Patent Application
20240207010
The present invention relates to an implantable guide hub for use in neurosurgery, neurotherapeutics and neurodiagnostics. The invention also relates to a jig for setting the depth of insertion of a surgical tool into a patient during surgery. The device and jig are particularly useful in image-guided stereotactic neurosurgery where accurate and reproducible targeting is required.
In image-guided neurosurgical procedures targets within the brain and trajectories to them are identified on radiological images and their image based 3D coordinates are co-registered with the 3D coordinate system of a surgical targeting device or stereoguide. This registration is conventionally achieved with reference to fiducials, visible on radiological images that are attached to a base frame fixed to the patients head. The derived target and trajectory coordinates are set in the stereoguide which is then fixed to the base frame and instruments guided to the target. Alternatively so-called frameless registration can be achieved by mechanical means using an arm with position sensors or optically or electromagnetically tracked instruments to locate the position of radio-opaque markers that were fixed to the patient's head during image acquisition or to trace the patient's facial profile with their head fixed to an operating table. Stereoguides may include a moveable and lockable arc or an arm and may be a surgical robot. Targets in the brain can include anatomical structures or pathological structures such as tumours.
A number of difficulties can be encountered in image-guided stereotactic neurosurgery. These include targeting inaccuracy resulting in inadequate therapeutic gain and off-target side-effects. Inaccuracy can also result in higher rates of complication and morbidity through injury to vasculature with haemorrhage or injury to vital brain structures. Satisfactory fixation of stereotactically-inserted devices to the skull can be difficult and can present attendant risks of device pull-out or migration into the brain.
Current stereotactic systems are complex and require the surgeon to make multiple measurements and adjustments in order to deliver devices into the brain. The risk of human error is high and multiplied when more than one trajectory and target is required. The complexity of current stereotactic systems results in prolonged operation times which add additional risks such as higher rates of infection.
Current stereotactic systems do not fully satisfy the desire for accurate reproducibility in repeated procedures. Repeated procedures can be of particular benefit when optimising genetic therapies, delivery of chemotherapeutics and lesioning procedures, for example.
If an implanted device does become misplaced or is removed, re-insertion requires the whole surgical workflow to be repeated. This can include pre-operative imaging, planning the procedure, and application of a stereotactic system.
It is an object of the invention to address at least some of the aforementioned problems, by the provision of an improved apparatus and method for targeted neurosurgical procedures.
According to a first aspect of the invention, there is provided a surgical guide hub for implanting in an aperture formed in a skull and made along a trajectory to a brain target,
The guide hub may have a cylindrical or generally cylindrical body. The throughbore may be along the axis of the cylindrical or generally cylindrical body.
The through-bore may be aligned to deliver an implantable device along the trajectory, for example into the brain, by methods described herein. Thus, the throughbore of the guide hub can provide guidance for a device along the trajectory. Thus, the guide hub finds application in neurosurgery, but may also be employed in other surgical uses, where fixation of a guide hub to bone is desired.
The guide hub may be configured to provide guidance along a trajectory to a brain target. The guide hub typically provides a guidance element in the skull, as close as possible to a target in the brain, thereby assisting accuracy of guided delivery along a trajectory. The aperture formed in the skull penetrates the entire thickness of the skull. Therefore, the guide hub can typically be configured to provide access between the exterior of the skull and the interior of the skull. The through-bore of the guide hub is suitable for delivering a device through the skull and into the cranial cavity and/or the brain. In particular, fluid transfer tubes such as catheters and cannulas may be delivered through the guide hub into the cranial cavity and/or brain.
The guide hub does not comprise a guide tube such as in the prior art apparatus of
The guide hub can be sized so that, when fitted to the skull of the patient, it does not protrude above the surface of the skull. Thus, guide hub can be for planting in an aperture formed in a skull at or below the skull surface. The guide hub can be of particular use when repeated procedures are envisaged. The guide hub may be closed with a cap fitting into the second formation and the scalp closed over it when not in use. When required to deliver a device, the scalp can be reopened, the cap removed, and the device delivered via the guide hub.
A wide range of devices can be delivered through the skull and into the cranial cavity and brain using the guide hub and systems described herein. Devices may include cannulas or catheters, for the delivery or removal of fluid for diagnosis or treatment; electrodes for recording, stimulating or blocking neural activity including radiofrequency lesioning; brachytherapy devices for delivering therapeutic radioisotopes; glass-fibres for delivering light, including laser, for lesioning or optic stimulation; probes for monitoring pressure, temperature, fluid flow, the concentration of metabolites or drugs or gasses; biopsy devices and stylets to provide markers in the brain or to maintain a track for later re-access of another device to a brain target.
More specifically, catheters and cannulas may be delivered through the guide hub into any intracranial space including into the ventricles, subdural or subarachnoid space, into abscesses, cysts, cavities and tumours as well as intraparenchymally. Fluids delivered for diagnostic purposes may include contrast agents visible on X-ray imaging including X ray computerised tomography (CT) and Magnetic Resonance Imaging (MRI), diagnostic radioisotopes and dyes. Fluids delivered for therapeutic purposes include, but are not limited to, chemotherapies, antibiotics, enzymes, neurotrophins, gene therapies, SiRNAs and antisense oligonucleotides, enzymes, immunomodulatory therapies (such as monoclonal antibodies and chimeric antigen receptor T-cell (CAR-T) therapy), Auger electron emitters, immunotoxins, molecular targeted therapies, monoclonal antibodies, oncolytic viruses, nanoparticles and botulinum toxin. Inert fluids (including artificial cerebrospinal fluid, normal saline, Hartmann's solution, Ringer's lactate) may also be infused for therapeutic purposes;
Devices may be delivered via the guide hub with the aid of a guide tube secured in the through bore.
