Neuroimaging in the high-risk infant: relationship to outcome

PURPOSE OF THE STUDY: Dislocation following total hip arthroplasty (THA) continues to be a problem. An innovative treatment is described with the intermediate Bousquet's prosthesis. This study reported 13 cases and demonstrates its high reliability despite the origins of the dislocation. Recurrent dislocation following initial dislocation, occurs in between 25 to 60 per cent of the cases reported in the literature. The main cause is a malpositioned prosthetic component and especially a retroverted acetabulum. The other reasons for dislocation were: trochanteric non-union, bone or cement impingement, previous surgery, age and neurologic disorder. In every case the instability of the hip may be caused or increased by muscular insufficiency. Various methods are described to control recurrent dislocation: repositioning the component, posterior acetabular wall component, trochanteric advancement, retentive acetabular component, bracing. When the cause is clear and isolated, the rate of success may be 70-80 per cent. This study examines the results of a revision procedure with the intermediate Bousquet's prosthesis. MATERIAL AND METHODS: 13 recurrent dislocations were treated with the intermediate Bousquet's prosthesis. There were 10 women and 3 men with an average age at operation of 73 years. The main cause in 7 cases was an abductor insufficiency including 4 trochanteric non unions. The other causes were 6 component malpositions, 7 previous surgery, 1 impingement. The average delay between the first dislocation and revision was one year. The Bousquet's acetabular component is an steel cup covered with alumina, impacted without cement. The polyethylene component is free in the cup and retentive on the femoral head. The femoral positioning was not modified. RESULTS: The revision did not correct all of the causes of luxation, however we noted only one case of dislocation and no recurrent dislocations. DISCUSSION: At last follow-up, all recurrent dislocations were controlled. Nevertheless, there remained 7 abductor insufficiencies and 4 femoral malpositionings. In the literature the rate of success depends on the cause. The main difficulty is the treatment of joint laxity. Some authors propose trochanteric advancement, a larger head, a posterior wall acetabular component, retentive acetabular component. Success is not uniform. The Bousquet's acetabular component supports joint laxity and femoral malpositioning. This allows to keep the same original femoral component when the risk is too high for a cemented prosthesis or impossible for a non cemented prosthesis. CONCLUSION: This treatment of the recurrent dislocation is reliable with a short and simple operation.