Mock surgery

Prior to the model group patient surgeries, a mock TPFO surgery was performed on the plastic 3D model by the lead surgeon, mimicking the tools and cut approaches used during surgery. Models were mounted in a vice and cut using a System Seven Precision Saw (Stryker, Kalamazoo, MI, USA). Based on evaluating the CT image and using clinical judgment, a wedge of plastic ‘bone’ was removed from the intertrochanteric region to allow for flexion and valgus correction of the proximal femur. The 3D model allowed the surgeon to visualise the head-neck junction and optimise the proximal femoral physeal orientation to obtain the desired correction. If a preliminary cut or removal of ‘bone’ wedge was inadequate for the desired anatomical correction during the mock surgery, additional cuts were made to achieve acceptable correction. The 3D model allowed 3D visualisation of the anatomical consequence of each cut and wedge removal. A Kirschner-wire was used to preserve the orientation of the femoral bone segments (Fig. 1).

(a) Pre-operative anteroposterior (AP) radiograph of a proximal femur of a 15-year-old girl with SCFE. (b) AP view of this patient’s proximal femur 3D model, (c) the mock surgery osteotomies were performed and wedge removed and (d) fragments in final position. (e) A radiograph taken three months post-operatively indicates the correction achieved by the TPFO.