WO2019123116A1

WO2019123116A1 - A medical anchor

Info

Publication number: WO2019123116A1
Application number: PCT/IB2018/059915
Authority: WO
Inventors: Dian Samuel PEACH
Original assignee: Peach Dian Samuel
Priority date: 2017-12-20
Filing date: 2018-12-12
Publication date: 2019-06-27

Abstract

This invention relates to a medical anchor (10) used during surgery, such as shoulder arthroscopic rotator cuff repairs. The medical anchor comprises a main body (12) having a first end (14) and a second end (16); a front portion (18) for releasably attaching to the first end (14) of the main body (12); an attachment formation (38) for operatively receiving one of a string, suture, stitch and tape (40), and means for fixing the anchor in bony tissue. The main body may typically be manufactured from a non-metallic material while the front portion may typically be manufactured from a metallic material, configured operatively to lead the anchor into bony tissue.

Description

A MEDICAL ANCHOR

INTRODUCTION AND BACKGROUND This invention relates to medical anchors. More particularly, the invention relates to a self-tapping suture anchor used during surgery, such as shoulder arthroscopic rotator cuff repairs.

From an anatomical view, the human shoulder is a joint that fixes the upper limb to the remainder body. The shoulder comprises a ball formation formed on the proximal humerus, and a socket formation formed on the scapula. The scapula connects the humerus to the clavicle. The shoulder also comprises a number of muscles and tendons. The“rotator cuff” comprises of four main muscles and the tendons that fixes these muscles to bones of the shoulder joint.

These four muscles are the supraspinatus, infraspinatus, teres minor and subscapularis. The rotator cuff lends stability, strength and movability to the shoulder joint. The rotator cuff facilitates flexion, abduction, internal rotation and external rotation of the upper limb relative to the scapula.

Injury to the rotator cuff occurs frequently and at all ages. Due, amongst others, to the range of motion of the shoulder, trauma related injuries of the rotator cuff are common, especially among younger patients, and are frequently caused by overhead activity such as volleyball, weight training, etc. The prevalence of these injuries generally increases with age. Rotator cuff injuries include rotator cuff tears, rotator cuff tendinitis and rotator cuff tendinopathy. When it comes to rotator cuff tears, the tendon of the supraspinatus is the most commonly affected.

Arthroscopy is a minimally invasive surgical procedure on a joint. During arthroscopic surgical repair of a torn rotator cuff tendon, sutures or strings are used to temporarily fix the tendon to, and align the tendon with the humerus, to facilitate the reattachment thereof to the bony tissue. The bony tissue of the humerus where the tendon is affixed is cancellous (spongy and porous). Anchors are required to hold the sutures in place. The suture anchors are fixed in the bony tissue, through the tendon, and therefore contributes directly to the fixing of the tendon or the muscle to the bony tissue. The suture anchors remain in situ permanently post-operatively.

Conventional suture anchors are manufactured from metal, such as titanium. These anchors interfere with radiological processes and may cause a scatter of X-rays and magnetic fields, radio waves and field gradients used during magnetic resonance imaging (MRI). This interference negatively impacts on post-operative follow-up procedures. For this reason, surgeons prefer utilising suture anchors of a non-metallic construction. However, when using a non-metallic suture anchor of a known kind, a pilot hole first needs to be drilled or tapped into the bony tissue before placement of the anchor. This negatively impacts on the complexity of, and the time required to perform, the arthroscopy, eventually negatively impacting on the total cost of the procedure.

Furthermore, the conventional suture anchors are pre-fixed to a disposable inserter. This makes provision, manufacturing, transport and packaging of the anchors bulky and expensive. These conventional anchors are pre threaded with a specific type of suture or string.

OBJECT OF THE INVENTION It is an object of the present invention to provide a medical anchor and method of placing a medical anchor with which the applicant believes the aforementioned disadvantages may at least be alleviated or which may provide a useful alternative for the known anchors and methods. SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided a medical anchor, comprising: a main body having a first end and a second end;

a front portion for releasably attaching to the first end of the main body; an attachment formation for operatively receiving one of a string, suture, stitch and tape; and

- means for fixing the anchor in bony tissue.

The main body may be manufactured from a non-metallic material. The front portion may be manufactured from a metallic material and may be configured to operatively lead the anchor into bony tissue.

