By Sean Fenske, Editor-in-Chief
 
Orthopedic device developers are often experts on designing technologies, but aren’t always intimately knowledgeable about the unique components that go into their products. As a result, they are often relying on specialists who focus on these subassemblies to help ensure they spec them into a design correctly and with all considerations taken into account.
 
One such device that has several advanced subsystems is a surgical power tool. At the top of the list, the drive system that powers the instrument is the most complex. Further, advancements within this space has resulted in improvements and changes. Designers may not be up-to-date on the latest features, making their relationship with the motor and motion control partner even more important.
 
Fortunately, Peter van Beek, Business Development Medical Manager at maxon, has taken time to address a number of questions around advancements in the surgical power tool space, with a specific emphasis on the motor and motion control systems. In the following Q&A, he responds to questions around the latest advancements, matching the right drive with an application, and the trends he’s seeing.
 
Sean Fenske: What type of surgeries are performed with surgical power tools?
 
Peter van Beek: There are many different types of surgeries including bone shaving or removal prior to a knee, hip, and shoulder replacement; large and small bone manipulation tools; cartilage repair or removal; spine drills, reamers, and saws; cranial bone cutting and tissue removal tools; biopsy tools; and staplers to close procedures. Surgical power tools are used both in conjunction with a surgical robot or simply handheld.
 
Fenske: How much customization goes into these devices? Can you outline both easy and complex customization examples?
 

van Beek: maxon has an extensive product offering (i.e., 600+ page catalog) of DC brushed and brushless motors, gears, sensors, and drive electronics that can be combined to make unique custom drive assemblies. Customers can purchase just a DC motor or customize further by attaching a gearbox and/or sensor. Some examples of simple modifications would be custom length of the shaft, steps in diameter, radial through holes, splines, flats, and attaching drive elements via pinning or welding. Cabling is another simple change as each customer wants their own cable length, crimps, and connector types.
 
More complex alterations would include custom motor windings for specific speed/torque outputs, adding brakes and encoders, combining several different gear types to make a hybrid gear (e.g., planetary plus right angle), beefing up radial/axial output shaft capabilities, adding a lead screw to a gearbox, housings, and full mechatronic assemblies. As a maxon employee of 30 years, I can tell you the motto is true, “If you can envision it, maxon can build it.”
 
Fenske: What innovation is occurring in the surgical power tool space? How is that impacting drive assembly suppliers?
 
van Beek: End users are looking for high reliability, validated quality, high power density, smaller physical size, lighter, quieter, longer life, and capable of withstanding harsher environments (e.g., saline, cleaning chemistry, autoclave sterilization). maxon continues to innovate and lead the industry in all of these areas.
 
In our experience, despite what innovation is needed in the final tool, engineers always need to start out with initial prototypes delivered quickly. This allows characterization of the unknown torques and speeds of their new power tool. maxon has this engineering development covered with our configurable “X-Series” products, which can provide fast prototypes in as little as 11 working days.
 
Fenske: Does a particular application dictate motor assembly selection or does the end user of the product? Or is it both?
 
van Beek: This is an interesting question. Ultimately, the end user dictates the best design that fulfills their specific needs. This design persists in the marketplace and carries forward over time, creating dominance over competitors. Engineers should always listen to their customers’ “wants” and “feedback,” and create designs that fulfill these needs. Do not make the mistake of thinking you know what is best for your customer; this could be a dangerous approach. So, in the end, the customer does drive the design, which in turn, pushes drive assembly manufacturers to fit within this said design and provide the application’s required torque and speed.
 
For specific applications, there are certain requirements necessary to function correctly and meet lifetime expectations. In turn, this pushes the assembly selection to certain maxon product families. For example, certain tools require cleaning with corrosive chemicals and autoclave sterilization between uses. maxon has a specific family of motors to address this need. With our modular series, motors, gears, sensors, and brakes can be combined interchangeability to create infinite combinations of parts and unique assemblies.
 
Fenske: What trends are you seeing with surgical robotics that are influencing the design and development of surgical power tools used in conjunction with them?
 
van Beek: A newer trend in surgical power tools, is utilizing continuous 3D-video surveillance to control handheld tools operated by the surgeon. The surgical cart, near the power tool being used, is not only monitoring and adjusting the tool-to-bone cutting interface, but also actively controlling the drive assemblies preforming the cutting. If the monitoring system determines the surgeon has drifted away from a prescribed cutting area, the cutting tool retracts and stops turning simultaneously. This application requires maxon’s proprietary ironless core designs or extremely low inertia rotors that allow both the retraction and stopping of the cutting tool in milliseconds. This is where precision matters!
 
Fenske: What required details do new surgical power tool manufacturers often overlook when working with a motor drive supplier?
 
van Beek: Surgical power tool manufacturers have several key aspects to consider when working with a motor drive supplier. The following points are a good start.
 

• It is important to select a drive assembly supplier that can not only communicate well but also work closely with your design team. maxon works in a highly collaborative manner with its customers to bring complex custom designs forward, holding frequent meetings and regularly communicating many quality and design details vital to product development.
• Do not forget about the many quality requirements your design will need, such as PPAP and validation requirements. It is necessary to run your design plan in parallel with your quality requirements.
• Fully understanding the time expectations to develop a product from start to finish.
• Compatibility of the drive electronics to the drive assembly.
• Lead-time for customization will take longer when working with a large production facility.

 
As a leading supplier of drive systems to the medical industry, maxon fully understands these key points and has over 60 years of experience addressing these needs for our customers.
 
Fenske: Do you have any additional comments you would like to share based on the topics discussed or something you’d like to suggest to orthopedic device manufacturers?
 
van Beek: Companies are very good at designing and bringing a design forward. An afterthought is often the quality and validation requirements associated with a project. In a perfect world, design and quality need to run in parallel to reach the finish line at the same time. Do not forget about quality or it will delay your launch to market. For a drive assembly manufacturer to be capable of producing a quality complex drive assembly, repeatedly and reliably, considerable time is required to order, receive, test, tweak, document, and validate fixtures, tooling, and assembly lines. At maxon, we have the know-how and expertise to guide our customers seamlessly through the quality and design process, saving them time and money.
 
Click here to find out more about maxon Group >>>>>