Abstract:
A method of performing a tibial tubercle osteotomy includes cutting a bone portion of a tibial tubercle from a remaining portion of the tibial tubercle, at least a portion of a patella ligament being attached to the bone portion. The bone portion of the tibial tubercle is separated from the remaining portion of the tibial tubercle such that the patella ligament remains attached to the bone portion. After completing a surgical procedure, the separated bone portion of the tibial tubercle is reattached to the remaining portion of the tibial tubercle.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a divisional of U.S. patent application Ser. No. 10/360,250, filed Feb. 6, 2003, which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. The Field of the Invention  
         [0003]     The present invention relates to methods and corresponding instruments for gaining surgical access to the knee cavity by performing a tibial tubercle osteotomy as part of a minimally invasive total or partial knee arthroplasty or other knee related surgery.  
         [0004]     2. Related Technology  
         [0005]     As a result of accident, deterioration, or other causes, it is often necessary to surgically replace all or portions of a knee joint. Joint replacement is referred to as arthroplasty. Conventional total knee arthroplasty requires a relatively long incision that typically extends longitudinally along the lateral side of the leg spanning across the knee joint. To allow the use of conventional techniques, instruments, and implants, the incision typically extends proximal of the knee and into the muscular tissue. In general, the longer the incision and the more muscular tissue that is cut, the longer it takes for the patient to recover and the greater the potential for infection.  
         [0006]     Accordingly, what is needed are minimally invasive procedures and corresponding apparatus for accessing the knee joint to perform total or partial knee arthroplasty.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     Various embodiments of the present invention will now be discussed with reference to the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope.  
         [0008]      FIG. 1  is an elevated front view of a leg in a bent position;  
         [0009]      FIG. 2  is a elevated front view of a tibia of the leg shown in  FIG. 1  with a portion of the tibial tuberosity removed;  
         [0010]      FIG. 3  is an elevated side view of the tibia shown in  FIG. 2 ;  
         [0011]      FIG. 4  is a perspective view of a die cutter;  
         [0012]      FIG. 5  is a perspective view of the arm assembly of the die cutter shown in  FIG. 4 ;  
         [0013]      FIG. 6  is an elevated front view of a guide;  
         [0014]      FIG. 7  is a perspective view of the guide shown in  FIG. 6 ; and  
         [0015]      FIG. 8  is a top plan view of the guide shown in  FIG. 6 .  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]     The present invention relates to methods and corresponding instruments for performing a tibial tubercle osteotomy to gain access to the knee cavity as part of a minimally invasive total or partial knee arthroplasty or other knee related surgery. By way of example and not by limitation, depicted in  FIG. 1  is a knee  10  having an anterior side  12 . Knee  10  is flexed to about 90 degrees. A transverse incision  14 , approximately 10 cm long, is made mediolaterally through the skin layer across the midline of knee  10  proximal of the tibial tuberosity. As depicted in  FIG. 2 , the tissue is retracted exposing in part a patellar ligament  18  and a tibial tuberosity  20  of a tibia  22 . A portion of tibial tuberosity  20  connected to patellar ligament  18  is now elevated such that patellar ligament  18  remains connected thereto.  
         [0017]     Specifically,  FIG. 2  shows a lateral view of the proximal end of tibia  22 . A distal portion  30  of tibial tuberosity  20  has been elevated while a proximal portion  32  of tibial tuberosity  20  remains integral with tibia  22 . Patellar ligament  18  is excised from proximal portion  30  of tibial tuberosity  20  so that the distal end of patellar ligament  18  can be freely elevated in connection with distal portion  30  of tibial tuberosity  20 . In one embodiment, distal portion  30  of tibial tuberosity  20  is sized such that between about ⅓ to about ½ of the central mediolateral width of patella ligament  18  and tibial tuberosity  20  is osteotimized from the proximal end of tibia  22 . Thus about ⅓ to about ½ of the distal contact surface of patellar ligament  18  remains connected to distal portion  30  of tibial tuberosity  20 .  
         [0018]     Tibia  22  has an anterior cut surface  34 . With reference to the lateral side view of tibia  22  depicted in  FIG. 2 , cut surface  34  includes a proximally arched undercut portion  36  formed on the distal end of proximal portion  32  of tibial tuberosity  20 . As a result of cut surface  34 , proximal portion  32  of tibial tuberosity  20  terminates at a distally projecting anterior ridge  42 .  
         [0019]     Cut surface  34  also includes a distally sloping portion  38  extending from undercut portion  36  to an anterior border  40  of tibia  22 . Cut surface  34  partially bounds a pocket  35  and has a transverse configuration taken along a plane extending proximal to distal that is similar to a vertically bisected heart design as depicted on conventional playing cards. In contrast to forming a smooth bisected heart shape design, cut surface  34  can also form a sharp or slightly rounded inside angle that is typically 90° or less.  
