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BACKGROUND: In vivo assessment of inflammatory responses in the synovia of patients with MoM hip replacements would be useful in the determination of the prognosis of the hip replacement. Aims of the study was to investigate the correlation between cobalt and chrome levels in joint fluid with histopathological findings and the predictive ability of metal ion levels for these findings. METHODS: In 163 revision surgeries (141 ASR THAs and 22 ASR hip resurfacings) joint fluid chrome and cobalt levels were assessed and histological analysis of synovial tissues was performed. Histological analysis included assessment of histiocytes, particle load, surface necrosis, lymphocyte cuffs and ALVAL-score. RESULTS: Surface necrosis correlated positively with cobalt levels both in both groups. Neither chrome nor cobalt level had even fair discriminative ability to predict the presence or severity of any histological finding in the THA group. In the hip resurfacing group, cobalt level had good discriminative ability to predict the presence of perivascular lymphocytes and ALVAL-score of ≥ 7 whereas chrome had good discriminative ability to predict surface necrosis, metal particle load and ALVAL-score of ≥ 7. CONCLUSIONS: Measurement of metal ion levels following joint fluid aspirate offers no relevant information with regard to histopathological findings in patients with large-diameter MoM THAs. Limited information may be gained from assessment of joint fluid metal ion levels in patients with hip resurfacings, but disadvantages of an aspirate must be carefully reviewed.

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BACKGROUND: Adverse soft-tissue reaction to metal debris (ARMD) continues to be major source of concern in metal-on-metal (MoM) hip replacements. In our earlier study we were able to establish several risk factors for ARMD in patients who had received a small-diameter (<50 mm) Articular Surface Replacement (ASR, DePuy, Warsaw, IN, USA). The aims of the present study were to analyze whether these previously established risk factors also apply to patients who have received a large-headed (>50 mm) ASR™ XL THR. METHODS: Large-headed ASR total hip replacements were used in 225 operations (196 patients) at our institution. 176 patients (203 hips) attended a screening programme, consisting of a clinical evaluation, whole blood cobalt and chromium measurements, and cross-sectional imaging. RESULTS: Revision surgery was performed on 84 hips (37%) in 75 patients. ARMD was diagnosed in the majority (n = 73 [87%]) of these revisions. Cumulative 8-year survivorship was 52%. The previously established risk factors for ARMD were not applicable. Interestingly, increasing femoral diameter and stem type were identified as independent risk factors for ARMD but reduced cup coverage had no significant association with ARMD. CONCLUSIONS: Stem type and increasing femoral size as independent risk factors for ARMD in the cohort of ASR XL THR patients, support the importance of taper failure in the development of ARMD. The present results suggest that the degree of taper failure may be variable and dependent on the taper design.