Thus, the guide hub and associated systems and methods described herein can have application in a wide range of surgical methods and treatments. For example, surgical treatment of abnormalities of brain function, including, but not limited to, treatment of neurodegenerative and movement diseases such as Parkinson's disease, Alzheimer's Disease, Huntington's Disease, tremor, cerebral palsy; neuro-oncological diseases such as glioblastoma, cerebral metastases, diffuse pontine glioma; neuro-inflammatory diseases such as multiple sclerosis; psychiatric disorders such as depression and obsessive compulsive disorder; metabolic diseases such as lysosomal storage disorders; hydrocephalus and intracranial hypertension; and epilepsy.
The guide hub may be generally cylindrical in form. The hub may have an outside diameter of from 3 mm to 12 mm, advantageously, from 3 mm to 6 mm. The height of the hub may be from 3 mm to 10 mm, advantageously from 4 mm to 6 mm. Thus, the guide hub can provide a compact fitment into the skull of a patient.
The throughbore may be reduced in diameter at its distal end (distal to the outer surface of the skull in use). For example, it may have a diameter of from 0.5 mm to 5 mm or even from 1 mm to 3 mm. The reduced diameter can be chosen to provide a close fit to the device being delivered, or to an associated guide tube.
The guide hub may further comprise a seal located within the through-bore and configured to provide sealing engagement with a device passing therethrough or with a cap fitted to the through-bore and engaging with the second formation. The seal may be an O-ring seal or washer with a central aperture sized to receive a device, guide tube, or cap therethrough. The O-ring seal or washer may be configured to compress axially and expand radially to provide sealing engagement with a guide device, implantable device, or a cap to the hub in the central aperture.
The guide hub may have a conical distal end. The throughbore may have a conical distal end and may be configured to engage with a corresponding conical portion on a guide device, implantable device, or a cap to the hub to provide a sealing engagement therebetween.
The guide hub may include a proximal rim that may extend outwards of the hub to provide a lip for sitting on a surface about an aperture on a skull. For example, the proximal rim may extend from the hub by from 0.5 mm to 2 mm. Guide hubs where the proximal rim does not extend from the hub are also contemplated.
The guide hub includes a first formation on its external surface for the hub to engage with and become fixed within an aperture in a skull. The guide hub may be fitted to an aperture in a skull without the use of small screws or other separate fixings as are often employed when fitting surgical devices to bone. The guide hub may be press fitted into the skull aperture and so the first formation may take the form of one or more projections enabling the press fit action and/or preventing rotation of the guide hub once fitted.
Thus, the first formation on the external surface of the hub may comprise at least one broaching tooth for securing the hub to the skull. There may be a gap between the broaching tooth or teeth and a proximal rim to allow bone ingrowth into the gap when in use. The at least one broaching tooth or teeth may be of triangular cross-section and are configured to bite into and lock the hub into the surrounding bone in use.
Additionally, or alternatively, the first formation on the external surface of the hub may comprise at least one rib for securing the hub relative to the skull. The rib or ribs may extend generally axially along the surface of the guide hub, from proximal to distal end.
Other patterned surfaces may be employed to provide grip between the guide hub and bone. For example, a pattern of protuberances may be distributed about the outer surface of the guide hub.
Alternatively, the first formation on the external surface of the hub may comprise a screw thread for securing the guide hub to the skull.
The second formation, on the surface of the throughbore, is for securing a guide device, implantable device, or a cap to the hub. The second formation can allow releasable securing of a guide device, implantable device, or a cap to the hub.
Conveniently the second formation can also be used for securing a hub insertion tool to the hub. The hub insertion tool can comprise a rod with a formation at its distal end for engaging with the second formation in a hub. Thus the hub insertion tool constitutes a guide device that can be used with a stereoguide system to insert the hub into the skull along a trajectory as described further hereafter and with reference to particular examples.
Conveniently the hub insertion tool may be hollow along its length to allow insertion of a surgical tool or implantable device down through the hub insertion tool, through an attached hub located in a skull, and thence into the brain of a patient. In this way the combination of a guide hub and a hollow hub insertion tool (or another hollow elongate tool fitting to the second formation) can be used in combination as an elongate guide, fixed to the patient's skull, for insertion of tools or devices along a trajectory and into the patient. For example, a surgical tool such as a track making probe for making a track in the brain to enable and guide insertion of an implantable device can be delivered along the selected trajectory, via the hub and hub insertion tool combination, into a patient's brain as described further hereafter, with reference to a particular example.
An elongate guide, comprising a guide hub and a hollow hub insertion tool (or another hollow elongate tool fitting to the second formation); and methods for using the elongate guide; constitute further aspects of the invention. The hollow hub insertion tool (or another hollow elongate tool) may be provided with a hole at its distal end for venting air as a tool or device is delivered through it.
The second formation on a guide hub may comprise a screw thread configured to engage with a corresponding thread on an insertion tool, or to a guide device, implantable device, or a cap to be inserted in the throughbore. Alternatively, a bayonet type fixing between a device or cap and the second formation may be employed.
Where the second formation and guide device, implantable device, or a cap comprise screw threads, the corresponding screw threads may be formed to allow rapid fitting of the device or cap, for example with only a half turn rotation of the device or cap. Thus, the screw thread may be a double-entry thread comprising a first thread portion and a second thread portion, wherein each thread portion sweeps around half a revolution of the hub such that a device or cap can be inserted fully within the thread and locked securely therein by a half turn rotation.
