[Aseptic loosening of a total hip prosthesis]

Detachment of a total hip prosthesis, whether or not it is cemented, presents as an abnormal mobility between the implant and the bone. Mechanical pain, which may be continuous from the time of the operation or which may appear after a variable pain free period, is the usual presenting symptom. Clinical examination may induce the pain by forced rotation, by a shaking maneuver or by traction-impaction of the lower limb. The most suggestive signs of detachment of the prosthesis are the inability to extend the limb and the instability of weight-bearing on one foot. At this stage, the findings of radiological and laboratory investigations are able to characterise the type of detachment and its septic or aseptic nature. Two clinical situations can be defined on the basis of this survey: the diagnosis of detachment is obvious due to rupture or fracture of the prosthesis, of the cement or of the bone, by displacement of the prosthetic elements or by the destruction of the bone in contact with the prosthetic elements; the diagnosis may be suspected and can be confirmed by careful comparative analysis with the initial films or by further investigations: dynamic tests, scintigraphy, arthrography under traction and possibly coxonar. There are a number of causes of detachment: poor positioning, incorrect conception or design of the prosthesis, poor bony support and host reaction to the implant.(ABSTRACT TRUNCATED AT 250 WORDS)