EP3082628A1

EP3082628A1 - Self-tapping, tension absorbing bone screw

Info

Publication number: EP3082628A1
Application number: EP14821165.9A
Authority: EP
Inventors: Rita Leibinger; Enrico Wirth
Original assignee: Rita Leibinger GmbH and Co KG
Current assignee: Rita Leibinger GmbH and Co KG
Priority date: 2013-12-19
Filing date: 2014-12-19
Publication date: 2016-10-26
Also published as: WO2015091916A1; DE102013226704A1; US20160310187A1

Abstract

The invention relates to a self-tapping, self-drilling, cannulated bone screw comprising a channel chamber. Said screw is characterised in that it comprises a centering tip which forms the front end of the bone screw.

Description

Self-drilling tension-absorbing bone screw

The invention relates to a self-tapping and self-drilling cannulated bone screw with a channel space. Such bone screws are used for example in osteosynthesis of complicated bone fractures. Self-tapping here means that the need for pre-cutting a thread in the bone structure to be treated is eliminated. Under self-drilling is to be understood that the bone screw can drill itself when introduced into the bone structure, whereby a pre-drilling can be omitted.
The object of the present invention is to provide a bone screw which simplifies the treatment of bone fractures, in particular reduces the number of work steps necessary for introducing the bone screw.
This object is achieved by a bone screw of the type mentioned in that it comprises a centering tip, which forms a front end of the bone screw. This allows easy placement and accurate introduction of the bone screw according to the invention in the bone structure to be treated.
In this case, it has proven particularly advantageous if at least one cutting device is arranged in the region of the centering tip. Thus, the cutting process begins immediately after the bone screw has been positioned precisely, which reduces the risk of the bone screw slipping off the desired setpoint position. In addition, only a small uncut depth of penetration of the centering tip is required in the bone, which reduces the force applied by the surgeon as well as the risk of stress damage to the bone. Overall, the time required to insert the bone screw is reduced. The entire duration of the operation is thereby shortened, which has an advantageous effect on wound healing. The channel space can be straight or spiral.
A development of the bone screw according to the invention is characterized in that the cutting device is associated with a preferably substantially axial access opening to the channel space. As a result, bone material that is released during self-drilling and self-tapping insertion of the bone screw of the bone structure to be treated, are introduced directly into the channel space. Moreover, if the access opening is at least substantially axial, the bone material will be removed by the shortest route and without significant change in direction, which reduces the risk of blockage. In addition, this promotes the ingrowth of the bone screw according to the invention with the bone structure to be treated. The self-tapping and self-drilling operation of the bone screw in combination with the removal of the removed bone material in the channel space, the occurrence of tension damage is reduced to the treated bone structure.
To be particularly advantageous has been found when the bone screw according to the invention has at least two preferably uniformly distributed around the circumference arranged cutting devices, and each cutter is associated with a substantially axial access opening to the channel space. Several cutting devices allow a more effective and thus faster cutting and drilling of the bone screw into the bone structure to be treated. Via the axial access openings, the ablated bone material accumulating at each cutting device can be supplied to the channel space, which, as stated above, has an advantageous effect on wound healing.
It is also advantageous if the channel space opens into a rear end face of the bone screw. As a result, the bone material discharged into the channel space can virtually migrate into the bone screw and excess bone material can emerge from the bone screw in the area of the rear end face. Thus, the cut bone material is collected in the channel space and can support ingrowth of the bone screw. This embodiment of the bone screw promotes the ingrowth of the bone screw into the bone structure to be treated.
It is particularly advantageous if the bone screw according to the invention is a Herbert screw. A Herbert screw is a special bone screw that is used, for example, in the osteosynthesis of fractures of the scaphoid bone. Such a bone screw is a double-threaded screw, that is, it has an external thread in both a front and in a rear area. Herbert screws are regularly cannulated, that is, they are hollow. However, known Herbert screws are neither self-tapping nor self-drilling, but are by means of a guide wire, also called Kirschner wire, introduced into a predrilled hole in the bone structure to be treated, in which a thread was cut. The two threads in the front and rear of the Herbert bone screw have different pitches. The thread pitch at the front thread is greater than at the rear thread, so that a rear bone fragment is mechanically used when screwing to a front bone fragment. This results in a fracture healing favored pressure on a fracture gap located between the anterior and posterior bone fragments. This is also called interfragmentary compression.
