A DEVICE FOR FIXING AN OBJECT BY A HOLE IN BONE TISSUE

Abstract: Device (1) for fixing an object at a recess (41) in bone tissue (42), said device (1) having a first longitudinal direction (L), a first transverse direction (T), a first upper end (2), a first lower end (3) and a first length (X), said first length (X) being measured from said first lower end (3) to said first upper end (2), and said device (1) comprises a head (4), said head (4) having a second upper end (5), a second lower end (6), a second length (Y), which second length (Y) is measured from said second lower end (6) to said second upper end (5), and a first external diameter (D1), and said head (4) comprises a base (7) at said second lower end (6), said head (4) having a compressible shell-shaped structure, and a first ratio (Y/D1) between said second length (Y) and said first external diameter (D1) is equal to or less than 1.0.

Description: A device for fixing an object by a hole in bone tissue TECHNICAL FIELD The present invention relates to a device for fixing an object at a recess in bone tissue and means for applying the device, said device having a first longitudinal direction, a first transverse direction, a first upper end, a first lower end and a first length, said first length being measured from said first lower end to said first upper end, and said device comprises a head, said head having a second upper end, a second lower end, a second length, which second length is measured from said second lower end to said second upper end, and a first external diameter, and said head compπses a base at said second lower end. PRIOR ART In surgical interventions, for example for treating soft-tissue ruptures, suture anchors are used for fixing soft tissue to bone in humans and animals. This is done by a suture anchor being fixed to the bone and by the soft tissue which is to be fixed being secured, for example with a suture thread, to the suture anchor. The various types of suture anchors which are used today have different type-specific advantages and disadvantages with respect to therapeutic effect, user-friendliness and risks of complications. Suture anchors which are relatively large cause unnecessary trauma to a patient's tissue since, in order to be applied, they require that relatively large holes be made in the bone tissue. The size of the holes needed in the bone tissue varies from ca. 2 to 4 mm for today's suture anchors, see for example Barber et al., Arthroscopy, 13(3), 1997, 355-362. A larger suture anchor causes greater trauma to a patient's tissue. Moreover, the relatively large suture anchors may be too large to be applied in small bones, for example in the hand, or if a number of suture anchors have to be applied close to each other. There are also suture anchors which consist of two or more parts, which makes these suture anchors difficult to handle, for example during application. A suture anchor made up of several parts probably involves tight fits, and such a suture anchor entails an increased risk of bacterial infections. Some of the suture anchors, which are described for example in Barber et al., Arthroscopy, 13(3), 1997, 355 to 362 or in US-A-5,236,445, have such a design that they do not provide sufficient guiding after they have been applied in a hole which has been made in bone tissue, i.e. they are not given a sufficiently defined anchoring site after they have been applied. The insufficient guiding, i.e. the insufficiently defined anchoring site, means that these suture anchors can change position or loosen, in which case a new surgical intervention is needed. Another type of suture anchor is provided with a thread. This type of suture anchor is either self-tapping or requires that a hole in the bone tissue be threaded before application. Threading before or at the time of application necessitates a torsional moment, which may be inappropriate if, for example, in addition to the soft tissue damage, there are also fractures present. The hardness of the bone tissue varies depending on where the suture anchor is to be anchored, which is of significance for the choice of application method and the choice of the material of the threaded suture anchors. In hard bone, the self-tapping suture anchors must be made of metal. The metal itself may constitute a risk of complications, such as foreign-body reactions and chronic inflammation, or may be a focus for infections. Threaded suture anchors have a further disadvantage that they obstruct the hole in the bone tissue in such a way that the important recruitment of bone-forming cells from the medullary cavity is prevented. There are also suture anchors which are made of various plastic materials, which plastic materials can be biodegradable. If the plastic material is biodegradable, it is broken down in the body and metabolized or excreted. There are biodegradable plastic materials with disadvantageous degradation kinetics which involve a high rate of release of acid degradation products, which can give rise to local corrosion lesions. DISCLOSURE OF THE INVENTION The present invention relates to a device for fixing an object at a recess in bone tissue. By means of a head with a shell-shaped structure, the device has a very considerable capacity to withstand compression in a first longitudinal direction of the device and a strength which is optimized in relation to the volume of the device. Moreover, the head can by contrast be compressed in a first transverse direction of the device, and said device is easily applied in a recess in bone tissue without any torsional moment. The device is held in engagement in a recess by virtue of the fact that the head comprises a base which is able to bear against a distinct edge. Said head has a shell-shaped structure, for example with the basic shape of a cupola, a semisphere or a partially semispherical shape, and the ratio between the height of the head, i.e. the second length of the head, and the first