Patent Application
20130158608
The invention generally relates to orthopedic implants, and more particularly to a plate and cannulated transfixation screw system for fixation of bones across a joint in a human hand.
Fractured or broken bones are often repaired by holding bone fragments together to achieve fusion. Also, rheumatoid arthritis, a chronic autoimmune disease, often causes destruction of joints, which requires reconstruction by fusion of bones across a joint. In a human finger, three bones are separated by two joints, called interphalangeal (IP) joints. The joint near the end of the finger is called a distal interphalangeal (DIP) joint and the joint near the hand is called a proximal interphalangeal (PIP) joint. If, for example, a bone across a DIP joint or a PIP joint is fractured, the bone fragments may be held together by an implant device such as, for example, a Kirschner wire (K-wire), a tension band wire, or a compression screw. A K-wire is a thin, rigid wire that is used to stabilize bone fragments. A K-wire can be drilled through a bone and through a joint to hold the fragments in place. A disadvantage of a K-wire is that it generally lacks structural rigidity. Consequently, bones fused across a joint with a K-wire often do not achieve a necessary degree of fusion. More importantly, a K-wire does not generally allow bones across a joint to be fused together in a configuration that provides versatility and improved usage.
A tension band wire uses tensile force to compress and hold bone fragments together. Since a tension band wire lacks structural rigidity, it does not allow bones across a joint to be fused in a configuration that provides versatility and improved usage.
Although compression screws provide the necessary degree of fusion, they typically limit the angle at which bones across a joint may be fused. For example, bones across a PIP joint of a finger preferably should be fused at an angle between 20 and 50 degrees for improved quality of life. In order to fuse bones within the desired range, a compression screw must be placed through the shaft of a bone, which may cause the screw to break out through the dorsal surface. Fixation plate and screw systems have been used to repair fractured bones across a joint. A fixation plate is typically placed upon bones across a joint, and the plate is thereafter secured to the bones by a plurality of attachment screws. While existing fixation plate and screw systems generally achieve the necessary degree of fusion, these systems typically do not allow bones across a joint to be fused in a configuration that provides improved quality of life.
Embodiments of the invention provide systems and methods which allow bones across a joint to be fused at a functional angle and provides for an improved quality of usage while also providing sufficient degree of fusion. Embodiments may include a transfixation screw having an elongate hollow body, which is configured to be inserted through a locking screw hole of a plate and extend through a first bone across a joint and into a second bone. Also, embodiments may include a fixation plate having a locking screw hole which will allow for an angle that is ideal for a specific joint.
In one embodiment a screw includes an elongate hollow body having openings at first and second ends and having a tip at the first end and a head at the second end. The body is configured to extend through a first bone across a joint and into a second bone. A first thread originates from the tip and extends proximate from the tip. The first thread has a first pitch. A second thread is disposed proximate to the head and extends distally from the head. The second thread has a second pitch. The second thread is preferably separated from the first thread by an unthreaded section of the body. A locking thread is disposed on the head proximal to the second thread. The locking thread has a third pitch.
In another embodiment a fixation plate includes a body having a longitudinal axis and first and second ends. The plate includes a locking screw aperture disposed proximate to the first end. The aperture includes an inner surface having an upper countersink and a threaded portion below the upper countersink. The threaded portion has double helical threads configured to engage the screw. The aperture has a central axis oriented at an angle between 20 to 50 degrees relative to the longitudinal axis of the body. One or more additional apertures are disposed within the body to accommodate additional attachment screws.
In yet another embodiment of the invention, a system comprises the fixation plate and the screw which transfixes across a joint to be fused. The fixation plate is configured to be placed upon a first bone proximate a joint. The fixation plate may be contoured proximate the first end to match the contour of the first bone. The screw has a first recessed region proximate to the tip to form a first cutting flute and a second recessed region proximate to the head to form a second cutting flute. The first thread has a different pitch than the second thread. The locking thread and the second thread may be separated or may be connected.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention.
The detailed description set forth below, in connection with the appended drawings, is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of the various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well-known structures and components are shown in block diagram form in order to avoid obscuring such concepts.
The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment or aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or aspects. In addition, references to “an,” “one,” “other,” or “various” embodiments or aspects should not be construed as limiting since various aspects of the disclosed embodiments may be used interchangeably within other embodiments.
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Fixation plate 100 includes one or more attachment screw holes 170, 174 and 178. Attachment screw holes 170, 174 and 178 are configured to receive attachment screws (see screws 182, 186, and 190 in
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Following drilling or placement of a K-wire or other well known guidance techniques, transfixation screw 300 is then inserted through screw hole 132 and rotated through the first bone 404, across the PIP joint and into the second bone 408. Nearing completion of the installation of screw 300, thread 328 engages bone 408 while thread 332 engages bone 404. Thus, it will be appreciated by those skilled in the art that due to the differing pitch of first and second threads, 328 and 332, respectively, transfixation screw 300 functions as a compression-type screw, firmly attaching or fixating first and second bones across joint 412. As the surgeon tightens screw 300 within the last bit of rotation within hole 132, locking threads 348 engage threads 156/162, deforming one relative to the other and locking screw 300 in place relative to plate 100 transfixing the first bone 404 relative to the second bone 408 across the PIP joint 412.
As discussed before, the trajectory of transfixation screw 300 is preliminarily determined by the angular orientation of central axis 152 relative to longitudinal axis 108 of between 20 and 50 degrees during the manufacture of plate 100. In addition, as noted above the present invention provides the surgeon with the flexibility of adjusting the orientation of screw 300 about the entire central axis 152 at an angle of between 0 and 18 degrees between the axis of the screw 300 and the central axis 152. Thus, within a plane parallel of the views shown in
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Fixation plate 500 includes a plurality of attachment screw holes 524A-524F arranged in two rows along axes 536 and 540. Attachment screw holes 524C and 524D are interconnected via bridge 544, and attachment screw holes 524E and 524F are interconnected via bridge 548. By arranging the first and second group of attachment screw holes in two rows and interconnecting pairs of attachment screw holes via respective bridges, a grid configuration is formed. Depending on the size of a bone upon which fixation plate 500 is intended to be placed, the length of fixation plate 500 may be shortened by, for example, sawing or snipping off along line 552. Consequently, the number of attachment screw holes may be reduced depending on the size of a bone upon which fixation plate 500 is placed. Attachment screw holes 524A-524E may be locking or non-locking type. Plate 500 may include more attachment screw holes and more rows, thereby increasing the size of the grid of the plate 500 based on the teachings of the present invention.
Locking screw hole 532 may have a locking mechanism comprising a pair of threads arranged in a double helix configuration as discussed above with respect to locking screw hole 132 as shown in
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
