Modern concepts of knee implants Modern concepts of knee implants Dr. Clemens Menapace Dr. Clemens...

Modern concepts of knee implantsModern concepts of knee implantsModern concepts of knee implantsModern concepts of knee implants

Dr. Clemens Dr. Clemens

MenapaceMenapace

FA für Orthopädie und orthop. ChirurgieFA für Orthopädie und orthop. Chirurgie

Ritter v. Schwarzstr. 8, 5400 - Hallein Ritter v. Schwarzstr. 8, 5400 - Hallein

www.menapace.comwww.menapace.com

Director of Director of the Departement for the Departement for

orthopedic and endoskopic orthopedic and endoskopic joint surgeryjoint surgery

Ritter v. Schwarzstr. 8 Ritter v. Schwarzstr. 8 5440-Hallein5440-Hallein

Guggenbichlerstr, 20Guggenbichlerstr, 205020-Salzburg5020-Salzburg

www.menapace.com

M.D. Orthopedy and M.D. Orthopedy and orthopedic surgeryorthopedic surgery

ClemensClemensMENAPACEMENAPACE

Modern concepts of knee implantsModern concepts of knee implants


Director of Director of the Departement for the Departement for

orthopedic and endoscopic orthopedic and endoscopic joint surgeryjoint surgery

Ritter v. Schwarzstr. 8 Ritter v. Schwarzstr. 8 5440-Hallein5440-Hallein

Guggenbichlerstr, 20Guggenbichlerstr, 205020-Salzburg5020-Salzburg

www.menapace.com

M.D. Orthopedics and M.D. Orthopedics and orthopedic surgeryorthopedic surgery

ClemensClemensMENAPACEMENAPACE


Dr. Clemens MenapaceDr. Clemens Menapace

Department for orthopedic and endoscopicDepartment for orthopedic and endoscopic

joint surgeryjoint surgery

www.menapace.comwww.menapace.com


Orthopedic surgery is getting more and more technically demandingOrthopedic surgery is getting more and more technically demanding


Component- design problems Component- design problems

Problems with materialsProblems with materials

complicated biomechanicscomplicated biomechanics

complicated anatomy of the kneecomplicated anatomy of the knee

Biological complexityBiological complexity

Technical complexityTechnical complexity

Developement of state of the art kneeimplant was impaired byDevelopement of state of the art kneeimplant was impaired by


Biomechanically the knee contains 3 separate jointsBiomechanically the knee contains 3 separate joints

MedialMedial

laterallateralFemorotibial jointFemorotibial joint

Femoropatellar jointFemoropatellar joint

The knee is a multi-ax system: center of ax-rotation changes during cycle The knee is a multi-ax system: center of ax-rotation changes during cycle of motionof motion

Flexion and Extension is a role- and glide - mechanism because of a Flexion and Extension is a role- and glide - mechanism because of a negativ (decreasing) condyle-radius causing shear-forcesnegativ (decreasing) condyle-radius causing shear-forces

During cycle of motion different combination of ligaments provide stabilityDuring cycle of motion different combination of ligaments provide stability

Complex BiomechanicsComplex Biomechanics


Complex Complex

BiomechanicsBiomechanics3 rotational axes of movement 3 rotational axes of movement

1 axis with moving center of rotation1 axis with moving center of rotation

rol & glide movement (translation-rol & glide movement (translation-rotation)rotation)

load-aera decreases in flexionload-aera decreases in flexion

(decreasing fc-radius)(decreasing fc-radius)

patellar biomechanicpatellar biomechanic


Complex AnatomyComplex Anatomy


In conclusion the Flexion / Extension movement of the knee is not a fixed hinge type system but rather a dynamic role- and glide- mechanism with an endrotation in full extension. Flexion and

extension is performed along several axes with dynamic centers of rotation secured statically by changing combinations of

ligaments and dynamically by groups/combinations of muscels.


Performance-requirements for an Performance-requirements for an efficent kneeimplnat/-endoprothesisefficent kneeimplnat/-endoprothesis

Physiological range of motion without undue stress on components

StabilityStability

LongevityLongevity


The ultimate goal is to imitate The ultimate goal is to imitate anatomy as anatomy as close as possibleclose as possible


Anatomically correctAnatomically correctDecreasing /negativ radius of femurcondyles has to be imitated Decreasing /negativ radius of femurcondyles has to be imitated

changing changing centers of centers of rotation rotation


Restore perfect alignementRestore perfect alignement

valgus varus

Alignement deficiencies have to be Alignement deficiencies have to be corrected painstakingly to avoid corrected painstakingly to avoid

peak-pressure locallypeak-pressure locally


preop postopPlanning of proper alignément


Restore perfect ligament Restore perfect ligament tension and balancetension and balance


Combination of low friction interfaceCombination of low friction interface

Ceeramics ceramicsCeeramics ceramics

Ceramics Ceramics PolyaethylenPolyaethylen

Metal PolyaethylenPolyaethylen

Metal Metal

FemurFemur TibiaTibia


stabel fixation of components to bonestabel fixation of components to bone

cementcement

Press fitPress fit

screw fixationscrew fixation


D e v e l o p m e n t

D e v e l o p m e n t


Stoneage of knee-implantsStoneage of knee-implants


GSB-Hinge-Type 1970 GSB-Hinge-Type 1970 semiconstraintsemiconstraint

Tour de France ?Tour de France ?


Fixed tbial bearing

The Vienna Derby


Mobile bearing Back into the futureBack into the future


CongruencyCongruency

High contact High contact stressstress

Low contact Low contact stressstress


Large contact area reduces Large contact area reduces contact stresscontact stress


Different qualities of force exacted on a fixed bearing implantDifferent qualities of force exacted on a fixed bearing implant


Constraint means that shear and torsion Constraint means that shear and torsion forces could be transmitted to fixation forces could be transmitted to fixation

interfaces and cause looseninginterfaces and cause loosening


Mobile bearing prevents sheering forcesMobile bearing prevents sheering forces


mobile patellar bearingmobile patellar bearing


cemented-noncemented mobile bearing systemcemented-noncemented mobile bearing system


Revision-surgeryRevision-surgery


Constraint systems in use for cases with severe bonedefectConstraint systems in use for cases with severe bonedefect

Tumor-surgery

Revison-surgery


Revision-surgery with semiconstraint knee -Revision-surgery with semiconstraint knee -prosthesis after failure of duocondylar implantprosthesis after failure of duocondylar implant


Semiconstraint implants for cases with sever Semiconstraint implants for cases with sever bonedefect, instability, malalignementbonedefect, instability, malalignement


Unicondylar implantsUnicondylar implants


MGII MGII NEXGENNEXGEN


Mobile bearing knee implantMobile bearing knee implant


Surgical Surgical principles principles of of

Duocondylar Duocondylar knee knee implnatsimplnats


Defining the resection lines by using a weight bearing total limb X-rayDefining the resection lines by using a weight bearing total limb X-ray

Ahlbäcks desease


Resect as little as possible Resect as little as possible and as much as necessaryand as much as necessary

Bonestock is the most valuable Bonestock is the most valuable resourceresource

StabilityStability

Revision surgeryRevision surgery


In conclusion, what do we expect In conclusion, what do we expect

from a modern knee implant from a modern knee implant

Surgical managability Surgical managability

Excuse me Doc, can I see your diploma?

Managable for the average orthopedic surgeon


DurabilityDurability


AffordabilityAffordability


Discussion welcomedDiscussion welcomed

BILIS

you will be answeredyou will be answered



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