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

Revision of metal-on-metal hip replacements with dual-mobility bearings and acetabular component retention

Aims

In metal-on-metal (MoM) hip arthroplasties and resurfacings, mechanically induced corrosion can lead to elevated serum metal ions, a local inflammatory response, and formation of pseudotumours, ultimately requiring revision. The size and diametral clearance of anatomical (ADM) and modular (MDM) dual-mobility polyethylene bearings match those of Birmingham hip MoM components. If the acetabular component is satisfactorily positioned, well integrated into the bone, and has no surface damage, this presents the opportunity for revision with exchange of the metal head for ADM/MDM polyethylene bearings without removal of the acetabular component.

Methods

Between 2012 and 2020, across two centres, 94 patients underwent revision of Birmingham MoM hip arthroplasties or resurfacings. Mean age was 65.5 years (33 to 87). In 53 patients (56.4%), the acetabular component was retained and dual-mobility bearings were used (DM); in 41 (43.6%) the acetabulum was revised (AR). Patients underwent follow-up of minimum two-years (mean 4.6 (2.1 to 8.5) years).

Results

In the DM group, two (3.8%) patients underwent further surgery: one (1.9%) for dislocation and one (1.9%) for infection. In the AR group, four (9.8%) underwent further procedures: two (4.9%) for loosening of the acetabular component and two (4.9%) following dislocations. There were no other dislocations in either group. In the DM group, operating time (68.4 vs 101.5 mins, p < 0.001), postoperative drop in haemoglobin (16.6 vs 27.8 g/L, p < 0.001), and length of stay (1.8 vs 2.4 days, p < 0.001) were significantly lower. There was a significant reduction in serum metal ions postoperatively in both groups (p < 0.001), although there was no difference between groups for this reduction (p = 0.674 (cobalt); p = 0.186 (chromium)).

Conclusion

In selected patients with Birmingham MoM hips, where the acetabular component is well-fixed and in a satisfactory position with no surface damage, the metal head can be exchanged for polyethylene ADM/MDM bearings with retention of the acetabular prosthesis. This presents significant benefits, with a shorter procedure and a lower risk of complications.

Long-term Follow-up on Revisions of a Recalled Large Head Metal-on-metal Hip Prosthesis: A Single Surgeon Series

Background

In 2010, a recall was issued for a specific monoblock large head metal-on-metal (MoM) hip prosthesis due to short-term revision rates of 12%-13% (articular surface replacement, DePuy Orthopaedics, Inc., Warsaw, IN). High complication, infection, and rerevision rates for revised MoM implants have been reported. The purpose of the study is to report long-term outcomes and trend metal ion levels of this recalled MoM prosthesis from a single surgeon series.

Methods

Retrospective chart review was performed on all patients that underwent revision of large MoM hip replacements between 2010 and 2015. Pre- and post-revision Harris Hip Score (HHS), cup abduction angles, anteversion angles, and cup sizes were compared. Survivorship and HHS were the primary outcomes measured; serum cobalt and chromium levels were secondary outcomes. Multivariate linear regression was used to examine the correlation between prerevision serum metal ion levels and HHS.

Results

A total of 24 hips (21 patients) met inclusion criteria. Mean time to revision was 4.12 years ± 1.1. Mean follow-up was 10.0 years (7-11.9 years). Mean HHS increased significantly after revision from 48.5 to 89.5 (P < .001). Higher prerevision cobalt levels were correlated with lower prerevision HHS (cobalt R = 0.25; chromium R = 0.3160). There was no correlation with prerevision cobalt (P = .2671) or chromium (P = .3160) with postrevision HHS. Most recent metal ion testing revealed a significant decrease in both cobalt (P = .0084) and chromium (P = .0115). Survival rate is 100%.

Conclusions

Our study showed excellent survivorship and outcomes at 10 years. There were no failures for any reason including infection. This differs from previous studies and confirms excellent long-term results are possible with revision of this recalled MoM implant.

Do cobalt and chromium blood metal ion levels normalize after revision of failed metal-on-metal total hip replacements?

INTRODUCTION

Increased cobalt (Co) and chromium (Cr) serum levels are one reason for revision surgery in metal on metal (MoM) total hip arthroplasty (THA) patients. Dual mobility liners are a simple revision option; however, they preserve the metal shell and stem and it is therefore not clear if metal ion levels will fully normalize after revision surgery.

