This is the first of two articles which describe a clinical and radiographic review of the reasons for dislocation in patients who have received customised total hip replacements. The researchers compared the alignment of 19 arthroplasties which had dislocated with 347 which had not. A number of factors were considered including pre- and post-operative factors, femoral component placement, component head size, and acetabular position and orientation. It was found that the femoral head size had the greatest influence on dislocation. However, the researchers point out that dislocation on these patients is a multifactoral problem and that prevention, through effective pre-operative and post-operative patient education in relation to care of the hip and mobilising, should be encouraged. They also advocate a multidisciplinary approach to improve patient outcomes. The second article will appear next week.