Risk factors for inflammatory pseudotumour formation following hip resurfacing

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.

Metal-on-Metal Hip Arthroplasty: A Comprehensive Review of the Current Literature

Metal-on-metal (MoM) total hip arthroplasty has been widely used since the end of the 20th century, although rates have now decreased due to concerns regarding adverse reactions and failure rates. The MoM implant has been replaced with other materials, such as ceramic-on-ceramic (CoC) and metal-on-polyethylene (MoP). This literature review looks at the past and present use of MoM prostheses to assess whether the turn away from MoM use is justified. Online literature searches were performed on PubMed, Ovid Medical Literature Analysis and Retrieval System Online (MEDLINE), and Web of Science online databases using the search terms "MoM and (ARMD and ALVAL)" (ARMD: adverse reaction to metal debris; ALVAL: aseptic lymphocyte-dominant vasculitis-associated lesion). A total of 64 relevant titles were included in the review. Although risk factors for adverse reactions and the causes of ARMD are generally agreed upon, more work is required to further understand the specific thresholds of blood metal ion levels that can be used to consistently identify ARMD and excessive metal wear-debris in patients who have not had their MoM implants revised. Metal-on-metal devices are not an acceptable option for total hip arthroplasties (THAs) in their current formulation due to the high rate and risk of ARMD. Some MoM hip resurfacing operations are appropriate for very carefully selected patients who are fully aware of the risks posed by the implant. It is recommended that device-specific thresholds for metal ion levels be developed to identify patients at risk of ARMD locally and systemically while using auxiliary tools to assist diagnosis, such as metal artefact reduction sequences (MARS)-MRI and hip scoring tools. Further work should investigate device-specific blood metal ion levels, the systemic effects of raised metal ion concentrations secondary to MoM arthroprosthetic wear, and the potential risks of ARMD caused by wear from tapered stems (including the implications this has for patients with CoC and MoP prostheses).

A Sarcoma Masquerading as a Pseudotumor After Total Hip Arthroplasty: A Case Report

CASE

There is an increasing emphasis on adverse reactions to metal debris around prosthetic hip implants. We present a case report of a patient with increasing pain around a previous total hip arthroplasty and magnetic resonance imaging findings consistent with a pseudotumor. Serum metal ion levels were not elevated and initial biopsy findings inconclusive. The patient was diagnosed with an extraskeletal chondrosarcoma after revision total hip arthroplasty and subsequently underwent external hemipelvectomy with negative margins.

CONCLUSION

This report highlights the importance of remaining vigilant for malignant sarcomas presenting as pseudotumors around hip replacements, particularly in the absence of abnormal metal ion levels or definitive biopsy results.

Birmingham Hip Resurfacing at 20 years

Aims

The Birmingham Hip Resurfacing (BHR) arthroplasty has been used as a surgical treatment of coxarthrosis since 1997. We present 20-year results of 234 consecutive BHRs performed in our unit.

Methods

Between 1999 and 2001, there were 217 patients: 142 males (65.4%), mean age 52 years (18 to 68) who had 234 implants (17 bilateral). They had patient-reported outcome measures collected, imaging (radiograph and ultrasound), and serum metal ion assessment. Survivorship analysis was performed using Kaplan-Meier estimates. Revision for any cause was considered as an endpoint for the analysis.

Results

Mean follow-up was 20.9 years (19.3 to 22.4). Registry data revealed that 19 hips (8.1%) had been revised and 26 patients (12%) had died from causes unrelated to the BHR. Among the remaining 189 hips, 61% were available for clinical follow-up at 20 years (n = 115) and 70% of patients had biochemical follow-up (n = 132). The cumulative implant survival rate at 20 years for male patients was 96.5% (95% confidence interval (CI) 93.5 to 99.6), and for female patients 87% (95% CI 79.7 to 94.9). The difference was statistically significant (p = 0.029). The mean Oxford Hip Score, Hip disability and Osteoarthritis Outcome Score, and Forgotten Joint Score were 45 (29 to 48), 89 (43 to 100), and 84 (19 to 100), respectively. The mean scores for each of the five domains of the EuroQol five-dimension three-level questionnaire were 1.2, 1.0, 1.2, 1.3, and 1.1, and mean overall score 82.6 (50 to 100). Ultrasound showed no pseudotumour. Mean cobalt and chromium levels were 32.1 nmol/l (1 to 374) and 45.5 nmol/l (9 to 408), respectively.

Conclusion

This study shows that BHRs provide excellent survivorship and functional outcomes in young male patients. At 20 years, soft-tissue imaging and serum metal ion studies suggest that a metal-on-metal resurfacing implant can be well tolerated in a group of young patients.

Rates of operative intervention for infection after synthetic or autologous cranioplasty: a National Readmissions Database analysis

OBJECTIVE

The aim of this study was to characterize the clinical utilization and associated charges of autologous bone flap (ABF) versus synthetic flap (SF) cranioplasty and to characterize the postoperative infection risk of SF versus ABF using the National Readmissions Database (NRD).

METHODS

The authors used the publicly available NRD to identify index hospitalizations from October 2015 to December 2018 involving elective ABF or SF cranioplasty after traumatic brain injury (TBI) or stroke. Subsequent readmissions were further characterized if patients underwent neurosurgical intervention for treatment of infection or suspected infection. Survey Cox proportional hazards models were used to assess risk of readmission.

