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
  • A61B17/84—Fasteners therefor or fasteners being internal fixation devices
  • A61B17/86—Pins or screws or threaded wires; nuts therefor
  • A61B17/866—Material or manufacture
• • 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
  • A61B17/8625—Shanks, i.e. parts contacting bone tissue
  • A61B17/863—Shanks, i.e. parts contacting bone tissue with thread interrupted or changing its form along shank, other than constant taper
• • 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
  • A61B17/8645—Headless screws, e.g. ligament interference screws
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B17/00—Surgical instruments, devices or methods
  • A61B2017/00831—Material properties
  • A61B2017/00933—Material properties bone or bone-like

Definitions

• the invention relates to an externally threaded pin and a cylindrical stud shank of allogenic cortical bone material for surgically operative osteosynthesis, wherein the bone material is traversed by Havers channels, according to the preamble of claim 1.
• the external thread of such a bolt over the entire longitudinal extent extends the bolt, can also be spoken by a set screw. If the bolt is also provided with a threadless head, it is also possible to speak of a bone screw. In the following, it is preferable to speak of bone screws, which embodiments should also include embodiments in the form of a threaded pin.
• Bone screws for surgically operative osteosynthesis are conventionally made of metal or metal alloys. Also known are bone screws made of resorbable material, such as polyglycolide and polylactide, as well as xenogenic bone screws.
• bone screws of this type have several disadvantages in surgical practice. Screws made of metal or metal alloys, on the one hand, have to be removed again by a second operation, on the other hand, they are subject to changes due to corrosion. This increases the costs in the health system. In addition, there is an additional health risk for each patient due to a recent operation that does not exist with allogenic bone screws. Although all resorbable materials in the human or animal body, depending on the material, form a more or less firm bridge between the osteosynthesizing bones, they are dissolved, which adversely affects the strength of the osteosynthesis of the affected bones. Furthermore, during their degradation, some resorbable synthesis materials lead to large osteolyses in the surrounding bone, ie to a deviation of the recipient bone from the screw.
• Xenogenic (non-species-related) materials in turn lead to rejection reactions and are for osteosynthesis also unsuitable because they are not incorporated in the surrounding recipient bone, but repelled and degraded, even if the protein in the bone was previously denatured by heat.
• the different modulus of elasticity of bovine corticalis and human corticalis contributes to the fact that human material can heal much better. Shape strength and modulus of elasticity of the cortical bone are species-dependent.
• allogenic bone screws (femur and tibial corticalis) have several advantages. They are vascularized and remodeled without rejection, and are particularly suitable for osteosynthesis where small bone fragments must be put together, as the screw already creates a supporting bone bridge during surgery which improves from the time of surgery by rebuilding itself and fully integrated and incorporated into the living bone.
• metal screws are more of an obstacle to bone regeneration, in particular, their mere presence reduces the available surface area available for bone healing.
• degradable materials have their maximum strength at the time of surgery. For them, the same disadvantages apply as for the metal screws, furthermore, the strength decreases rapidly as soon as the degradation process occurs, whereby at least temporarily re-weakening the osteo-to-be-digitized bone site.
• allograft bone screws may require a second operation to remove the osteosynthesis material as the bone is completely transformed (not resorbed) into its own bone.
• the health system are forced to reduce costs. Screws from allogeneic bone also do not interfere with the application of imaging techniques, in contrast to metal screws, the annoying artifacts in MRI and CT leave. Also follow-up examinations are possible without any problems, and allow a better assessment of the healing success.
• Claim 1 relates to an externally threaded pin and a cylindrical stud shank of allogeneic cortical bone material for surgically operative osteosynthesis, wherein the bone material is traversed by Havers channels.
