Abstract
Disclosed is a fenestrated bone anchor suitable for being anchored in live bone tissue of a human or animal patient. The bone anchor comprises a shaft with a proximal end and a distal end and a circumferential surface extending from the proximal end to the distal end. The shaft further comprises a longitudinal cavity extending from the proximal end towards the distal end and a plurality of lateral channels extending through a wall of the shaft from the axial cavity to the circumferential surface. The lateral channel has a pear-shaped cross section and/or the thickness of the wall increases gradually in selected ones of directions towards the lateral channels. The fenestrated bone anchor is e.g. a component of a surgical system comprising an interbody fusion device of the stand-alone type.
Claims
1. A fenestrated bone anchor suitable for being anchored in live bone tissue of a human or animal patient, wherein the bone anchor comprises a shaft with a proximal end, a distal end, a longitudinal axis and a circumferential surface extending from the proximal end to the distal end, wherein the shaft further comprises a longitudinal cavity extending in the direction of the axis from the proximal end towards the distal end and at least one lateral channel extending through a wall of the shaft from the axial cavity to the circumferential surface, the wall having a wall thickness and the lateral channel having a cross section with an axial length and a width smaller than the axial length, and wherein said width increases in a distal direction and, one of additionally or alternatively, said wall thickness increases gradually in at least selected ones of directions towards the lateral channel.
2. The bone anchor according to claim 1, comprising a plurality of lateral channels.
3. The bone anchor according to claim 2, wherein all lateral channels of the plurality of the lateral channels are arranged at a same first distance from the proximal end of the shaft and may be regularly spaced from each other around the circumferential surface.
4. The bone anchor according to claim 3, wherein the first distance is smaller than a second distance between the lateral channel and the distal end of the shaft.
5. The bone anchor according to claim 3 wherein the first distance is smaller than about one half of a total axial length of the shaft.
6. The bone anchor according to claim 1, wherein the wall thickness increases towards each one of the lateral channels and a cross section of the bone anchor or of the longitudinal cavity through the plurality of lateral channels has a lobed form having a lobe associated to each one of the channels.
7. The bone anchor according to claim 6, wherein in a proximal direction away from the plurality of lateral channels, the lobed form of the cross section of the bone anchor gradually transitions to a circular form.
8. The bone anchor according to claim 1 and further comprising a head and being suitable for fixating a bone plate relative to bone tissue, wherein the bone plate comprises a through opening adapted to the bone anchor.
9. The bone anchor according to claim 1 and further comprising retention structures arranged on the circumferential surface of the shaft.
10. The bone anchor according to claim 9, wherein the retention structures comprise at least one of a thread, circumferential ribs, sharp edges, teeth, surface roughness, undercut surface structures and an osseointegration enhancing surface coating.
11. The bone anchor according to claim 1, wherein at axial positions of the at least one lateral channel, the stiffness of the anchor against bending increases gradually towards proximally.
12. The bone anchor according to claim 1, wherein across a substantial portion an axial extension of the lateral channel the polar second moment of area of the bone anchor gradually increases towards proximally.
13. The bone anchor according to claim 1, wherein an average circumferential width of a proximal half of the at least one lateral channel is substantially smaller than an average circumferential width of a distal half of the lateral channel.
14. A surgical system comprising an implant with at least one through opening defining an opening axis and at least one bone anchor according to claim 1 and being suitable for fixating the implant relative to bone tissue of a human or animal patient, the bone anchor comprising a head and a shaft and an anchor axis, the through opening and the bone anchor being adapted to each other for the shaft to be able to pass through the through opening and the head to be retained by a proximal surface of the implant or within the through opening in a final position.
15. The system according to claim 14 wherein, for locking the anchor in said final position, the system further comprises at least one locking element being moveable between a relaxed position in which it protrudes from a general level of a surface portion of the anchor or the through opening and a resiliently tensioned position in which it protrudes less or not at all from said level, wherein the locking element is an integral part of the bone anchor or of the implant, constituting a part of said surface portion and of a bulk of the anchor or the implant situated underneath said surface portion, wherein a void in the surface portion delimits the locking element and further extends underneath the locking element or through said bulk.
