Cardiac function may be compromised in patients with elevated blood cobalt levels secondary to metal-on-metal hip implants.

Aims: Elevated blood cobalt levels secondary to metal-on-metal (MoM) hip arthroplasties are a suggested risk factor for developing cardiovascular complications including cardiomyopathy. Clinical studies assessing patients with MoM hips using left ventricular ejection fraction (LVEF) have found conflicting evidence of cobalt-induced cardiomyopathy. Global longitudinal strain (GLS) is an echocardiography measurement known to be more sensitive than LVEF when diagnosing early cardiomyopathies. The extent of cardiovascular injury, as measured by GLS, in patients with elevated blood cobalt levels has not previously been examined. Methods: A total of 16 patients with documented blood cobalt ion levels above 13 µg/l (13 ppb, 221 nmol/l) were identified from a regional arthroplasty database. They were matched with eight patients awaiting hip arthroplasty. All patients underwent echocardiography, including GLS, investigating potential signs of cardiomyopathy. Results: Patients with MoM hip arthroplasties had a mean blood cobalt level of 29 µg/l (495 nmol/l) compared to 0.01 µg/l (0.2 nmol/l) in the control group. GLS readings were available for seven of the MoM cohort, and were significantly lower when compared with controls (-15.5% vs -18% (MoM vs control); p = 0.025)). Pearson correlation demonstrated that GLS significantly correlated with blood cobalt level (r = 0.8521; p < 0.001). However, there were no differences or correlations for other echocardiography measurements, including LVEF (64.3% vs 63.7% (MoM vs control); p = 0.845). Conclusion: This study supports the hypothesis that patients with elevated blood cobalt levels above 13 µg/l in the presence of a MoM hip implant may have impaired cardiac function compared to a control group of patients awaiting hip arthroplasty. It is the first study to use the more sensitive parameter of GLS to assess for any cardiac contractile dysfunction in patients with a MoM hip implant and a normal LVEF. Larger studies should be performed to determine the potential of GLS as a predictor of cardiac complications in patients with MoM arthroplasties.

Metal levels and glomerular filtration rate after unilateral Birmingham Hip Resurfacing.

Aims: The first aim of this study was to evaluate whether preoperative renal function is associated with postoperative changes in whole blood levels of metal ions in patients who have undergone a Birmingham Hip Resurfacing (BHR) arthroplasty with a metal-on-metal bearing. The second aim was to evaluate whether exposure to increased cobalt (Co) and chromium (Cr) levels for ten years adversely affected renal function. Methods: As part of a multicentre, prospective post-approval study, whole blood samples were sent to a single specialized laboratory to determine Co and Cr levels, and the estimated glomerular filtration rate (eGFR). The study included patients with 117 unrevised unilateral BHRs. There were 36 females (31%). The mean age of the patients at the time of surgery of 51.3 years (SD 6.5), and they all had preoperative one-, four-, five-, and ten-year laboratory data. The mean follow-up was 10.1 years (SD 0.2). Results: Median Co levels at one year postoperatively increased significantly compared with the preoperative values, by a factor of 9.7, from 0.13 to 1.26 ppb (p < 0.001), and the median Cr levels increased significantly by a factor of 2.5, from 0.60 to 1.50 ppb (p < 0.001). Lower preoperative eGFRs were associated with significantly larger increases in Co at one year compared with the preoperative levels (ρ = -0.26; p = 0.005), but there was no relationship between preoperative eGFRs and changes in Cr at one year (ρ = -0.13; p = 0.153). Metal levels remained relatively constant with the passage of time, with a median ten-year value of 1.12 ppb for Co and 1.29 ppb for Cr. There was no significant relationship between the Co and Cr levels at ten-year follow-up and the change in eGFR from the preoperative level to that at ten years (ρ = -0.02; p = 0.827 for Co; ρ = -0.008; p = 0.933 for Cr). Conclusion: Although patients with lower preoperative eGFRs tended to have larger increases in Co levels at one year, increased metal levels for patients who underwent unilateral BHR did not adversely affect renal function during the first ten postoperative years.

Hypersensitivity to metals in metal-on-metal hip arthroplasty: a prospective study of one hundred and thirty five lymphocyte transformation tests.

