WO2014003688A1

WO2014003688A1 - A surgical cutting blade

Info

Publication number: WO2014003688A1
Application number: PCT/SG2013/000265
Authority: WO
Inventors: Jing Jin; Whye Kei Lye; Shahrzad RAYATPISHEH; Beng Hai Lim
Original assignee: Nanyang Technological University; Hands Surgery International Pte Ltd
Priority date: 2012-06-26
Filing date: 2013-06-26
Publication date: 2014-01-03

Abstract

A surgical cutting blade for cutting tissues is provided. The cutting blade is suitable for connection to a surgical cutting handle to form a scalpel, and comprises a body of electrically conductive material. The cutting blade includes an edge portion having a cutting edge, and first and second electrical terminals for connection to the cutting handle, which is capable of generating a voltage difference between the first and the second terminals. A switch can be provided to selectively apply the voltage difference across the blade for generating heat on the blade for hemostatic purpose. The cutting blade has an opening spaced from the cutting edge, the opening is positioned to reduce a cross sectional area of the body of electrically conductive material on an electrically conductive path between the first and second terminals. The cross sectional area refers to the area through which electrical current is configured to flow and perpendicular to that flow. The cutting edge of blade is capable of cutting tissues regardless if the blade is heated up.

Description

A Surgical Cutting Blade

Field of the Invention

The present invention relates to a surgical cutting blade and a scalpel comprising the same for cutting human or animal tissues. Background of the Invention

Scalpels comprising surgical blades are commonly used surgical tools for cutting human or animal tissues or other soft structures during surgery. Very often, tissue bleeds while being cut and consequently additional hemostatic procedures are required to alleviate post-operation hematoma and pain. Electro-cauterization is the process of destroying tissue using heat conduction from a metal probe. The metal probe is heated up electrically by DC current. The procedure may be used to cut through soft tissue as well as to stop bleeding by closing off a part of it as a result of the heat on the blade. The metal probe is usually a thin wire with a small cross section so that its electrical resistance is sufficiently high to generate enough heat in a simple DC circuit powered by, for example, batteries of a cordless device. The actual cutting mechanism of cauterization is to destroy the tissue by heat instead of by physical stress. Therefore, the metal probe used in cauterization typically has no or very limited cutting capability in, and it is not suitable for, cutting tissue when it is not heated up. Similar to the principle of electro-cautery, electro-surgery is also based on the use of heat to destroy tissue. Different from electro-cautery, in electro-surgery the heat is generated inside the tissue by using AC current to pass through the tissue itself and thus electro-surgery is usually performed in wet conditions for closing the electric circuit loop. In addition, an AC generator is required for electro-surgery and is usually bulky. A power cord is also necessary for connecting the probe to the power source.

Moreover, a common drawback of the above cauterizing procedures is the risk of burning or damaging excess tissues due to the intense heat generated. Therefore, it is crucial to control the temperature of the probe so as to minimize unnecessary tissue damages. To control the temperature of the blade for the purpose of hemostasis, Hemostatix Thermal System by Hemostatix Medical Technologies, discloses composite scalpels having multiple layers, such as blade layer, heat conduction layer, electric insulation layer, heating layer, etc, as described in US Patent No 5,308,311 and US Pat Publication No.2009/0112200 Al . However, these composite scalpels require separate electric power supplies and control circuits being connected via an electric cord. In addition, they are relatively expensive and bulky due to the complex layered structure.

Summary of the Invention

In general terms the invention proposes a surgical cutting blade having a body of electrical conductive material which is configured with an opening spaced away from the cutting edge of the blade. The opening is positioned to reduce a cross sectional area of the body of electrically conductive material on an electrically conductive path between first and second terminals of the body. The cross sectional area refers to the area through which electrical current is configured to flow and perpendicular to that flow.

Preferably, the opening is positioned to direct electrical current to an edge portion of the blade including the cutting edge upon the blade being subject to a voltage difference, and thereby cause effective power dissipation near the edge portion. The invention further proposes a surgical scalpel comprising the surgical cutting blade described above for cutting soft tissues and a method for cutting tissue using the surgical scalpel.

Specifically, in a first aspect of the invention, there is provided a surgical cutting blade for connection to a surgical cutting handle to form a scalpel, the surgical cutting blade being formed of electrically conductive material, the surgical cutting blade comprising: an edge portion including a cutting edge, and first and second terminals for connection to electrical terminals of the surgical cutting handle, whereby the surgical cutting handle is capable of generating a voltage difference between the first and the second terminals; the surgical cutting blade being configured with at least one opening spaced from the cutting edge, the at least one opening being positioned to reduce a cross sectional area of the body of electrically conductive material on an electrically conductive path between the first and second terminals, the cross sectional area being the area through which electrical current is configured to flow and perpendicular to that flow. In other words, the at least one opening creates at least one narrowed path (i.e. with reduced cross sectional area) on the body of electrical conductive material so as to increase resistance of the blade.

