Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
  • B25C—HAND-HELD NAILING OR STAPLING TOOLS; MANUALLY OPERATED PORTABLE STAPLING TOOLS
  • B25C11/00—Nail, spike, and staple extractors
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
  • 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, setting implements or the like
  • A61B17/88—Osteosynthesis instruments; Methods or means for implanting or extracting internal or external fixation devices
  • A61B17/92—Impactors or extractors, e.g. for removing intramedullary devices
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
  • 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, setting implements or the like
  • A61B17/88—Osteosynthesis instruments; Methods or means for implanting or extracting internal or external fixation devices
  • A61B17/92—Impactors or extractors, e.g. for removing intramedullary devices
  • A61B17/921—Impactors or extractors, e.g. for removing intramedullary devices for intramedullary devices
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/02—Prostheses implantable into the body
  • A61F2/30—Joints
  • A61F2/46—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor
  • A61F2/4603—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor for insertion or extraction of endoprosthetic joints or of accessories thereof
  • A61F2/4607—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor for insertion or extraction of endoprosthetic joints or of accessories thereof of hip femoral endoprostheses
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/02—Prostheses implantable into the body
  • A61F2/30—Joints
  • A61F2/46—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor
  • A61F2/4603—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor for insertion or extraction of endoprosthetic joints or of accessories thereof
  • A61F2/4609—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor for insertion or extraction of endoprosthetic joints or of accessories thereof of acetabular cups
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/02—Prostheses implantable into the body
  • A61F2/30—Joints
  • A61F2/46—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor
  • A61F2/4603—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor for insertion or extraction of endoprosthetic joints or of accessories thereof
  • A61F2/461—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor for insertion or extraction of endoprosthetic joints or of accessories thereof of knees
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
  • B25B—TOOLS OR BENCH DEVICES NOT OTHERWISE PROVIDED FOR, FOR FASTENING, CONNECTING, DISENGAGING OR HOLDING
  • B25B27/00—Hand tools, specially adapted for fitting together or separating parts or objects whether or not involving some deformation, not otherwise provided for
  • B25B27/02—Hand tools, specially adapted for fitting together or separating parts or objects whether or not involving some deformation, not otherwise provided for for connecting objects by press fit or detaching same
  • B25B27/026—Hand tools, specially adapted for fitting together or separating parts or objects whether or not involving some deformation, not otherwise provided for for connecting objects by press fit or detaching same fluid driven
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
  • B25D—PERCUSSIVE TOOLS
  • B25D9/00—Portable percussive tools with fluid-pressure drive, i.e. driven directly by fluids, e.g. having several percussive tool bits operated simultaneously
  • B25D9/14—Control devices for the reciprocating piston
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
  • A61B2017/00017—Electrical control of surgical instruments
  • A61B2017/00137—Details of operation mode
  • A61B2017/00154—Details of operation mode pulsed
  • A61B2017/00172—Pulse trains, bursts, intermittent continuous operation
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
  • A61B2017/00535—Surgical instruments, devices or methods, e.g. tourniquets pneumatically or hydraulically operated
  • A61B2017/00544—Surgical instruments, devices or methods, e.g. tourniquets pneumatically or hydraulically operated pneumatically
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
  • 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, setting implements or the like
  • A61B17/88—Osteosynthesis instruments; Methods or means for implanting or extracting internal or external fixation devices
  • A61B17/92—Impactors or extractors, e.g. for removing intramedullary devices
  • A61B2017/922—Devices for impaction, impact element
  • A61B2017/924—Impact element driving means
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/02—Prostheses implantable into the body
  • A61F2/30—Joints
  • A61F2/46—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor
  • A61F2/4603—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor for insertion or extraction of endoprosthetic joints or of accessories thereof
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/02—Prostheses implantable into the body
  • A61F2/30—Joints
  • A61F2/46—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor
  • A61F2/4603—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor for insertion or extraction of endoprosthetic joints or of accessories thereof
  • A61F2002/4619—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor for insertion or extraction of endoprosthetic joints or of accessories thereof for extraction
