ENDOSCOPIC INSTRUMENTATION WITH WORKING CHANNEL

Abstract: An endoscope (10) includes a housing (16) having a working channel (18) extending therethrough; an elongated insertion section (22) mounted to the housing (16) having a distal end to be inserted into the object, a detachable sheath (24) mechanically detachable, and replaceable on the housing to extend over the elongated insertion section. The sheath creates, and maintains a working space at the surgical site.

Description: ENDOSCOPIC INSTRUMENTATION WITH WORKING CHANNEL Background of the Invention The invention relates to endoscopes. Surgical procedures for treating incompetent perforated veins and for harvesting saphenous veins generally require long incisions to be made along the leg of the patient. Perforated veins run substantially perpendicularly through layers of subcutaneous fat and muscle fascia (i.e., the fibrous layer attached to underlying softer tissue) into the muscle to connect the deep and superficial vena systems. When the perforated veins become diseased (e.g., varicosed) , they may require ablation to disrupt flow of blood running therethrough. One conventional approach for ablating such perforated veins in the leg is to make a relatively long incision extending from the knee down to below the ankle. However, patients having incompetent perforated veins (particularly the elderly) may suffer from chronic venous insufficiency (CVI) , a condition in which the skin becomes ulcerated and often infected. Incisions made through skin in this condition have a relatively high wound complication rate. At best, patient recovery is significantly increased and, in some cases, a new, morbid wound is created. Saphenous vein harvesting is typically performed in conjunction with coronary bypass heart surgery. Under endoscopic visualization, the saphenous vein is harvested from the leg and grafted within the heart . In conventional approaches for removing the saphenous vein, a single long incision or several separate and spaced incisions are made along the length of the leg. A new approach, known as subfascial endoscopic perforator surgery (SEPS) , has recently developed as an alternative procedure for performing perforator ligation or for harvesting saphenous veins. In general, the SEPS procedure allows a working instrument to be introduced through a small incision and, with the aid of an endoscope, guided below the fascia to the surgical work area. This is particularly advantageous for patients suffering from chronic venous insufficiency since the SEPS approach allows incisions to be made in healthy tissue remote from the morbid tissue; one incision is generally required for the working instrument, another for the endoscope used to visualize the procedure. Thus, the SEPS approach reduces incidents of wound complication often associated with procedures involving long incisions . Summary of the Invention The invention features an endoscope having a working channel through which a working instrument is introduced for use at a worksite, and a detachable sheath for creating and maintaining a working space for the working instrument at the worksite. In a general aspect of the invention, the endoscope includes a housing having the working channel extending therethrough; and an elongated insertion section, mounted to the housing and having a distal end for insertion into an object; and a sheath configured to be inserted into the object and mechanically detachable and replaceable on the housing to extend over the elongated insertion section. Thus, the endoscope provides visualization of a surgical site while facilitating access for handheld surgical instruments to the site. The endoscope is adapted to receive one or more multi-purpose detachable sheaths. The sheaths primarily create and maintain a working space at the surgical site to improve - 3 - visualization by the endoscope. The sheaths also protect the elongated insertion section of the endoscope and the surgical instrument extending therethrough. In certain applications the sheaths may be used to perform limited dissection of tissue. Because no two patients and procedures are identical, the sheaths used with the endoscope are of different sizes and shapes. Thus, a family of reusable instruments is provided, each instrument being easily attachable and detachable from the endoscope and individually constructed for use in a particular anatomical situation. Advantageously, only a single incision is required for providing access to the surgical worksite for the working instrument and visualization of the worksite by the endoscope. Embodiments of the invention may include one or more of the following features. The endoscope includes a handle connected to the housing and extending in a direction offset from the optical axis defined by the elongated insertion section. In certain embodiments, the handle extends in a direction substantially transverse to the optical axis. Offsetting the handle in this manner provides an unobstructed space in the area where the surgical instruments introduced through the working channel of the endoscope are being manipulated. The elongated insertion section and handle of the endoscope includes an optical system. The handle includes a rotatable manipulator coupled to a mechanism for focusing the optical system. With this arrangement, the endoscope is easily rotated about the optical axis of the endoscope without cables and working instruments used with the endoscope becoming entangled. In addition, this