Abstract:
A surgical instrument in the form of a biopsy needle for removing tissue samples from a patient. The device has means for preloading to excise tissue samples of a preselected one of many possible tissue sample sizes. After preloading, the procedure is easily accomplished using a single hand. The tip is rendered less traumatic by positioning the distal end of the tissue sample notch relatively close to the very distal tip of the stylet. This is accomplished by grinding the distal tip of the stylet into an elliptical shape in a plane having a lateral projection which is away from the distal end of the tissue sample notch.

Description:
BACKGROUND OF THE INVENTION 
     1. Summary of the Invention 
     The present invention generally relates to medical devices and more particularly relates to surgical instruments. 
     2. Description of the Prior Art 
     The diagnostic advantages of obtaining and analyzing a tissue sample have been long known. This procedure is often termed biopsy. To be most useful, the surgical instrument or biopsy needle, utilized to obtain the tissue sample must be insertable through the skin of the patient, guidable through the body to the sample site, and capable of quickly and easily excising and removing the selected sample. 
     An early biopsy instrument is seen in U.S. Pat. No. 3,577,979, issued to van der Gaast, incorporated herein by reference. Called a disposable surgical skin punch by the inventor, the device is capable of taking manual core samples. U.S. Pat. No. 4,940,061, issued to Terwilliger et al., incorporated herein by reference, shows an extremely complex motorized version of a biopsy instrument. Though probably somewhat easier to operate, the cost of manufacturing such a device probably precludes disposable use, which has become a major health care consideration. Unlike the earlier device, Terwilliger et al. employs a stylet having a tissue notch concentrically slidable within a sharpened canula. This basic sampling technique has become the standard technique. 
     To facilitate maintenance of the tissue excising portion of the needle, U.S. Pat. No. 5,031,634, issued to Simon and incorporated herein by reference, shows the use of retractable barbs at the distal end. This may be particularly adapted to soft tissue use, particularly the breast. U.S. Pat. No. 5,036,860, issued to Leigh et al., incorporated herein by reference, shows a device especially intended to be disposable following single use. With the increasing awareness of blood borne viruses, disposability is now a key feature. 
     U.S. Pat. No. 5,125,413, issued to Baran and incorporated herein by reference, describes a spring loaded device permitting single hand operation by attending medical personnel. Before use, the spring is compressed providing retraction of the outer canula proximally of the distal stylet tip. The distal end of the instrument is advanced to the sample site. Releasing the spring advances the sharpened canula over the stylet thus excising the tissue sample within the sample notch (see FIG.  9 ). This has become the typical method for biopsy procedures. Alternative tissue notch configurations are shown in U.S. Pat. No. 5,127,419, issued to Kaldany. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the disadvantages found in the prior art devices by providing a convenient means for adjusting length of the core sample taken along with a less traumatic approach, which does not require excess distal extension of the needle beyond the tissue sample site. 
     To provide an adjustable length core sample, the tissue sample notch is relatively large in the longitudinal direction. However, the canula is retracted exposing the entire length of the tissue sample notch only when taking the largest tissue sample. For smaller tissue samples, the canula is only partially retracted to expose only a portion of the tissue sample notch. In the preferred mode of the present invention, two or three different tissue sample sizes are provided. To accomplish this, the canula may be retracted to one of two or three different positions, with the spring being adequately compressed at each. Release of the spring drives the sharpened canula distally excising and capturing a tissue sample having the corresponding one of the three possible sizes. 
     The biopsy needle is rendered less traumatic by restricting the distance between the most distal point of the stylet and the most distal face of the tissue sample notch. This means that the stylet need be advanced only slightly beyond the intended sample to accommodate the distal tip (i.e. the distance between the distal tip and the most distal face of the tissue sample notch). Rigidity and strength of the distal end of the stylet ar enhanced by grinding the point at the tip of the stylet in a plane having a lateral projection on the longitudinal axis of the stylet which is away from the location of the tissue sample notch. The canula is similarly ground to provide even greater assurance of tip stability. 