16. The system according to claim 14, wherein the implant is a load bearing bone implant suitable for being implanted in a human or animal patient between surfaces of live bones or bone fragments, suitable for transmitting forces acting between the bones or bone fragments, and suitable for being integrated between the bones or bone fragments by bone growth after surgery, the bone implant comprising a porous implant body and a support frame, wherein the porous implant body comprises: opposite ingrowth surfaces to be positioned against surfaces of the bones or bone fragments, an open porosity constituting throughout the porous implant body a three-dimensional network of porosity channels of dimensions suitable for bone ingrowth, and a plurality of supply channels, wherein each one of the supply channels has a mouth in at least one of the ingrowth surfaces and extends into or through the porous implant body substantially parallel to said forces, and wherein the supply channels have cross sections larger than the cross sections of the porosity channels and small enough for being bridgeable by spontaneous bone growth without additional bone growth enhancing material.
17. A surgical system comprising an implant with at least one through opening defining an opening axis and at least one bone anchor suitable for fixating the implant relative to bone tissue of a human or animal patient, the bone anchor comprising a head and a shaft and an anchor axis, the through opening and the bone anchor being adapted to each other for the shaft to be able to pass through the through opening and the head to be retained by a proximal surface of the implant or within the through opening in a final position, wherein, for locking the anchor in said final position, the system further comprises at least one locking element being moveable between a relaxed position in which it protrudes from a general level of a surface portion of the anchor or the through opening and a resiliently tensioned position in which it protrudes less or not at all from said level, wherein the locking element is an integral part of the bone anchor or of the implant, constituting a part of said surface portion and of a bulk of the anchor or the implant situated underneath said surface portion, wherein a void in the surface portion delimits the locking element and further extends underneath the locking element or through said bulk.
18. A load bearing bone implant suitable for being implanted in a human or animal patient between surfaces of live bones or bone fragments, suitable for transmitting forces acting between the bones or bone fragments, and suitable for being integrated between the bones or bone fragments by bone growth after surgery, the bone implant comprising a porous implant body and a support frame, wherein the porous implant body comprises: two opposite ingrowth surfaces to be positioned against surfaces of the bones or bone fragments, an open porosity constituting throughout the porous implant body a three-dimensional network of porosity channels of dimensions suitable for bone ingrowth, and a plurality of supply channels, wherein each one of the supply channels has a length and a mouth in at least one of the ingrowth surfaces and extends towards the other ingrowth surface into the porous implant body, and wherein the supply channels have, at least over part of their length, cross sections larger than the cross sections of the porosity channels and small enough for being bridgeable by spontaneous bone growth without additional bone growth enhancing material.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0103] The invention is described in further detail in connection with the appended FIGS., wherein:
[0104] FIGS. 1A/B/C illustrate an exemplary embodiment of the fenestrated bone anchor, the embodiment comprising three lateral channels with pear-shaped cross sections;
[0105] FIG. 2 is a plan view of the fenestrated bone anchor according to FIGS. 1A/B/C (viewing direction towards the head of the anchor)
[0106] FIGS. 3 and 4 are cross sections through further exemplary embodiments of the bone anchor, the embodiments comprising an increase in wall thickness in a direction towards the lateral channels;
[0107] FIGS. 5A/B/C illustrate the principle of an exemplary locking element of the system, the illustrated locking element having the form of a resilient cantilever;
[0108] FIGS. 6A/B/C illustrate the principle of an exemplary locking element of the system, the illustrated locking element having the form of a resilient bending beam;
[0109] FIGS. 7A/B/C shows an exemplary embodiment of a bone anchor of the system, the bone anchor comprising a locking element in the form of a resilient cantilever, the cantilever length extending substantially parallel to the movement of the bone anchor relative to the through opening;
[0110] FIGS. 8A/B show an exemplary embodiment of a bone anchor of the system, the bone anchor comprising a locking element in the form of a resilient cantilever, the cantilever length extending substantially perpendicular to the movement of the bone anchor relative to the through opening;
