Patent Publication Number: US-2007112366-A1

Title: Apparatus and method for releasing tendon sheath

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention generally relates to techniques for alleviating pain in the movement of limbs and, in particular, to techniques for releasing tendon sheaths where pain is due to inflammation of tissue within the sheath.  
      2. Background Description  
      In 1895, Fritz de Quervain, a Swiss surgeon, first described tenosynovitis (inflammation of the tendons) within the first dorsal wrist extensor compartment (tendon tunnel on the dorsal wrist surface) at the radial styloid (base of thumb). The usual complaint was pain in the region of the wrist joint. De Quervain&#39;s tenosynovitis is a painful and often disabling condition that is mainly observed in workers, athletes and musicians who perform repetitive manual tasks.  
      De Quervain tenosynovitis (sometimes also called de Quervain&#39;s tendinitis) is a result of friction of the tendon as it glides through narrow channels of the first dorsal compartment found along the thumb side of the wrist. This compartment contains abductor pollicis longus (APL) and extensor pollicis brevis (EPB) tendons. These channels or fascia tubes guide the tendons to their specific point of insertion where they act to position the wrist or fingers to accomplish a specific goal.  
      Anatomic variation within the first extensor compartment has been identified. One author (Harvey, F J, Harvey P M, Horsley M W. “De Quervain&#39;s disease: surgical or nonsurgical treatment”,  Journal of Hand SurgeryI,  1990; vol. 15, pp. 83-87) found a separate synovial compartment containing the extensor pollicis brevis at surgery in 91% of cases. There are also reports of a separate compartment for the EPB (Harvey F J 1990). Cadaveric dissection studies have shown that this variant is present in 40% of wrists (Witt J, Pess G, Gelberman R H. “Treatment of de Quervain tenosynovitis”,  Journal of Bone Joint Surgery,  1991; vol. 73, pp. 219-222).  
      The friction or resistance to tendon gliding results in injury which is manifested as inflammation and swelling of the tendons and compartment. With increasing inflammation local tissues begin to swell and tendon gliding becomes increasingly difficult with greater resistance to gliding and greater injury. Setting up an increasing exponential injury cycle which must be broken before pain relief can be achieved.  
      The superficial branch of the radial nerve crosses over the first dorsal compartment and is susceptible to both inflammation and injury. Injury to this nerve often results in severe pain syndrome (Regional Causalgia) which is sympathetically mediated. Local inflammation leads to swelling and in time the surrounding structures also become swollen and irritated including the Superficial Branch of the Radial Nerve which lies directly over the tendon sheath. Additional Injury to this nerve can result from increased inflammation, traction and disruption which greatly complicate treatment and delay functional recovery.  
      Swelling can cause pain and tenderness along the thumb side of the wrist, usually noticed when forming a fist, grasping or gripping things, or turning the wrist. Pain over the thumb side of the wrist is the main symptom. The pain may appear either gradually or suddenly. It is felt in the wrist and can travel up the forearm. The pain is usually worse with use of the hand and thumb, especially when forcefully grasping things or twisting the wrist. Swelling over the thumb side of the wrist is noticed and may be accompanied by a fluid-filled cyst in this region. There may be an occasional “catching” or “snapping” when moving the thumb. Because of the pain and swelling, it may be difficult to move the thumb and wrist, such as in pinching. Irritation of the nerve lying on top of the tendon sheath may cause severe pain and numbness on the back of the thumb and index finger.  
      Risk for these injuries is apparent in people employed in work requiring repetitive use of their hands. Upper extremity work-related diagnoses are becoming more frequent as a source of chronic pain and lost work time for the injured worker. De Quervain&#39;s tendinitis is reported to be one of the most common disorders reported by working people in the United States. Extensive epidemiological investigation indicates that the adverse ergonomic exposures of force, repetition, vibration and certain postures are risk factors for development these disorders. Annual incidence of hand and arm tendinitis from computer, data entry and keyboard use has been measured at 39 cases/100 person-years. The most common disorder was deQuervain&#39;s tendinitis. More than 50% of computer users reported tendinitis during the first year after starting a new job.  
      Treatment for the above described disorders is directed at decreasing tendon swelling and nerve irritation, thereby relieving pain caused by tendon and nerve irritation and swelling. Early treatment includes splinting, therapy and non-steriodal medication, resting by splinting the thumb and wrist, and anti-inflammatory medication. Injection of corticosteroid into the tendon compartment may help reduce the swelling and relieve the pain. One source reported 40% failure with single injection requiring multiple injections. These injections are not without possible complications. Cheiralgia paresthetica, a mononeuropathy of the superficial branch of the radial nerve, usually results from local trauma to the wrist. One report describes subdermal atrophy following local hydrocortisone injection, and also describes linear atrophy which traverse the superficial radial nerve and contribute to the symptoms.  
