TITLE: METHOD AND SYSTEM FOR INTRAOPERATIVELY MEASURING
AND TRIMMING THE LENGTH OF FRACTURE FIXATION DEVICES.
INVENTOR: Shawn T. Huxel
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims the priority of provisional U.S. application serial numer 60/644,279 filed on January 14, 2005 and entitled "Method and System for Intraoperatively Measuring and Trimming the Length of Fracture Fixation Devices" by Shawn T. Huxel, the entire contents and substance of which are hereby incorporated in total by reference.
BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a method of intraoperatively gauging and trimming a fracture fixation screw to a desired length, and a gauging system therefore.
2. Brief Description of the Related Art
When a patient suffers an injury in which a bone is fractured or fragmented, the injury often must be repaired by securing the bone fragments together with internal fixation devices such as pins and/or screws. The fixation devices may be removed after the bone fragments have fused back together, or alternatively they may be left in place permanently or until they are ultimately absorbed into the patient's body if the fixation devices are made of a bioabsorbable material.
A surgeon may choose to use either pins or screws or a combination of both to hold the bone fragments together, depending on the size of the fragments and the fixation strength necessary or desired to hold the fragments together. For example, screws provide greater fixation strength and greater pullout strength than pins, but pins may be more useful for securing smaller bone fragments in which the generally wider diameters of screws may risk further damaging the fragments.
When fixation screws are to be used, it is typically necessary for the surgeon to have all sizes (diameter and length) of the fixation screws on hand at the time of the surgery. This usually requires that the surgeon have available for each surgery a complete set of screws containing screws of every diameter and every length which may be encountered in any fracture fixation procedure. Of course, it is very costly and cumbersome to provide such a large number fixation elements for each procedure, both for the manufacturer to produce the fixation screws in many different lengths and diameters, and for the surgeon or medical facility to purchase and store all of the fixation screws in every available length and diameter.
During the surgery, the surgeon selects the length and diameter of each screw to be installed based upon the size of the bone fragments to be secured together and the depth of the hole drilled for the fixation element. The length of the screw is selected to accommodate the depth to which the fixation screw is to be inserted, and so that the head of the screw after installation does not sit above the bone surface, as this will interfere with proper healing, among other undesirable effects.
In the event that fixation pins are to be used, it may also be necessary for the surgeon to have pins in a variety of different diameters available in the operating room during surgery.
Given the superior fixation strength achievable by using fixation screws for bone fracture fixation, it would be desirable if the lengths of fixation screws could be revised instraoperatively without the necessity for a complex arrangement of cooperating parts in the fixation device.
Other types of fixation devices in which the length may be adjusted intraoperatively are disclosed in U.S. Pat. No. 6,780,115 to Schmieding et al. Schmieding discloses a method and device for intraoperative cutting and sharpening a screw. The cutting and sharpening device and method disclosed includes jig that require the indirect translation of the depth of the predrilled hole from a secondary source such as a depth gage. Markings on the jig correspond to incremental lengths called out from the secondary measurement device. This method and jig adds additional steps and instrumentation to the procedure, allowing for potential error in translating the depth to the jig.
It is also desirable to provide a gauging means which directly translates the depth of the predrilled hole to the length of the fixation device, in order for the fixation device to be trimmed to length.
SUMMARY OF THE INVENTION
The present invention addresses the needs of the prior art by providing a method and system for intraoperatively revising fixation screws used for bone fracture fixation. Specifically, the invention encompasses a carrier for intraoperatively gauging the depth of a predrilled hole and directly translating that depth to the length of the device, then cutting the device at the demarcation indicated on the carrier, a method for performing the revision technique, and a method for performing a bone fracture fixation procedure. The fracture fixation screws are preferably bioabsorbable screws having a head. The shaft may be fully threaded or partially threaded. The shaft may be solid or fully cannulated. Preferably, the screws are provided in a standard length but in a variety of diameters.
The length of the screws may be adjusted during a fracture fixation operation with the aid of a gauge that includes a device carrier which is slidable within the gauge that supports the screw to be trimmed adjacent to the demarcation point on the gauge. A tip finisher may be incorporated into the cutting instrument or may be provided separately, for reforming a chamfer at the distal tip of the trimmed fixation screw.