MATERIAL AND METHODS

Between April 2013 and December 2017 25 hips (24 patients) underwent revision from a MoM THA to an off-label dual mobility liner. Five patients were lost to follow-up and one patient refused leaving 18 patients (11 men, 7 female, average age 63.9 years) for pre- and postoperative metal ion level blood tests at a minimum follow-up of 2 years.

RESULTS

Fourteen patients were revised for osteolysis, two for elevated metal ion levels and two for fluid or cysts around the femoral or acetabular component. The average preoperative Co and Cr levels were 8.3 µg/l and 5.0 µg/l, respectively. At a minimum follow-up of 2 years (30-95 months), metal ions dropped to 0.8 µg/l. Harris Hip Score (HHS), Hip Osteoarthritis Outcome Score (HOOS), Visual Analog Scale (VAS) and the UCLA activity score improved non-significantly from pre- to postoperative. There was one postoperative complication in the study cohort. One patient with persisting pain required revision surgery to a standard acetabular component during the follow-up period.

CONCLUSION

The off-label use of a dual-mobility liner in the current study resulted in normalization of the metal ion levels suggesting that preserving the cobalt-chromium acetabular component has little impact on ion levels. In addition, dual mobility liners have a low complication and revision rate.

Surgical management of hip prosthetic failure in metallosis: A case series and literature review

Local and remote complications can be observed in hip prosthesis failures associated with metallosis. Structural changes in the periprosthetic bone and soft tissues may not always be precisely assessed preoperatively due to metal artifacts. The unpredictability of the damage extension, potentially leading to complex and insidious surgeries, requires the availability of alternative surgical plan(s) for the reconstruction of the joint. The aim of the study is to present and analyze, with the literature data support, practical tips for the revision of the prosthetic components, the management of ARMD and of intraoperative complications in the unusual scenario of metallosis.

Nontribological corrosion modes dominate wrought CoCrMo acetabular taper corrosion: A retrieval study

Corrosion of modular metal-on-metal acetabular tapers in total hip arthroplasty (THA) systems is often attributed to mechanically driven processes. Recent findings suggest that mechanically assisted crevice corrosion (MACC) might not be the dominant cause of corrosion in shell-liner tapers. This study aims to document and present the corrosion modes observed in metal-metal acetabular liners. Twenty-one retrieved wrought CoCrMo liners were examined using digital optical microscopy (DOM), scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). Corrosion-related damage was documented in nonengagement taper regions, outside of direct taper contact. Within engagement regions, nonmechanically driven corrosion features (pitting, intergranular corrosion) were observed adjacent to fretting and material transfer, which rely on mechanical contact; corrosion independent of MACC was observed even in contact regions. Corrosion types observed included intergranular corrosion (IGC), pitting attack, phase boundary dissolution, all both outside and inside of taper junctions, and MACC within contact regions of the taper. Typical fretting scars associated with MACC were mostly absent, and were not always associated with corrosion damage where present. Finally, hard phase particles (Mo-Si-O) released from the wrought CoCrMo microstructure had redeposited within regions with material loss. Acetabular taper corrosion modes differ significantly from those in head-neck tapers and are dominated by electrochemically driven processes, not mechanical processes, as indicated by corrosion in noncontact regions. With greater prevalence of dual mobility hip implants, acetabular taper corrosion processes must be understood in order to limit their impact on device performance.

Comparison of Constrained Acetabular Components and Dual Mobility Cups in Revision Total Hip Arthroplasty: A Literature Review

Recurrent instability remains a common cause of failure after revision total hip arthroplasty (THA). Dual mobility (DM) cups and designs with constrained acetabular liners (CAL) have both been developed to help overcome this challenge. The aim of this report is to compare safety and efficacy outcomes of both designs based on the literature. A comprehensive literature review including published evidence on the results of DM and CAL in revision THA was performed and summarized. Available literature focusing on overall survival, dislocation, loosening, intra-prosthetic dislocation (IPD), and functional outcomes were analysed. Forty-six reports including an evaluation of 5,617 total hips were evaluated were included in the review. The included studies were divided into two distinct groups based on implantation approach: i) CAL (n=15) and ii) DM (n=31). The DM group had higher overall survival rates (94.7% vs. 81.0%), lower dislocation rates (2.6% vs. 11.0%), and lower acetabular loosening rates (1.0% vs. 2.0%) compared to the CAL group. IPDs were reported in 6 studies (mean rate, 0.6%). No differences in functional outcomes were identified due to incomplete reports. Our observations reveal that designs with CAL have poorer outcomes as compared to DM cups in revision THA. Currently, the use of DM seems more appropriate since they offer lower rates of dislocations, loosening and re-revisions in the short- and mid-term. Concerns regarding the potential of increased wear in a younger, high-demand population require additional data and evaluation by long-term studies for the DM design.