      When symptoms are severe or do not improve, surgery may be recommended. The surgery opens the compartment covering, called the extensor retinaculum, which tightly secures the tendons against the radial styloid, to make more room for the irritated tendons. The surgeon then moves aside other tissues and locates the tendons and the tunnel. An incision is made to split the roof, or top, of the tunnel. This allows the tunnel to open up, creating more space for the tendons. The skin is then stitched together, and the hand is wrapped in a bulky dressing. The tunnel will eventually heal closed, but it will be larger than before. Scar tissue will fill the gap where the tunnel was cut.  
      However, traditional open surgical release has the potential for additional soft tissue injury. What is needed is minimally invasive surgery using an endoscopic technique to reduce local injury and avoid complications permitting a more rapid decline in symptoms.  
     SUMMARY OF THE INVENTION  
      It is therefore an object of the present invention to provide an endoscopic technique for release of tendon sheaths.  
      A further object of the invention is to provide a technique for release of tendon sheaths that is minimally invasive.  
      Yet another object of the invention is to provide supporting tools that make a technique for release of tendon sheaths reliable and routine.  
      The invention provides a rasp tool and and endoscopic cutting tool for release of tendon sheath, and in particular for use in release of tendon sheath in treatment of de Quervain&#39;s tenosynovitis. An aspect of the invention is a kit comprising a rasp tool having a body supporting a probe with a rasp surface at one end of the probe for removing soft tissue adhering to the tendon sheath after insertion of the probe into a pocket formed above the tendon sheath, and an endoscopic cutting tool having a probe with a blade at one end, the blade being extendable by operation of a trigger after insertion of the probe into the pocket, the blade being operable to cut the tendon sheath by pulling the tool out of the pocket with the blade extended. The rasp body and probe may be fitted over an endoscope, a field of view for an endoscope camera being provided by a groove on the rasp surface. Further, the rasp body, rasp probe and rasp surface may be of one piece, the one piece being removably attachable to the endoscope.  
      In a further aspect of the invention, an endoscopic cutting tool is provided for use in release of tendon sheath, comprising an endoscope having a body from which is extended an endoscope tube with a camera lens at a tube end away from the body, and a probe with a blade at one end, the probe being mounted on the endoscope tube so that the blade end extends beyond the end of the tube to allow for extension and retraction of the blade, the blade being extendable by operation of a trigger, the trigger being operated after insertion of the probe into a pocket formed above the tendon sheath, the blade being operable to cut the tendon sheath by pulling the tool out of the pocket with the blade extended. In another aspect of this invention, the trigger is part of a pistol grip assembly mounted on the endoscopic cutting tool, the assembly being able to rotate around the axis of the probe. The invention further a light source and fiber optic channels for delivering light from the light source along the endoscopic tube to illuminate objects observable by the camera lens. In one aspect of the invention the light source provides ultraviolet light.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The foregoing and other objects, aspects and advantages will be better understood from the following detailed description of a preferred embodiment of the invention with reference to the drawings, in which:  
       FIG. 1  is an isometric view of the hand showing the thumb tendons and covering sheath.  
       FIG. 2A  is a cross sectional cutaway view of the wrist showing the compartment containing the thumb tendons and a pocket cleared by a rasp in accordance with the invention.  FIG. 2B  is an expanded view from  FIG. 2A  of the portion of the wrist involving the thumb tendons.  
       FIG. 3A  is a side view of the rasp used to clear a pocket in accordance with the invention.  FIGS. 3B and 3C  are sectional and perspective views, respectively, of the rasp instrument.  
       FIG. 4A  is a side view of a pistol grip cutting tool used to release the tendon sheath.  FIGS. 4C and 4E  are perspective and sectional views, respectively, of the tool shown in  FIG. 4A .  FIG. 4B  shows the tool with its cutting blade extended.  FIGS. 4D and 4F  are perspective and sectional views, respectively, of the tool with blade extended as shown in  FIG. 4B .  
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION  
      Referring now to the drawings, and more particularly to  FIG. 1 , there is shown a schematic drawing of hand  100 , with particular attention to the thumb  105  and the two thumb tendons, the abductor pollicis longus (APL)  120  and extensor pollicis brevis (EPB)  110  tendons. Also shown is a portion of the upper side  130  of the sheath (the extensor retinaculum) holding the thumb tendons in place as they pass from the radius bone of the forearm along the inside edge of the wrist. The object of the instrument combination described herein and the methodology for using the instruments is to release the sheath  130  by cutting across the sheath between the two dotted lines  140 .  
      An incision is made on the proximal or distal side of the sheath  130  and, after dissection down to the sheath  130  and then dissection across the sheath to create a pocket above the first dorsal compartment, a rasp tool is used to clear the tissue that adheres to the surface of the first dorsal compartment.  
      The rasp tool is shown in  FIG. 3A . A sectional view of the rasp tool is shown in  FIG. 3B , and a perspective view is shown in  FIG. 3C . An endoscope is shown, having a handle  310  and endoscopic tube  315  to which is attached a removable a rasp  330  having a hollow probe  335  which fits conformably around endoscopic tube  315 . At the end of the probe  335  is a rasp surface  340  disposed at a slight angle. At the end of endoscopic tube  315  is a camera lens, and there is a groove  345  in the rasp surface  340  so that the camera lens will have an unobstructed field of view. The light for the endoscope is provided by fiber optic channels (not shown) within the endoscopic tube  315 . The light source is provided through endoscopic control  320 , which also channels the video signals coming from the camera lens.  