The means for fixing the anchor in the bony tissue may comprise a thread defined on an outer surface of the anchor. The thread may comprise a first portion that may extend at least partially along a length of the front portion, and a second portion that may extend from the first end of the main body, along the main body towards the second end thereof, so that the first and second portions operatively align to form a continuous thread. The second portion of the thread may extend to the second end of the main body and therefore along the whole length of the main body. The first and second portions of the thread may be integrally formed with the front portion and the main body respectively. The medical anchor may comprise an attachment arrangement for attaching the front portion to the first end of the main body. The attachment arrangement may comprise a protrusion located on the front portion and an aperture located on the main body. Alternatively, the attachment arrangement may comprise a protrusion located on the main body, and an aperture located on the front portion. The aperture may be in the form of a collar such as a rim or a flange. The protrusion and aperture may be non circular, to inhibit relative rotational displacement between the main body and the front portion, and to align the first and second portions of the thread.

Alternatively, protrusion and aperture may be substantially circular or cylindrical, in which case the attachment arrangement may further comprise locating means to restrict relative rotational displacement between the main body and the front portion, and to align the first and second portions of the thread. The locating means may be in the form of a key and a corresponding groove formed on the attachment arrangement.

A front region of the front portion may comprise a tapering body terminating in a tip for piercing the bony tissue in use.

The first portion of the thread may comprise a taper thread. The front portion may be manufactured from titanium. An outer surface of the front portion may be polished to facilitate the operative advancement of the front portion into the bony tissue. The main body may be manufactured from a polymer. Specifically, the main body may be manufactured from a thermoplastic polymer selected from the group comprising of polyether ether ketone (PEEK) and ultra-high- molecular-weight polyethylene (UHMWPE). The medical anchor may further comprise an attachment formation for attaching a suture, stitch, string or tape. The attachment formation may comprise one of a lug, hook, projection and pin for operatively winding the suture, stitch, string or tape around. The attachment formation may be formed on the front portion. Alternatively, the attachment formation may be formed on the main body.

The main body may comprise an axial passage extending from the second end of the main body towards the front portion. The axial passage may be provided in communication with the attachment formation. In us a portion of the suture, stitch, string or tape may pass through the axial passage and exit the main body at the second end. The second end of the main body may comprise a receiving formation for operatively receiving a tip of a fastening tool.

The receiving formation may be one of rectangular and hexagonal or may alternatively comprise any other suitable shape.

Both of the front portion and the main body may be cast or moulded.

The second portion of the thread may comprise a taper thread which may generally taper outwardly towards to the second end of the main body.

The front portion and main body may be fixed together by an adhesive substance. Alternatively, a string, suture, stitch or tape wound around the attachment formation may hold the front portion and the main body together in use.

According to a second aspect of the invention there is provided a method of fixing a medical anchor in bony tissue, which medical anchor comprises non-metallic main body and a metallic front portion, the method comprising: - positioning a tip of the front portion relative to the bony tissue;

providing an impact to a second end of the main body, to drive the tip at least partially into the bony tissue; and advancing the anchor into the bony tissue by utilising a tool to exert a torque on the main body, so that thread defined on the anchor interacts with the bony tissue, thereby driving the anchor further into the bony tissue, and fixing the anchor within the bony tissue.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The invention will now further be described, by way of example only, with reference to the accompanying diagrams wherein:

figure 1 is a top perspective view of a medical anchor in accordance with a first example embodiment of the invention; figure 2 is a bottom perspective view of the medical anchor of figure 1 ; figure 3 is a side view of the medical anchor of figure 1 ;

figure 4 is a top view of the medical anchor of figure 1 ;

figure 5 is a bottom view of the medical anchor of figure 1 ;

figure 6 is an exploded view from a bottom perspective of the medical anchor of figure 1 ;

figure 7 is an exploded view from a top perspective of the medical anchor of figure 1 ;

figure 8 is an exploded view of a first side of the medical anchor of figure 1 ;

figure 9 is a side view in section of the medical anchor of figure 1 , sectioned along line IX-IX’ indicated in figure 8; figure 10 is an exploded view of a second side of the medical anchor of figure 1 ;

figure 1 1 is a side view in section of the medical anchor of figure 1 , sectioned along line CI-CG indicated in figure 10; figure 12A shows a first step of fixing the medical anchor of figure 1 in bony tissue;

figure 12B shows a second step of fixing the medical anchor of figure 1 in bony tissue; and

figure 12C shows the medical anchor of figure 1 in situ.