Metal-on-Metal Total Hip Revisions: Pearls and Pitfalls

BACKGROUND

At the turn of the 21st century, there was a re-emergence of metal-on-metal (MoM) articulation with 35% of all total hip arthroplasty implants having MoM articulation. Approximately 10 years after its peak use, MoM articulation began to decrease dramatically as revisions became more apparent because of adverse reaction to metal debris. Today, there are surveillance guidelines and reconstructive clinical pearls a surgeon should recognize.

METHODS

This article gives a literature-based overview of clinical pearls and discusses how to avoid pitfalls when performing revision of a metal-on-metal total hip arthroplasty.

RESULTS

Patients with MoM can be risk-stratified based on symptom, implant, and testing variables. Those patients who are symptomatic and/or develop adverse reaction to metal debris with local tissue destruction will require a revision. The revision of MoM can be challenging due to bone and soft tissue destruction. Constraint may be needed in cases of abductor deficiency.

CONCLUSION

Although MoM implants for THA have declined significantly, surgeons are still faced with the revision burden from a decade of high use. Risk stratification tools are available to aid in revision decision making, and the surgeon should be prepared to address the challenges these revisions present.

In vitro test methods for seating and fretting corrosion behavior of modular metal-on-metal acetabular tapers

Retrieval studies show that metal-on-metal acetabular shell-liner tapers are susceptible to corrosion, which is hypothesized to arise from mechanically-assisted crevice corrosion (MACC). The role of materials on MACC of acetabular tapers has not been previously studied. In vitro tests of seating, pushout, and fretting corrosion performance of acetabular tapers are presented to assess the role of material combinations (Ti-6Al-4V shells, HC CoCrMo, LC CoCrMo, and 316L SS liners). The acetabular tapers were wet-assembled to a seating load of 1,000 N. The liner load-displacement seating mechanics were measured. Fretting corrosion currents were evaluated using a uniaxial incremental cyclic compression test up to 4,000 N, with the load applied at a 55° angle to the taper interface. Fretting currents, fretting onset loads, taper disengagement strength were measured and load-displacement plots were obtained. Pushout tests were also performed pre- and post-fretting corrosion. The average liner seating displacements varied from 134 to 226 μm across groups. Fretting currents at 3,600 N cyclic load were low and ranged between 0.05 and 0.27 μA and were independent of material combination (p > 0.05), reflecting small amounts of fretting. Fretting corrosion onset loads were between 1,800 and 2,100 N, and did not differ across groups (p > 0.05). Pushout loads were 27-43% of the maximum load applied. Fretting corrosion levels were very low for all material combinations and not different from one another. The seating and pushout responses were also not material dependent. The low fretting currents measured imply that MACC may not be a major cause for acetabular taper corrosion. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:00-111089, 2020.

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.

No Difference in Force Required for Intraprosthetic Dislocation of Mixed Manufacturer vs Same Manufacturer Dual Mobility Articulations

BACKGROUND

To avoid the morbidity of removing well-fixed implants during revision surgery, the off-label practice of mixing femoral heads with dual mobility (DM) polyethylene liners from different manufacturers is commonly performed. The resistance to intraprosthetic dislocation, when the inner prosthetic head disengages from the polyethylene bearing, between mixed and same manufacturer constructs remains unknown.

METHODS

Between January 2010 and July 2018, 168 DM liners were retrieved. Specimens were excluded for catastrophic wear (n = 14), previously levered-out (n = 17), and cases in legal proceedings (n = 8). Using a validated setup, 129 specimens were uniaxially loaded 100 mm from the femoral head until lever-out failure of the head from the liner. The difference in maximum lever-out force (LOF) was compared for same and mixed manufacturer retrievals (Student t-test). Multivariable regression analysis evaluated the influence of potential confounders (length of implantation, head size, head material, presence of skirt) on LOF.

