Pseudotumors in association with well-functioning metal-on-metal hip prostheses: a case-control study using three-dimensional computed tomography and magnetic resonance imaging

Association of Total Hip Arthroplasty Flexural Rigidity With Magnetic Resonance Imaging and Histological Findings

BACKGROUND

Modular connections in total hip arthroplasty (THA) offer surgical advantages, but can contribute to implant fretting and corrosion due to micromotion at the head-stem interface. Previous studies implicated lower flexural rigidity as a key contributing factor to THA corrosion and fretting, but none associated flexural rigidity with direct histological evaluation or magnetic resonance imaging (MRI) outcomes. The purpose of this study was to determine how implant flexural rigidity is associated with MRI imaging metrics and histopathological outcomes in patients who have a failed THA.

METHODS

Patients requiring revision THA surgery underwent preoperative MRIs with 3-dimensional multispectral imaging techniques to suppress metal artifacts. The MRI images were graded for adverse local tissue reactions. For each hip, trunnion flexural rigidity was measured from the retrieved femoral stem, and a periprosthetic tissue sample was retrieved and evaluated using semiquantitative histology. Generalized linear models and analyses of variance were used to assess associations between flexural rigidity and MRI and histology outcomes.

RESULTS

A total of 106 THA stems were retrieved (46 women and 60 men, age: 68 years (range, 60 to 73 years). After adjustment for length of implantation, flexural rigidity was negatively correlated with histologic aseptic lymphocyte-dominant vasculitis-associated lesion severity (β = -26.27, P = .018), Fujishiro lymphocyte grading (β = -13.4, P = .039), perivascular lymphocyte layers (β = -17.8, P = .022), the grade of tissue organization (β = -22.5, P = .009), the presence of diffuse synovitis (β = -66.5, P = .003), and the presence of lymphoid aggregates (β = -75.9, P = .022). No association was found between MRI metrics and flexural rigidity.

CONCLUSIONS

Among these implants, decreased trunnion stiffness was associated with increased histologic features of adverse host-mediated soft tissue reactions.

No Difference in Revision Rates and High Survival Rates in Large-head Metal-on-metal THA Versus Metal-on-polyethylene THA: Long-term Results of a Randomized Controlled Trial

BACKGROUND

Pseudotumor formation is a well-known complication in metal-on-metal (MoM) THA. Pseudotumors combined with elevated serum ion levels and complaints from patients can lead to high revision rates. Long-term (> 10 years) results obtained from randomized trials comparing large-head MoM THA and conventional metal-on-polyethylene (MoP) THA are lacking regarding revision and survival rates, pseudotumor formation, functional outcomes, and serum ion levels.

QUESTIONS/PURPOSES

At 10 years of follow-up, (1) what is the difference in survival and revision rates between large-head (38 to 60 mm) MoM THA and conventional 28-mm MoP THA? (2) What is the difference in pseudotumor formation between large-head MoM THA and MoP THA? (3) Is there a difference in functional outcome between large-head MoM THA and MoP THA? (4) What is the difference in serum ion levels between large-head MoM THA and MoP THA?

METHODS

Between January 2006 and December 2008, 104 patients were randomized to receive either cementless MoM THA (50 patients) or cementless MoP THA (54 patients). In all, 78% (81 of 104) of patients completed the 10-year postoperative follow-up: 36 patients with MoM THA (72%; six patients lost to follow-up) and 45 with MoP THA (83%; four lost to follow-up). In the MoM group, 47% (17) were men, and the patients had a mean ± SD age of 60 ± 5 years. In the MoP group, 38% (17) were men, and the patients had a mean age of 61 ± 5 years. All baseline characteristics were similar between the groups. At 10 years of follow-up, all patient records were screened for revision surgery or complications, and the primary endpoint was survivorship free from revision for any cause at the 10-year follow-up interval, which we analyzed using a Kaplan-Meier survival analysis. All patients had a CT scan to determine the pseudotumor classification, which was reviewed by an independent radiologist. Functional outcome was measured using the patient-reported Oxford Hip Score and Harris Hip Score; the latter was assessed by a blinded nurse practitioner. Finally, serum ion cobalt and chrome concentrations were measured at 10 years postoperatively. Because the a priori sample size calculation for this randomized controlled trial was based on a different endpoint, a post hoc power analysis was performed for this long-term follow-up study, with survival as the primary outcome. It showed that considering the number of included patients, this study would have sufficient power (one-sided testing, alpha 0.05, power 80%) to discern a difference of 20% in the survival rate between the MoP and MoM groups (95% versus 75%).

RESULTS

With the numbers available, there was no difference in survivorship free from revision for any cause between the MoP group and MoM group at 10 years (95% [95% CI 85% to 98%] versus 92% [95% CI 82% to 98%]; p = 0.6). A higher percentage of patients in the MoM group had pseudotumors on CT than those in the MoP group did, but pseudotumors were observed in both groups (56% [20 of 36] in the MoM group versus 22% [10 of 45] in the MoP group, relative risk 1.8 [95% CI 1.2 to 2.6]; p = 0.002). A higher proportion of elevated cobalt and chrome levels was found in the MoM group (19% and 14%, respectively) than in the MoP group (0% for both cobalt and chrome) (cobalt: RR 1.2 [95% CI 1.1 to 1.5]; p = 0.002; chrome: RR 1.2 [95% CI 1.0 to 1.3]; p = 0.01). In 25% of the patients with pseudotumors (5 of 20 patients), there were elevated serum cobalt levels. None of the 23 patients without pseudotumors had elevated cobalt levels (RR 1.3 [95% CI 1.0 to 1.7]; p = 0.01). There was no difference in functional outcome between study groups, nor a difference between patients with a pseudotumor and those without.

CONCLUSION

This study showed that the survival of patients with large-head MoM THA was high and comparable to that of those with MoP THA, which contrasts with the high revision rates reported by others. Although some patients with MoP THAs experienced pseudotumors, the risk of a pseudotumor was much greater in MoM hips, and serum ion levels were higher in patients who received an MoM THA. For these reasons and unknown future complications, continued surveillance of patients with MoM THAs seems important.

LEVEL OF EVIDENCE

Level I, therapeutic study.

The relationship between pseudotumours and infected complications in patients who have undergone metal-on-metal total hip arthroplasty

Aims

This study aims to assess the relationship between history of pseudotumour formation secondary to metal-on-metal (MoM) implants and periprosthetic joint infection (PJI) rate, as well as establish ESR and CRP thresholds that are suggestive of infection in these patients. We hypothesized that patients with a pseudotumour were at increased risk of infection.

Methods

A total of 1,171 total hip arthroplasty (THA) patients with MoM articulations from August 2000 to March 2014 were retrospectively identified. Of those, 328 patients underwent metal artefact reduction sequence MRI and had minimum two years' clinical follow-up, and met our inclusion criteria. Data collected included demographic details, surgical indication, laterality, implants used, history of pseudotumour, and their corresponding preoperative ESR (mm/hr) and CRP (mg/dl) levels. Multivariate logistic regression modelling was used to evaluate PJI and history of pseudotumour, and receiver operating characteristic curves were created to assess the diagnostic capabilities of ESR and CRP to determine the presence of infection in patients undergoing revision surgery.

Results

The rate of PJI for all identified MoM THAs was 3.5% (41/1,171), with a mean follow-up of 10.9 years (2.0 to 20.4). Of the patients included in the final cohort, 8.2% (27/328) had PJI, with a mean follow-up of 12.2 years (2.3 to 20.4). Among this cohort, 31.1% (102/328) had a history of pseudotumour. The rate of PJI in these patients was 14.7% (15/102), which was greater than those without pseudotumour, 5.3% (12/226) (p = 0.008). Additionally, logistic regression analysis showed an association between history of pseudotumour and PJI (odds ratio 4.36 (95% confidence interval 1.77 to 11.3); p = 0.002). Optimal diagnostic cutoffs for PJI in patients with history of pseudotumour versus those without were 33.1 mm/hr and 24.5 mm/hr for ESR and 7.37 mg/dl and 1.88 mg/dl for CRP, respectively.

Conclusion

Patients with history of pseudotumour secondary to MoM THA had a higher likelihood of infection than those without. While suspicion of infection should be high for these patients, ESR and CRP cutoffs published by the European Bone and Joint Infection Society may not be appropriate for patients with a history of pseudotumour, as ESR and CRP levels suggestive of PJI are likely to be higher than for those without a pseudotumour. Additional investigation, such as aspiration, is highly recommended for these patients unless clinical suspicion and laboratory markers are low.

Malseating of Modular Dual Mobility Liners: High Prevalence in Revision Total Hip Arthroplasty

BACKGROUND

Modular dual mobility (MDM) acetabular components have become increasingly more popular in total hip arthroplasty (THA). Uncertainty remains regarding liner malseating and its consequences after 5 to 10 years, especially in patients who undergo revision THA. The objective of this study was to analyze the prevalence of malseating and implant survivorship of patients who underwent revision THA using an MDM liner.

METHODS

We retrospectively identified patients who had a minimum 2-year follow-up and underwent revision THA using an MDM liner. Patient demographics, implant details, mortality, and all-cause revisions were recorded. Patients who had radiographic follow-up were assessed for malseating. Kaplan Meier survival was used to determine implant survivorship. We included 143 hips in 141 patients. Mean age was 70 years (35 - 93 years) and 86 patients (60.1%) were female.

