ES3001585T3 - Device for punching bone - Google Patents

Abstract

The invention falls within the field of medical technology. It relates in particular to a sonotrode suitable for use with an ultrasonic surgical instrument. The invention also relates to an ultrasonic surgical instrument for cutting or drilling bones, comprising such a sonotrode, as well as to a method for manufacturing the sonotrode of the invention. (Automatic translation with Google Translate, no legal value)

Description

DESCRIPTION

Bone punching device

Field of the invention

The invention relates to a device for puncturing or perforating hard tissue such as bone. It relates in particular to a sonotrode suitable for use with an ultrasonic surgical instrument.

Background of the invention

Among cutting devices for cutting bone tissue, ultrasonic instruments are particularly effective. The present invention relates to a surgical instrument for extracting bone, with a shaft extending longitudinally and a sonotrode at its distal end, which has a distal end piece equipped as a piercing end or a blade for penetrating bone using mechanical vibration.

Surgical punches are used, for example, in autologous chondrocyte transplantation (ACT); see DGU Mitteilungen und Nachrichten 45/2002 1, "ACI und Tissue Engineering" under the auspices of the DGU and DGOOC. A laminectomy or laminotomy is a surgical procedure that uses bone punches to remove a portion of the vertebral bone called the lamina, which is the roof of the spinal canal. Punches of this type, also called KERRISON bone punches, are sold by Aesculap®, Tuttlingen, Germany. However, they do not use oscillation to cut the bone.

Another area of application for a bone punch can be in arthroscopic treatments. Over time, arthroscopy has become one of the most popular orthopedic surgery techniques, making it possible to perform even very complex surgeries without opening a joint. Arthroscopic surgeries are widely supported by constantly improving medical devices and instruments. Modern medicine allows the use of arthroscopy not only for larger joints, such as a knee or shoulder, but it is also successfully used for small joints such as a wrist or ankle. A small incision is made for the introduction of a camera and thus a view of the joint and the device. Additional small incisions at different points around the joint allow the surgeon to insert surgical tools to grasp, cut, grind, and provide suction as needed for joint repair. Common blades for arthroscopic surgery consist of an outer hollow sheath and an inner hollow rotating cannula with corresponding windows for suction and cutting. A coating that acts as a lubricant should prevent and reduce the release of metal debris when these rotating blades are used against a hard surface. A known complication is heat injury to surrounding structures. The risk is greater with reuse practices, because dull blades increase the risk of heat injury and infection. Therefore, most modern instruments are single-use only.

Document WO 2013/057179 discloses a sonotrode for a surgical instrument. The sonotrode head serves as a cutting device that extends in a longitudinal direction. These sonotrodes have a flat blade body with a longitudinal cutting edge.

Document WO 2008/131884 relates to a punching device for preparing a cavity in a bone. The punching device has a punching tool that is an elongated member with a thin-walled portion having a non-rotational symmetrical cross-section.

US 2015/0182232 A1 discloses an ultrasonic bone cutting instrument comprising a lumen or channel for irrigating a surgical site or for suctioning out debris.

EP 1987784 B1 relates to implants to be inserted into a bone, adapted for use as a punching tool, and to a method for preparing a cavity in the bone. In this case, the sonotrode is coupled to a punching tool having a thin-walled portion that serves as an implant. No sonotrodes are known for an ultrasonic surgical instrument that are hollow or have a distal cutting edge corresponding to the contour of a tissue area to be punched and that are suitable for punching areas of bone tissue.

Bone punches, on the one hand, must be equipped to cut through very dense and strong cortical bone tissue, and do so at different angles (due to different access situations). On the other hand, cutting devices must be able to cut deeply, for example, into cancellous bone tissue.

Summary of the invention

Claim 1 defines the invention and the dependent claims disclose the embodiments. No surgical methods are claimed. An object of the present invention is to provide an improved sonotrode for an ultrasonic surgical instrument suitable for punching tissue areas, as well as an ultrasonic surgical instrument therefor, comprising an improved sonotrode and methods for manufacturing these sonotrodes. One objective that improved sonotrodes should achieve is improved cutting performance for cortical bone. Cortical bone is dense and compact. In this way, it has been conceived to reduce the heat produced during bone cutting. Furthermore, it would be advantageous to be able to use a sonotrode having a distal cutting edge corresponding to the contour of a tissue area to be punched. This can be a hollow blade or a sonotrode with a long, curved cutting edge. A problem for such sonotrodes are bending movements, such as out-of-plane oscillations, which should be avoided. At the same time, a thicker blade of the sonotrode should be avoided.

According to the invention, there is provided a sonotrode with the features of claim 1. The following disclosure describes embodiments that help to understand the invention.

A first aspect of the disclosure relates to a sonotrode for an ultrasonic surgical instrument suitable for punching out areas of bone tissue, the sonotrode having a head and a distal end piece, the distal end piece being equipped as a piercing end for penetrating bones using mechanical vibration. The cutting edge of the punch may be located in a plane perpendicular to the longitudinal axis of the tool holder. Alternatively, the distal end portion of the piercing end may be cut obliquely. Thus, the cutting edge of the punch is located in a plane forming an angle with the longitudinal axis of the tool, the angle being chosen such that the difference between the maximum and minimum blade length is less than 10% of the length of the resonator (the effective length of the vibrating portion). Said difference between the maximum and minimum blade length should be so small that no relevant difference in amplitude is obtained.

In many embodiments, therefore, the sonotrode has the shape of a tube (round or non-round in cross-section, forming a hollow sonotrode) toward its distal end, with the distal edge of the tube forming a cutting edge for piercing tissue. The distal cutting edge may, in particular, form a closed contour.

The cut can also have a parabolic shape.

An oblique cut at the distal end of the sonotrode is a preferred embodiment for sonotrodes used to penetrate the cortex of a bone. The oblique cut is also suitable for methods involving bone punching using only a portion of a hollow sonotrode's cutting edge. This method can be used to achieve predetermined geometries within the bone. Therefore, the sonotrodes are suitable as resection blades and as full-radius resectors.

The term "proximal," as used herein, refers to the point closest to the point of coupling to the housing of an ultrasonic surgical instrument or, respectively, to the user of that instrument. The term "distal," as used herein, refers to being located away from the point of coupling to the housing of an ultrasonic surgical instrument or, respectively, to the user of that instrument. The distal edge is used for punching or cutting bone. Thus, the distal end and the proximal end are opposite ends. An alternative formulation of the above embodiment is as follows: a sonotrode for an ultrasonic surgical instrument, wherein the sonotrode has a head and a distal end piece, the distal end piece being equipped as a punch or blade with a distal edge suitable for bone punching. The distal end piece of the sonotrode according to the first aspect can be forced through a bone or into a bone to create a hole. This means that using the sonotrode, a closed curve/contour can be cut or drilled in a bone. Cutting this curve requires only one cut or cutting step.

An embodiment of the first aspect relates to a sonotrode, wherein the distal end piece comprises a blade with a distal cutting edge that corresponds (fully) to the contour of an area of tissue to be punched.

In embodiments, the sonotrode comprises a head and a distal end piece having a longitudinal axis, wherein the distal end piece is a puncture device for penetrating bone. The distal end piece or piercing tool is disposed on said sonotrode head, said piercing tool being an awl or a hollow blade. The head and distal end piece should be oriented such that they have a common longitudinal central axis.

Another embodiment of the first aspect relates to a sonotrode, wherein the distal end piece or blade is designed as a hollow body that is open at its distal end. Thus, in the embodiments, the hollow body is not rotationally symmetrical. The hollow body may have the shape of a hollow cylinder, where the cross-section of the cylinder is a closed curve. The cross-section may be rounded, oval, elliptical, or polygonal. A preferred embodiment relates to a sonotrode, wherein the hollow body is a hollow elliptical cylinder, in particular, a hollow elliptical cylinder being open at its distal end.

The term "oval shape" or "oval," as used herein, refers to a two-dimensional shape that resembles an egg or an ellipse. It also refers to a figure that resembles two semicircles joined by a rectangle. Differentiable, non-self-intersecting, convex, closed plane curves are ovals.

To cut deeply into the bone, the sonotrode must be longer. But the longer the sonotrode, the greater the risk of torsional movement. The inventors discovered that a sonotrode with at least two ribs, such as reinforcing ribs, prevents torsional bending and buckling. The ribs can be located on any of the different sides (i.e., they can face inward and/or outward) and can be arranged symmetrically, in fact axisymmetrically, to the central axis.

