WO2014053850A1

WO2014053850A1 - Connector for biomedical purposes

Info

Publication number: WO2014053850A1
Application number: PCT/GB2013/052591
Authority: WO
Inventors: William Duncan ROBERTSON
Original assignee: Individual
Current assignee: Individual
Priority date: 2012-10-04
Filing date: 2013-10-04
Publication date: 2014-04-10
Anticipated expiration: 2015-04-04
Also published as: GB2506634A; GB201217785D0

Description

Connector for Biomedical Purposes

Field of the Invention The present invention relates to an adjustable fixed or moveable connector suitable for biomechanical purposes. Particularly, but not exclusively, it relates to a connector suitable to connect a bone anchor such as an implant, to a restorative component, e.g. a prosthetic device, such as a tooth or denture. Utility is, however, not constrained to dental use, but it could have applications in other areas of medicine, including orthopaedic surgery.

Background

There are a variety of situations where an adjustable connector is required to join two components in bio-medical situations, including dental and orthopaedic uses. For example, there may be a need to connect a prosthetic tooth to the jaw or to connect a skeletal bone to an artificial joint or prosthesis.

In some situations the location and orientation of anchors in bone is not

straightforward, and it is very difficult to combine suitable anchor placement and correct positioning of a restorative component, such as a prosthetic tooth, and ensure the load forces upon the anchor are balanced and are not excessive.

Existing connectors either have a fixed angle or are limited due to the range of movement of the connector and/or the areas available for connection. This may mean that one or more of the points of anchoring must be altered to place the connector in a suitable orientation or situation for use, which often leads to securing the connector in a less desirable region such as an area with a less secure base. Furthermore, it often leads to anchors which have unbalanced or excessive forces placed upon them which can lead to pain and failure.

In some instances a fine level of adjustment may be required after the initial fitting of the connector, e.g. to correct for minor errors in installation, and this is often not possible with existing systems. Prior Art

A number of patent applications have been filed in an attempt to resolve the problem or similar, including the following:

United States patent application US 2005 042 573 (Lustig ef a/.) discloses a dental implant comprising: an elongate implant fixture assembly having a first end and a second end, said implant fixture assembly being adapted for attachment to a jaw bone at a first end thereof and having a first longitudinal axis; an abutment for mounting on said second end of said implant fixture assembly, said abutment having a second longitudinal axis; a fastener for connecting said abutment to said second end of said implant fixture assembly such that (i) said abutment is adjustably movable on said second end of said implant fixture assembly when the connection formed by said fastener is loose, and (ii) upon disposition of said second longitudinal axis of a selected angle to said first longitudinal axis, said abutment is fixedly connectable on said second end of said implant fixture assembly when the connection formed by said fastener is tight; and securement means for preventing movement of said abutment relative to said implant fixture assembly when the connection formed by said fastener is tight.

Granted French patent FR 2 727 307 (Segura et al.) discloses a connector comprises a pivot secured via an articulated connection to a prosthesis support plate with an upper face cut-out to receive the lower end of a dental prosthesis. The upper end of the pivot component has a spherical head of greater diameter than an opening in the base of the support plate through which it passes. The lower surface of the cut-out in the support plate is covered by a sheet of flexible sealing material. In the assembled state of the anchorage, the sheet exerts a downward pressure on the spherical head to maintain the plate and pivot in a predetermined relative position.

Granted European patent EP 0 580 945 (Duerr) discloses an endo-osseous tooth implant for a fixed dental prosthesis has an essentially cylindrical round body of a metal for implantation in the jaw bone and a metal fastening head for a dental superstructure which can be firmly connected with an implant post. The metal implant post can be screwed into the inner bore, which is open at its coronal end, of the round body, if appropriate with interposition of an intermediate sleeve of an elastic material, and the round body has on its coronal end a cylindrical annular recess provided with at least one basic body engaging element for reception of a cervical centering collar, provided with at least one spacer sleeve engaging element complementary to the basic body engaging element(s), of a metal spacer sleeve whose internal diameter is larger than the internal diameter of the inner bore of the basic body or of the intermediate sleeve and which can be applied with a shoulder against the coronal edge of the basic body. In the used state of the tooth implant, complementary engaging elements of the basic body and the spacer sleeve secure the spacer sleeve against rotation about the longitudinal axis of the basic body relative to the basic body. The implant is characterised in that the implant post has on its coronal end a partially spherical head which is flattened so as to be essentially plane toward the coronal side and whose diameter is larger than the diameter of an implant post stem located between a cervical threaded section and the partially spherical head, in that the fastening head has on its cervical end a partially spherical shell which engages around the partially spherical head of the implant post and has on its cervical end a pivoting opening which can be penetrated by the thread-free implant post stem and whose diameter is smaller than the diameter of the partially spherical head but larger than the outer diameter of the implant post stem, in that the partially spherical head and the partially spherical shell are provided with

complementary carrier means for the cardanic connection of the fastening head to the implant post, in that the spacer sleeve forms a bearing socket in its coronal region for accommodation of the partially spherical shell, and in that the fastening head has at least one attachment means for a screwing tool, as well as a fixing tool for the implant.

US 5,133,662, WO 2012/142517, US 2003/0224329 and US 4,932,868 all disclose various implants/connectors, but each has significant shortcomings in versatility and the range of angular connection they provide.

In the dental field, currently more than 99% of implants placed are straight which can compromise both the optimal placement of the implant in the bone (where there is maximum bone density and avoiding anatomical structures) and the aesthetics of the restorative component, such as a prosthetic tooth. A number of dental implants and attachments are currently available which allow the restorative component to be connected to the dental implant at a chosen angle but these are limited to a range of pre-fabricated angle connectors and custom made connectors. Pre-fabricated angle connectors may not offer the optimal angular solution for a particular clinical case and custom made connectors are more expensive and extend the treatment time. In both cases no further angular adjustment is possible if required after implantation.