[0111] FIGS. 9A/B/C show an exemplary embodiment of a bone anchor of the system, the bone anchor comprising a locking element in the form of a resilient bending beam, the beam length extending substantially perpendicular to the movement of the bone anchor relative to the through opening;
[0112] FIGS. 10 and 11 illustrate the principle of a bone implant, the bone implant being shown in section perpendicular to ingrowth surfaces of the porous implant body;
[0113] FIGS. 12, 13, 14 are cross sections of exemplary embodiments of supply channel arrangements;
[0114] FIG. 15 illustrates a further exemplary embodiment of the bone implant;
[0115] FIG. 16 shows an interbody fusion device of the stand-alone type comprising a plate with through openings suitable for being fixated to vertebral bodies with the ais of bone anchors.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0116] In the whole of the present text the term “proximal” is used to designate a position nearer a surgeon and the term “distal” a position nearer the patient. Similarly, a proximal direction means a direction against the surgeon and a distal direction a direction against the patient or further into the patient. Each item has a proximal end and a distal end, the distal end being the leading end on implantation and the proximal end being the trailing end on implantation. Most described items have a proximal end and a distal end and an axis extending therebetween wherein this axis on implantation coincides or is parallel to the implantation direction and wherein the length of this axis may or may not be the longest extension of the item.
[0117] In the appended figures, similar elements or elements with same functions are designated with same reference numerals.
[0118] FIGS. 1A/B/C illustrate an exemplary embodiment of the fenestrated bone anchor, wherein FIG. 1A is a three-dimensional illustration of the anchor, and FIGS. 1A and 1B are lateral views differing from each other by an angle of 90° between the corresponding viewing directions. The bone anchor 210 comprises a head 211 and a shaft 212. The longitudinal cavity 300 reaches through the head 211 into the shaft to a closed distal end and it is connected with the circumferential surface of the shaft by three lateral channels 301. As described further above, the lateral channels 301 have a pear-shaped cross section, i.e. an axial length 1 (see FIG. 1C) greater than a circumferential width w. The width w decreases in a proximal direction. The cross section has in a per se known manner no sharp corners such preventing load concentrations. The lateral channels 301 have outer mouths positioned all at the same axial position situated in the proximal half of the shaft axis, the closed distal end of the longitudinal cavity 300 is situated about half way between the proximal shaft end and the distal shaft end. The circumferential surface of the distal part of the shaft is equipped with circumferential ribs constituting exemplary means for retaining the anchor in a bone opening provided for its implantation.
[0119] The overall pear shape of the lateral channels is such that the sidewalls 341 and the edges of their mouth are not parallel to each other also in a middle region (between the dotted lines in FIG. 1C), the middle region having a substantial axial extension l.sub.c compared to the axial extension l of the axial channel. Also, the average circumferential width w of a proximal half of the lateral channel (above the dashed line in FIG. 1C) is substantially smaller than the average circumferential width of the distal half. An angle between the sidewalls and the longitudinal axis in the depicted embodiment is about 5°
[0120] FIG. 2 is a plan view of the fenestrated bone anchor as shown in FIGS. 1A/B/C (viewing direction from the head towards the tip of the anchor). It illustrates the distal end of the longitudinal cavity, which is equipped with relatively sharp edges 306 or peaks serving as energy concentrators during the process of liquefaction of a material having thermoplastic properties being positioned in the longitudinal cavity and being pressed against the distal end of the longitudinal cavity, while ultrasonic vibration energy is applied to it. Also visible in FIG. 2 are the inner mouths of the lateral channels 301. Further exemplary embodiments of distal cavity ends suitable for the fenestrated bone anchor are e.g. disclosed in the publication WO2011/054122, the disclosure of which is enclosed herein in its entirety by reference.
[0121] More in concrete, the closed distal end of the longitudinal cavity 300 has a shape different from circularly symmetrical about the axis. Rather, the channels 301 have an inner portion at radial positions within a radius of the longitudinal cavity 300 in addition to an outer portion formed by the (pear-shaped) opening (exit opening) in the wall around the cavity 300. Thus, the distal end of the longitudinal cavity is angularly structured so as to direct different portions of the material (material having thermoplastic properties or bone cement) to the different exit openings.
