WO2008012357A1

WO2008012357A1 - Cutting instruments for ultrasonic surgery

Info

Publication number: WO2008012357A1
Application number: PCT/EP2007/057756
Authority: WO
Inventors: Cornelio Blus
Original assignee: Cornelio Blus
Priority date: 2006-07-27
Filing date: 2007-07-27
Publication date: 2008-01-31
Also published as: ITTO20060558A1

Abstract

A surgical instrument (10) is capable of cutting flesh and cartilage by vibrating at ultrasonic frequencies ranging between 23 kHz and 36 kHz. The instrument includes a titanium alloy body with a straight tang (11), a straight distal length (12) having a sharp free end (13), and an intermediate length (14) between the tang (11) and the distal length (12). The intermediate length has two successive curved portions (14a, 14b) with concavities facing towards opposite directions which are perpendicular to a central axis (x) of the instrument. The intermediate (14) and distal (12) lengths are progressively flattened and get thinner from the tang (11) towards the end (13).

Description

Cutting instruments for ultrasonic surgery

The present invention relates to cutting instruments to be used in ultrasonic surgery for cutting flesh and the like, such as mucosa, skin, vessels, cysts, tumoral tissues, gingival tissues, etc. and cartilage. The instruments according to the invention are intended for use, particularly but not exclusively, in the fields of orthopaedic surgery, otorhinolaringologic surgery, dentistry, neurosurgery, maxillofacial surgery, vascular surgery, cosmetic surgery and veterinary surgery.

The ultrasonic technique is widespread in bone surgery, where it is generally used also because it does not cause undesired cuts in the flesh. There are known surgical devices containing electrically supplied piezoelectric transducers which cause vibration of a metal instrument that can cut the bone or separate biological tissues. See, for example, patent publications US-2 984 241, US-4 188 952 and EP-O 238 667.

It is an object of the invention to provide a cutting instrument capable of making ultrasonic surgery applicable also for cutting flesh and cartilage.

This object is achieved, in accordance with the present invention, by a surgical instrument having the features defined in claim 1. Preferred embodiments of the invention are defined in the dependent claims.

The advantages of the invention will become apparent from the following detailed specification, given by way of example, reference being made to the accompanying drawings, in which: figures 1 and 2 are a perspective view and a side view, respectively, of a first embodiment of a surgical cutting instrument according to the invention; figure 3 is a side view of a second embodiment of an instrument according to the invention; figure 4 is a perspective view schematically showing an apparatus for vibrating the instruments of figures 1 to 3 at ultrasonic frequencies, and figure 5 schematically shows a control panel of the apparatus of figure 4. A first embodiment of a surgical instrument for ultrasonic bone surgery according to the invention (figures 1 and 2) is indicated as a whole at 10. The instrument 10, consisting of an elongate body made of titanium alloy, preferably titanium grade 5 alloy, extends along a central axis x having a succession of straight and curved lengths lying in a plane herein defined "vertical". The instrument 10 comprises a proximal length or locking tang 11 of rectilinear shape, a thin, straight distal length 12 with a sharp cutting end 13 and an intermediate length 14 which includes two successive curved portions with respective concavities facing opposite directions, as described hereinafter.

The tang 11, substantially cylindrical and having an increased diameter with respect to that of the distal length 12, is adapted to be clamped or screwed or otherwise steadily mounted onto a cylindrical handpiece M (shown only in part in figures 1 to 3) that the surgeon will grip. The handpiece M is part of a medical ultrasonic apparatus which electrically supplies a set of piezoelectric transducers housed in the handpiece, so as to vibrate the instrument 10 at a frequency in the ultrasonic range. The constructional and functional features of the aforementioned apparatus are not per se relevant for the understanding of the invention and will not therefore be described in detail. Suffice it here to say that said apparatus allows to adjust the input power and the frequency of the vibrations imparted to the instrument.

Figure 4 shows by way of example an ultrasonic apparatus A with a handpiece M connected through a cable C. Indicated F is a flowmeter for measuring the flow rate of a cooling physiological solution supplied by means of a peristaltic pump P. Apparatus A is equipped with an on/off foot pedal B and a control panel CP (figure 5) comprised of keys 1, 2, 3 for selecting frequency channels as a function of the type of instrument being used, keys 4, 5, 6 for adjusting the flow rate supplied by the pump P, a knob 8 for selecting the frequency of the instrument mounted on the handpiece. By acting on the knob 8, one varies the frequency of the electric power supply, with a consequent impedance variation that causes a change in the frequency of vibration of the instrument. Keys Bl and B2 allow to select the power level supplied to the handpiece M, whereas displays Dl and D2 show the selected power and flow rate levels. A further display D3 shows the time the apparatus has been used. It can be reset by a key 9. Vibrations are transmitted to the tang 11 in form of pulses along the axis x and are propagated and amplified through the intermediate length 14 and transmitted to the distal length 12 and the cutting end 13 that is brought in contact with the biological tissue to cut.

As shown, while the tang 11 has a substantially uniform thickness, the intermediate and distal lengths 14 and 12 are progressively flattened and get thinner when measured in directions yl, y2 which are perpendicular, in each point, to the central axis x and lie in the aforesaid vertical plane.

