Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberUS20070055238 A1
Publication typeApplication
Application numberUS 11/390,972
Publication dateMar 8, 2007
Filing dateMar 27, 2006
Priority dateDec 27, 2000
Also published asDE50100793D1, EP1219255A1, EP1219255B1, US7018378, US20020138076
Publication number11390972, 390972, US 2007/0055238 A1, US 2007/055238 A1, US 20070055238 A1, US 20070055238A1, US 2007055238 A1, US 2007055238A1, US-A1-20070055238, US-A1-2007055238, US2007/0055238A1, US2007/055238A1, US20070055238 A1, US20070055238A1, US2007055238 A1, US2007055238A1
InventorsLutz Biedermann, Dezso Jeszensky, Jurgen Harms, Helmar Rapp
Original AssigneeBiedermann Motech Gmbh
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Screw
US 20070055238 A1
Abstract
An element with a thread is created, in which both partial flanks enclose a negative angle with a plane extending perpendicular to the screw axis. Further, a screw or a hook for connecting to a rod, as used in particular in spinal column surgery, is created, wherein the inner thread of a holder, to which the rod is connected, and the associated thread of a nut comprise the thread according to the invention.
Images(3)
Previous page
Next page
Claims(4)
1. (canceled)
2. (canceled)
3. A device comprising:
a shank;
a holding component for engaging and holding a rod, the holding component comprising a recess having two legs, a U-shaped cross-section for accommodating the rod, an open end for receiving the rod into the U-shaped cross-section between the legs, and an inner thread on the legs; and a screw, which cooperates with the inner thread and directly or indirectly acts on the rod when positioned in the recess, the screw having a central axis;
wherein the inner thread comprises an inner thread base, first and second partial flanks adjacent to one another, and an internal thread edge between the first and second partial flanks;
wherein the screw has an outer thread for engagement with the inner thread of the legs, the outer thread comprising an outer thread base, third and fourth partial flanks adjacent to one another, and an external thread edge between the third and fourth partial flanks;
the first and third partial flanks, which face away from the open end, enclose a negative angle β2 with a plane which extends through the respective thread base and extends perpendicular to the central axis;
the second and fourth partial flanks, which face toward the open end, enclose a positive angle β1 with a plane which extends through the respective thread base and extends perpendicular to the central axis.
4. The device according to claim 3, wherein the internal thread base is rounded between adjacent first and second partial flanks.
Description
  • [0001]
    The invention relates to an element to be used in spinal column or accident surgery for connecting to a rod.
  • [0002]
    From U.S. Pat. No. 5,129,388 a pedicle screw is known which comprises a head with a U-shaped recess defining two free legs to accommodate a rod, wherein the legs are provided with an inner thread to receive a fixing screw for fixing the rod. To prevent spreading of the legs a cap is provided embracing the legs.
  • [0003]
    From U.S. Pat. No. 5,005,562 it is known with a pedicle screw according to the preamble of Patent claim 1 to construct the inner thread and the thread of the screw cooperating with it as a saw-tooth thread, so as in this way to avoid spreading out of the two flanks by completely eliminating the radial components of the force during screwing in.
  • [0004]
    A saw or else saw-tooth thread of this kind is known from Meyer's Enzyklopädisches Lexikon, Mannheim, 1974, page 302. From both the specifications U.S. Pat. Nos. 5,605,458 and 5,607,304, concerning implants, it is known with implants of this kind to be introduced into the body, in particular hip implants, also to construct the saw thread in such a way that the flank bearing the load is constructed not only at 90° to the thread axis but even at a negative angle. This is supposed to achieve that the connection obtained with the thread resists a radial relative movement of the connected parts and thus guarantees better fixing of the implant. From EP-A-1 128 773 a pedicle screw is known in which the inner thread of a head accommodating a rod has a negative thread and the screw cooperating with it is correspondingly constructed.
  • [0005]
    The object of the invention is to create an element of the kind initially described, which is suitable for avoiding the above described disadvantage. In particular bending up of the open ends of a mount of this kind and therefore loosening of the connection between screw and rod should be avoided.
  • [0006]
    This object is achieved by the element characterised in Patent claim 1.
  • [0007]
    This construction has the advantage that the action of force between the exposed legs and the inner thread happens in such a way that the open ends of the holding element are not pressed outwards, but instead are drawn inwards, so an intensive connection takes place between the cooperating elements.
