Abstract:
An orthopedic knee brace which will allow lateral-medial compensation to be obtained while still enabling the use of known joint mechanism which will constrain the leg to execute the correct natural movement of the knee by separating lateral-medial compensation and anterior posterior movement functions. More specifically, the present invention utilizes a pair of hinges, one of which provides for movement in a posterior-anterior plane and the other which provides for movement in a medial-lateral plane. In this way, any conventional knee joint mechanism may be employed and movement of the leg can be properly constrained to execute a prescribed motion.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention is directed to orthopedic knee braces and particularly those designed to provide medial (varus) and lateral (valgus) compensation. 
   2. Description of Related Art 
   Published U.S. Patent Application No. 2002/0183672 A1 discloses an orthopedic knee brace with adjustable length struts. Length adjustment is achieved via a telescopic adjustment assembly but no provision is made for medial or lateral adjustment of the length adjustment mechanism cannot be used for that purpose without producing binding of the joint mechanism. 
   A self-aligning adjustable orthopedic knee brace is disclosed in U.S. Pat. No. 6,387,066 B1. The brace of this patent has a self-aligning polycentric joint which utilizes an apertured spherical bearing element and an annular concave seat in which the bearing element is freely rotatable so as to permit not only anterior-posterior pivoting of the femoral and tibial arms with respect to each other, but also medial-lateral relative movement. Additionally, the femoral (upper) arm has a length adjustment arrangement with an adjustment screw, the head of which is rotatably retained in the top end of the femoral arm and the other of which is threaded into the facing end an adjustment arm so that rotation of the screw either draws the adjustment arm toward femoral arm or displaces it away from it. By adjustment of the arms, the angle of inclination of femoral half of the brace can be adjusted relative to the tibial half, the spherical polycentric joint allowing for the laterally or medially directed inclination without producing binding during posterior-anterior motion. However, the problem with the use of a spheric polycentric joint is that it imparts an inherent weakness to the brace in that it is not constrained against transverse rotation, i.e., rotation in a horizontal plan, and thus allows a degree of twisting between the femur and tibia. Furthermore, a joint of this type cannot duplicate the correct natural movement of the knee, such as is obtainable by the joints as disclosed in U.S. Pat. Nos. 4,773,404; 4,890,607; 5,259,832; and 5,330,418. 
   SUMMARY OF THE INVENTION 
   Therefore, it is a primary object of the present invention to provide orthopedic knee brace which will allow lateral-medial compensation to be obtained while still enabling the use of known joint mechanism which will constrain the leg to execute the correct natural movement of the knee. 
   In accordance with the invention, this object is achieved by separating the lateral-medial compensation and anterior posterior movement functions. More specifically, the present invention utilizes a pair of hinges, one of which provides for movement in a posterior-anterior plane and the other which provides for movement in a medial-lateral plane. In this way, any conventional knee joint mechanism may be employed and movement of the leg can be properly constrained to execute a prescribed motion. 
   These and other objects, features and advantages will become apparent from the following detailed description of a preferred embodiment when viewed in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view of a knee brace in accordance with a preferred embodiment of the invention; 
       FIG. 2  is a perspective view of the knee brace shown in  FIG. 1 ; 
       FIG. 3  is an exploded view of the joint mechanism of the  FIG. 1  knee brace; 
       FIGS. 4 &amp; 5  each show a perspective view of a respective version of the length adjustment mechanism of the  FIG. 1  knee brace; and 
       FIGS. 6–8  show the  FIG. 1  knee brace in neutral, medially shifted and laterally shifted positions, respectively. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   With reference to  FIGS. 1 &amp; 2 , it can be seen that knee brace  1  of the present invention, as is typical, has a medial femoral arm  3  and a lateral side femoral arm  5  which are connected, respectively, to a medial tibial arm  7  and a lateral side tibial arm  9 . In particular, an upper crossbar  11  connects the medial femoral arm  3  and lateral femoral arm  5  at a front side of the brace, and a pair of lower crossbars  12  connect the medial and lateral tibial arms  7 ,  9  at a front side of the brace. Additionally, upper and lower straps  13 ,  14  are provided for detachably securing the brace  1  on a leg of a user at the thigh and calf areas. In this regard, it is noted that, at least in the context of the present invention, it is important to provide at least a pair straps  13 ,  14  running between medial and lateral tibial arms, or other equivalent structure, in order to establish a fixed anchoring of the brace relative to the leg for reasons described more specifically below. 