When using a Herbert screw for osteosynthesis, for example, a damaged pelvic bone is first positioned the broken navicular and if necessary fixed, then the Herbert screw is introduced. In conventional Herbert screws this insertion requires as a first step drilling a hole. In a second step, this hole is threaded. Only in a third step, the Herbert screw can be introduced. When using the bone screw according to the invention eliminates the first two steps and the bone screw according to the invention can be introduced directly and thus very quickly in the bone structure to be treated.
To be particularly advantageous has been found when the bone screw has a screw head at its rear end, which preferably has a stop surface in the form of a radially outwardly extending collar. This can increase interfragmentary compression. In principle conceivable within the scope of the present invention, however, are also those bone screws which have no screw head.
Furthermore, it has proved particularly advantageous if at least one substantially radial opening extends from the channel space to a thread of an external thread present in a front region and / or in a rear region of the bone screw, preferably to a thread root. When the bone screw has been introduced into the bone structure to be treated, the inner channel space is filled with self-drilling or self-cutting bone material. Via the radial opening, this bone material can grow together with the surrounding bone structure. This reduces the time needed for wound healing of the treated fracture and improves the stability of the synthesis.
Within the meaning of the invention, the bone screw has at least one, for example approximately semicircular recess in a projecting edge of a flank of an external thread present in the front region of the bone screw, which recess at least partially forms another cutting device. Such a further cutting device further improves the self-cutting of the bone screw to be introduced into the bone structure to be treated. This also causes less irritation to the bone structure to be treated and the cutting process is cleaner.
In the context of the invention, the same applies if the bone screw has at least one essentially axial passage opening in an edge of an external thread present in a front region and / or in a rear region of the bone screw. As a result, the bone structure to be treated can, as it were, grow through the thread flanks of the bone screw according to the invention, which promotes coalescence of the bone screw with the bone structure. The required wound healing time is thereby reduced and the stability of the synthesis is further improved. Removed bone material may also accumulate in the through-holes, which leads to a reduction of stresses in the bone structure to be treated.
Within the meaning of the invention, a bone screw is likewise provided, which has in each case one passage opening in at least two successive flanks of at least one external thread, wherein the passage openings are preferably arranged in alignment with each other. This allows a stable ingrowth of the bone screw into the bone structure to be treated.
According to the invention, the bone screw also has an external thread which has at least one threaded channel running within an edge of the external thread and preferably at least partially in the circumferential direction, one end of which ends in an outer side of the external thread. It is particularly preferred if one end of the threaded channel is arranged in an additional cutting edge on the external thread of the bone screw, or one of the cutting devices extends to the channel space. It is also advantageous if the threaded channel essentially follows a slope of the external thread.
When introducing such a bone screw with at least one threaded channel in a bone structure bone material, which is removed by the additional cutting edge of the bone structure, discharged through the threaded channel of the cutting point.
It is also advantageous if the threaded channel opens with its other end in the channel space or in a next additional cutting edge on the external thread. Under the next additional cutting edge is to understand that additional cutting edge, which follows the view from the front end to the rear end of the bone screw along the course of the external thread on the previous additional cutting edge.
In this way, worn bone material is discharged to the channel space or removed from one additional cutting edge to the next additional cutting edge.
Both types just described of the removal of bone material away from the cutting point, ie through the thread channels towards the channel space and / or towards the next additional cutting edge, make it possible to insert the bone screw into a bone structure without tensions occurring during insertion through non-removed bone material, which can damage the bone structure. This is particularly advantageous if the bone screw is to be introduced into the bone structure without a separate pre-drilling step.
The at least partially within a flank of the external thread and preferably at least partially extending in the circumferential direction threaded channel whose one end opens into an outer side of the external thread, moreover, forms an independent invention, which is also worth protecting without the centering. This also applies to the specified developments and details of the said threaded channel.