Preferably, the at least one opening is positioned to direct electrical current caused by said voltage difference to be transmitted between the first and the second terminals through said edge portion. Advantageously, if the opening is positioned near the cutting edge, it reduces the cross sectional area of the edge portion and thus increase the electrical resistance of the edge portion. As a result, enhanced resistive heating effects are produced near the edge portion, which beneficial for hemostatic purposes.

Preferably, the surgical cutting blade further comprises at least one elongate member having a first end connected to the edge portion and a second end extending into the at least one opening. Advantageously, the connection between the at least one elongate member and the edge portion strengthens the edge portion which is generally thin.

Optionally, the surgical cutting blade comprises first and second elongate members connected by a conductive bridge portion at the second ends and the blade is configured to direct electrical current to flow through the first and the second members. Furthermore, the edge portion of the body of the electrical conductive material may comprise one or more gaps along the cutting edge. This effectively increases the resistance of the blade by forcing the electrical current to travel along an additional distance in the resistive medium as introduced by the elongate members and the bridge portion. The gap may have a length that is similar to or smaller than the separation between the first ends of the first and the second elongate members.

Optionally, the one or more gaps are filled with a second material configured to direct the electrical current to flow through the at least one members. The second material is usually an insulating material. This feature is advantageous because the cutting edge is made more continuous to achieve an enhanced cutting capability. At the same time, the one or more gaps filled with insulating material prevent the electrical current from flowing through the continuous edge portion. Instead, the electrical current is forced to travel along the elongate members and the bridge portion leading to increased resistive heating on the blade.

Preferably, the edge portion has a cross sectional area that is smaller than a cross sectional area of the conductive bridge portion, where the cross sectional area refers to the area through which the electrical current is configured to flow and is perpendicular to that flow. As a result, the larger resistance at the edge portion allows the heat dissipation to be focused along the edge portion so as to achieve increased heating efficiency.

Alternatively, the edge portion of the body of the electrical conductive material is continuous. Typically, the cutting edge has two ends and the length along the cutting edge is larger than the distance between the two ends of the cutting edge. Again, the extended length of the corresponding edge portion gives rise to the increased resistance and the resulting heating effects on the edge portion.

Preferably, the material forming the cutting blade has a negative temperature coefficient of resistance.

Preferably, the body of electrical conductive material is generally planar. Typically, the surgical cutting blade is generally planar.

In a second aspect of the invention, there is provided a surgical scalpel for cutting soft tissue, the scalpel comprising: a surgical cutting blade comprising a body of electrically conductive material, the surgical cutting blade having first and second terminals and an edge portion including a cutting edge, and

a surgical cutting handle having electrical terminals connected to the first and the second terminals of the surgical cutting blade, wherein the surgical cutting handle has a switch component configured to selectively cause the surgical cutting handle to apply a voltage difference generated by a power source between the first and the second terminals;

wherein the surgical cutting blade is configured with at least one opening spaced from the cutting edge, the at least one opening being positioned to reduce a cross sectional area of the body of electrically conductive material on an electrically conductive path between the first and second terminals, the cross sectional area being the area through which the electrical current is configured to flow and perpendicular to that flow.

Preferably, the surgical blade is configured with at least one opening spaced from the cutting edge, the at least one opening being positioned to direct electrical current caused by said voltage difference to be transmitted between the first and the second terminals through said edge portion.

Advantageously, the surgical scalpel is provided with a switch component for activating and deactivating the heating function such that it can be used as an ordinary scalpel (without hemostatic function) and/or a cauterizer for stopping bleeding, where necessary.

Preferably, the power source is a battery and the surgical cutting handle contains the battery. As a result, the surgical scalpel can be made a compact handheld device. Typically, the surgical cutting handle further comprises a control means for limiting the electrical current to a predetermined value. For example, the control means comprises a control circuit having a resistor element and/or a fuse.

Preferably, the surgical scalpel further comprises a sensing element for detecting a value indicative of the temperature of a part of the surgical scalpel, for example, the various components of the surgical cutting handle such as the batteries and/or the resistor, and/or the surgical cutting blade.

Preferably, the surgical cutting blade is a surgical cutting blade according to the first aspect of the invention.

In a third aspect of the invention, there is provided a method of cutting human or animal tissue, comprising: providing a surgical scalpel comprising: a surgical cutting blade comprising a body of electrically conductive material, the body of electrical conductive material having first and second terminals and an edge portion including a cutting edge, and a surgical cutting handle having electrical terminals connected to the first and the second terminals of the surgical cutting blade, wherein the surgical cutting handle has a switch component configured to selectively cause the surgical cutting handle to apply a voltage difference generated by a power source between the first and the second terminals; wherein the surgical cutting blade is configured with at least one opening spaced from the cutting edge, the at least one opening being positioned to reduce a cross sectional area of the body of electrically conductive material on an electrically conductive path between the first and second terminals, the cross sectional area being the area through which electrical current is configured to flow and perpendicular to that flow; and bringing the surgical scalpel in contact with the human or animal tissue.