A preferred method according to the present invention includes selecting an appropriately sized fixation screw to be installed; drilling a hole across the fracture site using an appropriately sized drill bit; forming a countersunk bore across the drilled hole; mounting the appropriately sized (diameter) screw on the device carrier, inserting a gauge and carrier into the drilled hole, advancing the carrier to the extent of the predrilled hole, trimming the fixation device at the demarcation point on the gauge, tapping either the entire length of the drilled hole or only the distal fragment thereof when the lag technique is to be performed; inserting the distal end of the trimmed fixation screw into the finisher; turning the screw until a chamfer has been re-formed at the distal end of the screw; aligning the revised screw with the drilled hole; engaging the revised screw with an appropriately sized driver; and advancing the screw into the drilled hole using the driver until the head of the screw is flush or countersunk with the surface of the bone.
Other features and advantages of the present invention will become apparent from the following description of the invention, which refers to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an elevational view of a first preferred embodiment of a bone fracture fixation screw usable in connection with the present invention.
FIG. IA is an elevational view of the proximal head of a first preferred embodiment of a bone fracture fixation screw usable in connection with the present invention.
FIG. IB is a hidden line elevational view of the proximal head of a first preferred embodiment of a bone fracture fixation screw usable in connection with the present invention.
FIG. 2 is an elevational view of a first preferred embodiment of a bone fracture fixation screw depth and length gauge in connection with the present invention. FIG. 2A is a close up elevational view of the distal end of a first preferred embodiment of a bone fracture fixation screw depth and length gauge in connection with the present invention.
FIG. 2B is a plan view of a first preferred embodiment of a bone fracture fixation screw depth and length gauge in connection with the present invention.
FIG. 2B is a close up plan view of the distal end of a first preferred embodiment of a bone fracture fixation screw depth and length gauge in connection with the present invention.
FIG. 3 is an elevational view of a first preferred embodiment of a bone fracture fixation screw depth and length gauge with a first preferred embodiment of a bone fracture fixation screw mounted to the proximal section of the gauge in connection with the present invention.
FIG. 3 A is a close up proximal elevational view of a first preferred embodiment of a bone fracture fixation screw depth and length gauge with a first preferred embodiment of a bone fracture fixation screw mounted to the proximal section of the gauge in connection with the present invention.
FIG. 3B is an plan view of a first preferred embodiment of a bone fracture fixation screw depth and length gauge with a first preferred embodiment of a bone fracture fixation screw mounted to the proximal section of the gauge in connection with the present invention.
FIG. 3C is a close up proximal plan view of a first preferred embodiment of a bone fracture fixation screw depth and length gauge with a first preferred embodiment of a bone fracture fixation screw mounted to the proximal section of the gauge in connection with the present invention.
FIG. 4 is an elevational view of a first preferred embodiment of a bone fracture fixation screw depth and length gauge with a first preferred embodiment of a bone fracture fixation screw mounted to the proximal section of the gauge in connection with the present invention showing advancement of the gauge probe distally.
FIG. 4A is a plan view of a first preferred embodiment of a bone fracture fixation screw depth and length gauge with a first preferred embodiment of a bone fracture fixation screw mounted to the proximal section of the gauge in connection with the present invention showing advancement of the gauge probe distally.
FIG. 4B is a close up plan view of a first preferred embodiment of a bone fracture fixation screw depth and length gauge with a first preferred embodiment of a bone fracture fixation screw mounted to the proximal section of the gauge in connection with the present invention showing advancement of the gauge probe distally. FIG. 4C is an elevational view of a first preferred embodiment of a bone fracture fixation screw depth and length gauge with a first preferred embodiment of a bone fracture fixation screw mounted to the proximal section of the gauge in connection with the present invention showing advancement of the gauge probe distally and showing a representative cutter and cut location for the present invention.
FIG. 5 is an elevational view of a first preferred embodiment of a bone fracture fixation screw depth and length gauge with a first preferred embodiment of a bone fracture fixation screw mounted to the proximal section of the gauge in connection with the present invention showing advancement of the gauge probe distally after cutting the screw at the proper location.
