Dual mobility in primary total hip arthroplasty: current concepts

Dislocation of primary total hip arthroplasty: Analysis of risk factors and preventive options

Total hip arthroplasty (THA) is one of the most successful elective operations in orthopedic surgery for improving pain and functional disability in patients with end-stage joint disease. However, dislocation continues to be a troublesome complication after THA, as it is a leading cause of revision and is associated with substantial social, health, and economic costs. It is a relatively rare, usually early occurrence that depends on both the patients' characteristics and the surgical aspects. The most recent and important finding is the special attention to be given preoperatively to spinopelvic mobility, which is closely related to the incidence of dislocation. Consequently, clinical and radiographic assessment of the lumbar spine is mandatory to identify an altered pelvic tilt that could suggest a different positioning of the cup. Lumbar spinal fusion is currently considered a risk factor for dislocation and revision regardless of whether it is performed prior to or after THA. Surgical options for its treatment and prevention include the use of prostheses with large diameter of femoral head size, dual mobility constructs, constrained liners, and modular neck stems.

The use of dual mobility cups in revision total hip arthroplasty for failed large head metal-on-metal bearings

PURPOSE

Revision of failed large head metal-on-metal (MoM) total hip arthroplasty (THA) is a challenging procedure particularly to reconstruct acetabular bone defect due to osteolysis and to achieve hip stability due to soft tissue damages, both potentially caused by adverse reaction to metal debris (ARMD). This study aimed to evaluate the outcome of dual mobility cup (DMC) constructs in revision THA for failed large head MoM bearings with a special attention to the occurrence of dislocation or re-revision.

METHODS

Between 2015 and 2019, 57 patients (64 THAs, 41 men, mean age = 65 ± 10 years) underwent revision for MoM THA with the use of DMC were prospectively included in our total joint registry. Mean time to revision was 11 ± 2.5 years. The causes for revision were adverse reaction to metal debris (ARMD) in 49 THAs (76%), painful hip with elevated blood cobalt-chromium ions in seven (11%), and acetabular aseptic loosening in eight (13%). The revision was complete in 22 THAs (34%) and acetabular only in 42 (66%). Clinical and radiographic outcomes, complications, and re-revisions were evaluated at most recent follow-up.

RESULTS

At mean follow-up of six ± 1.5 years, the pre- to postoperative Harris Hip Score improved from 74 ± 19 to 92 ± 4 (p = 0.004). Complications occurred in 11 cases (17%): five dislocations (8%), three periprosthetic infections (5%), two aseptic loosening of the acetabular component (3%), and two periprosthetic fractures (3%). Re-revision was required in six cases (9%).

CONCLUSION

The use of DMC is a reliable option to prevent instability and ensure a stable acetabular reconstruction in revision THA for failed large head MoM bearings. However, dislocation after revision remains a concern, particularly in cases of severe soft tissue damage related to ARMD.

Femoral Neck Design Does Not Impact Revision Risk After Primary Total Hip Arthroplasty Using a Dual Mobility Cup

Background

The use of dual mobility (DM) cups has increased quickly. It is hypothesized that femoral neck taper geometry may be involved in the risk of prosthetic impingement and DM cup revision. We aim to (1) explore the reasons for revision of DM cups or head/liners and (2) explore whether certain femoral neck characteristics are associated with a higher risk of revision of DM cups.

Methods

Primary total hip arthroplasties with a DM cup registered in the Dutch Arthroplasty Register between 2007 and 2021 were identified (n = 7603). Competing risk survival analyses were performed, with acetabular component and head/liner revision as the primary endpoint. Reasons for revision were categorized in cup-/liner-related revisions (dislocation, liner wear, acetabular loosening). Femoral neck characteristics were studied to assess whether there is an association between femoral neck design and the risk of DM cup/liner revision. Multivariable Cox proportional hazard analyses were performed.

Results

The 5- and 10-year crude cumulative incidence of DM cup or head/liner revision for dislocation, wear, and acetabular loosening was 0.5% (CI 0.4-0.8) and 1.9% (CI 1.3-2.8), respectively. After adjusting for confounders, we found no association between the examined femoral neck characteristics (alloy used, neck geometry, CCD angle, and surface roughness) and the risk for revision for dislocation, wear, and acetabular loosening.