BACKGROUND: Metal allergy remains a controversial topic in the orthopaedic community. It is not known if or to what degree metal sensitivity contributes to inflammatory soft tissue failures, unexplained residual pain, or clinical complications after total joint replacement with metal prostheses. METHODS: We investigated the efficacy of the lymphocyte transformation test (LTT) in predicting adverse outcomes in patients after receiving a metal joint replacement. Our study cohort consists of 135 metal-on-metal hip resurfacing arthroplasty cases performed between 2013 and 2015. All study patients had an LTT preoperatively. We retrospectively analyzed clinical outcomes and failures for our cohort. RESULTS: There was no difference in LTT reactivity between men and women. Of the 135 patients tested, 46 (34.1% of cohort) tested positive to at least one of the materials comprising their implant, and 78 patients (57.8%) had at least one reactive score to any component of the LTT. After a minimum follow-up of two years, we did not observe an allergic response to the implant in any patients. There were no failures requiring revision. We observed a 2.2% rate of moderate residual pain; no patients with residual pain tested positive for metal sensitivity. When patients with moderate-high LTT reactivity (30.4% of cohort) were compared to the remainder of the study group, there was no difference in HHS or UCLA activity score. There was no correlation between blood metal ion levels and LTT reactivity. CONCLUSION: We were unable to prove any predictive value of the LTT. We failed to identify hypersensitivity to metals in patients with metal-on-metal hip resurfacing arthroplasty.

Quantification and severity grading of femoral vessel compression by adverse reactions to metal debris in metal-on-metal total hip arthroplasty.

INTRODUCTION: Metal-on-metal (MoM) total hip arthroplasty (THA) may cause adverse reactions to metal debris (ARMD). ARMD causing femoral vessel compression with serious complications has been described in case reports, but the rate of compression by ARMD is not known. This study aims to investigate the rate, and quantify the severity, of femoral vessel compression in MoM hips with ARMD lesions. METHODS: Patients under surveillance for MoM THA investigated with MRI were studied. In patients with confirmed ARMD, femoral artery (FA) and vein (FV) diameters were measured at the point of maximal compression and compared to contralateral vessels. The primary outcome measure was presence or absence of compression. Cases were then classified by compression ratios. Secondary outcome measures were rates of deep vein thrombosis, revision surgery and time to ARMD from index procedure. RESULTS: MRI scans for 436 patients with MoM THA were screened. Of these, 211/436 (48.4%) showed evidence of ARMD. Measurements were obtained on 133/211 (63.0%) patients. The FV was compressed in 102/133 (76.7%) and FA in 58/133 (43.6%), while 31/133 (23.3%) patients had no compression. In FVs, 42 demonstrated mild compression, 39 moderate and 21 severe. In FAs, none were severely compressed, 6 were moderate and 52 showed mild compression. There were 3 DVT cases, 2 in patients with moderate FV compression and 1 in patients without FV compression. Revision rates were highest in patients with severe FV compression (14/21, 66.7%). The mean time for MRI-diagnosed ARMD from index procedure was 8 years and 1 month (range 11 months-14.5 years). CONCLUSIONS: Extra-luminal compression of the femoral vessels was found in >75% of patients with ARMD. Although it is not clear whether revision for femoral vessel compression is required, quantification of FV compression may be useful for surgeons and radiologists considering revision for ARMD.

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

PURPOSE: Revision of failed large head metal-on-metal (MoM) total hip arthroplasty (THA) is a challenging procedure particularly to reconstruct acetabular bone defect due to osteolysis and to achieve hip stability due to soft tissue damages, both potentially caused by adverse reaction to metal debris (ARMD). This study aimed to evaluate the outcome of dual mobility cup (DMC) constructs in revision THA for failed large head MoM bearings with a special attention to the occurrence of dislocation or re-revision. METHODS: Between 2015 and 2019, 57 patients (64 THAs, 41 men, mean age = 65 ± 10 years) underwent revision for MoM THA with the use of DMC were prospectively included in our total joint registry. Mean time to revision was 11 ± 2.5 years. The causes for revision were adverse reaction to metal debris (ARMD) in 49 THAs (76%), painful hip with elevated blood cobalt-chromium ions in seven (11%), and acetabular aseptic loosening in eight (13%). The revision was complete in 22 THAs (34%) and acetabular only in 42 (66%). Clinical and radiographic outcomes, complications, and re-revisions were evaluated at most recent follow-up. RESULTS: At mean follow-up of six ± 1.5 years, the pre- to postoperative Harris Hip Score improved from 74 ± 19 to 92 ± 4 (p = 0.004). Complications occurred in 11 cases (17%): five dislocations (8%), three periprosthetic infections (5%), two aseptic loosening of the acetabular component (3%), and two periprosthetic fractures (3%). Re-revision was required in six cases (9%). CONCLUSION: The use of DMC is a reliable option to prevent instability and ensure a stable acetabular reconstruction in revision THA for failed large head MoM bearings. However, dislocation after revision remains a concern, particularly in cases of severe soft tissue damage related to ARMD.

