# Patent

## Title
Surgical instrument with a separable coaxial joint

## Abstract

A surgical instrument includes an elongated shaft having a proximal structural member and a proximal drive member that is selectively movable with respect to the proximal structural member. A modular end effector is removably coupled to the elongated shaft, and has a distal structural member and a distal drive member that is operatively coupled to a pair of jaw members. A separable joint is defined between the elongated shaft and the end effector. The separable joint includes laterally prominent and laterally indented portions of each of the proximal and distal structural members and of each of the proximal and distal drive members. The structural members are interlocked to resist longitudinal separation and permit lateral separation. The drive members are movable relative to structural members to move the separable joint to a locked configuration wherein the drive members prohibit lateral separation of the structural members.

## Background
BACKGROUND
1. Technical Field separable
The present disclosure relates generally the field of reposable or reusable surgical instruments. In particular, the disclosure relates to instruments having separable and replaceable components to provide clean, sterile or refurbished surfaces in each instance of use.
2. Background of Related Art
Instruments such as electrosurgical forceps are commonly used in open and endoscopic surgical procedures to coagulate, cauterize and seal tissue. Such forceps typically include a pair of jaws that can be controlled by a surgeon to grasp targeted tissue, such as, e.g., a blood vessel. The jaws may be approximated to apply a mechanical clamping force to the tissue, and are associated with at least one electrode surface to permit the delivery of electrosurgical energy to the tissue. The combination of the mechanical clamping force and the electrosurgical energy has been demonstrated to join adjacent layers of tissue captured between the jaws. When the adjacent layers of tissue include the walls of a blood vessel, sealing the tissue may result in hemostasis. Thereafter, the sealed tissue may be transected by advancing a knife through the jaws. A detailed discussion of the use of an electrosurgical forceps may be found in U.S. Pat. No. 7,255,697 to Dycus et al.
In use, various tissue-contacting components of an electrosurgical forceps tend to become contaminated or degraded. For example, electrodes may become contaminated as portions of the treated tissue adhere to the tissue-contacting surfaces of the electrodes. Also, a knife blade may become dull and less effective in transecting sealed tissue after repeated use. In order to provide clean electrodes and a sharp knife for a particular surgical procedure, a brand new instrument is often used. Once the procedure is complete, the used instrument is discarded.
Instruments that may be reused for multiple procedures reduce the instrumentation costs per procedure. Some reusable forceps include a reusable base component adapted for persistent use and a removable and replaceable modular component adapted for limited use coupled thereto. The reusable base component may include, for example, a control element such as a handle that remains primarily outside the surgical field. The handle may be constructed ruggedly to sustain regular and recurring usage in numerous surgical procedures. The removable and replaceable component may include a tool element, such as an end effector containing the delicate and tissue-contacting wear surfaces. Replacing a worn end effector to refurbish an instrument provides refreshed surfaces with minimal waste.
Providing replaceable components for a reusable electrosurgical forceps, however, presents various challenges. For example, many of these instruments require arduous disassembly and reassembly procedures to ensure proper mechanical and electrical connections are made between the reusable and replaceable components.
SUMMARY
The present disclosure describes a reusable surgical instrument for treating tissue. The instrument includes a handle assembly supporting a first actuator. An elongated shaft extends distally from the handle assembly and defines a longitudinal axis. The elongated shaft includes a proximal structural member and a proximal drive member, and the proximal drive member is operatively coupled to the first actuator such that manipulation of the first actuator induces movement of the proximal drive member relative to the proximal structural member. A modular end effector is removably coupled to the elongated shaft, and includes a distal structural member and a distal drive member. The distal drive member is operatively coupled to a pair of jaw members such that movement of the distal drive member relative to the distal structural member induces movement of the jaw members between an open configuration wherein the jaw members are substantially spaced to a closed configuration wherein the jaw members are closer together. A separable joint is defined between the elongated shaft and the end effector. The separable joint includes a laterally prominent portion and a laterally indented portion defined on each of the proximal and distal structural members and configured to interlock with one another such that the proximal and distal structural members resist longitudinal separation and permit separation in a lateral direction. Laterally prominent portions and a laterally indented portions defined on the proximal and distal drive members are configured to interlock with one another such that the proximal and distal drive members transmit motion therebetween and permit separation in the at least one lateral direction. The drive members are movable relative to the structural members to move the separable joint between a locked configuration wherein the drive members prohibit separation of the structural members and an unlocked configuration wherein the drive members permit separation of the structural members in the lateral direction.
The structural members may define a generally tubular configuration about the longitudinal axis, and the drive members may be coaxially-arranged with respect to the structural members. The first actuator may be operable to induce longitudinal motion in the drive members to move the jaw members between the first and second configurations. The handle assembly may also support a second actuator, and the second actuator may be operable to induce rotational motion of the drive members to rotate the jaw members about the longitudinal axis.
The end effector may include a knife selectively movable through the jaw members, and the separable joint may include separable and interlocking portions of a distal knife rod and a proximal knife rod. The distal knife rod may be operatively coupled to the knife to move the knife through the jaw members, and the proximal knife rod selectively movable with respect to the structural members from the handle assembly.
The end effector may include an electrode configured for delivering electrosurgical energy to tissue, and the separable joint may include first and second electrical connectors. The first electrical connector may be supported by the elongated shaft and may be electrically coupled to a source of electrosurgical energy. The second electrical connector may be supported by the end effector and electrically coupled to the at least one electrode. The first and second electrical connectors may be configured to engage and disengage one another in the lateral direction in which the structural members are separable.
The interlocking portions of the structural members may define a first outer diameter. The distal structural member may be coupled to the end effector by a shaft portion defining a second outer diameter that is smaller than the first outer diameter.
According to another aspect of the disclosure, a method of assembling a surgical instrument includes the steps of providing the instrument with the end effector separated from the elongated shaft. Next, the elongated shaft and the end effector may be approximated in a lateral direction to simultaneously engage the proximal structural member with the distal structural member, and the proximal drive member with the distal drive member. Finally, the first actuator may be manipulated to move the drive members into a longitudinal position wherein the drive members prohibit separation of the structural members in the lateral direction.
According to another aspect of the disclosure, a surgical instrument includes a handle assembly supporting an actuator. A proximal tubular member extends distally from the handle assembly and defines a longitudinal axis. The proximal tubular member includes an inter-engaging mating portion at a distal end thereof. A proximal drive member extends through the proximal tubular member and is operatively coupled to the actuator such that manipulation of the actuator induces longitudinal movement of the proximal drive member relative to the proximal tubular member. The proximal drive member includes an inter-engaging mating portion at a distal end thereof. An end effector includes a movable end effector element adapted for moving between first and second configurations for manipulating tissue. A distal tubular member extends proximally from the end effector, and includes an inter-engaging mating portion at a proximal end thereof corresponding to the inter-engaging mating portion of the proximal tubular member. A distal drive member extends through the distal tubular member. The distal drive member is operatively coupled to the movable end effector element such that longitudinal movement of the distal drive member induces the movable end effector element to move between the first and second configurations. The distal drive member includes an inter-engaging mating portion at a proximal end thereof corresponding to the inter-engaging mating portion of the proximal drive member. The proximal drive member is movable from an unlocked configuration wherein the inter-engaging mating portion of the proximal drive member is generally aligned with the inter-engaging mating portion of the proximal tubular member to permit lateral engagement and disengagement of the inter-engaging mating portions of the tubular members and drive members simultaneously, and a locked configuration wherein the inter-engaging mating portion of the proximal drive member is longitudinally displaced with respect to the inter-engaging mating portion of the proximal tubular member. In the locked configuration, the proximal drive member is within one of the proximal and distal tubular members such that lateral disengagement of the inter-engaging mating portions of the tubular members and drive members is prohibited.
The movable end effector element may include a pair of jaw members movable between an open configuration wherein the jaw members are substantially spaced to a closed configuration wherein the jaw members are closer together. Each of the inter-engaging mating portions of the tubular members may include a laterally prominent hook portion and a laterally indented portion for receiving the hook portion of the inter-engaging mating portion of the other tubular member.
The actuator may be operable to move the proximal drive member between the locked and unlocked configurations, and to move the movable end effector element between the first and second configurations. The end effector may include an electrode disposed thereon adapted for delivering electrosurgical energy to tissue.



BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure and, together with the detailed description of the embodiments given below, serve to explain the principles of the disclosure.
FIG. 1 is a perspective view of an endoscopic surgical instrument in accordance with the present disclosure having a modular end effector removably coupled to a distal end of an elongated shaft by a separable coaxial joint;
FIG. 2 is an enlarged, side view of the end effector of FIG. 1 depicting a pair of jaw members in an open configuration;
FIG. 3 is an enlarged, cross-sectional view of the end effector depicting the jaw members in a closed configuration, and a reciprocating knife in a retracted position;
FIG. 4 is a perspective view of an underside of the distal end of the elongated shaft defining a first mating component of the separable coaxial joint;
FIG. 5 is a side view of the modular end effector defining a second mating component separated from the first mating component of the separable coaxial joint in a lateral direction;
FIG. 6 is a side view of the first and second mating components of the separable coaxial joint adjacent one another in an unlocked configuration wherein the first and second mating components may be separated in the lateral direction;
FIG. 7A is a side view of the first and second mating components of the separable coaxial joint adjacent one another in a locked configuration wherein the first and second mating components resist separation in the lateral direction;
FIG. 7B is a side view of the first and second mating components in an alternate locked configuration; and
FIG. 8 is a sectional, perspective view of an alternate embodiment of a separable coaxial joint in a locked configuration.