[0122] In the embodiment shown in FIGS. 1A-2, the structures of the distal end comprise directing walls 343 that extend radially between the inner portions of the channels 301. Proximal edges of such walls may optionally in addition to serving as directing structures serve as energy directors in the above-mentioned sense.
[0123] FIGS. 3 and 4 are cross sections through the shaft 212 of further exemplary embodiments of the fenestrated bone anchor. The section plane of these cross sections is situated in the axial position of the lateral channels 301 and illustrate in particular the wall 310 between the longitudinal cavity 300 and the circumferential shaft surface. This wall has a wall thickness which increases in a circumferential direction towards each lateral channel 301 from a minimum wall thickness t.sub.min in locations between the lateral channels 301 and a maximum wall thickness t.sub.max where the wall meets the lateral channel 301. The increase of the wall thickness is e.g. in the range of 20%. This design measure renders the cross section of the anchor shaft 212 and the cross section of the longitudinal cavity 300 to be different, wherein in the illustrated case showing three lateral channels 301 the one cross section is circular and the other one is three-lobed having a circular envelope. Accordingly, for an anchor having two lateral channels, the lobed cross section is like an oval (two-lobed), for four channels it is four-lobed, and so on.
[0124] The embodiment of wall 310 according to FIG. 3 for which the cross section of the shaft is lobed and the cross section of the longitudinal cavity is circular is advantageous when using the corresponding anchor for the above briefly described anchoring process with the aid of an element of a material having thermoplastic properties, as this element may be a simple pin having a circular cross section. On the other hand, it either necessitates a bone opening provided for the anchor having the trilobal cross section of the anchor shaft or a larger opening having a circular cross section substantially corresponding to the circular envelope or the trilobal shaft cross section. In an axial direction, in particular in a proximal direction, away from the lateral channels, the lobed cross section may change gradually into a circular cross section such guaranteeing good guidance of the anchor in an also circular through opening of e.g. a bone plate. The embodiment of the wall 310 according to FIG. 4 is advantageous for an anchor of an overall circular cross section, e.g. a fenestrated screw, but for the above-mentioned anchoring process it necessitates an element of the material having thermoplastic properties in the form a pin with a non-circular cross section.
[0125] Further embodiments of the fenestrated bone anchor differ from the embodiments illustrated in the appended figures by not comprising a head or a head of a different form, by comprising instead of three lateral channels only one or e.g. 2 or 4 lateral channels, by the lateral channels not being situated further proximal but in the middle of the axial shaft length or further distal, by the longitudinal cavity reaching right through the shaft and having an open distal end, by not having a general circular shaft cross section but a shaft cross sections as e.g. listed in the introductory part of the present disclosure, by the lateral channels being situated not in a same axial position but in differing axial positions, and/or by comprising different or no retention means as e.g. listed in the introductory part of the present disclosure. All the named alternative features can be selectively used or combined for a plurality of further exemplary embodiments of the fenestrated bone anchor and designed for specific applications.
[0126] FIGS. 5A/B/C and 6A/B/C illustrate each in a schematic manner the principle of exemplary embodiments of locking elements 200 suitable for a any embodiment of the fenestrated bone anchor, wherein the bone anchor cooperates with a through opening provided in an implant, bone anchor and implant forming together a system. Each one of these FIGS. shows a surface portion 201 of a bone anchor or through opening of an implant belonging to the system, wherein the locking element 200 is arranged within this surface portion 201. FIGS. 5A, 5C, 6A and 6C are sections through the surface portion 201 and the locking element 200, the section plane being oriented substantially parallel to the axis of the bone anchor or the through opening, or to the implantation direction respectively. These FIGS. show the locking element 200 in its relaxed position (uninterrupted lines), in which it protrudes from the general level of the surface portion 201, and in its resiliently tensioned position (interrupted lines) in which it protrudes less or not at all from the general level of the surface portion 201 (flush or countersunk). FIGS. 5B and 6B are plan views of surface portion 201 and locking element 200. The surface portions 201 may be portions of the circumferential surface of either the bone anchor head or the bone anchor shaft and are substantially convex. However, the illustrated surface portions 201 may also be portions of the inside surface of the through opening of the implant and, in such a case, are substantially concave. Locking elements arranged on the bone anchor (shaft or head) are moved relative to the through opening in a direction illustrated with an arrow I (implantation direction). Locking elements arranged in the through opening are moved relative to the bone anchor in an opposite direction indicated with the arrow I′.
