Bone cement removal device for orthopedics

Abstract

An ultrasonic vibrating surgical instrument (1, 21) for removing bone adhesive in revision joint replacement surgery includes an elongated solid shaft (2, 5, 6, 7, 8; 22, 25, 26, 27, 28). At its proximal end (3; 23), it can be mounted to an ultrasonic vibration source so that the shaft (2, 5, 6, 7, 8; 22, 25, 26, 27, 28) serves as a waveguide for propagating ultrasonic vibrations. At its distal end, the shaft (2, 5, 6, 7, 8; 22, 25, 26, 27, 28) has an operating head (9, 29) that can act on the bone adhesive. The middle portion (6, 26) of the elongated shaft (2, 5, 6, 7, 8; 22, 25, 26, 27, 28) is provided with at least one row (10) of recesses (11) extending spirally along and around the portion (6, 26) of the elongated shaft (2, 5, 6, 7, 8; 22, 25, 26, 27, 28). Each recess (11) is separate from each adjacent recess (11). The recesses (11) may have a shallow spherical cap profile.

Description

Technical Field

[0001] This invention relates to surgical instruments for removing surgical bone adhesive during orthopedic implant revision (revision joint replacement). More specifically, but not limited thereto, it relates to ultrasonic vibrating instruments for removing surgical bone adhesive associated with orthopedic implants from the bone cavity, particularly ultrasonic vibrating instruments for removing surgical bone adhesive associated with orthopedic implants from the bone cavity after implant removal. The invention also relates to a method for revising joint replacement or similar surgeries using such instruments. Background Technology

[0002] Orthopedic implants, such as hip replacements, are typically secured by at least one implant component with a slender, tapered shaft extending into the cavity of an adjacent hollow bone, such as the femur in the hip joint. Sometimes, this shaft is secured by cancellous bone that grows from the bone wall. However, surgical bone adhesives based on poly(methyl methacrylate) (PMMA) are more frequently used for anchoring implants.

[0003] These implants can last up to 20 years. However, nowadays, recipients of orthopedic implants typically live beyond 20 years after surgery. With increased life expectancy, the probability of implant failure also increases, necessitating revision surgery. "Failure" can include metal failure of the implant itself or localized failure of the bone adhesive holding it in place, leading to loosening. During revision surgery, the implant or any fragments thereof are first removed from the bone cavity, followed by the removal of any remaining bone adhesive. Not only large pieces of bone adhesive, but any visible trace of residual bone adhesive must be removed. Only then is implantation with new bone adhesive permitted, as residual bone adhesive can lead to poor adhesion or become a source of defects that propagate bone adhesive failure.

[0004] The initial surgical method for removing residual hardened PMMA bone adhesive is to chisel it out of the bone cavity. This is a slow, inefficient, and tiring process for the surgeon, often taking several hours to complete. The chisel always carries the risk of damaging the bone near the adhesive, especially in older patients with brittle bones. This lengthy procedure under general anesthesia also presents a significant risk to the patient.

[0005] A significant step forward was taken when it was discovered that the application of ultrasonic vibration devices could cause PMMA bone adhesive to soften rapidly, even flow, making it easier to remove. This procedure could even be performed with less invasive methods, such as laparoscopy. The resulting shorter procedure not only benefits the surgeon but also reduces the risks associated with prolonged anesthesia. Examples of such tools are disclosed, for instance, in European Patent No. EP0599950.

[0006] This method has been widely used since its introduction in the 1990s, but there is always a need for improvement for such major surgical procedures. For example, some early ultrasonic vibrating instruments could still cause localized bone damage if activated when the distal tip of the device was aligned with the bone.

[0007] Meanwhile, significant efforts have been made to explore the effects of different ultrasonic vibration modes. Traditionally, longitudinal vibration modes have been used because they are the easiest to generate. However, in the field of soft tissue surgery, torsional mode ultrasonic vibration devices have been found to have a significant advantage over longitudinal mode ultrasonic vibration devices. These surgical instruments used for soft tissue cutting and cauterization are useless in joint replacement surgery, but they have led to advancements in torsional mode ultrasonic vibration technology, which is speculated to have potential benefits in orthopedic surgery as well.