RESULTS

An estimated 2295 SF and 2072 ABF cranioplasties were performed from October 2015 to December 2018 in the United States. While the total number of cranioplasty operations decreased during the study period, the proportion of cranioplasties utilizing SF increased (p < 0.001), particularly in male patients (p = 0.011) and those with TBI (vs stroke, p = 0.012). The median total hospital charge for SF cranioplasty was $31,200 more costly than ABF cranioplasty (p < 0.001). Of all first-time readmissions, 20% involved surgical treatment for infectious reasons. Overall, 122 SF patients (5.3%) underwent surgical treatment of infection compared with 70 ABF patients (3.4%) on readmission. After accounting for confounders using a multivariable Cox model, female patients (vs male, p = 0.003), those discharged nonroutinely (vs discharge to home or self-care, p < 0.001), and patients who underwent SF cranioplasty (vs ABF, p = 0.011) were more likely to be readmitted for reoperation. Patients undergoing cranioplasty during more recent years (e.g., 2018 vs 2015) were less likely to be readmitted for reoperation because of infection (p = 0.024).

CONCLUSIONS

SFs are increasingly replacing ABFs as the material of choice for cranioplasty, despite their association with increased hospital charges. Female sex, nonroutine discharge, and SF cranioplasty are associated with increased risk for reoperation after cranioplasty.

Revision Total Hip Arthroplasty for Aseptically Failed Metal-On-Metal Hip Resurfacing Arthroplasty

BACKGROUND

While common, studies assessing outcomes of failed metal-on-metal (MoM) resurfacings converted to total hip arthroplasties (THAs) are limited. We determined the outcomes following revision THA of aseptic MoM hip resurfacings.

METHODS

Between 2000 and 2019, we identified 52 revision THAs for failed MoM hip resurfacings through our total joint registry. Mean age was 55 years, 42% were women, and mean body mass index was 28 kg/m². Adverse local tissue response led to THA in 67% of the cases. The most common revision articulation was metal-on-cross-linked or ceramic-on-cross-linked polyethylene (71%). Median head size was 36 mm. The acetabular component was retained in 21% and 28% used dual-mobility constructs. The mean follow-up was 6 years (range, 2-12 years).

RESULTS

The 5-year survivorships free of any re-revision or reoperation were 89% and 85%, respectively. The primary cause of re-revision (6) was dislocation (4). The 5-year cumulative probability of dislocation was 19% and was 13% in those patients treated with dual-mobility constructs versus 22% in those treated with standard articulations (P = .58). No dislocations occurred in THAs with retained acetabular components and dual-mobility constructs versus a 5-year cumulative probability of dislocation of 25% in those with revised acetabular components and standard articulations (P = .24).

CONCLUSION

Revision THAs for aseptically failed MoM hip resurfacings yielded a 5-year survivorship free of re-revision of 89%. The main reason for failure was dislocation, which was reduced, but not statistically significantly, when a dual-mobility construct was used, especially if the acetabular component was retained.

LEVEL OF EVIDENCE

IV.

Survival rates of different bearing surfaces with the same model of stem in total hip arthroplasty: predictive factors for revision surgery

INTRODUCTION

Few studies have examined the survival rates of total hip arthroplasty (THA) with the same femoral stem, and the predictive factors leading to the revision of stemmed metal-on-metal (MoM) THA remain unknown. We determined the long-term survival rate of stemmed MoM THA compared with that of metal-on-polyethylene (MoP) bearing THA, the effect of head size and cup placement angle on revision rate, and predictors of revision.

MATERIALS AND METHODS

A total of 130 hips in 110 patients who underwent primary THA by the same surgeon were included. M2a-RingLoc with a metal-on-polyethylene bearing (group P, 53 hips), M2a-Taper with MoM bearing (group T, 44 hips), and M2a-Magnum with MoM bearing (group M, 33 hips) were used. The mean age at surgery was 63.1 ± 9.5 years, and the mean postoperative follow-up duration was 133.7 ± 39.1 months. Whole blood metal ion concentrations were measured preoperatively and postoperatively, and magnetic resonance imaging was performed to identify aseptic local tissue reactions (ALTRs). Kaplan-Meier survivorship analysis and multiple logistic regression analysis were performed.

RESULTS

The THA survival rate up to the maximum postoperative follow-up period was 96.2% at 173 months, 46.6% at 179 months, and 47.8% at 145 months in groups P, T, and M, respectively, with revision as the endpoint. The stemmed MoM THA recorded a very low survival rate (p < 0.001). The ALTR rates were 70.5% and 63.6% in groups T and M, respectively. The risk factor for revision was the use of MoM bearing, and there was no difference in the results based on the head size in group M. Cobalt levels continued to increase postoperatively, although they were not accurate predictors of revision.

CONCLUSIONS

Stemmed MoM THA has a very low survival rate and should be used with caution. It is important to monitor the patient's symptoms and perform appropriate imaging to ensure timely revision.

Minimum 10-Year Results of Modular Metal-On-Metal Total Hip Arthroplasty

Background: this study aimed to assess the long-term outcomes of (a minimum of 10-years) total hip arthroplasty with a metal-on-metal acetabular prosthesis. Methods: Eighty-nine primary total hip arthroplasties (82 patients) were performed using a Pinnacle modular metal-on-metal acetabular prosthesis. Clinical hip function outcomes were evaluated using the Japanese Orthopaedic Association hip score preoperatively and at the final follow-up. Radiological analysis was performed at the final follow-up and magnetic resonance imaging in all hips postoperatively. Results: Out of 82 patients, 17 were excluded who were followed up for <10 years. Of the remaining 65 patients (70 hips), 19 (20 hips) developed pseudotumors during 2−10 years postoperatively. After 10 and 13 years, the survival rates of revision endpoint were 93.6% and 90.4%, respectively. Clinical hip function outcomes had improved significantly at the final follow-up. In the radiological analysis, the mean cup angle of inclination and mean ratio of femoral offset on the operated hip to the contralateral hip was highest in patients with revision surgery for adverse reactions to metal debris. Conclusions: This study showed a 29.0% prevalence of pseudotumors. Some cases required revisions even after 10 years following surgery. Regular clinical surveillance is recommended for the early detection of adverse reactions to metal debris.

