Surgical tubular shaft instrument

Abstract

Surgical tubular shaft instrument (1) with a handpiece (2), a tubular shaft (5) extending therefrom, a tool (7) mounted at the distal end of the tubular shaft (5) for rotation about the tubular shaft longitudinal axis, and with a drive shaft (6) extending in the tubular shaft (5) from the handpiece to the tool (7) and rotatable about the tubular shaft longitudinal axis by a motor drive, wherein the drive shaft (6) is designed as a tube over at least a substantial part of its length, characterized in that the drive shaft (6) is mounted in the tubular shaft (5) by balls (8) which bear on the one hand against the inner wall of the tubular shaft (5) and on the other hand against the outer wall of the drive shaft (6), that the balls (8) are freely rotatable and secured against displacement in wall openings (11) of a sleeve-shaped cage (9) which is arranged in a space (10) between the tubular shaft (5) and the drive shaft (6) surrounding the latter,and that the drive shaft (6) and the cage (9) are made of an elastic material which allows bending of the drive shaft (6) and the cage (9).

Description

[0001] The invention relates to a surgical tubular shaft instrument with a handpiece, a tubular shaft extending therefrom, a tool mounted at the distal end of the tubular shaft so as to be rotatable about the tubular shaft longitudinal axis, and with a drive shaft running in the tubular shaft from the handpiece to the tool and rotatable about the tubular shaft longitudinal axis by a motor drive, wherein the drive shaft is designed as a tube over at least a substantial part of its length.

[0002] Tubular-shaft surgical instruments are used for drilling or milling, for example, and are particularly employed in microsurgical and neurological operations where extremely small dimensions are required. It is known that such instruments use tools, such as milling heads, with an outer diameter between 1 mm and 4 mm. To achieve sufficient removal rates with such tools, these rotating tools must be operated at very high speeds; for example, such instruments are known to rotate at speeds between 20,000 and 60,000 rpm.

[0003] For many applications, it is desirable for the tubular shafts of these instruments to be bent or capable of being bent, rather than straight. This results in the drive shafts, which are rotatably mounted in the tubular shafts, also being bent accordingly, with each rotation. The associated deformation of the drive shafts leads to significant heating, and this heating can, of course, only be tolerated up to a certain temperature for instruments inserted into the body. In practice, this limits the speed at which such tubular shaft instruments can be operated, as increasing the speed leads to excessive heating.

[0004] To remedy this, it is known, for example in the case of tubular shaft instruments that operate at 60,000 rpm, to manufacture the drive shaft from special alloys, for example from a shape memory alloy, since these special alloys experience particularly low heating during deformation.

[0005] A tubular shaft instrument of this type is described in EP 0 286 415 A2.

[0006] Further embodiments of tubular shaft instruments are disclosed in DE 83 13 370 U1, CH 610 754 A5, EP 1 598 023 A2 and US 5 639 236 A.

[0007] The object of the invention is to design a generic surgical tubular shaft instrument in such a way that the heating of the drive shaft due to deformation when the tubular shaft is bent is reduced.

[0008] This object is achieved according to the invention in a surgical tubular shaft instrument of the type described at the outset in that the drive shaft is mounted by balls in the tubular shaft, which on the one hand rest against the inner wall of the tubular shaft and on the other hand against the outer wall of the drive shaft, that the balls are freely rotatable and secured against displacement in wall openings of a sleeve-shaped cage which is arranged in a space between the tubular shaft and the drive shaft surrounding the latter, and that the drive shaft and the cage are made of an elastic material which enables bending of the drive shaft and the cage.

[0009] Due to its particularly thin-walled tube design, the drive shaft offers significantly less resistance to deformation during rotation, resulting in significantly lower heating. A tubular drive shaft therefore allows significantly higher speeds to be achieved. For example, it is easily possible to operate a tubular shaft instrument with a tool with a diameter of 1 mm at a speed of 100,000 rpm. With a bent tubular shaft, heating levels that do not exceed a tolerable temperature, for example, a temperature of 43°C, are achieved.

[0010] The drive shaft can be designed as a tube over its entire length, but it is also possible in principle for the tubular design to extend over part of the length of the drive shaft. For example, the drive shaft can be solid at the distal end or at the proximal end to form a connection to the tool or to a drive.

