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

Archetype analysis of the spine-hip relationship identifies distinct spinopelvic profiles

INTRODUCTION

The position of the pelvis in the sagittal plane can vary considerably between different functional positions. Adapting the position of the acetabular cup in relation to the alignment between the spine and the hip of each individual, prior to prosthesis placement, can prevent the risk of prosthetic impingement. Taken individually, risk factors for unfavorable spinopelvic kinematics can be difficult to interpret when trying to precisely predict which patients are at risk. Furthermore, the use of classifications or algorithms can be complex, most often associated with limited values and often difficult to apply in current practices of risk assessment.

HYPOTHESIS

We hypothesized that the deconstruction of the data matrix including age and spinopelvic parameters (SPT, LL, PI, LF and PI-LL) correlated with the analysis of spinopelvic kinematics could be used to define an individualized hip-spine relationship.

MATERIAL AND METHOD

We applied archetypal analysis, which is a probabilistic, data-driven and unsupervised approach, to a complete phenotype cohort of 330 patients before total hip arthroplasty to define the spinopelvic profile of each individual using the spinopelvic parameters without threshold value. For each archetype, we analyzed the spinopelvic kinematics, not implemented in the creation of the archetypes.

RESULTS

An unsupervised learning method revealed seven archetypes with distinct spinopelvic kinematic profiles ranging from -8.9 ° to 13.15 ° (p = 0.0001) from standing to sitting and -5. 35 ° to -10.81 ° (p = 0.0001) from supine to standing. Archetype 1 represents the "ideal" patient (A1); young patients without spinopelvic anomaly and the least at risk of mobility anomaly. Followed by 3 archetypes without sagittal imbalance according to their lumbar lordosis and pelvic incidence, from the highest to the lowest (archetypes 2-4), archetype 4 exposing a greater risk of spinopelvic kinematic anomaly compared to others. Then 2 archetypes with sagittal imbalance: archetype 5, with an immobile pelvis in the horizontal plane from standing to sitting position in anterior tilt and archetype A6, with significant posterior pelvic tilt standing, likely compensating for the imbalance and associated with the greatest anomaly of spinopelvic kinematics. Finally, archetype 7 with the stiffest lumbar spine without sagittal imbalance and significant unfavorable kinematics from standing to sitting.

CONCLUSION

An archetypal approach to patients before hip replacement can refine diagnostic and prognostic features associated with the hip-spine relationship and reduced heterogeneity, thereby improving spinopelvic characterization. This risk stratification of spinopelvic kinematic abnormalities could make it possible to target patients who require adapted positioning or types of implants before prosthetic surgery.

LEVEL OF EVIDENCE

IV retrospective study.

In silico analysis of the patient-specific acetabular cup anteversion safe zone

INTRODUCTION

Various computer-assisted surgical systems claim to improve the accuracy of cup placement in total hip arthroplasties after assessing spinopelvic mobility to prevent prosthetic impingement. However, no study has yet analyzed the extent of the patient-specific cup anteversion safe zones.

HYPOTHESIS

We hypothesized that most patients have a safe zone >10 °, except those with abnormal spinopelvic mobility, who have a much narrower safe zone.

MATERIALS AND METHODS

We simulated the risks of prosthetic impingement using the planned cup anteversion. The consecutive cohort included 341 patients who underwent total hip arthroplasty. Our primary endpoint was the patient-specific impingement-free zone for cup anteversion, which was then divided into four subgroups: 0 °, 1 ° to 5 °, 6 ° to 10 °, and >10 °. This data was then secondarily analyzed for abnormal spinopelvic mobility (the difference in the spinopelvic tilt [ΔSPT] from a standing to a flexed seated position >20 °).

RESULTS

The mean anteversion safe zone was 22.8 ° with 82.4% (281/341) of patients with a zone strictly >10 °. The mean safe zone was 8.9 ° (+/- 9 °) in patients with an ΔSPT ≥20 ° (18.2%), with 37.1% of these patients having a zone of 0 °, 16.13% a zone between 1 ° and 5 °, 8.06% a zone between 6 ° and 10 ° and 38.71% a zone >10 °. The mean safe zone was 25.9 ° (+/- 9 °) in patients with an ΔSPT <20 ° (81.8%), and the proportion of cases in each zone was 2.51%, 1.08%, 4.3%, and 92.11%, respectively (p < 0.001).

CONCLUSION

The safe zone for anteversion appears to be fairly wide in most patients. However, identifying patients at risk of abnormal spinopelvic mobility seems necessary to identify the two-thirds of patients with a narrow safe zone.

LEVEL OF EVIDENCE

IV; retrospective study.