The 50 Most-Cited Articles Regarding Hip Resurfacing

Background

Hip resurfacing arthroplasty is an accepted treatment option for young patients presenting with osteoarthritis of the hip. The purpose of this review was to evaluate and identify the top 50 most-cited articles pertaining to hip resurfacing, to help clinicians identify influential articles and navigate the literature more effectively.

Material and methods

Clarivate Analytics Web of Science was used to identify all articles related to hip resurfacing. The screening was based on the number of citations for each article. The final list of articles was further reviewed, and further data including manuscript title, authors, total citation count, year of publication, journal, country of origin, and level of evidence were extracted.

Results

The most-cited publication was “Pseudotumors associated with metal-on-metal hip resurfacings”, which was cited 704 times. The average total number of citations per publication was 203. The most prolific publication year was 2008 with 8 publications, and the most recent article was published in 2012. The journals with the most attributable publications were Journal of Bone and Joint Surgery and Clinical and Orthopedic Related Research.

Conclusions

This review provides a comprehensive analysis of the most-cited articles pertaining to hip resurfacing.

Level of evidence

III.

A meta-analysis assessing time for return to sport following hip resurfacing

BACKGROUND

Hip resurfacing arthroplasty (HRA) is associated with excellent functional outcomes and return to pre-disease level of activity. The time for return to sport (RTS) following HRA remains unknown. The aim of this meta-analysis was to establish the time for RTS following HRA.

METHODS

A search was performed on PUBMED, MEDLINE, EMBASE, and the Cochrane Library for trials on HRA and RTS, in the English language, published from the inception of the database to October 2020. In addition, a manual search was performed of relevant sports medicine and orthopaedic journals, and the bibliographies reviewed for eligible trials. All clinical trials reporting on time to RTS following HRA were included. Data relating to patient demographics, methodological quality, operation type, RTS, clinical outcomes, and complications were recorded by two independent reviewers. The PRISMA guidelines for reporting meta-analyses was used to undertake this study.

RESULTS

The initial literature search identified 1559 studies and nine further studies were found. Of these, 11 studies with a total of 659 patients matched the inclusion criteria. Two studies involving a total of 94 patients demonstrated an overall pooled proportion of 91.8% (95% CI 71.8-100) of patients RTS by three months post-operatively. Four studies including a total of 265 patients determined a pooled proportion of 96.8% (95% CI 91.0-99.7) of patients able to RTS by the 6-month post-operative stage. Pooled proportion analysis from all 11 studies comprising 659 patients showed 90.9% (95% CI 82.2-96.9) of patients were able to RTS by final follow up of 3 years.

CONCLUSION

Pooled proportion analysis showed an increasing number of patients were able to RTS after HRA over the first one year after surgery. There remains marked inter and intra-study variations in time for RTS but the pooled analysis shows that over 80% of patients were able to RTS at 6 to 12 months after HRA. The findings of this meta-analysis will enable more informed discussions between patients and healthcare professionals about time for RTS following HRA.

Adverse Local Tissue Reaction Associated With Ceramic-On-Metal Bearing Surface in Primary Total Hip Arthroplasty: Report of Two Cases

Total hip arthroplasty (THA) is one of the most common and successful surgical procedures worldwide. At the same time, it is constantly evolving, and as a consequence, advances in implant technology have led to significant improvements in the different materials of the acetabular and femoral components. The selection of bearing surfaces and their tribology are critical to achieving a successful outcome. Pseudotumors are important, and usually misdiagnosed, complications associated with hard bearing surfaces such as metal-on-metal couples. They belong to a group of reactions called adverse local tissue reaction, which can occur in the vicinity of any THA. We present 2 cases of adverse local tissue reaction associated with the use of ceramic-on-metal bearings surfaces in 2 primary THAs that were treated with modular component exchange during single-stage revision surgery.

Level of Evidence

IV.

Limited need for screening of metal-on-metal hip resurfacing patients beyond 10 years of follow-up

BACKGROUND

National and international guidelines lack consistency on how to screen metal-on-metal (MoM) hip arthroplasty patients for adverse reactions to metal debris (ARMD). Long-term outcomes of MoM hip arthroplasty are scarce, hindering further development of such guidelines. We present the clinical, radiological and ARMD status of 158 cases of hip resurfacing with >10 years follow-up.

METHODS

A prospective analysis of a cohort of 298 consecutive hip resurfacing procedures was performed at a single institution. All patients underwent MARS-MRI scanning for pseudotumour screening at least once, regardless of symptoms. Implant survival and reasons for revision were analysed for all patients. Clinical, radiological and MARS-MRI results were analysed for 158 unrevised procedures with >10 years follow-up.

RESULTS

The implant survival was 85.9% at 14.5 years (95% CI, 81.9-90.6) with revision for all causes as endpoint and 92.3% with MoM disease-related revisions excluded (95% CI, 88.2-95.0). Of the 158 cases with >10 years follow-up, 1 had elevated metal ion levels, 29 had a stable C1 pseudotumour and 6 a stable C2 pseudotumour. All pseudotumours were observed within 3 years after initiating our intensified ARMD screening (2011), with no new pseudotumours observed after that period.

