Abstract:
The medical instrument disclosed includes a pair of jaws which are clamped to an end of a surgical wire or pin. The jaws are pressed together, not by the usual Jacobs&#39; chuck arrangement, but by the operation of a cam lever. The lever is mounted in the hand-grip of the instrument. This arrangement makes it possible for the wire or pin to be gripped with a large force, yet to be gripped delicately and precisely so that damage to the surrounding tissue is kept to a minimum. The instrument is T-shaped as to its general shape, and the cam lever operates the jaws by means of a collet action by which a jaw member is axially moved within the hollow stem of the T. The inside end of the stem and a portion of the outer end of the jaw member forming a pair of opposed camming surfaces.

Description:
FIELD OF THE INVENTION 
     This invention relates to surgical instruments for use in conjunction with bone fixation components such as pins and wires, and more particularly relates to instruments for the removal of such components. 
     1. Background of the Invention 
     It is quite common, when carrying out surgical procedures on bones, particularly in the hands, and also generally in the limbs, to implant a pin or wire into the injured or diseased bone. The purpose of the wire is to reinforce the bone during healing. Particularly in surgery of the hand, where wire is used, an end of the wire may be left protruding from the skin to make it easy to remove the wire later, or the wire may be trimmed below the level of the skin. 
     2. Description of the Prior Art 
     Instruments are available for extracting surgical wires and pins. Some such instruments are based on the principle of using a Jacobs&#39; chuck to tighten the instruments onto the wire, whereupon the wire can be drawn clear of the bone, and discarded. Other instruments are merely special forms of pliers adapted for a particular medical situation. 
     A problem that arises with most known instruments is that the tissues around the area from which the wire is extracted can become severely traumatised by the manipulation of the wire; and by the manipulation of the extractor so as to attach it to the wire. The reason is that the known instruments have been too heavy and cumbersome and awkward. It has proved to be too difficult for a surgeon to consistently tighten a chuck, using a chuck key, onto the wire with the degree of sensitivity and delicacy that is required to avoid damaging the surounding tissues. 
     An instrument that is somewhat lighter and easier to use than a typical Jacobs&#39; chuck is disclosed in U.S. Pat. No. 4,263,903. It comprises a one piece jaw that is contained in a slender body means. In order to close the jaws, it relies on the body means to act on a cam surface located on the outer surfaces of the jaws. As the jaws are pulled up into the body means, they are forced together. The jaws are pulled into the body means by rotating a screw thread assembly. This method of bringing the jaws together takes a longer period of time than is desirable and also requires a great deal of hand movement. It could therefore, cause necessary trauma and tissue damage. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the present invention, there is provided an instrument for extracting surgical wires, particularly surgical wires such as K-wire™. Surgical wires include such things as wires, pins, staples, and intramedullary nails. The instrument will permit the user to consistently tighten a portion of the instrument onto the wire with the appropriate delicacy. The present invention provides an instrument that can be tightened and otherwise manipulated by the user with the delicacy expected for work of this nature. This is in part due to the tactile feedback experienced by the user. This tactile feedback is a result of the reaction forces generated by the gripping of the pin or wire. These forces are transmitted, at least in part, back to the user&#39;s hand. 
     In the present invention, the instrument may be operated by a single hand. It is provided with a hand-grip, a cam lever, a pair of jaws, and a collet. The cam lever is operable by the hand while holding the hand-grip. The cam lever draws the jaws, which grip the surgical wire or pin, up into the collet. A tapered surface on the collet acts on the cam surface of the jaws to urge the jaws together. The action of closing the hand is sufficient to perform this action, thus making the gripping action very quick, which is effective in reducing trauma and tissue damage. 
     It has been found, by this invention, that the combination of the cam lever and the camming action between the jaws and the collet makes it possible to apply a strong gripping force to the jaws in a very controlled manner. The undesired side-forces that could hardly be avoided with the Jacobs&#39; chuck, are virtually non-existent with this invention. It is these uncontrolled side-forces particularly that typically lead to trauma and tissue damage. 
