Fixation failures of dual mobility cups: a mid-term study of 2601 hip replacements

Understanding wear in dual mobility total hip replacement: first generation explant wear patterns

PURPOSE

Dual mobility was introduced by Pr. G. Bousquet to improve the dislocation risk of total hip arthroplasty (THR). The wear mechanisms of this implant remain to be understood. Could enhanced explant wear analysis explain liner wear behaviour?

METHODS

Sixty-six explanted liners were selected. Non-destructive 3D scanning and heat colour treatment allowed reporting wear patterns on both convex and concave sides of the liners.

RESULTS

For many liners, liner convexity wear was found to be homogeneous, and linked to a longer implantation time. A few liners had signs of blocking of the convexity, leading to excessive internal damage. Intra prosthetic dislocations were found to only have internal circular wear without liner penetration.

CONCLUSION

Heat colour treatment showed its effectiveness for highlighting wear patterns. Optimal convexity mobility seemed to be leading to a longer implantation time, with decreased contact stresses on concavity. The retentive rim should have a distinct wear analysis.

Dual-mobility arthroplasty failure: a rationale review of causes and technical considerations for revision

PURPOSE

Dual-mobility arthroplasty is an alternative to conventional total hip arthroplasty (THA) in appropriately selected, active adults with degenerative, necrotic or post-traumatic hip disease or with revision hip arthroplasty. Numerous papers have been published with results of dual-mobility arthroplasty, but there have been no comprehensive literature reviews that summarise the most recent findings and help the orthopaedic surgeon facing different scenarios in which revision of one or both components of a dual-mobility arthroplasty is indicated.

METHODS

We performed a PubMed search for papers published on dual-mobility arthroplasty that provided data on revision and add our experience in order to describe different revision scenarios. We collected data on revision for any reason, for aseptic loosening, for infection, or for dislocation. For each complication, we summarise causes and diagnosis of this complication and describe the direction of possible therapeutic options.

RESULTS

The dual-mobility arthroplasty offers the benefit of increased stability without compromising clinical outcomes and implant longevity. However, as with conventional arthroplasties, complications are also reported, with the most frequent being cup loosening, dislocation, accelerated wear and infection. Dual-mobility implants also have some specific complications secondary to their specific design, with the presence of a third joint. For example, intraprosthetic dislocation due to retentive failure of the polyethylene (PE) liner on the femoral head is a complication observed exclusively with this type of implant and involves articulation failure between the femoral head and the PE liner. Mechanical conflict with the iliopsoas tendon has also been reported, probably due to femoral head size, cup design, and/or a dysplastic hip. This systematic review of the literature identified several options for treating each complication, and in particular, options regarding conserving or not of one the two articulating devices.

CONCLUSIONS

These findings can inform discussions relating to risks and benefits of different therapeutic options when performing revision of a dual-mobility arthroplasty.

Highly crosslinked polyethylene: a safe alternative to conventional polyethylene for dual mobility cup mobile component. A biomechanical validation

PURPOSE

Dual mobility cup (DMC) consists of a cobalt-chromium (CoCr) alloy cup articulated with a polyethylene (PE) mobile component capturing the femoral head in force using a snap-fit technique. This biomechanical study was the first to evaluate and compare the generation of cracks in the retentive area of DMC mobile components made of highly crosslinked PE (XLPE) or conventional ultra-high molecular weight PE (UHMWPE).

METHODS

Eighty mobile components designed for a 52-mm diameter Symbol® DMC (Dedienne Santé, Mauguio, France) and a 28-mm diameter femoral head were analyzed. Four groups of 20 mobile components were constituted according to the PE material: raw UHMWPE, sterilized UHMWPE, annealed XLPE and remelted XLPE. Ten mobile components in each group were impacted with a 28-mm diameter CoCr femoral head using a snap-fit technique. The occurrence, location and area of the cracks in the retentive area were investigated using micro-CT (Skyscan 1176®, Bruker, Aarsellar, Belgium) with a 35 μm nominal isotropic voxel size by two observers blinded to the PE material and impaction or not of the mobile components.

RESULTS

Compared to conventional UHMWPE, the femoral head snap-fit did not generate more or wider cracks in the retentive area of annealed or remelted XLPE mobile components.

CONCLUSION

This biomechanical study suggests that XLPE in DMC could be a safe alternative to conventional UHMWPE regarding the generation of cracks in the retentive area related to the femoral head snap-fit.

