Intramedullary fixation assembly and devices and methods for installing the same

Abstract

An intramedullary fixation assembly usable with different long bone types and a guide assembly for guiding deployment of the intramedullary fixation assembly. The intramedullary fixation assembly includes a fixation member that has ends and a curved body extending between the ends. The curved body of the fixation member has a radius of curvature configured to extend through the medullary canal regardless of the long bone anatomy. Fasteners fix the fixation member to the bone fragments and are guided by a guide assembly. The guide assembly includes a guide body defining openings configured to guide the fasteners through openings defined in the fixation member and into the bone fragments. A fixation end of the guide body includes a pair of opposing, converging surfaces that are configured to engage in a positive fit with an exposed end of the fixation member accessible through the side aperture in the first fragment.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention is related to the use of orthopedic fixation devices and devices for installing the same, and in particular, to intramedullary fixation devices and guides for facilitating installation and fixation of the same. [0003] 2. Description of Related Art [0004] Long bone fractures are fairly common in the elderly population, often due to the onset of osteoporosis. Long bone fractures may be reduced by the use of assorted conventional bone plates. For example, a bone plate may be attached to the outside surface of two adjacent fragments of a long bone and then secured by inserting bone screws through openings in the bone plate. Problems may arise with such bone plates, however, in that the soft tissues covering the bone plates may become irritated by passage or movement over the bone plates. [0005] An alternative to bone plates are intramedullary nails or rods that extend through a medullary canal defi...

AI Technical Summary

Benefits of technology

[0009] The present invention addresses the above needs and achieves other advantages by providing an intramedullary fixation assembly usable with different long bone types and a guide assembly for guiding deployment of the intramedullary fixation assembly. The intramedullary fixation assembly includes a fixation member that has ends and a curved body extending between the ends. The curved body of the fixation member has a radius of curvature extending from a first end configured to extend between a side aperture defined in a first fragment through the medulary canal and into a second fragment, regardless of the type of the long bone. Fasteners are used to fix the fixation member to the bone fragments and are guided by a guide assembly. The guide assembly includes a guide body defining openings configured to guide the fasteners through openings defined in the fixation member and into the bone fragments. A fixation end of the guide body includes a pair of opposing, converging surfaces that are configured to engage in a positive fit with an exposed end of the fixation member accessible through the side aperture in the first fragment. Advantageously, the positive fit facilitates accurate positioning of the guide body and, as a result, of the fixation member fasteners.

[0010] In one embodiment, the present invention includes an intramedullary fixation assembly for repairing any of a plurality of long bone types. Each of the long bones defines a medullary canal fractured into at least a first and second adjacent bone fragments. The first bone fragment has a free end with an articular cartilage surface and defines a side aperture. The side aperture is positioned subjacent the articular cartilage surface of the first bone fragment and extends into the medullary canal. Included in the intramedullary fixation device are a plurality of fasteners (e.g., a first fastener and a second fastener) each having an elongate body with a head end and an opposite, bone-securing end. A fixation member of the intramedullary fixation device includes a first end, a second end and a curved body extending between the first and second ends. The curved body defines at least one fastener opening positioned proximate the first end and configured to allow passage of the first fastener therethrough and into the first bone fragment. Also defined by the curved body is a second fastener opening positioned proximate the second end and configured to allow passage of the second fastener therethrough and into the second bone fragment. The curved body has a radius of curvature extending from the first end that is configured to allow passage of the fixation member through the side aperture of the first bone fragment and into the medullary canal until the first end of the fixation member is positioned adjacent the side aperture, and within a portion of the medullary canal defined within the first bone fragment, and the second end of the fixation member is positioned within a portion of the medullary canal defined within the second bone fragment. In this manner, the fixation assembly can be used to reduce and secure a fracture of any of the various types of human long bone types.

[0013] In another embodiment, the present invention includes a guide assembly for facilitating placement of a plurality of bone fasteners of an intramedullary fixation assembly through predefined locations on a fixation member of the intramedullary fixation assembly. The fixation member extends through a medullary canal defined within a long bone and has an exposed end accessible through a side aperture defined by the long bone. Included in the guide assembly is at least one guide fastener configured to extend into the exposed end of the fixation member so as to be secured to the fixation member. A guide body includes a fixation end and defines a plurality of fastener guide openings. These guide openings are configured to orient the bone fasteners extending through the guide openings with the predefined locations on the fixation member. The fixation end defines an opening configured to allow passage of the guide fastener through the guide body and into the exposed end of the fixation member. The fixation end includes at least one pair of surfaces positioned opposite each other and generally extending in a converging direction. These surfaces are, as a result, configured to engage in a positive fit with the exposed end of the fixation member when the guide body is secured thereto with the guide fastener. This positive fit reduces the motion between the guide body and the fixation member, thereby improving the ability of the guide openings to accurately guide the bone fasteners through the predetermined locations on the fixation member.

[0015] The present invention has many advantages. For example, the invention has many attributes that facilitate its use for different types of human long bone. Maintaining a constant radius of curvature of a first end of the curved body allows for different sized long bones and different types of long bone to be accommodated merely by extending the arc further to produce a greater “hook” on increasing sizes of fixation members. This overcomes the increase in not only the length of the long bone, but also the increase in distance between widened end and width of the medullary canal, facilitating its use on different and larger types of long bones. It has also been determined that use of a radius of curvature in the ranges of 1.5 to 5 inches facilitates use with different types of long bone, especially when the curved body curves continuously along its length and the ends are tapered for easy insertion. The use of a cruciform shape and positive fit or wedge effect used for the concave indentations and the prongs provides rotational and translational stability of the fixation member when attached to the guide assembly. In addition, the positive fit or wedge effect operates to center and reduce micro-motion between the targeting guide and the rest of the guide assembly.

Problems solved by technology

Problems may arise with such bone plates, however, in that the soft tissues covering the bone plates may become irritated by passage or movement over the bone plates.

However, insertion of these rods through holes in the ends of the longs bones requires damaging the articular cartilage on the ends of the long bones.

Although the '775 patent discloses an intramedullary fixation device for reducing a distal radius fracture without insertion through cartilage on the end of the distal radius, other long bones, such as the humerus, femur and tibia are also often fractured and require repair.

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