Purpose: Dislocation of total hip arthoplasties is a sad reality. The incidence of this complication is estimated from 0.6 to 8%. Dislocation can be a single event that never recurs, but half of all dislocations will reoccur again. We analysed outcome after treating chronically unstable total hip arthroplasties using a double-mobility cup. Material and methods: Between 1990 and 2000, we treated 42 cases of recurrent dislocation of total hip arthroplasties. Five were immediate, 33 early, and four late; five dislocations on the average. The prosthesis was implanted via the posterolateral approach for 36 patients. Thirteen patients treated in our unit had already had surgical treatment for chronic instability: 1 trochanteoplasty, 8 bone blocks, 5 restraining cups. A standing AP view of the pelvis was obtained in all patients before surgery to analyse shortening (gluteus medius insufficiency), cup tilt and anteversion, and stem lateralisation. Likewise a CT scan was performed systematically to analyse stem and cup anteversion. No position anomaly was found in 17 patients; at least one anomaly was found in the others. All patients were reoperated via the posterolateral approach. A double-mobility cup was implanted systematically without changing the stem. Results: Among the 42 patients, we had two with recurrent dislocation, one in a neurologic patient and one in a patient with major anomalies in the position of the femoral component that was not changed. The incidence of recurrent dislocation was thus 4.75%. Discussion: The therapeutic method used here can be compared with other solutions (trochanteroplasty, anti-dislocation crescent, antidislocation bone block, bipolar replacement). The double-mobility cup is particularly interesting for high-risk patients: neck fracture, tumour surgery, neurological disease, antecedent non-prosthetic surgery (dearthrodesis prosthesis). We advocate revision surgery after three dislocations. Conclusion: The double-mobility cup appears to be a valid therapeutic option, both for the treatment and prevention of chronic instability of total hip arthroplasty

Purpose of the study: An unstable hip prosthesis is a therapeutic challenge. The prevalence of revision is 5 to 26.6% in the literature. We evaluated the contribution of double-mobility implants for revisions of unstable hip implants. Material and methods: This series was composed of 45 patients who underwent revision between January 2000 and December 2003 for hip instability (44 dislocations, 1 subluxation). The same implant was used for all patients, either for the first-intention version (press-fit or cemented), or for the revision version (press-fit). For certain patients, the first-intention implant was cemented in an armature. The series included 28 females and 17 males, mean age 66.5 years (range 36–48 years). The initial diagnosis was osteoarthritis in 34 cases (76%), dysplasia in seven (16%), osteonecrosis in two (4%), Paget’s disease in one (2%) and rheumatoid disease in one (2%). The patients had had 2.8 dislocations on average (range 1 – 10). Time from first dislocation to the first-intention operation was 45.6 months (range 15 days – 20 years). Mean time from the first-intention operation to revision was 64.3 months (range 3 weeks – 20 years). Risk factors for instability were repeated hip surgery (> 3 operations) for 13 patients, wear for seven, nonunion of the greater trochanter for five, neurological and cognitive impairment in five, and malposition in three. Results: Mean follow-up was 25.2 months. None of the patients were lost to follow-up. Two patients died late after the operation. Among the complications observed, there were: two cases of recurrent dislocation, one case of subluxation, two cases of infection (one with favorable outcome after surgical cleaning and antibiotics the other followed by patient death), two cases of deep vein thrombosis, one case of popliteal paresia with favorable outcome, one case of delirium tremens. Surveillance was the therapeutic option for the patient with subluxation. For patients with dislocation, revision surgery was performed using the same implant. For one of these patients, the dislocation occurred following early loosening. Conclusion: Use of double-mobility implants for prosthetic revision undertaken because of prosthesis instability provides encouraging results, with a rate of dislocation (4%) close to that observed with first-intention implants

