The use of a cemented dual mobility socket to treat recurrent dislocation

Dual-mobility arthroplasty failure: a rationale review of causes and technical considerations for revision

PURPOSE

Dual-mobility arthroplasty is an alternative to conventional total hip arthroplasty (THA) in appropriately selected, active adults with degenerative, necrotic or post-traumatic hip disease or with revision hip arthroplasty. Numerous papers have been published with results of dual-mobility arthroplasty, but there have been no comprehensive literature reviews that summarise the most recent findings and help the orthopaedic surgeon facing different scenarios in which revision of one or both components of a dual-mobility arthroplasty is indicated.

METHODS

We performed a PubMed search for papers published on dual-mobility arthroplasty that provided data on revision and add our experience in order to describe different revision scenarios. We collected data on revision for any reason, for aseptic loosening, for infection, or for dislocation. For each complication, we summarise causes and diagnosis of this complication and describe the direction of possible therapeutic options.

RESULTS

The dual-mobility arthroplasty offers the benefit of increased stability without compromising clinical outcomes and implant longevity. However, as with conventional arthroplasties, complications are also reported, with the most frequent being cup loosening, dislocation, accelerated wear and infection. Dual-mobility implants also have some specific complications secondary to their specific design, with the presence of a third joint. For example, intraprosthetic dislocation due to retentive failure of the polyethylene (PE) liner on the femoral head is a complication observed exclusively with this type of implant and involves articulation failure between the femoral head and the PE liner. Mechanical conflict with the iliopsoas tendon has also been reported, probably due to femoral head size, cup design, and/or a dysplastic hip. This systematic review of the literature identified several options for treating each complication, and in particular, options regarding conserving or not of one the two articulating devices.

CONCLUSIONS

These findings can inform discussions relating to risks and benefits of different therapeutic options when performing revision of a dual-mobility arthroplasty.

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

Background:

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

Objective:

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

Methods:

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

Results:

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

Conclusion:

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

Dual-mobility or Constrained Liners Are More Effective Than Preoperative Bariatric Surgery in Prevention of THA Dislocation

BACKGROUND

Obesity is associated with an increased risk of dislocation after total hip arthroplasty (THA). However, in patients with obesity, it is not known whether the risk is only in the early postoperative period or whether it persists several years after surgery, and whether having bariatric surgery before undergoing THA and/or receiving a specific device (such as a dual-mobility or constrained acetabular liner) is more effective in terms of decreasing the risk of dislocation.

QUESTION/PURPOSES

(1) What is the cumulative risk of dislocation in patients with obesity after THA in the absence of a dual-mobility or constrained liner, and is this related to component positioning? (2) Does bariatric surgery before undergoing THA decrease dislocation risk in patients with obesity? (3) Are dual-mobility and constrained liners efficient in preventing dislocation in patients with obesity?

METHODS

At our university-based practice, all surgeons adhered to the following treatment approaches: Before 2000 no dual-mobility implants or constrained liners were used for primary THAs. Between 2000 and 2008, all patients whose body mass index (BMI) was greater than 30 kg/m(2) received dual-mobility liners (or constrained liners), except when they had previously had bariatric surgery. After 2008, all patients with BMIs over 30 kg/m(2) as well as those patients who were previously treated with bariatric surgery (regardless of BMI at the time of the index THA) received dual-mobility or constrained liners. This case-control study compared the dislocation percentage between 215 hips in nonobese patients (BMI ≤ 30 kg/m(2)), 215 hips in patients with obesity (BMI > 30 kg/m(2)) who received standard cups, 85 hips in patients with bariatric surgery before THA using standard cups (with reduction to a BMI < 30 kg/m(2)), and 155 hips in patients with obesity who received dual-mobility (when younger than 70 years) or constrained liners (when older than 70 years). All patients received the same implants except for different femoral head diameters (32-mm head with standard cups and 28-mm head with dual-mobility or constrained liners). The patients were followed at routine intervals and were specifically queried about dislocation. All the 670 hips had a minimum followup of 5 years with a mean followup of 14 years (range 5-25 years). At the most recent followup, 101 (15%) hips were lost to followup (respectively, 36 of 215, 34 of 215, five of 85, 24 of 155), which is the same ratio as observed among the underlying populations from which the patients were drawn.

RESULTS

With standard liners, more hips in patients with BMI > 30 kg/m(2) dislocated than did hips in nonobese (BMI < 30 kg/m(2)) patients. The cumulative number of dislocations (first time without recurrent dislocation) was 6% (13 of 215) at 1-year followup in obese patients compared with 2% (four of 215) in nonobese patients (odds ratio [OR], 3.4; 95% confidence interval [CI] 1.09-10.58; p = 0.03) and was 13% (28 of 215) at 15 years followup compared with 4% (eight of 215) in nonobese patients (OR, 3.9; 95% CI 1.72-8.71; p = 0.001). When bariatric surgery was performed before THA, BMI declined from 42 kg/m(2) to 28 kg/m(2), but with the same standard liners, more hips after bariatric surgery dislocated at 1-year followup than did hips in patients with obesity without preoperative bariatric surgery (13% [11 of 85] compared with 6% [13 of 215]; OR, 0.43; 95% CI 0.18-1.01; p = 0.05). Dual-mobility or constrained implants decreased the risk of dislocation, and fewer hips in patients with obesity with dual-mobility or constrained liners at 7 years followup had dislocated than did hips with standard liners (2% [three of 155] compared with 9% [20 of 215]; OR, 0.19; 95% CI 0.05-0.66; p = 0.01) bringing this number in line with the number observed in nonobese subjects with standard cups.

CONCLUSIONS

With standard liners, the risk of dislocation is increased in patients with obesity. Preoperative decrease of BMI (with bariatric surgery) in patients with obesity did not prevent the risk of dislocation with standard liners. Use of dual-mobility or constrained liners in these patients is an effective technique to reduce the risk of postoperative hip dislocation. However, we do not yet know the full risks of loosening of dual-mobility and constrained liners in this obese population.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Midterm Survivorship of the Lefèvre Constrained Liner: A Consecutive Multisurgeon Series of 166 Cases

BACKGROUND

Constrained liners are used as part of a salvage procedure to provide stability for patients at high risk for dislocation after a total hip arthroplasty. However, no recent studies exist highlighting their effectiveness and/or limitations.

METHOD

This prospective review included 166 consecutive hip arthroplasties, either primary (27%) or revision (73%), with a unique design of a constrained liner: Lefèvre retentive cup. There were 113 females (69%), and the average age at index surgery was 75.9 years (range, 35-94). The mean follow-up was 6.2 years (range, 0.3-11).

RESULTS

Twenty patients had a reoperation; 10 for infection (4 acute and 6 chronic joint infection) and 10 for cup failure (5 fixation failure, 3 aseptic loosening, and 2 dislocation). Ten-year survivals for cup revision were 89% (CI, 83-94) and 92% (CI, 89-97) for all revision and revision for noninfectious reasons, respectively. When solely evaluating for dislocation, the survival at 10 years was 99% (CI, 97-100). Considering primary and revision cases, 10-year survivals cup revision for aseptic reasons were 92.4% (CI, 84-100) and 92.5% (CI, 87-98), respectively.