The corresponding screw threads may be locking screw threads. For example, locking screw thread arrangements such as those of the Spiralock® type that make use of relatively free running threads that lock when a male thread engages a wedge ramp at the root of the female thread. For further example, at least one of the first thread portion and second thread portion may comprise a notch configured to temporarily lock a device or cap within the first or second thread portion by engagement of the notch with a corresponding rib on the device or cap. Each of the first and second thread portions may comprise a notch configured to temporarily lock a device, cap within the first and second thread portions by engagement of the notches with corresponding ribs on the device or cap.
Thus, the second formation can be used for rapid (e.g., half turn) screw fixing of a guide device, implantable device, or a cap to the guide hub, which can be done with a simple screwdriver tool with an end shaped for locating into a suitable formation on the device or cap. Conveniently the engagement between the screwdriver end and the formation on the guide device, implantable device, or a cap provides a releasable attachment. For example, the end of the screwdriver may be an interference fit with the formation on the device or cap so that the device or cap remains attached to the screwdriver until fitting to the guide hub is complete. Where the device being fitted is elongate and is to extend beyond the guide hub after fitting (e.g., a cannula for delivering a therapy as an infusate), the screwdriver tool may be hollow along its length to allow passage of the device therethrough. Where the screwdriver is hollow along its length, a vent hole may be provided at or near the distal end for venting air as a device or surgical tool is passed through the body of the tool and into a patient. This can aid in prevention of driving air into a patient, e.g., into a patient's brain. Alternatively, a screwdriver tool can be provided with distal (head) end that can accept an elongate device into a side slot and then passing through the extreme distal end of the tool, as described in more detail hereafter. The side slot can also act as an air vent. The side slot may extend to the extreme distal end of the screwdriver tool. This can allow easier fitting and removal of elongate devices such as cannulas as described further hereafter. The screwdriver tool constitutes another aspect of the invention.
The guide hub of the invention is for delivering a device through the throughbore and along a trajectory. The second formation on the surface of the through-bore is for securing a device or cap to the hub. A cap secured to the second formation may secure a device to the hub. Thus, the present invention also provides a system comprising a surgical guide hub according to the invention as described herein; and a device or cap configured to engage and preferably to also lock within the through-bore of the hub.
The device or cap may comprise a seal to provide sealing engagement with the through-bore of the hub. Alternatively, or additionally the seal may be provided on the throughbore.
The device or cap of the system may comprise a conical portion which is configured to engage with a corresponding conical portion of the hub to provide a seal therebetween.
The device or cap may comprise a screw thread configured to engage with a corresponding screw thread of the second formation on the through-bore of the hub.
Thus, the device may comprise a formation for securing into the second formation in the guide hub (e.g., a formation comprising an external thread may be secured about the body of the device).
A cap of the system may be for sealing the throughbore when entry to the cranial cavity is not required.
Alternatively, the cap may have a cap throughbore passing therethrough, which may be for securing an implantable device to the guide hub. For example, a cannula may pass freely though the cap throughbore. As the cap is secured e.g. screwed into the throughbore, the cannula can be gripped by an O ring seal within the throughbore that is compressed axially and expanded radially inwards by the cap.
The guide hub of the invention is implanted into an aperture of the skull in use. The guide hub acts as a guide for insertion of devices into the cranial cavity and in particular along a trajectory to a target in the brain. Following imaging and use of a stereotactic system to determine the trajectory, the general procedure employed to insert the hub may include the steps of:
The flat face made by the facing tool provides a surface, generally perpendicular to the trajectory, that allows drilling of the pilot hole whilst avoiding slippage of the pilot hole drill, which could occur if applying the pilot drill directly to the curvature of the skull surface.
Thereafter the guide hub is employed for insertion of a device. The preparation of the profiled hole, fitting of the guide hub, and delivery of a device, especially into the brain, requires careful guidance and accuracy throughout the procedure, including making use of stereotactic means such as stereotactic frames or robot arms.
Using conventional methods of drilling on the surface of the skull to form a profiled hole and fit devices into the brain typically requires many measurements to be taken, particularly when multiple different pieces of equipment are used to form the hole for the introduction of a hub or other apparatus.
When using conventional stereoguides, brain images are registered with the stereotactic reference system and the stereoguide is set to the target coordinates and along the desired trajectory. The stereoguide has its own datum point from which the target is at a measured distance along a selected trajectory. Currently available stereoguides have for example distances of 190 mm or 160 mm between the datum and the target. Robotic stereoguides can be pre-set with a desired distance between the datum of the robotic stereoguide and the target.
Brain imaging provides the skull thickness along the desired trajectory and the distance from the skull surface to the target. In conventional methods, this information is used to allow the surgeon to calculate the length of each piece of apparatus to be introduced along the trajectory into the head of the patient. For example, the surgeon will calculate that a particular depth into the brain must be reached by a first device and will therefore cut or adjust the length of the first piece of apparatus to allow that depth to be reached when using the stereoguide method. The next device to be introduced may be required to reach a different depth, often deeper into the brain. The surgeon will again use the data from the imaging to calculate the length the second device must be adjusted or cut to and make the adaption so that the desired depth is reached when using the stereoguide. This process can be laborious and requiring many calculations with the attendant risk of human error, particularly in the stressful and fatigue inducing environment of neurosurgery.
According to a further aspect the present invention provides a jig for setting the depth of insertion of a surgical tool into a patient during surgery, the jig comprising:
The jig may also be used for setting the depth of insertion of a device into the patient, such as any of the devices (cannulas, catheters, DBS electrodes etc) discussed herein with respect to use of the guide hub of the invention. Thus, the jig can be used in the insertion procedure and uses of the guide hub of the invention as described herein, but can also find more general use in neurosurgery and other surgical procedures. The datum surface on the reference guide represents the skull of a patient or any other surface or datum used in a surgical procedure, for example a datum based on the location of a guide hub of the invention in a patient's skull.