The present invention was developed in order to overcome problems associated with known connectors to provide a versatile connector with a wide range of movement and fine adjustment when in situ, thereby enabling a foundation component (anchor) to be placed where there is suitable and sufficient material such as bone, to afford optimum stability for function and longevity and to allow for more efficient installation and balancing of forces placed upon the anchor(s). The connector of the present invention may also allow less skilled clinicians to perform complex procedures which were previously not possible for them, or may allow complex procedures to be carried out more quickly - this is of obvious benefit to patients and health care providers. Summary of the Invention

According to the present invention there is provided a connector suitable for biomechanical purposes (e.g. dental or orthopaedic uses) comprising

a base unit having a concave recess adapted to receive part of a spherical body therein, and an interface member adapted for selectively rotatable connection to an anchor component;

a cover unit having a concave recess adapted to receive part of the spherical body therein and an aperture;

a core unit comprising a substantially spherical body and an elongate mounting arm projecting therefrom, the mounting arm being adapted to pass through the aperture in the cover unit when in position in the concave recess, the mounting arm having a connection means to allow connection to another component;

wherein the base unit and cover unit are adapted to be connected together, thereby retaining the core unit within their recesses. The aperture in the cover unit limits the movement of the elongate mounting arm and thus the core portion. The aperture can have any suitable shape, for example a slot, annulus, or the like. In one preferred embodiment a slot or channel can be provided which allows movement of up to 180 degrees, or even 220 degrees in a sagittal plane (as defined in respect of the connector). Preferably the aperture allows movement of at least 45 degrees, more preferably at least 65 degrees, yet more preferably at least 90 degrees, and most preferably at least 120 degrees. Preferred embodiments allow about 180 degrees of movement. In other embodiments movement would vary according to an annular, circular or other shaped aperture, e.g. cruciform, T- or Y-shaped or the like. The aperture can allow movement in a plane other than the sagittal plane, e.g. within a plane at any suitable angle (e.g. 45 degrees) relative to the plane of rotation of the base unit relative to the anchor component.

The connector can be adapted to clamp the core between the base and cover units. Thus the base and cover units can be connected together in such a way that pressure is exerted on the core unit whereupon core is held in position by friction in a set position. Other methods of locking the core unit in position are of course possible (e.g. a grub screw, corresponding protrusions and recesses in the base or cover units and the core and adhesive), but a friction-based system is preferable as it allows for very fine adjustment and is inherently simple. Such a configuration can be referred to as 'selectively lockable'. Another form of 'selectively lockable' configuration provides that when the base and cover units are securely connected together the core is able to move, but the core can thereafter be locked in position when the core unit is connected to the restorative component. In this case, suitably the core and restorative component are held in position by friction between the core and the interior of the cover and/or base unit, and between the restorative component and the exterior of the cover and/or base unit. This is achieved by clamping the core, cover and/or base unit and the restorative component together. Alternatively the connector can be adapted such that when the base and cover units are securely connected together the core is able to move, and remains so after the restorative component is attached. The range of movement is defined by the interaction between the elongate arm and the aperture in the cover unit, e.g.

movement in a sagittal plane defined by the orientation of a slot in the cover unit.

Suitably the recess in the base unit is substantially hemispherical. Suitably the recess in the cover unit is substantially hemispherical. Preferably both recesses are substantially hemispherical.

Suitably the base unit and cover unit are adapted to be connected together via corresponding screw threads provided on each unit. Suitably the screw threads are provided at the equator of each hemisphere. These equatorial regions of the two hemispheres can suitably comprise corresponding annular lips that comprise the threads. Where a greater range of movement of the elongate mounting arm is required, the position of the threads can be altered to another axis thereby extending the range of the slot or opening. Other means of connecting the base unit to the cover unit will be apparent to the skilled person, and include catches, clips, pins and the like, and/or an adhesive could be used.

Ideally the base portion and cover portion are connectable so as to form a watertight seal.

Preferably the cover unit is substantially hemispherical. Accordingly both the outer and inner surfaces are substantially hemispherical. Suitably the equatorial opening of the cover unit comprises the threads via which the cover can be connected to the base unit.

Preferably the base unit comprises a substantially hemispherical portion that comprises the concave recess. Suitably the equatorial opening of the base unit comprises the threads via which the base can be connected to the cover unit. The base unit also comprises the interface member, which can take a variety of forms. It is envisaged, however, that the base unit and cover unit may not be of equal size wherein the base unit may be less than hemispherical and the cover unit may be more than hemispherical, although when joined a general sphere is still formed. By 'substantially spherical' is meant that the core unit is generally spherical so that it is able rotate in a 'ball and socket' manner within the base and cover units. It will be apparent that a perfect or complete sphere is not required, and there can be recesses or scalloped portions on the spherical body, which would not prevent the desired movement. Projections from the spherical body may be permissible, especially if they correspond to recesses on the inner surfaces of the base/cover units, but are typically undesirable. Likewise the recesses and external surfaces of the base and cover unit should be suitably shaped to allow the core to move and be held as intended or to allow movement of a restorative component as required relative to the external surface, but they need not be perfect or complete partial spheres.

In preferred embodiments the base and cover units will typically have an external diameter from 3mm to 8mm, but larger or smaller versions are possible, especially for orthopaedic uses. Ideally the core unit has a diameter sufficient to achieve adequate strength within the constraints of the base and cover units and for the purposes required of the connector.