Conclusions

The risk of DM cup or head/liner revision for dislocation, wear, and acetabular loosening was low. We found no evidence that there is an association between femoral neck design and the risk of cup or head/liner revision.

Dual Mobility Articulation in Total Hip Arthroplasty: Mixed Femoral and Acetabular Components are a Feasible Option

BACKGROUND

The utilization of a different manufacturer for the prosthetic femoral head and the polyethylene insert in dual mobility (DM) for total hip arthroplasty (THA) may be necessary, especially in the revision setting. However, there is no data in the literature about this application. This study evaluated the outcomes of mixed manufacturer components, with the hypothesis that there would be no difference in measured outcomes compared to matched components.

METHODS

The DM articulations implanted during THA revision were retrospectively reviewed from 2011 to 2017. The study group was then stratified into 2 cohorts: matching components or mixed components. Of 130 hips included in the study with DM articulations with average follow-up of 7 years, 103 had mixed and 27 had matching manufacturer components. Rates of all cause reoperation and revision, intraprosthetic dislocation, dislocation, and aseptic loosening were compared using Chi-squared and Fisher's exact test; survival analysis was also performed.

RESULTS

Matched and mixed manufacturer implants had no significant difference between all cause reoperation (33 versus 25.2%), dislocation (14.8 versus 7.7%), and aseptic loosening (3.7 versus 3.9%), respectively. Higher rates of intraprosthetic dislocation (11 versus 0.97%) were observed in the matching component cohort. Survival analysis showed similar outcomes at 2, 5, and 10 years.

CONCLUSIONS

Mixed-component DM articulations show similar results compared to matching components. The off-label use of mixed manufacture DM articulation in THA is a feasible and safe option in the correct patient. Furthermore, when encountering a well-fixed femoral stem or acetabular shell, the use of a mixed component DM articulations may reduce the morbidity for the patient and prevent revision of all components.

What is the rate of successful closed reduction of dislocated dual mobility cups following complex revision hip arthroplasty?

PURPOSE

The aim of this study was to assess the difference in success rates of closed reduction in septic and aseptic revision total hip arthroplasty (THA) performed with a dual mobility (DM) implant. Our objective was to answer the following questions: (1) Is there a difference in success rates of closed reduction between septic and aseptic revision THA with a DM implant? (2) Is closed or open reduction more successful in preventing re-dislocation?

METHODS

Between January 2009 and October 2021, 924 revisions were performed with a DM implant. All patients presenting to our institution with a dislocation following septic or aseptic revision THA using a cemented DM cup were included in this study. We analyzed 106 cases of dislocation in 74 patients. For all patients, we collected reason for revision, and classified index surgery as septic or aseptic.

RESULTS

Overall, 106 dislocations occurred (106/924, 11.5%). Thirty-nine cases (52.7%) had a dislocation after a septic exchange THA, while in 35 patients (47.3%), a dislocation occurred after an aseptic rTHA. In 29 patients (39.2%), successful closed reduction under general anesthesia was feasible, while the majority of cases required open reduction. In 31 of these patients (67.4%), open reduction was combined with a revision arthroplasty.

CONCLUSIONS

In case of DM cup dislocation, there is a low success rate of closed reduction. To prevent re-dislocation, total revision leads to a significantly reduced risk compared to open or closed reduction alone. Careful X-ray analysis for a halo sign showing intra-prosthetic DM cup dislocation is mandatory to avoid futile reduction attempts.

LEVEL OF EVIDENCE

III.

Dual Mobility Total Hip Replacements in Young Patients- A Systematic Review

Background

There is little consensus on outcomes of dual Mobility total hip replacement (DM-THR) in younger patients. We performed a systematic review to examine this.

Methods

A systematic review of all observational studies and randomised controlled trials of patients under 70 with primary DM-THR in MEDLINE, EMBASE, Pubmed, Cochrane was performed according to PRISMA guidelines. Collected data included demographics, revision, dislocation and infection rates and functional scores.

Results

Twelve papers studying 738 DM-THR in 664 patients were included. The mean patient age was 46.9 years (13.5-69.0), with 319 (48.0%) being female and 419 (52.0%) being male. After an average follow-up of 90.0 months (1-371 months), the revision rate was 12.7% (84 hips), 0 dislocations were reported but 2.5% (15 hips) underwent intra-prosthetic dislocation. 32.1% hip revisions were due to aseptic loosening.

