Apparatus for performing endoscopic surgery

Abstract: An endoscopic surgical procedure and instruments are disclosed for the treatment of transverse carpal ligaments and similar anatomical structures. The procedure enables the release of the carpal ligament under endoscopic control and through only a single incision. A uniquely shaped grooved cannula (30) is provided to enable access to the carpal tunnel while also stabilizing instruments used in the procedure. The procedure involves the insertion of the cannula (30) into the carpal tunnel through a single incision. The cannula (30) has a longitudinal groove (40) which is positioned to face or abut the ligament and which axially receives an endoscope (50) through its proximal open end and obliquely receives a knife (54) which is then positioned to cut the ligament from the side where the scope (50) is placed.

Description: This invention relates to apparatus for use in performing endoscopic surgical procedures. More particularly, this invention relates to apparatus for performing a carpal tunnel release endoscopically. Because of the trauma associated with open surgical procedures, efforts have been recently accelerated to develop endoscopic alternatives to all types of open surgical procedures. This invention relates to an endoscopic alternative to one such open procedure -- the treatment of carpal tunnel syndrome, caused by the compression of the median nerve by the transverse carpal ligament. The treatment generally involves a procedure during which the carpal ligament is severed. While endoscopic versions of this procedure have been used in the past with varying degrees of success, continued development of endoscopic procedures to improve efficiencies and reduce patient trauma is always desirable. Although the preferred embodiment of this invention relates to carpal ligament release, it will be understood by those skilled in the art that the apparatus disclosed herein may be easily adapted to other surgical procedures. One system recently developed for the endoscopic treatment of carpal tunnel syndrome is descried in U.S. Patent No. 5,029,573 (Chow). Chow describes other prior art endoscopic carpal tunnel release procedures and claims his invention to be an improvement over the prior art in that the carpal ligament may be severed under direct viewing through an endoscope. As used herein, the term "endoscope" is intended to be generic and refers to any type of optical system used to view the interior of a patient. In the Chow procedure a cylindrical sheath, open at both ends and having a longitudinal slot in its periphery, is inserted through an incision in the wrist, under the carpal tunnel and out through an incision in the patient's palm. An endoscope is inserted in one end of the cannula and a cutting instrument is inserted in the other so that its cutting blade protrudes out of the longitudinal slot in order to cut the carpal ligament. While the Chow procedure is undoubtedly an improvement over open surgical procedures, the necessity to use two portals, one of them being in the palm, is a disadvantage which it would be preferable to avoid. One prior art system -- the Agee Inside Job™ Carpal Tunnel Release System -- has been known to provide a single portal endoscopic carpal tunnel release procedure. While avoiding some disadvantage associated with Chow's procedure and instruments, the Agee system has other disadvantages. The Agee system utilizes a cannula having a small proximal window through which a knife may be projected under the control of a trigger on a handpiece. The knife has a retrograde cutting edge and retraction of the knife cuts the carpal ligament. This type of motion has been found difficult to adequately control. Accordingly, while it is an aim of this invention to produce apparatus for the endoscopic treatment of carpal tunnel syndrome which avoids the necessity to create two incisions, it is also an aim to produce a single portal apparatus which is easier to use than known single portal procedures and instruments. An additional disadvantage associated with the Chow procedure is the relatively large number of cutting instruments required during the course of the procedure. This not only adds to the cost of the instrumentation but also adds to the time required to complete the procedure, thereby creating additional trauma for the patient. The Agee system, while having only one disposable blade assembly, has a complex, non-disposable handpiece. It is consequently another aim of a preferred embodiment of the invention to produce apparatus which can be used for the endoscopic release of a carpal tunnel ligament using a minimum of instruments in order to simplify the procedure and minimize the amount of time required for its completion. Another difficulty with prior art endoscopic carpal ligament release systems is that the cannula inserted under the carpal ligament is cylindrical, thereby making it hard to align the longitudinal slot or window properly and hold it in place during the cutting step. Prior art slotted cannulas have been found to rotate easily during the surgical procedure. It is extremely important that the cannula be maintained with the slot facing the ligament, even during manipulation of