     The resulting biopsy needle is a precision surgical instrument providing readily adjustable tissue sample size and atraumatic insertion, which is disposable after a single use. The attending personnel preload the canula for one of the two or three tissue sample sizes before use, thereby compressing the spring. Using the convenient finger holders, the instrument is inserted into the patient&#39;s body and advanced to the sample site by single handed control of the surgeon. The stylet is advanced through the sample site to present the tissue sample to the tissue sample notch. The canula is released, and the compressed spring advances the canula over the tissue sample notch of the stylet, thus excising the tissue sample. The instrument containing the tissue sample is removed from the patient. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other objects of the present invention and many of the attendant advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, in which like reference numerals designate like parts throughout the figures thereof and wherein: 
         FIG. 1  is a plan view of a surgical instrument employing the present invention; 
         FIG. 2  is a side view of the surgical instrument of  FIG. 1 ; 
         FIG. 3  is a partial side view preloaded for the smallest tissue sample size; 
         FIG. 4  is a partial side view preloaded for the intermediate tissue sample size; 
         FIG. 5  is a partial side view preloaded for the largest tissue sample size; 
         FIG. 6  is a cut away close up view of the distal tip showing the tissue sample notch preloaded for the three different tissue sample sizes; 
         FIG. 7  is a partially cut away rear view showing the means for preloading for different tissue sample sizes; and 
         FIG. 8  is a sectioned partial view of the preloading engagement means. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  is a frontal plan view of a surgical instrument, often called biopsy needle, made and used in accordance with the preferred mode of the present invention. Those of skill in the art will be readily able to apply the teachings found herein to yet other embodiments within the scope of the present invention. 
     To be inserted into the patient is long thin stainless steel canula  12 . Although not seen in this view, canula  12  is hollow, having a central lumen containing a longitudinally slidable stylet which is described in greater detail below. Of particular interest is distal tip  14  which is also described in greater detail below and shown in close up in FIG.  6 . 
     The proximal end of canula  12  is coupled to preloading engagement assembly  16  to permit retraction and advancement of canula  12  with respect to main housing  22 , which are preferably molded of a suitable polymer for disposability. Before insertion, the surgical instrument is preloaded by manually pulling actuation button  24  proximally of main housing  22  until engagement of the preloading engagement assembly  16  is achieved for the desired tissue sample size. 
     The preloaded surgical instrument  10  is grasped by the attending medical person using a single hand. The index finger is placed in finger hold  20  and the middle finger is placed in finger hold  18 . Distal tip is advanced into the patient to the tissue sample site. After distal tip  14  is located at the tissue sample site, thumb surface  26  is pressed to carefully advance actuation button  24  distally. This is done carefully to avoid applying sufficient force to disengage preloading engagement assembly  16 . This advances the distal tip of the stylet (not shown), which passes through grommet  28 , past the tissue sample site exposing the tissue sample notch of the selected size (i.e. size preloaded). Further pressure is exerted on thumb surface  26  to disengage preloading engagement assembly  16 . This permits the spring (not shown), which was compressed during the preloading procedure, to drive the sharpened distal tip of canula  12  in the distal direction to excise the tissue sample and encase it between the tissue sample notch and the inner wall of canula  12 . Surgical instrument  10  is removed, and the tissue sample it contains is removed and analyzed. 
       FIG. 2  is a side view of surgical instrument  10 . Preloading engagement assembly  16  is slidably contained within engagement track  30 , which is fixedly attached and preferably molded as part of housing  22 . A tab of preloading engagement assembly  16 , obscured in the view by fixed strut  46  and housing  22 , is fixedly coupled to the proximal end of canula  12  and impinges on the distal end of compression spring  32 . Therefore, as preloading engagement assembly  16  slides proximally within engagement track  30 , canula  12  moves in a proximal direction and compression spring  32  is further compressed. 
     During the preloading procedure, actuation button  24  is pulled proximally with regard to housing  22 . As a result, preloading engagement assembly  1  is pulled proximally within engagement track  30  by preloading strut  34 . In accordance with the above explanation, this tends to further compress compression spring  32  and to move canula  12  in a proximal direction. Engagement latch  38  latches preloading engagement assembly  16  in one of many possible positions (i.e. selections of the tissue sample size). Compression spring  32  tends to keep preloading engagement assembly  16  in the selected position by the distal force of its compression. Fixed strut  36 , which is preferably molded as a portion of housing  22 , maintains the position of preloading strut  34 . 
