349Biocompatible materials - LV 308.106

Biocompatible materials 12.12.2011

Non-metallic Materials

Implants for the muscoloskeletal system– Knee endoprosthesis systems

– Problems associated with (polymer) sliding surfaces

350Biocompatible materials - LV 308.106

Implants for the Muscoloskeletal SystemKnee Joint Endoprosthesis

SystemsBiofunctionality: load transfer, support and

movement

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Knee Joint

©Mysid

Quadriceps

Oberschenkel-knochen

Gelenk-knorpel

äußerer Gelenkknorrenhinteres Kreuzband

vorderes Kreuzband

Außenband

Wadenbein

Schienbein

Quadriceps-Sehne

Kniescheibe

Innenband

Meniskus

Kniescheiben-band

352Biocompatible materials - LV 308.106

Cartilage defectsSurgeons classify defects in the knee cartilage using a grading scale from I (one) to IV (four).

In a grade I tear, the cartilage has a soft spot.

Grade II lesions show minor tears in the surface of the cartilage.

Grade III lesions have deep crevices.

In grade IV lesions, the tear goes all theway to the underlyingbone.

eOrthopod.com

353Biocompatible materials - LV 308.106

www.unifr.ch

www.swissklinik.ch

354Biocompatible materials - LV 308.106

Knee Joint

Causes for knee joint disease– Leg axis defective position (varus = bow legged O-Beine;

valgus = knock-kneed X-Beine)– Rheumatism– Metabolic diseases

Result– Meniscus damage– Cartilage and bone abrasion

355Biocompatible materials - LV 308.106

Knee Endoprosthesis Systems

Constrained knee endoprosthesis– Removal of bigger bone parts– Femoral and tibial parts form a

hinged joint, that no longer allows rotation of the knee

– Functioning ligaments are not necessary

Resurfacing– Removal of damaged cartilage primarily– The knee ligament structures can be kept mostly

Resurfacing prosthesis are more frequently used than constrained ones

www.orthodynamics.de

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Knee Endoprosthesis: Resurfacing Prosthesis

Single-side endoprosthesis:

with replaced inner or outer joint parts

The healthy cartilage and the ligaments are kept.

Double-side endoprosthesis:

a) In the unhinged endoprosthesis (mid) the joint surfaces of the femur and the tibia are replaced. The posterior cruciateligament (PCL) is kept.

b) The hinged (right) endoprosthesis includes an additional spine, thus it does not need the lateral ligaments. The PCL can not be preserved. For stabilising the knee a mortise joint is realised (Posterior Stabilising tibial insert).

357Biocompatible materials - LV 308.106

Fixation

Cement-free knee endoprosthesis

Cemented knee endoprosthesis

Hybrid knee endoprosthesis

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Knee Endoprosthesis Mebio®

Femur component(Co-Cr-Mo) Tibia component

(Co-Cr-Mo)

PE Plateau (PE-UHMW)

Patella component(PE-UHMW)

Shape of the joint surface determines movability(rotation, backwards sliding)

Elements for anchorage in the cementStem geometry and texture ensure fixation and rotational stability

www.aap.de

359Biocompatible materials - LV 308.106 eOrthopod.com

Knee arthroplasty

M.S. Taljanovic et al., 2003

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Unicompartmental knee prosthesisZimmer® ZUK

Femur component(Co-Cr)

Tibia component(Ti6Al4V)

www.zimmer.ch

PE Plateau (PE-UHMW)

M.S. Taljanovic et al., 2003

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Zimmer® Gender Solutions™ NexGen® High-Flex Knee

www.zimmer.com