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

Outcomes of Dual Mobility Versus Fixed Bearing Components in Revision Total Hip Arthroplasty: A Systematic Review and Meta-Analysis

AIMS

Dual mobility (DM) implants have received increasing interest in revision surgery due to their increased stability. The aim of this systematic review was to compare outcomes of DM versus conventional fixed bearing (FB) implants in revision Total Hip Arthroplasty (r-THA).

METHODS

A comprehensive search was performed using the PubMed, Embase, and MEDLINE databases between January 2000 and 2023. Outcome measures included re-revision due to dislocation, re-revision for other causes, all-cause re-revision, total complication rate, and functional outcome measures. The Methodological Index for Non-Randomized Studies (MINORS) assessment tool was used to evaluate methodological quality and the risk of bias. A pooled meta-analysis was conducted, with an assessment of heterogeneity using the Chi-square and Higgins I2 tests. A further sub-group analysis was performed between DM implants and larger femoral head (> 36 mm) FB implants.

RESULTS

A total of 13 studies met the final inclusion criteria, with an overall number of 5,004 r-THA hips included (2,108 DM and 2,896 FB). The DM implants had significantly lower odds of re-revision due to dislocation (OR [odds ratio] 0.38, P < 0.001), aseptic loosening (OR 0.54, P = 0.004), and all-cause re-revision (OR 0.55, P < 0.001) compared to FB implants. No significant difference was seen in the odds of re-revision due to periprosthetic joint infection (PJI) (OR 0.99, P = 0.94) or periprosthetic fracture (OR 0.59, P = 0.13) between the two groups. The total number of complications showed an odds benefit in favor of DM implants (OR 0.43, P < 0.001). In the subgroup analysis, there was no significant difference in the odds of re-revision due to dislocation (OR 0.69, P = 0.11) between DM and larger femoral head FB implants.

CONCLUSION

Based upon current literature, it appears DM implants are an effective modality for reducing dislocation following r-THA with lower complication rates compared to FB implants. However, further prospective randomized controlled trials (RCTs) with longer term follow up are required.

Results of third generation dual mobility total hip arthroplasties with non-cross-linked polyethylene in patients under 60 years of age: comparative study of full pressfit vs. tripod cups after 8.6 years

BACKGROUND

The concept of dual mobility of total hip arthroplasties (THA) is a revolution in the prevention of dislocations and in the treatment of instability. Its use remains controversial in patients under 60 years old, providing poorer results with first generation cups coated with alumina. This study, carried out on modern dual mobility (DM) cups with a porous bilayer coating, in active patients under 60 years of age aimed to evaluate: (1) the mechanical survival of two latest generation DM THA, with failure defined as revision of acetabular or femoral implants for mechanical loosening, by comparing a tripod cup to a full pressfit cup, (2) to evaluate the complications, (3) to compare the rate of radiographic peri-prosthetic osteolysis between the 2 implants.

HYPOTHESIS

The hypothesis was that the medium-term survival of modern DM cups placed in young patients was the same regardless of the type of acetabular fixation used.

MATERIALS AND METHODS

This was a retrospective study of 119 latest generation DM THA with standard polyethylene, composed of 66 full pressfit cups and 53 tripod fixation cups, used in primary arthroplasty in 111 patients between 2005 and 2016. The survival study was carried out using medical records. The clinical evaluation was carried out using the modified Harris Hip Score (mHHS) as well as the self-administered Hip and Osteoarthritis Outcome Score (HOOS) and Oxford-12 questionnaires. Radiological analysis was carried out on radiographs looking for bone demineralization and acetabular and femoral lines.

RESULTS

At 8.6 years (5-16), no revision for mechanical loosening was observed regardless of the type of cup. The prosthesis dislocation rate (large joint) was 1.7%: 1 case in each group (p = 1), including one revision required in the full pressfit group. Three revisions for mechanical complications were recorded: a recurrent dislocating hip on a full pressfit cup that was not sufficiently anteverted, an acetabular peri-prosthetic fracture on a full pressfit cup and a case of iliopsoas impingement with a retroverted tripod cup. The survival rate for all-cause revision was 93.8% for pressfit (95% CI: 88.2%-99.9%) vs. 96.2% for tripod (95% CI: 91.1%-100%) (p = 0.63) and for revision due to any cause excluding infection, 96.9% for pressfit (95% CI: 92.8%-100%) vs. 98.1% for tripod (95% CI: 94.4%-100%) (p = 0.7). The rate of periacetabular osteolysis was 11%, significantly more present amongst tripod cups (24%, 9 cases) compared to full pressfit cups (2%, 1 case) (p < 0.01).

CONCLUSION

This series demonstrates good performance of 3rd generation DM cups with porous bilayer coating in patients under 60 years of age regardless of the type of acetabular fixation, at 8.6 years of follow-up. The rate of osteolysis around full pressfit cups remains very low, unlike that of tripod cups. The use of Double Mobility prostheses for primary hip osteoarthritis is possible in young patients, preferably with full pressfit cups (i.e., without any pegs or additional screws that may promote diffusion of polyethylene debris and osteolysis).

LEVEL OF EVIDENCE

III; comparative retrospective study.

Incidence, treatment, and outcomes of modern dual-mobility intraprosthetic dissociations

Aims

Dual-mobility (DM) components are increasingly used to prevent and treat dislocation after total hip arthroplasty (THA). Intraprosthetic dissociation (IPD) is a rare complication of DM that is believed to have decreased with contemporary implants. This study aimed to report incidence, treatment, and outcomes of contemporary DM IPD.

Methods

A total of 1,453 DM components were implanted at a single academic institution between January 2010 and December 2021: 695 in primary and 758 in revision THA. Of these, 49 presented with a dislocation of the large DM head and five presented with an IPD. At the time of closed reduction of the large DM dislocation, six additional IPDs occurred. The mean age was 64 years (SD 9.6), 54.5% were female (n = 6), and mean follow-up was 4.2 years (SD 1.8). Of the 11 IPDs, seven had a history of instability, five had abductor insufficiency, four had prior lumbar fusion, and two were conversions for failed fracture management.

Results

The incidence of IPD was 0.76%. Of the 11 IPDs, ten were missed either at presentation or after attempted reduction. All ten patients with a missed IPD were discharged with a presumed reduction. The mean time from IPD to surgical treatment was three weeks (0 to 23). One patient died after IPD prior to revision. Of the ten remaining hips with IPD, the DM head was exchanged in two, four underwent acetabular revision with DM exchange, and four were revised to a constrained liner. Of these, five (50%) underwent reoperation at a mean 1.8 years (SD 0.73), including one additional acetabular revision. No patients who underwent initial acetabular revision for IPD treatment required subsequent reoperation.

Conclusion

The overall rate of IPD was low at 0.76%. It is essential to identify an IPD on radiographs as the majority were missed at presentation or after iatrogenic dissociation. Surgeons should consider acetabular revision for IPD to allow conversion to a larger DM head, and take care to remove impinging structures that may increase the risk of subsequent failure.

A Meta-Analysis to Evaluate Implant Survival and Benefits of the Use of Dual Mobility Constructs in Total Hip Replacement Following Hip Fracture

Total hip replacement (THR) is commonly performed to treat hip fractures. Dual-mobility constructs (DMCs) are increasingly used for this indication. The aim of this study was to use evidence synthesis techniques to estimate net all-cause construct survival for THR with DMC performed for hip fracture. Additionally, we aimed to investigate and describe differences in all-cause construct survival (if present) between THRs performed with DMC (DMC-THR) or with a conventional bearing construct following hip fracture. We performed a systematic review and meta-analysis of published studies (including joint registries), including DMC-THR for hip fracture which provided Kaplan-Meier (KM) survival estimates. The primary outcome was all-cause construct survival over time. The study was prospectively registered on PROSPERO (CRD42020173117). A total of 557 papers and 17 registry reports were identified. Six studies (four registry reports, one matched-pair cohort study utilising joint registry data, and one single-institution case series) met the inclusion criteria, including 17,370 DMC THRs and 167,377 conventional THRs. Five-year KM survival estimates (95% confidence intervals) were similar at 95.4% (94.9 to 95.8%) for DMC-THR and 96.2% (96.0 to 96.4%) for conventional THR. The relative risk of revision for DMC-THR at five years was 1.21 (1.05 to 1.41). These results suggest that DMC-THR has a lower all-cause survival than conventional THR following hip fracture. This analysis does not support the routine use of DMC-THR over conventional bearing THR.