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BACKGROUND: High revision rates attributable to adverse reactions to metal debris have been reported for total hip arthroplasties (THAs) with metal-on-metal implants and hip resurfacings. The effect of revision on blood metal ion levels is described only in small series, the clinical results of revisions have been contradictory, and concerns regarding component loosening have been presented. QUESTIONS/PURPOSES: We asked: (1) Did revision surgery result in a reduction to normal for whole blood cobalt (Co) and chromium (Cr) levels (2) What changes to the Oxford Hip Score were observed after revision of these hips with metal-on-metal implants? (3) Were there radiologic signs of component loosening observed on 1-year followup radiographs? METHODS: Between September 2010 and April 2013, 154 patients (166 hips) who had THAs with implantation of the Articular Surface Replacement (ASR™) system and 44 patients (49 hips) who had hip resurfacings of the ASR™ implant underwent revision surgery for adverse reactions to metal debris at our institution, after recall of these components in August 2010. General indications for revision of these implants included a symptomatic hip and/or a predominantly solid pseudotumor seen on cross-sectional imaging. Since recall, patients were systematically followed after revision with Oxford Hip Score questionnaires, blood Co and Cr measurements (analyzed from whole blood with dynamic reaction-cell inductively coupled plasma-mass spectrometry), and plain radiographs at 2 and 12 months after revision surgery, and thereafter at 2-year intervals. Preoperative and 1-year postoperative blood Co and Cr values were available for 93% (185 of 198 patients), Oxford Hip Score for 76% (151 of 198 patients), and plain radiographs for all patients. RESULTS: Whole-blood levels of Co decreased below the 7 ppb cut-off value in all patients with revision of unilateral THA or resurfacing, however, blood Cr levels remained elevated in four of 90 patients (4%) in the unilateral THA group and four of 34 patients (12%) in the unilateral resurfacing group. All had ultrahigh (> 40 ppb) preoperative Cr levels. Cr levels remained elevated in six of the patients at the 3-year followup. The median Oxford Hip Score improved from preoperative to 1-year postoperative in the unilateral THA group (38 [4-48] to 40 [9-48], p = 0.049) and in the unilateral hip resurfacing group (37.5 [9-48] to 44 [13-48], p = 0.011). No improvement was seen in patients who had bilateral THAs (37 [14-48] to 41 [9-48], p = 0.196). Only minor radiographic abnormalities were seen, with no suspicion of component loosening. CONCLUSIONS: Metal-on-metal THAs and resurfacings have raised concerns and an emerging rate of revisions has been seen for many different metal-on-metal hip prostheses worldwide. Revision surgery seems to be effective for removal of the systemic metal ion burden, even though blood Cr remained elevated in a few patients for more than 3 years after removal of the metal-on-metal implant. In patients with bilateral metal-on-metal hip replacements the remaining metal-on-metal implant still supplies the body with Co and Cr ions after a unilateral revision, and therefore followup should be continued. Adverse reactions to metal debris do not seem to compromise implant ingrowth after revision surgery. However, as some of our patients still had a poor functional outcome at 12 months after revision surgery, additional research is warranted to determine the optimal time for patients to undergo revision surgery for suspected adverse reactions to metal debris. LEVEL OF EVIDENCE: Level IV, therapeutic study.

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BACKGROUND AND PURPOSE: Ultrasound is used for imaging of pseudotumors associated with metal-on-metal (MoM) hips. Ultrasound has been compared with magnetic resonance imaging, but to date there have been no studies comparing ultrasound findings and revision findings. METHODS: We evaluated the sensitivity and specificity of preoperative ultrasound for detecting pseudotumors in 82 patients with MoM hip replacement (82 hips). Ultrasound examinations were performed by 1 of 3 musculoskeletal radiologists, and pseudotumors seen by ultrasound were retrospectively classified as fluid-filled, mixed-type, or solid. Findings at revision surgery were retrieved from surgical notes and graded according to the same system as used for ultrasound findings. RESULTS: Ultrasound had a sensitivity of 83% (95% CI: 63-93) and a specificity of 92% (CI: 82-96) for detecting trochanteric region pseudotumors, and a sensitivity of 79% (CI: 62-89) and a specificity of 94% (CI: 83-98) for detecting iliopsoas-region pseudotumors. Type misclassification of pseudotumors found at revision occurred in 8 of 23 hips in the trochanteric region and in 19 of 33 hips in the iliopsoas region. INTERPRETATION: Despite the discrepancy in type classification between ultrasound and revision findings, the presence of pseudotumors was predicted well with ultrasound in our cohort of failed MoM hip replacements.

