Testing a Bone Fixation Device
Metallic prosthetic total hip implants are common surgical treatments for replacing femoral heads
damaged by arthritis or fracture due to osteoporosis. They can vulnerable when the bone remodels
around the implant loosening the fit. Modern bone cements have helped minimize the stress
concentrations that can lead to adverse bone remodeling. The objective here is to design a device for
measuring the strength and failure characteristics of the mechanical coupling between a cadaveric
femur and an implanted hip replacement like the one illustrated below in Figure (a). You may
be surprised to know that medical device companies are required to track the disposition of every
device they make after it is implanted. So testing them in cadaver bones provides valuable
information. Your design needs to consider the various loading configurations that might cause the
implanted to come loose. One obvious configuration is shown in the free body diagram in (b). Can you
think of others? You do not have test every case, but you should at least consider them in choosing your
design configuration. Assume that you have available standard transducers for measuring uniaxial
strains (strain gauge) and uniaxial forces (load cells). You may need to modify these transducers to
use them for your purpose.
Requirements (clearly labeled but not necessarily in this order)
1. Explain precisely and concisely what your apparatus is designed to measure and why you think those
measurements are important for this specific problem. Explain what you chose not to measure
especially if you think that could be important too. You don’t need to measure everything. (10 points)
2. A clear statement of all of the assumptions used in your design. Is any analysis of your measurements
required to obtain the desired information? If so, summarize that analysis and how you reached it.
3. A neat sketch of the key components of the test apparatus and their arrangement. (15 points)
4. One or more free-body diagrams showing how the measured quantities relate to the forces being
transmitted at the bone-implant interface. (10 points)
5. A description of how the apparatus would be used and other important testing considerations and
conditions that should be recorded or controlled. (10 points)
6. References to any published or Internet resources that you used. (5 points)
These solutions may offer step-by-step problem-solving explanations or good writing examples that include modern styles of formatting and construction
of bibliographies out of text citations and references. Students may use these solutions for personal skill-building and practice.
Unethical use is strictly forbidden.