It is also advantageous if the bone screw comprises a receiving part for connecting the bone screw with a rod system. It is particularly advantageous if the receiving part is connected polyaxially, uniplanar or monoaxially with the bone screw. This simplifies the use of the bone screw in stiffening or fixation measures.
According to the invention, even when the bone screw has a screw head which has a locking device, preferably a head-side external thread, for locking the bone screw with a bone plate in an angle-stable manner. It is particularly preferred if the locking device is a self-tapping head-side external thread for locking the bone screw with stable bone locking with a bone plate. This refinement has the advantage that a fast angular fixing which is individually adapted to the local conditions of the surgical area is made possible.
An alternative embodiment within the meaning of the invention is characterized in that the bone screw has a screw head, which is partially formed dome-shaped and over which the bone screw is variable angle connected to a bone plate. This allows mobility between the bone screw and the bone plate.
It should be pointed out that the bone screw according to the invention - regardless of its specific embodiment - is preferably produced by means of a 3D printing process. With such a 3D printing method, the most complex three-dimensional structures can be produced, in particular, for example, the above-mentioned internal channels and channel spaces. In this case, a powder or other "printable or sprayable" material, for example, printed from a titanium alloy and melted, for example by means of laser by the 3D printer in layers. Other candidate materials are ceramic, plastic, other metals such as magnesium, etc.
Further features, details and advantages of the invention will become apparent from the appended claims, the drawings and the following description of several preferred embodiments of the bone screw according to the invention. Hereinafter, an example of the present invention will be explained in detail with reference to the accompanying drawings.
In the drawings show:
1 shows a schematic sectional view of a first embodiment of a bone screw according to the invention;
Figure 2: a rear portion of the bone screw shown in Figure 1;
Figure 3: a front portion of the bone screw shown in Figure 1;
FIG. 4 is a perspective view of the bone screw shown in FIG. 1;
FIG. 5 shows a schematic side view of a further embodiment of a bone screw according to the invention;
FIG. 6 shows a section through the bone screw from FIG. 5 along the line VI-VI;
Figure 7a-e: different views of another embodiment of the bone screw according to the invention with a receiving part;
FIG. 8 shows a side view of a plurality of the bone screws illustrated in FIG. 7, which are connected via a rod system;
FIGS. 9a-c show various views of a further embodiment of the bone screw according to the invention;
Figure 10a-c: different views of another embodiment of the bone screw according to the invention; and
Figure 11a-c: different views of another embodiment of the bone screw according to the invention.
A bone screw according to the invention carries in the figures 1 to 4 in total the reference numeral 10. Inside the bone screw extends an elongated and presently a total straight channel space 12. In one embodiment, not shown, the channel space is a total of spiral or helical, or has at least one wall with a with respect to a longitudinal axis of the channel space spirally shaped outer wall. The channel space 12 is arranged in the embodiment shown a total of aligned with a longitudinal axis 14. The bone screw 10 extends along the longitudinal axis 14 from a rear end 16 to a front end 18. The rear end 16 is formed in the present embodiment by a rear end face 19.
The front end 18 is formed by a centering tip 20. The centering tip 20 is integrally formed on a front portion 24 of the bone screw 10. In the front region 24, a first external thread 28 is arranged on the bone screw 10. In the region of the centering tip 20, a first cutting device 32 and a second cutting device 34 are arranged. The first cutting device 32 is associated with a first access opening 38 to the channel space 12. The second cutting device 34 is associated with a second access opening 40 to the channel space 12. The first cutting device 32 and the second cutting device 34 are distributed uniformly around the circumference, so they are arranged diametrically with respect to the centering tip 20. The first access opening 38 and the second access opening 40 are axially, that is, they are substantially parallel to the longitudinal axis 14. The first access opening 38 and the second access opening 40 each extend from their associated cutting devices 32, 34 to the channel space 12th ,
Radial openings 44 extend from the channel space 12 to a thread 46 of the first outer thread 28 arranged in the front region 24. The illustrated radial openings 44 open in this embodiment, starting from the channel space 12 into the thread root 48 of the thread 46. However, it is also conceivable that these, starting from the channel space 12, open into a front or back side of a flank 52 of the first external thread 28. The flank 52 of the first external thread 28 has a projecting edge 56. This one still plays a role below.
