Reducing the distal profile of dual mobility liners can mitigate soft-tissue impingement and liner entrapment without affecting mechanical performance

Modular versus monobloc dual mobility components for primary cementless total hip arthroplasty: a systematic review and meta-analysis of implants' survival, complication rates, clinical and radiographic outcomes

PURPOSE

The dual mobility cup (DMC) reduces the dislocation rates in total hip arthroplasty (THA). DMC systems include anatomical (non-modular or monoblock) (ADM) and modular dual mobility (MDM) components (Stryker Orthopaedics, Mahwah, NJ, USA). This review aims to assess differences between these two types of DMC implants concerning dislocation and revision rates, as well as patient-reported outcomes.

METHODS

This systematic review and meta-analysis of studies reports data from patients undergoing primary THA using MDM and/or ADM implants. Following the PRISMA guidelines, we analyzed articles from Science Direct/Scopus, PubMed, and the Cochrane Database of Systematic Reviews. We compared dislocation rates, revisions for any reason, aseptic loosening, infections, fractures, and functional outcomes between ADM and MDM components.

RESULTS

Eleven studies were considered eligible for further analysis. A total of 3369 patients (mean age = 65.4 years) underwent primary THA, including 3386 DMC implants. The mean follow-up for the MDM and ADM groups was 2.9 years and 3.9 years, respectively. The study revealed one dislocation in the MDM and none in the ADM. By proportion metanalysis, the review did not show statistical differences in all-cause revisions (p = 0.93, [CI [0.01;0.02]) or periprosthetic fractures (p = 0.18, CI [0.01;0.02]).

CONCLUSIONS

MDM and ADM systems, both, represent safe DM options regarding dislocation, all-causes revisions and functional outcomes.

Less groin pain with dual-mobility bearings versus fixed bearings in total hip arthroplasty

INTRODUCTION

The relationship between implant type, dual mobility (DM) or fixed bearing (FB), and postoperative groin pain remains unexplored. We examined the incidence of groin pain in DM implants and compare this to a cohort of FB THA patients.

METHODS

From 2006 to 2018, a single surgeon performed 875 DM THA and 856 FB THA procedures with 2.8-year and 3.1-year follow-up, respectively. Each patient received a questionnaire postoperatively and was asked if they had any groin pain (yes/no). Secondary measurements were implant characteristics such as head size, head offset, cup size, and cup-to-head ratio. Additional PROMs that were collected included: Veterans RAND 12 (VR-12), University of California Los Angeles (UCLA) activity score, Pain visual analogue scale (Pain VAS), and range of motion (ROM).

RESULTS

The incidence of groin pain was 2.3% in the DM THA cohort and 6.3% in the FB THA group (p < 0.001). Also, low head offset (⩽0 mm) had a significant odds ratio (1.61) for groin pain in both cohorts. There was no significant difference in terms of revision rate between the cohorts (2.5% vs. 3.3%, p = 0.39) at the latest follow up.

CONCLUSIONS

This study demonstrated a lower incidence of groin pain (2.3%) in patients with a DM bearing compared to a FB (6.3%) and a greater risk of groin pain with low head offset (<0 mm). As such, surgeons should try to recreate offset of the hip compared to the contralateral side to avoid groin pain.

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.

Three-dimensional kinematic analysis of dislocation mechanism in dual mobility total hip arthroplasty constructs

Dual mobility (DM) total hip arthroplasty (THA) is associated with reduced dislocation rates; however, the kinematic mechanism of dislocation in DM THA constructs is still not well understood. This study hypothesizes that the difference in kinematics between DM THA and conventional THA designs contributes to reduced dislocation rates of DM THA. In addition, this study aims to quantify and compare those kinematic parameters between DM THA and conventional THA using a validated dual fluoroscopy imaging system (DFIS) and finite element (FE) modelling. Fresh frozen cadavers were measured to compare the impingement-free range of motion and provocative subluxation kinematics among three THA constructs: (1) DM, (2) constrained liner (CS), and (3) 36 mm head diameter neutral liner (NL). The DFIS was used to measure the in vitro kinematics of the hip. Subject-specific FE models were developed to assess the horizontal dislocation distance and resistive torque at dislocation. The DM construct head exhibited increased provocative anterior and posterior subluxation range of motion before dislocation when compared to CS constructs (p = .05; p = .03), as well as NL constructs (p = .05). The DM THA showed a significantly larger posterior horizontal dislocation distance, as well as smaller resistive torque at dislocation, when compared to NL (p = .05; p = .03) and CS constructs (p = .04; p = .01). Our findings demonstrate there was increased provocative subluxation range of motion as well as normalized jump distance for the DM constructs compared to the NL and CS constructs, suggesting the DM THA may provide increased stability hip during at-risk functional hip positions.

Ilio-psoas impingement with a dual-mobility liner: an original case report and review of literature

Ilio-psoas impingement after total hip arthroplasty often occurs with the metallic rim of the acetabular cup. The main causes are poor cup anteversion or anterior wall defect. We firstly report here the case of a patient complaining of iliopsoas impingement due to contact with the liner of a dual-mobility device. Ultrasonography and Computed Tomographic scan clearly showed the direct mechanical contact of the dual-mobility liner with the iliopsoas tendon.

