©1996 British Editorial Society of Bone and Joint Surgery

RSA in the assessment of aseptic loosening The introduction and sale of new designs of total joint prostheses have rarely been preceded by evaluation in prospective and controlled series. In some instances, early failure has caused unnecessary suffering to patients and increased costs to society. There is an obvious need for more precise tools which can evaluate new designs of implant as quickly as possible while exposing a minimum number of patients to any risk. Aseptic loosening and wear are now the major reasons for failure, but conventional radiography can provide only relatively crude measurements of these. Routine radio-graphs of the hip, without special precautions, can detect movement of about 5 mm (Malchau et al 1995). This should be compared with implant motion of 0.15 to 0.2 mm, which has been claimed to be the maximum compatible with bony ingrowth and stable long-term fixa-tion. Several special radiological methods can detect small-er movement or mean changes in large series (Jones et a