RESULTS

Ninety-seven same and 32 mixed manufacturer DM constructs were tested. The average LOF for same (272.6 ± 68.7 N) and mixed (299.2 ± 89.0 N) manufacturer specimens was not significantly different (P = .08). An inner head size of 22.2 mm was associated with 184.4-N increase in LOF (P < .001), the presence of a skirt was associated with 63.8-N increase in maximum LOF, and head material (ceramic vs metal) did not influence LOF.

CONCLUSION

We found no difference in the force required to lever-out same and mixed manufacturer inner heads from DM liners, suggesting that mixing manufacturers when placing DM articulations on well-fixed femoral stems should not increase the risk of intraprosthetic instability.

Dual Mobility for Monoblock Metal-on-Metal Revision-Is It Safe?

BACKGROUND

Revision of monoblock metal-on-metal (MoM) total hip arthroplasty (THA) is associated with high complication rates. Limited revision by conversion to a dual mobility (DM) without acetabular component extraction may mitigate these complications. However, the concern for polyethylene wear and osteolysis remains unsettled. This study investigates the results of DM conversion of monoblock MoM THA compared to formal acetabular revision.

METHODS

One hundred forty-three revisions of monoblock MoM THA were reviewed. Twenty-nine were revisions to a DM construct, and 114 were complete revisions of the acetabular component. Mean patient age was 61, 54% were women. Components used, acetabular cup position, radiographic outcomes, serum metal ion levels, and HOOS Jr clinical outcome scores were investigated.

RESULTS

At 3.9 years of follow-up (range 2-5), there were 2 revisions (6.9%) in the DM cohort, 1 for instability and another for periprosthetic fracture. Among the formal acetabular revision group there was a 20% major complication rate (23/114) and 16% underwent revision surgery (18/114) for aseptic loosening of the acetabular component (6%), deep infection (6%), dislocation (4%), acetabular fracture (3%), or delayed wound healing (6%). In the DM cohort, there were no radiographic signs of aseptic loosening, component migration, or polyethylene wear. One DM patient had a small posterior metadiaphyseal femur lesion that will require close monitoring. There were no other radiographic signs of osteolysis. There were no clinically significant elevations of serum metal ion levels. HOOS Jr scores were favorable.

CONCLUSION

Limited revision with conversion to DM is a viable treatment option for failed monoblock MoM THA with lower complication rates than formal revision. Limited revision to DM appears to be a safe option for revision of monoblock MoM THA with a cup in good position and an internal geometry free of sharp edges or articular surface damage. Longer follow-up is needed to demonstrate any potential wear implications of these articulations.

Conversion of Hip Resurfacing With Retention of Monoblock Acetabular Shell Using Dual-Mobility Components

BACKGROUND

Retention of the acetabular component is an option during conversion from hip resurfacing arthroplasty (HRA) to total hip arthroplasty (THA). The purpose of this study was to compare clinical outcomes of conversion of the femoral resurfacing component with retained acetabular components (RAC) and use of dual-mobility femoral heads to outcomes of patients treated with both component (BC) revisions.

METHODS

A retrospective review was performed of the clinical outcomes of HRA to THA conversions performed at a single institution between 2008 and 2017.

RESULTS

Seventy-one conversions were included (27 RAC and 44 BC). Average age at time of conversion was 54.4 years (range, 30-68 years). Median time to conversion was 5.14 (2.77-7.41) years and median follow-up post-conversion was 1.7 (0.33-4.0) years. There were no significant differences in indications for conversion between the 2 groups with the majority performed for complications related to elevated metal ions and aseptic loosening. Harris Hip Scores improved from pre-conversion to post-conversion in both cohorts (P < .01). There were no significant differences in pre-conversion and post-conversion metal ion levels between the RAC and BC groups. Serum metal ion levels decreased significantly in both cohorts (P < .01). There were 6 additional revisions in the cohort (4 in BC, 2 in RAC) at a median 2.94 (1.99-3.85) years post-conversion. Two RAC patients had intraprosthetic dislocations with extensive polyethylene wear requiring acetabular revision at median 3.92 (3.85-3.98) years post-conversion. Overall, there were a higher number of complications in the BC group related to acetabular fracture, failure of osseointegration, and periprosthetic joint infection; however, this did not reach statistical significance (P = .27).