RESULTS

Overall implant survival was 89.3% (95% Confidence Interval (CI) 0.843 - 0.946) at a mean follow-up of 6 years (range 2 to 10) years. There were eight patients excluded from malseating assessment. Upon radiological review, 15 liners (11.1%) were malseated. Survival for all-cause revision for patients with malseated liners was 80.0% (12/15, 95% CI 0.62 - 0.99, P= 0.15) versus 91.5% in patients who had non-malseated liners (110/120, 95% CI 0.86 - 0.96). There were no intraprosthetic dislocations and 3.5% of the patients were revised due to instability. No liners were revised due to malseating, and no patients who had malseated liners were revised due to instability.

CONCLUSIONS

Using MDM components in our cohort comprised of revision THA was associated with a high prevalence of malseating and an overall survival of 89.3% at a mean follow up of 6 years. Malseating does not appear to impact implant survival at a mean follow-up of 6 years.

Osteosarcoma Around a Ceramic-on-Ceramic Total Hip Arthroplasty

Sarcoma arising at the site of a total hip arthroplasty (THA) is uncommon. We present a case report of a patient diagnosed with an osteosarcoma around a ceramic-on-ceramic THA and a narrative literature review of sarcomas around THA. A search of PubMed MEDLINE was performed from inception. Our case report was included in the analysis. A total of 13 studies were included in the review. We report the first case of a sarcoma around a ceramic-on-ceramic hip implant. All cases in the literature reported poor outcomes with an average time from index THA to diagnosis of 9.3 ± 8.2 years. Sarcomas around THA are extremely rare. Despite the rarity of the diagnosis, osteosarcoma must be considered in the differential diagnosis when investigating a periprosthetic mass.

Imaging of total hip arthroplasty: Part I – Implant design, imaging techniques, and imaging of component wear and fracture

Despite being one of the most reliable procedures in orthopedic surgery, complications can occur after total hip arthroplasty, and radiology plays an essential role in their evaluation. This article will review the various types of hip arthroplasty and their normal appearances on imaging, followed by mechanisms and imaging appearances of component wear and fracture.

A Rare Case of Adverse Reaction to Metal Debris in a Ceramic-on-Ceramic Total Hip Replacement

Adverse Reaction to Metal Debris (ARMD) is one of the most frequent complications after Total Hip Replacement (THR) and often a cause of surgical revision. This is true especially for implants with Metal-on-Metal (MoM) and Large Diameter Heads (LDHs), which are frequently used to improve stability and reduce the risk of dislocation. However, ARMD is not exclusive to MoM replacement, as it can also occur in other implants such Ceramic-on-Ceramic (CoC), Metal-on-Polyethylene (MoP), and Ceramic-on-Polyethylene (CoP). In these non-MoM implants, ARMD is not caused by the tribo-corrosion between bearing surfaces but, rather, by the fretting at the interface between neck and stem of dissimilar metals. A case of a severe ARMD that happened to a 73-year-old female patient with CoC bearing THR at the right hip is presented in this case report. In this case, the ARMD was misdiagnosed for over a year, resulting in the development of a massive pseudotumor. The treatment of choice was a two-stage revision with the implant of a hip megaprosthesis. After more than 2 years of follow-up, complete recovery of hip Range of Motion (ROM) and normalization of chromium and cobalt levels in blood and urine were achieved. Despite the relatively short follow-up period, this can be considered a successful treatment of a major and misdiagnosed ARMD in a non-MoM hip replacement.

Hip Resurfacing: A Single Surgeon U.S. Series With Minimum Ten-Year Follow-up

BACKGROUND

Metal-on-metal hip resurfacing is an alternative to total hip arthroplasty (THA). The aim of this study was to determine implant survivorship, analyze patient-reported outcomes measures and to determine patient satisfaction for patients who underwent metal-on-metal hip resurfacing at a large US academic institution by a single surgeon with a minimum of 10-year follow-up.

METHODS

Patients who underwent hip resurfacing from September 2006 through November 2009 were included. Patient demographics and variables were collected from a prospectively maintained institutional database and patients completed an additional questionnaire with patient-reported outcomes measures.

RESULTS

A total of 350 patients (389 hips) out of 371 (433 hips) with a minimum 10-year follow-up were successfully contacted (94.3% follow-up). Mean age was 53 years, 258 were male (73%). 377 out of 389 hips (96.9%) did not require additional surgery. Gender was significantly related to implant survivorship (males 99.0%, females 90.9%; P < .001). 330 patients (369 hips, 94.8%) were satisfied with their surgery. Males had higher proportion of satisfaction scores (P = .02) and higher modified Harris Hip Score (odds ratio = 2.63 (1.39, 4.98), P = .003). Median modified Harris Hip Score score for non-revised hips was 84.0 [80.0; 86.0] versus those requiring revision, 81.5 [74.0; 83.0], (P = .009).

CONCLUSION

At a minimum 10-year follow-up, hip resurfacing, using an implant with a good track record, demonstrates 99.0% survivorship in male patients with an average age of 52 years. We believe that the continued use of metal-on-metal hip resurfacing arthroplasty in this population is justified by both positive patient reported outcomes and survivorship.

High Incidence of Mechanically Assisted Crevice Corrosion at 10 Years in Non-Cemented, Non-Recalled, Contemporary Total Hip Arthroplasties

BACKGROUND

One percent to 3% of contemporary non-cemented total hip arthroplasties (THAs) present with symptomatic mechanically assisted crevice corrosion (MACC). The incidence of this problem, however, as well as the rate of asymptomatic elevations in serum cobalt, is unknown.

METHODS

Cobalt and chromium levels were obtained in conjunction with radiographs at routine 10-year surveillance follow-up of THAs from a single manufacturer with a titanium stem, cobalt alloy femoral head, and cross-linked polyethylene countersurface.

RESULTS

Ten-year follow-up of patients with 162 consecutive THAs revealed that 17 patients with 18 hips had died of unrelated causes prior to metal ion testing. Two hips were revised for other reasons, and of the remaining 142 hips, 33 were in patients who were lost, leaving 109 hips (77% of those in alive patients and unrevised for other reasons and 67% of the entire cohort) for investigation. Sixty-three patients (58%) had a serum cobalt less than 1 ppb, and 35 (32%) a cobalt of ≥1 ppb, a cutoff consistent with MACC. Of the 32 hips with definite MACC, 15 of 32 (47%) patients were symptomatic, 16 of 30 (53%) patients had adverse local tissue reaction on magnetic resonance imaging, and 19 of 32 (59%) patients have undergone revision surgery for MACC to date.

CONCLUSION

At 10-year follow-up, a minimum of 22% (35/162) of hips had a cobalt level more than 1 ppb, consistent with MACC. Symptoms and adverse local tissue reactions are each present about one-half of the time, and 59% of those with documented MACC have undergone revision.

The incidence of adverse local tissue reaction due to head taper corrosion after total hip arthroplasty using V40 taper and 36 mm CoCr head

AIMS

Head-taper corrosion is a cause of failure in total hip arthroplasty (THA). Recent reports have described an increasing number of V40 taper failures with adverse local tissue reaction (ALTR). However, the real incidence of V40 taper damage and its cause remain unknown. The aim of this study was to evaluate the long-term incidence of ALTR in a consecutive series of THAs using a V40 taper and identify potentially related factors.

METHODS

Between January 2006 and June 2007, a total of 121 patients underwent THA using either an uncemented (Accolade I, made of Ti₁₂Mo₆Zr₂Fe; Stryker, USA) or a cemented (ABG II, made of cobalt-chrome-molybdenum (CoCrMo); Stryker) femoral component, both with a V40 taper (Stryker). Uncemented acetabular components (Trident; Stryker) with crosslinked polyethylene liners and CoCr femoral heads of 36 mm diameter were used in all patients. At a mean folllow-up of 10.8 years (SD 1.1), 94 patients (79%) were eligible for follow-up (six patients had already undergone a revision, 15 had died, and six were lost to follow-up). A total of 85 THAs in 80 patients (mean age 61 years (24 to 75); 47 (56%) were female) underwent clinical and radiological evaluation, including the measurement of whole blood levels of cobalt and chrome. Metal artifact reduction sequence MRI scans of the hip were performed in 71 patients.

RESULTS

A total of 20 ALTRs were identified on MRI, with an incidence of 26%. Patients with ALTR had significantly higher median Co levels compared with those without ALTR (2.96 μg/l (interquartile range (IQR) 1.35 to 4.98) vs 1.44 μg/l (IQR 0.79 to 2.5); p = 0.019). Radiological evidence of osteolysis was also significantly associated with ALTR (p = 0.014). Median Cr levels were not significantly higher in those with ALTR compared with those without one (0.97 μg/l (IQR 0.72 to 1.9) v 0.67 μg/l (IQR 0.5 to 1.19; p = 0.080). BMI, sex, age, type of femoral component, head length, the inclination of the acetabular component, and heterotopic ossification formation showed no significant relationship with ALTR.

CONCLUSION

Due to the high incidence of local ALTR in our cohort after more than ten years postoperatively, we recommend regular follow-up investigation even in asymptomatic patients with V40 taper and metal heads. As cobalt levels correlate with ALTR occurrence, routine metal ion screening and consecutive MRI investigation upon elevation could be discussed. Cite this article: Bone Joint J 2022;104-B(7):852-858.

