Abstract:
A method for elongating a tendon including by moving a cutting blade along the tendon in a helical path so as to make a helical cut in the tendon which allows elongation of the tendon.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a divisional of U.S. Ser. No. 13/301,384, filed Nov. 21, 2011, which claims priority to U.S. Provisional Ser. No. 61/419,143, filed Dec. 2, 2010, each of which is hereby incorporated herein in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Inventive Concepts 
     The inventive concepts disclosed herein generally relate to an apparatus and method for cutting a tendon in order to achieve a lengthening thereof without a continuous cut through the tendon. More particularly, the inventive concepts relate to an apparatus which allows a helical or spiral cutting of a tendon. The inventive concepts disclosed herein also relate to a method for lengthening a tendon by helical or spiral cutting. 
     2. Brief Description of Related Art 
     Additional tendon length is occasionally needed for the surgical reattachment of a retracted tendon and for the lengthening of an intact but contracted tendon. To achieve additional tendon length using established techniques, such as z-plasty, the tendon is completely transected into two parts, loses continuity and has to be sewn back together at a selected length. 
     Thus, a need exists for an improved instrument and method for the operative elongation of tendons overcoming the above disadvantages. It is to such an instrument and method that the inventive concepts disclosed herein are directed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of one embodiment of an apparatus constructed in accordance with the inventive concepts disclosed herein. 
         FIG. 2A  is an enlarged perspective view of a portion of the apparatus of  FIG. 1 . 
         FIG. 2B  is an exploded, perspective view of a portion of the apparatus of  FIG. 1 . 
         FIG. 3  is a front end view of the apparatus of  FIG. 1 . 
         FIG. 4  is a top plan view of a front portion of the apparatus of  FIG. 1 . 
         FIG. 5  is a sectional view along line  5 - 5  of  FIG. 4 . 
         FIG. 6  is sectional view of another embodiment of a cutting blade. 
         FIG. 7  is a top plan view of a front portion of another embodiment of an apparatus constructed in accordance with the inventive concepts disclosed herein. 
         FIG. 8  is a perspective view of another embodiment of an apparatus constructed in accordance with the inventive concepts disclosed herein. 
         FIG. 9  is an elevational view of the apparatus of  FIG. 8  shown attached to a tendon. 
         FIG. 10  is an elevational view of another embodiment of an apparatus constructed in accordance with the inventive concepts disclosed herein shown attached to a tendon. 
         FIG. 11  is a perspective view of a cutting guide constructed in accordance with the inventive concepts disclosed herein. 
         FIG. 12  is a perspective view of the cutting guide of  FIG. 11  shown positioned about a tendon. 
         FIG. 13  is a perspective view showing a cutting blade being guided by the cutting guide of  FIG. 11 . 
         FIG. 14  is a perspective view of another embodiment of a cutting guide constructed in accordance with the inventive concepts disclosed herein. 
         FIG. 15  is a perspective view of the cutting guide of  FIG. 14  shown positioned about a tendon. 
         FIG. 16  is a perspective view showing a cutting blade being guided by the cutting guide of  FIG. 14 . 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Before explaining at least one embodiment of the inventive concepts in detail, it is to be understood that the inventive concepts disclosed herein are not limited in its application to the details of construction, experiments, exemplary data, and the arrangement of the components set forth in the following description or illustrated in the drawings. The inventive concepts are capable of other embodiments or being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for purposes of description and should not be regarded as limiting. 
     Referring now to the drawings, and more particularly to  FIGS. 1-5 , one embodiment of an apparatus  10  for cutting soft tissue, such as a tendon  12  ( FIGS. 8 and 9 ) is illustrated. The apparatus  10  includes a cutting blade  13  and a cutting guide  14  for guiding the cutting blade  13  along the tendon in a helical path. The cutting guide  14  comprises a shaft  15  with a diameter d, a longitudinal axis  16 , a front end  18 , and a rear end  20 . The shaft  15  is provided with a groove  22  near the front end  18  of the shaft  15 . The groove  22  is formed so that cutting blade  13  is supported at the front end  18  of the shaft  15  so as to protrude unilaterally from the shaft  15 . 
     The cutting blade  13  has a cutting edge  24  extending from a front face  26  at the front end  18  of the shaft  15 . The cutting edge  24  increases its distance to the longitudinal axis  16  in a direction towards the rear end  20  of the shaft  15 . Further, the blade  13  has a middle plane  28  ( FIG. 4 ) which forms an angle α of exemplarily 45° with the longitudinal axis  16  of the shaft  15 . However, it should be understood that the angle α may be in a range from about 20° to about 70°. 