In embodiments, the distal end piece or blade is designed as a body having at least one hollow distal portion, wherein the distal end (front end) is open and forms a cutting edge. According to another embodiment, the sonotrode body may be configured as a hollow body (preferably a hollow cylinder) over approximately 80% of its longitudinal extension and preferably over at least the distal half of its longitudinal extension. An alternative embodiment relates to a sonotrode that is solid but has a hollow distal end piece. In this case, the distal end piece may represent only up to 10 percent or even up to 5 percent of the sonotrode's length.

A sonotrode according to the first aspect may have a stop. The stop may be provided on the distal end piece or the proximal head of the sonotrode, or both. By providing a stop that limits longitudinal movement to a minimum, it is possible to avoid cutting into the underlying tissue that is not to be punched.

Another embodiment of the first aspect relates to a sonotrode, wherein the sonotrode has at least one longitudinal rib. In this context, a longitudinal rib is a rib that extends along a blade-like portion of the sonotrode, for example, along a tube portion if the distal end is tube-like. Here, the longitudinal rib extends along a generally longitudinal direction, meaning that it is not perpendicular to the longitudinal axis, but is, for example, parallel thereto or at a preferably small angle (less than 45°, less than 30°, or less than 20°) so that it provides rigidity to the sonotrode or at least its blade-like portion with respect to bending forces away from the axis or to torsional forces. If the blade-like portion is bent (i.e., different from the plane, which is the case in many embodiments, especially, as will be evident, if the blade-like portion is tubular), said reinforcing rib may be arranged on an inner and/or outer side. Because said rib protrudes from a (local) blade plane, it is also referred to as a "lateral rib" in the present text.

Such a rib may extend along a substantial length of the sonotrode, for example, along at least 50% of its blade-like portion (i.e., along at least 50% of the axial length of the portion in which the sonotrode is flat and thin, for example, in the manner of a tube). It may extend to its distal end or it may narrow toward the distal end.

Particularly if the blade-like portion of the sonotrode (e.g., hollow, i.e., a tubular sonotrode) is comparably long, it may be advantageous if the center of mass line coincides with the longitudinal axis (i.e., in a section perpendicular to the longitudinal axis, the center of mass/center of gravity lies on the longitudinal axis). For this purpose, the blade-like portion may have a plurality of ribs, which are arranged symmetrically with respect to the longitudinal axis.

In embodiments having a more complicated sonotrode geometry, for example, having a cross-section as illustrated in Figure 7 described below, with a plurality of center of gravity lines, these may be symmetrical with respect to a central longitudinal axis. The arrangement of the ribs will be chosen accordingly, for example, having mirror symmetry. More generally, the sonotrode may be designed to have, in section perpendicular to the longitudinal axis, a mirror symmetry or an n-fold symmetry.

In view of this, in particular, in embodiments, the sonotrode has at least two lateral ribs extending along a longitudinal axis of the sonotrode. These ribs may also be referred to as reinforcing or stiffening ribs. An embodiment of the first aspect relates to a sonotrode, wherein the sonotrode has at least one lateral rib within the hollow distal end piece or the blade and a second lateral rib outside the hollow distal end piece or the blade. Another embodiment of said aspect relates to a sonotrode, wherein the sonotrode or, respectively, the distal end piece of the sonotrode has at least two lateral ribs on each side. Alternatively, the sonotrode may have two lateral ribs located outside the hollow distal end piece or blade or two lateral ribs located within the hollow distal end piece or blade. The sonotrode may also have four lateral ribs located outside the hollow distal end piece or blade and/or four lateral ribs located inside the hollow distal end piece or blade. Each rib or ridge may be radially vertical at a constant height above the blade or distal end piece. It is further preferred that two ribs be located so that they project from the same point on the circumference, with one rising inside and the other outside the hollow distal end piece or blade. In general, it is preferred that the ribs be arranged symmetrically. The ribs may be located at the points where the minor and major axes of an elliptical or oval cross-section intersect the circumference of the hollow distal end piece.

The ribs are present along the length of the sonotrode and/or, respectively, the distal end piece having a hollow longitudinal shape, for example, coupling to a body thereof. It is preferred that the at least two ribs extend along the central axis of the sonotrode. It has been found to be advantageous for the at least two ribs to extend along the head and the distal end piece. However, the at least two ribs may extend only along the distal end piece of the sonotrode. The ribs are preferably solid. The ribs may have a semicircular or angular cross-section. The ribs may be continuous. They may have a height and/or a width of 0.05 mm to 0.5 mm. In other words, the height and/or width of the ribs is between 20-100% or even better between 25-80% of the blade width. By adjusting the height of the ribs, the resonant frequency can be adjusted. Resonance can be shifted in a way that differs from the operating frequency. Therefore, the operating frequency under load can vary over a larger range (while maintaining axial vibration).

It is preferred that the ribs not have sharp edges and that the transition from the ribs to the distal end piece or blade be smooth. Therefore, it is preferred that the transition between the ribs and the surface of the distal end piece/blade be continuous or curved.

Another embodiment relates to a sonotrode, wherein the at least two ribs have a flattened distal end. The proximal end may also be flattened. In this case, the flattening at the proximal end may be more pronounced than at the distal end. The ribs of the sonotrode should not be the same length as the sonotrode or the distal end piece of the sonotrode. One embodiment relates to a sonotrode, wherein the ribs run solely along the distal end piece of the sonotrode. Another preferred embodiment relates to a sonotrode, wherein the distal end of the at least two ribs is located in the middle third of the length of the distal end piece or blade.

The extension of the distal end piece in the longitudinal direction may be between 10 mm and 80 mm, preferably between 15 mm and 30 mm. The largest diameter of the distal end piece may be, for example, between 3 mm and 20 mm, preferably between 5 mm and 10 mm. The sonotrode including the blade may have a length of 20 to 300 mm, preferably 150 to 250 mm.

A sonotrode according to the first aspect is particularly suitable for axial work. It allows for cutting or abrading the corners or foramina of bones. A preferred use is cutting osteophytes to achieve spinal decompression.

The blade extension of a sonotrode according to the first aspect in the longitudinal direction may be, for example, between 15 mm and 50 mm, preferably between 18 mm and 30 mm. The maximum blade extension in the transverse direction may be, for example, between 3 mm and 35 mm. The extension in the transverse direction is regularly smaller than the extension in the longitudinal direction. The depth perpendicular to the longitudinal direction and the transverse direction may likewise be between 1 mm and 30 mm. The sonotrode may have a length of 20 to 300 mm, preferably 50 to 250 mm and more preferably 100 to 200 mm.

The sonotrode can be connected to an ultrasound transducer of a surgical instrument. The instrument can be provided with a supply line through which a liquid can be supplied to the sonotrode. Additionally, or alternatively, the supply line can be designed such that a liquid is directed along the sonotrode on the outside and/or inside.

The sonotrode may further comprise a sleeve with a window that allows only a portion of the distal end of the sonotrode to protrude from the sleeve. The sleeve may be located around the sonotrode and may be connected to the housing or handle of the ultrasonic instrument. It is preferred that the sonotrode be symmetrically coupled within the sleeve. The sleeve may have a window at the distal end such that only a portion of the sonotrode protrudes from the sleeve and, preferably, only a portion of the cross-section of the distal portion protrudes. This portion may be used to punch bone. The sleeve may further be arranged so that it can be rotated around the sonotrode. In embodiments, the angular position of the sleeve relative to the sonotrode body may be adjusted using a scale or may be determined using a scale. The scale may be coupled to the housing. By rotating it, it is possible to utilize different portions of the distal cutting edge of the sonotrode, wherein the other portions are protected. This allows bone to be cut using different parts of the sonotrode while simultaneously protecting other parts that cannot be used, so that no damage is caused within the surrounding tissue by the unused parts of the sonotrode. The sleeve window can be shaped to protect at least half of the sonotrode cross-section at the distal end of the sonotrode. The sleeve cross-section can be round or can be adapted to the sonotrode cross-section. This means that the cross-section can have the same shape as the sonotrode cross-section, but can be slightly larger.

There are several possibilities for disposing of the removed bone fragments when drilling or punching the bone. One possibility is to impact the cut dense bone core into the underlying trabecular bone, which is compacted so that bleeding can be impaired. The fragments can further be aspirated or removed by special devices. Using the devices according to the present invention, the bone can alternatively be removed as a bone core or fragment and not as debris. This bone core can remain within the distal end of the sonotrode. The bone core can then be withdrawn outward and rinsed away from the operating side along with blood, etc., or it can be further aspirated into a space in the sonotrode and stored until the device of the invention is removed from the operating side. In this case, the sonotrode can be a disposable item that is removed from the device and discarded after each surgery along with the removed bone. This makes laborious cleaning of the device redundant. There are no bone debris that could obstruct a fluid supply or suction device and need to be removed.