CONCLUSIONS

The Lefèvre retentive cup demonstrated excellent 10-year's survivorship. With the rate of aseptic loosening around 2% and a dislocation rate around 1%, the cup is as effective as other available devices and is therefore a cost-effective tool to reduce the risk of dislocation in at-risk patients undergoing hip arthroplasty.

High Failure Rate of Modular Exchange With a Specific Design of a Constrained Liner in High-Risk Patients Undergoing Revision Total Hip Arthroplasty

BACKGROUND

Addressing recurrent instability in patients with poor bone stock and inadequate abductor tensioning remains a challenge in revision total hip arthroplasty. One treatment method is implantation of a constrained liner. The purpose of this study was to determine clinical outcomes, redislocation rate, and revisions of a focally constrained liner in a high-risk patient cohort.

METHODS

Fifty-eight hips between 2008 and 2011 underwent implantation of a focally constrained liner. Nineteen were placed concurrent with acetabular component revision and 39 were placed into a well-fixed acetabular shell. Mean age was 69 years and mean number of previous ipsilateral hip surgeries was 4.2. At mean follow-up of 3.5 years, we analyzed clinical outcomes, redislocation, and revisions.

RESULTS

Mean Harris Hip Scores was 74. Fourteen hips (24%) were revised and 3 hips (5%) required reoperation at final follow-up. Eleven hips (19%) redislocated at a mean time to dislocation of 12.2 months; 31% (11 of 36 patients) that underwent modular exchange specifically for instability redislocated. Risk factors for redislocation included number of previous surgeries (P = .013), implantation of a 28 mm femoral head (hazards ratio 12.8), revision indication of instability (P = .04), and modular exchange with constrained liner implantation without acetabular shell revision (P = .01).

CONCLUSION

Implantation of a focally constrained liner in revision total hip arthroplasty for recurrent instability has a high failure rate, especially with a modular exchange. Although concurrent acetabular revision had a lower redislocation rate, the decision to revise a well-fixed cup should be weighed with potential complications associated with cup revision.

Treatment of the Failed Modular Neck Stems: Tips and Tricks

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Analysis of Dual Mobility Liner Rim Damage Using Retrieved Components and Cadaver Models

BACKGROUND

The objective of this study was to assess the retentive rim of retrieved dual mobility liners for visible evidence of deformation from femoral neck contact and to use cadaver models to determine if anterior soft tissue impingement could contribute to such deformation.

METHODS

Fifteen surgically retrieved polyethylene liners were assessed for evidence of rim deformation. The average time in vivo was 31.4 months, and all patients were revised for reasons other than intraprosthetic dislocation. Liner interaction with the iliopsoas was studied visually and with fluoroscopy in cadaver specimens using a dual mobility system different than the retrieval study. For fluoroscopic visualization, a metal wire was sutured to the iliopsoas and wires were also embedded into grooves on the outer surface of the liner and the inner head.

RESULTS

All retrievals showed evidence of femoral neck contact. The cadaver experiments showed that liner motion was impeded by impingement with the iliopsoas tendon in low flexion angles. When observing the hip during maximum hyperextension, 0°, 15°, and 30° of flexion, there was noticeable tenting of the iliopsoas caused by impingement with the liner.

CONCLUSION

Liner rim deformation resulting from contact with the femoral neck likely begins during early in vivo function. The presence of deformation is indicative of a mechanism inhibiting mobility of the liner. The cadaver studies showed that liner motion could be impeded because of its impingement with the iliopsoas. Such soft tissue impingement may be one mechanism by which liner motion is routinely inhibited, which can result in load transfer from the neck to the rim.

Do Dual-Mobility Cups Reduce the Risk of Dislocation in Total Hip Arthroplasty for Fractured Neck of Femur in Patients Aged Older Than 75 Years?

BACKGROUND

Total hip arthroplasty (THA) for intracapsular neck of femur (NOF) fracture remains debatable as it is associated with higher rates of dislocation, notably in the older part of the population. We hypothesized this risk could be limited using dual-mobility cups (DMCs).

METHODS

Eighty-two patients (83 hips) aged older than 75 years underwent DMC-THA using a posterolateral approach for an intracapsular NOF fracture.

RESULTS

Clinical data were collected in 45 patients at a mean of 23.8 ± 9.4 months (12.1-42 months). The mortality rates were 19% (16 patients) and 36.5% (30 patients) at 1 year postoperatively and at the last follow-up, respectively. Postoperatively, there were 2 dislocations of the large articulation (4.4%) and one intraprosthetic dislocation (2.2%), all related to technical errors. Functional results were rated at least good in 71% cases, whereas the Parker and Devane scores were stable, indicating optimal restoration of autonomy and physical activity.

CONCLUSION

Although technically demanding, DMC-THA may prevent dislocation in intracapsular NOF fracture in elderly patients, while consistently limiting the risk of loss of independence.

Evaluation and management of chronic total hip instability

Given the increasing number of total hip arthroplasty procedures being performed annually, it is imperative that orthopaedic surgeons understand factors responsible for instability. In order to treat this potentially complex problem, we recommend correctly classifying the type of instability present based on component position, abductor function, impingement, and polyethylene wear. Correct classification allows the treating surgeon to choose the appropriate revision option that ultimately will allow for the best potential outcome.

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

Soft-tissue impingement with dual mobility liners can cause anterior hip pain and intra-prosthetic dislocation. The hypothesis of this study was that reducing liner profile below the equator (contoured design) can mitigate soft-tissue impingement without compromising inner-head pull-out resistance and hip joint stability. The interaction of conventional and contoured liners with anterior soft tissues was evaluated in cadaver specimens via visual observation and fluoroscopic imaging. Resistance to inner-head pull-out was evaluated via finite element analyses, and hip joint stability was evaluated by rigid-body mechanics simulation of dislocation in two modes (A, B). Cadaveric experiments showed that distal portion of conventional liners impinge on anterior hip capsule and cause iliopsoas tenting at low flexion angles (≤30°). During hip extension, the rotation imparted to the liner from posterior engagement with femoral neck was impeded by anterior soft-tissue impingement. The iliopsoas tenting was significantly reduced with contoured liners (p ≤ 0.04). Additionally, the contoured and conventional liners had identical inner-head pull-out resistance (901 N vs. 909 N), jump distance (9.4 mm mode-A, 11.7 mm mode-B) and impingement-free range of motion (47° mode-A, 29° mode-B). Thus, soft-tissue impingement with conventional dual mobility liners may be mitigated by reducing liner profile below the equator, without affecting mechanical performance. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:889-897, 2016.

Revision of a single type of large metal head metal-on-metal hip prosthesis

Large-head metal-on-metal (MoM) total hip arthroplasties were introduced because of their purported advantages. Inflammatory pseudotumours occasionally occur after MoM hip arthroplasty and often lead to revision. The purpose of this study was to assess the outcome of revision of large-head MoM total hip arthroplasties after an extensive screening protocol for all MoM articulations with a minimum 2 year follow-up. We identified 50 hips that had undergone large-head MoM total hip arthoplasty and required revision at a mean of 44 months after index operation. Of these, 38 were revised for pseudotumours, 7 for loosening, 2 for infection and 3 for instability. There was bone loss in 44 hips. The majority were revised to a 28 mm metal or ceramic head on a polyethylene-cemented cup. In 12 patients there was a complication. There was a decrease of whole blood cobalt from 20.8 µg/L preoperatively to 1.8 µg/L 1 year after revision. We found 6 residual masses on routine postoperative CT scans. The indication for revision of this cohort is inevitable but the clinical outcome 2 years after revision for pseudotumour is disappointing. Revising a MoM hip arthroplasty to a conventional cemented polyethylene or dual-mobility cup with bone impaction grafting and a 28 mm head can adequately treat the high ion levels and probably the disease of ARMD.

