Introduction of FIREFLY Technology FIREFLY Technology is a unique, patent-pending, pre-surgical planning and intra - operative navigation technology that is focused on spinal applications and is derived from a patient s 3D imaging data. (Mighty Oak Medical has multiple patent applications pending for this technology, including one that was recently allowed by the USPTO) As a navigation guide for pedicle screw placement in open surgeries, this technology can help to improve implant accuracy, and does so in a highly cost-effective manner. Mighty Oak Medical s FIREFLY Technology is a series of patient matched pedicle screw trajectory guides. These guides are used to create pilot and tapped holes that are specific to a particular patient s vertebrae. Surgeons submit patient image data in the form of magnetic resonance (MRI) or computed tomography (CT) imaging that has been run following specific protocols. MIMICS software is used to convert the patient s imaging data into a three-dimensional computer model of the spinal vertebrae that are to be instrumented with pedicle screws. The vertebral models are created through a process of segmentation and surface enhancements. Once the boney models are complete, a number of guides (one for each vertebral level to be instrumented) are designed with unique, patent-pending features to achieve an optimal trajectory for the pedicle screw. The trajectory guides conform to the patient s vertebrae at defined pre-determined contact points and are aligned based on the patient s pedicle axis (defined, chosen and approved by the surgeon). The guides are manufactured from a biocompatible resin and then used during a posterior approach to assist the surgeon in optimally placing pedicle screws. FIREFLY Technology enables optimal implant placement by assessing bone quality and incorporating surgeon-defined parameters such as depth control, screw diameter, medial line angle, and entry point into the design of the guides. The surgeon indicates these parameter preferences preoperatively. As a result of these guides, implant sizing can also be determined preoperatively. FIREFLY can be used with any existing pedicle screw implant system. The Need for FIREFLY Technology Free-hand pedicle screw placement can at times be challenging for any spine surgeon, especially in the thoracic space, extreme deformity cases, and revision surgeries. Literature shows a wide range of misplacement rates for pedicles screws. Some of the higher reported rates exceed 10%, and this rate would theoretically be higher in revision or deformity cases where anatomical references are absent or extremely distorted. This would also be true as pedicle dimensions get narrower in the thoracic region, where violating the medial cortex becomes more problematic.
Figure 1: Pedicle screw violating the canal The advent of surgical navigation has allowed for much greater accuracy in the placement of pedicle screws for challenging cases. Systems such as the StealthStation O-arm technology and Mazor robotics have found their way into operating rooms in order to address the widespread problem of misfired pedicle screws. This technology, however, is not financially feasible or accessible to most hospitals around the world, and it comes with some associated problems. The most prohibitive factor in current navigation technologies is the expense. These systems cost close to $1,000,000 in upfront costs with ongoing service contracts. Even if a large hospital can afford such an investment, the budget would not allow for multiple units; the need to share a single unit can create booking and scheduling issues in the operating room. Expense is not the only issue with current surgical navigation technologies. These systems are very complex and require OR staff training and set-up time. Reference arcs and registration points must remain stationary, as the system is unable to account for real time movement of anatomy. Additionally, the size of the O-arm system is disproportionately large to the operating room, creating both space and contamination problems. Moreover, hospitals are not reimbursed for this substantial investment by health insurers, and patients are exposed to radiation in the form of intra-operative CT scans. Figure 2: O-arm reference arc (left) and size of system (right) FIREFLY Technology provides a simple, cost-effective solution to accurately placing pedicle screws. By the nature of FIREFLY s approach, additional benefits include reduction in radiation exposure by reducing the number of fluoroscopy images taken during pedicle probing and elimination of O-arm CT scans. FIREFLY Technology s pre-surgical planning process also allows for identification of ideal implant sizes before the surgery -- thereby reducing the amount of inventory on the sterile table in the operating room. This reduction
