GB2443493A - Knee brace connected to a lower limb cast - Google Patents

Abstract

A knee brace has ribs or grooves <B>6</B> on a outside edge of a lower section thereof. A lower limb cast has corresponding grooves <B>7</B> on a inner portion at an upper section of the cast. These grooves <B>6, 7</B> enable the distance between the knee and ankle to be adjusted. The knee brace may have a single or double hinge joint <B>2</B> to enable flexion of the knee.

Description

Novel thermoformable (to tibial notch and blade) or part customised

(for size and contra-lateral choice) knee brace1 with medial single pivot and lateral double pivot hinge joint mechanisms to better simulate knee action between the femur and tibia.

(Singular and in combination to patent No: 0621749. 1, Backqround During 2001-2002 (following SMART award to Mr. S.M. Scott), Dr M. Gregory (l project mentor) identified a potential collaborator (Kelvin Doyle) towards a combination device with patent no. 0621749.1. (On the basis that it would be mutually beneficial not to be "one product companies").

The main market Kelvin addressed for his product was high performance sports (motorbike and siding/used by most Olympic skiers at time)-/-as opposed to medical), he received an excellent review in subjective testing ng*inst every other competitor as "most comfortable knee brace.. ever worn".

It has been also sought after by patients and clinicians (mentioned in at least one clinical blog), in one case offering an to option amputation [due to severe damage to the knee joint]. Its a Millennium Award Winner (exhibited in the New Millennium Dome 2000).

The main asset of the tibia! rotation component is that it moves to track the outer surface topography of the tibial notch and upper blade of shin. This can be seen looking at; the diagrams of left and right knees, the symmetrical form of the Dii knee brace, the common axis (to right'left knees and Dil brace) and overlapping the diagrams (4-6). It to rotate to fit left or right limbs. The niimaging directer of SkiRider.UK (also an ethusiastic customer of his product) said the knee brace "stabilises the knee". He also mentioned that Mr Doyle had stopped manufacting.."iooking towards refinancing... one and a half years ago" (stopped production around 2005/6).

Its fair to assume that although this device (in the sports arena) has been aclaimed (through subjective comparative testing for comfort and functionality/bracing-ligament support) as better than its competator braces...the high cost carbon/resin materials lost out to cheaper thermoplastic braces.

The DII braces however, were interchangRbie to right or left knees (they came in pairs), so the rotation clement merely alows the leg/ tibia! notch surface area to rotate into place. I.E.; the device is symetrical (if cut down the middle longitudinally and mirrored)...whereas the human leg isn't.

In hindsight, it would have been better to develop the Dii brace for left OR right knees (and double the size range), although for this high performance (impact etc) area of the brace market, the tooling costs may have been too high. Having the rotation aspect also may have looked good as a design feature in its "high tech" sports market place.

But in terms of mass production using lower cost tooling and materials (LB. high temperature oven -vaccuum formable) this would be "gimmicky" and unnecessary for the lower stress requirements and simple use of device (as independent item or combination) for remedial gait purposes.

(In my Initial patent for this combination device, I assumed that the rotation served to facilitate the rotation between tibia and femur that occurs during full leg extension.

However, this rotation occurs at the femur, with the lateral (outer (in surface topography and convex hinge function})condyle bone joint fact slightly projecting forwards during full leg extension-slight external femural rotation.) The comfort and stability of this device rests upon the brace being able to anchor the the precise surface topography of the upper tibial notch and blade. All other conventional knee braces merely anchor to the musculature/soft tissue (via straps and "space-age" open planed narrow ergonomic limb beams) and the sides of the tibial and femoral condyles (NB. even in the superior Dil device, this area recieves movement and friction, recommending a seperate knee sock (within padding), OR shaving the hairs around the condylar sides of the knee).

The essential design facet to this device is, either; 1) a low temperature thermoformable pannel OR/ 2) doubling any existing size range the size to re-distribute pressure evenly over every square millimeter of the right or left tibial notch and upper blade portion of the upper shin.

Ergonomic design.

By choosing the 2nd option, mimimal or no thermoplastic contour mouldable thermoplastic is required, where the brave follows the incline of the femur/shape of thigh, knee and leg topography (in frontal plane [see diagrams 4 & 9)]. It is specifical for right or left limb.

Simulation of knee joint using single and double hinge pivot wdi.

Studying radiographs (outlined in pen from photographic plates-refer to drawings 5& 6) to show progresion of femoral and tibial condyles during extension of the human knee, it can be noted that the inner/medial condyle of the femur stays fairly cenral to its pivot around 16) "point A",during extension (to full extension), whereas, the outer/lateral femoral codyle progresses significantly forward, 17) point B! and 18) point B2.