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

BACKGROUND

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

HYPOTHESIS

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE

III; comparative retrospective study.

Dual-mobility implants in primary and revision total hip arthroplasty: A systematic review and meta-analysis

Purpose

Total hip arthroplasty (THA) is a common and successful operation. However, dislocation remains a significant cause of implant failure in fixed-bearing designs. This study investigated the effect of dual-mobility implants (DM) compared to fixed-bearing (FB) implants on all-cause revisions, revisions due to dislocation, post-operative complications and functional scores in patients undergoing primary and revision THA.

Methods

A systematic review was performed including studies that compared DM with FB implants in primary or revision THA according to PRISMA guidelines, and was registered in PROSPERO (ID CRD42023403736). The Cochrane Library, Embase, MEDLINE, Web of Science, and Scopus were searched from the time of database inception to March 12, 2023. Eligible studies underwent meta-analysis and risk of bias assessment using the ROBINS-I tool. Treatment effects were assessed using odds ratios and data were pooled using a random-effects maximum-likelihood, where appropriate.

Results

Eight comparative, non-randomised studies involving 2810 DM implants and 3188 FB implants were included. In primary THA, there was an imprecise estimate of the difference in all-cause revision (OR 0.82, 95 % CI 0.25-2.72) and a significant benefit for the DM cohort in revision due to dislocation (OR 0.08, 95 % CI 0.02-0.28). In revision THA, the DM cohort showed benefit in all-cause revision (OR 0.57, 95 % CI 0.31-1.05) and revision due to dislocation (OR 0.14, 95 % CI 0.04-0.53). DM implants were associated with a lower incidence of implant dislocation and infection. The analysis of functional outcomes was limited due to reporting limitations. No intraprosthetic dislocations were observed.

Conclusion

The results suggest that contemporary DM designs may be advantageous in reducing the risk of all-cause revision, revision due to dislocation, and post-operative complication incidence at mid-term follow-up. Further high-quality prospective studies are needed to evaluate the long-term risk profile of this design, especially in the revision context.

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.

Closed reduction of dislocated hip prosthesis using a traction table

This article describes three cases in which a dislocated hip prosthesis was reduced by a new reduction technique - that we previously described - using traction table. The dissociation of a prosthesis is a rare but serious complication of closed reduction manoeuvre. The new reduction manoeuvre using a traction table may be a good option to avoid dissociation of the prosthesis during closed reduction for treatment of dislocation after total hip arthroplasty.

Survivorship of the dual-mobility construct in elective primary total hip replacement: a systematic review and meta-analysis including registry data

INTRODUCTION

Dislocation is a common complication associated with total hip replacement (THR). Dual-mobility constructs (DMC-THR) may be used in high-risk patients and have design features that may reduce the risk of dislocation. We aimed to report overall pooled estimates of all-cause construct survival for elective primary DMC-THR. Secondary outcomes included unadjusted dislocation rate, revision for instability, infection and fracture.

METHODS

MEDLINE, EMBASE, Web of Science, Cochrane Library and National Joint Registry reports were systematically searched (CRD42020189664). Studies reporting revision (all-cause) survival estimates and confidence intervals by brand and construct including DMC bearings were included. A meta-analysis was performed weighting series by the standard error.

RESULTS

Thirty-seven studies reporting 39 case series were identified; nine (10,494 DMC-THR) were included. Fourteen series (23,020 DMC-THR) from five national registries were included. Pooled case series data for all-cause construct survival was 99.7% (95% CI 99.5-100) at 5 years, 95.7% (95% CI 94.9-96.5) at 10 years, 96.1% (95% CI 91.8-100) at 15 years and 77% (95% CI 74.4-82.0) at 20 years. Pooled joint registry data showed an all-cause construct survivorship of 97.8% (95% CI 97.3-98.4) at 5 years and 96.3% (95% CI 95.6-96.9) at 10 years.

CONCLUSIONS

Survivorship of DMC-THR in primary THR is acceptable according to the national revision benchmark published by National Institute for Clinical Excellence (NICE).

Five-year polyethylene cup migration and PE wear of the Anatomic Dual Mobility acetabular construct

INTRODUCTION

Dual mobility implants have been successful in reducing postoperative hip dislocation but mid-term results of cup migration and polyethylene wear are missing in the literature. Therefore, we measured migration and wear at 5-year follow-up using radiostereometric analysis (RSA).