Conclusion

Limited literature surrounding the use of DM-THR suggests favourable stability but higher revision rates than conventional THR.

Dual-Mobility Cups in Primary Total Hip Arthroplasty

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

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Late intraprosthetic dislocation of a monoblock dual-mobility cup cemented into a well-fixed cementless acetabular shell. A case report

Intraprosthetic dislocation (IPD) is a specific implant-related complication of dual mobility (DM) implants, which is defined as a dissociation of polyethylene (PE) liner from the femoral head. We report a unique case of  late IPD of a monoblock DM cup cemented into a well-fixed cementless acetabular shell for recurrent dislocation of total hip arthroplasty (THA). A 77-year-old woman was admitted to our department for acute right hip pain, functional impairment and inability to bear weight without any trauma. Three years earlier, she underwent revision THA for recurrent dislocation with a monoblock DM cup cemented into a well-fixed cementless acetabular shell according to the "double-socket" technique. Three months after that revision the patient experienced an anterior THA dislocation, which was managed by closed reduction under sedation in the emergency room. No additional episodes of prosthesis instability occurred. Upon admission, radiographic evaluation showed  right THA dislocation. X-rays performed  after closed reduction revealed eccentric positioning of the head inside the cup, and a direct contact between the metal head and the cup was revealed by subsequent CT scan, confirming the suspicion of IPD. The patient underwent revision surgery, during which the PE liner was found lodged within the cup in a subluxated position, disassembled from the inner head. Both the acetabular cup and modular femoral stem proved well-fixed and impossible to remove, therefore they were retained. The explanted DM components were replaced with new ones of the same size and, thanks to the femoral neck's modular nature, it was substituted with a longer one, which resulted in improved stability against intraoperative stress maneuvers. The postoperative course was uncomplicated. At 1-year follow-up, the patient had a good functional recovery.

Acetabular morphological variation in Asian patients with femoral neck fracture: A three-dimensional CT-based study

AIMS

The acetabular morphology varies greatly among individuals, and hypoplasia is more common in Asia than in Europe. Dislocation after bipolar hip arthroplasty (BHA) for femoral neck fracture occurs at a constant rate, and is affected by the acetabular morphology. This study aimed to clarify individual differences in the acetabula of Asian patients with displaced femoral neck fractures.

PATIENTS AND METHODS

Fifty patients with displaced femoral neck fractures were assessed (50 fractured hips, 50 non-fractured hips). On CT corrected by the anterior pelvic plane, the 100 hips were assessed regarding acetabular coverage (six parameters), acetabular depth (two parameters), and acetabular opening angle (four parameters). Additional parameters related to the fracture and sex were examined. The percentile of each parameter was shown for all hips.

RESULTS

There was no patient with hip dysplasia defined as superior acetabular sector angle (SASA) less than 110° Compared with men, women had a significantly smaller anterior acetabular sector angle (AASA) (p = 0.016), and significantly larger acetabular inclination angle (p = 0.006) and acetabular index angle (p = 0.034). In the group with a normal SASA, seven hips (7.3%) had an anterior wall defect (AASA<50°) and five hips (5.2%) had a posterior wall defect (posterior acetabular sector angle<90°).

CONCLUSION

Older adults with femoral neck fractures can have anterior wall and posterior wall defects, even if their SASA is normal. Hidden acetabular dysplasia may be related to post-BHA dislocation. So, our results suggest that is important to accurately evaluate the acetabulum of patients with femoral neck fracture before surgery.

Similar Outcomes Achieved Between Anterior and Posterior Approach Total Hip Arthroplasty Using Dual Mobility Implants

BACKGROUND

Dual mobility (DM) bearings for total hip arthroplasty (THA) have been proposed to reduce the risk of instability in high-risk patients; however, their utility in primary THA remains relatively unexplored. No previous reports have described whether surgical approach influences outcomes associated with DM implant systems. This study aims to compare patient reported outcomes and post-operative groin pain between patients undergoing anterior approach versus posterior approach following primary THA with DM implants.