[0127] The locking element 200 comprises a protrusion with a guiding ramp 202 and a locking surface 203, wherein the guiding ramp 202 is situated upstream or downstream of the locking surface, depending on the moving direction I or I′. The illustrated locking elements comprise protrusions with ramps 202 and locking surfaces 203 extending over the full width of the locking element. Alternatively, the protrusion may be narrower.
[0128] The locking elements illustrated in FIGS. 5A/B/C have the form of a resilient cantilever pivoting in a plane substantially parallel to the directions I and I′ or to the axis of the bone anchor or the through opening respectively. The void 205 delimiting the cantilever extends along its length and on one side along its width also, and, depending on the thickness of the bulk beneath the surface portion 201 and on the bulk material, extends furthermore underneath the locking element (FIG. 5A) or fully through the bulk underneath the locking element (FIG. 5C).
[0129] The locking elements illustrated in FIGS. 6A/B/C have the form of a resilient bending beam with a bending movement in a plane substantially parallel to the directions I and I′ or to the axis of the bone anchor or the through opening respectively. The void 205 delimiting the bending beam extends along its length limiting its width, and, depending on the thickness of the bulk beneath the surface portion 201 and on the bulk material, extends furthermore underneath the locking element (FIG. 6C) or fully through the bulk underneath the locking element (FIG. 6C).
[0130] Dimensions of the cantilever or bending beam of the locking elements need to be adapted to the bulk material and bulk thickness in the region in which the locking element is situated. Generally speaking, deformation of the cantilever or bending beam needs to remain in the elastic range (less than 1%). For locking elements as shown in FIGS. 5A and 6A, there is more design freedom regarding thickness and therewith length of the locking element than there is for the locking elements as shown in FIGS. 5C and 6C, for which the thickness of the locking element is given by the bulk thickness. Whereas the embodiments of FIGS. 5A and 6A only require a minimum bulk thickness, the embodiments according to FIGS. 5C and 6C can only be realized within a limited range of bulk thickness (substantially limited to cannulated bone anchor). Applicability of the embodiments according to FIGS. 5C and 6C is further limited by the fact that these locking elements constitute through openings through e.g. a wall of a cannulated bone anchor which, in the location of the locking element may not be tolerable, in particular when the anchor is used e.g. for an augmentation process with the aid of a flowable material such as a bone cement.
[0131] The locking elements as illustrated in FIGS. 5A/B/C and 6A/B/C comprise cantilevers or bending beams with a length extending substantially parallel to the directions I and I′ or to the axis of the bone anchor or the through opening on which they are arranged. This is not a necessary feature of the locking element of the system. The lengths of such a cantilever or bending beam can also extend at an angle to the directions I and I′ or substantially perpendicular to them, wherein ramp and locking surface still have to be arranged following each other in the direction of the movement of bone anchor and through opening relative to each other. This means for a cantilever or bending beam length extending substantially perpendicular to the direction of this movement, that ramp and locking surface are arranged beside each other over the width of the cantilever or bending beam width. Two exemplary embodiments of locking elements in the forms of cantilever and bending beam having a length extending substantially perpendicular to the named moving direction or anchor axis respectively are illustrated in FIGS. 8A/B and 9A/B/C.