[0011] The drive shaft is supported by balls in the tubular shaft, which rest on the inner wall of the tubular shaft and the outer wall of the drive shaft. This allows the drive shaft to be mounted along the entire length of the tubular shaft in a very small space, especially with a curved tubular shaft, without requiring space for additional ball bearing rings.

[0012] The balls are designed to rotate freely and be secured against longitudinal displacement in the wall openings of a sleeve-shaped cage, which is arranged in a space between the tubular shaft and the drive shaft. Such a sleeve-shaped cage requires very little space between the tubular shaft and the drive shaft, yet can still secure the balls in their respective positions.

[0013] The drive shaft and cage are made of an elastic material.

[0014] In a first preferred embodiment, the drive shaft is connected to the tool in one piece, but in other embodiments it is also possible to connect the drive shaft to the tool, for example by welding or pressing.

[0015] The tool can carry a connecting piece that extends into the drive shaft.

[0016] If the drive shaft is formed as a tube at its proximal end, the wall thickness is usually so thin that machining in this area is hardly possible. Therefore, in this case, it is advantageous if the drive shaft has a non-circular coupling section at its proximal end due to permanent non-cutting deformation.

[0017] This can be achieved, for example, by having the drive shaft have a trough-shaped depression on opposite sides, for example with a circular cross-section.

[0018] By designing the drive shaft as a tube, the strength of the drive shaft is reduced compared to a solid drive shaft. This can lead, particularly in tools with a larger tool head diameter, to the drive shaft being unable to transmit the necessary torque to the tool. According to a preferred development, a tool head is therefore provided with a hollow design, so that the moment of inertia of the tool is significantly reduced.

[0019] It can be provided that the balls are held captive in the wall openings of the cage so that the drive shaft can be pulled out of the tubular shaft and replaced without the balls losing their position.

[0020] The ball bearings can cause relatively high surface pressures in the contact area between the balls and the inner wall of the tubular shaft and the outer wall of the drive shaft. It is therefore advisable to use materials that are highly wear-resistant and hard in this contact area.

[0021] For example, the balls can be made of ceramic or hard metal.

[0022] It may further be provided that the inner wall of the tubular shaft and / or the outer wall of the drive shaft have a wear-resistant coating, for example, a titanium nitride coating, a crystalline or amorphous diamond layer, or a hard chrome coating. It is also possible to harden the surface using special hardening processes.

[0023] Furthermore, it is advantageous if the tubular shaft is made of an elastic material so that the tubular shaft can be bent with the drive shaft.

[0024] In a preferred embodiment, the handpiece is designed as an angled handpiece. This makes it possible to position the connections to the angled handpiece, for example, for the power supply, irrigation fluid supply, compressed air supply, etc., laterally on the tubular shaft instrument rather than in the extension of the tubular shaft's longitudinal axis. This leaves the area along the tubular shaft free of such connections, allowing the surgeon to use this area for observation, whether for direct observation by the surgeon or for the installation of a microscope or camera to observe the working area of ​​the tool.

[0025] The handpiece may further be provided with gripping surfaces arranged such that parts of the hand resting against the gripping surfaces are not positioned in the extension of the longitudinal axis of the tubular shaft extending from the handpiece. This also ensures that an area immediately adjacent to the tubular shaft remains clear for observation purposes.

[0026] The following description of preferred embodiments of the invention serves to explain it in more detail in conjunction with the drawings. They show: Fig. 1: a perspective view of a tubular shaft instrument with a rotating tool; Fig. 2: a perspective view of a tubular shaft for use with the tubular shaft instrument of the Fig. 1 with a tubular shaft bent lengthwise; Fig. 3: a longitudinal sectional view through the distal part of a straight tubular shaft; Fig. 4: a view similar Fig. 3 with a bent tubular shaft; Fig. 5: a side view of a partially broken-away tool with attached drive shaft; Fig. 6: a side view of the tubular drive shaft, partially cut away, at its proximal end; Fig. 7: a view similar Fig. 5 with a solid tool and a connecting piece engaging into the tubular drive shaft; Fig. 8: a view similar Fig. 7 with a hollow tool.