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/02—Prostheses implantable into the body
  • A61F2/30—Joints
  • A61F2/46—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor
  • A61F2/4603—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor for insertion or extraction of endoprosthetic joints or of accessories thereof
  • A61F2002/4619—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor for insertion or extraction of endoprosthetic joints or of accessories thereof for extraction
  • A61F2002/462—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor for insertion or extraction of endoprosthetic joints or of accessories thereof for extraction of broken endoprosthetic joint parts
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/02—Prostheses implantable into the body
  • A61F2/30—Joints
  • A61F2/46—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor
  • A61F2002/4681—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor by applying mechanical shocks, e.g. by hammering
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/02—Prostheses implantable into the body
  • A61F2/30—Joints
  • A61F2/46—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor
  • A61F2002/4688—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor having operating or control means
  • A61F2002/4692—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor having operating or control means fluid
  • A61F2002/4694—Special tools or methods for implanting or extracting artificial joints, accessories, bone grafts or substitutes, or particular adaptations therefor having operating or control means fluid pneumatic
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
  • A61N7/00—Ultrasound therapy
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
  • B25D—PERCUSSIVE TOOLS
  • B25D2250/00—General details of portable percussive tools; Components used in portable percussive tools
  • B25D2250/171—Percussive pulling action of tools for extraction of elements

Definitions

• This invention relates to methods and means for removal and/or installation (or insertion) of embedded articles.
• Such articles include, but are not limited to, bone-related devices, including implants, support devices, and prosthetic devices. More particularly, the method involves the use of a hand-held tool to impart to an article to be implanted or removed a series of force impulses parallel to the direction of insertion or removal.
• the invention is applicable, for example, to implantations and removals of femoral stems, rods and nails.
• the invention is also applicable to non-surgical uses for implantation or removal of articles in other contexts, such as industrial settings. Further discussion, however, will assume the context of surgical uses.
• Surgical implants including dental implants, have been developed to a stage in which the implant bonds so securely to the bone or composite that, should it become necessary to remove the implant, great danger exists that the recipient bone will be severely damaged before the implant bond can be parted. It is not known to use titanium implants for femoral stems, as well as to support dental restorations, in which the implant stem has a microporous surface, or other porous coating, to provide an ingrowth stem into vhich multiple trabeculae grow to provide fixation.
• the bond formed between the recipient bone and the implant by such fixation is frequently stronger than the bone a short distance from the implant, with the result that attempts to remove the implant with known extraction techniques and implements will remove the implant with a mass of the trabeculae attached to it or, even worse, fracture the bone at a place some distance from the implant.
• it is necessary to remove, or adjust, the position of a rod placed within a femoral bone for example, presently-used techniques and implements risk fracturing the bone.
• a rod placed within a femoral bone can stick due to friction in the same manner as a rod being placed within a pipe, and if, like a bone, the pipe is frangible, hitting or pounding on an end of the rod presents a substantial risk that the pipe will fracture.
• a surgeon seeking to implant, or adjust the position of, a rod in a bone has available only the hammer-like means to hit or to pound on an end of the rod.
• the invention is applicable to the full range of surgical devices used in orthopedic surgery, dental surgery and prosthetic surgery, including without limitation ingrowth, gr.uted, cemented and pressure-fitted components, and stuck components.
• the invention applies a force to slide the device from the host.
• the invention produces microfractures to release the implant/host interface.
• the invention imparts a force to facilitate insertion.
• a mating fixture is attached to the implant to secure fixation for removal;
• a driving tool capable of applying force pulses which exert force primarily in a prescribed direction parallel to the longitudinal axis of the implant is fixed to the attachment, and the frequency and amplitude of the driving force is adjusted in accordance with the combined driven mass of the fixture and the driving tool to provica impulse forces which effect removal of the implant from the host (e.g., recipient bone) without causing any substantial structural damage to the recipient bone.
