TRACKABLE MARKER DISPENSER

A dispenser for dispensing and attaching individual markers to a reference array of a tracking system is described. A housing defines a cavity extending along a longitudinal axis. The housing has a dispensing end defining a dispensing aperture. A plurality of markers are stacked within the cavity. Each marker has a marker attachment feature by which the marker is attachable to an attachment site of a reference array. The dispensing end of the housing provides a retainer which exerts a retaining force on a bottom most marker sufficient to retain the plurality of markers within the cavity but permitting the bottom most marker to be released from the cavity when the bottom most marker has been attached by its attachment feature to the attachment site of the reference array.

The present invention relates to a dispenser and a method of use of the dispenser, and in particular to a dispenser for markers detectable by a tracking system used by a computer assisted surgery system.

Computer assisted surgery (CAS) systems are generally known and often use a tracking system which determines the location and/or orientation of various items in the operating theatre, including the body parts or the patient, surgical equipment, tools, instruments and implants and such like. Some CAS systems may also include robotic systems.

The items being tracked have markers which are detectable by the tracking system attached to them. The exact nature of the markers may vary depending on the tracking system. Some tracking systems may use wired markers and other may use wireless markers. Wireless markers are often active markers, which themselves emit some form of signal which is detected by the tracking system, or passive markers which reflect some form of signal emitted by the tracking system. For example, acoustic signals, magnetic signals and light signals, particularly infra-red light, may be used by wireless tracking systems.

At some stage, the markers are attached to the items that will be tracked. Sometimes, this involves attaching a reference array to the item being tracked and wherein the reference array includes a number of markers with a particular configuration, so that that particular reference array, and hence the item it is attached to, can be distinguished from other reference arrays that may be detectable by the tracking system.

Through repeated use, the markers may become damaged or otherwise require replacement.

It may be common for markers to be single use to ensure that they give the best performance for a surgery, and also because it is hard to reprocess them without effecting their performance. This means that it is common to attach new markers to all the arrays at the start of surgery.

When markers are disposable, then it may be necessary to replace the markers of a reference array.

A reference array may need to be modified or reconfigured by changing the relative locations of the markers on the reference array.

If a reference array becomes damaged, for example bent out of shape, then a replacement reference array may be needed and markers may need attaching.

If a further reference array is needed, for example because an uncommon instrument is to be used and needs to be tracked, then a new reference array may need assembling.

Sometimes, a marker may get dirty during surgery, and so will need to be replaced mid surgery.

Hence, there are a number of instances in which it would be beneficial to be able more efficiently to attach markers to a reference array.

A first aspect of the invention provides a dispenser for dispensing and attaching individual markers to a reference array of a tracking system, the dispenser comprising: a housing defining a cavity therein extending along a longitudinal axis of the housing and the housing having a dispensing end defining a dispensing aperture of the cavity; and a plurality of markers stacked within the cavity, each marker having a marker attachment feature by which the marker is attachable to an attachment site of a reference array, and wherein the dispensing end provides a retainer exerting a retaining force on a bottom most marker sufficient to retain markers within the cavity but permitting the bottom most marker to be released from the cavity via the dispensing aperture when the bottom most marker has been attached by its attachment feature to the attachment site of the reference array.

The retainer may include at least one sprung member. The retainer may include a plurality of sprung members. Adjacent pairs of sprung members may each define a respective slot between them. Free ends of the sprung members may define the dispensing aperture.

The dispensing end may be deformable to provide the retainer. The dispensing end may deform by flexing.

The marker attachment feature may be a thread. The thread may be a male thread or a female thread.

The attachment site may include a thread. The thread may be a male thread or a female thread.

Each marker may include an anti-rotation feature which interacts with a feature of an inner wall defining the cavity to prevent rotation of the marker relative to the housing.