In all embodiments of the disclosure comprising extracting bone tissue, the bone tissue may optionally be used for diagnostic purposes or, depending on where it was extracted and its condition, also for therapeutic purposes.

In special embodiments, the sonotrode further comprises at least one inner blade arranged inside a hollow body of the sonotrode. This at least one blade allows the bone portion to be broken (cut) into fragments to make it easier to remove. In a subset of these special embodiments, a plurality of inner blades can be arranged in a tiered arrangement. In this way, the required energy input can be distributed over time when a particularly hard bone portion (e.g., cortical bone tissue) is to be cut into smaller fragments.

An object is to provide a device suitable for reducing blockage by bone debris within the instrument. In a corresponding device, the sonotrode or housing comprises a vacuum suitable for storing removed bone fragments. Another embodiment relates to a device, wherein the sonotrode and/or housing comprises a line suitable for supplying liquid to the distal cutting edge or for applying a vacuum to the sonotrode. Using the liquid supply, it is possible to extract the bone core from the sonotrode, and the vacuum is suitable to support the retention of the bone core within the opening.

Specific elements may be located within the sonotrode that facilitate breaking up the bone core after cutting through the dense bone. Such elements may be internal ribs, for example, of the type discussed above that serve to provide rigidity. For example, if such ribs follow a helical path, the sonotrode will exert a torque on the bone tissue within the interior of the sonotrode, and this may facilitate the separation of underlying bone tissue portions. Similarly, if such an internal rib is longitudinal (runs in an axial direction), a rotation of the sonotrode by the operator (surgeon) may have a similar effect. Accordingly, another aspect relates to a device, wherein the sonotrode comprises protruding elements, such as ribs, on the internal surface suitable for exerting a torque on the cut bone.

One area of application for sonotrodes is spinal surgery. The synovial joints between the superior and inferior articular processes of adjacent vertebral bodies are called facet joints. Each vertebra contains two facet joints. These joints allow spinal mobility, such as bending forward, standing upright, and turning left and right. Facetectomy is a surgical procedure that can be part of a variety of procedures, such as decompression, where the cervical nerve roots within the intervertebral foramina are decompressed, or instrumented posterior lumbar interbody fusion (iPLIF) and transforaminal lumbar interbody fusion, a common spinal fusion surgical technique. Facetectomy is also performed to more clearly define the bony anatomy for the placement of pedicle hooks and thoracic pedicle screws.

Until now, facetectomy has been performed using a semilunar-shaped osteotome (or quarter-inch osteotome [1 inch = 25.4 mm]), identifying and delineating the inferior articular facet. Once the edges are profiled, the bone and cartilage are removed with a curette and rongeur. A small curette is then used to scrape away the remaining articular cartilage from the facet joint so that indented bony surfaces emerge. Using a sonotrode that has a trapezoidal cross-section tailored to the shape of the bone fragment to be removed and has a roughened surface, only one instrument is sufficient, and only one or two cuts are necessary for facetectomy. Thus, one embodiment relates to a sonotrode for an ultrasonic surgical instrument that is suitable for facetectomy (partial or complete) or laminectomy, wherein the sonotrode has a head and a distal end piece, the distal end piece being equipped as a piercing end for penetrating bones, respectively the facet joint, using mechanical vibration, wherein the distal end piece or the blade is designed as a hollow body that is open at its distal end. It is preferred that the distal end piece comprises a blade whose distal cutting edge is trapezoidal and corresponds to the contour of a bone (and cartilage) to be punched during the facetectomy.

Another aspect, not claimed, refers to a method that performs facetectomy comprising the following steps:

- expose an affected facet joint,

- remove the affected facet joint and, optionally,

- performing an additional action such as a microdiscectomy or discectomy, a laminotomy or laminectomy, a foraminotomy or foraminectomy, or a spinal fusion, wherein an ultrasonic surgical instrument with a sonotrode is used, wherein the sonotrode has a head and a distal end piece, the distal end piece being equipped as a piercing end for penetration of the facet joint, using mechanical vibration, wherein the distal end piece or blade is designed as a hollow body that is open at its distal end having a trapezoidal distal cutting edge corresponding to the contour of the bone (and cartilage) to be punched during the facetectomy. It is preferred that only one or two cuts of the instrument are sufficient to remove the facet joint and that no further instrument is required for the "removing the affected facet joint" step.

Another spinal surgery in which sonotrodes are useful is artificial disc replacement, which is a procedure that replaces damaged or degenerated cervical discs in the spine. Instead of fusing the vertebrae to prevent back pain, the damaged cervical disc is removed and replaced with an artificial one. It is preferred that the sonotrode used be a sonotrode for an ultrasonic surgical instrument that is suitable for punching out areas of bone tissue, wherein the sonotrode has a head and a distal end piece, the distal end piece being equipped as a piercing end for penetrating bones using mechanical vibration, wherein the distal end piece comprises a blade whose distal cutting edge has a rectangular cross-section that is designed as a hollow body that is open at its distal end. It is preferred that the distal end have additional structures fitted into its contour that correspond to inclined teeth that can be part of the disc replacement implants.

Another aspect, not claimed, relates to a method for disk replacement comprising the following steps:

- remove a disk

- clean the vertebra

- optionally, release pressure from the radicular nerve and

- inserting an implant, in particular a disc replacement device, wherein an ultrasonic surgical instrument with a sonotrode is used, the sonotrode having a head and a distal end piece, the distal end piece being equipped as a piercing end for bone penetration using mechanical vibration, the distal end piece comprising a blade whose distal cutting edge has a rectangular cross-section that is designed as a hollow body that is open at its distal end. It is preferred that the distal end has additional structures fitted into its contour corresponding to inclined teeth that may be part of the disc replacement implants.

A second aspect relates to a sonotrode for an ultrasonic surgical instrument having a head and a distal end piece, the distal end piece being equipped as a blade for cutting bones using mechanical vibration, wherein the blade is arcuate. The arcuate or crescent shape of the blade may be symmetrical to the longitudinal axis defined by the median axis of the sonotrode head. In addition, the tangent touching the curve of the blade at the point where the curve intersects the longitudinal median axis of the sonotrode head forms an acute angle of at least 5° with the tangent touching the curve at the outermost point.

The second aspect preferably relates to a sonotrode, wherein the sonotrode has a head and a distal end piece, the distal end piece being equipped as a bone-penetrating punch or a cutting blade, and the distal end piece having a maximum diameter that is at least one and a half times the size of the head diameter. It is preferred that the distal end piece have a maximum diameter that is at least twice, and even more preferably at least three times, the size of the head diameter.

The blade may be substantially rectangular. However, the blade or the distal end of the blade may be curved or bent. One embodiment relates to a sonotrode, wherein the sonotrode has a head and a distal end piece, the distal end piece being equipped as a punch for bone penetration or a cutting blade, and the distal end piece or the cutting edge of the distal end piece or of the blade has a shape that is different from the shape of the first sonotrode and has a larger diameter. It is preferred that the sonotrode have a curved blade or punch. A particular embodiment relates to a sonotrode, wherein the distal end piece comprises a blade having a distal cutting edge with a shape corresponding to the contour of a tissue area to be punched. The cutting edge may even completely correspond to the contour of a tissue area to be punched.

The sonotrode head according to the second aspect is preferably formed as a (solid) circular cylinder, but the blade is a rather thin part. One possibility of adapting the distal end of the head to the proximal end of the distal end piece is to include a flattened area at the distal end of the sonotrode head. Thus, one embodiment relates to a sonotrode wherein the head has a flattened distal end. Another possibility of adapting the distal end of the head to the proximal end of the distal end piece is to include an intermediate element. An embodiment of the third aspect relates to a sonotrode wherein the distal end piece comprises an intermediate element (between the sonotrode head and the blade). The intermediate element may also widen the diameter from the head to the diameter of the blade. The intermediate element and the blade may be manufactured separately or may be in one piece.

One embodiment, therefore, relates to a sonotrode in which the intermediate element comprises through holes. These holes can be in the form of elongated slits or cavities that run parallel to the longitudinal direction of the sonotrode or perpendicular to the cutting edge. The cavities can be through holes.

The intermediate element is preferably an oscillating body that can oscillate with an impedance matched to the frequency of the sonotrode and can thus free the frame from oscillations or keep it almost completely free of them. The cavities in the oscillating body can serve, in this regard, to adapt the resonant frequency of the oscillating body to the frequency of the sonotrode.

