Modern Dual-Mobility Cups in Revision Total Hip Arthroplasty: A Systematic Review and Meta-Analysis

How-To Create an Orthopaedic Systematic Review: A Step-by-Step Guide Part I: Study Design

Systematic reviews are conducted through a consistent and reproducible method to search, appraise, and summarize information. Within the evidence-based pyramid, systematic reviews can be at the apex when incorporating high-quality studies, presenting the strongest form of evidence given their synthesis of results from multiple primary studies to level IV evidence, depending on the studies they incorporate. When combined and supplemented with a meta-analysis using statistical methods to pool the results of 3 or more studies, systematic reviews are powerful tools to help answer research questions. The aim of this review is to serve as a guide on how to: (1) design; (2) execute; and (3) publish an orthopaedic arthroplasty systematic review and meta-analysis. In Part I, we discuss how to develop an appropriate research question as well as source and screen databases. To date, commonly used databases to source studies include PubMed/MEDLINE, Embase, Cochrane Library, Scopus, and Web of Science. Although not all-encompassing, this paper serves as a starting point for those interested in performing and/or critically reviewing lower extremity arthroplasty systematic reviews and meta-analyses.

How-To Create an Orthopaedic Systematic Review: A Step-by-step Guide Part II: Study Execution

Systematic reviews are the apex of the evidence-based pyramid, representing the strongest form of evidence synthesizing results from multiple primary studies. In particular, a quantitative systematic review, or meta-analysis, pools results from multiple studies to help answer a respective research question. The aim of this review is to serve as a guide on how to: (1) design, (2) execute, and (3) publish an orthopaedic arthroplasty systematic review. In Part II, we focus on methods to assess data quality through the Cochrane Risk of Bias, Methodological Index for Nonrandomized Studies criteria, or Newcastle-Ottawa scale; enumerate various methods for appropriate data interpretation and analysis; and summarize how to convert respective findings to a publishable manuscript (providing a previously published example). Use of the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines is recommended and standard in all scientific literature, including that of orthopedic surgery. Pooled analyses with forest plots and associated odds ratios and 95% confidence intervals are common ways to present data. When converting to a manuscript, it is important to consider and discuss the inherent limitations of systematic reviews, including their inclusion and/or exclusion criteria and overall quality, which can be limited based on the quality of individual studies (eg, publication bias, heterogeneity, search/selection bias). We hope our papers will serve as starting points for those interested in performing an orthopaedic arthroplasty systematic review.

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.

Revision Dual Mobility Constructs With Unmatched Acetabular and Femoral Components Do Not Increase Failure Rate

BACKGROUND

Dual mobility (DM) constructs for revision total hip arthroplasty (THA) have continued to grow in popularity to mitigate instability. This benefit comes at the cost of potential unique modes of failure, and there are theoretical concerns that combining femoral and acetabular components from different manufacturers could lead to increased failure rates. We aimed to investigate rates of reoperation between matched and unmatched DM implants used in revision THA.

METHODS

We retrospectively reviewed 217 revision THAs performed with DM constructs between July 2012 and September 2021 at a single institution. Dual mobility (DM) constructs were classified as "matched" if the acetabular and femoral components were manufactured by the same company. They were classified as "unmatched" if the acetabular and femoral components were manufactured by different companies. The primary outcome was reoperation for any reason.

RESULTS

There were 136 matched DM constructs and 81 unmatched constructs. Average follow-up was 4.6 years (range, 2.0 to 9.6 years). There was no difference in reoperation rate between matched and unmatched groups (11.0 versus 13.6%, P = .576). The most common reasons for reoperation in both groups were instability and periprosthetic joint infection. There was 1 revision for intraprosthetic dislocation in the matched group.

CONCLUSIONS

The use of unmatched DM components in revision THA was common and did not increase the risk of reoperation at an average of 4.6-year follow-up. This information can be helpful in operative planning, but further research on long-term survival will be necessary.

How-To Create an Orthopaedic Systematic Review: A Step-by-Step Guide. Part III: Executing a Meta-Analysis

At the top of the evidence-based pyramid, systematic reviews stand out as the most powerful, synthesizing findings from numerous primary studies. Specifically, a quantitative systematic review, known as a meta-analysis, combines results from various studies to address a specific research question. This review serves as a guide on how to: (1) design; (2) perform; and (3) publish an orthopedic arthroplasty systematic review. In Part III, we focus on how to design and perform a meta-analysis. We delineate the advantages and disadvantages of meta-analyses compared to systematic reviews, acknowledging their potential challenges due to time constraints and the complexities posed by study heterogeneity and data availability. Despite these obstacles, a well-executed meta-analysis contributes precision and heightened statistical power, standing at the apex of the evidence-based pyramid. The design of a meta-analysis closely mirrors that of a systematic review, but necessitates the inclusion of effect sizes, variability measures, sample sizes, outcome measures, and overall study characteristics. Effective data presentation involves the use of forest plots, along with analyses for heterogeneities and subgroups. Widely-used software tools are common in this domain, and there is a growing trend toward incorporating artificial intelligence software. Ultimately, the intention is for these papers to act as foundational resources for individuals interested in conducting systematic reviews and meta-analyses in the context of orthopaedic arthroplasty, where applicable.

Outcomes of Dual Mobility Bearings in Revision Total Hip Replacements

Background Dual mobility bearings have gained attention in the prevention of instability in revision total hip replacement. This study aimed to evaluate the use of dual mobility bearings in revision total hip replacement. The primary outcome was the rate of dislocation. Secondary outcomes included the rate of re-operation for any reason, surgical complications, serious medical adverse events, and 90-day mortality rate. Methods A single-centre case series of 55 consecutive operations in 49 patients who underwent revision total hip replacement using dual mobility bearings with a minimum follow-up of three months was studied.  Results Early dislocation occurred in one case (2%), and there were no intra-prosthetic dislocations at a mean follow-up of 16 months. The rate of re-operation for any reason was 6/55 (11%) cases, and the post-operative infection rate was 2/55 (4%) cases. Serious medical adverse events occurred in 2/55 (4%) cases. The 90-day mortality rate was 1/55 (2%) cases. Two cases (2%) had cup abduction or anteversion angles outside of the safe zones although there were no dislocations in these patients. Conclusion This case series demonstrates a low dislocation rate in the early post-operative period for dual mobility bearings in revision total hip replacement. Dual mobility bearings show promise as an early low dislocation implant in revision total hip replacement. It remains to be determined whether dual mobility bearings are low-wear implants in the long term.

Does-dual mobility still offer improved stability in smaller cup sizes? A computer modelling comparison of stability with 22-mm versus 28-mm inner heads in dual-mobility versus single-bearing constructs

PURPOSE

Dislocation remains 1 of the leading causes of revision after primary total hip arthroplasty (THA) and there is clear evidence the dual-mobility (DM) is used more frequently to minimise this. But in smaller cups, whether the use of DM with smaller 22-mm heads imparts any increased stability compared to standard bearing is unknown; especially when those smaller cups now allow for large single-bearing (SB) heads.

METHODS

3 primary cup sizes (48 mm, 50 mm, 52 mm) were chosen a priori for modelling. Head sizes trialled for the standard bearing (SB) constructs group were 28-0 mm, 32-0 mm and 36-0 mm against neutral polyethylene liners. In the modular sub-hemispheric DM constructs the inner head sizes for the DM constructs were altered where appropriate (22-0 mm vs. 28-0 mm). Cup position, stem offset, and stem size were standardised.