     As illustrated in  FIG. 2B , the groove  22  has a central axis  29  extending along the length of the groove  22 . The groove  22  is arranged in such a way that the central axis  29  of the groove  22  and the longitudinal axis  16  of the shaft  15  are skew lines. Further, the central axis  29  of the groove  22  forms the identical angle α with the longitudinal axis  16  of the shaft  15  as the middle plane  28  of the blade  13  ( FIG. 4 ). 
     As illustrated in  FIG. 5 , the blade  13  may be symmetrical in a cross-section along line  5 - 5  in  FIG. 4  so that the cutting edge  24  lies in the middle plane  28  of the blade  13 . Alternatively, as illustrated in  FIG. 6 , a blade  13   a  can be asymmetrical in a cross-section so that the cutting edge  24   a  lies in a plane which is parallel to the middle plane of the blade  13   a  and which coincides with one lateral surface of the blade  13 . 
     The cutting edge  24  of the blade  13  extends to a height H from the longitudinal axis  16  measured orthogonal to the longitudinal axis  16  of the shaft  15  and to a length L measured in the middle plane  28  orthogonal to the height H. The height H is dimensioned to cut a tendon  12  with a diameter of about 2×H. The cutting edge  24  curvedly extends from the shaft  15  on a plane curve which defines a plane coinciding with the middle plane  28  of the blade  13 . In one embodiment, the maximum ratio of L/H is about 0.70 
     The shaft  15  is provided with a cannula  30  ( FIGS. 2A and 3 ) so that the shaft  15  can be slid over and rotated about a K-wire  32  ( FIG. 8 ) which is positioned in the tendon  12  ( FIG. 9 ). The shaft  15  also includes an axial extension  38  extending from the rear end  20  of the shaft  15 . The axial extension  38  is provided with a first helical engagement member  40  extending along the longitudinal axis  16  of the shaft  15 . The axial extension  38  has a diameter D which is larger than the diameter d of the shaft  15  and has a handle  42  at its rearmost portion. The first helical engagement member  40  is configured as a helical ridge having a helix angle with respect to a plane orthogonal to the longitudinal axis  16  of the shaft  15  ( FIG. 1 ) wherein the helix angle corresponds to the angle α between the middle plane  28  of the blade  13  and the longitudinal axis  16  of the shaft  15 . 
     The cutting guide  14  further comprises a sleeve  44  with a central opening  46  for receiving the axial extension  38  of the shaft  15 . The sleeve  44  is provided with a second helical engagement member  48  ( FIG. 2A ) which is engageable with the first helical engagement member  40  of the axial extension  38 . The second engagement member  48  is configured as a helical groove in the inner wall of the sleeve  44 . Thereby, the first and second helical engagement members  40 ,  48  mate with each other allowing the shaft  15  to move axially relative to the sleeve  44  upon a relative rotation. 
       FIG. 7  illustrates an alternative embodiment of an instrument  10   a  which differs from the embodiment of  FIGS. 1-5  as described below. A blade  13   b  is incorporated as part of a cutting guide  14   a . The blade  13   b  is a helically twisted band with a helix angle δ between the middle plane  28  of the blade  13   b  and a plane orthogonal to the longitudinal axis  16  of the shaft  15  wherein the angle δ is complementary to the angle γ between the middle plane  28  of the blade  13   b  and the longitudinal axis  16  of the shaft  15 . The middle plane  28  is a helically twisted plane. The blade  13   b  has a cutting edge  13   a  extending in the helically twisted middle plane  28  of the blade  13   b  and has a distance to the longitudinal axis  16  of the shaft  15  which continuously increases from the foremost point of the cutting edge  24   b  at the front end  18  of the shaft  15  to the rearmost point of the cutting edge  24   b.    
       FIGS. 8 and 9  illustrate another embodiment of an apparatus  10   b  which differs from the embodiments of  FIGS. 1-5 and 7  as described below. More specifically, the apparatus  10   b  further comprises an adapter  50  which is attached to the sleeve  44 . The adapter  50  is configured to support the tendon  12  in a bent condition along a section  54  adjacent to a fixed end  56  of the tendon  12  in an S-shaped form so that a longitudinal section  58  of the tendon  12  is shifted with respect to the fixed end  56  of the tendon  12 . The adapter  50  is an elongated member extending along the longitudinal axis  16  of the shaft  15  and protruding distally from the sleeve  44  so as to form an extension arm  60  providing a first support surface and a second support surface longitudinally and laterally spaced from one another to which a section  54  of the tendon  12  which is adjacent the fixed end  56  of the tendon  12  can be affixed. At a front  66  of the sleeve  44 , the adapter  50  is stepped away from the longitudinal axis  16  of the shaft  15 , so that the adapter  50  can be fixed to the section  54  of the tendon  12  which is adjacent to the fixed end  56  of the tendon  12  in such a way that the axial extension  38  of the shaft  15  can be lead beside the fixed end  56  of the tendon  12  and towards the longitudinal section  58  of the tendon  12  to be treated. 
