Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
2000-06-02
2001-07-10
Hirsch, Paul J. (Department: 3732)
Surgery
Instruments
Orthopedic instrumentation
C606S102000
Reexamination Certificate
active
06258097
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to instruments used in performing orthopaedic surgery, and more particularly, to an instrument used to aid in properly positioning a prosthetic ball on a bone in a ball joint, such as the replacement of a femoral head during hip replacement surgery.
2. Description of the Related Art
When performing joint reconstruction surgical procedures, such as hip replacement surgery, it is important that the pre-surgical geometry of the bone structure be replicated in the post-surgical structure, including prosthetic implants. Duplicating the geometric relationships maintains the natural joint biomechanics, ensuring proper joint and soft tissue balancing forces. If, during hip replacement surgery, for example, the center of the femoral prosthetic implant is moved slightly to a position different from the original position of the natural femoral head, the result can be higher joint forces, weak abductor muscles and overall joint instability. Even relatively slight mis-positioning of the prosthetic joint component can lead to a negative surgical result.
While planning the procedure, x-rays can be used for pre-surgical templating, to assist in determining the apparent appropriate implant size, head offset and head neck length necessary to reestablish the joint biomechanics. However, while pre-surgical, two dimensional templating is useful in selecting the proper prosthetic implant, and for establishing the proper fit and positioning of the implant during surgery, even with careful and deliberate pre-surgical planning and calculation, it is common to also perform intra-operative verification of the natural joint geometry and of the geometry resulting after implant, to ensure proper function of the joint post-surgically.
It is known during hip surgery to determine the natural offset and neck length of the femoral head by measurement. Offset can be measured from the tip of the greater trochanter to the center of the femoral head. Neck length can be measured from the tip of the lesser trochanter to the center of the femoral head. When selecting the prosthetic components, an attempt is made to duplicate as closely as possible the same measurements taken with respect to the prosthetic devices, after the provisional implants have been positioned. While placing the prosthetic components, the measurements are repeated, to verify concurrence between the pre-surgical and post-surgical geometry of the joint, by reestablishing the measured values in the joint after implant.
Even with advance planning, selection of the appropriate modular head and neck components of the prosthetic implant can require the trial of several components, with the proper components being identified only after repeated measurements of the several components tried. Various measuring calipers, frames or positioning jigs have been suggested as ways to increase the accuracy in duplicating the pre-surgical geometry of the joint after implanting prosthetic components.
What is needed is an orthopaedic instrument, and a surgical procedure for use of the instrument, which can be used to precisely and accurately duplicate, in the post-surgical geometry, the geometry that existed in the joint, pre-surgically.
SUMMARY OF THE INVENTION
The present invention provides an orthopaedic instrument, and a procedure for use of the instrument, for duplicating the pre-surgical joint geometry of a ball joint in the geometry of the joint post-surgically, by establishing markings relating to the head center position of the natural femoral head, against which markings the head center of the prosthetic femoral head can be compared during surgery.
The invention comprises, in one form thereof, an orthopaedic instrument for establishing reference markings indicative of the pre-surgical joint geometry relative to the center of a ball in a ball joint, and for evaluating the post-surgical geometry relative to the head center of a prosthetic implant. The instrument includes a head chuck, with a plurality of locator devices adjustably retained by the head chuck. The locator devices are adapted to at least partially receive and engage the ball. An adjustment means associated with the head chuck and with the plurality of locator devices is used to bring each of the plurality of locator devices into engagement with the ball, for securing the position of the instrument head chuck relative to the ball. An orientation arm extends outwardly away from the head chuck and includes reference indicia for establishing and comparing bone markings.
In a second aspect thereof, the invention comprises a surgical procedure for comparing the neck angle and length of a prosthetic ball component of a ball joint to the neck angle and length of the natural ball. The procedure includes providing an instrument having a head chuck adapted to be secured in position relative to the natural ball of a ball joint and to the ball of a prosthetic implant; providing an arm on the instrument extending from the head, the arm being of sufficient length to reach a bone surface remaining after reduction; providing a plurality of reference indicia on the arm of the instrument; exposing the ball component of the ball joint, positioning the instrument over the ball, securing the position of the orientation arm relative to the center of the ball; establishing bone markings relative to selected ones of the plurality of indicia on the orientation arm; removing the instrument; replacing, surgically, the natural ball of the ball joint with a prosthetic ball component; securing the orientation arm relative to the center of the prosthetic ball; comparing the bone markings to the selected ones of the plurality of indicia on the orientation arm with respect to which the bone markings were made; and adjusting, as necessary, the neck length and angle of the prosthetic ball to match the bone markings against the selected ones of the plurality of indicia against which the bone markings were made.
In another aspect thereof, the invention comprises an orthopaedic instrument having a head chuck including a cylindrical body and a cap rotatably secured in the body. An orientation arm extends radially outwardly from the body. A plurality of locator devices are associated with the head chuck for securing the head chuck relative to the center of a ball component of a ball joint. Indicia on the orientation arm are reference points for making and comparing bone markings.
In still another aspect of the present invention, a method is provided for replacing a femoral head. The method includes exposing the femoral head surgically, securing a reference gauge against the posterior femur relative to the femoral head center; creating reference markings on the posterior femur; removing the reference gauge; replacing the femoral head with a prosthetic femoral head; re-securing the reference gauge against the posterior femur relative to the center of the prosthetic femoral head; comparing the bone markings against the reference gauge; and adjusting the prosthetic femoral head to achieve a relationship between the bone markings and the reference gauge similar to the relationship when the bone markings were made.
An advantage of the present invention is an instrument for accurately duplicating natural joint geometry following surgery to replace the ball of a ball joint, through the intra-operative verification of the prosthetic head center location relative to the head center location in the natural joint.
Another advantage of the present invention is an instrument that is simple and easy to use for comparing the natural femoral head neck length and neck angle to the prosthetic femoral head neck length and neck angle during surgery to replace a femoral head.
A further advantage is a surgical procedure to aid a surgeon in restoring proper joint biomechanics when performing joint replacement surgery.
REFERENCES:
patent: 5141512 (1992-08-01), Farmer et al.
patent: 5290315 (1994-03-01), DeCarlo, Jr.
patent: 5423827 (1995-06-01), Mumme et al.
patent: 5607431 (
Cook Kevin
Cooper John D.
Hickey Paul
Bristol-Myers Squibb Co
Hirsch Paul J.
LandOfFree
Head center instrument and method of using the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Head center instrument and method of using the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Head center instrument and method of using the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2527959