• the invention brings about fatigue fracture (micro-fracture) of the multiple trabeculae which provide fixations, with the result that the stem can be removed with only a thin layer of fractured trabeculae attached to it, rather than extracting from the recipient bone the entire mass of multiple trabeculae and some of the surrounding bone material. Similar results can be achieved in the removal of grouted, cemented or frictionally stuck components.
• the form or shape of the force pulses used in practicing the invention is preferably an oscillation having a steep initial rise in one direction to a first amplitude to provide a desired acceleration to the driven mass, followed by a swing back in the opposite direction to a smaller amplitude.
• This waveform provides a implanted component of motion which oscillates thecomponent back and forth while exerting force that is primarily in a prescribed direction, namely, the axial direction of the implanted component. With a steep rise, this pulse-form brings about a controllable acceleration of the driving mass.
• the amplitude achieved in a given time interval is the parameter determining the acceleration, and hence the velocity, of the driven mass at the peak amplitude of the pulse.
• the frequency of the pulses will determine the number of oscillations per unit of time and, therefore, the total energy applied to the component being removed.
• the implanted component can be removed over an interval of time which satisfies the need to remove it incrementally without unduly damaging the recipient bone. Instead of accomplishing this task with blows from a hammer in the hands of a surgeon who must rely on his own "touch" and experience, the invention permits a surgeon to slowly, incrementally force the component free, with only minimal damage to immediately surrounding cement or trabeculae.
• a desired instrument for practicing the invention will provide incremented force pulses, for (e.g.,) removal of femoral components, other intramedullary devices and items generally fixed to or into bone. The application of force by this instrument will be in the axial direction of the bone when addressing intramedullary implants, such as femoral stems or intramedullary rods.
• the instrument is not intended to provide rotational stresses, nor will it deliver forces in directions radial to the longitudinal axis of the bone. In the case of press-fit components or intramedullary rods that have become stuck in the course of insertion prior to the location of ideal placement, this instrument will insure easy removal without damage to the implant or further trauma to the recipient.
• the actual frequency of operation or impact repetition and the specific hammer masses involved will depend upon individual requirements.
• a separate instrument may be required for large intramedullary rods in comparison to ingrowth femoral stems. Specifically, large Sampson rods will probably require relatively larger hammer masses and lower operating frequencies. To break free ingrowth femoral stems, relatively small hammer masses and high operating frequencies will probably .be required.
• the instrument described below is, in the illustrated embodiment, pneumatically operated. However, the instrument is formed of a sealed enclosure, specifically to prevent the escape of exhausted air, thereby permitting use of the instrument in a sterile surgical field.
• Fig. 1 schematically illustrates the invention as applicable to the manipulation of a rod within a femoral bone
• Fig, 2 illustrates the general shape or waveform of a force pulses used in accordance with the present invention (such as to extract the implanted rod of Fig. 1);
• Fig. 3 schematically illustrates the invention as applicable to the removal of an ingrowth stem
• Fig. 4 illustrates the general shape or waveform of a second type of force pulse used in accordance with the present invention, particularly to extract a surgical implant having a microporous surface;
• Figs. 5A and 5B schematically outline, in cross-section, an instrument for practicing the invention;
• Fig. 6 is a cross-sectional diagrammatic illustration of a pneumatically powered instrument for practicing the invention.
• Fig. 7 is an expanded view of the control valving of the instrument of Fig. 6.
• a femoral bone 10 which is fractured on a jagged line 12 is being fitted with a rod 14.
• Fig. 2 shows a force pulse 16, which has a steep leading edge 16' this pulse represents a force applied at the end 15 of the rod which sticks out of the bone.
• the pulse 16 is applied to the end 15 of the rod 14, in the direction of the arrow 18, parallel to the long dimension of the rod and the bone, by means of a mass fixed to that end 15. The mass is accelerated quickly, as represented by the steep rise of the leading edge of the pulse 16, so as to overcome friction between the rod and bone.
• Each, pulse moves the rod a short increment into the bone (or out of the bone if a removal operation is being performed.
• the steepness of the leading edge and the amplitude of the pulse that is reached at the top of the leading edge are measures of the acceleration of, and final velocity, reached by the mass which is operating on the rod.