Typically, the method further comprises transferring thermal energy generated by the body of electrically conduct material to the tissue.

Optionally, the method further comprises delivering a chemical agent from the surgical cutting blade to the tissue. According to a particular example, the chemical agent is a hemostatic agent. Brief Description of the Figures

It will be convenient to further describe the present invention with respect to the accompanying drawings that illustrate possible arrangements of the invention. Other arrangements of the invention are possible, and consequently the particularity of the accompanying drawings is not to be understood as superseding the generality of the preceding description of the invention.

Figs. l(a)-(b) show a top view and a perspective view of a surgical cutting blade in accordance with an embodiment of the invention.

Fig. 2 shows a top view of the surgical cutting blade as shown in Fig. 1 when being secured and supported by a clamping device.

Fig. 3 shows a perspective view of a variation of the surgical cutting blade shown in Fig. 1.

Fig. 4(a) schematically illustrates a surgical cutting blade coupled to an electrical circuit comprising a battery in accordance with an embodiment of the invention.

Fig. 4(b) schematically illustrates a variation of the electrical circuit in Fig. 4(a).

Fig. 5 shows a top view and a side view of the surgical cutting blade in Fig. 4 when being secured and supported by a clamping device.

Figs. 6(a)-(b) show top views of two variations of the shape of the edge portion.

Fig. 7 shows a top view and a side view of a surgical cutting blade in accordance with an embodiment of the invention.

Fig. 8 shows a top view and a side view of a surgical cutting blade in accordance with a further embodiment of the invention. Fig. 9 schematically illustrates a control circuit design for connection to a surgical cutting blade in accordance with an embodiment of the invention. Fig. 10 shows the temperature evolution over time at the center and one end of the cutting edge in Fig. 9.

Fig. 1 1 shows a plot of the temperature evolution over time of the cutting edge in Fig. 9. Figs. 12(a)-(c) show the temperature evolution over time of various components of the control circuit in Fig. 9.

Fig. 13 shows a prototype of a surgical scalpel in accordance with an embodiment of the invention and its dimension.

Figs. 14(a)-(b) show another prototype of a surgical scalpel in accordance with an embodiment of the invention and its dimension.

Figs. 15(a)-(b) illustrate the use of the surgical scalpel as shown in Fig. 14 in cutting pig skin (under general anesthesia) with the scalpel when the switch is closed(the hemostatic function of the blade is activated).

Detailed Description of the Embodiments

Note that it is a purpose of this invention to provide a surgical cutting blade that can be heated up effectively to a desired range of temperature by a power source, which may include, for example, a power generator and transformer. However, the power source is preferred to be small in size and readily available such as batteries to achieve hemostatic function, i.e. by resistive heating. Preferably, no separate power cord is necessary for connecting the blade to a bulky power source and the scalpel can be made a compact handheld device capable of providing hemostatic functions. The heat generated by the surgical cutting blade also assists the cutting process via heat conduction to the tissue. At the same time, the blade is capable of cutting tissue without being heated up. This is an advantage over the commonly used metal probe in electro-cauterization.

Two batteries (AA), for example, can be used as the power supply in the electrical circuit. The internal resistance of the battery is typically between 0.1-0.4 Ohm. In order for the blade to be heated up effectively by the batteries, it is required that the blade has a resistance that is not much lower than the internal resistance of the batteries while it is preferred to have a resistance that is at least comparable to that of the batteries. Otherwise, the batteries will be heated up excessively due to their internal resistance before the blade is heated up. In this example, it is required that the blade has a resistance of much larger than 0.02 Ohm. However, the electric resistance of a piece of regular stainless blade (i.e. a solid piece of blade of a comparable dimension) is typically much less than 0.05 Ohm and therefore is not able to generate enough heat from the battery without the batteries being heated up excessively. The present invention addresses the above difficulties by proposing a blade that has a resistance large enough to cause a substantial portion the power/energy of the power source (such as, but not limited to, batteries) to dissipate on the blade itself, and especially at the edge portion comprising the cutting edge.

The term "an opening" refers a gap or a hole. In particular, the opening may be empty, i.e. a void, or filled with a second material thereby creating a gap.

The term "an electrical terminal" means any exposed conductive portion. In particular, it is not limited by any physical location within the structure (e.g. an end of a structure). For example, the terminal does not have to be near an end of a structure.

