Peter F. Ullrich, Jr., MD - Former Orthopedic Surgeon - Appleton, WI
Dr. Ullrich is a former board-certified orthopaedic spine surgeon. Now retired from clinical practice, Dr. Ullrich specialized in adult spine disorders. He is widely published on the topic of spinal care and has been involved in a number of clinical trials related to new techniques to treat spinal deformities and injuries. He is the inventor of the ENDOSKELETON® lumbar interbody fusion device and co-founded Titan Spine in 2005.
Q1: Can you describe Titan’s surface technology? What makes it unique?
All of our Endoskeleton® interbody implants feature our proprietary implant surface treatment technology, consisting of a unique combination of roughened topographies (textures) at the macro, micro, and cellular levels created through a subtractive process rather than a coating. This critical combination of surface levels is designed to create an optimal host-bone response and actively participate in the fusion process by promoting new bone growth, encouraging natural production of bone morphogenetic proteins (BMPs) and creating the potential for a faster and more robust fusion for our surgeons and patients.
The very unique textures we have created on the surface of our interbody devices promote the up-regulation of critical bone growth and angiogenic factors necessary for fusion. Our surface has three different levels of roughness – which we call a hierarchical surface – including a macro surface, micro surface and sub-micron or “cellular” surface.
The size people can feel is our macro surface that functions as an anti-expulsion surface without damaging the vertebral endplates. That is what allows the implant to resist migration and is important to the biomechanics of the device.
At the micron scale, which is below the macro level and measures 10 to the minus 6 meters, we give the cells a place to grow into the implant.
However, the most important level is the sub-micron level, which we call the cellular level, because it measures in at the 10 to the minus 9 scale and is what triggers the cells to differentiate into osteoblasts and begin the bone formation process.
This is all triggered just by the topography of our implant surface. In fact, much of our research is going into maximizing the benefits of the sub-micron surface.
Q2: What is the broader significance of the surface technology compared to other devices on the market?
As a result of the unique topography factors, our technology has been shown to produce an enhanced bone-forming (osteogenic) response compared to common interbody device materials, such as polyetheretherketone (PEEK) and smooth titanium.
Whereas PEEK primarily stimulates the growth of fibrous tissue, resulting in an effect in which the bone graft and PEEK fight each other, our surface technology works in concert, allowing synergy, with the surgeon's bone graft of choice. Ultimately, our surface technology and the bone graft are designed to generate, or grow, the desired boney tissue required for fusion.
Q3: How do Titan implants actively promote fusion?
This is a particularly unique process by which the roughened surface of our devices causes the endogenous recruitment of stem cells that subsequently differentiate in to bone-forming osteoblasts, which allows our devices to actively participate in the fusion process.
In other words, our surface technology allows the creation of textures that are small enough that they are able to interact with the host’s cell membranes and signal the cell to ramp up production of proteins. Cell attachment to the implant ramps up the production of mRNA, which, in turn, leads to an increase in the production of bone-producing proteins, which then signal osteoblasts to mature and produce bone.
In addition to local bone production, osteoblasts signal to other cells in the area to induce them to begin making bone. It is this early attachment and signaling that is essential in bone formation and the fusion healing process. Once new bone growth has begun, the process stimulates local production of natural BMPs to further accelerate the fusion process.
Q4: Why is stimulating production of natural BMP noteworthy?
While research has shown that adding exogenous Bone Morphogenetic Proteins (BMPs) in conjunction with an interbody device does induce the formation of new bone and suggests they may promote a faster and more successful fusion compared to alternative bone graft materials, external BMP can be costly, imprecise and, in certain cases, have been associated with serious side effects including soft tissue swelling, infection, nerve pain, and overabundant bone formation.
At Titan, we look at it differently because it never made sense to me as a surgeon to implant exogenous BMP at extreme hyperphsyiologic doses at the time of surgery. Instead, why not encourage the body to produce its own natural BMP through the textures of the implant? This way, we are prompting the body to heal itself.
Q5: Aside from the surface technology, how are Titan’s devices different from other interbody devices on the market?
In addition to our unique surfaces, our Endoskeleton® interbody devices feature extremely large windows for excellent postoperative radiographic visualization and fusion evaluation, as well as increased bone graft volume. Furthermore, the side windows of our devices allow for additional bone growth in the axial plane, unlike traditional interbody devices that only allow for cephalad/caudal bone growth.
The unique shapes enable the majority of our devices to be placed on the apophyseal ring, the strongest portion of the vertebral endplate, to preserve endplate integrity and reduce the risk of implant subsidence.
In addition, our ENDOSKELETON® line of devices is supported by simple, intuitive instrumentation for easy and consistent implantation. The devices are available in a variety of sizes to accommodate various patient anatomies.
Q6: Ultimately, how do Titan implants benefit patients?
The bottom line is that patients can get moving a lot quicker. An in-vivo study conducted by Buser et al in 2004 showed that around 70% of bone ongrowth occurs on roughened titanium surfaces within four weeks. Clinically, we have had Titan patients go back to manual labor in six weeks – which I would have not allowed my patients to do in the past. Longer term, a prospective study on our ALIF device has shown that our patients make significant gains in back and leg pain relief, as well as reductions in disability metrics, by 6 months. And these improvements have been shown to hold steady through two years post-op.
In my own practice, we used to worry about non-unions for lumbar fusions. Now, after using the Endoskeleton, non-unions are so rare that we usually don’t expect their occurrence. What we have found is that surgeons who test the Endoskeleton tend to continue using it because it works – it helps create bone in the interbody space. Of course, above all else, the number one driver of clinical success is choosing the right patients for fusion. The key change we’ve had in our practice is how quickly we can get patients back to their normal activities. Before, we had to have them wait for a solid fusion, but now, because of the stability of the bone /implant interface, we will allow patients to return to normal activities much quicker. This has made a huge difference in the lives of our patients, getting them back to work sooner or back caring for their family sooner. The post-op experience has been dramatically changed by this product.
For example, we’ve seen a dramatic shift in speed to recovery for our patients with isthmic spondylolisthesis. These patients tend to present with instability and nerve root pain in the leg, but we have found we can return them to normal life very quickly with the Endoskeleton. Once the incision heals, usually around the 2-3 week mark, we see patients able to increase their activity level dramatically. This is a major improvement from the past, where we had to wait for the fusion more typically around 3-6 months. We recently had a patient who underwent a fusion about 3 months ago for an isthmic spondylolisthesis and L5 radiculopathy. We did a front/back fusion, used an Endoskeleton cage in the front, pedicle screws in the back. He went home the day after the surgery and was back to work within 2 weeks. As a former ironman tri-athlete, he hadn’t been able to train for about a year and a half. When I saw him for his 3-month checkup, he had just gone for a 100-mile bike ride that he did within 5 hours and felt great.
Q7: Why do spine surgeons now care about implant surface technology?
The surface of the implant can affect fusion outcomes, so implant choice matters. The implant surface can be designed in such a way that it encourages
- the maturation and differentiation of osteoblasts (bone growing cells),
- the down regulation of the osteoclastic cells (bone eating cells), and
- the growth of blood vessels to bring in the nutrients needed for bone growth.
Tiny (sub-micron) spikes on the implant’s surface can trigger the cells to achieve these desired responses. Prior to the Endoskeleton, most of us surgeons weren’t aware of this level of micro-activity, but now after in-vitro testing we have proven we can activate this process and use the Endoskeleton to help create bone. The Endoskeleton implant is now a biologically active agent in the fusion process.