The invention relates to a device for working parts of any kind, in particular bones, organs, etc., of the human/animal body, with a housing, a tool attached to the housing and an actuating unit that produces relative motion between the housing and the tool.
For the operative manipulation of bones, particularly in orthopaedic surgery, passive navigators are already known, which assist the user in orienting the tool to the patient and in precise operative planning of the operation.
The disadvantage of these navigation systems is that computer-navigated tools do not automatically reach the desired position because of muscle tremor and involuntary transient movements of the operator during the work process.
In particular, in hip and knee endoprosthetics, hip joint revision surgery and anterior cruciate ligament replacement, the use of robots is known to be used to perform surgical steps on the patient as active navigators, which can be programmed in advance at a workstation or directly in the operating room.
The disadvantages of such systems are, on the one hand, the extended operating time, on the other hand, the very high purchase and maintenance costs and the additional space required for such systems.
The device is known from WO-A-9730826 as a robotic positioning device for positioning a positioning head in relation to a workpiece to be machined. The device comprises a positioning body and a location measurement system for determining the spatial coordinates of a workpiece to be machined on the one hand and of the positioning head on the other. The location measurement system communicates with a control data system for a positioning control unit, which allows the positioning head to be moved to a predetermined position in relation to the workpiece to be machined.
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EP-A-0 456 103 is a well-known image-guided robotic system for precision surgery.
A device of this type is already known from DE 197 00 402 C2. The instrument described therein makes it possible to compensate to the greatest extent for the involuntary hand tremors (tremor) during manual work on fine structures. This compensation of muscle tremor is particularly important in microsurgery. Acceleration and angular velocity sensors are attached to the instrument, which provide a mechanical or electrical signal correlated with the movement of the instrument. These sensors are first amplified and then analysed in terms of frequency, amplitude and direction and acceleration of the tool. In this way, the undesirable movements can be evaluated and differentiated from the intended treatments.
The problem with the known device is that, although the muscle tremor is largely excluded from the tool movement, the positioning of the tool cannot be controlled by programming, but must be done manually.
The present invention is now intended to describe a device for machining parts of any kind, particularly bones, organs, etc., of the human/animal body, of the type mentioned above, which combines the precision of robotic machining with the subjective sense of process control which a surgeon gets with a hand-held device.
According to the invention, the above problem is solved by the features of claim 1, according to which the device in question is designed to make the position of the tool detectable and the position of the part to be worked detectable and/or predictable, the control unit being controllable so that it moves the tool within a given working range into a predictable relative position to the part to be worked, and a control unit being provided for the evaluation of the position data and the generation of the control values for the control unit.
The invention first demonstrates that, even with a handheld device, despite the user's muscle tremor and other unavoidable mal-movements, machining precision can be achieved in the machining of parts of any kind, particularly in microsurgical operations, as is already known from procedures using robots as active or semi-active navigators.
The device is designed to detect the position of the tool and the part to be machined, and to compare the position data with the position data provided. This is done by a control unit which generates the control values for an operating unit which is placed in a predetermined relative position to the part to be machined. The operating unit causes the tool to move relative to the machine in front of the user's hand. The reaction movements of the user during the entire machining process are corrected by the machine due to mechanical feedback between the tool and the operator.
The control unit is advantageously designed as an adaptive control unit.
The two processes of detection of the position of the tool and the part to be worked and of the actuation of the control unit are preferably carried out continuously or repetitively, so that it is possible to detect and correct rapid or high frequency movements of the tool, e.g. caused by the surgeon's muscle tremor, and movements of the part to be worked, e.g. the patient's tremor.
The tool can be designed to move in all six degrees of freedom with respect to the housing. The degrees of freedom are composed of displacements along the three Cartesian axes (x, y, z), with a displacement along the z-axis representing the tool's forward motion. To compensate for angular misposition of the tool, the inclination angle α and the yaw angle ψ with respect to the housing could also be variable.
The housing, which is held in the hand by the user during machining, may be designed as a hand grip, pistol grip or similar, which gives the machine a good handling characteristic, giving the user maximum control over the work process.
An external positioning system could be provided for the purpose of capturing the position data of the tool and the part to be worked on, which could work in a beneficial manner with optical and/or acoustic, magnetic, mechanical or radioactive signals.
The use of more than two optical sensors can introduce redundancy into tracking systems, which can be used to increase tracking accuracy, speed and robustness, among other things, for example, a moving sensor can be calibrated using information from currently stationary sensors.
Furthermore, the use of passive or active colour markings on the objects to be tracked allows the differentiation of the different markers, which leads, among other things, to an increase in the tracking speed.
The image processing that occurs during optical tracking can be significantly accelerated by the use of special hardware, such as FPGAs (Field Programmable Gate Arrays). In a preferred variant of such a setup, each image sensor can be assigned a corresponding hardware.
The user thus has a large, flexible and unobstructed work area at his disposal, which allows him to work without changing the operating environment and the operation procedure.
To facilitate the identification of the objects to be tracked - tool and workpiece - they could be marked in a useful way, which could be detected by the tracking system. In an operating plan, the current position of the marker on the bone to be treated can be compared with a preoperative CT of the patient. The tool could be associated with at least three separate markers, which can be used to detect not only the position of the tool tip, for example, but also the orientation of the tool in space.
Since a marker mounted on the tip of the tool is no longer optically accessible after the tool has penetrated the part to be worked, it would be particularly advantageous to attach a detectable marker to the housing. In addition, an internal sensor could be provided, directly or indirectly attached to the housing and/or the tool, to determine the relative position between the housing and the tool. Mechanical routers or angle sensors could preferably be used for this purpose. This indirect positioning of the tool ensures the functioning of the device during the entire work process, in particular after the tip of the tool has penetrated the part to be worked.