The jig and associated tools described herein have the advantages that only a limited number of measurements or calculations of length are required. For example, only one baseline measurement may be required to prepare a jig for setting all the tools and device lengths or depths required for a complete surgical procedure. Furthermore, the tools and devices required for a procedure can be set in the jig ready to be transferred to the patient one after another, with minimal handing, thereby reducing the risk of the transfer of infection.
The jig may also comprise a target datum, representing a target position with respect to the stereoguide datum as used in a chosen stereotactic system or arrangement. Thus, the distance from the representative datum to the target datum on the jig corresponds to the stereoguide datum to target distance when carrying out a surgical procedure on a patient. For the commercially available Cosman Roberts Wells (CRW) stereotactic frame that distance is set at 160 mm from the target and the corresponding distance for a Leksell frame is 190 mm. The datum surface on the reference guide can therefore represent the skull surface, interposed between the representative datum and the target datum on the jig.
The jig may be generally rectangular in form. The jig may take the form of an open frame onto which surgical tools are placed. The jig may be provided with a back plate. The jig may be provided with a stand to hold the jig up from an angle to the horizontal (for example at 45 degrees).
The tool aligning device may comprise the representative datum.
The tool aligning device may comprise grooves provided on a back plate. The tool aligning device may comprise a bar including slots or grooves to receive generally elongate tools and direct their distal ends towards the reference guide. The reference guide may be in the form of a bar parallel to the bar of a tool aligning device. The reference guide may be moveable relative to the tool aligning device whilst retaining the parallel relationship.
In the jig, the reference guide is moveable relative to the representative datum. Conveniently this is achieved by having the reference guide moveable, and the representative datum fixed. For example, a representative datum may be provided as part of a tool aligning device in a fixed position in the jig. However, alternative arrangements are contemplated, for example where the reference guide and its associated datum surface are fixed; and the representative datum is moveable to set the baseline length. For example, the representative datum may be provided on a moveable tool aligning device. As a yet further example both the representative datum and the reference guide may move when setting the baseline length.
In a convenient form of the jig, the tool aligning device comprises a bar including slots or grooves to receive generally elongate surgical tools and direct their distal ends towards the reference guide;
In this form it can be particularly convenient for the tool aligning device (and associated reference datum) to be fixed and the reference guide moveable.
The jig may also comprise one or more cross members to provide bracing, for example extending between the at least two rails at each of their ends.
The bar of the reference guide may be in sliding engagement with the at least two rails and may be clampable to one or more of the rails to set the baseline length. There may be at least three rails connecting the tool aligning device and the reference guide, with the third rail disposed at a midpoint of the bar of the tool aligning device and at least extending to a corresponding midpoint of the bar of the reference guide.
As an alternative to sliding engagement between the rails and a moveable reference guide, the at least two rails may be threaded and operate as leadscrews passing through corresponding threads on the bar of the moveable reference guide; or
The jig may be motor driven; and may be computer controlled to set the baseline distance. The setting of the jig may even be directly from the surgical planning software. From the planning scan, information such as the target location relative to skull, the thickness and the skull and a trajectory from the skull to a target are obtained. Therefore, a jig may be set by computer control using scan data as input, prior to the surgical procedure. For example, by servomotors driving spindle shafts controlled by the computer.
In the jigs of the invention, the reference guide may comprise at least one guide channel extending therethrough, for passage of a surgical tool or device, the guide channel extending from the datum surface and continuing in the direction set by the tool aligning device. This allows the length of a device from the datum surface to be measured and adjusted or cut to a length as required, for example the required length of a cannula that in use will extend below a guide hub into the brain of a patient.
The jig allows setting of tools for creating a profiled hole in a skull and also the lengths of devices to be inserted into a skull, all determined from one setting of the baseline length and the scan data used when determining the trajectory and distances to target when planning surgery.
For use in the insertion of a guide hub in accordance with the present invention, or in similar surgical procedures where a hole is prepared in bone, the tool aligning device may be configured to receive one or more of:
The reference guide may further comprise a hole for receiving a surgical guide hub of the invention. This can be used to set tools and devices on the jig before transferring them to a patient. Thus, the reference guide may include a guide channel therethrough for passage of a surgical tool through the moveable reference guide and a surgical hub located in the hole.
The jig may further comprise a moveable cutting or depth measuring guide disposed further from the tool aligning device than the reference guide and configured for adjusting a tool or device to a selected length or for cutting a tool or device to a selected length (extending from the datum surface through the moveable reference guide). The moveable cutting or depth measuring guide may comprise a bar parallel to both the aligning device and the reference guide and have a guide surface for engaging with the distal end of a device or device part. The guide surface can be set at an appropriate distance from the datum surface on the reference guide to measure or cut to length a device that passes into the skull from a guide hub. The moveable cutting or depth measuring guide may comprise a slot, transverse to the direction of a device placed in the jig, to allow insertion of a knife for cutting the device to a selected length.
According to another aspect the present invention provides a system comprising a jig of the invention and further comprising:
According to another aspect the present invention provides a method of preparing an operative length of a surgical tool, comprising the steps of:
The step of setting the baseline length may comprise:
The jig and associated methods can find use in implantation of other devices into the skull of a patient. For example, in Deep brain Stimulation (DBS) procedures. In particular for fitting a skull mounted Deep Brain Stimulation (DBS) battery power supply (a ‘generator’).
DBS generators are used to power DBS electrodes fitted into the brain of a patient. Conventionally, DBS generators are mounted in the chest wall of patients, with wiring running subcutaneously to supply power to DBS electrodes at the skull via the neck. DBS generators may comprise a removable battery or may be rechargeable and for example charged wirelessly by inductive charging.