• the frequency of the pulses determines the total energy expended in moving the rod within the bone.
• the energy per pulse is maintained at a level that will not shatter the bone but will move the rod incrementally within the bone, and the frequency of the pulses establishes the number of increments of motion that will be effected per unit of time.
• the preferred operating frequency range of the instrument is in the sonic region from about 100 Hz to about 5 kHz. The surgeon thus has control over the size of his "hammer blows" and the frequency of them without having to rely on his own “touch " or skill in handling a hammer which impacts the end 15 in a manner that can hardly be predicted.
• Fig. 3 shows a portion of an ingrowth implant stem 20 which has a surface 22 on the kind sometimes known as "microporous". Surrounding the micrcporous surface 22 is mass of multiple trabeculae 24 grown into the stem 20 to provide fixations in a recipient bone 26. To remove the stem 20 from the bone 26 without damaging the bone, the present invention teaches a method of breaking the trabeculae close to the stem. Preferably this is done with oscillatory energy pulses having the general shape of the pulse 23 of Fig 4.
• the first half 32 of this pulse is similar to the pulse 16 described above with reference to Fig. 2. This half of the pulse has a steep leading edge 32 which is effective to accelerate the stem 20 in the direction of a larger arrow 34, for removal from the bone.
• the secondhalf 36 of the pulse 23 represents a back-swing applied to the stem 20, and preferably has a smaller amplitude than the first half, as is represented by the smaller arrow 38 opposite to the larger arrow 34.
• a pulse of energy having approximately the shape indicated in Fig. 4 is effective to exert strongpulling pulse force on the stem 20 and a smaller reverse force pulse after each pulling pulse. This acts to force the trabeculae to oscillate back and forth around their respective points of attachment to the stem, while at the same time the net force per pulse is a pulling force in the direction of the larger arrow 34.
• the steepness of the rise of the leading edge 32' and the amplitude of the first half 32 will again measure the energy per pulse as well as acceleration applied to the stem 20.
• the frequency of the pulses will again determine the total energy applied to the stem 20; but, in this embodiment since the second, reverse half 36 of the pulse will contribute a force which forces the trabeculae to oscillate around attachment points, the pulse frequency will also measure the frequency of oscillation, which weakens the trabeculae near the stem 20, and hastens the break-down of the mass of trabeculae between the bone 26 and the stem.
• the invention provides, for the first time, a way to remove ingrowth stems from recipient bone with little or no danger of damaging the recipient bone.
• FIG. 5A is an outline illustration of an instrument that is suitable for practicing the invention.
• a housing 50 preferably of hand-gun shape, has a main body 52 enclosing a force pulse generator 54 and a handle 56.
• a cap screw 58 having one end 60 threaded and a cap 62 at the other end fits through the main body via holes 64, 66, to engage a threaded hole 68 in an adapter 70 which in use is fixed to an article to which energy pulses are to be applied.
• the front or nose end 72 of the main body has a hard, smooth surface on which the adapter 70 is tightly drawn by the bolt 58.
• the adapter 70 that is illustrated represents one of several adapters that will be needed for fixation to the different shapes and sizes of prosthetic devices, implants, rods and other devices that will make use of the invention.
• the two nuts 74 areindicative of the case where the adapter 70 is made in two parts between which an article, such as rod 14, may be clamped when the end 15 protrudes from the bone 10.
• the adapter may hold an end of a screw that has been screwed into or onto the end 15 of the rod, or into or onto another form of implant, rod, bolt or the like.
• the adapter 70 provides fixation to the article towhich energy pulses are to be applied.
• the bolt 58 holds the adapter 70 tightly to the housing 50, so that the entire instrument is fixed to the article to which energy pulses are to be applied.
• the force pulse generator can take any form. Owing, to the ubiquitous presence of air or gas-driven instruments in the operating rooms of hospitals at the present time, it is presently preferred that an air or gas-driven pulse generator be used. However, electrical, electromagnetic, electromechanical and other forms of pulse generators can be used.