Hip resurfacing arthroplasty in young patients: international high-volume centres' report on the outcome of 11,382 metal-on-metal hip resurfacing arthroplasties in patients ⩽50 years at surgery

BACKGROUND

Total hip arthroplasty (THA) in patients younger than 50 years poses significant challenges including postoperative limitations of activity and higher failure rates. Sub-par outcomes of hip resurfacing arthroplasty (HRA) in registries remain controversial due to multiple confounders. Favourable HRA results in some studies are often regarded as irreproducible. The aim of this study is to analyse HRA outcomes in a large international cohort.

PATIENTS AND METHODS

We compiled a database of 11,382 HRA patients ⩽50 years from an international group of 27 experienced HRA centres from 13 countries. 18 different metal-on-metal (MoM) HRA designs were included with a mean follow-up of 7.6 years. Outcomes were implant survivorship, revision rates, causes for revision, clinical scores and metal ion levels. Outcomes were compared between genders, sizes, implant types and pre-operative diagnoses.

RESULTS

Overall cumulative Kaplan-Meier survivorship was 88.9% at 22 years (95% CI: 88.3-89.5%). 2 HRA designs (DePuy Articular Surface Replacement (ASR), and Corin Cormet Hip Resurfacing System (CORMET)) led to inferior results while all others yielded similar survivorships. Excluding ASR and CORMET, implant survivorship in 11,063 cases was 95% at 10 years and 90% at 22 years. In men, implant survivorship was excellent: 99% at 10 years and 92.5% at 21 years. In females, implant survivorship was 90% at 10 years and 81.3% at 22 years. The overall revision rate was 3.6% with most common reasons for revision being implant loosening and adverse local tissue reactions. The best survivorship was found in patients with osteoarthritis (95% CI, 92.1-93.3% at 22 years), the poorest was among dysplastic hips (78.3%; 95% CI, 76.5-80.1% at 20 years, p < 0.001).

CONCLUSIONS

Comparable revision rates demonstrated here may mitigate some concerns for safety and longevity of MoM HRA implants. Higher demands for activity and functionality in younger patients make HRA a potential alternative to THA.

Median 10-year whole blood metal ion levels and clinical outcome of ReCap-M2a-Magnum metal-on-metal total hip arthroplasty

BACKGROUND AND PURPOSE

We have previously reported that the whole blood (WB) chromium (Cr) and cobalt (Co) ion levels decrease in the short term after ReCap-M2a-Magnum large-diameter head (LDH) metal-on-metal (MoM) total hip arthroplasty (THA). This study reports long-term metal ion levels and clinical outcomes after ReCap-Magnum THA.

PATIENTS AND METHODS

ReCap-M2a-Magnum LDH THA was used in 1,450 patients in our hospital district from 2005 to 2012. Median follow-up time was 10 years. 991 patients had 2 or more metal ion measurements. The median measurement interval was 4 years. Individual metal ion change was assessed using logarithmic metal ion values in a random coefficient model. Kaplan-Meier survival estimates were calculated for revision surgery for any reason for revision, and separately for metal-related adverse events (metal ions above safe upper limit [SUL], revision due to ARMD, or pseudotumor).

RESULTS

Geometric mean of Cr decreased from 1.8 ppb (geometric standard deviation [GSD] 1.8) to 1.0 ppb (GSD 2.8, p < 0.001). The Co levels decreased from 1.7 ppb (GSD 2.4) to 1.4 ppb (GSD 2.8, p < 0.001). The hip-specific survival was 85% for revision due to any reason at 14 years and the hip-specific survival for any metal-related adverse event was 69% at 14 years.

INTERPRETATION

WB Cr and Co levels continued to decrease in the long-term follow-up of ReCap-M2a-Magnum THA patients. The amount of metal-related adverse events was rather high, but revision surgery was seldom required. We suggest that after 10 years from the implantation a 5-year measurement interval may be sufficient for asymptomatic ReCap-M2a-Magnum patients.

Adverse local tissue reaction after ceramic-on-ceramic total hip arthroplasty

We report a rare case of symptomatic adverse local tissue reaction in a patient with a ceramic-on-ceramic total hip bearing surface and review the literature. Probably, ceramic wear debris is not entirely inert and may lead to adverse local tissue reactions.

Long-term blood metal ion levels and clinical outcome after Birmingham hip arthroplasty

BACKGROUND AND OBJECTIVE

Our aim was to assess long-term metal ion level changes and clinical outcome in patients with a Birmingham hip arthroplasty.

METHODS

For the purpose of this study, we identified all BHR hip resurfacing arthroplasty (HRA) and total hip arthroplasty (THA) operations performed in Turku University Hospital. A random coefficient model was used to compare the change between the first and last metal ion measurement. A Kaplan-Meier estimator was used to assess the survivorship of the BHR HRA and BHR THA with metal related adverse events (pseudotumor, elevated metal ions above the safe upper limit, revision due to metallosis), or revision due to any reason as endpoints with 95% confidence intervals (CIs).

RESULTS

BHR HRA was used in 274 hips (233 patients). In addition, we identified 38 BHR-Synergy THAs (38 patients). Operations were performed between 2003 and 2010. Median follow-up time was 14 years for BHR HRA (range: 0.6-17) and 11 years for BHR THA (range: 4.7-13). In the BHR HRA group, geometric means of Cr and Co levels decreased from 2.1 to 1.6 ppb and 2.4 to 1.5 ppb, respectively, during a 3.0-year measurement interval. Metal ion levels in the BHR THA group did not show notable increase. The survivorship of BHR HRA was 66% in 16 years and 34% for BHR THA at 12 years for any metal-related adverse event.

CONCLUSIONS

Patients with a Birmingham hip device do not seem to benefit from frequent repeated metal ion measurements. The amount of patients with metal-related adverse events was relatively high, but many of them did not require surgery.

Repeated metal ion measurements and long-term outcome of Durom/MMC total hip arthroplasty

Background and purpose - Data regarding long-term behavior of metal ion levels in metal-on-metal total hip arthroplasty (MoM THA) patients is scarce. Therefore, we assessed whether there is any change in whole blood (WB) chromium (Cr), and cobalt (Co) ion measurements in Durom and MMC MoM THA patients over time. The secondary aim was to report the clinical outcomes using these devices in a single district. Patients and methods - Durom and MMC cups were used in 249 MoM THAs from 2005 to 2011 in our district. Median follow-up time was 12 years for Durom THA (interquartile range [IQR] = 3) and 9 years for MMC THA (IQR = 1). A random coefficient model was used to compare individual differences in repeated WB Cr and Co ion measurements. The Kaplan-Meier estimator was used to analyze implant survival with any reason for revision as the endpoint. Results - Geometric means of Cr in Durom THA and MMC THA patients decreased from 2.2 ppb (geometric standard deviation [SD] = 1.9) to 1.5 ppb (geometric SD = 2.5, p< 0.001) and from 1.8 ppb (geometric SD = 1.8) to 1.1 ppb (geometric SD = 2.8, p = 0.01) respectively. The geometric means of Co values remained unchanged. The 10-year survival of Durom THA was 82%, and that of MMC THA 89% for any revision reason as endpoint. Interpretation - WB Cr levels decreased over time, and Co levels remained unchanged at long-term follow-up. Despite this we recommend continuing the follow-up of these devices due to relatively low implant survival.

Adverse Local Tissue Reactions are Common in Asymptomatic Individuals After Hip Resurfacing Arthroplasty: Interim Report from a Prospective Longitudinal Study

BACKGROUND

The evaluation of the natural history prevalence of adverse local tissue reactions (ALTRs) using MRI has focused only on metal-on-metal (MoM) bearing surfaces without comparison to nonMoM bearing surfaces.

QUESTIONS/PURPOSES

To determine (1) the longitudinal changes and differences in blood metal ion levels in patients with hip resurfacing arthroplasty (HRA), ceramic-on-ceramic (CoC) THA, and metal-on-polyethylene (MoP) THA compared with those undergoing ceramic-on-polyethylene (CoP) THA; (2) how the longitudinal change of synovial reaction classification in patients with HRA, CoC THA, and MoP THA compares with those undergoing CoP THA, and whether there is an association between the presence of an ALTR or metallosis on MRI with corresponding patient-reported outcomes, or the presence of capsular dehiscence; and (3) differences in blood metal ion levels between patients undergoing HRA with an ALTR or metallosis on MRI and those with HRA without these conditions.

METHODS

Between March 2014 and February 2019, 22,723 patients underwent primary HRA and THA at one center. Patients received an HRA based on their desired athletic level after surgery and the presence of normal acetabular and proximal femoral bone morphology without osteopenia or osteoporosis. Two percent (342 of 22,723) of patients were contacted to participate, and 71% (243 of 342 hips in 206 patients) were enrolled for analysis at baseline. The patients underwent arthroplasty for degenerative joint disease, and 25 patients withdrew over the course of the study. We included patients who were more than 1 year postarthroplasty. All participants had an MRI examination and blood serum ion testing and completed a Hip Disability and Osteoarthritis Outcome Score survey annually for four years (baseline, year 1, year 2, year 3). Morphologic and susceptibility-reduced MR images were evaluated by a single radiologist not involved in the care of patients for the presence and classification of synovitis (Gwet AC1: 0.65 to 0.97), synovial thickness, and volume (coefficient of repeatability: 1.8 cm3). Linear mixed-effects models were used to compare the mean synovial thickness, synovial volume, and Hip Disability and Osteoarthritis Outcome Score subscales between bearing surfaces at each timepoint and within each bearing surface over time. Marginal Cox proportional hazards models were used to compare the time to and the risk of developing ALTR only, metallosis only, and ALTR or metallosis between bearing surfaces. All models were adjusted for age, sex, BMI, and length of implantation based on known confounders for hip arthroplasty. Adjustment for multiple comparisons was performed using the Dunnett-Hsu method.