Where DBS generators are mounted close to the DBS electrodes, such as in the skull of the patient, they are typically rectangular or square in form. To install such DBS generators, the surgeon must make a correspondingly shaped hole in the skull of the patient, which is time consuming. A jig of the present invention can be used to aid in preparing a hole in the skull of the patient and fitting of a cylindrical DBS generator as described in more detail hereafter and with reference to particular embodiments.
According to another aspect the present invention provides a system for implantation of a cylindrical DBS generator in the skull, the system comprising:
The milling tool may include a distal cutting surface for cutting a DBS generator mounting hole of a larger diameter than the core drill hole through the skull and a proximal cutting surface for creating a ledge in the skull around the DBS generator mounting hole to accommodate a corresponding lip of the cylindrical DBS generator. Alternatively, two milling tools may be employed, having different diameters, to cut a profiled hole including a ledge to accommodate a corresponding lip of the cylindrical DBS generator.
The system may further include a blunt hook used to free dura from under the inner table of the skull, following completion of the core drill hole. A haemostatic gel such as a DuraSeal® gel may also be provided and is injected into the extradural space to provide a protective barrier preventing tearing of the dura when the milling tool is used.
The present invention also provides methods of surgery making use of one or more of the guide hubs, the jigs, and the associated tools and devices as described herein.
Embodiments of the invention will now be described with reference to the following drawings, in which:
The guide device 100 is installed for use in the skull of a patient by first drilling a hole along a desired trajectory in the skull guided by a stereoguide. The guide device's tube 110 is cut to an appropriate length to provide access to a brain target e.g., for a cannula to be delivered through the tube 110. The tube 110 is delivered over a probe that is guided by the stereoguide through the hole formed in the skull such that when the distal end of the tube is at its planned location the guide device's hub 120 is secured in the pre-formed hole in the skull. With an appropriately sized drill hole the fixation may be a press fit or if pre-tapped it may be a screw fit or alternatively it may be bonded in the drill hole with acrylic cement. The probe is removed and the guide device 100 can remain, installed, at least temporarily, in the head of a patient to allow other neurosurgical apparatus such as a cannula to be guided therethrough to reach targets within the brain.
In some circumstances, the guide device 100 may be left in the skull and brain of a patient for a prolonged period of time. The guide device 100, which is fixed to the skull, does not move with the brain as the brain moves within the skull. Therefore relative movement of the brain against the tube 110 of the guide device 100 may occur and cause trauma to the brain tissue in the locality of the tube 110. The guide device 100 does not provide a seal between its bore and the surgical device that passes there through. There is thus a space between the guide device 100 and a surgical device through which infection can potentially enter into the brain. The guide device 100 does not provide a means of securing a surgical device that is delivered through its bore. For example, when the guide device 100 is used to deliver a Deep Brain Stimulation (DBS) lead, the lead is bent through 90° as it exits the hub 120 of the guide device 100 and is fixed to the skull by compression under a bone plate secured to the skull with small screws. This fixing process is awkward to carry out and carries the risk of inadvertently moving the DBS lead from its target location.
The guide devices 200 comprise a guide hub 220 but do not comprise a guide tube 110 as in the device of
The guide hubs 220 may be made of titanium or PEEK (polyether ether ketone) or another biocompatible material. A PEEK hub has the advantage of being a long-term implantable device that causes no artefact when imaged with MRI and will not heat up in a high magnetic field. Each hub 220 comprises a through-bore 221 and has a conical portion 222 at its distal end with a central hole 223 that forms the extreme end of the through-bore 221. The hubs 220 further comprise a proximal rim 224 at its proximal end. As will be explained in more detail later, the rim 224 provides a hub datum HD, allowing the distance between the hub datum HD and a brain target to be calculated.
The main bodies of the hubs 220 have a diameter (D) and length (L). The diameter of the hub 220 through bore 221 and distal central hole 223 can be sized for guiding and securing a range of surgical devices, for example ranging in diameter from 0.5 mm to 5 mm. By way of example the dimensions of a guide hub 200 for use in delivering and securing a device with a cross section diameter of 1.2 mm may have a diameter (D) of the main body of the hub 220 of around 4 to 5 mm. The hub 220 may be of a length (L) such that it can be fully implanted within the thickness of the skull of the majority of adults and children. Thus the length (L) may be around 4 to 5 mm. The through-bore 221 may be around 3 mm in diameter at the proximal end of the hub 220. The central hole 223 at the extreme end of the through-bore 221 may be typically about 1.2 mm in diameter. The rim 224 may be around 0.5 mm in length (l1) and 0.5 mm thick, with an outside diameter of around 5 mm and an inside diameter of around 4 mm. Guide hubs 220 with alternative dimensions are envisaged for use in delivering devices with different diameters to the brain in humans and other animals, or when employing them in other parts of the human body.
As can be seen in
Referring to
In the examples shown in
As an alternative to broaching teeth 225, a guide hub 220 may be provided with an external thread which is arranged to bite into the skull or the hub may have an interference pattern (not shown). The interference pattern, such as an array of protrusions, can provide for an interference fit to provide locking of the hub 220 into the surrounding bone as the hub 220 is pushed into the bone.
A proximal rim of the guide hub 220 may comprise hub engagement features for engagement with the hub insertion tool, which will be discussed in more detail below. The hub engagement features may comprise any suitable feature, for example grooves, protrusions, or notches. In the example of
A further embodiment of the guide hub 220 may have an external thread that is inserted into a tapped hole, rather than being self-tapping. This would be a preferred solution when the guide hub 220 is made from a material that is not suitable for forming self-tapping thread, for example PEEK. In this instance the jig would have an extra tool to tap the hole to the desired depth.