The term "an edge portion" generally refers to a structure of a surgical cutting blade, a rim of which forms the cutting edge of the cutting blade, and includes portions immediately adjacent to or in close proximity with the cutting edge.

The term "a cross section" generally means a section through which the electrical current is configured to flow and perpendicular to that flow, and the term "cross sectional area" is to be construed accordingly.

Fig. l(a)-(b) shows a surgical cutting blade 10 according to an embodiment of the invention. The surgical cutting blade 10 is formed of electrically conductive material and comprises an edge portion 12 including a cutting edge 14, an opening 20 spaced from the cutting edge 14, and a first and a second terminals 16, 18 for connection to electrical terminals of a cutting handle (not shown). The cutting handle is capable of generating a voltage difference 22 between the first and the second terminals 16, 18 of the blade 10, for example, upon connecting the first and the second terminals 16, 18 to a battery.

The opening 22 is positioned to reduce a cross sectional area of the body of electrically conductive material on an electrically conductive path between the first and second terminals 16, 18. The cross sectional area refers to the area through which electrical current is configured to flow and perpendicular to that flow.

Advantageously, the opening 22 is positioned near the cutting edge 14 so as to direct electrical current caused by said voltage difference to be transmitted between the first and the second terminals through the edge portion 12.

Due to the opening 20 as shown in Fig. 1(a), the width of the edge portion 12 is substantially reduced compared to a solid piece of surgical cutting blade of the same dimension. As a result, the electrical resistance of the surgical cutting blade 10 is substantially increased. The surgical cutting blade as shown in Fig. 1 is made of stainless steel and this configuration is able to achieve an increased resistance of about 0.3 Ohm. This forces electrical current caused by the voltage difference 22 to be transmitted between the first and the second terminals 16, 18 through the edge portion 12 of a narrow width, which in turn allows the blade to be electrically heated up effectively due to its increased resistance and thus achieve hemostatic function, for example, while the cutting edge 14 cuts through tissues.

This is advantageous because the opening 20 effectively causes the resistance of the surgical cutting blade 10 to increase substantially due to the reduced cross sectional area of the edge portion 12. Accordingly, the power or energy dissipation on the blade 10 itself will increase to heat up the blade more efficiently compared to the configuration of a solid piece of blade power in which the vast majority of power/energy is consumed by internal resistance of the batteries. In other words, the presence of an opening 12 on the blade 10 dramatically increases the electrical resistance and even makes it possible to achieve a resistance comparable to the internal resistance of the power source, for example, standard AA batteries. This is significant because it alleviates the problem of excessive heating of the batteries in the cutting handle which is undesirable for both power efficiency considerations and the usability of the device.

To further increase the resistance of the blade, the blade should be made from material that has generally good electric conductivity so as to allow the current to pass through, such as metallic material. At the same time, the material is preferred to have sufficiently high electric volume resistivity so as to cause effective heat generation as a result of a large resistance. For example, the blade can be made from metallic material with relatively high electric volume resistance such as stainless steel, Nichrome and/or NiTi. Table 1 below lists the electrical volume resistance of some metallic materials.

Table 1. Volume resistance of different materials

Further, the cutting edge 14 of the blade 10 is capable of cutting tissue without requiring the blade 10 to be heated up. Due to the enhanced cutting capability of the cutting edge 14 compared to the conventional metal probe for cauterization, high temperature for cauterizing and cutting tissue by heat is no longer required. This in turn mitigates the risks of unnecessary tissue damages. When in use, a switch for connecting the first and second terminals 16, 18 to a power source such as a battery (not shown) may be closed to activate the heating function for the purpose of hemostasis and assistive cutting, where necessary.

Fig. 1 further shows three elongate members 15, 17, 19 with their first ends coupled to the edge portion 12 and their second ends extending into the opening 20. The connections 21 between the three elongate members 15, 17, 19 to the edge portion 12 strengthen the edge portion 12 which is generally thin, and especially when the edge portion 12 has a narrow width. The blade shown in Fig. 1 further comprises two legs 25, 27, each being disposed between one of two ends 29, 31 of the edge portion 12 and the respective first or the second terminals 16, 18. The two legs 25, 27 of the blade 10 are optional since it will be understood by a skilled person in the art that one or both of the two legs 25, 27 may be omitted (in whole or in part) or may be a part of the cutting handle which is connectable to the blade 10 directly via the two ends 29, 31 of the edge portion 12. In this case, the two ends 29, 31 of the edge portion 12 serve the purpose of the first and second terminals 16, 18 for connection to the cutting handle.

The opening 20 of the blade 10 may be manufactured or fabricated by stamping, wire cutting or laser cutting from a solid plate. Other fabrication methods such as molding and welding are also possible as will be appreciated by a skilled person in the art.

