Abstract:
An interlocking intramedullary rod assembly for treating a fracture of a bone, said interlocking intramedullary rod assembly comprising:
       an intramedullary rod comprising a distal section and a proximal section;   a distal interlocking screw; and   a proximal interlocking screw;   wherein said distal section of said intramedullary rod comprises a static distal seat for receiving said distal interlocking screw, and said proximal section of said intramedullary rod comprises a dynamic proximal seat for receiving said proximal interlocking screw;   and further wherein said static distal seat is configured to secure said distal interlocking screw to said intramedullary rod such that said distal interlocking screw cannot move relative to said intramedullary rod, and said dynamic proximal seat is configured to secure said proximal interlocking screw to said interlocking rod such that a first end of said proximal interlocking screw cannot move relative to said intramedullary rod and the second end of said proximal interlocking screw can move relative to said intramedullary rod.

Description:
REFERENCE TO PENDING PRIOR PATENT APPLICATION 
       [0001]    This patent application claims benefit of pending prior U.S. Provisional Patent Application Ser. No. 61/958,281, filed Jul. 24, 2013 by Sreevathsa Boraiah for TENSION BAND NAIL: FOR PROXIMAL FRACTURES INCLUDING UNSTABLE HIP FRACTURES (Attorney&#39;s Docket No. VATHSA-1 PROV), which patent application is hereby incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to an interlocking intramedullary rod assembly for treatment of fractures of a long bone, and more particularly to an interlocking intramedullary rod assembly for treating proximal femoral fractures including unstable hip fractures. The interlocking intramedullary rod assembly can also be utilized in other applications in the body where the biomechanical principals of tension banding apply. The interlocking intramedullary rod assembly can also be used in situations where a fracture is to be at least partially reduced after introduction of the intramedullary rod, with fracture reduction being effected either by the surgeon or as a result of weight bearing. Even more particularly, the present invention relates to a load-bearing interlocking intramedullary rod assembly which comprises an intramedullary rod which is inserted into the intramedullary canal of a fractured proximal femur for treatment of a proximal femur fracture. 
       BACKGROUND OF THE INVENTION 
       [0003]    Hip fractures present significant healthcare issues. These healthcare issues includes mortality, morbidity and increased healthcare costs. Improvements to the rate of reliable healing would significantly benefit patient health and reduce healthcare costs. 
         [0004]    Proximal fractures of the femur are traditionally treated with either (i) an intramedullary rod (sometimes referred to as an intramedullary nail) which is positioned in the intramedullary canal of the femur, or (ii) a plate applied to the side of the femur and fixed in place with one or more screws set into the femur. The choice of using an intramedullary rod or a plate and screw is generally based on the location and complexity of the fracture. 
         [0005]    As noted above, the intramedullary rod is placed in the intramedullary canal of the femur and typically provides excellent mechanical stability for the bone. Among other things, the intramedullary rod exhibits good weight-sharing properties. However, the use of an intramedullary rod also involves a more complex surgical procedure and higher cost. 
         [0006]    Plates such as the Dynamic Hip Screw (DHS) plate are generally simpler to deploy and less expensive than intramedullary rods. Plates generally work well for stable intertrochanteric fractures. However, in subtrochanteric fractures and unstable intertrochanteric fractures, it is difficult to achieve proper compression of the fracture site with plates upon the application of weight. Therefore, most subtrochanteric fractures and unstable intertrochanteric fractures are treated with intramedullary rods. 
         [0007]    When the treatment of subtrochanteric fractures and unstable intertrochanteric fractures by intramedullary rods is unsuccessful, the fractures are typically treated with tension band plates (such as a tension band blade plate) which utilize the geometry of the femoral subtrochanteric region and the compressive forces imposed by the surrounding musculature. A tension band construct, by definition, utilizes tensile forces and converts them into compressive forces. At an advanced level, when a tension band blade plate is applied to the tension side of the femur and pressure is thereafter applied, the tension band blade plate converts the tension forces into compressive forces which can be used to stabilize the fracture. Tension band blade plates are known to be effective in treating proximal femoral fractures. However, installation of these tension band blade plates requires substantial technical skill and involves a more complex operation. Therefore, the use of tension band blade plates is generally not suited for index surgery (i.e., the first surgery performed after the occurrence of a fracture), and is best suited for revising failed fracture repairs. 
