Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
1999-07-01
2001-05-08
Smith, Jeffrey A. (Department: 3732)
Surgery
Instruments
Orthopedic instrumentation
C606S130000
Reexamination Certificate
active
06228089
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a national stage of PCT/EP97/07186 filed Dec. 19, 1997 and based upon German national application 19653966.8 of Dec. 21, 1996 under the International Convention.
FIELD OF THE INVENTION
The present invention relates to a device for positioning and guidance of a surgical instrument during orthopaedic operations, with
an industrial robot having a program-controlled multi-jointed robot arm with a mounting plate on its end,
an instrument for the surgical procedure held on the mounting plate, and
a program control system with computer, whereby sensors are arranged in the joints of the robot arm to determine the joint positions in an instrument coordinate system in the program control system and whereby the robot arm can be moved by means of the program control system to a working position for the surgical procedure.
BACKGROUND OF THE INVENTION
A device with the features described above is known from the Jul. 29, 1994 issue of VDI Nachrichten and is used in hip operations. Before the operation, three screws are initially implanted into the patient's knee and the thigh bone. The screws have a slight indentation into which fits the head of a feeler arranged at the end of a robot arm. A computer tomograph also carried out before the operation provides necessary patient data for the program control system. During the surgical procedure, the patient's thigh is clamped in a sterile holder arm that is rigidly attached to the foot of the industrial robot. A measuring arm placed on the bone records any positional changes. Firstly, the surgeon leads the robot arm with the feeler at its end to the reference points given by the indentations in the screws, the coordinates of which are compared with the data from the tomograph. From the data, the computer then determines the working position of the robot arm for the surgical procedure. Once the working position has been determined, the feeler is replaced by an instrument and the femur shaft is milled using appropriate feed movements of the robot arm under program control. Next, the surgeon can insert a previously selected prosthesis.
The application of the known device requires extensive preoperative planning and use of computer tomography, which are not only expensive, but also prolong the operation time to an overall extent that is problematic. Also unfavorable is the fact that the surgeon has no possibility of exerting an influence on the program-controlled course of the operation. In the event of positional changes of the bone and/or non-compliance with predetermined tolerances, the device immediately interrupts its work for safety reasons.
OBJECT OF THE INVENTION
The object of the invention is to provide a device of the type described at the outset, which is deployable intraoperatively and so designed that the surgeon can exercise an influence on the operation.
SUMMARY OF THE INVENTION
According to the invention the object is achieved in that a sensor arrangement manually controllable independently of the position of the robot arm is provided for three-dimensional object measurement in the instrument coordinate system of the industrial robot, such that, by means of the sensor arrangement, using a previously-assumed home position of the robot arm prescribed by the program control system, reference points on the patient's bone can be sensed and the computer determines the working position of the robot arm from the coordinates of the reference points related to the instrument coordinate system. It is taken that the working position of the robot arm can also include a sequence of robot arm positions, which must be visited in order to guide and position optimally the instrument arranged on the mounting plate for the execution of the surgical procedure. Independently of the technical implementation of the sensor arrangement, it is of fundamental significance to the invention that through a coupling of the sensor arrangement and the robot arm, which can be realized in differing ways explained in greater detail below, the coordinates of the reference points in the instrument coordinate system of the industrial robot are determined, this being defined in the program control system.
The sensor arrangement allows a sufficient number of clearly identifiable reference points on the patient to be determined for the calculation of the working position of the robot arm. During recording of these reference points, the robot arm remains stationary in the previously assumed known home position. Using the coordinates of the home position and the coordinates of the reference points, the working position that the robot arm subsequently assumes during the surgical procedure can be calculated exactly. Depending on the type of surgical procedure, a single working position or a sequence of working positions is determined. The device according to the invention permits intraoperative application. Preoperative planning on the basis, for example, of X-ray photographs or computer tomographs is not required in principle. Furthermore, the program control system can be set up so that, during the operation on bones that are exposed during the procedure, the surgeon records further characteristic points with the aid of the sensor arrangement, which are then processed for correction of the working position of the robot arm and/or to determine a sequence of working positions which the robot arm assumes one after the other as the operation proceeds.
According to the invention, it is possible to employ sensor arrangements based on various measuring principles. One embodiment consists of a multi-jointed manually moveable sensor arm connected to the mounting plate of the robot arm. The coupling to the instrument coordinate system of the robot is achieved in this case through a rigid mechanical connection, so that the fixing of the sensor arm on the mounting plate must take place precisely at an exactly defined position. The sensor arm has joints with sensors to detect the joint positions. By manual guidance of the sensor arm at a predetermined and previously assumed home position of the robot arm, reference points on the patient's bone can be sensed, the coordinates of which are passed to the computer. From these coordinates, the computer determines the working position of the robot arm. A sensor arm with six joints is preferable.
Multi-jointed sensor arms having sensors to determine the joint positions are already known. These are passive, exclusively manually steerable measuring instruments, which are used, within the scope of known techniques, as transportable devices for measuring workpieces. The invention starts with the recognition that the attachment of a multi-jointed sensor arm to the end of a program-controlled active robot arm brings significant advantages that can be utilized in surgical procedures. Of fundamental significance to the invention is the fact that the sensor arm arranged on the mounting plate is not replaced by instruments, but is available to the surgeon throughout the entire surgical procedure.
A further embodiment of the invention provides for the sensor arrangement consisting of a multi-jointed sensor arm connected to the computer, the arm being spatially so arranged that both the patient's bone to be sensed and the mounting plate of the robot arm placed in a home position are within the working space measurable with the sensor arm, such that with the aid of the sensor arm, at least one reference point on the mounting plate can be sensed so that, by means of the sensor arm, both the position and orientation of the mounting plate and the reference points sensed on the patient's bone are determined in a fixed three-dimensional coordinate system and such that the computer transforms the spatial coordinates found into the coordinates of the instrument coordinate system. Multiple points may be provided on the mounting plate, the positions of which are exactly defined and have been determined in relation to the instrument coordinate system. Another possibility consists in
Depuy International Limited
Dubno Herbert
Smith Jeffrey A.
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