Patent Publication Number: US-2009240252-A1

Title: Targeting apparatus connecting to locking nails for the correction and fixation of femur deformity of a child

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The invention relates to devices for correcting and fixing tubular bones, and more particularly to an improved targeting apparatus operatively connecting to locking nails for the correction of the deformity in proximal femur of a child. 
     2. Description of Related Art 
     Femoral varus osteotomy is one of the most common operations of children&#39;s hips to correct the dysplasia and deformity from neuromuscular disease, developmental dysplasia of the hip, Perthes&#39; disease, trauma and infection. The surgical procedures include osteotomy at femoral intertrochanteric area, varus deformation of femoral neck, and internal fixation by implants. The universal implant in varus osteotomy is angled blade plate in which the femoral neck is fixed by one smooth blade. However, blade loosening from the cancelleous bone in femoral neck is not uncommon. The resulting loss of correction, malunion, nonunion, and prolonged immobilization are major surgical complications. Besides, a big wound and massive muscle dissection are required to implant the plate. Prominence at trochanteric area by the plate and the concomitant pain and discomfort are the common complains from the patients and parents. 
     A conventional targeting apparatus for the correction and fixation of femur deformation of a child is shown in  FIG. 6 . The targeting apparatus comprises an angled blade plate  50  having three tubular locating members (not numbered) for fastening three screws  51 , and a thread-less blade  52  in which the screws  51  are threadedly inserted into the femoral shaft for fastening and the blade  52  is inserted into the femoral neck for fastening. However, the fastening of the blade  52  in the femoral neck is not reliable. Thus, time required for healing the femoral osteotomy may be prolonged undesirably. Moreover, the positioning of the angled blade plate  50  may cause a great pain to the leg. In addition, the angled blade plate  50  can cause bulging to the leg after surgery. 
     Therefore, the need for improvement still exists. 
     SUMMARY OF THE INVENTION 
     It is therefore one object of the invention to provide a targeting apparatus operatively connecting to locking nails for the correction of the deformity in proximal femur of a child. The invention has the advantages as detailed below. The femoral shaft is fixed by three cortical bones and thus is more reliable as compared with the conventional angled blade plate. Wound on femur has a lesser area and cut muscle is less. Torque of the locking nails is relatively small and thus is better than the conventional angled blade plate. A doctor can use first and second locking nails to fix the femoral osteotomy in a labor saving manner. The leg only has a small bulging and no blade plate is disposed between the skin and the bone after surgery. The locking nails are inserted into positions below the femoral head and thus cause no injury to the body and do not hinder blood circulation. 
     To achieve the above and other objects, the invention provides a targeting apparatus for correcting the deformity in proximal femur of a child, comprising retention means; a cylindrical nail retention member tapered toward its half-spherical bottom end and including an upper through hole, a lower through hole, and a top cavity having inner threads for releasably secured to the retention means; a first locking nail including a forward threaded portion, an enlarged head, and a retaining recess in the head thereof; and a second locking nail including a forward threaded portion, an enlarged head, and a retaining recess in the head thereof. 
     The above and other objects, features and advantages of the invention will become apparent from the following detailed description taken with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a preferred embodiment of targeting apparatus for the correction of the deformity in proximal femur of a child according to the invention; 
         FIG. 2  is an exploded view of  FIG. 1  with the locking nail and the screw driver removed and a sleeve added; 
         FIG. 3  is an exploded view of  FIG. 1 ; 
         FIG. 4  is a longitudinal sectional view of  FIG. 3 ; 
         FIG. 5  schematically depicts the for the correction of the deformity in proximal femur in a child by means of the targeting apparatus operatively connected to the locking nails according to the invention; and 
         FIG. 6  schematically depicts a conventional targeting apparatus for the correction of the deformity in proximal femur of a child. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1 to 5 , a targeting apparatus  500  for the correction of the deformity in proximal femur of a child in accordance with a preferred embodiment of the invention is shown. The targeting apparatus  500  operates in cooperation with a nail assembly (not numbered) which comprises the following components. 
     A nail retention member  10  is cylindrical. The nail retention member  10  is tapered toward its bottom end  104  which is half-spherical. The nail retention member  10  has an upper through hole  101 , a lower through hole  102 , and a top cavity  103  having inner threads. 
     A first locking nail  11  has a forward threaded portion  111 , an enlarged head  112 , and a recess  113  in the head  112 . 
     A second locking nail  12  has a forward threaded portion  121 , an enlarged head  122 , and a recess (not numbered) in the head  122 . 