Each marker may include a plurality of anti-rotation features which interact with a plurality of features of an inner wall defining the cavity to prevent rotation of the marker relative to the housing

The or each anti-rotation feature may interact with the or each feature via friction or friction alone.

The anti-rotation feature may be one of a male formation and a female formation and the feature of the inner wall may be the other of the male formation and the female formation.

The or each anti-rotation feature may comprise one or a plurality of male formations. The feature of the inner wall may comprise one or more female formations extending along the longitudinal axis of the housing.

The male formation may be a rib or a ridge. The female formation may be a groove or a slot. The female formation may have an upper part in the form of a groove and a lower part in the form of a slot.

The or each feature of the inner wall may extend along the longitudinal axis all the way to the dispensing aperture.

The dispenser includes a torque limiting mechanism. The torque limiting mechanism may interact with only the bottom most marker. The retainer may provide the torque limiting mechanism.

The torque limiting mechanism may permit the dispenser to rotate relative to a bottom most marker when a torque or rotational force being applied to the bottom most marker by the housing exceeds a limit.

The housing may comprise an upper part and a lower part. The upper part may define the cavity. The lower part may be movable along the longitudinal axis toward the upper part from a first position to a second position. The lower part may extend beyond the dispensing aperture in the first position and the lower part may not extend beyond the dispensing aperture in the second position.

The marker attachment feature may be an adhesive material. The marker attachment feature may be a push fit connection or a snap fit connection.

A spacer may be provided between each adjacent pair of markers. The or each spacer may be in the form of a ring or annulus.

Each marker may comprise a holder and a detection part which is detectable by the tracking system. The holder may provide the marker attachment feature

Each marker may include a circular, annular, spherical or hemi-spherical or spherical cap shaped reflector, transmitter or emitter of radiation. Said radiation may be light. The radiation may be infrared light.

The dispenser may further comprise a resilient element arranged to bias the plurality of markers toward the dispensing aperture. The resilient element may be arranged between an upper part of the cavity and a top most marker of the markers in the cavity. The resilient element may be a spring.

An upper end of the housing may include a drive connection by which a drive tool can be attached to the dispenser. The drive tool may be a power tool.

The dispenser may hold at least three markers. The dispenser may hold up to twenty markers. The number of markers may be in the range of three to twenty.

The number of markers in the dispenser may be an integer multiple of three or four. The number of markers may be three, six, nine, twelve, fifteen or eighteen. The number of markers may be four, eight, twelve, sixteen or twenty.

The dispenser may further include a packet within which the dispenser is contained. The packet may be made from a plastic or polymer. For example, nylon may be used or Polyethylene terephthalate (PET).

The dispenser and/or the markers may be sterile.

A second aspect of the invention provides a package comprising: a plurality of dispensers according to the first aspect of the invention and a container holding the plurality of dispensers. The container may be a box or carton or similar.

A third aspect of the invention provides a kit of parts comprising: one or more dispensers according to the first aspect or the package of the second aspect; and one or more reference arrays, each reference array having a plurality of attachment sites and wherein each of the plurality of attachment sites has an array attachment feature to which the respective marker attachment features are respectively attachable.

A fourth aspect of the invention provides a method of attaching markers to a reference array for a tracking system using a dispenser holding a plurality of markers, the method comprising: presenting a dispensing end of a dispenser holding a plurality of markers to an attachment site of the reference array; attaching a bottom most marker within the dispenser to the attachment site using the dispenser; and withdrawing the dispenser to release the distal most marker from the dispenser while retaining the marker attached to the attachment site.

The method may further comprise repeating the method for each of a plurality of attachment sites of the reference array.

The method may further comprise repeating the method for each of a plurality of reference arrays.

The method may further comprise rotating the dispenser to attach the distal most marker to the attachment site.

The method may further comprise attaching a power tool to the dispenser and/or using a power tool to rotate the dispenser.

The method may further comprise removing the or each dispenser from a sterile packet.

