Influence of the change in stem length on the load transfer and bone remodelling for a cemented resurfaced femur.

The effect of a short-stem femoral resurfacing component on load transfer and potential failure mechanisms has rarely been studied. The stem length has been reduced by approximately 50% as compared to the current long-stem design. Using 3-D FE models of natural and resurfaced femurs, the study is aimed at investigating the influence of a short-stem resurfacing component on load transfer and bone remodelling.

Strain and micromotion in intact and resurfaced composite femurs: experimental and numerical investigations.

Understanding the load transfer within a resurfaced femur is necessary to determine the influence of mechanical factors on potential failure mechanisms such as early femoral neck fractures and stress shielding. In this study, an attempt has been made to measure the stem-bone micromotion and implant cup-bone relative displacements (along medial-lateral and anterior-posterior direction), in addition to surface strains at different locations and orientations on the proximal femur and to compare these measurements with those predicted by equivalent FE models. The loading and the support conditions of the experiment were closely replicated in the FE models.

The effects of interfacial conditions and stem length on potential failure mechanisms in the uncemented resurfaced femur.

It is hypothesized that changes in stem length and implant-bone interfacial conditions would affect the mechanical environment within the uncemented resurfaced femur, thereby influencing potential short- and long-term failure mechanisms. This study is aimed at investigating the influence of changes in implant-bone interfacial conditions and stem length on eventual failure, using 3D FE models integrated with bone remodeling simulations. Musculoskeletal forces corresponding to normal walking and stair climbing were used as applied loading conditions.

Design considerations for ceramic resurfaced femoral head: effect of interface characteristics on failure mechanisms.

Ceramic hip resurfacing may offer improved wear resistance compared to metallic components. The study is aimed at investigating the effects of stiffer ceramic components on the stress/strain-related failure mechanisms in the resurfaced femur, using three-dimensional finite element models of intact and resurfaced femurs with varying stem–bone interface conditions. Tensile stresses in the cement varied between 1 and 5 MPa.

The role of vibration and drainage in femoral impaction bone grafting.

Vibration is commonly used in civil engineering applications to efficiently compact aggregates. This study examined the effect of vibration and drainage on bone graft compaction and cement penetration in an in vitro femoral impaction bone grafting model with the use of 3-dimensional micro-computed tomographic imaging. Three regions were analyzed.

Adult mesenchymal stem cells and impaction grafting: a new clinical paradigm shift.

The demographic challenges of an increasingly aging population emphasize the need for innovative approaches to skeletal reconstruction to augment and repair skeletal tissue lost as a consequence of implant loosening, trauma, degeneration or in situations involving revision surgery requiring bone stock. These clinical imperatives to augment skeletal tissue loss have brought mesenchymal stem cells to the fore in combination with the emerging discipline of tissue engineering. To date, impaction bone grafting for revision hip surgery is a recognized technique to reconstitute bone utilizing morselized allograft to provide a good mechanical scaffold, although with little osteoinductive biological potential.

Biological and mechanical enhancement of impacted allograft seeded with human bone marrow stromal cells: potential clinical role in impaction bone grafting.

With the demographics of an aging population the incidence of revision surgery is rapidly increasing. Clinical imperatives to augment skeletal tissue loss have brought mesenchymal stem cells to the fore in combination with the emerging discipline of tissue engineering. Impaction bone grafting for revision hip surgery is a recognized technique to reconstitute bone, the success of which relies on a combination of mechanical and biological factors.

Taking tissue-engineering principles into theater: augmentation of impacted allograft with human bone marrow stromal cells.

Human bone marrow contains bone progenitor cells that arise from multipotent mesenchymal stem cells. Seeding bone progenitor cells onto a scaffold can produce a 3D living composite with significant mechanical and biological potential. This article details laboratory and clinical findings from two clinical cases, where different proximal femoral conditions were treated using impacted allograft augmented with marrow-derived autogenous progenitor cells.

Bone remodelling inside a cemented resurfaced femoral head.

Background: Although the short-term performance of modern resurfacing hip arthroplasty is impressive, the long-term performance is still unknown. It is hypothesised that bone remodelling and the resulting changes in stress/strain distribution within the resurfaced femur influence the risk of fixation failure.

Method: Three-dimensional finite element models and adaptive bone remodelling algorithms have been used to predict long-term changes in bone density following cemented femoral head resurfacing.

A new bleeding model of the human acetabulum and a pilot comparison of 2 different cement pressurizers.

In this cadaver study, we compared 2 different acetabular cement pressurizers (Exeter and Bernoski type) in paired human acetabula with simulated intraosseous bleeding. Pressure transducers were used to record intra-acetabular pressures during pressurization. Anteroposterior radiographs of the entire specimens were taken.