From the front end 18 of the bone screw 10 along the longitudinal axis 14 to the rear end 16 seen from the rear end 16, the bone screw 10 has a rear portion 60. In this a second external thread 64 is arranged. Its pitch is greater than that of the first thread 28, so that a "Herbert screw" is formed. Integrally connected to the rear region 60 is a screw head 68. The screw head 68 has a radially outwardly extending collar 72, which forms an abutment surface 74 in the operating position toward the bone. On the screw head 72, a hexagon socket 78 is present, which represents a tool attachment point. For the purposes of the present invention, however, other types of Werkzeugansetzstellen, such as slot, Phillips, Torx, or the like.
In the rear region 60, radial openings 44 are likewise arranged, which extend from the channel space 12 to a thread bottom 82 of the rear external thread 64. Axial, ie extending parallel to the longitudinal axis 14 and aligned with each other passage openings 86 extend through the flanks 52 of the first external thread 28 and flanks 90 of the second external thread 64th
As can be seen in particular from FIG. 4, the projecting edge 56 of the flank 52 of the first external thread 28 present in the front region 24 of the bone screw 10 has approximately semicircular recesses 94. The recesses 94 form an additional cutting edge 98.
When using the bone screw 10 shown in FIG. 1 for osteosynthesis, the bone screw 10 with the centering tip 20 is placed. By means of a suitable tool, the bone screw 10 is then rotated via the tool attachment point designed as an internal hexagon 78 in the present embodiment. The first cutting device 32 and the second cutting device 34 carry bone material from the bone structure to be treated due to the rotation. This bone material is guided via the first axial access opening 38 and the second axial access opening 40 into the channel space 12.
If the bone screw 10 is completely inserted into the bone structure to be treated, then the channel space 12 is substantially filled with removed bone material. This bone material is partially guided outward via the radial openings 44. This causes it to come into contact with the surrounding bone structure. When the bone screw 10 remains in the bone structure to be treated, this promotes coalescence of the bone screw 10 with the surrounding bone structure. In addition, the bone structure can be fused through the flanks 52, 90 of the external threads 28, 64 via the axially extending passage openings 86. It is advantageous in the case of the bone screw 10 according to the invention that pre-drilling of a hole as well as pre-cutting of a thread into the bone structure can be dispensed with by the centering tip 20 in combination with the cutting devices 32, 34. In addition, no guide or Kirschner wire is required for introducing the bone screw 10 into the bone structure to be treated. By means of the centering tip 20, the bone screw 10 can be accurately placed and introduced into the bone structure. This shortens the operation time, thereby promoting wound healing. The use of the bone screw 10 therefore has an overall positive effect on the course of treatment.
FIG. 5 shows a further embodiment of the bone screw 10 according to the invention. The bone screw 10 shown in FIG. 5 has a plurality of additional cutting edges 98 in the case of the lower external thread 28 in FIG. The additional cutting edges 98 are formed by right-angled recesses 100 in the flank 52 of the external thread 28 as viewed in the direction of the longitudinal axis 14. Embodiments that are not shown may also have other recesses than those which have right-angled and straight boundary edges viewed in the longitudinal axis. For example, smaller or larger angles than 90 ° are conceivable as well as convex or concave curved boundary edges.
At the additional cutting edges 98, which belong to the outside of the external thread 28, openings are visible, which represent the one end of threaded channels 102 and 108 and in the present case are circular. For the purposes of the invention, however, other forms of openings, for example triangular, quadrangular, star-shaped, or the like. In this case, the threaded channels 102 extend from said openings to the channel space 12. The thread channels 102 extend within the flank 52 of the external thread 28 and approximately in the circumferential direction, but towards the channel space 12 towards spiral inside.
