Hip

The objective is to address a fundamental question in bone loss and rim defect in total hip repair and provide a closer look at defect protrusion position on the rim and when it becomes inadequate to provide the necessary mechanical support for a cementless cup. We investigated the cementless cup technique without defect reconstruction and whether it resulted in medial migration and loosening due to induced micromotion at the discontinuity edges of the defect interface with the cup. A rim defect that is greater than 50% is usually viewed as inadequate and reconstructed with a cage to gain fixation to the pelvis. Total hip arthroplasty in the presence of a significant defect less than 35% and positioned on the posterior or interior column of the ischium affects both the cementless stability as well as the cup migration. In the study, the rim defect is parametrically positioned around the circumference of the rim which is divided into 6 regions. A press fit against bony acetabular rim without defect repair was analysed for different rim defect position and loading conditions. Cup migration was assessed using a FEM model and the corresponding reaction forces used to support the cup were also computed for all causes. Results show a cementless cup with medial and lateral acetabular defect to be favorable, with success rates similar to conventional THA with the rim intact. Other regions of the rim resulted in a reduction of 21% of the reaction forces and a weakening of the acetabulum mechanical support.

In a study of human locomotion, estimation of muscle forces is essential to the assessment of patient's performance, joint movements, and activities. Current methodologies employ a combination of experimental measurements to compute the inverse dynamic problem and provide the resultant joint force and moment time history for these muscle forces. Most of the information derived from these simulations is based on one-dimension elements often treated as concentrated loads acting on the tendon's attachment points,.

Muscle dynamics govern the transformation o muscle fiber activation to muscle force transmitted by the tendons at the attachment point with the bone joint surface. Once the muscle begins to develop force, the tenson begins to carry load as well and transfers force from the muscle to the bone. The complexity of the muscle anatomy is often simplified and the relative length changes in the tendon-muscle are used as the overall dimension for the deformation and estimation of the muscle fibers.

To provide the new paradigm in musculoskeleton modeling of the kinetics and provide new tool that allows for the construction of 3-D muscle models, integrate their overall interface and account for the pressure that muscles exert on one another before transmitting the information to the join forms the current study objective. This research introduces a dynamic human anatomical leg which can be used to investigate intricate fiber-muscle tendon interactions and compute the forces of these muscles based on a CAD-Parametric model customized for each patient leg.

Acetabular cup position affects stability, range of motion and impingement in total hip arthroplasty (THA). Inclination and anteversion are the two most commonly analysed parameters of cup positioning. Several methods have been proposed to calculate acetabular cup version on anteroposterior cup radiographs. The circle theorem method first proposed by Koalyatrakul et at, is based on simple descriptive geometry and does not rely on conversion tables or complex computer calculations. The purpose of this study is to validate a modified circle method for the calculation of true version of the acetabular component on anteroposterior x-rays of the pelvis with intraoperative version data derived from robotic assisted THA. To our knowledge, this type of validation has not previously performed. The modification and methodology proposed is also more precise in defining the rim of an uncemented acetabular component.

Paxton et al[1] described six surgical categories where reconstruction of bone deficiency can be made and articulated the need of additional data on cementless reconstruction in the setting major osteolysis to address the durability of this approach. The current study was designed to address some of these concerns and develop a Finite Element model to analyse acetabulum defects that are less than 50% and reconstructed, reamed and fitted using porous coated cups. The aim is to further investigate if defect reconstruction of patients with osteoporosis would require additional fixation, or different construct as proposed by Paprosky [2].