         [0020]     As depicted in  FIG. 3 , cut surface  34  also has a substantially wedged shaped transverse configuration taken along a plane extending anterior to posterior. Specifically, cut surface  34  comprises a lateral side  24  and an opposing medial side  26  that each slope inwardly so as to intersect at a vertical midline  28 . In one embodiment, the inside angle θ between lateral side  24  and medial side  26  is in a range between about 60° to about 120° with about 80° to about 100° being more preferred. In alternative embodiments, cut surface  34  can be substantially flat extending mediolaterally or can form a rounded groove.  
         [0021]     Elevated distal portion  30  of tibial tuberosity  20  has a cut surface  46  that is complementary to cut surface  34 . As will be discussed below in greater detail, one of the benefits of the configuration of cut surfaces  34  and  46  is that once the procedure is complete, distal portion  30  of tibial tuberosity  20  is easily reinserted within pocket  35 . The complementary mating with undercut surface  36  helps lock distal portion  30  within pocket  35  as distal potion  30  is pulled proximal by patellar ligament  18 .  
         [0022]     Distal portion  30  of tibial tuberosity  20  can be elevated using a number of different techniques. By way of example and not by limitation, depicted in  FIG. 4  is one embodiment of a die cutter  50  incorporating features of the present invention. Die cutter  50  comprises a housing  52  having a substantially box shaped configuration. Housing  52  has a front face  56  and an opposing back face  57  with side faces  58  and  60  extending therebetween. A top face  54  and an opposing bottom face  55  also extend between faces  56  and  57 . Housing  52  bounds a chamber  62 . Chamber  62  communicates with the exterior through an elongated slot  64  formed on front face  52  and an opening  66  formed on each side face  58  and  60 .  
         [0023]     A handle  68  outwardly projects from top face  54  of housing  52 . A threaded alignment bolt  69  passes through handle  68  and a portion of housing  52  so as to centrally project beyond front face  56  of housing  52 . Alignment bolt  69  threadedly engages with handle  68  and/or housing  52  such that selective rotation of alignment bolt  69  facilitates selective positioning of alignment bolt  69  beyond front face  56  of housing  52 .  
         [0024]     Partially disposed within chamber  62  of housing  52  are a pair of translating arms  70  and  72 . As depicted in  FIG. 5 , each translating arm  70  and  72  has a distal end  74  and an opposing proximal end  76 . In one embodiment of the present invention, means are provided for selectively advancing at least one of the first and second translating arms  70 ,  72  toward the other. By way of example and not by limitation, a shaft  78  has threads formed along each end thereof with the threads being oriented in opposing directions. Each translating arm  70  and  72  is threaded onto a corresponding end of shaft  78 . Accordingly, selective rotation of shaft  78  causes translating arms  70 ,  72  to either move together or move apart. A socket  83  is formed on each end face of shaft  78 . Shaft  78  is selectively rotated by inserting a tool, such as a drill bit, through one of openings  66  ( FIG. 4 ) of housing  52  and into socket  83  of shaft  78 . Rotation of the tool thus facilitates rotation of shaft  78 .  
         [0025]     In alternative embodiments for the means for selectively advancing, it is appreciated that shaft  78  can be replaced with a variety of other conventional threaded shaft or bolt mechanisms. Furthermore, shaft  78  can be replaced with elongated levered handles or other conventional apparatus that facilitate manual movement of translating arms  70  and  72 . In yet other embodiments, it is appreciated that hydraulic, pneumatic, or electrical mechanisms can be used for movement of translating arms  70  and  72 .  
         [0026]     A plurality of spaced apart rails  79  outwardly project from each side of each translating arm  70 ,  72 . Rails  79  mesh with complementary rails  92  formed on the interior of housing  52 . The meshing of rails  79  and  92  helps to ensure that translating arms  70 ,  72  are maintained in alignment during movement. Proper alignment of translating arms  70 ,  72  is further maintained by a pin  75  slidably extending through each of translating arms  70 ,  72 .  
         [0027]     Returning to  FIG. 4 , distal end  74  of each translating arm  70 ,  72  extends outside of chamber  62  through slot  64 . Mounted at distal end  74  of each translating arm  70  and  72  is an outwardly sloping head plate  80 . Each head plate  80  has an interior face  81  with an undercut engagement slot  82  formed thereon. Each interior face  81  is disposed in a corresponding plane. The planes intersect so as to form an inside angle that is substantially equal to the angle θ formed on cut surface  34 . Slidably disposed within each slot  82  is a die  84 . Each die  84  has a base  86  that is connected with a corresponding head plate  80  by being slidably engaged within slot  82 . As a result, dies  84  can be easily replaced with new dies or with dies having an alternative configuration.  
         [0028]     A blade  88  outwardly projects from each base  86  so as to extend orthogonally from interior face  81  of the corresponding head plate  80 . Each blade  88  terminates at a free sharpened edge  90 . Each blade  88  and corresponding sharpened edge  90  has a profile that is the same configuration as the profile of cut surface  34  of tibial tuberosity  20  previously discussed. Blades  88  are disposed so as to opposingly face at an intersecting angle. Accordingly, as shaft  78  is selectively rotated, translating arms  70 ,  72  move together causing sharpened edges  90  to mate together.  