[0132] FIGS. 7A/B/C illustrate an exemplary embodiment of a bone anchor of the system. The bone anchor is shown viewed from a lateral side (FIG. 7A), sectioned along its axis (FIG. 7B), and in a three-dimensional representation (FIG. 7C). The bone anchor 210 comprises a head 211 and a shaft 212 on which two opposite integrated locking elements 200 of the type being illustrated in FIGS. 5A and 5B are provided. Each one of the locking elements 200 has the form of a resilient cantilever surrounded on three sides by a void 205 and having a length extending parallel to the anchor axis and the direction I. The locking element further comprises a ramp 202 and a locking surface 203 which, as best seen from FIG. 7A, have a width smaller than the width of the cantilever, and which, as seen best from FIG. 7B, are arranged adjacent to each over the cantilever length, wherein, in the direction I, the ramp 202 is arranged downstream of the locking surface 203.
[0133] FIGS. 8A/B show a further exemplary embodiment of the bone anchor 210 of the system. The bone anchor 210 is shown in a three-dimensional representation (FIG. 8A) and in a plan view viewed against its proximal surface (FIG. 8B). The bone anchor 210 comprises a head 211, a shaft 212 (only partially shown in FIG. 8B), and arranged on the head, two locking elements 200 in the form of cantilevers as illustrated and described in connection with FIGS. 8A and 8B. Other than shown in FIGS. 8A and 8B, the cantilever length is not oriented parallel to the direction I or the anchor axis respectively, but it is oriented perpendicularly to the latter, i.e. the cantilever length extends circumferentially and the ramp 202 and the locking surface 203 are arranged adjacent to each other over the cantilever width, with the ramp 202, relative to the direction I being arranged downstream of the locking surface 203.
[0134] FIGS. 9A/B/C show a further exemplary embodiment of the bone anchor 210 of the system. The bone anchor is shown in a three-dimensional representation (FIG. 9A) and in two lateral views (FIGS. 9B and 9C, angle between the two viewing directions of) 90°. The bone anchor 210 comprises again a head 211 and a proximally cannulated shaft 211 and, arranged on the head 211, two opposite locking elements 200 in the form of bending beams as illustrated in FIGS. 6A and 6B. Other than in FIGS. 6A and 6B, the beam length does not extend substantially parallel to the anchor axis but substantially perpendicular to it, i.e. circumferentially. extending substantially perpendicular to the anchor axis or the direction I respectively. Therefore, the ramp 202 and the locking face 203 of the locking elements 200 are arranged adjacent to each other over the beam width as above further described in connection with FIGS. 8A/B. In all previous FIGS., the bone anchor and therewith also the through opening of the implant have substantially circular cross sections. Of course, these cross sections may have other forms, such as e.g. oval, rectangular, polygonal with sharp or blunt edges. This means that the surface portions in which the locking elements are provided are not necessarily curved surfaces.
[0135] All bone anchors shown in FIGS. 7 to 9 are fenestrated bone anchors comprising a longitudinal cavity and lateral channels and are suitable for being retained in the bone tissue by being augmented using a bone cement or a material having thermoplastic properties. This is not a necessary feature of the system. The bone anchor of this system may comprise any per se known retention means, i.e. the bone anchor can be a bone screw (solid, cannulated or fenestrated) or it can comprise retention means in the form of ribs, edges, resilient elements etc. The bone anchor of the system may also be a simple headed pin with a possibly rough circumferential surface and being suitable to be retained in the bone tissue by a press fit.
[0136] FIGS. 10 and 11 illustrate the principle of the structure of the porous implant body of the bone implant, wherein FIG. 10 illustrates an implant example with two opposite substantially parallel ingrowth surfaces, e.g. an interbody fusion implant, and FIG. 11 illustrates an implant example with two ingrowth surfaces extending at an angle relative to each other, e.g. a wedge-shaped implant as often used in osteotomy procedures.