external diameter of the head is equal to or less than 1.0. Moreover, the device has a construction for securing said object, said construction being preferably arranged substantially centrally on the device. By means of the present invention, a device is made available for fixing an object at a recess in bone tissue, said device, by virtue of its design, being easy to apply in a recess in bone tissue, and the application being carried out without a torsional moment. By virtue of its design, for example the ratio between the height of the head, i.e. the second length of the head, and the first external diameter of the head, said device has a minimized risk of changing position or coming loose. Moreover, by virtue of its design, the device is subject to purely compressive loading and is centered in the recess upon use. Moreover, the ingenious design of the device means that the size of said device and the depth of said recess in the bone tissue can also be adapted so as to minimize any trauma to the patient. The device can also be made in one piece, which reduces the risk of bacterial infection since there are no tight fits in the device restricting the through-flow of serum. In addition, if the device is made of a biodegradable plastic material, for example polylactic acid or polyurethane plastic, any foreign-body reaction is also limited in time. If said device further comprises at least one radial opening, said opening functions as a channel from the medullary cavity, i.e. the recess in the bone tissue, to the soft tissue, i.e. said object. The design of the device also allows the soft tissue to be anchored partially inside the recess in the bone tissue. These factors increase the probability of bone-anchored incorporation of fixed tissue because bone-forming cells from the medullary cavity come into contact with the fixed soft tissue. Since said device permits the fastest possible incorporation of soft tissue, the conditions are excellent for achieving a good therapeutic effect and the shortest possible rehabilitation time. The present invention relates to a device for fixing an object at a recess in bone tissue, said device having a first longitudinal direction, a first transverse direction, a first upper end, a first lower end and a first length, said first length being measured from said first lower end to said first upper end, and said device comprises a head, said head having a second upper end, a second lower end, a second length, which second length is measured from said second lower end to said second upper end, and a first external diameter, and said head comprises a base at said second lower end, said head having a compressible shell-shaped structure, and a first ratio between said second length and said first external diameter is equal to or less than 1.0. Said device can be a suture anchor, a prosthetic attachment, another attachment means, or similar. Moreover, when said device is a suture anchor, said device comprises a construction for securing a suture thread, which construction can be, for example, a through-hole in said device, an eyelet, a projecting part, a groove or the like. Moreover, said device fixes an object at a recess in bone tissue by said object being anchored to said device, said device being introduced axially into said recess in the bone tissue and held in engagement there. Said object can be, for example, endogenous soft tissue, such as cartilage, meniscus, tendon, ligament, fascia or muscle tissue. Alternatively, it can be an exogenous implant such as an allograft, xenograft or artificial implant. Moreover, said object is anchored to said device by, for example, suture thread, adhesive or the like. Said recess in the bone tissue where said object is to be fixed can be, for example, a hole which has been drilled in the bone tissue and which has thereafter been widened inside the cortical part of said bone tissue with a surgical instrument. By means of said hole being widened inside the cortical part of said bone tissue, a distinct shoulder is formed. Said device has a first longitudinal direction and a first transverse direction, said first longitudinal direction, which is axial, extending from the first lower end of said device to the first upper end of said device, and said first transverse direction, which is radial, extending across said first longitudinal direction. When said device is held in engagement in a recess in bone tissue, said first upper end is that end of the device which is furthest inside the recess, and said first lower end is that end of the device which is nearest the opening of the recess in the bone tissue. Moreover, said device has a first length, said first length being measured from said first lower end to said first upper end. Moreover, said device comprises a head, said head having a second upper end, a second lower end, and a second length, which second length is measured from said second lower end to said second upper end. When said device is held in engagement in a recess in bone tissue, said second upper end is that end of said head which is furthest inside the recess, and said second lower end is that end of said head which is nearest the opening of the recess in the bone tissue. Said head also has a first external diameter, said first external diameter having its extent running in said first transverse direction. Said first external diameter is the greatest external diameter of said head and can be situated adjacent to said second lower end of said head. Said head moreover comprises a base at said second lower end, said base having its extent running substantially in the imaginary plane formed by said first transverse direction, which is radial, and a tangential direction to the periphery of the device in the first transverse direction. When said device has been introduced axially into a recess in the bone tissue, said device is held in engagement in the recess by means of said base bearing against a shoulder in the