• the pulse generator is fixed within the main housing body 52, and includes a mass W, here shown as annular in form, to which force pulses are applied.
• the mass W applies small hammer blows to the main housing body in the direction of the arrow 55 so as to apply the desired force pulses directly to the housing in directions parallel to the longitudinal axis of the bolt 58, when the latter is present in the main body 52.
• the mass W can be driven by pulses of air or other gas, controlled by programmed valving (not shown) .
• the block 54' is intended to represent an alternative source of force pulses, that can be substituted in the main body 52 for the block 54.
• this block 54' contains an electrical generator 80 for producing pulses 28 in electrical form, a mass W' to be accelerated, a tubular electrical conductor 84 having the mass W surrounding it, and a coil 86 around the conductor connected to the generator 86 so as to be furnished with current (pulses) according to the pulse 28.
• the mass W' will be accelerated in one direction by electrical repulsion so as to apply small hammer blows to the main housing body 52 under control of the pulses 28.
• the handle 56 has a fitting 90 for a source of driving gas, electricity, or whatever motive source is used, a trigger 92 for turning the instrument on and off, and a control 93 representing controls for adjusting the amplitude and frequency of the pulses 28. In some instances it may be desirable to control only pulse amplitude from the control 93, and to regulate pulse frequency with the trigger 92.
• composite means and includes bone-cement interfaces, bone derivatives with cement interfaces, bone or bone-derivative interfaces with metal, and synthetic bone analogues with cement or metal interfaces.
• bone structure shall include both bones and composite structures.
• Fig. 6 depicts a detailed embodiment of a practical air-driven extraction instrument for surgical use, in accordance with the present invention. Like the instrument of Fig. 5, the instrument 100 is made in a hand-gun shape.
• the first piece is an end cap 102; the second piece is a housing member 104 having a barrel portion 106 and a handle grip 108 depending therefrom; and the third member is long, hardened steel insert 110 which runs the length of the tool.
• the space between the interior of the barrel wall 106 and the insert 110 forms an elongated cylinder.
• a sliding piston 112 is disposed in the cylinder.
• housing member 104 The front end of housing member 104 is provided with an internally threaded recess 114 to provide a point of attachment for extracting adapters. Individual adapters can be threaded therein for securing to specific components to be inserted or removed.
• Steel insert 110 has a small shoulder 115 at the right end thereof and housing 104 is provided with a matching recess for receiving this shoulder, proximate the recess threaded 114. This arrangement centers insert 110 within the housing. At the opposite end of the instrument, insert 110 spreads to a flanged shoulder 118 which is designed to bear against the end of the barrel 106 of housing 104, as shown at mating interface 120. The end of the barrel proximate mating surface 120 is externally threaded. End cap 102 has a mating internal thread for threaded attachment to barrel 106. The interior surface of end cap 102 and the exterior surface of the rear end of insert 110 are shaped to conform to each other.
• insert 110 is preferably formed with a recessed shape in region 122, which serves as an anvil to accept impacts from the end face 124 of piston 112, as described below; for this reason, insert 110 may also be referred to as an "anvil member".
• Handle portion 108 of housing 104 has a coaxial air coupling device 130, various internal passages (the details and roles of which will be explained below), a valving mechanism 140 and a trigger 150.
• the trigger and valving mechanisms direct pressurized air from the coupling device 130 into the cylinder 202 to force the piston 112 to fly against the end of the cylinder, imparting an impact thereon, which impact is transmitted to the component attached at threaded recess 114.
• the trigger mechanism 150 and valving 140 are shown in an expanded view in Fig. 7.
• Figs. 6 and 7 operation of the instrument will now be explained.
• Pressurized air is supplied to inlet passage 162 from coupling 130.
• the inlet air enters a cavity 164 at port 166.
• Cavity 164 comprises the main volume of a control valve assembly 140, Cavity 164 is actually a cylindrical bore.
• the pressurized air entering port 166 is obstructed from passage into valve cavity 164 by a sliding valve member 168 of a shape conforming in a cross-section to the shape of the cavity 164.