FIG. 5A is an elevational view of a first preferred embodiment of a bone fracture fixation screw depth and length gauge with a first preferred embodiment of a bone fracture fixation screw after cutting the screw at the proper location and removal of the cutter.
FIG. 5B is a close-up plan view of a first preferred embodiment of a bone fracture fixation screw depth and length gauge with a first preferred embodiment of a bone fracture fixation screw after cutting the screw at the proper location and removal of the cutter.
FIG. 5C is a plan view of a first preferred embodiment of a bone fracture fixation screw depth and length gauge with a first preferred embodiment of a bone fracture fixation screw after cutting the screw at the proper location and removal of the cutter.
FIG. 5D is a close-up plan view of a first preferred embodiment of a bone fracture fixation screw depth and length gauge with a first preferred embodiment of a bone fracture fixation screw mounted to the proximal section of the gauge in connection with the present invention.
FIG. 6 is an elevational view of a first preferred embodiment of a bone fracture fixation screw usable in connection with the present invention after removing the screw from the carrier.
FIG. 6A is a plan view of a first preferred embodiment of a bone fracture fixation screw usable in connection with the present invention after removing the screw from the carrier.
FIG. 6B is a plan view of a first preferred embodiment of a bone fracture fixation screw usable in connection with the present invention after removing the screw from the carrier and finishing the distal tip of the screw.
FIG. 7 is an elevational view of a first preferred embodiment of a bone fracture fixation screw hex driver usable in connection with the present invention. FIG. 7 A is a close-up elevational view of the distal end of a first preferred embodiment of a bone fracture fixation screw hex driver usable in connection with the present invention.
FIG. 8 is an elevational view of a first preferred embodiment of the bone fracture fixation screw hex driver approaching a screw usable in connection with the present invention.
FIG. 8A is a close-up elevational view of the distal end of a first preferred embodiment of the bone fracture fixation screw hex driver approaching the proximal hex head of a screw usable in connection with the present invention.
FIG. 8B is a close-up elevational view of a first preferred embodiment of the bone fracture fixation screw hex driver fully seated and driving a screw usable in connection with the present invention.
FIG. 8C is a close-up elevational view of a first preferred embodiment of the bone fracture fixation screw hex driver after shearing hex from proximal portion of a screw usable in connection with the present invention.
FIG. 9 is an elevational view of a first preferred embodiment of a bone fracture fixation screw usable in connection with the present invention after shearing of the driving means.
FIG. 9A is a close-up elevational view of the proximal head of a first preferred embodiment of a bone fracture fixation screw usable in connection with the present invention after shearing of the driving means.
FIG. 9B is a close-up sectional view of the proximal head of a first preferred embodiment of a bone fracture fixation screw usable in connection with the present invention after shearing of the driving means.
FIG. 10 is an elevational view of a first preferred embodiment of a bone fracture fixation screw driver usable in connection with the present invention.
FIG. 1OA is a close-up elevational view of the distal end of a first preferred embodiment of a bone fracture fixation screw driver usable in connection with the present invention.
FIG. 1OB is an elevational view of a first preferred embodiment of the bone fracture fixation screw driver advancing toward a screw usable in connection with the present invention after shearing the hex driving means. FIG. 1OC is a close-up elevational view of the distal end a first preferred embodiment of the bone fracture fixation screw driver fully seated and driving a screw usable in connection with the present invention.
FIG. 1OD is a close-up elevational view of a first preferred embodiment of the bone fracture fixation screw driver after driving and disengaging from a screw usable in connection with the present invention.
FIG. 11 is a plan sectional view of a first preferred embodiment of a bone fracture fixation screw usable in connection with the present invention.
FIG. 1 IA is a hidden line sectional view of a second preferred embodiment of a bone fracture fixation screw usable in connection with the present invention showing full cannulation of the screw.
FIG. 12 is an elevational view of a third preferred embodiment of a bone fracture fixation screw usable in connection with the present invention.
FIG. 12A is a plan view of a third preferred embodiment of a bone fracture fixation screw usable in connection with the present invention.
FIG. 12B is a plan view of a third preferred embodiment of a bone fracture fixation screw usable in connection with the present invention.