In some embodiments the base and/or cover units may include at least one recess to accept a tool which may apply torque to alter orientation of the base unit or tighten the cover unit hemisphere. For example, the base or cover units may comprise one or more recesses adapted to accept a driver that connects to a torque measuring wrench (as with standard implant solutions) therefore enabling the degree of torque to be precisely measured so as to ensure the aperture in the cover unit is in the predetermined location.

The interface member is preferably adapted to allow the base unit to rotate relative to the anchor component. Suitably this rotation is in a transverse plane relative to the connector and anchor component. Once a suitable rotational position has been achieved, the interface portion is preferably locked in position relative to the anchor component. Locking is achieved through a locking means, which can have any suitable form; including mechanical locking means (such as a clip or catch, system of anti-rotation lugs, screws or bolts) and/or an adhesive could be used. Preferably the base unit is provided with one or more markings to aid a clinician in identifying when correct alignment has been achieved.

Thus the base unit is positioned on the anchor component, for example dental implant, bone or bone screw, at a selected angle (0-360 degrees) in the transverse plane so that, once the base and cover units are joined, the orientation of the slot, channel, annular or other opening in the cover is positioned to allow movement of the elongate mounting arm according to clinical requirements. Typically this will involve locating the base unit such that the core and elongate mounting arm are able to move in a sagittal plane (orthogonal to the transverse plane) within a slot, allowing movement of up to 180 degrees in this plane.

For example, in the case of a base unit and cover unit which are screwed together via threads on the corresponding equators of the cover and base unit, the orientation of the slot will be determined by the point of rotation at which the cover unit is secured completely onto the base unit. Accordingly, a marker can be provided which indicates the orientation that the slot will be in once the cover unit is screwed into position. The marker can take the form of a projection or recess on the base unit, or any other suitable marker such as an etching, laser markings, anodising or the like.

In a preferred embodiment the interface means comprises an annular member adapted to cooperate with a corresponding annular member in the anchor component. For example, an annular projection on the base unit can interact with an annular recess on the anchor component, or vice versa. The outer diameter of the projection and the inner diameter of the recess are selected accordingly to permit cooperation. Thus the annular members can rotate relative to one another, with one annular member rotating relative to the other.

Locking can suitably be achieved via a bolt extending from the base portion into the anchor component, e.g. located at the axis of the annular member on the base unit, which screws into a corresponding threaded receiver in the anchor component. Thus the bolt and the receiver are concentric to the annular members. Tightening of the bolt will hold the base unit and the anchor component in position, thus locking them and preventing relative rotation. The position may be defined and further stabilised by the use of anti-rotation lugs and/or tapers, as discussed further below.

In a preferred embodiment the annular members are adapted to provide

corresponding machine tapers to increase friction and thus improve locking performance. Machine tapers are well known for locking two components to prevent relative rotation between the components, and are conventionally used on bench drills, lathes and other machining systems. The most commonly known system is the Morse taper, but other types of taper are known. By providing the annular members with suitable cooperating machine tapers, a very strong lock can be achieved with relatively little drawing force upon the bolt; this is highly desirable where relatively small bolts with fine threads are used, to prevent damage to threads or the bolt through over tightening. Of course it will be apparent that a machine taper can be used in cases where locking means other than a bolt are used, provided that the corresponding tapers are pushed together to establish a friction lock, and preferably held in that position to prevent loosening over time. Where a machine taper is used, or other such friction locking system, it may be possible to dispense with further securing means, e.g. a screw or plug from the connector to the anchor component, as the inherent lock achieved may be of sufficient strength. Thus the base unit can be attached to the anchor component using only a machine taper, or the like.

Other systems such as splined interfaces and the like can be used, provided they provide the required level of adjustability.

It is a significant advantage of the present invention that by providing an interface that is connectable to a range of anchors, it allows for versatile use of one connector (or a limited number of variants) according the present invention to be used with a wide range of implants. All that is required is that the implants have an appropriate portion to engage with the interface member on the base unit. This allows the clinician to select the best anchor for any given application and then add the connector of the present invention to provide a secure but flexible means of connecting another component (e.g. a dental prosthesis) to the anchor.

It is envisaged that parts such as the core and elongate mounting arm, anchor component and/or base/cover unit may be interchangeable and available in a number of sizes depending upon the requirement in use.

Suitably the connection means of the elongate mounting arm comprises a bore passing through the arm and preferably into the spherical body of the core unit. Preferably this bore is threaded along at least a portion, preferably all, of its length.

It is advantageous that such a bore is used as it allows the loading of the connector to be transmitted to the core unit, thus distributing force throughout the connector. This can be very useful to distribute forces and minimise loading on the anchor component.

In some embodiments the elongate mounting arm is used to mount a restorative component (e.g. prosthetic component or orthopaedic device), e.g. a prosthetic tooth, denture, crown, or a bone screw, bone pin, artificial joint, etc.). Alternatively, an anatomical object such as a bone can be mounted directly to the mounting arm.

Attachment of this restorative component can be used to lock the core in position within the base and cover units, and thus prevent movement of the core relative to the cover and base units. When the component is tightened against the elongate arm, the component, cover unit and core are drawn together, and frictional forces between the core and the cover unit and the base unit and the component can lock the core and component in position.

Preferably the restorative component is adapted to interact with the cover portion and/or base unit in a manner conducive to providing a friction lock against the cover unit. For example, the restorative component is provided with a recess that is generally complimentary to the shape of the exterior of the connector. For example the recess is concave and thus complimentary to a sphere. Thus when the structure is tightened together it is firmly held in position by friction. An additional advantage of this arrangement is that a seal can be achieved between the additional component and the exterior surface of the cover and/or base unit, thus preventing ingress of material (including microbes and the like) into the connector. This depends, of course, upon the restorative component having a suitable shape to sealingly engage with the cover unit. Additional sealing means can also be provided on the restorative component, e.g. a resilient gasket or the like. Filler or luting materials may be used to further enhance the seal or security of the components and prevent ingress of microbial agents.