MATERIALS AND METHODS

A cohort of 44 patients (mean age 73, 36 female) with heterogeneous indications for hip arthroplasty but all with a high risk of hip dislocation received total hip replacement (THA) with The Anatomic Dual Mobility X3 monoblock acetabular construct and a highly crosslinked polyethylene liner. RSA images and Oxford Hip Scores were obtained perioperatively and 1, 2, and 5 years postoperatively. Cup migration and polyethylene wear were calculated using RSA.

RESULTS

Mean 2-year proximal cup translation was 0.26 mm (95% CI 0.17; 0.36). Proximal cup translation was stable from 1- to 5-year follow-up. Mean 2-year cup inclination (z-rotation) was 0.23° (95% CI - 0.22; 0.68) and was greater in patients with osteoporosis compared to patients without osteoporosis (p = 0.04). Using 1-year follow-up as baseline, the 3D polyethylene wear rate was 0.07 mm/year (0.05; 0.10). Oxford hip scores improved 19 (95% CI 14; 24) points from mean 21 (range 4; 39) at baseline, to 40 (9; 48) 2 years postoperatively. There were no progressive radiolucent lines > 1 mm. There was 1 revision for offset correction.

CONCLUSIONS

Anatomic Dual Mobility monoblock cups were well-fixed, the polyethylene wear rate was low, and the clinical outcomes were good until 5-year follow-up suggesting good implant survival in patients of different age groups and with heterogeneous indications for THA.

Is Modular Dual Mobility Superior to Standard Bearings for Reducing Dislocation Risk after Primary Total Hip Arthroplasty? A Retrospective Comparative Multicenter Study

BACKGROUND

Dual mobility (DM) has been proven to reduce dislocation risk after total hip arthroplasty (THA). In the last decade modular DM (modDM) constructs have been introduced to allow the use of DM articulation with standard cementless acetabular shells. However, clinical evidence of modDM effectiveness is still low in primary THA and concerns about implant-related complications are increasing. This retrospective comparative multicenter study is aimed to investigate if the dislocation rate after primary THA could be reduced with modDM in comparison to standard bearing (SB).

METHODS

262 THAs were performed between 2017 and 2019, using SB (129 hips) or modDM (133) with the same cementless highly porous modular acetabular cup. Dislocations, complications and revisions were recorded and implant survival was analyzed.

RESULTS

At 2.5-year mean follow-up, dislocation occurred in 4 hips (3.1%) within the SB group while intraprosthetic dislocation in 2 hips (1.5%) within the modDM group (p = 0.44). Implant survivals with revision due to dislocation were 95.2% and 95.9% at 4-year follow-up for SB and modDM, respectively (p = 0.50).

CONCLUSIONS

modDM used in primary THA might reduce dislocation rate in comparison to SB, even in high-risk patients, however, caution is advocated due to specific intraprosthetic dislocation.

Dual-Mobility Cups in Primary Total Hip Arthroplasty

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

Is the Revision Rate for Femoral Neck Fracture Lower for Total Hip Arthroplasty Than for Hemiarthroplasty?: A Comparison of Registry Data for Contemporary Surgical Options

BACKGROUND

When arthroplasty is indicated for a femoral neck fracture (FNF), it is unclear whether total hip arthroplasty (THA) or hemiarthroplasty (HA) is best. This study compares data from the Australian Orthopaedic Association National Joint Replacement Registry using contemporary surgical options.

METHODS

Patients from 60 to 85 years old who were treated with arthroplasty for FNF, between September 1999 and December 2019, were included if the femoral stems were cemented. Only THAs with femoral heads of ≥36 mm or dual-mobility articulations were included. Patients who had monoblock HA were excluded. Rates of revision for all aseptic failures and dislocation were compared. Competing risks of revision and death were considered using the cumulative incidence function. Subdistribution hazard ratios (HRs) for revision or death from a Fine-Gray regression model were used to compare THA and HA. Interactions of procedure with age group and sex were considered. Secondary analysis adjusting for body mass index (BMI) and American Society of Anesthesiologists (ASA) classification was also considered.

RESULTS

There were 4,551 THA and 29,714 HA procedures included. The rate of revision for THA was lower for women from 60 to 69 years old (HR = 0.58 [95% confidence interval (CI), 0.39 to 0.85]) and from 70 to 74 years old (HR = 0.65 [95% CI, 0.43 to 0.98]) compared with HA. However, women from 80 to 85 years old (HR = 1.56 [95% CI, 1.03 to 2.35]) and men from 75 to 79 years old (HR = 1.61 [95% CI, 1.05 to 2.46]) and 80 to 85 years old (HR = 2.73 [95% CI, 1.89 to 3.95]) had an increased rate of revision when THA was undertaken compared with HA. There was no difference in the rate of revision for dislocation between THA and HA for either sex or age categories.