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BACKGROUND AND PURPOSE: The US Food and Drug Administration and the UK Medicines and Health Regulation Agency recommend using MRI in the evaluation of patients with large-diameter metal-on-metal (LD-MoM) hips. Such recommendations do not take into account the relevance of repeated cross-sectional imaging. We therefore investigated the natural course of pseudotumors in patients with LD-MoM hip replacements. PATIENTS AND METHODS: Of 888 ASR patients (1,036 hips) 674 patients (798 hips) underwent 2 follow-up visits at our institution. Of these, we identified 124 patients (154 hips) who had undergone repeated clinical assessment including MRI and whole-blood metal ion assessment. RESULTS: A change in classification in imaging findings between the 2 MRIs was seen in 17 of the 154 hips (11%). In 13 hips (8%), a significant progression of the pseudotumor was evident, while in 4 (3 %) there was a retrogressive change. 10 of these 13 hips had had a normal first MRI. Patients with a progressive change in the scans did not differ significantly from those without a change in MRI classification regarding follow-up time, time interval between MRIs, or changes in whole-blood Cr and Co levels between assessments. INTERPRETATION: A change in classification was rare, considering that all patients had a clinical indication for repeated imaging. Progression of the findings did not appear to correlate clearly with symptoms or whole-blood metal values.

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PURPOSE: Emerging concern has arisen because of recent papers reporting a high prevalence of pseudotumours (PTs), even in patients with surface arthroplasties with a good clinical track record. The aim of our study was to establish the ten year survivorship of Birmingham hip resurfacing (BHR), to investigate whole blood (WB) metal ion levels and prevalence of adverse reactions to metal debris (ARMeD) and to determine the association of blood metal ion levels and symptoms with ARMeD in patients operated on with BHR at our institution. METHODS: Between May 2001 and May 2004, 261 consecutive BHRs were implanted in 219 patients. All living, nonrevised patients underwent a systematic screening programme consisting of clinical examination, WB cobalt and chromium measurements and targeted cross-sectional imaging. RESULTS: The ten year survival for the entire cohort was 91% (89-93%), with any revision as the endpoint. Prevalence of ARMeD was 6.9% in male and 8.8% in female patients. Symptomatic patients with elevated metal ion levels evinced highest prevalence (63%) of PTs compared with asymptomatic patients with elevated metal ion levels (42%) and symptomatic patients with nonelevated metal ions (11%). CONCLUSIONS: Contradicting the current international guidelines, our results suggest that it seems beneficial to combine routine metal ion measurement with clinical assessment, even in patients with well-functioning BHRs. Further follow-up will reveal whether new PTs will develop in these patients and BHR survivorship in the longer term.

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BACKGROUND AND PURPOSE: Magnetic resonance imaging (MRI) is important for detecting extracapsular pseudotumors, but there is little information on the accuracy of MRI and appropriate intervals for repeated imaging. We evaluated the sensitivity and specificity of MRI for detecting pseudotumors in 155 patients (167 hips) with metal-on-metal (MoM) hip arthroplasties that failed due to adverse reactions to metal debris (ARMD). METHODS: Preoperative MRIs were performed with two 1.5 T MRI scanners and graded by a senior musculoskeletal radiologist using a previously described MRI pseudotumor grading system. Revision findings were retrieved from surgical notes, and pseudotumors were retrospectively graded as fluid-filled, mixed-type, or solid. RESULTS: The sensitivity of MRI was 71% and the specificity was 87% for detecting extracapsular pseudotumors. The sensitivity was 88% (95% CI: 70-96) when MRI was performed less than 3 months before the revision surgery. Interestingly, when the time that elapsed between MRI and revision was more than 1 year, the sensitivity calculated was only 29% (95% CI: 14-56). Comparison between MRI and revision classifications gave moderate agreement (Cohen's kappa = 0.4). INTERPRETATION: A recent MRI predicts the presence of a pseudotumor well, but there is more discrepancy when the MRI examination is over a year old, most likely due to the formation of new pseudotumors. 1 year could be a justifiable limit for considering a new MRI if development of ARMD is suspected. MRI images over a year old should not be used in decision making or in planning of revision surgery for MoM hips.