Accordingly, it is preferred that the restorative component comprises a recess, e.g. a substantially hemispherical recess, which allows it to nest against the cover and/or base units. The present invention also contemplates an adaptor that can be used as an intermediary to facilitate connection of the restorative component to the connector, the adaptor being provided with a suitable recess to engage with the connector.

Another advantage of this arrangement is that it allows the final locking of the core to be deferred until the additional component is in position and final alignment of the connector to ensure balancing of load has been achieved.

Where a moveable (i.e. non fixed) connection of the restorative component to the connector is required, the connection can be adapted such that the component is secured without the component pressing against the cover and causing compression of the core, cover and component together. In this case the core remains free to move, limited by the shape and size of the aperture in the cover unit relative to the mounting arm. In such embodiments a low friction (glideable), lubricated or durable (e.g. extremely hard) surface such as ceramic, metallic or polymeric (e.g.

fluoropolymer) material may be provided on at least one of the spherical portions of the core, the recess of the base unit, the recess of the cover unit and/or on the mounting arm.

The core can be locked in position in terms of both lateral rotation relative to an anchor component and movement of the core relative to the base and cover units prior to mounting of the additional component. This can be achieved by locking the core in position when the base unit and cover unit are connected together.

In another embodiment the base unit comprises an anchor component, such as a dental implant, bone screw or the like, which may be directly screwed into bone. The anchor component can be rotatably connected to the remainder of the base unit, with locking means provided to set the relative rotational position of the anchor component and the remainder of the base unit in the desired position. In one embodiment of the invention the base unit, anchor component and interface member are a single structure. This integrated base structure is placed conventionally in the bone using markings to suitably rotationally align the base unit to receive the cover unit and core unit. Thereafter the core unit can be positioned as required, and optionally locked in position. Typically such embodiments are less preferred as they do not provide the versatility of a connector which can be used with a range of anchor components, thus allowing clinicians to have on hand only a limited number of connectors (e.g. different sizes) which can be used with many different anchors.

In all preferred embodiments corrosion-proof or corrosion-resistant materials are used on all parts, and finishes are adapted to resist capture of matter. Typically the base and cover units, the core and elongated arm and the screws are formed of durable, non-reactive material such as titanium, stainless steel, gold alloys, synthetic polymeric materials or other materials, so as to provide a durable and long-lasting connection. The present invention allows for an anchor to be secured in the strongest location, for example where bone is more abundant and thereby avoiding thinner, weaker areas such as diseased or atrophic tissue, damaged bone or anatomical structures.

In some embodiments the elongate mounting arm of the core is adjusted and then fixed in position within the sagittal plane of the slot or channel (0-180 degrees) as required by the item to be connected to the arm, for example a restorative

component such as a prosthetic tooth. The restorative component would receive the screw and the screw would connect directly to the elongate arm and core thereby linking all components together. Typically this allows the restorative component to be fixed at any chosen angle in relation to the dental implant. The restorative

component will be in direct contact with, in most instances, the cover unit but sometimes a proportion of both cover and base unit, providing a water and microbially tight seal and, advantageously, distributing loading forces for greater stability.

In some embodiments the additional component, such as a denture or the like, may be removably attached to the mounting arm by means of special attachments such as friction grip, clips or magnets.

In some embodiments a plurality of connectors may be used to retain an additional component. Advantageously this allows individual and precise angular adjustment of the elongate arm of each connector to facilitate optimal positioning of the restorative component and to permit equal distribution of loading forces for greater stability.

In the example of fracture reduction two connectors can be linked by an extendable, adjustable ladder profiled at either end with an inner concave hemispherical surface matching the radius of the connectors. The reduction of the fracture can be stabilised by tightening the screws of the elongate arm in each connector against the ladder.

Advantageously this allows individual and precise angular adjustment of the elongate arms of the connectors to accurately approximate the fractured surfaces together, irrespective of the contour of the bones supporting the connectors. In some embodiments, such as corrective surgery for scoliosis, a plurality of adjustable connectors may be used to retain a longer ladder allowing for each connector to define the precise position of the attached bone.

The height of the interface member of the base unit can be varied to suit either internal or external fixation.

In further orthopaedic applications the connector can be fixed to a receiving body such as the distal end of a bone. In the embodiment of a moveable joint the range and orientation of movement can be defined by the upper cover slot, channel or annular opening. The elongate mounting arm can be attached by a screw fastener to the proximal end of a second bone, thereby affording a compact prosthetic joint.

In some embodiments the moveable joint can be fixed to a prosthetic component such as a prosthetic finger.

It is envisaged that parts such as the core and mounting arm, base and cover units, interface may be available in a number of sizes depending upon the biomechanical requirement. The overall size of the connector and the size ratio of the core to the recesses will vary according to the physical requirements of the connector or of the materials chosen.

Advantageously the use of retaining screws and threads allows the connector to be dismantled and refitted, or parts replaced if required. In orthopaedic applications this advantageously allows the replacement of worn components without complete joint replacement surgery, therefore causing less morbidity than current systems of multiple bone screws and plates.

In some embodiments the connector is integrated into or integratable into an existing anchor or implant.

In a further aspect of the present invention there is provided a restorative structure comprising at least one connector as set out above, in association with or connected to an anchor component and a restorative component.

In some embodiments a plurality of connectors may be used, for example in a row, to form a bridge.