the scope, so that the surgeon can be assured that the slot does not face any critical features such as the median nerve. Therefore, it is an aim of a preferred embodiment of the invention to produce apparatus which facilitates the alignment of a cannula under the carpal ligament. It is still another aim of this invention to produce an endoscopic surgical apparatus suitable for use in surgical procedures other than carpal ligament release. It is yet another aim of this invention to produce disposable devices for use in endoscopic carpal ligament release procedures as well as other endoscopic surgical procedures. These and other aims may be achieved by the preferred embodiments of the invention which are devices for use in an endoscopic surgical procedure which, in one preferred embodiment, is a carpal ligament release procedure. According to the invention, there is provided a device for use in an endoscopic surgical procedure, comprising an elongated cannula having a closed distal end, an open proximal end and a longitudinal slot extending from a point adjacent said closed end to a point adjacent said open end, said slot having a D-shaped cross-section extending over substantially the full length thereof, the flat part of said D-shaped cross-section lying along the rim of said longitudinal slot, said D-shaped cross-section having a predetermined size for receiving and guiding an instrument inserted axially into the cannula from said open end. The device may be used in endoscopic treatment of a portion of the human anatomy by inserting it into a body through a single incision; placing the longitudinal slot adjacent a work site; inserting an endoscope through the open (proximal) end of the cannula into a position to view a desired work site adjacent the longitudinal slot of the cannula; inserting through the longitudinal slot, obliquely to the axis of the cannula and in front of the viewing port of the endoscope, an instrument (such as a knife) for treatment of the work site adjacent the longitudinal slot. Preferred features of the invention are hereinafter set out in the dependent claims and in the following description. Preferred embodiments of the invention will now be described by way of example with reference to the drawings in which:- Figure 1 is a schematic view of a human palm and wrist showing the locations of various anatomical features. Figure 2 is a schematic view of a human palm and wrist showing additional anatomical features and showing some of the landmarks used during the procedure descried herein. Figures 3, 4, 5, and 6 are schematic views of a human palm and wrist showing the positions of some of the surgical instruments during various portions of a procedure. Figure 7 is a larger scale view of a portion of Figure 6 showing a knife cutting the transverse carpal ligament. Figure 8 is a side elevational view of the cannula which is part of the invention descried herein. Figure 9 is a cross-sectional view of Figure 8 taken along the line 9-9. Figure 10 is a plan view of the cannula shown in Figure 8. Figure 11 is a plan view of a cannula introducer or obturator for use with the cannula of Figure 8, the proximal end of the introducer being partially in cross-section. Figure 12 is a plan view of a dilator for use in the invention. Figure 13 is a plan view of a knife suitable for use in the procedure which is the subject hereof. Figure 14 is a side elevational view of the knife of Figure 13. Figure 15 is a schematic representation of a view of the transverse carpal ligament as seen through an endoscope during a portion of the procedure described herein. Referring to the drawings, Figures 1-7 and 15 show schematic representations of a human palm and wrist with various anatomical features identified, and describe various steps. Figures 8-14 show the devices which are used to perform various surgical steps. First, various landmarks shown in Figures 1 and 2 are marked. The pisiform bone 100 is palpated and marked on the ulnar aspect of the wrist. The cardinal line of Kaplan 102 is drawn from the apex of the interdigital space between the thumb and the index finger towards the ulnar side of the hand parallel to the proximal palmar crease 104. This line passes 4-5 millimeters in front of the pisiform. A second line 106 is drawn as a continuation of the ulnar border of the ring finger in the proximal direction towards the wrist. This line intersects the cardinal line at a point 108 radial and distal to the pisiform 100. The point of intersection of these lines corresponds to the hook of the hamate 110 (i.e. the distal ulnar attachment of the transverse carpal ligament 111). One additional point of reference, point 112, is the intersection of the thenar crease 114 with the cardinal line 102. The motor branch of the median nerve 116 emerges from beneath the transverse carpal ligament 111 and makes a recurrent course at this point. The distal border of the transverse carpal ligament 111 will lie between points 108 and 112. A one centimeter oblique incision 118 is then made ulnar to the palmaris longus tendon 120 starting at the junction of the distal wrist crease with a line drawn along the radial border of the ring finger (best seen in Figure 2). By blunt and sharp dissection