WO1988002246A2

WO1988002246A2 - Method and apparatus for extraction and insertion of embedded articles including bone-related devices

Info

Publication number: WO1988002246A2
Application number: PCT/US1987/002496
Authority: WO
Inventors: Charles A. Dicecca; Frederick G. Heller
Original assignee: Dicecca Charles A; Heller Frederick G
Priority date: 1986-09-26
Filing date: 1987-09-28
Publication date: 1988-04-07
Also published as: WO1988002246A3; EP0287614A1

Abstract

Method and means to remove, implant, attach and otherwise fit or adjust bone-related articles such as surgical implants, rods, nails, prosthetic and similar devices, dental restorations, and the like, without destruction of or damage to the recipient bone or composite, using a series or train of force pulses to move the article incrementally with relation to the recipient bone or composite. The waveshape of the force pulses is designed, in some cases, to oscillate the article relative to the recipient bone structure, to produce microfractures at the interface between the article and the bone or composite. A hand-held pneumatic tool is shown for providing the force pulses. The tool and method may be used for non-surgical applications such as to remove construction nails, plastic shafts, bearing races and other objects.

Description

METHOD AND APPARATUS FOR EXTRACTION AND INSERTION OF EMBEDDED ARTICLES INCLUDING BONE-RELATED DEVICES

Field of the Invention

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.

Background of the Invention

Some specific examples of applications of the invention, as it concerns removal of bone-related devices, are:

1. Removal of collar-type smooth femoral stems with fixed heads. 2. Removal of collarless-type femoral stems with trunion necks.

3. Removal of fenestrated Moore prostheses, Moore-relazed designs and Thompson femoral stems.

4. Removal of current design femoral stems with threaded holes in the greater trochanteric region.

5. Removal of broken distal stem section in cases of failed longitudinal stem implants.

6. Removal of stuck or previously placed Sampson rods, Kuchner rods or Hansen street nails.

7. Removal of ingrown distal femoral rotal knee components.

8. Removal of distal femoral total knee components fixed with cement.

9. Removal of acetabular components provided with central threaded attachment holes.

10. Removal of blade plate and femoral osteotomy devices. As it concerns installation or removal of an article into or from a larger body, 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. In cases where 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. Yet, in the present state of the medical art, 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.

Similar problems are presented to the implantation and removal of grouted or cemented components. One device and method for dissolving cemented bonds is shown in U.S. Patent No. 4,248,232 to Engelbrecht et al. That method uses a vibrating ultrasonic tool to soften plastic bone cement. Often, some excavation work will still be required around the implant, to remove the cement so as to free the implant. The Engelbrecht et al device does not control the force applied (as it does not apply extractive or insertive force) and does not reduce the potential for overstressing the implant component.

While the use of tools to facilitate surgical implantation and removal of bone-related devices is a recognized objective, fulfillment of this objective is complicated by the restrictions imposed by operating-room protocols. For example, to maintain the integrity of the surgical field, fluid may not leak from a pneumatic or hydraulic tool. This greatly complicates the design of a reciprocating device, such as an insertion/removal tool.

General Nature of the Invention

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. To remove smooth-surfaced devices which are held in place frictionally, the invention applies a force to slide the device from the host. To remove devices with microporous surfaces, the invention produces microfractures to release the implant/host interface. To implant a device, the invention imparts a force to facilitate insertion.

According to the invention in one of its aspects, as it concerns the removal of an implant, for example, 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. In particular, in the case of an ingrowth stem, 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 (for removal, at least) 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.

In the case of implants, porous or smooth, imbedded in cement, the reverse-directed impacts create a release of the implanted component as described above. For smooth objects, the frictional or tight appositional interface (between the implant and bone) is overcome by the reverse impacts above. In the case of cement interdigitation with the surface of a porous implant, the cement itself is fractured or broken. 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.

Brief Description of the Drawing:

The invention will be further explained with reference to certain embodiments illustrated in the accompanying drawings, in which:

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; and

Fig. 7 is an expanded view of the control valving of the instrument of Fig. 6.

Detailed Description:

In Fig. 1 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. As will be explained with reference to Figures 5A, 5B and 6, 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. According to the invention, 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.

For removal of the rod 14 from the bone 10, present-day techniques have provided only means to effect a steady pulling force, which must be increased until friction between the rod and the bone is ovecome, if at all, in one big jump. If the bone cannot withstand the ever-increasing pulling force, it may shatter before the retaining friction is overcome. This is not overcome with the aforementioned invention of Patent No. 4,248,232, though that invention may reduce the needed extraction force in some circumstances. With the present invention, the pulses 16 are applied in the reverse direction from that shown by arrow 18, thorugh a fixture fixed on the end 15, enabling the surgeon to ease the rod 14 out of the bone in small increments, without risk of damaging the bone.

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. In another case, 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. In all cases, 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. In any case, 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) .

I.i Fig. 5B, 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. In block-diagram form, 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. With this arrangement, 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.

While the illustrated embodiments of the invention have been described with reference to a recipient bone, the invention is applicable to bone or composite structures, as has been mentioned earlier in this specification. The term "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. Hereafter the term "bone structure" shall include both bones and composite structures.