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The technical implementation of the control unit could be advantageously provided by a hexapod (steward or flight simulator platform). This could be formed by particularly small and highly dynamic linear motors, so that a unit of the appropriate size could be realized. This could be easily integrated into the handheld housing. The hexapod offers the possibility of performing movements in all six degrees of freedom in a sufficiently large working area for the application.
In an alternative embodiment, the control unit could be designed to be equipped with two epicyclic gears arranged in parallel, which, with a purely rotary control, would allow the drill axis to move in four degrees of freedom, i.e. in the x and γ directions and around the x and γ axes.
The design of the device is not in principle restricted. Medical applications include, for example, drills, milling tools for milling cavities in bones or even pliers for use in a biopsy. It should be emphasized that the device is not limited to medical, in particular surgical, applications but also allows precise cutting, spanning, sawing or similar machining operations in the field of automated industrial manufacturing and/or home improvement.
In order to ensure sufficient mobility of the tool in relation to the vibrations or wobbles of the hand of the user, it could be envisaged that the tool in a special embodiment would have a cylindrical working area of 40 mm in diameter and 40 mm in length, corresponding to an angular mobility of the tool in the zx and zy planes of approximately ± 20°.
Within the working area, in a special embodiment, the precision of the tool bearing may be such that the tool tip is always defined in a cube of 0.1 mm edge length, the orientation of the tool not deviating more than 0.1° from the ideal direction.
In particular, for the use of the device in the operating area, provision could be made for both the tool and the housing to be sterile. With regard to the ease of use of the device, provision could be made for the work process, e.g. the drilling operation, to be initially locked. Only when the device has been brought by the operator close to the planned drilling position and the control unit has correctly aligned the drill in its angular position and position, the drilling operation is automatically released. This could be indicated, for example, by an acoustic and/or optical signal.
During the operation, certain machining parameters could be automatically monitored. In the case of a drilling operation, the speed, thrust and speed of the drill may be taken into account.
The position detection system has an advantageous sampling rate of at least 50 Hz. This frequency is necessary to detect even rapid movements or higher frequency vibrations in the range of 12 Hz in the case of muscle tremor. The system could be designed to detect a total of six markers with a sampling rate of 50 Hz. As regards the accuracy in the position determination, the position detection system could be designed to detect an error of less than 0,1 mm, or even less than 0,07 mm depending on the area of use.
The present invention is now usefully designed and furthered in several ways, namely by reference to the claims subordinate to claim 1 and by the following illustration of a preferred embodiment of the invention by means of the drawing. In conjunction with the illustration of the preferred embodiment of the invention by means of the drawing, the general design and further development of the invention are also described.
The example of a device according to the invention shown in Fig. 1 has a tool 1 trained as a drill bit attached to a tool 2 socket. By means of an actuator not shown in Fig. 1, the drill bit 1 can be moved in six degrees of freedom towards a housing 3: movements along the three Cartesian axes x, y and z and rotations around the three axes, with the shift in the z direction being the forward motion of the drill bit and the rotation around the axis of the drill bit being the crushing rotation.
An optical positioning system captures the objects of interest. The objects to be detected are the drill 1 and/or the housing 3 as well as a part to be processed, which is shown in Fig. 1 in the form of a spine 5. The images of the cameras 4 are analyzed in the PC. By stereoscopic reverse projection, the camera images can be used to determine the position of the objects in the room.
Fig. 2 shows a schematic side and front view of a hand-held device of the device of the invention. Inside a housing 3 is a support 6 with a tool jack 2 at the front end, in which different tools can be interchangeably tightened. The support 6 includes an electrically controlled rotating axis to drive the tool, e.g. a drill. Between the support 6 and the housing 3 there are linear actuators 7 which can move the support 6 and the drill into a position relative to the drill 3 within a given working range. The front of the tool is mounted on a flexible axis behind the tool, so that the tool can be operated by an electrically controlled device of varying hardness.
The housing 3 is equipped with a handle 10 which has a counterweight 11 at its end facing the housing 3 to balance the weight of the control unit. At the handle 10 there is an actuator 12 which allows the user to interrupt or continue the operation manually. The housing opening through which the carrier 6 exits is closed with an insulating membrane 13 to protect the control unit and the internal sensors from damage and contamination.
Fig. 3 illustrates in a schematic the interaction of the individual components of a device according to the invention. A position detection system 14 detects, at a certain sampling rate, the IST coordinates A of a patient 15 or more generally of a part to be worked and the IST coordinates B of the handheld device 16 or more precisely the IST coordinates of the tool. The corresponding points to be detected are marked, e.g. for the purposes of the application DE 102 25 077.4 and others. The IST position of the tool can be determined either directly or the IST position of the brain is determined by the position detection system 14 and the relative position of the sensor's coordinate system C in the ear is measured with an additional sensor not shown in Fig. 2.
The relative position C and D of the housing 3 in the patient-based coordinate system are passed on to an adaptive and rapid control unit 17 for evaluation, which compares the IST position data with the SOLL position data E from the (preoperative) O.P. planning and generates a control value F for an also non-represented actuator unit.
As regards further advantages and further training in the theory of the invention, reference is made to the general part of the specification and to the patent claims attached thereto.
Finally, it should be emphasised in particular that the example of implementation previously chosen purely arbitrarily is merely intended to discuss the theory of the invention, but does not limit it to the example of implementation.