figure 13 is a section side view showing two of the medical anchors of figure 12, in situ, post operatively;

figure 14 is a side view of a shoulder joint, showing the medical anchors of figure 1 in situ after a shoulder arthroscopic rotator cuff repair has been performed;

figure 15 is a top perspective view of a medical anchor in accordance with an alternative example embodiment of the invention; figure 16 is an exploded view from a side perspective of the alternative medical anchor of figure 15;

figure 17 is an exploded view from a bottom perspective of the medical anchor of figure 15;

figure 18 is a section side view of the medical anchor of figure 15; figure 19 is a side view of a main body of the medical anchor of figure

15; DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

A first example embodiment of a medical anchor according to the invention is generally designated by the reference numeral 10 in figures 1 to 14.

The medical anchor 10 comprises a main body 12 comprising a first end 14 (which is best shown in figure 6) and a second end 16. The medical anchor 10 furthermore comprises a front portion 18. In use, the front portion 18 is releasably attached to or at the first end 14 of the main body 12. The anchor also comprises an attachment formation 38 (which is best shown in figure

11 ) for operatively receiving a string, suture, stitch or tape 40. As described more fully below, the anchor 10 is furthermore provided with means for fixing the anchor in bony tissue 20. The anchor 10 is therefore an assembly of two distinct modular parts, namely the main body 12 and the front portion 18.

The main body 12 is manufactured from a non-metallic, inert material while the front portion 18 is manufactured from a metallic material. The front portion is configured to operatively lead the anchor into bony tissue. A front region 22 of the front portion 18 terminates in a tip 24 (which is best shown in figure 3). When utilised during shoulder surgery, to repair torn or severed muscles or tendons, the anchor is fixed in cancellous bone. The tip 24 is utilised to pierce the bony tissue 20 of the cancellous bone. The means for fixing the anchor to the bony tissue 20 comprises a thread 26 which is defined on an outer surface 28 of the anchor 10. A first portion 26.1 of the thread extends at least partially along a length of the front portion 18, whereas a second portion 26.2 of the thread extends from the first end 14 of the main body 12, along the main body 12 and towards the second end

16 thereof, such that the first and second portions (26.1 , 26.2) form a continuous thread, when the front portion 18 is attached or fixed to the main body 12. As illustrated in the figures, the second portion 26.2 of the thread may extend to, and therefore terminate at, the second end 16 of the main body 12.

As is best illustrated in figures 6 to 1 1 , the front portion 18 is attached to the main body 12 by means of an attachment arrangement 30, which comprises a protrusion 32 formed on the front portion 18, and an aperture 34 (or collar in the form of a rim or a flange) extending from the first end 14 into the main body 12. It will readily be appreciated that the protrusion 32 and aperture 34 may alternatively be formed on the main body 12 and front portion 18 respectively without departing from the scope of the invention. As shown in figures 6 to 1 1 , the protrusion 32 and aperture 34 are non circular to thereby inhibit relative rotational displacement between the main body 12 and the front portion 18. A top edge of the protrusion 32 is chamfered to ease the receiving thereof within the aperture 34. This configuration of the attachment arrangement furthermore ensures that the first portion 26.1 of the thread formed on the front portion 18 and the second portion 26.2 of the thread formed on the main body 12 properly align, as is illustrated, thereby to form the continuous thread.

The attachment formation 38, which is provided for attaching the suture, string, stitch or tape 40 thereto is in the form of a lug, hook, projection or pin, around which the suture, string, stitch or tape 40 is wound in use - see figure 11. An axial passage 41 extends along the length of the main body 12, so that the suture, string, stitch or tape 40 may extend there through in use.

The axial passage 41 extends from the second end 16 of the main body 12 towards the first end 14 and is provided in communication with the attachment formation 38, so that the suture, string, stitch or tape 40 is operatively wound around the attachment formation 38, to pass along the axial passage 41 and exit the axial passage 41 at the second end 16 of the main body 12. The attachment formation 38 may be provided on either the main body 12 or the front portion 18. When provided on the main body 12, additional means for fixing the main body 12 and front portion 18 is required and may be provided in the form of a suitable adhesive or a reverse thread. However, as is illustrated, and as will be described in more detail below, preferably the attachment formation 38 is formed on the front portion 18. When the attachment formation 38 is provided on the front portion 18, tension within the suture, string, stitch or tape 40 may sufficiently hold the front portion 18 and main body 12 together, obviating the need to provide further means of fixing these together. The fit between the protrusion 32 and the aperture 34 may be tight.

