United States Patent [191
`Rogers et al.
`
`llllllllllillllllllllllllllllllllllllIllllwilllllllllllllllllllllllll
`
`USOO51078
`[111
`Patent Number:
`[45] Date of Patent:
`
`5,107,824
`Apr. 28, 1992
`
`[54]
`
`[75]
`
`[73]
`i [21]
`[22]
`[51]
`[52]
`[53]
`
`[56]
`
`ANATOMICALLY CORRECT KNEE BRACE
`HINGE
`Inventors: Michael M. Rogers; Linda L. Rogers,
`both of Mountain View, Calif.
`Anodyne, Inc., Boulder, Colo.
`407,185
`Sep. 14, 1989
`
`Assignee:
`Appl. No.:
`Filed:
`
`Int. Cl.5 ............................... .. A61F 5/00
`US. Cl. ......................... .. 602/16; 602/26
`Field of Search ................... .. 128/80 C, 80 R, 77,
`128/88, 80 F; 623/27, 32, 39, 45
`References Cited
`U.S. PATENT DOCUMENTS
`
`1,390,915 9/1921 Loth ................................ .. 623/27 X
`
`3,779,654 12/1973 Horne . . . . . .
`. . . .. 128/80 C X
`3,902,482 9/1975 Taylor ............................ .. 128/88 X
`4,361,142 11/1982 Lewis et al. .................... .. 128/80 C
`
`4,463,751 8/1984 Bledsoe
`4,723,539 2/1988 Townsend
`
`128/80C
`..12s/soc
`
`FOREIGN PATENT DOCUMENTS
`
`2600528 12/1987 France ............................ .._ 128/80 C
`Primary Examiner-Richard J. Apley
`Assistant Examiner-Lynne A. Reichard
`[57]
`ABSTRACT
`An improved hinge design for an articulating knee
`brace utilizing nested spherical hinge cups to accurately
`mimic the actual movement of the human knee. The
`movements of ?exion/extension, rotation, abduction
`/adduction, and rollback and glide are tracked by the
`brace during knee movement through the use of slots
`and rivets to manipulate the relationship between upper
`and lower brace structures to support the knee in its
`natural positions.
`
`14 Claims, 5 Drawing Sheets
`
`-1-
`
`Smith & Nephew Ex. 1043
`IPR Petition - USP 7,534,263
`
`

`
`US. Patent
`
`Apr. 28, 1992
`
`Sheet 1 of 5
`
`5,107,824
`
`G F
`
`‘ TRANSVERSE
`KNEE AXIS
`
`SAGITTAL PLANE
`( FLEXION~EXTENSIONI
`
`POSTERIOR
`
`E N A .l. P
`L A N o R 0 c
`(ABDU CTION ¢- ADDUCTIN]
`
`TRANSVERSE PLANE
`
`ROLLBACK )
`
`-2-
`
`

`
`US. Patent
`U.S. Patent
`
`om,2L
`Apr. 28, 1992
`2991
`
`5f02tee..nS
`Sheet 2 of 5
`
`5,107,824
`5,107,824
`
`H65
`
`30
`
`D.’’Asovvfivflvs
`
`-3-
`
`
`

`
`U.S. Patent
`US. Patent
`
`Apr. is, 1992
`Apr. is, 1992
`
`Sheet 3 of 5
`Sheet 3 of 5
`
`5,107,824
`5,107,824
`
`-4-
`
`

`
`U.S. Patent
`US. Patent
`
`Apr. 28, 1992
`Apr. 28, 1992
`
`Sheet 4 of 5
`Sheet 4 of 5
`
`5,107,824
`5,107,824
`
`-5-
`
`

`
`U.S. Patent
`
`Apr. 28, 1992
`
`Sheet 5 of 5
`
`5,107,824
`
`FIGJOA
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`30°FLEXl0N
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`
`-6-
`
`

`
`1
`
`ANATOMICALLY CORRECT KNEE BRACE
`HINGE
`
`5,107,824
`2
`tibial plateaus. Rolling motion determines the “roll
`back" of the femur on the tibia during ?exion. The ratio
`of rolling to gliding motion differs in the lateral com
`partment compared to the medial. This kinematic fac
`gives rise to the phenomenon known as “differential
`roll-back.”
