Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
2002-05-15
2004-12-07
O'Connor, Cary E. (Department: 3732)
Surgery
Instruments
Orthopedic instrumentation
Reexamination Certificate
active
06827721
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a method for the determination of reduction parameters for the subsequent adjustment of a reduction device in order to reduce the fragments of a fractured bone.
BACKGROUND OF THE INVENTION
In the field of osteosynthesis, bone fragments of a patient's fractured bone must often be correctly relocated. Only after such a correct relocation (reduction) of the bone fragments may a fixing device, such as an external or internal fixation, be applied in order to fix the bone fragments in a rigid position. In other applications, wherein the patient has a bone malformation for example, the bone or bones must be treated.
At present, the dislocation of fragments of fractured bones must be determined by means of X-ray imaging. When using or installing an external fixation, the corrections to be made through adjustment of the respective clamps and pins or screws is based upon on these X-ray images. The verification of the reduction of the fractured bone by means of the external fixation must be effected with subsequent X-ray imaging. This procedure may be cumbersome, especially in case of multiple steps of adjustment of the fragments.
In this regard, remedial measures are desired. A need exists for a method and a device based upon the comparison of the bone contour of the fractured bone with the corresponding healthy bone on the patient's healthy side of the body without using X-ray imaging.
SUMMARY OF THE INVENTION
The invention is related to a method for the determination of reduction parameters for the subsequent adjustment of a reduction device to reduce the fragments of a fractured bone, comprising the steps of: (A) comparing the contour of a first bone on a first side of a patient's body with respect to a corresponding second bone on the opposite side of the patient's body, wherein the first bone is a non-fractured bone and the second bone is a fractured bone; (B) determining the positions of a first set of points on the first bone, and establishing a three-dimensional coordinate system with respect to the body of the patient; (C) determining the positions of a second set of on the second bone within the coordinate system, wherein the second set of points corresponds to the first set of points; (D) establishing a plane of symmetry by dividing vectors between each point of the first set and its corresponding point of the second set in two parts, and defining central points of the vectors which define the plane of symmetry within the coordinate system; (E) generating a mirror image of the first bone symmetrically to the plane of symmetry by determining the positions of a third set of points on the first bone at each section corresponding to a fragment of the second bone and by forming the mirror image of the first bone by determining the positions of a fourth set of points that are symmetrical to the third set of points with respect to the plane of symmetry; (F) determining the positions of a fifth set of points on the second bone at each fragment section, wherein the fifth set of points corresponds to the third set of points on the first bone; and (G) determining the reduction parameters by comparing the different positions of the fifth set of points on the second bone with the positions of the fourth set of points within the mirror image. In one preferred embodiment, the second set of points includes at least three points situated on a proximal fragment of the bone. In one embodiment, a plane of symmetry containing an anterior-posterior axis and a proximal-distal axis is established by means of dividing the connecting vectors between each point and its corresponding point in two equal parts therewith defining central points of the vectors which determine three points of the plane of symmetry within the coordinate system.
The coordinates are preferably measured within the coordinate system defined under step (B). The determination of the reduction parameters is then preferably executed by means of calculating the differences between the coordinates of the points at the fractured bone and the coordinates of the points within the mirror image in the medial-lateral direction, the anterior-posterior direction and the proximal-distal direction.
In another preferred embodiment of the method according to the invention, the determination of the position of the points on the surface of the fractured and the non-fractured bone is performed by means of touching these points with the tip of a pointer which is provided with at least three markers whose position is determinable within an on-site three-dimensional coordinate system by means of an optical position measurement device and respective data management via a computer.
The position measurement device may be an optical position measurement device, an acoustic position measurement device or an electromagnetic position measurement device.
Corresponding to the mode of operation of the position measurement device, the markers attached to the pointer may be energy emitting, receiving or reflecting means. For example, suitable energy emitting means that may be installed include: Light sources; light emitting diodes (LEDs); infrared light emitting diodes (IREDs); acoustic transmitters; or coils in order to establish a magnetic field. Also, suitable energy receiving means that may be installed include: photodiodes; microphones; or hall-effect components.
In another embodiment according to the invention, the method comprises: (A) the determination of the position of the at least three points at the surface of one of the bones by means of fastening one reference bar through two screws or pins to the bone and determining a third point with an adjustable pin fastenable to the reference bar; (B) the determination of the position of the identical points at the surface of the other bone by means of fastening a second reference bar through two screws or pins to the other bone and determining the third point with an adjustable pin fastenable to the reference bar; and (C) the coordinates of the tips of the adjustable pins relative to particularly defined points on the reference bars are compared in order to estimate the reduction parameters.
The method may also include: (A) the measurement of the reduction parameters relative to the medial-lateral plane by means of attaching one reference bar at the non-fractured bone in the medial-lateral plane and one reference bar at the fractured bone in the medial-lateral plane; (B) the measurement of the reduction parameters relative to the anterior-posterior plane by means of attaching one reference bar at the non-fractured bone, in the anterior-posterior plane and one reference bar at the fractured bone in the anterior-posterior plane; or (C) the measurement of the reduction parameters relative to the medial-lateral plane and relative to the anterior-posterior plane by means of attaching one reference bar each at the non-fractured bone in the medial-lateral plane and in the anterior-posterior plane and one reference bar each at the fractured bone in the medial lateral plane and in the anterior-posterior plane.
The method according to the invention is preferably performed by the surgeon as an additional step during planning and preparation of the surgical treatment of the fractured bone as for example the selection of an adequate reduction apparatus and method as well as adequate internal or external fixators.
Also disclosed is a device according to the invention comprising: a cylindric or prismatic reference bar having a longitudinal axis; clamps displaceable on the reference bar in the direction of the longitudinal axis and fastenable to the reference bar; screws or pins loosenable and fixable transversely to the reference bar within the clamps whereby the screws are screwable into the bone therewith attaching the reference bar to the bone; and one or more adjustable clamps to loosenably fasten one or more pins capable of being set with their tips to desired points on the surface of the bone.
In a preferred embodiment of the device a
Hehli Markus
Mitkovic Milorad
Perren Stephan
Jones Day
Melson Candice C.
O'Connor Cary E.
Synthes (USA)
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