The method may further comprise taking the or each dispenser from a container holding a plurality of dispensers.

In the Figures, similar items share common reference signs unless indicated otherwise. With reference toFIG. 1, there is shown a perspective view of a dispenser100according to an embodiment of the invention. The dispenser100has a generally tubular construction and has an upper, connecting end102and a lower, dispensing end104. The dispenser100generally has a two part construction and includes an upper part110and a lower part150. The connecting end102includes a connection formation106by which a drive tool, for example a manual tool or a power tool, may be releasably attached to the dispenser to rotate the dispenser in use, as described in greater detail below. However, in other embodiments, no drive connection need be provided. In the illustrated embodiment the connection formation106generally has the form of a cylindrical wall having an inner surface comprising a plurality of flat surfaces, e.g., surface108, which defines a generally hexagonal cavity for receiving a hex head of a drive tool. However, other forms of connection formation may also be used so long as they allow a rotational force to be applied to the dispenser100in use.

FIG. 2shows a cross sectional view of the dispenser100. The dispenser100generally comprises a housing within which a plurality of markers are stored, as further illustrated inFIG. 9, and from which markers can individually be dispensed. As best illustrated inFIG. 2, the housing including a first or upper part110and a second or lower part150. The upper part110of the housing has a generally cylindrical form and includes an outer wall112and an inner wall114with an annular cavity116defined there between. An inner surface115of the inner curved wall114defines a cylindrical cavity118extending generally along a longitudinal axis of the dispenser100. Four grooves, e.g., groove117, extending along the longitudinal axis of the dispenser100are defined in the inner surface115. The four grooves are generally equi-angularly disposed about the longitudinal axis, for example at approximately 0°, 90°, 1800 and 270° respectively.

A lower end120of the inner wall114defines a lower dispensing aperture122or mouth of the cavity118. The lower end of the inner wall20also provides a retainer for retaining markers within the cavity118. In the illustrated embodiment, the retainer is in the form of a plurality of limbs, e.g. limb124, defining slots, e.g.126, between adjacent pairs of limbs. A free end of each limb, e.g.128, is directed inwardly toward the centre of the dispenser such that the diameter of the dispensing aperture122is slightly less than the diameter of the markers when located within the cavity118.

As illustrated inFIG. 2, the four grooves, e.g. groove117, within the inner wall115are each aligned with a corresponding slot, e.g. slot126, to allow markers to be dispensed from the dispenser and to provide a mechanism by which to transfer torque from the dispenser to the markers within it as described in greater detail below. It will be noted that the grooves, e.g.117, are closed whereas the slots, e.g.126, are open.

The slots126between the limbs124allow the limbs124to flex outwardly thereby increasing the diameter of the distal aperture122to permit markers to be released from the dispenser. The limbs124are resilient and will return to the configuration illustrated inFIG. 2after releasing a marker170thereby retaining a subsequent marker within the dispenser in use. Further, the ability of the limbs124to flex may provide a torque limiting function in some embodiments as this permits corresponding ribs on the markers to escape from the slots126to permit the dispenser to rotate relative to the marker when a marker has been sufficiently secured in use as described below.

A shoulder130is provided on an outer surface of the second wall114and extending around the circumference thereof.

The second or lower part150of the housing has a generally tubular construction and includes a cylindrical wall152having a greater diameter at a lower end154and a lesser diameter at an upper end156. A shoulder158connects the upper156and lower154parts of the second part150of the housing. The upper wall156is received within the annular aperture116of the upper part110of the housing. A spring or other biasing element140is provided within the annular aperture116and between the upper and lower parts of the housing and acts to urge the lower part of the housing150in a direction away from the upper part of the housing110and toward the lower end104of the dispenser. The shoulder158of the lower part abuts the shoulder130of the upper part and provides a stop to limit the travel of the lower part relative to the upper part of the housing, while permitting a bottom most marked to be dispensed.

