Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B17/00—Surgical instruments, devices or methods
  • A61B17/56—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor
  • A61B17/58—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor for osteosynthesis, e.g. bone plates, screws or setting implements
  • A61B17/68—Internal fixation devices, including fasteners and spinal fixators, even if a part thereof projects from the skin
  • A61B17/70—Spinal positioners or stabilisers, e.g. stabilisers comprising fluid filler in an implant
  • A61B17/7059—Cortical plates
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B17/00—Surgical instruments, devices or methods
  • A61B17/56—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor
  • A61B17/58—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor for osteosynthesis, e.g. bone plates, screws or setting implements
  • A61B17/68—Internal fixation devices, including fasteners and spinal fixators, even if a part thereof projects from the skin
  • A61B17/84—Fasteners therefor or fasteners being internal fixation devices
  • A61B17/86—Pins or screws or threaded wires; nuts therefor
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B17/00—Surgical instruments, devices or methods
  • A61B17/56—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor
  • A61B17/58—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor for osteosynthesis, e.g. bone plates, screws or setting implements
  • A61B17/68—Internal fixation devices, including fasteners and spinal fixators, even if a part thereof projects from the skin
  • A61B17/80—Cortical plates, i.e. bone plates; Instruments for holding or positioning cortical plates, or for compressing bones attached to cortical plates
  • A61B17/809—Cortical plates, i.e. bone plates; Instruments for holding or positioning cortical plates, or for compressing bones attached to cortical plates with bone-penetrating elements, e.g. blades or prongs

Definitions

• This invention relates to a system of treating spine pathologies following implantation of a graft in the intervertebral space formed by disc removal, and more particularly to a system having a plate and expandable anchor members to immobilize the vertebrae and graft to attain good bone consolidation.
• cervical region which is further defined as the high cervical spine, which includes the first and second cervical vertebrae, and the lower cervical spine, which includes the 3rd-7th vertebral segments. Injuries at these levels are much more frequent and require specific surgical treatment more often.
• cervical spine pathologies can be approached from two directions: the posterior approach which requires performing a laminectomy and the anterior approach which involves access through the anterior or anterolateral aspect of the neck.
• the latter is more widely used since the pathology has a more frequently anterior location in the vertebrae themselves or the intervertebral discs.
• a vertical or transverse incision located on the anterior edge of the sternocleidomastoid muscle, is made to access the prevertebral space between the vascularcarotid-jugular bundle on the outside and the pharynx-larynx on the inside.
• the anterior common longitudinal ligament is removed, exposing the discs and vertebrae at one or more levels.
• the next step depends on the type of pathology to be treated (somatic or discal vertebral) , but in any case, a general repercussion is a uni- or multi-segment instability caused by the pathology itself, the ligament interruption or the removal of the disc or portions of the vertebrae. Cervical spine instability therefore is the most frequent side-effect of a surgical procedure using the anterior approach..
• Cloward proposed the placement of an intersomatic graft in the intervertebral space produced upon disc removal.
• a cylindrical cavity extending to the body of the superior and inferior vertebrae is created in the intervertebral space, following which another drill of similar diameter is used to obtain a cylinder of spongy bone tissue from the ala of the ilium.
• This cylinder is introduced into the cavity created in the intervertebral space in order to attain bone fusion.
• Recently Otero modified the technique in such a way that the bone cylinder and the intervertebral cavity are threaded so as to facilitate graft placement.
• Cloward' s technique has been and is still being widely utilized. It achieves good bone consolidation in the space of two or three months. Its disadvantages are the obtaining of the graft and the risk of perforating the posterior vertebral wall, thus producing a medullar injury.
• Verbiest to avoid this latter problem, proposes carving the vertebral platforms after removing the disc in such a way that they form a wedge-shaped cavity with an anterior base.
• the graft is also cut in the shape of a wedge.
