Abstract:
An orthopedic intramedullary fixation apparatus and system for use in hip and femur fracture surgery comprises an intramedullary nail, a dynamic lag screw structure comprising a longitudinal sheath and a lag screw, and securing means to fix the intramedullary nail relative to a femur. A dynamic channel created by the lag screw structure allows the lag screw to adjust dynamically, and thereby may permit further compression of the fractured bone to an optimal level as a patient begins to bear weight on it following surgery. Surgical fixation may be expedited, as a favorable point of access for a lag screw may be determined readily, particularly with obese patients in whom access to the trochanter may be problematic. Complications during surgery, such as accidental fracturing of the femoral neck and head and over-penetration of the lag screw may be avoided.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/990,741, filed 9 May 2014. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     MICROFICHE APPENDIX 
     Not applicable. 
     DESCRIPTION 
     1. Field of Technology 
     At least some embodiments disclosed herein relate, in general, to the field of orthopaedic implant apparatus and systems for bone and joint surgery, and more specifically, to intramedullary fixation apparatus and systems for certain types of fractures, including, but not limited to, fractures of the hip and femur. 
     2. Background 
     An open reduction and internal fixation (ORIF) is a type of orthopaedic surgery used to repair fractured bones. This is a two-part surgery. First, the broken bone is reduced or put back into place. Next, an internal fixation device is placed on or in the bone, or both, typically through the use of screws, plates, rods, pins or nails used to hold the broken bone together. The Dynamic Hip Screw and the Gamma Nail are currently two acceptable fixation apparatus to treat unstable intertrochanteric and sub-trochanteric fractures, which are common in the old osteoporotic patient but can be challenging to fix and problematic to manage. 
     In the 1980s, perhaps the most common method of fixation employed the Dynamic Hip Screw. Typically, there are three (3) components of a Dynamic Hip Screw, including a dynamic lag screw (inserted into the neck of a femur), a side plate, and a plurality of cortical screws (fixated to proximal or distal femoral shaft, or both). The idea behind this design is that the femoral head component is allowed to move along one plane—a Dynamic Hip Screw allows controlled dynamic sliding of the femoral head component along the construct—and since bone responds to dynamic stresses, the native femur may undergo remodeling and proper fracture healing through compression of the fracture line. A disadvantage of this technique, however, was that the plate was lateral to the load-bearing line of the hip, such that any defect in the medial cortex of the femur, whether due to imperfect reduction, comminution, or a metastasis meant that a varus stress would be applied to the fixation with every weight-bearing step, which could, in turn, cause the cutting-out of the screw from the head of the femur, or failure at the nail-plate junction or of the screws securing the plate to the bone. 
     An intramedullary appliance, the Zickel Nail, addressed some of these problems, but it proved technically difficult to insert, even in experienced hands, and presented its own problems. Among these was the increased likelihood of fracture at the base of the greater trochanter. 
     The Gamma Nail is also of an intramedullary fixation design, developed for semi-closed insertion. A Gamma Nail has three principle components: an intramedullary rod (nail) passed down the medullary cavity of the upper shaft of the femur, a lag screw passed through a hole in the proximal part of the rod and from there inserted into the head of the femur, and a set screw which prevents rotation of the main screw. The Gamma Nail itself can be somewhat difficult to place, and biomechanical experiments have suggested that while the sliding ability of the lag screw is maintained in the Gamma Nail, it is decreased in comparison with that of the Dynamic Hip Screw. This may be a particular problem in heavy set or obese patients, for whom it may be difficult to obtain access to the trochanter and find an optimal access point for introduction of a lag screw. Moreover, accidental fracture and over-penetration by the lag screw are not uncommon with the Gamma Nail design, and an optimal level of compression of the fractured bone may not always be obtained during surgery. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The embodiments illustrated are by way of example, and not limitation, in the figures of the accompanying drawings in which like references indicate similar elements. 
         FIG. 1  is an isometric view of an intramedullary nail, a dynamic lag screw structure comprised of a longitudinal sheath and a lag screw, and a surgical screw as a fixation means. 
         FIG. 2  is cutaway view of a dynamic lag screw structure with a lag screw inserted fully into a longitudinal sheath, revealing a dynamic channel for introduction of an intramedullary nail through the dynamic lag screw structure. 