Dual-Mobility Articulations for Patients at High Risk for Dislocation

BACKGROUND

The purpose of this study was to evaluate the performance of dual-mobility articulations in patients at high risk for dislocation after revision total hip arthroplasty.

METHODS

We reviewed the results of 36 consecutive revision total hip arthroplasties performed on patients considered high risk for instability. Indications for inclusion included abductor insufficiency, recurrent instability, failure of constrained liner, or inadequate intraoperative stability when trialing.

RESULTS

At a minimum of 2 years, there were 4 (11.1%) repeat revisions including both dual-mobility liners that were cemented into an acetabular shell and 2 for deep infection treated with a 2-stage exchange. There was one dislocation that was successfully closed reduced but no revisions for recurrent instability. The mean Harris hip score improved from 45 to 90 points (P < .001).

CONCLUSION

Dual-mobility articulations are associated with a low rate of failure with no revisions for instability in this challenging group of patients.

Salvage of Monoblock Metal-on-Metal Acetabular Components Using a Dual-Mobility Bearing

BACKGROUND

Large-diameter, monoblock acetabular components have been used for both hip resurfacing arthroplasty and metal-on-metal (MoM) total hip arthroplasty (THA). If revision is required, one solution is to retain the shell and use a dual-mobility bearing.

METHODS

We reviewed the results of 25 revision THAs including 11 hip resurfacing arthroplasty and 14 MoM THAs where a monoblock acetabular component was mated to a dual-mobility bearing.

RESULTS

At a mean of 29 months, there was one failure, an intraprosthetic dislocation of the dual-mobility bearing. There was a significant decrease in serum metal ion levels postoperatively.

CONCLUSION

Retention of a well-fixed, monoblock MoM acetabular shell and mating it to a dual-mobility bearing in the setting of revision surgery seems to be a reasonable, low-morbidity option at short-term follow-up in appropriately positioned cups.

A forty millimetre head significantly improves range of motion compared with a twenty eight millimetre head in total hip arthroplasty using a computed tomography-based navigation system

PURPOSE

Larger-diameter (≥40 mm) femoral heads decrease the incidence of post-operative dislocation in total hip arthroplasty (THA). This study was conducted to discover whether larger-diameter femoral heads result in greater range of motion of the hip with the use of a computed tomography (CT)-based navigation system.

METHODS

Thirty-nine primary THAs were performed via a posterolateral approach using a CT-based navigation system. The stem was inserted in the femur in line with the original femoral neck anteversion. Considering the range of motion during various daily activities which could occur without impingement, the cup anteversion was decided at 10 ° increments according to the stem anteversion. While the cup inclination was set at 40 ° in order to avoid a high inclination angle to prevent the edge roading between the HXLPE liner and ceramic head. After implantation, trial liners and femoral heads were used with either 28 or 40 mm diameter. Maximal hip flexion, extension, abduction, external rotation in extension at 0° and internal rotation angles in flexion at 90 ° were measured. The differences between the ranges of motion with the 40-mm and 28-mm heads were tested. The results were assessed with paired Student t-tests.

RESULTS

The ranges of motion in flexion, extension, abduction and internal rotation angles improved significantly with the 40-mm heads compared with the 28-mm heads. The ranges of motion of cases where maximal flexion angle was 90° or less were excluded, improved significantly with the 40 mm heads.

CONCLUSIONS

We concluded that the larger-diameter 40-mm femoral prosthetic heads result in greater ranges of motion in flexion, extension, abduction and internal rotation.

Can cemented dual-mobility cups be used without a reinforcement device in cases of mild acetabular bone stock alteration in total hip arthroplasty?

INTRODUCTION

Cemented versions of dual-mobility cups (DMCs), helpful in cases of bone stock alteration, are usually used in association with a reinforcement device. To simplify the intervention in elderly subjects or those with a poor bone stock, the cups can be cemented directly into the bone, but the long-term result remains uncertain. We conducted a retrospective study in this population so as to: (1) assess whether cemented fixation of a DMC without a reinforcement device leads to a higher loosening rate, (2) confirm its efficacy in preventing dislocations in subjects at high risk of instability, and (3) measure the functional results.

HYPOTHESIS

Cemented fixation of a DMC is reliable in cases of moderate alteration of bone stock.