Intraprosthetic dislocation of dual-mobility total hip arthroplasty implant

Dual-mobility total hip arthroplasties were developed to decrease the risk of dislocation and instability seen with traditional fixed-bearing total hip arthroplasties. However, dual-mobility constructs, notably the first-generation design, come with a risk of intraprosthetic dislocation (IPD). These dislocations occur when the polyethylene femoral head component is dislodged, causing direct articulation between the inner ceramic femoral head and the metal acetabular shell. This is different than a polyethylene liner dislocation in a standard total hip arthroplasty. Causes of IPD include polyethylene wear and iatrogenic dislocation from closed reduction attempts. Timely identification is essential to reduce the risk of soft tissue metallosis, raised cobalt and chromium levels, and the need for major revisions. This complication can be seen on imaging, but radiologists must be aware of the various components and mechanisms of failure to recognize this unique complication. We present a case of a dual-mobility construct with IPD between the femoral head components, illustrated on radiographs and CT and subsequently confirmed at the time of surgery.

Evolution and New Generation of Dual Mobility Cups

Although total hip arthroplasty (THA) is considered a successful procedure, hip dislocation remains the main cause of early failure. Dual mobility cups (DMCs) have been shown to significantly reduce the dislocation rate in both primary and revision THAs. During the past several decades, DMCs have evolved in design and fixation interface. There have been three generations of DMCs. This article addresses the rationale for a new cementless highly porous titanium DMC to improve component fixation and implant biocompatibility. [Orthopedics. 2023;46(5):e273-e280.].

Dislocated and Dissociated Dual-Mobility Components Are Easily Missed and More Than Half Fail Closed Reduction: Six Tips to Aid Management

Dual-mobility (DM) implants reduce the risk of dislocation in patients who have undergone total hip arthroplasty (THA); however, DM implants are at risk for large-head dislocation and intraprosthetic dissociation (IPD), where the inner femoral head dissociates from the outer polyethylene head. This study aimed to report the incidence of DM dislocation and IPD, evaluate the rate of recognition of IPD before and after reduction, investigate the outcomes of these complications, and provide treatment recommendations for their management.

Methods

Between 2010 and 2021, 695 primary and 758 revision THAs were performed with DM constructs at a single institution. There were 44 large-head dislocations (3.0%) and 10 IPDs (0.7%). Four additional IPDs occurred during attempted closed reduction, increasing the IPD incidence to 0.96%. We reviewed prior instability history, dislocation management, success of reduction, recognition of IPD, and subsequent rates of revision and complications. The mean follow-up was 2.5 years.

Results

Nine of 10 IPDs were missed at presentation and thus not treated as such. Sixty-three percent of attempted closed reductions in the emergency department failed and led to 4 IPDs and 1 periprosthetic fracture. Reduction success was associated with the following factors: use of general anesthesia with paralysis (p = 0.02), having the reduction performed by an orthopaedist (p = 0.03), and undergoing only 1 reduction attempt (p = 0.015). Two-thirds of dislocations required revision. The rate of redislocation was 33%, and 5 hips required subsequent revision at a mean of 1.8 years after the initial dislocation.

Conclusions

We present an evaluation of DM-implant dislocation and dissociation along with management recommendations based on these data. Given the low success and high complication rates of attempted closed reduction and the need for eventual revision, we recommend that all patients with dislocated DM implants be brought to the operating room for closed reduction as well as potential revision if the reduction fails.

Level of Evidence

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Comparing dislocation rates by approach following elective primary dual mobility total hip arthroplasty: a systematic review

BACKGROUND

Dual mobility components can be implanted during total hip arthroplasty (THA) for primary osteoarthritis via a direct anterior approach (DAA), anterolateral approach (ALA), direct lateral approach (DLA), or posterior/posterolateral approach (PLA). This review compares dual mobility hip dislocation rates using these approaches for elective primary THA.

METHODS

PubMed, Embase, and Cochrane databases were systematically searched for articles published after January 1, 2006 that reported dislocation rates for adult patients after primary THA with dual mobility implants. Articles were excluded if they reported revision procedures, nonelective THA for femoral neck fractures, acetabular defects requiring supplemental implants, prior surgery, or ≤ 5 patients. The primary outcome was hip dislocation rate. Secondary outcomes included infection, Harris Hip Score (HHS), and Postel-Merle d'Aubigné (PMA) score.

RESULTS

After screening 542 articles, 63 met inclusion criteria. Due to study heterogeneity, we did not perform a meta-analysis. Eight studies reported DAA, 5 reported ALA, 6 reported the DLA, and 56 reported PLA. Study size ranged from 41 to 2,601 patients. Mean follow-up time ranged from 6 months to 25 years. Rates of infection and dislocation were low; 80% of ALA, 87.5% of DAA, 100% of DLA, and 82.1% of PLA studies reported zero postoperative dislocations. Studies reporting postoperative HHS and PMA scores showed considerable improvement for all approaches.

CONCLUSIONS

Patients undergoing primary THA with dual mobility implants rarely experience postoperative dislocation, regardless of surgical approach. Additional studies directly comparing DAA, ALA, DLA, and PLA are needed to confirm these findings.

Wear debris in metal-on-metal bearings and modular junctions : What have we learned from the last decades?

Metal-on-metal (MoM) bearing hip arthroplasty saw increasing utilization and peaked in the 1990s and early 2000s. Although the linear and volumetric wear rate for a MoM bearings was lower than its polyethylene counterpart, metal ion particles were found to be approximately 10 × smaller and 500 × higher in quantity compared to polyethylene wear debris. Research into these articulations have demonstrated their relationship to the formation of lymphocyte-mediated adverse local tissue reactions. The work-up for metal particle-associated conditions (metallosis) includes a thorough patient history and physical examination, blood laboratory studies for metal ion concentrations, and advanced imaging studies including magnetic resonance imaging (MRI). The treatment of metallosis and adverse local tissue reactions ranges from close serial observation to extensive debridement and full revision of arthroplasty components, when indicated.

The Role of Dual-Mobility Components in Total Hip Arthroplasty

➤

Dual mobility (DM) refers to a now widely available option for total hip articulation. DM implants feature a small inner head, a hard bearing, that connects via a taper fit onto the femoral trunnion. This head freely rotates but is encased inside a larger, outer polyethylene head that articulates with a smooth acetabular component.

➤

DM acetabular components are available in the form of a monoblock shell or as a liner that is impacted into a modular shell, providing a metal articulation for the polyethylene outer head.

➤

DM is designed to increase hip stability by providing the arthroplasty construct with a higher jump distance, head-to-neck ratio, and range of motion prior to impingement.

➤

The use of DM in total hip arthroplasty continues to increase in the United States for both primary and revision arthroplasty. Surgeons should be aware of the potential benefits and pitfalls.

➤

Long-term data are lacking, especially for modular DM implants. Points of concern include a potential for accelerated polyethylene wear, intraprosthetic dislocation, and modular backside fretting corrosion.