Purpose: The double mobility of the G. Bousquet cup—head-polyethylene,polyethylene metal cup—considerably reduces the risk of total hip arthroplasty displacement. Material and methods: We observed seven cases of “intra-prosthetic” displacement in patients with this type of cup. Progressive wear of the polyethylene retention ring allowed displacement of the femoral head. These displacements occurred in six patients (one bilateral case) aged 43–58 years, on the average ten years after the implantation (range 3.5 – 15 years). All patients underwent revision. Results: The polyethylene retention ring was worn in all cases allowing the femoral head to escape. Revision surgery was performed very early in six hips to change the modular base and the polyethylene ring and re-establish retaining capacity. A satisfactory result was achieved in all cases. One patient required revision five years later to change the prosthesis subsequent to haematogenous infection. Another patient underwent a late revision to change the modular base and the entire cup of a press fit implant. This hip was in excellent condition but revision was decided on because of four dislocations. Discussion: Intra-prosthetic displacement of the polyethylene head of a double-mobility cup is exceptional in our experience. Wear of the retention ring is favoured by different elements: 1) direct phenomena: neck and head diameter causing early contact between the neck and the cup; 2) indirect phenomena: factors limiting the mobility of the polyethylene metal cup couple (fibrosis, repeated interventions, ossification). In our experience, intra-prosthetic displacement occurs more readily in patients with favouring conditions (alcoholism, muscle deficiency, psychiatric disorder, obesity) observed in six of our seven cases. Conclusion: Intra-prosthetic displacement of a double-mobility cup is a possible but exceptional complication requiring a technically simple revision. Some teams use this type of cup systematically and for us is an essential element for preventive treatment in high-risk patients and for curative revision of recurrent dislocation

Uncemented double-mobility acetabular cups, first used in the late 1970s as a solution to recurrent hip dislocations, have proved efficient in reducing dislocation rates while preserving an important range of motion. The low wear-rate and low mechanical stress on the bone to cup interface enhances survival. New instrumentation has permitted design changes that improve the dislocation coverage of the cup (upper part of the cup) and reduce the risk of impingement with the femoral stem (lower part of the cup). Indications for the use of double-mobility cups have increased. They include primary total hip arthroplasty in relatively unstable hips, in which cases we use the Avantage® press-fit or 3P cup with an AURA II anatomical uncemented or cemented stem, dysplasia (in congenital high dislocations we use the press-fit or 3P or revision cup with an AURA revision stem, and in dysplasia we use small AURA II or Vectra or CMK dysplastic stems), muscular deficiency, in which Avantage® cups can be used with AURA II or revision stems, resection prosthesis or ARMEL calcar prosthesis, etc.)

Purpose of the study: The double-mobility concept was introduced for clinical applications for total hip arthroplasty in 1976. The concept preserves joint range of motion while increasing stability. In this study we evaluated the consequences of these advantages in terms of polyethylene wear, measuring wear both on the concave and convex surfaces and volumetrically. Material and methods: Forty polyethylene inserts were explanted and analyzed. Explantation had been performed for mechanical or septic failure after eight years implantation on average. Mean age of patients at implantation was 46 years. After examining the gross aspect of the insert, surface analysis was performed with direct measurement of changes in the curvature using a BHN 706 position sensor for the inner concave surface and lateral projection for the outer convex surface. Estimated measurement error was ±5μm for each method; the manufacturer's tolerance for production of the inserts was 50μm. Volumetric wear was determined by reference to the manufacturer’s data. Student’s t test for paired series was applied. Results: At gross inspection, all inserts had lost the strips originally present on the convex surface; 40% presented visible wear of the retaining ring. Mean annual wear (± standard deviation, SD) obtained with the measuring system was 9±9 μm/yr) for the convex surface and 73 ± 69 μm/yr for the concave surface. Total annual wear, the sum of inner and outer surface wear, was 82±72 μm/yr. The mean volumetric wear was 28±28 mm3/year for the convex surface and 25±23 mm3/year for the concave surface and 53.4±40 mm3/year for total wear. Discussion: Total wear for these 40 double-mobility inserts which had functioned in vivo was not greater than the values reported for the metal-polyethylene bearing with 22.2 mm femoral heads. The double mobility is not associated with greater wear. While there was no significant difference between the wear volume of the convex versus the concave surfaces, the differentials wear were widespread, which can be considered to result from functional differences

