Patent Application
20190070009
The present invention relates to a device and system for surgical fixation of small bones, small bone fragments, and osteotomies and more particularly to compression screw having an elongated and slowly tapered threaded leading portion which is joined to a section that is free from threads and a threaded trailing portion and more sharply tapered head which has threads that continue from the threads of the leading portion.
Patients often suffer from late stage arthritis in phalangeal joints of the hands and feet, and this presents a variety of challenges for attending physicians. While current treatment protocols usually provide acceptable results, there is a likelihood of straight distal interphalangeal joint fusion which provides for sub-optimal outcomes. Research has shown that when a patient's distal interphalangeal joint is fused in a functional position, finger dexterity and grip strength improve over that of a patient with a straight fusion. Physicians can achieve angled fusions by using k-wire fixation, however, this immobilization protocol can fail, and lead to several complications and varied results. While the utilization of compression screws can provide reliable, strong repairs, it does not offer the additional benefit of function flexion which is provide by a properly angled and oriented implant fixation device, especially one, which provides the added benefit of compression across the joint during fusion.
Advantageous locations the use of the present invention is in the phalanges of the hand or foot. In each finger, there are three phalanges that are separated by two joints called the interphalangeal joints (IP joints). The proximal IP joint (PIP joint) is the one closest to the MCP joint. The other joint closest to the end of the finger is the distal IP joint (DIP joint). The thumb just has one IP joint. The joints are covered on the ends with articular cartilage. The foot has an analogous structure substituting the large toe for the thumb. It should be understood that there may be additional surgical techniques or locations in the body where the device of the present invention may be suitable for use.
The present invention solves the problems associated with performing a fusion technique or an osteotomy, in particular in the interphalangeal joints. The device of the invention is a compression screw having a shaft with a longitudinal axis along which there is a leading portion including a sharp spiked threaded tip, and an intermediate unthreaded portion, and a trailing threaded portion which joins the intermediate portion and the more sharply expanding or tapered head portion, which may include the same thread pitch, size and shape of the trailing shaft portion having a constant inner diameter and outer diameter. Alternatively, the trailing portion may have a lesser thread pitch compared to the tapered tip. It should be noted while that the trailing portion may be considered to be proximal to the leading portion relative to the screw itself, in use, the leading portion is intended to be implanted more proximally relative to the joint than the trailing portion. Moreover, the head portion is configured to provide for compression across the fusion joint, and to inhibit rotation of the compression device in the interphalangeal position as the leading portion is embedded into the intermediate phalange which is positioned at an angle with respect to the distal phalange. In addition, the present invention by provides for a percutaneous insertion in a surgical technique with an intramedullary implant designed to minimize soft tissue, cartilage and vascular damage upon insertion; and to facilitate early, active mobilization post-operative protocols for accelerated healing and earlier return to work.
The head at the trailing end includes a driving recess, such as a hexalobe, capable of being driven by a suitable driver into the opening.
The angle of the leading tapered area is from 4° to 12°, and preferably 5-8° which is defined at the intersection of a line at the outer surface of the inner diameter of the leading area and the central axis and the compression head has an angle which is similarly determined and is from 5° to 16°, but preferably is 9-14°, and is at least 2° greater than the taper of the leading end and extends for a distance longitudinally that is 25% to 75% of the distance of the leading taper. Ideally, the leading taper extends for from 25% to 50% of the length of the screw, and the intermediate portion extends of 25% to 50% of the length and the trailing portion of the shaft extends for 15% to 50% of the length of the screw and the head extends for 5% to 15% of the length of the screw, with the screw shaft nominally comprising ⅓ trailing portion, ⅓ intermediate portion and ⅓ leading portion+/−5-10% for each portion.
The spiked end can be driven into the intermediate phalange at an angle to create the position of functional flexion. The aggressive taper on the leading tip allows the screw to be used in facilitating angulation between two bone while still fitting into the bone, which the prior art screws do not accommodate. The driving surface 32 of the head has a hexalobe drive configuration, although any suitable driving configuration may be used. Other driving configurations that may be used include slotted, Pozidriv, Robertson, tri-wing, Torq-Set, SpannerHead, Triple Square and hex head.
The leading and trailing portions of the device includes a thread which is defined between the outer diameter and the inner diameter and can suitably include a right handed single start thread with a pitch of from 3-4, and preferably at 3+/−0.5 with a similar lead value. In the second embodiment the tip pitch is from 0.9 to 1.0 mm and preferably 0.95+/−0.02 mm, and the head pitch is from 0.70 to 0.85 mm, and preferably 0.75 mm The trailing section and following profiles of the threads together form an angle of 25° to 75° and preferably 30°+/−15°, and preferably +/−10°, and with a thread depth of 0.1 mm to 0.4 mm+/−0.02 mm, and optionally a thrust profile or a traditional bone screw buttress thread. There is a pitch differential between the threads of the conical section of the head and the spiked taper of the leading end of the screw, with the leading thread pitch being about 0.75 to 1.25, but in any case, from 1.2 to 1.5 times the pitch of the compression head, which is 0.5 to 1.0.
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Having thus described some embodiments of the invention, other variations and embodiments that do not depart from the spirit of the invention will become apparent to those skilled in the art. The scope of the present invention is thus not limited to any particular embodiment, but is instead set forth in the appended claims and the legal equivalents thereof. Unless expressly stated in the written description or claims, the steps of any method recited in the claims may be performed in any order capable of yielding the desired result.
| Number | Date | Country | |
|---|---|---|---|
| 62554133 | Sep 2017 | US |
