An Engineering Evaluation of the Oxford External Fixator with Sliding Clamps: Fixator Stiffness and Fracture Healing Assessment

Abstract

A theoretical and experimental evaluation of the Mark II Oxford External Fixator with sliding clamps has shown that:

the effective axial stiffness may readily be varied over a wide range;

significant load-bearing may be achieved on the fractured bone while maintaining adequate fracture alignment and stability;

the axial sliding facility is likely to be of greatest benefit in the early stages of fracture healing. Sliding decreases rapidly as fracture stiffness increases and ceases altogether at a relatively early stage in the healing process;

the effects of bone pin loosening are similar to those previously reported for the fixed-clamp Oxford External Fixator;

bone healing assessment using a strain-gauge transducer clamped to the fixator column may become difficult and inaccurate when sliding of the clamps occurs. Temporary locking of the clamps is recommended during the assessment procedure to ensure that sequential tests are strictly comparable.