The main causes of total hip arthroplasty (THA) revisions are loosening and instability. Use of a dual mobility cup cemented in a acetabular reconstruction cage device limits the risk of instability and does not hinder the acetabular fixation during THA revisions. The objective of this study was to analyse a retrospective series of 123 THA revisions with antiprotusio cage and dual mobility socket.

Patients and methods: At a mean follow-up of 10 years, we analysed a continuous series of 123 revisions using a reconstruction device (87 Kerboull cross-plates, 12 Burch-Schneider antiprotrusio cages, 24 custom-fit Novae ARM cages associated in all cases with a Novae Stick dual mobility cup cemented into the cage). There were 80 women and 43 males. The mean age at the surgery was 69.2 years old.

PMA score increased from 9.6 +/− 3.06 preoperatively to 14.2 +/− 2. at the follow-up. 9 early dislocations occurred and one late dislocation. At the last follow-up, the X-rays showed nine hardware failures, including one cross-plate fracture, one hook fracture, and one flange fracture. Analysis of the radiological position of the cup showed a mean lowering of 13 mm and a 7 mm lateralisation compared to the preoperative position. 2 revisions for aseptic loosening and 3 for septic loosening were performed.

This study confirms the advantage of dual mobility cups during acetabular reconstruction cemented in antiprotrusio cages as a way to limit, without eliminating, the risk of dislocation. Therefore cemented fixation of dual mobility cups in cages appears to be a reliable short-term option.

Dual mobility significantly reduces the risk of prosthetic instability. This mechanical complication occurs when the prosthetic head moves out from the retentive polyethylene liner, such phenomenon called intra-prosthetic dislocation reports a ten-year incidence of 2% in the literature.

We prospectively analysed all intra-prosthetic dislocations having occurred since 1985 in our department in order to investigate patient- and implant-related risk factors.

91 intra-prosthetic dislocations occurred with NOVAE (SERF) cups in 85 patients of mean age 50.7 years. Intra-prosthetic dislocation occurred after a mean period of 8.8 years.

A PRO (SERF) stem was implanted in 56 cases and a PF (SERF) stem in 35. The stems were different from one another in their neck diameter and material: 13 mm titanium neck and 16 mm stainless steel neck respectively.

When taking both prosthetic features into account, no significant difference could be established regarding the time between implantation and dislocation.

Comparison between these two prosthetic features was performed by means of two continuous homogeneous series which included 240 patients implanted with PF stems and 382 patients with PRO stems. At a mean 15-year follow-up, the two series reported a non-statistically different intra-prosthetic dislocation rate of 4%.

In both series, young age and large diameter cups were considered predisposing factors for intra-prosthetic dislocation.

Therefore, unlike suggested by several authors, prosthetic neck material and diameter do not appear as the main predictors for intra-prosthetic dislocation which is highly promoted by patient-related features.

The concept of stainless steel dual mobility cups in total hip arthroplasty has demonstrated very low long-term instability rates and a 98% survival rate after 12 years. We systematically implanted titanium alloy acetabular cups during a one year period. The purpose of our retrospective study was to report the 18-year clinical outcome data in a homogeneous and continuous series of 103 primary total hip replacements after implantation of a cementless titanium cup.

All patients were implanted with NOVAE Ti (SERF) cups made of titanium alloy combined with a retentive polyethylene liner and a 22.2 mm cobalt chrome prosthetic head. Mean patient age at the time of surgery was 53 years. All patients were clinically and radiographically evaluated.

The overall 18-year actuarial cup survival rate with a 95% confidence interval was 87.4%. At last follow-up, there was no evidence of implant instability whereas acetabular aseptic loosening was reported in one case and high wear of the retentive liner in 9.

The results of this investigation confirmed the long-term stability of dual-mobility implants. The main limitation of this system was early wear of the polyethylene liner in contact with the titanium metal back and reaction with third body along with loss of liner retentivity. In our study, titanium demonstrated favourable osteointegration properties but poor tribologic characteristics, therefore suggesting its interest at the bone-cup interface only.

Purpose of the study: From a biomechanical view, the medial force stabilising the patella is assured for 50 to 60% by the medial patellofemoral ligament (MPFL). The purpose of this cadaver study was to present a precise description of the anatomic features of the MPFL concerning its femoral insertion, its relations with the oblique vastus medialis (OVM) and its relation with the medial collateral ligament (MCL) in order to optimise surgical reconstruction.

Material and methods: This cadaver study was performed on 23 knees from fresh cadavers. All measures were made knee flexed 30° by the same operator. Insertions of the OVM on the MPFL, when present, were identified. The length of the zone of reflexion was recorded. For these measurements, a orthonormal landmark centred on the femoral insertion of the MPFL was established. This landmark was used to position the medial epicondyle and the adductor tubercle for each knee.