[0008] One particular problem with the initial ultrasonic vibrating instruments used in revision joint replacement surgery was that the softened bone adhesive could easily harden again before collection, escaping removal, or the softened bone adhesive could harden again after collection, making it difficult to adhere to the instrument itself, becoming hard to remove, and potentially even impairing the instrument's function. Summary of the Invention

[0009] Therefore, the objective of this invention is to provide an improved ultrasonic vibration surgical instrument to avoid the disadvantages of existing tools in orthopedic surgery, such as in the removal of bone adhesive in revision joint replacement surgery, thereby allowing for faster and easier removal of surgical bone adhesive residue in hollow bone.

[0010] According to a first aspect of the invention, an ultrasonic vibration surgical instrument suitable for removing bone adhesive in revision joint replacement surgery is provided, comprising an elongated solid shaft structure proximally mountable to an ultrasonic vibration source to serve as a waveguide for propagating the ultrasonic vibration, and having an operating head disposed near the distal end of the shaft structure suitable for acting on the bone adhesive, wherein a portion of the elongated shaft structure between the proximal and distal ends is provided with at least one row of recessed structures extending helically along and around said portion of the elongated shaft structure, each recessed structure being spaced apart from each adjacent recessed structure.

[0011] Preferably, the depth to which each of the recessed structures extends into the shaft structure is less than half the maximum width of the recessed structure.

[0012] Advantageously, the depth to which each of the recessed structures extends into the shaft structure is less than one-quarter of the maximum width.

[0013] Each of the recessed structures may include a pit structure formed on the surface of an elongated solid shaft structure.

[0014] Preferably, each of the recessed structures is identical to each of the other recessed structures.

[0015] Preferably, each recessed structure includes a circular depression.

[0016] Advantageously, each circular depression has the profile of a spherical notch.

[0017] Each of the circular recesses may have a shallower spherical profile than a hemispherical one.

[0018] Alternatively, each indentation can have a roughly cylindrical shape.

[0019] The bottom of each of the generally cylindrical recesses may have a slightly concave profile.

[0020] Preferably, the extension length of the at least one column of recessed structures or each row of the at least one column of recessed structures is less than the total length of the portion of the slender shaft structure.

[0021] Advantageously, the extension length of the at least one column of recessed structures or each row of the at least one column of recessed structures is greater than half the total length of the portion.

[0022] The extension length of the at least one column of recessed structures or each column of the at least one column of recessed structures is less than three-quarters of the total length of the portion.

[0023] Optionally, the extension length of the at least one column of recessed structures or each column of the at least one column of recessed structures is approximately two-thirds of the total length of the portion.

[0024] Preferably, there are at least two columns of the recessed structures.

[0025] Advantageously, the concave structure in each column is substantially the same as the concave structure in the other columns.

[0026] Each of the aforementioned recessed structures may be spaced apart from each adjacent recessed structure in the same column, with the spacing being less than one-fifth, and optionally less than one-tenth, of the maximum diameter of each of the aforementioned recessed structures.

[0027] Each row of the at least two columns of recessed structures may be spaced from each adjacent column by at least twice the maximum diameter of the recessed structure, optionally at least three times the maximum diameter, and preferably about four times the maximum diameter.

[0028] Preferably, the slender solid shaft structure of the tool includes at least one truncated tapered gain section.

[0029] Advantageously, the tool's slender solid shaft structure includes two of the aforementioned truncated tapered gain sections.

[0030] Ideally, the gain section, or each gain section, tapers towards the distal end of the slender solid shaft structure.

[0031] Preferably, the elongated solid shaft structure includes at least one generally cylindrical element.

[0032] Advantageously, the slender solid shaft structure includes at least two of the generally cylindrical elements.

[0033] Ideally, the slender solid shaft structure includes more generally cylindrical elements than the truncated tapered gain section.

[0034] The tapered, tapered gain section and the generally cylindrical section are preferably arranged alternately along the slender axis.

[0035] The portion of the slender shaft structure having one or more rows of recessed structures preferably includes the generally cylindrical element or one of them.

[0036] Then, a truncated tapered gain section can be set at both the far end and the near end of the portion.

[0037] Preferably, each of the truncated tapered gain segments and each generally cylindrical element extends coaxially along a common longitudinal axis.

[0038] In a first preferred embodiment, the tool's operating head includes a first operating head adapted to pierce hardened surgical bone adhesive when subjected to ultrasonic vibration.