As illustrated inFIG. 2, the lower part150, under action of spring140, adopts a first position in which the lower part150extends beyond the dispensing mouth122. As described in greater detail below, in use, the lower part150can travel toward the upper part110when sufficient force is applied to overcome the action of spring140so as to expose the dispensing mouth122. The lower part150can move toward the upper part110by an amount approximately equal to the height of a marker to be dispensed, as controlled by the position of shoulder158relative to the lower end113of outer wall112. The movement of the lower part relative to the upper part can assist in avoiding cross threading of a threaded attachment formation in embodiments using threaded attachment formations.

FIG. 3shows a perspective view generally from above of the upper part110of the dispenser100, illustrating the connection formation106and hexagonal cavity109defined by the inner flat walls108thereof, as well as the plurality of slots, e.g. slot126, defined between adjacent limbs, e.g. limb124.

FIG. 4shows a perspective view generally from below of the upper part110of the dispenser100, illustrating a groove, e.g.117, aligned with a slot126, and also the dispensing mouth122defined by the free ends128of the limbs124

The upper110and lower150parts of the dispenser may be made from plastic or metal. For example, plastic may be used for disposable versions of the dispensers. Suitable plastics include various polymers including Polyetheretherketone (PEEK), Polyoxymethylene (POM), glass reinforced Nylon, Polyphenylsulfone (PPSU) and similar. For reusable versions of the dispensers, metal may be used instead, including stainless steel, such as 17-4 stainless steel for example.

FIG. 5shows a side elevation of a first embodiment of a marker170which may be used with the dispenser100.FIG. 6shows a transverse cross section view of the marker170. Although only a single marker is illustrated inFIG. 5, in practice, a plurality of markers arranged in a stack are provided within cavity118. The plurality of markers are free to travel within the cylindrical cavity118and a bottom most marker will be positioned adjacent the dispensing122but retained within the dispenser.

As illustrated inFIGS. 5 and 6, each marker170includes a holder172and a detection part174which is detectable by the tracking system. The detection part174includes a transparent hemispherical component176with a coating of an infra-red reflective material on a back surface and mounted on a disc178. The detection part functions similarly to a road ‘cats eye’. The holder172includes an upper recess within which the disc178is received and has a side wall173defining an internal thread180which provides a marker attachment feature for the marker170.

As discussed above, a plurality of markers170are provided within the cavity118in a stacked formation. A benefit of the internal thread180is that the detection part174of a lower marker can be received within the holder part172of an adjacent upper marker when stacked. Hence, the dispenser may hold, for example, six markers within the cavity118.

The marker170does not include ribs on an outer surface of the holder part172and so friction between the holder part and the inner surface115of the inner wall114may be used to transfer rotation from the dispenser to the marker. Also, the magnitude of the frictional force between the dispenser and the marker holder may provide a torque limiter to allow relative rotation between the dispenser and marker when the marker has been sufficiently secured in use.

FIG. 7shows a perspective view of a second embodiment of a marker190, generally similar to the first embodiment 170, except that the marker holder172includes four equi-angularly spaced ribs,182,184,186and188on an outer surface of the marker holder172. These four ribs are arranged to co-operate with the correspondingly positioned grooves within the inner wall of the dispenser to provide a mechanism to transfer rotation from the dispenser to the markers within the dispenser. The markers190can slide along the longitudinal axis of the dispenser, guided by the ribs sliding within the slots, as markers are dispensed. When a maker190has been sufficiently secured, then the flexible limbs124can flex outwardly and ride over the ribs182-188, to provide a torque limitation mechanism, and allow the dispenser to continue to rotate relative to the stationary marker.

FIG. 8shows a perspective view of a third embodiment of a marker192, generally similar to the second embodiment 190, but in which the detection part comprises a larger hemispherical component194with its convex surface covered with a reflective material which may be painted onto the hemispherical member. Suitable reflective materials are provided by the3M company under the trade mark SCOTCHLITE Other types of markers with different detection parts may also be used. Other detection parts may simply be in the form of circles or discs of a reflective material or a material with a reflective coating.

