Various projects from the archive
The Corin MiniHip conservative hip stem
Two models are needed for site-specific bone remodelling: (i) the pre-operative femur (above) and (ii) the post-operative femur (below)
Bone remodelling procedure
The tri-linear remodelling curve
Changes in the Bone Mineral Density (BMD) over time for several Regions of Interest (ROIs)
Contour surfaces of (a) increase and (b) decrease in Bone Mineral Density (g/cm³) to help visualise adaption
Bone remodelling of Corin MiniHip conservative
Introduction: Total Hip Replacement (THR) has gained acceptance as an effective treatment for patients experiencing end-stage osteoarthritis. In recent times, Hip Resurfacing (HR) has emerged as a popular alternative to THR, however is not always a suitable option. Conservative hip stems attempt to fill the gap between HR and THR, combining the bone conserving benefits of HR with the stability of THR.
The introduction of an implant leads to a change in mechanical loading and invokes a bone remodelling response in an attempt to bring the system back into equilibrium; this is known as Wolff’s law. Bone resorption due to stress shielding may occur, which can result in aseptic loosening of the implant, pain and possible revision surgery.
Computer simulations can be used to predict such changes and therefore used to predict the long-term clinical success of an implant.
Methods: This study used computer simulation to predict the long-term stability of the MiniHip bone conserving hip replacement (Corin Group PLC). The simulation implemented a strain-adaptive bone remodelling algorithm coupled to Finite Element Analysis solver ABAQUS (SIMULIA). The changes in bone density were governed by the tri-linear remodelling curve using an equivalent strain as the mechanical signal.
At various points in time “virtual x-rays” were created and analysed to give the changes in the Bone Mineral Density (BMD) for several Regions of Interest (ROIs) over time, similar to a clinical DEXA study.
Results: Some stress shielding was present, resulting in a 35% loss in BMD on the medio-posterior surface of the femur. This is comparable to losses seen in successful THR implants.