Dual-Mobility Cups in Primary Total Hip Arthroplasty

Dual-mobility cups (DMCs) were introduced in France more than 40 years ago and are increasingly used not only in hip revision but also primary hip arthroplasty. Due to a simulated large-head articulation and increased jumping distance, DMCs can contribute to a high range of motion in the hip joint and reduce the risk of instability. Numerous studies have reported low dislocation rates and high survival rates in the mid-term follow-up. Nevertheless, long-term data, especially on primary hip replacement, remain limited, and the effect of recent designs and material innovations is still unclear. Therefore, primary DMCs are mainly proposed in patients at high risk for dislocation (i.e. pelvitrochanteric insufficiency, compromised spinopelvic mobility, neuromuscular disorders, obesity and femoral neck fractures). Based on a review of recently published studies referring to these indications, the current study discusses the advantages and disadvantages of DMCs.

Use of dual-mobility cup in primary total hip arthroplasties: an Italian regional register (RIPO) study on three thousand, seven hundred and ten cases

PURPOSE

The purpose of the study was to investigate the outcome of dual-mobility cup (DM) compared with a standard cup (SC) in primary total hip arthroplasty (THA) in the long-term follow-up based on a regional Italian joint registry (RIPO).

METHODS

The Registry of Prosthetic Orthopaedic Implant (RIPO) was consulted, looking for all primary THAs implanted from 2000 to 2019. Three thousand seven hundred ten were dual-mobility cup (DM) total hip arthroplasties (THA) and 85.816 were standard cup (SC) THAs, on a total of 89.526 primary THA. Demographics, survival rates and causes of revision were evaluated and compared between the two groups.

RESULTS

The use of DM progressively increased from 0.4% in 2000 to 7.5% in 2018 of all primary THAs. Revision rate was 3.5% (128 on 3710) for DMC and 4.7% (4061 on 85,816) for SC. DM presented lower dislocation rate if compared to SC with 22-28-mm femoral head diameter. However, DM showed a higher risk of revision for any causes than SC with 32-mm femoral head diameter in long-term follow-up. Nevertheless, no significant difference was measured in terms of demographics and surgical approach for dislocation rate.

CONCLUSIONS

The DM cup represents a valid implant solution and has a lower dislocation rate than 22-28-mm SC. A slight increase in the use of DM implants over time was observed in the RIPO. However, a larger population and a longer follow-up are needed to further monitor the survival rate of new-generation DM implants.

The Incidence and Temporal Trends of Dislocation After the Use of Constrained Acetabular Components and Dual Mobility Implants in Primary Total Hip Replacements: A Systematic Review and Meta-Analysis of Longitudinal Observational Studies

BACKGROUND

Dislocation after a primary total hip replacement (pTHR) remains a common cause of treatment failure. Constrained acetabular components (CACs) and dual mobility implants (DMIs) may mitigate this in patients at high risk of dislocation or with significant intraoperative instability. This meta-analysis evaluated the incidence and temporal trends of dislocation after implantation with CACs and DMIs in pTHR.

METHODS

Longitudinal studies reporting dislocation after the use of CACs or DMIs in pTHR were sought from Medline and Embase to September 2020. Secondary outcomes included revision surgery for dislocation and for all causes.

RESULTS

A total of 46 studies (3 CAC and 43 DMI) comprising 582 CACs and 18,748 DMIs were included. The pooled incidence of dislocation was 1.08% (95% confidence interval [CI]: 0.00-3.72; range 0.27%-2.60%) over a weighted mean follow-up of 4.1 years for CACs, compared with 0.25% (95% CI: 0.08-0.46; range 0.00%-4.72%) over 6.2 years for DMIs. For DMIs, there was a temporal decline in dislocations from the 1980s onward, and dislocation rates remained low (<1%) until 15 years postoperatively. There were insufficient data for similar analysis of CACs. All studies were at high risk of bias. The incidence of revision for dislocation after CACs was 0.3% vs 0.1% for DMIs, and the incidence of revision for all causes after CACs was 4.8% vs 2.7% for DMIs.

CONCLUSION

DMIs demonstrated a lower incidence of dislocation compared with CACs; however, there was a relative absence of CACs used in the context of pTHR in the literature. Temporal trends in dislocation have improved over time for DMIs.

Survival and complications of total hip arthroplasty using third-generation dual-mobility cups with non-cross-linked polyethylene liners in patients younger than 55years

BACKGROUND

In younger patients, total hip prostheses are subjected to wide motion ranges and wear-inducing forces. Dual-mobility cups (DMCs) are effective in decreasing the risk of dislocation. However, wear and osteolysis have been reported with first-generation DMCs. These complications have not been assessed in younger patients managed with third-generation DMCs associated with a lower risk of intra-prosthetic dislocation (IPD). We therefore designed a retrospective study of patients younger than 55years at THA with third-generation DMCs. Our objectives were to evaluate (1) the complication rate, and (2) the survival rate.

HYPOTHESIS

The rate of complications of THA with third-generation DMCs in patients younger than 55years of age is comparable to that in the general population of THA patients.

MATERIAL AND METHODS

This retrospective study included 79 consecutive patients (91 hips) who had total hip arthroplasty (THA) between 2007 and 2012. We included all patients younger than 55years who underwent primary THA with a third-generation DMC and a liner made of non-cross-linked polyethylene. The patients were evaluated clinically and radiologically.

RESULTS

Mean follow-up was 9.8years (range: 2-13years). At last follow-up, no patient had experienced prosthetic dislocation or IPD. Aseptic and septic cup loosening each occurred in 1 patient. In all, 7 (7.7%) patients required revision surgery with exchange of at least one component (cup loosening, n=2; neck fracture with a short stem fixed to the neck, n=1; peri-prosthetic femoral fracture, n=1; infection, n=1; and femoral-stem loosening, n=2). Peri-acetabular osteolysis developed in 2 (2.2%) hips. Cup survival to aseptic loosening was 98.9% (95% confidence interval, 97%-100%) and survival to revision for any reason except infection was 95.6% (95% confidence interval, 82%-100%).

DISCUSSION

In patients younger than 55years, third-generation DMCs were associated with absence of prosthetic dislocation, absence of IPD, and a low revision rate for cup loosening, in the medium term. These implants therefore constitute a viable treatment option in younger patients requiring THA.

LEVEL OF EVIDENCE

IV, retrospective study.

Dual mobility hip arthroplasty: iatrogenic intraprosthetic dislocation of a 22 mm head

We describe the first intraprosthetic dislocations of a 22 mm head in a dual mobility hip replacement in the literature. This case emphasises the importance of information gathering and planning when dealing with arthroplasty complications. Furthermore, it highlights the necessity of adequate muscle relaxation and analgesia when dealing with hip dislocations. A 78-year-old patient presented to the emergency department (ED) with a spontaneous dislocation of her left dual-mobility total hip replacement 3 months after first-stage revision surgery for infection. Reduction via manipulation under analgesia was then attempted in the ED but was ultimately unsuccessful; an iatrogenic intraprosthetic dislocation of the polyethylene liner was sustained. Several factors may have contributed to liner dislocation: a failure to appreciate the implant type, multiple manipulations in ED were attempted under analgesia, but no sedation or muscle relaxation was administered to the patient. The patient subsequently underwent revision surgery.

Intraprosthetic Dislocation of Dual-Mobility Total Hip Arthroplasty: The Unforeseen Complication

Total hip arthroplasty (THA) is one of the most successful and widely accepted orthopedic procedures. Instability after THA is one of the most significant postoperative complications. Dual-mobility THA components were introduced in 1974 to overcome the risk of instability by increasing the jump distance. Dual-mobility bearings couple two articulations, namely, one between a 22-28 mm prosthetic head and polyethylene liner and another larger articulation between the polyethylene liner and the metal cup. Dislocation of the polyethylene liner and the consequent direct articulation between the prosthetic head and metal cup is recognized as intraprosthetic dislocation (IPD). This mode of THA failure is specific to dual-mobility implants. Despite the reduced incidence of IPD in modern dual-mobility implants compared to the early designs, iatrogenic IPD can occur during closed reduction of dislocated polyethylene liner-metal cup articulation. IPD requires timely diagnosis and early surgical intervention to minimize the necessity of major revision surgeries. This study presents a comprehensive review for dual-mobility-bearing THA, including the history and biomechanics, and focuses on the pathomechanics, diagnosis, and management of IPD.