Results: The MPFL was found in all 23 knees (100%); the length of the MPFL was 57.7±5.8 mm; its femoral insertion measured 12.2±2.6 mm (8–136); its patellar insertion measured 24.4±4.8 mm. A junction between the OVM and the MPFL was found for all 23 knees (100%). This zone appeared to be a veritable reflexion zone with the OVM fibres arching over the MPFL fibres for a length of 25.7±6 mm.

Discussion: Our study confirms the constant presence of the MPFL, observed in 100% of the knees studied. During the reconstruction of the MPFL, the key point is the position of the femoral insertion of the ligament, in order to restore the native femoral insertion of the MPFL surgically and thus attempt to recreate perfect isometry of the graft. The graft must be positions 10 mm posteriorly to the medial epicondyle and 10 mm distally to the adductor tubercle. In our cadaver the MPFL, the main medial stabilising force of the patella was a constant finding, always located in the second thickness of the medial plane of the knee.

Conclusion: We detailed the native femoral insertion of the MPFL and described its relations with the medial femoral epicondyle and the adductor tubercle using an orthonormal landmark. Long-term function of the graft depends on proper positioning.

Background: Implant instability is a major complication of total hip arthroplasty. The concept of dual articulation invented by Prof. Bousquet in 1974 is now increasingly recognized in Europe. This concept has proved to provide high stability after total hip arthroplasty revision, and to successfully address chronic instability after total hip arthroplasty. The aim of our study was to evaluate the incidence of prosthetic instability in a consecutive homogeneous series of three hundred and eighty four hips primary cases with a mean follow-up of fifteen years.

Methods: Three hundred and eighty four hips have been implanted with a dual articulation acetabular cup system. This system consists of a cementless acetabular shell, and a polyethylene liner which freely rotates within the shell and positively captures the prosthetic head. It was a consecutive and homogeneous series of cases. Only primary cases were included in the study. A final evaluation was performed at the last follow-up. Implant survival was evaluated using the Kaplan-Meier method (p< 0.05), with surgical revision for aseptic loosening as the endpoint for failure. We have evaluated the incidence of instability by prospectively listing all the episodes of implant instability.

Results: At the last follow-up, 6 patients could not be located and 92 were deceased.

Mean follow-up was 15.3 years. The mean Merle d’Aubigner hip score was 16.3±1.8 at the latest follow-up. There was no early or late instability. Radiologically, there were 31% of severe granuloma formation extending beyond zones I and VII. However, granuloma remained asymptomatic in all of the cases and did not require surgical revision of the femoral component. On the acetabular side, late complications occurred: aseptic loosening (3.3%), intra-prosthetic dislocation (3.6%), polyethylene wear that required replacement of the liner (1.8%). Survival of dual-articulation acetabular system with surgical revision for aseptic loosening as the end-point for failure was 96.4% at 15 years and 94.9% at 18 years postoperatively (p< 0.05).

Conclusion: Our consecutive homogeneous series proves the good long-term behaviour of dual-articulation acetabular components in primary arthroplasty. Their excellent survivorship rate at 18 years increases our confidence in this concept. Considering the absence of episodes of prosthetic instability in our series, we can rightly claim that the goal of decreasing instability has been achieved.

Introduction: Many publications have already shown the great interest of dual-mobility concept which significantly reduces the rate of prosthetic dislocation and thus find its place for patients at high risk of post operative instability. The aim of our study is to evaluate the prevalence of prosthetic instability in revision total hip arthroplasty using a dualmobility cup.

Materials and Methods: Our multicentric series consists of 163 revision total hip arthroplasties performed between may 1999 and may 2004. The mean age at revision was 70 years and the mean follow-up period was 56 months.

The primary etiology necessitating revision is aseptic loosening.

According to the SOFCOT classification, the acetabular deficiency was grade IV 9 times, grade III 47 times, grade I or II 107 times.

All the implanted acetabular components are SERF dual-mobility implants. This system consists of a metal back which can be HA-coated and Press Fit or cemented in a Kerboull cross or in a Novae Arm. The mobile-bearing insert which allows a dual articulation between the head and the metal back is of polyethylene.

We implanted 119 HA-coated press-fit cups and cemented 44 dual-mobility cups in a support ring or in a Kerboull cross.

Results: The mean Merle d’Aubigné and Postel score is 14,1 at the last follow-up and 4,2 in the preoperative period.

We reported 8 complications: 6 early dislocations and 2 acetabular revisions for secondary mobilisation of the cup.

Discussion: According to Huten’s 1996 SOFCOT teaching conference, this rate ranges between 2 and 5% and we have already published a series of 106 dual-mobility with no dislocation at a 10 year follow-up period.

With 4% dislocations at a mean follow-up of 56 months, the dual-mobility cup seems to provide high stability in revision hip surgery when other factors such as muscular deficiency, extended synovectomies, difficult implant placement, encourage an uncertain postoperative prosthetic stability.