         FIG. 3  is an isometric view of a femur, the head and neck of which have been reamed to accept a dynamic lag screw structure, with the longitudinal sheath thereof in position for insertion. 
         FIG. 4  is an isometric view of a femur into which the longitudinal sheath of a dynamic lag screw structure has been inserted, and the lag screw of the dynamic lag screw structure is in position for insertion within the sheath and thence into the neck and head of the femur. 
         FIG. 5  is an isometric view of a femur, reamed for placement of an intramedullary nail through a dynamic lag screw structure via a dynamic channel created by the alignment of an upper orifice and a lower orifice of a longitudinal sheath with a slot in a lag screw. 
         FIG. 6  is an isometric view of a femur into which an intramedullary nail has been inserted through the dynamic lag screw structure, and of a surgical screw in position to be installed distally as a fixation means to secure the intramedullary nail in position with respect to the femur. 
         FIG. 7  is an isometric view of a femur into which an intramedullary nail has been inserted through the dynamic lag screw structure, and into which a surgical screw has been inserted distally through a lateral orifice in the intramedullary nail. 
         FIG. 8  is a cross-sectional view of an intramedullary nail that has been inserted into the medullary shaft of a femur through the dynamic lag screw structure, revealing an external lip of a lag screw engaged with the inner lip of a longitudinal sheath, and the external rim of a longitudinal sheath engaged against the lateral cortex of the femur. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description and drawings are illustrative and are not to be construed as limiting. Numerous specific details are described to provide a thorough understanding. However, in certain instances, well-known or conventional details are not described in order to avoid obscuring the description. References to “one embodiment” or “an embodiment” in the present disclosure are not necessarily references to the same embodiment; and, such references mean at least one. 
     Reference in this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. The appearances of the phrase “in one embodiment” or substantially similar phrases in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Moreover, various features are described which may be exhibited by some embodiments and not by others. Similarly, various requirements are described which may be requirements for some embodiments but not other embodiments. 
     As illustrated in  FIG. 1 , an embodiment of the system comprises an intramedullary nail (intramedullary rod)  101 , a dynamic lag screw structure  102  including a longitudinal sheath  103  open at a distal end  116  and at a proximal end  117  with an upper orifice  109  and lower orifice  110 , and further including a lag screw  104  with a longitudinal slot, configured to be inserted into the proximal end of the longitudinal sheath, and may further have some securing means known in the art, such as surgical screws, bolts, or tightrope fixation, configured to keep an intramedullary nail  101  in a proper position relative to a bone. By way of illustration and without limitation, in an embodiment, an intramedullary nail  101  may have one or more lateral orifices  105  passing through it proximally or distally, or both, with respect to a long bone, each such lateral orifice  105  configured to accept one or more surgical screws  106  configured to pass into or through an intramedullary nail  101 . As is known in the art, an intramedullary nail  101  may have a solid, semi-solid, or hollow core, may be curved to accommodate the anterior curvature of a femur of a patient, and may be of varying length and proximal and distal diameter, as may be appropriate to a given patient. An intramedullary nail  101  may be tapered at its distal end  107 , inter alia, to facilitate insertion, and may be configured at its proximal end  108  to receive a guidance device or comparable instrument known in the art. 
     In an embodiment, a longitudinal sheath  103  of a dynamic lag screw structure  102  is open at a distal end  116  and at a proximal end  117 , with an upper orifice  109  and lower orifice  110 , said upper orifice  109  and lower orifice  110  together configured to accept an intramedullary nail  101  and allowing at least a portion of said intramedullary nail  101  to be passed transversely through said longitudinal sheath  103 . In an embodiment, the distal end (insertion end)  116  of a longitudinal sheath  103  may be tapered, may have an outer rim at its proximal end  117 , and may have an inner lip  119 . An outer rim  118  may be configured to ensure that a longitudinal sheath  103  cannot be inserted beyond the lateral cortex of a femur. In an embodiment, a longitudinal sheath  103  may be pressed or tapped into the bone through a hole or channel that has been reamed in a bone. 