• Codman and Shirtleff sells a screw and plate system having a small, oval-headed locking screw which is installed in the plate next to the scalloped head of the main anchoring screw to interlock the main screw to the plate. If the locking screw rotates, however, the plate may shift thereafter:
• a vertebral fusion system and method according to the present inventor ensures a solid anchoring of a plate to the vertebrae.
• the preferred embodiment includes a plate installed on the anterior face of the vertebrae, expandable anchor screws which pass through the plate and are then attached to the vertebrae itself, and a screw or screws which also pass through the plate and are attached to a graft implanted between the vertebrae.
• the anchoring screws for the vertebrae are cylindrical, preferably 12mm long and 7-8mm in diameter, have a wide thread and a blunt point, and are self-tapping. These screws are called anchoring screws because another small screw is placed within their center.
• the anchoring screw features longitudinal slits about 4- 5mm long and is hollow and threaded on the inside so as to hold the inner screw.
• This inner screw opens the anchoring screw's legs as it enters and increases its diameter when the inner screw is in place. This increase typically is 25-30% with respect to the original diameter and provides a solid anchoring to the vertebra.
• the screw or screws which pass through the plate and anchor the graft are conventional screws with a head which stays positioned in the previously mentioned recess in the corresponding plate. These screws consist solely of a simple shank with an appropriate thread and its respective head.
• Both the vertebrae anchoring screws and the graft anchoring screws, as well as the plates themselves, are made preferably of titanium to ensure the possibility of post-operative exploration through magnetic resonance imaging.
• the anchoring screw's external surface, including its spiral or thread, is coated with hydroxyapatite to facilitate the implant's solidity and encourage bone growth around it.
• the system includes a locking washer having two or more legs which straddle recesses in the head of an anchoring screw and interlock with recesses in the plate to positively ensure immobilization.
• Fig. 1 is a schematic vertical lateral view of cervical vertebrae with the system implemented according to the present invention
• Fig. 2 is a schematic front (anterior) view of the same applied system
• Fig. 3 is a lateral exploded view of the different elements making up the present invention
• Fig. 4 is a longitudinal cross-sectional view of the expandable anchor screw according to the present invention.
• Fig. 5 is a bottom-end view of the distal point of the anchoring screw of Fig. 4 in which the slits in form of a cross can be seen;
• Fig. 6 is a top view of one construction of the plate used according to the present invention.
• Fig. 7 is a cross-sectional view of the plate shown in Fig. 6;
• Fig. 8 is a side view of another construction of the expandable screw
• Fig. 9 is a cross-sectional view of another construction of a plate with two expandable screws, of the type shown in Fig. 8, inserted at divergent angles;
• Fig. 10 shows another construction of the plate with two orifices and a central orifice with a smaller radius
• Fig. 11 is a cross-sectional view of the plate of Fig. 10 along the line A-A;
• Fig. 12 is a longitudinal profile of the non-bendable plate curved to match the anterior profile of the cervical spine;
• Fig. 13 is a schematic perspective view of a locking washer according to the present invention.
• Fig. 14 is a schematic view of a presently preferred anchor member according to the present invention having recesses for receiving the locking washer of Fig. 13;
• Fig. 15 is a schematic perspective view of a plate according to the present invention having channels for receiving the legs of the locking washer of Fig. 13;
• Fig. 16 is a schematic perspective view of the locking washer, anchor, and plate of Figs. 13-15 assembled together with an inner screw for securing the assembly together.
• the present system and method are particularly useful for treating cervical spine pathologies through the anterior approach and are specifically applicable to intervertebral disc surgeries, so that once the disc is removed, the resulting intervertebral cavity contains a graft, Figs. 1 and 2.
• This graft 1 is immobilized precisely by the invention's system which consists of two anchoring screw assemblies 2, a graft screw 3, and a plate 4 in such a way that the screw assemblies 2 are anchored to the corresponding vertebrae 5 while the screw 3 is anchored to the graft 1. This secures the plate to the anterior face of the vertebrae 5 precisely by means of these screws.