[0039] The first operating head is preferably suitable for operation that pushes the material into the bone adhesive at the distal end.

[0040] Preferably, the first operating head includes a generally tapered body extending coaxially from the distal end of an elongated shaft structure, the apex of which includes the distal end of the operating head.

[0041] Advantageously, the first operating head is provided with a plurality of channel structures extending from its distal end through its proximal end.

[0042] The channel structure may include cylindrical holes or passages extending parallel to the longitudinal axis of the tool and the operating head.

[0043] Alternatively, the channel structure may include elongated grooves extending parallel to the longitudinal axis of the tool and the operating head, each groove extending through a peripheral portion of the operating head to intersect the widest circumference of the tapered body.

[0044] Therefore, the channel structure provides a pathway for the bone adhesive, which is contacted and softened by the first operating head vibrating with ultrasound, to flow through the operating head to its proximal face for collection.

[0045] The channel structure can extend proximally beyond the furthest point where the operating head enters the slender shaft structure, thereby forming a further groove extending proximally along the slender shaft structure.

[0046] The further grooves can then guide the softened bone adhesive to move further along the elongated axial structure to reduce the accumulation of bone adhesive near the operating head.

[0047] The distal end of the cone-shaped body should ideally be shaped.

[0048] This avoids damage to the distal bone when the operating head is activated by ultrasound.

[0049] In a second preferred embodiment, the tool's operating head includes a second operating head adapted to collect softened surgical bone adhesive during ultrasonic vibration.

[0050] The second operating head is preferably suitable for operations that pull the bone adhesive proximally back.

[0051] Preferably, the second operating head includes a generally disc-shaped body that is coaxially positioned to the distal end of the elongated shaft structure and extends radially therefrom at right angles to the longitudinal axis of the tool.

[0052] Advantageously, the disc-shaped body has multiple elongated radial grooves on its near-end face.

[0053] The radial groove may have a partially cylindrical profile.

[0054] Therefore, the softened bone adhesive that comes into contact with the proximal surface of the second operating head can be guided toward the elongated shaft structure and collected around it.

[0055] Preferably, the distal surface of the disc-shaped body comprises a generally flat disc.

[0056] Advantageously, the circumferential annular portion of the disc-shaped body can have a truncated conical profile, tapering slightly from its proximal edge to its distal edge.

[0057] Then, an inclined annular portion may extend between the distal edge of the circumferential portion and the circumferential surface of the distal disk.

[0058] Then, the outermost end of each elongated radial groove on the proximal end face of the disc-shaped body can intersect with the widest edge of the proximal end of the circumferential portion, creating a fan-shaped profile around the proximal edge.

[0059] Alternatively, some or all of the elongated radial grooves may extend from the farthest end of the elongated axial structure toward the proximal end.

[0060] According to a second aspect of the invention, a method for removing surgical bone adhesive from a bone cavity is provided, comprising, after removing a damaged implant from the cavity, the steps of: providing a surgical instrument according to a first aspect of the invention, applying the operating head of the surgical instrument to the solid surgical bone adhesive within the cavity, and subjecting the operating head to ultrasonic vibration in a mixed torsion / longitudinal mode to soften the bone adhesive for subsequent removal.

[0061] According to a first embodiment of this second aspect, the surgical instrument includes a surgical instrument according to a first embodiment of the first aspect of the invention, which causes the operating head to vibrate ultrasonically by contacting the bone adhesive with the distal surface of the operating head, and pushes the operating head distally through the bone adhesive as the bone adhesive softens.

[0062] According to a second embodiment of this second aspect, the surgical instrument includes a surgical instrument according to a second embodiment of the first aspect of the invention, which causes the surgical head to vibrate ultrasonically by contacting the peripheral portion of the proximal face of the surgical head with the bone adhesive, and pulls the surgical head proximally through the softened or softened bone adhesive. Attached Figure Description

[0063] Embodiments of the invention will now be described in more detail by way of examples and with reference to the illustrations in the accompanying drawings, wherein:

[0064] Figure 1A This is a side view of the first tool embodying the present invention, which has a puncture operation head;

[0065] Figure 1B yes Figure 1A A partial isometric view of the puncture head of the tool;

[0066] Figure 1C yes Figure 1B A partial side view of the puncture head;