CONCLUSION

Salvage of an appropriately positioned, well-fixed HRA acetabular component is a reasonable option in the setting of conversion to THA using dual-mobility components. This technique avoids the morbidity of acetabular revision and was associated with a decrease in metal ion levels and improvements in short-term functional outcomes comparable to a BC revision.

Revision of Failed Metal-on-Metal Total Hip Arthroplasty: Midterm Outcomes of 203 Consecutive Cases

BACKGROUND

Metal-on-metal (MoM) revisions have shown high rates of complications from aseptic loosening, deep infection, and dislocation. The purpose of this study is to report on outcomes and complications of a large consecutive series of patients who were revised for failed MoM total hip arthroplasty (THA).

METHODS

We evaluated 188 patients (203 hips) who underwent revisions of failed MoM THA. Mean age at the revision was 60 years old. Gender was female in 112 hips (55%) and male in 91 hips (45%). Mean interval to failure after primary THA was 4.9 years (range, 0-18 years). The acetabular component was revised in 183 cases (92%). Clinical outcomes assessed included pain score and Harris hip score.

RESULTS

Mean follow-up from revision was 4.2 years. Harris hip score improved from 53.6 pre-revision to 73.5 at most recent follow-up (P < .001). Pain level significantly improved from 17.2 pre-revision to 32.8 post-revision (P < .001). Reoperations occurred in 28 (14%) hips. Re-revision was required in 16 hips (7.9%). The most common reasons for re-revision were aseptic loosening (5), dislocation (3), infection (2), and iliopsoas tendonitis (2). Re-revision was significantly higher in cases of pseudotumor. There was no difference in survival with ultraporous cups. Three hips required re-revision to custom triflange components. All-cause survival was 90.5% at 4.2 years. Metal ion levels significantly declined after revision.

CONCLUSION

Revisions of failed MoM THA showed improvements in clinical outcomes, but present significant surgical challenges and complications especially in cases with soft tissue damage and pseudotumor.

Rapid return to function and stability with dual mobility components cemented into an acetabular reconstructive cage for large osseous defects in the setting of periacetabular metastatic disease

BACKGROUND AND OBJECTIVES

Large acetabular defects secondary to metastatic disease frequently require extensive acetabular reconstruction. Techniques of acetabular reconstruction have been described, but no consensus for the management of these defects has been reached so far. We present our technique and patient outcomes for acetabular reconstruction by cementing a dual mobility cup into an acetabular cage.

METHODS

We reviewed 152 total hip arthroplasties and identified 19 patients with periacetabular metastatic disease and large defects who required acetabular reconstruction utilizing a dual mobility cup cemented into an acetabular reconstructive cage. The following outcomes were evaluated: pain relief, functional improvement, postoperative complications.

RESULTS

Mean follow-up was 3 years, with 13 of the 19 patients eligible for 2-year follow-up. Patients reported a significant improvement in both pain and functional outcomes. There were no dislocations or signs of loosening. Two patients developed postoperative infections. One patient required hemipelvectomy 16 months postop due to recurrence of metastatic disease.

CONCLUSIONS

Cementing a dual mobility cup into an acetabular cage provides a highly stable and durable option for patients with periacetabular metastatic disease and large defects. Patients are able to return to immediate full weight bearing with significant improvement in both function and pain at 2 years.

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

BACKGROUND

The purpose of this systematic review is to analyze the outcomes of dual-mobility (DM) cups in revision total hip arthroplasty (THA). Specifically, we evaluated the following: (1) all-cause and aseptic survivorship rates; (2) dislocation rates; (3) complications; and (4) clinical outcomes reported using validated health status measures.

METHODS

A comprehensive literature search included studies that reported the following: (1) re-revision rates, (2) complications, and (3) clinical outcomes following DM use in revision THA. The following exclusion criteria were used: (1) studies that did not stratify their analysis between primary and revision THA, (2) studies that utilized off-label techniques, (3) review articles, (4) case studies, (5) basic science articles, (6) non-English language reports, and (6) reports on patients who underwent surgery before 2010, in order to reflect modern DM implants use and technology. A total of 9 studies were included in our final analysis.