Fig. 2 illustrates that a holder such as a clamp 26, may be provided between the cutting edge 14 and the cutting handle to hold any structure in between, for example, the elongate members 15, 17, 19 and/or the legs 25, 27 to further secure and support the cutting edge 14. The clamp 26 is made of insulating materials. In another embodiment, the holder is provided by a part of the cutting handle.

Fig. 3 shows a variation of the configuration of the blade in Fig. 1, in which the two legs 25, 27 have an extended length compared to the blade 10 in Fig. 1. This configuration further increases the overall resistance of the blade 10 thus further focuses heat generation on the blade and reduces excessive heat generation at the battery.

Fig. 4(a) shows a cutting blade 10 coupled to an electrical circuit comprising a battery 30. For example, this illustrates the connection between the surgical cutting blade and the surgical cutting handle which forms a surgical scalpel. Specifically, the surgical cutting handle has electrical terminals connected to the first and the second terminals 16, 18 of the surgical cutting blade 10 and the battery 30 having an internal resistance 30a may be contained in the surgical cutting handle. A switch component 32 is provided at the cutting handle configured to selectively cause the surgical cutting handle to apply a voltage difference generated by the battery 30 between the first and the second terminals 16, 18. When the switch 32 is closed, a closed loop is formed between the cutting blade 10 and the battery 30. Electrical current caused by the voltage difference of the battery is transmitted through the edge portion 12 of the blade 10 and thus heats up the edge portion 12 by resistive heating.

Referring to Fig. 4(b), a resistor element 36 may be provided in the electrical circuit as a control means for limiting the electrical current to a predetermined value and thus the resulting temperature of the cutting blade 10. For example, the control means comprises a control circuit having a resistor element and/or a fuse. In this example, the resistor 36 has a large positive temperature coefficient. Specifically, when the electrical current passes through and heats up the resistor 36, the resistance of the resistor 36 is increased. The increased resistance in turn limits the electrical current in the circuit and thus prevents the blade 10 from being overheated. In another example, the resistor 36 can be replaced by or used together with a fuse to cause a disconnection in circuit when the current is larger than a predetermined value. In yet another example, the resistor 36 is a standard resistor with a low temperature coefficient. In yet another example, the control means may be provided by the resistance of the blade 10 itself. For example, the two legs 25, 27 of the blade 10 can be long enough, such as those in Fig.3, to provide sufficient resistance so that the resistor 36 is no longer necessary. Furthermore, the resistance of various parts of the blade 10 may be configured to limit the electrical current in the circuit and/or along a certain part of the blade such as the two legs 25, 27, the edge portion 12, and/or the elongate members 15, 17, 19.

The surgical scalpel may comprise a sensing element for detecting a value indicative of the temperature of a part of the surgical scalpel, for example, the surgical cutting handle including its various components and/or the surgical cutting blade 10. For example, a thermal sensor may be included to the contact or provided in close proximity to the blade 10 or the surgical cutting handle, for sensing and possibly regulating the temperature of the blade or its holder. In another example, the cutting blade 10 itself may be utilized as a sensor for detecting temperature changes, for example, by measuring the change of its electric resistance or the resultant change of the current or voltage in the circuit. In yet another example, the resistor 36 described above may function as the sensing element. In some embodiments, the material forming the cutting blade 10 has a negative temperature coefficient of resistance. In particular, when the electrical current passes through the circuit shown in Fig 4(a)-(b), the blade 10 is heated up and its resistance reduces accordingly due to the negative temperature coefficient. As the resistance reduces, the current will increase which leads to more power being drawn by the resistor 36. The current of the circuit may reach a state of dynamic equilibrium. In other words, when the heat generated on the cutting blade 10 gets dissipated by the tissue, the resistance of the cutting blade increases due to the lowered temperature of the cutting blade 10, and hence more electric power will be generate on the blade, as P ^~ ¾, where P is the electric power, I_e is the equilibrium current, and R_b is the resistance of the blade (1). The increased power, P, in turn gets converted to thermal energy to heat up the blade to the equilibrium temperature. Therefore, the blade 10 could be configured to maintain a relatively constant temperature. More importantly, by employing the resistor 36 with an appropriate resistance property at a certain value, the blade 10 can be configured to maintain the temperature at a predetermined value.