The distal (cutting) end of the blade may be flattened or sharpened. Thus, one embodiment relates to a sonotrode for an ultrasonic surgical instrument having a head and a distal end piece, the distal end piece being equipped as a blade for cutting bones using mechanical vibration, wherein the blade has a sharp distal edge as a cutting edge. In another embodiment of the sonotrode according to the third aspect, the corners of the distal edge are not rounded but sharp and serve as a cutting edge.

A sonotrode for an ultrasonic surgical instrument having a head and a distal end piece may be equipped with a blade having a lateral depression.

Specifically, the sonotrode may comprise a distal rim, which is an outwardly distal projection extending along the cutting edge, e.g., circumferentially along the cutting edge. In this manner, an outer cross-section of the sonotrode proximal to the rim is smaller than an outer cross-section of the rim. In embodiments, therefore, a sonotrode for an ultrasonic surgical instrument is suggested, having a head and a distal end piece, the distal end piece being equipped as a blade for cutting bones using mechanical vibration, wherein the blade has an area of reduced thickness proximal to the distal end. The central depression or area of reduced thickness may optionally be rectangular in cross-section. The central depression or area of reduced thickness may encompass 50 to 90% of the surface of the blade. Thus, the sonotrode may comprise a blade having a rim surrounding the central depression or area of reduced thickness. The width of said rim may be 0.3 to 1.5 mm. An embodiment of the first aspect relates to a sonotrode in which the lateral depressions have the same depth and are arranged symmetrically within the blade. The blade or the rim around the depression may have a constant or unchanging thickness. It is possible for the blade of the sonotrode, as well as the sonotrode, to be constructed symmetrically.

Another embodiment of the first aspect relates to a sonotrode, wherein the lateral depressions each have a depth of 0.2 to 5 mm and preferably about 0.1 mm. This means that the blade has an area (which may be central with respect to the axial dimension, meaning that the thickness is greatest both proximally and distally of this area) where the thickness is reduced. It is preferably reduced by about 0.5 to 10 mm and, more preferably, the thickness is reduced by about 0.2 mm. Another embodiment of the first aspect relates to a sonotrode, wherein the sonotrode blade has a rim surrounding the depression or the central area of reduced thickness and further has a slot running parallel to that rim. In other words, the depression or the central area of reduced thickness of the sonotrode blade is joined by a rim and a slot within that rim. The slot defines a level that is lower than the level of the rim and the depression. It is preferred that the depression not have sharp edges and that the transition from the shoulder to the depression or groove be smooth. Therefore, it is preferred that the transition between the shoulder and the groove surface or, respectively, the depression be continuous or curved. If the transition is curved, it is possible to create a defined yet stable cutting edge.

Furthermore, the reduced thickness area of a sonotrode according to the first aspect may have a raised structure. This structure may comprise ribs running parallel to one another and preferably parallel to the longitudinal axis of the sonotrode blade. The ribs may also be arranged to form a regular grid or mesh. It is preferred that the cross-section of the raised structure, and in particular of the at least one rib, be selected such that the structure (or rib) does not protrude above the blade flange surrounding the depression. The ribs increase the rigidity of the blade and, respectively, of the sonotrode. However, friction is reduced and the cooling capacity is further improved. As an alternative to ribs, the raised structure may also be formed from cubes, cuboids, truncated pyramids, cylinders (right circular cylinder, oblique circular cylinder), or n-gonal prisms where n is between 3 and 16.

To reduce sonotrode torsion, the raised rib-shaped structure may be oblique to the longitudinal axis of the blade. It may be preferred for the ribs to form an angle with the longitudinal axis of the sonotrode or the blade of 10° to 60° or 30° to 60°. These oblique ribs may intersect and thus form a grid. The distance between the ribs may be between 0.2 and 0.7 mm. The distance between the raised structures may also be formed by cubes, cuboids, truncated pyramids, cylinders (right circular cylinder, oblique circular cylinder), or n-gonal prisms where n is between 3 and 16 may be between 0.2 and 1.0 mm. The height of the raised structures is preferably between 0.1 and 0.5 mm.

Another embodiment of the first aspect relates to a sonotrode, wherein the sonotrode blade has channels running from the depression area to the edge of the blade. In other words, there are channels or grooves running from the reduced thickness area to the edge of the blade. The channels or grooves can have the same depth as the depression. It is preferred that the channels or grooves be present on each lateral side of the blade. The channels can be in the corresponding position on each side or be staggered. It is preferred that the channels or grooves be open towards the blade surface. Therefore, they can have a semicircular shape or be edged. The channels or grooves can be arranged only towards the cutting edge. They can also run towards the distal end. There may also be embodiments where the channels and grooves are arranged symmetrically around the depression or reduced thickness area. There may be between 5 and 10 channels or grooves per lateral side of the blade.

The blade extension in the longitudinal direction can be between 15 mm and 40 mm, preferably between 18 mm and 30 mm. The maximum blade extension in the transverse direction can be, for example, between 20 mm and 75 mm. The extension in the longitudinal direction is typically smaller than the extension in the transverse direction. The depth perpendicular to the longitudinal and transverse directions can also be between 1 mm and 30 mm. One embodiment relates to a sonotrode, wherein the sonotrode blade has a length of 15 to 40 mm. The sonotrode (including the intermediate element and the blade) can have a length of 20 to 300 mm, preferably 150 to 250 mm. The distal end of the sonotrode can be rounded. This means that the corners of the rectangular blade are rounded. Therefore, it is preferred that the radius of the circular arcs forming the edges be <0.5 mm.

The following questions apply to all sonotrodes (not just one aspect):

The sonotrode may be part of a surgical punching device, which also has a tube surrounding the sonotrode. In a space between the sonotrode and the tube, a cooling and/or rinsing liquid may be transported to the distal cutting edge or possibly also away from it.

The ultrasonic system can be any conventional system and typically comprises a press and a vibrating acoustic element consisting of a transmitter, an amplifier, and a sonotrode powered by a high-frequency generator. Longitudinal vibrations at frequencies between 20 kHz and 40 kHz with tool amplitudes between 5 pm and 50 pm are introduced into the bone under the action of force. The ultrasonic vibrations can be focused by means of specially designed components or tools.

A sonotrode may comprise a shaft that forms part of the sonotrode head. A connection to the ultrasound transducer may be established via the proximal end of the shaft. The shaft is preferably aligned in the longitudinal direction of the distal end piece. The shaft forms the proximal end of the sonotrode head; the distal end is located opposite it. For the connection of the sonotrode, the shaft may comprise or be constructed by means of a thread. Therefore, one embodiment relates to a sonotrode wherein the head has a thread at its proximal end. Furthermore, the sonotrode head and the distal end piece, respectively, the blade, are formed together as a single piece or are rigidly coupled to one another. Therefore, the distal end of the sonotrode head may have the same cross-section as the proximal end of the distal end piece or, respectively, the blade, or a cross-section adapted to the proximal end of the distal end piece. The inventors discovered that sonotrodes manufactured by additive manufacturing methods, particularly using sintering (such as selective laser sintering), have some surprising advantages. The ultrasonic surgical instrument is typically equipped with a line through which a flushing liquid (e.g., water) can be supplied to the operating field. The surface structure generated using the aforementioned manufacturing method increases the cooling efficiency of that liquid. One explanation could be that the surface structure provides and maintains a suitable liquid film on the sonotrode blade surface. One possible effect appears to be that the pockets created by the sintering process, which are not open to one side, provide a hydrostatic cushion.

One embodiment relates to a sonotrode, wherein the surface of the sonotrode or the surface of the distal end piece has convex microstructures. Said microstructures are curved or rounded outward like the outside of a sphere or circle. Another embodiment relates to a sonotrode, wherein the surface of the sonotrode or the surface of the distal end piece has an average roughness Ra between 5-20 pm. Thus, surface roughness as a component of surface texture is quantified by deviations in the direction of the normal vector of an actual surface from its ideal shape. The arithmetic average roughness, Ra, is the arithmetic average value of the filtered roughness profile determined from deviations around the centerline within the evaluation length and is the most widely used one-dimensional roughness parameter.

Due to the surface roughness resulting from the sintering process, there are point contacts between the distal end piece and the bone. This results in a higher energy density. However, the convex surface portions resulting from grain size distribution are more stable than, for example, roughness structures created by abrasive blasting.

Accordingly, one embodiment relates to a method for manufacturing a sonotrode as defined herein, wherein the sonotrode is manufactured using an additive manufacturing method. Direct metal laser sintering (DMLS) is one such additive manufacturing process suitable for use in producing the sonotrodes. Thus, the sonotrodes, or at least the distal end pieces, are constructed using a laser to selectively sinter (heat and fuse) a layered powdered metal material.

