Viscoelastic properties of cartilage-subchondral bone complex in osteoarthritis.
OBJECTIVE
This study examines viscoelastic properties of the 'unaffected' tibial condyle in unicompartmental osteoarthritic knees, in order to determine whether to preserve it or not in knee replacement operations.


METHODS
The viscoelastic properties of longitudinal strips of cartilage and subchondral bone from osteoarthritic and healthy knees were studied.


METHODS
Nine medial compartment osteoarthritic and nine cadaveric knees, all age- and gender-matched, were studied. Samples from polyethylene and methacrylate cement were also obtained and all then tested in the DMA (Dynamic Mechanical Analysis) testing apparatus. The dynamic modulus of elasticity (E(dyn)) and the loss factor (tan delta) were measured.


RESULTS
The medial compartment in osteoarthritic knees had lost its viscoelastic properties, having a significantly higher E(dyn) compared to the lateral one, and lower values of loss factor. In healthy knees there was no significant difference (p=0.18) in viscoelastic properties between both compartments and with the unaffected side of the osteoarthritic knee. Polyethylene and cement appear to have a high modulus of elasticity compared to both the healthy and the osteoarthritic knees.


CONCLUSIONS
The 'unaffected' (lateral) tibial condyles in medial compartment osteoarthritic knees seem to preserve their viscoelastic properties; it is worth considering a hemiarthroplasty. The significant modulus of elasticity difference between the condyles-polyethylene-cement results in different deformation in the interface between them and induces micromotion and loosening.
Fortis
A P
AP
Orthopaedic Department, Panarkadion General Hospital, Tripolis, 22100 Arcadia, Greece.
Kostopoulos
V
V
Panagiotopoulos
E
E
Tsantzalis
S
S
Kokkinos
A
A
D001843:Bone Cements / Q000737:chemistry*; D018786:Bone Substitutes / Q000737:chemistry*; D002358:Cartilage, Articular / Q000503:physiopathology*; D004548:Elasticity; D006801:Humans; D066298:In Vitro Techniques; D008422:Materials Testing; D020370:Osteoarthritis, Knee / Q000503:physiopathology*; D013977:Tibia / Q000503:physiopathology*; D014783:Viscosity
D001843:Bone Cements; D018786:Bone Substitutes