RESULTS

Both DM constructs outperformed all SB constructs because of a statistically significant jump distance increase (p < 0.001). However, there was no difference in range of motion (ROM) or jump distances between the 22-mm and 28-mm DM inner heads.The ROM angle before impingement between the DM (with 22-mm or 28-mm heads) and SB (with different head sizes where appropriate) showed no statistically significant difference. However, DM constructs presented significantly larger jump distances than SB constructs for both provocative dislocation tests across all 3 cup sizes.Of interest, for 50-mm and 52-mm cup sizes (for which this particular DM construct design can accommodate both 22-mm and 28-mm inner heads), there were no differences in ROM or jump distance between 22-mm versus 28-mm inner heads.

CONCLUSIONS

In this computer-modelling study, DM constructs are advantageous over SB constructs for improving jump distances in clinically provocative positions, but not range of motion angles. Inner head diameter of DM has no effect on stability.

Revision Total Hip Arthroplasty in Octogenarians Compared with Septuagenarians: Is There a Real Difference?

BACKGROUND

The increasing frequency of total hip arthroplasty (THA) as well as an aging population indicate that the need for revision THA will continue to grow, especially in older and potentially medically complex patients. The purpose of this study was to compare THA revision indications, perioperative complications, and readmissions between octogenarian and septuagenarian patients. We hypothesized that patients aged 80 to 89 years would have similar outcomes to patients aged 70 to 79 years undergoing revision THA.

METHODS

Between 2008 and 2019, 572 revision THAs were performed at a single tertiary care hospital. Patients were stratified by age group: 70 to 79 years (n = 407) and 80 to 89 years (n = 165). Indication for revision, perioperative medical complications, and 90-day readmission were identified for each patient. Chi-square tests and t-tests were used to compare the groups. Logistic regression was used to assess medical complications and readmissions.

RESULTS

Aseptic loosening was a more common indication for revision in patients aged 70 to 79 years (33.4% versus 26.7%; p < 0.001), while periprosthetic fracture was a more common indication for revision in those aged 80 to 89 years (30.9% versus 13.0%). Perioperative medical complications occurred more often in octogenarians (10.9% versus 3.0%; p = 0.001), with arrythmia being the most common type. Patients aged 80 to 89 years were at increased risk for medical complications (odds ratio [OR], 3.2; 95% confidence interval [CI], 1.5 to 7.3; p = 0.004) and readmission (OR, 3.2; 95% CI, 1.7 to 6.3; p < 0.001) when adjusting for body mass index (BMI) and indication for revision. Octogenarians had a higher rate of reoperation following first-time revision than septuagenarians (10.3% versus 4.2%, p = 0.009).

CONCLUSIONS

Octogenarians more commonly underwent revision THA for periprosthetic fracture and had higher rates of perioperative medical complications, 90-day readmissions, and reoperations than septuagenarians. Such findings should be considered when counseling patients on both primary and revision THAs.

LEVEL OF EVIDENCE

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

Megaprosthesis in Non-Oncologic Settings-A Systematic Review of the Literature

Modular megaprostheses (MPs) are commonly used after bone-tumor resection, but they can offer a limb salvage solution in massive bone defects. The aim of this systematic review of the Literature is to provide a comprehensive data collection concerning the use of MPs in non-oncologic cases, and to provide an overview of this topic, especially from an epidemiologic point of view. Three different databases (PubMed, Scopus, and Web of Science) were searched for relevant articles, and further references were obtained by cross-referencing. Sixty-nine studies met the inclusion criteria, reporting on cases of MP in non-oncologic cases. A total of 2598 MPs were retrieved. Among these, 1353 (52.1%) were distal femur MPs, 941 (36.2%) were proximal femur MPs, 29 (1.4%) were proximal tibia MPs and 259 (10.0%) were total femur MPs. Megaprostheses were most commonly used to treat periprosthetic fractures (1158 cases, 44.6%), in particular in the distal femur (859, 74.2%). Overall, complications were observed in 513 cases (19.7%). Type I (soft tissue failures) and type IV (infection) according to the Henderson classification were the most frequent (158 and 213, respectively). In conclusion, patients with severe post-traumatic deformities and/or significant bone loss who have had previous septic complications should be considered as oncologic patients, not because of the disease, but because of the limited therapeutic options available. The benefits of this treatment include relatively short operative times and immediate weight-bearing, thus making MP particularly attractive in the lower limb.

Dislocation and survival rate of dual mobility cups in revision total hip arthroplasty in patients with high risk of instability

PURPOSE

Instability remains as an unsolved complication after revision total hip arthroplasty (rTHA). Dual mobility (DM) cups have decreased dislocation rate in rTHA; however, there are few clinical studies that evaluate the risk of dislocation after rTHA in patients with high risk of instability.

METHODS

Between 2007 and 2019, 95 consecutive rTHA using a DM cup, in 93 patients with instability risk factors were retrospectively reviewed. Instability risk factors were defined as follows: deficient abductor mechanism (22.1%), previous dislocation (68.4%), Paprosky 3 acetabular bone defect (21.1%), neuromuscular disease (4.2%), lumbar spine arthrodesis (6.3%), and more than one previous surgery (33.6%). Mean follow-up was 4.3 ± 2.4 years. Clinical and radiographic parameters were reported. DM cup survival was determined using a Kaplan-Meier analysis with re-revision for any cause as the end-point. Surgical complications and re-dislocation rate was recorded.

RESULTS

Seven DM cups were re-revised; three due to aseptic loosening, three due to peri-prosthetic joint infection (PJI), and one due to instability. At seven years follow-up, the survival rate of the DM cup using re-revision for any reason as the end-point was 82.4% (95% confidence interval, 66.4-98.4%). There were 12 (12.6%) complications: two (2.1%) dislocations, six (6.3%) PJI, four (4.2%) peri-prosthetic fractures.

CONCLUSION

Our findings suggest DM cups are effective reducing dislocation rate in rTHA in patients with a high risk of instability, without increasing early aseptic loosening and with a low rate of dislocation. Nevertheless, longer follow-up is needed to confirm implant stability and dislocation rates in the long term.

Dual-Mobility Versus Large Femoral Heads in Revision Total Hip Arthroplasty: Interim Analysis of A Randomized Controlled Trial

INTRODUCTION

This multicenter randomized controlled trial evaluated if dual-mobility bearings (DM) lower the risk of dislocation compared to large femoral heads (≥36mm) for patients undergoing revision total hip arthroplasty (THA) via a posterior approach.

METHODS

A total of 146 Patients were randomized to a DM (n=76; 46 mm median effective head size, range 36 to 59 mm) or a large femoral head (n=70; twenty-five 36 mm heads [35.7%], forty-one 40 mm heads [58.6%], and four 44mm heads [5.7%]). There were 71 single-component revisions (48.6%), 39 both-component revisions (26.7%), 24 reimplantations of THA after 2-stage revision (16.4%), seven isolated head and liner exchanges (4.8%), four conversions of hemiarthroplasty (2.7%), and one revision of a hip resurfacing (0.7%). Power analysis determined that 161 patients were required in each group to lower the dislocation rate from 8.4 to 2.2% (power=0.8, alpha=0.05).