A suitable alternative method for manufacturing sonotrodes or their distal end parts is shot peening or, respectively, impact shot peening. Abrasive blasting is less suitable. The surface structure resulting from the metal grain sintering process cannot be fully described by parameters such as roughness and grain size. However, this particular surface structure must be demonstrated to be advantageous. Therefore, the sonotrode, or at least the distal end part of the sonotrode, can be manufactured using an additive manufacturing method such as direct metal laser sintering. In particular, a sonotrode for an ultrasonic surgical instrument may be suitable for punching through areas of bone tissue, wherein the sonotrode has a head and a distal end piece, the distal end piece being equipped as a piercing end for bone penetration using mechanical vibration, wherein the sonotrode or at least the sonotrode blade is manufactured using an additive manufacturing method such as direct metal laser sintering. The powder to be used may have an average particle diameter of 40-80 µm. Furthermore, a sonotrode for an ultrasonic surgical instrument may have a head and a distal end piece, the distal end piece being equipped as a bone penetration punch or a cutting blade, and the distal end piece having a maximum diameter that is at least one and a half times the size of the diameter of the head, wherein the sonotrode or at least the sonotrode blade is manufactured using an additive manufacturing method such as direct metal laser sintering. The method may further comprise one or more heat treatment steps. It is preferred that the surface resulting from additive manufacturing is not smoothed (leveled or polished). It is further preferred that the sonotrode manufactured using additive manufacturing can be subjected to a heat treatment but not to a smoothing process (surface smoothing).

The ultrasonic surgical instrument may be suitable for punching out areas of bone tissue, comprising a handpiece containing an ultrasonic transducer and a sonotrode as defined herein that is mechanically coupled to said transducer.

The term "ultrasonic surgical instrument" as used herein refers to a surgical instrument with an ultrasound transducer. This ultrasonic surgical instrument comprises a sonotrode as described herein that is connected to the ultrasound transducer. The ultrasound transducer may comprise a piezoelectric element, by means of which a high-frequency AC voltage is converted into a corresponding mechanical vibration. For example, the vibration frequency may be between 20 kHz and 40 kHz.

Preferably, the ultrasonic transducer or the housing of the ultrasonic surgical instrument and the sonotrode head (via the head shaft) are coupled to each other, wherein the head shaft is designed to transmit the vibration energy as completely as possible from its proximal end to the distal end piece or the blade of the sonotrode, respectively.

Another aspect relates to an ultrasonic surgical instrument suitable for puncturing areas of bone tissue during arthroscopy, comprising a handpiece containing an ultrasonic transducer and a sonotrode as defined herein, which is mechanically coupled to said transducer. It also relates to a system of a sonotrode as described herein together with a commonly known catheter or arthroscopic tube. The sonotrode or the arthroscopic catheter/tube may be coupled to a handpiece. A clearance must exist between the sonotrode and the catheter tube or the arthroscopic tube. This clearance may have a width of 0.2 to 1 mm. This clearance may be used for a fluid that can flow along the sonotrode. The fluid may be used to cool the sonotrode, to fill the joint, and/or to flush the operating side. Alternatively, fluid can be introduced through the hollow sonotrode, and the space between the sonotrode and the tube can be used to aspirate fluid and bone debris away from the operating side. Therefore, the arthroscopic catheter or tube can have at least one feeding line.

The sonotrode is preferably designed to adapt to a vibration frequency, for example in the range of 20 to 40 kHz and to vibrate substantially longitudinally in a standing wave with antinode positions (positions with maximum amplitude) and at least one node position (position of minimum amplitude) between the two ends of the sonotrode.

The sonotrode may comprise, at least in the most distal node position, an enlarged cross-section. The portion extending between two node positions of the sonotrode may comprise a constant cross-section. Adjacent to the sonotrode portion with an enlarged cross-section at the most distal node position in the distal and proximal directions are sonotrode portions with a smaller cross-section (larger radial clearance). The transition between the different cross-sections may comprise a step or may be a gradual transition. The cross-section of the sonotrode portion on the distal side of the portion with an enlarged cross-section may be smaller than the cross-section of the sonotrode on the proximal side of the portion with an enlarged cross-section. This means that the radial clearance between the sonotrode and the arthroscopic catheter or tube is reduced at at least one distal node position of the sonotrode.

One method, not claimed, comprises

providing an ultrasound catheter comprising a handpiece containing an ultrasonic transducer and a sonotrode as defined herein that is mechanically coupled to said transducer, inserting the catheter (or arthroscopic tube) into a joint by using conventional arthroscopic portals, and

cutting, drilling, or punching the bone within the joint using mechanical vibration.

In this method, the sonotrode located on an arthroscopic catheter or tube can be displaced or moved relative to the catheter or tube. This means that the sonotrode can move longitudinally relative to the catheter or arthroscopic tube.

Preferably, the sonotrode material is a metallic material, such as, for example, stainless steel or titanium. The sonotrode, or at least the distal end piece thereof, may be coated with titanium nitride (TiN). Thus, the sonotrode for an ultrasonic surgical instrument may be suitable for punching through areas of bone tissue, wherein the sonotrode has a head and a distal end piece, the distal end piece being equipped as a piercing end for penetrating bones using mechanical vibration, wherein the sonotrode, or at least the distal end piece of the sonotrode, is coated with titanium nitride and is preferably manufactured using an additive manufacturing method such as direct metal laser sintering. Furthermore, the sonotrode for an ultrasonic surgical instrument may have a head and a distal end piece, the distal end piece being equipped as a punch for bone penetration or a blade for cutting and the distal end piece having a maximum diameter that is at least one and a half times the size of the diameter of the head wherein the sonotrode or at least the distal end piece of the sonotrode is coated with titanium nitride and is preferably manufactured using an additive manufacturing method such as direct metal laser sintering.

It has been shown that spherical microstructures on the surface of the sonotrode or, respectively, the blade can be deformed by the forces acting during bone cutting or scraping. Therefore, coating sonotrodes or blades to harden the surface is preferred. TiN has an ideal combination of hardness, strength, adhesion, and inertness, and will not blister, flake, or chip during bone cutting or scraping.

Another advantage is the optimized heat distribution along the surface created by the TiN coating. This prevents hot spots, and the distribution or dispersion of heat along the length of the cutting surgical instrument prevents heat concentration at the cutting edge or the tips of convex microstructures on the surface, as would occur without coating or with coating only on the cutting edge.

The TiN coating can be applied using an environmentally safe physical vapor deposition (PVD) vacuum system. Some processes use low-temperature arc vapor deposition to deposit the titanium nitride coating, but it could also be applied by high-temperature sputtering or other well-known coating processes (electron beam heating or chemical vapor deposition (CVD)). Generally, pure titanium is sublimated and reacted with nitrogen in a high-energy, vacuum environment. The TiN film can also be produced on Ti workpieces by reactive growth (e.g., annealing) in a nitrogen atmosphere.

The TiN coating is preferably applied as a thin coating of less than 5 µm, more preferably less than 3 µm. The thin titanium nitride coating provides the blade with a hard outer surface with a low coefficient of friction.

Preferably, the connection between the head and the vibration generator is releasable and the sonotrode comprising the head and the distal end piece is disposable.

The ultrasonic surgical instrument is, for example, a handheld device wherein a handle portion thereof houses the vibration generator, which is supplied with the necessary power by a battery or through a corresponding cable connecting the handpiece to a control and supply unit. The preferred frequency for the vibration is in the ultrasonic range, preferably in the range of 15 to 40 kHz or between 20 and 30 kHz, and has sufficient energy to achieve an amplitude in the micrometer range for the distal end of the perforator, between 20 and 120 pm or preferably between 60 and 100 pm.

The device may further comprise a cannula or a guide shaft around the shaft and the sonotrode of the ultrasonic surgical instrument. In this way, the transmission of vibration energy through the axis of the instrument should be as efficient as possible and the friction between the shaft and the cannula as low as possible. This can be achieved by providing, in an axial position where the most distal node position of the shaft is located, a region in which the radial clearance between the instrument and the cannula is minimal. This is achieved by the shaft of the instrument comprising, at least in the most distal node position, an enlarged cross-section, and by the through opening of the cannula portion extending from the distal end portion to beyond the most distal node position of the sonotrode comprising a constant cross-section. The shaft may further comprise portions of a larger cross-section at other node positions. In addition, the cannula may also have regions of larger cross-sections at one or more node positions. It is further preferred that the arrangement comprising the shaft and the cannula have polymeric sliding surfaces to minimize friction loss. These surfaces may be formed by a polymeric ring around the distal end of the shaft or the perforator, respectively, its cutting tube. The polymeric ring may be made of PEEK. Alternatively, a polymeric shield may be coupled to the inner surface of the cannula, which may also be made of PEEK. Accordingly, the larger region or cross-section may be formed as a polymeric coupling to the cannula or shaft. The larger cross-sectional region may also have a polymeric coating.