RESULTS

Patients with unilateral HRA had higher cobalt and chromium serum ion levels (baseline: 1.8 ± 0.8 ppb, year 1: 2.0 ± 1.5 ppb, year 2: 2.1 ± 1.2 ppb, year 3: 1.6 ± 0.7 ppb) than those with unilateral CoP bearings (baseline: 0.0 ± 0.1 ppb, year 1: 0.1 ± 0.3 ppb, year 2: 0.0 ± 0.2 ppb, year 3: 0.0 ± 0.0 ppb) at all timepoints (p < 0.001 for each time point). More patients who received an HRA developed ALTR or metallosis on MRI than did patients with CoP bearings (hazard ratio 4.8 [95% confidence interval 1.2 to 18.4]; p = 0.02). There was no association between the longitudinal change of synovial reaction to ALTR or metallosis on MRI with patient-reported outcomes. In addition, there was no association between the presence of dehiscence at baseline and the subsequent development of ALTR or metallosis, as seen on MRI. There were elevated cobalt (4.7 ± 3.5 ppb) and chromium (4.7 ± 2.6 ppb) serum levels in patients with unilateral HRA who had an ALTR or metallosis present on MRI at year 1 compared with patients without an ALTR or metallosis on MRI (cobalt: 1.8 ± 1.0 ppb, mean difference 4.7 ppb [95% CI 3.3 to 6.0]; p < 0.001; chromium: 2.3 ± 0.5 ppb, mean difference 3.6 ppb [95% CI 2.2 to 5.0]; p < 0.001) as well as for chromium at year 3 (3.9 ± 2.4 ppb versus 2.2 ± 1.1 ppb, mean difference 1.3 ppb [95% CI 0.3 to 2.4]; p = 0.01).

CONCLUSION

We found a higher proportion of ALTR or metallosis on MRI in patients with HRA compared with patients with CoP, even when patient self-assessed symptomatology of those with an ALTR or metallosis on MRI was not different than the absence of these features. MRI detected ALTRs in high-function patients, emphasizing that an annual clinical assessment dependent on survey or blood ion testing alone may not detect soft tissue complications. The results of this study are in line with prior consensus recommendations of using MRI as part of a routine follow-up protocol for this patient population.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Magnetic Resonance Imaging Around Metal at 1.5 Tesla: Techniques From Basic to Advanced and Clinical Impact

ABSTRACT

During the last decade, metal artifact reduction in magnetic resonance imaging (MRI) has been an area of intensive research and substantial improvement. The demand for an excellent diagnostic MRI scan quality of tissues around metal implants is closely linked to the steadily increasing number of joint arthroplasty (especially knee and hip arthroplasties) and spinal stabilization procedures. Its unmatched soft tissue contrast and cross-sectional nature make MRI a valuable tool in early detection of frequently encountered postoperative complications, such as periprosthetic infection, material wear-induced synovitis, osteolysis, or damage of the soft tissues. However, metal-induced artifacts remain a constant challenge. Successful artifact reduction plays an important role in the diagnostic workup of patients with painful/dysfunctional arthroplasties and helps to improve patient outcome. The artifact severity depends both on the implant and the acquisition technique. The implant's material, in particular its magnetic susceptibility and electrical conductivity, its size, geometry, and orientation in the MRI magnet are critical. On the acquisition side, the magnetic field strength, the employed imaging pulse sequence, and several acquisition parameters can be optimized. As a rule of thumb, the choice of a 1.5-T over a 3.0-T magnet, a fast spin-echo sequence over a spin-echo or gradient-echo sequence, a high receive bandwidth, a small voxel size, and short tau inversion recovery-based fat suppression can mitigate the impact of metal artifacts on diagnostic image quality. However, successful imaging of large orthopedic implants (eg, arthroplasties) often requires further optimized artifact reduction methods, such as slice encoding for metal artifact correction or multiacquisition variable-resonance image combination. With these tools, MRI at 1.5 T is now widely considered the modality of choice for the clinical evaluation of patients with metal implants.

Cobalt Levels and Pseudotumor Characteristics Vary due to Metal Ion Source: Modular Femoral Neck vs Metal-on-Metal Articulations

BACKGROUND

This study examines cobalt levels and pseudotumor characteristics in a non-recalled modular femoral prosthesis. We sought to determine relationships between serum cobalt levels and pseudotumors following modular and metal-on-metal (MoM) total hip arthroplasty (THA), the location and size of pseudotumors, and changes to pseudotumor grade over time.

METHODS

We retrospectively evaluated a cohort of 190 primary THAs implanted with a dual-modular femoral stem by one surgeon from 2005 to 2013. One hundred seventeen THAs used a cobalt-chromium modular neck (CoCrMN) component and non-MoM articulation, 63 THAs had a titanium neck component and MoM articulation, and 10 had a titanium neck component and polyethylene liner. Serum ion levels were recorded for all patients. Pseudotumor grade and location were measured by musculoskeletal-trained radiologists.

RESULTS

Cobalt levels did not correlate to time after index arthroplasty. In the CoCrMN group, cobalt levels were elevated in 11 of 19 (57.9%) patients with pseudotumor compared to 14 of 19 (73.7%) in the MoM group. Pseudotumors were more often located lateral to the hip joint in the CoCrMN group compared to anteromedial following MoM arthroplasty. In CoCrMN THAs, pseudotumors were visualized in 12 of 51 (23.5%) initial MARS MRIs within 40 months compared to 5 of 66 (7.6%) performed later (P = .02).

CONCLUSION

Pseudotumor characteristics differ between patients with CoCrMN designs vs those with an MoM articulation. Normal serum cobalt levels did not exclude the presence of a pseudotumor and routine MARS MRI should be included in follow-up of patients with this CoCrMN prostheses.

Fluorodeoxyglucose Positron-Emission Tomography/Computed Tomography and Magnetic Resonance Imaging for Adverse Local Tissue Reactions near Metal Implants after Total Hip Arthroplasty: A Preliminary Report

Background

Plain computed tomography (CT) and magnetic resonance imaging (MRI) are useful for diagnosing adverse local tissue reactions after metal-on-metal total hip arthroplasty (THA), but metal artifacts can hamper radiological assessments near the implants. We sought to clarify the usefulness of 18F-fluorodeoxyglucose positron-emission tomography (18F-FDG-PET) CT and MRI in the periprosthetic region, which is difficult to assess after THA due to metal artifacts.

Methods

We performed preoperative 18F-FDG-PET/CT and 18F-FDG-PET/MRI, as well as plain CT and MRI, in 11 metal-on-metal THA patients who underwent revision surgery.

Results

Most patients showed high FDG uptake in the metal artifact areas and pseudotumors in the 18-F-FDG-PET/CT and 18-F-FDG-PET/MRI scans. Intraoperative intra-articular macroscopic and histopathological intra-articular granulation tissue findings were suggestive of adverse local tissue reaction.

Conclusions

The enhanced uptake in the metal artifact areas seemed to reflect adverse local tissue reaction. Therefore, 18F-FDG-PET/CT and 18-F-FDG-PET/MRI can be useful for the auxiliary diagnosis of adverse local tissue reactions after metal-on-metal THA.

Pseudotumors in Small-Head Metal-on-Metal Total Hip Arthroplasties at a Minimum Follow-Up of 20 Years

BACKGROUND

Metal-on-metal (MOM) surfaces in total hip arthroplasty (THA) have been used widely. Serum cobalt and chromium levels have been the standard investigation for follow-up examinations, but magnetic resonance imaging (MRI) with metal artifact reducing sequences has shown good results in detecting pseudotumors. The aim of this study is to survey a significant correlation among MRI findings, serum metal levels, and clinical scores in patients with small-head MOM implants and if serum cobalt and chromium levels are sufficient in detecting patients with pseudotumors in the long-term follow-up.

METHODS

At a minimum follow-up of 20 years, 26 patients (29 THAs) of the original 98 patients (105 THAs) included in this study between November 1992 and May 1994 were available for follow-up examination. Clinical scores, serum metal ion levels, and MRIs were obtained.

RESULTS

We found mean serum cobalt levels of 1.87 μg/L (±3.44) and chromium levels of 2.23 μg/L (±2.96) and very good clinical and functional results (mean Harris Hip Score 88.6) in the long-term follow-up. Pseudotumors were detected in MRIs of 21 hips. There were no significant differences between patients with or without pseudotumors regarding serum metal levels and the correlation for clinical outcome scores, demographic data, and cup inclination. The cumulative rate of survival was still at 91.4% at 22.8 years.

CONCLUSION

This study presents the first published data on small-head MOM hips, comparing metal ion levels, pseudotumors, clinical, and radiological results in a follow-up period of more than 20 years and reveals that serum metal levels are not significantly higher in patients with pseudotumors.

LEVEL OF EVIDENCE

Therapeutic Level III.