recess. Said shoulder in the recess may have been created by first having drilled a hole in the bone tissue, which hole has then been milled inside the cortical part of the bone tissue. The recess which has been created there has a diameter, inside the cortical part of the bone tissue, which is greater than the diameter in the cortical part of the bone tissue, i.e. greater than the external diameter of said recess. As has previously been described, said head has a compressible shell- shaped structure. The fact that said shell-shaped structure is compressible means that the first external diameter of said head can be reduced by said head being pressed together and, consequently, the size of said device in said first transverse direction can also be reduced. Said head is pressed together, and the size of said device in said first transverse direction is thus also reduced, using a means for applying said device. Moreover, the first external diameter of said head and the size of said device are both reduced elastically in said first transverse direction upon compression. The fact that said reductions take place elastically means that the first external diameter of said head and the size of said device in said first transverse direction both recover their normal dimensions when the compression ceases. Said compressible shell-shaped structure allows said device to be introduced axially into a recess with an external diameter which is smaller than the first external diameter of said device. If the recess has been milled inside the cortical part of the bone tissue, as has previously been described, said head can thus recover its normal dimensions when said device has been introduced axially and the compression of said head ceases. Moreover, a shoulder has been formed inside the cortical part of the bone tissue by means of the milling of the recess. Said device is thus held in engagement when said head has recovered its normal dimensions by virtue of the fact that the base of said head bears against the shoulder in the recess. A shoulder in a recess is thus formed here by a transition from the greater internal diameter to the smaller external diameter. The shell shape in the structure of said head means that said head gives a hollowed-out appearance since said head could be likened to a shell having been formed from a hollowed-out geometric body. Upon a substantially axial pressure load, such a shell shape of said head gives a ratio between the strength of the head and its volume which is much greater than the corresponding ratio in a corresponding solid head. Said compressible shell-shaped structure can have any suitable basic shape, for example a cupola shape, which cupola shape can be complete or interrupted, a semi-spherical shape, which semi-spherical shape can be complete or interrupted, a combined shape such as a semi-spherical shape merging into a conical shape, which combined shape can be complete or interrupted, or the like. Moreover, the fact that said compressible shell- shaped structure can be interrupted signifies all suitable variants ranging from the basic shape of said compressible shell-shaped structure being only partially interrupted, to said compressible shell-shaped structure lacking large parts of its basic shape. As has previously been described, said device fixes an anchored object at a recess in bone tissue by means of said device being introduced axially into said recess in the bone tissue and being held in engagement there. Said recess in the bone tissue has a second external diameter nearest the opening of said recess in the bone tissue, which second external diameter is smaller than the first external diameter of said head when said head, and thus said device, is not in a compressed state. It is therefore necessary for said head, and thus said device, to be compressed in order for said device to be able to be introduced axially into said recess. Compressing said head, and thus said device, is made possible by said head's compressible shell- shaped structure. Said head is compressed, and thus the size of the device in said first transverse direction is also reduced, using a tool for applying said device. When said head and thus said device are compressed, the first external diameter of said head and the size of said device in said first transverse direction are reduced elastically. By means of said reductions taking place elastically, the first external diameter of said head and the size of said device in said first transverse direction both recover their normal dimensions when the compression ceases. Said device is compressed and is introduced axially into said recess in the bone tissue using said tool for application. When said tool for application is removed from said device and said device is no longer compressed, the first external diameter of the head and the size of said device in said first transverse direction both recover their normal dimensions, whereupon said device is held in engagement. Moreover, it is also possible to conceive of situations for application of said device in which the first external diameter of said head and the size of said device in said first transverse direction are not permitted to completely recover their normal dimensions. Such situations can arise when said device is introduced axially into the recess by means of the external and/or internal diameter of the recess being made slightly smaller than the dimensions of the adjacent parts of said device. Moreover, a first ratio between the second length of said head and the first external diameter of said head is equal to or less than 1.0, said first ratio giving a device which is stable in the case of a central compressive load, where the angle of attack of the compressive load is less than 26.5°. Compressive load is to be understood as meaning that the direction of action of the load is from the first upper end of said device to the first lower end of said device. The angle of