[0067] Figure 1D yes Figure 1B Distal view of the puncture head;

[0068] Figure 2A This is a side view illustrating the second tool of the present invention, which has a scraping operating head;

[0069] Figure 2B yes Figure 2AA partial isometric view of the scraping head of the tool;

[0070] Figure 2C yes Figure 2B A partial side view of the scraping head;

[0071] Figure 2D yes Figure 2B A remote view of the scraping head;

[0072] Figure 3A yes Figure 1A tools or Figure 2A A partial side view of the slender cylindrical intermediate transition section of the tool; and

[0073] Figure 3B yes Figure 3A A schematic side view of the recess in the middle transition section of the slender column, showing details of its geometry. Detailed Implementation

[0074] Now please look at the picture, and especially Figure 1A The diagram illustrates a first puncture probe 1 embodying the present invention. The puncture probe 1 is formed from a single solid titanium sheet. It has an elongated shape and (unless otherwise noted) is columnar symmetrical about a longitudinal axis extending between its proximal and distal ends.

[0075] The slender proximal end 2 of the puncture probe 1 is generally cylindrical, having a proximal shoulder near its proximal end from which a threaded connector 3 extends. Through this connector, the puncture probe 1 is operatively mounted to a longitudinal mode ultrasonic vibration source, such as a transducer stack, typically via a conversion / amplification boom, as known in the art (not shown). A pair of opposing wrench planes 4 are provided near the proximal shoulder to facilitate tightening the threaded connector 3, for example, by fixing it to a mating threaded socket at the distal end of the angle.

[0076] At the distal end of the proximal end 2, a coaxial, elongated, truncated cone-shaped first conical gain section 5 extends, the function of which will be described below.

[0077] From the distal end of this first conical gain section 5, a slender cylindrical intermediate transition section 6 of the puncture probe 1, which is also coaxially aligned, extends.

[0078] At the distal end of this intermediate conversion section 6, a coaxially aligned, elongated, truncated, second conical gain section 7 extends out, and at the distal end of this second conical gain section 7, a once again coaxially aligned, elongated cylindrical distal end 8 of the puncture probe 1 extends out.

[0079] At the distal end 8 of the puncture probe 1, a puncture head 9 is established. The puncture head 9 is approximately conical and coaxially aligned with the rest of the puncture probe 1. (Refer to the following text.) Figures 1B to 1DDescribe the detailed structure of the puncture head 9.

[0080] When the proximal threaded connector 3 of the puncture probe 1 is connected to the ultrasonic vibration source and then activated, the proximal end 2, the middle part 6 and the distal end 8 of the puncture probe 1, together with the first tapered gain part 5 and the second tapered gain part 7 connecting them, thus act as a slender waveguide to propagate the ultrasonic vibration to the puncture head 9 located at the distal end.

[0081] The tapered gain sections 5 and 7 are used to amplify these ultrasonic vibrations. The resulting gain is inversely proportional to the reduction in cross-sectional area from one side to the other of each gain section 5 and 7 (in other words, the gain is inversely proportional to the reduction in diameter with a square relationship). This allows high-amplitude ultrasonic vibrations to be transmitted to the puncture head 9 without requiring excessive signal intensity from the ultrasonic vibration source. The special arrangement shown also allows the relatively thin distal section 8 and the operating head 9 to be combined with the robust proximal section 2 for fixation to the vibration source.

[0082] However, another feature of the puncture probe 1 is the presence of two rows of adjacent, spirally extending shallow pits 11 that extend along and surround the central transition portion 6 of the puncture probe 1. These pits 11 have a recessed, disc-shaped profile that corresponds to the shallow portion of the sphere.

[0083] The function of the spirally extending array of recesses 11 is to convert the longitudinal mode of ultrasound transmitted from the proximal end of the puncture probe 1 into a torsional mode of ultrasound vibration. The specific arrangement shown converts 20% of the vibration energy into the torsional mode. Therefore, the mixed-mode ultrasound vibration is transmitted to the second conical gain section 7, the distal section 8, and then to the puncture head 9, with the ratio of the longitudinal to torsional sections being 4:1.

