Surgery – Instruments – Stereotaxic device
Reexamination Certificate
2000-07-20
2001-12-11
Smith, Jeffrey A. (Department: 3732)
Surgery
Instruments
Stereotaxic device
Reexamination Certificate
active
06328748
ABSTRACT:
The present invention concerns a device for adjustment of different stereotactically and endoscopically located equipment, including pharmaceutical agents, radiation sources and organic material and a method for adjustment of stereotactically and endoscopically located equipment.
Brain surgery procedures, where precise placement of instruments or other aids is required, are generally performed in several steps:
1. X-rays are taken of the patient.
2. The patient's head is firmly screwed to a frame which is provided with position indicators (stereotactic frame).
3. New X-rays are taken where markers on the frame permit calculations to be performed, thus enabling aids to be inserted into a desired area.
4. The patient is taken to the operating theatre.
An essential condition for the use of all such instrumentation with present day equipment is that the patient's head is fixed to the stereotactic equipment. The frame is usually attached by screws to the skullbone. The head is then fixed by means of arm devices, usually to the operating table.
U.S. Pat. No. 5,263,956 concerns a device for use in neurosurgery. A ball joint is arranged to hold a neurosurgery tool in a predetermined orientation relative to the patient's skull. A plate with sharpened corners is placed against the skull. The plate has a recess in which a ball joint is placed. A bore passes through the ball joint, permitting the introduction of neurosurgery equipment. The ball can be rotated, thus enabling the orientation of the neurosurgery probe to be adjusted relative to the skull. Screws are used to hold the neurosurgery probe stationary relative to the plate. A ball holder ring holds the ball against the plate. The device has several disadvantages in use, including the fact that it comprises several loose parts (including small screws) and the mechanism fixing the ball in position is a screw which grips the ball. This makes the equipment difficult to handle, and the screw can easily be lost. The devices for securing the ring to the skull are not adequate to ensure the absence of relative movements. The main drawback of this device is that the radius of action is severely restricted, since the ball's central point is located outside the area defined by the cranium.
U.S. Pat. No. 4,681,103 discloses a guiding device for ultrasound adjustment of surgical instruments. The device consists of an adaptor housing which is securely screwed to the skull and which has a longitudinal opening through which instruments are passed. For screwing purposes the device is provided with a gripping surface which is held by the fingers. Such an attachment mechanism makes the device difficult to secure on those areas of the head where there is very little room round the adaptor housing (e.g. near shoulders and at the back of the head).
At the same time it is difficult to exercise sufficient force when screwing into the compact outer bone layer of the cranium. The ball's optimal position is an abutment against the surface of the brain, since the closer to the surface of the brain the centre of the ball is located, the smaller the opening in the skull which is necessary to reach a large area of the skull. In the adaptor housing described in U.S. Pat. No. 4,681,103 the position of the attachment threads in the housing and the position of the ball in the socket are such that the ball is not located in the said optimal position. In addition to this the ball's diameter is the same size as the longitudinal opening. The combination of these features means that the angular area which is available when using this known device is no greater than 60°. Moreover, several parts are required to lock the ball in a specific position, leading to a reduction in reliability.
U.S. Pat. No. 4,809,694 shows a biopsy guide including a cranial tap, a spherical member and a retaining structure attachable to the tap to immobilize the spherical member in a desired orientation. The cranial tap places the spherical member quite “far” from the skull surface and this leads to a reduced working range in the actual brain zone. The retaining structure contributes also to limit the instrument's working range by limiting the angle of movement of the instrument in the area above the spherical member. This device is thus not satisfactory because the working range is greatly reduced. Besides the device contains several small pieces and this is not advisable because it leads to problems in operation. It is also known to employ ball joints for securing equipment in a specific position relative to the brain (U.S. Pat. No. 4,681,103). In this case soft or collapsible balls are employed which, when secured in a specific angular position, clamp the tubes together, thereby securing the tubes' angular position. However, these devices do not permit any further movement of the tubes relative to the ball. Thus they do not permit any advance adjustment of the ball's angular position before the equipment is passed through it.
These and other problems associated with the known solutions are solved by means of the device and method according to the invention. The device according to the invention comprises a holder and a fixing key, wherein the holder comprises a lower ring for receiving a ball which will form a ball joint, and an upper ring for locking the ball in a specific position, where the ball has a channel for insertion of medical instruments, and where the lower ring has an external threaded surface for direct screwing to an area of a patient's skull. The device is characterized in that the ball's central point, and thereby the ball joint's fulcrum is arranged for positioning on a level with the patient's cranium by means of a groove-like or curved surface on the holder which forms an abutment for the ball. The invention also concerns a method for adjustment of different stereotactically and endoscopically located equipment, including pharmaceutical agents, by means of the holder, characterized by:
localising a point on the skull,
making a burr hole
attaching the holder's lower ring to the wall of the formed burr hole by means of the key,
placing the ball on the lower ring in such a manner that the ball's central point is on a level with the patient's cranium,
attaching the upper ring to the lower ring without locking the ball,
passing a stereotactic pointer through the ball in order to adjust direction,
locking the ball in a specific angular position,
replacing the stereotactic pointer with implantable equipment, such as a drain, an electrode, etc., or with temporarily introduceable equipment, such as an endoscope, a biopsy needle etc.
The invention also concerns the application of the device and the method for:
biopsy taking,
puncture of, e.g., cysts, abscesses and other expansive processes,
puncture of the ventricle system by placing drains and equipment,
placing of markers, isotopes and biological or other material, such as neuroactive cells,
placing of electrodes or other equipment for recording/stimulation of the brain.
The holder's lower ring is equipped with grooves for co-operation with protrusions in the fixing key which is employed for screwing the ring's threaded surface on to and off an area of the skull. The use of the fixing key, has several advantages including the fact that it permits great force to be exerted, thus securing the ring in the compact outer bone layer of the cranium. In addition to this the use of a key gives access to difficult areas (the key is long and narrow and does not require extra space round the securing ring). The equipment is designed in such a manner that the ball's lower part is on a level with the surface of the dura. This ensures the best possible accessibility for reaching various brain structures through a small burr hole.
The holder's upper ring is equipped with notches on the circumference whose object is to obtain a good grip for securing the upper ring to the lower ring, thereby facilitating correct positioning. Both the upper and the
Elekta AB (publ.)
Finnegan, Henderson, Farabow, Garrett & Dunnerr, L.L.P.
Robert Eduardo C.
Smith Jeffrey A.
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