         [0008]    It is believed that a device that can combine the mechanical advantages of intramedullary rods with the mechanical advantages of tension band blade plates would be extremely useful for treating all kinds of proximal femoral fractures, including not only the aforementioned subtrochanteric fractures and unstable intertrochanteric fractures, but also including stable intertrochanteric fractures and other types of proximal femoral fractures. Such a device would also be extremely useful for treating fractures of other bones in the body. For the sake of clarity, even though the present invention may be used for all hip fractures (including stable and unstable intertrochanteric fractures, subtrochanteric fractures, and other types of proximal femoral fractures), and even though the present invention may be used for fractures of other bones in the body, the following discussion of the present invention will focus on subtrochanteric fractures and unstable intertrochanteric fractures. 
         [0009]    Intramedullary rods have evolved over time. The first generation of intramedullary rods essentially involved inserting a solid rod down the intramedullary canal of the femur. This type of intramedullary rod is relatively primitive and only grossly aligns the bone. The first generation of intramedullary rods does not control motion at the fracture line in any specific plane. 
         [0010]    The second generation of intramedullary rods was the dynamic interlocking intramedullary rod. The dynamic interlocking intramedullary rod allows for compression of the bone at the fracture site by allowing axial compression of the fracture. This axial compression of the fracture is achieved through the use of lag screws which pass through the bone, across the intramedullary rod and back into the bone. However, existing lag screw constructs do not control the coronal plane motion of the unstable and subtrochanteric fractures. Studies have shown that the dynamic interlocking intramedullary rod has not been as effective as desired. More particularly, for the repair of subtrochanteric fractures and fractures of the femoral neck or femoral head using a dynamic interlocking intramedullary rod, the intramedullary rod is driven into the femur from the proximal end and a femoral neck pin is introduced into the femoral head via the femoral neck of the femur, with the femoral neck pin passing through a bore formed in the intramedullary rod at an oblique angle to the axis of the intramedullary rod. The dynamic interlocking intramedullary rod, when placed under a load, is subjected to a combined stress which is composed of compressive and tensile stresses and shear loads. In the case of delayed healing and overload, a crack or fissure may develop in the bone, namely at the site at which the highest shear stress occurs. Current dynamic interlocking intramedullary rods do not provide any kind of unique biomechanical advantage for fracture healing in unstable intertrochanteric and subtrochanteric fractures except acting as an intramedullary buttress. The dynamic interlocking intramedullary rod does not offer any anatomic site-specific advantage for healing of the fracture. 
         [0011]    The present invention addresses this biomechanical problem by reducing the shear loads on the intramedullary rod and provides a more stable biomechanical environment for a more accelerated and reliable healing of the fracture. 
       SUMMARY OF THE INVENTION 
       [0012]    It is an object of the present invention to provide a novel interlocking intramedullary rod assembly for the treatment of a proximal femur fracture whereby the interlocking intramedullary rod assembly exhibits load bearing properties and creates a biomechanically-conducive environment for reliable fracture healing. 
         [0013]    In one form of the present invention, the new interlocking intramedullary rod assembly comprises an intramedullary rod that is positioned in the intramedullary canal of the femur, a distal interlocking screw that locks the distal part of the intramedullary rod to the distal femur, and a proximal interlocking screw which secures the intramedullary rod to the proximal femur in a new and unique manner. More particularly, the intramedullary rod is placed in the intramedullary canal of the femur antegrade (i.e., distally from the proximal trochanter). The intramedullary rod has an approximately 12 degree bend at its proximal end to accommodate the natural geometry of the proximal femur. After the intramedullary rod has been placed in the intramedullary canal of the femur, the proximal interlocking screw is deployed. The proximal interlocking screw is a lag screw and is advanced from the lateral aspect of the femur through a dynamic proximal seat formed in the intramedullary rod and then into the femoral head. This dynamic proximal seat extends lateral-to-medial, and has a circular configuration on its medial end and a slot configuration on its lateral end. The dynamic proximal seat is referred to as a “dynamic” seat inasmuch as this seat allows for selected motion of the proximal interlocking screw relative to the intramedullary rod. The proximal interlocking screw is placed at an angle of approximately 124-127 degrees to the longitudinal axis of the intramedullary rod, based on the patient&#39;s anatomy. The angle between the intramedullary rod and the proximal interlocking screw is pre-selected by the surgeon after templating pre-operative radiographs. Note that this is a fixed angle for any given intramedullary rod and proximal interlocking screw combination. Therefore, the surgeon will select the appropriate intramedullary rod and proximal interlocking screw combination from inventory. After the proximal interlocking screw is deployed in the dynamic proximal seat, the distal interlocking screw is deployed in the distal part of the intramedullary rod. The distal interlocking screw is placed from the lateral side of the femur through a static distal seat in the intramedullary rod and into the medial side of the femur. The static distal seat in the distal part of the intramedullary rod extends lateral-to-distal and comprises a circular opening on its medial end and a circular opening on its lateral end. The static distal seat is referred to as a “static” seat inasmuch as this seat does not allow for motion of the distal interlocking screw relative to the intramedullary rod. 