attack of the compressive load is a measure of how much the direction of the compressive load deviates from the first longitudinal direction of the device. For example, if a device is used for fixing an object in a recess in bone tissue where the first diameter of said head is 3.0 mm, the second length of said head is 3.0 mm, the diameter of the recess in the cortical part of the bone tissue is 2.0 mm and the cortical part of the bone tissue has a thickness which is 2.0 mm, then the angle of attack for a central compressive load, which compressive load is generated outside the bone tissue, can be a maximum of 11.3°. In the case of an angle of attack of maximum 11.3° for a central compressive load, the illustrated device cannot change position because a device in which said first ratio between the second length of said head and the first external diameter of said head is 1.0 is stable under a central compressive load with angles of attack of up to 26.5°. Further embodiments of said device concern devices in which said first ratio between said second length of said head and said first external diameter is a maximum of 0.9, 0.8 or 0.7, which first ratios give devices which are stable under a central compressive load with angles of attack of up to 29.0°, 32.0° and 35.5°, respectively. A further embodiment according to the present invention concerns a device in which the base of said head comprises flange edges, which flange edges have a radial extent in said first transverse direction. Said flange edges are thus situated at said second lower end, and, when said device has been introduced axially into a recess in the bone tissue, said device is held in engagement in the recess by means of said flange edges, and thus the base of said head, bearing against a shoulder in the recess. Said shoulder in the recess has been created in the manner previously described. Said compressible shell-shaped structure makes it possible, as has previously been described, for said device to be introduced axially into a recess with a shoulder, as above. When the compression ceases once the device has been introduced into the recess as far as the milled area, said head and said device are able to spring out inside the cortical part of the bone tissue. Said device can therefore be held in engagement by means of said flange edges, and thus the base of said head, bearing against the shoulder in the recess. A further embodiment according to the present invention concerns a device which comprises an outer part, said outer part having a third length and a third external diameter. Said outer part and thus said third length extend from the first lower end of said device to the second lower end of said head. If so required, said outer part can also be elastically deformed upon application of said device. Said third external diameter can expediently be adapted so that said outer part bears, completely or partially, against the inside of the cortical part of a recess, as has previously been described, when said device is held in engagement in the recess. Moreover, said outer part is substantially centered axially in relation to said head. The adaptation and axial centering of said outer part mean that said device is held in engagement axially centered in a recess after application. Moreover, said third length can be adapted so that said outer part, and thus said device, do not stick out of said recess when said device is held in engagement in the recess. Said outer part also comprises a through-opening in the axial direction, which gives said outer part a tube-like shape. The tube-like shape allows said tool for application to be introduced through said outer part. Yet another embodiment according to the present invention concerns a device in which said outer part comprises one or more continuous channels which extend in the axial direction. Said one or more continuous channels give said outer part a form comprising one or more arches in a radial cross section. A radial cross section in the form of one or more arches further increases the ability of said outer part to deform elastically. Yet another embodiment according to the present invention concerns a device in which a second ratio between said first length and said first external diameter is a maximum of 1.2. Further embodiments of said device concern devices in which said second ratio between said second length of said head and said first external diameter is a maximum of 1.15 or 1.10. Yet another embodiment according to the present invention concerns a device in which a third ratio between the radial extent of said flange edges and the outer radius of said head, i.e. half the first external diameter of said head, is a maximum of 0.70. In further embodiments according to the present invention, said third ratio between the radial extent of said flange edges and the outer radius of said head is a maximum of 0.60 or 0.50. One embodiment according to the present invention concerns a device in which said head comprises a construction for anchoring said object to said device. Another embodiment according to the present invention concerns a device in which said construction for anchoring said object to said device is placed centrally in said device in relation to the first transverse direction of the device. Yet another embodiment according to the present invention concerns a device in which said device comprises at least one radial opening. Said radial opening has a function as a connection between bone marrow, in said recess in the bone tissue, and said object. The present invention includes an embodiment in which said device is a suture anchor. In addition, the present invention concerns an embodiment in which said device is made of a plastic material, which plastic material is biodegradable in the human body or animal body. Said plastic material can be, for example, polyurethane, polyglycolic acid, polylactic acid, or copolymers of polylactic and polyglycolic acid. Another