     Preferably, the first locking nail  11  is a cannulated screw, and the second locking nail  12  is a cortical screw. Also, the first locking nail  11  has a diameter larger than that of the second locking nail  12 . 
     The targeting apparatus  500  comprises the following components as detailed below. A handle  20  comprises an upright section having transverse upper and lower guide holes  201 ,  202 , a horizontal section having a downward extension having a longitudinal channel  203  therethrough, and an inclined section interconnecting the upright and the horizontal sections. 
     A retention assembly  30  comprises a fastening unit  31  including a shank  313  having a threaded end  3131 , a hexagonal head  311 , and a recess  312  having inner threads in the head  311 ; and a retention unit  32  including an enlarged cylindrical head  321  and a shank  322  having outer threads  3221  which are adapted to threadedly secure to the recess  312 . 
     A fastening assembly  40  comprises a joining sleeve  41  including an enlarged cylindrical head  411  and a central bore  412  through the joining sleeve  41 ; and a screw driver  44  including an enlarged handle  441  and a shank  442 . The fastening assembly  40  further comprises a sleeve  42  including an enlarged cylindrical head  421 , a shank (not numbered), and a central bore  422  through the shank. The shank of the sleeve  42  is adapted to insert into the central bore  412  of the joining sleeve  41 . 
     Referring to  FIG. 5  in conjunction with  FIGS. 1 to 4 , an operation of the invention will be described in detail below. It is envisaged that the nail retention member  10  is adapted to insert into the femoral neck of a child in a neck-shaft angle. First, align the top cavity  103  with the channel  203 . Next, threadedly secure the threaded end  3131  to the cavity  103  after inserting the threaded end  3131  through the channel  203  into the cavity  103 . Next, use a hammer to pound the head  321  of the retention unit  32  until the nail retention member  10  is implanted in the femur. Next, cut the femur with the nail retention member  10  being fastened in the cortical bone. Next, insert the nail retention member  10  into the femur and turn the handle  20  to position the nail retention member  10 . That is, the nail retention member  10  passes through the femoral neck and the femoral shaft. Next, use one hand to hold the handle and the other hand to insert the first locking nail  11  through the upper through hole  101 . Next, insert the joining sleeve  41  through the upper guide hole  201  until the head  112  is received in the front portion of the joining sleeve  41 . Next, insert the shank  442  of the screw driver  44  into the central bore  412  of the joining sleeve  41  until the end of the shank  442  engages the recess  113  in the head  112 . Next, turn the screw driver  44  to drive the first locking nail  11  into the femoral neck. Similarly, use the other hand to insert the second locking nail  12  through the lower through hole  102 . Next, insert the joining sleeve  41  through the lower guide hole  202  until the head  122  is received in the front portion of the joining sleeve  41 . Next, insert the shank  442  of the screw driver  44  into the central bore  412  of the joining sleeve  41  until the end of the shank  442  engages the head  122 . Next, turn the screw driver  44  to drive the second locking nail  12  into the femoral shaft. As a result, the femur is fixed to be readily for correction. Intramedullary interlocking nail fixation is the standard treatment for femoral fracture in adults. Intramedullary nailing bears less bending strain than plate fixation because the center of motion of nail is closer to the center of motion of femur. Minimal scaring of thigh muscles by intramedullary fixation allows early recovery of muscle function and bone healing. A new interlocking nail is specially designed for femoral varus osteotomy of a child. As the interlocking nail in adults, the nail is intramedullary fixation and offers additional stability by two locking screws. In addition, the nail is smaller in size (5 mm to 7 mm in diameter) to fit the smaller canal of a child&#39;s femurs. The nail is designed to insert form the area lateral to greater trochanter tip to avoid injury to structure and circulation of femoral head. 
     The nail system of the invention thus offers the following advantages as compared with the traditional blade plate. Better fixation at femoral neck by purchasing three locations of cortical bone. Biomechanical advantage of intramedullary fixation over plate fixation. Smaller wound and less muscle dissection for nail insertion. Less prominence at trochanter area after operation. 
     Moreover, the nail of the invention also offers the following technological advantages for the surgeons. It is possible of holding and targeting device for easier insertion of nail and locking screws. It is possible of controlling the anteversion of femur by two locking screws. Concomitant greater trochanter distal transfer is made possible. 
     While the invention herein disclosed has been described by means of specific embodiments, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope and spirit of the invention set forth in the claims.