In a further aspect of the present invention there is provided a kit or system comprising at least one connector as set out above and one or more (preferably a plurality) anchors comprising interface members adapted to cooperate with the interface member of the base unit of the at least one connector. It is an advantage of the present invention that one connector can be used with (i.e. connected to) many different anchors, ensuring that the optimum anchor can be used, without the need to have a wide range of different connectors each having different anchors integral with them.

In a further aspect of the present invention there is provided a method of connecting two or more biomechanical components (e.g. an anchor component and a restorative component) using at least one connector as described above.

Preferably the method comprises:

- connecting the base unit to an anchor component (e.g. a bone screw, pin or dental implant);

- placing the core unit in the recess in the base unit;

- connecting the cover unit to the base unit; and

- optionally locking the core unit in position. Suitably the method comprises affixing a restorative component to the mounting arm of the core unit.

Locking of the core unit in position within the recesses can be achieved by mounting the restorative component, or by clamping the core unit between the base and cover units, each of which are described in more detail above.

Preferably the step of connecting the base unit to the anchor component comprises setting the transverse orientation and then locking the base unit in position relative to the anchor component.

The method is suitably a method of dental restoration, whereby the anchor component is a dental implant or something connected to a dental implant. The method can involve placing one or more anchor components in a subject. Alternatively the method is an orthopaedic surgical method, e.g. bone repair (e.g. fracture reduction), correction of bone shaping or position (e.g. correction of scoliosis or other deformities), or joint replacement. Embodiments of the present invention will now be described, by way of non-limiting example only, with reference to the accompanying figures.

Brief Description of the Figures

Figure 1 shows an isometric exploded cross sectional view of a preferred

embodiment of the connector of the present invention associated with a dental implant;

Figure 2A and 2B show an illustration of possible core movement in the embodiment pictured in Figure 1 ;

Figure 3 shows an isometric cross section of the embodiment of Figure 1 as assembled; and

Figure 4A and 4B show views of the embodiment of Figure 1 in use in dental situations;

Figure 5 shows a diagram illustrating two connectors of the present invention being used to reduce a fracture; and

Figure 6 shows a diagram of a connector of the present invention in use as a prosthetic joint, with an exemplary range of motion illustrated by an arrow. One end of the connector is connected to a first bone, and the movable end of the connector is shown both connected to (at the lower end of the range of motion), and

disconnected from (at the upper limit of the range of motion), a second bone.

In the embodiment pictured in Figure 1 the principal components are visible:

Core unit with mounting arm - 1

Cover unit - 2

Base unit - 3

Screws - 4,5

Dental implant (anchor) - 6

In essence the connector comprises the cover unit, base unit and the core unit. Other parts such as the screws, anchor component, and restorative components can be provided as parts of the connector.

The core unit 1 comprises a spherical body with an elongate mounting arm 1 a projecting therefrom. An elongate aperture (a bore) passes down the length of the elongate mounting arm and approximately to the centre of the spherical body. This aperture is provided with a screw thread, and is adapted to receive a screw (or bolt) 4. The base unit 3 comprises a hemispherical recess that is adapted to receive approximately half of the spherical body of the core unit 1. The base unit also comprises an interface member in the form of an annular collar 8. An aperture passes from the bottom of the hemispherical recess and through the axis of the interface member. This aperture is adapted to receive a screw (or bolt) 5, which can be used to secure the base unit to an anchor component, e.g. a dental implant 6. At the top of the base unit, i.e. the equatorial opening, there is provided an annular lip that has a screw thread provided thereon.

The cover unit 2 also comprises a hemispherical recess that is adapted to receive approximately half of the spherical body of the core unit 1. The cover unit also comprises an aperture in the form of a slot. The slot follows the curve of the cover unit, but is linear when viewed from above; thus the slot defines an arc in a sagittal plane of the connector. The slot is sized to receive the mounting arm 1 a and allow it to move in the sagittal plane (through approximately 180 degrees) but does not allow any substantial movement in any other plane. Other forms of aperture are of course possible, but the slot as described here is a preferred form. The cover unit also comprises an equatorial annular lip that has a screw thread provided thereon.

There is also shown a dental implant (i.e. an anchor component), which is adapted to be screwed into a bone, i.e. the jaw. Other forms of bone screws, or indeed other types of anchor components, could of course be used, and indeed the connector can be attached directly to bone in certain, less preferred embodiments. A hexagonal drive means 1 1 can be seen at the top of the implant, which is used to drive the implant into a hole drilled in the jaw. The implant does not typically form part of the connector, but in certain embodiments of the invention, the anchor can be integral to the connector, as described above. The implant comprises an elongate aperture 7 (i.e. a bore) which passes down the axis of the implant. The bore is provided with a screw thread and is adapted to receive the screw 5. The implant comprises an annular surface 9 that is adapted to receive the annular interface member of the base unit. Although it cannot be clearly seen in the drawings, the annular interface and the annular surface of the implant comprise corresponding Morse machine tapers, which allow the implant and the base unit to be locked relative to one another when urged together. Thus the base unit can be brought into position whereby the interface member is within the annular recess on the implant, the base unit can then be rotated into the desired angular position relative to the anchor (in the transverse plane), and the screw 5 can then be tightened which draws the interface portion into the anchor and thus locks the corresponding tapered surfaces together.

In this way the rotational orientation of the base unit in the transverse plane can be set. Markings on the base unit and implant (not shown) assist in this process. The core unit can then be positioned in the base unit and the cover unit placed over it, with the mounting arm extending through the slot on the cover portion. In the embodiment shown the cover unit can be secured to the base unit by engaging the corresponding screw threads on the lips of the base unit and cover unit and rotating the cover unit relative to the base unit to screw the cover to the base unit. A suitable torque setting will be used to ensure the cover is screwed down with the appropriate force. Once the cover unit and base unit are screwed into position, the rotational orientation of the slot in the cover unit will be in the desired position.