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.

Mid-term clinical and radiographic outcome of metal-on-metal hip resurfacing through an anterolateral approach.

PURPOSE: The aim of this retrospective study was to evaluate the medium-term clinical and radiographic results of current generation metal-on-metal resurfacing prostheses performed through anterolateral approach. MATERIALS AND METHODS: Fifty-seven hips in 52 patients underwent resurfacing arthroplasty. Two patients died from unrelated causes, leaving 55 hips in 35 males (3 bilateral) and 15 females (2 bilateral), with a mean age at surgery of 56.2 years (range, 27-70 years). Clinical and radiographic assessment was carried out preoperatively and at follow-up in all the survived cases. The cumulative survival rate was determined according to the method of Kaplan-Meier. RESULTS: At a mean follow-up of 5.2 years (range, 1.8-9.1 years), 2 HRs of the same female patient were revised because of early loosening of the acetabular component. Deep venous thrombosis and transient femoral nerve palsy occurred both in 1 case. No specific complications of HR were observed. Average Harris hip score improved significantly from 59.8 points (range, 30.4-90.6) preoperatively to 93.7 points (range, 53-100) at the latest examination. Neck narrowing showed an average of 3.27%, but it never exceeded 10%. Nonprogressive acetabular radiolucencies and osteolysis were detected both in 2 hips. A high rate of patients (32, 60.4%) developed heterotopic ossifications, although low-grade in most cases (27, 84.4%). The cumulative survival rate at 9.1 years with revision for any reason as the end point was 93.0%. CONCLUSIONS: The early clinical and radiographic results of modern metal-on-metal hip resurfacing performed through an anterolateral approach are promising, but longer-term follow-up studies are necessary.

Constrained metal-on-metal hip arthroplasty: ever heard of a 50-year survival story?

BACKGROUND: The history of total hip arthroplasty dates back to the first half of the twentieth century. Data on hip endoprostheses implanted during the 1960s and 1970s suggest widely varying survival rates of the prosthesis. CASE: A case of a patient who underwent total hip arthroplasty in 1972 using a Sivash prosthesis, developed in 1956 in the former Soviet Union, is presented in this article. The prosthesis has remained unrevised in the patient's body for 50 years and he continues to be widely free of implant-related symptoms. Despite the constrained metal-on-metal design of the implant, which can lead to adverse reactions to metal debris, no elevated systemic metal ion levels were detected. CONCLUSION: The likelihood of encountering patients with prosthesis survival beyond 50 years is still rare. Nevertheless, changing demographics and the steadily improving designs and materials of hip endoprostheses may likely result in such cases.

Metal-on-metal metaphyseal and ceramic-on-ceramic femoral neck arthroplasty: the impact on clinical results, oxidative stress and concentration of metal ions in serum and blood.

