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

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

you will be answeredyou will be answered

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

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