         [0014]    In accordance with the present invention, after the proximal interlocking screw is inserted into the dynamic proximal seat at an angle of between approximately 124-127 degrees to the longitudinal axis of the intramedullary rod, the surgeon may choose to further change the angle at which the proximal interlocking screw extends through the dynamic proximal seat (e.g., up to approximately 138 degrees) depending on the patient&#39;s anatomy, fracture configuration and the opposition of fracture fragments. Also, upon the application of weight (i.e., when the patient stands), the proximal interlocking screw shifts position within the dynamic proximal seat in order to allow a partial reduction of the fracture, e.g., within the given range of approximately 124-138 degrees. Angular locking means are provided for locking the proximal interlocking screw relative to the intramedullary rod. The proximal interlocking screw can be locked to the intramedullary rod at various stages of the procedure, e.g., (i) when the surgeon deems that the angle subtended at the insertion is good, or (ii) after the surgeon increases the valgus angle (if the surgeon deems that the option needs to exist to further increase the valgus angle after weight bearing, then the angular locking means are left open), or (iii) upon weight bearing, the fracture settles into its desired valgus, whereupon the proximal interlocking screw can be locked to the intramedullary rod. 
         [0015]    In one preferred form of the invention, there is provided an interlocking intramedullary rod assembly for treating a fracture of a bone, said interlocking intramedullary rod assembly comprising: 
         [0016]    an intramedullary rod comprising a distal section and a proximal section; 
         [0017]    a distal interlocking screw; and 
         [0018]    a proximal interlocking screw; 
         [0019]    wherein said distal section of said intramedullary rod comprises a static distal seat for receiving said distal interlocking screw, and said proximal section of said intramedullary rod comprises a dynamic proximal seat for receiving said proximal interlocking screw; 
         [0020]    and further wherein said static distal seat is configured to secure said distal interlocking screw to said intramedullary rod such that said distal interlocking screw cannot move relative to said intramedullary rod, and said dynamic proximal seat is configured to secure said proximal interlocking screw to said interlocking rod such that a first end of said proximal interlocking screw cannot move relative to said intramedullary rod and the second end of said proximal interlocking screw can move relative to said intramedullary rod. 
         [0021]    In another preferred form of the invention, there is provided a method for treating a fracture in the proximal femur, said method comprising: 
         [0022]    providing an interlocking intramedullary rod assembly comprising:
       an intramedullary rod comprising a distal section and a proximal section;   a distal interlocking screw; and   a proximal interlocking screw;   wherein said distal section of said intramedullary rod comprises a static distal seat for receiving said distal interlocking screw, and said proximal section of said intramedullary rod comprises a dynamic proximal seat for receiving said proximal interlocking screw;   and further wherein said static distal seat is configured to secure said distal interlocking screw to said intramedullary rod such that said distal interlocking screw cannot move relative to said intramedullary rod, and said dynamic proximal seat is configured to secure said proximal interlocking screw to said interlocking rod such that a first end of said proximal interlocking screw cannot move relative to said intramedullary rod and the second end of said proximal interlocking screw can move relative to said intramedullary rod;       
 
         [0028]    positioning said intramedullary rod in the intramedullary canal of the femur so that said distal section of said intramedullary rod resides within the shaft of the femur and said proximal section of said intramedullary rod resides within a proximal portion of the femur; 
         [0029]    inserting said proximal interlocking screw through the proximal portion of the femur, through said dynamic proximal seat and into the proximal portion of the femur, and inserting said distal interlocking screw through the shaft of the femur, through said static distal seat and into the shaft of the femur; and 
         [0030]    adjusting the disposition of said proximal interlocking screw within said dynamic proximal seat so as to at least partially reduce the fracture. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]    These and other objects and features of the present invention will be more fully disclosed or rendered obvious by the following detailed description of the preferred embodiments of the invention, which is to be considered together with the accompanying drawings wherein like numbers refer to like parts, and further wherein: 
           [0032]      FIG. 1  is a schematic view showing a novel interlocking intramedullary rod assembly formed in accordance with the present invention, with the novel interlocking intramedullary rod assembly being disposed in a fractured femur, and with the interlocking intramedullary rod assembly and the fractured femur being shown prior to partial reduction of the fracture; 
           [0033]      FIG. 2  is a schematic view showing the intramedullary rod of the novel interlocking intramedullary rod assembly of  FIG. 1 ; 
           [0034]      FIG. 3  is a schematic view showing the distal interlocking screw of the novel interlocking intramedullary rod assembly of  FIG. 1 ; 
           [0035]      FIG. 4  is a schematic view showing the proximal interlocking screw of the novel interlocking intramedullary rod assembly of  FIG. 1 ; 
           [0036]      FIG. 5  is a schematic view showing the locking finger which comprises an exemplary embodiment of the angular locking means of the novel interlocking intramedullary rod assembly of  FIG. 1 ; and 
           [0037]      FIG. 6  is a schematic view like that of  FIG. 1 , except showing the interlocking intramedullary rod assembly and the fractured femur after partial reduction of the fracture. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0038]    The present invention comprises the provision and use of a novel interlocking intramedullary rod assembly for treating proximal femoral fractures and other fractures in the body. 