Purpose of the study: Double mobility prostheses are increasingly popular. Evidence in the literature demonstrates greater efficacy for the treatment and prevention of prosthesis instability. Ten-year survival is to the order of 95% (Aubriot, Philippot). One of the drawbacks is the risk of prosthetic head displacement outside the retaining polyethylene ring, i.e. intraprosthetic dislocation. We searched for factors causing this complication. Material and methods: We reviewed retrospectively 67 files concerning intraprosthetic dislocation among a series of Novae cups (Serf) implanted from 1982. Head diameter was 22.2 mm for 59 cases, with a Pro stem (Serf) for 31 cases and a PF stem (Serf) for 36. Each type of stem has a specific neck design. All patients underwent revision surgery; the retaining function of the explanted pieces was analyzed. Results: Mean time to the complication was 91 months; mean patient age at implantation was 54 years. Early cases exhibited macroscopically intact retaining capacity. Intermediary and late cases exhibited macroscopic wear with an oval shaped retaining ring. For three cases, intraprosthetic dislocation followed an episode of dislocation reduced under sedation. The cups measured 53 mm on average. The rate of calcification was high in this population (15 cases of Brooker grade 3 or 4). Mean survival was significantly different between the Pro and PF stems. Discussion: Early dislocations were related to insufficient retaining capacity of the initially inserted ring. After a corrective measure by the manufacturer, this type of early complication has disappeared. Late dislocations resulted from impingement wear. Dislocation of a prosthesis with a double-mobility cup increases the risk of intraprosthetic dislocation after reduction; reduction procedures should thus be performed under general anesthesia with curare treatment. We analyzed the different parameters involved: head-neck relation, activity, periprosthetic calcification, cup diameter, resurfacing of the prosthetic neck. Observations were compared with data in the literature

Purpose of the study: This series included 50 consecutive cases of titanium hydroxyapatite coated cups impacted directly on live bone of the neoacetabulum after removal of a loosened cup implanted and reviewed at more than ten years. Material and methods: The goal was to insert a titanium hydroxyapatite-coated cup on the largest quantity of healthy cancellous bone in the neocavity without using a graft and without worrying about the future height of the center of rotation nor the medial offset. The shortened impaction related to the neoacetabulum formed by the loosening could be compensated for by descending the femoral stem a bit further. This method of acetabular revision was performed for 75 hips before 1993. At more than ten years follow-up, four hips were lost to follow-up, 20 patients had died, and one case of early suppuration was noted. The series thus included 50 cups in 48 patients (22 men and 26 women, mean age 67 years at revision surgery). The Charnley classification was: A:21, B:22, C:7. Mean follow-up was 11 years. The SOFCOT staging was: I=0, II=33, III=14, IV=3. AAOS I=0, II=32, III=18, IV=0. The number of prior cup replacements: 0=46, 1=4. Approach: trochanterotomy (n=44), femorotomy (n=0), posterolateral alone (n=6). Mean cup diameter 60 (range 48–68). Femoral stems changed = 20. Preoperative PMA = 12 and postoperative PMA = 16. Results: Among the 50 hips, 48 exhibited optimal fixation without lucent line or bone defect. One patient presented a partial lucent line and one had revision at nine years. At five years, all cups (100%) were in place and at ten years 98%. There were no cases of pelvic fracture and only three stage IV hips. Discussion: The advantages of this method are to avoid the use of a graft or frozen head, and the generally immediate/rapid weight bearing. This series raises the question of whether it is advisable to replace the new cup in the position of the paleoacetabulum. These implants can be improved with screwed cups onto which a double-mobility cup can be press-fit. This technique has enabled weight-bearing in conditions which otherwise would not have been possible for these frail elderly patients. Conclusion: In light of this consecutive series reviewed at more than ten years, we have decided to continue this approach