THA in patients with acetabular bone defects is associated with a high risk of dislocation. Dual mobility (DM) cups are known to prevent and treat chronic instability. The aim of this study was to evaluate the dislocation rate and survival of jumbo DM cups. This was a retrospective, continuous, multicenter study of all the cases of jumbo DM cup implantation between 2010 and 2017 in patients with acetabular bone loss (Paprosky 2A: 46%, 2B: 32%, 2C: 15% and 3A: 6%). The indications for implantation were revisions for aseptic loosening of the cup (n=45), aseptic loosening of the femoral stem (n=3), bipolar loosening (n=11), septic loosening (n=10), periprosthetic fracture (n=5), chronic dislocation (n=4), intraprosthetic dislocation (n=2), cup impingement (n=1), primary posttraumatic arthroplasty (n=8), and acetabular dysplasia (n=4). The jumbo cups used were COPTOS TH (SERF), which combines press-fit fixation with supplemental fixation (acetabular hook, two superior flanges with one to four screws, two acetabular pegs). A bone graft was added in 74 cases (80%). The clinical assessment consisted of the Harris hip score. The primary endpoint was surgical revision for aseptic acetabular loosening or the occurrence of a dislocation episode. In all, 93 patients were reviewed at a mean follow-up of 5.3 ± 2.3 years [0, 10]. As of the last follow-up, the acetabular cup had been changed in five cases: three due to aseptic loosening (3.2%) and two due to infection (2.1%). The survivorship free of aseptic loosening was 96.8%. Three patients (3%) suffered a dislocation. At the last follow-up visit, the mean HSS scores were 72.15, (p < 0.05). Use of a jumbo DM cup in cases of acetabular bone defects leads to satisfactory medium-term results with low dislocation and loosening rates

The dual mobility design concept for acetabular components is intended to reduce the risk of dislocation and increase range of motion, but the wear pattern of this design is unclear and may have implications in implant fixation. Additionally, the solid back cups do not have the option for supplementary screw fixation, providing an additional smooth articulating surface for the liner to move against. The objective of this study was to assess cup fixation by measuring implant migration as well as proximal femoral head penetration to evaluate wear performance.

Thirty subjects were recruited in a consecutive series prospective study and received dual mobility uncemented acetabular components with mobile bearing polyethylene liners through a direct lateral approach. Femoral stems were cemented or uncemented. All subjects had 28 mm femoral heads. The femur, acetabulum, and non-articulating surface of the mobile polyethylene liner were marked with tantalum beads. Radiostereometric analysis (RSA) exams were performed post-operatively and at 6 weeks, 3 months, 6 months, 1 year, 2 years, and 3 years. Oxford 12 Hip and Satisfaction questionnaire responses were recorded. Mobile bearing motion was assessed under fluoroscopy for a single case under loaded and unloaded conditions.

Twenty-nine subjects (17 female) proceeded to surgery. Subjects were 63±11 years of age with BMIs of 28±4.7 kg/m2. Cup migration reached 0.16 ± 0.31 mm of proximal translation and 0.29±1.03 degrees of sagittal rotation at three years. A single individual had more than 3 degrees of cup rotation, occurring by 6 months and not substantially increasing after this time. Proximal translation was low for this subject. Wear of the highly cross-linked mobile bearings was 0.18 ± 0.30 mm of proximal femoral head penetration from 0 to 3 years. The mean wear rate from 1 to 3 years was 0.02 mm/year. One subject was an outlier for wear, with more than 1 mm of femoral head penetration at 1 year. However, wear did not increase after 1 year for this subject and cup migrations were below average for this individual. Similarly, the outlier for cup rotation had below average wear. Satisfaction (out of 100%) improved from 25±27% to 96±7% pre-operatively to 3 years post-operatively. Oxford 12 scores (best possible score of 48) improved from 21±7 to 43±7 over the same period. The fluoroscopic case study demonstrated visible motion of the mobile bearing during hip rotation tasks.

The overall migration of the cup was low and demonstrated favorable patterns suggesting low risk of aseptic loosening. Wear rates are also within the expected range of 0 to 0.06 mm/year for highly cross-linked polyethylene. The combination of low subsidence and low sagittal rotations of the cup, and low wear of the polyethylene are favorable predictors of good long-term performance.