Can cemented dual-mobility cups be used without a reinforcement device in cases of mild acetabular bone stock alteration in total hip arthroplasty?

INTRODUCTION

Cemented versions of dual-mobility cups (DMCs), helpful in cases of bone stock alteration, are usually used in association with a reinforcement device. To simplify the intervention in elderly subjects or those with a poor bone stock, the cups can be cemented directly into the bone, but the long-term result remains uncertain. We conducted a retrospective study in this population so as to: (1) assess whether cemented fixation of a DMC without a reinforcement device leads to a higher loosening rate, (2) confirm its efficacy in preventing dislocations in subjects at high risk of instability, and (3) measure the functional results.

HYPOTHESIS

Cemented fixation of a DMC is reliable in cases of moderate alteration of bone stock.

MATERIAL AND METHODS

Sixty-four patients (66 hips) undergoing implantation of a cemented DMC (Saturne™) without a reinforcement device were included in this single-center retrospective study. Their mean age was 79.8 years (range, 40-95 years). The indications varied: hip osteoarthritis (30.3%), prosthesis revision (44.0%), and trauma (25.8%). The patients were evaluated radiologically and clinically at follow-up. The main evaluation criterion was the revision rate for aseptic loosening. Dislocations, the infection rate, and the Postel Merle d'Aubigné (PMA) score were noted.

RESULTS

At the mean follow-up of 4.2 years, three (4.6%) patients had been lost to follow-up and 22 (33.3%) had died. There was one case of aseptic loosening (1.5%). Cup survival was 98% at 5 years (95%CI [94-100]). There were no dislocations. There was one revision for infection. The mean PMA score was 15.5 (range, 9-18).

DISCUSSION

The frequency of acetabular loosening was comparable to the frequency in cemented DMCs with a reinforcement device. A cemented DMC without a reinforcement device is possible and is a simple and viable option when there is moderate bone stock alteration.

LEVEL OF EVIDENCE

IV, retrospective cohort study.

Lack of early dislocation following total hip arthroplasty with a new dual mobility acetabular design

Dual mobility implant designs minimise the risk of dislocation without sacrificing range of motion. Between 1st September 2008 and 31st July 2011, 5 institutions examined early clinical outcomes of a new dual mobility bearing hip system implanted in 485 primary THAs in 452 patients. Patient demographics were 46% female, a mean age of 67 years and a mean BMI of 30. Complications at a minimum of 2 years after surgery included 1 femur fracture, 1 DVT and 4 unrelated deaths. There were no dislocations. For functional outcomes, Harris Hip Scores increased from 41 to 86 (p<0.001), while VAS pain scores decreased from 5.9 to 0.7 (p<0.001). Minimal complications, excellent early clinical outcomes and the absence of early dislocations demonstrate the improved stability of this dual mobility implant system.

Intra-prosthetic dislocation of dual-mobility cups after total hip arthroplasty: potential causes from a clinical and biomechanical perspective

INTRODUCTION

Recurrent dislocation of total hip arthroplasty is a frequent indication for revision surgery. Hip joint stability depends on implant design, cup position and crucially on femoral head diameter. Due to an effective ultra-large diameter femoral head, dual-mobility cups are considered an attractive solution to prevent dislocation in unstable conditions. Although patients obviously benefit for many years in terms of mobility and pain, an increase of intra-prosthetic dislocation reports using dual-mobility cups has been recently observed. However, the failure mechanism of this implant-specific complication, which is characterized by the loss of the positive-locking between the femoral head and the mobile liner, is not yet completely understood.

METHODS

A comprehensive search was performed with the PubMed database and a search engine to overview this topic and to identify potential causes for this implant-specific failure from a clinical and biomechanical perspective.

RESULTS

Peri-operative findings indicate extensive fibrosis at the large articulation as well as cup loosening as potential causes. In addition, current research has shown that the failure mechanism is affected by the surface topography of the femoral neck and in particular by the design of the mobile liner.

DISCUSSION

In clinical practice it is necessary to differentiate a classic dislocation between the mobile liner and the metallic shell from an intra-prosthetic dislocation between the femoral head and the liner.

CONCLUSION

Due to the increasing popularity of dual-mobility cups in total hip arthroplasty, the understanding of which implant-specific features or tissue response may increase the risk of intra-prosthetic dislocation is of major importance for reduced revision rates by using optimized surgical techniques and implant designs.

Dual mobility cup in revision total hip arthroplasty: dislocation rate and survival after 5 years

BACKGROUND

Dislocation is a common complication of total hip arthroplasty (THA), particularly when performed as revision surgery. Dual mobility cups (DMCs) minimize the risk of instability when implanted during primary THA. However, their usefulness and survival in revision THA remain unclear. We therefore conducted a retrospective study to assess DMC stability and survival at a minimal follow-up period of 5years after revision THA.

HYPOTHESIS

The dislocation rate associated with DMCs for revision THA is similar to that seen after primary THA.

MATERIALS AND METHODS

Cup exchange with implantation of a DMC was performed in 71 patients (74 hips) between 2000 and 2007, for the following reasons: recurrent dislocation (n=22), aseptic loosening (n=38), and infection (n=14). The DMCs were cemented in 47 cases and cementless in 27 cases. The clinical variables (Merle d'Aubigné-Postel score and Harris Hip Score) and radiological findings were collected retrospectively from the medical records and compared with those obtained at the last follow-up visit.

RESULTS

Of the 74 cases, 2 were lost to follow-up. At last follow-up, the mean Merle d'Aubigné-Postel score was 15.2 (11-18) and the mean Harris Hip Score was 80.4 (51-98). Of the 8 failures, 2 (2/72, 2.7%) were related to mechanical factors (1 case each of aseptic loosening and dislocation) and 6 were changed because of infection (recurrent infection, n=4). Mechanical failure was not linked to a specific reason for revision THA. A radiolucent line was visible in 4 cases but this finding was not associated with clinical manifestations. When failure was defined as cup revision for any non-infectious complication, 5-year implant survival was 99% (95% confidence interval, 93-100%).

DISCUSSION

Use of a DMC in revision THA was associated with a slightly higher dislocation rate (1/72, 1.4%) than in primary THA, whereas 5-year survival was comparable. Cemented DMCs were not associated with a greater risk of loosening.

CONCLUSION

DMCs are useful to decrease the risk of dislocation in revision THA performed for any reason. The low rate of loosening indicates that DMCs do not result in high stresses at the bone-implant interface.

LEVEL OF EVIDENCE

IV, retrospective study.