      A cross sectional view of the hand  200  at the wrist is shown in  FIG. 2A , with an expanded view of the portion of the wrist containing the thumb tendons shown in  FIG. 2B . The thumb tendons (EPB  110  and APL  120 ) are held within a tunnel formed between an upper sheath surface  240  and a lower sheath surface  260 . The pocket  220  above the upper sheath  240  contains a nerve  210  (the superficial branch of the radial nerve), which must be avoided. The rasp tool is inserted into the incision along the pocket  220 , with the rasp surface  340  oriented so that the rasp surface  340  faces the upper sheath surface  240  from direction of the pocket  220 . The rasp tool  300  is manipulated with the visual aid provided by the endoscope  310  to remove the soft tissue adhering to the outer surface  240  of the first dorsal compartment. Tissue removal will be complete when the operator of the rasp tool  300  detects a gritty or rough surface sensation, indicating abrasion against the surface of the sheath  240 .  
      Then the cutting tool  400  is inserted into the incision and along the pocket  220 . The cutting tool  400  is shown in  FIGS. 4A  (with cutting blade retracted) and  4 B (with cutting blade extended). Corresponding perspective views of the cutting tool are shown in  FIGS. 4C and 4D , respectively. Corresponding sectional views of the cutting tool are shown in  FIGS. 4E and 4F , respectively. An endoscope body  410  supports an endoscopic tube  415  above which is mounted a probe  430 , at the end of which is a retractable blade  445 . The probe  430  contains the mechanism for retracting and extending the cutting blade  445 . The probe  430  extends beyond the endoscopic tube  415 , forming a recess  440 . The recess  440  provides space for extension and retraction of the cutting blade  445 , and also allows a clear field of view for a camera lens at the end of the endoscopic tube  415 .  
      A pistol grip  450  has a trigger  455 . When the trigger  455  is pulled toward the pistol grip  450 , the blade  445  is extended from the recess  440 . The pistol grip  450  and trigger  455  assembly are mounted on the endoscope so that the pistol grip  450  and trigger  455  assembly may be rotated around the axis of the endoscopic tube  415  and probe  430 , so that the trigger  455  may be operated to retract and extend the cutting blade  445  without interfering with the hand or arm of the patient, while at the same time maintaining the orientation of the cutting blade  445  with respect to the sheath surrounding the tendons. The light for the endoscope is provided by fiber optic channels (not shown) within the endoscopic tube  415 . The light source is provided through endoscopic control  420 , which also channels the video signals coming from the camera lens.  
      A cross sectional representation of the cutting tool after insertion along the pocket  220  is shown as item  230  in  FIG. 2A . The tissue clearing provided by the above described operation of the rasp tool improves the field of view provided by the camera lens at the end of endoscopic tube  415 . Further improvement in the field of view is provided by controlling the light shown in the field of view. For example, ultraviolet light exposes features within the pocket  220  that would otherwise be obscured.  
      The cutting tool  400  is inserted into the pocket  220  until the depression  440  is beyond the edge of the upper sheath surface  240 . The following description assumes that the incision has been made on the proximal side of the sheath, but those skilled in the art will understand that the incision could also be made on the distal side of the sheath. The probe  430  is oriented so that the tip of the probe is aligned so as to avoid nerve  210  and positioned on the sheath  240  within the pocket  220  as shown between the dotted lines  270 . Trigger  455  is then actuated, extending blade  445  in a downward direction toward upper sheath surface  240 . The blade  445  is shaped and extended at an angle so as to catch the sheath  240  on the cutting surface of the blade  445  as the cutting tool is pulled back out of the pocket. The cutting surface is located on the side of the extended blade  445  facing the pistol grip. The cutting blade  445 , when extended, protrudes a certain distance outside the cross section formed by the probe  430  and endoscopic tube  415 , enough to catch the edge of the sheath  240 . The blade is guided by a smooth protrusion  447  on the lower edge of the blade  445 , which operates so that the protrusion  447  remains beneath the sheath  240 . As the cutting tool  400  is operated to cut the sheath  240  by pulling the tool out of the pocket, it may be necessary to reinsert the extended blade  445  into the line of the cut, so that a full release of the sheath is accomplished. A full release may be understood with reference to  FIG. 1 , where a cut begins at the edge of sheath  130  away from the incision and proceeds to the edge nearest the incision, between the dotted lines  140 .  
      It should be noted that in a significant number of cases there may be a separate compartment around one of the wrist tendons, in which case an additional cut may be required to fully release the sheath enclosing both tendons. The need for an additional cut is usually confirmed by moving the thumb so as to observe movement of the tendons individually.  
      While the invention has been described in terms of a single preferred embodiment, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the appended claims.