Splitting plaster with a scalpel blade: a safe way to allow easy splitting of a plaster.

INTRODUCTION: Splitting of a plaster cast is frequently required to accommodate post-operative limb swelling. Oscillating saws are often used but can cause injury and distress and cannot be used when the plaster is drying. At these times plaster shears are used. A safe technique is described which safely divides drying plaster using a sharp scalpel. METHOD: Plaster casts were applied to 40 modelling balloons, consisting of one roll of 3-in. and one roll of 4-in. plaster. The balloons had either two or four wool layers beneath the plaster. Ten from each group were split using our technique and 10 from each group were split with plaster shears. The number of balloons that were not burst during the splitting process was recorded. RESULTS: Of the 20 plasters split with a scalpel, all of the balloons remained inflated. The balloons underneath two of the plasters with two layers of wool that were split using plaster shears burst during splitting. When the plasters split with a scalpel were dry they could be opened easily using cast spreaders and the wool cut with scissors without the balloons bursting. CONCLUSION: This is a safe and simple technique for splitting a drying plaster without the need for extra materials. It allows easy completion of the release with scissors alone should swelling of the soft tissues become excessive. The need for plaster shears or oscillating saws with the potential trauma associated with these established methods is eliminated.

Acute bilateral forearm compartment syndrome of unknown aetiology.

This is the first reported case of non-traumatic, acute bilateral forearm compartment syndrome. Despite a delay of over 24 hours until surgical decompression and 50% muscle fibre necrosis in the histopathological examination, the clinical outcome was excellent after fasciotomy, delayed primary wound closure and early institution of a range of motion exercise programme. The literature on non-traumatic causes of compartment syndrome is reviewed.

Young's moduli and shear moduli in cortical bone.

Young's modulus and shear modulus are determined for cortical bone from mammals and birds and for antler bone, using three-point bending at a range of span-to-depth ratios between 25 and 10. Young's modulus is obtained by extrapolating the values for the flexural modulus Eapp to infinite span-to-depth ratios. The shear modulus is obtained from the dependance of Eapp on this ratio. The main determinant for the mechanical properties is the mineral content. For mammalian bone the frequency of Haversian systems correlates negatively with stiffness and resistance to shear. However, because Haversian systems have a lower mineral content than laminar bone (the main component), material and structural determinants can not be separated at present. The ratio of Young's modulus to shear modulus is of the order of 20:1. This high value is discussed in terms of the Cook-Gordon theory of controlled crack propagation as well as in its significance for protecting hollow bones from failing upon local impact.