[0084] Currently, it is believed that the degree of transition from the longitudinal mode to the torsional mode may depend on the depth of the pits 11, their relative diameters, their spacing from adjacent pits 11 in the same column 10, the length of these columns 10 relative to the intermediate transition section 6, and the spacing between these columns 10, although there may be other factors that have not yet been determined. It is believed that variations in these parameters could allow the probe to be designed to select the degree of transition from the longitudinal mode to the torsional mode.

[0085] The advantages of the combined longitudinal / torsional vibration mode when applied to the puncture head 9 will be described below.

[0086] Reference Figure 1B , Figure 1C and Figure 1DThe puncture head 9 is shown in more detail. The puncture head 9 includes a straight-edged cone 12 with a radially radiating distal apex 13 and a short cylindrical segment 14 extending distally from the wider proximal end of the cone 12. In this case, the cone 12 is approximately an equilateral triangle in cross-section (see...). Figure 1C Its maximum width is at least 50% larger than the diameter of the distal portion 8 of the waveguide. Other embodiments of the puncture probe (not shown) generally have the same cone 12 proportions, but the overall dimensions of the cone 12 are different.

[0087] In this embodiment, five cylindrical holes 15 are drilled from the inclined distal end face of the cone 12 to the flat proximal end face of the short cylindrical segment 14 of the head 9. Each hole has a hole parallel to the connecting longitudinal axis of waveguides 2, 5, 6, 7, 8 and the cone 12. These holes 15 are arranged equidistantly around the head 9. Figure 1D The best illustration is shown in the diagram. The hole 15 also extends to the proximal end of the puncture head 9, forming a short longitudinal groove 16 in the distal end 8 of waveguides 2, 5, 6, 7, and 8.

[0088] Each hole 15 is slightly flared where it appears from the inclined distal surface of the cone 12. A first bevel 17 extends from the inner edge, distal edge of each hole 15, causing the hole 15 to taper inward toward the distal end 13 of the cone 12. A second bevel 18 extends from the outer edge, proximal edge of each hole 15, thus causing these bevels 17, 18 to flare the distal end of each originally cylindrical hole 15 into a funnel shape.

[0089] Other sizes of puncture heads 9 have a different number of such holes 15, all of which still extend longitudinally, passing exactly through the cone 12 and the proximal end section 14. The smallest size of puncture head 9 has grooves with a partially cylindrical cross-section, which are machined to extend longitudinally through the circumferential region of the cone 12 and the proximal end section 14 (in fact, these grooves include cylindrical holes 15 with a diameter large enough to break through the circumference of the cone 12 and the proximal end section 14; they may also still have a first bevel 17 extending from the inner edge of the distal end of each groove).

[0090] The manipulation of the puncture head 9 is considered to be performed as follows: Longitudinal mode ultrasonic vibrations are applied to the proximal end of the probe 1 and partially converted to a torsional mode in the middle portion 6 of the probe 1. The cone 12 of the puncture head 9 contacts the solid bone adhesive within the bone cavity, and these ultrasonic vibrations are transmitted into the bone adhesive, softening it and allowing the puncture head 9 to be driven distally for further penetration into the bone adhesive. Because the puncture head 9 vibrates both longitudinally and torsionally simultaneously, the ultrasonic vibration energy is effectively transmitted into the bone adhesive. The lower proportion of longitudinal mode in the vibration means that for a given vibration energy, the effective longitudinal displacement is lower than that for conventional instruments, and therefore, the risk of damaging the bone wall by projecting the vibration distally into the bone is reduced. Simultaneously, the torsional mode portion is effectively transmitted into the adjacent bone adhesive, rather than being transmitted from the head 9 to a considerably distant location.

[0091] When the vibrating puncture head 9 is pushed into the softened bone adhesive, the adhesive is guided by surfaces 17 and 18 into the longitudinally extending orifice 15 passing through the puncture head 9. Thus, the softened bone adhesive reaches the proximal face of the puncture head 9 and the longitudinal groove 16 of the distal portion 8 of waveguides 2, 5, 6, 7, and 8. It has been found that using a certain proportion of torsional mode vibration alters the flow of the softened bone adhesive through the puncture head 9 and along the proximal end of the distal portion 8. As a result, when the bone adhesive begins to re-coagulate, the "sheath" it forms around the distal portion 8 is more compact than the sheath present only with longitudinal mode vibration. This makes cleaning this re-hardened bone adhesive from the puncture probe 1 between uses much easier than with current probes, which present significant inconvenience in cleaning re-coagulated bone adhesive from the head and shaft of conventional probes.