CONCLUSIONS

When contemporary surgical options for FNF are used, there is a benefit with respect to revision outcomes for THA in women who are <75 years old and a benefit for HA in women who are ≥80 years old and men who are ≥75 years old. There is no difference in dislocation rates.

LEVEL OF EVIDENCE

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

Current Evidence for Spinopelvic Characteristics Influencing Total Hip Arthroplasty Dislocation Risk

BACKGROUND

Decreased pelvic mobility and pelvic retroversion may result from spinal degeneration and lead to changes in the orientation of the acetabular implant after total hip arthroplasty (THA). While multiple patient and surgery-related factors contribute to THA dislocations, there is increasing evidence that sagittal spinopelvic dynamics are relevant for THA stability. The aim of this systematic review was to assess the relationship between previously described sagittal spinopelvic characteristics and implant dislocations after primary THA.

METHODS

A comprehensive literature search in the PubMed and Embase databases was conducted for studies reporting on spinopelvic morphology, alignment, pathology, or surgery and THA dislocations. Risk of bias was assessed using the MINORS criteria. Because of high heterogeneity in study methodology, a synthesis of best evidence was performed. Odds ratios (ORs), relative risks (RRs), and effect sizes (g) were calculated.

RESULTS

Fifteen studies (1,007,900 THAs) with quality scores of 15 to 23 out of 24 were included. Nine different spinopelvic alignment parameters (8 studies, g = 0.14 to 2.02), spinal pathology (2 studies, OR = 1.9 to 29.2), and previous spinal fusion surgery (8 studies, OR = 1.59 to 23.7, RR = 3.0) were found to be related to THA dislocation. Conflicting results were found for another sagittal pelvic morphology parameter, pelvic incidence.

CONCLUSIONS

Several sagittal spinopelvic patient characteristics were found to be related to THA dislocation, and the associated risks were greater than for other patient and surgery-related factors. Future research is needed to determine which of those characteristics and parameters should be taken into account in patients undergoing primary THA.

LEVEL OF EVIDENCE

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

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.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Dual-mobility constructs versus large femoral head bearings in primary and revision total hip arthroplasty: a systematic review and meta-analysis of comparative studies

BACKGROUND

Both dual-mobility (DM) constructs and large femoral head bearings (⩾36 mm) reduce dislocation following total hip arthroplasty (THA). There is limited research comparing DM with large bearings.

METHODS

A systematic review of published literature was performed including studies that compared DM with large femoral head bearings in primary or revision THA according to PRISMA guidelines. The primary outcome was revision surgery for dislocation. The secondary outcome was all-cause revision surgery. Other complications were recorded. 2 authors independently selected studies, performed data extraction, and risk of bias assessment. Treatment effects were assessed using odds ratios and data were pooled using a fixed-effect model, where appropriate.

RESULTS

9 studies, all retrospective, met the final inclusion criteria. 2722 patients received DM and 9,789 large femoral head bearings. The difference in the odds of revision surgery for dislocation (OR 0.67; 95% CI, 0.45-1.01; p = 0.06) and aseptic loosening are unclear (OR 0.61; 95% CI, 0.36-1.05; p = 0.07); including important benefits and no difference. There was a benefit favouring DM for the risk of all-cause revision (OR 0.70; 95% CI, 0.56-0.86; p = 0.001), revision for fracture (OR 0.49; 95% CI, 0.29-0.81; p = 0.005) and dislocation not requiring revision (OR 0.29; 95% CI, 0.14-0.57; p < 0.001). The estimate in the difference in the odds of revision surgery for infection was imprecise (OR 0.78; 95% CI, 05.1-1.20; p = 0.26).

CONCLUSIONS

This study provides evidence that there may be clinically relevant benefits of DM constructs over large femoral head bearings. Prospective randomised studies are warranted given these findings.

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

BACKGROUND

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

HYPOTHESIS

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

MATERIAL AND METHODS

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

RESULTS

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

DISCUSSION

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

LEVEL OF EVIDENCE

IV, retrospective study.

Long-term survival of the Lefèvre retentive cup: 12-year follow-up analysis of 466 consecutive cases

INTRODUCTION

The Lefèvre retentive cup is a salvage solution for total hip replacement at high risk of dislocation. Only a few studies have reported the medium or long-term survival; most often, only a small number of patients were included in these studies. This led us to conduct a retrospective analysis of a large population to determine: 1) the 10-year survival rate after primary or revision arthroplasty, 2) the complication rate.

HYPOTHESIS

The dislocation rate is<5% for revision arthroplasty and<2% for primary arthroplasty.