RESULTS

Aseptic and all-cause survivorship rates were 97.7% and 94.5%. Prevalence of dislocation was 2.2%, and 0.3% for intraprosthetic dislocation. Meta-analysis comparing DM to fixed-bearing prostheses demonstrated a significantly lower odds of dislocation in the DM cohort (odds ratio 0.24, P = .002). Complications occurred in 7.4% of revision THAs with DM cups, while infection rates totaled to 3.3% of cases. Studies comparing outcomes using Harris Hip Scores did not demonstrate a statistically significant difference in improved postoperative scores (P > .05).

CONCLUSION

DM cups have demonstrated excellent survivorship, low dislocation, and overall complication rates. Therefore, it can be considered a safe and effective option, particularly in the high-risk patients who undergo revision THA.

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.

Cementation of a Dual Mobility Construct in Recurrently Dislocating and High Risk Patients Undergoing Revision Total Arthroplasty

BACKGROUND

Recurrent instability remains a challenge after revision total hip arthroplasty (THA). We report the outcomes of cementing a cementless dual mobility (DM) component into a stable acetabular shell for the treatment and/or prevention of instability in revision THA.

METHODS

Eighteen patients (18 THAs) undergoing revision THA with a specific monoblock DM construct cemented into a new acetabular component or an existing well-fixed component from 2011 to 2014 were retrospectively reviewed. Tumor prostheses and total femoral replacements were excluded. In 9 patients (50%), components were implanted specifically for recurrent dislocations. Mean age was 64 years; mean follow-up was 3 years. Patients underwent an average of 4 prior hip operations (range 2-6).

RESULTS

No cemented DM cups dissociated at the cement-cup interface. Three patients (17%) experienced a postoperative dislocation. One required a revision to constrained liner and 2 underwent open reduction with retention of the DM construct. Harris Hip Scores improved from 53 to 82 postoperatively (P < .001).

CONCLUSION

Cementation of a monoblock cup DM construct, an off-label use as the construct is not specifically made for cementation, into a well-fixed acetabular component provides an alternative to enhance prosthetic stability in (1) recurrently dislocating THAs with well fixed, well-positioned acetabular components and (2) complex acetabular reconstructions in which constraint should be avoided. While not a perfect solution in this series, DM constructs provide a number of advantages including no added constraint at the interface and a large effective femoral head to diminish prosthetic impingement.

Damage Assessment of Retrieved Birmingham Monoblock Cups: Is Conversion to Dual-Mobility Head a Viable Revision Option?

BACKGROUND

A novel revision technique for failed hip resurfacings involves retention of the acetabular cup, if well-fixed, which is mated to dual-mobility (DM) prosthesis in a traditional hip replacement configuration. It is unknown whether existing damage on the retained cup will result in unacceptable wear of the DM prosthesis.

METHODS

Thirty retrieved Birmingham (Smith & Nephew) monoblock cups were visually scored for damage features and area of coverage. Surface roughness measurements were obtained within each damage feature as well as reference points on each cup. Analysis of prior metal-on-metal wear was also performed to determine the maximum change in diameter of the cup.

RESULTS

Scratching and grooving (deep, singular scratches) were the most common damage features. Overall bearing surface roughness was estimated as 0.059 μm (±0.030 μm) based on percent area coverage of each damage feature. Dimensional change of the bearing surface was negligible for most cups (18 of 30) but ranged from 0.20 to 0.38 mm for the most severely worn samples (5 of 30).

CONCLUSION

Average surface roughness of the retrieved Birmingham cups was low, suggesting an expected 10%-20% increase in DM prosthesis wear. Similarly, dimensional change of the cup due to prior wear is not believed to significantly affect wear. Our findings support the use of a DM head in appropriate scenarios but suggest caution when applied to younger, more active patients whom may be adversely affected by increased prosthesis wear in the long term.

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.

Salvage of a monoblock metal-on-metal cup using a dual mobility liner: a two-year MRI follow-up study

PURPOSE

Revision of failed modular metal-on-metal total hip replacement (MoM-THA) can be technically difficult. A dual mobility liner can help to salvage a well-fixed acetabular component. The present paper reports the clinical and radiographic outcome of revision of failed Birmingham modular MoM-THA using a dual mobility liner.