METHODS

We retrospectively reviewed all patients who underwent primary THA and received a DM implant between 2011-2021. Patients were stratified into two cohorts based on surgical approach (anterior vs. posterior approach). Primary outcomes included the presence of substantial postoperative groin pain as well as readmission and revision rates. Demographic differences were assessed using chi-square and independent sample t-tests. Outcomes were compared using multilinear and logistic regressions.

RESULTS

Of the 495 patients identified, 55 (11%) underwent THA via the anterior approach and 440 (89%) via the posterior approach. Surgical time (100.24 vs. 109.42 minutes, p=0.070), length of stay (2.19vs.2.67 days,p=0.072), discharge disposition (p=0.151), and significant postoperative groin pain (1.8%vs.0.7%,p=0.966) did not statistically differ between the cohorts. 90-day readmission (9.1%vs.7.7%,p=0.823) and revision rate (0.0%vs.3.0%,p=0.993) did not significantly differ as well. Specifically, readmission (p=0.993) and revision (p=0.998) for instability did not significantly differ between the cohorts. We found no statistical difference in HOOS, JR (p=0.425), VR-12 PCS (p=0.718), and VR-12 MCS (p=0.257) delta score improvement from preoperative to 1-year follow-up between the two groups.

CONCLUSION

Comparable outcomes following implantation of DM constructs may be achievable irrespective of the surgical approach employed. The incidence of iliopsoas injections for groin pain did not significantly differ between anterior and posterior approaches. Future investigation is needed to determine whether surgical approach influences long-term outcomes in patients receiving DM implants. Level of Evidence: III.

Fraturas intracapsulares do colo femoral no idoso

Currently, intracapsular femoral neck fracture (IFNF) is still a great challenge for orthopedists. In spite of the progress that has been made, a high mortality rate persists in the first year, especially in Brazil, where there is no awareness that such fractures in elderly patients should be treated as a medical emergency. The present article seeks to provide an update on the preoperative, surgical, and postoperative approaches.

Dual Mobility Cups as the Routine Choice in Total Hip Arthroplasty

Background and Objectives: Total hip arthroplasty (THA) is considered the most successful surgical procedure in orthopedics. However, dislocation remains the main indication for surgical revision. New designs of dual mobility cups (DMC) have lowered the classical complications and have extended the indications of DMC in elective surgeries. Our aim is to assess the trend of DMC indications in THA as well as the incidence of their dislocation. Materials and Methods: We retrospectively reviewed all patients undergoing THA with DMC during the years 2015 and 2021. The original indication for DMC included patients sustaining neck of femur fractures (NOF#) and associated risk factors for dislocations. Five years later, DMC was considered our standard of care in total hip arthroplasty. The approach (anterolateral or posterolateral) was chosen by the surgeon according to his/her preferences, as was the implant. Data collected included patients’ demographics, diagnosis, admission time, surgical approach, cup models, and inclination and complications. Patients sustaining a hip dislocation were prospectively reviewed and assessed for treatment received, new dislocations, and need for surgical revision. Two groups were created for the analysis according to the presence or absence of dislocation during follow-up. Results: In the analysis, 531 arthroplasties were included (mean age 72.2 years) with a mean follow-up of 2.86 years. The trend of indications for DMC increased from 16% of THA in 2015 to 78% of THA in 2021. We found a total of 8 dislocations (1.5%), none of them associated with elective surgery. Closed reduction was unsatisfactory in four cases (50%). There was one case of intraprosthetic dislocation. Dislocations were associated to smaller heads (22 mm) (1.5% vs. 25%, p = 0.008) and cups (51.2 mm vs. 48.7 mm, p = 0.038) and posterior approach (62.5% vs. 37.5%, p = 0.011). Conclusion: Dual mobility cups are a great option to reduce the risk of dislocation after a THA both in the neck of femur fractures and elective cases. The use of an anterolateral approach in THA after a neck or femur fracture might considerably decrease the risk of dislocation.

Trends of Femoral Neck Fracture Treatment Using Total Hip Arthroplasty: Reported From the American Joint Replacement Registry

INTRODUCTION

Total hip arthroplasty (THA) rather than hemiarthroplasty for displaced femoral neck fracture (FNF) is often chosen for younger patients who are more active and/or have underlying hip osteoarthritis. However, instability remains the primary concern of doing THA. Dual mobility (DM) has been shown to decrease this risk through a larger effective head size and greater head-to-neck ratio compared with conventional THA. The purpose of this study was to identify femoral head size and DM usage patterns for the treatment of FNF with THA in the United States using the American Joint Replacement Registry.

