Use of 3D Imaging in Planning Varus Derotation Osteotomy in Neuromuscular Hip Subluxation

Proximal femur varus derotation osteotomy (VDRO) is a primary component of hip reconstruction surgery for the management of hip subluxation/dislocation in patients with neuromuscular dysplasia. Understanding the pathophysiology and abnormal proximal femur geometry is crucial to performing a successful surgery and dosing the surgical correction accurately. Children with neuromuscular hip dysplasia experience increased coxa valga, femoral anteversion, and variable degrees of acetabular dysplasia. Understanding the relationship between these three anatomic aberrations can be difficult with standard two-dimension plain radiography. In this paper, we will review our novel three-dimensional imaging protocol to assess the pathologic anatomy of the proximal femur and acetabulum in children undergoing neuromuscular hip reconstruction. Understanding the anatomic relationship between the neck shaft angle, anteversion and acetabular dysplasia aids in the planning and execution of effective VDRO and hip reconstruction surgery. Key Concepts • Preoperative understanding of the unique hip anatomy in a patient with cerebral palsy allows for precise preoperative surgical reconstructive planning and intraoperative execution. • A preoperative CT, with the described CT Murphy imaging protocol, allows for improved preoperative understanding of patient anatomy. • 3D reconstruction of the preoperative CT images allows for accurate measurement of the femoral neck angle and femoral anteversion while radial sequence reconstruction allows for accurate assessment of the femoral neck width which further aids with implant selection.