Distal Radius Shadow Fixation System with PEEK-OPTIMA (TM)

Reference #:

2007-051

Inventors/Contributors

Scott F. M. Duncan, M.D.

Description

The Shadow Fixation System allows open reduction and internal fixation of distal radius fractures utilizing plates made out of a unique material called PEEK. PEEK has been utilized in orthopedic implants such as suture anchors and most recently has been utilized for small bone plates in the wrist. The advantage of utilizing this system for distal radius fractures is that these frequently are intraarticular injuries with significant comminution along the metaphyseal region as well as the epiphyseal region and joint line. By having a fixation device that does not obscure the bone or joint line that one is trying to reduce, it may allow the surgeon to more accurately reduce and restore the patient's shattered anatomy. Utilizing this material, metallic screws can be placed through it that provide for secure fixation. Another unique feature of the Shadow System would be that the radiolucent material allows for implantation of radiopaque lines. These radiopaque lines could be placed around the rim of the plastic plate in order to provide an outline or shadow of where the hardware has been placed on the bone. However, more interestingly, is the fact that lines could be placed to outline what would be considered normal anatomical angles so that the plate actually serves as a radiographic template for restoration of anatomy. Please see the attached hand drawings. The construction of this plate, again, is made out of PEEK, which is a polyetherketone, hence PEEK. PEEK is an advanced biomaterial used in other medical implants. It has a very high strength to weight ratio. It has a high Young's modulus and a moderate tensile strength. The problem that is solved with making a distal radius plate out of PEEK is that it allows the surgeon to finally see the fracture that he or she is trying to fix. Current plating systems utilize either stainless steel or titanium, which on anterior to posterior views block the articular surface to some degree and metaphyseal regions. This makes it more challenging for the surgeon to try and reduce the fracture in an anatomic pattern. Furthermore, it can make it more difficult to assess bony healing in the followup radiographs. The other issue is that when screws are being placed into these metal plates, you cannot always see where the screws are going, but with a PEEK plate, the metallic screws would be easily visible as to their precise direction. Furthermore, by having the anatomic angles that need to be achieved for more exact fixation actually implanted as radiopaque markers within the plate, potentially better anatomic reductions could be performed by the surgeon, hopefully leading to better outcomes or at least fewer complications due to malreduction. The plate, as I envision it in design, is actually two different types of plates, one is a unibody construction type plate. This unibody plate would be similar to existing distal radius plates except that it would be made out of PEEK. It would have the radiopaque angles built into the plate showing a 22° angle for radial inclination, as well as potentially the side view showing the 10° volar tilt. The slotted hole could be made in a center-wise fashion as is currently done on most plates or could be made in proximal fashion to allow for the plate to better correct any translational reduction problems. The plate would have temporary K-wire fixation holes. The diaphyseal portion of the plate would have 2.7mm screws. The distal aspect of the plate would either have 1.8  2.0mm screws. There would be two styloid screws that would be divergent to hopefully provide for better grasping of a styloid fragment. The double row metaphyseal portion would have differentially angled screws. Ideally, these would be multiaxial screws that would allow for some degree of back angling on the most distal row to capture the lower part of the radiolunate fossa and radioscaphoid fossa bone and then would have a antegrade angulation on the second row to capture the dorsal aspect of the radiolunate fossa and radioscaphoid fossa bone. The second type of plate that is envisioned is a two-part plate that has a vaginating or sliding component where the distal component of the plate actually slides into the proximal component. This type of plate could be useful in two types of situations. One situation is a significantly shortened angulated or comminuted fracture in which the distal aspect of the plate could essentially be fixed to the bone distal to the fracture first. The proximal aspect of the sliding plate would then be secured to the diaphyseal bone through a special oval drill hole that would allow the screw to lock in at 2mm increments so that the surgeon could adjust the plate in 2mm increments. This same type of slotted hole is what I would envision for the previously discussed plate as well. These interdigitations allow the screw to lock into the plate and prevent the plate from sliding without committing the surgeon to that specific alignment. The fracture and limb could then be distracted, angulated, and the plate rotated in a radial to ulnar direction in order to help try and further reduce the fracture components. Once these were in a favorable position, the most proximal screw would then be tightened, potentially or the surgeon could then lock the sliding component by drilling through both parts of the plate and into bone. There would be small facets where the peak could be drilled into with a special type of drill and then a screw placed through this, thus again, locking the plate and preventing it from any further sliding. There would also be special tongs to utilize for this plate to allow for compression and/or distraction when needed. This plate could be very useful in performing osteotomies in that it would allow the osteotomy to be made and then essentially for the plate to be manipulated in both distraction methods and radial and ulnar inclination methods to improve the patient's alignment. The current status of the invention development is again, purely conceptual based on my own drawings and experience with PEEK materials. The other aspect of the plate that I envision would be that it would be highly polished or smooth on the surface to help facilitate soft tissue gliding, especially flexor tendons. Every effort would be made to try and minimize any potential irritation to the tendons and other soft tissues. This plate would need to be as low profile as possible out distally, this is probably less of a concern in the proximal portions where the sliding or invaginating part of the plate would be. The experiments that would need to be run would really be more materials testing type, just testing the pull out strength of the screws, load bearing capacity of the screws within the PEEK material given that there would be metal on plastic, and the ability and strength of the PEEK material itself in load bearing or holding a fracture. These would be relatively simple experiments to perform.

Patent Status

None