The thread channels 108 each extend from the said openings in an additional cutting edge 98 to a circumferentially next cutting edge 98. Under the next cutting device 98 is thus understood along the course of the flank 52 of the external thread 28 following cutting device 98, as seen from the front End 18 to the rear end 16 of the bone screw 10th
The course of the thread channels 102 is particularly clear from the view in Figure 6, which shows a section through the bone screw 10 shown in Figure 5 along the line VI-VI. The threaded channel 102 shown extends approximately in the circumferential direction and follows substantially the course of the flank 52 of the first external thread 28. The threaded channel 102 thus follows a slope of the first external thread 28 and thereby runs slightly helical radially inward in the direction of the channel space 12. The course of The thread channels 108, which are not visible in FIG. 6, likewise essentially follow the course of the external thread 28. However, the thread channels 108 do not run like the thread channels 102 towards the channel space 12, but run at an approximately constant distance from the longitudinal axis 14 of the bone screw 10 For example, the bone screw 10 shown in FIGS. 5 and 6 may be produced by means of a 3D printing process in which ceramic, plastic or metal, for example titanium or magnesium, as a powder or similar. applied in layers and fused for example by means of a laser.
When introducing the bone screw 10 shown in FIGS. 5 and 6 into a bone structure, bone material which is removed by the additional cutting edges 98 from the bone structure passes through the threaded channels 102, which extend from the external thread 28 to the channel space 12, from the interface into the channel space 12 discharged.
The thread channels 108, which extend from one additional cutting edge 98 to a next additional cutting edge 98, carry away worn bone material from one additional cutting edge 98 to the next additional cutting edge 98.
Both types of removal of bone material from the cutting site just described, through the threaded channels 102 to the channel space 12 and through the chip-passing openings 108 to the next additional cutting edge 98, allow the bone screw 10 to be introduced into a bone structure without tensions occurring during insertion, which can damage the bone structure. This is particularly advantageous if the bone screw 10 is to be introduced into the bone structure without a separate pre-drilling step.
FIGS. 7a to 7d show a further embodiment of the bone screw according to the invention. The further embodiment according to FIGS. 7 a to 7 d comprises a receiving part 110, which serves to connect the bone screw 10 to a rod system 114.
In the present case, the receiving part 110 is connected polyaxially to the bone screw 10. By "polyaxial" is to be understood a connection in which the receiving part 110 relative to the rest of the bone screw 10 is pivotable and rotatable. The polyaxial connection between the receiving part 110 and the rest of the bone screw 10 is realized via a dome-shaped, in particular on its underside, screw head 68 and a corresponding complementary mating surface on the receiving part 110. The dome-like screw head 68 is shown in FIG. 7e, which shows a region of the bone screw 10, which is shown in FIGS. 7a to 7d, without the receiving part 110.
For the purposes of the invention, in addition to a polyaxial compound but also a uniplanar compound. Under a uniplanar connection is a connection to understand in which the receiving part 110 relative to the rest of the bone screw 10 is pivotable only within a plane. For the purposes of the invention is also a monoaxial connection, that is, a compound in which the receiving part is not pivotable relative to the rest of the bone screw. In the case of a monoaxial connection, the receiving part 110 can be rotatable relative to the rest of the bone screw 10 or can be rigidly connected to the remainder of the bone screw 10, for example in one piece with it.
FIG. 8 shows three bone screws 10 which correspond to the bone screw 10 shown in FIGS. 7a to 7d and are connected to a rod system 114 via their respective receiving part 110. The rod system 114 is fixed in the respective receiving parts 110 via a respective fastening element 116 on the receiving part 110. Such a rod system 114 is used in surgical procedures for the treatment of spinal injuries.
FIGS. 9a-c each show different views of a further embodiment of a bone screw 10 according to the invention. The bone screw 10 shown in FIGS. 9a-c has a screw head 68 formed in a dome-like manner on its underside, which serves to fix the bone screw 10 to a bone plate at variable angles having a corresponding complementary formed receiving opening. The bone plate is not shown here.
FIGS. 10a-c respectively show different views of a bone screw 10 according to the invention, which comprises a screw head with a locking device 120. The locking device 120 is presently designed as a head-side external thread 122. The locking device 120 is used for locking the bone screw 10 with a stable bone, with a bone plate, not shown. For said locking the bone screw 10 is screwed with the head-side external thread in a complementary trained internal thread at an opening in the bone plate. Through this screwing creates a stable angle connection between the bone plate and the bone screw 10th
FIGS. 11a-c show various views of a further embodiment of the bone screw 10 according to the invention. The bone screw 10 shown in FIGS. 11a-c has a self-cutting head-side external thread 124 on its screw head 68. This self-tapping head-side external thread 124 can be screwed into an opening in a bone plate, wherein when screwing a thread is cut into this opening of the bone plate. After screwing the bone screw 10 is then locked stable angle in the bone plate.