`'
`The knee joint is often times subjected to a loading
`force equal to several times the body weight in level
`walking. These forces increase with running or other
`“impact loading” activities. Loads are not transmitted
`over the joint surface equally but rather over a rela
`tively small area of each femora condyle and the tibial
`plateau. The medial side of the joint bears a larger load
`than the lateral; but the medial plateau is also larger
`than the lateral; therefore, the force per unit ar is ap
`proximately equal.
`The con?guration of the femoral condyles is asym
`metric. The lateral condyle is broader in the sagittal an
`transverse planes than the medial condyle The medial
`condyle projects distally to a level slightly lower than
`the lateral. This distal projection helps to compensate
`for the varus (toward) inclination in the femur with
`respect to the vertical axis. As a result, in the erect,
`in~line position, the transverse plane of the condyles lies
`near the horizontal.
`_
`As the knee approaches full extension, it can be con
`sidered that the femur rotates internally (as concur
`rently the tibia is rotating externally) allowing the ante
`rior articular surface of the medial femoral condyle to
`come in contact with the anterior portion of the medial
`tibial plateau. The lateral condyle moves anteriorly
`(forward) more rapidly than the medial, thus producing
`the phenomenon of the “screw home mechanism", until
`the knee is “locked” in the fully extended position. This
`rotary movement passes through a series of polycentric
`
`5
`
`30
`
`BACKGROUND OF THE INVENTION
`Many brace devices have been advanced to provide
`control for the movement of the human knee after in
`jury, during recuperation after injury, and to optimize
`the protection and healing thereof. Prior devices have
`exhibited a conspicuous absence of satisfactory under
`standing of knee anatomy and especially knee kinemat
`ics. In order to appreciate the full worth of this inven
`tion, a general understanding of knee anatomy and kine
`matics is desirable.
`The knee joint includes three bones, the patella, the
`femur and the tibia. The distal end of the femur consists
`of a bicondylar structure which refers to the two blunt
`projections, known as “condyles", forming the lower
`end of the femur. These two condyles, medial (inner)
`and lateral (outer), are asymmetrically cam-shaped. The
`proximal end of the tibia is comprised of a specialized
`surface termed the tibial plateaus upon which the corre
`sponding condyles articulate.
`Unlike the hip joint, where the contour of the joint is
`a primary stabilizing factor, a primary stabilizing factor
`in the knee is the surrounding supporting tissue such as
`the fibrous capsule with its specialized components, the
`capsular ligaments and the menisci. Most important to
`stabilization in the knee, are the two intra-articularly
`located cruciate ligaments.
`Knee stability can be considered in terms of static and
`dynamic stability. The above-noted structures are im- _
`portant in both instances, but during motion, certain
`muscle units become increasingly important, not only in
`terms of knee joint stability, but also in terms of carry
`ing out the normal knee kinematics.
`The mechanical axis of the lower limb can be said to
`extend from the center of the femoral head to the center
`of the ankle joint, passing near to the center of the knee.
`40
`The true vertical axis is a line that extends from the
`center of gravity of the body down in the direction of
`gravity in a plane perpendicular to gravity. In the nor
`mally aligned lower limb, the mean mechanical axis of
`the leg is angled 3 degrees toward the true vertical axis.
`The femoral shaft is angled downward approximately 9
`degrees toward the vertical axis and the tibia is angled
`approximately 6 degrees outward (valgus) with rela
`tionship to the femur.
`The knee is a complex joint with multiple move
`ments. Anatomically, the knee is classi?ed as a diarthro
`dial joint of the ginglyrnus (hinge) type; however, even
`this broad de?nition does not do justice to the complex
`series of movements that occur during normal knee
`motion.