DETAILED DESCRIPTION
Referring initially to FIG. 1, an embodiment of an electrosurgical instrument 10 is depicted. The instrument 10 includes a handle assembly 12, a modular end effector 14 and an elongated shaft 16 therebetween defining a longitudinal axis A-A. A surgeon may manipulate the handle assembly 12 to remotely control the end effector 14 through the elongated shaft 16. This configuration is typically associated with instruments for use in laparoscopic or endoscopic surgical procedures. Various aspects of the present disclosure may also be practiced with traditional open instruments and in connection with endoluminal procedures as well.
The instrument 10 is coupled to a source of electrosurgical energy, e.g., an electrosurgical generator 18. The generator 18 may include devices such as the LIGASURE® Vessel Sealing Generator and the Force Triad® Generator as sold by Covidien. A cable 20 extends between the handle assembly 12 and the generator 18, and includes a connector 22 for coupling the instrument 10 to the generator 18. The connector 22 includes two prong members 22a and 22b that are dimensioned to mechanically and electrically connect the instrument 10 to opposite poles (+), (−) associated with the generator 18. Thus, bipolar energy may be provided through the instrument 10. Alternatively, the instrument 10 may be configured for delivering monopolar energy to the tissue. In a monopolar configuration, the instrument 10 delivers electrosurgical energy of a first potential, e.g. (+), while a return pad (not shown) is placed generally beneath a patient and provides a return path to the opposite pole, e.g. (−), of the generator 18. A footswitch (not shown) may be provided to initiate and terminate the delivery of electrosurgical energy to the end effector 14.
To control movement of the end effector 14, the handle assembly 12 includes various actuators that may be manipulated by a surgeon during a surgical procedure. The actuators include a stationary handle 24 and movable handle 26 that may be separated and approximated relative to one another, in the direction of arrows “B0,” to respectively open and close a pair of jaw members 32, 34 in the direction of arrows “B1.” A surgeon may also rotate a rotation knob 36 about the longitudinal axis A-A in the direction of arrows “C0” to rotate the end effector 14 about the longitudinal axis A-A in the direction of arrows “C1.” The embodiment depicted in FIG. 1 may be considered a “tip rotation” embodiment since manipulation of the rotation knob 36 induces rotation only at the distal “tip” of the elongated shaft 16, e.g., only the end effector 14. As described in greater detail below, the rotation knob 36 is coupled to interior components of the elongated shaft 16 to cause the end effector 14 to rotate. The outermost components of the elongated shaft 16 remain stationary relative to the stationary handle 24. Other embodiments are contemplated in which the outermost components of the elongated shaft 16 may be induced to rotate. These embodiments may be considered “shaft rotation” embodiments. A more detailed discussion of a “shaft rotation” instrument may be found in the above mentioned U.S. Pat. No. 7,255,697 to Dycus et al.
Another actuator provided on the handle 12 is trigger 38. Trigger 38 is movable relative to the stationary handle 24 in the direction of arrows “D0,” and is operable to extend and retract a knife 40 (FIG. 3) through the end effector 14 in the direction of arrows “D1.” Each of theses actuators is mechanically coupled to the end effector 14 through the elongated shaft 16 as described in greater detail below.
A separable coaxial joint 100 is defined between the end effector 14 and the elongated shaft 16. The joint 100 permits the end effector 14 to be removed from the elongated shaft 16 such that a new or refurbished end effector (not shown) may be coupled to the elongated shaft 16 following a surgical procedure. The handle assembly 12 may be subsequently reused with the new or refurbished end effector. As described in greater detail below, the joint 100 includes a first mating component 102a defined at a distal end of the elongated shaft 16 and a second mating component 102b defined at a proximal end of the end effector 14. The first and second mating components 102a and 102b provide electrical connections to operatively couple the end effector 14 to the generator 18 and the mechanical connections to operatively couple the end effector 14 to the actuators, e.g., movable handle 26, rotation knob 36 and trigger 38. The joint 100 provides a positive mechanical connection between the end effector 14 and the elongated shaft 16 such that the end effector 14 will not inadvertently be detached during a surgical procedure.
Referring now to FIG. 2, end effector 14 is depicted in an open configuration wherein upper and lower jaw members, 32 and 34 respectively, are substantially spaced from one another. In the open configuration, the jaw members 32, 34 may be maneuvered into position to capture tissue therebetween. To facilitate maneuvering the end effector 14 into position, the end effector 14 may be rotated about longitudinal axis A-A with respect to an outer tubular member 104 of the second mating component 102b. The outer tubular member 104 thus provides a distal stationary reference structure for various relative motions of the end effector 14. The end effector 14 is operatively coupled to the rotation knob 36 (FIG. 1) through the through separable coaxial joint 100 as described below with reference to FIGS. 4 through 7B.