   A medial side joint mechanism  16  couples the medial side femoral arm  3  to the medial side tibial arm  7 , and a lateral side joint mechanism  17  couples the lateral side femoral arm  5  to the lateral side tibial arm  9 . Each of the joint mechanisms  16 ,  17  comprise upper and lower hinges  19 ,  20 , the lower hinges  20  enabling relative movement between the femoral and tibial arms in posterior-anterior planes and the upper hinges  19  enabling relative movement between the femoral and tibial arms in medial-lateral planes. 
   The upper hinges  19  are unicentric hinges and the lower hinges  20  are polycentric. Each of the upper hinges  19  preferably comprises a pin  22  that is engaged in pin-receiving openings  23  of the femoral arms and  24  of the joint mechanisms. While the lower hinges  20  can be of any known polycentric type, it is advantageous to use which duplicates the natural motion of the knee by providing a means for constraining the tibia to slide rearwardly relative to the femur for a predetermined distance during an initial range of flexion of the knee from a straight leg position, and beyond the initial range of flexion to, thereafter, rotate relative thereto in a predetermined arcuate path as is the case for the joints as disclosed in U.S. Pat. Nos. 4,773,404; 4,890,607; 5,259,832; and 5,330,418, all of which are hereby incorporated by reference. 
   A lower hinge construction for the joint mechanism that is particularly advantageous is one of the type described in U.S. Pat. No. 5,259,832, which comprises a four bar linkage. With reference to  FIG. 3  the four bar linkage forming the joint mechanism  17  of the preferred embodiment of the present invention will be described. 
   Firstly, to provide self-lubricating bearings which will also prevent, e.g., aluminum links from reacting with titanium arms, male plastic bearing elements  27 ,  28  are inserted into the openings  30   a ,  30   b  of the tibial arms  7 ,  9  and openings  31   a ,  31   b  of a lower part of the upper hinges  19 , respectively. Bearing retainers  33 ,  34  are then snapped onto ends of the bearing elements  27 ,  28  which have passed through and out of the openings  30   a ,  30   b , and  31   a ,  30   b.    
   A first pivot link is formed by link elements  36 ,  37 , which are secured together by rivets  38  after the male link element  36  has been insert through openings  30   a  and  31   a  and female link element  37  has been mounted over the ends of the link element  36  which have passed through and out of the openings  30   a ,  31   a , thus forming first and second pivot points. Alternatively, the rivets  38  can be omitted and other fastening methods used, such as crimping of the projecting ends of the male link element  36 . After attachment of the first pivot link, the hinge cover  40 , which is C-shaped or clam shell-shaped, is slid over the area of the openings  30   a ,  30   b , and  31   a ,  30   b  and the first pivot link. Then, rivets  42  are inserted into the openings  43 ,  44  of the hinge cover  40 , through the openings  30   b  and  31   b , and back out though the corresponding openings  43 ,  44  at the opposite side of the hinge cover  40 , after which they are fixed in place. Thus, the portion of the hinge cover  40  between the rivets  42  constitutes the second pivot link of the four bar linkage forming the polycentric lower hinges  17  with the rivets  42  forming third and fourth pivot points. 
   In accordance with the concept of U.S. Pat. No. 5,259,832, an angle of intersection between an imaginary line drawn through the first and second pivot points of first pivot link and an imaginary line drawn through the third and fourth pivot points of the second pivot link is at least 24° throughout a full range of flexion from a straight leg position to a fully flexed position. 
   In accordance with the invention, at least one of the femoral arms  3 ,  5  has a length adjustment mechanism. In the case of an off the shelf (OTS) knee brace, both of the femoral arms  3 ,  5 , would normally be provided with a length adjustment mechanism, as is the case for the knee brace  1  shown in  FIG. 2 . On the other hand, a custom fitted knee brace will normally require a length adjustment mechanism in only one of the femoral arms  3 ,  5  and the range of adjustability provided will not be as great since adjustability will be required only for fine-tuning purposes, as opposed to the case of an OTS model where it will function to a greater extent to provide a proper fit and proper medial-lateral loading, e.g., up to 1.5″ of height adjustment and up to 18° of medial/lateral angular adjustment. 