       FIG. 3  is a partial side view showing surgical instrument  10  preloaded for the smallest tissue sample size. Preloading engagement assembly  16  has been slid proximally the distance  40 , exposing a partial view of tab  17 , which is preferably molded as a portion of preloading engagement assembly  16 . It is latched by engagement latch  38  at corresponding distance  42 . In the preloaded state, the proximal end of stylet  44  can be seen protruding from grommet  28  and attached to actuation button  24 . All other referenced elements are as previously described. 
       FIG. 4  is a partial side view, similar to  FIG. 3 , showing surgical instrument  10  preloaded to an intermediate tissue sample size. Distance  48  is greater than distance  40  (see also  FIG. 3 ) and directly corresponds to distance  50 . Also show is a larger view of tab  17  of preloading engagement assembly  16 . 
       FIG. 5  is a partial side view, similar to  FIG. 4 , showing surgical instrument  10  preloaded to the largest tissue sample size. Distances  52  and  54  are at a maximum. All other referenced elements are as previously described. 
       FIG. 6  shows three close up view of distal tip  14 . View  66  corresponds to preloading of the device for the smallest tissue sample size  60 A with stylet  44  advanced to the distal most position for exposure of the tissue sample notch. 
     View  68  shows stylet  44  advanced distally after preloading to intermediate tissue sample size  60 B. Similarly, view  70  shows largest tissue sample size  60 C. 
     For each of these configurations, the tissue sample present within the tissue sample notch is excised by sharpened edge  56  of canula  12  as compression spring  32  drives canula  12  distally over stylet  44  upon disengagement of preloading engagement assembly  16  (see also FIGS.  1 - 5 ). In the completely disengaged position, canula  12  preferably covers stylet  44  completely, thus encasing the excised tissue sample. 
     In the preferred embodiment, distal end  64  of stylet  44  is ground to an elliptical shape in a plane directed away from distal end  62  of the tissue notch. This permits the distance from distal edge  62  to the most distal point of stylet  44  to be minimized for a given rigidity of the distal end of stylet  44 , because it maximizes the distance from distal edge  62  to distal end  64 . Minimizing the distance from distal edge  62  to the most distal point of stylet  44  tends to limit the trauma to the patient because it minimizes the distance beyond the tissue sample which must be pierced by stylet  44  (i.e. the distance from distal end  62  to the most distal point of distal end  64 ). Further rigidity is achieved by grinding sharpened edge  56  in the same plane as distal end  64 . 
       FIG. 7  is a rear view of surgical instrument  10  preloaded to the largest tissue sample size with engagement latch  38  and a portion of engagement track  30  removed to show details of preloading engagement assembly  16 . A portion of the rear of preloading engagement assembly  16  is concavely recessed creating general recess  84 . This recess permits advancement of engagement strut  34  distally to advance stylet  44  distally of canula  12  to expose the tissue sample notch to the tissue sample (see also FIG.  6 ). However, proximal movement of engagement strut  34  engages preloading stop  86  to permit preloading. 
     General recess  84  contains stop members  72  and  74  for the smallest tissue sample size; stop members  76  and  78  for the intermediate tissue sample size; and stop members  80  and  82  for the largest tissue sample size. These stop members latch against engagement latch  38  (see also  FIG. 3-5 ) to maintain the preselected tissue sample size. However, engagement strut  34  is free to move distally of stop members  72 ,  74 ,  76 ,  78 ,  80 , and  82  within general recess  84  to permit advancement of stylet  44  distally of canula  12  (see also FIG.  6 ). 
       FIG. 8  is a partial sectioned view of preloading engagement assembly  16 . Projections  88  and  90  of preloading engagement assembly  16  slide within corresponding recesses within engagement track  30 . All other referenced elements are as previously described. Preferably canula  12 , stylet  44  and compression spring  32  are fabricated of stainless steel and all other elements are molded of a convenient disposable polymer. 
     Having thus described the preferred embodiments of the present invention, those of skill in the art will be readily able to apply these teachings to yet other embodiments within the scope of the claims hereto attached, and wherein