WO2022046901A1

WO2022046901A1 - Helical bone fixation device

Info

Publication number: WO2022046901A1
Application number: PCT/US2021/047545
Authority: WO
Inventors: Christopher P. Chiodo; Max MICHALSKI
Original assignee: The Brigham And Women's Hospital, Inc.
Priority date: 2020-08-27
Filing date: 2021-08-25
Publication date: 2022-03-03

Abstract

A helical bone fixation screw is provided. The bone fixation device can be an intramedullary fixation device that can be used for bone fracture or osteotomy stabilization Specifically, the device can be used to stabilize and/or compress two or more bone fragments or segments. The helical bone fixation screw has a plurality of threads with a leading end and a trailing end. The pitch between the plurality of threads is non-uniform and the bone fixation screw lacks a central longitudinally extending shaft about which the plurality of threads is disposed.

Description

HELICAL BONE FIXATION DEVICE

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional Application No. 63,071 ,103 filed on August 27, 2020 and is incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present application relates to a helical bone screw.

BACKGROUND

Surgical intervention with screw fixation for 5^th metatarsal base fractures has increased due to recent research and trials that show improved outcomes relative to non-surgical treatment. In obtaining optimal interference fit, however, the screws that are currently used for intra-medullary fixation of a fracture or osteotomy also obliterate the intra-medullary space including the internal blood supply of the bone. This may have a critical impact on healing. Even with surgical intervention, fractures of the base of the 5^th metatarsal frequently can result in delayed union and some proceed to non-union due to the tenuous nature of the local blood supply. The screw head of such bone screws is also frequently prominent, causing soft tissue irritation and pain. Specifically, the screw head can end up being positioned immediately adjacent to, or even within, the insertion of the peroneus brevis tendon. Additionally, the screw head has been shown to abut the metatarso-cuboid joint, causing significant joint erosion and arthritis.

These problems exist in anatomic regions outside the 5^th metatarsal. For instance, olecranon fractures and olecranon osteotomies are commonplace in orthopedics and nearly all require surgical fixation. By some reports, 20-40% of these patients require secondary surgeries to remove prominent irritating hardware.

SUMMARY

A bone fixation device comprising a helical screw is provided. The bone fixation device can be an intramedullary fixation device that can be used for bone fracture or osteotomy stabilization, for example. Specifically, the device can be used to stabilize and/or compress two or more bone fragments or segments. In an aspect, a bone fixation device is provided that comprises a helical screw with a plurality of threads having a leading end and a trailing end. The pitch between the plurality of threads is non-uniform. The bone fixation device lacks a central longitudinally extending shaft about which the plurality of threads is disposed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is side view of a bone fixation device according to an aspect of the present disclosure.

FIG. 2 is an end view of a trailing end of a helical screw of a bone fixation device according to an aspect of the present disclosure.

FIG. 3 is a side view of a bone fixation device according to an aspect of the present disclosure.

FIG. 4 is a side view of a bone fixation device according to an aspect of the present disclosure.

FIG. 5 is a side view of a prior art bone screw.

DETAILED DESCRIPTION

The present invention relates to bone/osseous fixation devices that can provide intra-medullary compression and fixation without obliterating the intraosseous canal and blood supply. Additionally, the devices have a limited extra- osseous surface to decrease surrounding soft tissue irritation.

As used herein with respect to a described element, the terms “a,” “an,” and “the” include at least one or more of the described element including combinations thereof unless otherwise indicated. Further, the terms “or” and “and” refer to “and/or” and combinations thereof unless otherwise indicated. By “substantially” is meant that the distance, shape, or configuration of the described element need not have the mathematically exact described distance, shape, or configuration of the described element but can have a distance, shape, or configuration that is recognizable by one skilled in the art as generally or approximately having the described distance, shape, or configuration of the described element. The terms “first,” “second,” etc. are only used to distinguish one element from another and are not used in a quantitative sense unless indicated otherwise. Thus, a “first” element described below could also be termed a “second” element. By "integral" or "integrated" is meant that the described components are fabricated as one piece or multiple pieces affixed during manufacturing or the described components are otherwise not separable using a normal amount of force without damaging the integrity (/.e. tearing) of either of the components. A normal amount of force is the amount of force a user would use to remove a component meant to be separated from another component without damaging either component. As used herein a “patient” includes a mammal such as a human being. All bone fixation devices as described herein are used for medical purposes and are therefore sterile. Although the drawings show certain elements of a bone fixation device in combination, it should be noted that such elements can be included in other embodiments or aspects illustrated in other drawings. In other words, each of the disclosed aspects and embodiments of the present disclosure may be considered individually or in combination with other aspects and embodiments of the disclosure.

As stated above, it has been shown that surgical fixation of 5^th metatarsal base fractures provides better outcome compared to non-operative treatment. However, surgical treatment provides certain challenges such as delayed healing, non-union, and hardware prominence. Further, it is important for the fracture site to receive a sufficient blood supply since the local vascular anatomy is a relative watershed region at the fracture site and is dependent upon both intra- and extra- osseous blood supply. Further as stated above, the most commonly used fixation devices for fifth metatarsal fractures are intramedullary screws. Screws, however, achieve fixation through an interference fit within the intramedullary canal which causes permanent disruption of the intra-medullary blood supply. Additionally, most of these screws use a larger diameter screw head to achieve compression of the osseous fragments. The head is larger than the diameter of the shaft of the screw to provide compression through pressure at the insertion point. The large head can irritate the adjacent bone and the local soft tissues, including the peroneus brevis tendon insertion. Alternatively, plates can be used both in the primary fixation setting or during revision of a non-union. However, plates require more extensive dissection with further stripping of the extra-osseous blood supply and much more soft tissue irritation. These problems apply not only to the 5^th metatarsal base but to other bones, such as the olecranon in the elbow and the scaphoid bone in the wrist. Given these shortcomings, there is a need for a bone fixation device that does not obliterate the intra-osseous canal and does not have a prominent head yet still stabilizes the bone and provides compression across the fracture site or osteotomy.