   While various types of length adjustment mechanisms are known and may be used in accordance with the present invention, it is preferred that the length adjustment mechanism be a slide mechanism. In particular, the slide mechanism  45  illustrated in  FIGS. 1–4  comprises a slotted guide  46  and a slider  47  which is fixable at selected locations along the length of the slotted guide  46  by loosening the screws  48  to free the slotted guide  46  for adjustment movement relative to the slider  47  and then re-tightening the screws  48  when the desired adjustment position has been reached. The slotted guide  46  is formed as an extension of an upper part of the upper hinge  19  of the joint mechanism  16 ,  17 . The slotted guide  46  is received in a recess  50  that is formed in a side of a respective one of the femoral arms  3 ,  5 . The slider  47  is a link member that is slidably received in the slot of the slotted guide  46  but is fixed relative to the respective femoral arm  3 ,  5  by the pair of screws  48  which are threaded into the link member and extend through the side of the respective femoral arm  3 ,  5  via apertures formed in the base wall of the recess  50 . 
   Alternatively, as shown in  FIG. 5 , the slotted guide  46 ′ formed as an extension of an upper part of said joint mechanism is telescopically received within an interior space of the respective femoral arm  3 ,  5 . In this case, the slider is only a single screw  48  is used which extends through the slot of the slotted guide  46 ′ between and through opposite sides of the respective femoral arm. Since there is no separate slider as in the embodiment of  FIG. 4 , a nut  49  is threaded onto the end of the screw. Tightening of the nut on screw  48  resiliently draws the opposed walls of the hollow portion of the femoral arm  3 ,  5  together so as to clamp the slotted guide  46 ′ therebetween, and loosening of the nut  49  on the screw  48  allows the opposed walls to move back to their unstressed positions, freeing the slotted guide to move in and out of the femoral arm  3 ,  5 . This construction is particular useful for a custom fitted knee brace where a lesser degree of sliding movement is required and a more finished look may be desired given the extra cost of a custom fitted brace. 
     FIGS. 6–8  show examples of the operation of the length adjustment mechanisms  45  and double hinge joint mechanism of the present invention with the OTS knee brace of the invention.  FIG. 6  shows the situation where both length adjustment mechanisms  45  are fully extend in a neutral angular position.  FIG. 7  shows the medial side adjustment mechanism  45  maximally extended and the lateral side length adjustment mechanism  45  maximally retracted resulting in a maximally lateral angular correction of about 18°, the femoral arms  3 ,  5  pivoting about the unicentric hinges  19 .  FIG. 8  shows the lateral side adjustment mechanism  45  maximally extended and the medial side length adjustment mechanism  45  maximally retracted resulting in a maximally medial angular correction of about 18°, the femoral arms  3 ,  5  pivoting about the unicentric hinges  19 . Because of the action of the unicentric hinges  19 , lateral/medial loads that could produce binding of the polycentric hinges  16 ,  17 , are not transmitted to the polycentric hinges so that the can move freely despite and angular corrections that are set. 
     FIGS. 6–8  show examples of the operation of the length adjustment mechanisms  45  and double hinge joint mechanism of the present invention with the OTS knee brace of the invention.  FIG. 6  shows the situation where both length adjustment mechanisms  45  are fully extend in a neutral angular position.  FIG. 7  shows the medial side adjustment mechanism  45  maximally extended and the lateral side length adjustment mechanism  45  maximally retracted resulting in a maximally lateral angular correction of about 18°, the femoral arms  3 ,  5  pivoting about the unicentric hinges  19 .  FIG. 8  shows the lateral side adjustment mechanism  45  maximally extended and the medial side length adjustment mechanism  45  maximally retracted resulting in a maximally medial angular correction of about 18°, the femoral arms  3 ,  5  pivoting about the unicentric hinges  19 . Because of the action of the unicentric hinges  19 , lateral/medial loads that could produce binding of the polycentric hinges  16 ,  17 , are not transmitted to the polycentric hinges so that they can move freely despite any angular corrections that are set. 
   While preferred embodiments of the invention have been shown and described, it should be appreciated that the invention is not limited to the specifics of these embodiments. To the contrary, numerous variations and modifications within the scope of the disclosed concepts will be apparent to those of ordinary skill, e.g, through the use of different types of hinge mechanisms, different types of adjustment mechanisms and different manners for attachment of the brace to a wearer&#39;s leg, as well as the provision of various ancillary features, such as angular adjustment stops. As such, the invention should be considered as being fully commensurate with the scope of the appended claims.