A review of the clinical and engineering performance of dual-mobility cups for total hip arthroplasty

Charnley's low-friction principle of total hip arthroplasty (THA) is recognized as the gold standard. However, complications may arise, and one of the major reasons for revising THA is dislocation. Under such a background, Pr. Gilles Bousquet invented dual-mobility cups (DMC) in the 1970s to fight against hip instability. Despite the excellent clinical results of DMC compared with conventional implants, the clinical application of DMC is limited by concerns about the dual articulations, leading to rapid wear and the subsequent osteolysis and the wear on the retaining rim of the liner due to its contact with the femoral neck causing intraprosthetic dislocation (IPD). As a result, the original design of DMC has been upgraded by using highly cross-linked polyethylene, refining the geometry of the femoral neck, etc. After the improvement, the wear rate of the contemporary DMC liners has been largely reduced compared with the first generation DMC, and the IPD incidence rate has been controlled. However, with the increasing fretting corrosion damage found at the taper-trunnion interfaces in conventional implants, the contemporary DMC may face a similar problem. This is because the additional articulation and the larger head design of DMC gain the risk of articulation wear and taper-trunnion interface corrosion. Since there are still many potential DMC engineering issues that have not been extensively researched, future studies focusing on the wear and corrosion aspects are required. The purpose of this review article is to summarize both the clinical and engineering issues for DMC with possible directions for future research.

Dual Mobility Reduces Dislocations-Why I Use It in All Revisions

BACKGROUND

Instability remains the most common complication after revision total hip arthroplasty (THA) and presents a unique treatment dilemma for the orthopedic surgeon. Dual mobility (DM) bearing articulations have been used in France since the 1970s, but have only become more widely adopted in the United States over the last decade. The purpose of this symposium was to discuss the role for DM bearings in revision THA.

METHODS

We reviewed the existing literature on outcomes after DM bearing articulations in revision THA. We also report several case examples of the use of DM in difficult revision THA cases, including acetabular bone loss, failed constrained liner, and adverse local tissue reaction. Finally, we briefly discuss the limitations associated with the use of DM.

RESULTS

Several large retrospective series demonstrate that DM bearings reduce the incidence of dislocation after revision THA when compared with conventional single bearing THA. Specific complications related to DM bearings including polyethylene wear, loosening, intraprosthetic dislocation, and corrosion remain a concern, but appear to have drastically improved over time with modern implant designs.

CONCLUSION

Contemporary DM designs have been established as an effective bearing option to reduce instability in revision THA, although concerns do exist. High-quality prospective studies are necessary to further define the role this bearing option has in the coming years.

Instability After Total Hip Arthroplasty and the Role of Advanced and Robotic Technology

Instability remains the leading cause of reoperation following total hip arthroplasty (THA). In this article, the risk factors for instability after THA are reviewed, including patient-related characteristics, surgical techniques, positioning of implants, and the role of advanced technology and robotics as a platform that may reduce the incidence of instability.

Risk factors and modes of failure in the modern dual mobility implant. A systematic review and meta-analysis

Background

The aims of this meta-analysis were to: (1) validate the outcome of modern dual mobility (DM) designs in patients who had undergone primary and revision total hip arthroplasty (THA) procedures and (2) to identify factors that affect the outcome.

Methods

We searched for studies that assessed the outcome of modern DM-THA in primary and revision procedures that were conducted between January, 2000 to August, 2020 on PubMed, MEDLINE, Cochrane Reviews and Embase. The pooled incidence of the most common failure modes and patient reported outcomes were evaluated in patients who have received: (1) primary THA, (2) revision THA for all causes or (3) for recurrent dislocation. A meta-regression analysis was performed for each parameter to determine the association with the outcome. The study design of each study was assessed for potential bias and flaws by using the quality assessment tool for case series studies.

Results

A total of 119 studies (N= 30016 DM-THAs) were included for analysis. The mean follow-up duration was 47.3 months. The overall implant failure rate was 4.2% (primary: 2.3%, revision for all causes: 5.5%, recurrent dislocation: 6.0%). The most common failure modes were aseptic loosening (primary: 0.9%, revision for all causes: 2.2%, recurrent dislocation: 2.4%), septic loosening (primary:0.8%, revision for all causes: 2.3%, recurrent dislocation: 2.5%), extra-articular dislocation (primary:0.6%, revision for all causes:1.3%, recurrent dislocation:2.5%), intra-prosthetic dislocation (primary:0.8%, revision for all causes:1.0%, recurrent dislocation:1.6%) and periprosthetic fracture (primary:0.9%, revision for all causes:0.9%, recurrent dislocation:1.3%). The multi-regression analysis identified younger age (β=-0.04, 95% CI -0.07 – -0.02) and female patients (β=3.34, 95% CI 0.91–5.78) were correlated with higher implant failure rate. Age, gender, posterolateral approach and body mass index (BMI) were not risk factors for extra-articular or intra-prosthetic dislocation in this cohort. The overall Harris hip score and Merle d’Aubigné score were 84.87 and 16.36, respectively. Level of evidence of this meta-analysis was IV.

Conclusion

Modern dual-mobility designs provide satisfactory mid-term implant survival and clinical performance. Younger age and female patients might impact the outcome after DM-THA. Future research directions should focus on, (1) long-term outcome of modern dual-mobility design, including specific concerns such as intra-prosthetic dislocation and elevated metal ion, and (2) cost-effectiveness analysis of dual-mobility implant as an alternative to conventional THA for patients who are at high risk of dislocation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04404-4.

Outcomes of total hip arthroplasty using dual-mobility cups for femoral neck fractures: a systematic review and meta-analysis

OBJECTIVES

Femoral neck fractures (FNFs), with up to 15% mortality, are prominent orthopaedic emergencies. After treating FNFs, dislocation is another challenge increasing morbidity, mortality and treatment costs substantially. The emerging dual-mobility cup (DMC) may decrease dislocation rates following total hip arthroplasty (THA) for FNFs. We performed a systematic review of literature reporting dislocation and mortality rates with DMC-THA for the treatment of FNFs.

METHODS

2 authors independently searched PubMed (MEDLINE), Google Scholar and Cochrane library for studies reporting dislocation and mortality rates for FNFs treated with DMC-THA since inception up to January 2019. Data on outcomes of interest was extracted from all studies and assessed for eligibility for a meta-analysis.

RESULTS

Out of 522 search results, 18 studies were included in the systematic review and 4 in the meta-analysis. The mean rate of dislocation following DMC-THA for FNFs was found to be 1.87% ± 2.11, with a 1-year mortality rate of 14.0% ± 10.55. Results of meta-analysis showed that dislocation and 1-year postoperative mortality rates were significantly lower for DMC-THA with a risk ratio 0.31 (95% CI, 0.16-0.59; I² = 0%, p = 0.0003) and 0.55 (0.40, 0.77; I² = 0%, p = 0.003) respectively when compared to biploar hemiathroplasty (BHA).

CONCLUSIONS

The mean dislocation and mortality rates in DMC-THA are lower than previously reported rates for THA with single cup and comparable to unipolar and bipolar hemiarthroplasty. Further research involving randomised control trials to assess differences in outcomes, longevity and cost-effectiveness needs to be conducted to make recommendations for the use of DMC in treating FNFs.

Dual Mobility Bearing Articulations Result in Lower Rates of Dislocation After Revision Total Hip Arthroplasty

INTRODUCTION

The purpose of our study is to directly compare the rates of instability after revision total hip arthroplasty (THA) between a modular dual mobility (DM) and a conventional polyethylene single-bearing surface.

