One of the problems of keeping an orthopaedic register is that radiographs, which are an integral part of records (particularly with total joint arthroplasties) are cumbersome and costly to store.

We have developed a cheap and simple digital storage system, photographing radiographs with a digital camera and storing pictures in a specially designed database. Retrieval is rapid and hard copies can be printed.

Over 10 000 arthroplasty radiographs have been digitalised by this inexpensive method, which could prove useful for most orthopaedic surgeons.

The radiation crosslinking of high-density polyethylene prostheses was investigated over a wide range of doses in the presence and absence of gaseous crosslinking agents. It was found that in the bulk polymer the crosslinking pattern is completely different from the homogeneous crosslinking that occurs in polymer films. The presence of crosslinking agents causes highly crosslinked polymer to be formed on the surface while the bulk of the polymer is largely unaffected--which is explained in terms of diffusion phenomena. This surface crosslinking has a profound effect on the mechanical properties of the prostheses and restricts cold flow and deformation of the polymer without sacrificing the excellent abrasion-resistance properties of the polyethylene when subjected to high pressures. Based on this research a number of high-density polyethylene knee prostheses have been radiation-crosslinked and the results in vitro appear to be very promising.