MATERIAL AND METHODS

This single-center retrospective study included 466 consecutive total hip replacements performed with the Lefèvre retentive cup with a 12-year theoretical minimum follow-up (1/1/1998 to 31/8/2006). There were 257 indications for primary arthroplasty and 209 for revision arthroplasty. The cohort had 316 women and the mean age at surgery was 72.9years (30.2-89.9). The mean follow-up was 10.2±5 years (0.1-19.3). A statistical analysis was done based on the Kaplan-Meier survival curves in two subsets of patients: primary and revision surgery.

RESULTS

At the final review, 264 patients had died because of reasons unrelated to the procedures (mean 7.8±4.7years after the procedure), 48 were lost to follow-up (mean 3.0±3.3years after the procedure), and 39 patients (8%) had undergone acetabular revision of which 12 were for infection (2.5%), 25 were for loosening (5.4%) (5 femoral loosening only) and 2 were for dislocation (0.4%). In all, there were 10/466 dislocations (2.1%) of which 5/257 (1.9%) were in the primary group and 5/209 (2.4%) were in the revision group: 2 had a cup exchange and 8 were reduced by closed procedures. The probability of survival free of mechanical complications at 10years was estimated at 94.8%±1.6% (95% CI: 91.6%-98.0%) for the primary group and 87.8%±2.7% (95% CI: 82.4%-93.2%) for the revision groups (p=0.0017). There were 39 re-operations in the overall cohort: 1/257 (0.4%) for dislocation, 7/257 (2.7%) for aseptic loosening and 3/257 (1.2%) for infection in the primary group, while in the revision group, 1/209 (0.5%) was for dislocation, 18/209 (8.6%) for aseptic loosening and 9/209 (4.3%) for infection.

CONCLUSION

The Lefèvre retentive cup has good long-term survival with a low mechanical complication rate, both in primary and revision surgery. To us, this implant appears to be a reliable salvage procedure for total hip replacement in patients at high risk for dislocation.

LEVEL OF EVIDENCE

IV; retrospective study without control group.

Cementless hydroxyapatite-coated stem with dual mobility and posterior approach in over-80 year-old patients with osteoarthritis: Rates of dislocation and periprosthetic fracture at a mean 8 years' follow-up

BACKGROUND

Straight cementless stems are common in primary total hip arthroplasty (THA) in the elderly, but controversial due to higher risk of loosening and periprosthetic fracture (PPF). Apart from registries, results for the Corail implant and dual mobility (DM) in over-80 years-old are not known, notably in case of systematic association to a DM cup. We therefore performed a retrospective analysis of Corail implants in patients aged≥80years at implantation for osteoarthritis of the hip, assessing 1) PPF rate and survival for cementless straight stems associated to DM cups, 2) complications, and dislocation in particular, and 3) clinical scores.

HYPOTHESIS

PPF and dislocation rates are low in THA with cementless straight stem associated to DM cup in patients aged≥80years.

PATIENTS METHODS

A retrospective study was conducted in our department for the period July 2007 to December 2012. Inclusion criteria were age≥80years, with primary THA for osteoarthritis. Exclusion criteria were revision procedure and femoral neck fracture. One hundred and twenty-eight consecutive THAs were included, in 120 patients, with a minimum 5years' follow-up. Clinical results were assessed on Harris Hip Score (HHS) and Oxford Hip Score (OHS). Data were collected for PPF or dislocation and other complications.

RESULTS

At a mean 8±1 years' follow-up (range, 5-10 years), 66 patients (55%, for 68 hips) were alive, 48 (40%, for 54 hips) had died, and 6 (5%, for 6 hips) were lost to follow-up. Median age at surgery was 83years (range, 80-93years). Mean OHS at last follow-up was 41±6 (range, 21-48) and HHS 83±14 (range, 23-100) with mean gain of 32 points (95% CI, [28-36]; p<0.001)). There were 2 cases (1.6%) of PPF, at 2 and 65months, and no dislocations or cases of aseptic loosening. There were 2 cases (1.6%) of intraoperative calcar fracture, treated by wire cerclage with immediate complete weight-bearing, without further complications. With death as a competing risk, cumulative 10-year incidence of femoral stem revision was 1.6% [95% CI: 0.4-6.5], and cumulative incidence of all-cause revision was 4.1% [95% CI: 1.7-9.7].

DISCUSSION

In an over-80 year-old population, primary THA with straight cementless stem and 2nd generation dual mobility cup was an effective option with low risk of PPF or dislocation after a minimum 5-year of follow-up.

LEVEL OF EVIDENCE

IV; retrospective study.

