SURGICAL ORIENTATION DEVICE AND METHOD
A device for detecting and measuring a change in angular position with respect to a reference plane is useful in surgical procedures for orienting various instruments, prosthesis, and implants with respect to anatomical landmarks. One embodiment of the device uses three orthogonal rate sensors, along with integrators and averagers, to determine angular position changes using rate of change information. A display provides position changes from a reference position. Various alignment guides are useful with surgical instruments to obtain a reference plane.
1 . A method of using an alignment instrument to align a prosthesis with an implant site comprising the steps of:
a. providing the instrument with a three dimensional measuring system capable of measuring angular position changes from a reference position;
b. locating the instrument at a reference position with respect to the implant site using an alignment guide to contact the implant site;
c. zeroing the measuring system while the alignment guide is in contact with the implant site and in the reference position;
d. replacing the alignment guide with a prosthetic implant member; and
e. positioning the instrument to a desired angular orientation with respect to the reference position using the measuring system to align the prosthesis with the implant site.
2 . The method of claim 1 wherein the alignment guide includes a plurality of arms extending generally radially from a body portion and step b. includes contacting the implant site with the plurality of arms.
3 . The method of claim 2 wherein the alignment instrument is an acetabular alignment instrument and the prosthetic implant member is a prosthetic socket and the implant site is an acetabulum.
4 . The method of claim 3 wherein step e. further comprises positioning the instrument to a predetermined angular orientation.
5 . The method of claim 4 wherein the predetermined angular orientation is a predetermined anteversion angle.
6 . The method of claim 5 wherein the anteversion is about twenty five degrees.
7 . The method of claim 1 wherein step b. includes resting the alignment guide on a rim of an acetabulum.
8 . The method of claim 1 wherein the alignment instrument is a glenoid implant insertion instrument and the prosthetic implant member is a glenoid implant and the implant site is a glenoid vault.
9 . The method of claim 7 wherein the alignment guide includes a plurality of arms extending generally radially from a body portion and step b. includes contacting the rim of the acetabulum with the plurality of arms.
10 . The method of claim 9 wherein the plurality of arms comprises three arms, and step b. includes placing a first arm on a most superior point of the acetabulum.
11 . The method of claim 10 wherein step b. further includes placing a second arm at a lowest point of an acetabular sulcus of an ischium.
12 . The method of claim 11 wherein step b. further includes placing a third arm at a saddle point at a confluence between an illiopubic eminence and a superior pubic ramus.
13 . A method of orienting an instrument for aligning a medical prosthesis with an anatomical location in a patient, the instrument of the type having a prosthetic support structure, the improvement comprising the step of
a. associating an electronic goniometer with the prosthetic support structure of the instrument;
b. positioning the prosthetic support structure of the instrument to a reference position in contact with an anatomical site in which a prosthesis is to be implanted;
c. zeroing a digital display of the electronic goniometer while the support structure is at the reference position; and
d. moving the support structure to a desired angle by observing the digital display while maintaining the support structure in contact with the anatomical site to position the prosthesis at the desired angle to the anatomical site.
14 . The method of claim 13 wherein step b. further comprises using an alignment guide removably mounted on the prosthetic support structure to contact the anatomical site.
15 . The method of claim 14 further comprising an additional step c1. after step c. and before step d. comprising:
c1. removing the alignment guide from the prosthetic support structure and mounting the prosthesis to the support structure in place of the alignment guide.
16 . The method of claim 13 further comprising an additional step d0. before step d. comprising:
d0. associating the prosthesis with the support structure.