Simulation-Based Process Design for Asymmetric Single-Point Incremental Forming of Individual Titanium Alloy Hip Cup Prosthesis.

Advanced manufacturing techniques aimed at implants with high dependability, flexibility, and low manufacturing costs are crucial in meeting the growing demand for high-quality products such as biomedical implants. Incremental sheet forming is a promising flexible manufacturing approach for rapidly prototyping sheet metal components using low-cost tools. Titanium and its alloys are used to shape most biomedical implants because of their superior mechanical qualities, biocompatibility, low weight, and great structural strength.

'Pre-launch' finite element analysis of a short-stem total hip arthroplasty system consisting of two implant types.

Background: We applied a previously established and validated numerical model to a novel short-stemmed implant for a 'pre-launch' investigation.

Methods: The implant system consists of two different implant geometries for valgus/varus-positioned proximal femurs with differences in volume distribution, head/neck angle, and calcar alignment. The aim of the design was to achieve a better adaption to the anatomic conditions, resulting in a favourable load transfer.

Bone cyst formation after ankle arthroplasty may be caused by stress shielding. A numerical simulation of the strain adaptive bone remodelling.

Background: The history of total ankle arthroplasty (TAA) has different evolution steps to improve the outcome. The third generation implants show an overall 8-year survival rate up to 93%. The main reported reason for early failure of TAA is aseptic loosening, cyst formation is also frequently reported.

Comparative investigation of bone mineral density using CT and DEXA in a canine femoral model.

Bone density measurements using computed tomography (CT) instead of dual-energy X-ray absorptiometry (DEXA) are currently of great interest in human and veterinary medical research as it would be beneficial to use CT scans obtained for other indications also for determining bone density. For Hounsfield units (HU) measured with CT in specific regions of interests (ROIs) in one or several slice/s a correlation with bone mineral density (BMD) measured by DEXA in humans and dogs of between 0.44 and 0.

Finite element model of a novel short stemmed total hip arthroplasty implant developed from cross sectional CT scans.

Background: Numerous short stemmed total hip arthroplasty (THA) implants have been introduced over the last decades. It is questionable if little differences between the implant designs affect stress shielding and bone remodeling. The finite element analysis allows an evaluation of the design rationale of the implant without negative side effects for the patient.

Finite element model of a novel short stemmed total hip arthroplasty implant developed from cross sectional CT scans.

Background: Numerous short stemmed total hip arthroplasty (THA) implants have been introduced over the last decades. It is questionable if little differences between the implant designs affect stress shielding and bone remodeling. The finite element analysis allows an evaluation of the design rationale of the implant without negative side effects for the patient.

Numeric simulation of bone remodelling patterns after implantation of a cementless straight stem.

Purpose: For further development of better bone-preserving implants in total hip arthroplasty (THA), we need to look back and analyse established and clinically approved implants to find out what made them successful. Finite element analysis can help do this by simulating periprosthetic bone remodelling under different conditions. Our aim was thus to establish a numerical model of the cementless straight stem for which good long-term results have been obtained.

The cementless Bicontact stem in a prospective dual-energy X-ray absorptiometry study.

Purpose: The cementless Bicontact total hip arthroplasty (THA) system (AESCULAP AG, Tuttlingen, Germany) was introduced in 1986/1987 and has been in successful clinical use in an unaltered form up to today. Although good long-term results with the Bicontact stem have been published, it is questionable whether the implant provides the criteria for a state-of-the-art stem regarding proximal bone stock preservation. The purpose of the study was to monitor the periprosthetic bone mineral density (BMD) in a prospective two-year follow-up dual-energy X-ray absorptiometry (DEXA) study.

Bone remodelling around a cementless straight THA stem: a prospective dual-energy X-ray absorptiometry study.

The design of the Bicontact® stem (BBraun, Aesculap, Tuttlingen, Germany) and the implantation technique have undergone no major alterations in the last 20 years leading, and good clinical results have been reported. The aim of our study was to investigate whether the implant encourages beneficial bone remodelling. Twenty-four patients were included in a prospective dual-energy X-ray absorptiometry (DEXA) study of this stem, after appropriate statistical power analysis.

Bone remodeling after total hip arthroplasty with a short stemmed metaphyseal loading implant: finite element analysis validated by a prospective DEXA investigation.

In total hip arthroplasty (THA), short stemmed cementless implants are used because they are thought to stimulate physiological bone remodeling and reduce stress shielding. We performed a numerical investigation on bone remodeling after implantation of a specific short stemmed implant using finite element analysis (FEA). Overall bone mass loss was 2.

Numerical simulation of strain-adaptive bone remodelling in the ankle joint.

Background: The use of artificial endoprostheses has become a routine procedure for knee and hip joints while ankle arthritis has traditionally been treated by means of arthrodesis. Due to its advantages, the implantation of endoprostheses is constantly increasing. While finite element analyses (FEA) of strain-adaptive bone remodelling have been carried out for the hip joint in previous studies, to our knowledge there are no investigations that have considered remodelling processes of the ankle joint.

Finite element modelling of the canine and feline outer ear canal: benefits for local drug delivery?

Current therapeutic regimes of outer ear infections in dogs and cats aim at the application of efficient local therapeutics after cleaning of the acoustic meatus. One so far insufficiently answered question is if the local application of these substances results in an individually suitable drug concentration in the external ear canal. Thus, the purpose of the present study was to develop a finite element model to calculate the values of the different areas of the external acoustic meatus in dogs and cats in order to provide a tool for the benefit of an appropriate local drug dosage determination.

[Numerical investigations of the strain adaptive bone remodelling in the periprosthetic canine femur].

After surgical treatment of severe hip diseases with artificial joint prostheses aseptic loosening of the implants can occur. Unphysiologic load distribution in the periprosthetic femur and stress shielding by the prosthesis can result in bone remodelling processes. In particular a cutback of the bone mass is followed by an aseptic loosening of the prosthesis.

Numerical investigations on the strain-adaptive bone remodelling in the periprosthetic femur: influence of the boundary conditions.

Background: There are several numerical investigations on bone remodelling after total hip arthroplasty (THA) on the basis of the finite element analysis (FEA). For such computations certain boundary conditions have to be defined. The authors chose a maximum of three static load situations, usually taken from the gait cycle because this is the most frequent dynamic activity of a patient after THA.

[Measurement of the elastic properties of the cancellous bone in the femoral head of the dog].

The degenerative wear and pathologic damage of the joints are reasons for total endoprotheses in man as well as in dogs. The main problem is the aseptic loosening of the protheses. By usig the finite-element-method, the total endoprothesis is designed with new features, with the purpose of preventing loosening and being better adapted to load transmission.

Mechanical properties of femoral trabecular bone in dogs.

Background: Studying mechanical properties of canine trabecular bone is important for a better understanding of fracture mechanics or bone disorders and is also needed for numerical simulation of canine femora. No detailed data about elastic moduli and degrees of anisotropy of canine femoral trabecular bone has been published so far, hence the purpose of this study was to measure the elastic modulus of trabecular bone in canine femoral heads by ultrasound testing and to assess whether assuming isotropy of the cancellous bone in femoral heads in dogs is a valid simplification.

Methods: From 8 euthanized dogs, both femora were obtained and cubic specimens were cut from the centre of the femoral head which were oriented along the main pressure and tension trajectories.