Instability and aseptic loosening are the two main complications after revision total hip arthroplasty (rTHA). Dual-mobility (DM) cups were shown to counteract implant instability during rTHA. To our knowledge, no study evaluated the 10-year outcomes of rTHA using DM cups, cemented into a metal reinforcement ring, in cases of severe acetabular bone loss. We hypothesized that using a DM cup cemented into a metal ring is a reliable technique for rTHA at 10 years, with few revisions for acetabular loosening and/or instability. This is a retrospective study of 77 rTHA cases with severe acetabular bone loss (Paprosky ≥ 2C) treated exclusively with a DM cup (NOVAE STICK; SERF, DÉCINES-CHARPIEU, FRANCE) cemented into a cage (Kerboull cross, Burch-Schneider, or ARM rings). Clinical scores and radiological assessments were performed preoperatively and at the last follow-up. The main endpoints were revision surgery for aseptic loosening or recurring dislocation. With a mean follow-up of 10.7 years [2.1-16.2], 3 patients were reoperated because of aseptic acetabular loosening (3.9%) at 9.6 years [7-12]. Seven patients (9.45%) dislocated their hip implant, only 1 suffered from chronic instability (1.3%). Cup survivorship was 96.1% at 10 years. No sign of progressive radiolucent lines were found and bone graft integration was satisfactory for 91% of the patients. The use of a DM cup cemented into a metal ring during rTHA with complex acetabular bone loss was associated with low revision rates for either acetabular loosening or chronic instability at 10 years. That's why we also recommend DM cup for all high risk of dislocation situations

Introduction. The dual mobility cup was introduced in the 1970s to allow extensive range of motion associated with great stability thanks to double articulation; the first between the head and polyethylene, the second between the polyethylene and the cup. The original plan was to install a stainless-steel uncemented cup coated with a thin layer of alumina and a metal head of 22,2 mm with a polyethylene liner of first generation. Long term follow-up case studies are cited in the literature showing excellent results in reducing dislocations; however wearing and aseptic loosening are noted. The new dual-mobility cups, with reticular polyethylene and titanium and hydroxyapatite coating are proving as reliable as the older ones in terms of stability whilst they appear to be more durable. Furthermore, cemented dual-mobility cups are available, these are the topic of this study. One of the most frequent complications in the major revisions of hip replacement is dislocation. This study summarises our experience gathered in the use of dual-mobility cups during revisions of complex cases (GIR III-IV femoral or acetabular). Materials and Methods. Between July 2014 to March 2015, we have implanted 13 cemented cups with dual-mobility (Avantage® Biomet) each in different patients, who have undergone revision with severe ostheolysis (GIR III-IV femoral or acetabular). The mean age of patients was 71.5 years old (46 to 89). Indications for revisions were: aseptic loosening in 7 patients (two at third surgery), recurrent dislocation in 3 patients, 1 septic loosening, 1 revision after spacer removal e 1 post-traumatic. We used dual-mobility cup in revision surgery when implant stability could have been compromised due to difficult positioning of acetabular component in cases of walls defects or muscolar laxity. The patients have been evaluated clinically and radiographically. Results. In most difficult cases with a severe lack of acetabular walls (9 patients), and thus difficulties in correct cup positioning, we have choosen to implant a cemented cup inside a Burch-schneider® (Zimmer) ring; in those cases where acetabular morphology was still sufficient, a dual-mobility cup was directly cemented to the bone. No dislocations occured during the folllow-up, neither infections, neurological events or DVT. Discussion. Dual mobility cups are often used both as primary implant or as a revision cup. Dislocation rate in primary total hip replacement is comparable to other kind of cup normally used, while in revision cases, the incidence of dislocation decrease from a range of 5–30% to 1,1–5,5%. Our results are not yet comparable to those in literature due to short follow-up, but first impressions are comforting thanks to the lack of dislocation even in really severe cases. Conclusions. The dual-mobility cup in acetabular revisions, is one of the possible choice to keep in mind in more complex cases, where obtaining stability is difficult or impossible using other revision implants. In the literature, the available follow up are not yet long enough to be sure of implant longevity and so it's important to pay attention to use this cup in those patients with long life expectancy