[0092] The puncture tip 9 is primarily used to puncture and break up large amounts of hardened bone adhesive at the distal end of the implant site, including puncturing and breaking up plugs made of bone adhesive used to block the distal end of the bone cavity.

[0093] Once large pieces of bone adhesive have been broken up with the puncture probe 9, it is generally found more effective to remove residual bone adhesive with an ultrasonic vibrating scraping probe. This is done by moving the probe's operating head to the distal end of the bone adhesive and retracting the ultrasonic vibrating probe through the adhesive, softening, scraping, and digging up the softened bone adhesive. This allows for the removal of any remaining large pieces of bone adhesive near the gap left by the puncture probe 1 and allows residual bone adhesive to be scraped off the bone wall.

[0094] Figure 2A The second scraping probe 21, embodying the invention, is shown for this step of the procedure. Like the puncture probe 1, the scraping probe 21 is also made of a single solid titanium sheet and, except where mentioned below, has an elongated shape with cylindrical symmetry about its longitudinal axis.

[0095] The scraping probe 21 has a similar main structure to the puncture probe 1, but with different proportions. Therefore, it has an elongated proximal portion 22, which is generally cylindrical, with a threaded connector 23 extending from its proximal end through which the probe 21 can be operatively mounted onto a conventional form of transducer stack, such as a conversion / amplification boom (not shown) in the prior art. Near the proximal shoulder of the proximal end 22, a pair of opposing wrench planes 24 are provided, corresponding to the wrench planes 4 of the puncture probe 1.

[0096] A first tapered gain portion 25, coaxially aligned and elongated, extends from the distal end of the proximal portion 22, and an elongated cylindrical intermediate transition portion 26 extends coaxially from the distal end of the first tapered gain portion 25. A second elongated tapered gain portion 27 extends coaxially from the distal end of the intermediate portion 26, and the elongated cylindrical distal portion 28 of the scraping probe 21 extends coaxially from the distal end of the second tapered gain portion 27. Similar to the puncture probe 1, the proximal end 22, the first tapered gain portion 25, the intermediate portion 26, the second tapered gain portion 27, and the distal portion 28 of the scraping probe 21 extend coaxially along the longitudinal axis of the probe 21.

[0097] At the distal end of the distal portion 28, a generally disc-shaped scraper head 29 is provided, which is also coaxially aligned with the rest of the scraper probe 21. The structure and function of the scraper head 29 will be described in reference to... Figures 2B to 2D As described below.

[0098] Therefore, when the proximal threaded connector 23 is connected to the ultrasonic vibration source and activated, the proximal portion 22, the middle portion 26, and the distal portion 28 of the probe 21, together with the first tapered gain section 25 and the second tapered gain section 27, act as waveguides to transmit ultrasonic vibrations to the scraping head 29. The functions of the tapered gain sections 25 and 27 are the same as those of the corresponding tapered gain sections 5 and 7 of the puncture probe 1.

[0099] In addition, with Figure 1A The puncture probe 1 is the same. Figure 2A The scraping probe 21 has two rows of 10 adjacent shallow recesses 11 extending in a spiral pattern, along and around its central conversion portion 26. These rows of 10 recesses 11 also serve to convert the longitudinal mode ultrasonic vibration portion into a torsional mode ultrasonic vibration. The arrangement shown produces approximately 20% conversion, thereby allowing mixed-mode ultrasonic vibration to propagate to the scraping head 29, which also has a 4:1 ratio of longitudinal and torsional mode portions.

[0100] Now for reference Figure 2B , Figure 2C and Figure 2DThe scraper head 29 is shown in more detail. The head 29 is generally disc-shaped. The distal surface 30 of the head 29 includes a flat disc orthogonally aligned with the longitudinal axis of the probe 21. The periphery of the scraper head 29 includes a narrow tapered region 32 that tapers distally and widens proximally, connecting to the distal disc 30 via an annular radial region 31, effectively blending the contours of the disc 30 with the contours of the tapered region 32. The proximal surface 33 of the scraper head 29 is provided with a series of radially extending grooves (not visible in these figures) that extend outward from the distal portion 28 of the probe 21, passing through the periphery of the tapered region 32 of the scraper head 29, thereby forming a series of fan-shaped sections 34 around the periphery of the scraper head 29.