FIG. 12C is a sectional view of a fourth preferred embodiment of a bone fracture fixation screw usable in connection with the present invention showing full cannulation of the screw.
FIG. 13 is an elevational view of a first preferred embodiment of a bone fracture fixation device finisher usable in connection with the present invention.
FIG. 13A is a plan view of a first preferred embodiment of a bone fracture fixation device finisher usable in connection with the present invention.
FIG. 14 is a plan view of a first preferred embodiment of a drill bit usable in connection with the present invention.
FIG. 15 is a plan view of a first preferred embodiment of a driver handle usable in connection with the present invention.
FIG. 16 is a plan view of a first preferred embodiment of a tapping die usable in connection with the present invention.
FIG. 17 is a plan view of a first preferred embodiment of a countersink die usable in connection with the present invention.
FIG. 18 is a plan view of a second preferred embodiment of a driver handle usable in connection with the present invention. FIG. 19A is a cross-sectional view of a fractured bone to be repaired in connection with the present invention.
FIG. 19B is a sketch of the drilling across a fractured bone to be repaired in connection with the present invention.
FIG. 19C shows the drill through a fractured bone to be repaired in connection with the present invention.
FIG. 19D is a sketch of the process of creating the countersink in connection with the present invention.
FIGS. 2OA and 2OB are representations of the method of gauging the depth of the drilled hole through a fractured bone to be repaired in connection with the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS During the course of this description like numbers will be used to identify like elements according to the different views which illustrate the invention.
A first preferred embodiment of a fracture fixation screw usable in connection with the present invention is shown in FIG. 1. As shown, fixation screw 10 includes proximal head 12, having at least one external slot 14, body 15 having external threads 16 and distal tip 18. A hub 20 having a cavity 22 therein is integrally attached to proximal head 12, at head face 24, intersecting edge 23 is shown as the intersection of hub 20 and screw 10. Referring to FIG IA, the hub 20 has a proximal surface 25. In FIG IB, the cross-section of screw 10 is shown. Hub cavity 22 transitions to head 12 through zone 26 and terminates in head cavity 28 partially into head 12. It is preferred that screw 10 be provided a length sufficient to cover all surgical indications for the device. For example, screw 10 can be provided at a length between 30mm and 60mm, depending upon the diameter which is generally between 1.5mm and 6.5mm.
A first preferred embodiment of a depth gage assembly usable in connection with the present invention is shown in FIG. 2. As shown, depth gage assembly 30 includes slidable member 40 having markings 46 on its upper surface; slidable member 40 is inserted into body 50 having distal end 52, distal tip 54 and proximal tip 58. As seen in FIG 2 A, slidable member 40 has proximal protrusion 42 having a rod 44, further defining the proximal extents and indentation 48 on at least one lateral surface. FIG 2B shows distal tip 41 of slide 40 and proximal section 56 of body 50, having proximal tip 58. FIG 2C shows a close-up plan view of the proximal ends of slidable member 40 and body 50. FIGS. 3 thru 3 C illustrate the method of mounting screw 10 to depth gage 30. As shown, screw 10 is mounted to slidable member 40 by placing cavity 22 over proximal slide protrusion 42, further aligned with the male-female match of head cavity 28 and proximal slide rod 44. Screw 10 is inserted onto slide 40 until face 25 mates with face 45.
FIGS. 4 thru 4B illustrate the method of translating depth 'd' of a predrilled hole in bone to the desired length of the screw 10. After the surgeon drills a hole across the fracture, it is necessary to determine the length of bone fastener 10 required for surgical fixation. The surgeon places the screw 10 on the proximal slide protrusion 42 and inserts depth gage 30 slide distal tip 41 into the predrilled bone hole, advancing the tip 41 to the extent of the predrilled hole, gauging the depth 'd' of the predrilled hole. The depth 'd' is directly translated to the screw 10 as the screw 10 moves coincidentally with slide 40. Distal tip 54 rests against the near cortical surface where the screw head 12 would appose. Figure 4C shows representative cutter 200 of the present invention that is used to cut screw 10 at the location indicated to provide a screw 10 that would be used to affix bone to a depth 'd'. In the method of cutting, surface 420 of cutter 200 is mated with proximal tip 58 of body 50. Cutter 200, upon placement of surface 420 against distal tip 58 and actuation, cuts screw 10 to the predetermined length. The distance 'f is representative of the offset distance from face 420 to shearing surface of cutter 200. The predrilled hole is then tapped by the surgeon to match the threads of the appropriate screw 10.