Revision of Failed Hip Resurfacing and Large Metal-on-Metal Total Hip Arthroplasty Using Dual-Mobility Components

Revision of metal-on-metal (MoM) total hip arthroplasty (THA) or hip resurfacing is associated with high complication rates. The authors propose dual-mobility components as a surgical option and present short- to mid-term results of MoM hips revised with dual-mobility components. Eighteen consecutive hips that underwent revision of MoM THA or hip resurfacing using dual-mobility components were identified. At final follow-up (mean, 17.5 months), the visual analog scale, modified Harris Hip Score, and SF-12 scores had all improved (P<.05, P<.01, and P<.05, respectively). There were no dislocations or other complications. Revision of failed MoM THA or hip resurfacing using a dual-mobility device is an effective strategy.

Revision of metal-on-metal hip replacements and resurfacings for adverse reaction to metal debris: a systematic review of outcomes

PURPOSE

This systematic review assessed evidence on outcomes following revision of MoM hip resurfacings (HRs) and total hip replacements (THRs) for adverse reaction to metal debris (ARMD).

METHODS

Four electronic databases were searched between January 2009 and July 2013 to identify studies reporting clinical outcomes following revision of MoM HRs and THRs for ARMD. Only studies reporting cohorts with more than 10 metal-on-metal (MoM) hips revised for ARMD were included. Outcomes of interest following ARMD revision were: (1) complication rates; (2) re-revision rates; (3) surgical intervention other than re-revision; (4) functional outcome.

RESULTS

Of 148 unique studies identified, six studies were eligible for inclusion containing 216 MoM hips (197 HRs and 19 THRs) revised for ARMD. Mean follow-up time from ARMD revision ranged between 21-61 months. Complication rates were 4%-50% for HR and 68% for THR. Re-revision rates were 3%-38% for HR and 21% for THR. Dislocation (n = 14), ARMD recurrence (n = 11), and acetabular loosening (n = 9) were the three commonest complications and indications for re-revision. All six studies reported between one and three cases of ARMD recurrence during follow-up. One study specifically reported on performing procedures other than re-revision with 26% requiring closed reductions for dislocated THRs. Functional outcomes following ARMD revision were good or satisfactory in all but two studies.

CONCLUSIONS

Limited evidence exists regarding outcomes following revision of MoM hips for ARMD, especially for THRs. This should be addressed in future studies and may be important when counselling asymptomatic individuals in whom revision is considered for raised blood metal ions.

Intraprosthetic Dislocation of Dual-Mobility Bearings Associated with Closed Reduction

CASE

We present two patients with dual-mobility total hip arthroplasty components who underwent closed reduction of posterior dislocations with conscious sedation in the emergency room. Following closed reduction, both patients had immediate pain, clicking, and grinding of the hip. Radiographs identified intraprosthetic dislocation of the dual-mobility components, and revision surgery was required.

CONCLUSION

When dislocation of a dual-mobility bearing occurs, the surgeon should consider performing a careful closed reduction with muscle paralysis and use of fluoroscopic guidance in the operating room to avoid intraprosthetic dislocation.

A double mobility acetabular implant for primary hip arthroplasty in patients at high risk of dislocation

INTRODUCTION

Dislocation following total hip replacement continues to be a problem for which no completely satisfactory solution has been found. Several methods have been proposed to reduce the incidence of hip dislocations with varying degrees of success, including elevated rim liners, constrained liners and large diameter bearings. We present our experience with the double mobility acetabular component in patients at high risk of instability.

METHODS

This was a retrospective review of 65 primary total hip arthroplasties in 55 patients (15 men, 40 women), performed between October 2005 and November 2009. The majority (80%) of patients had at least two and 26% had at least three risk factors for instability. The mean age was 76 years (range: 44-92 years). The patients were followed up for a mean duration of 60 months (range: 36-85 months).

RESULTS

Fourteen patients died and one was lost to follow-up, leaving fifty hips for final assessment. Until the final follow-up appointment, no patients had dislocation and none required revision surgery. The mean Oxford hip score improved from 45.0 to 26.5 (p<0.0001). The mean Merle d'Aubigné pain score improved from 1.4 to 4.9 (p<0.0001), the walking score from 2.3 to 3.1 (p<0.07) and the absolute hip function score from 5.4 to 10.8 (p<0.0001). There were no clinical or radiographic signs of loosening.

CONCLUSIONS

The double mobility acetabular component was successful at preventing dislocation during early to medium-term follow-up. However, as data are still lacking with regard to polyethylene wear rates at the additional bearing surface, it would be prudent to restrict the use of this implant to selected patients at high risk of instability.

Outcomes of dual-mobility acetabular cup for instability in primary and revision total hip arthroplasty

Background

The concept of a dual-mobility hip socket involves the standard femoral head component encased in a larger polyethylene liner, which in turn articulates inside a metal shell implanted in the native acetabulum. The aim of this study was to assess outcomes from using a Serf Novae^® Dual Mobility Acetabular cup (Orthodynamics Ltd, Gloucestershire, UK) to address the problem of instability in primary and revision total hip arthroplasty (THA).

Materials and methods

A retrospective review was carried out of all hip arthroplasties performed in a District General Hospital utilising the dual-mobility socket from January 2007 to December 2012. Clinical and radiological outcomes were analysed for 44 hips in 41 patients, comprising 20 primary and 24 revision THA. The average age of the study group was 70.8 years (range 56–84 years) for primary and 76.4 years (range 56–89 years) for revision arthroplasty. Among the primary THA, always performed for hip osteoarthritis or in presence of osteoarthritic changes, the reasons to choose a dual mobility cup were central nervous system problems such as Parkinson’s disease, stroke, dementia (10), hip fracture (5), failed hip fracture fixation (2), severe fixed hip deformity (2) and diffuse peripheral neuropathy (1). The indications for revisions were recurrent dislocation (17), aseptic loosening with abductor deficiency (4), failed hemiarthroplasty with abductor deficiency (2) and neglected dislocation (1).

Results

At a mean follow-up of 22 months (range 6–63 months), none of the hips had any dislocation, instability or infection and no further surgical intervention was required. Radiological assessment showed that one uncemented socket in a revision arthroplasty performed for recurrent dislocation had changed position, but was stable in the new position. The patient did not have complications from this and did not need any surgical intervention.

Conclusions

Even though postoperative hip stability depends on several factors other than design-related ones, our study shows promising early results for reducing the risk of instability in this challenging group of patients undergoing primary and revision hip arthroplasty.

Level of evidence

IV.

Dual mobility cups in total hip arthroplasty

Total hip arthroplasty (THA) is considered one of the most successful surgical procedures in orthopaedics. With the increase in the number of THAs performed in the world in the next decades, reducing or preventing medical and mechanical complications such as post-operative THA instability will be of paramount importance, particularly in an emerging health care environment based on quality control and patient outcome. Dual mobility acetabular component (also known as unconstrained tripolar implant) was introduced in France at the end of the 1970s as an alternative to standard sockets, to reduce the risk of THA dislocation in patients undergoing primary THA in France. Dual mobility cups have recently gained wider attention in the United States as an alternative option in the prevention and treatment of instability in both primary and revision THA and offer the benefit of increased stability without compromising clinical outcomes and implant longevity. In this article, we review the use of dual mobility cup in total hip arthroplasty in terms of its history, biomechanics, outcomes and complications based on more than 20 years of medical literature.