Each of the jaw members 32, 34 is coupled to the second mating portion 102b about a pivot pin 42 such that the jaw members 32, 34 are pivotable to a closed configuration (FIG. 3) where the jaw members 32, 34 are closer together to clamp the tissue therebetween. The jaw members 32, 34 include respective proximal drive flanges 44, 46 extending into the second mating portion 102b, where the proximal drive flanges 44, 46 engage a drive pin 48. The drive pin 48 is movably disposed in a longitudinal drive slot 50 extending through the second mating portion 102b. The drive pin is operatively associated with the movable handle 26 (FIG. 1) through the separable coaxial joint 100 to reciprocate through the drive slot 50. Each of the proximal drive flanges 44, 46 of the jaw members 32, 34 include a respective cam slot 52, 54 that engages the drive pin 48 as the drive pin 48 reciprocates through the longitudinal drive slot 50. The cam slots 52 and 54 are disposed obliquely with respect to the longitudinal drive slot 50 such that longitudinal movement of the drive pin 48 in the direction of arrows “B2” induce the jaw members 32, 34 to pivot about the pivot pin 42 in the direction of arrows “B1.” This type of construction induces bilateral jaw motion. Other unilateral constructions are also envisioned in which only one of the jaw members 32, 34 moves with respect to the elongated shaft 16 to move between the open and closed configurations.
The pair of jaw members 32, 34 includes a pair of opposed electrodes 58, 60 positioned to contact tissue situated between the jaw members 32, 34. The opposed electrodes 58, 60 are associated with opposite electrical potentials (+), (−) to permit an electrosurgical current to flow through the tissue situated between the jaw members 32, 34. The electrosurgical current, when applied in conjunction with an appropriate amount of pressure to the tissue, may effect a tissue seal. To form an effective tissue seal, a relatively high clamping force is typically generated to impart a closure pressure on the tissue in the range of from about 3 kg/cm2 to about 16 kg/cm2. An appropriate gap distance of about 0.001 inches to about 0.006 inches may be maintained between the electrodes 58 and 60, although other gap distances are contemplated.
Referring now to FIG. 3, end effector 14 is depicted in a closed configuration wherein the upper and lower jaw members 32, 34 are closer together than when in the open configuration. The drive pin 48 is moved to a proximal position in the drive slot 50 and cam slots 52, 54 to induce the jaw members 32, 34 to pivot toward one another about pivot pin 42. In the closed configuration, the jaw members 32, 34 may apply a clamping force to tissue, and the electrodes may deliver electrosurgical energy to the tissue to generate a tissue seal. Thereafter, the reciprocating knife 40 may be advanced to transect the sealed tissue captured between the jaw members 32, 34.
The reciprocating knife 40 includes a sharp distal edge 62 and a bifurcated proximal shank 64. The proximal shank 64 is operatively coupled to the trigger 38 (FIG. 1) through separable coaxial joint 100 as described below with reference to FIGS. 4 through 7. The trigger 38 is operable to drive the knife 40 in a longitudinal direction “D1.” The sharp distal edge 62 may be driven into a knife channel 68 defined in each of the jaw members 32, 34, and thus, sealed tissue captured between the electrodes 58, 60 may be transected. The knife 40 may be rotated about longitudinal axis A-A in the direction of arrows “C1” along with the end effector 14, and thus, the knife 40 may be operable irrespective of the rotational orientation of the end effector 14.
Referring now to FIGS. 4 and 5, a distal end of elongated shaft 16 defines first mating component 102a. The first mating component 102a includes a structural, outer tubular member 106, a radially intermediate, proximal jaw drive shaft 108, and a central, proximal knife drive rod 110. The outer tubular member 106 may be fixedly coupled to stationary handle 24 (FIG. 1) and thus provides a proximal stationary reference structure for the relative motions of the proximal jaw drive shaft 108 and the proximal knife drive rod 110. Alternatively, in a “shaft rotation” embodiment (not shown) the outer tubular member 106 may be fixedly coupled to an actuator configured to rotate relative to the stationary handle 24.