Dual mobility (DM) cups have 2 points of articulation – between the shell and the polyethylene (external bearing) and between the polyethylene and the femoral head (internal bearing). Primary motion occurs at the inner bearing while the outer bearing moves only in cases of extreme range of motion. Dislocation is a top reason for revision surgery and a major cost burden on society. Instability is also a significant problem after revision THA. While a variety of factors are important in hip stability, DM cups provide the safety of larger femoral heads in virtually all patients. These larger heads increase jump distance (the distance the femoral must travel before dislocation occurs) and they also increase ROM before impingement occurs. ROM and impingement are competing with each in primary THA. Especially in the flexible female with small bone structure, their increased ROM significantly increases the risk of impingement during physiologic activities. While not necessarily leading to dislocation, subluxation can occur resulting in pain. Further, ongoing impingement reduces the longevity of the PE. The ability to increase head size and head-neck ration with the DM cups in these patients is both an immediate and long-term advantage. PE thickness still can compromise the integrity of the liner. DM cups have thicker PE, especially in the smaller size cups than standard PE inserts. Even with the dual articulation, PE wear in DM cups are less, or at worst, equivalent to standard cups while at the same time providing adequate PE thickness for PE integrity and longevity

Introduction:. The higher resisting torque against dislocation and the large range of motion due to the enlarged effective head diameter substantiate the use of eccentric dual-mobility cups in case of total hip joint instability [1,2]. As a result of force-dependent self-centering mechanism, an increased movement of the intermediate-component can be expected whose effect on wear propagation is unknown so far. Currently available hip joint simulators are only able to vary the load by the absolute value and not by the direction of resulting force. Therefore, the uniaxial force transmission may lead to a unique and stable alignment of the intermediate-component during testing. The purpose of this numerical study was to evaluate relative movements of the intermediate-component during daily life activities with respect to wear propagation. Method:. The numerical analysis was based on a standard dual-mobility system consisting of a polished metallic cup, a UHMWPE intermediate-component (40 mm outer diameter) with an eccentric offset of 2 mm and a 28 mm ceramic femoral head [Fig. 1]. The relative motion of the intermediate-component was affected by the geometrically generated self-centering torque (T. C. ) and the friction torque for inner (T. Fi. ) and outer (T. Fo. ) articulation around the centre of rotation Z. 1. [Fig. 2]. In order to consider lubrication conditions the lambda ratio was estimated for different daily life activities [3], including the calculation of composite roughness and minimum film thickness for a ball-on-plate configuration. The friction torque was related to the product of load (FRes), lever arm and the coefficients of friction which were determined using the equation proposed by [4]. Depending on load FRes and load orientation angle βthe equilibrium of moments around Z. 1. was established. Results:. Due to surface roughness and calculated minimum film thickness (0.1 to 0.62 μm), boundary lubrication was determined for both inner and outer articulation. The average coefficient of friction was 0.01825 for inner and 0.0751 for outer bearing. Torque patterns were obtained for different load orientation angles [Fig. 3]. In case of an angle β between 15° and 45° the friction torque dominated compared to the self-centering mechanism which resulted in a fixed intermediate-component position. Increasing the orientation angle β above 45° lead to a superiority of the self-centering effect as can be found for varus positions. Discussion:. In case of daily life activities the load vector FRes varies within the range of 30° in the frontal plane [3]. Therefore, the angle β ranges below 30° which leads to a fixed position of the intermediate-component. Consequently, the self-centering mechanism seems to have no negative influence on the wear propagation of dual-mobility cup systems. The presented numerical analysis permits a variation of implant-specific dimensions, but is limited to polyethylene wear couples