     It has also been found to be beneficial that there are only two opposed jaw surfaces, rather than the three wedge-shaped jaw pieces usual to a Jacobs&#39; chuck. 
     There is some friction associated with both the tapered collet and cam surface mechanism and the sliding and rubbing cam lever mechanism. It is recognized in the present invention that some friction here is beneficial, since it may be desirable that the gripping force be partially locked in even if the grip on the cam lever should be relaxed. If there were to be a frictionless connection between the jaws and the cam lever, then the grip of the jaws would relax as the force on the cam lever was relaxed. 
     On the other hand, the friction should not be so great that the magnitude of the jaw gripping force is unduly diminished. It has been found, in the present invention, that the combination of the tapered collet and cam mechanism and the cam lever mechanism gives a suitable degree of friction. 
     In this invention, the cam lever is operated by the hand that grips the hand-grip. This frees the other hand for the purpose of steadying the instrument, or otherwise manipulating the patient&#39;s body or surgical site using the surgeon&#39;s own hand-eye co-ordination without the need for voice commands to a nurse or other surgical assistant—or indeed, to the patient. This, again, reduces the likelihood of generating side-forces, which would result in trauma or tissue damage. 
     Additionally, a squeeze grip type of action is one of the easiest ways of applying a large force in a well controlled manner. This is due to the relatively high gripping strength of a human hand and to the fact that the gripping forces are applied roughly co-linearly to the direction of application of gross force during the removal of the surgical wire. 
     The strength of the grip needed from the instrument, to pull the wire or pin out, can be quite large. Thus, the jaw must be robust enough to withstand a heavy twisting action, because it may be necessary to rotate the instrument to make it easier to extract the wire or pin. The collet and cam combination of the present invention permits construction of an instrument having jaws of sufficient size, and of suitable material, that can easily cope with the noted forces, without undue distortion. In the present invention, all the components of the instruments, though simple to construct, can be sturdy and reliable over a long service life, with none of the components being subject to undue wear. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features which are believed to be characteristic of the present invention, as to its structure, organization, use and method of operation, together with further objectives and advantages thereof, will be better understood from the following drawings in which a presently preferred embodiment of the invention will now be illustrated by way of example. It is expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention. Embodiments of this invention will now be described by way of example in association with the accompanying drawings in which: 
     FIG. 1 is a partial cross-section of an instrument that embodies this invention; 
     FIG. 2 is a view corresponding to that of FIG. 1, showing the instrument at a different stage of use; 
     FIG. 3 is a view similar to FIG. 1, showing an alternative embodiment of the invention; 
     FIG. 4 is a view similar to FIG. 1, showing an alternative embodiment of the invention that incorporates a different cam lever configuration; 
     FIG. 5 is a view similar to FIG. 1, showing an alternative embodiment of the invention that incorporates a different type of cam; and 
     FIG. 6 is a view similar to FIG. 1, showing an alternative embodiment of the invention that incorporates a different type of lever arm system. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The novel features which are believed to be characteristic of the present invention, as to its structure, organization, use and method of operation, together with further objectives and advantages thereof, will be better understood from the following discussion. 
     The instrument illustrated is generally T-shaped, as can be seen in FIG.  1 . It is sized to be easily gripped in the hand, with the fingers and thumb wrapped around the hand-grip  20 . The palm of the hand is generally in intimate contact with the top surface  22  of a cam lever  24 . The hand-grip  20  includes a slot  26  for receiving the cam lever  24 . 
     Depending from the bottom of the hand-grip  20  is a stem member  28 . The hand-grip  20  and the stem member  28  are joined together in a threadible relation in order to permit relative adjustment of these two parts. Such adjustment may become necessary as the instrument becomes worn through use. This method of adjoinment also allows the stem to be replaced if necessary, or for alternate stems to be used. 
     The stem member  28  comprises a hollow stem portion  30  and a sleeve means  32 , which is typically a collet. Hollow stem portion  30  and sleeve means  32  are preferably adjoined in threadible relation. 