FIG. 9shows a cross sectional view of the dispenser100with a stack of four markers190located within the inner cavity118.

Use of the dispenser100to dispense and attach markers to a reference array will now be described in greater detail with reference toFIGS. 10 and 11.

FIG. 10shows a schematic diagram showing the dispenser100being used to attach markers190to a reference array200.

The reference array200includes a support202having a bone anchor201or some other attachment formation, for example a clamp or clip, by which the reference array200can be attached to a patient's bone or an instrument in use. A first204, second206and third208arms extend from the support202and each arm includes a threaded boss210,212, at a free end thereof. The threaded bosses210,212, each provide a separate attachment site on the reference array to which a respective marker can be attached using the dispenser100. As illustrated inFIG. 10, a first marker190has already been attached to arm206.FIG. 11shows a flow chart illustrating a method of use300of the dispenser100as illustrated inFIG. 10. The user may be provided with a container or package holding a plurality of dispensers100. Each dispenser is pre-loaded with a plurality of markers and each dispenser, and its contents, may itself be sterile and may also be provided in a sterile packet that provides a sterile barrier and which the user removes before using the sterile dispenser100. The packet, dispenser and markers may be sterilised with gamma radiation, for example. The packet may take various forms. For example, the packet may be provided as a double nylon peel pouch, or in a PET double blister pack with a polyethylene fiber lid. A suitable material for the lid is provide under the trade mark TYVEK by the DuPont company. As the dispenser at least is sterile, there is no need to provide individual packaging for each marker.

The dispenser100is provided pre-loaded with a plurality of markers. Reference arrays commonly require at least three markers and therefore the dispenser storing an integer multiple of three markers, e.g. 3, 6, 9, can be preferable. However, a greater or lesser number of markers may be provided depending on the circumstances.

Any drive tool, for example a power tool, maybe connected to the dispenser after it has been removed from its sterile packet. At302, an initial marker array is selected. Then at304an initial attachment site for the current marker array is selected. At306, a user presents the dispensing end of the dispenser100to the attachment site by moving the dispenser100toward the attachment site along the direction generally of arrow214. The plane of the mouth on the lower part150of the housing is generally perpendicular to the longitudinal axis of the dispenser. The lower part150of the dispenser is rested against the arm208of the reference array and with the bottom most marker generally aligned with the centre of the attachment site212. By pressing on the upper part110of the housing, the distal aperture122and bottom most marker190may be moved toward the attachment site generally along the longitudinal axis of the dispenser and generally parallel to the axis of the threaded boss212thereby helping to avoid cross threading.

At308, the user may rotate the dispenser100to engage the threaded boss212and internal thread180of the bottom most marker190so as to attach the marker to the attachment site. In some embodiments, this may be done using a power tool attached to the dispenser100or a manual tool. In other embodiments, the user may simply twist the dispenser manually.

Once the bottom most marker has been securely attached to the attachment site, the bottom most marker will become stationary and the dispenser can rotate relative to the bottom most marker either owing to the frictional force being overcome or because of the members124flexing a riding over the ribs182-188on the marker holder. The dispenser may be withdrawn away from the attachment site, generally along the direction of arrow214. The flexible elements124provide a retaining force sufficient to retain the markers190within the cavity118. However, when the dispenser is withdrawn from the attachment site, the elements124may deform outwardly, thereby releasing the bottom most marker190from the dispenser100. As soon as the bottom most marker has been dispensed, the elements124spring back into position and prevent a next marker from being released.