The first portion 26.1 of the thread comprises a taper thread, that tapers from proximate the front region 22 outwardly in the direction of the main body 12 so that, when the anchor is in the assembled configuration, an outer diameter of the first portion 26.1 which is in contact with the first end 14, matches an outer diameter of the second portion 26.2 at the first end 14 to form a continuous thread as shown.

The front portion 18 is manufactured from medical grade titanium, and has a polished outer surface finish, which eases the advancement of the front portion 18 into the bony tissue 20, as will be described in more detail below. Alternatively, the front portion may be manufactured from other metals suitable for medical use. The use of a metal such as titanium ensures that the tip 24 is hard and sturdy enough to pierce the bony material, without the need of first providing a tapped guide or pilot hole (as would be required in cases where non- metallic anchors are used). The taper thread of the first portion 26.1 (which is also manufactured from a metal such as titanium) facilitates the cutting of an internal thread in the bony tissue, when the anchor is placed into the bony tissue, as discussed more fully below. The main body 12 is manufactured from a polymer (typically a thermoplastic polymer). Preferably the polymer is polyether ether ketone (PEEK). PEEK is a suitable material in the current application, as it is inert, stable and does not dissolve which means that the PEEK will not cause localized tissue reactions. Furthermore, PEEK is“radiolucent” on x-rays which means that it doesn’t impede post-operative examinations as much as metallic anchors would.

Alternatively, the thermoplastic polymer may be ultra-high-molecular-weight polyethylene (UHMWPE) or other suitable polymers. The polymer is specifically selected based thereon that it does not cause interference with radiological processes, such as x-rays, MRI scans etc.

The first portion 26.1 and the second portion 26.2 of the thread 26 are integrally formed with the front portion 18 and main body 12 respectively. Both the main body 12 and the front portion 18 are manufactured by means of a casting or moulding process, although the use of other known manufacturing processes is also feasible. The surface finish of the front portion 18 is obtained by polishing the front portion 18 after being cast or moulded.

As shown in figures 1 and 7, the second end 16 of the main body 12 comprises a receiving formation 42 which is shaped to receive a tip of a fastening tool 44, such as a screw-driver or a hex key. The fastening tool 44 is therefore not integrally formed with the anchor, which means the fastening tool 44 is not a consumable item. A shoulder 43 (which is shown in figure 9) in the axial passage 41 limits the extent to which the tip of the fastening tool may extend beyond the second end 16 into the anchor 10.

Depending on the type of fastening tool 44 used, the receiving formation 42 may be rectangular, square, or hexagonal. It will be appreciated that receiving formations 42 having other shapes, capable of enabling the fasting tool 44 to exert a torque on the anchor 10, may be provided without departing from the scope of the invention.

The second portion 26.2 of the thread comprises a taper thread that tapers from the first end 14, outwardly towards the second end 16. The outer surface 28 of the main body 12 may similarly taper outwardly from the first end 14 towards the second end 16. The taper thread of the second portion 26.2 is best illustrated in figure 3, where an extent of a first outer dimension 46, of portion 26.2 of the thread 26 located towards the first end 14 of the main body 12, is less than an extent of a second outer dimension 48, of portion 26.2 of the thread 26 located towards the second end 16 of the main body 12. Therefore, the second portion 26.2 of the thread generally tapers outwardly from the first end 14 towards the second end 16 of the main body 12.