RESULTS

At a mean of 18.2 months (range, 1.4 to 48.2), there were three dislocations in the large femoral head group compared to two in the DM cohort (4.3 vs. 2.6%; P=0.67). One patient in the large head group and none in the DM group were successfully treated with closed reduction without subsequent revision.

CONCLUSION

Interim analysis of this randomized controlled trial found no difference in the risk of dislocation between DM and large femoral heads in revision THA, although the rate of dislocation was lower than anticipated and continued follow up is needed.

The Role of Dual-Mobility Components in Total Hip Arthroplasty

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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.

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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.

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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.

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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.

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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.

Unstable Total Hip Arthroplasty: Should It Be Revised Using Dual Mobility Implants? A Retrospective Analysis from the R.I.P.O. Registry

Total hip arthroplasty (THA) is one of the most common surgical procedures in orthopedics; however, it is subjected to different kinds of failures, one of them being dislocation. Many different prosthetic designs have been developed to overcome this problem, such as dual mobility coupling. The main purpose of this article is to determine whether there are differences regarding the revision surgery of unstable THA comparing the risk of failure between dual mobility cup (DMC) implants, standard implants, and among different head sizes. A registry-based population study has been conducted by analyzing data collected by the Emilia Romagna Registry of Orthopedic Prosthetic Implants (RIPO), including a total of 253 implants failed for dislocation and instability that were operated on by cup revision surgery between 2000 and 2019. The selected population has been divided into two groups based on the insert type: standard and DMC. The age at revision surgery was significantly lower in the standard cup group with respect to DMC (p = 0.014 t-test), with an average age of 71.2 years (33-96 years range) for the standard cups and 74.8 years (48-92 years range) for the DMC group. The cumulative survival of DMC implants was 82.0% at 5-years, decreasing to 77.5% at a 10-year follow-up, which is not significantly different from standard cups (p = 0.676, Log-Rank test). DMC implants showed a significantly lower risk of re-revision for dislocation compared to standard cups (p = 0.049). Femoral heads ≥36 mm had a higher overall survival compared to smaller femoral heads (p = 0.030). This study demonstrated that DMC or femoral heads ≥36 mm are a valid choice to manage THA instability and to reduce the revision rate for dislocation at a mid-term follow-up; in those selected and targeted patients, these options should be taken into consideration because they are associated with better outcomes.

A Meta-Analysis of the Incidence and Temporal Trends of Postoperative Dislocation in Revision Total Hip Arthroplasty Utilizing Constrained Acetabular Components or Dual Mobility Implants

BACKGROUND

The incidence of dislocation after revision total hip arthroplasty (rTHA) is reported to be up to 25% and remains a common source of failure. Constrained acetabular components and dual mobility implants are two implant classes being utilized to alleviate this burden in patients who have recurrent instability or major intraoperative instability. This meta-analysis evaluated the incidence and temporal trends of dislocation after implantation with constrained acetabular components and dual mobility implants in rTHA.

METHODS

Longitudinal studies reporting dislocation after the use of constrained acetabular components or dual mobility implants in rTHA were sought from Medline and Embase to October 2022. Secondary outcomes included re-revision surgery for dislocation and all causes. A total of 75 relevant citations were identified comprising 36 datasets of 3,784 constrained acetabular components and 47 datasets of 10,216 dual mobility implants.

RESULTS

For constrained acetabular components, the pooled incidence of dislocation was 9% (95% confidence interval: 7.2, 11.7) (range 0.0%-35.3%) over a weighted mean follow-up of 6 years, in contrast to 3% (95% confidence interval: 2.2, 4.4) (range 0.0%-21.4%) over 5 years for dual mobility implants. Re-revision rates for dislocation after using constrained acetabular components were around 9%, in contrast to 2% for dual mobility implants. Re-revision rates for all causes after using constrained acetabular components were around 19%, in contrast to 8% for dual mobility implants.

CONCLUSION

Dual mobility implants in the context of rTHA demonstrate lower incidences of dislocation (3% versus 9%), re-revision for dislocation (2% versus 9%), and rer-evision for any cause (8% versus 19%) in contrast to constrained acetabular components. This must be considered by surgeons when implanting such devices, often selected to treat instability.

In Revision THA, Is the Re-revision Risk for Dislocation and Aseptic Causes Greater in Dual-mobility Constructs or Large Femoral Head Bearings? A Study from the Australian Orthopaedic Association National Joint Replacement Registry

BACKGROUND

Dislocation is one of the most common causes of a re-revision after a revision THA. Dual-mobility constructs and large femoral head bearings (≥ 36 mm) are known options for mitigating this risk. However, it is unknown which of these choices is better for reducing the risk of dislocation and all-cause re-revision surgery. It is also unknown whether there is a difference between dual-mobility constructs and large femoral head bearings according to the size of the acetabular component.

QUESTIONS/PURPOSES

We used data from a large national registry to ask: In patients undergoing revision THA for aseptic causes after a primary THA performed for osteoarthritis, (1) Does the proportion of re-revision surgery for prosthesis dislocation differ between revision THAs performed with dual-mobility constructs and those performed with large femoral head bearings? (2) Does the proportion of re-revision surgery for all aseptic causes differ between revision THAs performed with dual-mobility constructs and those performed with large femoral head bearings? (3) Is there a difference when the results are stratified by acetabular component size?

METHODS

Data from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) were analyzed for 1295 first-revision THAs for aseptic causes after a primary THA performed for osteoarthritis. The study period was from January 2008-when the first dual-mobility prosthesis was recorded-to December 2019. There were 502 dual-mobility constructs and 793 large femoral head bearings. There was a larger percentage of women in the dual-mobility construct group (67% [334 of 502]) compared with the large femoral head bearing group (51% [402 of 793]), but this was adjusted for in the statistical analysis. Patient ages were similar for the dual-mobility construct group (67 ± 11 years) and the large femoral head group (65 ± 12 years). American Society of Anesthesiologists (ASA) class and BMI distributions were similar. The mean follow-up was shorter for dual-mobility constructs at 2 ± 1.8 years compared with 4 ± 2.9 years for large femoral head bearings. The cumulative percent revision (CPR) was determined for a diagnosis of prosthesis dislocation as well as for all aseptic causes (excluding infection). Procedures using metal-on-metal bearings were excluded. The time to the re-revision was described using Kaplan-Meier estimates of survivorship, with right censoring for death or database closure at the time of analysis. The unadjusted CPR was estimated each year of the first 5 years for dual-mobility constructs and for each of the first 9 years for large femoral head bearings, with 95% confidence intervals using unadjusted pointwise Greenwood estimates. The apparent shorter follow-up of the dual-mobility construct group relates to the more recent increase in dual-mobility numbers recorded in the registry. The results were adjusted for age, gender, and femoral fixation. Results were subanalyzed for acetabular component sizes < 58 mm and ≥ 58 mm, set a priori on the basis of biomechanical and other registry data.