[0101] These recessed grooves on the proximal face 33 serve to concentrate ultrasonic vibrations onto the bone adhesive in contact with the proximal face 33, especially when using mixed-mode ultrasonic vibrations with a torsional section. Thus, as the scraper head 29 is pulled proximally through the hardened bone adhesive, the bone adhesive softens rapidly upon approaching and contacting the proximal face 33 where the ultrasonic vibrations are occurring.

[0102] The grooves also help guide the softened bone adhesive away from the proximal face 33 and to the distal portion 28 of the probe 21. Similarly, under vibration in the presence of a torsional mode, the softened bone adhesive re-coagulates in the "sleeve" surrounding the distal portion 28, and is found to be more loosely anchored in place compared to vibration using a purely longitudinal mode, thus making it easier to remove from the scraping probe 21 between uses.

[0103] Therefore, this scraping probe 21 can be used to remove and clean residual bone adhesive in the second stage of the bone adhesive removal procedure, which is faster and more effective than existing longitudinal vibration devices.

[0104] Figure 3A and Figure 3B The differences between the recess 11 of the spiral string or spiral array 10 in the tool of the present invention and the known spiral string recess in the known system that punctures the hollow waveguide wall, the latter generating the complete conversion of longitudinal mode ultrasonic vibrations from the conventional Langevin transducer input to the proximal end of the tool, generating torsional mode ultrasonic vibrations at the distal end of the tool's operation.

[0105] For various reasons, such a vibration, which is entirely converted to torsional mode, has been found to be unsatisfactory in use. As mentioned above, it has been found that converting a portion of the input longitudinal mode vibration to torsional mode improves overall performance when removing PMMA bone adhesive during revision joint replacement surgery.

[0106] It has been found that the torsional stiffness of the elongated cylindrical probes 1, 21 can be appropriately modified by forming a spiral string 10 with shallow depressions / pits 11 having a ball-cap profile, which are formed by cutting into the cylindrical surface of the elongated cylindrical portions 6, 26 of the instruments 1, 21 using a bulbous cutter. When these shallow pits 11 are used to replace deep penetration holes, they can be conveniently configured to convert a desired proportion of the longitudinal mode displacement input from the proximal end of the instruments 1, 21 into a torsional mode displacement in the respective distal effectors 9, 29. Significant improvements in the performance of probes 1, 21 have been observed when a longitudinal / torsional (L / T) ratio as high as 4 / 1 is generated at the output / effector 9, 29 of the puncture probe 1 or scraping probe 21.

[0107] Refer to again Figure 3A and Figure 3B This illustrates the relationship between system parameters that affect the conversion amplitude. In summary:

[0108] (i) R = radius of the bulbous cutter 41 used to create the pit 11

[0109] (ii) P = the probe shafts 6 and 26 cut into by the recess 11 of the spiral string 10.

[0110] (iii) h = depth of the pit

[0111] (iv) A = Distance from the center of the tool 41 to the line of intersection between the recess 11 and the cylindrical probe surface (v) d = Diameter of the recess at the intersection with the cylindrical probe surface

[0112] (vi)D = Diameter of probe shaft P

[0113] (vii)a = Angle between the line of intersection of the radius of the tool 41 and the diameter of the pit

[0114] (viii) S = half the spiral length of the string 10 of the pit 11 located on the outer surface of the probe P.

[0115] (ix)L = the linear projection of pit 11 string 10 along the surface of probe P, parallel to the axis of the slender cylindrical probe P.

[0116] (x)C = Waveguide / Probe P cycles = πD / 2

[0117] The following equation links the above variables, allowing for explicit control over the characteristics of pit 11:

[0118] (1) A = Rh

[0119] (2) sinα=d / 2R

[0120] (3) S = [L 2 +(Dπ / 2) 2] 1 / 2

[0121] exist Figure 3A In the particular embodiment shown, there are two overlapping helical strings 10 with recesses 11 aligned at opposite points around the probe circumference, each extending 360° around the cylindrical surface of the probe.

[0122] The diameter D of probe P is 7.6 mm.

