Surgery – Instruments – Stereotaxic device
Reexamination Certificate
1999-12-13
2001-09-04
Smith, Jeffrey A. (Department: 1731)
Surgery
Instruments
Stereotaxic device
Reexamination Certificate
active
06283977
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to a stereotactic apparatus for use with a stereotactic frame, for mounting to a skull of a patient and a stereotactic arc mounted to said frame, extending over the skull of the patient, and specifically to a stereotactic apparatus comprising a support slide, slidably mounted to said arc, a microdrive unit comprising an instrument holder for depth adjustment of an instrument along a depth axis, in an arc parallel plane, an arc perpendicular adjusting means for adjustment of the microdrive unit along an arc perpendicular axis, an arc parallel adjusting means for adjustment of the microdrive unit along an arc parallel axis.
BACKGROUND OF THE INVENTION
In neurosurgery a stereotactic frame, for example a Leksell Stereotactic Instrument, is mounted to the skull of a patient to provide fixed references to the brain of the patient. The frame encircles the head of the patient and is mounted with screws to the skull of the patient. On the frame a stereotactic arc is mounted, which crosses over and above the head of the patient. A stereotactic apparatus is slidably mounted on the stereotactic arc via a support slide.
A stereotactic apparatus comprises a microdrive, which comprises an instrument holder, for insertion and withdrawal of an instrument with respect to a target area of the brain of the patient. The microdrive is mounted on top of an X-Y-table for fine adjustment of the instrument along the X and Y-axes. Adjustment of the microdrive at the stereotactic arc makes it possible to achieve parallel insertion paths.
Stereotactic surgery is used, for example, for brain mapping using microelectrodes, brain biopsies, DBS implantation and lesioning.
From U.S. Pat. No. 5,817,106, Real, a stereotactic guide apparatus for use with a neurosurgical headframe is known. The stereotactic guide apparatus is mounted on a slide, which is movable along a stereotactic arc. On top of the slide a platform, comprising an X-Y-table, is mounted. In the platform there is a hole for a tubular instrument guide, through which an instrument, attached to an instrument holder in connection with a microdrive, may be inserted by the microdrive.
A problem with this stereotactic guide apparatus is to be accurate in positioning of the instrument. To obtain accuracy the different parts of the X-Y-table must all have extremely small tolerances.
Another problem is the high postion of the centre of gravity, which makes the apparatus unstable.
A further problem is that the hole through the platform limits the possibility of adjustment along the X- and Y-axes.
A still further problem is that it is extremely difficult to keep the apparatus clean, which is an important factor in surgery.
SUMMARY OF THE INVENTION
It is an aim of the present invention to provide a stereotactic apparatus that is accurate without requiring small tolerances.
Another aim of the present invention is to provide a stereotactic apparatus with improved stability in the construction.
A further aim of the present invention is to provide a stereotactic apparatus with greater possibilities of adjustments.
A still further aim of the present invention is to provide a stereotactic apparatus that is easy to keep clean.
According to these aims and in an aspect of the present invention is a stereotactic apparatus according to the preamble provided which is characterised in that the arc perpendicular adjusting means is an arc perpendicular slide, which is movably mounted to the support slide, the arc parallel adjusting means is mounted at an end of the arc perpendicular slide, so that by movement along the arc perpendicular axis the arc parallel adjusting means also moves in said direction, and comprising an arc parallel slide movably mounted to the arc parallel adjusting means, the arc parallel slide being positioned at a different level with respect to the arc perpendicular slide, and that the microdrive unit is rigidly mounted with its portion that is furthest apart from the patient to the arc parallel slide, and by movement of the slide in the arc parallel direction the microdrive also moves in said direction.
The adjustment in the arc perpendicular and arc parallel direction is carried out in different planes and so is the depth adjustment.
These features give the advantages that it is easy to reach all the parts of the stereotactic apparatus and it is easier for a surgeon to survey what he/she is doing.
Further advantages is that the centre of gravity is much closer to the patient, which provides a more stabilised construction, and the path for the instrument is shorter, which minimise angle deviation of the instrument path.
In one embodiment of the present invention the instrument holder comprises an arm which is moved by the microdrive in a governed motion along the depth axis.
Said arm is preferably turnable aside for easy mounting and demounting of an instrument or a cannula and easy access to the microdrive and its inner parts.
In another embodiment of the invention, the microdrive preferably comprises a motor, which through a gear drives a screw on which the instrument holder is provided for a governed motion along the screw, which is orientated along the depth axis.
In a further embodiment of the invention, a screw in a motorised microdrive may also be manoeuvred manually by turning a knob connected to an extended axle of the motor. This has the advantage that an instrument always can be manually manoeuvred, even if, for example, there will be a power failure.
Preferably, in another embodiment of the invention, a gear changes the ratio between an extended axle of a motor and a screw, both positioned in a motorised microdrive, so that the screw rotates with a speed different to that of the axle of the motor for accurate depth adjustment and also reverses the rotational direction of the screw, which transfers a manual rotation of the extended axle of the motor to a logical movement of the instrument holder.
In a further embodiment of the present invention a fixed guide for an instrument may be provided at the portion of the microdrive that is closest to the patient. This is for guiding of an instrument.
In another embodiment of the invention, if a cannula is used, cannula adjusting means may be provided in a fixed guide on the microdrive for adjustment of the cannula along the depth axis. The cannula adjusting means makes it possible to adjust the position of the cannula tip in respect to a target point in the brain and thus how much of the instrument that should extend from the cannula.
Preferably, in a still further embodiment of the invention, a settable guide for an instrument, which has a guide member, is settable mounted along the depth axis by means of a slide and a fixing screw at the microdrive so that the guide member can be provided between the microdrive and the patient. The advantage is that a guide can be positioned close to the skull of the patient for a more precise guiding of an instrument, independently of the mounting of the stereotactic frame.
As will be evident to a person skilled in the art these different embodiments may be used one by one or combined in any arbitrary way.
These and other embodiments and advantages of the present invention will be evident from the appended claims and the following description.
REFERENCES:
patent: 3196875 (1965-07-01), Pfeifer
patent: 4350159 (1982-09-01), Gouda
patent: 4465069 (1984-08-01), Barbier et al.
patent: 4875478 (1989-10-01), Chen
patent: 5649936 (1997-07-01), Real
patent: 5817106 (1998-10-01), Real
patent: 5871487 (1999-02-01), Warner et al.
Leksell Micro-Stereotactic System Product Publication, Elekta Instrument AB, Sweden (1990) pp. 1-11.
Leksell Stereotactic System Product Publication, Elekta Instrument AB, Sweden (1986) pp. 1-20.
Ericsson Per
Hugosson Christina
Jakobsson Anders
Burns Doane Swecker & Mathis L.L.P.
Elekta AB
Robert Edvando C.
Smith Jeffrey A.
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