MATERIAL AND METHODS

Sixty-four patients (66 hips) undergoing implantation of a cemented DMC (Saturne™) without a reinforcement device were included in this single-center retrospective study. Their mean age was 79.8 years (range, 40-95 years). The indications varied: hip osteoarthritis (30.3%), prosthesis revision (44.0%), and trauma (25.8%). The patients were evaluated radiologically and clinically at follow-up. The main evaluation criterion was the revision rate for aseptic loosening. Dislocations, the infection rate, and the Postel Merle d'Aubigné (PMA) score were noted.

RESULTS

At the mean follow-up of 4.2 years, three (4.6%) patients had been lost to follow-up and 22 (33.3%) had died. There was one case of aseptic loosening (1.5%). Cup survival was 98% at 5 years (95%CI [94-100]). There were no dislocations. There was one revision for infection. The mean PMA score was 15.5 (range, 9-18).

DISCUSSION

The frequency of acetabular loosening was comparable to the frequency in cemented DMCs with a reinforcement device. A cemented DMC without a reinforcement device is possible and is a simple and viable option when there is moderate bone stock alteration.

LEVEL OF EVIDENCE

IV, retrospective cohort study.

Intra-prosthetic dislocation of dual-mobility cups after total hip arthroplasty: potential causes from a clinical and biomechanical perspective

INTRODUCTION

Recurrent dislocation of total hip arthroplasty is a frequent indication for revision surgery. Hip joint stability depends on implant design, cup position and crucially on femoral head diameter. Due to an effective ultra-large diameter femoral head, dual-mobility cups are considered an attractive solution to prevent dislocation in unstable conditions. Although patients obviously benefit for many years in terms of mobility and pain, an increase of intra-prosthetic dislocation reports using dual-mobility cups has been recently observed. However, the failure mechanism of this implant-specific complication, which is characterized by the loss of the positive-locking between the femoral head and the mobile liner, is not yet completely understood.

METHODS

A comprehensive search was performed with the PubMed database and a search engine to overview this topic and to identify potential causes for this implant-specific failure from a clinical and biomechanical perspective.

RESULTS

Peri-operative findings indicate extensive fibrosis at the large articulation as well as cup loosening as potential causes. In addition, current research has shown that the failure mechanism is affected by the surface topography of the femoral neck and in particular by the design of the mobile liner.

DISCUSSION

In clinical practice it is necessary to differentiate a classic dislocation between the mobile liner and the metallic shell from an intra-prosthetic dislocation between the femoral head and the liner.

CONCLUSION

Due to the increasing popularity of dual-mobility cups in total hip arthroplasty, the understanding of which implant-specific features or tissue response may increase the risk of intra-prosthetic dislocation is of major importance for reduced revision rates by using optimized surgical techniques and implant designs.

Can Dual Mobility Cups prevent Dislocation in All Situations After Revision Total Hip Arthroplasty?

The outcome of a single design of dual mobility cup was prospectively evaluated in a continuous series of 994 revision THAs with respect to dislocation and intra-prosthetic dislocation (IPD). At a 7.3-year mean follow-up, the dislocation rate was 1.5% and the IPD rate was 0.2%. The 2 IPD occurred in acetabular-only revisions and were related to a poor head-to-neck ratio with early impingement and wear at the polyethylene mobile component chamfer. Dual mobility cups demonstrated a low dislocation rate in revision THA but did not compensate for potential perioperative technical errors. In addition, IPD did not appear to be a concern with respect to the benefit in term of instability prevention though caution is advised in acetabular-only revision associated with a poor head-to-neck ratio.

LEVEL OF EVIDENCE

Therapeutic study-Level IV.

Intraprosthetic Dislocation of Dual-Mobility Bearings Associated with Closed Reduction

CASE

We present two patients with dual-mobility total hip arthroplasty components who underwent closed reduction of posterior dislocations with conscious sedation in the emergency room. Following closed reduction, both patients had immediate pain, clicking, and grinding of the hip. Radiographs identified intraprosthetic dislocation of the dual-mobility components, and revision surgery was required.

CONCLUSION

When dislocation of a dual-mobility bearing occurs, the surgeon should consider performing a careful closed reduction with muscle paralysis and use of fluoroscopic guidance in the operating room to avoid intraprosthetic dislocation.