Referring now to
As shown in
In an exemplary use of the hub 220, an exemplary cap 300 is described with reference to
As also shown in
The cap 300 comprises a corresponding double male thread 326 to engage with the double entry female thread 226 of the hub 220 (
In a second example use of the hub 220, a second example of a cap 400 is used, as shown in
A method of insertion of the hub 220 into the skull 500 of a patient is now provided with reference to
Imaging scans provide the surgeon with information relating to the skull thickness and location and arrangement of areas of interest within the brain. The known distance between the stereoguide datum 503 and the target 501 allows the surgeon to accurately plan surgery using instruments delivered using the stereotactic guidance system.
Conveniently the setting of tools and devices for surgery when employing the guide hubs of the invention makes use of the jigs of the invention, as described in more detail and with respect to
More generally, and as illustrated in
As shown in
After making the flat surface 541, a pilot drill 550 is then used to penetrate the full thickness of the skull 500, thereby creating a pilot hole 551 as shown in
A detailed view of the profiled hole 561 is shown in
The profiled hole 561 has been made along the desired trajectory 502 (
Referring now to
The hub 220 can be aligned and accurately positioned in the profiled hole 561 of the skull 500 using the insertion tool 570. The shank 571 is dimensioned to be operable with a stereotactic guide. For example, insertion tool 570 comprises a shank of 150 mm length and 10 mm diameter. This allows the insertion tool 570 to be used with existing stereotactic guides and provides a sufficiently long insertion tool 570 to deliver the hub 220 to the profiled hole 561 using the stereotactic guide. The insertion tool 570 also comprises a chamfer 573 between the threaded distal end 572 and the shank 571. The chamfer 573 allows for a line of sight between the hub 220 and the medical professional when the hub 220 is brought into the profiled hole 561. The insertion tool 570 can be used to drive the hub 220 into the skull 500 with a force sufficient to enable broaching teeth or other external profile to bite or cut into the skull 500 and thereby secure the hub 220 into the skull 500 with the through-bore 221 co-axial with the trajectory 502 to the target 501. When an external thread or interference pattern is used instead of broaching teeth 225, the insertion tool 570 may have further features that are used to immobilise the tool with respect to the hub internal thread to allow an unscrewing action between the hub external thread and bone.
The insertion tool 570 can then be unscrewed from within the hub 220, leaving the hub 220 implanted in the profiled hole 561 in the skull 500.
The formation at the distal end of the rod 1804, which in this example is the threaded distal end 572, may be configured to be movable relative to the shank 571 of the insertion tool 570. Preferably, the formation at the distal end of the rod 1804 is rotatable relative to the shank 571. The tool engagement feature 1802 may be provided on the shank 571 of the insertion tool 570, such that the shank 571 of the insertion tool 570 engages with the guide hub 220 via the tool engagement features 1802. This means that, following insertion of the guide hub 220 into the aperture, the insertion tool 570 can easily be disengaged from the guide hub 220 by moving (e.g. rotating) the formation at the distal end of the rod 1804 relative to the shank 571, without disturbing the placement of the guide hub 220 in the aperture. In addition, the engagement of the insertion tool 570 with the guide hub 220 via the tool engagement features 1802 can be used to apply a force to the guide hub 220 to insert the guide hub 220 into the aperture formed in the skull. This is particularly advantageous when the guide hub 220 comprises self-tapping threads, and a larger rotational force is required to cut into the skull as the guide hub 220 is inserted into the aperture.
The insertion tool 570 may also comprise a depth stop 1806 as shown in
A system including the guide hub 220 may include a shortened tool 1850 as shown in
The hub 220 can be located in the skull wholly within the recess 561 previously formed by the core drill. If desired the through bore of the hub 220 can be sealed, when not used for delivery of a device through the skull, by inserting a grub screw into the proximal end of the hub, which when fully inserted with e.g., an Alan key, has a proximal end that becomes flush with the proximal face of the guide hub.
Use of a hollow screwdriver 590 and through-bore of the cap 400 allow delivery of the device 593 through both the hollow screwdriver 590 and the cap 400. Turning the cap 400 with the hollow screwdriver 590 moves the cap 400 downwards and into engagement with the seal 230, thus compressing the seal 230 axially and thereby expanding it radially. The seal 230 then provides a fluid, gas and bacterial seal between the hub 220 and the cap 400 that securely grips the device 593 passing through hub 220.
In the example of
As shown in
The screwdriver 590 or 591 may further comprise a latch 1902, for example in the form of a rotating collar or rotating disc as shown in
Referring back to
Removal of a device from the patient can be straightforward. Referring again to the sequence of
The implanted guide hub 220 can facilitate repeated access to intracranial targets without the requirement for further stereotactic surgery. To replace a faulty electrode or a ventricular catheter for example, the device is removed as described above and the cap 400 is screwed back into the hub 220 without compressing the O-ring. This aligns the hollow screwdriver 590 along the axis of the trajectory 502 to the target 501. The distance from the hub datum HD to the target 501 is known and will have been recorded in the surgical notes (
Approximately one third of Intraventricular catheters implanted for the treatment of hydrocephalus will become blocked and need replacing every 10 years. Re-accessing the ventricle for replacement of a catheter can be technically difficult. Advantageously the guide hub may be employed to accurately place and secure a ventricular catheter and simplify its accurate replacement should it become blocked. In such an example, removal of a blocked catheter is achieved by attaching a screwdriver 591 to the cap 400 and unscrewing it. This releases the catheter which can then be withdrawn through the side slot in the distal end of the screwdriver 591. A new catheter is now delivered through the hollow screwdriver 591 and through the cap 400 and hub 220 to the same depth as the original catheter. The new catheter is secured by re locking the cap 400 into the hub 220.