PURPOSE: Growing number of hip arthroplasty in Poland performed with the use of metaphyseal stems results from the decreasing age of patients qualified for procedures and is consistent with the corresponding trends in European countries. To this day, a significant population functions after undergoing hip replacement using metal-on-metal implant. This study was aimed at the assessment of the variability of the oxidative system, as well as the concentrations of chromium and cobalt ions in serum and blood and their potential impact on postoperative clinical status. MATERIAL AND METHODS: The analysis included 58 men. The first group-operated using J&J DePuy ASR metal-on-metal implant with metaphyseal stem ProximaTm. Second group-operated using K-Implant SPIRON® femoral neck prosthesis in full ceramic articulation. Selected parameters of oxidative stress and the antioxidant system as well as the concentration of metal ions in blood were determined twice. Each patient underwent two clinical evaluations using acclaimed physical examination scale systems. RESULTS: In the first group, significantly higher concentrations of Cr (p = 0.028) and Co (p = 0.002) were demonstrated compared to the group of femoral neck arthroplasty. The mean concentrations of Cr and Co, 10.45 and 9.26 µg/l, respectively, were higher in patients operated bilaterally. In the ASR group, greater pain intensity in the operated hip and higher indicators of oxidative stress were found. CONCLUSIONS: Metal-on-metal articulation of the hip significantly increases the concentration of Cr and Co in blood, induces oxidative stress and modifies function of the antioxidant system and generates greater pain in the operated hip.

Wear debris in metal-on-metal bearings and modular junctions : What have we learned from the last decades?

Metal-on-metal (MoM) bearing hip arthroplasty saw increasing utilization and peaked in the 1990s and early 2000s. Although the linear and volumetric wear rate for a MoM bearings was lower than its polyethylene counterpart, metal ion particles were found to be approximately 10â€¯× smaller and 500â€¯× higher in quantity compared to polyethylene wear debris. Research into these articulations have demonstrated their relationship to the formation of lymphocyte-mediated adverse local tissue reactions. The work-up for metal particle-associated conditions (metallosis) includes a thorough patient history and physical examination, blood laboratory studies for metal ion concentrations, and advanced imaging studies including magnetic resonance imaging (MRI). The treatment of metallosis and adverse local tissue reactions ranges from close serial observation to extensive debridement and full revision of arthroplasty components, when indicated.

Careful patient selection together with optimal implant positioning may reduce but does not eliminate the risk of elevated serum cobalt and chrome levels following metal-on-metal hip resurfacing.

BACKGROUND: Elevated serum chrome (sCr) and cobalt (sCo) concentrations are associated with local tissue adverse reactions to metal debris following metal-on-metal hip resurfacing (MoM-HR). Serum metal ions <2 µg/l are probably of little clinical relevance and a pragmatic "safe" threshold <5 µg/l has been suggested.The primary aim of this study was to evaluate if a careful selection of patients combined with optimal implant positioning could eliminate cases with "unsafe" serum metal ion levels. A secondary aim was to study the association between different risk factors and having Co and/or Cr levels >5 µg/l. PATIENTS AND METHODS: This is a retrospective, single-institution cohort study of 410 consecutive patients operated on with a Birmingham Hip Resurfacing (BHR) implant between 2001 and 2014. 288 of these had a unilateral MoM-HR, pelvic and true lateral radiographs, and a related sCo and sCr sample, and were included in the final analysis. They were allocated to either a presumed "optimal group" consisting of only men aged <60 years old, with femoral head component >48 mm diameter, and with a cup positioned within Lewinnek's safe zones, or a "suboptimal group" consisting of the remaining patients. Fisher's exact test and multiple logistic regression analyses were performed. RESULTS: In the optimal group 48% (47/97) had serum metal ions >2 µg/l and 8% (8/97) >5 µg/l compared to 61% (116/191) and 18% (34/191) in the suboptimal group, p = 0.059 and p = 0.034 respectively. Acetabular cups with an anteversion <5 degrees had the highest odds ratio, 6.5 (95% CI, 3.0-14.3), of having sCo and sCr concentrations exceeding 5 µg/l. CONCLUSIONS: A well oriented BHR acetabular component in a presumably "optimal" patient reduces the risk of having elevated serum metal ions but does not eliminate it. Insufficient cup anteversion seems to be the strongest associated factor of elevated serum metals.

Midterm Results of Contemporary Uncemented Total Hip Arthroplasty in Patients 45 Years or Younger.