[0027] The tubular shaft instrument 1 shown in the drawing comprises a handpiece 2 with a front, essentially cylindrical part 3 and a rear connection part 4 which is angled relative to the cylindrical part and to which supply lines not shown in the drawing can be connected, for example for supplying electrical energy, rinsing fluid, compressed air, etc. It is also possible for a rotating drive shaft to be connected directly in this area, so that the drive is then arranged away from the handpiece.

[0028] At the end of the handpiece 2 opposite the connecting part 4, a tubular shaft 5 extends from the handpiece 2, within which a drive shaft 6 is mounted, which extends through the tubular shaft and is rotatable about the longitudinal axis of the drive shaft and thus of the tubular shaft. The drive shaft 6 is coupled to a drive arranged in the front part 3 of the handpiece 2 and not shown in the drawing, which rotates the drive shaft 6 about its longitudinal axis. At the distal end, the drive shaft 6 carries a tool 7, for example a milling head, which can be rotated by the rotation of the drive shaft 6.

[0029] The drive shaft 6 is mounted inside the tubular shaft 5 by a plurality of balls 8, which rest on the one hand against the outer wall of the drive shaft 6 and on the other hand against the inner wall of the tubular shaft 5 and are secured against lateral displacement by sleeve-shaped cages 9. These cages 9 are arranged in a space 10 formed between the drive shaft 6 and the tubular shaft 5, and the cages 9 concentrically surround the drive shaft 6. Openings 11 are arranged in the wall of the cages 9, each of which accommodates a ball 8 and thereby secures it against lateral displacement. The openings 11 are designed such that the balls 8 are held captive in the cages and therefore do not escape from the openings 11 even when the drive shaft 6 is pulled out of the tubular shaft 5. This can be achieved by appropriately shaping the edges of the opening 11.

[0030] The openings 11 with balls 8 mounted therein extend over the entire length of the tubular shaft 5, so that the drive shaft 6 is mounted in the tubular shaft 5 in all longitudinal areas of the tubular shaft 5.

[0031] The tubular shaft 5 can be straight, as shown in Fig. 3, but it is also possible that the tubular shaft 5 is bent, as can be seen from the illustration of Fig. 4. This bend can be permanent, but it is also possible for the tubular shaft 5 itself to be bendable to a certain extent. For this reason, it is intended that an elastic material be used for the tubular shaft, the drive shaft, and the cages that allows for bending; for example, stainless steel could be used.

[0032] The outer wall of the drive shaft 6, the inner wall of the tubular shaft 5 and the surface of the balls 8 are preferably made of a hard and wear-resistant material; this can be achieved either by a corresponding coating, for example with titanium nitride or with a crystalline or amorphous diamond layer, or a correspondingly hard material is used, for example the balls 8 could be made of ceramic or hard metal.

[0033] In the embodiment shown in the drawing, the drive shaft 6 is designed as a tube with a relatively thin outer wall. For example, the diameter of the drive shaft can be between 1 mm and 1.2 mm, with the wall thickness of the tube between 0.1 mm and 0.2 mm. This tubular design allows the drive shaft 6 to be bent relatively easily, so that the deformation energy, and thus the heating, that the drive shaft 6 undergoes during rotation in a bent tubular shaft is minimized.

[0034] The drive shaft 6 can be connected to the tool 7 in one piece, but it is also possible for the tool 7 and the drive shaft 6 to be connected to one another by a suitable connection technique. For example, a tool 7 can carry a connecting piece 12 that extends into the tubular drive shaft 6 and is connected there to the drive shaft 6 by welding, in particular laser welding ( Fig. 8), or by pressing the tubular drive shaft 6 with the connecting piece 12 ( Fig. 7) is connected.

[0035] In the embodiment of the Fig. 7 the tool is solid, whereas in the embodiments of the Fig. 5, in which the tool and the drive shaft are formed in one piece, or the Fig. 8, in which the drive shaft 6 is connected to the tool 7 by welding, uses tools 7 that are hollow and therefore have a significantly lower moment of inertia than solid tools. Such hollow tools can also be operated with drive shafts, which, due to their tubular design, are less stable and can only transmit lower torques.