`The ginglymus connotation refers to the llexion and
`extension movement, but ?exion and extension do not
`occur about a ?xed transverse axis but rather about a
`constantly changing center of rotation. This particular
`aspect of knee motion has been appropriately labeled
`“polycentric rotation”. This phenomenon; however,
`considered by itself, falls short of describing the kine
`matics of the human knee.
`.
`During ?exion and extension in the sagittal plane,
`simultaneously abduction and adduction are occurring
`in the coronal plane and internal rotation and external
`rotation are occurring in the transverse plane. To carry
`the complexity further is the phenomenon of combined
`rolling and gliding motio of the femoral condyles on the
`
`45
`
`50
`
`55
`
`60
`
`axes.
`
`’
`
`The workers in the prior art have utilized a variety of
`hinge members in an attempt to track the sliding and
`roll-back of the condyles with respect to the tibia pla
`teaus. However, none of the prior art has accomplished
`an external knee hinge mechanism that accounts simul
`taneously for the differential roll-back, the rotation of
`the tibia with respect to the femur during ?exion and
`extension, and the abduction/adduction movement that
`occurs concurrently with the other movements. A pre
`ferred embodiment of this invention has accomplished
`this through a series of slotted curvilinear shells all of
`which have their concave surfaces facing in the same
`direction.
`
`FIELD OF THE INVENTION
`This invention relates to a hinge mechanism that
`tracks the aforementioned complex movements of the
`knee when the hinge is used with leg bracing.
`A principal objective of this invention is to provide
`better protection to the knee, to allow for better healing
`of an injured knee and/or to protect the knee during
`sports activity. The hinge is utilized with bracing de
`signed for the aforementioned activities.
`It is another principal objective of this invention to
`provide a knee brace having novel hinging that im
`proves the prior art by providing apparatus that accu
`rately reflects average normal knee behavior so as to
`reduce the strain on all connecting elements of the knee
`during recuperation.
`Another important objective of the invention is to
`provide a novel hinging arrangement which can be used
`
`-7-
`
`

`
`3
`on devices that permit normal knee movement over a
`selected portion of the knee's ilexion and extension
`capability.
`Another important objective of the invention is to
`provide a novel hinge mechanism that utilizes a series of 5
`curved shells, all of which are facing in the same direc
`tion, which positioning maximizes the ability of the
`brace to track knee movements anatomically, including
`"the rotation, the abduction/adduction, and the differen
`tial roll back movements.
`Still another important objective of this invention is
`to provide a hinge for use with a bracing mechanism
`having means to engage the tibia section of the leg and
`means to engage the femur section of the leg, with an
`interconnecting hinge arrangement on either side of the 15
`knee, to permit limited ?exion and extension of the knee
`motion, in an adjustable manner
`Another objective of this invention, because of its
`relative simplicity, lightweight design and its ability to
`track normal knee movement, is to provide an accident- 20
`preventative apparatus for use by athletes whose legs
`are subjected to severe stresses; and by the athlete who
`has pre-existing ligament and cartilage injury that must
`be protected.
`‘
`Another objective of this invention is to provide a 25
`hinging arrangement that includes a series of cup
`shaped elements which are used in conjunction with
`slots formed therein to accurately track the anatomical
`movement of the knee during flexion and extension.
`Another objective of this invention is to provide
`hinging that is uniquely designed to allow for polyaxial,
`multi-planar, asymmetrical movement._
`These and other objectives of this invention can be
`more readily understood by reference to the attached
`speci?cation and drawings.
`
`30
`
`35
`
`5,107,824
`4
`FIG. 6 is an exploded, diagrammatic-schematic per
`spective view of the hinge at the normal or full exten
`sion position of the leg;
`FIG. 7 is an exploded diagrammatic-schematic per
`spective view of the hinge showing the tibia with re
`spect to the femur at 45° of flexion;
`FIG. 8 is an exploded, diagrammatic-schematic per
`spective view of the hinge with the knee in its 75° ?exed
`position;
`FIGS. 9A, 9B, and 9C are diagrammatic views illus
`trating how the curvilinear components account for
`abduction/adduction and rotation during knee flexion;
`FIGS. 10A through 10D are further diagrammatic
`representations of knee positions during various phases
`of ?exion.
