Various surgical instruments use a shaft formed by concentric tubes. In some cases, one or both of the concentric tubes is a flexible tube. For example, surgical shavers sometimes have a shaft assembly formed by concentric wound wires or helical ribbons of material. Such wound wires or ribbons extend continuously to form a flexible section of the shaft, and act as a spring to restore the shaft to a predetermined orientation (typically straight) in the absence of loads on the shaft.
Segmented flexible tubes (i.e., those with fully separate “floating” links rather than a continuous wire or ribbon) are also known as an alternative for providing a flexible shaft section. Segmented flexible tubes are formed by interconnected flexible links that allow the flexible section to bend freely, without any inherent restoring force to hold them in any particular position.
Under conventional thinking, the inability of a segmented flexible tube to naturally assume a particular orientation (i.e., the lack of inherent resilience) has been considered a problem to be overcome, typically by coupling the segmented flexible tube with a resilient polymeric liner or sheath, or using the segmented flexible tube in a concentric relation with a conventional flexible tube having a spring-like flexible section.
With this conventional understanding in place, the concept of using multiple concentric segmented flexible tubes has not been developed, and its benefits have remained undiscovered.
In a first exemplary embodiment, there is provided a surgical instrument shaft assembly comprising: an outer shaft extending from a proximal outer shaft end to a distal outer shaft end and having an outer shaft cannula extending from the proximal outer shaft end to the distal outer shaft end, wherein at least a portion of the outer shaft comprises an outer shaft flexible section located between the proximal outer shaft end and the distal outer shaft end, and the outer shaft flexible section comprises a plurality of first segmented floating links; and an inner shaft extending from a proximal inner shaft end to a distal inner shaft end and having an inner shaft cannula extending from the proximal inner shaft end to the distal inner shaft end, wherein at least a portion of the inner shaft comprises an inner shaft flexible section located between the proximal inner shaft end and the distal inner shaft end, and the inner shaft flexible section comprises a plurality of second segmented floating links. The inner shaft is configured and dimensioned to be inserted into the outer shaft in an operating position in which: at least a portion of the inner shaft flexible section is surrounded by at least a portion of the outer shaft flexible section, such that the inner shaft flexible section and the outer shaft flexible section can flex in unison, and the inner shaft is rotatable within the outer shaft.
In some embodiments, the distal outer shaft end comprises an outer cutter head extending along a first longitudinal axis and having an outer cutter opening in fluid communication with the outer shaft cannula and facing perpendicular to the first longitudinal axis, and the distal inner shaft end comprises an inner cutter head extending along a second longitudinal axis and having an inner cutter opening in fluid communication with the inner shaft cannula and facing perpendicular to the second axis direction. In such embodiments, in the operating position, at least a portion of the inner cutter head is surrounded by at least a portion of the outer cutter head with the first longitudinal axis collinear with the second longitudinal axis, and the inner cutter opening is rotatable about the second longitudinal axis, upon rotating the inner shaft relative to the outer shaft, to selectively move between a first state of alignment between the inner cutter opening and the outer cutter opening, and a second state of alignment between the inner cutter opening and the outer cutter opening, the second state of alignment being different from the first state of alignment.
In another exemplary embodiment, there is provided a method for operating a surgical instrument comprising a guide tube, an outer shaft having an outer shaft cannula and a first plurality of first segmented floating links defining an outer shaft flexible section, and an inner shaft having an inner shaft cannula and a plurality of second segmented floating links defining an inner shaft flexible section. The method comprises: inserting the inner shaft and the outer shaft into the guide tube; positioning the inner shaft flexible section concentrically within the outer shaft flexible section; rotating the outer shaft relative to the guide tube; and rotating the inner shaft relative to the outer shaft.
The following is a description of exemplary embodiments of a surgical instrument shaft assembly that may be used with surgical instruments configured to perform various surgical procedures. In the examples below, the surgical instrument is a shaver, such as a tissue shaver that might be used during arthroscopic surgical procedures to collect body tissue (bone, ligament, muscle, lesions, etc.). Other instrument may include reamers, drills, screwdrivers, and so on.
