Abstract:
An orthopaedic implant knee hinge and surgical method for minimally invasive insertion of the orthopaedic implant knee hinge. The apparatus and method stabilizes the knee in patients after ligament surgery, conventional fixation of supracondylar and intracondylar fractures of the femur and/or tibial plateau and proximal tibia fractures. The knee hinge is inserted subcutaneously (but supra-muscularly) on one of both of the medial or lateral side of the knee.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to orthopedic implants and minimally invasive methods for insertion thereof. Specifically the present invention relates to an orthopaedic implant knee hinge and surgical method for minimally invasive insertion thereof. 
     BACKGROUND OF THE INVENTION 
       FIG. 1  depicts an anteromedial aspect of knee. The knee joint joins the thigh with the lower leg and consists of two articulations: one between the femur  1  and tibia  2 , and one between the femur  1  and patella  3 . It is the largest joint in the human body and is very complicated. The knee is a pivotal hinge joint, which permits flexion and extension as well as a slight medial and lateral rotation. Since in humans the knee supports nearly the whole weight of the body, it is vulnerable to acute injury. 
     The quadriceps tendon  4  connects the femur  1  to the patella  3  and the patellar tendon  5  connects the patella  3  to the tibia  2 . The articular cartilage  6  ensures supple knee movement while the meniscus  7  serves to protect the ends of the bones from rubbing on each other and to effectively deepen the tibial sockets into which the femur  1  attaches. 
     The ligaments surrounding the knee joint offer stability by limiting movements and, together with several menisci and bursae, protect the articular capsule. Knee laxity, due to ligament injury, can cause significant instability to the knee joint thereby predisposing the joint to further instability and additional injury. The medial collateral ligament (MCL)  11  and lateral collateral ligament (LCL)  10  provide side to side stability of the knee joint. Injury to the MCL  11  or LCL  10  can result in lateral instability of the knee. 
     The anterior cruciate ligament (ACL)  8  is responsible for controlling the forward glide of the tibia  2  in relation to the femur  1 . This movement is called “anterior tibial translation.” The ACL  8 , in combination with the other ligaments, of a healthy knee joint restrict the rotation or twisting of the knee. Injury to the ACL  8  can result in rotational and anterior instability of the knee. 
     The posterior cruciate ligament (PCL)  9  is the primary restraint to post translation of the tibia  2  on the femur  1  and acts as a secondary restraint to varus/valgus movements and external rotation. Injury to the PCL  9  can result in posterior instability of the knee whereby the patient feels that the knee can “pop-out” of place. PCL  9  injuries are the least common form of knee instability injury. 
     An injury or tear of any one of the aforementioned ligament predisposes the knee joint to secondary injuries to the other ligaments, as well as to the meniscus  7  and articular cartilage  6  of the knee. Approximately 50% of all ACL  8  injuries occur in combination with damage to the meniscus  7 , articular cartilage  6  or other ligaments ( 9 ,  10 ,  11 ). Protecting and supporting a weakened knee joint after injury or pre or post-operatively, from the medial, lateral or rotational forces exerted upon the knee during walking, squatting and other movements is the primary purpose of a knee orthosis device for knee instability. Unfortunately such knee orthoses do not always work, especially with in big or obese patients. 
     Supracondylar and Intracondylar Fractures of the Femur 
     The rounded ends of the femur are called condyles. There is a type of fracture of the lower end of the femur that starts above the condyles and may pass down into the joint. There is a great deal of variation in the pattern of these fractures. At one extreme is a simple transverse fracture which does not enter the joint. At the other there may be splintering of the bone and multiple fragments including joint surface. The more severe injuries are caused by high energy trauma and may be open fractures. Fractures of the kneecap and tibial plateau may be involved as well. These injuries are amongst the most challenging fractures to treat.  FIGS. 1 b  and 1 c    show the conventional means to fix the fractures  19  in the supracondylar and intracondylar regions. Bone screws  21  with or without bone plates  20  are typically used to fix these fractures  19 . Unfortunately, with fixation by these conventional techniques, there is generally no ability to bear weight on the leg and the leg may be unable to bend at the knee, causing reduced range of motion in the patient&#39;s leg after healing. 
     Tibial Plateau and Proximal Tibia Fractures 
     The flat parts of the tibia which form a joint with the femur are called the tibial plateau. On the outside, or lateral side, of the knee is the lateral tibial plateau and on the inside, or medial side, is medial tibial plateau. Compression forces may be too great for this region and the lower end of the femur may be driven into the tibial plateau on the inner or outer side—or occasionally both. 