RESULTS

There was no difference in the proportion of re-revision for prosthesis dislocation between dual-mobility constructs and large femoral head bearings (hazard ratio 1.22 [95% CI 0.70 to 2.12]; p = 0.49). At 5 years, the CPR of the re-revision for prosthesis dislocation was 4.0% for dual mobility constructs (95% CI 2.3% to 6.8%) and 4.1% for large femoral head bearings (95% CI 2.7% to 6.1%). There was no difference in the proportion of all aseptic-cause second revisions between dual-mobility constructs and large femoral head bearings (HR 1.02 [95% CI 0.76 to 1.37]; p = 0.89). At 5 years, the CPR of dual-mobility constructs was 17.6% for all aseptic-cause second revision (95% CI 12.6% to 24.3%) and 17.8% for large femoral head bearings (95% CI 14.9% to 21.2%). When stratified by acetabular component sizes less than 58 mm and at least 58 mm, there was no difference in the re-revision CPR for dislocation or for all aseptic causes between dual-mobility constructs and large femoral head bearings.

CONCLUSION

Either dual-mobility constructs or large femoral head bearings can be used in revision THA, regardless of acetabular component size, as they did not differ in terms of re-revision rates for dislocation and all aseptic causes in this registry study. Longer term follow-up is required to assess whether complications develop with either implant or whether a difference in revision rates becomes apparent. Ongoing follow-up and comparison in a registry format would seem the best way to compare long-term complications and revision rates. Future studies should also compare surgeon factors and whether they influence decision-making between prosthesis options and second revision rates. Nested randomized controlled trials in national registries would seem a viable option for future research.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Dual-mobility versus Fixed-bearing in Primary Total Hip Arthroplasty: Outcome Comparison

Purpose

Use of dual mobility (DM) articulations can reduce the risk of instability in both primary and revision total hip arthroplasty (THA). Knowledge regarding the impact of this design on patient-reported outcome measures (PROMs) is limited. This study aims to compare clinical outcomes between DM and fixed bearing (FB) prostheses following primary THA.

Materials and Methods

All patients who underwent primary THA between 2011-2021 were reviewed retrospectively. Patients were separated into three cohorts: FB vs monoblock-D vs modular-DM. An evaluation of PROMs including HOOS, JR, and FJS-12, as well as discharge-disposition, 90-day readmissions, and revisions rates was performed. Propensity-score matching was performed to limit significant demographic differences, while ANOVA and chi-squared test were used for comparison of outcomes.

Results

Of the 15,184 patients identified, 14,652 patients (96.5%) had a FB, 185 patients (1.2%) had a monoblock-DM, and 347 patients (2.3%) had a modular-DM prosthesis. After propensity-score matching, a total of 447 patients were matched comparison. There was no statistical difference in the 90-day readmission (P=0.584), revision rate (P=0.265), and 90-day readmission (P=0.365) and revision rate due to dislocation (P=0.365) between the cohorts. Discharge disposition was also non-significant (P=0.124). There was no statistical difference in FJS-12 scores at 3-months (P=0.820), 1-year (P=0.982), and 2-years (P=0.608) between the groups.

Conclusion

DM bearings yield PROMs similar to those of FB implants in patients undergoing primary THA. Although DM implants are utilized more often in patients at higher-risk for instability, we suggest that similar patient satisfaction may be attained while achieving similar dislocation rates.

No Difference in Dislocation Rates Comparing Large Diameter Jumbo Femoral Heads and Dual-Mobility Bearings in Revision Total Hip Arthroplasty

BACKGROUND

Dual-mobility (DM) bearings reduce instability in revision total hip arthroplasty (THA); however, DM bearings are costly and reports of corrosion have recently emerged. Furthermore, no study has compared DM to standard bearings with large diameter femoral heads ≥40-mm. This study's purpose was to compare postoperative dislocation rates of standard and DM bearings with large femoral heads after revision THA.

METHODS

A retrospective review of 301 consecutive revision THAs was performed. The mean follow-up was 37.1 months. To isolate the effect of the double articulation, standard and DM bearings with femoral heads ≥40-mm were compared. Outcomes were postoperative dislocation and reoperation within 90 days.

RESULTS

The cohort consisted of 182 standard bearings and 75 DM bearings. There were no differences in revision indication comparing standard and DM bearings (P = .258). Overall dislocation rate was 8.6% (22 of 257). The dislocation rate was 5.7% for standard bearings with ≥40-mm femoral heads compared with 6.9% in DM bearings with ≥40-mm femoral heads (P = 1.000). In multivariate analysis, lower body mass index (odds ratio 1.72), female sex (odds ratio 2.01), and decreased outer femoral head diameter-to-cup component size ratio (odds ratio 1.64) were predictors of postoperative dislocation regardless of bearing type.

CONCLUSION

This study showed no difference in dislocation rates between standard and DM bearings when comparing similar femoral head diameters of ≥40-mm used in revision THAs. Considering the cost and potential deleterious issues associated with additional interfaces, DM bearings should be used judiciously considering similar results may be achieved with single-articulation bearings using large femoral heads.

LEVEL OF EVIDENCE

Level III.

A Comparison of Revision Rates for Dislocation and Aseptic Causes Between Dual Mobility and Large Femoral Head Bearings in Primary Total Hip Arthroplasty With Subanalysis by Acetabular Component Size: An Analysis of 106,163 Primary Total Hip Arthroplasties

BACKGROUND

Dual mobility (DM) and large femoral head bearings (≥36 mm) both decrease the risk of dislocation in total hip arthroplasty (THA). There is limited comparable data in primary THA. This study compared the revision rates for dislocation and aseptic causes between DM and large femoral heads and subanalyzed by acetabular component size.

METHODS

Data from the Australian Orthopedic Association National Joint Replacement Registry were analyzed for patients undergoing primary THA for osteoarthritis from January 2008 (the year of first recorded DM use) to December 2019. All DM and large femoral head bearings were identified. The primary outcome measure was the cumulative percent revision (CPR) for dislocation and for all aseptic causes. The results were adjusted by age, sex, and femoral fixation. A subanalysis was performed stratifying acetabular component diameter <58 m and ≥58 mm.

RESULTS

There were 4942 DM and 101,221 large femoral head bearings recorded. There was no difference in the CPR for dislocation (HR = 0.69 (95% CI 0.42, 1.13), P = .138) or aseptic causes (HR = 0.91 (95% CI 0.70, 1.18), P = .457). When stratified by acetabular component size, DM reduced the CPR for dislocation in acetabular component diameter <58 mm (HR = 0.55 (95% CI 0.30, 1.00), P = .049). There was no difference for diameter ≥58 mm. There was no difference in aseptic revision when stratified by acetabular component diameter.

CONCLUSION

There is no difference in revision rates for dislocation or aseptic causes between DM and large femoral heads in primary THA. When stratified by acetabular component size, DM reduces dislocation for acetabular component diameter <58 mm.

LEVEL OF EVIDENCE

Level III.