Referring to
The outer shaft 100 comprises a generally tubular structure made of surgical-grade material, such as stainless steel or the like. The outer shaft 100 has an outer shaft cannula 102 (
At least a portion of the outer shaft 100 comprises an outer shaft flexible section 108 located between the proximal outer shaft end 104 and the distal outer shaft end 106. The outer shaft flexible section 108 comprises a plurality of first segmented floating links 110, as discussed in more detail below.
The inner shaft 200 extends from a proximal inner shaft end 204 to a distal inner shaft end 206. The inner shaft 200 may have an inner shaft cannula 202 (
The inner shaft 200 is dimensioned to fit concentrically within the outer shaft 100 to place the inner shaft 200 and outer shaft 100 into an operating position. In the operating position, the inner shaft flexible section 208 at least partially overlaps with the outer shaft flexible section 108, such that the overlapping portions of the inner shaft flexible section 208 and the outer shaft flexible section 108 can flex in unison relative to remaining portions of the outer shaft 200 and inner shaft 100.
Also, when in the operating position, the inner shaft 200 is rotatable within the outer shaft 100. As used herein, the term “rotatable,” as it relates to relative movement between the outer shaft 100, inner shaft 200 and guide tube 300, refers to rotation about the respective central cylindrical axes of the parts. Rotation can be complete (i.e. relative rotation about a range of 360°) or limited to a specific range (e.g., relative rotation about a range of less than 360°, as may be determined by adding rotational travel stops to the parts).
Relative rotation between the outer shaft 200 and the inner shaft 200 is provided by forming the inner shaft 200 with an outer diameter OD2 that is less than an inner diameter ID1 of the outer shaft cannula 102 at all locations along the overlapping lengths of the inner shaft 200 and outer shaft 100. It will be appreciated that one or both of the inner shaft outer diameter OD2 and outer cannula inner diameter ID1 may vary as a function of position between their respective proximal and distal ends, such as by having diameter changes occurring at discrete steps or gradual changes. In a preferred embodiment, however, the outer diameter OD2 of the inner shaft 200 is generally constant, and so too is the inner diameter ID1 of the outer shaft cannula 102.
When the surgical instrument shaft assembly 10 is provided with a guide tube 300, the guide tube comprises a rigid tubular structure formed of stainless steel, plastic, or any other material having sufficient rigidity and sterility for the desired application. The guide tube 300 extends from a proximal guide tube end 304 to a distal guide tube end 306, and a guide tube cannula 302 extends the full distance from the proximal guide tube end 304 to a distal guide tube end 306. The guide tube cannula 302 is dimensioned to concentrically receive the outer shaft 100, which can be accomplished by making the guide tube cannula 302 with an inner diameter that is larger than the corresponding outer diameter OD1 of the outer shaft 100. The guide tube cannula 302 may have a constant inner diameter, and the outer shaft 100 may have a constant outer diameter OD1, but neither feature is required in all embodiments. In addition, the guide tube 300 and outer shaft 100 may be configured to allow relative rotation of the outer shaft 100 and the guide tube 300, such as by providing sufficient open space between their respective facing surfaces, but this is not strictly required in all embodiments.
In the operating position, the proximal inner shaft end 204 may extend in the proximal direction P from the proximal outer shaft end 104, such as shown in
As noted above, the outer shaft flexible section 108 comprises a plurality of first segmented floating links 110, and the inner shaft flexible section 208 comprises a plurality of second segmented floating links 210. Each segmented floating link 110, 210 is a discrete structure that is not joined by a continuous material connection to each adjacent segmented floating link 110, 210. Furthermore, each segmented floating link 110, 210 has interlocking structures that loosely engage each adjacent segmented floating link 110, 210 in a manner that allows the adjacent segmented floating links 110, 210 to freely move relative to each other through a limited range of travel, but does not allow the adjacent segmented floating links 110, 210 to completely separate from one another.
Referring to
Each pin link 114 has a central body 114a that extends circumferentially to define a closed loop that forms part of the outer surface of the outer shaft 100 and outer shaft cannula 102, and at least two pins 114b extending in each of the distal direction D and proximal direction P from the central body 114a. Each pin 114b is defined by inner and outer circumferential surfaces having a trapezoidal shape as viewed perpendicular to the outer shaft 100, with the narrow side of the trapezoid joined to the central body 114a. The inner and outer trapezoidal surfaces form portions of the outer shaft cannula 102 and outer surface of the outer shaft 100, respectively.
