Locking plate for bone anchors

Abstract

Disclosed is a bone fracture fixation system, such as for reducing and compressing fractures in the proximal femur. The fixation system includes a plurality of elongated bodies with a helical cancellous bone anchor on a distal end of each of the bodies. An axially moveable plate with a plurality of openings is carried by the proximal end of the elongated bodies. The elongated bodies are rotated into position across the fracture or separation between adjacent bones and into the adjacent bone or bone fragment, and the plate is distally advanced to apply secondary compression and lock the device into place. The device may also be used for soft tissue attachments.

Description

PRIORITY INFORMATION [0001] This application is a divisional of U.S. patent application Ser. No. 10 / 756,892, filed Jan. 14, 2004, which claims the priority benefit under 35 U.S.C. § 119(e) of Provisional Application 60 / 440,765, filed Jan. 16, 2003, the entire contents of these applications being hereby incorporated by reference herein.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to internal bone fracture fixation devices. In one application, the present invention relates to bone fracture fixation devices and methods adapted for fixation, among other fractures, of femoral neck and other proximal femoral fractures. [0004] 2. Description of the Related Art [0005] The femur, otherwise known as the thigh bone, generally comprises an elongate shaft extending from the hip to the knee. The proximal end of the shaft includes a head, a neck, a greater trochanter and a lesser trochanter. The head of the femur fits into the acetabular cup of ...

AI Technical Summary

Benefits of technology

"The present invention is a femoral neck fracture fixation system that includes a plurality of elongated bodies and a plate that can be movably carried by the elongated bodies. The elongated bodies have a proximal end and a distal end, with a distal anchor and a first retention structure provided on each elongated body. The plate can be moved in the distal direction with respect to the elongated bodies and the retention structure resists proximal movement of the plate with respect to the elongated bodies. The system also includes complimentary surface structures that permit advancing the plate in the distal direction to tighten the fixation device but resist axial proximal movement of the plate with respect to the elongated bodies. The method of treating a femoral fracture involves drilling bores in the femur, advancing fixation devices through the bores, rotating the fixation devices to secure the fixation devices to the second fragment, and axially advancing a plate with a plurality of openings over the fixation devices to engage the first fragment. The technical effects of the invention include simplifying the procedure of installing the plurality of implants by providing a predetermined spatial and / or angular relationship between the implants, increasing overall stability and resistance to failure, and facilitating the treatment of femoral fractures."

Problems solved by technology

However, portions of the femur are extremely susceptible to fracturing.

Fractures of the femur which extend into the neck of the bone are generally more difficult to treat than fractures restricted to the shaft of the femur.

The leading end portion of the implant typically includes means to positively grip the femoral head bone (external threads, expanding arms, etc.), but the inclusion of such gripping means can introduce several significant problems.

First, implants with sharp edges on the leading end portion, such as the externally threaded implants, exhibit a tendency to migrate proximally towards the hip joint weight bearing surface after implantation.

This can occur when the proximal cortical bone has insufficient integrity to resist distal movement of the screw head.

Such proximal migration under physiological loading, which is also referred to as femoral head cut-out, can lead to significant damage to the adjacent hip joint.

Also, the externally threaded implants can generate large stress concentrations in the bone during implantation which can lead to stripping of the threads formed in the bone and thus a weakened grip.

As a result, all fatigue loading is concentrated at the attached ends of the arms and undesirably large bending moments are realized at the points of attachment.

In addition, conventional threaded implants generally exhibit insufficient holding power under tension, such that the threads can be stripped out of the femoral head either by overtightening during the implantation procedure or during post operative loading by the patient's weight.

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