Clinical Feasibility of Multi-Acquisition Variable-Resonance Image Combination-Based T2 Mapping near Hip Arthroplasty

Background: Hip arthroplasty is increasingly prevalent, and early detection of complications can improve outcomes. Quantitative magnetic resonance imaging (qMRI) methods using multi-acquisition variable-resonance image combination (MAVRIC) may allow for the assessment of soft tissues in close proximity to hip arthroplasty devices. Question/Purposes: We sought to determine the clinical feasibility of MAVRIC-based T2 mapping as a qMRI approach for assessing synovial reactions in patients with a hip arthroplasty device. We hypothesized that there would be differences in T2 metrics by synovial type, clinical impression, and clinical findings related to synovitis. Methods: We conducted a cross-sectional study of 141 subjects with 171 hip arthroplasties with greater than 1 year post-implantation. We enrolled subjects who had had a primary total hip arthroplasty or hip resurfacing arthroplasty between May 2019 and March 2020, excluding those with a revision hip arthroplasty and those with standard safety contraindications for receiving an MRI. Institutional standard 2D fast spin echo (FSE), short-tau inversion recovery (STIR), and susceptibility-reduced MAVRIC morphological MR images were acquired for each hip and followed by a dual-echo acquisition MAVRIC T2 mapping sequence. Results: While 131 subjects (81%) were classified as having a "normal" synovial reaction, significantly longer T2 values were found for fluid synovial reactions compared with mixed reactions. In addition, subjects with synovial dehiscence and decompression present had T2 prolongation. Larger synovial volumes were found in subjects with low-signal intensity deposits. Conclusions: MAVRIC-based T2 mapping is clinically feasible and there are significant quantitative differences based on type of synovial reaction. Patients undergoing hip arthroscopy revision surgery will warrant comparison of T2 values with direct histologic assessment of a tissue sample obtained intraoperatively. The approach used in this study may be used for a quantitative evaluation and monitoring of soft tissues around metal implants.

The contribution of the histopathological examination to the diagnosis of adverse local tissue reactions in arthroplasty

The histopathological examination of the periprosthetic soft tissue and bone has contributed to the identification and description of the morphological features of adverse local tissue reactions (ALTR)/adverse reactions to metallic debris (ARMD). The need of a uniform vocabulary for all disciplines involved in the diagnosis and management of ALTR/ARMD and of clarification of the parameters used in the semi-quantitative scoring systems for their classification has been considered a pre-requisite for a meaningful interdisciplinary evaluation.

This review of key terms used for ALTR/ARMD has resulted in the following outcomes: (a) pseudotumor is a descriptive term for ALTR/ARMD, classifiable in two main types according to its cellular composition defining its clinical course; (b) the substitution of the term metallosis with presence of metallic wear debris, since it cannot be used as a category of implant failure or histological diagnosis; (c) the term aseptic lymphocytic-dominated vasculitis- associated lesion (ALVAL) should be replaced due to the absence of a vasculitis with ALLTR/ALRMD for lymphocytic-predominant and AMLTR/AMRMD for macrophage-predominant reaction.

This review of the histopathological classifications of ALTR/ARMD has resulted in the following outcomes: (a) distinction between cell death and tissue necrosis; (b) the association of corrosion metallic debris with adverse local lymphocytic reaction and tissue necrosis; (c) the importance of cell and particle debris for the viscosity and density of the lubricating synovial fluid; (d) a consensus classification of lymphocytic infiltrate in soft tissue and bone marrow; (e) evaluation of the macrophage infiltrate in soft tissues and bone marrow; (f) classification of macrophage induced osteolysis/aseptic loosening as a delayed type of ALTR/ARMD; (g) macrophage motility and migration as possible driving factor for osteolysis; (h) usefulness of the histopathological examination for the natural history of the adverse reactions, radiological correlation, post-marketing surveillance, and implant registries.

The review of key terms used for the description and histopathological classification of ALTR/ARMD has resulted in a comprehensive, new standard for all disciplines involved in their diagnosis, clinical management, and long-term clinical follow-up.

Cite this article: EFORT Open Rev 2021;6:399-419. DOI: 10.1302/2058-5241.6.210013

Haemorrhagic Pseudotumour Following Metal-on-Metal Hip Replacement

We present a unique report of a spontaneous haemorrhage into a pseudotumour five years following revision surgery for failed metal-on-metal hip arthroplasty. The patient sustained no trauma, was not taking anticoagulants and had no bleeding disorder. Rapid progression in the size of the pseudotumour caused significant symptoms and functional impairment. Surgical excision was recommended by a national specialist centre, but with conservative management, significant regression of the pseudotumour was noted, with complete resolution of symptoms. This case is the first report of haemorrhage into a pseudotumour, which is an important differential and can be managed non-operatively.

Inflammatory responses to metal oxide ceramic nanopowders

Ceramic orthopaedic implants are increasingly popular due to the need for robust total joint replacement implants that have a high success rate long-term and do not induce biological responses in patients. This study was designed to investigate the biological effects of ceramic nanopowders containing aluminium oxide or zirconium oxide to activate the human macrophage THP-1 cell line. In vitro investigation of pro-inflammatory gene expression and chemokine secretion was performed studied using RT-qPCR and ELISA, respectively. TLR4 inhibition, using a small-molecule inhibitor, was used to determine whether ceramic-mediated inflammation occurs in a similar manner to that of metals such as cobalt. THP-1 macrophages were primed with ceramics or LPS and then treated with ATP or ceramics, respectively, to determine whether these nanopowders are involved in the priming or activation of the NLRP3 inflammasome through IL-1β secretion. Cells treated with ceramics significantly increased pro-inflammatory gene expression and protein secretion which was attenuated through TLR4 blockade. Addition of ATP to cells following ceramic treatment significantly increased IL-1β secretion. Therefore, we identify the ability of ceramic metal oxides to cause a pro-inflammatory phenotype in THP-1 macrophages and propose the mechanism by which this occurs is primarily via the TLR4 pathway which contributes to inflammasome signalling.

Progression of adverse local tissue reaction in ASR metal-on-metal hip arthroplasty: a longitudinal MARS-MRI study at mid- to long-term

BACKGROUND

Despite the large number of studies assessing adverse local tissue reaction (ALTR) in metal-on-metal (MoM) hip implants, there is still a lack of knowledge about the natural progression of ALTR. The aims of this study were to describe the natural course of changes in ALTR at mid- to long-term follow-up for patients treated with metal-on-metal hip arthroplasty and to determine possible risk factors associated with change in ALTR.

METHODS

A total of 158 patients (158 hips), 109 MoM hip resurfacing arthroplasties (HRAs) and 49 MoM total hip arthroplasties (THAs), with 2 clinical follow-ups including MARS-MRIs were included. The mean time from index operation to the first visit was 7.6 years (range 3.4-11.4 years), and the mean time between the 2 visits was 1.0 year (range 0.7-1.6 years).

RESULTS

The proportion of patients with moderate or severe ALTR did not increase significantly between the first and second visit for the MoM HRA group (14.7-15.6%; p = 0.850) or the MoM THA group (32.7-36.7%; p = 0.671). 8 (7.3%) HRA patients and 9 (18.4%) THA patients progressed in ALTR grade. None of the collected clinical variables was sensitive or specific in identifying patients with ALTR progression.

CONCLUSIONS

Although ALTR prevalence was high in our cohort, clinically significant ALTR progression was rare. We were unable to find any predictors associated with ALTR change. This indicates that MARS-MRI remains a valuable tool in the follow-up of patients treated with MoM hip devices in identifying patients who may need revision surgery.

Predictive Factors for Revision and Survivorship Analysis of a Prevalent 36-mm Metal-on-Metal Total Hip Replacement System: A Large Single-Center Retrospective Cohort Study

BACKGROUND

To our knowledge, this is the largest single-center cohort of the 36-mm Corail-Pinnacle metal-on-metal total hip replacements system, aiming to determine 10-year survivorship and identify predictors of revision. We further assessed year of implantation given reports of manufacturing variations affecting shells made after 2006 predisposing these components to increasing wear.

METHODS

All Corail-Pinnacle 36-mm metal-on-metal hips implanted in a single center (2005-2012). The effect of patient and implant-related variables, and year of implantation on revision risk was assessed using Kaplan-Meier, Cox regression, and interrupted time series analysis.

RESULTS

In total, 1212 metal-on-metal total hip replacements were implanted with a 10-year survival rate of 83.4% (95% confidence interval [CI] = 81.3-85.5). Mean follow-up duration was 7.3 years with 61% of patients reaching a minimum of 7 years of follow-up. One hundred nineteen patients required revision surgery (9.8%). Univariate analysis identified female gender (hazard ratio [HR] = 1.608, CI = 1.093-2.364, P = .016), age at implantation (HR = 0.982, CI = 0.968-0.997, P = .019), smaller 50-mm to 54-mm cup diameter (HR = 1.527, CI = 1.026-2.274, P = .037), and high-offset stems (HR = 2.573, CI = 1.619-4.089, P < .001) as predictors of revision. Multivariate modeling confirmed female gender and high-offset stems as significant predictors of revision. For components implanted after 2007, the number of revisions showed no statistically significant step increase compared to pre-2007 implantation.

CONCLUSION

We observed a high 10-year failure rate (16.6%) with this implant, mostly due to adverse reaction to metal debris. Female gender and high femoral offset stems were significant predictors for all-cause revision. Year of implantation was not significantly associated with an increasing number of revisions from 2007 onwards, although further studies to validate the impact of manufacturing discrepancies are recommended.

Metal Artifact Reduction Sequence Magnetic Resonance Imaging Abnormalities in Asymptomatic Patients With a Ceramic-on-Ceramic Total Hip Replacement

BACKGROUND

Metal artifact reduction sequence (MARS) magnetic resonance imaging (MRI) has recently gained increased utilization as a screening modality in patients with a total hip arthroplasty (THA). Fluid collections have been documented in asymptomatic patients with various bearing surfaces. The purpose of this study is to determine the frequency and types of MARS MRI-documented abnormalities in asymptomatic patients with a ceramic-on-ceramic (CoC) THA.