The dovetails 112b and pins 114b are shaped and dimensioned to engage one another to prevent the dovetail links 112 from separating from the pin links 114. However, as best shown in
The ends of the outer shaft flexible section 108 are defined by dovetails 112b and/or pins 114b formed on or attached to adjacent rigid portions 110a, 110b of the outer shaft 110.
It will be appreciated that the pins 114b and dovetails 112b can have essentially the same shape (i.e., trapezoidal in this case), but this is not strictly required. For example, the pins 114 may have a trapezoidal shape with rounded corners, or an ovate or circular shape. Also, both the dovetails 112b and the pins 114b may have interlocking shapes other than trapezoidal shapes.
Segmented floating links of various types are known in the art, and other constructions may be used in other embodiments. Further examples of segmented floating links are described, for example, in U.S. Pat. No. 8,366,559, which is incorporated herein by reference in its entirety.
The dovetail links 112 and pin links 114 may be constructed using any suitable manufacturing technique. In a preferred embodiment the dovetail links 112 and pin links 114 are formed from a single continuous tube by cutting the clearance gaps 116 using a laser.
Regarding the inner shaft 200, the second segmented floating links 210 defining the inner shaft flexible section 208 are constructed in a manner similar to the first segmented floating links 110 of the outer shaft flexible section 108, and the foregoing description of the first segmented floating links 110 is sufficient to describe exemplary embodiments and alternatives for the second segmented floating links 210. It will also be understood that, in any given embodiment, the first segmented floating links 110 and second segmented floating links 210 can have similar constructions (e.g., all trapezoidal dovetails and pins) or they may have dissimilar constructions (e.g., trapezoidal dovetails and pins for the first segmented floating links 110 and interlocking circular dovetails and pins for the second segmented floating links 210). Other alternatives and embodiments will be apparent to persons of ordinary skill in the art in view of the present disclosure.
In the shown exemplary embodiment, the overlapping portions of the outer shaft flexible section 108 and the inner shaft flexible section 208 also do not include any resilient supporting structures. For example, neither the outer shaft flexible section 108 nor the inner shaft flexible section 208 includes an internal or external polymeric or elastic tube, coil spring, wire spring, or other structure to bias the assembled flexible sections 108, 208 into a particular orientation (e.g., straight). Thus, in this embodiment, the combined inner shaft 200 and outer shaft 100 can flex freely and essentially without resistance to any particular orientation.
This arrangement is contrary to conventional concentric surgical instrument shaft constructions in which an inner shaft is rotatably positioned within an outer shaft (e.g., as might be used for a tissue shaver). In conventional devices, one or both of the inner and outer shafts is either formed by a rigid structure, or with a resilient spring or the like to bias the flexible sections of the shafts to a particular position. Such rigidity or biasing force was considered favorable to allow a surgeon to guide the working end of the shaft assembly to a desired location, and hold the working end near or against tissue to perform a procedure. Additionally, by forming one or both of the inner and outer shafts as a rigid member or with a resilient bias, it was not necessary to provide other mechanisms to help guide and hold the working end of the shaft assembly, which avoided adding additional parts that would increase the diameter of the assembly. Thus, the assembly could be used in narrow or confined spaces, and would require less tissue trauma to the patient.
The inventor has discovered, however, that conventional concentric surgical instrument shafts, particularly those with flexible sections, have a significant shortcoming. Specifically, the resilient force generated by the flexible shaft (whether it is the inner shaft, the outer shaft, or both) creates friction between the two shafts, which increases the drive force necessary to rotate the inner shaft relative to the outer shaft, increases heat generation and wear, and potentially leads to erosion of fragments of the shafts that can end up in the removed tissue. Furthermore, the resilience of the flexible shaft(s) can generate a “bouncing” effect as the inner shaft rotates, leading to reduced positional control and less consistent application of the working end to the target tissue.