Intraprosthetic dislocation: a potentially serious complication of dual mobility acetabular cups

Though dual mobility cups have gained growing popularity as a solution for instability in total hip replacements, these promising devices are subject to a specific implant failure mode, named intraprosthetic dislocation. We present the case of a patient sustaining such an adverse event. The planned revision surgery was postponed 12 months due to a severe heart condition, allowing a rare opportunity to document the natural history of this unusual complication. The small femoral head was found dislodged in the superior part of the metallic shell and had remarkably lost its sphericity. Severe metallic debris and granuloma were found in the proximal femoral region, associated with major periprosthetic bony and soft tissue damage. Surgeons, radiologists, and general practitioners should be aware of this specific complication, its incidence (almost 5%) and mechanisms (femoral neck to mobile polyethylene insert impingement, leading to rim fatigue and wear of the insert at the capturing area). Diagnosis is mainly based on anteroposterior and modified Lowenstein lateral radiographs of the hip, as an eccentric position of the small femoral head, lying against the concave inner surface of the shell. Prompt component revision should be planned, since delayed management could lead to severe irretrievable damages.

Does dual-mobility cup geometry affect posterior horizontal dislocation distance?

BACKGROUND

Dual-mobility acetabular cups have been marketed with the purported advantages of reduced dislocation rates and improvements in ROM; however, the relative efficacies of these designs in terms of changing joint stability via ROM and dislocation distance have not been thoroughly evaluated.

QUESTIONS/PURPOSES

In custom computer simulation studies, we addressed the following questions: (1) Do variations in component geometry across dual-mobility designs (anatomic, modular, and subhemispheric) affect the posterior horizontal dislocation distances? (2) How do these compare with the measurements obtained with standard hemispheric fixed bearings? (3) What is the effect of head size on posterior horizontal dislocation distances for dual-mobility and standard hemispheric fixed bearings? (4) What are the comparative differences in prosthetic impingement-free ROM between three modern dual-mobility components (anatomic, modular, and subhemispheric), and standard hemispheric fixed bearings?

METHODS

CT scans of an adult pelvis were imported into computer-aided design software to generate a dynamic three-dimensional model of the pelvis. Using this software, computer-aided design models of three dual-mobility designs (anatomic, modular, and subhemispheric) and standard hemispheric fixed bearings were implanted in the pelvic model and the posterior horizontal dislocation distances measured. Hip ROM simulator software was used to compare the prosthetic impingement-free ROMs of dual-mobility bearings with standard hemispheric fixed-bearing designs.

RESULTS

Variations in component design had greater effect on posterior horizontal dislocation distance values than increases in head size in a specific design (p < 0.001). Anatomic and modular dual-mobility designs were found to have greater posterior horizontal dislocation distances than the subhemispheric dual-mobility and standard hemispheric fixed-bearing designs (p < 0.001). Increasing head sizes increased posterior horizontal dislocation distances across all designs (p < 0.001). The subhemispheric dual-mobility implant was found to have the greatest prosthetic impingement-free ROM among all prosthetic designs (p < 0.001; R(2) = 0.86).

CONCLUSIONS

The posterior horizontal dislocation distances differ with the individual component geometries of dual-mobility designs, with the anatomic and modular designs showing higher posterior horizontal dislocation distances compared with subhemispheric dual-mobility and standard hemispheric fixed-bearing designs.

CLINICAL RELEVANCE

Static, three-dimensional computerized simulation studies suggest differences that may influence the risk of dislocation among components with varying geometries, favoring anatomic and modular dual-mobility designs. Clinical studies are needed to confirm these observations.

Self-centering dual-mobility total hip systems: Prediction of relative movements and realignment of different intermediate components

The increased jump distance against dislocation and the large range of motion due to the enlarged effective head diameter substantiate the use of dual-mobility systems in cases of total hip joint instability. For this type of total hip endoprostheses, an eccentric design of the outer bearing is assumed in order to provide a force-dependent self-centering mechanism and an improved joint stability against dislocation. The purpose of this study was to determine the relative movements and realignment of different intermediate components during various motion cycles as a result of the eccentric design. We established a validated mathematical model for eccentric dual-mobility systems, which allowed a comparison of relative movements, self-centering torque and overall frictional torque during four different activities in order to analyze their motion behavior in everyday life. In addition, the impact of different radial clearances on the dynamic performance of the self-centering mechanism was investigated. According to torque patterns and the validation experiment, the main articulation of eccentric dual-mobility systems was limited to the smaller inner bearing for the most daily life activities, i.e. the eccentric intermediate component remained in its current position and only with changing activity did the intermediate component realign clearly. However, an inappropriate dimensioning of the radial clearance could lead to a permanent realignment of the intermediate component during the motion cycles. In general, the self-centering mechanism of the intermediate component seems to have no negative influence on relative movements and wear propagation of dual-mobility cup systems if the clearance and eccentricity are appropriately dimensioned.

Surgical management of recurrent dislocation after total hip arthroplasty

Dislocation is a major complication of total hip arthroplasty (THA), whose frequency has been unaffected by improvements in surgical techniques and implants. The dislocation rate depends on multiple factors related to the patient, hip disease, and surgical procedure and is therefore also dependent on the surgeon. The many published studies on THA dislocation, its causes, and its treatment have produced conflicting results. The objective of this work is to review the management of THA dislocation, which is a severe event for both the patient and the surgeon. This lecture starts with a brief review of data on THA dislocation rates and the many factors that influence them. Emphasis is then put on the evaluation for a cause and, more specifically, on the challenges raised by detecting suboptimal cup position. Next, reported techniques for treating THA dislocation and the outcomes of each are discussed. Finally, a management strategy for patients selected for revision surgery is suggested.

Proximal femoral reconstruction with a constrained acetabulum in oncologic patients

Metallic endoprostheses are used for oncological reconstruction around the proximal femur and hip joint. Common modes of failure with hemiarthroplasty or standard hip arthroplasty after proximal femoral replacement include dislocation, late hip pain, and infection. The authors reviewed hospital records to identify patients undergoing constrained tripolar hip arthroplasty for oncological reasons between 2002 and 2012. Inclusion criterion was at least 12-cm proximal femoral resection, including patients with total femur reconstruction. A total of 33 patients were reviewed. Information regarding demographics, length of follow-up, treatment characteristics, and patient outcomes was extracted. Average follow-up for all patients was 912.33 days (30.4 months). Average follow-up was 1396.1 days for living patients and 428.6 days for deceased patients. Average estimated blood loss was 462.12 cc: an average of 1080 cc for patients undergoing total femoral resection and replacement and 315.8 cc for patients undergoing proximal femoral resection and replacement. Average operative time was 137.7 minutes: an average of 205 minutes for patients undergoing total femoral resection and replacement and 119.1 minutes for patients undergoing proximal femoral resection and replacement. Average Musculoskeletal Tumor Society score was 21.7. There were no dislocations in the cohort. A constrained tripolar device can be safely used for oncological proximal femoral reconstructions while minimizing the risk of dislocation. Positioning of the acetabular implant in neutral anatomic version in conjunction with a neutral-placed femoral component provides the greatest range of motion, reduction of liner impingement, and improved hip stability.

