A computational investigation of patient factors contributing to contact stress abnormalities in the dysplastic hip joint

Abstract

Theses and DissertationsFall 2017 A computational investigation of patient factors contributing to A computational investigation of patient factors contributing to contact stress abnormalities in the dysplastic hip joint contact stress abnormalities in the dysplastic hip joint ABSTRACT Acetabular dysplasia, a deformity characterized by the presence of a shallow acetabulum inadequately covering the femoral head, alters force transfer through a joint, causing early-onset hip pain and degeneration. Dysplasia is often treated surgically with a periacetabular osteotomy (PAO), which permits multiplanar acetabular reorientation to stabilize the joint and alleviate pain. PAO alters joint mechanics, including contact stress, which can be assessed via computational methods.This work sought to enhance a discrete element analysis (DEA) model for assessment of the dysplastic hip. The primary focus was on understanding how the gait parameters used to load a DEA model affect the computed contact stress. Several additional studies focused on understanding specific anatomic and demographic factors contributing to the contact stress evaluation were also performed.Implementation of a dysplastic gait pattern to load the DEA models resulted in more cases with improved contact stress and clinical measures after PAO, which concurred with clinical findings. Patient demographics and acetabular and femoral geometry all affected the computed contact stress distributions, emphasizing the importance of proper cohort categorization prior to interpretation of DEA-calculated contact stress. These results indicate that accurate modeling of the particular deformity in this cohort likely requires evaluation of both functional and anatomic differences.These studies improve the ability to realistically model and characterize dysplastic hip contact mechanics. DEA is a valuable tool for assessing contact stress in dysplastic joints, which has the potential to improve patient outcomes by guiding clinicians in nonoperative treatment, pre-operative PAO planning, and evaluating intraoperative success. iv PUBLIC ABSTRACTHip dysplasia is a deformity of the pelvic bone that results in a mechanically unstable hip joint. This can be painful and lead to development of arthritis at a young age.Treatment may involve surgery to change how the hip socket is positioned and oriented in the pelvis to improve hip stability and decrease the damaging, painful stresses on the hip socket. Success of this realignment is largely determined by the ability of the surgeon to determine hip function in 3D from 2D X-ray images that can be obtained during surgery.Computational modeling offers the opportunity for analysis of joint mechanical function in 3D, which provides a much more realistic assessment of the mechanical changes after surgery.The purpose of this work was to develop the best method for using a specific type of computational modeling to evaluate changes in the joint mechanics of dysplastic hips before and after corrective surgery. This involved an investigation of mo...

Patient Age and Hip Morphology Alter Joint Mechanics in Computational Models of Patients With Hip Dysplasia

“…Comparison among three different segmenters (HDT-A, MA, KS) over 3 nonconsecutive days resulted in a median absolute difference of 0.8 MPa (range, 0-2.1 MPa) in the computed peak contact stress and 0.1 MPa (range, 0-0.2 MPa) in the computed mean contact stress. Variation in segmentation by the same segmenter over 3 nonconsecutive days resulted in a median absolute difference of 1.2 MPa (range, 0.3-2.1 MPa) in the computed peak contact stress and 0.1 MPa (range, 0-0.2 MPa) in the computed mean contact stress [40]. These results indicate a minimal effect of manual segmentation on the resulting contact stress calculation.…”