METHODS

We retrospectively reviewed a consecutive series of patients who underwent revision THA from 2012 to 2016 at a single institution with a minimum of 2 years of follow-up. Rates of re-revision, dislocation, complications, and short-form (SF-12) scores were compared between the DM and single-bearing groups. To control for confounding variables, a multivariate logistic regression analysis was performed.

RESULTS

Of the 267 revision THA patients, 94 patients had a DM bearing articulation (36%), whereas 173 patients (64%) had a conventional single-bearing with a mean follow-up of 37.8 months (range 24 to 73 months). The DM group was more likely to undergo revision THA for instability compared with the single-bearing group (8.5% versus 1.2%, P ≤ 0.005) but had reduced incidence of postoperative dislocations (2.1% versus 8.7%, P = 0.067) and no difference in the rates of re-revisions (9.6% versus 11.6%, P = 0.770). When controlling for confounding variables, patients who received a DM liner had lower rates of dislocation postoperatively than those of single-bearing (odds ratio 0.12, P = 0.019).

DISCUSSION

Even with a selection bias of surgeons using DM for patients at high risk of instability, patients undergoing revision THA with a DM bearing have reduced rates of dislocation at the intermediate-term follow-up. Further study is needed to identify any potential longer-term complications which may result from a modular DM bearing.

Use of dual mobility components in total hip arthroplasty: Indications and outcomes

Instability after total hip arthroplasty (THA) can be a problematic complication and remains one of the leading causes of revision surgery in the early post-operative period. Dual mobility (DM) implants decrease dislocation risk after THA but they come with their own set of complications. Selective use of DM implants for THA in high risk groups can confer the advantages of this construct while mitigating the risks. In this paper, we review the current literature to examine the evidence for or against use of DM implants in various clinical scenarios and provide an algorithm for when to consider using DM design construct in THA.

Global diversity in bearings in primary THA

Choice of articulating materials, head size and the design of the articulation will become decisive for the long-term performance of a total hip arthroplasty (THA) and especially in terms of risk for dislocation and wear-related problems. Here we account for common alternatives based on available studies and the evidence that can be derived from them.Metal or ceramic femoral heads articulating against a liner or cup made of highly cross-linked polyethylene and ceramic-on-ceramic articulations have about similar risk for complications leading to revision, whereas the performance of metal-on-metal articulations, especially with use of big heads, is inferior. The clinical significance of problems related to ceramic-on-ceramic articulations such as squeaking remains unclear. With use of current technology ceramic fractures are rare.Large femoral heads have the potential to increase the range of hip movement before impingement occurs and are therefore expected to reduce dislocation rates. On the other hand, issues related to bearing wear, corrosion at the taper-trunnion junction and groin pain may arise with larger heads and jeopardize the longevity of THA. Based on current knowledge, 32-mm heads seem to be optimal for metal-on-polyethylene bearings. Patients with ceramic-on-ceramic bearings may benefit from even larger heads such as 36 or 40 mm, but so far there are no long-term reports that confirm the safety of bearings larger than 36 mm.Assessment of lipped liners is difficult because randomized studies are lacking, but retrospective clinical studies and registry data seem to indicate that this liner modification will reduce the rate of dislocation or revision due to dislocation without clear evidence of clinically obvious problems due to neck-liner impingement.The majority of studies support the view that constrained liners and dual mobility cups (DMC) will reduce the risk of revision due to dislocation both in primary and revision THA, the latter gaining increasing popularity in some countries. Both these devices suffer from implant-specific problems, which seem to be more common for the constrained liner designs. The majority of studies of these implants suffer from various methodological problems, not least selection bias, which calls for randomized studies preferably in a multi-centre setting to obtain sufficient power. In the 2020s, the orthopaedic profession should place more effort on such studies, as has already been achieved within other medical specialties, to improve the level of evidence in the choice of articulation when performing one of the most common in-hospital surgical procedures in Europe. Cite this article: EFORT Open Rev 2020;5:763-775. DOI: 10.1302/2058-5241.5.200002.

Iatrogenic intraprosthetic dislocation after closed reduction of dual mobility total hip arthroplasty: Report of two cases

INTRODUCTION

Among hip arthroplasty, dual mobility aims to improve ROM and reduce dislocation rates, however this particular implant can fail in specific ways. Iatrogenic intraprosthetic dislocation (IPD) is a rare occurrence that can happen during closed reduction of a dislocated dual mobility total hip arthroplasty.

PRESENTATION OF CASE

#1 - A 34-year-old male who came to our attention with an undiagnosed IPD. He had experienced a classic dislocation 6 days earlier, which was treated with closed reduction. CT-scan confirmed decoupling of the metal head and PE liner. #2 - An 89-year-old male came to our attention for THA dislocation. During closed reduction manouvers he suffered IPD of the implant. Both patients were treated with revision surgery.

DISCUSSION

Despite being already reported in literature, IPD are still not well known to practitioners and sometimes overlooked even by orthopaedic specialists. Given the good results and diffusion of this kind of implant, iatrogenic IPD in the contest of a classic dislocation might become more frequent in the clinical practice.

CONCLUSION

When performing reduction maneuvers for a dislocated dual mobility total hip arthroplasty, X-rays must be carefully inspected for signs of IPD which, if undiagnosed, can lead to major implant damage and the need for extensive revision surgery.

Revision of a Monoblock Metal-on-Metal Cup Using a Dual Mobility Component: Is It a Reasonable Option?

Revision of large-diameter, monoblock acetabular components for both hip resurfacing arthroplasty and metal-on-metal (MoM) total hip arthroplasty (THA) is correlated to a high amount of complications. For this reason, performing a limited revision by conversion to a dual mobility (DM) without acetabular component exchange has been proposed in order to limit these complications. Although DM bearing offers an easy solution avoiding the intraoperative and time-associated complications, concern about polyethylene wear and stability remains due to the difference regarding the design, the coverage angle and the clearance of the two implants. In order to evaluate the performance of this new solution with the new material to prevent the possibility of failure it is essential to conduct a review of the literature A qualitative systematic review of the literature has been conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. A comprehensive search of PubMed, EMBASE, Google Scholar, and Scopus for English and French articles between January 2000 and October 2019 was performed, with the primary objective of finding articles about dual mobility bearing coupling with large metal-on-metal cup in the case of hip revision procedure. Various combinations of the key words were used in the search strategy. Thirteen articles with DM bearing mated with MoM cup were analyzed. Of the 130 hip revisions selected, with a follow-up from 6 to 53 months, there were a total of 14 with complications (10.77%): four true dislocations (3.08%); six intra-prosthetic dislocations (IPD, 4.6%), two of which presented plastic deformation and polyethylene wear; four other complications (3.08%), included a cup osteolysis, a clicking noise, a superficial infection and a periprosthetic fracture. All the mentioned true dislocations occurred during the first month while IPDs appeared during the first two years from the index revision. In conclusion, according to the literature analyzed, we can stress that the concerns and doubts about mating a DM bearing with large MoM cup cannot be dissolved. It has been pointed out that a DM bearing is not designed for a MoM cup; it is not mechanically tested on MoM cups, which presents different clearance and coverage angles. Predictable complications may occur, such as IPD, polyethylene wear and true dislocation. These complications have been reported at an even higher rate than they were in the eighties, when the first generation of DM implants were of a lower quality of polyethylene and the characteristic of the design was less optimal than modern ones.

Midterm Clinical and Radiographic Outcomes of a Contemporary Monoblock Dual-Mobility Cup in Uncemented Total Hip Arthroplasty

BACKGROUND

The efficacy of contemporary monoblock dual-mobility (DM) cups to prevent dislocations in total hip arthroplasty (THA) is well reported, but there is little published data on their mid- to long-term outcomes. The authors aimed at reporting the 10-year survival of a contemporary DM cup as well as its clinical and radiographic outcomes.