FIGS. 5 thru 5D show the result of cutting screw 10 using the method described above. After cutting surface 60 of screw 10 is created that is substantially perpendicular to the axis of screw 10. In FIG 5D the distance 't' is represented as the difference between surface 60 and distal tip 58. The distance 'd' is shown on the cut screw 10, equal to the distal travel of proximal slide protrusion 41 shown in FIG 5C.
FIGS. 6 and 6 A show screw 10 after being cut and removed from depth gage 30. Surface 60 is created substantially perpendicular to the axis of screw 10. It is necessary to recover the lost chamfer from the original screw 10. A tool is provided that recreates the chamfer 62 at the distal tip 60 of screw 10 shown in FIG 6B and is described in more detail later in this specification.
A first preferred embodiment of a hex driver 70 usable in connection with the present invention is shown in FIG. 7. Hex driver 70 has proximal section 72 and distal end 74, spanned by shaft 76. Proximal section 72 has a mating face 78 that mates with instrumentation found in the operating room. Cannulation 80 continues from proximal section 72 through shaft 76 through distal end 74. FIG 7A shows a close-up of distal end 74 of hex driver 70. Distal end 74 has at least one radial face 82, preferably (6) faces, and internal axial face 84, formed substantially perpendicular to face 82. Distal surface 86 defines the distal extent of hex head 74.
FIGS. 8 thru 8C illustrates the preferred method of driving screw 10 using hex driver 70 acting on hex head 20. FIG 8 shows hex driver 70 located coaxially with screw 10, just proximal to hex head 20. FIG 8 A shows the advancement of hex driver 70 toward hex head 20 up until face 25 of hex head 20 mates with face 84 of hex driver 74. As FIG 8B shows, the surgeon then rotates hex shaft 70, driving screw 10 into the predrilled, pretapped hole across the fracture. Once the screw 10 is seated in the pretapped hole and head 12 apposes the upper surface of the bone, screw 10 stops turning and torque increases. At a predetermined torque that is a function of the mechanical properties of the material used to fabricate screw 10 and the cross-sectional area of the interface between hub 20 and head 12 of screw 10, the hex head 20 shears away from the head 12, leaving shear surface 88 that is substantially parallel to surface 24 of screw 10 shown by FIG 8C. Cavity 28 is shown in head 12. The hex head 20 is captured in the distal end 74 of hex driver 70 to be discarded.
FIGS. 9 thru 9B show screw 10 after hex hub 20 has been sheared as described above. The cut screw 10 has at least one external slot 14 on the outside of head 12. Cavity 28 is shown at least partially into head 12. Shear surface 88 is shown substantially parallel to surface 24.
A first preferred embodiment of a screw driver 90 usable in connection with the present invention is shown in FIGS.. 10 & 1OA. Screw driver 90 has proximal section 92 and distal end 94, spanned by shaft 96. Proximal section 92 has a mating face 98 that mates with instrumentation found in the operating room. Cannulation 100 continues from proximal section 92 through shaft 96 through distal end 94. FIG 1OA shows a close-up of distal end 94 of screw driver 90. Distal end 94 has at least two distal ears 104, and internal axial face 108, formed substantially perpendicular to face 102. Distal surface 106 defines the distal extent of screw head 94. Each ear 104 has two radial faces 105.
FIGS. 1OB thru 1OD illustrate the preferred method of driving screw 10 using screw driver 90 acting on screw head 12. FIG 1OB shows screw driver 90 located coaxially with screw 10, just proximal to screw head 12. FIG 1OB also shows the advancement of screw driver 90 toward screw head 12 up until face 24 of screw head 12 mates with face 102 of screw driver 70. Ear 104 mates with slot 14 of screw head 12. As FIG 1OC shows, the surgeon then rotates screw shaft 90, driving (or removing) screw 10 into the predrilled, pretapped hole across the fracture. Once the screw 10 is seated in the pretapped hole and head 12 apposes the upper surface of the bone, screw 10 stops turning and torque increases. Screw driver 90 can be used to adjust the screw 10 as needed.
