Thom Bitter, Ph.D.

About me

In 2004 I started my study mechanical engineering at the “Hogeschool van Arnhem en Nijmegen”. In 2008 I graduated and got my Bachelor in Engineering degree. I decided to do a Master in Mechanical engineering at the University of Twente in Enschede. During this master I did my final master assignment at the ORL and graduated June 2012. In September 2012 I started as a Ph.D. student at the ORL. I graduated December 17th, 2018, after which I became post-doc at the ORL.

Thom Bitter PhD

Research Impression

During my masters internship at the ORL I created a material model for ligaments, see image below. This is a transverse isotropic hyperelastic material model based on experimental testing results. This material model can be used to more accurately model knee behavior in a Finite Element Analysis.

Finite Element knee model
Figure 1:Finite Element knee model
Finite Element Hip Model developed by Thom Bitter. Orthopaedic Research Lab Nijmegen; Radboud university medical centre
Figure 2: Finite Element hip model

My PhD project focuses on the modeling of wear in total hip arthroplasty. In a total hip arthroplasty conical shaped metal on metal connections are present which, while loaded, can move against each other. These so called micromotions in combination with the forces present can cause metal wear particles to form. To prevent wear of implants, a finite element model will be developed. This model can be used to evaluate the effect of several surgical, patient and implant factors on the wear process. Hopefully this model will be able to help in the prevention of wear in total hip arthroplasties and thereby reducing the need of revision surgery.

Short Summary of My Thesis

Most common hip implants consist of multiple parts, like the stem, head and cup. During surgery the head is assembled onto the stem using a conical (tapered) interface. Due to loading of the hip implant, at the taper interface between the stem and the head, micromotions can occur, which can result in wear. Wear in hip implants could lead to problems like implant loosening from the bone, or in rare cases implant fractures. Using an experimental set up, capable of mimicking wear marks seen on retrieved implants, in this thesis a computer model was developed with which wear at the taper interface can be predicted. This model can help identifying parameters contributing to taper wear. In this work the importance of sufficient assembly force and the need of minimizing mismatch between components is emphasized. Using this model more device, patient, and surgical parameters can be investigated for their influence on taper wear.