Still further, it has been found that conventional resilient shafts that are made of one or more layers of continuous coiled spring (e.g., as in a typical shaver shaft assembly) have very particular and distinct problems. An example of a prior art shaft of this sort is shown in
The conventional device shown in
During unidirectional rotation, this results in angular velocity changes at the working tube end 608 as resistance against the tissue changes. During bi-directional oscillating rotation, and especially the high oscillation rates used in tissue shavers (e.g., 5,000 to 12,000 cycles per minute), this results in lagging and irregular application of the shaver to the tissue. Without being bound to any theory of operation, it is believed this happens because torque loads bias the flexible section of the inner tube 600 to assume a helical shape, which causes the working tube end 608 to move out of unison with the drive tube end 606.
The detrimental effect of the lagging spring-like behavior at the working tube end 608 becomes apparent when comparing the operation of a conventional tissue shaver with the operation of a tissue shaver having a shaft assembly according to the foregoing embodiments. In particular, it has been found that embodiments of the invention provide faster and more effective tissue removal.
Furthermore, the utility and benefits of instrument shafts according to embodiments of the present invention were unexpected. First, without including any kind of smooth layer of material (e.g., a flexible sheath) between the outer shaft 100 and the inner shaft 200, it would be expected that the segmented floating links 110, 210 of each shaft could contact each other at their edges at the gaps formed by the clearance gaps 116. This would lead to hard strikes that generate spikes in the torsional resistance, excess friction, possible damage to the segmented floating links 110, 210, or even complete prevention of relative rotation between the outer shaft 100 and the inner shaft 200 (i.e. jamming). Such potential problems would be even more expected in instruments having high oscillation frequencies, such as tissue shavers. Furthermore, the improved performance provided by two unbiased flexible shafts, which is believed to be obtained by omitting or at least minimizing any spring-like resilient forces in the flexible shafts (particularly in tissue shavers, but also potentially in other applications) was heretofore undiscovered and unexpected. Thus, while not strictly required in all cases, it is preferred for the inner shaft flexible section 208, or more preferably both the outer shaft flexible section 108 and the inner shaft flexible section 208, to be devoid of any kind of flexible sheath (i.e., no internal or external liner that provides a resilient restoring force).
It has also been surprisingly discovered that omitting the flexible sheath from the inner, or inner and outer, flexible sections 108, 208 also provides a benefit of reducing removed tissue into smaller pieces, which helps facilitate removal. Without being bound to any theory of operation, it is believed that such size reduction is caused by particles being ground between adjacent floating links 110, 210 of each flexible section, and possibly also by grinding between the outer surfaces of the inner floating links 210 and the inner surfaces of the outer floating links 110.
Referring to
The illustrated bent section 308 is shaped as a circular segment that lies in a single plane and is defined by a radius R. In other cases, the bent section 308 may have an elliptical shape, a hyperbolic shape, a shape that bends in three dimensions, or any other shape that may be desired while still allowing proper operation of the outer shaft 100 and inner shaft 200. Other examples are shown in
As noted above, the bent section 308 may have any shape that allows suitable rotation of the inner shaft 200 relative to the outer shaft 100, and (if required) the outer shaft 100 relative to the guide tube 300. It has been found that embodiments may have relatively large bend angles A and relatively small bend radii R as compared to conventional devices, such as conventional tissue shavers. For example, in one embodiment the bend angle A may be 90° or greater (e.g., 180° or even greater), as compared to a typical conventional bend angle of 30° or less. As another example, the bend radius R may be on inch or less, as compared to a larger conventional bend radii. Still other embodiments may have both a bend angle of 90° or more, and a bend radius R of one inch or less.
It has also been found that embodiments also may have smaller diameters than conventional concentric flexible shaft assemblies. For example, the first segmented floating links 110 of the outer shaft 100 may have a diameter OD1 of 0.150 inches or less (e.g., 0.138 inches), and the second segmented floating links 210 of the second shaft 20 may have an outer diameter OD2 of 0.120 inches or less (e.g., 0.105 inches).
These improvements to bend angle A, bend radius R and outer diameter OD1, OD2 can be used to provide surgical instrument shaft assemblies 10 that are significantly more useful than conventional devices. For example, embodiments may allow greater access to certain regions of the body, and provide less extensive trauma to the patient.