arrangement allows the surgeon to hold and manipulate (e.g., positioning and focusing) the endoscope with one - 4 - hand while freeing the use of the other hand for manipulating the working instrument. The detachable sheath includes an outwardly tapering distal end to increase the visualization space at the surgical site. In certain embodiments, the detachable sheath has an open medial portion, allowing greater maneuverability of the surgical instrument and reducing trauma to the tissue during its introduction through tissue. Alternatively, in other embodiments, the detachable sheath has a closed medial section forming a tube to enclose the elongated insertion section, thereby creating a sealed working space for procedures requiring gas insufflation. The endoscopic instrumentation system utilizes a bayonet mount for mechanically coupling the housing and detachable sheath. The bayonet mount is mechanically robust and provides a quick and reliable approach for attaching and detaching the sheaths from the endoscope. Where gas insufflation is required, an airtight sealing ring can be provided between the housing of the endoscope and the detachable sheath. During manipulation of the endoscope and working instruments extending therethrough, significant forces can be imparted both longitudinally and radially to the distal end of the sheath. The rugged construction and mount of the sheaths prevent them from bending to eliminate risk of impingement on the elongated insertion section with its optical elements and working instrument. The working channel has an exit port having a semi-circular (D-shaped) opening to increase lateral movement of the working instrument passing therethrough. The elongated insertion section includes light transmissive elements (e.g. a fiber optic bundle) for conveying light from an external light source to the object. The housing further includes an insufflation - 5 - port which, when used with a closed sheath, permits delivery of gas or fluid insufflation to the worksite. Another aspect of the invention relates to a method of visualizing a surgical procedure on a body using an endoscope of the type described above. The method includes attaching a sheath on the housing to extend in parallel with the optical axis and over the elongated insertion section; positioning the insertion section and sheath through an incision port in the body and to a surgical worksite; and introducing a working instrument to the surgical worksite through the working channel of the housing. Embodiments of this aspect of the invention may include one or more of the following features. Positioning the insertion section and sheath includes manipulating a handle which is attached to the housing and extends in a direction substantially transverse to the optical axis of the endoscope. The handle is manipulated by the user using one hand while the working instrument is introduced using the other hand. The endoscope is focused by actuating a focusing mechanism disposed on the handle. The method further includes introducing gas insufflation to the surgical worksite. Other features and advantages of the invention will become apparent from the following detailed description, and from the claims. Brief Description of the Drawing Fig. 1 shows an endoscope according to the invention and a handheld instrument positioned for use in a surgical procedure . Fig. 2 is a rear perspective view of the endoscope of Fig. 1. Fig. 3 is a front perspective view of the endoscope of Fig. 1. Fig. 4 is a front perspective view of a housing of the endoscope of Fig. 1. Fig. 5 is a cross-sectional side view of the endoscope of Fig. 1. Fig. 6 is a cross-sectional side view of the housing of the endoscope of Fig. 1. Fig. 7 is a front view of the housing of the endoscope having an insufflation channel. Fig. 8 is a perspective view of the bayonet mount used to attach the interchangeable sheath to the endoscope . Fig. 9 is a perspective view of a family of interchangeable sheaths for use with the endoscope of Fig. 1. Figs. 10A and 10B are cross-sectional side and front views, respectively, of the distal end of one of the interchangeable sheaths of Fig. 9. Fig. 11 is a side view of a portion of the endoscope of Fig. 1 having a closed sheath and gas seal attachment . Fig. 12 shows the endoscope of Fig. 1 in use. Description Referring to Fig. 1, an electronic endoscope 10 is shown prior to being inserted within an incision port 12 in the body, here a leg 14 of a patient. Endoscope 10 is of the type including an optical system (described in detail below) for conveying an optical image from a distal end of the endoscope to a video camera 28 attached to the endoscope . Referring to Figs. 2-3, endoscope 10 includes a housing 16 having a working channel 18 for allowing a handheld instrument 20 (e.g., ligator, dissector, cutter, - 7 - abrader) to extend through the housing for use in a surgical procedure being viewed with endoscope 10. An elongated insertion section 22 (which defines an optical axis 25 of the endoscope) and a detachable sheath 24 extend from housing 16. A handle 26 for manipulating endoscope 10 extends in a direction substantially perpendicular to optical axis 25 so that the area at the entrance of working channel 18 is unobstructed and free from other components. In addition, a rounded heel region 27 of handle 26 has a low profile to facilitate introduction and manipulation of working instruments through working channel 18. A video camera 28 having an electro-optical