FIG 11 shows a cross-sectional view of a preferred embodiment of screw 10 of the present invention. Cavity. 28 intrudes partially into head 12 and shaft 15 of the screw 10 is substantially solid with external threads 16 substantially along its entire length.
FIG HA shows a cross-sectional view of a second preferred embodiment of screw 110 of the present invention. Screw 110 has distal tip 60 at the end of shaft 115 that leads into head 112 having slots 114 and surface 124 connecting to hex head 120 having cavity 122. This embodiment includes cannulation 128 that continues from distal tip 160 through the shaft 115 and the head 112.
FIGS. 12 and 12A show yet another preferred embodiment of screw 210 of the present invention. Screw 210 has distal tip 218 at the end of shaft 215 that leads into head 212 having slots 214 and surface 224 connecting to hex head 220 having cavity 222. Shaft 215 has an unthreaded portion 217 and a threaded portion 216. As shown by the cross- sectional view 12B, this embodiment has cavity 228 within head 212.
FIGS. 12B shows yet another preferred embodiment of screw 510 of the present invention. Screw 510 has distal tip 518 at the end of shaft 515 that leads into head 512 having slots 514 and surface 524 connecting to hex head 520 having cavity 522. Shaft 515 has an unthreaded portion 517 and a threaded portion 516. As shown, this embodiment includes cannulation 528 that continues from distal tip 518 through the shaft 515 and the head 512.
A first preferred embodiment of a finisher 500 usable in connection with the present invention is shown in FIGS. 13 and 13 A. As shown finisher 500 includes body 501 having an internal conical surface 503. Surface 503 has at least one finishing feature 502 running substantially parallel with surface 503. Finishing feature 502 has one rounded edge 504 and one sharpened edge 506. In a preferred embodiment, finisher 500 is intimately connected to cutter 200 of the present invention and shares axis 202 with cutter 200, but may also be a separate device. A method of finishing screw 10 after being cut by cutter 200 by rotating screw 10 in a clockwise direction while statically supporting finisher 500 is disclosed herein where cutting edge 506 acts on screw 10 to reform chamfer 62 on the edge of face 60.
A first preferred embodiment of a drill bit 600 usable in connection with the present invention is shown in FIG14. A first preferred embodiment of a driver handle 602 usable in connection with the present invention is shown in FIG 15. A first preferred embodiment of a tap bit 604 usable in connection with the present invention is shown in FIG 16. A first preferred embodiment of a countersink bit 606 usable in connection with the present invention is shown in FIG 17. Countersink bit 606 has a distal tip 608 shown at the end of distal body 610. At least one edge 612 is sharpened.
A second preferred embodiment of a driver handle 620 usable in connection with the present invention is shown in FIG 18.
FIG 19A shows a representation of fractured bone 700 treatable in connection with the present invention. Fractured bone 700 has a proximal cortical surface 702 and distal cortical surface 704. Cancellous bone 706 is traversed by fracture 708. FIGS. 19B and 19C show the use of drill 600 drilling through proximal cortical surface 702, across fracture 708 and through distal cortical surface 704. FIG 19D shows the use of countersink bit 606 after drilling across the fracture 708 to be repaired. Distal tip 608 is inserted into the drilled hole 710 until sharpened edge 612 contacts distal cortical surface 702. Countersink bit 606 is turned until a recess is cut out of proxima cortex 702 that mates with head 12 of the present invention.
A first preferred method of translating the depth 'd' of hole 710 is shown in FIGS. 2OA and 20B. The surgeon loads screw 10 onto depth gage proximal slide 40 as described previously. Depth guide 30 is inserted into hole 710 into tip 54 abuts with the bottom surface of countersink in proximal surface 702. The surgeon advances proximal slide 40 until nose 41 emerges from distal cortical surface 704. The surgeon then removes depth gage 30 from the patient and trims screw 10 as described previously.
Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. Therefore, the present invention is to be limited not by the specific disclosure herein, but only by the appended claims.