MOBILE BEARING TOTAL MOBILE BEARING TOTAL KNEE REPLACEMENTKNEE REPLACEMENT

Naval Hospital of AthensNaval Hospital of Athens

1st Orthopaedic Department1st Orthopaedic Department

Kinematic conflictKinematic conflict

Reproduction of normal knee Reproduction of normal knee biomechanics- reduction of contact forcesbiomechanics- reduction of contact forces

Surfaces “convex to flat” produce high Surfaces “convex to flat” produce high contact forces but have freedom in torsion contact forces but have freedom in torsion & reduced strain to PCL during posterior & reduced strain to PCL during posterior femoral condyle movementfemoral condyle movement

““Concave to convex” reduced contact Concave to convex” reduced contact forces & reduced torsion forces & reduced torsion

Mobile bearing polyethyleneMobile bearing polyethylene

Restricts torsion between femorotibial joint Restricts torsion between femorotibial joint allowing torsion between tibial plateau and allowing torsion between tibial plateau and polyethylenepolyethyleneContact surface increases very muchContact surface increases very muchContact forces decrease respectivelyContact forces decrease respectivelyCloser to normal posterior movement of Closer to normal posterior movement of femoral condyles, at least during the first femoral condyles, at least during the first degrees of flexiondegrees of flexionCallaghan et al, JBJS (Am)Callaghan et al, JBJS (Am)

ΜΜobile bearingobile bearing

Allow the torques and shear forces of gait Allow the torques and shear forces of gait to be transferred to soft tissues in a to be transferred to soft tissues in a fashion similar to normal knee.fashion similar to normal knee.Soft tissue strengthening – remodeling Soft tissue strengthening – remodeling during rehabilitationduring rehabilitationBetter patellar trackingBetter patellar trackingRotation of polyethylene can forgive Rotation of polyethylene can forgive SMALL errors of orientationSMALL errors of orientation

Sansone et al ,j arthroplasty 2004Sansone et al ,j arthroplasty 2004

Bartel et al, 1985,1991Bartel et al, 1985,1991

Our experienceOur experience

527 total knee replacements with mobile 527 total knee replacements with mobile bearingbearing

Period 1987- 2005Period 1987- 2005

48% left knee, 52% right knee48% left knee, 52% right knee

94 male, 433 female94 male, 433 female

ΔΙΑΓΝΩΣΗ n % ΗΛΙΚΙΑ

ΟΣΤΕΟΑΡΘΡΙΤΙΔΑ 452 87,9 69,5

ΡΕΥΜΑΤΟΕΙΔΗΣ ΑΡΘΡΙΤΙΔΑ 45 7,7 61,5

ΜΕΤΑΤΡΑΥΜΑΤΙΚΗ ΑΡΘΡΙΤΙΔΑ 17 2,6 59,2

ΑΛΛΑ ΑΙΤΙΑ 12 1,7 59,2

ΣΥΝΟΛΟ 527 100 63,5

ΤΥΠΟΣ ΑΡΘΟΠΛΑΣΤΙΚΗΣ

n CEM/ED CEM/LESSCEM/ED TIBIAL

TACK 80 0 0 80

LCS 276 30 162 84

GENESIS II M.b 171 27 0 144

Patelofemoral jointPatelofemoral joint

No patella replacementsNo patella replacements

Shaving of pathological cartilage resulting Shaving of pathological cartilage resulting in smooth articular surfacein smooth articular surface

Denervation of the periphery of the patellaDenervation of the periphery of the patella

Removal of osteophytesRemoval of osteophytes

Subvastus approachSubvastus approach

Surgical preparationSurgical preparation

1.5gr cefuroxim on admission. Antibiotic 1.5gr cefuroxim on admission. Antibiotic regime for 3 days post opregime for 3 days post op

Skin preparation with Betadine scrub, Skin preparation with Betadine scrub, Betadine solution (3 times) starting from Betadine solution (3 times) starting from the footthe foot

Strict rules in theatres room in all levelsStrict rules in theatres room in all levels

InfectionsInfections

10 superficial postoperative infections 10 superficial postoperative infections which were treated with antibioticswhich were treated with antibiotics

No revisions because of infectionNo revisions because of infection

Follow upFollow up

Patients followed up clinically and Patients followed up clinically and radiologically in 6 weeks, 6 months, 1 year radiologically in 6 weeks, 6 months, 1 year and periodically every 2 yearsand periodically every 2 years

10-20% of the patients were not examined 10-20% of the patients were not examined after the two year follow up unless there after the two year follow up unless there was a problemwas a problem

Range of motionRange of motion

RevisionsRevisions

One LCS and one Genesis II because of One LCS and one Genesis II because of aseptic loosening of femoral componentaseptic loosening of femoral component

Two revisions because of trauma- Two revisions because of trauma- supracondylar femoral fracture in one and supracondylar femoral fracture in one and tibial fracture in the secondtibial fracture in the second

One Polyethylene dislocationOne Polyethylene dislocation

ConclusionsConclusions

The results of 18 years experience in The results of 18 years experience in mobile bearing TKR, justify our choice mobile bearing TKR, justify our choice

These results are a strong confirmation of These results are a strong confirmation of the theoritical advantages of mobile the theoritical advantages of mobile bearing in knee kinematicsbearing in knee kinematics

THANK YOUTHANK YOU