CONCLUSIONS

We suggest that follow-up of MoM hip resurfacing patients beyond 10 years after surgery can be done with large intervals (i.e. every 5 years), and only earlier if a patient becomes symptomatic.

Ten-year results of a prospective cohort of large-head metal-on-metal total hip arthroplasty

Aims

Large-diameter metal-on-metal (MoM) total hip arthroplasty (THA) has demonstrated unexpected high failure rates and pseudotumour formation. The purpose of this prospective cohort study is to report ten-year results in order to establish revision rate, prevalence of pseudotumour formation, and relation with whole blood cobalt levels.

Methods

All patients were recalled according to the guidelines of the Dutch Orthopaedic Association. They underwent clinical and radiographical assessments (radiograph and CT scan) of the hip prosthesis and whole blood cobalt ion measurements. Overall, 94 patients (95 hips) fulfilled our requirements for a minimum ten-year follow-up.

Results

Mean follow-up was 10.9 years (10 to 12), with a cumulative survival rate of 82.4%. Reason for revision was predominantly pseudotumour formation (68%), apart from loosening, pain, infection, and osteolysis. The prevalence of pseudotumour formation around the prostheses was 41%, while our previous report of this cohort (with a mean follow-up of 3.6 years) revealed a 39% prevalence. The ten-year revision-free survival with pseudotumour was 66.7% and without pseudotumour 92.4% (p < 0.05). There was poor discriminatory ability for cobalt for pseudotumour formation.

Conclusion

This prospective study reports a minimum ten-year follow-up of large-head MoM THA. Revision rates are high, with the main reason being the sequelae of pseudotumour formation, which were rarely observed after five years of implantation. Blood ion measurements show limited discriminatory capacity in diagnosing pseudotumour formation. Our results evidence that an early comprehensive follow-up strategy is essential for MoM THA to promptly identify and manage early complications and revise on time. After ten years follow-up, we do not recommend continuing routine CT scanning or whole cobalt blood measurements, but instead enrolling these patients in routine follow-up protocols for THA.

Cite this article: Bone Jt Open 2022;3(1):61–67.

Hip Resurfacing vs Total Hip Arthroplasty in Patients Younger than 35 Years: A Comparison of Revision Rates and Patient-Reported Outcomes

Background

Hip resurfacing arthroplasty (HRA) and total hip arthroplasty (THA) are two treatment options for end-stage degenerative hip conditions. The objective of this single-center retrospective cohort study was to compare implant survival and patient-reported outcomes (PROs) in young patients (≤35 years) who underwent HRA or THA.

Methods

All patients aged 35 years or younger who underwent HRA or THA with a single high-volume arthroplasty surgeon between 2004 and 2015 were reviewed. The sample included 33 THAs (26 patients) and 76 HRAs (65 patients). Five-year implant survival and minimum 2-year PROs were compared between patient cohorts.

Results

Three patients in the THA group (9%) were revised within 5 years for instability (n = 1), squeaking (n = 1), or squeaking with a ceramic liner fracture (n = 1). No patients who underwent HRA were revised. The University of California, Los Angeles, activity score, modified Harris Hip score, and Hip Dysfunction and Osteoarthritis Outcome Scores for Joint Replacement increased by 74%, 64%, and 49%, respectively, among all patients. Compared to the HRA cohort, patients who underwent THA had lower preoperative and postoperative University of California, Los Angeles, activity, modified Harris Hip score, and Hip Dysfunction and Osteoarthritis Outcome Scores for Joint Replacement scores, yet there were no differences in the absolute improvements in any of the three measures between the two groups.

Conclusions

Excellent functional outcomes were seen in young patients undergoing either HRA or THA. Although young patients undergoing THA started at lower preoperative baseline and postoperative PROs than patients undergoing HRA, both groups improved by an equal amount after surgery, suggesting that both HRA and THA afford a similar degree of potential improvement in a young population.

Rheologic Behavior of Bovine Calf Serum

Recent studies have illuminated the rheological behavior of synovial fluid and the role of protein and hyaluronan (HA). However, with respect to artificial joint replacement in standardized wear simulations, bovine serum is used as fluid test medium. Little is known about the rheological characteristics of bovine serum, which are needed for precise tribological investigations. The steady shear viscosity η of bovine calf serum is determined for protein concentrations used in standardized wear simulations depending on shear rate γ˙ and temperature T. Additionally, the density of the serum is determined for both protein concentrations. The results show shear thinning behavior of bovine calf serum with a nearly Newtonian behavior in the range of high shear rates. Within the range of high shear rates, mean viscosities of η = 0.82-0.88 mPa·s were found for protein concentrations of 20 g/L and mean viscosities of η = 0.88-0.94 mPa·s for 30 g/L, decreasing with temperature. Densities of 1.004-1.005 g/cm³ and 1.007-1.008 g/cm³ were found for 20 and 30 g/L protein concentrations, respectively.

Fatal vascular complication due to metallosis

Metallosis is a well-known complication at the site of total hip and knee arthroplasty. Vascular involvement of this complication is rare and generally results from vascular compression by a mass or pseudotumor. In the present report, we have described a case of lower limb acute arterial ischemia due to arterial injury as a complication of metallosis with a fatal outcome.

Pseudotumors in Total Joint Arthroplasty

»

The true incidence of pseudotumors in association with total joint arthroplasty is underestimated.

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Pseudotumors occur with metal-on-metal, metal-on-polyethylene, and metal-on-ceramic articulations.

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Metal ion levels should not be the only factor in decision-making regarding revision surgery.

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Revision surgery is only indicated in symptomatic patients with clinical and radiographic findings and elevated metal ion levels.

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Revision to a non-metal articulation is strongly suggested.

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.