The use of the anchor 10 is now described with reference to figures 12 to 14. Please note that the suture, string, stitch or tape 40 is not indicated in figure 12. In cases where muscle tissue or tendons 50 become severed from the bony tissue 20 of a joint, (typically in the case of a shoulder joint as shown in figure 14), a number of anchors 10 are inserted into the bony tissue 20, so that sutures, strings, stitches or tapes 40 may be strategically used to keep the muscle tissue or tendons 50 in place relative to the bony tissue

20, to encourage the reattachment thereof. Some of the anchors may be provided in locations underneath the muscle tissue or tendons 50, and may, when inserted, pierce the muscle tissue or tendons 50. The anchors 10 are fixed in position by firstly positioning and aligning the tip

24 thereof with a position on an outer surface of the bony tissue 20 where the anchor needs to be located. An impact is provided to the second end 16 of the main body 12, typically by means of a hammer 52, as shown in figure 12A. Alternatively, the tip of the fastening tool 44 may be located within the receiving formation 42, and the impact may be provided to a rear end of the fastening tool 44. This drives the tip 24, at least partially, into the bony tissue 20 to the extent that the first portion 26.1 of the thread makes contact with the bony tissue. Next, the fastening tool 44 is utilised to exert a torque, through the main body 12, on the front portion 18, so that the first portion 26.1 of the thread cuts an internal thread into the bony tissue 20. The anchor is therefore self-tapping. This is shown in figure 12B. The interaction between the first portion 26.1 of the thread and the bony tissue 20 therefore drives the front portion 18, and thus the anchor 10, deeper into bony tissue

20, until the second end 16 is flush with the outer surface of the bony tissue 20, as is shown in figure 12C (this is the final position of the anchor 10). Since the second portion 26.2 of the thread aligns with the first portion 26.1 , the second portion 26.2 therefore follows in the internal thread cut by the first portion 26.1. The thread ensures that the anchor is able to resist axial forces exerted by the suture, string, stitch or tape 40 on the anchor (and therefore resists being pulled or sheared out of the bony tissue).

Furthermore, the taper of the second portion 26.2 of the thread assists in fixing the anchor 10 in the bony tissue 20, as a compressive force is exerted by the bony tissue on the second portion 26.2 of the thread 26, thereby increasing the resistance of the anchor 10 against being pulled out of the bony tissue 20. Figure 13 shows a cross-sectional view through two anchors 10 inserted in accordance with the steps discussed above with reference to figure 12. As can be seen, a suture extends between the attachment formations 38 of the two anchors 10 and holds muscle tissue 50 down relative to the bony tissue

20.

The anchors 10 are typically used during an arthroscopic procedure as a fixation point to re-attach rotator cuff muscles in the shoulder. Figure 14 shows such a rotator cuff repair, post-operatively. Due to an injury, the supraspinatus 54 has become severed from the humerus 56, and a tear 58 is clearly visible. The subscapularis 60 was not affected, as its fixation 62 to the humerus 56 is clearly intact. Similarly, the infraspinatus 64 was not affected, as its fixation 66 to the humerus 56 is also intact. The tear 58 was repaired by way of an arthroscopic procedure. Four anchors 10 were fixed to the humerus 56 as previously described. Of these, the first anchor 10.1 and second anchor 10.2 were advanced into the humerus 56 through the supraspinatus 54, while the third anchor 10.3 and fourth anchor 10.4 were advanced directly into the humerus 56, and not through a tendon or muscle tissue. The anchors (10.1 to 10.4) serve as fixation points for the sutures 40 used to keep the supraspinatus 54 in place, to facilitate the reattachment thereof to the humerus 56. An alternative example embodiment of a medical anchor 100 in accordance with the current invention is shown in figures 15 to 19. In figures 15 to 19, like reference numerals refer to like features as disclosed above in relation to the medical anchor 10.

The alternative medical anchor 100 differs from the first example medical anchor 10 in that the front region (22 of the first embodiment 10) is replaced by a tapering body 23 that terminates in the tip 24. Furthermore, the protrusion 32 of the alternative medical anchor 100 comprises a round peg. The attachment arrangement 30 of the alternative medical anchor 100 further comprises locating means which is in the form of a key 36 and a corresponding groove or slot 37. The locating means (36, 37) ensures that the first portion 26.1 of the thread aligns with the second portion 26.2 of the thread, while also preventing rotation between the main body 12 and front portion 18 relative to one another.

It will readily be appreciated that the alternative anchor 100 can be used in similar fashion as described above in relation to the first example medical anchor 10, without departing from the invention, and that use of the alternative anchor 100 may bring about similar advantages as those described in respect of the first example medical anchor 10. The overall length of the anchor (10 or 100) may typically be between 16 and 20 mm, and may more particularly be 17 mm, 18 mm or 19 mm. The length of the main body may be between 10 and 14 mm, and may more typically be 12 mm or 13 mm. The diameter of the main body (excluding the thread 26) may be around 5 mm, while the size of the axial passage 41 may be around 3.5 mm. The extent of the second outer dimension 48 may be around 7 mm.