Total hip arthroplasty (THA) in young patients has varying results, and some reports show inferior results when compared with those of older patients. This study evaluated the outcomes of contemporary uncemented THA in patients 45 years or younger. This was a retrospective review from 2003 to 2015 at an academic institution. Three hundred one uncemented THAs in 232 patients 45 years or younger were evaluated. All patients had a minimum follow-up of 5 years. Ninety-day complications, survivorship free of revision, and dislocations were evaluated. Mean age was 35.7 years, 43.1% of patients were women, and mean follow-up was 9.3 years. Ninety-day complications included 26 emergency department visits, 11 readmissions, 3 revisions, and 3 dislocations. The rate of 10-year survivorship free of revision was 85.5%, and the rate of 10-year survivorship free of aseptic revision was 87.7%. Excluding metal-on-metal (MOM) THAs, 10-year aseptic survivorship was 93.3%. The most common reasons for revision were adverse local tissue reaction after MOM THA (16 hips) and periprosthetic joint infection (6 hips). In a multivariable logistic regression model, sickle cell disease (SCD) and conversion THA were associated with 90-day readmissions. Both MOM THA and SCD were associated with revision (P<.05). Patients who are 45 years or younger undergoing THA (excluding MOM articulation) had a rate of 10-year survival free of aseptic revision of 93.3%. At 9.3 years' mean follow-up, THA in young patients was associated with low revision rates with acceptable risk of prosthetic joint infection and dislocation. Patients with SCD are at increased risk for early readmission and revision at latest follow-up. [Orthopedics. 2023;46(1):e45-e51.].

Long-term changes in blood metal ion levels in patients with hip resurfacing implants: implications for patient surveillance after 10 years follow-up.

BACKGROUND: Studies investigating changes in blood metal ion levels during the second decade of the implant lifetime in MoM hip resurfacing patients are scarce. METHODS: Patients implanted with either Birmingham Hip Resurfacing (BHR) or Articular Surface Replacement (ASR) hip resurfacings with >10 years follow-up and repeated blood metal ion measurements were identified at 2 large specialist European arthroplasty centres. After excluding patients with initial metal ion levels >7 ppb, the proportion of patients with an increase in blood metal ion levels above previously validated implant-specific thresholds (cobalt 2.15 ppb for unilateral implants, cobalt or chromium 5.5 ppb for bilateral) was assessed. RESULTS: We included 2743 blood metal ion measurements from 457 BHR patients (555 hips) and 216 ASR patients (263 hips). Of patients with initial metal ion levels below implant specific thresholds, increases in cobalt or chromium level, respectively, to above these thresholds during the second decade were seen as follows: unilateral BHR (cobalt = 15.6%), unilateral ASR (cobalt = 13.8%), bilateral BHR (cobalt = 8.2%, chromium = 11.8%), bilateral ASR (cobalt = 8.5%, chromium = 4.3%). Measurement-to-measurement changes exceeding +2.15 ppb or +5.5 ppb were, however, uncommon during the second decade. Subgroup results with small diameter (<50 mm) implants were similar. CONCLUSIONS: We recommend less frequent blood metal ion measurements are needed (every 3 to 5 years) for hip resurfacing patients if initial values were below 7ppb.

Long-term survival analysis of cementless large-diameter head metal-on-metal total hip arthroplasty.

INTRODUCTION: The aim of this retrospective study was to study the long-term survival and reasons for revisions of a single-type, large-diameter head (LDH) metal-on-metal (MoM) implant. A special study interest was to find the threshold level for revision in terms of adverse reaction to metal debris (ARMD). MATERIALS AND METHODS: In this cohort study, we retrospectively reviewed 234 patients (253 hips) who received 38 mm head size LDH MoM total hip arthroplasties (THAs) between 01 January 2004 and 31 December 2009 at our institution. Patient symptoms, conventional radiographs, magnetic resonance imaging (MRI) findings and whole blood metal ions were studied. RESULTS: The median follow-up time was 11.5 years. The Kaplan-Meier cumulative survival estimate of the implant was 89.6% at 10 years and 82.9% at 14.6 years. Overall, 34/253 (13.4%) hips were revised during the follow-up period and of these; 19/34 (55.9%) were revised due to ARMD. The prevalence of ARMD was 12.4% (29/234 patients). CONCLUSIONS: The survival of the implant was on a moderate level as the 10-year cumulative survival rate was 89.6%. The exact threshold level for ARMD revision cannot be determined due to multiple variables affecting factors in re-operation decision-making.

No difference in implant survival between 28-mm M2a RingLoc metal-on-metal and metal-on-polyethylene total hip arthroplasty: results from the Finnish Arthroplasty Register.