  • [0008]
    Further features and advantages of the invention emerge from the description of the embodiment examples using the figures.
  • [0009]
    FIG. 1 shows a side view of a monoaxial pedicle screw in a bisected exploded illustration.
  • [0010]
    FIG. 2 shows the head of the pedicle screw shown in FIG. 1 with inserted rod and inserted nut.
  • [0011]
    FIG. 3 shows the detail III indicated in FIG. 2 in enlarged scale.
  • [0012]
    FIG. 4 shows a section corresponding to the illustration chosen in FIG. 2 for a polyaxial screw.
  • [0013]
    FIG. 5 shows a schematically illustrated holding element with inserted rod and loosely screwed in inner screw.
  • [0014]
    FIG. 6 shows the detail VI in FIG. 5 in enlarged scale.
  • [0015]
    FIG. 7 shows the illustration corresponding to the illustration shown in FIG. 5 after the inner screw has been tightened.
  • [0016]
    FIG. 8 shows the detail VIII shown in FIG. 7 in enlarged scale.
  • [0017]
    The pedicle screw according to FIG. 1, which can, of course, also be used generally as a bone screw or constructed as a hook, has a thread shank 1 and a head 2. The head 2 has a U-shaped recess 4, extending in the direction of the longitudinal axis 3 of the screw and with a predetermined depth. On the two thereby constructed legs 5, 6 an inner thread 8 is provided coming from the open end 7 of the legs. Matched to the inner thread 8, a screw 9 is provided, the outer thread of which is constructed in such a way that it cooperates with the inner thread 8.
  • [0018]
    In operation a rod 10, to be connected to the screw, is placed in the U-shaped recess 4 in such a way that the rod comes to rest on the base of the U-shaped recess. The screw 9 is then screwed in far enough for it to exert sufficient stopping pressure on the rod 10 located in the U-shaped recess.
  • [0019]
    As can be seen more clearly in FIGS. 2 and 3, the inner thread in the head 2 and the outer thread of the screw 9 are constructed in the way of a saw thread. On the surface 11 facing away from the rod 10 to be fixed the screw 9 has a slit or a hexagonal recess for the insertion of a screwdriver.
  • [0020]
    In the thread in each case two adjacent partial flanks 12, 13 form a thread pitch. The two partial flanks 12, 13 enclose the flank angle β. The flank side 13 facing the open end 7 encloses a positive angle β1 with a plane 40, extending perpendicular to the longitudinal axis 3 and intersecting the flank side 13 on the base 23 of the thread (see FIG. 3). The partial flank 12 facing away from the open end is inclined in such a way that in the manner shown in FIG. 3 it encloses a negative angle β2 with a corresponding plane 40. As can be seen from the figures the thread of the screw 9 is made correspondingly, so the pitches of the screw 9 engage appropriately in the inner thread 8. In screw 9 therefore each flank 26 facing the open end 7 or the surface 11 forms the negative angle β2, which cooperates with the corresponding flank 12.
  • [0021]
    The embodiment shown in FIG. 4 corresponds identically in the construction of the inner thread 8 and the screw 9 cooperating with it and of the rod 10. Corresponding features are characterised by the same reference numerals.
  • [0022]
    By contrast with the first embodiment here there is a so-called polyaxial screw, in which the thread shank 1 is connected to a receiving part 15 via a spherical head 14. The receiving part has on one end an axially symmetrically aligned first bore 16, the diameter of which is larger than that of the thread section 1 and smaller than that of the head 14. The receiving part further has a coaxial second bore 17, which is open on the end located opposite the first bore and the diameter of which is large enough for the screw element to be guided through the open end with its thread section through the first bore and with the head 14 to the base of the second bore. Between the first and the second bore a small coaxial section us provided, which directly borders on the first bore and is constructed as spherical towards the open end, wherein the radius is substantially identical to the radius of the ball-segment-shaped section of the head 14. The inner thread 8 is again provided bordering on the open ends 7 of the legs 5, 6. The receiving part 15 further has a U-shaped recess 18, arranged symmetrical to the centre of the part, the base of which is directed towards the first bore, the two side legs 5, 6 of which extend towards the open end 7. Further, in the second bore 17 a pressure element is placed, which is situated on the spherical head 14. In operation the rod 10 is inserted into the U-shaped recess. Then the screw 9 is turned and screwed, in the same way as shown in FIG. 2, until it exerts a desired pressure on the pressure element 19 and therefore on the head 14 to stop it.