• a Havers Canal is the central bone canal in the middle of an osteone, which is the basic component of the cortex.
• An osteon consists of concentrically arranged lamellae, which are also referred to as special lamellae, a central Havers canal and the, located between the lamellae osteocytes.
• the Havers Canal has blood vessels, connective tissue cells and fibers as well as individual nerve fibers. According to the invention, it is now provided that the Havers channels run obliquely to the longitudinal axis of the bolt shank.
• Osteone and Havers canals occur only in the cortex of long bones, with the Havers' canals extending substantially in the longitudinal direction of the bone.
• the bone screw is cut in the longitudinal direction of the donor bone so that the longitudinal axis of the pin shaft extends substantially in the longitudinal direction of the donor bone.
• the Havers channels in the bolt shank also run essentially parallel to the longitudinal axis of the bolt shank.
• Such a blank is also chosen because on the one hand, the strength of the thus cut bone screws is greatest, and on the other hand, an economic utilization of the donor bone material is possible.
• the blank of the bone screw so that the Havers channels extend obliquely to the longitudinal axis of the bolt shank, and in particular at an angle between 5 ° and 15 ° to the longitudinal axis of the bolt shank.
• the integration of the bone screw extends to a considerable extent via the Havers channels, which, however, are hardly accessible when the bone screw is cut parallel to the longitudinal axis of the donor bone.
• the blank is selected so that the Havers channels run obliquely to the longitudinal axis of the bolt shank, open the Havers channels in the lateral surface of the bolt shank and are thus for a
• the bone screw increasingly loses strength, so that an optimal angle of the Havers channels between 5 ° and 15 ° is proposed to the longitudinal axis of the bolt shank.
• FIG. 2 is a schematic representation of the fracture of a bone with an inserted pin according to the invention in the context of surgical osteosynthesis
• FIG. 3 shows a detail of a cross section transverse to the longitudinal axis of a donor bone illustrating the structure of an osteone and its Havers channel
• Fig. 4a is a schematic representation of a conventional pin in the recipient bone with marked course of the Havers channels, and the
• Fig. 4b is a schematic representation of a bolt according to the invention in the recipient bone with marked course of the Havers channels.
• the present invention relates to the optimization of bone screws 1 from allogenic bone, as shown schematically in Fig. 1, in terms of their properties in the context of surgical osteosynthesis, in particular with respect to the faster integration of the bone screw in the recipient bone.
• bone screws with symmetrical pointed thread are preferably provided in order to exert no compression on the bone parts to be connected.
• the bone screws are preferably designed to be have the highest possible number of threads per millimeter along the entire bolt shank to ensure that the cortical bone 3 is in conjunction with a correspondingly high number of threads. With a ratio of thread depth to thread diameter between 0.10 and 0.15, a product of this ratio and the number of threads per millimeter of 0.10 to 0.30 is provided for this purpose.
• the symmetrical pointed thread is also performed over the entire length of the bolt shank with a constant thread diameter, so that a bone screw 1 as shown in FIG. 1 results.
• the bone screw 1 itself may have a square, hexagon or star head as a screw head 2 (see FIG. 1), but only serves to introduce torque in the course of screwing, and after placement of the bone screw 1 is cut off, so that a configuration shown in FIG. 2 is reached.
• the fixation and compression of the bone parts to be joined is first ensured by appropriate surgical instruments. Subsequently, a core hole is set, in which a thread is cut.
• the bone screw 1 according to the invention can now be introduced with a torque wrench, the bone screw 1 traverses the bone parts along the cancellous bone 4 and the cortex 3, and holds in a stable state with a predetermined distance, without exerting a compression as a Symmetrical pointed thread hardly allows tensile loads (see Fig. 2). Therefore, the illustrated bone screw 1 is not a lag screw. Due to the high number of threads and the associated friction forces but high rotational stability of the bone screw 1 is still given.