The blade 10 in this embodiment has an edge portion 12 that is different from the blade of Fig. 1. Specifically, the surgical cutting blade 10 comprises four elongate members 15, 17, 19. 21, and each has a first end connected to the edge portion 12 and a second end extending into the at least one opening 20. The first and second elongate members 15, 17 are connected by a conductive bridge portion 38 at the second ends. The third and fourth elongate members 19, 21 are connected by a conductive bridge portion 39 at the second ends. The blade 10 is configured to direct electrical current to flow through the four elongate members 15, 17, 19. 21 and respective bridge portions 38, 39 in a serial manner. The edge portion of the body of electrically conductive material 12 as shown in Fig. 4 further comprises gaps 34, 35 along the cutting edge 14. This effectively increases the resistance of the blade by forcing the electrical current to travel along an additional distance in the resistive medium introduced by the elongate members 15, 17, 19. 21 and respective bridge portions 38, 39. The first gap 34 located between the first ends of the first and the second elongate members 15, 17 may have length that is similar to or much smaller than (see item 44 of Fig. 7) the separation between the respective first ends. Similarly, the second gap 35 located between the first ends of the third and the fourth elongate members 19, 21 may have length that is similar to or much smaller than (see item 44 of Fig. 7) the separation between the respective first ends. The edge portion of the electrically conductive material 12 and the four elongate members 15, 17, 19, 21 together with the respective bridge portions 38, 39 is configured to collectively form a labyrinth path between the first and the second electrical terminals 16, 18. In this example, the path is castellated. This leads to the increased resistance of the surgical cutting blade 12 as a result of the extended length of the labyrinth path. The surgical cutting blade Fig. 4 further shows that the edge portion 12 has a cross sectional area that is smaller than a cross sectional area of the conductive bridge portions 38, 39, where the cross sectional area refers to the area through which the electrical current is configured to flow. Accordingly, the resulting larger resistance at the edge portion allows the heat dissipation to be focused along the edge portion leading to increased heating efficiency.

Fig. 5 shows that a clamping device 26 may be provided to further reinforce and support the cutting edge 14.

Figs. 6(a) and (b) illustrate two possible variations of the shape of the edge portion 12 compared to the one shown Fig. 4. The edge portion 12 and the four elongate members 15, 17, 19, 21 together with the respective bridge portions 38, 39 is configured to collectively form a labyrinth path between the first and the second electrical terminals 16, 18. In Fig. 6(a), the shape of the edge portion 12 convex outwards with respect to two ends 29, 31 of the edge portion 12. In particular, the center 27 of the cutting edge 14 is forward of the two ends 29, 31. Alternatively, as shown in Fig. 6(b), the shape of the edge portion 12 generally curves inward with respect to two ends 29, 31 of the edge portion 12 and the center 27 of the cutting edge 14 is at the rear of the two ends 29, 31 of the edge portion 12. Additionally, the profile along the cutting edge may comprise a smooth curve with graduated changes in the tangential direction as provided in Fig. 6(a) or comprise an angled profile with abrupt changes in the tangential direction along the cutting edge 14. It will be understood by a person skilled in the art that the edge portion 12 can come in many possible shapes and the illustrations provided herewith is not meant to be exhaustive.

Fig. 7 shows another possible variation of the edge portion of the body of electrically conductive material 12 in accordance with the present invention. In particular, the edge portion 12 may be configured with a reduced the gaps 44 along the cutting edge 14 as compared to the surgical cutting blade 10 as shown in Figs. 4-6. Additionally, each of the gaps 44 may be completely filled by one or more additional materials which include at least one insulating material. This is for directing the electrical current to flow through the labyrinth path and thus maintain the large resistance of the surgical cutting blade 10 while making the profile along the cutting edge 14 more continuous for an enhanced cutting performance and/or improved strength.

Fig. 8 shows yet another possible variation of the edge portion in accordance with the present invention. It is different from the embodiment in Fig. 3 in that the gaps 34 are eliminated by a second electrically conductive material 54, thus making the cutting edge 14 a continuous one. The second electrically conductive material 54 may be the same as the material of the blade. The second electrically conductive material 54 formed near the edge portion 12 of the body of electrically conductive material has a further reduced cross sectional area compared to that of the adjacent edge portion 12, where the cross sectional area refers to the area through which the electrical current is configured to flow. As a result, the larger resistance near the cutting edge contributed by the reduced cross section of the second electrically conductive material 54 allows the heat dissipation to be further focused near the cutting edge leading to increased heating efficiency.

Applications and Test results

As an example, a surgical blade with haemostasis function in accordance with an embodiment of the present invention is designed for closed Carpal Tunnel Syndrome (CTS) surgery. It is appreciated that the surgical blade can be adapted for use in other types of surgery depending on the configuration of the blade 10 and the various components in the cutting handle. Non-exhaustive examples of the considerations for designing the surgical scalpel would be the shape and dimension of the blade, the property of the control circuit, and batteries/power supply requirements. For example, the duration or temperature requirement of certain types of surgery may be generally longer or higher, and the required power supply may increase accordingly. As the circumstances may require, the use of a cord and a transformer/power generator instead of batteries may be necessary. It is noted that the desired temperature range and heat duration for the haemostatic blade used in this particular example, i.e. the CTS surgery, are typically 50-60° C and the same temperature range should last for about 10 min. Note that the desired temperature range or heat duration may change depending on the surgical requirements. For example, the temperature may be required to increase by 5 to 15 ° C for this surgery and/or for other surgical purposes.