Depending on the intended use of the connector, when the cover unit is completely screwed onto the base unit, the core may either be locked in position (e.g. because it is clamped between the base and cover units), or it may be free to move within the base and cover units, the range of motion being determined by the slot (in which case the core unit is not clamped sufficiently to cause a friction lock to occur); locking can subsequently be achieved by mounting a suitably shaped and sized restorative component onto the mounting arm, as described above. Obviously fine engineering tolerances will be used to ensure the connector performs as intended, and this is conventional in medical and dental implants. Where a locking interaction is intended the surfaces of the recesses and the spherical body of the core unit may be left bare or may have a high friction coating or rough surface texture. If a sliding interaction is desired, the surfaces may be smooth and/or a low friction coating (e.g. PTFE) may be applied.

Any desired restorative component, e.g. a dental prosthesis, an orthopaedic device, or the like can then be attached to the mounting arm. In the present case this is achieved by screwing the screw 4 into the bore, thereby mounting the restorative component. Obviously if the core is free to move within the base and cover units, then it will need to be held during this process to prevent the core unit from simply rotating as torque is applied to the screw 4. Where the core is locked in position, this will not be required.

In certain, and in many cases preferred, configurations, the act of screwing or otherwise mounting the restorative component to the mounting arm can be used to cause the core to be locked in position relative to the base and cover units. In this case, when the screw 4 is tightened, a portion of the restorative component abuts against the outer surface of the cover unit and the core unit is drawn against the surface of the recess of the cover unit. This creates a friction lock between the respective surfaces, which thereby locks the core and the restorative component in position. Sealing means such as an appropriate filler can be applied.

The length of the screw 4 is selected so that, when secured in position and fully tightened, it extends along the major part of the bore and to, or near to, the centre of the spherical body of the core unit, thereby ensuring that forces applied to the restorative component are transmitted to the core of the connector, thereby distributing forces throughout the connector.

It will be appreciated that configurations where the core is locked in position within the connector will assist in forming a secure and stable structure comprising the restorative component, one or more connectors and one or more anchor

components. Figure 2 illustrates the transverse rotation and sagittal rotation of the connector provided by, respectively, rotation of the interface relative to the anchor component, and rotation of the core within the recesses provided by the base and cover portions. Assembly

Methods of assembly of a connector according to the present invention will now be described in the context of a dental application. Connection in which core position is fixed during attachment of restorative component:

- the interface member of the base unit is fitted, according to the implant design, to the annular recess or external connection of the dental implant, i.e. jaw bone anchor.

- the anchoring screw 5 is tightened to hold the base unit in the transverse

orientation to give the required sagittal orientation and freedom for the mounting arm of the core unit.

- the cover unit 2 and core 1 can be assembled using a bespoke 'carrier'. This consists of a central screw connecting through the mounting arm into the core. Additional guides or lugs fit on either side of the elongate arm and into the remaining space of the slot. This provides the necessary lock to drive the cover unit screw threads fully home against the base unit threads.

- the central screw in the 'carrier' is loosened and the carrier is removed.

- the mounting arm of the core is checked to ensure full range of movement.

- in most instances a temporary prosthesis can be immediately attached.

- in an 'AII-on-4' (full arch restoration) procedure the mounting arms can be easily adjusted to make them parallel allowing the connecting framework that supports the arch of teeth to be easily guided into place. This also ensures even distribution of load.

- the carrier screw is re-used to unite the restorative component (single, multiple or special attachment) to the connector.

Moveable Connection - the base portion and interface member are fixed into the implant. The interface member can be modified to either accept a central screw for fixation into bone or, in some embodiments can be provided with an anchoring member provided with screw threads for fixation into bone.

- the cover unit and core are delivered in a 'carrier' system.

- the cover unit is screwed onto the base unit in a similar fashion to the fixed

connection.

- the carrier is disengaged and the end of the mounting arm can receive the

connection for the restorative component to be mounted.

- once mounted the restorative component and core are free to move within the range of motion permitted by the aperture in the cover unit.

Surface Modifications Fixed Connector

The internal surfaces of base and cover units, and the outer surface of the core, may have a high friction finish designed to provide an immoveable connection once the screw retaining the restorative component is tightened. The concave surface of the restorative component may also be finished to enhance the stability of the

component under load. With some metals there will be a 'cold weld' creating a very stable connection.

The connector design of a spherical core housed within hemispherical recesses allows the radial distribution of compression force within the hemispheres and provides the greatest strength of design without 'stress concentration'. The threading of the extension arm screw through to the core will maximise the spread of load within the hemispheres. These factors improve the robustness of the connection and its ability to withstand repeated load or load cycles such as chewing. Moveable Connector

The internal and external surfaces of the connector can be modified to provide a glideable (i.e. low friction) surface. The inner surfaces of the hemispheres can be modified by

- plasma sprays; - heat treatments;

- lining in a material such as a fluoropolymer (e.g. PTFE) or polyethylene

commonly used in prosthetic joints;

- dissimilar metal or non-metal components between the hemispheres and the core, e.g. titanium, cobalt chrome, stainless steel, ceramic, etc.

The surface of the core can be modified on both the spherical body and the mounting arm part (allowing free sliding against gliding aperture) to reduce the coefficient of friction.

In some designs base and cover units and the core may be contained in a

'membrane' allowing a lubricating 'synovial fluid' to exist within the space of the core, slot and hemispheres. This cover or gaiter can be made of elastomeric material allowing the joint to move freely.

As it is unlikely that wear will be totally eliminated, the core and base and cover units can be designed to be replaceable. The connector is designed to be able to be disassembled so worn surfaces of the core or base or cover units could be replaced or new replacement components could be added without replacement of the whole unit.