These results have to be compared to those of other systems such as constrained acetabular cups or tripolar cups.

Conclusion: This is why dual-mobility remains an efficient and reliable choice to avoid prosthetic dislocation in revision surgery. Moreover, we encourage the use of dual-mobility cup in any high risk situation in terms of post-operative instability such as for old or neurological patients.

Introduction: In the last years, the use of second generation cementless anatomical stems has generated an increasing interest in primary total hip arthroplasty. They are believed to offer long term stability through appropriate stress transfer and bone remodelling in the proximal femur. We conducted a monocentric prospective study on a homogeneous series of total hip replacements performed with a cementless anatomic, hydroxyapatite-coated stem. The purpose of the study was to evaluate the contribution of this implant in terms of clinical and radiological results at a minimum 5-year follow-up.

Material and Methods: The continuous homogeneous series included 176 THA performed between September 1997 and December 1998 by a single surgeon with the same implant system (SPS femoral stem and Hilock acetabular cup, Symbios Orthopédie SA). Indications were restricted to primary or secondary degenerative hip diseases. Revisions were excluded. Patients were reviewed for clinical performance (Harris hip score), satisfaction, and radiological outcome. The radiological analysis (implant migration, Ara and Engh scores, Brooker classification) was performed by an independent surgeon unaware of the clinical performance outcome. The survival curve was determined with the Kaplan-Meier method at 95% confidence interval, using exclusively implant revision as the criteria for failure.

Results: The follow-up rate in the series was 93.2%. The five-year implant survival was 98.8%. Two revisions were recorded: one for early instability due to excessive joint laxity after surgery, one due to recurrent dislocation following improper cup positioning during surgery. The clinical improvement was obvious, as the Harris hip score improved significantly (p< 0.0001) from 32.9±1.2 preoperatively to 93.1±0.8 at five years follow-up. Pain was the item exhibiting the largest improvement with only 10.2% of patients complaining of mild pain at last follow-up. The radiological analysis revealed a high stability of the femoral implant with Ara and Engh scores reaching 5.0±0.2 and 20.7±0.5 respectively. The migration remained low at 2.4 mm ±0.3 (p=0.02) and had no incidence on the clinical outcome. Heterotopic ossifications at various grades were observed in a large proportion of patients (65.1%). The polyethylene wear rate was 0.075 mm/yr in the series, below most values commonly reported for Ø28mm PE inserts.

Discussion: The survival rate of the SPS stem is comparable with that of other published series at same follow-up. Both the stem and cup implants used provided good clinical and radiological results at five years. The objectives of good integration and stability of the cementless anatomical stem appeared to be met, despite a significant rate of heterotopic ossifications. The excellent clinical and radiological results recorded at five years should be confirmed at longer follow-up.

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: Fracture of the neck of the femur in elderly subjects is generally treated by arthroplasty, either using a total or intermediary hip prosthesis, but with a high risk of dislocation, estimated at about 10% in the literature. We investigated the contribution of a double mobile cup to lower this risk.

Material and methods: This prospective study was conducted by several operators in the same university unit between 1998 and 2001. A total of 177 mobile prostheses were implanted in patients with fracture of the anatomic neck of the femur (n=145), the neck and trochanter (n=22), or pathologic fracture (n=4). For six patients, the prosthesis was implanted after failed osteosynthesis of a trochanteric fracture. The postero-lateral approach was used for 136 women and 41 men (age range 61 – 92 years) living at home (n=124), or in an institution with a high degree of independence (n=53). The femoral stem was cemented (n=115) or impacted (n=62). A double mobile cup was used in all cases. A chromium-cobalt/ polyethylene couple was used and head diameters were 28 mm (n=150) or 22.2 mm (n=27). We studied outcome and risk of dislocation one year after implantation.

Results: There were six deaths during the postoperative period. Among the 171 patients, 134 were seen at two months, 108 at six months and 89 at one year: 39 were questioned to ascertain outcome. During the first postoperative year, there were 37 deaths; these patients were followed. Six patients were lost to follow-up. We had two cases of intraprosthetic dislocation related to a defect in the chromium-cobalt head retention of the polyethylene insert. These two cases required revision and were reported to material surveillance with corrective measures for the manufacturer.

There were three true dislocations (2%): 1) a posterior dislocation on day 24 in a female patient presenting a fracture with impaction of the femoral stem; 2) a posterior dislocation on day 22 in a female patient in very poor general condition (severe cardiorespiratory failure, death at 48 hr); 3) one recurrent posterior dislocation related to major acetabular retroversion, revised at four months.

Discussion and conclusion: The double-mobile cup appears to be a simple reproducible method for preventing dislocation of prostheses implanted for fracture of the neck of the femur.

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.