Acetabular reconstruction using a Kerboull cross-plate, structural allograft and cemented dual-mobility cup in revision THA at a minimum 5-year follow-up

The current study aimed to evaluate the outcome of a continuous and prospective series of 61 revision THAs with AAOS grade III and IV acetabular bone defect reconstruction using a Kerboull cross-plate, structural allograft and cemented dual mobility cup (Saturne, Amplitude, Valence, France). At a 7.5-year mean follow-up, no instability was reported after revision. In addition, no failure of the acetabular reconstruction was observed in 98% of the patients with complete allograft osseointegration and no evidence of mechanical rupture of the Kerboull cross-plate and/or loosening of the cemented dual mobility cup. In conclusion, such reconstruction technique demonstrated excellent results at mid-term follow-up in terms of prevention of instability after revision, restoration of the acetabular bone stock, and stable cemented fixation of the dual mobility cup.

High complication rate after revision of large-head metal-on-metal total hip arthroplasty

BACKGROUND

Previous studies have indicated poor outcomes in patients having revision of hip resurfacing resulting from adverse local tissue reaction and pseudotumor.

QUESTIONS/PURPOSES

We reviewed all patients at our institution who had revision of failed large-head metal-on-metal total hip arthroplasty to determine (1) complications including reoperations; (2) radiologic outcomes; and (3) changes in serum ions after removal of the metal bearing.

METHODS

From our research database, we identified 32 hips in 30 patients. Revisions were performed through a posterior approach; 17 were performed with a titanium fiber-metal shell and 15 with a porous tantalum shell, and 29 of the 32 revisions were performed with large (36- or 40-mm) femoral heads. Clinical records were reviewed and interviews conducted in the clinic or by telephone. Nineteen hips had a pre- or intraoperative diagnosis of adverse local tissue reaction, three had deep infection, and 10 had loosening of the acetabular component.

RESULTS

Major complications occurred in 12 (38%) of the 32 revisions. Nine of 32 hips (28%) sustained dislocations. Four of 17 fiber-metal acetabular components failed to ingrow; none of the porous tantalum cups failed to ingrow. Seven repeat revisions were performed in six patients: three for acetabular loosening, three for recurrent dislocation, and one for recurrent adverse local tissue reaction. The mean WOMAC pain score was 78 of 100 and the function score was 83 of 100. Metal ion levels decreased after revision in most patients.

CONCLUSIONS

As a result of the high rate of failure of the fiber metal cups, we have elected to use an enhanced fixation surface with a high-porosity cup for revision of these cases. We observed a high rate of dislocation despite the use of 36-mm and 40-mm heads.

Dual mobility in total hip arthroplasty

Dual-mobility articulations have shown promising results. Postoperative instability remains the most common reason for revision of a total hip arthroplasty (THA). Dual-mobility cups have been shown to decrease the rate of dislocation in primary THA and have been used to treat and prevent instability in revision THA. Greater range of motion and a greater head-to-neck ratio and a greater jump distance are achieved, resulting in a lower risk of instability. Concerns with dual-mobility cups include wear and intraprosthetic dislocation. Specific design modifications have aimed to improve cup fixation and decrease polyethylene wear and the risks of intraprosthetic dislocation.

What are the causes for failures of primary hip arthroplasties in France?

BACKGROUND

There are no large database cohorts describing the causes for failure of primary THAs in France. Because implants and causes for revision vary between national registers, it is important to obtain data from all countries.

QUESTIONS/PURPOSES

We therefore determined (1) the mechanisms of failure of primary THAs, (2) their order of appearance with time, (3) the types of surgical techniques and implant designs used to perform revision THAs, and (4) 90-day complications after revision THA in France.

METHODS

We prospectively collected data on all 2107 first-time revision THAs from 30 tertiary centers from January 1, 2010, to December 31, 2011. A dual-mobility liner had been used in 251 hips. Mean time from primary procedure to revision THA was 11.2 years (range, 1 day to 42 years). Mean age at revision was 70 years (range, 17-104 years).

RESULTS

The causes for revision were mechanical loosening (42%), periprosthetic fracture (12%), infection (11%), wear/osteolysis (11%), dislocation (10%), surgical technique error (6%), and implant fracture (3%). The most common type of revision procedure was all-component revision (49%). A dual-mobility liner was used in 1184 hips (62%). The 90-day dislocation rate was less than 4%, and mortality rate was 1.6%.

CONCLUSIONS

Contrary to other reported data, we found dislocation was not the main cause for failure of primary THAs but was still the more frequent early complication after revision. These findings might be related to the use of dual-mobility sockets in more than 10% of primary THAs and more than 60% of revision THAs.

Acetabular liner with focal constraint to prevent dislocation after THA

BACKGROUND

Dislocation continues to commonly cause failure after primary and revision total hip arthroplasty (THA). Fully constrained liners intended to prevent dislocation are nonetheless associated with a substantial incidence of failure by redislocation, mechanical failure, aseptic loosening, or a combination. Constrained liners with cutouts of the elevated rims can theoretically increase range of movement and therefore decrease the risk dislocation, but it is unclear if they do so in practice and whether they are associated with early wear or loosening.

QUESTIONS/PURPOSES

We therefore determined (1) occurrence or recurrence of dislocation and (2) rate of complications associated with constrained implants with cutouts; and (3) assessed for early cup loosening.

METHODS

We retrospectively reviewed the records of 81 patients at high risk for dislocation who had 82 constrained liners inserted for primary (n = 10) or revision (n = 72) THA between 2008 and 2010. From the records we extracted demographic and implant data and instances of recurrent dislocation, implant failure, osteolysis, loosening, or construct failure. The minimum followup was 24 months (mean, 34 months; range, 24-49 months).

RESULTS

Three liners failed as a result of further dislocation (3%). Three deep infections occurred. One patient had progressive loosening at the shell-bone interface.

CONCLUSIONS

Our observations suggest this liner is associated with a relatively low risk of dislocation in patients at high risk for dislocation and those with recurrent dislocation.

Oxinium femoral head damage generated by a metallic foreign body within the polyethylene cup following recurrent dislocation episodes

Oxinium femoral heads are supposed to be more scratch-resistant thanks to their oxidized layer. However, damages to this thin layer can jeopardize implant's properties. Following revision total hip arthroplasty performed for recurrent posterior dislocations, the Oxinium femoral head initially implanted was observed to be dramatically damaged. A metallic foreign body from a trochanteric fixation wire was found within the polyethylene cup. Only few cases of damaged Oxinium femoral heads have been reported and all were related to either dislocation or reduction of THA. The aim of this report is to describe a non-reported mechanism of damaged Oxinium femoral head due to a broken trochanteric fixation wire device. Any broken metallic wire from a transtrochanteric approach should be carefully followed to detect migration within the polyethylene cup. If such a migration occurs, revision surgery should be rapidly scheduled.

Primary total hip arthroplasty revision due to dislocation: prospective French multicenter study

INTRODUCTION

Dislocation following total hip arthroplasty (THA) may require surgical revision, and is one of the most frequent causes for revision in national registers. The goals of this study were to determine the characteristics of revision THA for dislocation and identify the typical features of hips revised due to dislocation.

