Overview of Knee Disarticulation

Gerald Stark,BSME,CP,FAAOP

Knee DisarticulationAdvantages/ChallengesBiomechanicsImpression TechniquesInterface DesignsKnee Types

Knee Disarticulation Prevalence0.7-2%1

20% in Some Centers2

CopenhagenToronto

Superior FunctionPoor CosmesisMost aren’t Optimized

Socket DesignAlignment

Slowly Declining KD NumbersMedicare KD Services

0

50

100

150

200

250

300

350

400

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001

Year

Num

. of S

ervi

ces

L5310-11L5150

Knee Disartic AdvantagesDr. Pinzur, Loyola Univ. 2

Full EndbearingMore Physiologic than AK,BK

Longer Lever ArmBetter Sitting BalanceSelf-Suspension

Lower TrimlinesPhysiologic

Decreased Blood LossResistance to Infection

Growing Use in ChildrenPreserves Femoral EpiphysisAvoids Bony OvergrowthDirect Load TransferGrows at a Slower Rate

Growth RestrictionFit as Transfemoral

Knee Disartic ChallengesDifferent than Transfemoral

Fewer NumbersLess CosmeticLength for Componentry

Limited componentryAccommodate Bulbous EndKC Proximal to Distal End

Surgical TechniquesPat. Tendon Sutured to Cruciate

Retain PatellaGastroc Wrapped Anterior for PadReduction Osteoplasty

Not for Vascular PatientsSagittal or A-P ClosureGritti-Stokes AmputationIPOP Rarely Provided

Knee Disartic BiomechanicsFull Weight BearingFulcrum Under Knee

Center of Rotation DistalNo Prox. Weight Bearing

Non-ischial Wt. BearingProximal Medial PressuresKD inverse of TFLower Trimlines

Impression TakingSelf-Suspension & Load Bearing 50%-50%Load Bearing

Adjustable StandVolumetric Control

Not Applying TensionMedial Wall ShapingNo Ischial or Gluteal Wt Bearing

Can’t Tolerate the Weight

Interface DesignsMolded LeatherMedial DoorStovepipe-Pelite BuildupPneumatic Pads or SleeveLiner w/SuctionLiner w/LockPartial Suction w/TES BeltSegmental Socket w/Strap

Molded Leather LinerUncosmetic & CumbersomeAdjustable ContoursDifficult to Make

Leather LinerAdaptable ShapeCreates Suspension

Different Tensions

Medial DoorExternal Strap & DoorVolume Adjustable

Don’t Need PadsCondylar Shape CrucialSlightly More ComplicatedFull End BearingCan use a Sock

Stovepipe-Pelite BuildupMore Bulky

Increased Wall ThicknessEasy to Use & MakeMore EnclosedMore PaddingGood for Bony LimbsSplit Distal Cup over Condyles

Pneumatic Pads or BuildupPneumatic PadsSilicone BuildupExcellent Suspension

Superior ComfortDifficult to Fix Volume ChangeComplicated ConstructionThicker Wall

Liner w/SuctionGel Liner w/ Leak ValveDistal Valve

Constant LeakMini Valve in Attachment

Most PopularMay Inhibit Weight BearingVolume Dependent

Add PadsIncreases Distal Bulk

Partial Suction w/TES BeltHypobaric Sock w/ ValveProximal Suspension

TES BeltBulky; Could use Self-Suspension

Not as Volume DependentCan use a SockMore End Bearing

Liner w/LockLiner w/ External Lock

Summit Lock~Coyote DesignsSki Binding LockMust Glue OnExternal HoleAccommodate Volume Change

Segmental Socket w/StrapZettl Type-Growth Comp. 3

Distal End CupProximal Cuff

Expanding BarsSupracondylar StrapsGrowth Compensation

JuvenilesLess Contact w/Skin

Knee DesignsExternal Knee HingesSingle Axis KneeWeight Act. Friction ControlPolycentric HingesManual LockingControl Options

FrictionHydraulicPneumatic

External HingesLess Cosmetic

Cumbersome, Damages ClothsNo Inherent Stability

Set More AnteriorDictated by KC

Back Check & Ext. AssistLeather Upper

Great Custom FitEasy to SuspendAccommodates Bulbous End

Exoskeletal Variations

PolycentricKD Specific Kinematics

Smoother MovementShin Shortening

Less Stability RequiredVertical Anterior Link

Longer Posterior LinkGreater Translation

Proteval Acphapend

More ProximalMore AnteriorDescends DistallyMore Voluntary Control Some Involuntary Stability

Century 22 Total Knee

Very Proximal CenterDescends RapidlyLock Mechanism

Toe Moment NeededEasy Moving 15 mm Clearance

Enhanced Voluntary Control

Proximal CentrodeMoves AnteriorEasy to FlexDoes not Lock Patient“Triggered” 4-Bar24mm Clearance

Control OptionsFriction Control

Mechanical SpringHydraulic

Hosmer YokePneumaticManual Locking KneeStance Flexion Control

References1) Bennet, A, Limb Prosthetics, 6th edition, Demos Publications, New York, NY, 1989.2) Pinzur, M., Chapter 19A: Knee Disarticulation/Surgical Procedures, Atlas of Limb Prosthetics, 2nd Edition, Mosby Year book, St. Louis, MO, 1992.3) Michael, J., Chapter 19A: Knee Disarticulation/Prosthetic Management, Atlas of Limb Prosthetics, 2nd Edition,, Mosby Year book, St. Louis, MO, 1992.4) Jennings, J., Wontorcik, L., “Fitting a Knee Disarticulation as a BK Utilizing the ALPS Locking Pin as a Pseudo-Tibial Lever: A Single Case Review”, Journal of Prosthetics & Orthotics, 1998, Vol. 10, Num. 1, pp. 7-10.5) Kempfer, J. “Technical Note: Thermoplastic Use in the Geriatric Knee

Disarticulation Prosthesis”, Journal of Prosthetics & Orthotics, 1991, Vol. 3, Num. 1, pp. 38-40.