Dual mobility cups in total hip arthroplasty

Total hip arthroplasty (THA) is considered one of the most successful surgical procedures in orthopaedics. With the increase in the number of THAs performed in the world in the next decades, reducing or preventing medical and mechanical complications such as post-operative THA instability will be of paramount importance, particularly in an emerging health care environment based on quality control and patient outcome. Dual mobility acetabular component (also known as unconstrained tripolar implant) was introduced in France at the end of the 1970s as an alternative to standard sockets, to reduce the risk of THA dislocation in patients undergoing primary THA in France. Dual mobility cups have recently gained wider attention in the United States as an alternative option in the prevention and treatment of instability in both primary and revision THA and offer the benefit of increased stability without compromising clinical outcomes and implant longevity. In this article, we review the use of dual mobility cup in total hip arthroplasty in terms of its history, biomechanics, outcomes and complications based on more than 20 years of medical literature.

Surgical management of recurrent dislocation after total hip arthroplasty

Dislocation is a major complication of total hip arthroplasty (THA), whose frequency has been unaffected by improvements in surgical techniques and implants. The dislocation rate depends on multiple factors related to the patient, hip disease, and surgical procedure and is therefore also dependent on the surgeon. The many published studies on THA dislocation, its causes, and its treatment have produced conflicting results. The objective of this work is to review the management of THA dislocation, which is a severe event for both the patient and the surgeon. This lecture starts with a brief review of data on THA dislocation rates and the many factors that influence them. Emphasis is then put on the evaluation for a cause and, more specifically, on the challenges raised by detecting suboptimal cup position. Next, reported techniques for treating THA dislocation and the outcomes of each are discussed. Finally, a management strategy for patients selected for revision surgery is suggested.

Dual mobility in total hip arthroplasty

Dual-mobility articulations have shown promising results. Postoperative instability remains the most common reason for revision of a total hip arthroplasty (THA). Dual-mobility cups have been shown to decrease the rate of dislocation in primary THA and have been used to treat and prevent instability in revision THA. Greater range of motion and a greater head-to-neck ratio and a greater jump distance are achieved, resulting in a lower risk of instability. Concerns with dual-mobility cups include wear and intraprosthetic dislocation. Specific design modifications have aimed to improve cup fixation and decrease polyethylene wear and the risks of intraprosthetic dislocation.

Evora® chromium-cobalt dual mobility socket: results at a minimum 10 years' follow-up

INTRODUCTION

The Evora chromium-cobalt alloy dual mobility socket claims to display a large articulation tribology different from that of stainless steel models, limiting the risk of intraprosthetic dislocation and wear. The present study reports a minimum of 10years' follow-up in a multicenter prospective series of 200 sockets previously reported on at 5years.

HYPOTHESIS

The use of chromium-cobalt in dual mobility sockets provides a low rate of failure at 10years, especially as regards to osteolysis and intraprosthetic dislocation.

MATERIALS AND METHODS

Two hundred hydroxyapatite-coated molded chromium-cobalt sockets without titanium interface were implanted without cement in 194 patients with a mean age of 70 years (range, 32-91 years). Clinical results were assessed on Postel Merle d'Aubigné and Harris scores, plain radiographs and survival analysis.

RESULTS

At a mean 11 years' follow-up (10-13 years), 56 patients had died and 31 were lost to follow-up. Four underwent surgical revision (3 femoral components, and 1 socket for migration at 9 years with complete disappearance of the hydroxyapatite). A total of 109 implants were analyzable in 107 patients with a mean age of 81 years (55-93 years). At follow-up, the mean Harris score was 90 (75-96) and the PMA score 16.3 (14-18). There were no cases of loosening (except for the case reoperated on at 9 years) and no acetabular radiolucency or cysts. There were 2 cases of non-evolutive femoral radiolucency and 10 of femoral granuloma, involving head size > 22 mm (P<0.0001) and a cemented titanium stem (P=0.004) as risk factors. There were no dislocations in the large or small articulation. Ten-year survival was 99% (95% CI: 97.3%-100%) with socket revision as censorship criterion.

DISCUSSION

The absence of dislocation in both small and large articulations confirmed the efficacy of the dual mobility concept and suggested an advantage for chromium-cobalt sockets in reducing the rate of intraprosthetic dislocation and preventing blockage of the large articulation by a better performance in the friction couple. Granulomas were associated with wear in cemented titanium stems and with heads greater than 22 mm in diameter. Ten-year survival was 99% (censorship criterion: revision for socket failure); there was, however, one case of socket loosening with disappearance of the hydroxyapatite, indicating that surveillance should be continued in this cohort.