Effect of intraoperative treatment options on hip joint stability following total hip arthroplasty

Dislocation remains the leading indication for revision of total hip arthroplasty (THA). The objective of this study was to use a computational model to compare the overall resistance to both anterior and posterior dislocation for the available THA constructs commonly considered by surgeons attempting to produce a stable joint. Patient-specific musculoskeletal models of THA patients performing activities consistent with anterior and posterior dislocation were developed to calculate joint contact forces and joint positions used for simulations of dislocation in a finite element model of the implanted hip that included an experimentally calibrated hip capsule representation. Dislocations were then performed with consideration of offset using +5 and +9 offset, iteratively with three lipped liner variations in jump distance (10°, 15°, and 20° lips), a size 40 head, and a dual-mobility construct. Dislocation resistance was quantified as the moment required to dislocate the hip and the integral of the moment-flexion angle (dislocation energy). Increasing head diameter increased resistive moment on average for anterior and posterior dislocation by 22% relative to a neutral configuration. A lipped liner resulted in increases in the resistive moment to posterior dislocation of 9%, 19%, and 47% for 10°, 15°, and 20° lips, a sensitivity of approximately 2.8 Nm/mm of additional jump distance. A dual-mobility acetabular design resulted in an average 38% increase in resistive moment and 92% increase in dislocation energy for anterior and posterior dislocation. A quantitative understanding of tradeoffs in the dislocation risk inherent to THA construct options is valuable in supporting surgical decision making.

Outcomes and survival of a modern dual mobility cup and uncemented collared stem in displaced femoral neck fractures at a minimum 5-year follow-up

INTRODUCTION

The choice of implant type for total hip replacement in the treatment of femoral neck fractures remains debated. Some authors advocate for the systematic use of cemented stems, while others do not use dual mobility first-line. We therefore conducted a retrospective study using a dual mobility cup (DMC) and an uncemented collared stem (UCS) in order to: (1) confirm the low dislocation rate in this indication, (2) assess other surgical complications, in particular periprosthetic fractures, (3) ensure that these benefits are maintained over time, at a minimum follow-up of 5 years and, (4) assess the rate of revision of the implants.

HYPOTHESIS

Our hypothesis was that the dual mobility dislocation rate for the treatment of femoral neck fractures was lower than for bipolar hemiarthroplasties or single mobility hip prostheses.

PATIENTS AND METHODS

A retrospective study of 244 femoral neck fractures (242 patients) treated with DMC and UCS was conducted, between 2013 and 2014. The mean age was 83±10 years (60-104). The occurrence of dislocation, periprosthetic fracture, infection of the surgical site, loosening, reoperation and revision were investigated. The HOOS Joint Replacement (JR) score was collected. The cumulative incidence with mortality was used as a competing risk.

RESULTS

The mean follow-up was 6 years±0.5 (5-7). At the last follow-up, 108 patients (50%) had died. Twenty-three patients (9.5%) were lost to follow-up. One case of symptomatic aseptic loosening of DMC was observed. The cumulative incidence of dislocations and periprosthetic fractures at 5 years were 2% (95% CI: 0.9-5.4) and 3% (95% CI: 1.2-6), respectively. The 5-year cumulative incidence of surgical site infections was 3.5% (95% CI: 1.8-7). The cumulative incidence of reoperations at 5 years was 7% (95% CI: 4.5-11). The causes of reoperation were periprosthetic fracture (n=6), infection (n=8), postoperative hematoma (n=2) and cup malposition (n=2). The cumulative incidence of a revision at 5 years was 2.7% (95% CI: 1.2-6). The cumulative incidence of a surgical complication from any cause at 5 years was 9% (95% CI: 6.7-14.8). The mean HOOS JR score was 79±5 (52-92).

DISCUSSION

The cumulative incidence of dislocation at 5 years is low and other surgical complications (including periprosthetic fractures) do not increase during this period for DMC associated with UCS, in femoral neck fractures. The use of this type of implant is reliable in the treatment of femoral neck fractures.

LEVEL OF EVIDENCE

IV; retrospective study without control group.

How to Prevent Aseptic Loosening in Cementless Arthroplasty: A Review

Aseptic loosening is the main late postoperative complication of cementless total hip arthroplasties (THAs), leading to pain and functional impairment. This article aims to update the orthopedic surgeon on the various methods by which the aseptic loosening rate can be reduced. We performed a systematic review by searching the PubMed database for hip aseptic loosening. We included meta-analysis, randomized controlled trials, reviews, and systematic reviews in the last 10 years, which provided information on techniques that can prevent aseptic loosening in total hip arthroplasty. From a total of 3205 articles identified, 69 articles (2%) met the inclusion criteria, leading to a total of 36 recommendations. A lot of research has been conducted in terms of septic loosening in the last decade. Currently, we have various techniques by which we can reduce the rate of aseptic loosening. Nevertheless, further randomized clinical trials are needed to expand the recommendations for aseptic loosening prevention.

