Smooth Shaving Device for Arthroscopic Surgeries
|$1500 Shave Club Members|
|Sponsors||Dr. William Hiller, MD|
|Team Name||$1500 Shave Club|
|Duration||Fall 2020 - Spring 2021|
|Faculty Adviser||Dr. Joel Perry|
With an interdisciplinary team of engineers working together to solve problems faced by members of the Palouse, we hope to garner technical engineering experience while also creating a product that satisfies our client. The goal from our client is to create a production-ready smooth arthroscopic shaver, capable of robust sterilization and prepared for animal testing. We are working with Dr. Hiller to ensure that our device will be suitable for use in operating rooms around the country by utilizing variable speeds, orbital sanding, and a compact ergonomic design.
We were tasked with developing a smooth sanding device to be used in arthroscopic surgeries in hopes that it will ease the recovery process for patients. In order to properly sand articular cartilage, variable speed with orbital sanding motion is required to accomplish the desired effect. Our device will also be designed with ergonomics in mind to prevent operating fatigue for surgeons.
Arthritis is a characteristic roughening of a joint, and causes joint breakdown leading to chronic pain and inflammation. Annually, there are roughly 750,000 knee arthroscopies in the United States, many of which focus on alleviation of arthritic pain in the joint. However, current techniques require cutting out afflicted cartilage or bone, contributing to longer recovery times and increased cost of care. In addition, arthroscopic tooltips are designed for single-use, increasing patient out-of-pocket costs. The goal of this project is to create a device with reusable tooltips that can arthroscopically shave arthritic joint surfaces smooth to lessen pain and lower rehabilitation time. Our device will embody these capabilities via approximation of a random-orbital sanding motion of the shaving platform, as well as offer better ergonomics and user comfort than traditional arthroscopic tools. This tool will enable those suffering arthritic pain to lead comfortable and fulfilling lives.
This project was brought to us and sponsored by the incredible, Dr. Doug Hiller. Dr. Hiller is a fellowship trained, sports medicine orthopedic surgeon who participated as the active physician for the Olympic and Paralympic Games. Throughout his years of practice, he found a general consensus amongst experts in the field that there is a gap in the treatment of arthroscopically shaping cartilage in the knee joint. Without the right tool, there is no way to induce cartilage to regenerate without proper stimulation, however no such tool exists. On the other hand, totally replacing the knee could also be appropriate repairable if a device were to be constructed that could smooth the irregular surfaces in the knee. Using instruments designed for other purposes to try to achieve the same results as depicted above typically results in less than ideal outcomes, therefore there is a need for a tool that can work as a smooth arthroscopic shaver.
Current shavers work with solely rotary shaving motions, ripping bits of flesh in a high-speed biting affect. These shavers do not have any sanding mechanism for fine bits of cartilage so the current devices leave ripples or grooves in the tissue. Similarly, the design of current devices has a pencil shaped housing unit opposed to a more ergonomic design.
Our device is intended to be used on cartilage, a tissue that decreases friction and distributes loads. Cartilage has a high water content and intensive structural properties which help it shield stress in joints. In cartilage there are 3 layers of collagen fibers running from the superficial, through the middle, to the deep zone. Unlike bone which has faster healing properties, cartilage has a poor capacity for healing which commonly leads to degradation needing surgical intervention.
We are not the first group to be tackling this project, so fortunately we have received a lot of great feedback from the previous group. Although they had a rudimentary prototype, it was inconsistent and not suitable for sustained use. Therefore, we have been asked to take their extensive research and apply it so that a working prototype can be made. In their design, the device operated using an external battery pack and a Sonicare toothbrush motor, however both were recommended for change. The external battery pack prevented the design from being portable and only had a 17 minute run time. The toothbrush motor, although fast, stopped easily due to overloaded force in typical conditions and didn't provide a repeatable manufacturing design. Their design also did not have any speed variability which is crucial for the project. However, the last team did conduct thorough research into sanding grits to find which was the best for articular cartilage. In their tests, they found that 100-400grit sandpaper performed well, with optimal grit being 300. This will be the basis for our design assumptions.
Our deliverable is a working prototype that could be put to production at the end of this course. It must have variable speed, orbital sanding, an ergonomic handle, and be capable of running for extended periods of time at a load. Our objective is to work together as a team to create the said deliverable and give it to the client with the expectation that his money was put to valuable use. Besides that deliverable to our client, each of the team members is responsible for a logbook and the team as a whole is responsible for all of the coursework associated with the Capstone Design Class. This includes a Team Contract, Budget, Project Requirements Document, Project Schedule, Logbook Checks, Portfolio Checks, Wikipage Checks, Snapshots, Deesign Validation Plan, Value Proposition, Concept Design Review, Team Member Citizenships, Design Expo Registration, Engineering Release Review, Technical Presentation, and the Final Expo.
