Final answer:
The most common complication of a distal femur physeal fracture is growth disturbance, which can lead to significant issues such as limb length discrepancy or angular deformities.
Step-by-step explanation:
The most common complication of a distal femur physeal fracture is growth disturbance leading to limb length discrepancy or angular deformities. This is due to the injury to the growth plate (physis) which can disrupt normal bone growth. Physeal fractures may require surgical intervention with open reduction and internal fixation to ensure proper healing and to minimize complications. However, even with appropriate treatment, complications such as necrosis of the femoral head can occur, especially if there is an accompanying disruption of blood supply to the bone. It is critical that such injuries are closely monitored by orthopedic specialists to manage potential complications effectively.