METHODS

From a retrospective consecutive multicentric series of 516 patients (541 hips) that received uncemented THA between June 2007 and June 2010, 6 patients (6 hips) had cup and stem revisions, 5 patients (5 hips) had isolated stem revision, and 2 patients (2 hips) had isolated insert revision. A total of 103 patients (111 hips) died with their original implants, and 41 patients (42 hips) were lost to follow-up. This left 358 patients (375 hips) for clinical assessment at a median follow-up of 8.7 years (range, 6.8-10.5 years), including 279 patients (290 hips) with postoperative radiographs. Implant survival was calculated using the Kaplan-Meier method, and multivariable analyses were performed to determine whether clinical outcomes are associated with patient or surgical factors.

RESULTS

The 10-year survival considering revision for aseptic loosening as end point was 100% for the cup and 99.2% for the stem. No dislocations were observed, and radiographic assessment revealed 1 acetabular granuloma (0.3%), but no radiolucencies nor fractures. The Harris hip score improved from 49.6 ± 15.5 to 85.2 ± 14.5, and the postoperative Oxford hip score was 19.2 ± 7.6. Multivariable analyses revealed that improvement in Harris hip score increased with cup diameter (beta, 1.28; P = .039).

CONCLUSION

Our data confirmed satisfactory midterm outcomes of uncemented THA using a contemporary DM cup, with no dislocations nor cup revisions due to aseptic loosening.

LEVEL OF EVIDENCE

Level IV, retrospective cohort study.

Long-term outcomes of a dual-mobility cup and cementless triple-taper femoral stem combination in total hip replacement: a multicenter retrospective analysis

BACKGROUND

The separate design concepts of dual-mobility cups and triple-taper femoral stems were developed to improve survivorship following total hip replacement (THR) by reducing instability/dislocation and enabling enhanced fixation. Successful outcomes at over two decades have been reported with earlier-generation devices based on these concepts. The current study aimed to provide the first long-term results with a unique pairing of later-generation dual-mobility cup and triple-taper cementless femoral stem after a decade of use in patients undergoing THR.

METHODS

In this retrospective analysis, records were reviewed for all subjects implanted with this dual-mobility cup/cementless femoral stem combination at three centers between 2002 and 2005. Any subject who had not already had follow-up visit beyond 10 years, was not previously revised, and still living were invited for a single follow-up visit consisting of Merle d'Aubgine Scores, the Western Ontario and McMaster Universities Osteoarthritis (WOMAC) index, and standard radiographs.

RESULTS

There were 244 THRs available for analysis. At a mean follow-up of 11.9 years, the Kaplan-Meier survivorship (endpoint: revision for any reason) was 99.1% (95% CI, 97.6-99.7) for the stem and 95.9% (95% CI, 93.1-97.6) for the cup. Merle d'Aubigne Scores were significantly improved from baseline and WOMAC scores were in the satisfactory range at the final follow-up. Radiographic analysis revealed no cases of stem subsidence, no cases of bone hypertrophy, 1 (0.4%) case of bone atrophy, and 3 (1.2%) cases of osteolysis around the stem. No subjects had radiolucent lines greater than 1 mm in any femoral Gruen zone. Evidence of cup migration was seen in 1 (0.4%) subject and 1 (0.4%) subject had evidence of osteolysis that was seen in Gruen zones I, II, IV, and V.

CONCLUSIONS

This combination of a later-generation dual-mobility cup and cementless triple-taper stem was associated with excellent survivorship and satisfactory functional outcomes at over 10 years follow-up.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02648152. Date of registration: January 6, 2016. Retrospectively registered.

Ten- to 16-Year Results of a Modern Cementless Dual-Mobility Acetabular Implant in Primary Total Hip Arthroplasty

BACKGROUND

The purpose of this study is to assess the radiographic results, clinical outcomes, and survivorship of a modern cementless dual-mobility cup (DMC) implant as a primary THA with a minimum of 10 years follow-up.

METHODS

This study retrospectively assessed a series of 310 primary THAs using a modern-generation cementless DMC (Saturne acetabular cup) between April 2001 and December 2005 at a single center. Patients were followed prospectively clinically and radiographically after surgery. Hips with follow-up less than 120 months were excluded from the study (5 lost to follow-up and 167 deceased). In total, a cohort of 138 hips were included for preoperative and postoperative analysis with an average follow-up of 152.4 months. All complications were collected, and a Kaplan-Meier survival analysis was performed.

RESULTS

There was a significant increase in the mean Harris and Postel-Merle d'Aubigne scores between preoperative and postoperative cohorts (P < .001). No loosening of the cup and no acetabular osteolysis were found at final follow-up. No prosthetic dislocation, no intraprosthetic dislocation, and no infections were reported. The survival curve of THA in the total cohort (N = 310) was about 98% at 10 years with 3 stem revisions for femoral fracture. One psoas impingement was also described.

CONCLUSION

This study showed no acetabular component failure and no reported cases of acetabular osteolysis with this DMC acetabular component retention at 10 years. No prosthetic or intraprosthetic dislocation was reported.

Cost-Effectiveness of Dual Mobility and a Value-Based Algorithm of Utilization

Hip dislocation remains a major concern following total hip arthroplasty due to its high frequency and economic burden. This article evaluates the cost-effectiveness regarding dual mobility as an alternative to standard implant designs. A review of literature analyzing the PubMed Central database was undertaken using the following terms in the primary query: dual mobility, cost-effectiveness, cost-analysis, or economic analysis. Dual mobility systems may be a cost-effective alternative when the price of the implant does not exceed the traditional system by $1023. Dual mobility cups may be an essential component for the future success of value-based total hip arthroplasty.

Dual Mobility Cups: Effect on Risk of Revision of Primary Total Hip Arthroplasty Due to Osteoarthritis: A Matched Population-Based Study Using the Nordic Arthroplasty Register Association Database

BACKGROUND

The dual mobility acetabular cup (DMC) was designed to reduce prosthetic instability and has gained popularity for both primary and revision total hip arthroplasty (THA). We compared the risk of revision of primary THA for primary osteoarthritis between patients treated with a DMC and those who received a metal-on-polyethylene (MoP) or ceramic-on-polyethylene (CoP) bearing.

METHODS

A search of the Nordic Arthroplasty Register Association (NARA) database identified THAs performed with a DMC during 1995 to 2013. With use of propensity score matching, 2,277 of these patients were matched (1:1), with regard to sex, age, component fixation, and year of surgery, with patients with an MoP or CoP bearing. We estimated the cumulative incidence of revision taking death as a competing risk into consideration and performed competing risk regression with revision or death as end points.

RESULTS

There was no difference in the overall risk of revision between the DMC group and the propensity-score-matched MoP/CoP group (adjusted hazard ratio [HR] = 1.18; 95% confidence interval [95% CI] = 0.87 to 1.62). Patients with a DMC bearing had a lower risk of revision due to dislocation (adjusted HR = 0.09; 95% CI = 0.03 to 0.29) but a higher risk of revision caused by infection (adjusted HR = 3.20; 95% CI = 1.49 to 6.85).

CONCLUSIONS

There was no difference in overall risk of revision between the DMC and MoP/CoP groups. The DMCs protected against revision due to dislocation but THAs performed with this bearing were more commonly revised because of infection. There may have been a selection bias toward placing DMC implants in patients with greater frailty as the mortality rates were higher in the DMC group than in the age and sex-matched MoP/CoP group.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Dual mobility acetabular cups for total hip arthroplasty: advantages and drawbacks

INTRODUCTION

The dual mobility cup (DMC) concept was proposed by Professor Gilles Bousquet in 1974. Its' aims were to prevent postoperative dislocation, restore the physiological range of motion of the hip, and reduce the stresses at the interface. Since it was created, this design has been modified multiple times to reduce the complication rate, improve implant survival, and expand the indications.