Superior functional outcome with dual mobility THR as compared to conventional THR in fracture neck femur: a prospective cohort study

Introduction: Total Hip Replacement (THR) in displaced Fracture Neck of Femur (FNOF) is associated with higher dislocation rates. Conventional THR with a large femoral head and anterior approach has reduced the instability, but it remains higher than THR done for other aetiology. Recent studies have shown reduced dislocation rates with dual mobility THR (DMTHR) for FNOF; however, there is a lack of comparative research to show its superiority over conventional THR. Further, its role in the Asian subcontinent, where the patient requires sitting cross-legged or squatting, has not been studied. Methods: A prospective cohort study of 103 elderly patients with displaced FNOF with a minimum follow-up of 1-year. Fifty-two patients were operated on with DMTHR and fifty-one patients with conventional THR. Both the groups were matched in terms of demographic data, surgical approach, and postoperative protocol. Radiological and functional outcomes in terms of Harris Hip Score (HHS), Range of motion, Patient Reported Outcome Measures (PROM), and Dislocation rate were compared between the two groups. Results: Mean HHS of the DMTHR group was 76.37 at three months and 87.02 at the end of the 1-year postoperatively, which was significantly better than the conventional THR group 65.65 at three months and 72.96 at 1-year. The range of motion was significantly better in the DMTHR group than the conventional THR group. There was no significant difference in radiological outcomes and postoperative dislocation rate between the two groups. Conclusion: Dual mobility implants give better results than conventional implants for primary THA in elderly patients of displaced FNOF regarding better function and greater range of motion.

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.

Spine Fusions, Yoga Instructors, and Hip Fractures: The Role of Dual Mobility in Primary Total Hip Arthroplasty

BACKGROUND

Despite the increased use of dual mobility (DM) in primary total hip arthroplasty (THA), debate exists regarding the indications for its use. No specific algorithm exists to guide this decision-making process. Therefore, the purpose of this article is to summarize the currently available literature regarding the use of DM in primary THA and provide evidence-based guidelines based on specific patient populations and risk factors for instability.

METHODS

We reviewed the current literature for studies evaluating risk factors for dislocation in primary THA, as well as the clinical use and results of DM in primary THA. Based on the strength of the literature, we discuss the use of DM in specific patient populations. We provide a decision-making algorithm to determine whether a patient may be indicated for DM in primary THA.

RESULTS

Surgeons should consider preoperative patient demographics, risk factors for instability (eg, significant hip-spine issues), type of procedure to be performed (eg, conversion arthroplasty), and indications for surgery (eg, THA for femoral neck fracture). Based on this algorithmic assessment, DM may be warranted in the primary THA setting if a patient's combined risk reaches an established threshold based on the literature.

CONCLUSION

This evidence-based algorithm may help guide current practice in the use of DM in primary THA. We advocate the continued judicious use of DM in hip arthroplasty. Longer term studies are needed in order to evaluate the durability of DM, as well as any complications related to the DM articulation.

The diagnostic effect of α-defensin, D-dimer, and IL-6 in periprosthetic joint infection: A systematic review and diagnostic meta-analysis

BACKGROUND

Periprosthetic joint infection (PJI) is the most common complication after artificial joint replacement as previously reported. However, the main problem at present is its difficulty in diagnosis. This systematic review and meta-analysis aimed to compare the diagnostic accuracy of α-defensin, D-dimer, and interleukin-6 (IL-6) in clinical practice.

METHOD

Online databases were systematically searched until June 18th, 2020 with keywords and medical sub-headings terms. Studies mentioned the sensitivity and specificity of biological markers in detecting PJI were included in our study. The sensitivity, specificity, and diagnostic odds ratios (DORs) were obtained after integration.

RESULTS

A total of 34 studies with 1036 patients diagnosing as PJI were included for comparing α-defensin, D-dimer, and IL-6. The sensitivity and specificity of α-defensin for PJI were 0.88 and 0.96, and the DOR was 189 (95% CI 72-496), respectively. The sensitivity and specificity of D-dimer (0.82 and 0.72) and IL-6 (0.80 and 0.89) were lower than α-defensin.

CONCLUSION

The detection of α-defensin is a promising biomarker for diagnosing PJI. The optional cut-off needs to be curtained when using other biomarkers.

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.

Use of a modular hip dual-mobility articulation in patients with high risk of dislocation: a relatively small-sized acetabulum in Asian patients may limit its use

BACKGROUND

Dual-mobility hip component is widely used in Europe and North America, because it effectively reduces hip dislocation in primary and revision total hip arthroplasties. However, reports were limited on the use of dual-mobility articulation in Asian populations.

PURPOSE

The aim of this retrospective study was to review the use of modular dual-mobility hip articulation in Asian patients with the high risk factor for hip dislocation. We also discussed the potential concern on the use of dual-mobility articulation in Asian patients.

METHODS

From Jan 2018 to June 2019, 17 patients were included in this study. The mean age of the patients was (73.8 ± 9.5) years (range: 57-88 years). The mean size of acetabular cup and modular DM liner were (49.5 ± 3.4) mm (range, 46-58 mm) and (40.7 ± 3.4) mm (range, 38-48 mm), respectively. The mean follow-up period was (15.8 ± 3.9) months (range, 11-24 months). The primary outcome was the rate of hip dislocation. The secondary outcomes included the Harris Hip Score. Differences were considered statistically significant at p < 0.05.

RESULTS

Hip dislocation, loosening, peri-prosthetic fractures, or intra-prosthetic dislocation was not found in the series. The mean preoperative and postoperative Harris Hip Scores were 42.2 ± 17.2 (range, 15-80) and 74.7 ± 13.5 (range, 52-97), respectively, giving a mean improvement of 32.5 ± 17.2 (range, 4-72). The improvement was statistically significant (p < 0.05).

CONCLUSIONS

In Asian patients with high risk of hip dislocation, the use of modular dual-mobility hip component produces promising outcomes without hip dislocation, but the relatively small-sized acetabulum may limit it widespread application in other populations worldwide.

TRIAL REGISTRATION

HKUCTR-2913 .

Dual Mobility and Conventional Bearings Have Comparably Low Dislocation Rates for Anterior-Based Approaches in Total Hip Arthroplasty

BACKGROUND

Dual mobility (DM) bearings for total hip arthroplasty (THA) have been proposed to reduce the risk of instability in select patients, especially those undergoing revision surgery. The use of DM bearings has not been studied as extensively for use in primary THA. The purpose of this study is to compare outcomes following primary THA with anterior-based approaches between patients receiving DM bearings vs standard bearing hip implants.

METHODS

We retrospectively reviewed a consecutive series of patients undergoing primary THA through an anterior-based approach. A 3:1 propensity score match was performed between the standard and DM bearing patients to control for possible risk factors for instability. Functional outcomes, dislocations, and aseptic revisions were identified for each patient. The effect of DM on postoperative outcomes was determined using univariate statistical analyses.

RESULTS

In total, 250 DM bearings were compared to 753 standard bearings. We found no difference in dislocation rate between single bearings and DM bearings (0.53% vs 0.4%). There was 1 DM dislocation occurring in a liner with outer diameter of 38 mm. There were no DM dislocations with outer diameter >38 mm. Aseptic revision surgery was more common in DM. This difference was driven by higher incidence of femoral periprosthetic fracture. There were no differences in functional outcomes.

CONCLUSION

Dislocation rates are comparably low between DM bearings and standard bearings for THA done using an anterior approach to the hip. Further investigation is needed to determine if specific patient populations may benefit from DM implants for primary THA when an anterior approach to the hip is being used.

Dual-Mobility Cup Total Hip Arthroplasty for Displaced Femoral Neck Fractures: A Retrospective Study With a Median Follow-Up of 5 Years

Introduction:

Patient outcomes following modern dual-mobility cup total hip arthroplasty (DM-THA) remains a concern. Few reports have focused on the use of modern DM-THA in the setting of Asian populations for displaced osteoporotic femoral neck fractures (FNFs). This study aimed to investigate the outcomes of Chinese population with displaced osteoporotic FNFs initially treated with modern DM-THA.