Acetabular Component and Liner Selection for the Prevention of Dislocation After Primary Total Hip Arthroplasty

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Primary total hip arthroplasty (THA) is a reproducible and efficacious procedure for patients with end-stage osteoarthritis; however, dislocation remains the most common cause of revision arthroplasty.

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Technological advancements in acetabular component design and liner options, in conjunction with a more comprehensive understanding of the spinopelvic factors that influence dislocation, will likely reduce the risk of dislocation and revision over time.

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The contemporary liner and shell options for primary THA, in order of increasing constraint and stability, include (1) neutral, (2) lateralized, (3) face-changing (oblique), (4) lipped (high-wall) with or without lateralization, (5) modular and anatomic dual-mobility, and (6) constrained options.

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Different liner designs can alter functional anteversion, inclination, and jump distance, and can be used to minimize a single predictable dislocation vector (lipped [high-wall] liners) or multiple vectors of instability risk when the dislocation direction is unpredictable (dual-mobility liners).

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Liner selection should be based on the patient-specific risk of dislocation, including static anatomic (e.g., large anterior inferior iliac spine or greater trochanter morphology), dynamic anatomic (e.g., limited sitting-standing change in the sacral slope), and demographic or medical (e.g., neurocognitive disorders and obesity) risk factors.

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.

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.

Total Hip Arthroplasty Using a Hemispherical Uncemented Dual-Mobility Cup Results in Satisfactory Clinical Outcomes and No Dislocations at 2 years

BACKGROUND

The authors performed total hip arthroplasty (THA) using a novel hemispherical dual-mobility (DM) acetabular cup without a protrusive cylindro-spherical rim, intended to reduce risks of iliopsoas impingement without requiring changes to conventional intraoperative positioning as with unipolar cups. We aim to determine clinical scores and rates of dislocations, complications, and revisions of this hemispherical DM cup, with the hypothesis that this novel design would result in clinical scores and dislocation rates comparable to other contemporary DM cups with protrusive cylindro-spherical rims.

METHODS

We assessed 332 consecutive uncemented THAs performed using a hemispherical DM cup, at a minimum 2-year follow-up, using modified Harris Hip Score (mHHS) and Oxford Hip Score (OHS), and noting complications and revisions. Regression analyses were conducted to determine if mHHS and OHS depended on any independent factors.

RESULTS

At 2.8 ± 0.5 years (range, 2-5), 2 patients (0.6%) had stem and cup revisions, 3 patients (1%) had isolated stem revisions, 13 patients (4%) died, and none were lost to follow-up. No dislocations occurred. For the final cohort of 305 patients (314 hips) with their original implants in place, mHHS was 92 ± 12 (range, 46-100), and OHS was 57 ± 5 (range, 34-60). Multivariable analyses revealed that mHHS and OHS decreased significantly with age (β = -0.35, P < .001, and β = -0.15, P < .001, respectively).

CONCLUSIONS

With no dislocations and satisfactory clinical scores, this sizable cohort confirms that the novel hemispherical DM cup studied is effective at preventing dislocations, although longer-term follow-up remains necessary to ascertain the longevity of clinical outcomes and radiographic stability.

LEVEL OF EVIDENCE

Level IV, multicentric retrospective case series.

Simultaneous bilateral dual mobility total hip arthroplasty dislocation in a patient with hepatic encephalopathy: A case report

INTRODUCTION AND IMPORTANCE

Dislocation is a severe complication after total hip arthroplasty (THA). It is one of the most common reasons for failure and revision surgery. This is the first case of a documented simultaneous bilateral dual mobility (DM) THA dislocation.

CASE PRESENTATION

A forty-nine-year-old man presented with bilateral hip pain, immobility and deformity. X-ray images demonstrated simultaneous bilateral posterior THA dislocation. Previously, the patient had presented atraumatic dislocations recurrently. When he was thoroughly re-interrogated, he complained of uncontrolled and generalized muscle contractions, which were compatible with myoclonus due to hepatic encephalopathy (HE). Multidisciplinary treatment was performed satisfactorily to control myoclonus symptomatology and to prevent dislocation.