`
`10
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`FIG. 1 is a diagrammatic front elevation showing the
`leg components and their relationship with one another.
`As shown, the approximate mechanical axis of the nor
`mal or average human leg extends from the center of
`the hip joint to the center of the ankle joint and passes
`near to the center of the knee. This axis of the leg is
`angled 3 degrees toward the vertical axis of the body.
`The femur shaft axis is directed at an angle of 9 degrees
`toward the true vertical axis of the body and the tibia is
`aligned with the mechanical axis which is directed 3
`degrees toward the vertical axis of the body. Thus,
`there is approximately a 6° outward (valgus) angle be
`tween the femur and the tibia in the mean con?guration
`of a human knee.
`FIG. 2 discloses the knee joint in perspective and
`superimposes three perpendicular planes therethrough;
`namely, the sagittal plane in which flexion-extension
`movements occur; the transverse plane in which roll
`back and rotational movements occur; and the coronal
`plane in which abduction and adduction occurs. Move
`ments are concurrent but it is convenient for purposes
`of description to identify the planes in which the princi
`pal components of movement take place.
`Referring now to the other drawings wherein like
`numerals refer to like parts, the numeral 10 refers to the
`brace of this invention. An essential component of the
`brace is its hinging apparatus, two principal elements of
`which are an outer or “lateral” hinge 12 and an inner or
`“media ” hinge 14. In this description, only the brace
`and hinge mechanism for the left leg is described. It is to
`be understood, of course, that the brace for the right leg
`will be a mirror image of that described herein.
`The femur of the wearer is indicated by the numeral
`16 and the tibia by numeral 18 in FIG. 6. At its upper
`BRIEF DESCRIPTION OF THE DRAWINGS
`- end, the tibia has two generally planar or plateau sur
`‘ faces indicated jointly by the numeral 20. The plateaus
`FIG. 1 is a front view of the skeletal framework of
`the lower body showing femoral, tibial, and mechanical 55
`are curved slightly but for purposes of this description
`are shown‘ as generally flat in FIGS. 6 and 7. The lower
`axes angles with respect to the vertical;
`end of the femur is bicondylar and is formed with a
`FIG. 2 is a perspective of the knee joint with the
`generally cam shaped lateral condyle 22 and a generally
`sagittal, coronal and transverse planes related thereto;
`cam shaped medial condyle 24. The lateral condyle 22 is
`FIG. 3 is a perspective view of a brace for the right
`larger than the medial condyle 24.
`leg of the wearer;
`The lateral hinge 12 (FIGS. 5 and 5A) is comprised of
`FIG. 4 is a side interior elevational view of the medial,
`(inner) leg hinge component of FIG. 3;
`an inner shell or cup 26 having an extension 28 that is
`generally parallel to the femur and an outer shell 30
`FIG. 4A is a cross-sectional view along the lines
`having a downwardly directed extension 32 that is gen
`4A—4A of FIG. 4;
`erally parallel to the tibia. The outer shell 30 has an
`FIG. 5 is a side exterior elevational view of the lateral 65
`(outer) leg hinge component of FIG. 3;
`inner curvilinear surface 31 having the same radius of
`FIG. 5A is a cross-sectional view along the line
`curvature as, and mates with, the outer spherical surface
`5A-—5A of FIG. 5;
`34 of shell 26.
`
`SUMMARY OF THE INVENTION
`The brace of this invention provides a mechanism to
`accurately track the anatomical motion of the human ,
`knee. This anatomical tracking, when used with brac
`40
`ing, protects the knee and reduces stress on the anatomi
`cal parts of the knee, particularly the ligaments.
`Treatments for which the brace is used include,
`among other applications, rehabilitation following sur
`gery to the knee, protection for an injured or surgically 45
`repaired knee, and protection for an uninjured knee Its
`use will be applicable for most types of surgical repairs
`to the knee and in the prevention of many types of
`damage to the knee. The brace of this invention and its
`unique hinging apparatus permits movement of four
`distinct types in three dimensions simultaneously.
