A radiological study of the movements of the two components of the Monk prosthesis (hard-top 'duo-pleet') in patients.

Following replacement of the femoral head with the Monk hard-top 'duo-pleet' prosthesis, radiological studies show that movement of the replaced hip takes place between the acetabulum and the metal shell and between the high density polyethylene cup and metal ball. Movements improve with the passage of time. The two sites of movement may contribute to a greater range of hip movement, a better safeguard against loosening and possibly less medial migration of the prosthesis than solid metal prostheses like the Thompson and Austin Moore types.