Fig. 9 shows a circuit design 50 in connection with the cutting blade 10. In particular, the circuit 50 comprises of two AAA-batteries 30 and a resistor element 36 including resistors 36a, 36b, 37c. The cutting blade 10 is coupled to the circuit via the electrical terminals. The heating function of the cutting blade 10 is demonstrated below.

The temperature evolution of the cutting blade 10 was recorded over time using FLUKE thermal imager and the results are shown in Fig. 10. It was observed that the temperature of the blade at the end 31 of cutting edge 14 rose to 60.1°C after 30 seconds. It was the highest temperature recorded. From 30 seconds onwards to the 13 min, the temperature slowly dropped from 60.1° C to 50.0° C due to reduced power supply as a result of a battery power issue, as shown in Fig 10. This demonstrates that the blade could stay in the desired range of 50-60 ° C for more than 10 minutes, which is sufficient for the application of closed CTS surgery.

Fig. 10 also shows the temperature at the centre 27 of the cutting edge 14. Temperature fluctuations within 56.3 °C-50.4 °C from 30 sec onwards till the 11 min was observed, which demonstrate that the temperature at the center 27 of the cutting edge 14 is within the desired range of 50-60 °C for about at least 10 min.

Fig. 11 shows a plot of the temperature evolution of the cutting edge, in which the desired range of temperature is annotated. This clearly shows that the temperature at the end 31 and the center 27 of the cutting edge 14 is within the desired range over the desired heat duration (10 min). Thus, the circuit design 50 together with the blade 10 is suitable for the closed CTS surgery. As will be appreciated by a skilled person in the art, the electrical current may be controlled by the resistance of the blade 10 itself. As a particular example, the two legs 25, 27 of the blade 10 as shown Fig.3 are long enough, to provide sufficient resistance so that one or more of the resistors 36a, 36b, 36c, 46a, 46b are no longer necessary. Furthermore, the resistance of various parts of the blade 10 may be configured to limit the electrical current in the circuit and/or along a certain part of the blade such as the two legs 25, 27, the edge portion 12, the elongate members 15, 17, 19, 21 and/or the bridge portion 38, 39, where applicable. The temperature of the various components of the circuit design 50 such as the resistors 36a, 36b, 36c and battery 30 were recorded for every 5 minutes interval, as shown in Figs. 12(a)-(b). Fig. 12(a) shows that the three resistors 36a, 36b, 36c are heated up to a temperature of 49.3 °C, 61.6 and 85.3°C, respectively after 5 mins. Fig. 12(b) shows that after 10 mins the temperatures of the three resistors are changed to 47.9°C, 63.5°C and 82.8°C, respectively. As shown in Fig. 12(c), the battery 30 has a temperature around 53-55 °C after 10 mins which suggests that the excessive heat generation at the battery has been mitigated.

Fig.13 shows the initial prototype of a surgical scalpel in accordance with an embodiment of the invention. The surgical scalpel 100 comprises a surgical cutting blade 10, a cutting handle 60 containing batteries 30, a control circuit 50 including a switch (not shown), and optionally a digital thermometer 62 attached to the end of the cutting handle 60 or alternatively forming a part of the cutting handle 60.

The surgical scalpel prototype as shown in Fig. 13 was tested on isolated porcine tendons to evaluate the sharpness and cutting capability of the surgical cutting blade 10 with the thermal function turned off.

The cutting experience using the surgical scalpel 100 without haemostatic function was successful. It was demonstrated that the surgical cutting blade 10 of the surgical scalpel 100 was able to cut smoothly through the tendon. Improvements on the cutting handle 60 may be made to make it more ergonomic and efficient. Figs. 14(a)-(b) show a second prototype of a surgical scalpel in accordance with an embodiment of the invention and its dimension.

Figs. 15(a)-(b) illustrate the use of the surgical scalpel as shown in Fig. 14 in cutting pig skin (under general anesthesia) with the scalpel when the switch is closed (i.e. the hemostatic function of the blade is activated). Fig.15(b) shows that no bleeding is observed after cutting the skin with the surgical scalpel. The hemostatic function of the surgical scalpel has been successfully demonstrated.

In summary, the present invention provides a blade with the ability to facilitate hemostasis in the tissues through which it passes. Temperature of the blade can be controlled to facilitate hemostasis and/or cauterization of tissue. In variants of the invention, methods by which hemostasis is induced may include the application of thermal and/or electrical energy. Furthermore, the blade may be configured to elute or deliver chemical agents such as hemostatic agents during the cutting process. For example, the hemostatic agents may form a coating on the cutting blade and get eluted to the tissue while the cutting blade cuts through the tissue.

