WO2005107605A1

WO2005107605A1 - Surgical instrument

Info

Publication number: WO2005107605A1
Application number: PCT/GB2005/001746
Authority: WO
Inventors: Martin Tonbridge Norton Knight
Original assignee: Endospine Kinetics Limited
Priority date: 2004-05-10
Filing date: 2005-05-10
Publication date: 2005-11-17
Also published as: GB0410250D0

Abstract

A surgical instrument comprising an elongate shaft (1) having an arm (2) moveably mounted at one end and a user operable control (10, 12) mounted at or towards the opposite end, the control being operable to move the arm relative to the shaft. The instrument may be a nerve retractor and/or a tissue dissector, the arm being a retraction arm and/or dissection arm. The arm (2) may be generally flat with a curved working surface (3) and may be pivoted. relative to the shaft (1) between, at least a position where it extends in a direction perpendicular to the long axis and a position where it extends generally along the long axis. The elongate shaft may be rotatably connected to the user operable control enabling the shaft and arm to be rotated independently of the user operable control. Means (14) to lock the elongated shaft and/or the arm may be provided.

Description

SURGICAL INSTRUMENT

The present invention relates to a surgical instrument, particularly to a nerve root retractor and/or dissector, and to a method of use of the instrument. The instrument is intended for use in surgery on the spine, specifically to retract nerves contained within or associated with the spinal column to allow access to the spinal canal and in particular spinal discs and/or to dissect tissue planes such as between the dura and adjacent tissues, and within scar tissue. Conventionally, to operate on the spine and gain access to spinal discs it is necessary to perform open surgery. Nerves contained in the spinal column are retracted as necessary by use of a retractor comprising an elongate shaft with a fixed trough shaped member extending transversely to the elongate shaft, at one end of the shaft. A problem with such conventional retractors is that considerable manipulation of the elongate shaft is required to position the trough shaped member to accommodate and retract a nerve. This manipulation can cause trauma to the nerve and adjacent structures. Because the trough shaped portion is supported by an elongate shaft parts of the shaft remote from the trough shaped portion may be required to undergo much greater spatial movement than the end of the shaft supporting the trough shaped portion in order to orient the trough shaped portion as desired. This increases the risk of trauma, particularly when working in larger wound depths. This limits the manner in which conventional retractors may be used. Also, the absolute size of the trough shaped member demands a minimum size of opening for access to the operation site which effectively necessitates that open surgery is performed. It is an object of embodiments of the present invention to provide an improved instrument for use as a nerve root retractor and/or dissector. It is a further object of embodiments of the invention to provide a nerve root retractor suitable for use in keyhole and/or endoscopic surgical techniques, as well as open surgery. According to a first aspect of the present invention there is provided a surgical instrument comprising an elongate shaft having an arm moveably mounted at one end and a user operable control mounted at or towards the opposite end, the control being operable to move the arm relative to the shaft. According to a second aspect of the present invention there is provided a method of retracting a nerve or dissecting tissue within or associated with a spinal column comprising using an instrument according to the first aspect of the present invention. Provision and use of a movable arm confers many benefits over the prior art. Where the arm may be positioned so that it lies substantially co-axially with the elongate shaft of the instrument this enables use of the instrument in keyhole and endoscopic techniques as the arm and shaft may be introduced through a small opening and upon reaching the operation site the arm moved into a working position. This also confers advantages in open surgery as the reduction in profile of the instrument when the arm is substantially coaxial with the elongate shaft reduces the size of opening required to insert the instrument into an operation site, and trauma on insertion. Further, when the instrument is used for nerve retraction, the ability to move the arm relative to the shaft facilitates engagement of the arm with a nerve to be retracted and subsequent retraction of the nerve with considerably reduced overall movement of the shaft as compared to the prior art. This again reduces trauma, and avoids compression of the nerve or adjacent tissues. The instrument may be a nerve retractor and/or a tissue dissector. The arm may therefore be a retraction arm and/or dissection arm. The arm may be pivotally mounted at one end of the elongate shaft, with the user operable control being operable to pivot the ami relative to the shaft. The arm is preferably generally flat. The arm preferably has a concave curved working surface. The shape of the working surface may be shaped to enable it to coapt to the shape of a nerve to be retracted. The opposite surface of the arm to the working surface may be generally flat. All external surfaces of the arm are preferably curved. The elongate shaft preferably has a long axis and the arm may be pivoted relative to the shaft between, at least, a position where it extends in a direction perpendicular to the long axis and a position where it extends generally along, or parallel to, the long axis. In one embodiment the arm may be pivoted in one direction so that it extends in a direction generally perpendicular to the long axis of the elongate shaft, and in an opposite direction so that it moves slightly beyond a position where it extends generally along the long axis of the shaft, for example so that it extends at an angle of less than twenty degrees, or preferably less than ten degrees, to the shaft. When the arm extends along the long axis it preferably lies within the dimensions of the periphery of the elongate shaft. This enables the shaft and arm to be inserted into an aperture which is of sufficient size to just accommodate the shaft. The user operable control may comprise two movably connected arms, preferable each with a finger loop, akin to a pair of scissors. Moving the arms relative to one another preferably causes the arm to move relative to the elongate shaft. The elongate shaft may be tubular and the user operable control may be connected to the arm by means of a rod extending within the tubular elongate shaft. The elongate shaft is preferably rotatably connected to the user operable control. This enables the shaft and arm to be rotated independently of the user operable control. This facilitates manipulation of the arm in use for retraction and dissection purposes. The elongate shaft may be provided with a grip to facilitate its rotation. The grip may be disposed on a body mounted on the shaft, which may have a larger external dimension than the shaft. A locking means is preferably provided which enables the arm to be locked in a position relative to the elongate shaft. A locking means may also be provided which enables the elongate shaft to be rotationally locked relative to the user operable control. A single locking means may operate to simultaneously lock both the arm and shaft. This enables the arm to be fixed in a desired position when in use, for example to hold a nerve in a desired retracted position freeing a surgeon for other tasks, or to lock the arm in an extended position for introduction or retraction from an operation site. Means may be provided for connection of a fluid supply to the elongate shaft in order to flush fluid along the shaft towards the retraction arm for cleaning of the instrument and/or to keep the instrument clear of debris during use. In order that the invention may be more clearly understood an embodiment thereof will now be described by way of example with reference to the accompanying drawings, of which: Figure 1 shows a side view of a nerve retractor/dissector according to the invention;