METHODS

A retrospective cohort study was conducted, including all primary THAs done for FNF from 2012 to 2019. THA and FNF were defined using Current Procedural Terminology or International Classification of Diseases-9 or -10 diagnosis and procedure codes. Analysis was based on patient demographics, femoral head size, and DM usage. Descriptive statistics were used using a Pearson chi-square test. All analyses were conducted using SAS version 9.4, and statistical significance was set at P < 0.05.

RESULTS

There were 18,752 THAs done by 3,242 surgeons at 789 institutions during the 8-year study period. The overall population was 66% female, and the mean age was 72.3 ± 11.8 years. The most commonly used femoral head size was 36 mm (48.5%) followed by 32 mm (24.5%), ≤28 mm (10.7%), DM (10.8%), and ≥40 mm (5.7%). A trend was observed toward decreased use of ≤28, 32, and ≥40-mm heads starting in 2016 across the years and increased use of 36-mm heads (P < 0.0001). A significant increase was observed in the usage of DM over time from 6.4% in 2012 to 16.2% in 2019 (P < 0.0001).

DISCUSSION

Most of the femoral heads used were ≥36 mm, and the use of DM increased during the study period. Additional analysis is warranted to understand how these trends will affect overall outcomes and postoperative dislocation rates.

Dual Mobility hip replacement in hip fractures offer functional equivalence and a stability advantage - A case-controlled study

BACKGROUND

Hip fracture is a common and serious injury in the elderly. Hip arthroplasty is the most frequently performed procedure for patients with an  intracapsular hip fracture. The majority of national guidelines recommend total hip arthroplasty (THA) for more active patients. Literature indicates significant stability advantages for dual mobility (DM) acetabular components in non-emergent scenarios. Evidence supporting the use of DM in hip fracture patients is limited.

AIM

We set out to ascertain if DM implants offer stability and/or functional advantages over standard THA in patients with hip fracture.

METHODS

We utilised our local National Hip Fracture Database to identify all patients undergoing either a standard or DM THA for hip fracture (n=477) We matched cohorts based on age, AMTS, mobility status pre-operatively, gender, ASA and source of admission. Our primary outcome of interest was functional status using the oxford hip score (OHS). Secondary outcome measures included  dislocation, fracture and deep infection requiring further surgery.

RESULTS

62 patient pairs were available for this study. Mean OHS for DM THA was 41.5 and for standard THA this was 42.7 (p=0.58). There were 4 dislocations in the standard THA group and 0 with DM THA. No difference was seen with infection or peri-prosthetic fracture.

CONCLUSION

This study demonstrates functional equivalence between DM and standard THA. In addition it shows a trend towards less dislocation with DM THA. Cost savings from less instability may outweigh initial prosthesis costs. This study suggests a suitably powered RCT using instability as the primary outcome measure is indicated.

Femoral Neck Notching in Dual Mobility Implants: Is This a Reason for Concern?

BACKGROUND

Dual mobility (DM) total hip arthroplasty (THA) implants have been advocated for patients at risk for impingement due to abnormal spinopelvic mobility. Impingement against cobalt-chromium acetabular bearings, however, can result in notching of titanium femoral stems. This study investigated the incidence of femoral stem notching associated with DM implants and sought to identify risk factors.

METHODS

A multicenter retrospective study reviewed 256 modular and 32 monoblock DM components with minimum 1-year clinical and radiographic follow-up, including 112 revisions, 4 conversion THAs, and 172 primary THAs. Radiographs were inspected for evidence of femoral notching and to calculate acetabular inclination and anteversion. Revisions and dislocations were recorded.

RESULTS

Ten cases of femoral notching were discovered (3.5%), all associated with modular cylindrospheric cobalt-chromium DM implants (P = .049). Notches were first observed radiographically at mean 1.3 years after surgery (range 0.5-2.7 years). Notch location was anterior (20%), superior (60%), or posterior (20%) on the prosthetic femoral neck. Notch depth ranged from 1.7% to 20% of the prosthetic neck diameter. Eight cases with notching had lumbar pathology that can affect spinopelvic mobility. None of these notches resulted in stem fracture, at mean 2.7-year follow-up (range 1-7.6 years). There were no dislocations or revisions in patients with notching.