METHODS

Thirty-seven patients (42 hips) with a minimum 2-year follow-up after THA with CoC THA implants were enrolled in this study. The inclusion criteria were the absence of hip pain and the availability of appropriate follow-up radiographs. All patients underwent a MARS MRI. Abnormalities were documented using a previously described method.

RESULTS

Fluid collections were observed in 8 (19%) asymptomatic hips in this cohort. Four of the 8 hips demonstrated intracapsular synovitis, and 3 of these hips had a thickened synovium. Extra-articular fluid collections with direct intra-articular communication were identified in 4 hips, with 2 of these hips demonstrating synovial thickening. No signs of osteolysis were noted on radiographs or the MARS MRI scans.

CONCLUSION

Asymptomatic fluid collections occur in patients after CoC THA similar to other bearing surfaces. We continue to follow these patients in an effort to determine the clinical significance and natural history of these findings.

LEVEL OF EVIDENCE

Diagnostic Level IV.

Midterm outcomes of total hip arthroplasty with a modular Birmingham head

INTRODUCTION

Birmingham Hip Resurfacing (BHR) implants may be combined with a conventional femoral stem to create a modular metal-on-metal total hip arthroplasty (BHR MoM THA). There is little outcome data regarding this construct. This study examines midterm outcomes of BHR MoM THA compared to oxidised zirconium total hip arthroplasty (THA).

METHODS

A retrospective institutional review identified all patients receiving BHR MoM THA between April 2005 and February 2011 and a matched control cohort of zirconium THA patients. Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Harris Hip Score (HHS), and SF-12 Health status scores were obtained. Revisions and complications were collected from clinical records. Radiographs were assessed for evidence of component malposition, loosening, osteolysis, or heterotopic ossification.

RESULTS

63 modular BHR MoM THA were identified in 61 patients (36 with BHR cups, 27 with R3 cups) and 63 zirconium THA in 58 matched controls. Mean follow-up was 58 months. 14 BHR MoM THA hips (22.2%) were revised (4 infections, 1 dislocation, 9 soft tissue reactions) compared to 3 (4.8%) zirconium THA (all infections). At latest follow-up, 18.4% of surviving BHR MoM THA hips were painful compared to 0.5% of zirconium THA controls (p < 0.001). WOMAC, HHS, and SF-12 did not differ significantly between surviving members of the 2 groups.

DISCUSSION

BHR MoM THA demonstrated a high revision rate, largely for adverse local soft tissue reaction and pain. Among those not revised, many reported some residual pain despite similar quality of life measures to those who received zirconium THA.

The Calpain Gene is Correlated With Metal-on-Metal Hip Replacement Failures

BACKGROUND

Metal-on-metal (MOM) total hip arthroplasty is associated with unacceptable failure rates secondary to metal ion reactions. Efforts to identify which patients will go on to failure have been limited; recently, there has been a suggestion for a potential genetic basis for the increased risk of revision in MOM hip replacements (MOMHRs). The purpose of this study is to determine whether certain immunologic genotypes are predictive of the need for revision in patients with MOM total hip implants.

METHODS

This is a case-control study of all patients undergoing primary MOMHR between September 2002 and January 2012 with a minimum of 5-year follow-up. Our investigational "case" cohort was comprised of patients who underwent revision for MOMHR for a reason other than infection. A single-nucleotide polymorphism (SNP) array analysis was performed to identify a potential genetic basis for failure.

RESULTS

Thirty-two patients (15 case and 17 control) were included in our analysis. All patients in the revision group had a chief complain of pain; revision patients were more likely to have a posterior approach (P = .01) and larger head size (P = .04) than nonrevision patients. No patient or implant characteristics were independently associated with revision in a multivariate analysis. Patients with SNP kgp9316441 were identified as having an increased odds of revision for MOM failure (P < .001).

CONCLUSION

This study identified an SNP, kgp9316441, encoding proteins associated with inflammation and macrophage activation. This SNP was associated with significantly increased odds of revision for MOMHR. Future studies are warranted to validate this gene target both in vitro and in vivo.

LEVEL OF EVIDENCE

III.

Is there a relation between clinical scores and serum ion levels after MoM-THA? One year results in 383 implants

Background and aim of the work:

Adverse reaction to metal debris is the major cause of the high revision rates of metal on metal hip implants with femoral head size ≥ 36mm. Health authorities recommend regular surveillance even for asymptomatic individuals. The main investigations used are Co+ and Cr+ serum levels, x-rays and, eventually, ultrasound and MARS-MRI. Clinic is also assessed. The aim of this study is to identify if there is a relation between ion levels and the clinical scores in order to evaluate the outcome and plan the correct management after this type of implant.

Methods:

383 subjects were included and divided in 3 groups (serum ion levels >, < and >60 µg/L). Co+, Cr+, HHS and OHS results of 1 year (2017) were analysed in order to show a correlation between ion levels and clinical scores.

Results:

Clinical scores were similar in group 1 and 2. Differences were observed comparing the group 1 and 2 with group 3 for both variables.

Discussion and Conclusions:

Surveillance algorithms have been introduced by health authorities. Nevertheless, the indication to revision surgery is not simple especially in those cases in which a discrepancy between clinic and investigations is present. In this study clinical scores seem to be less important than ion levels in the evaluation of outcomes and in order to plan the correct management in the majority of cases. Larger studies are needed to highlight the real importance of clinical scores in the decision making after these type of implants.

MARS MRI Characteristics of Adverse Local Tissue Reactions in Taper Corrosion of Metal-On-Polyethylene THA Differ From Metal-On-Metal THA

BACKGROUND

Metal artifact reduction sequence (MARS) magnetic resonance imaging (MRI) has been recommended as a cross-sectional imaging modality in clinical evaluation of adverse local tissue reactions (ALTRs) in metal-on-metal (MoM) patients and metal-on-polyethylene (MoP) patients with taper corrosion. The aim of the study was to compare MARS MRI characteristics of ALTR in MoM total hip arthroplasty (THA) with ALTR in MoP THA with modular taper corrosion.

METHODS

A total of 197 patients with ALTR were evaluated: 86 patients with MoM THA; 37 MoP patients with head-neck taper corrosion; and 74 MoP patients with neck-stem dual taper corrosion. MARS MRI scans were evaluated to identify location, size, type of ALTR (I-III), and associated ALTR synovitis (cystic, solid, and mixed).

RESULTS

MARS MRI characteristics of ALTR were significantly different between the MoM and MoP groups (P = .017). The MoP group demonstrated the highest proportion of thick-walled cystic masses type II (56.7% in head-neck taper corrosion MoP and 46.5% in dual taper corrosion MoP vs 28.7% in MoM), whereas the MoM group had the highest proportion of thin-walled cystic masses type I. MoM implants (96.8%) were significantly more likely to have ALTR in multiple locations compared with both MoP groups (P = .001).

CONCLUSION

This study demonstrates that MARS MRI characteristics of ALTR differ by bearing type with a significantly higher percentage of mixed type and solid type ALTR in the taper corrosion MoP THA compared with MoM THA. This information provides clinically useful information in evaluation of symptomatic MoP and MoM THA patients for ALTRs.

Retention of metals in periprosthetic tissues of patients with metal-on-metal total hip arthroplasty is reflected in the synovial fluid to blood cobalt transfer ratio in the presence of a pseudotumour

Background

Modern metal-on-metal (MOM) arthroplasties were performed for over a decade before alarming reports of adverse metal reactions dramatically reduced their use. Failures are seen more often with high-wearing implants, but also well-positioned components with more favourable wear patterns can cause problems. There are no specific clinical indicators that could help us to predict the prognosis of these implants. For this reason, we still need more information on the effect of underlying factors that contribute to this process.

Methods

In this prospective cohort study, we investigated how cup orientation and type of pseudotumour determined by the Hart classification effect the distribution of metals in blood, synovial fluid and tissues surrounding the metal-on-metal hip prosthesis in revision surgery patients. One thousand two hundred twenty-nine metal-on-metal hip patients were screened and of those, 60 patients that had a revision surgery due to adverse metal reaction were included. Whole blood, synovial fluid and synovial/pseudotumour tissue samples were analysed for metal ion concentrations (Co, Cr, Mo and Ti).

Results

The lowest metal concentrations were found when both cup anteversion and inclination were optimal, and the highest when both were suboptimal. Suboptimal anteversion alone raised Cr-ion concentrations more than suboptimal inclination. The concentrations of metals in blood, synovial fluid or synovial soft tissue were the same in patients with and without a pseudotumour, but the relative transfer percentage of cobalt from synovial fluid to blood was higher in patients with a pseudotumour.

Conclusions

The implant orientation alone does not explain the metal concentrations found in tissues or distribution of metals between different tissues. The accumulation of metals in periprosthetic soft tissues increase the total metal load, and in the presence of a pseudotumour this is reflected in the transfer ratio of Co from synovial fluid to the blood. The total metal load of the pseudotumour tissue should be defined in future studies to determine if this will provide new insights for clinical practice.

Short to mid-term outcome of total hip arthroplasty with cementless implants in patients younger than 25 years old

BACKGROUND

Total hip arthroplasty (THA) was once reserved for old patients with hip arthritis but has become more common in very young patients (≤25 years old) diagnosed with various joint disease that were not relieved with conservative treatment. The purpose of this study was to evaluate short to mid-term outcome of THA in patients younger than 25 years old.

