As with all great inventions, the steerable punch, a medical instrument to assist arthroscopic surgery in the knee, has a deceptively simple design. Nevertheless, it took an inspired approach to develop the now multi-patented instrument.
Those involved have many names for the approach they took: “disruptive designing”, “design by dissection” or “bare-minimum designing”. Whatever the name, the result is nearly ready to make a splash across the world through its spin-off company: Surge-On Medical BV.
Teamwork is the basis of innovation. Because of this, the website for Surge-On Medical first and foremost pays tribute to everyone involved in developing the steerable punch. It was designed by Dr. Tim Horeman and Dr. Gabrielle Tuijthof of the Department of Biomechanical Engineering at TU Delft and affiliated with Zuyd University of Applied Sciences and the Academic Centre for Evidence-Based Sport Medicine (ACES). Medtech entrepreneur Benno Groosman subsequently joined the initiative to create a company around it: Surge-On Medical BV. The team is supported by medical experts such as Professor Gino Kerkhoffs, affiliated with the Academic Medical Centre in Amsterdam. Beyond giving credit to relevant parties, the website of the newly founded company does not reveal much about the surgical cutting and steering mechanism the research team developed, which now assists surgeons operating in the knee. “We’re currently working behind the scenes,” says Horeman. “We don’t want to give away too much too soon.”
One of the most common operations in sports medicine – indeed in all orthopaedic procedures – is surgery for a meniscus tear. Although some meniscus tears can be repaired, most require the inner, torn part of the meniscus to be removed. This partial meniscectomy is done using arthroscopic (“keyhole”) surgery: small incisions are made to allow special instruments, including a fibre-optic camera and a cutter, to be inserted into the knee. The surgeon uses the cutter to smooth and stabilise the torn meniscus edges. Every year, this medical procedure is performed over four million times in Western Europe and in the US.
Lifting 20 kg
“For 15 years,” says Horeman, “we’ve had surgeons and researchers like Professor Kerkhoffs highlighting the challenges involved in this procedure, asking us to come up with a better instrument.” The procedure requires rather large forces, equivalent to lifting 20 kg, to be applied by the tip of the surgical cutter. As the instrument used so far is non-steerable, the surgeon needs to bring along various different cutters, each with a different tip angle to reach all pathologic locations in the tight knee joint. Can such a slender arthroscopic instrument be made steerable, while still allowing the application of large forces inside the cramped space of the knee joint?
Shaft-actuated tip articulation
Most steerable surgical instruments used in other surgical procedures consist of the thin shaft acting as a feedthrough for the wires that transduce the forces the surgeon applies to a moving tip. Such wires have an unavoidable level of flexibility, which becomes a problem when large forces are at play. “So far, all prototypes of a steerable punch using the shaft-and-wire design have failed,” says Horeman. Because of this, the team discarded the wires and re-designed the instrument, ending up with a shaft within the shaft. The two rotate with respect to each other and this rotation is transduced into tip action: shaft-actuated tip articulation (SATA). This design allows the surgeon to steer the instrument, while still being able to apply large forces onto the meniscus, increasing the success rate of the procedure.
Several consecutive prototypes were made, and surgeons from various medical centres tested them on human cadavers. “When we handed surgeons our prototype,” says Horeman, “they closed their eyes, went through the procedure in their heads, and refused to give the instrument back. That’s when we knew we were on to something.” To develop their design into an actual instrument, Horeman and Tuijthof were joined by Kerkhoffs (among others), who now co-leads the scientific underpinning. An “elite team of surgeons”, as Horeman calls it, was assembled to test the new instrument. The team didn’t take the surgical tests lightly: “We’ve gone beyond asking the surgeons to complete questionnaires,” explains Horeman. “We’ve precisely analysed all hand movements and forces applied during the mock procedures in order to perfect the instrument.”
Now that preliminary testing has been finished, the concept has been transferred to Surge-on Medical BV, funded by Dutch technology foundation STW and an “angel investor” from the US. The company, which is headed by Horeman and Groosman, is currently revisiting the design from a commercial point of view. “We’re simplifying it, stripping its nice-to-have features and retaining the essential 60%,” says Horeman. “We’re also developing cleaning procedures. The instrument can be completely taken apart and cleaned using standard sterilisation procedures. It’s the first of its kind to allow full cleaning and re-use.”
It took a consortium of experienced partners and a strong network Dr. Gabrielle Tuijthof, TU Delft
From patent to prototype
The first production series of 20 steerable punches is currently being developed. “We need to get every hospital in the Netherlands to start using our prototypes,” says Horeman. After the beta test, which is expected to take three months, the next step awaits. “Industry partners are lined up and ready to distribute the instruments as soon as possible.” Looking back on the road from patent to prototype, Tuijthof summarises what it took to get this far: “First of all, a brilliant patent. It took Tim a few sleepless nights, but he delivered. Second, a consortium of experienced partners and a strong network. Third, insight into the relevant requirements and regulations, as this represents the bulk of the development costs.” While the steerable punch is ready to make a difference in operating theatres, all those involved are passing the lessons learned on to new generations of students.
Interview by: DBAR