sensor (not shown) is mounted to the upper end of handle 26. The electro-optical sensor may be, for example, a charge-coupled device (CCD) for converting optical images received by the endoscope to electrical image signals. Referring again to Fig. 1, electrical image signals from video camera 28 are conveyed to a camera control unit 30, via a cable 32, for view on a display monitor, such as color CRT 34. The upper end of handle 26 also includes a fitting 36 (Fig. 2) which receives a fiber optic cable 38 connected to a light source 40. A second fitting 42 (Fig. 2) , adjacent fitting 36, receives a tube 44 connected to a gas (e.g., C0 2 ) or fluid insufflation source 46. A focusing ring 48 is positioned at the upper end of handle 26 to allow the user to focus endoscope 10. This arrangement provides several advantages. Arranging handle 16 to be offset from optical axis 25 provides an unobstructed space for manipulating handheld instrument 20. Attachments to endoscope 10 are also located away from optical axis 25 so that the surgeon can manipulate the endoscope and working instruments extending therethrough without interference from cables 32, 38, 44. Further, because - 8 - the optical, illumination and gas insufflation systems are all arranged along the same plane of handle 16, endoscope 10 can be easily rotated around optical axis 25 without the cables becoming entangled with each other or any working instruments used with the endoscope. Further still, the contour of handle 26 allows its use by a surgeon with either hand (i.e., left to right or vice versa) . Referring to Fig. 4, insertion section 22 is shown with sheath 24 removed to reveal an optical support tube 50 disposed between a pair of illumination support tubes 52, 54. Each tube has a length of approximately 230 mm. Fiber optic bundles 55 (Fig. 7) are positioned within and extend the length of support tubes 52, 54, and through housing 16 to fitting 36 on handle 26. Referring to Fig. 5, an objective lens assembly 56 is disposed within a distal end 58 of optical support tube 52 to receive and convey the image of the object being viewed to a series of relay lens systems 60 within the support tube. Objective lens assembly 56 is positioned within distal end 58 to provide a direction of view pointing downward toward the open portion of the sheath and at an angle of about 12 degrees from optical axis 25. This configuration provides a field of view of about 85 degrees. Thus, the range of movement permitted for a working instrument passing through endoscope 10 is substantial (e.g., as much as 2 inches). However, because the view provided by objective lens assembly 56 is directed slightly downward, if endoscope 10 is required to be moved at all, it is most likely tilted in a direction upward, consistent with the direction endoscope 10 tilts due to the weight of cables 32, 38, 44. Relay lens systems 60 convey images to a prism 62, positioned within housing 16, which translates the image to an axis 64 defined by handle 16. In particular, the image is received by a series of a relay lenses 66 disposed within a vertical tube 68. An ocular lens 70 is positioned at the proximal end of vertical tube 68 to receive and convey the image to a focusing lens 72. Focusing lens 72 is supported within a sleeve 74 mechanically coupled to focusing ring 48 which, when rotated, moves focusing lens 72 along axis 64 of handle 16. Handle 26 includes, at its proximal end, a centering mount ring 76 for receiving video camera 28. Referring again to Fig. 4, as well as Figs. 6-7, working channel 18 is positioned adjacently below optical support tube 50 and illumination support tubes 52. Working channel 18 has a working length between about 200 and 230 mm and a diameter in a range between about 5.5 mm and 7 mm for an endoscope 10 having an insertion section with a diameter between 10 and 11 mm. A working channel of this dimension is sufficiently sized to receive handheld working instruments having shafts of 4 to 5 mm diameter. Working channel 18 includes a circularly- shaped entrance port 80 which flares laterally outward to form a larger substantially semi-circularly shaped exit port 82 to allow greater maneuverability of instruments used through the working channel . Due to the larger semi-circularly shaped exit port 82 and the length of the insertion section 22, a relatively small movement of working instrument 20 at the proximal end of endoscope translates to a much larger movement at the worksite with sheath 24 providing better visibility by moving tissue away. Housing 16 includes a distal end 84 having a tapering outer surface 86 for mating with a corresponding tapering inner surface 88 of a locking ring 90. Locking - 10 - ring 90 rotates freely about the proximal end of detachable sheath 24. In one embodiment, outer surface 86 is tapered relative to optical axis 25 at an angle of 16 degrees and 35 minutes. For applications requiring gas insufflation, housing 16 also includes a gas port 59 (Fig. 7) which connects to a conduit extending through handle 26 to fitting 36. In such applications, an optional threaded fitting 85 is shown attached to entrance port 80 for receiving a gas seal member 81 (Fig. 11) to provide an air-tight seal between a working instrument passing through working channel 18. Referring to Fig. 8, the coupling between detachable sheath 24 and housing 16 is accomplished using a bayonet mount. In particular, a pin 92 projects upwardly from outer surface 86 of housing 16 and is received