Referring to FIG. 1 , in an aspect, a bone fixation device 10 is provided comprising a helical screw 12. Helical screw 12 comprises a plurality of threads 14 having a leading end 16 and a trailing end 18. The helical configuration of the screw prevents or minimizes occlusion of the intramedullary canal and preserves medullary bone, which may in turn promote improved bony healing through less disruption of the medullary bone stock and blood supply. Bone fixation device 10 lacks a central longitudinally extending shaft about which the plurality of threads is disposed. In contrast, FIG. 5 illustrates a traditional bone screw 20 where a plurality of threads 22 is disposed about a central longitudinally extending shaft 24. As can be seen by a comparison of FIG. 1 and FIG. 5, a bone fixation device 10 as disclosed herein lacks such a central longitudinally extending shaft 24, which is present in the traditional bone screw 20. The lack of such a central shaft or core renders the device less obstructive, renders the device less disruptive of intramedullary vascularity, allows or maintains maximal intramedullary bone continuity across a fracture or osteotomy, and provides less occlusion of the available area to place supplementary extramedullary fixation (such as between the threads of the screw, for example). The helical nature of the screw and the lack of a central shaft is also beneficial as bone graft, bone graft substitutes, or biological adjuncts, for example, can be placed within the device and therefore can be delivered into the intra-osseous canal to promote healing.

The bone fixation device can be headed or headless. FIG. 4 illustrates a bone fixation device 36 comprising a helical screw 40 with a screw head 38. FIGs. 1 and 3 illustrate a headless helical screw. Such helical screws can have variable, differential pitch and a low-profile proximal end. In particular, the pitch between the plurality of threads can be non-uniform. In other words, the pitch between adjacent threads of all of the plurality of threads is not the same although the pitch between some adjacent threads may be the same or substantially the same. A differential, non-uniform pitch between adjacent threads can provide compression between two or more bone fragments or segments without the need for an extra-osseous head that can potentially cause local soft tissue irritation. For example and with reference to FIG. 3, a bone fixation device 26 can comprise helical screw 28 where compression of two or more bone fragments is obtained through longer pitch Pi between adjacent threads 34 in the leading end 30 of helical screw 28 and a shorter pitch Pi between adjacent threads in the trailing end 32. Such differential pitch between adjacent threads 42 can also be seen in FIG. 1 . In particular, the pitch between adjacent threads of the plurality of threads at the proximal most region of the trailing end of the helical screw can be less than the pitch between adjacent threads of the plurality of threads at the leading end of the helical screw. Further, the proximal most region of the trailing end can have a constant diameter. As such, with respect to a headless helical screw, the proximal most region of the trailing end of the helical screw can replace the functionality of a screw head. When implanted, such a region is disposed inside the bone and therefore irritation of the peroneal tendons and other soft tissue is avoided or minimized. Such a region can also serve as a receptable for a delivery/insertion tool. FIG. 2 is an end view of the proximal most region of the trailing end 18. The inner configuration of the trailing end is hexagonal, which can be used with a driver, but the trailing end can have other inner shapes such as rectangular, star-shaped or other shapes. The bone fixation device can be used with a helical tap that has a cannulated core that can be used over a guidewire. The cannulated core can provide increased strength to create a pathway for the leading end with the longer pitch between adjacent threads. In certain aspects, the distal most end of the leading end of the helical screw is a relatively sharp cutting tip (as illustrated in all the figures) that can cut a path through the intramedullary canal or medullary/cortical junction of bone.

Although the above-described bone fixation devices has been described primarily with respect to fractures of the 5^th metatarsal, the bone fixation device can be used to compress other bone fragments. For example, the devices can be used for fixation of olecranon fractures, scaphoid fractures, and other types of fractures or osteotomies.

Each of the disclosed aspects and embodiments of the present disclosure may be considered individually or in combination with other aspects and embodiments. Further, while certain features of embodiments may be shown in only certain figures, such features can be incorporated into or deleted from other embodiments shown in other figures or otherwise disclosed in the specification. Additionally, when describing a range, all points within that range are included in this disclosure.

Claims

What is claimed is:

1 . A bone fixation device comprising: a helical screw comprising a plurality of threads having a leading end and a trailing end, the pitch between the plurality of threads being non-uniform, the bone fixation device lacking a central longitudinally extending shaft about which the plurality of threads is disposed.

2. The bone fixation device of claim 1 , wherein the helical screw at the trailing end is headless.

3. The bone fixation device of claim 1 , wherein the pitch between adjacent threads of the plurality of threads at the proximal most region of the trailing end of the helical screw is less than the pitch between adjacent threads of the plurality of threads at the leading end of the helical screw.

4. The bone fixation device of claim 1 , wherein adjacent threads of the plurality of threads at the trailing end have substantially the same diameter.

5. The bone fixation device of claim 1 , wherein the trailing end of the helical screw comprises a screw head.

6. The bone fixation device of claim 1 , wherein the trailing end of the helical screw defines a lumen having a shape configured to accept an insertion tool.

7. The bone fixation device of claim 1 , wherein the distal most end of the leading end of the helical screw is a substantially sharp cutting tip.

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