In the design of instruments for practicing the invention, it is preferred to provide high-energy pulses and a low mass (W or W' for example). While the mass does reciprocate, the return motion will produce very little impact, so tnat the instrument can be made to be substantially recoilless. With the invention, a surgeon can ease an implant, rod or nail, for example, into or out of a recipient bone or composite in small controlled increments, applying only steady pressure or traction; friction in either direction is easily overcome, with no need to risk shattering or otherwise damaging the recipient bone or composite. 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. It has a three-piece body. 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.

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. The shoulder 118 of 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. By reference to Figs. 6 and 7 together, operation of the instrument will now be explained. In this explanation, the instrument has been adapted for extraction of surgical implants. With a change of inlet and exhaust valving, the same arrangement can be used for driving an implant into place. 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. 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.

Once the air has entered the finger-controlled chamber 164, pressure builds up at port 192 against the face of poppet 194. Poppet 194 is urged to obstruct or close port 192 by a spring 196 which bears against the opposite wall of a control valve chamber 198. When the pressure is sufficient to move the poppet 194 from port 192, pressurized air enters control valve chamber 198. Poppet 194 and port 192 does comprise a needle valve assembly. The pressurized air exits control valve chamber 198 via port 200 and connected passages, finally exiting into the main cylinder 202 at port 204. Poppet 194 and control valve chamber 198 regulate the air flow into main cylinder 202 in a manner described below.

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.

As the piston 112 continues its excursion toward the back of the instrument, the pressure will build up "in front" of the piston as it slides toward the rear of the instrument. This accumulated pressure, which would otherwise resist the acceleration of the sliding piston, is vented and relieved through port 230. 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. Optionally, additional valving and ports may be provided to facilitate the backward motion of the piston following its impact with the anvil surface. With the pressure in the rear of the chamber 202 essentially falling off to zero, there is no balance of pressures at either the primary or secondary control chambers 164 and 19B. This allows both valves to deliver a sharp pulse of air to the high pressure side of the piston 112 through port 204. The process repeats itself over and over again, creating a source of a train of reverse-driven impulses for extraction.

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.

Claims

1. A method for removing a bone-related article from a recipient bone structure, comprising the steps of attaching to the article a mating fixture to secure fixation of said fixture to said article, applying to said fixture with a hand-held tool a train of force pulses in the sonic range, which pulses exert force substantially only in a prescribed direction parallel to the direction of removal, and adjusting the pulse frequency and amplitude so as to effect incremental removal of said bone-related article without bringing about any substantial damage to the recipient bone.

2. The method of claim 1, wherein the bone-related article is an ingrowth implant stem and wherein the pulse amplitude and frequency are adjusted so as to incrementally break trabeculae close to the stem, whereby the stem is removed from the recipient bone structure with a minimum of bone mass attached to it.

3. The method of claim 1 wherein the force pulses are oscillatory, having a larger amplitude in the direction of article removal and a smaller amplitude in the opposite direction, for providing an oscillatory relation between said article and said recipient bone structure during the process of removal.

4. The method of claim 3, in which said pulses have a steep leading edge in the direction of removal so as to bring about larger acceleration of said article in said direction than in the opposite direction, with relation to the recipient bone structure.

5. The method of any of claims 1-4 wherein therepetition rate of said pulses is in the range from about 100 Hz to about 5 kHz.

6. In combination, a prosthetic device installed in or on a living bone structure to which a surface of said prosthetic device is bonded, and removal means for breaking the bond between said prosthetic device surface and said bone structure by applying asuccession of farce pulses substantially only in a direction parallel to the direction of removal, to remove the device substantially without damage to said bone.

7. The combination of claim 6 wherein the removalmeans further comprises means for applying to said prosthetic device force pulses oscillating in a path along which it is desired to remove said device, which path is substantially parallel to said surface, said pulses having a larger component of force in the direction of removal than in the opposite direction.

8. The combination of claim 7 wherein the removal means is adapted to provide rapid acceleration of said prosthetic device in the direction of removal.

9. The combination of claim 7 wherein the means for applying force pulses includes a fixture affixed to said prosthetic device and drive means connected to the fixture to transmit force pulses therefrom to said fixture.

10. The combination of claim 9 wherein said drive means is pneumatically-powered.

10. The combination of any of claims 6-10 wherein the repetition rate of said pulses is in the range from about 100 Hz to about 5 kHz.

12. In combination, a bone-related article, a force pulse generator and means to apply force pulses from the force pulse generator to manipulate the article relative to a recipient living bone structure, for removing said article from said bone structure incrementally with a series of force pulses so as to effect said removal substantially without damage to said recipient bone structure.

13. A hand-held tool for use in the removal from a recipient bone structure of a bone-related article, comprising a fixture adapted for fixation to said article, a tool body, means to fix said fixture removably to said tool body, and pulse generating means for applying to the tool body a series of force pulses having a major component of force in the direction of removing said article with respect to said bone structure.

