Final answer:
The primary complication of physeal separation is the potential for altered bone development and growth leading to permanent discrepancies in limb length and joint misalignment, which may result in growth arrest and other deformities or functional impairments.
Step-by-step explanation:
The primary complication of physeal separation, which is an injury to the growth plate, can lead to altered development and growth of the bone. When speaking of large bones, like the femur, multiple secondary ossification centers and associated epiphyseal plates are involved in longitudinal bone growth. Therefore, damage to these plates can result in permanent discrepancies in limb length and joint misalignment. A prominent concern in managing physeal fractures is the potential for growth arrest, which can culminate in deformities or functional impairments. Timely diagnosis using radiographs (X-rays) and appropriate interventions, such as surgery to stabilize the separated growth plate, are crucial for minimizing long-term consequences from these types of injuries.