     The stem member  28  contains a jaw member  34  which is arranged for axial movement within the hollow interior  36  thereof. The jaw member  34  comprises a proximal end  38  and a distal end  40 . The distal end  40  comprises a pair of opposed jaws  42  and  44 . These opposed jaws  42  and  44  are defined by a slit  46  in jaw member  34 . Jaws  42  and  44  therefore comprise the material of the jaw member  34  at the sides of the slit  46 . The width of the slit  46  can be controlled by changing the length of stem member  28 . This is accomplished by adjusting sleeve means  32  until the desired size of the slit is obtained. The inner sides of jaws  42  and  44  form substantially planar opposing surfaces  48  to be used for gripping surgical wire, pins, and the like. 
     As will be observed from the illustrations, when the jaw member  34  is moved upwardly, the jaws  42  and  44  are squeezed together by a camming or wedging action. Together, jaws  42  and  44  and sleeve means  32  form a gripping means. 
     The slit  46  extends a substantial distance up the length of the jaw member  34 , such that the jaws  42  and  44  are of sufficient length so as to be fairly readily elastically deformed. The slit  46  has an enlarged end  50  to dissipate any stresses that may have been caused by cutting or otherwise forming the slit  46  into the material of the jaw member  34 . The slit can also be used to accommodate a portion of the length of the wire or pin that has been pulled out of the patient. This allows the instrument to be easily repositioned closer to the point at which the wire or pin exits the tissue. 
     It is necessary when removing a pin or wire, to grip the pin or wire with substantial force. The gripping force typically generated by a human hand is insufficient for holding onto a pin or wire for the purpose of removal by pulling. In order to generate the amount of force necessary, some sort of mechanical means must be used to multiply the forces generated by the hand. The present invention uses a double camming action in order to gain the necessary mechanical advantage for producing sufficient gripping strength. 
     The first camming action is produced by a lever means in form of a cam lever  24  located at the top of the instrument. The cam lever  24  includes a cam surface  52  which comprises a plurality of radii that are preferably substantially concentric. The cam surface  52  is actually formed on a tongue portion  54  of cam lever  24 . Included in the tongue portion  54  is a substantially circular aperture  56 , which is preferably located centrally to the radii of cam surface  52 . When the cam lever  24  is in position shown in FIG. 1, a first portion  58  of the cam surface  52  engages a cam reaction surface  60  at the top of the stem member  28 . When the cam lever  24  is in the position shown in FIG. 2, a second portion  62  of the cam surface  52  engages the cam reaction surface  60  of the stem  28 . The respective radii of the first and second portions of  58  and  62  respectively of the cam surface  52  are different, with the radius at first portion  58  being lesser and the radius at second portion  62  being greater. As the cam lever  24  is rotated from the position shown in FIG. 1 to the position shown in FIG. 2, the aperture is displaced to a greater distance from the reaction surface  60 . The distance along the cam lever  24  from the aperture  56  to the area  64 , where hand grip forces are applied, is a plurality of times greater than the largest radius of the cam, thus providing the required mechanical advantage. 
     The proximal end  38  of the jaw member  34  includes a slot  66  for receiving tongue portion  54  of cam lever  24 . Jaw member  34  is pivotally connected to the cam lever  24  through pin  68 , which is adapted to fit snugly into aperture  56  of the cam lever. 
     The axial movement of the jaw member  34  within the stem member  28  is controlled through the use of cam lever  24 . As the cam lever is rotated, the pivot pin  68  is moved along guide slot  70 , from the position shown in FIG. 1 to the position shown in FIG.  2 . The force on the pin is in turn transmitted to the jaw member  34 . This force pulls the jaw member  34  into the hollow interior  36  of the stem member  28  which in turn initiates the second camming action, thereby causing a change in the relative opening of jaws  42  and  44 . 