One possible use of such a moveable connection is in providing a replacement joint, e.g. a hinge joint. Applications

Dental

The connector can be used to provide a fixed connection at any chosen angle between a dental implant and a restorative component. The interface member of the base unit can be fabricated to fit all internal and external dental implant connections.

The surface of the base unit and cover unit (especially the base unit) can be treated to provide additional connective tissue attachment. This would enhance the preservation of the soft tissue surrounding the connector and further safeguard the bone tissues surrounding the upper part of the implant.

The angular versatility of the connector allows dental implants to be placed at more extreme angles to utilise optimal bone density and avoid anatomical structures, while allowing the restorative component to be fixed at the most appropriate angle for dental function. In multiple implants it also makes it easy to adjust the angles of the mounting arms to compensate for anatomical variations of the jaw bones to maintain parallelism and provide equal load distribution.

The connector will be particularly useful in multiple implant arch restoration. These patients have significant loss of bone volume due to atrophy and even more care needs to be taken to avoid anatomical structures. Many patients face complex and painful treatment to augment bone volume and the process has significant morbidity and complications from donor sites. It also significantly adds to treatment time - often 8 months longer than the normal restorative and implant timetable. Costs also rise by approximately 20-30%. The angular flexibility of the connector of the present invention allows implants to be placed where bone is sufficiently abundant, at more extreme angles than is currently possible. The adjustability of the elongate mounting arm of the connector allows these steeply angled implants to be 'normalised' so that the connecting framework of the restorative component can be easily attached. This will save the patient considerable cost, time and morbidity. It also saves the surgeon significant time in implant placement, impression stages and assembly of the final restoration and reduces component costs.

The hemispherical design of the connector has advantages over the 'flat' platform systems currently in use as it establishes a 'passive' fit of the prosthesis. The passivity of the dental arch is fundamental to the long-term stability of the bone supporting the bridge and soft tissues.

Figures 4A and 4B show two dental applications of connectors of the present invention. Figure 4A shows the use of two connectors 10 to mount two separate prosthetic teeth 18a and 18b. The connectors allow for convenient and simple positioning of the prosthetic teeth, by virtue of the movable nature of the core unit. Figure 4B shows the use of four connectors 10 to mount a full arch restoration 19.

Facial surgical reconstruction - big losses of tissue and bone cause extreme facial deformity and restoration of these patients is very time consuming. The connector of the present invention allows the surgeon to place implants in the remaining bone and select the best angle for connecting the facial prosthesis.

Additionally facial prostheses (nose, cheek, eye, ear, etc.) can have magnetic or frictional components that can attach to the implant-retained part. The implant can therefore be placed even at 90 degrees to the final fitting path of the prosthesis.

Medical

The connector of the present invention also has potential applications in:

- reuniting fractured bone (either by external or internal fixation);

- distraction osseogenesis;

- treating deformities such as scoliosis; and

- carrying out certain types of joint replacement.

In broad terms the ability of the connector of the present invention to provide a fixed or moveable angular connection between two parts (typically an anchor and a prosthetic component) means that it will have a vast range of applications in orthopaedic surgery. Furthermore, the connector's ability to provide a compact moveable joint, providing very definite ranges of movement, enables it to be used in applications where such treatment is not currently possible. For instance it is conceivable that the joint can be fabricated small enough to replace the joints in the auditory ossicles to return a patient's hearing or, more commonly, to replace joints in arthritic fingers. The ability to easily replace worn articular surfaces of the connector without having to carry out complete joint replacement means it could also be useful in larger joints such as hip.

Fracture reduction - with most long bones where fractures occur a complicated system of casts or internal/external mechanical fixations are necessary. The connector of the present invention can be used as a fixed connector on both fractured parts, allowing the surgeon to use an extendable framework (e.g. a lockable ladder system) with two or more attachment points (e.g. hemispherical recesses with suitable means for attachment to the mounting arm) to be mounted on two or more connectors, to reduce the fracture. Because the connectors of the present invention can accommodate any angle the surgeon can select the safest place to connect the connector to the bone, minimising morbidity, reducing risk of further bone damage and simplifying the surgical technique of approximating the two fractured surfaces (this is an essential part of enabling successful bony healing). In larger cases connectors can be used on opposing sides of the bone (e.g. femur) that is being reduced, thus achieving a very stable and secure fixation. This would enable early mobility and reduce the patient's incapacity.

An illustration of the use of the connectors of the present invention to assist in fracture reduction is shown in Figure 5. As can be seen, two connectors are placed, one on each side of the fracture. The bones are drawn together and then a frame made of two parts 20a and 20b is connected to the connectors to hold the bones in position and set the fracture. A screw connector 21 holds the two parts of the frame together. Of course, the frame could be more elaborate, and more than two connectors could be used. Correction of deformities - as with fracture reduction the connector of the present invention can be used as a fixed connector to realign damaged or atrophic bone, and thereby save the patient from nerve compression, or to allow correction of scoliosis. In these cases the connector of the present invention can engage each of the vertebral bodies and, using a framework (ladder) system, the surgeon can manipulate each body to the correct position before locking it in place. As the connectors can connect securely to bony parts, in certain cases a system of external springs, screws or the like can be used with the laddering connections to allow a type of external osseogenic distraction (i.e. bone lengthening). The connectors could be used to connect a 'spatial frame' or the like, e.g. a Taylor spatial frame, to allow corrections to be made.

Joint replacement - currently prosthetic joints are either a simple ball and socket or hinge axis design. They have limitations in the range of movement, the relationship with the connecting bones and the level of morbidity that patients experience when the joints wear out and require replacement, which often involves further bone loss. A moveable connector according to the present invention can be used to improve the outcome of joint rehabilitation by providing a more compact articular unit, with easy replaceability of wearing components without 'total' joint replacement. By tailoring the slot or annular aperture in the cover unit, joint movement can be defined even to the point of making the joint movement non-linear which would be beneficial for many joints such as hip and knee joints.