within an L-shaped slot 94 of locking ring 90. L-shaped slot 94 includes a longitudinal groove 96 terminating at a helical groove 98. To lock detachable sheath 24 to housing 16, pin 92 is slid within longitudinal groove 96 until it reaches helical groove 98. A projecting shaft 100 formed on locking ring 90 is then rotated counterclockwise to draw surfaces 86, 88 of respective ones of housing 16 and locking ring 90 together in a self-locking manner. The bayonet mount also includes an O-ring 102 (Fig. 6) to seal the interface between housing 16 and sheath 24 in the event that gas insufflation is required. Referring to Fig. 9, a set of detachable sheaths 24a-24e, each being approximately 230 mm in length have the same locking ring 90 for attachment to housing 16 of endoscope 10. However, sheaths 24a-24e include distal end members HOa-llOe, sized and configured differently to adapt to anatomical differences between patients as well as the particular worksite within a patient. In - 11 - general, sheaths 24a-24d are open along substantially their entire length to allow a larger range of movement (particularly lateral movement) of handheld instruments introduced through working channel 18 and hooded by the sheaths. In addition, the absence of the lateral sidewall minimizes pressure and trauma inflicted upon the surrounding anatomy as endoscope 10 and sheath 24 is forced through tissue. Each of open sheaths 24a-24d include distal end members 110a-llOd shaped to create and maintain a working space at the surgical site. Distal end members HOa-llOd can be attached (e.g., soldered) to the end of the sheaths, as is the case for sheaths 24a- 24c. Alternatively, as is the case with sheath 24d, distal end member llOd may be integrally-formed to the sheath. Referring to Figs. 10A-10B, in one embodiment of an open sheath 24, a distal end member 110 has a flaring end 114 for creating and maintaining the working space at the surgical worksite. End 114 has a length of about 0.75 inches and extends outwardly, relative to optical axis, at an angle of 25 degrees. End 114, in cross- section, extends about 58 degrees to either side of an imaginary vertical plane 116 passing through optical axis 25. With this configuration, a working instrument passed through working channel 18 and hooded by sheath 24 is capable of being maneuvered at the distal end of the sheath as much as 1 inch to either side of plane 116. Referring again to Fig. 9, in applications (e.g., SEPS) , where gas insufflation is required at the surgical site, a closed sheath 24e provides a supply channel for gas provided from insufflation source 46 (Fig. 1) through handle 26, housing 16 and through the closed sheath. Because gas insufflation is relied upon to maintain a working space at the surgical worksite, sheath 24e does not require a flared distal end typical of open sheaths - 12 - 24a-24d. In essence, sheath 24e creates a common working channel endoscope while allowing simultaneous viewing of the surgical worksite at the end of the sheath. The inner surface of closed sheath 24e also serves to guide the surgical instrument to the worksite. Referring to Fig. 11, a threaded seal 120 having a is slid over and positioned at the proximal end of closed sheath 24e and secured in place using locking ring 122. Seal 120 is then threaded into incision port 12 to prevent escape of the gas from the incision port. Gas seal member 81 is placed over threaded fitting 85 of housing 16 to provide an air-tight seal between a working instrument passing through working channel 18. Referring again to Fig. 1, endoscope 10 having an open sheath 24 is shown in use in a procedure for harvesting a saphenous vein. Prior to placing endoscope 10 within incision port 12, a dissector 20 is used at incision port 12 to separate the fascia from the tissue. Dissection by direct visualization is generally limited to an area of only about 5 cm from incision port 12. Referring to Fig. 12, after this initial dissection procedure, sheath 24 of endoscope 10 is inserted through port 10 with the sheath held generally parallel to leg 14. Dissector 20 is then introduced through working channel 18 of endoscope 10 and separation of the fascia and tissue is continued with endoscope 10 used to visualize the dissection. Dissection continues in this manner, with sheath 24 maintaining a working space for dissector 20, until the surgical site is reached. Throughout this dissection procedure, endoscope 10 is not required to be removed, unless the surgeon requires a different sheath. Upon reaching the surgical worksite, endoscope 10 may be removed if a different sheath 24 needs to be attached to the endoscope 10. For example, a larger sheath may be required to accommodate a - 13 - different working instrument (e.g., ligator) . Alternatively, a closed sheath may be required. Other embodiments and applications are within the claims. For example, although endoscope 10 is described as being useful for a saphenous vein harvesting procedure, it can be used in wide variety of surgical applications, including treatment of patients having incompetent perforated veins in a leg and suffering from chronic vena insufficiency. In addition, use of endoscope 10 is not limited to vascular procedures, but has application in other surgical procedures where a working space needs to be maintained and simultaneous visualization is required. For example, endoscope 10 may be used to examine the thoracic cavity or to perform certain plastic surgical procedures .