Figure 2 is an enlarged view of the end of the retractor of Figure 1 including the user operable control;

Figure 3 is an enlarged view of the end of the retractor of Figure 1 including the retractor arm shown in a retracted position; and

Figure 4 is the same view as Figure 3, save that the retractor arm is in an extended position. Referring to the drawings a nerve retractor/dissector comprises an elongate tubular shaft 1. The shaft 1 may be of any convenient length, diameter and cross- section. Preferred embodiments are of substantially annular cross-section and have diameters of 2.5, 3.5 or 5.0mm. Shaft lengths of 5 to 400mm are convenient, depending upon application. For open surgery, and posterior approaches to the spine shorter lengths can be used. For endoscopic procedures and other approaches longer lengths are required. A retraction arm 2 is pivotally mounted at one end of the shaft 1. The refraction arm 2 is generally flat and spatula like with a concave, curved working surface 3 and a generally flat opposite surface 4. The working surface 3 has a flatter region bordered at each end by upwardly curved regions and is shaped to facilitate its coaption to the surface of a nerve to be retracted. The free end of the arm tapers slightly facilitating its ability to dissect tissue and develop planes in tissue, in particular between a nerve and surrounding tissue. The refraction arm 2 may be pivoted relative to the tubular shaft 1 between, at least, a position where it extends in a direction perpendicular to the long axis of the shaft 1, as shown in Figures 1 and 3, and a position where it extends generally along the long axis of the shaft 1, as shown in Figure 4. When the refraction arm is in the position shown in Figure 4 it lies within an axial extension of the circumference of the tubular shaft 1. The refraction arm 2 may be of any suitable length, but is typically of length in the range 2 to 7mm. The opposite end of the tubular shaft 1 extends into a generally cylindrical body 5 to which it is rigidly attached. The cylindrical body has an external circumferential knurled surface. A second, shorter, tubular shaft 9 extends coaxially with the tubular shaft 1 from the opposite end of the cylindrical body 5. The cylindrical body 5 comprises a fluid coupling with a cap 7 for closing the coupling connected to the body 5 by a flexible s ap 8. The fluid coupling 6 commi. ,. _ S ( with the axial bore of the tubular shaft 1 to enable fluid from a fluid line connected to the coupling to be flushed along the inside of the shaft 1 in order to clean the shaft and keep it clear of debris. Seals within the cylindrical body prevent fluid introduced through the coupling from flowing along the second tubular shaft 9. The second tubular shaft 9 is rotationally mounted in the cylindrical body enabling rotation of the body, and hence elongate tubular shaft 1. The second tubular shaft is mounted in the tubular body by way of a bi-directional ratchet (not shown). An arm 10 extends from the end of the second tubular shaft 9 and ends in a finger loop 11. A second arm 12, also with a finger loop 11, is pivotally connected to the first arm, much like the handle of a pair of scissors. Thus the two arms 10,12 can be moved relative to each other by the fingers of one hand. An extension of the second arm 12 beyond its pivotal connection to the first arm is connected, by way of a ball joint, to a rod 13 which extends through tubular shafts 1 and 9 and whose opposite end is connected to the refractor arm 2, such that movement of the two arms