  • [0023]
    Instead of the above described embodiments, in which the head or the receiving part are connected in each case to a bone screw, the head or the receiving part can also be connected to a hook, as used in spinal column surgery for hooking in behind bone projections of the spinal column.
  • [0024]
    When a saw thread is spoken of above this is only supposed to characterise the direction of the partial flanks. Threads with rounded tips and rounded base, pointed threads and pointed thread base and flat thread edges and flat thread base should be also be included, as is also the case with a triangular thread, round thread and trapezoidal thread.
  • [0025]
    Whereas with known screws with a metric thread, in which the screw presses on a rod in the way shown in FIG. 2, one force component acts towards the open side 11 of the screw and a second force component acts outwards in each case, with the above described thread according to the invention again one component acts towards the open end 7, but the second component acts in the direction of the longitudinal axis 3. The result of this is that the exposed legs 5, 6 are not pressed outwards, but are drawn towards the symmetrical axis.
  • [0026]
    In FIG. 5, as in FIG. 2, the head of the pedicle screw shown in FIG. 1 is shown with inserted rod and only initially inserted inner thread 9. In FIG. 6 section VI from FIG. 5 is illustrated in larger detail. As emerges from this enlarged illustration, the inner screw 9 and the outer thread of the legs 5 are dimensioned relative to one another as follows: radius r1 from the centre of the screw coinciding with the longitudinal axis 3 to the base 21 of the thread of the screw 9 is smaller than radius r2 from the central axis of the holding element coinciding with the symmetrical axis 3 to the tip of its spiral 20. Radius r3 from the centre of the screw coinciding with the longitudinal axis 3 to the tip of the spiral 22 of the screw 9 is smaller than radius r4 from the central axis of the holding element coinciding with the longitudinal axis 3 to the base 23 of the thread of its inner thread.
  • [0027]
    As can be seen in particular in FIG. 6, when screw 9 and exposed legs 5, 6 of the holding element are brought into engagement without load, when the cooperating flanks 13 of the inner thread and 24 of the screw, having the positive flank angles, are adjacent to one another there is a gap 25 between the flanks 12, 26, having a negative flank angle, facing one another in each case.
  • [0028]
    FIG. 7 shows the same object as in FIGS. 5 and 6, wherein the screw 9 is now screwed inwards far enough for it to press on the rod 10 and thereby to effect a counter-force, indicated by the arrow 27, on the screw 9. As a result of this, as can be seen in FIG. 8, the flanks 12, 26 facing one another in each case thereby end up on top of one another at a negative flank angle β2, whereby the spirals 28, 29 of the inner thread are drawn inwards towards the respective base 21 of the pitches of the thread of the screw 9 in the manner shown in FIG. 8, with the result that the exposed legs are biased not outwards but inwards.
  • [0029]
    In a preferred embodiment the difference between the measurement of radii r1 and r2 is about 1 to 5% of the outer diameter of the thread or 0.1 to 0.5 mm with a screw diameter of 5 to 12 mm.
Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US5092635 *Apr 27, 1990Mar 3, 1992Baker Hughes IncorporatedButtress thread form
US5419595 *Sep 23, 1994May 30, 1995Sumitomo Metal Industries, Ltd.Threaded joint for oil well pipes
US5829797 *Nov 21, 1995Nov 3, 1998Sumitomo Metal Industries, Ltd.Threaded joint for oil well pipes
US6074391 *Jun 15, 1998Jun 13, 2000Howmedica GmbhReceiving part for a retaining component of a vertebral column implant
US6412831 *Sep 2, 1999Jul 2, 2002Vallourec Mannesmann Oil & Gas FranceThreaded connection of two metal tubes with high tightening torque
US6485491 *Sep 15, 2000Nov 26, 2002Sdgi Holdings, Inc.Posterior fixation system