Materials and Methods:

Data from 112 consecutive patients (112 hips) with displaced osteoporotic FNFs initially treated with modern DM-THA during 2011-2018 were retrospectively analyzed. Follow-ups were performed at 3 months, 6 months, 12 months, and then every 1 year after surgery. The primary endpoint was the Harris Hip Score (HHS); the secondary endpoint was the main orthopedic complication rate.

Results:

The mean HHS improved from 58.62 (±15.79) prior to surgery to 86.13 (±9.92) at the final follow-up. The main complication rate was 14.2% (16/112). Sixteen complications in 10 patients were recorded. Of the 16 complications, there were 2 (1.7%) cases requiring revision DM-THA, 3 (2.6%) cases of loosening, 2 (1.7%) cases of migration, 3 (2.6%) intra-prosthetic dislocation (IPD), 4 (3.5%) cases of tilting, and 2 (1.7%) cases of severe wear. The need for revision was attributed to prosthesis loosening associated with poor bony quality.

Conclusion:

In patients with displaced osteoporotic FNFs, DM-THA may yield favorable functional outcomes and a low rate of main orthopedic complications, in particular, a low dislocation rate.

Effect of liner offset and inclination on cement retention strength of metal-in-metal acetabular constructs: A biomechanical study

Cementing metallic liners into well-fixed acetabular shells facilitates utilizing dual-mobility cups in revision total hip arthroplasty without shell replacement. The current biomechanical study investigated the effect of increasing cemented liner (a) inclination; and (b) offset on the cement retention strength measured as the lever-out moment at cement failure. Eighteen metallic liner prototypes were cemented into cluster-hole acetabular shells at variable inclinations (0°, 10°, and 20°) and offsets (0 and 10 mm) relative to the enclosing acetabular shell (6 groups; n = 3 constructs per group). The constructs were connected to a material testing frame, and lever-out failure moments were tested through an established protocol. Failure occurred at the liner-cement interface (18/18). There was no correlation between liner inclination and the lever-out failure moment (r = -0.327, P = .185). Liner offset demonstrated a strong negative correlation to mean lever-out failure moments (r = -0.788, P < .001). There was no significant difference between mean lever-out failure moments at variable liner inclinations, regardless of offset (P = .358). Greater liner offset was associated with diminished mean lever-out failure moments (P < .001). Compared with neutral (0° inclination, 0 mm offset), the maximum inclination and offset group had the lowest mean lever-out failure moment (P = .011). Cemented metal-in-metal constructs are significantly affected by the liner positioning. While a correlation between liner inclination and cement retention strength could not be asserted, cement retention strength is significantly diminished by increased liner offset.

Adverse Local Tissue Reaction due to Acetabular Corrosion in Modular Dual-Mobility Constructs

Dual-mobility (DM) bearings in total hip arthroplasty (THA) have been reported to reduce dislocation rates, especially in high-risk patients, and are being rapidly adopted in primary and revision THAs. However, this technology introduces additional interfaces that have the potential to result in unforeseen complications. We present a series of 3 patients with mechanically assisted crevice corrosion at the acetabular component-metal dual-mobility liner interface. Consequently, we urge judicious use and close clinical observation of this new, effective technology in THA.

Standard, Large-Head, Dual-Mobility, or Constrained-Liner Revision Total Hip Arthroplasty for a Diagnosis of Dislocation: An Analysis of 1,275 Revision Total Hip Replacements

BACKGROUND

Dislocation remains a leading cause of revision following primary and revision total hip arthroplasty (THA). The aim of the present study was to compare the rate of second revision THA following a major first revision for the treatment of dislocation using an implant with a standard, large head, dual-mobility, or constrained acetabular liner.

METHODS

Data were obtained from the Australian Orthopaedic Association National Joint Replacement Registry from September 1999 through December 2018. All primary THAs that had been performed for the treatment of osteoarthritis and subsequently revised for dislocation were included. All revision THA prostheses with a standard head (≤32 mm), large head (≥36 mm), dual-mobility, or constrained acetabular liner that were used for the first revision procedure were identified. The primary outcome measures were the cumulative rates of second revisions for all causes and for a subsequent diagnosis of dislocation for the 4 different constructs used in the first revision.

RESULTS

A total of 1,275 hips underwent a major first revision because of prosthesis dislocation, with 203 of these hips going on to have a second revision. The rate of all-cause second revision was significantly higher in the standard-head group compared with the constrained-acetabular-liner group (hazard ratio [HR], 1.53 [95% confidence interval (CI), 1.01 to 2.30]; p = 0.044). There was no difference in the rates of revision between other articulations. The most common cause of second revision for all implants was dislocation. There were a total of 91 second revisions for a diagnosis of dislocation. Standard heads had a higher rate of second revision compared with constrained acetabular liners (HR, 2.44 [95% CI, 1.30 to 4.60]; p = 0.005), dual-mobility implants (HR, 2.04 [95% CI, 1.03 to 4.01]; p = 0.039), and large heads (HR, 1.80 [95% CI, 1.09, 2.99]; p = 0.022). There was no difference in the rates of second revision between other articulations.

CONCLUSIONS

Surgeons have a number of options for prostheses when performing a first revision for the treatment of dislocation following a primary THA. The most common cause of a second revision is recurrent dislocation. The use of constrained acetabular liners, dual-mobility liners, and large heads (≥36 mm) are options for reducing subsequent dislocation. Standard head sizes have a higher rate of second revision for further dislocation.

LEVEL OF EVIDENCE

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

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.

A cost-effectiveness assessment of dual-mobility bearings in revision hip arthroplasty

Aims

The rate of dislocation when traditional single bearing implants are used in revision total hip arthroplasty (THA) has been reported to be between 8% and 10%. The use of dual mobility bearings can reduce this risk to between 0.5% and 2%. Dual mobility bearings are more expensive, and it is not clear if the additional clinical benefits constitute value for money for the payers. We aimed to estimate the cost-effectiveness of dual mobility compared with single bearings for patients undergoing revision THA.

Methods

We developed a Markov model to estimate the expected cost and benefits of dual mobility compared with single bearing implants in patients undergoing revision THA. The rates of revision and further revision were calculated from the National Joint Registry of England and Wales, while rates of transition from one health state to another were estimated from the literature, and the data were stratified by sex and age. Implant and healthcare costs were estimated from local procurement prices and national tariffs. Quality-adjusted life-years (QALYs) were calculated using published utility estimates for patients undergoing THA.

Results

At a minimum five-year follow-up, the use of dual mobility was cost-effective with an estimated incremental cost-effectiveness ratio (ICER) of between £3,006 and £18,745/QALY for patients aged < 55 years and between 64 and 75 years, respectively. For those aged > 75 years dual mobility was only cost-effective if the timeline was beyond seven years. The use of dual mobility bearings was cost-saving for patients aged < 75 years and cost-effective for those aged > 75 years if the time horizon was beyond ten years.

Conclusion

The use of dual mobility bearings is cost-effective compared with single bearings in patients undergoing revision THA. The younger the patient is, the more likely it is that a dual mobility bearing can be more cost-effective and even cost-saving. The results are affected by the time horizon and cost of bearings for those aged > 75 years. For patients aged > 75 years, the surgeon must decide whether the use of a dual mobility bearing is a viable economic and clinical option.