• the invention's system which consists of two anchoring screw assemblies 2, a graft screw 3, and a plate 4 in such a way that the screw assemblies 2 are anchored to the corresponding vertebrae 5 while the screw 3 is anchored to the graft 1.
• each screw assembly 2 includes an anchoring screw 6 and an inner cam screw 7, both preferably made of the same material, particularly titanium.
• the anchoring screw 6 is hollow and contains an outer spiral 8 consisting of a thread, a distal blunt point 9 and longitudinal slits 10 in the form of a cross to establish four outwardly expandable legs.
• the inside of this anchoring screw 6 defines an internal bore 30 having a thread or spiral 11 to match the thread of the inner screw 7.
• This inner screw has a head 12 with a drive socket permitting the use of an Allen wrench, screwdriver or other appropriate tool.
• the anchoring screw 6 also has the unique feature that its head 13 has a cavity 14 designed to hold the head 12 of screw 7 and also has several slots 15 to allow it to be handled by an appropriate tool or similar instrument.
• the anchoring screws 6 defines inner camming surfaces 32, 34, Fig. 4, distal to the internal threads 11, which are slideably engaged by camming surfaces 36, Fig 3, of the inner screws 7.
• the anchoring screws 6 are thereby driven from the contracted position shown in Fig. 3 to the expanded position schematically shown in Fig. 1.
• the plate 4, Figs. 6-7 preferably is also made of titanium and has a flat-rectangular configuration, with orifices 16 to permit the passage of screws 2 and 3 which are indented around their perimeter 17 to accommodate the respective heads 13 of screws 2 and for the heads 18 of the screws 3 utilized for the graft.
• These latter screws consist of a simple shank with a distal rounded point 19, a thread or external spiral 20 and head 18, also with the necessary slots 21 to permit handling with an appropriate tool.
• These screws 3 preferably are made of titanium just as are the elements previously mentioned.
• first and second holes are drilled in first and second vertebrae 5, Fig. l.
• the anchoring screws 6 are introduced in the contracted condition into the corresponding vertebrae 5, after passing through the orifice 16 of the plate , then the inner cam screw 7 is inserted into each anchoring screw 6. As this inner screw 7 is advanced, it causes the legs and therefore the distal region of the anchoring screw 6 to expand into the expanded condition as is presented schematically in Fig. 1.
• the anchoring screws 6 shown in Figs. 8 and 9, have the advantage that their heads 18 are curved at edges 22 to permit the angle of insertion into the hole 16 of the plate 4 to be varied and not necessarily be perpendicular. Thus, each screw can be inserted in a different direction relative to the plate, reinforcing the stability of the axial and lateral rotation of the vertebrae.
• Plate 4 which has been shown in one of its possible applications with three orifices 16 can contain more orifices and even be wider or narrower. Thus, as shown in Figs. 10, 11 and 12, the plates for two vertebral levels will have two large orifices 16 and a central orifice 24 of smaller radius. As a result, the plate 4 is more solid and weak points are eliminated.
• the two-level plates can be constructed in various sizes and with lengths of 23, 27, 31 and 34 millimeters to accommodate the size of each patient's vertebrae.
• the plates 4 in one construction have a three-millimeter prong 23 emerging perpendicularly from its posterior face - the one applied to the vertebra - and at the same horizontal level as the orifices 16 for the expandable screw. These prongs are located on each side and are embedded into the vertebra's anterior face, thus preventing shifts during lateral flexion and axial rotation.
• a vertebral fusion system includes a rigid plate defining first and second orifices spaced from each other, and at least two anchor assemblies, each assembly including an outer anchor member and an inner cam member, each of the inner and outer “ members having a distal region and a proximal region.
• Each outer anchor member is insertable in a contracted condition through one of the first and second orifices and into one of the first and second holes.
• Each outer anchor member defines an internal bore for receiving the inner cam member therein, and portions of the internal bore and of the inner cam member define matching detent and recess regions, such as matching threads, to enable the inner cam member to be successively interlocked at positions of increasing depth within the outer anchor member as the inner member is driven into the outer member.