[0137] The implant 100 shown in FIG. 10 in section perpendicular to the live bone surfaces 101 between which it is implanted is e.g. an interbody fusion implant, the live bone surfaces 101, in such a case, being suitably prepared lower and upper surfaces of neighboring vertebral bodies, wherein forces acting on the implanted implant are mainly compressing forces (arrows F) acting substantially perpendicular to the live bone surfaces 101 or the ingrowth surfaces 104 respectively. The implant 100 comprises a porous implant body 102 of an open porosity constituting a three-dimensional network of porosity channels 103. Ingrowth surfaces 104 are opposite surfaces of the porous implant body 102 which, in the implanted state of the implant, are in direct contact with the live bone surfaces 101. The implant body further comprises a plurality of supply channels 105 extending between the two ingrowth surfaces 104 substantially in the direction of the forces acting on the implanted implant. Whereas the porosity channels 103 have cross sections with diameters in the range of a few tenths of a millimeter, the supply channels 105 have cross sections of a diameter d1 of a few millimeters (such as 1-3 mm). The distances d2 between the supply channels 105 are in the range of 2 to 6 mm (for example 3 to 5 mm). For example, but not necessarily, the distances d2 between the supply channels 105 are, throughout the porous implant body, about constant, and, in no case, are larger than about 5 to 6 mm. This means that the supply channels 105 may extend through the porous implant body 100 in a substantially regular pattern.
[0138] Also shown in FIG. 10 are substantially non-porous edge members 108 of a support frame surrounding at least partially the porous implant body 102, as well as substantially non-porous surface elements 109 arranged to extend flush in the ingrowth surfaces 104 and e.g. surrounding mouths of supply channels 105 and/or extending between such mouths. Also shown in FIG. 11 is a strut 110 extending along the wall of one of the supply channels 105, wherein more than one strut 110 may be provided in one and the same supply channel 105 and wherein distances between struts are to be in the range of 0.5 to 2 mm. Surface elements 109 and struts 110 may be provided for each one of the supply channels 105 or for selected ones only.
[0139] FIG. 11 is a very schematic representation (again in a section perpendicular to the ingrowth surfaces 104) of an exemplary wedge-shaped implant 100, which implant is possibly suitable for use in an osteotomy operation. The main features of the implant are the same as the features of the implant as shown in FIG. 10, namely the porous implant body 102 with ingrowth surfaces 104 (in FIG. 11 two ingrowth surfaces at an angle relative to each other), supply channels 105 extending from one ingrowth surface 104 towards the other one, and members 108 of a support frame. In addition to the supply channels 105 extending from one ingrowth surface 104 to the other one and having a mouth in either one of the ingrowth surfaces 104, there are illustrated two blind supply channels 105′, which only have one mouth and a closed end opposite the mouth. For guaranteeing satisfactory supply for bone ingrowth beyond the closed end, the dead end is to be positioned not more than 5 to 6 mm (for example between 3 to 5 mm) distanced from the neighboring ingrowth surface (same as distance between supply channels). The support frame of the implant according to FIG. 11 differs from the support frame of the implant according to FIG. 10 in that it comprises, in addition to an edge member 108 arranged at the distal end of the porous implant body 102, a member 120 constituting a proximal implant surface and at least one central member 121 extending through the implant body. The implant according to FIG. 11 may or may not comprise surface elements or struts (none shown) as described further above in connection with FIG. 10.
[0140] Any embodiment of the bone implant may comprise in addition or alternatively to supply channels extending from one ingrowth surface to another one (as shown in FIG. 10), blind supply channels as illustrated in FIG. 11.
[0141] FIG. 12 further illustrates a preferred embodiment of the arrangement of supply channels 105 in a bone implant, namely the above-mentioned hexagonal arrangement. The arrangement is shown in section substantially perpendicular to the supply channels. In this arrangement, every supply channel 105 has six nearest neighbor channels, wherein all positions between the channels can be safely supplied if the distance d3 (radius of circles marked with dash-dotted lines) corresponds to the given limit of 1 to 3 mm. With the hexagonal arrangement the largest volume of porous structure can be supplied with the smallest number of supply channels.
[0142] Also shown in FIG. 12 are exemplary supply channels bring equipped with surface elements 109 surrounding supply channel mouths or connecting them and supply channels comprising varying numbers of struts 110, wherein supply channels 105 in any supply channel arrangement and of any bone implant as above described may or may not be correspondingly equipped.