The proximal jaw drive shaft 108 is operatively coupled to the movable handle 26 (FIG. 1) such that manipulation of the movable handle 26 induces longitudinal motion of the proximal jaw drive shaft 108 relative to the outer tubular member 106 in the direction of arrows “B3.” The proximal jaw drive shaft 108 is also operatively coupled to the rotation knob 36 such that manipulation of the rotation knob 36 induces rotational motion of the proximal jaw drive shaft 108 relative to the stationary outer tubular member 106 in the direction of arrows “C2a.” In an alternative “shaft rotation” embodiment (not shown) the outer tubular member 106 may be induced to rotate in the direction of arrows “C2b.” The proximal knife drive rod 110 is operatively coupled to the trigger 38 (FIG. 1) such that manipulation of the trigger 38 induces longitudinal motion of the proximal knife drive rod 110 in the direction of mows “D2.” The proximal knife drive rod 110 is longitudinally movable with respect to the proximal jaw drive shaft 108, but may maintain a rotational orientation with respect to the proximal jaw drive shaft 108. The proximal knife drive rod 110 may be keyed to the jaw drive shaft 108 such that rotational motion of the proximal jaw drive shaft 108 in the direction of arrows “C2a” induces a corresponding rotational motion of the proximal knife drive rod 110 in the direction of arrows “D3.” In other embodiments, the proximal jaw drive shaft 108 and proximal knife drive rod 110 may be independently rotatable with respect to one another.
Each of the outer tubular member 106, proximal jaw drive shaft 108 and proximal knife drive rod 110 exhibits an undercut profile at the distal end thereof. This profile permits each component 106, 108, 110 of the first mating component 102a to interlock with respective corresponding component of the second mating component 102b (see FIG. 5). For example, the outer tubular member 106 of the first mating component 102a interlocks with the outer tubular member 104 of the second mating component 102b. The outer tubular member 106 exhibits an undercut profile as exemplified by a laterally prominent distal hook portion 106a and a laterally indented, recessed or undercut hook receiving portion 106b. A laterally prominent hook portion 104a of the outer tubular member 104 may be received in the hook receiving portion 106b, and a hook receiving portion 104b of the outer tubular member 104 may receive the hook portion 106a of outer tubular member 106. When thus engaged, the outer tubular members 104, 106 are axially aligned about the longitudinal axis A-A, and resist longitudinal separation because of the interlocking hook portions 104a, 106a. However, the outer tubular members 104, 106 are susceptible to lateral separation as described in greater detail below.
Inner drive members 108, 110, 112, 114 of first and second mating components 102a and 102b also exhibit interlocking undercut profiles. For example, the proximal jaw drive shaft 108 interlocks with a distal jaw drive shaft 112 and the proximal knife drive rod 110 interlocks with a distal knife drive rod 114. This interlocking arrangement permits the motions the proximal jaw drive shaft 108 and proximal knife drive rod 110 of the first mating component 102a to be transmitted the distal jaw drive shaft 112 and distal knife drive rod 114 of the second mating component 102b. Additional inner members (not shown) may be provided in other embodiments to provide additional functionality to the end effector 14 by enabling additional independent movements to be transmitted between the handle assembly 12 and the end effector 14.
The undercut profile of the inner drive members 108, 110, 112, 114 is exemplified by the proximal jaw drive shaft 108 as depicted in FIG. 4. The interlocking portion of the proximal jaw drive shaft 108 includes a laterally prominent, distal hook portion 120 and a laterally indented, proximal hook receiving portion 122. The hook receiving portion 122 is undercut with respect to the hook portion 120 in that the hook receiving portion 122 is less prominent laterally than the hook portion 120. The hook receiving portion 122 includes a floor surface 124 that lies in a plane parallel to the longitudinal axis A-A, and pair of wall surfaces 126 and 128 that lie in planes perpendicular to the longitudinal axis A-A.
The floor surface 124 is arranged to transfer torque to the distal jaw drive shaft 112 as the proximal jaw drive shaft 108 is rotated in the direction of arrows “C2a.” The wall surfaces 126 and 128 are arranged to transfer compressive and tensile loads respectively to the distal jaw drive shaft 112 as the proximal jaw drive shaft 108 is translated in the direction of arrows “B3.” A hook portion 132 of the second jaw drive shaft is configured to engage the floor surface 124 and wall surfaces 126, 128 of the proximal jaw drive shaft 108 when the proximal and distal jaw drive shafts 108, 112 are interlocked (see FIG. 6). The hook portion 132 may thus receive the longitudinal and rotational mechanical forces for driving the jaw members 32, 34. Specifically, the compressive and tensile loads may be transmitted to the drive pin 48 to open and close the jaw members 32, 34, and the torsional loads may be transmitted to the end effector 14 to rotate the end effector 14 in the direction of arrows “C1” as described above with reference to FIGS. 2 and 3.
