Ex vivo cyclic mechanical behaviour of 2.4 mm locking plates compared with 2.4 mm limited contact plates in a cadaveric diaphyseal gap model

Iban Irubetagoyena (1) , Michaël Verset (1) , Sophie Palierne (1) , Pascal Swider (2) , André Autefage (1)

1 Laboratoire de biomécanique
2 IMFT - Institut de mécanique des fluides de Toulouse

OBJECTIVES: To compare the mechanical properties of locking compression plate (LCP) and limited contact dynamic compression plate (LC-DCP) constructs in an experimental model of comminuted fracture of the canine femur during eccentric cyclic loading. METHODS: A 20 mm mid-diaphyseal gap was created in eighteen canine femora. A 10-hole, 2.4 mm stainless steel plate (LCP or LC-DCP) was applied with three bicortical screws in each bone fragment. Eccentric cyclic loadings were applied at 10 Hertz for 610,000 cycles. Quasistatic loading / unloading cycles were applied at 0 and 10,000 cycles, and then every 50,000 cycles. Structural stiffness was calculated as the slope of the linear portion of the load-displacement curves during quasistatic loading / unloading cycles. RESULTS: No bone failure or screw loosening occurred. Two of the nine LCP constructs failed by plate breakage during fatigue testing, whereas no gross failure occurred with the LC-DCP constructs. The mean first stiffness of the LCP constructs over the course of testing was 24.0% lower than that of constructs stabilized by LC-DCP. Construct stiffness increased in some specimens during testing, presumably due to changes in bone-plate contact. The first stiffness of LC-DCP constructs decreased by 19.4% and that of locked constructs by 34.3% during the cycling period. A biphasic stiffness profile was observed: the second stiffness was significantly greater than the first stiffness in both groups, which allowed progressive stabilization at elevated load levels. CLINICAL SIGNIFICANCE: Because LCP are not compressed to the bone, they may have a longer working length across a fracture, and thus be less stiff. However, this may cause them to be more susceptible to fatigue failure if healing is delayed.

Mots clés: Cyclic mechanical testing; Dogs; Femur; Gap model; Limited contact plate; Locking plate

Domaines: Biomécanique [physics.med-ph]; Mécanique des fluides [physics.class-ph]; Médecine vétérinaire et santé animale

Iban Irubetagoyena, Michaël Verset, Sophie Palierne, Pascal Swider, André Autefage. Ex vivo cyclic mechanical behaviour of 2.4 mm locking plates compared with 2.4 mm limited contact plates in a cadaveric diaphyseal gap model. Veterinary and Comparative Orthopaedics and Traumatology, 2013, vol. 26 (n° 6), pp. 479-488. ⟨10.3415/VCOT-13-07-0089⟩. ⟨hal-01793186⟩