     These are severe and troublesome injuries which damage the weight bearing surfaces of this major joint. The focus of treatment of a tibial plateau fracture is to restore the smoothness of the joint surface as best as possible. Like supracondylar and intracondylar fractures of the femur there is a wide spectrum of tibial plateau fractures ranging from simple injuries which damage one plateau to extensive fractures with many fragments and involvement of the shaft of the tibia.  FIGS. 1 d  and 1 e    show the conventional means to fix the fractures  19  in the tibial plateau and proximal tibia regions. Bone screws  21  with or without bone plates  20  are typically used to fix these fractures  19 . Again, with fixation by these conventional techniques, there is generally no ability to bear weight on the leg and the leg may be unable to bend at the knee, causing reduced range of motion in the patient&#39;s leg after healing. 
     Thus, there is a need in the art for an apparatus and method for stabilizing the knee in patients after ligament surgery and after fixation of supracondylar and intracondylar fractures of the femur or tibial plateau and proximal tibia fractures. 
     SUMMARY OF THE INVENTION 
     An orthopaedic implant knee hinge and surgical method for minimally invasive insertion thereof in the subcutaneous fat layer between the skin and the muscle. That is, the implant is placed subcutaneously, but supra-muscularly on one or both sides of the knee. The orthopaedic implant knee hinge may include two elongated plates, each of said elongated plates may have more than one affixation opening therein to accommodate affixation means passing through said affixation opening; said two elongated plates may be pivotally connected to one another at an end thereof by a pivotal connector. The hinge device may further include at least four affixation means to affix the knee hinge to the bones of the femur and tibia, at least two of said at least four affixation means passing through said more than one affixation opening in each of said elongated plates. The openings may be threaded, said affixation means may be a screw and said screw may have a threaded head which cooperates with said threading in said affixation openings. 
     The affixation means may be a screw and said screw may have threading on the shaft only on the end thereof that will be inserted into the bone. One or both of said elongated plates may include an offset plate to provide for proper placement of said elongated plate along the femur or tibia. The affixation means may be a threaded rod combined with nuts to anchor said elongated plates to said rods. The elongated plates, said attachment means and said pivotal connector may be formed from a material selected from the group consisting of titanium, stainless steel or a bio-compatible polymer material. 
     The method for minimally invasive insertion of an orthopaedic implant knee hinge may comprising the step providing the orthopaedic implant knee hinge and tunneling said orthopaedic implant knee hinge subcutaneously in the subcutaneous fat layer parallel to the length dimension of the femur and tibia along either the lateral of medial side of the leg. The method may further include the step of attaching the ends of the orthopaedic implant knee hinge to the distal end of the femur and the proximal end of the tibia; said pivotal connector should be located adjacent the distal end of the femur close to the knee joint. The orthopaedic implant knee hinge may remain disposed in the subcutaneous fat layer and away from, but parallel to the femur and tibia once attached thereto. 
     The surgical method may include the step of tunneling by creating one or more incisions in the skin through which said orthopaedic implant knee hinge can be inserted. The one or more incisions in the skin may be created on the lateral or medial side of the leg near both the distal end of the femur and the proximal end of the tibia. The one or more incisions in the skin may also be created on both the lateral and medial side of the leg near both the distal end of the femur and the proximal end of the tibia, and two orthopaedic implant knee hinges may be implanted, one on the lateral side and one on medial side of the knee. 
     The step of attaching the ends of the orthopaedic implant knee hinge to the distal end of the femur and the proximal end of the tibia may include inserting at least four affixation means to affix the knee hinge to the bones of the femur and tibia, at least two of said at least four affixation means passing through said more than one affixation opening in each of said elongated plates and into the bone. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1 a    depicts an anteromedial aspect of knee; 
         FIG. 1 b    depicts the conventional fixation of supracondylar and intracondylar fractures of the femur using only bone screws; 
         FIG. 1 c    depicts the conventional fixation of supracondylar and intracondylar fractures of the femur using bone screws and a bone plate; 
         FIG. 1 d    depicts the conventional fixation of tibial plateau and proximal tibia fractures using only bone screws; 
         FIG. 1 e    depicts the conventional fixation of tibial plateau and proximal tibia fractures using bone screws and a bone plate; 
         FIG. 2  is a depiction of a side view of a knee joint with the knee hinge of the present invention attached thereto; 
         FIG. 3  is a depiction of the front view of the knee joint with the knee hinge of the present invention attached thereto; 
         FIG. 4  is a depiction of the front view of the knee joint with two of the knee hinges of the present invention attached thereto along with conventional bone screw fixation of tibial plateau fractures and/or proximal tibia fractures; 
         FIG. 5  is a depiction of the front view of the knee joint with two of the knee hinges of the present invention attached thereto along with conventional bone screw and bone plate fixation of supracondylar and intracondylar fractures of the femur; 
         FIG. 6  depicts a preferred affixation means, a screw, useful to affix the inventive knee hinge. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is a knee hinge fixation device and method for application thereof.  FIG. 2  is a depiction of a side view of a knee joint with the knee hinge of the present invention attached thereto. The knee joint does not show and of the muscles, ligaments or tendons. In its most basic form the knee hinge is composed of two elongated plates with multiple affixation openings therein. 