Claims

Claims:

1. A surgical cutting blade for connection to a surgical cutting handle to form a scalpel, the surgical cutting blade comprising a body of electrically conductive material, the body of the electrically conductive material comprising: an edge portion including a cutting edge, and first and second terminals for connection to electrical terminals of the surgical cutting handle, whereby the surgical cutting handle is capable of generating a voltage difference between the first and the second terminals; the surgical cutting blade being configured with at least one opening spaced from the cutting edge, the at least one opening being positioned to reduce a cross sectional area of the body of electrically conductive material on an electrically conductive path between the first and second terminals, the cross sectional area being the area through which electrical current is configured to flow and perpendicular to that flow.

2. A surgical cutting blade according to claim 1, wherein the at least one opening is positioned to direct electrical current caused by said voltage difference to be transmitted between the first and the second terminals through said edge portion.

3. A surgical cutting blade according to claim 1 or claim 2, wherein the surgical cutting blade further comprises at least one elongate member having a first end connected to the edge portion and a second end extending into the at least one opening.

4. A surgical cutting blade according to any of claims 1-3, wherein the surgical cutting blade comprises a first and a second of the at least one elongate members connected by a conductive bridge portion at the second ends and the blade is configured to direct electrical current to flow through the first and the second elongate members.

5. A surgical cutting blade according to any of claims 1-4, wherein the edge portion of the body of the electrical conductive material comprises one or more gaps along the cutting edge.

6. A surgical cutting blade according to claim 5, wherein the one or more gaps are filled with a second material configured to direct the electrical current to flow through the at least one members.

7. A surgical cutting blade according to any of claims 4-6, wherein the edge portion has a cross sectional area smaller than a cross sectional area of the conductive bridge portion.

8. A surgical cutting blade according to any of claims 1-4, wherein the edge portion of the body of the electrical conductive material is continuous.

9. A surgical cutting blade according to any of the preceding claims, wherein the cutting edge has two ends and the length along the cutting edge is larger than the distance between the two ends of the cutting edge.

10. A surgical cutting blade according to any of the preceding claims, wherein the material forming the cutting blade has a negative temperature coefficient of resistance.

11. A surgical scalpel for cutting soft tissue, the scalpel comprising:

a surgical cutting blade comprising a body of electrically conductive material, the body of electrical conductive material having first and second terminals and an edge portion including a cutting edge, and a surgical cutting handle having electrical terminals connected to the first and the second terminals of the surgical cutting blade, wherein the surgical cutting handle has a switch component configured to selectively cause the surgical cutting handle to apply a voltage difference generated by a power source between the first and the second terminals;

wherein the surgical cutting blade is configured with at least one opening spaced from the cutting edge, the at least one opening being positioned to reduce a cross sectional area of the body of electrically conductive material on an electrically conductive path between the first and second terminals, the cross sectional area being the area through which electrical current is configured to flow and perpendicular to that flow.

12. A surgical scalpel according to claim 11, wherein the at least one opening is positioned to direct electrical current caused by said voltage difference to be transmitted between the first and the second terminals through said edge portion.

13. A surgical scalpel according to claim 11 or claim 12, wherein the power source is a battery and the surgical cutting handle contains the battery.

14. A surgical scalpel according to any of claims 11-13, wherein the surgical cutting handle further comprises a control means for limiting the electrical current to a predetermined value.

15. A surgical scalpel according to any of claims 14, wherein the control means comprises a resistor element and/or a fuse.

16. A surgical scalpel according to any of claims 11-15, wherein the surgical scalpel further comprises a sensing element for detecting a value indicative of the temperature of a part of the surgical scalpel.

17. A surgical scalpel according to any of claims 11-16, wherein the surgical cutting blade is a surgical cutting blade according to any of claims 2-10.

18. A method of cutting human or animal tissue, comprising:

providing a surgical scalpel comprising:

a surgical cutting blade comprising a body of electrically conductive material, the body of electrical conductive material having first and second terminals and an edge portion including a cutting edge, and

wherein the surgical cutting blade is configured with at least one opening spaced from the cutting edge, the at least one opening being positioned to reduce a cross sectional area of the body of electrically conductive material on an electrically conductive path between the first and second terminals, the cross sectional area being the area through which electrical current is configured to flow and perpendicular to that flow; and

bringing the surgical scalpel in contact with the human or animal tissue.

19. A method of cutting human or animal tissue according to claim 18 further comprising transferring thermal energy generated by the body of electrically conduct material to the tissue.

20. A method of cutting human or animal tissue according to claim 18 or claim 19 further comprising delivering a chemical agent from the surgical cutting blade to the tissue.

21. A method of cutting human or animal tissue according to claim 20, wherein the chemical agent is a hemostatic agent.