[0036] The proximal end of the drive shaft 6 is designed as a coupling section 13. This coupling section 13 is non-circular so that it can form a rotationally fixed connection with a corresponding coupling piece in the handpiece 2 when this coupling section 13 is inserted into the handpiece. Since the drive shaft 6 is designed as a tube, machining in this area is generally not possible due to the small wall thicknesses. It is therefore advantageous if the wall of the drive shaft 6 in the coupling section 13 is transformed into a non-circular configuration by non-cutting deformation, in the example of the Fig. 6 this is done by pressing in recesses 14 with a circular cross-section on opposite sides of the drive shaft 6, and also the end regions of the drive shaft 6 are pressed together to form a tip 15.

[0037] The tubular shaft 5 does not exit the handpiece 2 centrally, but is laterally offset from the central axis of the front part 3 of the handpiece 2 such that the tubular shaft 5 and the angled connecting part 4 are arranged on opposite sides of the central longitudinal axis of the front part 3. In this way, the area of ​​the tubular shaft is free of connections and is accessible either to the surgeon or to an optical observation instrument. This freedom is also ensured by the fact that gripping surfaces 16 are arranged on the handpiece 2 such that parts of the surgeon's hand resting against them are not arranged in the extension of the longitudinal axis of the tubular shaft and therefore cannot obstruct observation in this area.

Claims

[1] Surgical tubular shaft instrument (1) with a handpiece (2), a tubular shaft (5) extending therefrom, a tool (7) mounted at the distal end of the tubular shaft (5) so as to be rotatable about the tubular shaft longitudinal axis, and with a drive shaft (6) extending in the tubular shaft (5) from the handpiece to the tool (7) and rotatable about the tubular shaft longitudinal axis by a motor drive, the drive shaft (6) being designed as a tube at least over a substantial part of its length, characterized bythat the drive shaft (6) is mounted in the tubular shaft (5) by balls (8) which bear on the one hand against the inner wall of the tubular shaft (5) and on the other hand against the outer wall of the drive shaft (6), that the balls (8) are freely rotatable and secured against displacement in wall openings (11) of a sleeve-shaped cage (9) which is arranged in a space (10) between the tubular shaft (5) and the drive shaft (6) surrounding the latter, and that the drive shaft (6) and the cage (9) are made of an elastic material which enables the drive shaft (6) and the cage (9) to bend. [2] Surgical tubular shaft instrument (1) according to claim 1, characterized by that the drive shaft (6) is integrally connected to the tool (7). [3] Surgical tubular shaft instrument (1) according to claim 1, characterized by that the drive shaft (6) is welded or pressed to the tool (7). [4] Surgical tubular shaft instrument (1) according to claim 1 or 3, characterized by that the tool (7) carries a connecting piece (12) which extends into the drive shaft (6). [5] Surgical tubular shaft instrument (1) according to one of the preceding claims, characterized by that the drive shaft (6) has a non-circular coupling section (13) at its proximal end due to a permanent non-cutting deformation. [6] Surgical tubular shaft instrument (1) according to claim 5, characterized by that the drive shaft (6) has a trough-shaped recess (14) on each of the opposite sides. [7] Surgical tubular shaft instrument (1) according to one of the preceding claims, characterized by that the tool (7) or a tool head is hollow. [8] Surgical tubular shaft instrument (1) according to one of the preceding claims, characterized by that the balls (8) are held captive in the wall openings (11) of the cage (9). [9] Surgical tubular shaft instrument (1) according to one of the preceding claims, characterized by that the balls (8) are made of ceramic or hard metal. [10] Surgical tubular shaft instrument (1) according to one of the preceding claims, characterized by that the inner wall of the tubular shaft (5) and / or the outer wall of the drive shaft (6) have a wear-resistant coating. [11] Surgical tubular shaft instrument (1) according to one of the preceding claims, characterized by that the tubular shaft (5) consists of an elastic material, so that the tubular shaft (5) can be bent with the drive shaft (6), or that the tubular shaft (5) has a fixed bend. [12] Surgical tubular shaft instrument (1) according to one of the preceding claims, characterized by that the handpiece (2) is designed as an angle handpiece. [13] Surgical tubular shaft instrument (1) according to one of the preceding claims, characterized bythat the handpiece (2) has gripping surfaces (16) which are arranged in such a way that parts of the hand resting on the gripping surfaces (16) are not positioned in the extension of the longitudinal axis of the tubular shaft (5) emerging from the handpiece (2).

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