METHODS

The present study reports on ten patients (3 female and 7 male) with 11 revision THAs. Patients underwent revision an average of 51 months (range 40-73 months) after index procedure. Mean follow-up after the revision was 31 months (range 24-37 months) and all patients underwent an MRI with metal artifact reduction software (MARS) at least two years after revision to assess for local polyethylene wear and osteolysis.

RESULTS

The Harris Hip score improved from 92.2 (range 63.0-100.0) to 100.0 (p = 0.072). One patient had a one-time dislocation within seven days of surgery. No patient required additional surgeries. Radiographs showed no signs of component loosening and osteolysis and MRI imaging revealed no evidence of polyethylene wear or osteolysis.

CONCLUSION

A dual mobility liner in an existing Birmingham cup can provide excellent clinical and radiological short-term results without MRI evidence of increased polyethylene wear. Post-operative hip precautions should be enforced.

Outcomes of Modular Dual Mobility Acetabular Components in Revision Total Hip Arthroplasty

BACKGROUND

There is a high rate of dislocation after revision total hip arthroplasty. This study evaluated the outcomes of 1 modular dual mobility component in revision total hip arthroplasty in patients at high risk of dislocation.

METHODS

We reviewed 64 revisions performed in 27 (42%) patients for recurrent dislocation, 16 (25%) for adverse local tissue reaction, 11 (17%) for reimplantation infection, and 10 (16%) for aseptic loosening, malposition, or fracture. Complications, reoperations, and survivorship were evaluated.

RESULTS

Three-year survival was 98% with failure defined as aseptic loosening and 91% with failure as cup removal for any reason. With mean follow-up time of 38 months, there were 14 complications, including 2 dislocations treated with closed reduction, 9 infections, and 12 reoperations. All complications occurred in patients revised for instability, adverse local tissue reaction, or infection.

CONCLUSION

The early results of this component are promising, with good overall survival and low rate of dislocation.

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.

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.

Revision of Metal-on-metal Hip Arthroplasty with Well Fixed and Positioned Acetabular Component Using a Dual-mobility Head and Review of Literature

Background:

As a consequence of use of metal-on-metal hip arthroplasties some patients have precised revision for pain or metal hipersensivity reactions among other causes. We propose to salvage monoblock acetabular component and femoral component using a dual-mobility head and perform a lower morbidity operation in young patients preserving host bone stock in cases with well fixed and positioned components.

Objective:

(1) What clinical problems have been reported in patients with Metal-on-metal hip arthroplasties? (2) Could the tribocorrosion potentially cause a fracture of neck femoral component? (3) Can be the dual-mobility head a recourse in metal-on-metal hip revision?

Methods:

Ten patients were revised for pain or/and raised Cobalt/Chromium levels between August 2012 and December 2015. In three cases femoral neck component was fractured and femoral revision was necessary. In four hips, acetabular and femoral components could be maintained. Age, body index mass, ion levels, acetabular position, size of acetabular component and femoral head, approach, blood transfunsion and time of hospitalization were analized.

Results:

At a mean follow-up of 25,6 months (6 to 45) the mean postoperative HHS was 92. It was not statistically significant because several patients were low sintomatic before surgery, but had raised Cobalt/Chromium levels in the blood. All patients had near-normal levels of Cobalt/Chromium during the first 6 months after revision surgery. No relevant complications were reported.

Conclusion:

The use of dual-mobility head can be an acceptable option to revise metal-on-metal arthroplasties correctly oriented with abscence of loosening or infection signs and keeping bone stock in young patients.

Treatment of the Failed Modular Neck Stems: Tips and Tricks

BACKGROUND

Modular femoral components emerged because of the advantages of recreating limb length, offset, and native femoral version in total hip arthroplasty. Despite its potential benefits, the increase in modularity at the head-neck junction can lead to corrosion and subsequently failure of the implant.

METHODS

We present 3 case examples of patients who underwent revision surgery secondary to corrosion of their modular femoral components.

RESULTS

Issues addressed include understanding corrosion at the head-neck junction, presentations of adverse local tissue reactions, efficacy of metal ion testing and metal artifact reduction sequence magnetic resonance imaging, and approaches to revision surgery for failed modular neck stems.

CONCLUSIONS

When revision surgery is indicated for failed modular neck stems, we recommend a thoughtful approach with contemporary extraction techniques and options to enhance stability. Furthermore, long-term follow-up is needed to define the growing effect of modularity in total hip arthroplasty.