in inventory could reduce sterilization time and costs for the hospital, ease the logistics and cost of shipping for the implant manufacturer, and reduce the risk of infection for the patient. We liken the use of FIREFLY Technology to a NASCAR pit stop in terms of its added efficiency in a high-stakes setting where OR time and surgeon time is extremely valuable. The FIREFLY Technology Process and Methods The FIREFLY creation process begins with patient imaging data acquisition, which can come in the form of CT or MRI. (Since surgical candidates already have such scans, there is typically no additional expense or radiation exposure with respect to this requirement.) This imaging data is then uploaded or sent via mail to Mighty Oak Medical. A custom software interface is being developed whereby the surgeon can access the company s FTP site through a desktop link and upload imaging data electronically. This link is used later in the process for pre-surgical planning and 3D visualization. The second step in the creation process is turning the two dimensional stack of DICOM images into a three dimensional body that can be used in a traditional engineering CAD (computer aided design) software. Using MIMICS, the 2D imaging data is segmented from the surrounding soft tissue. The anatomy in between slices is interpolated, and a 3D body representative of the patient s spinal anatomy is created. An individual file is created for each vertebral level that is to be instrumented with spinal fusion hardware. Figure 3: FIREFLY Technology Process Once a 3D body has been created for each level to be instrumented, a unique, patient-specific plan is created pursuant to our proprietary navigation guide technology by a Mighty Oak Medical engineer. The engineer optimizes screw size, entry point, and screw location in the pedicle. This unique 3D processing provides an opportunity to easily create trajectories in the virtual world for difficult revision cases, plan inout-in trajectories for narrow pedicles commonly seen in the thoracic region of the spine, and plan optimal endosteal contact in osteoporosis patients. The pre-surgical plan is reviewed by the surgeon via the desktop link described previously where a 3D representation of the vertebrae and surgical plan is present. Software such as SurgiCase could easily be adapted for this purpose. Once the surgical plan is approved by the surgeon, the Mighty Oak Engineering team designs a custom guide for each level using its patent-pending IP. Using the surgical plan approved by the surgeon, a custom, patient-matched guide is built around the chosen pedicle trajectories. A traditional CAD program is used to build the guide consisting of specific, patient-matched contact points and features that allow the guide to avoid troublesome soft tissue areas. FIREFLY guides are manufactured by additive SLA manufacturing from a biocompatible, autoclavable photoresin. The guides can be sterile-packed and sent to the hospital or can be shipped non-sterile and autoclaved immediately prior to surgery. For each level, there are at least two inserts and two fixation screws to
maximize controlled contact with patient-matched surfaces. The use of FIREFLY Technology is described as follows: Following the general exposure of the spine and soft tissue removal, the FIREFLY guides are placed onto the vertebrae manually to find the best fit at each level. Once the proper location is found, the fixation screws are used to attach the guide to the specific vertebra. This allows the guide to be hands-free after placement and provides free use of both hands by the surgeon for other tasks. After fixation to the vertebrae, a series of inserts interact with the guides and aid in the cannulation and tapping of the pedicle. In the lumbar spine, the fixation screws are inserted into the inferior facet complex and are directed divergently away from the spinal canal; while in the thoracic spine, the fixation screws are inserted into the transverse process. Each FIREFLY guide comes with a series of inserts that interact with the surgical instruments used to place pedicle screws. These inserts have holes that come in a variety of difference tool diameters (1/8 inch, 3.5 mm, 4.5, mm 5.5 mm, etc) These inserts are used with drill bits, taps, etc. that aid in the creation of the correct trajectory for the placement of pedicle screws. These inserts are also patient matched on their distal end. This feature provides a check that the guide is in the proper location. These inserts can be inserted prior to fixation to help medially locate the guide. Figure 4: Fixation of FIREFLY guides (inserts already present) Figure 5: Guides and Inserts for two level spinal fusion (L4 and L5)