with either the instruments described below or with other, standard instruments, the transverse fibers of the antebrachial fascia of the forearm are split and the carpal tunnel is reached. With the wrist slightly extended, the proximal edge of the carpal ligament 111 is lifted with an instrument of choice (such as forceps 11) and blunt cannula inserter or obturator 10 (best seen in Figures 3 and 11) is introduced into the carpal tunnel. Obturator 10 comprises a cylindrical shaft 12 having a blunt distal tip 14 and a proximal handle portion 16. In Figure 11 the proximal portion 16 is shown partly in cross-section to disclose a thumb recess 17 molded into the proximal end of the obturator. A tapered shoulder portion 18 is provided between the proximal end of shaft 12 and the distal end of handle 16. In the preferred embodiment, obturator 10 is a single molded piece and shaft 12 has a circular cross-section with a diameter of 4 millimeters and a length of 100 millimeters. After obturator 10 has been introduced into the carpal tunnel, it is removed and replaced with a dilator 20 (best seen in Figures 4 and 12). Dilator 20 has a cylindrical shaft 22 with a relatively blunt distal tip 24 and a proximal handle portion 26. In the preferred embodiment, dilator 20 is also molded as an integral piece with the diameter of shaft 22 equal to 5.5 millimeters and its length equal to 75 millimeters. The overall length of the dilator (approximately 115 millimeters) is made the same as the cannula descried below in order to give the surgeon the feel of working with similar instrument lengths as he or she works with different instruments during the course of a procedure. Progressive dilation of the carpal tunnel continues by removing dilator 20 and inserting another dilator (not shown) having a similar shape and length although a larger shaft diameter. In the preferred embodiment the use of a 5.5 millimeter dilator followed by a 7 millimeter dilator has been satisfactory. Cannula 30 comprises an elongated shaft 32, distal tip 34 and proximal handle portion 36. In the preferred embodiment distal tip 34 is closed although it will be understood that apertures necessary or convenient for the injection molding of cannula 30 may be present in distal tip 34. As best seen in Figures 9 and 10, shaft 32 has a top opening 38 extending from distal tip 34 to a point slightly in front of handle portion 36. Opening 38 forms a longitudinal slot or groove 40 and clearly allows full access to the interior of shaft 32 which is also accessible through a longitudinal bore 42 formed along the axis of cannula 30 and through handle portion 36. In the preferred embodiment the internal width 41 of the slot is 4.5 millimeters, the external width 43 of the slot is 7 millimeters and the height 45 of shaft 32 is 6 millimeters. The diameter of bore 42 equals the width of interior 40 and, in the preferred embodiment is made to receive a 4 millimeter arthroscope (without sheath) as will be understood below. The width of interior 40 should be sufficient to enable the chosen arthroscope to slide freely. If it is too wide the surgeon would have to be too concerned about aiming the scope rather than merely following the path of the slot. Having the width of opening 38 equal to interior 40 enables the scope to move upwardly (relative to Figure 9) as necessary. The proximal end of bore 42 is enlarged to form bore 44 which has a slight taper and is shaped to receive shoulder portion 18 of obturator 10. After the largest diameter dilator is inserted under the carpal ligament and removed, obturator 10 is inserted through the proximal end of cannula 30 until its shoulder 18 seats within bore 44 of the cannula. The obturator and cannula are sized appropriately so that when shoulder 18 is so seated distal tip 14 is either contiguous to or near the interior surface of distal tip 34 and shaft 12 substantially fills the interior of shaft 32. The combined cannula/obturator is then introduced into the carpal tunnel with opening 38 facing upwardly against the bottom of the carpal ligament, as best seen in Figure 5. The cannula/obturator is inserted until distal tip 34 is approximately at the distal margin of the carpal ligament. At this point it may be helpful to extend the wrist over 2 to 3 folded towels or some other support and press the proximal part of the cannula down in order to stretch the carpal ligament over opening 38. The obturator is then removed and a standard 4 millimeter arthroscope 50 is inserted into the proximal end of cannula 30 through bore 42 and into slot 40. For this surgical application the term "arthroscope" is interchangeable with "endoscope". The arthroscope is positioned within cannula 32 sufficiently to enable the surgeon to view the carpal ligament. It has been found that using an arthroscope with a 30° viewing angle provides a satisfactory field of view for this procedure. A standard needle 52 (preferably on the order of 25 gauge) is inserted through the palmar skin at the distal border of the transverse carpal ligament and visualized with the endoscope. The needle serves as a mark to prevent the surgeon from inadvertently cutting too deeply into the palm. Arthroscope 50 is then retracted within slot 40 sufficiently