     The second camming action occurs at the distal end of the stem member  28 . The sleeve means  32  contained thereon is thereby provided with a female camming surface  72 . The jaw member  34  is provided with a male curved camming surface  74 . When the cam lever  24  is in an upwardly oriented position, as in FIG. 1, the camming surfaces  72  and  74  are disengaged and the jaws  42  and  44  are therefore spread apart. As the jaw member  34  is pulled into the stem member  28 , the male curved camming surface  74  contacts the female camming surface  72  thereby transmitting the pulling force to jaws  42  and  44 . When the cam lever  24  is in a downwardly oriented position, as in FIG. 2, the jaws  42  and  44  have moved together sufficiently to grip a surgical wire or pin that is to be extracted. 
     The male curved camming surface  74  is shaped so as to provide a more severe camming action as the jaws  42  and  44  first contact the stem member  28 , and to provide less severe camming action after the jaws  42  and  44  have entered at least part way into the stem. This non-linear camming configuration accommodates the increased resistance to the pulling of the jaw member  34  due to increased friction caused by the outwardly exerted force of the jaws  42  and  44 . 
     In order to improve the grip of the jaws  42  and  44  onto the surgical wire being extracted, the opposing surfaces  48  may be modified so as to have enhanced gripping characteristics. Typically, diamond dust may be adhered to or otherwise cemented to the opposing surfaces  48 ; or alternatively, the opposing surfaces  48  may be machined in such a manner as to create a frictional or serrated surface on each. 
     An alternative embodiment of the invention is disclosed in FIG. 3 which shows a spring member  80  securely fastened to hand-grip  82 , and preferably located in the slot  84 . The spring member acts against the undersurface  86  of cam lever  88  thus providing a resistive force as the handle is pressed down. The main purpose of the spring is to provide an unlocking force to assist in moving cam lever in an upward direction. The friction between the jaw member  90  and the stem member  92  resists the lever from moving upwardly. 
     Another alternative embodiment of the invention is disclosed in FIG. 4 which shows a downwardly extending cam lever configuration. The cam lever  100  includes a gripping portion  102  that extends from the bottom of the hand-grip  104 , and is therefore in intimate contact with the fingers rather than the palm of the hand. The forces are transmitted from the cam lever  100  to the jaws  106  in a manner analogous to the embodiment of FIG.  1 . 
     Another alternative embodiment of the invention is disclosed in FIG. 5 which shows a cam lever configuration that is operable bi-directionally. The cam lever  110  is symmetrical about its centre line  112  and the cam surface  114  is of a constant radius, with the centre  115  of the radius substantially on the centre line  112 . The aperture  116  in the tongue portion  118  of the cam lever  110 , is also substantially on the centre line  112 , but is offset from the centre  115  of the radius toward the cam surface end  119  of the cam lever. The camming action is produced as a result of this offset. It is readily apparent that the similar camming action would be produced by rotating the cam lever in either direction. 
     A further alternative embodiment of the invention is disclosed in FIG. 6, which shows a simple first order lever system that is used to lift the jaw member  120  when the lever arm  122  is moved toward the handle-grip  124 . 
     A still further embodiment, not shown in the figures, includes a cam surface that has a maximum radius between the two ends of the cam surface, and thus incorporates an over-the-centre action as the cam lever is rotated. This feature serves to lock the lever in place, thus freeing the user&#39;s gripping hand while maintaining the gripping force on the pin or wire. 
     In addition to the instrument herein described being used to remove surgical pins and wires, it is possible to use the instrument for insertion of surgical pins and wires. It may be necessary, however, to use additional apparatus in conjunction with the instrument when used as an insertion device. 
     Furthermore, this instrument could also be adapted for use in conjunction with other surgical bone fixation means such as staples, intramedullary nails, or drills. Such adaptation could require the jaws to be of a particular configuration for each specific use. 
     Other modifications and alterations may be used in the design and manufacture of the surgical wire and pin puller of the present invention without departing from the spirit and scope of the accompanying claims. 
     Throughout this specification and the claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not to the exclusion of any other integer or step or group of integers or steps. 
     Moreover, the word “substantially” when used with an adjective or adverb is intended to enhance the scope of the particular characteristic; e.g., substantially planar is intended to mean planar, nearly planar and/or exhibiting characteristics associated with a planar element.