example of a material from which said device can be made is the polyurethane resin plastic described in SE-C2-510,868, which document is here referred to in its entirety. Yet another embodiment according to the present invention concerns a device in which the first external diameter of said head is greater than a second external diameter of said recess. The first external diameter of said head is therefore greater than the second external diameter of said recess when the compressible shell-shaped structure of said head is not subjected to any external action such as being compressed. A further embodiment according to the present invention concerns a device in which the third external diameter of said outer part is at least as great as the second external diameter of said recess. The third external diameter of said outer part is therefore at least as great as the second external diameter of said recess when the compressible shell-shaped structure of said head, and thus said outer part, is not subjected to any external action such as being compressed. Yet another embodiment according to the present invention concerns a device in which a fourth ratio between the third external diameter of said outer part and the first external diameter of said head is less than 0.98. In further embodiments according to the present invention, said fourth ratio between the third external diameter of said outer part and the first external diameter of said head is at most 0.9 or 0.8. Said device can be produced by any suitable method which is obvious to a person skilled in the art, examples of production methods including casting, injection-moulding or machine-cutting. If production is by casting, a mixture of a two-component polyurethane resin, for example, can be poured into a split polypropylene mould and thereafter hardened. The present invention also relates to a tool for applying a device which has been described. Said tool for applying said device comprises an application part, a handle part, and an adjusting part situated on the application part. Said application part has a head end and a handle end, the head end of the application part being designed to receive said device before application. Moreover, said application part has a fourth external diameter, which fourth external diameter is smaller than said second diameter in the recess in the bone tissue. Said tool for application also has a second transverse direction and a second longitudinal direction, which second transverse direction and second longitudinal direction substantially coincide with the first transverse direction and first longitudinal direction, respectively, of said device when said device has been received by the tool for application. There is also a clearance between the head end of the application part and said device when the head end of the application part has received said device, said clearance making it possible, among other things, to reduce the size of said device in said first transverse direction upon application of said device. The handle part expediently has a shape and design which mean that said tool for application is easy to handle upon application of said device. The handle part is also arranged at the handle end of the application part. Said adjusting part has a fifth external diameter, which fifth external diameter is greater than both the fourth external diameter of the application part and the second external diameter of said recess, the adjusting part acting as a stop at a specific depth of application in the recess in the bone tissue. The position of the adjusting part on the application part can also be varied, making it possible to set different depths of application of said device. Upon application of said device, a depth is preferably set at which said device is applied inside the cortical part of the bone tissue. The position of said adjusting part on the application part can be varied for example by a machined element being arranged on said application part, which machined element can be, for example, a right-hand or left-hand thread. Said tool for application can also have a central cutting, i.e. a groove, extending along the application part from the head end of said application part and past the position of the adjusting part on the application part. Along its length, the central cutting can accommodate, for example, a suitable suture thread which is secured to said device in a suitable manner, for example with a knot or adhesive. Said application part can also be provided with a scale, which scale facilitates the setting of said adjusting part and thus the setting of the depth for said application. A further embodiment according to the present invention concerns a tool in which, upon application of said device, there is a clearance between said head end and said device, so that the device can be compressed elastically on passage through the cortical part of the bone tissue. Said surgical instrument, which is used here to widen a hole inside the cortical part of the bone tissue so that a distinct shoulder is formed, is a novel orthopaedic instrument which we have developed. With said instrument it is easy to create holes having a diameter which is greater internally than at the mouth of the hole in the bone tissue, by virtue of the fact that the instrument comprises an instrument shaft which extends in the longitudinal direction of the instrument, and a cutting part which, upon internal cutting work, is partially situated outside a first cross-sectional surface of the shaft of the instrument in relation to the transverse direction of the instrument. BRIEF DESCRIPTION OF THE FIGURES Figure 1 shows a perspective view of an embodiment of a device according to the present invention. Figure 2 shows a plan bottom view of the embodiment of the device in Figure 1. Figure 3 shows a perspective view of an embodiment of a tool for application according to the present invention. Figure 4 shows a