[0143] In all previous FIGS. the supply channels have a substantially circular cross section. This is not an obligatory feature of the bone implant. On the contrary, in all embodiments of the bone implant, the supply channels may have cross sections of any other form, as long as for these cross sections the smallest dimension is in the range of 1 to 3 mm. This means that the supply channels may have e.g. square, rectangular, slot-shaped, triangular, oval, lobed, pentagonal, hexagonal etc. cross sections, wherein in one implant all supply channels may have the same or different cross sections.
[0144] FIGS. 13 and 14 illustrate schematically two supply channel arrangements (sectioned again perpendicular to the supply channels), comprising supply channels having elongate, i.e. slot-shaped cross sections.
[0145] The arrangement shown in FIG. 13 is a staggered arrangement of supply channels 105 with slot-shaped cross sections having a width (smallest dimensions) in the range of 1 to 3 mm, and distances from each other in the given range of 2 to 6 mm, for example 3 to 5 mm. Dash-dotted lines indicate, as in FIG. 12, the volume of porous structure which can be supplied by each one of the supply channels 105.
[0146] The arrangement shown in FIG. 14 comprises supply channels 105 with slot-shaped and supply channels 105 with circular (or any other shape having a rotational symmetry) cross sections arranged in a regular pattern, and therewith constitutes an example of a supply channel arrangement comprising supply channels with differing cross sections. In any bone implant as above described, supply channels of other and possibly differing cross section shapes may be combined in varying numbers, wherein it is not necessary that the arrangement is as regular as shown in FIGS. 12 to 14.
[0147] FIG. 15 illustrates in a very schematic manner an exemplary bone implant, wherein for this implant, the distance between the two ingrowth surfaces 104 is in a range (20 to 40 mm) for which it is preferable to design the supply channels 105 to have enlarged mouth portions 125. Such enlarged mouth portions for example have dimensions in a range of 3 to 10 mm such that they are still able to be bridged by long-term bone growth without the necessity of bone growth enhancing material. Larger such enlarged mouth portions constituting critical size defects are not recommended because introduction of bone growth enhancing material is not really feasible. As shown in FIG. 15, the enlarged mouth portions 125 of the supply channels 105 are arranged alternatively in one and the other one of the ingrowth surfaces, which makes it possible to guarantee the given distances between the supply channels in the range of for example 3 to 5 mm. The axial length of the enlarged mouth portions 125 of the supply channels 105 may have a short axial length only, such maximizing spontaneous bone growth filling as much of the supply channels as possible.
[0148] All the above described features of bone implants, in particular regarding support frames and cross section shapes and supply channel arrangements are applicable also for embodiments comprising supply channels with enlarged mouth portions.
[0149] FIG. 16 is a top view (viewed against one of the ingrowth surfaces 104) of a further exemplary embodiment of the bone implant. The implant 100 is an interbody fusion device of the stand-alone type and comprises, as described above, a porous implant body 102 with supply channels 105 and a support frame with members 108 to be positioned between adjacent vertebral bodies. The interbody fusion device further comprises a bone plate 130 (retention means) and a plurality of bone anchors (not shown) suitable for fixating the bone plate 130 to lateral or posterior wall portions of the vertebral bodies. In the shown embodiment, the bone plate 130 is reduced to a plurality of lobes 135 each comprising a through opening for receiving one of the bone anchors. The porous implant body 102, the support frame members 108, the bone plate 130, and, if applicable, surface elements 109 or struts may be made of the same material, as one piece, which is for example manufactured in one single additive manufacturing process.
[0150] The porous implant body 102 comprises supply channels 105 as described above, mouths of the supply channels being at least partly surrounded by surface elements 109, possibly being connected to each other by connecting elements 111 (illustrated on left hand side of ingrowth surface). The support frame comprises edge members 108 and two central members 132, which extend through the porous implant body from the one ingrowth surface to the other one and which may or may not encircle a central cavity 133 suitable for being filled with bone growth enhancing graft material for which purpose this cavity 133 comprises a feed opening 134 connecting it with the proximal surface of the implant.