Referring back to
As also shown in
Embodiments such as those discussed above may be used with various surgical instruments. The examples herein are shown, in a non-limiting manner, in the context of a tissue shaver. In this configuration, the distal outer shaft end 106 comprises an outer cutter head 118 having an outer cutter opening 120. The outer cutter head 118 comprises a generally cylindrical body that extends along a first longitudinal axis 122, and the outer cutter opening 120 faces perpendicular to the first longitudinal axis 122. The outer cutter opening 120 is in fluid communication with the outer shaft cannula 102.
Similarly, the distal inner shaft end 206 comprises an inner cutter head 218 having an inner cutter opening 220. The inner cutter head 218 comprises a generally cylindrical body that extends along a second longitudinal axis 222, and the inner cutter opening 220 faces perpendicular to the second longitudinal axis 222. The inner cutter opening 220 is in fluid communication with the inner shaft cannula 202.
In the operating position, the distal outer shaft end 106 at least partially surrounds the distal inner shaft end 206, with the first longitudinal axis 122 being collinear with the second longitudinal axis 222. In this position, the inner cutter head 218 is at least partially surrounded by the outer cutter head 118, and rotating the inner shaft 200 relative to the outer shaft 100 causes the inner cutter head 218 to rotate, relative to the outer cutter head 118, about the collinear first and second longitudinal axes 122, 222.
The outer cutter opening 120 and inner cutter opening 220 are positioned on their respective cutter heads such that rotation of the inner cutter head 218 relative to the outer cutter head 118 causes the inner cutter opening 220 to move between different states of alignment relative to the outer cutter opening 120. Such movement causes the edges of the cutter openings 120, 220 to close together to sever adjacent tissue, and then separate to form a fluid communication path into the inner shaft cannula 202 to allow tissue to be removed by suction or the like.
For example, as shown in
In use, the inner shaft 200 may be selectively rotated in one direction or the other, or cyclically rotated in both directions in an oscillating manner. In typical use, the inner cutter head 218 is oscillated back and forth between the fully-open position as shown in
The outer shaft 100 and inner shaft 200 also may include features to ensure that they remain in the operating position to properly align the outer cutter opening 120 and inner cutter opening 220. For example, the outer cutter head 118 may include a first end stop 126 that abuts a second end stop 226 on the inner cutter head 218, to prevent motion of the inner cutter head 218 beyond the desired position. In this case, the end stops 126, 226 comprise hemispherical end walls of the respective shaft, but other configurations are possible.
Other embodiments also may use different types of tissue shaver devices. For example, the inner cutter head 218 may be replaced by a helical auger or a round cutting burr, and the outer cutter head 118 may comprise a simple circular opening against which the auger or burr acts to remove tissue. Other alternatives and embodiments will be apparent to persons of ordinary skill in the art in view of the present disclosure.
Referring now to
As noted above, a guide tube 300 may be used to hold the working ends of the inner shaft 100 and outer shaft 200 at a desired location. However, other embodiments may use other mechanisms to perform this function. For example,
The embodiment of
In still other embodiments, the outer cutter head 118 may be held in place by engaging an existing surgical implant (e.g., secured to an existing hole in a trauma plate or implant to perform further procedures in the area), held by forceps or the like, and so on.
Other alternatives and embodiments will be apparent to persons of ordinary skill in the art in view of the present disclosure.
Embodiments of surgical instrument shaft assemblies such as described herein may be used in various ways, with the particular details possibly varying depending on the type of surgical instrument, location of the surgical site, type of tissue being address, and the purpose of the procedure.
The present disclosure provides a number of exemplary embodiments of the invention defined by the appended claims. The description of such embodiments is not intended to limit the scope of the claims beyond what is defined in the claims. It will also be understood that, while embodiments may provide particular advantages in certain cases, the scope of the claims is not limited to embodiments providing any particular advantage or functionality. It will further be appreciated that other embodiments encompassed by the claims may diverge from those described herein in both appearance and functionality, and the various features of particular described herein may be used with other embodiments without departing from the scope of the claims.