• the matching detent and recess regions alternatively are a series of ribs and grooves into which the ribs successively snap when at least one of the inner and outer members are formed of a sufficiently resilient material.
• the outer anchor member defines a plurality of outwardly expandable legs, each leg having outer ridges on its outer surface, the ridges being barbs, ribs, or a helical thread.
• Vertebral fusion system 50 is a preferred construction in which a plate 52 is secured in position with an anchor assembly 54 including an outer anchor member 56 and an inner cam member 58.
• Fusion system 50 further includes a locking washer 60 having at least first and second legs 62, 64, Fig. 13, connected by a ring 66 defining a central passage 68 through which inner camming member 58 is insertable as shown in Fig. 16.
• Each leg 62, 64 includes first, horizontal portions 70, 72 and second, vertical portions 74, 76, respectively. The first portions 70, 72 rests within recesses 80, 82 of anchor member 56, and the second portions 74, 76 slideably engage washer leg slots 90, 92 of plate 52, Fig. 15.
• Plate 52 further defines first orifice 94, second orifice 96 , and a smaller-diameter third orifice 98 located between the first and second orifices 94, 96.
• a graft screw (not shown) is insertable through the third orifice 98 to engage a graft placed between first and second vertebrae positioned under orifices 94, 96, respectively.
• the vertebral side of the plate 52 is textured with a diamond-type knurl finish to enhance bone-to-plate interlocking and resist shifting.
• Recesses 80, 82, of outer anchor member 56 are defined by posts 100, 102, 104 and 106 which abut against the sides of first portions 70, 72 of the washer 60.
• the washer 60 includes four legs which rest between all four posts 100, 102, 104 and 106, and plate 52 defines at least four washer leg slots communicating with each outer orifice 94, 96.
• Outer anchor member 56 defines four legs, three of which are shown as legs 110, 112, and 114.
• smooth outer camming surface 118, Fig. 16 engages smooth inner camming surfaces on the legs 110, 112, 114 and 116 to drive the legs outwardly from the contracted condition shown in Figs. 14 and 16 into an expanded condition in which the walls of holes drilled in the vertebrae are securely engaged by the interrupted helical thread 120.
• Matching detent and recess regions are provided in outer anchor member 56 and as region 122 of inner cam member 58. In one construction, the matching detent and recess regions include number ten machine threads.
• a hexagonal socket 124 mates with a driver to enable the inner cam member 58 to be rotatably driven into the outer anchor member 56.
• each outer anchor member defines an enlarged proximal head having a collar or annulus and a smaller-diameter polygonal projection, such as a hexagonal plateau, which extends proximally beyond the collar.
• the plate defines orifices shaped in matching polygons.
• Inner cam members are provided with enlarged proximal heads to lock the plate to the outer anchor members.
• the heads of the cam members define one or more channels engagable by a slotted screw driver.
• the edges of the orifices at the upper, distal side of the plate define recesses into which the heads of the cam members are positionable to reduce the profile of the fusion system.
• the outer anchor member has an overall length of 14.8mm, a root diameter of 5.5mm, an outer thread diameter of 7.5mm, and four leg-defining slots of 10.7mm length.
• Inner camming surfaces are defined at thirty degree angles relative to the longitudinal axis of the outer anchor member.

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• Health & Medical Sciences (AREA)
• Orthopedic Medicine & Surgery (AREA)
• Life Sciences & Earth Sciences (AREA)
• Surgery (AREA)
• Neurology (AREA)
• Heart & Thoracic Surgery (AREA)
• Engineering & Computer Science (AREA)
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• 1995
  • 1995-05-24 EP EP95921382A patent/EP0746256A1/de not_active Withdrawn
  • 1995-05-24 WO PCT/US1995/006561 patent/WO1995031941A1/en not_active Ceased
  • 1995-05-24 AU AU26477/95A patent/AU2647795A/en not_active Abandoned

Non-Patent Citations (1)

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