Stryker Orthopaedics has carved new territory in the knee implant market with its groundbreaking Triathlon™ Knee System. Launched in October 2004, the Triathlon Knee is designed to provide patients more natural-like motion and the potential for greater implant longevity. And according to preliminary field data, performance of the knee has been outstanding. “The product has been very well-received in the market,” says John Grecco, Triathlon Knee System designer.
As the knee system was being developed, Stryker also wanted to design an instrumentation set, including related cases and trays, that would accent the revolutionary implant. “We looked at a matrix of instrument users — surgeons, nurses, even cleaning and distribution staff – and configured cases & trays to satisfy their specific wish lists,” says Stryker Chief Engineer Scott Logan. “Then we talked to manufacturers whose bread and butter was making cases & trays. I was completely disillusioned with all of them because they were trying to force fit us into a generic package that made sense to them as manufacturers, but ignored the needs of our stakeholders.”
At that same time, Stryker was already working with Mack Molding to co-develop ergonomic (coined Orthonomic™ by Stryker) overmolded handles for their top-of-the-line titanium instruments for the system. During a tour of its headquarters plant, Logan noticed Mack’s significant sheet metal fabricating capabilities in addition to its molding expertise “and realized that because we also do metal, we could produce a hybrid case & tray,” explains Larry Walck, Mack’s director of business development. “That was the beginning of a collaborative effort among Stryker designers and engineers and Mack process development and project managers that resulted in a distinctive delivery system to complete the knee implant package.”
Getting there wasn’t easy, however. The list of criteria was long. Based on Stryker’s 30-year orthopaedic history and input from surgeons and operating room (OR) staffs worldwide, “we were striving to incorporate everything our stakeholders needed into a modular case & tray set that was both lightweight and multi-tasking,” says Grecco.
Specifically, the delivery system needed to:
- Properly package the new flagship product by reflecting the same branding initiative, so that the Stryker system would be immediately recognizable by OR staff
- Consolidate the number of instruments and cases to use space more efficiently in the surgical theatre and minimize costly cleaning procedures
- Configure the instruments in stackable modules that correspond to surgical procedure and flow
- Withstand shipping and handling
- Remain under a specified weight for ease of handling
- Resist harsh chemicals used to meet worldwide cleaning standards
- Provide adequate steam flow during autoclaving to thoroughly clean instruments and eliminate wet-packing
- Provide instrument constraint with minimum contact for improved cleaning and autoclaving
- Stack in a sterility tub for shipping, which requires standardized sizes
- Avoid sharp edges that tear the sterile wraps and compromise the sterility of both the system and the surgical theatre.
“Time was another challenge,” adds Chris Wartinger, Mack program manager. “Cases & trays traditionally are the final piece of the puzzle. The design team has to finish the instruments and protocol first, which typically require some last minute tweaking to satisfy user needs. Those changes move down the line, impacting the delivery system as well. For example, if you make an instrument handle two millimeters larger, then we have to similarly adjust all brackets in all cases & trays, as well as all assembly prints. Consequently, we generally develop cases & trays when the rest of the program is 80 percent complete, leaving 100 percent of the work to do in 20 percent of the time.”
The collaborative design team addressed the branding initiative with material, color and corporate identification. Titanium became the material of choice because it not only addresses several performance criteria, but also matches the instrumentation and distinguishes the sets from all others in the field. All plastic resin used on the instrument handles and case is custom formulated to match the Stryker brand. Both company and product identification are laser-cut into the case and molded into the instrument handles.
The redesigned instruments feature a basic handle style with ergonomic soft-grip handles that are insert molded with a double overmold. The first material is a high heat polypropylene, and the second is a custom blended, thermoplastic elastomer (TPE).
To address the consolidation issue, the handle design introduces a quick attach-and-release mechanism that saves time in fixture assembly and minimizes the number of instruments required.
Downsizing the number of instruments allowed for consolidation of cases & trays as well. “In fact, we reduced the amount of cases required in the surgical theatre by 50 percent,” says Grecco, “saving space, an important commodity in the OR, and reducing costly cleaning procedures.”
The case & tray sets are two-tiered systems configured intuitively to correspond to the surgical procedure. They are laser-cut from titanium, a lightweight but durable material that withstands harsh cleaning solvents, as well as Stryker’s rigorous testing procedures.
Numerous aeration holes are laser-cut into the case to provide a sufficient flow of steam during autoclaving, as well as proper ventilation for drying. In addition, titanium brackets provide adequate instrument constraint with minimum contact for improved cleaning and autoclaving.
“Mack uses laser welding and special forming techniques to support the instrumentation with titanium brackets,” adds Grecco. “We also anodize the titanium for an anti-galling effect and improved silk screening and cosmetics.”
The corners of the case are fitted with plastic bumpers molded of TPE for shock absorption and sterilization protection, since the TPE eliminates rough edges and corners. Plastic handles are also integrated into the trays. Again, both are color matched to the branding initiative, making the delivery system easily recognizable as a Stryker product, both in the OR and the marketplace.
To better accommodate Stryker’s case & tray program, Mack invested $1.4 million to shorten the supply chain and lengthen its vertical integration in sheet metal fabrication, a core competency. “We added more laser-cutting capacity, as well as laser welding and other secondary operations,” says Walck. “The product is now manufactured almost completely in-house, which helps minimize risk in the supply chain. I can’t emphasize enough how important it is for OEMs to choose manufacturing partners who have the financial wherewithal and expertise to see them through the product launch, invest in their needs, and minimize all that can go wrong when dealing with multiple outside suppliers.”
“Mack Molding is by far the most aggressive and enthusiastic organization I’ve every dealt with,” adds Grecco. “They made the capital investment to grow with us. The engineering resources were there. And they put in the time it took to get the job done. We built a relationship that’s growing in an exponential way.”
“We had very specific criteria for what we wanted,” concludes Logan, “and Mack met those criteria. That’s why I believe we’ve got a product that satisfies peoples’ needs. The success of this program really boils down to two words for me – collaborative effort.”
Contacts: Larry Walck, Director of Business Development
Chris Wartinger, Mack Program Manager
About Stryker Orthopaedics
Stryker Orthopaedics is a global leader in the development, manufacture and sale of orthopaedic products and services. Its hip, knee, upper extremity and trauma systems, as well as bone cement and bone substitutes, are designed to help patients lead healthier, more active lives. Stryker Orthopaedics is the largest subsidiary of the Stryker Corporation, which has delivered more than two decades of 20 percent annual net earnings growth.
Products referenced with ™ designation are trademarks of Stryker®.