Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
1999-11-01
2001-08-14
Reip, David O. (Department: 3731)
Surgery
Instruments
Orthopedic instrumentation
C606S092000, C623S022320
Reexamination Certificate
active
06273891
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to the field of prosthetics and, in particular, to methods and apparatus for positioning an implant relative to a bone so as to achieve a desired orientation. More specifically, the invention is directed toward instrumentation and surgical techniques which ensure an accurately aligned acetabular prosthetic element.
BACKGROUND OF THE INVENTION
Improved orthopedic procedures have made joint replacement and augmentation techniques commonplace. In total hip arthroplasty, both the femoral or ball aspect of the joint as well as the acetabular or socket portion are replaced with prosthetic implants. A wealth of references exist in this field, and many patents have been issued with respect to the implants themselves, as well as the tools used in such procedures and various methods associated with such procedures.
Although different techniques have been proposed to ensure correct placement of the femoral portion of a hip replacement, techniques associated with the implantation of acetabular prostheses are far less developed. There are several reasons for the lack of progress in this area. First, perhaps, exposure and resection of the femoral shaft is surgically more straightforward, facilitating a wider variety of alignment procedures. Access to the acetabulum is more challenging since the pelvic region, unlike the femoral counterpart, is relatively stationary during surgery, and the bones comprising the socket region to accept the implant are geometrically more complex, particularly if considerable deterioration or deformity are present.
This situation has led to the use of imperfect techniques associated with prosthetic acetabula implantation, often involving the use of manually operated instrumentation which relies only on the surgeon's hand and eye coordination to install the implant, occasionally relying upon visual markers. Existing tools in this area are described in U.S. Pat. Nos. 5,037,424, 5,116,339, 5,141,512, and 5,527,317.
With the increasing awareness that alignment accuracy fosters implant longevity, the need remains for instrumentation and/or techniques associated with the positioning an implant relative to a bone so as to achieve a desired orientation. Such advances could assist in the alignment of the acetabular component during hip arthroplasty, for example, to ensure a co-acting joint which more faithfully reproduces natural movements and reduces complications such as dislocation and wear.
SUMMARY OF THE INVENTION
The present invention resides in apparatus and associated methods for positioning a prosthetic element relative to a bone so as to achieve a desired orientation. Broadly, an anchoring unit rigidly attaches to a point of the bone surrounding a region associated with receiving the prosthetic element, and at least one structural member is used to rigidly couple the prosthetic element to the anchoring unit. The combination of the anchoring unit and structural element preferably includes one or more fasteners which may be loosened to temporarily remove the prosthetic element once a desired orientation is achieved, while facilitating re-installation of the element in accordance with the desired orientation following the temporary removal. In a preferred embodiment, the prosthetic element is an acetabular implant, and the surrounding bone forms part of a human pelvis.
Regardless of the application, the element may take the form of a trial or a final implant. More particularly, the prosthetic element may be a non-final implant of the type provided and used for trialing or “fitting” purposes, which would require replacement with a final implant prior to fixation. In the alternative, the final implant itself may provide means facilitating a temporary connection thereto, or the invention may grasp the final implant in some manner, enabling the final itself to be used for trialing purposes prior to its own fixation. Given this versatility of the invention, use of the term “implant” should be taken to mean the final implant adapted for fixation or any other device shaped at least partially like the final for test purposes. In addition, although reference is made herein to cementation, it will be noted and understood by those of skill given applicant's specification that non-cemented implants may be utilized as well, including those having surfaces adapted for bone ingrowth.
In certain configurations the apparatus includes one or more adjustment devices enabling the anchoring unit to be moveably positioned prior to its rigid attachment to the surrounding bone while the prosthetic element remains in position at the desired orientation. In this case, the apparatus preferably features a plurality of such adjustment devices, facilitating a multidimensional desired orientation of the prosthetic element. The anchoring unit may conveniently include a sleeve through which a threaded rod may be removably inserted into the surrounding bone, thus providing an exposed post over which the sleeve of the anchoring unit may be removably installed.
If cementation of the final implant is used, apparatus according to the invention may further include devices to facilitate the formation of a uniform-thickness cement mantle, which has been shown to promote implant stability. In one embodiment of this aspect of the invention, an implant having an outer lip is provided which covers the surrounding bone immediately adjacent to the region associated with receiving the prosthetic element. One or more cement injection ports, and one or more cement release ports are provided, enabling the cement to be injected with the implant in place. Such release ports may be designed to expel cement upon the occurrence a cement over-pressurization. In an alternative embodiment of this aspect of the invention, a cup-shaped cement injection device is provided, which is temporarily inserted into the socket then removed, leaving a substantially uniform-thickness uncured cement bed into which a final implant is urged until fixation occurs.
A method aspect associated with the positioning of a prosthetic element relative to a bone so as to achieve a desired orientation according to the invention includes the steps of attaching an anchoring unit to surrounding bone, including an adjustable structural assembly having an end adapted for attachment to the prosthetic element; adjusting the orientation of the prosthetic element relative to the bone with the structural assembly attached thereto; and locking the prosthetic element into position once achieving the desired orientation. Importantly, the steps of adjusting the orientation of the prosthetic element and locking the prosthetic element into position may be performed as part of a joint reduction, enabling modification to permit optimal re-positioning, as desired.
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patent: 5037424 (1991-08-01), Aboczsky
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patent: 5501687 (1996-03-01), Willert et al.
patent: 5527317 (1996-06-01), Ashby et al.
patent: 5702477 (1997-12-01), Capello et al.
patent: 5879399 (1999-03-01), Church
Gifford Krass Groh Sprinkle Anderson & Citkowski PC
MedIdea LLC
Reip David O.
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