US7018378 *Mar 15, 2002Mar 28, 2006Biedermann Motech GmbhScrew
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US7722652Jan 27, 2006May 25, 2010Warsaw Orthopedic, Inc.Pivoting joints for spinal implants including designed resistance to motion and methods of use
US7833252Jul 26, 2006Nov 16, 2010Warsaw Orthopedic, Inc.Pivoting joints for spinal implants including designed resistance to motion and methods of use
US7875065Jan 25, 2011Jackson Roger PPolyaxial bone screw with multi-part shank retainer and pressure insert
US7901435Mar 8, 2011Depuy Spine, Inc.Anchoring systems and methods for correcting spinal deformities
US7955363Jul 20, 2007Jun 7, 2011Aesculap Implant Systems, LlcScrew and rod fixation assembly and device
US7967850Oct 29, 2008Jun 28, 2011Jackson Roger PPolyaxial bone anchor with helical capture connection, insert and dual locking assembly
US8057519Nov 15, 2011Warsaw Orthopedic, Inc.Multi-axial screw assembly
US8066739Nov 29, 2011Jackson Roger PTool system for dynamic spinal implants
US8100915Jan 24, 2012Jackson Roger POrthopedic implant rod reduction tool set and method
US8105368Aug 1, 2007Jan 31, 2012Jackson Roger PDynamic stabilization connecting member with slitted core and outer sleeve
US8137386Aug 28, 2003Mar 20, 2012Jackson Roger PPolyaxial bone screw apparatus
US8152810Nov 23, 2004Apr 10, 2012Jackson Roger PSpinal fixation tool set and method
US8162948Apr 24, 2012Jackson Roger POrthopedic implant rod reduction tool set and method
US8211156Jul 3, 2012Andersen Bruce JOsteoporatic screw and expansion sleeve
US8257396May 23, 2008Sep 4, 2012Jackson Roger PPolyaxial bone screw with shank-retainer inset capture
US8257398Sep 4, 2012Jackson Roger PPolyaxial bone screw with cam capture
US8273089Sep 25, 2012Jackson Roger PSpinal fixation tool set and method
US8292892May 13, 2009Oct 23, 2012Jackson Roger POrthopedic implant rod reduction tool set and method
US8308773Dec 14, 2006Nov 13, 2012Medyssey Co., Ltd.Pedicle screw
US8308782Nov 13, 2012Jackson Roger PBone anchors with longitudinal connecting member engaging inserts and closures for fixation and optional angulation
US8353932Jan 15, 2013Jackson Roger PPolyaxial bone anchor assembly with one-piece closure, pressure insert and plastic elongate member
US8366745Jul 1, 2009Feb 5, 2013Jackson Roger PDynamic stabilization assembly having pre-compressed spacers with differential displacements
US8377067Feb 19, 2013Roger P. JacksonOrthopedic implant rod reduction tool set and method
US8377102Mar 26, 2010Feb 19, 2013Roger P. JacksonPolyaxial bone anchor with spline capture connection and lower pressure insert
US8394133Jul 23, 2010Mar 12, 2013Roger P. JacksonDynamic fixation assemblies with inner core and outer coil-like member
US8398682May 12, 2010Mar 19, 2013Roger P. JacksonPolyaxial bone screw assembly
US8409255May 10, 2011Apr 2, 2013Aesculap Implant Systems, LlcScrew and rod fixation assembly and device
US8444681May 21, 2013Roger P. JacksonPolyaxial bone anchor with pop-on shank, friction fit retainer and winged insert
US8475498Jan 3, 2008Jul 2, 2013Roger P. JacksonDynamic stabilization connecting member with cord connection
US8540754Dec 8, 2010Sep 24, 2013DePuy Synthes Products, LLCAnchoring systems and methods for correcting spinal deformities
US8556938Oct 5, 2010Oct 15, 2013Roger P. JacksonPolyaxial bone anchor with non-pivotable retainer and pop-on shank, some with friction fit
US8591515Aug 26, 2009Nov 26, 2013Roger P. JacksonSpinal fixation tool set and method
US8591560Aug 2, 2012Nov 26, 2013Roger P. JacksonDynamic stabilization connecting member with elastic core and outer sleeve
US8613760Dec 14, 2011Dec 24, 2013Roger P. JacksonDynamic stabilization connecting member with slitted core and outer sleeve
US8636769Jun 18, 2012Jan 28, 2014Roger P. JacksonPolyaxial bone screw with shank-retainer insert capture
US8696711Jul 30, 2012Apr 15, 2014Roger P. JacksonPolyaxial bone anchor assembly with one-piece closure, pressure insert and plastic elongate member