MATERIALS AND METHODS

A prospective multicenter study (30 centers) was performed in first revision THA performed between January 1, 2010 and December 31, 2011 (multiple revisions were excluded).

RESULTS

Two hundred nineteen (10.4%) of all first revisions (2153 cases in 2107 patients) were for dislocation, which was the fifth cause of revision. There were 135 men and 84 women, mean age 65.9 years old (24.3-92.4) at primary THA and 72.9 years old (31.9-98.8) at revision. Revision surgery was performed a mean 7.1 years (± 7.1) after primary THA. The predictive risk factors for dislocation were: a 22.2mm diameter femoral head (risk × 2.4), a posterolateral approach (risk × 1.7), older age (risk × 1.1), an elevated rim liner for primary THA (risk × 6.6). The use of a dual mobility cup did not influence the rate of revision for dislocation (8.8%) compared to the use of a flat rim liner (9.1%).

DISCUSSION

The 10.4% rate of revision of THA for dislocation seems markedly lower than the results in the literature both for frequency and ranking. The use of elevated rim or constrained liners designed to decrease the risk of dislocation does not improve results compared to standard liners.

LEVEL OF EVIDENCE

Level IV, prospective prognostic study without a control group.

Infection as a cause of primary total hip arthroplasty revision and its predictive factors

INTRODUCTION

Infection is a serious complication of total hip arthroplasty (THA) and is one of the most frequent causes of failure. The goal of this study was to evaluate the importance of infection among the different causes of revision THA and identify any risk factors specifically associated with this cause of revision.

MATERIALS AND METHODS

All patients who underwent a first revision of THA were included in a prospective multicenter study. Postoperative clinical and radiological evaluation and follow-up of morbidity and mortality were performed at 3 months.

RESULTS

Two hundred forty out of 2107 revisions (11.4%) were performed for infected THA, which was the third cause after aseptic loosening (42.3%) and peri-prosthetic fractures (11.8%). These patients had a higher BMI associated with co-morbidities and lower clinical scores than patients with other causes of revision. One-stage revision was performed in most cases (66%) with replacement of the complete implant in 86% of cases, resulting in longer surgery compared to that for other causes. Male gender (OR 2.3), avascular necrosis (OR 2.4), arthroplasties with dual mobility cups (OR 2.5) and a Rottinger anterolateral approach (OR 3.4) were all associated with an increased risk of infection.

DISCUSSION

Some of these risk factors are not or have rarely been reported in the literature. They should be taken into consideration to help in the prevention and continuing battle against THA infection.

LEVEL OF EVIDENCE

Level IV, prospective cohort study.

Dual mobility cups for preventing early hip arthroplasty dislocation in patients at risk: experience in a county hospital

Dislocation remains a major concern after hip arthroplasty. We asked whether dual mobility cups (DMC) would improve early hip stability in patients with high risk of dislocation. We followed 34 patients (21 females, 13 males) treated between 2009 and 2012 with cemented DMC for hip revisions caused recurrent hip prosthetic dislocation or as a primary procedure in patients with high risk of instability. Functional outcome and quality of life were evaluated using Harris Hip Score and EQ-5D respectively. We found that the cemented DMC gave stability in 94%. Seven patients (20%) were re-operated due to infection. One patient sustained a periprosthetic fracture. At follow-up (6 to 36 months, mean 18), the mean Harris hip score was 67 (standard deviation: 14) and mean EQ-5D was 0.76 (standard deviation: 0.12). We concluded that treating patients with high risk of dislocation with DMC can give good stability. However, complications such as postoperative infection can be frequent and should be managed carefully.

Cementation of a dual-mobility acetabular component into a well-fixed metal shell during revision total hip arthroplasty: a biomechanical validation

Cementation of polyethylene (PE) liners into well-fixed metal shells has become a popular option during revision total hip arthroplasty (THA) particularly for older and frail patients. Although dramatic results were reported with dual-mobility acetabular components to manage hip instability during revision THA, no study evaluated the fixation strength of the cementation of dual-mobility components into well-fixed metal shells. Eight dual-mobility and eight all-PE components were cemented into a metal shell with a uniform 2- to 3-mm cement mantle. The cemented fixation strength was evaluated using lever-out and torsion testing. The interface at which failure occurred was determined. Lever-out testing showed that dual-mobility components failed at significantly higher maximum moment than the all-PE components. No direct comparison could be performed with torsion testing due to early failure of the all-PE component itself before failure of the cement fixation. However, the maximum moments measured were dramatically higher than the in vivo frictional moments classically reported in THA. In addition, failure was always observed at the metal shell/cement interface whenever it did occur. In conclusion, a dual-mobility acetabular component cemented into a well-fixed metal shell could constitute a biomechanically acceptable alternative to acetabular shell removal or PE liner cementation while simultaneously preventing instability of the THA revision. Clinical studies are warranted.

What factors affect posterior dislocation distance in THA?

BACKGROUND

Dislocation remains common after total hip arthroplasty. Efforts have been made to identify and minimize risk factors. One such factor, jump distance, or the distance the femoral head must travel before dislocating, has been poorly characterized with respect to three-dimensional kinematics.

QUESTIONS/PURPOSES

We therefore determined: (1) the three-dimensional stability of four different component designs; (2) whether the degree of abduction and anteversion affects the stability; (3) whether pelvic inclination angles affected stability; and (4) which combination of these three factors had the greatest stability.

METHODS

We created a positionable three-dimensional model of a THA. Acetabular components were modeled in various abduction and anteversion angles and in two different pelvic inclinations which simulate standing and chair-rising activities.

RESULTS

The posterior horizontal dislocation distance increased as inclination angle and femoral head size increased. The 48-mm resurfacing typically had lower jump distances and was at risk of posterior edge loading at 30° inclination. The highest jump distance for all positions and activities occurred with the dual-mobility bearing.

CONCLUSION

These findings suggest that monoblock cups require extremely accurate positioning for low dislocation risk and that pelvic orientation may increase dislocation risks.

CLINICAL RELEVANCE

As a result of the dual-mobility designs having the greatest resistance to dislocation, these cups may be appropriate for patients who are at risk for dislocation in difficult primary situations and in revision hip arthroplasty procedures in which proper component orientation may be less likely to be achieved.

Is a cementless dual mobility socket in primary THA a reasonable option?

BACKGROUND

Dislocation after THA continues to be relatively common. Dual mobility sockets have been associated with low dislocation rates, but it remains unclear whether their use in primary THA would not introduce additional complications.

QUESTIONS/PURPOSES

We therefore asked whether a current cementless dual mobility socket (1) reduced the dislocation rate after primary THA, (2) provided a pain-free and mobile hip, and (3) provided durable radiographic fixation of the acetabular component without any unique modes of failure.

METHODS

We retrospectively reviewed 168 patients who underwent primary THA using a dual mobility socket between January 2000 and June 2002. The average age at surgery was 67 years. We assessed the rate of dislocation, hip function, and acetabular fixation on serial radiographs. Of the 168 patients, 119 (71%) had clinical and radiographic evaluation at a minimum of 5 years (mean, 6 years; range, 5-8 years).

RESULTS

A long-neck option left the base of the Morse taper uncovered in 53 hips. Four patients underwent revision for dislocation between the femoral head and the mobile insert (intraprosthetic dislocation) at a mean 6 years; all four revisions occurred among the 53 hips with an incompletely covered Morse taper.

