MOBILE BEARING TOTAL KNEE REPLACEMENT

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MOBILE BEARING TOTAL KNEE REPLACEMENT

• Naval Hospital of Athens
• 1st Orthopaedic Department

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Kinematic conflict

• Reproduction of normal knee biomechanics-
  reduction of contact forces
• Surfaces convex to flat produce high contact
  forces but have freedom in torsion reduced
  strain to PCL during posterior femoral condyle
  movement
• Concave to convex reduced contact forces
  reduced torsion

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Mobile bearing polyethylene

• Restricts torsion between femorotibial joint
  allowing torsion between tibial plateau and
  polyethylene
• Contact surface increases very much
• Contact forces decrease respectively
• Closer to normal posterior movement of femoral
  condyles, at least during the first degrees of
  flexion
• Callaghan et al, JBJS (Am)

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?obile bearing

• Allow the torques and shear forces of gait to be
  transferred to soft tissues in a fashion similar
  to normal knee.
• Soft tissue strengthening remodeling during
  rehabilitation
• Better patellar tracking
• Rotation of polyethylene can forgive SMALL errors
  of orientation
• Sansone et al ,j arthroplasty 2004

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Bartel et al, 1985,1991
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Our experience

• 527 total knee replacements with mobile bearing
• Period 1987- 2005
• 48 left knee, 52 right knee
• 94 male, 433 female

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???G?OS? n ??????
?S?????T?????? 452 87,9 69,5
???????????S ??T?????? 45 7,7 61,5
?????????????? ??T?????? 17 2,6 59,2
???? ????? 12 1,7 59,2
S????? 527 100 63,5
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????S ??T????S????S n CEM/ED CEM/LESS CEM/ED TIBIAL
TACK 80 0 0 80
LCS 276 30 162 84
GENESIS II M.b 171 27 0 144
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Patelofemoral joint

• No patella replacements
• Shaving of pathological cartilage resulting in
  smooth articular surface
• Denervation of the periphery of the patella
• Removal of osteophytes

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Subvastus approach
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Surgical preparation

• 1.5gr cefuroxim on admission. Antibiotic regime
  for 3 days post op
• Skin preparation with Betadine scrub, Betadine
  solution (3 times) starting from the foot
• Strict rules in theatres room in all levels

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Infections

• 10 superficial postoperative infections which
  were treated with antibiotics
• No revisions because of infection

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Follow up

• Patients followed up clinically and
  radiologically in 6 weeks, 6 months, 1 year and
  periodically every 2 years
• 10-20 of the patients were not examined after
  the two year follow up unless there was a problem

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Range of motion
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Revisions

• One LCS and one Genesis II because of aseptic
  loosening of femoral component
• Two revisions because of trauma- supracondylar
  femoral fracture in one and tibial fracture in
  the second
• One Polyethylene dislocation

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Conclusions

• The results of 18 years experience in mobile
  bearing TKR, justify our choice
• These results are a strong confirmation of the
  theoritical advantages of mobile bearing in knee
  kinematics

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THANK YOU
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