Brief description of the drawings

Illustrative embodiments of the device and the illustrative method are described in more detail in connection with the accompanying figures.

Figure 1 shows a schematic drawing of a cross-section through an illustrative embodiment of a sonotrode.

Figure 2 shows a schematic drawing of a cross-section of an illustrative embodiment of a sonotrode.

Figure 3 shows the distal portion of an ultrasonic surgical instrument for bone cutting comprising a piezoelectric stack located within a housing with a sonotrode at the tip of the housing.

Figure 4 shows a schematic drawing of an illustrative embodiment of a sonotrode.

Figure 5 shows a schematic drawing of a cross-section of an illustrative embodiment of a sonotrode.

Figure 6 shows a schematic drawing of a cross-section of an illustrative embodiment of a sonotrode.

Figure 7 shows a schematic drawing of a cross-section of an implant that can be cut using a sonotrode according to Figure 5 or 6.

Figure 8 shows a schematic drawing of an illustrative embodiment of a sonotrode with an inclined section.

Figure 9 shows a schematic drawing of an illustrative embodiment of a sonotrode with a parabolic cut.

Figure 10 shows a schematic drawing of an illustrative embodiment of a sonotrode with a flange. Figure 11 shows a schematic drawing of an illustrative embodiment of a sonotrode with a flange. Figure 12 shows a schematic drawing of an illustrative embodiment of a sonotrode within an arthroscopic tube.

Figure 13 illustrates two examples of the sonotrode (B and C).

Figure 14 shows a cross-section of a sonotrode according to Figure 13 B located inside an arthroscopic tube.

Figure 15 shows the distal part of an ultrasonic surgical instrument.

Figure 16 shows the cross-section of an illustrative embodiment of a sonotrode.

Figure 17 shows the distal portion of an illustrative embodiment of a sonotrode.

Figure 18 shows a longitudinal section of an illustrative embodiment of a sonotrode.

Figure 19 shows a longitudinal section of an illustrative embodiment of a sonotrode.

Figure 20 shows an illustrative embodiment of a sonotrode.

Figure 21 represents the distal part of another surrounding tube.

Figures 22-24 show, in longitudinal section and bottom view, distal ends of sonotrodes with inner blades.

Description of preferred embodiments

In all attached figures, the same reference numbers designate the same or similar elements that perform the same functions.

Figures 1 and 2 each illustrate an embodiment of a sonotrode according to the first aspect. A cross-section of the distal end piece 5 of the sonotrode is shown. The distal end piece 5 is designed as a hollow elliptical cylinder that is open at the very distal end by having a cylindrical body. The distal end piece can serve as a hollow punch or cutting device using mechanical vibration. Therefore, the very distal end of the hollow punch or cutting device can be flattened. The sonotrode or, respectively, the distal end piece may have lateral ribs 7. These ribs run along a longitudinal axis of the distal end piece and are oriented inwardly from the body.

The sonotrode of Figure 1 has four ribs 7. Each rib 7 is located within the distal end piece. It is preferred that these ribs 7 be evenly distributed, in particular, the ribs 7 are located at points where the minor axis and the major axis of the elliptical cross-section intersect the circumference of the cross-section or, respectively, the surface of the distal end piece. It is also possible that the ribs 7 can each be positioned at points on the circumference located midway between the aforementioned points. Each rib 7 can be radially vertical (radially protruding, protruding inwards in the embodiment shown) at a constant height above the inner surface of the distal end piece. The cross-section of the ribs can vary. In this case, the cross-section of the ribs is almost triangular, but it can also be almost semicircular or rectangular. However, it is generally preferred that there be no sharp edges on the ribs and at the transition between the rib and the surface of the sonotrode body.

The sonotrode of Figure 2 has eight ribs 7. Four ribs 7a are located inside the distal end piece body and four ribs 7b are located outside the distal end piece body. In case a sonotrode has several ribs, it has proven advantageous if these ribs are arranged symmetrically. It is preferred if the ribs 7 are located at the points where the minor axis and the major axis of the elliptical cross-section intersect the circumference of the cross-section or, respectively, the surface of the distal end piece. Each rib 7a may be radially vertical (projecting radially inward) up to a constant height above the inner surface of the distal end piece and, furthermore, each rib 7b may be radially vertical (projecting radially outward) up to a constant height above the outer surface of the distal end piece. Sonotrodes according to Figure 1 and 2 are suitable for use in treating spinal stenosis, in particular for lowering or removing bone spurs or synovial cysts.

Figure 3 shows the distal part of an ultrasonic surgical instrument comprising a transducer, such as a piezoelectric stack 3 located within a housing 2 with a sonotrode 1 at the tip of the housing. The sonotrode 1 has been coupled to the housing 2 through its proximal head end. Therefore, the head may have a thread or a plug-in connector or a bayonet coupling or other suitable coupling structure at its proximal end. The sonotrode 1 connected to the housing may have longitudinal ribs 7. The ribs 7 may be located only on the distal end piece of the sonotrode, as an alternative to extending to the proximal head of the sonotrode as shown in this case. The sonotrode 1 may be a sonotrode according to Figure 1 or 2 having an oval or elliptical cross-section. Alternatively, it may have a different hollow cross-section. However, it is preferred that the cross-section does not vary along the length of the sonotrode 1, i.e., the sonotrode is cylindrical (in this text generally "cylindrical"), not restricted to the shape of a rotating cylinder, but belongs to any general cylinder whose base is a closed curve. The oscillation direction is indicated by arrow 11. The oscillation is therefore a longitudinal oscillation.

Figure 4 shows a schematic side view of a sonotrode arrangement comprising a piezoelectric stack 3 (not shown) located within a housing 2 coupled to a sonotrode according to the second aspect. The head 9 of the sonotrode may be formed as a solid rod. At the distal end of the sonotrode head 9 there follows an intermediate element 8, which may be a separate part or a main body when a workpiece is produced with the blade 5. The sonotrode blade 5 and/or the intermediate element (if present) comprise elongated holes 10 (through slits) in the oscillation direction 11. Furthermore, the blade 5 may narrow towards the cutting edge 12. The width of the blade is approximately 5 times the size of the diameter of the sonotrode head 9. The intermediate element or the main body may have a thickness of 5-12 mm at the point of connection to the sonotrode head 9, which thickness narrows to 2-6 mm towards the cutting edge 12 of the blade 5, whose width may be between 10 and 60 mm.

The blade 5 may have a straight cutting edge 12. However, the cutting edge is preferably formed to conform to the contour of the area to be cut or perforated. The intermediate element 8 is used to transfer the oscillation to the blade and the cutting edge. Thus, the intermediate element may be a driver. Alternatively, the arrangement does not comprise a separate intermediate element, but the structure thereof may be formed by a blade main body 5. In addition to serving as a driver or as an alternative thereto, the intermediate element or the corresponding structure forming the blade main body may serve for width expansion (see Figure 5) and the transition to the cutting edge shape.

Figures 5 and 6 each show schematic bottom views on the cutting edge 12 of a blade of an illustrative sonotrode according to the second aspect. Both blades are adapted to cut (for an extraction process) an implant as shown in Figure 7. Figure 7 shows a cross-section of an implant to be extracted with the aid of sonotrodes having blades as illustrated in Figures 5 and 6. The implant is a dual anchor with two pin-shaped anchoring portions 13 and a stabilizing portion 14 located between the two anchoring portions 13, for example, as taught in WO2010/045749. It may be used as a fusion device particularly suitable for the fusion of a human lumbar facet joint. The blade, as shown in Figure 5, is formed to have the contour of one half of the implant. This means that the sonotrode must be used twice (once on each side of the implant) to drill the implant after it has been implanted and integrated into the bone. The blade, as shown in Figure 6, is shaped to encircle, on one side, slightly more than half the contour of the implant to be drilled. This ensures an overlap of the cuts when the sonotrodes are used twice, once on each side.

Figure 8 shows a sonotrode with a distal end piece that is hollow and has an inclined cut. The distal end portion of the sonotrode is cut obliquely. Therefore, the cutting edge 12 of the punch is located in a plane that forms an angle with the longitudinal axis 40 of the sonotrode. The distance d between the maximum and minimum length of the distal end portion or the blade is less than 10% of the resonator length (the effective length of the vibrating part). Figure 9 shows a sonotrode with a distal end piece having a parabolic cut 16 at the distal end.