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.

Recommendations for return to sports after total hip arthroplasty are becoming less restrictive as implants improve

INTRODUCTION

Total hip arthroplasty (THA) surgeries are expected to exponentially increase in the upcoming years, likely because of the overall broader indication of THAs. With these developments, an increasing number of younger (< 50 years) and active patients will receive surgical interventions, and expectations for an active lifestyle will accordingly increase. In addition, surgeons now have a growing array of techniques and implant materials to choose from. Despite these developments, evidence to provide the best standard-of-care to patients with high expectations for return to sports (RTS) is scarce and urgently needed. What recommendations do arthroplasty surgeons currently make to patients with high return to sports expectations, what factors may influence their recommendations and what surgical techniques and implant specifications are considered favorable in the treatment of patients with a more active lifestyle? This study was conducted to analyze the current recommendations, patient assessment, and patient counseling after THA to identify trends and relevant factors for surgical decision-making in patients with high-RTS expectations.

MATERIAL AND METHODS

We designed a questionnaire comprising five general items and 19 specific items that included 46 sub-items for hip arthroplasty and conducted a survey among 300 German surgeons specialized in arthroplasty at the German Arthroplasty Society (AE) to assess expert opinions, recommendations, surgical decision-making, and patient counseling for patients with high expectations for RTS after THA.

RESULTS

The majority of surgeons (81.9%) were in favor of RTS after THA. Risks associated with sports after THA were considered minimal (1%), with periprosthetic fractures ranking highest, followed by hip dislocation and polyethylene wear. Some surgical decision-making was influenced by high-RTS expectations in regard to implant fixation, stem type, femoral head diameter, and bearing-surface tribology. We observed an increasingly liberal counseling of patients for high-impact sports.

CONCLUSION

With the improvement of implants and surgical techniques, surgeons are more willing to encourage patients to adopt a more active lifestyle. However, the true long-term limitations need further investigation in future studies.

LEVEL OF EVIDENCE

5 Expert opinions.

A Comparative Cohort Study With a 20-Year Age Gap: Hip Resurfacing in Patients Aged ≤35 Years and Patients Aged ≥55 Years

Background

This single-center retrospective cohort study aimed to evaluate and compare implant survival and patient-reported outcome measures in 2 distinct age groups separated by 20 years who underwent hip resurfacing arthroplasty (HRA).

Methods

Between 2005 and 2014, 2042 HRAs were performed by a single-surgeon, and 75 and 377 hips from patients aged ≤35 years and ≥55 years, respectively, were included in this study. Implant survival was determined for all available hips. Clinical features and patient-reported outcome measures were collected.

Results

Seven hips were revised, 4 for aseptic loosening of one or both components, one for infection, one for accelerated wear and metallosis, and one for femoral neck fracture. There was no difference in all-cause 10-year revision, with 97.1% (95% confidence interval 80.9 to 99.6) and 99.6% (95% confidence interval: 97 to 99.9) survivorship in younger and older patients, respectively (P = .246). Preoperatively, younger patients were less active than older patients on the Lower Extremity Activity Scale (LEAS) or University of California, Los Angeles, activity scale, but at follow-up, younger patients outpaced older ones.

Conclusion

Original to our study was the isolation and comparison of 2 distinct age groups. With excellent results in disparate age groups, HRA can be applied to a broad patient demographic and is suitable for those patients who want to achieve a high activity level as defined by Lower Extremity Activity Scale or University of California, Los Angeles, scores.

Low Revision Rates at 10 years for Metal on Metal Hip Implants in a Military Population

INTRODUCTION

Prior to being largely abandoned due to unacceptably high failure rates and the adverse physiologic reactions to metal ions, metal-on-metal (MoM) total hip arthroplasty (THA) and hip resurfacing (HR) were in widespread use throughout the USA, and the potential benefit of decreased volumetric wear rates made it of particular interest to those who serve a young active population, such as military surgeons. The aim of our study was to determine the revision rate of metal on metal hip implants performed at our military institution and obtain current patient reported outcomes from this cohort.

MATERIALS AND METHODS

We conducted a retrospective review of patients who underwent MoM total hip arthroplasty (THA) or hip resurfacing (HR) at our institution from 2006 to 2012. Revision status and component type were determined, and patients were contacted to obtain current HOOS JR scores.

RESULTS

We identified 103 THAs in 88 patients and 38 HRs in 33 patients, with mean follow up of 10.2 years. Average age at time of surgery was 48 years, and 85% of the patients were male. The mean HOOS JR score in the THA and HR groups were 84.9 ± 17.6 and 75.8 ± 24.9, respectively (p = 0.38), and were not significantly lower in those who were revised. Two THA revisions occurred for metallosis and one for aseptic loosening of the femoral component. One HR revision occurred for breach of the anterior femoral neck, and one occurred for heterotopicossification.

CONCLUSIONS

Revision rates of MoM THA and HR in this young, predominantly male population were 2.9% and 5.3%, respectively, and patients maintained generally good hip-specific outcomes.

Mechanically Assisted Crevice Corrosion in a Metal-on-Polyethylene Total Hip Presenting With Lower Extremity Vascular Compromise

Mechanically assisted crevice corrosion in modular total hip replacements may lead to an adverse local tissue reaction (ALTR) with a variety of sequelae. Although an ALTR is most commonly recognized with metal-on-metal modular hip constructs, tribocorrosion at the head-neck junction of metal-on-polyethylene (MoP) total hip arthroplasties may also lead to an ALTR. We present a case of a 79-year-old woman with a history of MoP total hip arthroplasty who presented with unilateral leg swelling, joint pain, and stiffness and subsequently underwent revision for an ALTR secondary to mechanically assisted crevice corrosion. This unique case of lower extremity vascular compromise resulting from an ALTR is important because clinicians should consider corrosion-related ALTRs when treating patients with an MoP hip prosthesis presenting with new-onset lower extremity swelling.