METHOD

This retrospective study included 45 patients younger than 25 years (mean age 21.8 ± 2.14 years) who underwent THA. The surgical indications, implant selection, leg length discrepancy, medication history, radiographic outcome, survival and clinical results including the modified Harris hip score (mHHS) and SF-36 score were assessed.

RESULT

The mean follow-up period recorded for patients was 7.82 years (range 5-12 years). The most common diagnosis was avascular necrosis (37.7%) followed by ankylosing spondylitis (24.4%), developmental dysplasia of the hip (17.7%) and rheumatoid arthritis (8.8%). The preoperative leg length discrepancy (LLD), which ranged from 0.5-7 cm significantly improved after surgery ranging from 0-1 cm. The mean preoperative mHHS was 32.44 ± 18.90 compared with the postoperative score of 94.54 ± 5.81 (p < 0.001). The preoperative p-value of SF-36 was lower compared to the postoperative value in all subgroups of SF-36 (p < 0.001). At the latest follow-up there were no radiological signs of loosening and all the implants were classified as well-integrated.

CONCLUSION

At present total hip arthroplasty is considered to be safe and a good solution for young patients below 25 years suffering from end-stage joint disease; however, longer follow-up is required to evaluate the long-term function and outcome of the prosthesis in order to restore the normal lifestyle of the patients.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Pseudotumor in the Setting of Metal-on-Metal Total Hip Arthroplasty

Metal-on-metal (MoM) hip resurfacing/replacement is a highly discussed topic in arthropathy, and the impact of its complications is still being elucidated. We report the case of a patient who presented with severe stomach pain due to a symptomatic psoas fluid collection that was later shown to communicate with a MoM total hip prosthesis. A MoM pseudotumor presenting as persistent stomach pain due to an aseptic psoas fluid collection is a rare complication. The case may support an earlier diagnosis in at-risk patients, and it outlines a suggested workup and treatment plan.

Pseudotumor recurrence in a post-revision total hip arthroplasty with stem neck modularity: A case report

BACKGROUND

This unique presentation of hip swelling is only the seventh reported case of pseudotumor recurrence in a non-metal-on-metal total hip arthroplasty (THA) construct. The constellation of patient symptoms and laboratory findings contradict the expected elevated serum metal ion levels associated with the formation of pseudotumor. The presentation, lab trends, and imaging findings contribute to the growing base of knowledge surrounding the effects of corrosion in arthroplasty constructs with stem-neck modularity.

CASE SUMMARY

A 74-year-old man status post primary THA presented with left hip swelling and elevated serum metal ions five years after implantation of a modular stem-neck prosthesis. The swelling was diagnosed as pseudotumor based on laboratory trends and imaging findings and was treated with revision arthroplasty that completely resolved the initial hip swelling. The patient presented with recurrent hip swelling and recurrent pseudotumor findings on imaging in the same hip four months later. Non-operative management with ultrasound-guided hip aspiration resulted in symptom relief and resolution of the recurrent swelling. After one year of follow-up, the patient had no further recurrences of hip swelling.

CONCLUSION

This case of post-revision pseudotumor recurrence elucidates attributable patient, surgical, and implant factors with a discussion of diagnostics, management, and prognosis for patients with pseudotumor in non-metal-on-metal arthroplasty constructs.

Ultrasound-based decision making following metal-on-metal hip arthroplasty

BACKGROUND

Metal-on-Metal (MoM) total hip arthroplasty (THA) represents a very controversial procedure because of the possibility of postoperative adverse local tissue reaction (ALTR). This study investigates the reliability of the ultrasound scan as a diagnostic tool to quantify a clinically useful threshold in the level of periprosthetic fluid collection to suggest implant revision.

METHODS

This study includes 116 patients (123 implants) who received an Articular Surface Replacement XL (ASRTMXL, De Puy Synthes, USA) MoM THA. The study group included 56 males and 60 females with a mean age of 66.6 years (range, 15-86 years). All patients were clinically and radiologically annually evaluated (according to the Harris Hip Score) up to a mean follow-up of 7.5 years (min. 1.4 - max. 10.3 years) from the primary surgery: all patients underwent standard ultrasound evaluation of the affected hip and Cobalt/Chromium blood detection testing according to a custom-made diagnostic algorithm for MoM THA revision.

RESULTS

At final follow-up, 51 (43.1%) of 117 implants underwent revision after a mean of 6 years (1.79-9.26) from the primary ASR implant. The authors found a statistically significant correlation between Cr (p = 0.015) and Co (p = 0.009) blood values and different ultrasound grades. Statistical analysis showed a significant association between periprosthetic fluid collection and revision surgery (p < 0.0001) and the final revision risk was estimated to be 7 times greater in patients with ultrasound grade ≥ 2 (peri-prosthetic collection ≥ 20 mm).

CONCLUSIONS

This study confirms the reliability of ultrasound evaluation in detecting clinically significant peri-prosthetic joint effusions: a new diagnostic algorithm for MoM THA revision is here presented. Longer follow up studies are mandatory to better understand the potential advantages of this diagnostic protocol.

Revision total hip arthroplasty for metal-on-metal failure

Metal-on-metal (MoM) arthroplasty systems became popular in the early-2000s due to presumed advantages of improved wear characteristics and superior stability. However, subsequent reports of abnormal soft-tissue reactions to MoM implants and national registry data reporting high failure rates raised concerns. Early outcomes of revision total hip arthroplasty (THA) for adverse reaction to metal debris (ARMD) were poor, leading to development of surveillance programs and a trend towards early revision surgery. Patients with MoM arthroplasties require surveillance, comprehensive history and physical examination, imaging with ultrasound or magnetic resonance imaging (MRI), and laboratory evaluation including metal ion levels. Operative strategies for revision THA vary from exchange of modular components to extensive debridement and reconstruction with revision components. Surgeons should be aware of the increased risks of dislocation and infection following revision THA for ARMD. However, there is growing evidence that early revision surgery prior to extensive soft tissue destruction results in improved outcomes and decreased re-operation rates. It is estimated that >1 million MoM articulations have been implanted, with a large proportion still in situ. It is imperative to understand the aetiology, presentation, and management strategies for these patients to optimise their clinical outcomes.

Metal ion concentrations after metal-on-metal hip arthroplasty are not correlated with habitual physical activity levels

INTRODUCTION

Metal-on-metal (MoM) hip arthroplasties have shown high clinical failure rates with many patients at risk for a revision and under surveillance for high metal ion concentrations. Implant wear releasing such ions is assumed to be a function of use, i.e. the patient's physical activity. This study aimed to assess whether habitual physical activity levels of MoM patients are correlated with metal ion concentrations and are higher in patients with high (at risk) than in patients with low (safe) metal ion concentrations.

METHODS

A cohort study was conducted of patients with any type of MoM hip prosthesis. Metal ion concentrations were determined using ICP-MS. Habitual physical activity of subjects was measured in daily living using an acceleration-based activity monitor. Outcome consisted of quantitative and qualitative activity parameters.

RESULTS

In total, 62 patients were included. Mean age at surgery was 60.8 ± 9.3 years and follow-up was 6.3 ± 1.4 years. Cobalt concentrations were highly elevated overall (112.4 ± 137.9 nmol/L) and significantly more in bilateral (184.8 ± 106.5 nmol/L) than in unilateral cases (87.8 ± 139.4 nmol/L). No correlations were found between physical activity parameters and metal ion concentrations. Subgroup analysis of patients with low versus high cobalt concentration showed no significant differences in habitual physical activity.

DISCUSSION

No correlation was found between physical activity levels and metal ion concentrations. Implant use by normal habitual activities of daily living seems not to influence metal ion concentrations.

The 10-year outcomes of the ASR XL Acetabular System: a single-center experience from China

Background

The revision rate of articular surface replacement (ASR) implants continues to rise in China because of metal debris. However, there are few reports on the clinical results of ASR implants with prolonged follow-up time in China. This study investigated the clinical outcomes and the risk factors of revision surgery in patients with ASR implants.

Methods

In total, 74 patients (74 hips) who underwent primary total hip arthroplasty (THA) with ASR implants over the past 4 to 10 years were retrospectively analyzed. Relevant clinical, radiographic, and biochemical data were examined.

Results

The average follow-up time was 88.46 (range 23–114) months, and the ASR implants of 18 hips (24.3%) were revised. Patients who received revision surgery had worse joint function with significantly lower Harris Hip Score and Western Ontario and McMaster Universities index than non-revision patients (61.11 ± 6.68 vs 85.30 ± 9.16, p < 0.001; 61.00 ± 3.83 vs 79.04 ± 14.49, p < 0.001; respectively). Higher acetabular abduction angle and serum Co and Cr concentration were significantly relevant to worse joint function as measured by HSS (p = 0.018, 0.009, 0.043, respectively). ROC curve analysis was applied to categorize the optimal cutoff values of acetabular abduction angle and serum Cr and Co concentration for revision surgery, which were settled as 47.80°, 98.44 μg/L, and 6.95 μg/L, respectively. Overall survival of the prostheses with high acetabular abduction angle (> 47.80°, HR = 70.145, 95% CI 1.558–3158.213, p = 0.029), high serum Cr concentration (98.44 μg/L, HR = 58.956, 95% CI 1.294–2685.203, p = 0.036), and high serum Co concentration (> 6.95 μg/L, HR = 179.511, 95% CI 2.360–13656.941, p = 0.019) decreased significantly than the lower groups.