CONCLUSION

Femoral notching was identified in 3.5% of DM cases, slightly surpassing the dislocation rate in a cohort selected for risk of impingement and instability. Although these cases of notching have not resulted in catastrophic failures thus far, further study of clinical sequelae is warranted. Component position, spinopelvic mobility, and implant design may influence risk.

Fretting Corrosion, Third-Body Polyethylene Damage, and Cup Positioning in Primary vs Revision Dual Mobility Total Hip Arthroplasty

BACKGROUND

Dual mobility (DM) articulations were introduced for total hip arthroplasty to reduce the risk of instability for patients who have a high risk of dislocation. The use of DM constructs in both primary and revision total hip arthroplasty has been steadily increasing, leading to concerns regarding potential risks of fretting corrosion, polyethylene wear, metal release, and failure due to component positioning.

METHODS

A total of 56 retrieved DM constructs were collected. The inner and outer polyethylene liner surfaces were assessed for 7 damage mechanisms, and fretting corrosion was evaluated for the femoral stem, head, and modular liner. Three polyethylene liners with the greatest amounts of embedded debris were examined using scanning electron microscopy. Energy-dispersive X-ray spectroscopy was used to determine the elemental content of the debris. Acetabular cup orientation was analyzed radiographically using the EBRA (Einzel-Bild-Roentgen-Analyse) method.

RESULTS

The devices were revised most frequently for infection (36%), loosening (21%), and instability/dislocation (18%). The most common polyethylene damage mechanisms were scratching, pitting, burnishing, and embedded debris, and no difference in total damage was found between primary and revision cases. Scanning electron microscopy/energy-dispersive X-ray spectroscopy revealed that debris morphology and composition were consistent with porous titanium coating, resulting from cup loosening or broken screws and augments. A total of 71% and 50% of the constructs were determined to be within the Lewinnek safe zone for inclination and anteversion, respectively.

CONCLUSION

The most notable mechanisms of surface damage were due to third-body debris, especially for the polyethylene surfaces which articulate against cobalt-chromium femoral heads and acetabular liners. Scratching of the femoral head and the metal liner from this debris may support the clinical use of ceramic for DM bearing surfaces in the future.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

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

BACKGROUND

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

TRIAL REGISTRATION

HKUCTR-2913 .

Preliminary Results of Total Hip Arthroplasty in Subjects at Risk for Dislocation Using a Novel Modular Cementless Dual-Mobility Cup. A Single-Center Prospective Study

Nowadays total hip arthroplasty (THA) is widely considered the operation of the century in orthopedic and traumatological fields. Despite this fact, instability and dislocation after THA are a common reason for revision surgery. The purpose of this prospective study is to evaluate the preliminary clinical and radiological results of a novel dual mobility cup. We evaluated 32 consecutive cases of patients who underwent THA using a novel dual mobility cup—with holes in the cup, a modular metallic inlay and a crosslinked polyethylene. All of them were considered at risk of instability of the implant due to primary or concomitant diagnosis. The preoperative Harris hip score was 54.7 on average. At a minimum 2 years follow-up, the mean HHS raised up to a mean value of 88.4; this improvement was statistically significant (p < 0.0001). None of the patients enrolled in this study sustained a postoperative dislocation at a mean follow-up of 39.6 months. Furthermore, no patients sustained modular liner dissociation or an intraprosthetic dislocation. As such, survivorship free from dislocation was 100% at both 2 and 5 years. This study demonstrates that the modular dual mobility (DM) socket provides dual articulation, larger jump distance, and greater range of motion before impingement, which significantly reduce the rate of dislocation.

Two-year results of the Moovis trapeziometacarpal joint arthroplasty with focus on early complications

In this prospective study, we aimed to analyse the early results of 200 consecutive total trapeziometacarpal joint arthroplasties using the Moovis cup, a new generation, dual-mobility, uncemented conical cup, with special focus on early complications. At the 24-month follow-up, we found clinically relevant improvement of function and comfort. Among intraoperative complications were nine intraoperative trapezial fractures, which were treated by screw osteosynthesis; prolonged immobilization; and conversion to cemented cup fixation or primary or secondary trapeziectomy. One was left untreated as the loose cup did not cause notable symptoms. There were three implants with polyethylene wear and two with liner dislocation. We conclude that early outcomes of this new-generation implant are favourable, but its surgery is challenging and associated with important intraoperative and early postoperative complications related to the learning curve. Attentive reaming of the trapezium and careful cup impaction are crucial steps to avoid trapezial fracture and early cup failure. Level of evidence: II.

