Thermoplastic Product Corporation and Implant Patients Thrive by the Axiom that “Custom is Better” with 3D Systems' Geomagic Freeform software
Twenty-seven years ago, doctors told Barry Fell that his knee had had enough. It was worn out, and they suggested the usual: a knee replacement with a stock implant. After a long surgery and weeks of rehabilitation, he’d be up and walking again without pain. The ideal outcome, right? Not exactly. “I didn’t like it,” he said. “The high success rate with stock implants has to do with alleviating pain. But with a manmade replica of a knee, in terms of structure, ligaments, et cetera, it’s not even close to what you’re giving up. You can’t do what you did before. And once you get the implant, there’s no going back.” He decided to wait until there was better technology for his knee. And in fact, decided that he should be the one to create it.
So Fell, with his bum knee, graduate degree in chemistry, and years of experience in the textile and aerospace industries, jumped square into orthopedics. His mission: to find himself a better knee implant, a task that proved to involve more than just biomechanics, physics and materials. “My very way of thinking wasn’t typical of how orthopedic surgeons thought. They didn’t want to change,” Fell said. That is, most surgeons were comfortable sticking with stock, one-size-fits-all implants. “But,” he continued, “custom is better.”
Since then he’s proven just that, and his small mission has morphed into a full-fledged business. And the industry has started to come around, largely due to the successful outcomes produced by Fell’s company, Thermoplastic Products Corporation (TPC) of Hummelstown, Pa. Fell has positioned TPC at the forefront of the custom medical device industry by utilizing a combination of 3D Systems’ Geomagic Freeform 3D modeling software, proven CAD, rapid prototyping and additive manufacturing techniques on some of the most challenging implant cases.
In fact, Fell relies heavily on Geomagic Freeform because it does what traditional CAD simply can’t do, giving designers the ability to sculpt 3D clay models using a touch-enabled interface and to construct them quickly. As they are essentially extensions of the human body, organic components in and of themselves, his implants and surgical guides require a high degree of design freedom. They require the ability to shape natural, curved solids, which Freeform provides unlike anything else.
“Freeform manipulates .stl’s like nothing else can,” says Fell. “There’s not another good way that we’ve found in terms of speed and efficiency.”
Improving Patient Outcomes
A previously active 60-year-old, only four months removed from her second hip implant, was admitted to the hospital in extreme pain. The femoral head, the ball that normally fits into the hip socket, was resting above her belt line.
Osteoporosis and bone erosion had caused the implant cup to dislodge and collapse into her pelvis, resulting in not only a severely dislocated hip but also allowing the implant cup to tread dangerously close to vital organs.
Doctors at the Orthopedic Institute of Pennsylvania determined that a third implant in her continually eroding, delicate pelvic bone would be most successful if they used a then-new trabecular metal material. Trabecular metal encourages new bone cells to grow into the implant itself rather than relying on screws and the usually heavy volume of cement to keep the cup in place. If done correctly, this implant would be secure enough to keep her out of the operating room for a fourth time.
However, at the time, custom trabecular metal implants had a 24-week development window, due largely to the extensive effort required to create the material itself. In that amount of time, her anatomy would change, the very expensive custom implant wouldn’t fit, and they’d be back at the drawing board. In another wrinkle, the woman was in the process of rehabilitating a recent knee replacement when her hip went out. Lying motionless for so long would cause a major setback in her rehab. She needed to move. 24 weeks was too long.
So, TPC cut it to two days. Using Geomagic Freeform’s unique features, they altered an off-the-shelf trabecular implant cup prior to surgery and provided pre-surgical visualization. The result: Surgeons didn’t have to alter it in the operating room, and the patient wasn’t exposed to infection and anesthesia for long periods of time.
“This case represented an amazing marriage of technology and medicine, a marriage that benefited the patient tremendously,” said Dr. Richard H. Hallock of the Orthopedic Institute of Pennsylvania.
The process began on a Wednesday. After converting the patient’s CT scan into an .stl file, TPC used Geomagic Freeform to make a mirror image of her healthy right hip to use as an overlay for the damaged left. Able to see where her pelvic bone and femur naturally aligned, TPC designed, sourced and provided the required cup implant and augments for surgery by Friday. In fact, the design alone took less than an hour, a far cry from the full day required to create the same piece using traditional CAD software. Because Freeform includes four different modeling representations – voxels, NURBS, polygons and SubD – TPC was able to quickly work in the right mode for a given task while readily altering and reshaping components for fit.
To verify accuracy, TPC used Freeform to fit the cup within the patient’s virtual 3D pelvic structure and to assure that it wouldn’t impinge on nearby organs. Once the design was complete, Freeform’s measurement functions allowed TPC to verify that an off-the-shelf acetabular cup and set of augments would be suitable in creating the final implant.
Perhaps even more amazing, Freeform and its realistic touch-based interface allowed surgeons to review and practice the surgery on an exact virtual model of the patient’s anatomy. This level of preparation was vital considering that the patient’s flimsy existing pelvic bone measured anywhere from 20 mm in spots to a mere 1 mm in others. So, rather than relying on flat images and scans, the surgeons used Freeform and haptic devices with force feedback to physically feel the simulations they were performing on screen. They were able to detect points of resistance as they placed long rods through the proposed screw holes and verify that the hardware would retain the new cup in her dangerously thin pelvic structure.
Once the design was complete, TPC provided measurements and made a 3D-printed study model for the surgeon’s final approval. This model was also instrumental, as it functioned as a reference during the surgery.
“This woman was walking again thanks to this custom implant,” said Dr. Hallock at the time of the surgery. Even now, seven-plus years later, her implant is still functioning properly, and she’s able to get around like she was before. Dr. Hallock reports that she continues to do extremely well.
More Than Just Implant Hardware
Beyond joint implants, TPC is making great strides with patented knee interpositional spacer devices; minimally invasive surgical instruments for orthopedic, general and plastic surgery applications; custom surgical guides; and new orthopedic, cardiovascular and gastrointestinal devices that all allow more possibilities and a higher grade of patient care. As for developments to come, Freeform is currently a key part in developing minimally invasive, fast methods and new implants for the repair of life-threatening rib fractures called “flail chest.” Since its development, this technology has been licensed to a major orthopedic company with an anticipated market release of early 2014.
TPC is supplying customization services to an industry in which every project truly is a different animal. “It’s all about getting the right shape,” says Fell. And because customization is king, they’re using Freeform to provide unparalleled modeling flexibility and power their forward motion. That forward motion means dividends in patient care and vastly improved results. Each patient, each joint movement, each rotation and flexion is a testament to TPC’s work.
Perhaps all that progress is even enough to convince a certain someone that they ought to get that knee replacement, the one that’s now twenty-seven years overdue.