At312, a next attachment site of the reference array200may be selected and the method returns, as illustrated by the line314, to step304. The method may then repeat so as to attach another marker to a next attachment site of the current reference array. Once markers have been attached to all of the attachment sites, at316, a next reference array may be selected and the method may repeat for a next reference array, as illustrated by return line318. However, it is not essential that the method be repeated for multiple reference arrays and there is benefit in using the dispenser of the invention irrespective of the number of reference arrays and number of attachment sites. It will be appreciated that if at any time all of the markers within the dispenser currently being used have been dispensed, then the user can simply take another dispenser from the package of dispensers, remove the sterile packet and then use a next dispenser to attach a next marker.

Use of the dispenser100of the invention may provide a number of benefits.

For example, use of the dispenser helps to avoid handling difficulties in manually attaching markers to a reference array. The markers may be reasonably small and difficult to handle manually.

This may be exacerbated if used in theatre if theatre staff are wearing gloves.

Further, it may help to avoid damage to the surface of the marker which may need to have specific optical properties in order to be reliably tracked.

Further, there is no need to remove markers from external packaging that might otherwise be provided to protect the surface of the markers. Furthermore, manual or power tools may be attached to the dispenser rather than having to rely on manual attachment of the marker to the reference array which may also be difficult in theatre when using gloves.

Furthermore, the dispenser100may improve the reliability with which markers can be attached to a reference array, for example by avoiding marker arrays being dropped or lost and thereby helping to reduce wastage. This may also improve safety by avoiding marker arrays being dropped into the operating site.

Various modifications and variations of the dispenser100and markers170,190,192will now be described.

In some embodiments, a spring or other biasing device may be provided within the cavity118to bias the stack of markers toward the dispensing mouth of aperture122. Hence, irrespective of the angle at which the dispenser is used, a marker will always be available at the dispensing aperture122and available for attachment. This can be particularly preferred when friction is used to transfer rotation between the dispenser and marker, e.g. marker170, but may also be of benefit when marker190is used and which may be freely movable along the longitudinal axis of the dispenser.

It will be appreciated that the marker attachment feature is not limited to a threaded attachment formation. In other embodiments, an adhesive material may be provided on an underside of the marker. This also obviates the need for a threaded formation on the reference array arms. Instead, the marker may simply be stuck to the attachment site by the adhesive material on the marker. In this embodiment, a spacer may be provided between adjacent markers within the cavity118to prevent adhesive material of an upper marker contacting the detection part of a lower marker.

In other embodiments, a snap fit or push fit attachment feature may be provided on the marker. A corresponding push fit or snap fit feature may then be provided on the reference array and to which the marker may then be connected.

As illustrated inFIG. 12, instead of using an internal thread, an external thread402may be provided on the holder part404of the marker408. In that case, the attachment sites on the reference array are in the form of a recess with an internal thread into which the markers408may be screwed.

Further, if no internal thread and recess is provided, then a spacer, for example an annular ring or similar, may be provided between each adjacent pair of markers408in order to separate adjacent markers and prevent an upper marker from damaging the detection part of a lower marker.

When using screw threads for the marker attachment feature, preferably the markers include an anti-rotation feature. As illustrated inFIGS. 7 and 8the marker may include ribs which co-operates with grooves within the dispenser, but other arrangements are also possible. For example, one or more grooves may be provided in an outer surface of the holder, and which may cooperate with one or more corresponding anti-rotation features, e.g. one or more ribs, extending along the inner surface115of the inner wall114and in the direction of the longitudinal axis of the dispenser. As discussed above, these anti-rotation features cooperate to prevent rotation of the marker170relative to the dispenser when the dispenser is rotated.

In some aspect, multiple dispensers100, each within a sterile packet, may be provided in a single container, such as a box or carton, and then dispensers taken from the container when required before or during a surgical procedure.

In other approaches, one or more dispensers may be provided as part of a kit of parts including one or more reference arrays and optionally one or more instruments to which the reference array may be attached in use. Hence, the dispenser may serve to both protect and package the reference markers and also provide a mechanism by which the markers may be more easily and reliably attached to the reference array when required.