Sex-specific risk factors determine the survivorship of female and male patients after metal-on-metal hip resurfacing

BACKGROUND

The need for revision surgery after hip resurfacing arthroplasty (HRA) is more prevalent for women than for men. However, there is a paucity of information to explain this observation. We aimed (1) to determine sex-specific risk factors leading to revision surgery; and (2) to correlate these risk factors to the dominant modes of failure of HRA.

METHODS

1101 patients (1375 consecutive hips) including 292 women (355 hips) and 809 men (1020 hips) with a mean age of 51.3 years were included regardless of bone quality. The contact patch to rim distance was computed.

RESULTS

A contact patch to rim (CPR) distance of ⩽7 mm, an aetiology of developmental dysplasia, a postoperative abduction-adduction arc of ⩾95°, and a metaphyseal stem left uncemented were risk factors associated with revision surgery for female patients, while a CPR distance of ⩽10 mm, a component size of ⩽46 mm, an age at surgery of ⩽55 years, and an early femoral preparation technique were risk factors for male patients. Hips with no risk factors from the female group had a survivorship of 98.7% at 15 years, matching or exceeding the results of all male subgroups. However the risk factors in the female group increased the risk of revision much more than in the male group.

CONCLUSIONS

In the absence of risk factors, the survivorship of HRA in female patients is equal to that of males. Many female patients can safely benefit from HRA by excluding severe dysplasia and optimising surgical technique.

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.

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.

Granulomatous Reaction on a Double-Level Cervical Total Disc Arthroplasty

BACKGROUND

Cervical total disc arthroplasty (TDA), or cervical artificial disc replacement, is an alternative technique to anterior cervical discectomy and fusion for treatment of symptomatic degenerative cervical spine disease. The main goal of TDA is to maintain cervical motion and lower the risk of deterioration of adjacent levels. Granuloma formation on a cervical TDA is exceptional.

CASE DESCRIPTION

A 48-year-old woman with left cervicobrachialgia underwent a double-level TDA (M6-C Artificial Cervical Disc) on C5-C6 and C6-C7 at another hospital in 2010. Two years later, she reported a recurrence of cervicalgia, which was refractory to conservative treatment by rigid collar and analgesics. Cervical magnetic resonance imaging suggested a granulomatous formation on the C6-C7 prosthesis. She underwent removal of the C6-C7 prosthesis, which showed a rupture with nylon thread extrusion. An arthrodesis with plate was subsequently performed. Follow-up showed improvement of her clinical status. Histopathologic studies showed a giant cell granulomatous formation in contact with nylon threads described in hip, shoulder, and ankle arthroplasty. It has been described in 6 cases following lumbar TDA and 2 cases following cervical TDA.

CONCLUSIONS

We report a third case of granulomatous reaction on nylon thread extrusion after partial breakdown of a prosthesis for cervical TDA.

Mid- to long-term results of resurfacing hip arthroplasty in Japanese patients: a comparison of osteoarthritic vs non-osteoarthritic patients

Past reports showed good mid-term results of RHA for Japanese patients. However, few reports have compared the mid- to long-term results for RHA in Japanese patients with and without osteoarthritis. Therefore, this study investigated the mid- to long-term results of RHA in Japanese patients with osteoarthritis compared to those without. We conducted a retrospective review of a consecutive series of 92 hips in 80 patients (59 men and 21 women). The minimum follow-up period was 5 years. The JOA hip scoring system was used to clinically evaluate hip function. In the radiological assessment, stem-shaft angle, inclination of the acetabular component, postoperative complications, and adverse reactions around RHA were evaluated. The 10-year survival rate using the Kaplan-Meier method was investigated to compare patients with and without osteoarthritis. A significant difference was observed between the preoperative and postoperative JOA hip scores of either group. Also, the radiological assessment revealed no significant changes in either group. All three revision THAs were performed on patients in the only non-osteoarthritis group. In the osteoarthritis group, the 10-year survival rate was 94% (95% CI 81.8-100) in males and 100% (95% CI 100) for females; in the non-osteoarthritis group, the rate was 80% (95% CI 55.1-100) in males and 66.7% (95% CI 13.3-100) for females. In conclusion, this study showed good mid- to long-term clinical results for young Japanese osteoarthritis patients, with less satisfactory mid- to long-term results in patients without osteoarthritis.

Long - term survivorship and clinical results of the navigated withdrawn ASR ™

Introduction

Primary goals of the study were to present the mid - to long - term survivorship and clinical, radiological and metal serological results of the first stem - navigated ASR™ resurfacing at our clinic. Secondary goals were to determine the influence of stem - navigation on the outcome and risk factors for revision in our cohort.

Methods

From Mai 2006 to Mai 2009 46 ASR™ resurfacing hip systems have been implanted in 43 patients with a median age of 55 years. At final follow - up (33 patients with a mean follow -up of 89,6 months) guidelines were followed and HHS and HOOS were completed. Inclination, NSA and SSA were measured on radiographs and signs of loosening were graded. Risk factors for revision were compared in the non - revision and revision group.

Results

Mean cumulative survival of the prosthesis after 99,9 Months was 81,8%. At final follow - up 8 revisions were performed. Median HHS was 97, HOOS was 87,2. Four prostheses showed signs of loosening and nine heterotopic ossifications. All shaft components, except one, were placed in minimal valgus position to avoid risk for fracture. Age and diameter of the femoral component were significantly different between the non - revision and revision group.