Figures 10 and 11 each show an axial section through alternative distal end pieces of a sonotrode. The sonotrode according to Figure 10 has a shoulder 17, i.e., a radially outwardly projecting feature that is, for example, flange-like. The shoulder 17 at the distal end of the sonotrode according to Figure 11 borders a depression. The depression consists of a groove 19, in particular a circumferential groove, which runs parallel to the shoulder 17. The area 18 proximal to the shoulder 17 and the groove 19 is raised relative to the groove 19 but lowered compared to the shoulder 17, i.e. the outer diameter of the section 18 proximal to the groove is smaller than the outer diameter of the shoulder but larger than the outer diameter of the sonotrode at the axial position of the groove 19. The area 18 may be between 0.1 and 5 pm lower than the shoulder 17. The groove 19 may be between 0.2 and 5 pm lower than the area 18. The minimum depth of the area 18 is sufficient to adequately reduce friction compared to a situation where there was no shoulder or where the proximal outer diameter of the groove was the same as the outer diameter of the shoulder.

The flange 17 can also be curved or parabolic. The (axial) width of the flange can be <1 mm and preferably between 0.2 and 0.5 mm. The flange 17 preferably runs perpendicular to the longitudinal axis of the sonotrode.

Figure 12 shows in axial section a distal part of a sonotrode 1 inside an arthroscopic tube 20. The sonotrode can be moved in a distal direction with respect to the tube 20. Inside the tube 20 there is a lumen which is, in general, a lumen similar to a lumen such as that used for optical instruments (camera) used in arthroscopy. The sonotrode is equipped with a portion 21 of a larger cross-section at a node position N. This larger cross-section is caused by a ring around the wall of the sonotrode. This ring can be a polymer ring or a ring made of the same material as the sonotrode.

The arthroscopic tube may comprise a supply 23 for a fluid that can be used to cool the sonotrode, to fill the joint, and/or to flush the operative side of the sonotrode. The fluid must be sterile and may be a physiological saline solution.

Figures 13 B and C are axial sections and each show a distal portion of a sonotrode, which is adapted to a selected vibration frequency to vibrate at a node position N. Figure 13 A illustrates the vibration of the sonotrode showing the deflection as a function of axial position. N1 and N2 indicate nodes.

An arthroscopic tube (not shown in Figures 13B and 13C) extends distally to cover the distal end of the sonotrode 1. The sonotrode 1 is equipped with a portion 22 of a larger cross-section at node position N. The larger cross-section is caused by a protrusion of the sonotrode wall. The protrusion may be an integral part of the sonotrode wall and may be formed as a ring around the sonotrode having a square cross-section (Figure 13B). Alternatively, there may be several rectangles seated in a cycle around the sonotrode with a certain space between them. These rectangles may be arranged within a constant interval on that circle. Instead of rectangles, there may also be spherical protrusions fitted in a circle around the sonotrode. The circle is always located at node position N.

Figure 14 shows a cross-section of the sonotrode according to Figure 13 B at node position N1. The sonotrode 1 is located within an arthroscopic tube 20. As can be seen, four rectangular protrusions result in a larger cross-section of the sonotrode at node position N. Between these protrusions there is a space 61, which can serve as a channel for a (cooling/rinsing) liquid. Alternatively, the liquid can flow through the lumen of the sonotrode 1 and the space 61 can be used to aspirate liquid and debris.

Figure 15 shows the distal portion of an ultrasonic surgical instrument comprising a transducer 3 located within a housing 2 with a sonotrode 1 at the tip of the housing. The sonotrode 1 has been coupled to the housing 2 through its proximal head end. The device may further comprise a bushing 24 around the sonotrode 1, the bushing may be connected to the housing. The sonotrode 1 may be any sonotrode according to an embodiment described herein. In many embodiments, it is preferred that the sonotrode be symmetrical. The bushing may have a window at the distal end such that only a portion of the sonotrode protrudes from the bushing. Thus, the window is like a longitudinal cut starting at the distal edge and ending in a leveling curve. Alternatively, the window is like a cut that cuts through a portion of the cross-section of the bushing. The window of the sleeve 24 may be formed to protect at least half of the cross section of the sonotrode at the distal end of the sonotrode.

Figure 16 shows a cross-section of one embodiment of a sonotrode. This sonotrode is particularly suitable for use during total disc replacement surgery. The sonotrode shown in Figure 16 can be used to prepare a vertebral body prior to implantation of a disc replacement implant or artificial disc. It can also be used to remove the problematic or damaged disc and/or to clean the space between vertebral bodies. The most commonly used total disc replacement designs have two plates. One attaches to the vertebrae above the disc being replaced, and the other to the vertebrae below. The plates have a substantially flat level, side, or area for contacting the vertebral body. However, the vertebral body is not flat.

The surgeon can therefore cut the vertebral body. It is preferred that the cross-section of the sonotrode be (substantially) rectangular or have at least one flat side. These plates may have inclined teeth to generate stability. Therefore, the sonotrode may have structures 29 attached to the distal end corresponding to the inclined teeth of the plates. Alternatively, the distal end piece may have a cross-section that includes structures 29 corresponding to such teeth. The structures 29 may be ribs attached to the sonotrode that have a triangular cross-section, or the cross-section of the sonotrode may comprise triangular protrusions.

The sonotrode may optionally comprise a bushing 24 as described for the sonotrode shown in Figures 15 and 17.

Figure 17 shows the distal portion of a sonotrode 1. A bushing 24 is fitted around the sonotrode 1. The sonotrode 1 may be any sonotrode according to an embodiment described herein. It is preferred that the sonotrode be located symmetrically within the bushing. The sonotrode may have a symmetrical cross-section. The bushing may have a window at the distal end such that only a portion of the sonotrode protrudes from the bushing. Alternatively, the bushing may be fully or partially (with respect to only a portion of the cross-section) retractable. The portion of the sonotrode protruding from the bushing may be used for punching bone.

Figure 18 shows the longitudinal section of a sonotrode 1. It illustrates that behind a distance used for punching, structures 27 can be attached, which are suitable for scraping or grinding bone. In addition, they can be suitable for cutting bone by moving the sonotrode along a longitudinal direction. Preferably, it is possible to extract or ablate the bone by a backward and/or forward movement (bidirectional movement with respect to the surgeon). As shown, structure 27 may comprise circumferential ribs that may have a triangular cross-section or a rectangular cross-section. Alternatively, this structure may be formed as spikes or may be helical.

Figure 19 shows a longitudinal section of a sonotrode 1 having a stepped structure 27, for example, being formed by several strips (bands) of rectangular cross-section that are coupled around the circumference.

Figure 20 shows another embodiment of a sonotrode. The sonotrode is particularly suitable for creating a plurality of bone openings before removal from the operation site, and for removing bone tissue (in particular, the punched-out complete bone fragments) from the openings created using the device. The bone fragments 30 from punching out a bone opening created with the aid of the sonotrode 1 may be stored within the hollow sonotrode or in a space within the sonotrode, which may be formed by an extended cross-section of the sonotrode. Thus, the sonotrode may comprise a space suitable as a reservoir for bone fragments 30 or bone debris. The sonotrode 1 may be designed as a disposable article, suitable for creating several bone openings within an operation site and storing the resulting bone fragments (from drilling or punching). After removal from the surgical site, the bone fragments can be used as a test sample or as allogeneic transplant material. The sonotrode can be discarded (with or without the bone fragments) or can be easily cleaned. The embodiment can be designed so that the vibration of the sonotrode facilitates transport of the bone fragments 30 and retains them within the open space.

In another embodiment, the bone fragments may also be transported using hydraulic pressure. Thus, there may be a channel within the device that supplies a liquid such as water from the handle to the sonotrode. This flow of liquid may be stopped or reversed to generate negative pressure. Alternatively, the liquid may be used to transport (or eject) the bone fragment out of the sonotrode. The bone fragment may be ejected on the operating side and removed using the liquid typically used to clean the operating side (e.g., of blood). When this alternative is used, the flow of liquid into the sonotrode is not stopped, but the moment the sonotrode cuts the bone, the outflow of liquid is stopped. Therefore, the pressure within the sonotrode increases, and this pressure may be used to extract the bone fragment from the sonotrode. In case negative pressure is used to transport and store drilled bone fragments, the bone fragments are suctioned out. This supports the breaking process of the punched-out portion of dense bone. Therefore, it is possible to remove the bone within the sonotrode's cutting edge in a single piece and with less damage to the surrounding tissue.