         [0039]    Looking first at  FIG. 1 , there is shown a novel interlocking intramedullary rod assembly  5  formed in accordance with the present invention. Novel interlocking intramedullary rod assembly  5  generally comprises an intramedullary rod  10 , a distal interlocking screw  15 , a proximal interlocking screw  20  and a locking finger  25  mounted to intramedullary rod  10  for selectively engaging proximal interlocking screw  20  as will hereinafter be discussed. 
       Intramedullary Rod 
       [0040]    Looking now at  FIGS. 1 and 2 , intramedullary rod  10  generally comprises a shaft  30  having a distal section  35  terminating in a distal end  40  and a proximal section  45  terminating in a proximal end  50 . Distal section  35  and proximal section  45  are formed integral with one another. The longitudinal axis  55  of proximal section  45  is offset from the longitudinal axis  60  of distal section  35  (e.g., at an approximately 12 degree angle). The length and diameters of distal section  35  and proximal section  45 , and the degree of offset of the longitudinal axis  55  of proximal section  45  from the longitudinal axis  60  of distal section  35 , are dependent on the size of the bone receiving intramedullary rod  10 , such that intramedullary rod  10  may be deployed in an antegrade fashion down the intramedullary canal of the femur of a patient, with distal section  35  being disposed in the shaft of the femur and proximal section  45  being disposed in the proximal femur (e.g., in the trochanteric area). In one preferred form of the invention, proximal section  45  has a larger diameter than distal section  35 . And in one preferred form of the invention, distal section  35  and proximal section  45  are both tapered, and their respective tapers are coordinated so as to form a substantially smooth taper across the length of intramedullary rod  10 . 
         [0041]    Preferably intramedullary rod  10  is hollow along its length, from distal end  40  to proximal end  50 . 
         [0042]    Distal section  35  comprises a static distal seat  65  for receiving distal interlocking screw  15  as distal interlocking screw  15  passes through a lateral portion of the femur, across distal section  35  of intramedullary rod  10  and into a medial portion of the femur ( FIG. 1 ). To this end, static distal seat  65  comprises a round opening  70  on the lateral side of distal section  35  and a round opening  75  on the medial side of distal section  35 . Round openings  70  and  75  are disposed on an axis  80  which preferably extends substantially perpendicular to the longitudinal axis  60  of distal section  35 . In one preferred form of the invention, round openings  70  and  75  are of the same size, such that static distal seat  65  essentially comprises a cylindrical seat. Furthermore, round openings  70  and  75  are sized relative to distal interlocking screw  15  such that distal interlocking screw  15  will be unable to move relative to intramedullary rod  10  when distal interlocking screw  15  is disposed in static distal seat  65 . 