Anatomic dual mobility compared to modular dual mobility in primary total hip arthroplasty: a matched cohort study

Background

Dual mobility (DM) has been used in primary total hip arthroplasty recently for their low dislocation rates, low revision rates, and improved patient functional outcomes. We compared 2 DM systems, anatomic dual mobility (ADM; Stryker, Mahwah, NJ) and modular dual mobility (MDM; Stryker, Mahwah, NJ), to determine differences in dislocation rates, revision rates, and patient outcome scores.

Methods

The study was a single-center matched retrospective review of prospectively collected data of patients who underwent primary total hip arthroplasty surgery with an ADM or MDM system by a single surgeon from 2012 to 2017. Demographics, operative details, postoperative patient-reported outcomes, and clinical outcomes were recorded. A Kaplan-Meier survivorship curve to compare survival time between groups was collected as well.

Results

Five hundred seventy-four patients were included in the study with 287 patients matched in each group with mean 2.86 years of follow-up. The dislocation rate in each cohort was 0%, the acetabular-specific revision rate was 0%, and in each cohort, overall revision rate in each cohort was 1.7%. In general, patient-reported outcomes were similar for each group (Harris Hip Score Pain (P = .919), Harris Hip Score Function (P = .736), Western Ontario and McMaster Universities Osteoarthritis Index (P = .139), Pain Visual Analog Scale (P = .146), Veterans RAND 12-Item Health Survey (P = .99), University of California, Los Angeles (P = .417), and Harris Hip Score Total (P = .136). There was a slight clinically insignificant increase in hip flexion between the cohorts favoring the ADM group (98.6 ± 9.8 vs 94.0 ± 9.7, P < .001).

Conclusions

Both DM systems had similar patient-reported outcomes that were quite favorable. At 2.86 years of follow-up, neither the ADM nor MDM systems demonstrated dislocation, and both had low acetabular-specific and overall revision rates in this matched cohort study.

Cadaver-Specific Models for Finite-Element Analysis of Iliopsoas Impingement in Dual-Mobility Hip Implants

BACKGROUND

Joint dislocation is a major cause of failure in total hip arthroplasty. Dual-mobility implants provide a femoral head diameter that can match the native hip size for greater stability against dislocation. However, such large heads are prone to impingement against surrounding soft tissues. To address this concern, the concept of an anatomically contoured dual-mobility implant was evaluated using cadaver-specific finite-element analysis (FEA).

METHODS

The stiffness of 10 iliopsoas tendons was measured and also 3D bone models, contact pressure, and iliopsoas tendon stress were evaluated for 2 implant designs according to a previous cadaveric experiment. The iliopsoas interaction with an anatomically contoured and conventional dual-mobility implant was analyzed throughout hip flexion.

RESULTS

The tensile test of cadaveric iliopsoas tendons revealed an average linear stiffness of 339.4 N/mm, which was used as an input for the FEA. Tendon-liner contact pressure and tendon von Mises stress decreased with increasing hip flexion for both implants. Average contact pressure and von Mises stresses were lower in the anatomically contoured design compared with the conventional implant across all specimens and hip flexion angles.

CONCLUSIONS

This study was built upon a previous cadaver study showing reduced tenting of the iliopsoas tendon for an anatomically contoured design compared with a conventional dual-mobility implant. The present cadaver-specific FEA study found reduced tendon-liner contact pressure and tendon stresses with contoured dual-mobility liners. Anatomical contoured design may be a solution to avoid anterior soft-tissue impingement when using hip prostheses with large femoral heads.

Does the Dual-Mobility Hip Prosthesis Produce Better Joint Kinematics During Extreme Hip Flexion Task?

BACKGROUND

Total hip arthroplasty (THA) using dual-mobility (DM) design permits larger hip range of motion. However, it is unclear how it benefits the patients during activities of daily living. The purpose was to compare kinematic variables of the operated limb between THA patients using either DM or single-bearing (SB) implants during a squat task.

METHODS

Twenty-four THA patients were randomly assigned to either a DM or SB implant and matched to 12 healthy controls (CTRLs). They underwent 3-dimensional squat motion analysis before and 9 months after surgery. Sagittal and frontal plane angles of the pelvis and the hip were analyzed using statistical parametric mapping. Paired analyses compared presurgery and postsurgery squat depth.

RESULTS

Peak sagittal pelvis angle of DM was closer to normal compared with that of SB. Both implant groups had similar hip angle patterns and magnitude but significantly lower than the CTRLs. SB reached a much large hip abduction compared with the other groups. Both surgical groups had significantly worst squat depth than the CTRLs.

CONCLUSION

Neither THA implant groups were able to return pelvis and hip kinematics to the level of CTRLs. The deficit of DM implants at the pelvis combined with the poorer functional scores should caution clinicians to use this implant design in active patients. SB design causes a larger hip abduction to reach their maximum squat depth. Post-THA rehabilitation should focus on improving joint range of motion and strength.

All dual mobility cups are not the same

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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