BACKGROUND AND PURPOSE: Long-term outcome of small head (28 mm) metal-on-metal (MoM) total hip arthroplasty (THA) is available mainly for Metasul devices (Sulzer Medica, Winterthur, Switzerland). Biomet MoM THA was frequently used in Finland. Therefore, we assessed long-term survivorship of the M2a 28-mm RingLoc MoM THA (Biomet, Warsaw, IN, USA) and compared it with the metal-on-polyethylene (MoP) RingLoc THA from the same manufacturer. PATIENTS AND METHODS: We conducted a register study based on THAs from the Finnish Arthroplasty Register performed between January 1, 2000 and December 31, 2007. 290 28-mm head M2a MoM THAs and 1,647 28-mm head MoP THAs (reference group) were included. The endpoint was revision for any reason, or revision for aseptic loosening, osteolysis, liner wear, or metallosis as one group. Kaplan-Meier survival estimates were calculated, and revision risks were assessed using a Cox multiple regression model, both with 95% confidence intervals (CI). RESULTS: No difference was found in the 15-year Kaplan-Meier survivorship between the 28-mm head M2a RingLoc MoM THA and the reference group for any reason for revision (87.7% [82.9-92.1] and 83.3% [81.0-85.3], respectively). The adjusted hazard ratio (HR) for any reason for revision for the MoM THA group compared with the reference group was at least equal or better (0.70 [0.48-1.02]). Both groups presented similar survival for revision for aseptic loosening of the cup, osteolysis, liner wear, or metallosis, at 96.2% (92.7-98.0) and 95.4% (93.9-96.5), respectively. INTERPRETATION: In the long-term survival there was no difference between the M2a 28-mm RingLoc MoM THA and 28-mm MoP THA. Further follow-up regimens for M2a 28-mm RingLoc THA patients may be unnecessary, but long-term metal ion and radiological data is needed before any formal suggestions.

Comparing 1-year and 10-year whole blood metal ion results following Birmingham hip resurfacing for osteoarthritis.

BACKGROUND: Patients with metal-on-metal hip arthroplasty may develop adverse reactions to metal debris that can lead to clinically concerning symptoms, often needing revision surgery. As such, many regulatory authorities advocate for routine blood metal ion measurement. This study compares whole blood metal ion levels obtained 1 year following Birmingham Hip Resurfacing (BHR) to levels obtained at a minimum 10-year follow-up. METHODS: A retrospective chart review was conducted to identify all patients who underwent a BHR for osteoarthritis with a minimum 10-year follow-up. Whole blood metal ion levels were obtained at final follow-up in June 2019. These results were compared with patients' metal ion levels at 1 year. RESULTS: Of the 211 patients who received a BHR, 71 patients (54 males and 17 females) had long-term metal ion levels assessed (mean follow-up 12.7 ± 1.4 yr). The mean cobalt and chromium levels for patients with unilateral BHRs (43 males and 13 females) were 3.12 ± 6.31 µg/L and 2.62 ± 2.69 µg/L, respectively; for patients with bilateral BHRs (11 males and 4 females) cobalt and chromium levels were 2.78 ± 1.02 µg/L and 1.83 ± 0.65 µg/L, respectively. Thirty-five patients (27 male and 8 female) had metal ion levels tested at 1 year postoperatively. The mean changes in cobalt and chromium levels were 2.29 µg/L (p = 0.0919) and 0.57 µg/L (p = 0.1612), respectively. CONCLUSION: Our results suggest that regular metal ion testing as per current regulatory agency guidelines may be impractical for asymptomatic patients. Metal ion levels may in fact have little utility in determining the risk of failure and should be paired with radiographic and clinical findings to determine the need for revision.

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.

Non-ischaemic cardiomyopathy associated with elevated serum cobalt and accelerated wear of a metal-on-metal hip resurfacing.

A man in his late 30s developed non-ischaemic cardiomyopathy due to systemic cobalt toxicity associated with accelerated bearing surface wear from metal-on-metal hip resurfacing implanted in the previous 6 years. Following revision arthroplasty, the patient regained baseline cardiac function. Cobalt-induced cardiomyopathy is a grave condition that deserves early consideration due to potentially irreversible morbidity. We present this case to increase awareness, facilitate early detection and emphasise the need for research into the diagnosis and management of at-risk patients.