CLINICAL DISCUSSION

Patient's most important risk factor was a neuromuscular disorder, which we initially gave little notice and undervalued. HE is a serious but reversible syndrome, observed in patients with liver dysfunction. It leads to a wide spectrum of neuropsychiatric abnormalities. Management is based on prevention of episodes, avoiding the underlying triggers. Due to the high risk for dislocation of our patient, we decided to use DM cups bilaterally. This system has demonstrated lower rates of dislocation.

CONCLUSION

This case report reminds us that a careful evaluation through meticulous history and physical examination are mandatory when faced with recurrent instability. Furthermore, prevention of dislocation is vastly preferable to treating this challenging complication. High-risk patients should be identified, and appropriate surgical approach, technique and implants have to be collectively used to reach a strategy that mitigates and ideally prevents dislocation.

Study protocol: Effectiveness of dual-mobility cups compared with uni-polar cups for preventing dislocation after primary total hip arthroplasty in elderly patients - design of a randomized controlled trial nested in the Dutch Arthroplasty Registry

Background and purpose - Dislocation is the leading reason for early revision surgery after total hip arthroplasty (THA). The dual-mobility (DM) cup was developed to provide more stability and mechanically reduce the risk of dislocation. Despite the increased use of DM cups, high-quality evidence of their (cost-)effectiveness is lacking. The primary objective of this randomized controlled trial (RCT) is to investigate whether there is a difference in the number of hip dislocations following primary THA, using the posterolateral approach, with a DM cup compared with a unipolar (UP) cup in elderly patients 1 year after surgery. Secondary outcomes include the number of revision surgeries, patient-reported outcome measures (PROMs), and cost-effectiveness.Methods and analysis - This is a prospective multicenter nationwide, single-blinded RCT nested in the Dutch Arthroplasty Registry. Patients ≥ 70 years old, undergoing elective primary THA using the posterolateral approach, will be eligible. After written informed consent, 1,100 participants will be randomly allocated to the intervention or control group. The intervention group receives a THA with a DM cup and the control group a THA with a UP cup. PROMs are collected preoperatively, and 3 months, 1 and 2 years postoperatively. Primary outcome is the difference in number of dislocations between the UP and DM cup within 1 year, reported in the registry (revisions), or by the patients (closed or open reduction). Data will be analyzed using multilevel models as appropriate for each outcome (linear/logistic/survival). An economic evaluation will be performed from the healthcare and societal perspective, for dislocation and quality adjusted life years (QALYs).Trial registration - This RCT is registered at www.clinicaltrials.gov with identification number NCT04031820.

Dual mobility acetabular construct with freedom constrained liner for treatment of recurrent dislocations after total hip arthroplasty: A case report and literature review

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Dual-mobility bearings improve stability in total hip arthroplasty (THA) but may fail to prevent postoperative dislocation.

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Dry revision with a compatible constrained liner system can provide an effective salvage option for instability after THA.

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The unique G7 constrained liner system offers good short-term stability and range of motion.

Introduction

Recurrent dislocation after total hip arthroplasty (THA) using the dual mobility cup system can present challenges, while dual-mobility THA bearings can improve stability in both primary and revision total hip arthroplasties.

Presentation of case

A 72-year-old woman with a history of schizophrenia underwent a left primary THA using the G7 dual mobility system. Two postoperative posterior dislocations occurred within 2 months post-surgery. The patient underwent revision surgery in which the metal liner and dual mobility head were exchanged using the Freedom constrained liner system without revision of the cup and stem. As of this writing, 28 months after the revision surgery, no further dislocations have occurred. The implants are stable, and the patient has good range of motion.

Discussion

Dual-mobility bearings are utilized to improve stability in both primary and revision total hip arthroplasties, but even if the dual mobility system is chosen, it sometimes fails to prevent postoperative dislocation. Although a relatively high failure rate has been reported in THA using the constrained liner system, this patient’s clinical course suggests that the G7 Freedom constrained liner system can be an efficacious option for some patients with unstable hip joints who undergo THA using the dual mobility system.

Conclusion

A modern constrained liner system such as the G7 Freedom liner may provide an improved salvage solution for joint instability in dual mobility THA.

Dual mobility cups for total hip arthroplasty: tips and tricks

Since its creation in 1974, the Dual Mobility Cup (DMC) has been gaining in popularity, especially in the past decade. This intensive use could lead to inappropriate use and consequently to an increased complication rate. Compliance with conceptual requirements and surgical techniques will prevent the occurrence of complications that can be wrongly attributed to implants. In this context, we feel that it is essential to share our tips and tricks as well as an overview and an explanation of common errors, based on more than 45 years of clinical and research experience. From basic principles, including indications, implant choice and implant compatibility, to surgical tips, in this article orthopedic surgeons will find a practical overview of DMC in order to use it safely and with confidence.