Re-access to the same target 501 for repeated treatment without the need for further stereotactic surgery may also be achieved with the guide hub 220 by replacing a device such as a lesioning electrode, catheter or cannula with a plastic stylet of the same length. The stylet, fixed in the hub 220 by a proximal threaded cap will maintain patency of the track and facilitate re-access to the target 501 days, months or years later. Alternatively, following removal of a device a blind cap (not shown but a cap 300, 400 without a central through-bore), may be located in the hub 220 and secured and sealed in the same manner as previously described with reference to either
Referring again to
Using conventional methods of drilling on the surface of the skull to form a profiled hole and deliver a device typically requires many measurements to be taken, particularly when multiple different pieces of equipment are used to form the hole for the introduction of a hub. The risk of human error across the entire surgical procedure increases when repeated procedures are required, as the calculations of each step must be performed again during the repeated procedure.
Jigs are now described which assist in setting tools for neurosurgery and cutting the length of implantable devices with reduced calculation and adjustment required.
A jig 600 is shown in
The jig 600 comprises an open rectangular frame and has an upper cross bar that provides a tool aligning device 610 and has a representative datum 503′ that represents the stereoguide datum 503 of
The tool aligning device 610 is provided with slots or grooves to receive and align generally elongate tools and tool stops and direct their distal ends orthogonally towards a moveable reference guide 620 that is parallel to the tool aligning device 610. The reference guide 620 is in a form of a bar parallel to the tool aligning device 610 and is moveable relative to the tool aligning device 610 whilst retaining the parallel relationship. The means for maintaining a parallel relationship are described hereafter and with reference to
The jig 600 may further comprise a moveable cutting or depth measuring guide 630 having a surface 631 to be located at selected distances from the target datum 641 as will be explained in more detail later. The moveable surface 630 is in the form of a bar parallel to and positioned below the reference guide 620 and above the lower crossbar 640 providing the target datum 641. A further device cutting surface 635 may be provided at the target datum 641.
As will be shown in other examples, the jig 600 may be laid at an angle, for example 45 degrees to the horizontal. This can be convenient in allowing tools placed on the jig 600 (e.g. located in the aligning device 610) to move into place under gravity.
The use of the jig 600 to prepare tools to make a profiled hole 561 in a skull, such as illustrated in
A stereoguide is aligned to the planned trajectory 502 directed to the target 501 in the patient's brain. After making an incision to expose the surface of the skull 500 a datum measurement tool 535 in the form of a rod is held in the stereoguide and brought into contact with the skull of the patient (
The reference guide 620 is then moved up so that the datum surface 621 of the reference guide 620 comes into contact with the distal end of the datum measurement tool 535 and the reference guide 620 is then locked or held in position. Thus, the distance from stereoguide datum 503 to skull surface 500 on the patient is established on the jig 600 as the baseline distance from representative datum 503′ to datum surface 621.
Alternatively the baseline length from 503′ to 621 in the jig 600 can be set by using a measured distance obtained using the datum measurement tool 535 or by any other means such as a laser rangefinder, other measuring tool, or imaging technique employed with a robot arm or stereotactic frame.
The reference guide 620 has multiple offsets or channels through from datum surface 621 which allow setting different lengths for surgical tools and devices with different functions, as will now be described.
For preparing a hole in the skull and inserting a guide hub 220 the sequence may be as follows. A first offset 650 in the form of a depression in the datum surface 621 is for setting the facing tool 540. A second offset 651 including a channel through the reference guide 620 is for setting the pilot drill 550. A third offset 652 is for setting the core drill 560. Each offset 650, 651, 652 provides a distance from the datum surface 621 corresponding to a distance beyond the skull surface on the patient to which each tool should extend when carrying out its task during surgery. Therefore, the offsets 650, 651, 652 in the reference guide 620 to allow the setting of different tools following only one initial measurement, i.e. establishing the baseline length.
To set the length of the facing tool 540 from representative datum 503′, the facing tool 540 is located in the tool aligning device 610 and its distal end brought to the first offset 650. The length of the facing tool 540 from representative datum 503′ to distal end is set by clamping a tool datum marker 537 to the tool 540. The tool 540 can then be used with the stereoguide to cut a flat face on the skull, as shown in
In a similar fashion, the pilot drill 550 is brought to the second offset 651 and the length required (to bore through the skull but avoid entering the brain—
In this example, a first offset 650 of 1 mm and a baseline length of 100 mm would result in the facing tool 540 being prepared to a length of 101 mm from datum 503 (or representative datum 503′) for preparing a flat face on a skull during surgery. In other examples, the offset may be negative, that is to say the offset may be a protrusion on the datum surface 621 extending towards the tool aligning device 610. In such an example, if the first offset 650 is −2 mm (i.e. a 2 mm protrusion towards the tool aligning device 610) and the baseline length is 100 mm, the tool concerned would be set at 98 mm from datum 503 for surgery.
In the above examples, each tool 540, 550, 560 is fitted with a tool datum marker 537, 538, 539 that can be used in conjunction with a stereoguide to progress the tool into the skull to a carefully measured depth. The datum marker 537, 538, 539 may comprise an indicator 2301 that indicates whether the datum marker 537, 538, 539 is locked to the tool, or in an unlocked state where it can be moved up or down the tool. An example of such an indicator 2301 is shown in
The jig 600 may also be used in a similar fashion, to assist in inserting a guide hub 220 as illustrated in
The use of the jig 600 to prepare surgical tools or devices for delivery through a guide hub 220 into the brain is now described.