Discussion

Survivorship is comparable to numbers found in other studies. Patients with complete final follow - up in general had good objective and subjective scores and few signs of loosening in the radiological follow - up. Navigation might have a positive effect on reduction of risk for fracture. Age and diameter of the femoral component seem to influence the outcome.

[Mid-term effectiveness of large-head metal-on-metal total hip arthroplasty]

Objective

To explore the mid-term effectiveness of large-head metal-on-metal total hip arthroplasty (THA).

Methods

A retrospective analysis was made on the clinical date of 40 patients (43 hips) who were treated with the large-head metal-on-metal THA between April 2009 and June 2010. There were 18 males (20 hips) and 22 females (23 hips) with an average age of 55.1 years (range, 20-85 years). Unilateral hip was involved in 37 cases and bilateral hips in 3 cases. The disease causes included osteonecrosis of the femoral head in 14 cases (15 hips), osteoarthritis in 6 cases (7 hips), rheumatoid arthritis in 4 cases (4 hips), femoral neck fracture in 4 cases (4 hips), and developmental dysplasia of the hip in 12 cases (13 hips). Before operation, the Harris score and University of California Los Angeles (UCLA) score were 38.51±5.62 and 4.21±1.43, respectively. The visual analogue scale (VAS) score was 6.78±0.95.

Results

All patients were followed up 6.7-8.3 years (mean 7.5 years). All incisions healed primarily and no neurovascular injury, infection, and hip dislocation occurred. At last follow-up, the Harris score and UCLA score were 93.33±3.21 and 7.32±1.45, respectively, showing significant differences when compared with preoperative scores ( t=51.753, P=0.000; t=23.232, P=0.000). The thigh pain occurred in 3 cases (3 hips) in whom the inflammatory pseudotumor of soft tissues was found in 1 case (1 hip). Postoperative X-ray films showed that the acetabular abduction angle and anteversion angle were (46.5±3.2)° and (14.8±3.6) °, respectively. The initial stability of femoral stem prosthesis was excellent in 39 hips and good in 4 hips according to Mulliken standard. Osteolysis occurred in 2 hips and revision was performed in 1 hip of secondary loosening of prosthesis. The rest patients had no prosthesis loosening or sinking.

Conclusion

The mid-term effectiveness of large-head mental-on-mental THA in treatment of the terminal diseases of hips are good.

Pseudotumor from Metal-on-Metal Total Hip Arthroplasty Causing Unilateral Leg Edema: Case Presentation and Literature Review

Metal-on-metal (MoM) total hip arthroplasty (THA) can be associated with adverse metal reactions, including pseudotumors. This case report describes a 58-year-old female with an MoM THA-related pseudotumor that caused unilateral leg edema from compression of her external iliac vein. After thorough preoperative workup to rule out infection and deep vein thrombosis and consultation with a vascular surgeon, the patient underwent revision THA and excision of her pseudotumor. She had complete resolution of her swelling at 4 years after surgery. Review of all available case reports for this rare complication revealed that almost all patients were female. All patients underwent revision THA, with resolution of their symptoms. Literature review demonstrates that women are disproportionally affected by complications associated with MoM THA. We recommend close monitoring of patients with MoM THA, particularly women, for development of adverse metal reactions.

Microstructure and Surface Damage in Retrieved Metal-on-Metal Hip Arthroplasties

BACKGROUND

Besides promising results of metal-on-metal (MOM) hip arthroplasty (HA), frequent failures have been reported even in the short term. Many host, surgical, design, metallurgical, and processing factors have been evoked in the base of these events. We have tried to characterize and to evaluate metallurgical and processing features present in this type of implants.

METHODS

The acetabular and femoral components of 20 MOM HAs collected from a multicenter retrieval program were examined. All the specimens were inspected with naked eye, with confocal microscopy and vertical scanning interferometry, scanning electron microscopy, back-scattered electron imaging, and energy-dispersive X-ray spectroscopy, in 25 zones of each articular component.

RESULTS

Gas pores, shrinkage voids and holes of detached carbides, carbides on surface, embedded particles, scratches and marks of wear, surface discoloration, surface deposits, and tribochemical reaction layers were widely dispersed through a substantial percentage of the total bearing surface in all the implanted components. Surface cup and head voids, and cup scratches showed significant correlation with the clearance of pair. A higher surface damage of the cup and head was observed mainly in the low clearance prostheses. There was no other significant correlation or difference in the incidence and importance of any of these defects between resurfacing hip arthroplasties and total hip arthroplasties, or according to the pair diameter.

CONCLUSION

Some metallurgical features and surface damage were significantly present in the retrieved implants of MoM HAs. It would be desirable to improve the structure and metallurgical characteristics of these implants to avoid those effects and optimize their performance.

Biological effects of metal degradation in hip arthroplasties

Metals and metal alloys are the most used materials in orthopedic implants. The focus is on total hip arthroplasty (THA) that, though well tolerated, may be associated with local and remote adverse effects in the medium-long term. This review aims to summarize data on the biological consequences of the metal implant degradation that have been attributed predominantly to metal-on-metal (MoM) THA. Local responses to metals consist of a broad clinical spectrum ranging from small asymptomatic tissue lesions to severe destruction of bone and soft tissues, which are designated as metallosis, adverse reactions to metal debris (ARMD), aseptic lymphocytic vasculitis associated lesion (ALVAL), and pseudotumors. In addition, the dissemination of metal particles and ions throughout the body has been associated with systemic adverse effects, including organ toxicity, cancerogenesis, teratogenicity, and immunotoxicity. As proved by the multitude of studies in this field, metal degradation may increase safety issues associated with THA, especially with MoM hip systems. Data collection regarding local, systemic and long-term effects plays an essential role to better define any safety risks and to generate scientifically based recommendations.