perspective view of a device according to the present invention upon application in a recess in bone tissue, said device being arranged on a tool for its application. ILLUSTRATIVE EMBODIMENT Said device is here produced by a casting procedure in which a mixture of a two-component polyurethane resin is poured into a split polypropylene mould and then hardened. Figure 1 shows a perspective view of a device 1 which is a suture anchor. Said device 1 has a first longitudinal direction L, a first transverse direction T, a first upper end 2, a first lower end 3, and a first length X, said first length X being measured from said first lower end 3 to said first upper end 2. Said device 1 also comprises a head 4, said head 4 having a second upper end 5, a second lower end 6, a second length Y, which second length Y is measured from said second lower end 6 to said second upper end 5, and a first external diameter D1. Said head 4 comprises a base 7 at said second lower end 6, said head 4 having a compressible shell-shaped structure and a first ratio Y/D1 between said second length Y and said first external diameter D1 of less than 1.0. Said base 7 is formed by flange edges 8, which flange edges 8 have an extent B (not shown in Figure 1 ) in the first transverse direction T. The device 1 moreover comprises an outer part 9, said outer part 9 having a third length Z and a third external diameter D3. Said outer part 9, and thus said third length Z, extends from the first lower end 3 of said device to the second lower end 6 of said head. In addition, the device 1 comprises a construction for anchoring said object to said device (here a through-hole) 10 in which a suture thread 11 is secured with a knot 12. The device also has two radial openings 13 which have a function as a connection between bone marrow in said recess in the bone tissue (see Figure 4, reference number 41 and reference number 42) and said object. Figure 2 shows a plan bottom view of the device 1 in Figure 1 , i.e. a plan view from the first lower end 3 of the device, so that the first longitudinal direction L of the device runs in the plane transverse to the first transverse direction T of the device, said first transverse direction T being radial. The figure also shows the outer part 9 with the third external diameter D3, the second lower end 6 of the head, with the first external diameter D1 , and into the compressible shell-shaped structure of the head 4. The second lower end 6 of the head comprises a base 7 which is made up of flange edges 8, which flange edges 8 have an extent B in the first transverse direction T. Figure 2 also shows the through-hole 10 of the device. Figure 3 shows a perspective view of a tool 31 for application of a device 1. Said tool 31 comprises an application part 32, a handle part (not shown in Figure 3), and an adjusting part 33 situated on the application part 32. Said application part 32 has a head end 34, a thread 37, and a handle end 35, the head end 34 of the application part being designed to receive said device 1 before application. Said application part 32 moreover has a fourth external diameter D4. Said tool 31 also has a second transverse direction T1 , and a second longitudinal direction L1 , which second transverse direction T1 and second longitudinal direction L1 substantially coincide with the first transverse direction T (see Figure 1 ) and the first longitudinal direction L (see Figure 1 ) respectively when said device 1 has been received by the tool 31 for application. There is also a clearance 36 between the head end 34 of the application part and said device 1 when the head end 34 of the application part has received said device 1 , said clearance 36 making it possible, among other things, to reduce the size of said device in said first transverse direction T (see Figure 1), i.e. said first external diameter D1 (see Figure 1 ) and said third external diameter D3 (see Figure 1 ), upon application of said device 1. The handle part cannot be seen in Figure 3 but is arranged on the handle end 35 of the application part. Said adjusting part 33 has a fifth external diameter D5, which fifth external diameter D5 is greater than both the fourth external diameter D4 of the application part and the second external diameter D2 of the recess (not shown in Figure 3), said adjusting part 33 acting as a stop at a specific depth of application in the recess (not shown in Figure 3) in the bone tissue. The position of said adjusting part on the application part 32 can be varied by means of a right- hand thread 37 being arranged on the application part 32. Said tool 31 also has a central cutting 38 which extends along the application part 32 and the adjusting part 33 from the head end 34 of the application part and past the position of the adjusting part on the application part 32. Along its length, the central cutting 38 accommodates a suture thread 11 which runs through a hole 10 in said device 1 and is secured with a knot 12. In addition, said application part 32 is provided with a scale 39, which scale 39 facilitates the setting of said adjusting part 33 and thus the setting of the depth of said application. Said application part 32 is also provided with a cutting 40 which extends in said transverse direction T1 and in which an operator can clamp the suture thread 11 in place with his or her thumb during application of said device 1. Figure 4 shows a perspective view of a device 1 during application in a recess 41 in bone tissue 42, said device 1 being arranged on a tool 31 for application. In said tool 31 , the suture thread 11 can be clamped by thumb securely in a cutting 40 in said transverse direction T1 , and said suture thread 11 is also secured in said device 1. Suture needles 52 are also secured to said suture thread 11. Said bone tissue 42 here belongs to a human thumb 43, and said recess 41 has a second external diameter D2. The handle part 44 belonging to said device 31 can also be seen here.