AREAS COVERED

The objective of this review is to discuss the advantages and disadvantages of this implant based on its 40-year history and also to propose a range of indications based on published results. This will provide surgeons with a complete overview of DMC.

EXPERT COMMENTARY

Published studies on DMC confirm the low dislocation rate. Improvements made to DMC overtime have greatly reduced the complications related to wear, such as aseptic loosening and intraprosthetic dislocation (IPD). According to the literature, the indications have expanded and are no longer limited to revision surgery only. Long-term studies are needed before we can draw formal conclusions and consolidate these promising results.

Intraprosthetic dislocation of dual mobility total hip arthroplasty: still occurring?

PURPOSE

The objective was to identify predictive factors for intraprosthetic dislocation (IPD) and to understand how improvements in dual mobility cups (DMC) have helped to reduce dramatically the occurrence of this complication.

METHODS

DM mobile inserts retrieved from 93 hips were divided into three groups: first-generation DMC with IPD ("firstDMC-IPD"), first-generation DMC with over 15 years of implantation without IPD ("firstDMC-noIPD"), and latest-generation DMC ("newDMC"). The predictive factors for IPD based on clinical, prosthetic, radiological and intraoperative characteristics were analysed by multivariate analysis. The surface of each retrieved mobile insert was analysed using three-dimensional CT scan in order to compare their rim wear.

RESULTS

Three predictive factors for IPD were found: a high BMI, a wide rough stem neck and a large cup size. Wear of the firstDMC-noIPD inserts was significantly less than those of firstDMC-IPD inserts and significantly more than those of newDMC inserts. For the firstDMC-IPD inserts, the rim's outer surface wear was significantly greater than the rim's inner surface wear.

CONCLUSIONS

IPD is a specific complication related to wear of the DM mobile insert due to failure of the liner's retaining rim, especially from the rim's outer surface. This long-term issue is different to the early traumatic complication, which can happen after an attempt at closed reduction of a DM THA dislocation. Recent modifications in the design and the coating of contemporary DMC and femoral stems, as well as improvements in the mobile insert itself, seem to corroborate our assumptions about the IPD mechanism and contribute to the quasi-disappearance of this complication.

Comprehensive Review of Current Constraining Devices in Total Hip Arthroplasty

Hip instability after total joint arthroplasty is a devastating complication. Appropriate management of instability is a challenge. Three components that are commonly used in these challenging scenarios are constrained liners, constrained tripolar components, and nonconstrained tripolar components. The biomaterials and biomechanics of these devices vary. Surgeons must take into account the risks associated with each of these components and some surgical pearls for their use. A thorough review of the recent literature allows comparison of results addressing the short-, medium-, and long-term survival of each component. Constraining devices are a good option when used in salvage procedures in elderly and/or low-demand patients with hip instability. However, constraining devices should not be used to correct deficiencies in surgical technique or implant placement.

Outcomes of dual mobility components in total hip arthroplasty

Aims

Instability remains a challenging problem in both primary and revision total hip arthroplasty (THA). Dual mobility components confer increased stability, but there are concerns about the unique complications associated with these designs, as well as the long-term survivorship.

Materials and Methods

We performed a systematic review of all English language articles dealing with dual mobility THAs published between 2007 and 2016 in the MEDLINE and Embase electronic databases. A total of 54 articles met inclusion criteria for the final analysis of primary and revision dual mobility THAs and dual mobility THAs used in the treatment of fractures of the femoral neck. We analysed the survivorship and rates of aseptic loosening and of intraprosthetic and extra-articular dislocation.

Results

For the 10 783 primary dual mobility THAs, the incidence of aseptic loosening was 1.3% (142 hips); the rate of intraprosthetic dislocation was 1.1% (122 hips) and the incidence of extra-articular dislocation was 0.46% (41 hips). The overall survivorship of the acetabular component and the dual mobility components was 98.0%, with all-cause revision as the endpoint at a mean follow-up of 8.5 years (2 to 16.5). For the 3008 revision dual mobility THAs, the rate of aseptic acetabular loosening was 1.4% (29 hips); the rate of intraprosthetic dislocation was 0.3% (eight hips) and the rate of extra-articular dislocation was 2.2% (67 hips). The survivorship of the acatabular and dual mobility components was 96.6% at a mean of 5.4 years (2 to 8). For the 554 dual mobility THAs which were undertaken in patients with a fracture of the femoral neck, the rate of intraprosthetic dislocation was 0.18% (one hip), the rate of extra-articular dislocation was 2.3% (13 hips) and there was one aseptic loosening. The survivorship was 97.8% at a mean of 1.3 years (0.75 to 2).

Conclusion

Dual mobility articulations are a viable alternative to traditional bearing surfaces, with low rates of instability and good overall survivorship in primary and revision THAs, and in those undertaken in patients with a fracture of the femoral neck. The incidence of intraprosthetic dislocation is low and limited mainly to earlier designs. High-quality, prospective, comparative studies are needed to evaluate further the use of dual mobility components in THA. Cite this article: Bone Joint J 2018;100-B:11–19.

Early intraprosthetic dislocation in dual-mobility implants: a systematic review

BACKGROUND

Dual mobility implants are subject to a specific implant-related complication, intraprosthetic dislocation (IPD), in which the polyethylene liner dissociates from the femoral head. For older generation designs, IPD was attributable to late polyethylene wear and subsequent failure of the head capture mechanism. However, early IPDs have been reportedly affecting contemporary designs.

METHODS

A systematic review of the literature according to the preferred reporting items for systematic reviews and meta-analyses guidelines was performed. A comprehensive search of PubMed, MEDLINE, Embase, and Google Scholar was conducted for English articles between January 1974 and August 2016 using various combinations of the keywords "intraprosthetic dislocation," "dual mobility," "dual-mobility," "tripolar," "double mobility," "double-mobility," "hip," "cup," "socket," and "dislocation."

RESULTS

In all, 16 articles met our inclusion criteria. Fourteen were case reports and 2 were retrospective case series. These included a total of 19 total hip arthroplasties, which were divided into 2 groups: studies dealing with early IPD after attempted closed reduction and those dealing with early IPD with no history of previous attempted closed reduction. Early IPD was reported in 15 patients after a mean follow-up of 3.2 months (2.9 SD) in the first group and in 4 patients after a mean follow-up of 15.1 months (9.9 SD) in the second group.

CONCLUSIONS

Based on the current data, most cases have been preceded by an attempted closed reduction in the setting of outer, large articulation dislocation, perhaps indicating an iatrogenic etiology for early IPD. Recognition of this possible failure mode is essential to its prevention and treatment.

Retrieval evidence of impingement at the third articulation in contemporary dual mobility cups for total hip arthroplasty

PURPOSE

We aimed to assess polyethylene liners of retrieved hips of one design of a dual mobility (DM) cup liner and two designs of femoral stems to better understand the role of femoral stem design on polyethylene impingement.

METHODS

This was a case-control study involving 70 retrieved highly cross-linked polyethylene (X3) liners used with ABGII (n = 35) and Rejuvenate (n = 35) stems (Stryker). All polyethylene liners were assessed for evidence of rim deformation and the damage quantified using metrology methods.

RESULTS

A total of 80% of polyethylene liners paired with ABGII necks had macroscopic evidence of neck impingement resulting in a raised lip whilst 23% of liners paired with Rejuvenate necks had evidence of a raised lip (p < 0.0001). The height of the raised rims of the DM cups paired with ABGII necks had a median (range) of 139 μm (72-255). The height of the raised rims of the DM cups paired with Rejuvenate necks had a median (range) of 52 μm (45-90) (p < 0.0001).