Claims: 14 What is claimed is: 1. An endoscope for internal inspection of an object comprising: a housing having a working channel extending therethrough, the working channel configured to allow passage of a surgical instrument; and an elongated insertion section having a proximal end mounted to the housing and a distal end to be inserted into the object, the elongated insertion section defining an optical axis of the endoscope; and a sheath configured to be inserted into the object and mechanically detachable and replaceable on the housing, the sheath extending along the optical axis and over the elongated insertion section. 2. The endoscope of claim 1 further comprising a handle connected to the housing, the handle extending in a direction offset from the optical axis of the endoscope . 3. The endoscope of claim 2 wherein the handle extends in a direction substantially transverse to the optical axis of the endoscope. 4. The endoscope of claim 2 further comprising an optical system disposed within the elongated insertion second and extending through the handle, the optical system including a focusing mechanism and a rotatable manipulator coupled to the focusing mechanism. 5. The endoscope of claim 1 wherein a distal end of the sheath is sized and shaped to temporarily displace portions of the object. - 15 - 6. The endoscope of claim 1 wherein the sheath includes an opening extending substantially the length of the sheath. 7. The endoscope of claim 1 wherein the sheath is a tube surrounding the elongated insertion section. 8. The endoscope of claim 7 further comprises an insufflation channel extending through the housing. 9. The endoscope of claim 1 further comprising a bayonet mount for mechanically coupling the sheath to the housing. 10. The endoscope of claim 8 wherein the bayonet mount includes a sealing ring for providing an airtight seal between the housing and sheath. 11. The endoscope of claim 1 wherein the working channel has an exit port having a semi-circular shape. 12. The endoscope of claim 2 wherein the insertion section includes: a light transmissive element for conveying light from an external light source to the object. 13. A method of visualizing a surgical procedure on a body using an endoscope, the endoscope of the type including an elongated insertion section defining an optical axis of the endoscope and having a distal end to be inserted into the body; and a housing attached to a proximal end of the insertion section and having a working channel extending therethrough and substantially in parallel with the optical axis, the method comprising: - 16 - attaching a sheath on the housing to extend in parallel with the optical axis and over the elongated insertion section, the sheath configured to be inserted into the body and mechanically detachable and replaceable on the housing of the endoscope; positioning the insertion section and sheath through an incision port in the body and to a surgical worksite; and introducing a working instrument to the surgical worksite through the working channel of the housing. 14. The method of claim 13 wherein positioning the insertion section and sheath includes manipulating a handle attached to the housing and extending in a direction substantially transverse to the optical axis of the endoscope . 15. The method of claim 14 wherein manipulating the handle is performed using one hand of a user and introducing the working instrument is performed using the other hand of the user. 16. The method of claim 15 further comprising focusing the endoscope by actuating a focusing mechanism disposed on the handle. 17. The method of claim 13 further comprising introducing gas insufflation to the surgical worksite.

Inventors: IAFRATI MARK, MIHALCA GHEOGHE, IAFRATI, MARK, MIHALCA, GHEOGHE
Applicants: NEW ENGLAND MEDICAL CENTER INC, NEW ENGLAND MEDICAL CENTER HOSPITALS, INC.
Application year: 1999
Main classification: A61B1
IPC codes: A61B1, A61B17, A61B19