`
`50
`
`-8-
`
`

`
`5,107,324
`5
`The medial hinge 14 (FIGS. 4 and 4A) has an inner
`shell 36, the convex surface 38 of which is placed adja
`cent the knee. The concave surface 40 of shell 36 mates
`with the convex surface 42 of a medial shell 44. All of
`the above-de?ned spherical surfaces have approxi-_
`mately the same degree of curvature and are facing in
`the same direction; that is, for the right leg, the concave
`surfaces 40 and 44 face to the left of the leg, and for the
`left leg, the concave surfaces face to the right of the leg.
`The shell 36 has a downwardly directed extension mem
`ber 48 and the shell 44 has an upwardly directed exten
`sion member 50. The extensions 28, 32, 48 and 50 pro
`vide anchoring means for brace shafts 116, 118, 136,
`138.
`'
`As seen in FIGS. 5 and 5A, the outer shell 30 or
`lateral hinge 12 is formed with a generally horizontal,
`slightly curved, slot 82 and a generally vertical, curvi
`linear slot 84. Shell 26 is formed with a pair of openings
`86 and 88 in which a pair of rivets 90 and 92 are re
`ceived. The rivets 90 and 92 respectively extend
`20
`through slots 82 and 84 in sliding engagement. The
`rivets secure shell 26 in close sliding engagement with
`shell 30. The rivets can be formed with headed ends or
`can take the form of a headed nut and screw. The rivets
`are stationary with respect to shell 26. Shell 30 moves
`relative to the rivets along a course de?ned by slots 82
`and 84.
`The inner shell 36 of the medial hinge 14 (FIG. 4)is
`formed with a generally vertical, slightly curved, slot
`94 and a curvilinear slot 96. The slot 96 extends from a
`generally vertical straight position to a generally
`straight horizontal position with an arcuate position
`therebetween. The shell 44 is formed with openings 98
`and 99 (not shown, in FIG. 40 but similar to openings 86
`and 88) in which rivets 100 and 102 are received. Rivets
`100 and 102 are also received respectively by slots 94
`and 96. The rivets secure shell 44 and shell 36 together.
`These rivets can also be formed with heads or with nut
`and bolt arrangements In either event, the rivets are
`stationary with respect to shell 44, shell 32 moves along
`a course de?ned by slots 94 and 96. Three-dimensional
`movement of the knee brace is governed by the shapes
`of the slots and the spherical shape of the shells.
`As stated above, the mating surfaces of the shells
`45
`have approximately the same radius of curvature. The
`radil are close enough to permit a close sliding engage
`ment. In the disclosure, the reference apices of these
`curves are represented by the pinholes P1, P2, P3 and
`P4 respectively formed in the shells 30, 26, 36 and 44.
`When the brace 10 is secured to the leg of a wearer in its
`extended or unflexed position, pinholes P1, P2, P3 and
`P4 are coaxially aligned on the transverse axis of the
`condyles 22 and 24 as shown in FIG. 6. See axis 152.
`The aforementioned hinge elements 12 and 14 form
`the movable portion of brace 10. Although hidden in
`FIG. 6, P2 and P4 are directly behind P1 and P3 respec
`tively. At its upper end, brace 10 includes a pair of
`opposing plastic cuffs 110 and 112 to grasp the thigh of
`a wearer. Between the cuffs and the leg is a foam pad
`ding 114.
`Extending upwardly from extension 50 and con
`nected thereto is a bracing shaft 116 that is ?xedly se
`cured to cuff 112. Extending upwardly from extension
`28 of shell 26 is a bracing shaft 118 that is ?xedly se
`cured to cuff 110. Circumscribing the cuffs and shafts
`are a pair of straps 120 and 122. The straps can have a
`buckle or be equipped with a Velcro fastening means.
`After the cuffs are placed about the thigh, the straps 120
`
`6
`and 122 are tightened so as to provide a snug ?t. A pair
`of retainers 124 and 126 connect the cuff units to reduce
`rotational slippage between the thigh and the cuffs. It
`should be noted here that extensions 116 and 118 are
`aligned with one another and the femur. Respective
`movement among these members and the femur is not
`desirable. The purpose of the cuffs and upper bracing is
`to minimize such respective movement.