Claims

Self-tapping and self-drilling cannulated bone screw (10) having a channel space (12), characterized in that it comprises a centering tip (20) forming a front end (18) of the bone screw (10).
Bone screw (10) according to claim 1, characterized in that in the region of the centering tip (20) at least one cutting device (32, 34) is arranged.
Bone screw (10) according to claim 2, characterized in that it comprises a channel space (12) and the cutting device (32, 34) is associated with a preferably substantially axial access opening (38, 40) to the channel space (12).
Bone screw according to claim 3, characterized in that it comprises at least two cutters (32, 34), preferably uniformly distributed around the circumference, and each cutting device (32, 34) has a substantially axial access opening (38, 40) to the channel space (12 ) assigned.
Bone screw (10) according to one or more of the preceding claims, characterized in that the channel space (12) opens into a rear end face (19) of the bone screw (10).
Bone screw (10) according to one or more of the preceding claims, characterized in that the bone screw (10) is a Herbert screw.
Bone screw (10) according to one or more of the preceding claims, characterized in that at a rear end (16) of the bone screw (10) a screw head (68) is present, which a stop surface (74) preferably in the form of a radially extending federal (72).
Bone screw (10) according to one or more of the preceding claims, characterized in that at least one substantially radial opening (44) from the channel space (12) to a thread (46) in a front region (24) and / or in a rear portion (60) of the bone screw (10) existing external thread (28, 64) extends, preferably to a thread root (48).
Bone screw (10) according to one or more of the preceding claims, characterized in that it comprises at least one substantially axial passage opening (86) in a flank (52, 90) of a in a front region (24) and / or in a rear region ( 60) of the bone screw (10) existing external thread (28, 64).
Bone screw (10) according to claim 9, characterized in that in at least two successive flanks (52, 90) of at least one external thread (28, 64) each have a passage opening (86), and that the passage openings (86) are preferably aligned ,
Bone screw (10) according to one or more of the preceding claims, characterized in that it comprises at least one recess (94) in a projecting edge (56) of an edge (52) of a first outer thread present in the front region (24) of the bone screw (10) (28, 64), which recess (94) at least partially forms an additional cutting edge (98).
Bone screw (10) according to one or more of the preceding claims, characterized in that it has an external thread (28, 64) which at least one at least partially within a flank (52) of the external thread (28, 64) and preferably at least partially in the circumferential direction extending threaded channel (102, 108), one end of which opens into an outer side of the external thread (28, 64).
Bone screw (10) according to claim 12, characterized in that the one end of the threaded channel (102, 108) in an additional cutting edge (98) on the external thread (28, 64) of the bone screw (10) is arranged.
Bone screw (10) according to claim 13, characterized in that the threaded channel (102, 108) substantially follows a pitch of the external thread (28, 64).
Bone screw (10) according to one or more of claims 12 to 14, characterized in that the threaded channel (102, 108) with its other end in the channel space (12) or in a circumferentially next next cutting edge (98) on the external thread ( 28, 64) opens.
Bone screw (10) according to one or more of the preceding claims, characterized in that the bone screw (10) comprises a receiving part (110) for connecting the bone screw (10) with a rod system (114).
Bone screw (10) according to claim 13, characterized in that the receiving part (110) is connected polyaxially, uniplanar or monoaxially with the bone screw (10).
Bone screw (10) according to one or more of the preceding claims, characterized in that it comprises a screw head (68) having a locking device (120), preferably a head-side external thread (122) for locking the bone screw (10) with a bone plate in an angularly stable manner , having.
Bone screw (10) according to one or more of the preceding claims, characterized in that it has a self-tapping head-side external thread (124) for locking the bone screw (10) with a bone plate in an angularly stable manner.
Bone screw (10) according to one or more of the preceding claims 1 to 17, characterized in that it comprises a screw head (68), which is partially formed dome-like and over which the bone screw (10) is variable angle connected to a bone plate.