14. A tool according to claim 13 wherein the tool body encloses said pulse generating means.

15. A tool according to claim 13 including means for regulating at least one of the amplitude and frequency of said pulses.

16. A tool according to claim 13 in which said force pulses are shaped so as to accelerate the combined mass of said tool and said fixture more rapidly inthe direction of removal than in the reverse direction.

17. A tool according to claim 13 in which each force pulse has a steep leading edge.

18. A tool according to claim 17 in which each pulse has a first half-cycle including said steep leading edge, followed by a half-cycle in the reverse- direction.

19. A tool according to any of claims 13-18 wherein the generator means is adapted to supply pulses at a repetition rate in the range from about 100 Hz to about 5 kHz.

20. A method for implanting a bone-related article in a recipient bone structure, comprising at least the steps of attaching to the article a mating fixture to secure fixation of said fixture to said article, applying to said fixture with a hand-held tool force pulses in the sonic range, said pulses exerting force on the article substantially only in a prescribed direction parallel to the direction of implantation, and adjusting the pulse frequency and amplitude so as to effect incremental implantation of said bone-related article without bringing about any substantial damage to the recipient bone.

21. In combination, a prosthetic device for installation in or on a living bone structure to which a surface of said prosthetic device is to be bonded, and hand-held implantation means for implanting said prosthetic device in said bone structure by applying to said device a succession of force pulses substantially only in a direction parallel to the direction of implantation.

22. The combination of claim 21 wherein the implantation means is adapted to provide rapid acceleration of said prosthetic device in the direction of implantation.

23. The combination of claim 22 wherein the means for applying force pulses includes a fixture affixed to said prosthetic device and drive means connected to the fixture to transmit force pulses therefrom to said fixture.

24. The combination of claim 23 wherein said drive means is pneumatically-powered.

25. In combination, a bone-related article, a force pulse generator and means to apply force pulses from the force pulse generator to manipulate the article relative to a recipient living bone structure, for implanting said article in said bone structure incrementally with a series of force pulses.

26. A hand-held tool for use in the implantation in a recipient bone structure of a bone-related article, comprising a fixture adapted for fixation to said article a tool body, means to fix saidfixture removably to said tool body, and pulse generating means for applying to the tool body a series of force pulses having a major component of force in the direction of implanting said article with respect to said bone structure.

27. A tool according to claim 26 wherein the tool body encloses said pulse generating means.

28. A tool according to claim 26 including means for regulating at least one of the amplitude and frequency of said pulses.

29. A method for removing an implanted article from a recipient structure, comprising the steps of attaching to the article a mating fixture to secure fixation of said fixture to said article, applying to said fixture with a hand-held tool a train of force pulses in the sonic range, which pulses exert force substantially only in a prescribed direction parallel to the direction of removal, and adjusting the pulse frequency and amplitude so as to effect incremental removal of said article without bringing about any substantial damage to the recipient structure.

30. The method of claim 29 wherein the force pulses are oscillatory, having a larger amplitude in the direction of article removal and a smaller amplitude in the opposite direction, for providing an oscillatory relation between said article and said recipient structure during the process of removal.

31. The method of claim 30, in which said pulses have a steep leading edge in the direction of removal so as to bring about larger acceleration of said article in said direction than in the opposite direction, with relation to the recipient structure.

32. The method of any of claims 29-31 wherein the repetition rate of said pulses is in the range from about 100 Hz to about 5 kHz.

33. A hand-held tool for use in the removal from a recipient structure of an article, comprising a fixture adapted for fixation to said article, a tool body, means to fix said fixture removably to said tool body, and pulse generating means for applying to the tool body a series of force pulses having a major component of force in the direction of removing said article with respect to said structure.

34. A tool according to claim 33 wherein the tool body encloses said pulse generating means.

35. A tool according to claim 33 including means for regulating at least one of the amplitude and frequency of said pulses. 36. A tool according to claim 33 in which said forcepulses are shaped so as to accelerate the combined mass of said tool and said fixture more rapidly in the direction of removal than in the reverse direction. 37. A tool according to claim 33 in which each force pulse has a steep leading edge.

38. A tool according to claim 37 in which each pulse has a first half-cycle including said steep leading edge, followed by a half-cycle in the reverse- direction.

39. A tool according to any of claims 33-38 wherein the generator means is adapted to supply pulses at a repetition rate in the range from about 100 Hz to about 5 kHz.

40. A tool for use in removing an article embedded or implanted in a recipient structure, comprising: a. a housing defining an elongated barrel internal thereto; b. an anvil member closing one end of the barrel, secured to the housing; c. a sliding piston disposed in the barrel; d. means for fixing the housing directly or indirectly to the article; e. means for accelerating the piston within the barrel to cause the piston to strike the anvil member, the force of the impact being transmitted via the housing to the article.

41. The tool of claim 1 wherein the means for accelerating the piston comprises a valve assembly for selectively admitting into the barrel chamber a pressurized fluid.

42. The tool of claim 40 or claim 41 wherein the means of accelerating the piston comprises means for causing the piston to impact the anvil member at a repetitive rate.

43. The tool of claim 42 wherein said rate is in the range from about 100 to 5,000 times per second.