US8814911May 12, 2011Aug 26, 2014Roger P. JacksonPolyaxial bone screw with cam connection and lock and release insert
US8814913Sep 3, 2013Aug 26, 2014Roger P JacksonHelical guide and advancement flange with break-off extensions
US8840652Oct 22, 2012Sep 23, 2014Roger P. JacksonBone anchors with longitudinal connecting member engaging inserts and closures for fixation and optional angulation
US8845649May 13, 2009Sep 30, 2014Roger P. JacksonSpinal fixation tool set and method for rod reduction and fastener insertion
US8894657Nov 28, 2011Nov 25, 2014Roger P. JacksonTool system for dynamic spinal implants
US8911479Jan 10, 2013Dec 16, 2014Roger P. JacksonMulti-start closures for open implants
US8936623Mar 15, 2013Jan 20, 2015Roger P. JacksonPolyaxial bone screw assembly
US8979904Sep 7, 2012Mar 17, 2015Roger P JacksonConnecting member with tensioned cord, low profile rigid sleeve and spacer with torsion control
US8992578Jul 9, 2013Mar 31, 2015Depuy Synthes Products LlcAnchoring systems and methods for correcting spinal deformities
US8998959Oct 19, 2011Apr 7, 2015Roger P JacksonPolyaxial bone anchors with pop-on shank, fully constrained friction fit retainer and lock and release insert
US9050139Mar 15, 2013Jun 9, 2015Roger P. JacksonOrthopedic implant rod reduction tool set and method
US9055978Oct 2, 2012Jun 16, 2015Roger P. JacksonOrthopedic implant rod reduction tool set and method
US9144444May 12, 2011Sep 29, 2015Roger P JacksonPolyaxial bone anchor with helical capture connection, insert and dual locking assembly
US9168069Oct 26, 2012Oct 27, 2015Roger P. JacksonPolyaxial bone anchor with pop-on shank and winged insert with lower skirt for engaging a friction fit retainer
US9211150Sep 23, 2010Dec 15, 2015Roger P. JacksonSpinal fixation tool set and method
US9216039Nov 19, 2010Dec 22, 2015Roger P. JacksonDynamic spinal stabilization assemblies, tool set and method
US9216041Feb 8, 2012Dec 22, 2015Roger P. JacksonSpinal connecting members with tensioned cords and rigid sleeves for engaging compression inserts
US9320545Jan 14, 2011Apr 26, 2016Roger P. JacksonPolyaxial bone screw with multi-part shank retainer and pressure insert
US9393047Sep 7, 2012Jul 19, 2016Roger P. JacksonPolyaxial bone anchor with pop-on shank and friction fit retainer with low profile edge lock
US9414863Jul 31, 2012Aug 16, 2016Roger P. JacksonPolyaxial bone screw with spherical capture, compression insert and alignment and retention structures
US20050277919 *May 28, 2004Dec 15, 2005Depuy Spine, Inc.Anchoring systems and methods for correcting spinal deformities
US20080140076 *Feb 11, 2008Jun 12, 2008Jackson Roger PDynamic stabilization connecting member with slitted segment and surrounding external elastomer
US20080147121 *Feb 27, 2008Jun 19, 2008Warsaw Orthopedic, Inc.Multi-Axial Screw Assembly
US20080177317 *Jan 3, 2008Jul 24, 2008Jackson Roger PDynamic stabilization connecting member with cord connection
US20080188898 *Apr 1, 2008Aug 7, 2008Jackson Roger PPolyaxial bone screw with multi-part shank retainer and pressure insert
US20090192552 *Jul 30, 2009Andersen Bruce JOsteoporatic screw and expansion sleeve
US20090275985 *Nov 5, 2009Jackson Roger PDynamic stabilization assembly having pre-compressed spacers with differential displacements
US20100010542 *Sep 15, 2009Jan 14, 2010Jackson Roger PFlexible spinal stbilization assembly with spacer having off-axis core member
US20100016904 *Aug 7, 2009Jan 21, 2010Jackson Roger PUpload shank swivel head bone screw spinal implant
US20100087874 *Dec 14, 2006Apr 8, 2010Jong Wuk JangPedicle screw
US20100174319 *Mar 10, 2010Jul 8, 2010Jackson Roger PDynamic spinal stabilization assembly with elastic bumpers and locking limited travel closure mechanisms
US20110106176 *May 5, 2011Jackson Roger PPolyaxial bone screw with multi-part shank retainer and pressure insert
Classifications
U.S. Classification606/308
International ClassificationF16B35/06, A61F2/30, F16B33/02, A61B17/58, A61B17/70, A61B17/86
Cooperative ClassificationA61B17/7037, A61B17/7032
European ClassificationA61B17/70B2, A61B17/70B5B