Electrical connectivity may also be established by interlocking the first and second jaw drive shafts 108, 112. The proximal jaw drive shaft 108 includes an electrically conductive pin 136 protruding from a distal end thereof and an electrically conductive pin-receiving slot 138 on a lateral side thereof. The pin 136 and slot 138 may be electrically coupled to opposite poles (+), (−) of the generator 18 (FIG. 1). The slot 138(−) is configured to receive an electrically conductive pin 140(−) protruding from a proximal end of the distal jaw drive shaft 112. The electrically conductive pin 140(−) is in electrical communication with electrode 60(−). Thus, by establishing electrical communication between the slot 138 and the pin 140, electrical connectivity may be established between the electrode 60 and the generator 18. Similarly, the pin 136 may be electrically coupled to a slot 142 defined in the distal jaw drive shaft 112 to establish electrical continuity between electrode 58(+) and the generator 18.
The proximal knife drive rod 110 also exhibits an undercut profile that allows the proximal knife drive rod 110 to transmit torsional, compressive and tensile loads to the distal knife drive rod 114 of the second mating component 102b. The proximal knife drive rod 110 includes a floor surface 148 for transmitting torsional loads and wall surfaces 150, 152 for transmitting compressive and tensile loads. The proximal knife drive rod 110 is operatively coupled to the trigger 38 (FIG. 1) and the distal knife drive rod 114 is operatively coupled to the knife 64. Thus, interlocking first and second knife drive rods 110, 114 operatively couples the knife 64 with the trigger 38.
Referring now to FIGS. 5 through 7B, a procedure for interlocking the first and second mating components 102a, 102b is described. First, the proximal jaw drive shaft 108 and proximal knife drive rod 110 are moved longitudinally to a mating location with respect to the outer tubular member 106 as depicted in FIG. 5. An appropriate longitudinal mating location is where the inter-engaging mating portion of the proximal jaw drive shaft 108 is generally aligned with the inter-engaging mating portion of the proximal tubular member 106 such that the laterally prominent hook portion 120 and laterally indented hook receiving slot 122 are exposed on an open lateral side of the tubular member 106. In this mating position, the laterally prominent portions of the proximal jaw drive shaft 108 and proximal knife drive rod 110 are aligned with the laterally indented portions of the distal jaw drive shaft 112 and distal knife drive rod 114 respectively, and the laterally prominent portions 160a of the outer tubular member 106 are aligned with the laterally indented portions 104b of the outer tubular member 104.
The movable handle 26 and the trigger 38 (FIG. 1) may be employed to move the proximal jaw drive shaft 108 and first knife drive shaft may be moved to the mating position. Various mechanisms such as detents or other indicators may be incorporated into the actuators 26, 38 to provide a tactile indication that the mating location has been achieved. The mating location may be achieved by moving the actuators to a location outside the range of motion required for normal use of the instrument 10. Similarly, a rotational orientation of the proximal jaw drive shaft 108 and proximal knife drive rod 110 may be achieved using rotation knob 36. The mating rotational orientation is characterized in that the pins 136, 140 align with the respective slots 142, 138.
When an appropriate mating location and orientation is achieved, the first and second mating portions 102a, 102b may be approximated in a lateral direction indicated by arrows “E1” and “E2” in FIG. 5 to the engaged configuration of FIG. 6. With this single lateral motion, simultaneously the outer tubular member 106 interlocks with the outer tubular member 104, the proximal jaw drive shaft 108 interlocks with the distal jaw drive shaft 112, the proximal knife drive rod 110 interlocks with the distal knife drive rod 114, and the pins 136, 140 engage the respective slots 142, 138. The configuration of FIG. 6, however, may be characterized as an unlocked configuration. This is because the first and second mating portions 102a, 102b may be laterally separated by applying laterally directed forces to the first and second mating portions 102a, 102b in the relative directions of arrows “E3” and “E4.”
The first and second mating components 102a, 102b may be moved to a locked configuration as depicted in FIG. 7A, wherein the first and second mating components 102a, 102b resist separation from one another. The proximal jaw drive shaft 108 may be advanced distally until a portion of the proximal jaw drive shaft 108 extends into outer tubular member 104 of the second mating component 102b. This arrangement causes interference between the proximal jaw drive shaft 108 and the outer tubular member 104, prohibiting the separation of the first and second mating components 102a, 102b in the lateral direction of arrows “E3” and “E4.” The movable handle 26 (FIG. 1) may again be employed to advance the proximal jaw drive shaft 108 to the locked position of FIG. 7A. Alternatively, the proximal jaw drive shaft 108 may be retracted proximally until the proximal jaw drive shaft 108 and a portion of the second jaw drive shaft 114 is drawn into the first mating component 102a to lock the first and second mating components 102a, 102b. 