         [0029]     During use, once tibial tuberosity  20  is exposed as discussed above, die cutter  50  is positioned such that dies  84  are positioned on the lateral and medial side of tibial tuberosity  20 . The free end of bolt  69  rests against the anterior surface of tibial tuberosity  20  and helps to facilitate proper positioning of dies  84 . In this regard, bolt  69  functions as a spacer. In alternative embodiments, bolt  69  can be replace with a variety of other mechanism that permit selective spacing adjustment. For example, a rod and clamp configuration can be used.  
         [0030]     Once die cutter  50  is appropriately positioned, shaft  78  is selectively rotated, such as by the use of a drill, so that translating arm  70  and  72  are advanced together. In so doing, the dies  84  penetrate laterally and medially into tibial tuberosity  20 . Dies  84  continue to advanced until distal portion  30  of tibial tuberosity  20  is separated from proximal portion  32  thereof.  
         [0031]     One of the benefits of using this process is that dies  84  produce very clean cut surfaces  34  and  46  with minimal bone loss. As a result, once the subsequent surgical procedure is completed, distal portion  30  can be fit back into pocket  35  with a close tolerance fit. It is appreciated that a variety of alternative configurations of die cutters can be used for selective die cutting of tibial tuberosity  20 .  
         [0032]     In contrast to die cutting tibial tuberosity  20 , distal portion  30  of tibial tuberosity  20  can also be elevated using a saw blade. For example, depicted in  FIGS. 6-8  is a guide  100 . Guide  100  comprises a central plate  102  having a front face  104  and an opposing back face  106 . Each of faces  104  and  106  extend between opposing sides  108  and  110 . Extending between front face  104  and back face  106  are a plurality of passageways  112 .  
         [0033]     Formed on sides  108  and  110  of central plate  102  is a first side housing  114  and a second side housing  116 , respectively. Each side housing  114  and  116  is formed so as to project beyond front face  104  of central plate  102 . Each of side housings  114  and  116  has an inside face  118  and an opposing outside face  120 . A cavity  122  extends through each of side housings  114  and  116  between faces  118  and  120 . Removably disposed within cavity  122  of side housing  114  is a first template  124 . A second template  126  is disposed within cavity  122  of side housing  116 . Each template  124  and  126  has a substantially box-shaped configuration which includes an inside face  128  and an opposing outside face  130 . Inside face  128  of templates  124  and  126  are each disposed in a corresponding plane. The planes intersect so as to form an inside angle that is substantially equal to the angle θ formed on cut surface  34 .  
         [0034]     A guide slot  132  extends through each of templates  124  and  126  between inside face  128  and outside face  130 . Each guide slot  132  has a configuration complementary to the profile of cut surface  34  and extends through templates  124  and  126  at an orientation perpendicular to inside face  128 .  
         [0035]     During use, once tibial tuberosity  20  is exposed, front face  104  of central plate  102  is biased against the anterior side of tibial tuberosity  20  such that templates  124  and  126  are disposed on the lateral and medial side thereof. Guide slots  132  are aligned with distal portion  30  of tibial tuberosity  20  to be elevated. Once guide  100  is appropriately positioned, fasteners, such as screws, nails, or the like, are passed through passageways  112  and into tibia  22  so as to securely retain guide  100  to tibia  22 . It is noted that passageways  112  are sloped such that the fasteners extending therethrough extend into portions of tibia  22  outside of distal portion  30  which is to be elevated.  
         [0036]     Once guide  100  is positioned in place, a saw blade  140  is passed through guide slot  132  of template  124  from outside face  130  to inside face  128 . Saw blade  140  is moved in a reciprocating manner so as to penetrate half way into tibial tuberosity  20 . Once the reciprocating saw blade  140  has completed passage along guide slot  132 , saw blade  140  is moved over to template  126  and passed through the guide slot  132  thereof. The process is then repeated. Once both cuttings are performed, distal portion  30  of tibial tuberosity  20  is freely removable from the remainder of tibia  22 . The fasteners are then removed along with guide  100 . As with die cutters  50 , it is appreciated that guide  100  can come in a variety of alternative configurations.  
         [0037]     As previously mentioned, once distal portion  30  of tibial tuberosity  20  is elevated, patellar ligament  18  is retracted proximally, thereby exposing the knee joint. Once the knee joint is exposed, any number of knee related surgical procedures, such as total or partial knee arthroplasty, can be performed. Referring back to  FIG. 2 , upon completion of the surgical procedure, patellar ligament  18  is secured back in place by inserting distal portion  30  of tibial tuberosity  20  back into pocket  35 . As a result of undercut portion  36 , distal portion  30  of tibial tuberosity  20  is self-locking within pocket  35 . If desired, however, various types of conventional bone anchors can be used to further secure distal portion  30  of tibial tuberosity  20  within pocket  35 .  
         [0038]     The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.