• FIG. 3 shows a section of a cross-section transverse to the longitudinal axis of a donor bone to illustrate the structure of an osteone 5 and its Havers channel 6.
• An osteon 5 consists of concentrically arranged lamellae, which are also referred to as special lamellae, the centrally located Havers Channel 6 and the lying between the lamellae osteocytes.
• Havers Channel 6 there are blood vessels, connective tissue cells and fibers as well as individual nerve fibers.
• the individual osteons 5 are in turn connected to each other by so-called switching lamellae 7, whereby the hermaphroditic Channels 6 of the individual osteons 5 are interconnected by transverse channels also containing blood vessels, which are also referred to as Volkmann channels (not visible in FIG. 3).
• Osteone 5 and Havers 'canals 6 occur only in the cortex 3 of long bones, with the Havers' canals 6 extending substantially in the longitudinal direction of the donor bone.
• the symmetry of the bone structure is conventionally followed and the bone screw 1 is cut in the longitudinal direction of the donor bone so that the longitudinal axis L of the pin shaft extends substantially in the longitudinal direction of the donor bone.
• the Havers channels 6 extend in the bolt shank of the bone screw 1 substantially parallel to the longitudinal axis L of the bolt shank, as shown with reference to FIG. 4a.
• the Havers channels 6 extend obliquely to the longitudinal axis L of the bolt shank of the bone screw 1, and in particular at an angle between 5 ° and 15 ° to the longitudinal axis of the bolt shank, as in Fig. 4b is shown. In this way it is achieved that there are more openings of Havers channels 6 along the lateral surface of the bolt shank, so that they for a
• Metabolic exchange with the recipient bone are accessible, as indicated by the small arrows normal to the lateral surface of the bolt shank in Fig. 4b.
• the integration of the bone screw 1 in the recipient bone is thereby significantly accelerated, since the integration of the bone screw 1 in the recipient bone and their transformation into their own bone for the most part on the Havers channels 6.
• the bone screw 1 if the blank of the bone screw 1 is selected with increasing angle between the longitudinal axis L of the bolt shank and the Havers channels 6, the bone screw 1 increasingly loses strength, so that an optimum angle of the Havers channels 6 between 5 ° and 15 ° Longitudinal axis L of the bolt shank of the bone screw 1 is proposed.
• the Havers channels 6 are easy to observe and determine using a microscope. Of course, they do not run along perfect straight lines and in perfect parallelism with each other.
• the geometric orientation of the Havers channels 6 according to the invention is rather to be understood that the course of a Havers channel 6 can be approximated with a straight line, which according to the invention extends obliquely to the longitudinal axis L of the bolt shank of the bone screw 1, preferably in one Angular range between 5 ° and 15 °.
• This criterion can also be formulated such that the average directional vector of all Havers channels 6 has an angle between 5 ° and 15 ° to the longitudinal axis L of the bolt shank.
• the averaged direction vector can be approximately determined by adding for the direction vectors of individual Havers channels 6 all components parallel to the longitudinal axis L of the bolt shank and divided by the number of summands to obtain a mean parallel vector. In addition, all components can be added perpendicular to the longitudinal axis L of the bolt shank and divided by the number of summands to obtain a mean normal vector. The mean parallel vector and the mean normal vector finally form the mean direction vector of all Havers channels 6.

Landscapes

• Health & Medical Sciences (AREA)
• Orthopedic Medicine & Surgery (AREA)
• Surgery (AREA)
• Life Sciences & Earth Sciences (AREA)
• Heart & Thoracic Surgery (AREA)
• Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
• Engineering & Computer Science (AREA)
• Biomedical Technology (AREA)
• Neurology (AREA)
• Medical Informatics (AREA)
• Molecular Biology (AREA)
• Animal Behavior & Ethology (AREA)
• General Health & Medical Sciences (AREA)
• Public Health (AREA)
• Veterinary Medicine (AREA)
• Surgical Instruments (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=47716033

Family Applications (1)

Country Status (2)

Cited By (1)

Citations (2)

Family Cites Families (3)

• 2012
  • 2012-05-04 AT AT5292012A patent/AT511944B1/de not_active IP Right Cessation
• 2013
  • 2013-02-13 WO PCT/EP2013/052857 patent/WO2013164106A1/fr not_active Ceased

Patent Citations (2)

Also Published As

Similar Documents

Legal Events