As will readily be appreciated when studying the figures, the overall size of the main body 12 significantly exceeds the overall size of the front portion

18.

Therefore, the extent to which interference with radiological processes is caused by the anchors (10 and 100) are limited by the limited size of the metallic components. However, the inclusion of a metallic tip still ensures functionality, effectiveness and ease of use of the anchor and reduces the number of steps required to insert the anchor into position.

Because of the modular construction of the anchor (comprising two modules, namely the main body 12 and the front portion 18), and as more fully discussed below, the anchors (10 and 100) can be inserted into the bony tissue by means of a non-disposable instrument. The anchors (10 and 100) may be loaded onto the instrument intra-operatively. Other than conventional suture anchors, each of which is associated with a distinct disposable tool and pre-threaded with a specific type of suture, the current invention can be threaded and simply attached to a non-disposable tool, intra-operatively. This significantly reduces the cost of each anchor and the size and cost of the packaging. The anchors can now be packaged into smaller packets and the anchors and non-disposable tool can be sterilized separately.

Various types of sutures, such as braided sutures, reinforced sutures or tapes, are available for use during surgery. A suitable suture type is selected based on the tear pattern of the tendon or muscle tissue. This can often only be determined intra-operatively. The tapes, for instance, are a flat type of suture material which has a very low knot construct and which makes for lower and more secure knot tying.

The modular construction of the anchors (10 and 100) enables the surgeon or an assistant to assemble an anchor intra-operatively, and to thread the anchor with the required or most suitable type of suture (conventional suture anchors come pre-threaded with a specific type of suture, which may not always be suitable). The fact that the suture anchor is modular therefore also enables the surgeon select a different suture, even if a specific suture has already been threaded onto the anchor. This change can be effected intraoperatively. In cases where tears in the rotator cuff are small, only two or three sutures are required. Since conventional suture anchors are pre-threaded with a suture, two or three suture anchors still need to be utilised. However, since the front portion 18 of the current invention can be removed from the main body 12 during the procedure, and before being placed in the bony tissue, a second or even third suture may be added to a single suture anchor (10 or 100), and in the case of a small tear requiring only two or three sutures, a single suture anchor may be used.

While the anchors (10 and 100) are exemplified herein only in respect of its use during shoulder arthroscopic rotator cuff repairs, the bony tissue 20 referred to herein should be taken to include bony tissue located anywhere in the human or animal body, and typically where muscle tissue, tendons or ligaments are attached thereto. The use of the medical anchors (10 and

100) in accordance with the methods as exemplified herein, can therefore similarly be applied elsewhere in the human or animal body.

It will be appreciated by those skilled in the art that the invention is not limited to the precise details as described herein and that many variations are possible without departing from the scope and spirit of the claimed invention. For example, the current invention extends to an embodiment of similar construction of either the first example medical anchor 10 or the alternative medical anchor 100, with the exception that the front portion is manufactured from a similar material than the main body. The advantages described above and associated with the modular construction (namely the intra-operative assembly of the anchor, which enables the selection of any suitable suture, string, stitch or tape) are therefore retained. However, in cases where both the main body 12 and the front portion 18 are manufactured from a non-metallic material, such as a polymer, the anchor will not have a self-tapping characteristic, and a pilot hole will have to be created before insertion of the anchor. Similarly, in cases where both the main body 12 and the front portion 18 are manufactured from a metallic material, such as titanium, the disadvantages related with metallic anchors as disclosed herein (namely interference with radiological processes) will still be present.

The description above is presented in the cause of providing what is believed to be the most useful and readily understandable description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention. The words used should therefore be interpreted as words of description rather than words of limitation.

Claims

1 . A medical anchor, comprising:

a main body having a first end and a second end;

a front portion for releasably attaching to the first end of the main body;

an attachment formation for operatively receiving one of a string, suture, stitch and tape; and

means for fixing the anchor in bony tissue.

2. A medical anchor according to claim 1 , wherein the main body is manufactured from a non-metallic material and wherein the front portion is manufactured from a metallic material and configured to operatively lead the anchor into bony tissue.