Devices that may be delivered through a guide hub 220 include guide tubes, electrodes and cannulas, however it will be understood that other types of device may be delivered through the hub 220.
Referring still to
In this way, the length of a device or tool required to extend from the hub 220 can be set in the jig 600. In this example, if the track making probe 596 is to prepare a track within the brain, the length of the probe 596 from the hub 220 to the desired position in the brain can be set as follows. The insertion tool 570, hub 220 and probe 596 combination are arranged as shown in
As shown in
In this example of the jig, the reference guide 620 comprises a first indicator 623 in the form of a first pointer which indicates a point on a scale 624. The scale 624 provides measurement along one side of the jig 600. The scale 624 provides a distance from the target datum 641 of the lower cross member 640. Using this scale 624, a surgeon can set the position of the reference guide 620, if the baseline length is not provided by a datum measurement tool 535. If, as in the present example, a datum measurement tool 535 is used, the set baseline length can be confirmed using the scale 624. The cutting or depth measuring guide 630 also has an indicator 633 in the form of a pointer which runs along scale 624. Using this second indicator 633, the position of the measuring guide 630 can be set based on a measurement provided by imaging studies of the patient.
A surgeon may set all of the tools and devices before starting surgery on the patient by making use of the jig 600. This may be manually or by computer control of a motorised jig, making use of scan data and the surgical planning software. Alternatively, the surgeon may set the reference guide 620 and measuring guide 630 and then set tools or devices on the jig 600 as required throughout a surgical procedure. The hub insertion tool 570 or another tool of the same type may be used to deliver a track making probe 596 into the brain of the patient, and then be set again on the jig 600 with the next device to be inserted into the brain. In
The jig 600 can also be used to set guide tubes and cannulas. The reference guide 620 comprises a profiled hole 561 which can match the depth within the throughbore of a guide hub 220. A guide tube 598 is located in the profiled hole 561 and extends downwards. The guide tube can then be cut to the desired length for insertion into the brain. The position to cut the guide tube 598 can be measured using scale 624 to set the position of guide 630 and the cut can be made using a knife passing through cutting slot 634.
The jig 600 is also shown for setting a cannula 599. A cap 300 carrying the cannula 599 is fitted into the reference guide 620 in a profiled hole corresponding to the internal through bore of a guide hub. The cannula 599 can then be cut to length by a knife inserted through cutting slot 635. As shown in
Another jig 700 is now described with reference to
The jig 700 comprises a lower cross member 740 but a datum 741 corresponding to the location of a target (501 in
The jig 700 further comprises a second cutting device 744 with a corresponding second cutting slot 745.
A convenient use of a hollow insertion tool 770 is now described with reference to
As shown in
In the jig 700, the reference guide 720 and cutting or depth measuring guide 730 are moveable and lockable.
As shown in
The outer guide rails 701, 702 provide a means by which the reference guide 720 and the cutting or measuring guide 730 can be moved whilst remaining parallel to each other and to the tool aligning device 710. The reference guide 720 has a first locking screw 747 which can be turned to clamp the reference guide 720 to the central guide rail 703. Thus the reference guide 720 can be fixed in a selected position. The measuring guide 730 comprises a similar second locking screw 748 which screws down onto the backplate 798 for locking engagement.
In partially exploded view
A cutting and measuring guide can also be arranged to move in the same fashion.
As illustrated, the reference guide 720 is also attached to the central guide rail 703 such that it can slide up and down the central guide rail 703 when unlocked, and be locked to the central guide rail 703 by use of a first locking screw 747.
Alternatively, as shown in partially exploded view
In some arrangements it may be desirable to provide particularly fine adjustments to the positioning of a reference guide or a cutting and measuring guide. If so the central guide rail 703 may be screw threaded where it fits to lower cross member 740 (not shown). Rotation of the guide rail 703 can then be used to give small movement of the reference guide or cutting and measuring guide in the jig frame.
Starting from the left hand illustration of
A milling tool 960 then mills around the enlarged hole 932 previously created by the core drill 930. The milling tool 960 in this example comprises a first mill body 961 and a second mill body 962. The first mill body 961 has a cutting surface that opens the enlarged hole 932 to a first diameter and the second mill body 962 has a cutting surface opens the enlarged hole to a second diameter, smaller than the first diameter. In this way, a ledge 963 is created within the hole. The milling tool 960 further comprises a blunt nib 964 which is sized and dimensioned to locate within the enlarged hole 932 during milling, thereby providing stabilisation and ensuring the milling tool 960 remains on its desired trajectory. The milling tool 960 is attached to the threaded shaft 970 enabling the attachment of the larger diameter milling tool below the stereoguide which is of a smaller diameter. As an alternative two milling tools, with different diameters, may be employed to form the hole including a ledge.
After the above steps the hole prepared in the skull is then ready to receive the DBS generator 980 as will now be explained with reference to
In
Electrical cables 984, 985 can then be attached to the DBS generator 980 by inserting the cables 984, 985 through correspondingly dimensioned holes in the DBS generator 980. The cables 984, 985 are secured to the DBS generator 980 by a second sets of grub screws (not shown) which are located within corresponding second grub screw holes 986 or by operating captured cam-locks that engage with the lateral aspect of the inserted DBS electrode leads 984, 985 that are implanted through the skull of the patient to brain targets.
The DBS generator 980 may be around 2 cm-6 cm in diameter. Alternatively, the DBS generator 980 may be around 3-4 cm in diameter.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2106203.9 | Apr 2021 | GB | national |
| 2106210.4 | Apr 2021 | GB | national |
| 2106224.5 | Apr 2021 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2022/051104 | 4/29/2022 | WO |