         [0043]    Proximal section  45  comprises a dynamic proximal seat  85  for receiving proximal interlocking screw  20  as proximal interlocking screw  20  passes through a lateral portion of the femur, across proximal section  45  of intramedullary rod  10  and into a medial portion of the femur ( FIG. 1 ). To this end, dynamic proximal seat  85  comprises a slot opening  90  on the lateral side of proximal section  45  and a round opening  95  on the medial side of proximal section  45 . Slot opening  90  is larger than round opening  95  in the proximal-to-distal direction, such that dynamic proximal seat  85  essentially comprises an offset frustorectangular seat. Furthermore, round opening  95  is sized relative to proximal interlocking screw  20 , and slot opening  90  is sized relative to proximal interlocking screw  20 , such that when proximal interlocking screw  20  is disposed in dynamic proximal seat  85 , proximal interlocking screw  20  will be unable to move relative to round opening  95  but will be able to move relative to slot opening  90 . The center of slot opening  90  and the center of round opening  95  are disposed on an axis  100  which is set at an angle of approximately 124-137 degrees to the longitudinal axis  55  of proximal section  45 . The locus of fixation of proximal interlocking screw  20  with intramedullary rod  10  is via the medial round opening  95  in intramedullary rod  10 . As will hereinafter be discussed, when proximal interlocking screw  20  is disposed in dynamic proximal seat  85 , proximal interlocking screw  20  will initially reside in the proximal portion of slot opening  90  on the lateral side of intramedullary rod  10 , and in round opening  95  on the medial side of the intramedullary rod. After load is applied (either by the surgeon to change the angle of proximal interlocking screw  20  with intramedullary rod  10  or when the patient weightbears), the bone will shift so that proximal interlocking screw  20  will thereafter reside in the distal portion of slot opening  90  on the lateral side of the intramedullary rod and in round opening  95  on the medial side of the intramedullary rod. 
       Distal Interlocking Screw 
       [0044]    Looking next at  FIGS. 1 and 3 , distal interlocking screw  15  is designed to be deployed in static distal seat  65  of distal section  35  of intramedullary rod  10 . To this end, distal interlocking screw  15  comprises a threaded shaft  105  terminating in a head  110 . 
       Proximal Interlocking Screw 
       [0045]    Looking next at  FIGS. 1 and 4 , proximal interlocking screw  20  is designed to be deployed in dynamic proximal seat  85  of proximal section  45  of intramedullary rod  10 . To this end, proximal interlocking screw  20  comprises a shaft  115  having threads  120  on its distal end and ratchet teeth  125  on its proximal end. 
         [0046]    If desired, proximal interlocking screw  20  may be hollow. 
       Locking Finger 
       [0047]    As noted above, angular locking means are provided for locking proximal interlocking screw  20  relative to intramedullary rod  10 , i.e., within dynamic proximal seat  85 . 
         [0048]    To this end, and looking next at  FIGS. 1 and 5 , in one preferred form of the invention, a locking finger  25  is provided for engaging proximal interlocking screw  20  when proximal interlocking screw  20  is disposed in dynamic proximal seat  85 . Locking finger  25  is mounted within proximal section  45  of intramedullary rod  10  and serves to engage proximal interlocking screw  20  as will hereinafter be discussed. Locking finger  25  allows for a specific kind of motion between proximal interlocking screw  20  and intramedullary rod  10  (and hence a specific kind of motion between the proximal end of the femur and the distal end of the femur). 
         [0049]    More particularly, locking finger  25  generally comprises a lever  130  and a spring  135 . One end  140  of lever  130  is pivotally mounted to the lateral side of intramedullary rod  10  (e.g., to the lateral side wall of proximal section  45 ) so as to allow for angular movement of lever  130  relative to intramedullary rod  10 . The free end  145  of lever  130  engages the teeth  125  on proximal interlocking screw  20  with a one-way action as will hereinafter be discussed. This one-way action is the result of lever  130  being under constant lateral pressure from spring  135 , as will also hereinafter be discussed. 
         [0050]    Spring  135  is also mounted within proximal section  45  of intramedullary rod  10 . One end  150  of spring  135  is mounted to the medial side of intramedullary rod  10  (e.g., to the medial side wall of proximal section  45 ), and the other end  155  of spring  135  is mounted to lever  135  so as to bias lever  135  laterally (i.e., counterclockwise from the angle of view of  FIG. 5 ). 
       The Mechanism of Tension Banding using Interlocking Intramedullary Rod Assembly 
       [0051]    The mechanism of tension banding using interlocking intramedullary rod assembly  5  will now be discussed. For the purposes of example but not limitation, the mechanism of tension banding using interlocking intramedullary rod assembly  5  will be discussed in the context of a subtrochanteric fracture gap model, i.e., a 1 cm fracture gap  160  ( FIG. 1 ) in the subtrochanteric area  165  of a femur  170 . 
         [0052]    First, intramedullary rod  10  is inserted into the fractured femur as shown in  FIG. 1 . 