For the thoracolumbar spine, the first insert would be for a small diameter drill bit or awl. The insert is placed into the guide sleeve, and drilling or awl advancement through the pedicle is commenced. The drilling inserts are removed and replaced with the appropriately sized tap insert corresponding to the chosen pedicle screw diameter (as determined in the pre-surgical plan). In the lumbar spine, the insert sizes are typically 4.5 or 5.5 mm. As development continues and production pieces are finalized, a dedicated FIREFLY instrument set would be created. The taps and drill bits in the set would have stops located on their shafts at a defined distance from the tip, so that depth control can be provided. Following tapping, the selected trajectories from the pre-surgical plan are in place, and the pedicle screws are ready to be placed. FIREFLY guides in the lumbar and lower thoracic spine are designed with a break-away feature that allows the surgeon to place screws without removing the guide, and, therefore, the guide does not interrupt the normal flow of the surgical procedure. With smaller tulip diameters in the upper thoracic region, the pedicle screw can be placed directly through the guide. Figure 6: Drilling of pedicle in sawbones model (left) and cadaveric specimen (right) FIREFLY Trials Figure 7: Tapping of pedicle in cadaveric specimen (left) and Sawbones model (right) FIREFLY Technology has been tested in multiple cadaveric specimens and two live patient trials. In all cases where fluoroscopy was used, there were zero inappropriately placed screws. Lumbar and thoracic cadaveric trials commenced in early 2011, and additional cadaveric quantitative validation analyses are currently underway. Fourteen screws have been placed in the lumbar spine using FIREFLY Technology in live patient trials, and the trajectories were exactly as planned. In the lumbar spine, guides have been designed and manufactured for L1 through S1 in cadaveric specimens and L2 through S1 for live patients. Thoracic guides have been designed and manufactured for levels T1 through T12 for cadaveric specimens only. A sample lumbar and thoracic cadaveric test and resulting CT scan is depicted below.
Figure 8: FIREFLY Cadaveric Trials in Lumbar and Thoracic Specimens FIREFLY has been used in two live patient trials. The first trial was a female patient presenting with a slight scoliosis and moderate stenosis. Two levels (L4 and L5) in the fusion surgery were instrumented using FIREFLY guides. The guides were placed on the patient s anatomy, and inserts corresponding to a powered drill and 5.5 tap were used to cannulate and prepare the pedicle for screw insertion. Following guided cannulation two 6.5x40 mm screws were inserted into L4 and L5. The second trial was a male patient presenting with fairly severe scoliosis. Five levels (L2-S1) were instrumented using FIREFLY Technology. Inserts corresponding to a powered drill and the appropriate tap for the pedicle screw to be used at each level were used to guide the instrumentation for pedicle cannulation. Following tapping, two 4.5x55 mm screws were placed into L2 and eight 6.5x50 mm screws were placed into the remaining 4 levels. Photographs and 2D fluoroscopy images from both surgeries are provided.
Figure 9: Patient One Instrumented Using FIREFLY Technology In the figures above and below, three photographic images are provided demonstrating the use of FIREFLY technology. From left to right, the guide is placed on the vertebra, fixated to the boney anatomy, and then drilling of the pedicle commences. In the 2D radiographic images provided, the outline of the FIREFLY guide can be seen on the levels being instrumented with the fixation screws also being visible. These images also show evidence of the guides providing the proper orientation of the drill bit and tap as these tools are advanced through the pedicle and into the vertebral body.
Figure 11: Patient Two Instrumented Using FIREFLY Technology Summary With today s pressures on cost and uncertain reimbursement policies, FIREFLY Technology is an important step in the right direction as a disposable, patient-specific guide that competes with the current capital intensive navigation technologies. It has significant clinical advantages in terms of reduced radiation exposure and risk of contamination. But more importantly, by offering the same accuracy at a fraction of the price, hospitals and patients worldwide can have access to a cutting-edge technology that reduces the risk of misplaced pedicle screws. Health care economics always has a huge impact on which medical device technologies will become both widely available and commercially successful. FIREFLY Technology has such an affordable price point, and addresses such a critical issue in spine surgery, that it has the potential to be the first navigation system accessible to all spine surgeons both within the U.S. and internationally.