     The adapter  50  has a nose  64  located at the free end of the adapter  50 . The nose  64  has a contact surface  68  which is spaced apart from the longitudinal axis  16  of the shaft  15  about half of the diameter of the tendon  12 , so that the longitudinal section  58  of the tendon  12  that abuts the contact surface  68  comes at rest essentially coaxial to the longitudinal axis  16  of the shaft  15 . The apparatus  10   b  is fixed to the tendon  12  by means of a fastener, such as a suture  70 , in the proximity of the fixed end  56  of the tendon  12 . For this purpose, the suture  70  is lead around the tendon  12  and fixed in two notches  72  which are located on opposite lateral sides of the adapter  50 . The adapter  50  is fixable to the sleeve  44  by means of two fasteners, such as screws. 
       FIG. 10  illustrates another embodiment of an apparatus  10   c  which differs from the embodiment of  FIG. 8 , as described below. More specifically, the apparatus  10   c  has an adapter  50   a  which comprises an extension arm  60   a  which protrudes distally from the sleeve  44  and which extends along the longitudinal axis  16  of the shaft  15 . The adapter  50   a  comprises two pins  78  that are spaced apart from each other in a direction along the longitudinal axis  16  of the shaft  15 . The pins  78  are differently spaced apart from the longitudinal axis  16  in a direction orthogonal to the longitudinal axis  16  of the shaft  15 . The pins  78  can be positioned on opposite sides of the tendon  12  and the shaft  15  including the extension arm  60   a  can be twisted in such a way that the longitudinal section  58  of the tendon  12  comes at rest essentially coaxial to the longitudinal axis  16  of the shaft  15 . Thereby, a section  54  of the tendon  12  which is located between the fixed end  56  of the tendon  12  and the longitudinal section  58  of the tendon  12  to be shifted is positioned between the two pins  78  and bent in a S-shaped form. 
     In use, the tendon  12  is bent on a section  54  adjacent to one of the fixed ends  56  of the tendon  12  in such a way that a longitudinal section  58  of the tendon  12  is shifted with respect to the fixed end  56  of the tendon  12 . This longitudinal section  58  of the tendon  12  then extends in a direction which is offset from the natural direction of the tendon  12  and offset from the fixed end  56  of the tendon  12 . Thereby, a section  54  of the tendon  12  which is located between the fixed end  56  of the tendon  12  and the longitudinal section  58  of the tendon  12  to be shifted is bent into an S-shaped form. The tendon  12  can be bent either by using tweezers or by using an embodiment of the apparatus  10   a  or  10   b  of  FIGS. 8 and 10 . 
     By using the embodiment of the apparatus  10   a  of  FIG. 8 , the tendon  12  can be fixed to the adapter  50  with a suture  70 . A strand of the suture  70  which is fixed to the adapter  50  is led around the tendon  12  and can be clamped to the adapter  50  near the sleeve  44 . The clamping of the suture  70  can be realized with a notch  72  located in the extension arm  60  of the adapter  50  into which the suture  70  is wedged. 
     By using the embodiment of the apparatus  10   b  of  FIG. 10 , the adapter  50   a  including pins  78  mounted on the extension arm  60  can be chosen of the size of the tendon  12 . From a set of pins  78  with different diameters, two pins  78  can be selected to adapt the adapter  50   a  to the respective tendon  12 . A section  54  of the tendon  12  which is located between the fixed end  56  of the tendon  12  and the longitudinal section  58  of the tendon  12  to be shifted is positioned between the two pins  78  and bent in an S-shaped form by twisting the apparatus  10  about an axis transverse to the longitudinal axis  16  of the shaft  15 . 
     In a second step, a K-wire  32  is inserted into the shifted longitudinal section  58  of the tendon  12  in a direction essentially coaxial with the central axis of the shifted longitudinal section  58  of the tendon  12 . 
     In a third step, the shaft  15  of the apparatus  10  is slid over the K-wire  32  into the human body until the blade  13  contacts the longitudinal section  58  of the tendon  12 . 