to enable knife 54 to be inserted into slot 40, as best seen in Figures 6, 7, 13 and 15. The knife is placed into slot 40 distally to the tip of the arthroscope and its distal cutting edge 56 (set between non-sharpened borders 58 and 59) is engaged on the proximal edge of the transverse carpal ligament while viewing it with the scope, best seen in Figures 7 and 15. The transverse carpal ligament is cut by pushing the knife distally under endoscopic control. A characteristic gritty sensation is felt as the ligament is cut and once the distal margin is cut the knife "gives". Using a probe, the cut margins of the ligament should be palpated to ensure that the ligament has been completely divided. The cannula may be turned radially to inspect the median nerve and then removed. The skin is then closed with an appropriate closure and a volar splint is applied for one week. It will be noted that slot 40 is defined on each longitudinal side by two parallel wall sections 60 and 61 the bottom ends of which are joined by a semi-circular connecting portion 62 (best seen in Figure 9). The top sides of the parallel wail sections are formed as top surfaces 64 and 66 which together with transverse top surfaces at the distal and proximal ends of the slot form a rim 68 in which all these top surfaces lie in a common plane; the cross-section of the slot as shown in Fig. 9 thus has a D-shape, the flat part of the D-shape lying along the rim 68. When opening 38 is inserted under the carpal ligament, rim 68 serves as a planar tissue or ligament contacting surface and top surfaces 64 and 66 serve to rotationally stabilize cannula 30 and help to maintain opening 38 in the proper orientation under the ligament. This may be considered an automatic orientation feature which facilitates the surgical procedure by eliminating any need for the surgeon to be concerned about properly orienting opening 38 once the cannula is properly placed under the ligament. The natural tension of the ligament tends to keep opening 38 properly oriented.

Claims: A device for use in an endoscopic surgical procedure, comprising an elongated cannula (30) having a closed distal end (34), an open proximal end (44) and a longitudinal slot (40) extending from a point adjacent said closed end (34) to a point adjacent said open end (44), said slot (40) having a D-shaped cross-section extending over substantially the full length thereof, the flat part of said D-shaped cross-section lying along the rim (68) of said longitudinal slot (40), said D-shaped cross-section having a predetermined size for receiving and guiding an instrument inserted axially into the cannula (30) from said open end (44). A device according to claim 1 wherein the interior surfaces of the longitudinal sides (60, 61) of said slot (40) are transversely and longitudinally parallel over a predetermined portion of their surfaces. A device according to claim 1 or 2 wherein said cannula (30) also has a D-shaped exterior cross-section. A device according to claim 1, 2 or 3 wherein, in use, said slot (40) is adapted to extend along said cannula from a first point on the interior of a body to a second point exterior to said body. A device according to any preceding claim wherein said cannula cross-section comprises: a first straight wall portion (60), a second straight wall portion (61) parallel to and spaced from said first portion, and a third, substantially semi-circular wall portion (62) connecting one end of said first wall portion (60) to one end of said second wall portion (61), the radius of curvature of said third portion (62) being substantially equal to one-half the distance between said first and second portions (60, 61). A device according to any preceding claim wherein said cannula (30) is provided with a planar tissue contacting surface (64, 66) on each side of said slot (40), said contacting surface (64, 66) being adapted to maintain the rim of said longitudinal slot (40) in abutting engagement with selected tissue and to resist rotation of said cannula (30) about its axis. A device according to claim 6 wherein said planar surfaces (64, 66) lie in a common plane. A device according to claim 7 wherein said rim further comprises distal and proximal transverse surfaces contiguous to said planar tissue contacting surfaces and situated at the distal and proximal ends of said groove, respectively. A device according to any one of claims 1-8 comprising an endoscope (50) inserted along the axis of said cannula (30) through the open proximal end (44) of the cannula into a position to view a desired work site adjacent said longitudinal slot (40) of the cannula. A device according to claim 9 which also comprises an instrument (54) for treatment of the work site adjacent said longitudinal slot (40) which is inserted through said longitudinal slot (40) obliquely to the axis of said cannula (30) and in front of the viewing port of the endoscope. A device according to any one of claims 1-5 comprising an obturator (10) inserted into said cannula (30) through its proximal open end (44).

Inventors: MENON JAY, WINKLER RANCE A, MENON, JAY, WINKLER, RANCE A.
Applicants: LINVATEC CORP, LINVATEC CORPORATION
Application year: 1993
Main classification: A61B17
IPC codes: A61B17