Claims: CLAIMS 1. Device (1 ) for fixing an object at a recess (41 ) in bone tissue (42), said device (1 ) having a first longitudinal direction (L), a first transverse direction (T), a first upper end (2), a first lower end (3) and a first length (X), said first length (X) being measured from said first lower end (3) to said first upper end (2), and said device (1 ) comprises a head (4), said head (4) having a second upper end (5), a second lower end (6), a second length (Y), which second length (Y) is measured from said second lower end (6) to said second upper end (5), and a first external diameter (D1 ), and said head (4) comprises a base (7) at said second lower end (6), characterized in that said head (4) has a compressible shell-shaped structure, and in that a first ratio (Y/D1 ) between said second length (Y) and said first external diameter (D1 ) is equal to or less than 1.0. 2. Device (1 ) according to Claim 1 , characterized in that said base (7) comprises flange edges (8), said flange edges (8) having an extent (B) radially in said first transverse direction (T). 3. Device (1 ) according to any of the preceding claims, characterized in that said device (1 ) comprises an outer part (9), said outer part (9) extending from the first lower end (3) of said device to the second lower end (6) of said head, and said outer part (9) has a third external diameter (D3). 4. Device (1 ) according to any of the preceding claims, characterized in that a second ratio (X/D1 ) between said first length (X) and said first external diameter (D1 ) is at most 1.2. 5. Device (1 ) according to any of the preceding claims, characterized in that a third ratio (2B/D1 ) between the radial extent (B) of said flange edges and the external radius (D1/2) of said head is at most 0.7. 6. Device (1 ) according to any of the preceding claims, characterized in that said head (4) comprises a construction (10) for anchoring said object to said device (1 ). 7. Device (1 ) according to any of the preceding claims, characterized in that said construction (10) for anchoring said object to said device (1 ) is placed centrally in said device (1 ) in relation to the first transverse direction (T) of the device. 8. Device (1 ) according to any of the preceding claims, characterized in that said device (1 ) comprises at least one radial opening (13). 9. Device (1 ) according to any of the preceding claims, characterized in that said device (1 ) is a suture anchor. 10. Device (1 ) according to any of the preceding claims, characterized in that said device (1 ) is made of a plastic material, which plastic material is biodegradable in the human body or animal body. 11. Device (1 ) according to any of Claims 3 to 10, characterized in that a fourth ratio (D3/D1 ) between the third external diameter (D3) of said outer part and the first external diameter (D1 ) of said head is less than 0.98. 12. Tool (31 ) for applying a device (1 ) according to any of Claims 1 to 11 , said tool (31 ) comprising an application part (32) and a handle part (44), characterized in that said tool (31 ) can apply said device (1 ) at a defined depth in a recess (41 ) in bone tissue (42), the defined depth being defined by an adjusting part (33) which is connected to said application part (32). 3. Tool (31 ) for applying a device (1 ) according to any of Claims 1 to 11 , said tool (31 ) having a head end (34), characterized in that, upon application of said device (1 ), there is a clearance (36) between said head end (34) and said device (1 ).

Inventors: NILSSON ANDERS, PERSSON ANDERS L, NILSSON, ANDERS, PERSSON, ANDERS, L.
Applicants: ARTIMPLANT AB, NILSSON ANDERS, PERSSON ANDERS L, NILSSON, ANDERS, PERSSON, ANDERS, L.
Application year: 2001
Main classification: A61B17
IPC codes: A61B17