     After the apparatus  10  has been correctly positioned, the shaft  15  is rotated about its longitudinal axis  16  and simultaneously axially advanced through the shifted longitudinal section  58  of the tendon  12  in a helical path to thereby make a helical cut into the tendon  12  by means of the cutting edge  24 . By holding the sleeve  44  in a fixed position relative to the tendon  12  and turning the shaft  15  clockwise, the blade  13  moves towards the tendon  12 . As a result of the number of turns and the cutting angle α with its corresponding pitch, the length of the helix can be defined. After having achieved the desired length of the helix, the blade  13  can be reversed without injuring the tissue because the back side of the blade  13  is blunt. 
     Referring now to  FIGS. 11-13 , another embodiment of a cutting guide  100  is illustrated. The cutting guide  100  is to be used in combination with a blade, such as a blade  102  ( FIG. 13 ), for making a helical cut along a portion of a tendon. The cutting guide  100  includes a helical body  104 . The helical body  104  has a first end  106 , a second end  108 , an interior side  110 , and an exterior side  112 . 
     The helical body  104  has a blade receiving slot  114  extending through the helical body  104  from the exterior side  112  to the interior side  110 . The blade receiving slot  114  is dimensioned to slidably receive a blade, such as the blade  102 . Further, the blade receiving slot  114  illustrated in  FIG. 11  has a closed first end  116  and a closed second end  118 , but it will be appreciated that one of the ends of the blade receiving slot  114  may be open. 
     To facilitate positioning the helical body  104  about a tendon, the first end  106  and the second end  108  of the helical body  104  are open in such a way that the helical body  104  may be rotated about a segment of a tendon to position the helical body  104  about the tendon as shown in  FIG. 12 . It will be appreciated by those of ordinary skill in the art that the helical body  104  may be formed from any suitable material, such as metal or plastic, and may be made using conventional methods, such as injection molding, laser melting, casting, machining, molding, and combinations thereof, for example. It will also be appreciated that the helical body  104  may be constructed in a variety of lengths and widths and with a variety of helix angles. 
     In use, the helical body  104  is positioned about a selected section of a tendon  12  by rotating the helical body  104  about the tendon. A surgeon then utilizes a cutting blade, such as the cutting blade  102 , and the cutting guide  100  to make a helical cut in the tendon. The cutting blade  102  may be provided with a stop member  122  that contacts the exterior side  112  of the helical body  104  to limit the depth which the cutting blade  102  can penetrate into the tendon  12 . It will be appreciated by those of ordinary skill in the art the limit to depth can be any depth suitable to achieve a desired tendon elongation. A preferred limit to the depth may be, limiting the cutting to the center of the tendon. Once the desired cut in the tendon  12  has been made, the helical body  104  may be removed from the tendon  12 . 
       FIGS. 14-16  illustrate another embodiment of a cutting guide  150 . The cutting guide  150  is to be used in combination with a blade, such as a blade  102  ( FIG. 16 ), for making a helical cut along a portion of a tendon. The cutting guide  150  includes a helical body  152 . The helical body  152  has a first end  156 , a second end  158 , an interior side  160 , and an exterior side  162 . 
     To facilitate positioning the helical body  152  about a tendon, the first end  156  and the second end  158  of the helical body  152  are open in such a way that the helical body  152  may be rotated about a segment of a tendon to position the helical body  152  about the tendon as shown in  FIG. 15 . It will be appreciated by those of ordinary skill in the art that the helical body  152  may be formed from any suitable material, such as metal or plastic, and may be made using conventional methods, such as injection molding, laser melting, casting, machining, molding, and combinations thereof, for example. It will also be appreciated that the helical body  152  may be constructed in a variety of lengths and widths. 
     In use, the cutting guide  150  is used in a manner similar to the cutting guide  100  described above, except a surgeon moves the cutting blade  102  along one side of the helical body  152  until the desired but has been made. The cutting blade  102  may again include the stop member  122  that contacts exterior side  162  of the helical body  152  to limit the depth which the cutting blade  102  penetrates the tendon. 
     From the above description, it is clear that the inventive concepts disclosed and claimed herein are well adapted to carry out the objects and to attain the advantages mentioned herein, as well as those inherent in the invention. While exemplary embodiments of the inventive concepts have been described for purposes of this disclosure, it will be understood that numerous changes may be made which will readily suggest themselves to those skilled in the art and which are accomplished within the spirit of the inventive concepts disclosed and/or as defined in the appended claims.