10,12 relative to one another causes the refractor arm 2 to pivot relative to the tubular shaft 1. A lock lever 14 is pivotally mounted on the second tubular shaft 9. The lock ( ; lever 14 is connected to a cam disposed within the second tubular shaft 9 and is operative to rotate the cam between a locked position in which it bears against rod 13 preventing its movement relative to the second tubular shaft 9 and an unlocked position in which it does not contact the rod 13. When the cam is in the locked position, therefore, movement of the retractor arm 2 relative to the first tubular shaft 1 is prevented or restricted, as is rotation of the first tubular shaft and therefore body relative to the rod 13, and hence also the second tubular shaft 9. The second tubular shaft 9 is rotatably connected to the cylindrical body 5 to enable the scissor handle levers 10 and 12 to be rotated relative to the first tubular shaft 1 and refractor arm 2. In use in surgery a supply of saline solution may be connected to the fluid coupling 6 in order to keep the first shaft flushed. The refraction arm is moved into the position shown in Figure 4 to enable infroduction of the elongate shaft and retraction arm to the operation site through an aperture of minimum size to minimise frauma and enable infroduction, if desired, by way of a tubular approach device. On reaching the operation site the instrument may be manipulated as a whole and the refraction arm 2 pivoted relative to the tubular shaft 1 by movement of the scissor arms 10 and 12 in order to engage the refraction arm around a nerve to be retracted and refract the nerve and or to develop tissue planes. During this procedure rotation of the scissor arms 10,12 relative to the tubular shaft 1 and refraction arm 2 enables the operator to keep his controlling hand in a preferred comfortable orientation irrespective of the orientation of the refraction arm. During use when a nerve has been refracted and it is desired to hold it in position or whenever else it may be appropriate the locking lever 14 can be moved so as to lock the rod 13 relative to the second cylindrical shaft 9 in order to retain the refraction arm in position relative to the elongate shaft 1. Prior to locking the user operable controls may be rotated relative to the cylindrical body to a convenient out of the way position so as not to impede operation of other instruments at the operation site. Means may be provided to secure the instrument relative to a tubular approach device. The instrument enables keyhole spinal surgery to be conducted using a variety of approaches, for example posterior, and posterolateral approaches. This has not been possible with conventional nerve root refrators. Use of a keyhole technique leads to reduced trauma compared to existing techniques, although use of instruments according to the invention in existing open techniques will also lead to a reduction in frauma compared to the use of conventional instruments. The instrument may be used fluoroscopically, under x-ray guidance and introduced into an approach device together with other instruments. It will be appreciated that a single instrument may be used both for nerve refraction and tissue plane dissection. The instrument could be provided with a removable arm to enable replacement with arms of different shape for performing different tasks. The above embodiment is described by way of example only. Many variations are possible without departing from the invention.

Claims

1. A surgical instrument comprising an elongate shaft having an arm moveably mounted at one end and a user operable control mounted at or towards the opposite end, the control being operable to move the arm relative to the shaft.

2. A surgical instrument as claimed in claim 1, wherein the instrument is a nerve refractor and/or a tissue dissector, the arm being a refraction arm and/or dissection arm.

3. A surgical instrument as claimed in either claim 1 or 2 wherein the arm is generally flat with a curved working surface.

4. A surgical instrument as claimed in claim 3 wherein the working surface of the arm is shaped to enable it to coapt to the shape of a nerve to be refracted.

5. A surgical instrument as claimed in any preceding claim wherein the elongate shaft has a long axis and the arm may be pivoted relative to the shaft between, at least, a position where it extends in a direction perpendicular to the long axis and a position where it extends generally parallel to the long axis.

6. A surgical instrument as claimed in claim 5 wherein the arm may be pivoted in one direction so that it extends in a direction generally perpendicular to the long axis of the elongate shaft, and in an opposite direction so that it moves slightly beyond a position where it extends generally parallel to the long axis of the shaft.

7. A surgical instrument as claimed in either claim 5 or 6 wherein, when the arm extends parallel to the long axis it lies within the dimensions of the periphery of the elongate shaft.

8. A surgical instrument as claimed in any preceding claim wherein the user operable confrol comprises two movably connected arms and moving the arms relative to one another causes the arm to move relative to the elongate shaft.

9. A surgical instrument as claimed in any preceding claim wherein the elongate shaft is rotatably connected to the user operable control enabling the shaft and arm to be rotated independently of the user operable control.

10. A surgical instrument as claimed in claim 9 comprising a locking means which enables the elongate shaft to be rotationally locked relative to the user operable confrol.

11. A surgical instrument as claimed in any preceding claim comprising a locking means which enables the arm to be locked in a position relative to the elongate shaft.

12. A surgical instrument as claimed in 11 wherein a single locking means operates to simultaneously lock both the arm and shaft.

13. A surgical instrument as claimed in any preceding claim comprising means for connection of a fluid supply to the elongate shaft in order to flush fluid along the shaft towards the arm.

14. A method of refracting a nerve or dissecting tissue within or associated with a spinal column comprising using an instrument as claimed in any preceding claim.

15. A method as claimed in claim 14 comprising the step of introducing the instrument to the nerve via a tubular approach device.

16. A method as claimed in either claim 14 or 15 performed on a human body using a posterior or posterolateral approach to the spinal column.