         [0053]    Second, proximal interlocking screw  20  is inserted, lateral-to-medial, through a lateral portion  175  of the femur, across dynamic proximal seat  85  in proximal section  45  of intramedullary rod  10  and then into the medial portion  180  of femur  170 . Note that proximal interlocking screw  20  is inserted adjacent the proximal end of lateral slot opening  90  ( FIGS. 1 and 5 ) and through medial round opening  95  until the threaded distal end  120  of proximal interlocking screw  20  is secured in the femoral head. As this occurs, the advancing proximal interlocking screw  20  engages lever  130  and forces the free end  145  of lever  130  medially, against the power of spring  135 , with the free end  145  of lever  130  engaging teeth  125  formed in proximal interlocking screw  20 . Note that teeth  125  prevent lever  130  from returning laterally under the power of spring  135 . 
         [0054]    Third, distal interlocking screw  15  is inserted, lateral-to-medial, through a lateral portion of the femur, across static distal seat  65  ( FIG. 2 ) in distal section  35  and into a medial portion of the femur. Note that distal interlocking screw  15  is securely mounted to distal section  35  of intramedullary rod  10  (by virtue of the disposition of distal interlocking screw  15  in circular openings  70  and  75  of intramedullary rod  10 ) as well as to the lateral and medial portions of the femur. 
         [0055]    At this point, interlocking intramedullary rod assembly  5  and femur  170  are in the positions shown in  FIGS. 1 and 5 . 
         [0056]    Upon the application of force to the proximal end of the femur (e.g., by the surgeon during the procedure or upon the application of weight to the proximal end of the femur), the stress at the fracture site increases. Since the medial portion of dynamic proximal seat  85  is circular (i.e., round hole  95 ), the medial portion of dynamic proximal seat  85  acts as a static hole, preventing any kind of angular motion between proximal interlocking screw  20  and the medial wall of the femur. However, since the lateral portion of dynamic proximal seat  85  is a slot (i.e., slot opening  90 ), proximal interlocking screw  20  will slide inferiorly in lateral slot opening  90 . This will create an angular collapse of the fracture site ( FIG. 6 ). Significantly, as this angular collapse of the fracture site occurs, the free end  145  of lever  130  is moved counterclockwise (from the angle of view of  FIG. 6 ) by spring  135 . The free end  145  of lever  130  slides along the distally-moving teeth  125  of proximal interlocking screw  20  until, at the limit of the angular collapse, the free end of lever  130  lodges in teeth  125 . Thereafter, when surgeon-applied force or weight-applied force is no longer applied to the proximal end of the femur, lever  130  and spring  135  prevent the bone from returning to its original fracture disposition, i.e., lever  130  and spring  135  cooperate with teeth  125  on proximal interlocking screw  20  to prevent any upward movement of proximal interlocking screw  20  within slot opening  90  on the lateral side of the femur. 
         [0057]    Thus it will be seen that interlocking intramedullary rod assembly  5  creates a one-way angular collapse of the proximal fracture fragment into valgus, i.e., into an outward angulation of the distal portion of the femur. The center of rotation of the proximal fracture fragment is through of the point where proximal interlocking screw  20  engages the medial round opening  95  of intramedullary rod  10 . The valgus collapse of the fracture is accompanied by the following dynamic processes: 
         [0058]    (i) valgus collapse—the medial fracture gap is maintained, the lateral fracture gap is decreased; 
         [0059]    (ii) proximal interlocking screw  20  moves distally in slot opening  90  on the lateral side of intramedullary rod  10 ; 
         [0060]    (iii) the position of lever  130  changes with respect to teeth  125 , i.e., the disposition of lever  130  changes and engages different teeth as the result of the distal movement of the lateral end of proximal interlocking screw  20 ; and (iv) intramedullary rod  10  is medialized in the intramedullary canal of the femur. 
         [0061]    Thus it will be seen that novel interlocking intramedullary rod assembly  5  combines the mechanical advantages of intramedullary rods with the mechanical advantages of tension banding, whereby to provide a device which is capable of treating all kinds of proximal femoral fractures (including not only subtrochanteric fractures and unstable intertrochanteric fractures, but also stable intertrochanteric fractures and other types of proximal femoral fractures), as well as treating fractures of other bones in the body. 
       Modifications of the Preferred Embodiments 
       [0062]    Although the present invention has been described herein with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is, therefore, to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention. This devise and application of its components can be used for both proximal and distal fractures of the femur, tibia, and humerus.