CONCLUSIONS

A current cementless dual mobility socket was associated with a pain-free and mobile hip and durable acetabular fixation without dislocations if the long-neck option was not used. However, intraprosthetic dislocation related to contact at the femoral neck to mobile insert articulation required revision in four hips. Surgeons should be aware of this specific complication.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.

Biomechanical concept and clinical outcome of dual mobility cups

Dual mobility cup systems in total hip arthroplasty consist of a metal back with a non-constrained liner, in which a constrained standard head articulates. While superior stability of such implants in comparison with standard total hip replacements is assumed, it is the purpose of this study to outline the biomechanical concept of dual mobility cups and to describe implant survival and dislocation rate based on the series published in the English-speaking and Francophone literature. A growing body of evidence indicates reduced dislocation rates in primary and revision total hip arthroplasty and in selected tumour cases. The limited availability of studies evaluating long-term implant survival and existing concerns with regard to increased wear rates and aseptic loosening, leads to the conclusion that such implants have to be used with prudence, particularly in standard primary hip arthroplasty and in young patients.

Recurrence of dislocation following total hip arthroplasty revision using dual mobility cups was rare in 180 hips followed over 7 years

BACKGROUND

Dual mobility (DM) cups of mobile polyethylene were introduced to prevent total hip arthroplasty (THA) dislocation, but no large series with this design to treat recurrent instability have been reported.

PURPOSE

Our retrospective investigation ascertained the efficiency of DM cups in correction of recurrent dislocation and assessed any adverse effects.

METHODS

One hundred eighty THAs with recurrent instability were revised to DM cups in 180 patients (mean age, 67.4 ± 11.7 years; range, 19 to 92 years). Thirty-one patients (17.2%) underwent at least one earlier THA revision, and 15 (10.3%) incurred non-union of the greater trochanter. Of the initial group in 2009, 145 patients had completed evaluations which included assessment of the Harris Hip Score and a radiographic assessment at a mean follow-up of 7.7 ± 2.2 years (range, 4 to 14 years). The rate of survival was calculated considering any reason for revision as failure.

RESULTS

At follow-up, Harris hip score was 83.9 ± 16.1 (range, 21 to 100). Dislocation of the large articulation occurred in seven hips (4.8%), and only two recurred (1.4%) (one requiring additional revision). In addition, two intra-prosthetic dislocations of the small articulation (1.4%) were observed and needed revision surgery. The large number of earlier surgeries and non-union of the greater trochanter were related to recurrent instability. Two cups (1.4%) showed signs of definite loosening; six (4.1%) presented signs of possible loosening. Twenty-nine hips manifested femoral or acetabular osteolysis (20%), but only three were severe. Eight-year survival rate considering revision for any reason was 92.6% (95% CI, 85.5-96.4%).

CONCLUSIONS

This series indicates that DM cups are a viable option to treat recurrent THA instability. Their design provides a low risk of recurrent instability without increasing mechanical complications.

The use of dual-mobility components in total hip arthroplasty

Dual-mobility hip components provide for an additional articular surface, with the goal of improving range of motion, jump distance (ie, vertical or inferior head displacement required for dislocation), and stability of the total hip arthroplasty. A large polyethylene head articulates with a polished metal acetabular component, and an additional smaller metal head is snap-fit within the polyethylene. New components have recently been released for use in North America. Although these devices are routinely used in some European centers for primary hip arthroplasty, their greatest utility may be to manage recurrent dislocation in the setting of revision hip arthroplasty. Several small retrospective series have shown satisfactory results for this indication at short- to midterm follow-up. Polyethylene wear and intraprosthetic dislocation are concerns, as is the lack of long-term data. Caution is thus advised in the routine use of dual-mobility components in primary and revision total hip arthroplasty.

Dual-mobility bearings: a review of the literature

Dislocation after total hip arthroplasty remains a major problem and hip instability is the most common reason for revision. These complications are costly to both patients and the healthcare system, and efforts to reduce them have had varied degrees of success. Although there are well documented patient and surgical risk factors for dislocation, the typical surgical solutions offered (constrained liners, large femoral heads) have the drawbacks of reduced range-of-motion and high rates of revision. Dual-mobility prostheses (unconstrained tripolar prostheses) are hip design solutions to dislocation that aim to provide a greater stability with an increased range-of-motion, along with potentially reduced wear. The mean overall dislocation rate from multiple combined studies using dual-mobility prostheses was 0.1% for primary total hip arthroplasty and 3.5% for revisions, compared with 2-7% for standard primary total hip arthroplasties and up to 16% for revisions. Dual-mobility prostheses offer a viable option for treating recurrent dislocation as well as for primary and revision arthroplasty.

The double-mobility acetabular component in revision total hip replacement

We present our experience with a double-mobility acetabular component in 155 consecutive revision total hip replacements in 149 patients undertaken between 2005 and 2009, with particular emphasis on the incidence of further dislocation. The mean age of the patients was 77 years (42 to 89) with 59 males and 90 females. In all, five patients died and seven were lost to follow-up. Indications for revision were aseptic loosening in 113 hips, recurrent instability in 29, peri-prosthetic fracture in 11 and sepsis in two. The mean follow-up was 42 months (18 to 68). Three hips (2%) in three patients dislocated within six weeks of surgery; one of these dislocated again after one year. All three were managed successfully with closed reduction. Two of the three dislocations occurred in patients who had undergone revision for recurrent dislocation. All three were found at revision to have abductor deficiency. There were no dislocations in those revised for either aseptic loosening or sepsis.

These results demonstrate a good mid-term outcome for this component. In the 29 patients revised for instability, only two had a further dislocation, both of which were managed by closed reduction.

Dual poly liner mobility optimizes wear and stability in THA: opposes

Total hip arthroplasty (THA) is an effective intervention for the treatment of arthrosis with excellent survivorship. Nonetheless, dislocation and osteolysis remain significant complications. A dual-mobility acetabular component has been advocated to improve stability and wear. Stability is imparted by increasing the effective femoral head size, which allows a larger range of motion (ROM) before neck-socket impingement occurs. Increasing ROM, however, introduces an additional problem of bony impingement of the trochanter against the pelvis. Consequently, there is little improvement in ROM for heads >36 to 40 mm. A 0.4% incidence of instability at the larger articulation has been reported in primary THA using the dual-mobility liner, which is equivalent to reports for conventional THA. The dual-mobility liner has introduced the unique complication of intraprosthetic dislocation, where the femoral head dissociates at the smaller articulation as a result of polyethylene wear. An incidence of intraprosthetic dislocation of 3.6% has been reported, which far exceeds dislocation of conventional arthroplasty. The dual-mobility liner is a monoblock acetabular component without the capacity for augmented bony fixation. Inability to achieve primary stability has been reported as high as 18% and therefore its usefulness in revision THA is questionable. Proponents of the dual-mobility liner cite improved wear characteristics over conventional THA; however, few studies support this proposition. Retrieval studies have reported that the dual-mobility liner does not avoid wear or osteolysis. Theoretically, it is inconceivable that wear would be diminished with an additional articulation with a huge surface area, where the differential hardness has been reversed to a soft-on-hard bearing.