The intermediate length 14 has a first curved portion 14a with its concavity directed upwardly in the vertical plane, a second curved portion 14b with a downwardly facing concavity radiused to the distal length 12 so that the latter is inclined (at an angle α of about 45°-70°) with respect to the tang 11. The bending radius of the first curved portion 14a is definitely greater than that of the second curved portion 14b. Furthermore, the intermediate length 14 has a straight portion 14c, substantially aligned with the tang 11 and connecting the first curved portion 14a with the tang.

Preferably the thickness S 1 , as measured in direction y at the junction between the tang 11 and the intermediate length 14, ranges between 2.0 and 3.0 mm, whereas the thickness S2 of distal length 12 near the sharp cutting end 13 is preferably ranging between 0.4 and 0.6 mm. The overall length of the instrument, without the tang, is preferably of about 30 mm.

The instrument shown in figures 3 differs from that of figures 1 and 2 in the orientation of the blades of the sharp cutting end 13, which lie in a vertical plane instead of an inclined plane perpendicular to said vertical plane.

Whilst it is not desired to be bound to any specific theory in this connection, tests carried out by the Applicant show that, as a result of the shape of the instruments as described herein above and owing to the choice of titanium alloy as a material for their construction, these instruments lend themselves ideal to cut flesh and cartilage if applied to ultrasonic apparatus in certain operational conditions. More particularly, instruments according to the invention have displayed surprising performances if used within a frequency range between about 23 kHz and about 36 kHz. At higher frequencies, above 37 kHz, the instrument still works well but the handpiece reaches excessively high temperatures. With all the instruments of the present invention, best results have been attained using on the apparatus an input power ranging between 20 and 90 W, particularly between 42 and 90 W, with a sinusoidal wave.

It has been noted that the instruments of the present invention, when used in the aforesaid operational conditions, cut the flesh without causing appreciable bleeding, by causing the cut blood vessels to close temporarily. This result controverts the opinion, widespread in the medical field, that the ultrasonic technique, widely used in bone surgery, does not cause cuts in the flesh. The instruments of the present invention have proven to operate practically as an electrosurgical knife since almost no bleeding occurs, but with the advantage of not burning, and therefore not necrotizing, the flesh being cut. Another advantageous aspect of the invention is that the cut resulting from the use of an instrument according to the invention is particularly accurate and thin.

The above results have been attained with instruments manufactured by chip-forming machining from a blank. The same instruments are then subjected to a normalizing step in order to preserve the molecular properties of the titanium alloy. It is believed that this machining and this treatment confer better elastic properties to the instrument in terms of wider oscillations of its free cutting end.

The invention is not intended to be limited to the embodiments described and illustrated herein, which should be considered as examples of a surgical cutting instrument. Rather, the invention may be modified with regard to constructional and functional details, particularly concerning the shape of the sharp cutting end and the orientation of its blade (or blades) which, depending on the specific use the instrument is intended for, may indifferently be straight or saw -toothed, with one or two straight or curved blades, etc.

Claims

1. A surgical instrument (10) for cutting flesh and the like by vibrating at ultrasonic frequencies, including an elongate metal body extending along a central axis (x), the body lying in a plane and having a succession of straight and curved lengths, characterised in that the instrument is made of titanium alloy and comprises: a straight tang (11) adapted to be locked to a surgical device (M) capable of imparting to the instrument vibrations at frequencies ranging between about 23 kHz and about 36 kHz, - a straight distal length (12) inclined with respect to the tang (11), thinner than the tang and having a sharp free end (13), an intermediate length (14) between the tang (11) and the distal length (12), the intermediate length having two successive curved portions (14a, 14b) with respective concavities facing towards directions (yl, y2) which are substantially opposite and perpendicular to the central axis (x), wherein the intermediate (14) and distal (12) lengths are progressively flattened and get thinner when measured in directions (y) which are perpendicular, in each point, to the central axis (x) and lie in said plane.

2. A surgical instrument according to claim 1, characterised in that the distal length (12) is inclined at an angle of about 45°-70° with respect to the tang (11).

3. A surgical instrument according to claim 1, characterised in that the intermediate length (14) includes a straight portion (14c) which is substantially aligned with the tang (11) and connects the tang (11) to the curved portion (14a) nearer thereto.

4. A surgical instrument according to any one of the preceding claims, characterised in that the thickness (Sl) of the instrument, measured in said perpendicular direction (y) at the junction between the tang (11) and the intermediate length (14) ranges between about 2.0 and about 3.0 mm, and that the thickness (S2) of the distal length (12) near the sharp free end (13) ranges between about 0.4 and about 0.6 mm.

5. A surgical instrument according to any one of the preceding claims, characterised in that the overall length of the instrument (10), without the tang (11), is about 30 mm.

6. A surgical instrument according to any one of the preceding claims, characterised in that the instrument (10) is made of titanium grade 5 alloy.

7. A method of vibrating a sharp surgical instrument so as to cut flesh and the like, the method including the steps of: providing a surgical instrument according to claim 1 ; - provide apparatus electrically supplying at least one piezoelectric transducer located in a handpiece mechanically connected to the surgical instrument; selecting on the apparatus a frequency of said electric supply so as to cause the instrument to vibrate at a frequency ranging between about 23 kHz and about 36 kHz; selecting on the apparatus a level of electric power supplied to the handpiece ranging between about 20 W and about 90 W; electrically supplying the piezoelectric transducer with the selected frequency and power through the apparatus, thereby causing the surgical instrument to vibrate at an ultrasonic frequency ranging between about 23 kHz and about 36 kHz.