`At its lower end, the brace 10 includes a pair of op
`posing plastic cuffs 130 and 132 that grasp the lower leg
`therebetween. Extending downwardly from extension
`48 is an inner tibia limb brace 136 and extending down
`wardly from extension 32 is an outer tibia limb brace
`138. The braces 136 and 138 are respectively secured to
`cuffs 132 and 130. A foam padding 134 is disposed be
`tween the rigid cuffs and the lower leg. The cuffs 130
`and 132 are retained in a close and snug engagement
`with the lower leg by buckled belts or straps 142 and
`144 similar to straps 120 and 122. These four straps can
`also be equipped with Velcro surfaces. As noted with
`respect to the femur above, this system of cuffs and
`braces is intended to minimize movement between the
`wearer's leg and the brace structure.
`As noted above, the knee is a complex joint which
`exhibits of several distinct movements occurring simul
`taneously. It is the ability of the present invention to
`accommodate these movements which allows close
`tracking of the anatomical movement of the human
`knee. These movements can be reduced to four basic
`types consisting first of the ?exion/extension movement
`in the sagittal plane (FIG. 2); second, the internal/exter
`nal rotation movement in the transverse plane (FIG. 2);
`third, the abduction/adduction movement in the coro
`nal plane; fourth, “rollback”, is a combination of the
`rolling motion and the gliding (spinning) motion of the
`femur on the tibia in the transverse plane (FIGS. 10
`A'-l00”)
`The ?rst element of ?exion and extension is the rota
`tion (swinging) of the tibia about the transverse condy
`lar axis 152. Rather than simple mechanical hinging
`about this axis, the tibia undergoes polycentric motion
`travelling about a continuously changing center of rota
`tion as flexion progresses. The tibia does not in fact
`swing about the condylar axis but rather rotates about a
`point which changes as a function of the ?exion angle.
`As such, a simple pin hinge design knee brace fails to
`accommodate this polycentric movement.
`FIG. 7 depicts a ?exion position of approximately 45°
`between the femur and the tibia. In this description, the
`tibia is shown as it ?exes and rotates with respect to the
`femur. Of course, the tibia could be held stationary and
`the femur flexed as there is a degree of ?exion in both.
`But, for purposes of clarity, FIG. 7 suggests a ?exion of
`the femur with respect to the tibia. The various ?gures
`of FIG. 10 display this swinging movement.
`The second of the four distinct movements inherent
`in the physiological motion of the knee is found in that
`‘ the tibia rotates slightly counter-clockwise (viewed
`from the top of the right knee) with respect to the femur
`during ?exion. This rotation can best be understood
`with reference to FIGS. l0A-10D. This is a ?gure of
`the right knee when viewed from the top. Note ‘the
`counter-clockwise progression of the foot orientation D
`in the transverse plane as ?exion continues from FIG.
`10A to FIG. 10D, thus exhibiting rotation of the tibia
`with respect to the stationary femur.
`The third distinct movement of the knee is the abduc
`tion/adduction motion. As the knee flexes, the tibia
`
`40
`
`55
`
`65
`
`-9-
`
`

`
`5,107,824
`8
`the new points of contact A1 and B1 remain relatively
`constant with respect to surface 20.
`At 90° ?exion, the areas of contact A2 and B2 move
`slightly rearwardly (FIG. 10C) Note that E2 (the lateral
`point of contact) has moved more than A2. Note that
`foot orientation has moved from slight external rotation
`(slewfoot) to slight internal rotation (pidgeon-toed).
`FIGS. 10C’ and FIG. 10C" show that the lateral con
`dyle has shifted posteriorly (backward) more than the
`
`medial condyle. ,
`
`.
`
`_
`
`7
`undergoes a side-to-side swinging movement in the
`coronal plane known as abduction/adduction. See ar
`rows A-A in FIG. 1. As flexion begins, the tibia moves
`toward the midline (vertical axis) and at about 90 de
`grees the tibia moves then slightly back away from the
`midline until full ?exion is reached.