[0123] The minimum distance between radially opposite pits (shown as Dl) = 6.91 mm

[0124] The depth of the pit, h = (D - D1) / 2 = 0.345 mm

[0125] The ball of the cutting tool has a diameter of 6.0 mm and a radius R of 3.0 mm.

[0126] use Figure 3A / Figure 3B The geometry of the pit shown allows for the determination of pit features, namely:

[0127] A = Rh = 2.655 mm

[0128] cosα=A / R=0.885

[0129] a = 27.75°

[0130] sinα=0.4656

[0131] d = sin ax 2R = 2.8mm

[0132] d / 2 = 1.4 mm

[0133] C = πD / 2 = 11.94 mm

[0134] S = [L 2 +C 2 ] 1 / 2 Therefore, S = 19.14 mm and L is 15 mm here. These values ​​allow for seven complete pits in half of the probe, with a total overlap of 0.139.

Claims

1. An ultrasonic vibratory surgical instrument suitable for removing bone adhesive in revision joint replacement surgery, comprising an elongated solid shaft structure, the proximal end of which is mountable to an ultrasonic vibration source as a waveguide for propagating ultrasonic vibrations, and having an operating head located near the distal end of the shaft structure suitable for acting on bone adhesive, wherein a portion of the elongated solid shaft structure between the proximal and distal ends is provided with at least one row of recessed structures formed in the surface of the elongated solid shaft structure and extending helically along and around said portion of the elongated solid shaft structure, each recessed structure being spaced apart from each adjacent recessed structure.

2. The ultrasonic vibration surgical instrument according to claim 1, wherein the depth to which each recess structure extends into the elongated solid shaft structure is less than half the maximum width of the recess structure.

3. The ultrasonic vibration surgical instrument according to claim 1 or claim 2, wherein the depth of each recess structure extending into the elongated solid shaft structure is less than one-quarter of the maximum width of the recess structure.

4. The ultrasonic vibration surgical instrument according to claim 1, wherein each recess structure is identical to each of the other recess structures.

5. The ultrasonic vibration surgical instrument according to claim 1, wherein each recess structure comprises a circular recess.

6. The ultrasonic vibration surgical instrument according to claim 5, wherein each circular recess has a spherical notch profile.

7. The ultrasonic vibration surgical instrument according to claim 1, wherein the extension length of the at least one row of recessed structures or the extension length of each row of the at least one row of recessed structures is less than the total length of the portion of the slender solid shaft structure.

8. The ultrasonic vibration surgical instrument according to claim 1, wherein the extension length of the at least one row of recessed structures or the extension length of each row of the at least one row of recessed structures is greater than half the total length of the portion.

9. The ultrasonic vibration surgical instrument according to claim 1, wherein at least two rows of the aforementioned recessed structures are provided.

10. The ultrasonic vibration surgical instrument according to claim 9, wherein each row of recessed structures is identical to the other rows of recessed structures.

11. The ultrasonic vibration surgical instrument according to claim 1, wherein the elongated solid shaft structure of the instrument includes at least one truncated conical tapered gain section.

12. The ultrasonic vibration surgical instrument according to claim 1, wherein the elongated solid shaft structure comprises at least one cylindrical element.

13. The ultrasonic vibration surgical instrument of claim 1, wherein the operating head of the instrument includes a first operating head adapted to puncture hardened surgical bone adhesive when subjected to ultrasonic vibration.

14. The ultrasonic vibration surgical instrument of claim 13, wherein the first operating head comprises a tapered body extending coaxially from the distal end of the elongated solid shaft structure, the apex of the tapered body comprising the distal end of the operating head.

15. The ultrasonic vibration surgical instrument according to claim 13 or claim 14, wherein the first operating head is provided with a plurality of channel structures extending from its distal end through its proximal end.

16. The ultrasonic vibration surgical instrument of claim 1, wherein the operating head of the instrument includes a second operating head adapted to collect softened surgical bone adhesive during ultrasonic vibration.

17. The ultrasonic vibration surgical instrument of claim 16, wherein the second operating head comprises a disc-shaped body coaxially located at the distal end of the elongated solid shaft structure and extending radially therefrom at right angles to the longitudinal axis of the instrument.

18. The ultrasonic vibration surgical instrument according to claim 17, wherein the disc-shaped body has a plurality of elongated radial grooves on its proximal end face.

Images