SUCTION FORCE OF METAL ON METAL HIP JOINTS WITH DIFFERENT CLEARANCES AND VISCOSITIES

Abstract

Introduction: Traditionally Short arm plaster casts have been used to treat distal radius fractures. Judging adequacy of immobilisation has never been defined. A significant proportion of these fractures loose reduction due to inadequate immobilisation. A new non-invasive external fixator technology has been introduced to address the shortcomings of plaster casts. Aim: Is the new non invasive fixator better at reducing skin device interface movement, than conventional plasters.

Materials and Methods: A prospective healthy volunteer study involving application of Short arm plaster of Paris cast, fibreglass cast and a new device Cambfix non-invasive wrist fixator with 15 forearms in each group, was undertaken. IRB approval and informed consent obtained from the volunteers. Colle’s type cast configuration was used. Displacement at the skin-cast and skin-new device interface was measured at proximal and distal ends. Maximal displacements noted immediately after application and after a specified intervals. Casts were windowed at the end of experiment and Cast index and Gap index were measured as ratios at the time of removal of casts. Statistical analysis was done using T-test and SPSS.

Results: The non-invasive Cambfix fixator showed less mean displacement at both the proximal and distal parts compared to plaster and fibreglass casts (p< 0.01). The mean gap index for the Cambfix device was 0.09, which was statistically significantly less than 0.15 and 0.14 for Plaster of Paris and fibreglass casts respectively (p< 0.01). Casts with higher gap index showed increased displacement, however cast index was less predictive of skin-cast displacement.

Conclusions: Skin-device interface movement was significantly better reduced with the Cambfix non-invasive fixator as compared with Short arm plaster of Paris and fibreglass casts. Lesser gap index is known to provide less interface movement. The Cambfix non-invasive fixator appears to achieve a better gap index more consistently. Limitations include healthy volunteer group, and relatively small numbers.