• the valve member 168 is balanced by a first spring 172 and a second spring 174.
• Spring 172 rests between the left, or rear, end of cavity 164 and valve member 168.
• Spring 174 rests between the opposite side of valve member 168 and an interior shoulder, or flange, 182 of a trigger piece 180. It maintains sufficient pressure on valve component 168 to obstruct the air flow from port 166 when member 168 is in its neutral, or resting, position.
• Spring 174 rests in a substantially zero compression position.
• trigger piece 180 When trigger piece 180 is depressed by the operator's finger, the spring 174 comes under compression, sliding towards the rear of the valve cavity or chamber 164, eventually overcoming the load provided by spring 172 behind body 168. This pushes body 168 sufficiently away from port 166 to allow air to enter cavity 164.
• the overall excursion of the trigger piece 180 is limited by the length of the trigger shaft 184 which is outside the housing flange 186 when the trigger is in its rest position.
• An O-ring seal 190 is provided between the shaft 184 of the trigger piece and the housing aperture through which it passes, to prevent escape of pressurized air.
• piston 112 As the front (i.e., right-hand) end of the main cylinder 202 is pressurized, piston 112 is forced to the rear of the instrument, allowing an impact against the portion 122 of the recessed region of element 110. As the piston 112 slides back, along the cylinder wall, the first phase of cylinder is dumped, or relieved, through port 210. As the air exits through port 210, it passes through channel 212 and, upon reaching branch point 214, a portion cf the exiting air flow is directed through port 216 into control valve chamber 198, to counterbalance the force on poppet 194 and thereby limit air delivery to the main cylinders, to a degree.
• the bulk of the residual exhausted air passes beyond branch point 214 into channel 218, past branch point 220 and out the exhaust port of coupling device 130 via channels 222 and 224.
• a small amount of the exhaust pressurized air is directed at branch point (i.e., port) 220) into cavity 164 via a small relief port 226 on the left-hand side of valve member 168.
• Port 230 communicates through various channels with the main exhaust channel 224.
• the pressure generated in the rear part of the cylinder 202 will also interact with the exhaust gas having vented through port 210 to further balance the delivery of air through the chambers 164 and 198 (which may now be referred as primary and secondary control chambers, respectively).
• the piston then impacts against the rear recess (i.e., anvil portion) 122 of member 110. This drives the tool in a reverse direction with one applied stroke, The piston next will recoil, both from accumulated air pressure and from an impact on the anvil surface of insert 110. It will cycle back to the front of the instrument and again be driven back by a pulse of air exiting from port 204.
• additional valving and ports may be provided to facilitate the backward motion of the piston following its impact with the anvil surface.
• the frequency of operation and the actual reverse applied force are. determined by the pressure and volume of air delivered through the control chambers. A balance of valve and spring functions determine the frequency and force applied.
• the piston 112 can exist in different weights and sizes to additionally change the applied force through the effect of mass acceleration.
• the entire instrument is a sealed enclosure, specifically preventing the escape of exhausted air so as to permit use in a surgical field.

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• Health & Medical Sciences (AREA)
• Orthopedic Medicine & Surgery (AREA)
• Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Transplantation (AREA)
• General Health & Medical Sciences (AREA)
• Public Health (AREA)
• Biomedical Technology (AREA)
• Heart & Thoracic Surgery (AREA)
• Veterinary Medicine (AREA)
• Animal Behavior & Ethology (AREA)
• Surgery (AREA)
• Cardiology (AREA)
• Physical Education & Sports Medicine (AREA)
• Oral & Maxillofacial Surgery (AREA)
• Vascular Medicine (AREA)
• Mechanical Engineering (AREA)
• Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
• Medical Informatics (AREA)
• Molecular Biology (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Prostheses (AREA)
• Dental Prosthetics (AREA)

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• 1987
  • 1987-09-28 WO PCT/US1987/002496 patent/WO1988002246A2/en not_active Application Discontinuation
  • 1987-09-28 EP EP87906885A patent/EP0287614A1/de not_active Ceased

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