Highly Cross-Linked Polyethylene Reduces Wear and Revision Rates in Total Hip Arthroplasty: A 10-Year Double-Blinded Randomized Controlled Trial

BACKGROUND

Highly cross-linked polyethylene (XLPE) was developed to address the problem of wear and osteolysis associated with metal-on-conventional ultra-high molecular weight polyethylene (UHMWPE) bearing surfaces. The purpose of this study was to compare in vivo wear rates and clinical and radiographic outcomes between XLPE and UHMWPE in a prospective double-blinded randomized controlled trial with a minimum of 10 years of follow-up.

METHODS

We randomized 122 patients to receive either a conventional UHMWPE liner (Enduron; DePuy) or an XLPE liner (Marathon; DePuy). Ninety-one patients were assessed clinically and radiographically at a minimum of 10 years (range, 10.08 to 12.17 years). Oxford Hip Scores and Short Form-12 Health Survey scores were collected. The radiographs were analyzed for osteolysis and for 2-dimensional (2-D), 3-dimensional (3-D), and volumetric wear using validated software.

RESULTS

All 122 patients were accounted for at the 10-year follow-up evaluation. Twelve patients had undergone revision surgery, 21 patients had died (1 of whom had previously undergone revision surgery), and 2 patients were unable to return for follow-up, leaving 91 patients available for clinical and radiographic evaluation. At a minimum of 10 years, 3-D wear rates were significantly lower (p < 0.001) in the XLPE group (mean, 0.03 mm/yr) than in the conventional UHMWPE group (mean, 0.27 mm/yr). The prevalence of osteolysis was also significantly lower in the XLPE group (38% versus 8%, p < 0.005), as was the revision rate (14.6% versus 1.9%, p = 0.012), with 10 of the 12 revisions being in the Enduron group. There was no significant difference between the clinical scores of the 2 groups.

CONCLUSIONS

XLPE liners have significantly reduced wear and are associated with a greater implant survival rate at 10 years compared with conventional UHMWPE liners.

LEVEL OF EVIDENCE

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

MRI Findings in Patients After Small-Head Metal-on-Metal Total Hip Arthroplasty with a Minimum Follow-up of 10 Years

BACKGROUND

Concern has been raised about the late onset of adverse reactions to metal debris (ARMD) in patients with a small-head metal-on-metal total hip replacement. The aims of this study were to assess the frequency and characteristic appearance of ARMD in patients with a small-head (28-mm) metal-on-metal total hip replacement and elevated blood ion levels (>1 μg/L) after a minimum follow-up of 10 years and to analyze the possible risk factors associated with the prevalence of these lesions.

METHODS

In the present study, we used metal artifact reduction sequence magnetic resonance imaging (MARS MRI) to investigate the cases of 53 patients (66 hips) with a small-head (28-mm) metal-on-metal total hip replacement and elevated blood ion levels at a mean follow-up interval of 15.5 years (range, 10.6 to 19.3 years). Whole blood metal ion levels (cobalt and chromium), clinical outcome scores (Harris hip score), and radiographs were obtained for each patient. Tissue samples from patients who had revision surgery were histologically examined.

RESULTS

MARS MRI revealed ARMD in 27 hips (41%). Most hips with ARMD (67%) were asymptomatic. ARMD were generally small, with a median lesion size of 2.3 cm (range, 0.3 to 71.4 cm) and predominantly cystic in nature. Multivariate regression analysis revealed positive correlation between cobalt ion levels and the presence of ARMD. In this case series, the risk for the development of ARMD was 2.87 times higher for every 1 μg/L increase of blood cobalt ion concentration (95% confidence interval, 1.01 to 8.17; p = 0.048).

CONCLUSIONS

In this case series, ARMD were seen in 41% of the hips following small-head metal-on-metal total hip arthroplasty at long-term follow-up, and most patients with ARMD were asymptomatic. Blood cobalt ion levels could be identified as a risk factor for ARMD. However, ARMD also occurred in patients with low metal ion levels. Further studies are necessary to investigate the role of ARMD in asymptomatic patients with this bearing type.

LEVEL OF EVIDENCE

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

Correlation between serum metal ion levels and adverse local tissue reactions after Conserve® Plus hip resurfacing arthroplasty

BACKGROUND

Adverse local tissue reactions (ALTR) have been associated with the use of metal-on-metal (MoM) bearings and the monitoring of cobalt (Co) and chromium (Cr) ion levels in blood or serum may be the best way to evaluate in vivo the wear of these bearings. However, the relationship between Co and Cr ion concentrations and the formation of ALTR remains unclear.

METHODS

We investigated the relationship between ALTR and serum Co and Cr ion levels and identified the clinical factors influencing the formation of ALTR in patients treated with MoM hip resurfacing arthroplasties. 228 patients with unilateral Conserve® Plus MoM hip resurfacing had serum metal ion studies performed more than 1 year after surgery. Metal artifact reduction sequence magnetic resonance imaging (MARS MRI) was performed on subjects at risk for ALTR as determined by a screening protocol.

RESULTS

12 patients had ALTR. Logistic regression showed a strong association of ALTR with elevated ion levels and with low (<10 mm) contact patch to rim distance.

CONCLUSIONS

MoM bearings require enough functional coverage of the socket by design and then precise implantation to maximise functional coverage of the femoral ball, enhance lubrication, and avoid edge-loading wear.