Introduction. Pelvic posterior tilt change (PPTC) after THA is caused by release of joint contracture and degenerative lumbar kyphosis. PPTC increases cup anteversion and inclination and results in a risk of prosthesis impingement (PI) and edge loading (EL). There was reportedly no component orientation of fixed bearing which can avoid PI and EL against 20°PPTC. However, dual mobility bearing (DM) has been reported to have a large oscillation angle and potential to withstand EL without increasing polyethylene (PE) wear against high cup inclination such as 60∼65°. Objective. The purpose of this study was to investigate the optimal orientation of DM-THA for avoiding PI and EL against postoperative 20°PPTC. Methods. Our study was performed with computer tomography -based three-dimensional simulation software (ZedHip. LEXI co. Japan). The CT data of hip was derived from asian typical woman with normal hips. Used prosthesises were 50mm cup and 42mm outer head of modular dual mobility system and Accolade II 127°(stryker). Femoral coordinate system was retrocondylar plane with z-axis from trochanteric fossa to intercondylar notch. Cup orientation was described as anatomical definition. The safe zone was calculated by the required hip range of motion which was defined as 130°flexion, 40°extension, 30°external rotation, and 50°internal rotation with 90°flexion and the maximum inclination of DM cup which was 60°in consideration of withstanding EL. Cup orientations withstanding 20°PPTC were defined as the primary cup orientation which changes consistently within the safe zone with the match of 20°PPTC. And among them cup orientation with lowest inclination was defined as the optimal cup orientation. result. The optimal orientations could be identified only within stem anteversion from 15°to 40°. The relationship between the optimal cup orientation and stem anteversion could be automatically identified. The correlation between stem anteversion and cup anteversion was linearly distributed and could be expressed as an approximated line of the formula that (stem anteversion)+(cup anteversion)=36.8. And likewise the relationship between stem anteversion and cup inclination was curved-linerly distributed and could be expressed as an approximated curved line of the formula that (cup inclination)=0.04(stem anteversion). 2. 2.18(stem anteversion)+74.8. Cup orientation calculated by the Widmer's combined anteversion theory is easily deviated from the safe zone by PPTC. The optimal cup orientation calculated in this study could be set more inclination and retroversion than it calculated by the Widmer's theory in contribution of large oscillation angle and admissibility of high inclination cup setting of DM. Therefore it could be possible to withstand 20°PPTC. Conclusion. Performing THA with considering postoperative PPTC is necessary for good long term outcome without dislocation and PE wear. The solution for 20°PPTC after THA is to apply dual mobility bearing and the formula of combined orientation theory calculated in this study

INTRODUCTION. THA as primary treatment for displaced femoral neck fractures in elderly still remains a prominent concern. Overall dislocation rate after total hip arthroplasty (THA) is reported form 1∼5%. But, it is quiet different in situation of femur neck fracture in elderly. The THA is associated with higher rates of dislocation (8%∼11%) in eldery compared to hemiarthroplasty even though THA showed better clinical and functional scores. Recently resurgence about THA using DMC comes after improvement of manufacturing technology. The aim of this prospective multicenter study is to assess the rates of dislocation and re-operation for displaced femoral neck fractures in elderly with THA with Dual Mobility Cup (DMC) and to review systematically comparison of previous reports. Up to our knowledge, this is first report from asian conutry about the clinical outcomes THA using DMC for displaced femur neck fracture in elderly. METHODS. Prospective consecutive groups of patients treated for displaced femoral neck fractures by three surgeons at each three center were included. 131 hips underwent THA with DMC for acute displaced femoral neck fracture in patients aged older than 70 years. Data regarding rates of dislocation and re-operation were obtained by review of medical records. Additionally From 2009 which the US FDA first approved the DMC, the authors searched reports regarding to THA using DMC for displaced femur neck fracture in elderly using the MEDLINE including cases series and comparative studies with bipolar hemiarthroplasty and THA. Therefore, current report was compared with previous reports. RESULTS. The reports about THA using DMC for displaced femur neck fracture in elderly were limited. Most of them comes from European countries. Comparative study with THA from Sweden reported the dislocation rate of THA using DMC with average aged 75-year is 0%. In Denmark study, the bipolar hemiarthroplasty showed 14% of dislocation rate for femur neck fracture in patient aged 75 years but, THA using DMC is 4.6%. Two cases series from French reported about 1–4% in patients aged 80 years. In our multicenter study, dislocation occurred in 6/131 hips (4.6%) treated with total hip arthroplasty using DMC for displaced femur neck fracture over 70 years older patients. Reoperations including periprosthetic fracture and fixation failure of cup were required in 1/43 (2.3%) hips treated with total hip arthroplasty using DM cup. These result is comparable to European reports. DISCUSSION AND CONCLUSION. Our findings indicate that THA with DMC can not guarantee to prevent the dislocation for high risk elderly patients, but the overall rate of dislocation can be comparable to those of bipolar hemiarthroplasty and reduced compared to conventional total hip arthroplasty. This result might be a valuable messages for burden of the medical cost by dislocation after arthroplasty especially for older patient. Therefore, adding advnatages of THA compared with hemiarthroplasty, the THA with DMC can be a wise option for displaced femoral neck fracture in eldely. But, the randomized controlled study still is needed to clarify to confirm this findings