Modelling Surgical Management of Complex Hip Deformities

Abstract

Slipped Capital Femoral Epiphysis (SCFE) is the most common hip condition occurring in adolescents. This condition involves a deformation of the femoral head along the femoral neck and is believed to be caused by abnormal biomechanical loading. Treatment of SCFE is controversial among surgeons with the best treatment method often ambiguous. However, surgical management of SCFE usually involves an osteotomy to correct the deformation followed by the fixation of screws through the proximal section of the femur to prevent further deformation. The aim of this thesis was to develop a modelling workflow to generate a finite element model of the hip joint to calculate biomechanical parameters of interest following a ‘virtual’ osteotomy surgery. CT-images of a post-op SCFE patients’ proximal femur and acetabulum were segmented. The subchondral surface of the two bones was selected and a cartilage mesh was generated by lofting the surface elements into 3D meshes. A virtual cuneiform osteotomy was then performed on the femur and then the pre-op and post-op femurs were aligned to different stances of the gait cycle so contact mechanics on the cartilage layers could be performed and the results compared. This study successfully created the components of a workflow to create a subject specific hip joint model of a SCFE patient using CT-images. The generated finite element model can then be subjected to realistic gait forces based on the patient’s weight with the femur aligned to any position of stance phase to observe the stresses within the femoral and acetabular cartilage over the gait cycle. This study also showed how sensitive the cartilage stresses are to an osteotomy surgery. For example, a rotation osteotomy of 5o in correction increased the peak acetabular cartilage stress by 18%. This work has laid the foundation for a clinical tool that can be used for pre-operative planning and surgical training. Furthermore, the results of this study can be also be used as an educational tool for SCFE patients and their parents, to better understand their condition and the long-term health of their hip joints.