After discussions with our client, we have narrowed down the feasible design constraints into the following list:
- Pistol grip style handle
- Variable speed output with 900-6000 RPM oscillation settings
- Random orbital sanding action
- Maximum output shaft diameter of 4mm. Output shaft should be able to withstand corrosion in saline-rich environments
- Compatibility with 100-400 grit shaver heads/burs. 300 grit shaver heads/burs have been previously noted to work the best
- Reliable two-hour battery life
- Compatibility with existing surgical suction pumps. Debris removal during shaving (condyle, menisci cartilage, bone fragments)
- The device should be reusable, and compatible with different shaver heads. Autoclaving (60kPa, 150 degrees Celsius)
- Biologically compatible materials
- Comfortable and lightweight
- Sturdy design suitable for accidental drops
- Less than $1500 to build
Due to the success of the last group, we have decided to adopt a number of their successful features. We will use a similar pistol grip style handle that houses all of our working pieces. We will be using an Arduino Trinket as a microcontroller to control the entire device seamlessly through Arduino coding. We have also decided to use an outer and inner shaft design with a trigger actuator. However, then we took liberties to solve the problems that the last group struggled with. We initially settled on two designs, one of them being a sawzol style DC motor linkage system with a linear actuator to move the DC motor in a slot. This can be seen in Figure 1. Then due to size concerns and considerations of actual feasibility, we moved away from this design to our current prototype, which is a rotational DC motor with a linear solenoid and a keyed inner shaft. This can be seen in Figure 2 and 3.
The outer shaft will be made from 1060 Alloy Aluminum due to its high strength to weight ratio as well as the fact that it is inexpensive and non-toxic. Another unique property that is highly useful to our project is that it is sterilizable, which makes it perfect for handles in surgical equipment. However, due to the high saline environment during use, the aluminum should be coated to reduce corrosion. The inner shaft will be made from 316L medical grade stainless steel because it is still relatively inexpensive, particularly compared to other surgical materials like titanium. Additionally, this allow of steel is commonly used in surgical instruments because it is resistant to corrosion in aqueous and saline environments. This was also chosen because it is strong enough to withstand sandblasting so we could create an integrated gritted sanding head design.
So far, we have yet to begin actually creating our device, so instead we have begun modeling the most important part, our motor linkage system. The following parts are used in our linkage device and will be machined, while the last one is an example of the working assembly.
Inner Rod Linear Actuation Mount:
DC Motor Shaft Groove Mount:
We have a completed electrical design, however we are missing our solenoid, so this is the current electrical design.
We have completed the Arduino Code and it works to allow a potentiometer to control a DC motor speed with a button to activate the circuit. Without our solenoid however, we do not have the code perfected to incorporate that into our system so here is our current iteration.
Just from our initial attempts at prototyping early on, we are quickly learning one of the most prominent lessons of Capstone: time moves very fast and innovation moves very slow. We have already encountered many roadblocks in our designing, however now we have finally broken through the conceptualization phase and are beginning to actually formulate our prototype. We have already learned that team communication is absolutely vital so that everyone is always on the same page, thus preventing re-explaining of concepts and saving precious time. We are also quickly learning that every project has its own unique challenges associated with development. For our project, we are struggling with ensuring that size constraints are met and material considerations are viable. We have also begun to notice that when dealing with housing units, it is better to create the product first without a housing unit, in order to get a proof of concept, before beginning on figuring out how to house the whole thing.
We were given a $1500 budget to spend on the project for developmental costs. We do not necessarily plan to use this budget, however, we have broken it down into every category in the maximum amounts that we anticipated, just to be sure that we could meet our funding goal.
Given that we are expected to have our project completed by April 2020, we have created a preliminary schedule to ensure that we are reaching our project goals in the time that we want. We plan to follow this loose timeline with the expectation that things will change as our design begins realization.
File:1500 Team Meeting 1.pdf
File:1500 Team Meeting 2.pdf
File:1500 Team Meeting 3.pdf
File:1500 Team Meeting 4.pdf
File:1500 Team Meeting 5.pdf
File:Team Meeting -6 Agenda, Minutes 10-06.pdf
File:1500 Team Meeting 7.pdf
File:1500 Team Meeting 8.pdf
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File:1500 Team Meeting 10.pdf
File:1500 Team Meeting 11.pdf
Snapshot Day #1:
File:1500 Snapshot Day -1.pdf