Similarly, the proximal jaw drive shaft 108 may be rotated in the direction of arrows “C2a” to move the first and second mating components 102a, 102b to the locked configuration depicted in FIG. 7B. In this locked configuration, the lateral direction in which the outer tubular members 104, 106 tend to separate is dissimilar from the lateral direction in which the first and second jaw drive shafts 108, 114 tend to separate. Thus, the first and second mating components 102a, 102b are positively locked since there is no lateral direction in which all interlocking members of the first and second mating components 102a, 102b will tend to separate. The rotation knob 36 may be employed to rotate the proximal jaw drive shaft 108 into the locked configuration of FIG. 7B.
Various other locked configurations are contemplated. For example, an additional tubular member 170 (shown in phantom in FIG. 7B) may be placed over the first and second mating components 102a, 102b to prohibit separation thereof. An inner diameter of the tubular member 170 is slightly larger than an outer diameter of the outer tubular members 104, 106. Also, a locked configuration may be achieved by translating the first knife rod 110 (FIG. 4). The trigger 38 may be employed to advance the first knife rod 110 into the second jaw drive shaft 114, and thus create an interference that prohibits separation of the first and second mating components 102a, 102b. Any combination of translation and rotation of the proximal jaw drive shaft 108 and the first knife rod 110 may be employed to move the first and second mating components 102a, 102b from the unlocked mating configuration of FIG. 6 to a locked configuration suitable for performing a surgical procedure. Following the procedure, the proximal jaw drive shaft 108 and the first knife rod 110 may be returned to the unlocked configuration of FIG. 6 to permit de-mating of the first and second mating components 102a, 102b. 
Referring now to FIG. 8, another embodiment of a separable coaxial joint 200 is depicted with first and second mating components 202a, 202b in a locked configuration. The first and second mating components 202a, 202b include outer tubular members 204, 206 each exhibiting an undercut profile that permits the outer tubular members 204, 206 to interlock with one another and resist longitudinal separation. First and second jaw drive shafts 208, 212, and first and second knife rods 210, 214 interlock to transmit rotational and longitudinal motion, and a pin 236 engages slot 242 to transmit electrical energy between the first and second mating components 202a, 202b. 
Outer tubular members 204, 206 exhibit a first outer diameter OD1 that is sufficiently large to facilitate manual manipulation of the separable coaxial joint 200 such that the first and second mating components 202a, 202b may be laterally approximated by hand. The first outer diameter OD1 also provides robustness to the outer tubular members 204, 206 that permits the coaxial joint 200 to withstand the various loads that may tend to separate first and second mating components 202a, 202b. In some applications, it may be advantageous for portions of an elongated shaft to exhibit an outer diameter OD2 that is smaller than the first outer diameter OD1. For example, the portions of an elongated shaft that enter a surgical field in an endoscopic procedure may be configured with a smaller outer diameter OD2 to permit the procedure to be performed through a smaller incision.
Outer tubular member 204 is fixedly coupled to a shaft portion 260 extending proximally therefrom. The shaft portion 206 exhibits the smaller outer diameter OD2 and may couple the outer tubular member 204 to a reusable handle assembly of a surgical instrument. The outer tubular member 204 is fixedly coupled to a shaft portion 262 extending distally therefrom. The shaft portion 262 exhibits the smaller outer diameter OD2 and may couple the outer tubular member 204 to a modular end effector. A first jaw drive tube 264 extends slidably through the shaft portion 260, and may couple the proximal jaw drive shaft 208 to an actuator. A second jaw drive tube 266 extends slidably through the shaft portion 262, and may couple the second jaw drive shaft 212 to a jaw member on the end effector. Thus, the jaw drive tube 264 may be translated and rotated to induce a corresponding translation and rotation of first and second jaw drive shafts 208, 212 and the second jaw drive tube 262. The outer tubular members 204, 206 provide sufficient clearance for the first and second jaw drive shafts 208, 212 to translate through a distance of G1 and G2. This distance is sufficient to provide functionality to an end effector such as opening and closing a pair of jaw members.
Although the foregoing disclosure has been described in some detail by way of illustration and example, for purposes of clarity or understanding, it will be obvious that certain changes and modifications may be practiced within the scope of the appended claims.