3. A medical anchor according to claim 1 or 2, wherein the means for fixing the anchor in the bony tissue comprises a thread defined on an outer surface of the anchor.

4. A medical anchor according to claim 3, wherein the thread comprises a first portion that extends at least partially along a length of the front portion, and a second portion that extends from the first end of the main body, along the main body towards the second end thereof, such that the first and second portions operatively align to form a continuous thread.

5. A medical anchor according to claim 4, wherein the second portion of the thread extends to the second end of the main body.

6. A medical anchor according to claim 4 or 5, wherein the first and second portions of the thread are integrally formed with the front portion and the main body respectively.

7. A medical anchor according to any one of the preceding claims, comprising an attachment arrangement for attaching the front portion to the first end of the main body.

8. A medical anchor according to claim 7, wherein the attachment arrangement comprises a protrusion located on one of the front portion and the main body and an aperture located on the other one of the front portion and the main body.

9. A medical anchor according to claim 8, wherein the aperture is in the form of a collar, a rim or a flange.

10. A medical anchor according to claim 8 or claim 9, wherein the protrusion and aperture are non-circular, to operatively inhibit relative rotational displacement between the main body and the front portion, and to align the first and second portions of the thread.

11. A medical anchor according to claim 8 or claim 9, wherein the attachment arrangement further comprises locating means to restrict relative rotational displacement between the main body and the front portion, and to align the first and second portions of the thread.

12. A medical anchor according to claim 1 1 , wherein the locating means is in the form of a key and a corresponding groove formed on the attachment arrangement.

13. A medical anchor according to any one of the preceding claims, wherein a front region of the front portion comprises a tapering body terminating in a tip for piercing the bony tissue in use.

14. A medical anchor according to claim 4, wherein the first portion of the thread comprises a taper thread.

15. A medical anchor according to any one of the preceding claims, wherein the front portion is manufactured from titanium.

16. A medical anchor according to any one of the preceding claims, wherein an outer surface of the front portion is polished to facilitate the operative advancement of the front portion into the bony tissue.

17. A medical anchor according to any one of the preceding claims, wherein the main body is manufactured from a polymer.

18. A medical anchor according to claim 17, wherein the main body is manufactured from a thermoplastic polymer selected from the group comprising of polyether ether ketone (PEEK) and ultra-high-molecular- weight polyethylene (UHMWPE).

19. A medical anchor according to any one of the preceding claims, wherein the attachment formation comprises one of a lug, hook, projection and pin for operatively winding the suture, stitch, string or tape around.

20. A medical anchor according to any one of the preceding claims, wherein the attachment formation is formed on the front portion.

21 . A medical anchor according to any one of the preceding claims, wherein the main body comprises an axial passage extending from the second end of the main body towards the front portion, which axial passage is provided in communication with the attachment formation, wherein a portion of the suture, stitch, string or tape passes through the axial passage in use.

22. A medical anchor according any one of the preceding claims, wherein the second end of the main body comprises a receiving formation for operatively receiving a tip of a fastening tool.

23. A medical anchor according to claim 22, wherein the receiving formation is one of rectangular and hexagonal.

24. A medical anchor according to any one of the preceding claims, wherein both of the front portion and the main body are moulded.

25. A medical anchor according to claim 4, wherein the second portion of the thread comprises a taper thread which tapers outwardly towards to the second end of the main body.

26. A medical anchor according to any one of the preceding claims, wherein the front portion and main body are fixed together by an adhesive substance.

27. A medical anchor according to claim 20, wherein a string wound around the attachment formation holds the front portion and the main body together in use.

28. A method of fixing a medical anchor in bony tissue, which medical anchor comprises non-metallic main body and a metallic front portion, the method comprising:

- positioning a tip of the front portion relative to the bony tissue;

- providing an impact to a second end of the main body, to drive the tip at least partially into the bony tissue; and

- advancing the anchor into the bony tissue by utilising a tool to exert a torque on the main body, so that thread defined on the anchor interacts with the bony tissue, thereby driving the anchor further into the bony tissue, and fixing the anchor within the bony tissue.

29. A medical anchor according to claim 1 , substantially as herein described and exemplified, with reference to figures 1 to 14.

30. A medical anchor according to claim 1 , substantially as herein described and exemplified, with reference to figures 15 to 19.