Healthcare resource utilization and costs for hip dislocation following primary total hip arthroplasty in the medicare population

AIM

To estimate 2-year healthcare resource utilization (HCRU) and costs of dislocation following primary total hip arthroplasty (THA).

MATERIALS AND METHODS

This retrospective evaluation used medical claims from the US Medicare database. Patients were eligible if they were ≥65 years old, underwent a primary elective inpatient THA between 1 January 2010 and 31 December 2016 (index), and had continuous Medicare coverage and enrollment ≥365 days prior to index (baseline). Exclusion criteria were prior THA, concomitant infection, non-Medicare primary payer, or enrolled in Medicare due to end-stage renal disease. One- and 2-year HCRU and costs across all service types and settings of care excluding retail pharmacy were evaluated. Propensity score matching and direct matching adjusted for confounding.

RESULTS

Among Medicare patients who underwent THA and met inclusion criteria (n = 450,355; mean age ∼74, and two-thirds female), 7,680 (1.7%) had a hip dislocation. After matching, 4,551 patients without and 4,551 patients with dislocation were selected. Percentage utilization, mean days of service, and claims payments amounts were significantly greater for patients with vs without THA dislocation for variables such as THA hospitalization, home health agency, skilled nursing facility, inpatient rehabilitation facility, other inpatient admission, long-term care hospital, and outpatient care. Findings were consistent for 1- and 2-year follow-up, although differences were more pronounced for 1-year. Per-patient-cost increases with dislocation were $19,590 over 1 year and $24,211 over 2 years. Two-thirds of the cost increase was due to other inpatient admission and the remaining one-third was due to skilled nursing facility, outpatient, inpatient rehabilitation facility, and home health agency costs.

LIMITATIONS

Administrative claims are not collected for research and lack clinical information. Results may not be generalizable to other patients or settings of care.

CONCLUSIONS

This large US retrospective database study demonstrated the substantial HCRU and cost burden of THA dislocation.

Study protocol: The DUALITY trial-a register-based, randomized controlled trial to investigate dual mobility cups in hip fracture patients

Background and purpose - Physically and mentally fit patients with a displaced femoral neck fracture (FNF) are mostly treated with total hip arthroplasty (THA). Dislocation is a severe and frequent complication in this group, and dual mobility cups (DMC) were developed to reduce the risk of dislocation after THA. The DUALITY trial investigates whether the use of DMC in FNF patients treated with a THA reduces the risk of dislocation.Patients and methods - The trial is a national, multicenter, register-based, randomized controlled trial (rRCT). Patients ≥ 65 years with a non-pathological, displaced FNF (Type Garden 3-4/AO 31-B2 or B3) who are suitable for a THA according to local guidelines are assessed for eligibility using the web-based registration platform of the Swedish Fracture Register (SFR). 1,600 patients will be randomized 1:1 to either insertion of a DMC (intervention group) or a standard cup (control group). The study is pragmatic in that the choice of implant brands, surgical approach, and peri- and postoperative protocols follow the local routines of each participating unit. All outcome variables will be retrieved after linkage of the study cohort obtained from the SFR with the Swedish Hip Arthroplasty Register and the National Patient Register.Outcomes - The primary outcome is the occurrence of any dislocation of the index joint treated with closed or open reduction within 1 year after surgery, expressed as a relative risk when comparing groups, and a risk reduction of at least 45% is considered clinically relevant. Secondary outcomes are the relative risk of any reoperation of the index joint, periprosthetic joint infection, and mortality within 90 days and 1 year. Patient-reported outcomes and health economics are evaluated.Start of trial and estimated duration - The DUALITY trial started recruiting patients in January 2020 and will continue for approximately 5 years.Trial registration - The trial is registered at clinicaltrials.gov (NCT03909815; December 12, 2019).