CONCLUSION

Our new findings from retrieved dual mobility bearings showed that polyethylene liner rim deformation resulting from impingement with the femoral neck occurs in early in-human function, is circumferential in distribution, and is affected by the stem neck design. We recommend the use of highly polished and non-edged neck designs when used in conjunction with DM cups.

Constrained liners, dual mobility or large diameter heads to avoid dislocation in THA

Dislocation remains a common cause of failure after total hip arthroplasty. The limitations of existing approaches to address instability have led to the development of powerfull options: constrained liners, dual mobility and large heads. These implant-related options have proven to be very efficient, but have raised concerns.With constrained liners, restricted range of motion (ROM) is responsible for impingement leading to high likelihood of failure, depending on the design, with various failure modes.Improvements of the bearing materials have addressed some of the concerns about increased volumetric wear of conventional polyethylene and offer an option to reduce instability: large diameter heads have the advantage of increased ROM before impingement, increased head-neck ratio, and jump distance. Highly cross-linked polyethylene helps address the risk for increased wear, and also large heads provide improved stability without the risk of mechanical failures observed with constrained liners. However, the increase of the head size remains limited as reducing the thickness of the liner may lead to fractures. In addition, the jump distance decreases as the cup abduction increases.The dual mobility concept simultaneously attempts to address head-neck ratio, constraint, and jump distance. Despite the need for longer follow-up, concerns raised about potential increased wear and intra-prosthetic dislocation with first generation implants have been addressed with modern designs.With a dramatic increase of the head-neck ratio whilst reducing the risk of mechanical failure or excessive wear, dual mobility THA outperforms large diameter heads and constrained liners at 10 years follow-up. For these reasons, dual mobility continues to gain interest worldwide and is becoming the most popular option to manage instability. Cite this article: Guyen O. Constrained liners, dual mobility or large diameter heads to avoid dislocation in THA. EFORT Open Rev 2016;1:197-204. DOI: 10.1302/2058-5241.1.000054.

Dislocation following total hip arthroplasty using dual mobility acetabular components: a systematic review

AIMS

The aim of this systematic review was to report the rate of dislocation following the use of dual mobility (DM) acetabular components in primary and revision total hip arthroplasty (THA).

MATERIALS AND METHODS

A systematic review of the literature according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines was performed. A comprehensive search of Pubmed/Medline, Cochrane Library and Embase (Scopus) was conducted for English articles between January 1974 and March 2016 using various combinations of the keywords "dual mobility", "dual-mobility", "tripolar", "double-mobility", "double mobility", "hip", "cup", "socket". The following data were extracted by two investigators independently: demographics, whether the operation was a primary or revision THA, length of follow-up, the design of the components, diameter of the femoral head, and type of fixation of the acetabular component.

RESULTS

In all, 59 articles met our inclusion criteria. These included a total of 17 908 THAs which were divided into two groups: studies dealing with DM components in primary THA and those dealing with these components in revision THA. The mean rate of dislocation was 0.9% in the primary THA group, and 3.0% in the revision THA group. The mean rate of intraprosthetic dislocation was 0.7% in primary and 1.3% in revision THAs.

CONCLUSION

Based on the current data, the use of DM acetabular components are effective in minimising the risk of instability after both primary and revision THA. This benefit must be balanced against continuing concerns about the additional modularity, and the new mode of failure of intraprosthetic dislocation. Longer term studies are needed to assess the function of these newer materials compared with previous generations. Cite this article: Bone Joint J 2017;99-B(1 Supple A):18-24.

[Use of dual mobility cups for revision hip arthroplasty]

The dual mobility cup (DMC) is an increasingly important tool not only in primary but also in revision total hip arthroplasty to prevent dislocation and eventually reduce postoperative complication rates. Various studies have shown survival rates with DMCs of up to 100% with an average dislocation rate of less than 1.5% after primary hip arthroplasty and a follow-up of 10 years. In revision surgery, survival rates of up to 99% were reported with dislocation rates between 0 and 10% after an average of 5 years after implantation. This article is intended to provide an overview of the principle and function of DMCs. Furthermore, indications as well as complications are presented.

All dual mobility cups are not the same

PURPOSE

Although the natural history of dual mobility has been exclusively borne for 20 years by a single company (due to industrial ownership), the concept has undeniably been very widely popularised with nearly 40 cups on the French market which should be regarded as a weight bearing surface, both broadly and in their own right. However, within the same original idea, these implants are not all identical (design, material, fixation ect.).The aim of this work is to propose a classification of different dual mobility cups by distinguishing between thegeneral characteristics of a conventional cup and those particular to this type of implant.

METHODS

By comparison with a standard metal-back cup, dual mobility is based on at least one additional interface corresponding to the mobility of the polyethylene insert in the concavity of the acetabular cup called the outersurface. Design, constitutive material, fixation of the cup and characteristics of the retentive insert are analysed through the published results.

RESULTS

The complications associated, in particular, the intraprosthetic dislocation and to a lesser extent fixation failures undoubtedly condemned the dissemination of the dual mobility concept, as witnessed by the fact that despite the precedence of this 40-year old concept, the overriding majority of publications (more than 95%) have only appeared in the last ten years.

CONCLUSION

The latest generation of dual mobility cups combines: 1) a cast chrome-cobalt alloy cup covered with a bilayer coating of porous titanium and hydroxyapatite for long-term press-fit fixation to 2) an insert designed to eliminate all of the risks of intraprosthetic dislocation, whilst keeping all of the elasticity properties of the polyethylene, which has demonstrated its medium and long term effectiveness on preventing instability by overcoming other complications.

The evolution of outcomes and indications for the dual-mobility cup: a systematic review

PURPOSE

Instability following total hip arthroplasty remains a common and disabling complication. The dual mobility cup (DMC) allows a reduction in the dislocation rate. An increasing number of studies have been undertaken to better understand DMC long term outcomes and complications. The goal of this systematic review was to clarify its different uses and outcomes according to the indications.

METHODS

A comprehensive literature review was performed using the keywords 'dual mobility' and 'tripolar cup' with no limit regarding the year of publication. One hundred seventy six publications were identified.

RESULTS

Current literature shows that "contemporary" dual mobility cup are a significant indication to manage instability following primary and revision hip arthroplasty. Survivorship at midterm is comparable to other articulations for primary THA, but is more difficult to evaluate in revision. Intra-prosthetic dislocation, wear, and loosening are now uncommon with new generations of DMC.

CONCLUSIONS

Compared to previous generations of DMC, the current "contemporary" DMC presents a significant improvement. Current literature reveals a tendency to increase the indications but further studies with long term follow up remain important to consolidate these findings.

Total hip arthroplasty instability in Italy

Hip dislocation is a major and common complication of total hip arthroplasty (THA), which appears with an incidence between 0.3% and 10% in primary total hip arthroplasties and up to 28% in revision THA. The hip dislocations can be classified into three groups: early, intermediate and late. Approximately two-thirds of cases can be treated successfully with a non-operative approach. The rest require further surgical intervention. The prerequisite to developing an appropriate treatment strategy is a thorough evaluation to identify the causes of the dislocation. In addition, many factors that contribute to THA dislocation are related to the surgical technique, mainly including component orientation, femoral head diameter, restoration of femoral offset and leg length, cam impingement and condition of the soft tissues. The diagnosis of a dislocated hip is relatively easy because the clinical situation is very typical. Having identified a dislocated hip, the first step is to perform a closed reduction of the implant. After reduction you must perform a computed tomography scan to evaluate the surgical options for treatment of recurrent dislocation that include: revision arthroplasty, modular components exchange, dual-mobility cups, large femoral heads, constrained cups, elimination of impingement and soft tissue procedures. The objective is to avoid further dislocation, a devastating event which is increasing the number of operations on the hip. To obtain this goal is useful to follow an algorithm of treatment, but the best treatment remains prevention.