Week 1 (August 31st-September 7th)

This week, our team created requirements that were necessary to design our device in the future. It is derived from user needs, regulations, industry standards, manufacturing needs, marketing, safety, economics, environmental concerns, and aspects of a product life cycle. There was a lot of research into what was needed to first design a hip implant and what the major cause of aseptic loosening was, which was stress shielding. By looking into standards and research papers, we created our requirements below (subject to change in the future):

Requirements

1. The device must distribute the applied loads to the femur such that stress shielding is minimized

2. The device must carry applied loads during clinically allowed normal daily activities.

3. The anchoring portion of the device must be an appropriate size to fit within the shaft of the femur.

4. The device must withstand normal daily activities over decades worth of loading cycles.

5. The device must be implantable using current surgical techniques

6. The device must exhibit an equal or greater pull-out strength compared to that of current hip implants on the market

7. The device must exhibit an equal resistance to torsional stresses compared to current hip implants on the market

8. The device must be sterilizable

9. The device must be biocompatible

Week 2 (September 7th-September 14th)

In week 2, we found specifications that will help us achieve the requirements created in week 1. Specifications help determine the type of measurement we want to successfully complete the requirements and it gives us an outline of how to express the expected performance of the device. Below are the specifications created (subject to change in the future), each specification number that matches the requirement’s number above are paired together:

Specifications

1. Min Strain to Maintain healthy bone cells: 0.004%

2. Max Load: average ± 3 Standard Deviations 2. Stair climbing: joint contact force of 251% of body weight 2. Walking: load on the hip joint of up to 238% of body weight.

3. Minimum Femoral Medullary Canal Diameter: 9 mm 3. Anchoring Length: TBD

4. ISO 7206-4 Standard: 2300N over 5 million cycles

5. N/A

6. Metric: N

7. Torsional moment: 50-80 Nm

8. SAL of 10-6

9. ISO 10 993

 

Week 3 (September 14th-September 21st)

During this week, our team created realistic constraints for our device. The constraints fell under 9 different categories: global, economic, environmental, manufacturability, social, political, ethical, sustainability, and regulatory. With these constraints, it helps influence our design decisions and could potentially lead to additional design requirements. This will also help us recognize the external factors that may affect our design for the device too. Here is our list of constraints that we have created so far, along with our justification and its effect on the requirements for this device:

Category	Constraints	Justification	Requirement
Global	1. The device must fit people of different ethnicities and genders	1. Humans are different and femur anatomy changes slightly between gender and ethnicity	1. New Requirement: Must be available in a range of sizes to fit 6 Standard Deviations of femur sizes 1. Affects Requirement 3: The anchoring portion of the device must be an appropriate size to fit within the shaft of the femur.
Economic	1. Project budget must be within $400 2. Materials used for prototyping must be within budget	1. We are given $100 per team member 2. We are only allotted $400 for the entire project	1. New Design Requirement (TBD)
Environmental	1. Materials used to make the prototype implant, such as aluminum or stainless steel, are limited resources.	1. Any metals mined from the ground are considered a limited resource.	1. New Design Requirement (TBD)
Manufacturability	1. Prototype must be manufactured with existing methods and technology at TCNJ	1. We are limited to what TCNJ has to offer, which we must use to build the final product	1. Affects Requirement 1: The device must distribute the applied loads to the femur such that stress shielding is minimized
Social	1. Product should not only be available to those who are wealthy	1. By targeting the majority of patients of any socioeconomic status, it gives many more patients the option to choose this device if they decide to have this implant	May not be associated with a new or existing project design requirement
Political	1. (If we were making this out of the real material) Locations where we can obtain titanium are limited	1. A place to mine  titanium is in Russia, a place where there exists political tension with the US	May not be associated with a new or existing project design requirement
Ethical	1. All testing must be performed under GLP standards	1. It is an FDA requirement that all testing must go through	1. Affects Requirement 4: The device must withstand normal daily activities over decades worth of loading cycles
Sustainability	1. Medical devices cannot be reused in other patients, but the metal can be recycled for use in supporting societal projects	1. Hip implants are single-use devices according to the FDA since they are considered high risk medical devices. Therefore, it is not approved for reuse or refurbishment. However, materials could be recycled for other use.	May not be associated with a new or existing project design requirement
Regulatory	1. Testing of our device is restricted to standards set by the FDA	1. The FDA requires that hip implants meet certain testing standards 1. Testing must also be in compliance with ISO standards	1. Affects Requirement 4: The device must withstand normal daily activities over decades worth of loading cycles