`The fourth distinct movement of the human knee is
`the posterior (backward) migration of the femur with
`respect to the tibia during flexion. This posterior migra
`tion is referred to as “rollback”. In the human knee this
`motion is asymmetrical. The lateral femoral condyle’s
`“rollback” is greater than that of the medial. This move
`ment can be quanti?ed in terms of millimeters. The
`mean rollback for the lateral femoral condyle is 24 mm
`whereas for the medial it is 10 mm. Naturally, as with all
`movements of the human knee, these are mean quantita
`tive values but qualitatively relate to the~anatomical
`phenomenon of “differential
`rollback.” FIGS.
`10A-10D demonstrate this phenomenon.
`FIGS. 10A’-10D’ are a schematic side view of the
`medial femoral condyle in relationship to the medial
`tibial plateau As the femur ?exes on the tibia the con
`dyle “rollsback” to contact a progressional more poste
`rior point on the plateau
`
`20
`
`25
`
`FIGS. 10D, 10D’ and 10D" show position at l40°
`?exion. In FIG. 10D the foot orientation is in further
`internal rotation. The lateral condyle has shifted poste
`riorly (backward) further than the medial condyle as
`depicted in 0 FIGS. 10D, 10D‘, and 10D" as stated
`previously, this ultimate change from 0° ?exion for the
`medial condoyle is roughly 10 min and for the lateral is
`roughly 24 mm.
`The hinge herein presented is designed to produce an
`anatomically correct position for each degree of flexion
`with respect to the above four movements to closely
`mimic the natural state of the knee. The ?rst distinct
`motion, the ?exion/extension is accomplished through
`the path of rivets 90 and 92 in conjunction with rivets
`100 and 102. For the purposes of the ?rst distinct move
`ment, the respective shells can be considered to be ?at
`as only the projections in the sagit'tal plane have bearing
`on this motion. As noted above, the knee changing.
`Respective shell movement is restricted to that de?ned
`by the rivets and slots and thus produces the required
`polycentric movement.
`As shown in FIG. 5, the center of rotation C of hinge
`member 30 at any time is determined by the intersection
`of the normal lines to the curves 82 and 84 at the points
`of rivets 90 and 92 respectively. Similarly, the center of
`rotation of hinge member 36 at any time is determined
`by the intersection of the normal lines to the curves 94
`and 96 at the points of rivets 100 and 102 respectively.
`Given the changing degree of curvature of respective
`slots, the normal lines to these curves intersect at differ
`H ent points as ?exion proceeds. Thus, although the cen
`ters of rotation of hinge members 30 and 36 remain
`?xed, the center of rotation of the upper hinge members
`26 and 44 or-the centers of rotation of each hinge
`changes continuously. Since the overall axis of the
`brace is determined by the line which joins the centers
`of rotation of hinges 30 and 36, the end result is that the
`brace rotates about a constantly changing axis, closely
`approximating the actual movement of the human knee.
`For example, at full extension, rivets 92 and 102 are at
`the lowest point of their paths, rivets 90 and 100 are at
`their frontmost positions, de?ning an axis of rotation for
`the brace which approximately lies on the condylar axis
`152 at C1. As ?exion begins, the rivets 92 and 102 begin
`moving up, (superiorly) while rivets 90 and 100 move
`rearwardly (posteriorly), leading to an axis of rotation
`which lies to the rear and below the original condylar
`axis 152 at C2.
`The particular curve shapes necessary to accomplish
`polycentric motion which accurately tracks knee move
`ment was determined empirically to be as shown in the
`drawings.
`_
`To accommodate the second distinct movement, ro
`tation, the present hinge design provides a spherical
`component in hinge members 30 and 36 which produces
`a rotation during ?exion between upper and lower
`brace portions FIG. 6 depicts the femur 16 disposed
`centrally of tibia plateau 20. The leg is in its unflexed or
`
`This rolling distance traveled is approximately 10 mm in
`the mean (average) human knee.
