Straight From The Hip
Ana Arenas & Alex Dabaghi: Reducing Avascular Necrosis in DDH
On today’s episode, I speak with Ana Laura Arenas and Alejandro Dabaghi from Shriners Children’s Mexico. We discuss their recent paper published in Archives of Orthopaedic and Trauma Surgery , titled Protective Effect of Modified Lange “Second Position” for Developing Avascular Necrosis Following Closed Reduction for Developmental Dysplasia of the Hip . This is an important topic because closed reduction remains one of the central treatments for infants with a dislocated hip, but one of its most feared complications is avascular necrosis, or what we increasingly think of as proximal femoral growth disturbance. The balance is delicate: we want the hip reduced and stable, but we also want to avoid positioning that compromises the blood supply to the femoral head. Their study compares two immobilization strategies after closed reduction. One group remained in the traditional human position throughout casting, while the other transitioned to a modified Lange second position for the second cast. They reported a lower rate of avascular necrosis in the modified Lange group, with no significant difference in redislocation or residual dysplasia. In our conversation, we go beyond the headline. We discuss what these positions actually mean, why eponyms can sometimes obscure the mechanics, and whether we should be speaking less about named positions and more about exact degrees of flexion, abduction, and rotation. We also talk about Robert Bruce Salter’s work, the vascular rationale behind the human position, the timing of vascular injury, and whether cast positioning may have a more cumulative effect than we sometimes assume. This is a technical but very practical discussion about closed reduction, hip stability, femoral head perfusion, and how we interpret clinical studies that may influence practice