During knee flexion (from upright, fully extended "closed packed" position of knee joint, the politeus muscle serves to pull the lateral/outer femoral conyle back (see drawing 18) during external rotation of femur This motion can be externally simulated around the knee by employing two different hinge type mechanisms; the single hinge mechanism (as employed by "Ortholnnovations" and other knee brace companies) to simulate action around the medial tibial and femoral; codyles and the double hinge mechanism (as employed by DonJoy, Roadrunner and other companies) to simulate the action around the outer/lateral condyles.

Combination Device of total contact Cast and Knee Brace Before selling off its 50% share of BSN, Smith and Nephew saw the market potential of internal hip joints. A robust adjuct towards remedial gait management has economic advantages. The work! (Sean Scott) propose is of another perspective...ergonomic support to better enable natural bone or ulcer healing, as a functional anatomical exoskeleton.

The non-removable total contact cast (aside from immobilising against shear forces) off-loads around 30% of direct vertical forces/stresses onto the leg portion of the cast alone. .with further off-loading to knee and thigh, the applications are exciting: Case scenerio 1]; Patient with extensive plantar foot ulceration and severe limb ischaemia. A non-removable total contact cast will be employed by some clinicians to off-load weight from some ulccis in an ischaemic limb, but this isnt general theraputic style. Off.loading ground reaction forces to the the leg AND thigh would be more acceptable to many clinicians.

Case scenerio 2]; Severe destruction of talus or severe compound fracture of tibia where maximum vertical off-loading would be a great advantage.

Case scenerio 3]; Very severe compound fracture or multiple fractures to long leg bones as adjunct or independent to external surgical fixation.

Case sceneno 4]; Option to expensive below the knee prostheses (for example to manage land mine victims).

In terms of dynamic stress, an ergonomic leg cast walker that off-loads vertical weight to leg/knee and thigh would have tremendous implications for fracture and ulcer mmingement...it would also offer a far cheaper alternative to {argueably) "over-engineered", heavy, uncomfortable, un-aesthetic and expensive below the knee titanium-steel tubular prostheses. Its comfort would derive from off loading ground force reation to knee and thigh as oppossed to just a raw stump.

A combined device of ergonomic removable cast walker and knee brace presents exciting potential for management of severe injury and postoperative off-loading, it might for example have a role in the care of land mine victims as the knee can provide significant off-loading (from foot/leg), during the various forces occurring during gait that would be present around the lower limb.

Furthermore, the fore-foot area of the leg cast component could be adapted to retain elastic recoil of potential gait energy by hinging a line between the first and fifth metatarsal /toe joint axii to simulate the action of the Achilles tendon and other foot and leg muscular and joint facet tendon/collegen -elastic recoil during midstance and propulsion/toe off phase of gait.

The Knee hinge mecahnism as simulated by single and double hinge mechanismsAn ergonomic Dii type of device can also be further improved in 3 areas; 1) Choice of cushioning materials. (Comfort and better functional off-loading) The only criticism the Dil ergonomic brace received in subjective testing review was that the sides of the knee need to be shaved to prevent hair entrapment around the condyles of the knee.

A polymer-gel material (such as Neoprene) would help here, with respect to negotiating shear forces. Other padding could be replaced with thinner tn-density cushioning material as mentioned in uK patent 0623055.1.

A viable option to cushioning a combination device would be to extend I modify Patent 0623055.1 (removable casting sock) above the knee.

2) Increased redistribution of weight I pressure around thigh, h2mtrings, and back of calL (Comfort and better functional off-loading).

The Dii knee brace has straps behind hamstrings and calf. These could be replaced with a more continuous (breathable material) with a padded insert between the tendons of the hamstrings to prevent said straps "digging in".

A "basket weave" fabric would also give better conformity to curved ergonomic portion of calf and back of thigh. Allowing better "drape" to curved, dome-like surfaces (better than linear I flat biaxial fabric). The thigh portion of brace could also be extended further by an 1-3 inches, affording better off-loading and redistribution of forces during gait / ground reaction forces.

3) Increased size range and cheaper tooling (and materials) without the tibial rotation device features.

Increase/double size to fit left or right legs. Thus dispensing with any need to rotate shin portion into correct place for a unilateral device.

While the femur rotates slightly above the tibia during extension, this movement can be compensated surrounding muscular/soft-conformable tissue and a polymer gel at the condyles. /0W Tibial notch and blade conformed to by thermoplastic mesh within hinged outer frame.

Insert low temperature thermoplastic mesh pannels (3-7 sheets depending on size and body weight) within a sufficiently robust hinged frame of composite (glass/carbon short/medium strand) and high temperature thermoplastic sandwich.

These could also be adapted/gauged to height of knee (from sole offoof according to individual) by interlocking "ribs" set a 1-2 nun or so apart on knee brace and extensions front UK patent 0621749.1, surrounded by retaining thermoplastic moldable panels, retainingfabric and straps. (,4li streamlined and engineered to loading requiremenb fnol too bulky and over-engineered!).