`FIGS. 10A"—10D” are a schematic side view of the
`lateral femoral condyle in relationship to the lateral
`tibial plateau. As the femur ?exes on the tibia, the lateral
`condyle “rollsback” to contact a progressively more
`posterior point on the plateau
`
`(B1, B2, B3)
`
`30
`
`35
`
`50
`
`On this lateral side, the distance traveled is greater,
`approximately 2.4 times greater, than on the medial
`side. This difference produces the phenomenon of “dif
`ferential rollback”.
`These movements are not in fact isolated but actually
`occur concurrently. The resulting motion is a complex
`composite of ?exion-extension, internal-external rota
`tion, absduction-adduction and “differential rollback”.
`The prior art, heretofore, has not been able to accom
`modate this complex movement to accurately track the
`true anatomical motion of the knee. Reference to the
`various ?gures of FIG. 10 illustrates the relationship
`between these four basic movements. FIG. 10A shows
`the right'knee at 0° ?exion looking downwardly in the
`traverse plane. It shows foot orientation is slightly an
`gled to the right FIG. 10A’ is a side view of the medial
`femoral condyle and tibial plateau 10A” a side view
`from the lateral femoral condyle and tibial plateau. The
`letter A represents the point of contact of the medial
`condyle and the letter B the point of contact‘of the
`lateral condyle with surface 20.
`FIGS. 10B, 10B’ and 10B" show position at 30° ?ex
`ion. In FIG. 10B note that foot orientation has moved
`counterclockwise, exhibiting rotation, and the condyles
`have glided slightly backward so that their areas of 65
`contact remains generally central of the tibia plateau,
`thus exhibiting roll-back. At 30°, although the original
`areas of condyle contact with surface 20 have moved,
`
`55
`
`60
`
`-10-
`
`

`
`5
`
`25
`
`20
`
`5,107,824
`10
`9 .
`movement is greater on the lateral side of the knee than
`extended position. The femur 16 and the tibia 18 lie
`.it is on the medial side to accommodate “differential
`along the generally vertical axis 150. The centers of
`rollback”. The generally horizontal slot 82 permits
`curvatures of the shell units are disposed along the
`greater rotational movement about the knee on the
`transverse axis 152, which axis is also aligned with the
`lateral side whereas the vertical slot 94 restrains rota
`transverse omit axis of condyles 22 and 24. Because of
`the spherical character of the shells, rivets 90, 92, 100,
`tion on the medial side movement. The above men
`tioned polycentric rotation completes the accommoda
`and 102 induce movement between the respective shells
`tion qf “rollback”. As the center of rotation changes,
`in the coronal plane during ?exion. Note that, in the
`the femur condyles are guided posteriorly to closely
`fully extended position, rivet 92 is at the lower (distal)
`end of slot 84, rivet 90 is at the forward (anterior) end of
`mimic the actual movement of the knee.
`slot 82, rivet 102 is at the lower (distal) end of slot 96,
`FIG. 7 shows a series of apertures 160 are formed in
`and rivet 100 is at the upper (anterior superior) end of
`shell 26. These apertures are located along a path fol
`lowed by an upwardly (superiorly) extending lug 162 of
`slot 94. Thus, when the hinges are viewed from the
`front of the right knee of the wearer, rivets 92 and 102
`shell 30. The apertures and slots are adapted to receive
`are located in their inward, (closer to the knee) loca
`a nut and bolt and used to prevent any movement in the
`tions and rivets 90 and 100 are located near the apexes
`hinge. More commonly, stop cams 166 are inserted into
`of the shells and are at, or near, their outward positions
`apertures on either side of lug 162. This limits the move
`(farthest from the knee). The differences in relative
`ment of shell 30 with respect to shell 26 to the area
`movement between hinges 30 and 36 produce the afore
`between stop cams 166. Thus, the attending physician
`mentioned rotation.
`can adjust the degree of movement permitted during
`Rotation can be best understood with reference to
`each stage of rehabilitation.
`FIGS. 9A, 9B, and 9C hereinafter described. In FIGS.
`It should be understood that rotation, roll-back, a