     In an embodiment, a lag screw  104  may employ at its distal end (insertion end) a self-tapping thread  111 . In an embodiment, a lag screw  104  may have at its proximal end a drive  112 . Said drive  112  may include some form of internal threading  113  or other securing means configured to receive a self-holding screwdriver or comparable tool known in the art. In an embodiment, a lag screw  104  may have longitudinal slot  114  through its shank  115  configured to accept an intramedullary nail  101  and allowing at least a portion of it to pass through said lag screw  104 . In an embodiment, a lag screw  104  may have an external lip  120  at its proximal end configured to engage an inner lip  119  of a longitudinal sheath  103  so as to prevent said lag screw  104  from further penetrating the bone. 
     As illustrated in  FIG. 2 , in an embodiment, a lag screw  104  may be inserted into the proximal end of a longitudinal sheath  103 , and at least a portion of an intramedullary nail  101  passed through a dynamic channel formed by the alignment of both an upper orifice  109  and a lower orifice  110  of said longitudinal sheath  103  with a longitudinal slot  114  in the shank  115  of an inserted lag screw  104 —said dynamic channel configured to allow movement of said lag screw relative to said intramedullary nail  101  following surgery—and thence into the medullary shaft of a femur. Such a dynamic lag screw structure  102  or comparable structure may be configured to allow the dynamic adjustment of the position of the lag screw  104  in three dimensions—longitudinally, laterally, and normally (i.e., vertically)—relative to the intramedullary nail  101 , and hence, to the shaft of the femur and to the neck and head of the femur, respectively, permitting further compression of the fractured bone as a patient begins to bear weight on the joint following surgery. 
     An embodiment may be comprised of various types of stainless steel, titanium, titanium alloys, biodegradables and other suitable materials, alone or in combination, known in the art. 
     An embodiment of the current invention allows it to be placed in the hip simply and quickly using an external guidance device or system. Such an initial placement may be thought of as similar to the placement of a screw for in-situ pinning. 
     As illustrated in  FIG. 3  and  FIG. 4 , the neck  301  and head  302  of a femur  303  then may be reamed in a two-step process. First, a channel may be reamed at a desired angle from the lateral cortex of the fractured proximal femur to the center of the head of the fractured proximal femur at the desired depth for the lag screw previously determined. Second, a wider and shorter channel may be reamed at approximately the same angle to accommodate a longitudinal sheath  103 . Next, a longitudinal sheath  103  may be pressed or tapped into the bone until any external rim of the sheath reaches the lateral cortex of the fractured proximal femur. 
     As illustrated in  FIG. 3  and  FIG. 4 , the neck  301  and head  302  of a femur  303  then may be reamed in a two-step process. First, a channel may be reamed at a desired angle from the lateral cortex of the fractured proximal femur to the center of the head of the fractured proximal femur at the desired depth for the lag screw previously determined. Second, a wider and shorter channel may be reamed at approximately the same angle to accommodate a longitudinal sheath  103 . Next, a longitudinal sheath  103  may be pressed or tapped into the bone until any external rim of the sheath reaches the lateral cortex of the fractured proximal femur. 
     As illustrated in  FIG. 4  and  FIG. 5 , a lag screw  104 , which may have been attached to a self-holding screwdriver or comparable device, may then be inserted into and through the longitudinal sheath  103  embedded in the bone and screwed or otherwise inserted into the neck and head of a femur and into the longer, narrower channel initially reamed. As illustrated in  FIG. 6 , an upper orifice  109  and a lower orifice  110  in a longitudinal sheath  103  and a slot  114  in a lag screw  104  which has been inserted into a longitudinal sheath  103  may aligned, and the resulting dynamic channel for introduction of an intramedullary nail  101  lined up with the medullary canal of a femoral shaft. A fluoroscope or other guidance device or system then may be used to place an intramedullary nail  101  through the trochanter into the construct and canal of a femur. As depicted in  FIG. 6 ,  FIG. 7  and  FIG. 8 , an intramedullary nail  101  then may be secured to the bone with one or more surgical screws  106  utilizing a fluoroscope or other guidance device or system. 
     In the foregoing specification, the disclosure has been described with reference to specific exemplary embodiments thereof. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.