With increasing human longevity, arthritic changes can be profoundly debilitating, especially in the hands and feet. Currently there are very few surgical treatments for these conditions. A moveable connector of the present invention can be used to replace many of these arthritic joints with a small, compact and fully articulating joint option. In a similar fashion to placing a dental implant in the jaw bone, an implant can be placed in the end of the phalange or carpal bones. The connector can then be fixed to the implant at the appropriate angle and the mounting arm of the core can fit a morse taper connection (or other suitable connection) in the second bone.

Alternatively the base portion can be provided with an osseo screw that can be fixed in the terminal end of the diseased bone. The cover unit and core can then be assembled with the mounting arm providing a secondary screw fixation to the connecting bone.

Figure 6 shows an example of a connector according the present invention in use as a replacement joint. One end of the connector 10 is attached to a first bone 22, e.g. via a suitable anchor. The other end is connected to a second bone 23 to be connected to the first bone in an articulated manner. As can be seen, the connector allows relative rotational movement of the two bones, as illustrated the arrow from one position 24a to a second position 24b.

Claims

1. According to the present invention there is provided a connector suitable for

biomechanical purposes comprising:

a core unit comprising a spherical body and an elongate mounting arm projecting therefrom, the mounting arm being adapted to pass through the aperture in the cover unit when in position in the concave recess, the mounting arm having a connection means to allow connection to another component;

wherein the base unit and cover unit are adapted to be connected together and thereby retain the core unit within their recesses.

2. The connector of claim 1 wherein the aperture comprises a slot or channel which allows rotation of the core unit, and thereby movement of the elongate mounting arm of the core unit, in a selected plane, preferably a sagittal plane.

3. The connector of claim 1 or 2 which is adapted to clamp the core unit between the base and cover units, and thereby lock the core unit in position, when the base and cover units are connected together.

4. The connector of claim 1 or 2 which is adapted to clamp the core unit against the cover and/or base unit, and thereby lock the core unit in position, when a restorative component is connected to the core unit.

5. The connector of claim 1 or 2 which is adapted so that when the base and cover units are connected together the core is able to move.

6. The connector of any preceding claim wherein the recess in the base unit and/or cover unit is substantially hemispherical.

7. The connector of any preceding claim which is adapted such that the rotational orientation of the aperture in the transverse plane is set by connecting the cover unit to the base unit.

8. The connector of any preceding claim wherein the base unit and cover unit are adapted to be connected together via corresponding screw threads provided on each unit.

9. The connector of any preceding claim wherein the cover unit is substantially hemispherical.

10. The connector of any preceding claim wherein the base unit comprises a

substantially hemispherical portion that comprises the concave recess.

1 1. The connector of any preceding claim wherein the interface member is adapted to allow the base unit to rotate relative to the anchor component.

12. The connector of claim 1 1 wherein this rotation is in a transverse plane relative to the connector and anchor component.

13. The connector of any preceding claim wherein the interface means comprises an annular member.

14. The connector of claim 13 wherein the annular member comprises a machine taper.

15. The connector of any preceding claim wherein the core and elongate mounting arm are adapted to move in a sagittal plane, i.e. orthogonal to the transverse plane.

16. The connector of any preceding claim wherein a marker is provided which

indicates the orientation that the aperture will be in once the cover unit is connected to the base unit.

17. The connector of any preceding claim wherein the connection means of the elongate mounting arm comprises a bore passing through the mounting arm, and preferably into the spherical body of the core unit.

18. The connector of claim 17 wherein the bore is threaded along at least a portion, preferably all, of its length.

19. The connector of any preceding claim wherein a restorative component is

provided which is adapted to interact with the cover portion and/or base unit to provide a friction lock against the cover unit when secured in place at a selected angle.

20. The connector of claim 19 wherein the restorative component is provided with a recess that is complimentary to the shape of the exterior of the connector.

21. The connector of claim 19 or 20 wherein the restorative component comprises a suitable shape to sealingly engage with the cover and/or base unit.

22. The connector of any one of claims 19 to 21 wherein the restorative component comprises a part-spherical recess, which allows the restorative component to nest against the cover and/or base units.

23. The connector of any preceding claim wherein the base unit comprises an anchor component.

24. The connector of claim 23 wherein the base unit, anchor and interface member are a single structure.

25. A a restorative structure comprising at least one connector according to any one of claims 1 to 24 connected to at least one anchor component and at least one restorative component.

26. A kit or system comprising at least one connector according to any one of claims 1 to 24 and one or more anchors comprising interface members adapted to cooperate with the interface member of the base unit of the at least one connector.

27. A method of connecting at least two biomechanical components using at least one connector according to any one of claims 1 to 24.

28. The method of claim 26 wherein the method comprises:

- connecting the base unit to an anchor component;

- placing the core unit in the recess in the base unit;

- connecting the cover unit to the base unit; and

- optionally, locking the core unit in position.

29. The method of claim 26 or 27, which comprises affixing a restorative component to the mounting arm of the core unit.

30. The method of any one of claims 26 to 28 comprising locking the core unit in position within the recesses by mounting the restorative component, or by clamping the core unit between the base and cover units.

31. The method of any one of claims 26 to 29 wherein the step of connecting the base unit to the anchor component comprises setting the transverse orientation and then locking the base unit in position relative to the anchor component.

32. The method of any one of claims 26 to 31 , which is a method of dental

restoration.

33. The method of any one of claims 26 to 31 , which is an orthopaedic surgical method.