Guide to DrawingslDiagrams Drawings 1 Fig! Where 1) shows novel knee brace customised to right knee, with, 2) single pivot hinge on inner/medial side. 3),4) and 5) shows adjustable thermoplastic mesh.

6) shows grooves I "ribs" on leg portion of knee brace removable leg walker leg component extension and 7) interlocking grooves within connecting wings of leg component of GB 0621749.1. 8) is the outer corresponding wing cut away to better reveal 7).

9) reveals recess to remove pressure away from base of head of flbula..where vthe popliteal nerve passes superficially. Nerve entrapment is a common cause of problems following serial casting of non removable total contact casting (below the knee t.c.c.-plaster /bandage/fibre-glass). Fig2

Shows sagittal cross section of interlocking "ribs", with 4) the lower outer leg poition and 5) the inner knee brace portion.

Drawings 2 Fig3 Shows 5) upper back low temperature panneis to hamsting area oppened to view with 10) padding to fit inbetween hamstring tendons and reduce pressure on hamstring tendons and Ii) overlying straps. Fig4

Shows transverse plane cross section through tibia! portion of knee brace with taper of thermoplastic mesh layers from 3) bony shin to 4) calf/ bi-lobes of gastrocnemius.

Drawings 3 Fig 5 Shows 1) knee brace with overlying leg walker connective extensions and I2XAs combination item -I-with media! and lateral shin extensions to lock onto GB 0.0621749.1 / removable leg walker) -leg walker to form a single off loading exo-skeleton from thigh, knee and leg to ground reaction forces.

Drawings 4 Fig 6 and Fig 6a Shows 13) right tibia/lower limb with 14) tibial notch and tibia! blade of shin.and 15) axis of knee hinge motion Fig 7 Shows example of 16) left leg/tibia/knee and thigh with 15) axis of joint and 14) tibia! notch and blade 11). Fig 8

Shows overlap of left and right legs.

Figs 9 and Fig 9a Shows outline of Dii type of device and 15) Axis of joint.

Fig 10 Shows overlap of left and right legs within Dil type of device, with 17) different positions of left and right shins Drawings 5 Fig 11 Radiographic outlined to show progresion of fèmoral and tibial condyles during extension of knee.

Note that the inner/medial condyle of the femur stays fairly cenral to its pivet around 16) "point A", whereas, during extension (to full extension), the outer/lateral femoral codyle progresses slightly but significantly forward, 17) point BI and 18) point 82.

Where, 18) is tibia, 19) is fibula, 20) is patella, 21) is inner/medial femoral condyle and 22) is lateral/outer feinoral condyle.

Drawings 6 Fig 12 Radiograph of knee with outer/lateral condyles removed to clearer see medial condyles of femur and tibia.

Fig 13 Simulation of inner condyles using single pivot/hinge.

Drawings 7 Fig 14 Radiograph of knee with inner/medial condyles removed.

Fig 15 Simulation of outer condyles using a double pivot/hinge mechanism.

Drawings 8 Fig 16 and Fig 16a Double hinge joint showing 23) cogs, 24) retaining bar and 25) "extension stop" facets of outer knee brace bars.

Fig 17 Frontal back view of knee bones and popliteus muscle with inner and outer single and double hinge/pivot joint mechanisms.

26) Popliteal muscle.

Fig 18 Shows 27) thinner lateral co-lateral ligament (allowing more forward/backward movement on outer/lateral condyles) and 28) wider medial/inner co-lateral ligament.

Drawings 9 Fig 19 Overlap of right and left limbs within Dii type of device.

FIg 20 Ergonic design to fir right lower limb.

Claims (1)

1. Claims Claim I A removable combination device comprising of removable

   knee brace and removable cast walker.

   Claim 2 A removable device as claimed in claim 1) where the lower portion of the knee brace component is attached to the upper leg component by way of inter-locking ribs.

   Claim 3 A removable device as claimed in claim 1) where the height of the knee brace can be adjusted by virtue of the spaces between the interlocking ribs and said spaces married with the lower limb partially weight bearing on lower limb (with both device components in place before fastening together with external bett etc).

   Claim 4 A removable device as claimed in claIm 1) where the knee brace portion of the combination device can be used/manufactured as a seperate item.

   ClaIm 5 A removable device as claimed in claim 4), where the tibia notch and blade of shin can be conformed to and held fast to knee brace by a thermoplastic insert between high temperature rigid sides/window descending from hinges.

   ClaIm 6 A knee brace as claimed in claim 4), where a single hinge pivot (with centre point axis at/very near swing/pivot centre of inner/medial femoral condyle. Comprising of just one central pin/rivot/retaining screw/bolt.

   ClaIm 7 A knee brace as claimed in claim 4), where a double hinge pivot (with centre point axii at outer/lateral femoral condyle. Comprising of two central pin/rivot/retaining screw/bolts. Allowing forward progression/movement of lateral femoral condyle during leg extension (thus simulating natural movement of knee within an exoskeletal brace.