Conclusions

Evaluation of the DePuy ASR XL articulation demonstrated increased rates of revision following a longer follow-up period. High acetabular abduction angle and serum Cr and Co concentration correlated with worse clinical outcomes and high revision rate. Therefore, we advocate that patients with DePuy ASR XL implants be followed up more closely than those with other implants, especially with high acetabular abduction angle and serum Cr or Co concentration.

Host-specific factors affect the pathogenesis of adverse reaction to metal debris

Background

Adverse Reaction to Metal Debris (ARMD) is a major reason for revision surgeries in patients with metal-on-metal (MoM) hip replacements. Most failures are related to excessively wearing implant producing harmful metal debris (extrinsic factor). As ARMD may also occur in patients with low-wearing implants, it has been suggested that there are differences in host-specific intrinsic factors contributing to the development of ARMD. However, there are no studies that have directly assessed whether the development of ARMD is actually affected by these intrinsic factors.

Methods

We included all 29 patients (out of 33 patients) with sufficient data who had undergone bilateral revision of ASR MoM hips (58 hips) at our institution. Samples of the inflamed synovia and/or pseudotumour were obtained perioperatively and sent to histopathological analysis. Total wear volumes of the implants were assessed. Patients underwent MARS-MRI imaging of the hips preoperatively. Histological findings, imaging findings and total wear volumes between the hips of each patient were compared.

Results

The difference in wear volume between the hips was clinically and statistically significant (median difference 15.35 mm³, range 1 to 39 mm³, IQR 6 to 23 mm³) (p < 0.001). The median ratio of total wear volume between the hips was 2.0 (range 1.09 to 10.0, IQR 1.67 to 3.72). In majority of the histological features and in presence of pseudotumour, there were no differences between the left and right hip of each patient (p > 0.05 for all comparisons). These features included macrophage sheet thickness, perivascular lymphocyte cuff thickness, presence of plasma cells, presence of diffuse lymphocytic infiltration and presence of germinal centers.

Conclusions

Despite the significantly differing amounts of wear (extrinsic factor) seen between the sides, majority of the histological findings were similar in both hips and the presence of pseudotumour was symmetrical in most hips. As a direct consequence, it follows that there must be intrinsic factors which contribute to the symmetry of the findings, ie. the pathogenesis of ARMD, on individual level. This has been hypothesized in the literature but no studies have been conducted to confirm the hypothesis. Further, as the threshold of metal debris needed to develop ARMD appears to be largely variable based on the previous literature, it is likely that there are between-patient differences in these intrinsic factors, ie. the host response to metal debris is individual.

Electronic supplementary material

The online version of this article (10.1186/s12891-019-2578-0) contains supplementary material, which is available to authorized users.

Tuning the tribofilm nanostructures of polymer-on-metal joint replacements for simultaneously enhancing anti-wear performance and corrosion resistance

Total joint replacement is currently the most successful clinical treatment for improving the life quality of individuals afflicted with end-stage osteoarthritis of knee or hip joints. However, release of wear and corrosion products from the prostheses is a critical issue causing adverse physiological responses of local issues. β-SiC nanoparticles were dispersed into polyetheretherketone (PEEK) materials and their role in tribocorrosion performance of PEEK-steel joints exposed to simulated body fluid was investigated. It is demonstrated that β-SiC nanoparticles increase greatly the wear resistance of the PEEK materials, and meanwhile mitigate significantly corrosion of the steel counterpart. It is revealed that tribochemical reactions of β-SiC nanoparticles promoted formation of a robust tribofilm having complex structures providing protection and shielding effects. The present work proposes a strategy for developing high-performance polymer-on-metal joint replacement materials of enhanced lifespan and biocompatibility via tuning interface nanostructures. STATEMENT OF SIGNIFICANCE: Adverse tissue responses to metal wear and corrosion products from metal base implants remain a challenge to surgeons and patients. We demonstrated that leaching of metal ions and release of metallic debris are well decreased via tuning interface nanostructures of metal-polymer joint bearings by dispersing β-SiC nanoparticles into polyetheretherketone (PEEK). It is identified that the addition of β-SiC greatly improves the tribological performances of the PEEK materials and mitigated corrosion of the steel. Tribo-chemistry reactions of SiC induce the formation of complex structures which provide protection and shielding effects. Nanostructures of the tribofilm were also comprehensively investigated. These novel findings proposed a potential route for designing high performance metal-polymer joint replacement materials.

In vivo blood metal ion levels in patients after total shoulder arthroplasty

BACKGROUND

Products from metal wear have been identified as a potential cause of adverse local tissue reactions and implant failure in total hip arthroplasty. However, the role of metal ion exposure in patients after total shoulder replacement is unclear. The objective of the present study was to determine in vivo blood metal ion levels of cobalt, chromium, and titanium in patients after anatomic total shoulder arthroplasty (TSA) or reverse TSA.

METHODS

A consecutive series of patients after anatomic TSA or reverse TSA was evaluated retrospectively. After exclusion of patients with additional metal implants, 40 patients with unilateral anatomic TSA (n = 20) or reverse TSA (n = 20) were available for whole-blood metal ion analysis at a mean follow-up of 28 ± 9.6 months. Twenty-three healthy individuals without metal implants served as a control group.

RESULTS

Mean cobalt ion concentrations were 0.18 µg/L (range, 0.1-0.66 µg/L), 0.15 µg/L (range, 0.03-0.48 µg/L), and 0.11 µg/L (range, 0.03-0.19 µg/L), mean chromium ion levels were 0.48 µg/L (range, 0.17-2.41 µg/L), 0.31 µg/L (range, 0.09-1.26 µg/L), and 0.14 µg/L (range, 0.04-0.99 µg/L), and mean titanium ion concentrations were 1.31 µg/L (range, 0.75-4.52 µg/L), 0.84 µg/L (range, 0.1-1.64 µg/L), and 0.62 µg/L (range, 0.32-2.14 µg/L) in the reverse TSA group, the anatomic TSA group, and the control group, respectively.

CONCLUSIONS

TSA resulted in elevated metal ion levels compared with healthy controls, although overall metal ion concentrations measured in this study were relatively low. The role of local metal ion exposure in patients with total shoulder replacements should be further investigated.

Revisions of Modular Metal-on-metal THA Have a High Risk of Early Complications

BACKGROUND

The risk of early complications is high after monoblock acetabular metal-on-metal (MoM) THA revisions. However, there is a paucity of evidence regarding clinical complications after isolated head-liner exchange of modular MoM THA.

QUESTIONS/PURPOSES

The purposes of this study were (1) to describe the frequency of early complications after an isolated head-liner exchange revision of modular MoM THA; and (2) to determine whether patients who experienced complications or dislocation after head-liner exchanges had higher serum chromium (Cr) or cobalt (Co) ion levels than those who did not.

METHODS

A review of our institution's total joint registry retrospectively identified 53 patients who underwent 54 liner exchange revisions of a modular acetabular MoM THA. The study period was from April 2008 to April 2016 at a single tertiary care center. During this period, isolated head-liner exchanges (rather than more extensive revisions) were performed in patients if they did not have evidence of loosening of the acetabular or femoral components. Reasons for revision surgery included pain, mechanical symptoms, radiographic evidence of osteolysis, elevated serum metal ions, and MRI abnormalities with 40 of the 54 hips having pain or mechanical symptoms and 38 of 54 hips having multiple reasons for revision before surgery. Patients were excluded if they did not meet the minimum postrevision followup or had the modular liner exchange secondary to infection. All revisions were from a single manufacturer with one head-liner exchange of a MoM THA from another manufacturer excluded during the study period. The mean time from index MoM THA to modular exchange was 96 (SD ± 36) months. Because the focus of this study was early complications, we had a minimum 90-day followup duration for inclusion. Mean followup after revision was 15 months (SD ± 12); a total of 56% (30 of 54) had followup of at least 12 months' duration. Complications (dislocation, infection) and reoperations were obtained by chart review performed by individuals other than the treating physician(s). Serum metal ion levels were obtained before head-liner exchange. The median serum Cr and Co levels were 6 µg/L (range, 0-76 µg/L) and 12 µg/L (range, 0-163 µg/L), respectively.

RESULTS

Of the 54 revision THAs, 15 (28%) developed complications. Nine (17%) occurred within 90 days of the revision surgery and 11 (20%) resulted in reoperation. The most common complication was dislocation (12 of 54 [22%]) with recurrent dislocation noted in eight of these 12 patients. All patients with recurrent dislocation continued to dislocate and underwent repeat revision. Patients with dislocation had higher median serum Cr and Co ion levels than those without dislocation (Cr: 24 [range, 11-76] versus 4 [range, 0-70], p = 0.001 [95% confidence interval {CI}, 10-57]; Co: 41 [range, 6-163] versus 8 [range, 0-133], p = 0.016 [95% CI, 6-141]). Three (6%) of the 54 patients underwent repeat surgery for deep space infection.

CONCLUSIONS

Complications and reoperations are common after modular head-liner exchange in the setting of a failed MoM THA. Our study likely underestimates the frequency of complications and revisions because the followup period in this report was relatively short. Dislocation is the most common complication and elevated serum metal ion levels may be a predictor of dislocation. These findings are concerning and surgeons should be aware of the high complication risk associated with this procedure.

LEVEL OF EVIDENCE

Level IV, therapeutic study.