable to damage from valgus loads. Because of growth-related anatomic factors, distal femoral physeal fractures are more frequent in adolscents than in younger childern amd more likely to result from relatively minor trauma, such as sports activities. During adolescents, the periosteum overlying the physis is a thin and relatively weak compared with the strong metaphyeal bone. Also, at this time the MCL remains stronger than the castilaginous physis. This makes the distal femoral physeal particularly prone to injury. Furthermore, the knee is subjected to increasing forces during the athletic activities in adolscence. In younger children fractures of the distal femoral physeal are more often a result of more severe trauma, such as a car-pedestrian accident.