Cite this article: Bone Joint J 2020;102-B(9):1128–1135.

Modular Dual-Mobility Liner Malseating: A Radiographic Analysis

Background

With dislocation as a leading cause for revision after total hip arthroplasty (THA), modular dual-mobility (MDM) constructs are more commonly used at present in an attempt to decrease postoperative instability. With modularity, there is potential for additional complications, including malseating of the liner. The goal of this study was to perform a radiographic analysis on the incidence of MDM liner malseating.

Methods

We retrospectively identified 305 patients (305 THAs) who underwent primary THA with an MDM liner from a single manufacturer inserted by a single surgeon. One hundred fifty-six (51%) patients were male. The mean age was 68 years, and the mean body mass index was 31 kg/m². Only patients with both anteroposterior and cross-table lateral radiographs at a minimum of 6 weeks postoperatively were included. Dislocations and reoperations were determined at 1 year after the procedure. All MDM liners were routinely tested intraoperatively with a "4-quadrant test" to assess for proper seating.

Results

Four (4/305, 1.3%) MDM liners were noted to be radiographically malseated at early follow-up with three (3/147, 2.0%) occurring in a thinner two dimentional (2D) ongrowth shell and only one (1/158, 0.6%) observed in a thicker three dimentional (3D) additively manufactured shell. They were inferiorly prominent by a median of 1.2 mm, best seen on the cross-table lateral radiograph. In patients with at least 1-year follow-up, no MDM liners dissociated and no patients sustained a dislocation. Five (1.6%) patients required reoperation unrelated to the acetabular or MDM construct.

Conclusions

Surgeons should be aware that malseating of dual-mobility liners may occur. However, with utilization of a consistent surgical technique to test for seating of the liner, the radiographic incidence of MDM liner malseating was low at 1%. Although there were no short-term clinical implications of liner malseating, long-term follow-up is needed.

Trends in the use of dual mobility bearings in hip arthroplasty

Aims

Dual mobility (DM) bearings are an attractive treatment option to obtain hip stability during challenging primary and revision total hip arthroplasty (THA) cases. The purpose of this study was to analyze data submitted to the American Joint Replacement Registry (AJRR) to characterize utilization trends of DM bearings in the USA.

Methods

All primary and revision THA procedures reported to AJRR from 2012 to 2018 were analyzed. Patients of all ages were included and subdivided into DM and traditional bearing surface cohorts. Patient demographics, geographical region, hospital size, and teaching affiliation were assessed. Associations were determined by chi-squared analysis and logistic regression was performed to assess outcome variables.

Results

A total of 406,900 primary and 34,745 revision THAs were identified, of which 35,455 (8.7%) and 8,031 (23.1%) received DM implants respectively. For primary THA, DM usage increased from 6.7% in 2012 to 12.0% in 2018. Among revision THA, DM use increased from 19.5% in 2012 to 30.6% in 2018. Patients < 50 years of age had the highest rates of DM implantation in every year examined. For each year of increase in age, there was a 0.4% decrease in the rate of DM utilization (odds ratio (OR) 0.996 (95% confidence interval (CI) 0.995 to 0.997); p < 0.001). Females were more likely to receive a DM implant compared to males (OR 1.077 (95% CI 1.054 to 1.100); p < 0.001). Major teaching institutions and smaller hospitals were associated with higher rates of utilization. DM articulations were used more commonly for dysplasia compared with osteoarthritis (OR 2.448 (95% CI 2.032 to 2.949); p < 0.001) during primary THA and for instability (OR 3.130 (95% CI 2.751 to 3.562) vs poly-wear; p < 0.001) in the revision setting.

Conclusion

DM articulations showed a marked increase in utilization during the period examined. Younger patient age, female sex, and hospital characteristics such as teaching status, smaller size, and geographical location were associated with increased utilization. DM articulations were used more frequently for primary THA in patients with dysplasia and for revision THA in patients being treated for instability. Cite this article: Bone Joint J 2020;102-B(7 Supple B):27–32.

Patients Following Revision Total Hip Arthroplasty With Modular Dual Mobility Components and Cobalt-Chromium Inner Metal Head are at Risk of Increased Serum Metal Ion Levels

BACKGROUND

Modular dual-mobility (MDM) total hip arthroplasty (THA) is designed with a cobalt-chromium liner inserted into a titanium acetabular component. The purpose of this study is to investigate the potential risks for fretting corrosion at this junction, by measuring serum metal ions, after MDM acetabular revision.

METHODS

Thirty-seven patients with well-functioning revision THAs participated in a cross-sectional study at mean 5.1 (2-10) years after surgery. All received a trabecular titanium MDM acetabular component. The serum levels of cobalt and chromium were measured using mass spectrometry.

RESULTS

The mean values of chromium and cobalt were 2.08 μg/L (95% confidence interval 0.9-3.2, range 0.02-11.8) and 1.99 μg/L (95% confidence interval 0.81-3.17, range 0.07-16.05), respectively. Eleven patients (29, 7%) had ion levels above the normal range, with 6 (16.2%) above 5 μg/L and 5 (13.5%) between 1 and 5 μg/L. A significant correlation was found between an elevated serum metal ion level and University of California Los Angeles score (P = .016).

CONCLUSION

We conclude that serum metal level elevation may occur secondary to metal debris resulting from corrosion of the index MDM THA. This potential risk should be included in the decision-making process when dealing with revision arthroplasty in young and active patients.

Can dual mobility cups prevent dislocation without increasing revision rates in primary total hip arthroplasty? A systematic review

BACKGROUND

Dislocation is one of the leading causes for early revision surgery after total hip arthroplasty (THA). To address this problem, the dual mobility (DM) cup was developed in the 1970s by the French. Despite the increased and, in some countries, broad use of DM cups, high quality evidence of their effectiveness compared to traditional unipolar (UP) cups is lacking. There are a few well-conducted literature reviews, but the level of evidence of the included studies was moderate to low and the rates of revision were not specifically investigated. Therefore, we did a systematic review to investigate whether there is a difference in the rate of dislocations and revisions after primary THA with a DM cup or a UP cup.

METHODS

We conducted a systematic literature search in PubMed, Embase and Cochrane databases in July 2019. The articles were selected based upon their quality, relevance and measurement of the predictive factor. We used the MINORS criteria to determine the methodological quality of all studies.

RESULTS

The initial search resulted in 702 citations. After application of the inclusion and exclusion criteria, eight articles met our eligibility criteria and were graded. Included studies were of medium to low methodological quality with a mean score of 14/24 (11-16) points following the MINORS criteria. In the case-control studies, a total of 549 DM cups and 649 UP cups were included. In the registry studies, a total of 5.935 DM cups and 217.362 UP cups were included. In the case-control studies, one (0.2%) dislocation was reported for the DM cups and 46 (7.1%) for the UP cup (p=0.009, IQR=0.00-7.00). Nine (1.6%) revisions, of which zero due to dislocation, were reported for the DM cup and 39 (6.0%), of which 30 due to dislocation, for the UP cup (p=0.046, CI=-16.93-5.73). In the registry studies 161 (2.7%) revisions were reported for the DM cup, of which 14 (8.7%) due to dislocation. For the UP cup, 3.332 (1.5%) revisions were reported (p=0.275, IQR=41.00-866.25), of which 1.093 (32.8%) due to dislocation (p=0.050, IQR=3.50-293.25).