The fluid fed through the instrument can also be used to cool the sonotrode and/or to flush the operating side. A space between the sonotrode and a cannula or guide shaft can be used to aspirate fluid and bone debris from the operating side.

In another embodiment of the sonotrode 1 for removing bone tissue (in particular, the punched-out whole bone fragments) from bone openings created using the sonotrode, the sonotrode may be designed such that a vacuum facilitates transport of the bone fragments 30 and retains them within the sonotrode 1. Thus, there may be a suction port 30.1 communicating with an interior 42 of the sonotrode 1 for removing air and applying vacuum inside the sonotrode. Figure 20 illustrates two possibilities (in reality, the sonotrode will often have only one suction port). A first suction port 30.1 (first possibility) is laterally coupled to the head of the sonotrode. A second suction port 30.2 (second possibility) communicates with a proximal end of the sonotrode. In particular, the suction port may be present in a connecting piece 31 which is coupled to the proximal end of the sonotrode 1 in a hermetically sealed manner but from which the sonotrode can be removed.

In embodiments, the suction port 30.1, 30.2 is coupled to the sonotrode in a node position. A suction port 30.1, 30.2 comprised within the sonotrode head and perhaps the handle or housing has to be cleaned after each operation (each treatment of a patient). A suction port 30.1 integrated into the distal end piece of the sonotrode 1 has the advantage that it does not have to be cleaned in case the sonotrode is a disposable article or is easier to clean because it is very short and has no bent structure. On the other hand, it is more expensive to include such a suction port in the sonotrode, particularly in case it is a disposable article.

A vacuum applied through a suction port can also be used to support or facilitate the breaking of the punched portion of dense bone. Thus, the bone within the cut edge can be removed in one piece and with less damage to the surrounding tissue. In Figure 20, reference number 25 indicates dense bone tissue (cortical bone), and reference number 26 indicates cancellous bone tissue.

Figure 21 illustrates the possibility of using a tube 20 or a socket to deliver a liquid, as explained with reference to Figure 24 above, in combination with the extraction of material through the interior 42 of the sonotrode. The liquid is delivered to the tube 20 and flows in the space between the tube and the sonotrode forward distally. It flows, along with any entrained tissue/material, back through the sonotrode, as illustrated by the arrows. As mentioned above with reference to Figure 14, the reverse arrangement is also possible.

In such approaches, the liquid is not only a cooling/rinsing liquid, but also serves to promote the transport of tissue and debris away from the surgical site. For this purpose, a vacuum may be applied to the interior 42 of the sonotrode, for example, by providing a suction port as explained above.

In embodiments, it may be advantageous if the tissue to be removed, especially dense bone tissue, is not only drilled out of the living tissue, but also broken into smaller pieces, since a larger bone fragment 30 of the type illustrated in Figure 20 may obstruct the transport path. Figure 22 illustrates the sonotrode with at least one inner blade 51 that disintegrates bone fragments that are transported forward proximally relative to the sonotrode.

In a simpler design, such an inner blade simply extends transversely through the interior of the sonotrode.

The inner blade (this refers to all embodiments with an inner blade) may have a cutting edge extending in a plane perpendicular to the axis of the sonotrode, or, often preferably, may have a cutting edge which is not parallel to said plane, but is curved and/or at an angle thereto, as illustrated in Figure 22, to cut more smoothly into the tissue.

In particular embodiments, a plurality of inner blades are present in a tiered arrangement, with a first inner blade 51 distally and a second inner blade 52 being in a different angular position (i.e., angularly offset) more proximally (by a distance d). This is schematically illustrated in Figure 22 and, in bottom views, in Figures 23 and 24 for different inner blade geometries.

In embodiments comprising breaking the tissue to be removed into smaller pieces, the device comprising the sonotrode can be used as a morcellator.

As will be understood, the approaches of Figures 20/21 and Figures 22-24 can be combined. Also, combinations of one or both with the features described in reference to the other embodiments, especially an outwardly projecting distal projection and/or inwardly oriented ribs, are possible and often also advantageous.

Embodiments comprising delivering a liquid to the site where the sonotrode acts (operating site) may comprise using the cavitation effect for targeted tissue treatment. Cavitation (the creation and implosion of small vapor-filled bubbles due to pressure variations) can lead to a highly aggressive environment around the sonotrode. This can be used in a targeted manner for tumor removal, etc. In view of this, the configuration of Figures 20-24 involving tissue removal through the interior of the sonotrode may be advantageous by preventing tissue and debris from spreading in an uncontrolled manner.

In embodiments, the effect of piercing (punching) and cavitation may be supplemented by supplying a corresponding chemical agent, for example, a cytostatic, in the supplied liquid.

The distal end piece of the hollow sonotrode may have ribs on its inner side. These ribs may run parallel to the longitudinal axis of the sonotrode and along its entire length, or they may be arranged only on a distal portion. Alternatively, the ribs may run along paths other than parallel to the longitudinal axis, for example, along a helical or other curve on the inner side of the distal end piece of the sonotrode. Alternative ribs or protruding spikes or protruding elements attached to the inner side of the sonotrode may facilitate breaking up bone fragments after the sonotrode has been introduced into dense bone. Therefore, the sonotrode or the entire device may be rotated so that torque is applied to the bone fragment within the sonotrode. Alternatively, slicing elements may be arranged within the tube or sonotrode. These elements are suitable for cutting or breaking the bone core into small fragments, respectively, bone remnants that can be aspirated from the sonotrode. The slicing elements can be formed as thin blades (e.g., two, three, four, or five blades) arranged so that they meet one another on the central axis of the tube. The sonotrode can cut into dense bone with its distal end, and when cutting deeper into the bone, the slicing elements cut the bone core into smaller fragments. The distal ends of the slicing elements or blades can be sharp and can be angled. The scope of the invention is defined by the following claims.

Claims (13)

1. A sonotrode (1) for an ultrasonic surgical instrument which is suitable for punching out areas of bone tissue, wherein the sonotrode (1) has a head and a distal end piece (5), the distal end piece (5) being equipped as a piercing end for bone penetration using mechanical vibration, wherein the distal end piece (5) or the blade is designed as a hollow body that is open at its distal end, characterized in that the sonotrode comprises a suction port (30.1, 30.2) for applying a vacuum to an interior of the sonotrode (1), the sonotrode (1) being also surrounded by a tube (20), where the tube is equipped to supply a liquid to the distal end of the sonotrode (1). 2. The sonotrode (1) according to claim 1, wherein the distal end piece (5) comprises a blade whose distal cutting edge (12) corresponds to the contour of a tissue area to be punched. 3. The sonotrode (1) according to claim 1, wherein the hollow body is not rotationally symmetrical. 4. The sonotrode (1) according to any one of the preceding claims, wherein the sonotrode has a lateral rib (7) running along a longitudinal axis of the sonotrode (1). 5. The sonotrode (1) according to any one of the preceding claims, further comprising a bushing (24) with a window allowing only a portion of the distal end of the sonotrode (1) to protrude from the bushing (24). 6. The sonotrode (1) according to any one of the preceding claims, comprising a distal flange which is a distal outward projection extending along the cutting edge, such that an outer cross-section of the sonotrode proximally of the flange is smaller than an outer cross-section of the flange. 7. The sonotrode (1) according to any one of the preceding claims, further comprising a suction port (30.1, 30.2) for applying a vacuum to an interior of the sonotrode (1). 8. The sonotrode (1) according to any one of the preceding claims, comprising at least one inner blade (51, 52) arranged inside a hollow body of the sonotrode (1), the hollow body being open at its distal end, the blade configured to break punched bone fragments. 9. The sonotrode (1) according to claim 8, comprising a plurality of inner blades (51, 52), at least two of the inner blades (51, 52) being arranged in levels. 10. The sonotrode (1) according to any one of the preceding claims, wherein a distal end forming a cutting edge (12) forms a closed contour. 11. The sonotrode (1) according to any one of the preceding claims, wherein the distal end piece (5) defines an axis around which the distal end piece (5) extends, and wherein a distal end forming a cutting edge (12) follows a curve in 3D space, said curve being different from a curve extending in a plane perpendicular to the axis. 12. The sonotrode (1) according to claim 11, wherein the curve extends in a plane forming an angle with the axis, said angle being different from 90° and different from 0°. 13. An ultrasonic surgical instrument for cutting bones, comprising a housing (2) containing an ultrasonic transducer (3) and a sonotrode (1) as defined in any one of claims 1-12 mechanically coupled to said transducer (3), the instrument further comprising a suction device equipped to apply a vacuum inside the sonotrode (1) or in the vicinity of the sonotrode, and the instrument further comprising a liquid supply for supplying a liquid to a distal end of the sonotrode (1).