Infection as a cause of primary total hip arthroplasty revision and its predictive factors

INTRODUCTION

Infection is a serious complication of total hip arthroplasty (THA) and is one of the most frequent causes of failure. The goal of this study was to evaluate the importance of infection among the different causes of revision THA and identify any risk factors specifically associated with this cause of revision.

MATERIALS AND METHODS

All patients who underwent a first revision of THA were included in a prospective multicenter study. Postoperative clinical and radiological evaluation and follow-up of morbidity and mortality were performed at 3 months.

RESULTS

Two hundred forty out of 2107 revisions (11.4%) were performed for infected THA, which was the third cause after aseptic loosening (42.3%) and peri-prosthetic fractures (11.8%). These patients had a higher BMI associated with co-morbidities and lower clinical scores than patients with other causes of revision. One-stage revision was performed in most cases (66%) with replacement of the complete implant in 86% of cases, resulting in longer surgery compared to that for other causes. Male gender (OR 2.3), avascular necrosis (OR 2.4), arthroplasties with dual mobility cups (OR 2.5) and a Rottinger anterolateral approach (OR 3.4) were all associated with an increased risk of infection.

DISCUSSION

Some of these risk factors are not or have rarely been reported in the literature. They should be taken into consideration to help in the prevention and continuing battle against THA infection.

LEVEL OF EVIDENCE

Level IV, prospective cohort study.

Intraprosthetic dislocation: a specific complication of the dual-mobility system

BACKGROUND

The dual-mobility concept was proposed as an alternative to prevent postoperative dislocation events. However, intraprosthetic dislocation (IPD) is a troublesome and specific complication induced by the loss of the polyethylene retentive rim and escape of the femoral head from the polyethylene liner. The factors associated with IPD are unknown as only isolated cases have been reported and do not provide a clear understanding of the mechanisms of failure.

QUESTIONS/PURPOSES

We therefore (1) identified features related to different types of IPD and (2) determined factors related to the timing of IPD.

METHODS

We identified 81 cases (80 patients) with IPD from among 1960 primary THAs performed between January 1985 and December 1998. To classify the types of IPD we considered perioperative (presence of arthrofibrosis, cup loosening, and type of liner wear) and radiographic (radiographic cup loosening or migration, and ossification) features.

RESULTS

We identified three types of IPD with the following causal mechanisms: Type 1 was pure IPD without arthrofibrosis and without cup loosening (n = 26), Type 2 was IPD secondary to blocking of the liner (n = 41), and Type 3 was IPD associated with a cup loosening (n = 14). The mean times of onset were, 11, 8, and 9 years after THA, respectively. We found no difference according to the stem design regarding timing of the IPD.

CONCLUSIONS

This new IPD classification allows clinicians to anticipate the possible conditions they will encounter with revision surgery and plan surgery (cup removal, liner exchange, synovectomy). The implant characteristics and this new classification accounted for the differences in the timing of occurrence.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Large diameter heads

Large femoral heads have been used with increasing frequency over the last decade. The prime reason is likely the effect of large heads on stability. The larger head neck ratio, combined with the increased jump distance of larger heads result in a greater arc of impingement free motion, and greater resistance to dislocation in a provocative position. Multiple studies have demonstrated clear clinical efficacy in diminishing dislocation rates with the use of large femoral heads. With crosslinked polyethylene, wear has been shown to be equivalent between larger and smaller heads. However, the stability advantages of increasing diameter beyond 38 mm have not been clearly demonstrated. More importantly, recent data implicates large heads in the increasing prevalence of groin pain and psoas impingement. There are clear benefits with larger femoral head diameters, but the advantages of diameters beyond 38 mm have not yet been demonstrated clinically.

Biomechanical concept and clinical outcome of dual mobility cups

Dual mobility cup systems in total hip arthroplasty consist of a metal back with a non-constrained liner, in which a constrained standard head articulates. While superior stability of such implants in comparison with standard total hip replacements is assumed, it is the purpose of this study to outline the biomechanical concept of dual mobility cups and to describe implant survival and dislocation rate based on the series published in the English-speaking and Francophone literature. A growing body of evidence indicates reduced dislocation rates in primary and revision total hip arthroplasty and in selected tumour cases. The limited availability of studies evaluating long-term implant survival and existing concerns with regard to increased wear rates and aseptic loosening, leads to the conclusion that such implants have to be used with prudence, particularly in standard primary hip arthroplasty and in young patients.