## Claims

1. A surgical instrument, comprising:
a handle assembly supporting a first actuator thereon;
an elongated shaft extending distally from the handle assembly and defining a longitudinal axis, the elongated shaft including a proximal structural member and a proximal drive member, the proximal drive member operatively coupled to the first actuator such that manipulation of the first actuator induces movement of the proximal drive member relative to the proximal structural member;
a modular end effector removably coupled to the elongated shaft, the end effector including a distal structural member and a distal drive member, the distal drive member operatively coupled to a pair of jaw members such that movement of the distal drive member relative to the distal structural member induces movement of the jaw members from an open configuration wherein the jaw members are substantially spaced to a closed configuration wherein the jaw members are closer together, wherein the end effector includes a knife selectively movable with respect to the jaw members; and
a separable joint defined between the elongated shaft and the end effector, the separable joint comprising:
a laterally prominent portion and a laterally indented portion defined on each of the proximal and distal structural members and configured to interlock with one another such that the proximal and distal structural members resist longitudinal separation and permit separation in at least one lateral direction;
a laterally prominent portion and a laterally indented portion defined on each of the proximal and distal drive members and configured to interlock with one another such that the proximal and distal drive members transmit motion therebetween and permit separation in the at least one lateral direction; and
a distal knife rod and a proximal knife rod, the distal knife rod operatively coupled to the knife to move the knife through the jaw members, the proximal knife rod selectively movable with respect to the structural members, the distal knife rod and the proximal knife rod being separable from each other and including interlocking portions;
wherein the drive members are movable relative to the structural members to move the separable joint between a locked configuration wherein the drive members prohibit separation of the structural members and an unlocked configuration wherein the drive members permit separation of the structural members in the at least one lateral direction.

2. The surgical instrument according to claim 1, wherein the structural members define a generally tubular configuration about the longitudinal axis, and wherein the drive members are coaxially-arranged with respect to the structural members.

3. The surgical instrument according to claim 2, wherein the first actuator is operable to induce longitudinal motion in the drive members to move the jaw members between the open and closed configurations.

4. The surgical instrument according to claim 3, wherein the handle assembly supports a second actuator, and wherein the second actuator is operable to induce rotational motion of the drive members to rotate the jaw members about the longitudinal axis.

5. The surgical instrument according to claim 1, wherein the end effector includes at least one electrode configured for delivering electrosurgical energy to tissue.

6. The surgical instrument according to claim 5, wherein the separable joint includes first and second electrical connectors, the first electrical connector supported by the elongated shaft and electrically coupled to a source of electrosurgical energy, the second electrical connector supported by the end effector and electrically coupled to the at least one electrode.

7. The surgical instrument according to claim 6, wherein the first and second electrical connectors are configured to engage and disengage one another in the at least one lateral direction in which the structural members are separable.

8. The surgical instrument according to claim 1, wherein the interlocking portions of the structural members define a first outer diameter, and wherein the distal structural member is coupled to the end effector by a shaft portion defining a second outer diameter smaller than the first outer diameter.

9. The surgical instrument according to claim 1, wherein each of the proximal and distal structural members includes an outer diameter, and wherein when the proximal and distal structural members are interlocked, the outer diameter of the proximal and distal structural members is equal along an entire length of the separable joint.

10. The surgical instrument according to claim 9, wherein each of the proximal and distal structural members includes an inner diameter, and wherein when the proximal and distal structural members are interlocked, the inner diameter of the proximal and distal structural members is equal along the entire length of the separable joint.

11. The surgical instrument according to claim 1, wherein the drive members and the knife rods are coaxially-arranged with respect to the structural members.