     In  FIG. 2 , the two elongated plates  15  and  16  are attached to the femur  1  and the tibia  2 , respectively. The two elongated plates  15  and  16  are connected together pivotally by a connector  18 . The two elongated plates  15  and  16  are connected to the tibia and femur using attachment means  12  which pass through the elongated plates  15  and  16  via affixation openings  15 ′ and  16 ′ and into the femur  1  and tibia  2 . As the knee is flexed and extended, the two elongated plates act as a hinge by pivoting at connector  18 . 
     If needed, one or both of the elongated plates may have an offset plate  17  attached thereto to provide for proper placement on the femur and tibia. It should be noted that when the knee hinge is in place, the point of joining between the two elongated plates  15  and  16  at the pivotal connector  18  should be located at the distal end of the femur, to allow for proper extension and flexion of the knee. 
       FIG. 3  is a depiction of the front view of the knee joint with the knee hinge of the present invention attached thereto. Again the knee joint does not show any of the muscles, ligaments or tendons.  FIG. 3  indicates how the elongated plates  15  and  16  are attached to the femur  1  and tibia  2 , respectively. It can be seen that the attachments means  12  pass-through the elongated plates via the add fixation openings  15 ′ and  16 ′, and into the bones. It should be noted that the elongated plates of the knee hinge of the present invention are placed subcutaneously but supra-muscularly. This allows for proper stabilization of the knee without having to cut through the muscles and tendons to place the plates against the bones. 
       FIG. 4  is a depiction of the front view of the knee joint with two of the knee hinges of the present invention attached thereto. Again the knee joint does not show any of the muscles, ligaments or tendons. The knee has tibial plateau fractures  19  and/or proximal tibia fractures  19  which have been conventionally fixed as shown in  FIG. 1 d    using bone screws  21  (the fixation could also have used a bone plate  20  as in  FIG. 1 e   ). However, unlike the conventional fixation technique, two of the inventive knee hinges have been inserted subcutaneously (and supra-muscularly) on both the medial and lateral sides of the knee joint. The hinges allow the leg to bear weight and allows for bending of the knee (if appropriate). This allows the patient to retain range of motion in the knee joint from the beginning of the healing process. The hinges also allow the weight of the body to be off loaded from the fracture after fixation and the patient will be able walk on the extremity. 
       FIG. 5  is a depiction of the front view of the knee joint with two of the knee hinges of the present invention attached thereto. As before, the knee joint does not show any of the muscles, ligaments or tendons. The knee has supracondylar and intracondylar fractures  19  of the femur which have been conventionally fixed as shown in  FIG. 1 c    using bone screws  21  and a bone plate  20  (the fixation could also have used just bone screws  21  as in  FIG. 1 b   ). Again, unlike the conventional fixation technique, two of the inventive knee hinges have been inserted subcutaneously (and supra-muscularly) on both the medial and lateral sides of the knee joint. The hinges allow the leg to bear weight and allow for bending of the knee (if appropriate). 
       FIG. 6  depicts a preferred affixation means  12 , a screw. The screw  12  may preferably have a threaded head  13  which may cooperate with threading in the affixation openings  15 ′ and  16 ′ of the elongated plates  15  and  16 . The affixation openings  15 ′ and  16 ′ may be threaded as in locking plate technology. This feature allows the elongated plates  15  and  16  to remain in place subcutaneously but supra-muscularly without being pressed against the muscles, yet holding the bones firmly in place. The screw  12  also preferably has thread  14  only on the end thereof that will be inserted into the bone. Alternatively, a threaded rod may also be used to attach the plates to the bones using nuts or the like to anchor the plates to the rods in the subcutaneous position. The elongated plates  15  and  16 , the attachment means  12  and the pivotal connector  18  may be formed from titanium, stainless steel or a bio-compatible polymer material. 
     The knee hinge may be placed into the subcutaneous fat layer through two incisions in the skin. One incision is near the distal end of the femur  1  and the other is near the proximal end of the tibia  2 . The incisions may be approximately two inches or less on each end. Of course, the plates  15  and  16  may come in many different sizes to accommodate different sized people and bones. This placement of the elongated plates  15  and  16  just under the skin prevents disruption of the muscle tissue and since there is no dissection, there is little chance for infection. The hinges may have a locking feature if there is a need to prevent the knee from bending. It should be noted that the hinges are not a permanent implant, but rather should be removed after the injury to knee joint has healed. 
     It is to be expected that considerable variations may be made in the embodiments disclosed herein without departing from the spirit and scope of this invention. Accordingly, the significant improvements offered by this invention are to be limited only by the scope of the following claims.