Method and instruments for inserting modular implant components

Abstract

An instrument is disclosed for inserting a modular implant, the instrument comprising a first end and a second end, the first end having engagement means for engaging a stem component of the modular implant, the engagement means comprising separation means for separating a body component of the modular implant and the stem component from one another so as to permit rotational positioning of the body component and the stem component relative to one another.

Description

REFERENCE TO PENDING PRIOR PATENT APPLICATION[0001]This patent application claims benefit of pending prior U.S. Provisional Patent Application Ser. No. 60 / 378,986, filed May 9, 2002 by Steven C. Pubols et al. for METHOD FOR INSERTING MODULAR IMPLANT COMPONENTS, which patent application is hereby incorporated herein by reference.FIELD OF THE INVENTION[0002]This invention is related to modular orthopedic apparatus and methods in general, and more particularly to apparatus and methods for inserting modular implant components.BACKGROUND OF THE INVENTION[0003]The aim of Total Hip Arthroplasty (THA) is the reduction of pain and the restoration of function to a diseased hip joint via the substitution of engineered materials for the diseased tissue. Successful outcomes depend largely on the proper sizing, placement and orientation of the implant. Incorrect biomechanics (e.g. joint reaction forces, soft tissue balancing) can slow or prevent healing, cause gait abnormalities and lead directly...

AI Technical Summary

Benefits of technology

[0009]An object of the invention is to provide an instrument for inserting a modular implant in which the instrument allows the rotational positioning of the body component, neck component and stem component relative to one another.

[0010]Another object of the invention is to provide an instrument for inserting a modular implant which allows rotational positioning of a neck and body component relative to a stem component.

[0011]A further object of the invention is to provide a system for inserting a modular implant in which the insertion tool provided with the body component and the stem component allows positioning of the body component and the stem component relative to one another.

[0013]This invention provides for an improved apparatus and method of inserting or implanting a modular orthopedic prosthesis. The improved apparatus and method allows the components of the implant to be assembled together and inserted into the femur without the need for the modular connections to be locked together, thereby permitting each component to seek its best fitting position within the canal. Further, this permits the orientation of the neck component relative to the body and stem after they have achieved this best fitting position. The implant neck, body, and stem may rotate freely with respect to one another until the components are fully seated in the bone. The results in improved alignment between the implant and the bone, which in turn reduces the time and force required to implant the prosthesis. For example, this method may be used in implanting hip, shoulder, and knee prostheses.

[0014]In accordance with a further feature of the invention there is provided a system for inserting a modular implant, the system comprising: a body component having a neck segment extending therefrom, and the body component forming a bore and counterbore therein; a stem component having a threaded end configured for selective disposal within the bore and counterbore so as to expose through the counterbore a given length thereof; and an insertion tool comprising a first end and a second end, the first end forming a threaded recess for engaging the stem component of the modular implant, the threaded recess having a depth less than the length of the threaded end so as to permit rotational positioning of the body component and the stem component relative to one another.

[0015]The present invention improves upon existing techniques by allowing for the complete (fully seated) implantation of the stem and body while maintaining rotational freedom between the stem, body, and neck components. Alternatively, the surgeon may elect to assemble the neck and body at the desired orientation as determined during the trialing phase of surgery. A method of a preferred embodiment of the present invention allows for the stem to be held securely during insertion, while the neck and body assembly may rotate freely about the stem positioning in order to seat the stem in a best fitting position. Once the body is fully seated, the driver may be removed and the implants may be fully assembled using an assembly tool or another instrument. The present invention is not limited to the use of three-piece designs. The present invention may be used in a two-piece design where the neck and body portions of the implant are manufactured as a one-piece component.

Problems solved by technology

Incorrect biomechanics (e.g. joint reaction forces, soft tissue balancing) can slow or prevent healing, cause gait abnormalities and lead directly to early implant failure.

This iterative approach to neck placement is time consuming, damages the bone / implant interface, and results in the loss of implant stability.

This problem is compounded when a bowed stem is used in place of a straight stem.

Without this alignment, the stem may be off axis, making it difficult or impossible to assemble the neck and body segments along an axis.

One disadvantage of this method is that stem / body orientation must be determined visually prior to full seating and may shift during implantation.

Another disadvantage is that the assembly force is equivalent to the resistance of the stem sliding down the canal.

If the stem moves in the canal during final assembly, the stem may be driven too deeply into the canal causing surgical delays, or the stem and body will not be tightly assembled, leading to fretting, corrosion, and early failure of the construct.

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