Semi-rigid vs rigid glass fibre casting: a biomechanical assessment.

OBJECTIVES

To determine if semi-rigid synthetic casts provide any measurable advantages compared to rigid synthetic casts.

BACKGROUND

Glass fibre bandages are now commonly applied immediately post-injury to provide rigid immobilisation of the limb, for both weight bearing and non-weight bearing casts. However, composite casts that have inherent flexibility are also available and it is claimed they provide some functionality.

METHODS

Five members of the orthopaedic department each applied a rigid and a semi-rigid below elbow (Colles) and a below knee walking cast to a single volunteer subject. Joint immobilisation and functional movement was assessed using electrogoniometry and limb support using pressure transducers.

RESULTS

Semi-rigid Colles casts provided slightly greater immobilisation at the wrist while allowing full finger function and greater support to the forearm during hand movements. Similarly, semi-rigid below knee walking casts produced greater immobilisation at the ankle while allowing more forefoot movement and were less of an impediment to walking.

CONCLUSIONS

Semi-rigid casting techniques have measurable advantages compared to rigid synthetic casts and represent a further development in the conservative management of fractures and soft tissue injuries.

RELEVANCE: Semi-rigid casting is a relatively new technique that can reduce some of the problems of rigid cast immobilisation and could potentially shorten the rehabilitation phase following injury. Information about the performance of these casts to assess their value in specific applications is very limited.