The unsuitability of polythene for movable weight-bearing prostheses; report of a case of cup arthroplasty of the hip.

Polythene is a synthetic thermo-plastic material formed by the polymerisation of the gas ethylene (C2H4). The polymer produced is a hydro-carbon of high molecular weight, belonging to the paraffin series, the carbon chain being 1 000 to 2,000 carbon atoms long. It Ilas, therefore, the stability and high resistance to chemical change characteristic of ordinary paraffins, but at the same time possesses considerably better mechanical properties. Being a hydro-carbon it is insoluble in and not wetted by water or tissue fluids. It absorbs water very slightly but even after prolonged immersion gains less than 0 05 per cent in weight. Polythene would seem to be an ideal material for implantation purposes in view of the above chemical properties. Animal experiments which we have carried out, and the findings of other investigators (Brown et al. 1947, Ingraham el al. 1947, Clagett et al. 1948, I)onovan and Zimmermann 1949, Seybold et al. 1949, Grindlay and Mann 1948, Busch ci al. 1949, Condon and Harper 1949, \‘eager and Cowley 1948) have encouraged us in this belief.