CONCLUSION

This review suggests lower rates of dislocation and lower rates of revision for dislocation in favor of the DM cups. Concluding, DM cups might be an effective solution to reduce dislocation in primary THA. To evaluate the efficacy of DM cups compared to UP cups, an economic evaluation alongside a randomized controlled trial is needed focusing on patient important endpoints.

LEVEL OF EVIDENCE

III, systematic review of level III studies.

Dual Mobility Cups in Revision Total Hip Arthroplasty: Efficient Strategy to Decrease Dislocation Risk

BACKGROUND

Revision total hip arthroplasty (rTHA) is a challenging surgery with a higher rate of complications than primary arthroplasty, particularly instability and aseptic loosening. The purpose of this study is to compare dual mobility cup (DMC) and standard mobility cup (SMC) in all rTHAs performed at our institution over a decade with a 1 year minimum follow-up.

METHODS

Two hundred ninety-five rTHAs (acetabular only and bipolar revisions) between 2006 and 2016 were retrospectively reviewed. These were divided into those with a DMC (184 revisions) or SMC (111 revisions). Dislocation and complications requiring re-revision were reported.

RESULTS

The rTHA mean age was 69 years ± 13.9 (19-92) and the mean follow-up was 2.3 years. Dislocation risk was statistically lower (P = .01) with a DMC (3.8%; 7/184) than with an SMC (13.5%; 15/111). DMC required re-rTHA in 24/184 (13%) for any reason compared to SMC in 19/111 (17.1%) (P = .34). There was no significant difference in early aseptic loosening (P = .28) between the 2 groups. For young patients (≤55 years), results were similar with a lower dislocation rate in the DMC group (P = .24) and no increased risk of early aseptic loosening (P = .49).

CONCLUSION

This study demonstrates that for all rTHA indications DMC compared to SMC has a significantly decreased risk of postoperative dislocation without risk of early aseptic loosening at medium term follow-up. The use of DMC in rTHA is an important consideration particularly with the predicted increased incidence of both primary and revision THA globally.

Cemented Proximal Femoral Replacement for the Management of Non-Neoplastic Conditions: A Versatile Implant but Not Without Its Risks

BACKGROUND

The demand for revision arthroplasty continues to grow. Proximal femoral bone loss poses a significant challenge to surgeons and proximal femoral replacements (PFRs) are one option to address this problem. The aim of our study is to assess the reoperation, complication, and mortality rates following PFR for treatment of non-neoplastic conditions.

METHODS

A retrospective observational study was conducted of a consecutive group of patients treated with a PFR for non-neoplastic conditions between 2010 and 2018. Mortality was confirmed using the Irish national death events publication service.

RESULTS

Over the 8-year study period, 79 PFRs in 78 patients were performed. Mean age of patients was 78.3 years (standard deviation 11.9), of which 37.2% were male. Periprosthetic fracture was the most common indication for PFR (63.3%). The 30-day mortality rate was 7.6% (6 patients), of which bone cement implantation syndrome occurred in 4 patients. One-year mortality was 12.7%. Complications occurred in 22.8%.

CONCLUSION

A cemented PFR is a versatile prosthesis in the armamentarium of a revision arthroplasty surgeon that allows immediate full weight-bearing. However, it may appropriately be considered a last resort procedure that poses specific risks that must be explained to patients and family. We present the short-term outcomes on one of the largest series of PFR to date.

Dual mobility in primary total hip arthroplasty: current concepts

Total hip arthroplasty (THA) is one of the most successful surgical procedures – reducing pain and providing functional improvement. However, THA instability is a disabling condition and remains the most common indication for revision THA. To combat the risk of instability, the concept of dual mobility (DM) was developed. This article provides a comprehensive review of DM in the literature.

Widespread use of first-generation DM was limited due to concern regarding wear of the polyethylene head and the unique complication of intraprosthetic dislocation (IPD). Implant modifications using highly cross-linked, durable polyethylene and a smooth, cylindrical femoral neck have all but eliminated IPD in contemporary DM.

In multiple studies, DM demonstrates statistically significant reductions in dislocation rates comparative to standard bearing primary THA. These results have been particular promising in high-risk patient populations and femoral neck fractures – where low dislocation rates and improved functional outcomes are a recurrent theme. From an economic perspective, DM is equally exciting – with lower accrued costs and higher accrued utility comparative to standard bearing THA.

Longer-term clinical evidence and higher-quality prospective comparative studies are required to strengthen current research. Dual mobility may well represent the future gold standard for THA in high-risk patient populations and femoral neck fractures, but due diligence of long-term performance is needed before recommendations for widespread use can be justified.

Cite this article: EFORT Open Rev 2019;4:640-646. DOI: 10.1302/2058-5241.4.180089

Cementation of a monoblock dual mobility bearing in a newly implanted porous revision acetabular component in patients undergoing revision total hip arthroplasty

Background

The most common indications for revision total hip arthroplasty are instability/dislocation and mechanical loosening. Efforts to address this have included the use of dual mobility (DM) articulations. The aim of this study is to report on the use of cemented DM cups in complex acetabular revision total hip arthroplasty cases with a high risk of recurrent instability.

Methods

A multicenter, retrospective study was conducted. Patients who received a novel acetabular construct consisting of a monoblock DM cup cemented into a fully porous metal shell were included. Outcome data included 90-day complications and readmissions, revision for any reason, and Harris Hip Scores.

Results

Thirty-eight hips in 38 patients were included for this study. At a median follow-up of 215.5 days (range 6-783), the Harris Hip Score improved from a mean of 50 ± 12.2 to 78 ± 11.2 (P < .001). One (2.6%) patient experienced a dislocation on postoperative day 1, and was closed reduced with no further complications. There was 1 (2.6%) reoperation for periprosthetic joint infection treated with a 2-stage exchange.

Conclusions

In this complex series of patients, cementation of a monoblock DM cup into a newly implanted fully porous revision shell reliably provided solid fixation with a low risk of dislocation at short-term follow-up. Although longer term follow-up is needed, utilization of this novel construct should be considered in patients at high risk for instability.

Total hip arthroplasty in the setting of tuberculosis infection of the hip: a systematic analysis of the current evidence

INTRODUCTION

Total hip arthroplasty (THA) is a viable option to restore mobility and relieve pain in patients with severe post-tuberculous arthritis, but has been controversial due to concerns of disease reactivation. Over the past several decades, a number of authors have reported outcomes of THA for tuberculosis (TB) infections. However, there is marked heterogeneity in regard to disease activity, surgical approaches, and the use of chemoprophylaxis in these studies.

AREAS COVERED

The purpose of this review was to critically assess: 1) patient characteristics; 2) perioperative planning; 3) clinical outcomes; 4) radiographic outcomes; and 5) complications of THA in the setting of tuberculosis of the hip.

EXPERT OPINION

THA is an effective treatment for post-TB hip arthritis. There has been controversy regarding its safety during the past several decades, as it has been thought to increase the risk of disease reactivation. While studies thus far have shown generally favorable results, they have been limited by small sample sizes and their design as retrospective case series. Comparison of these studies reveals marked heterogeneity in the clinical management of this complex disease. However, synthesis of their findings demonstrates favorable outcomes and low rates of complication, including disease reactivation particularly when perioperative anti-tuberculosis therapy is instituted.