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PURPOSE: Conventional follow-up methods are not sufficient to identify adverse soft tissue reactions in patients with metal-on-metal hip replacements. The national guidelines regarding metal ion measurements are debatable. The aims of our study were to investigate (1) if there is a clinically significant change in whole blood (WB) cobalt (Co) or chrome (Cr) levels in repeated WB assessment in patients operated on with ASR hip replacements, and (2) what proportion of patients has WB Co or Cr level below the previously established safe upper limits (SUL) in the repeated WB metal ion assessment. METHODS: We identified all patients (n = 254) with unilateral ASR implants who had second blood sample taken eight to 16 months after the first. RESULTS: WB Co and Cr levels remained below SUL and within their initial values during a mean one-year measurement interval in the majority of patients with a high risk HR device. In contrast to this, 50 % of patients with THRs had metal ion levels exceeding the SUL in the first measurement. WB Co values significantly increased over the measurement interval in the THR group. CONCLUSION: In patients with a high risk HR, repeated metal ion measurement did not provide useful information for clinical decision-making. In patients with a LD MoM THR repeated measurements revealed a large number of patients with metal ion levels exceeding SUL and might thus be clinically beneficial.

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BACKGROUND: There has been increasing concern of metal-on-metal (MOM) hip replacements regarding adverse reactions to metal debris. Information regarding prevalence and risk factors for these adverse reactions is scarce. QUESTIONS/PURPOSES: The primary purposes of our study were to determine (1) the prevalence of adverse reactions to metal debris among patients who received small-headed (< 50 mm) Articular Surface Replacement (ASR™) prostheses in hip resurfacing procedures or the ASR™ XL prostheses during THAs at our institution, and (2) the risk factors for adverse reactions to metal debris and if they are different in hip resurfacing replacements compared with THAs? METHODS: Small-headed ASR™ prostheses were used in 482 operations (424 patients) at our institution. After the recall of ASR™ prostheses, we established a systematic screening program to find patients with adverse reactions to metal debris. At a mean of 4.9 years (range, 0.2-8.1 years) postoperatively, 379 patients (435 hips) attended a screening program, which consisted of clinical evaluation, whole blood cobalt and chromium measurements, and cross-sectional imaging. RESULTS: At followup, 162 hips (34%) have been revised. The majority (85%) were revised owing to causes related to adverse reactions to metal debris. The 7-year survivorship was 51% for the ASR™ hip replacement cohort and 38% for the ASR™ XL THA cohort, respectively. Reduced cup coverage was an independent risk factor for adverse reactions to metal debris in both cohorts. High preoperative ROM, use of the Corail(®) stem, and female gender were associated with an increased risk of adverse reactions to metal debris only in patients undergoing THA. CONCLUSIONS: Adverse reactions to metal debris are common with small-headed ASR™ prostheses. Risk factors for these adverse reactions differ between hip resurfacing procedures and THAs. Our results suggest a more complicated failure mechanism in THAs than in hip resurfacing procedures.

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The prevalence of total hip arthroplasty in young patients is small but increasing. We analyzed the results of metal-on-metal hip resurfacing (MMHR) in patients aged 40 years or less. In total 74 operations were performed on 64 patients. Mean age at operation was 33.2 years. HHS averaged 92.3 points at latest follow-up, mean UCLA activity was 8.2. Patients with comorbidity evinced lower scores in HHS, in UCLA activity and in quality of life than patients without comorbidities. Eight revisions (10.8 %) were performed, of which seven due to adverse reaction to metal debris. Seven-year survival was 90.5 %. The functional outcome of hip resurfacing in this cohort was excellent, but overall survival was unsatisfactory. Further analysis is required to verify the role of hip resurfacing among young and active patients.

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PURPOSE: Determination of the cup orientation after metal-on-metal hip resurfacing may provide important information in the postoperative follow-up. We present a mathematical method based on a previously described approach to assess the version and inclination of the cup in the metal-on-metal bearing without a separate software computation from plain radiographs. The aim of the study was to assess the intra- and inter-observer reliability of this method. METHODS: Calculation of version and inclination were done twice for 20 hip resurfacings by four observers. Intra-observer reliability was estimated by mean error and correlation of the two sets of measurement for version and inclination. Bland-Altman plots, intra-class coefficient and mean error were used to assess the inter-observer reliability of the measurements. RESULTS: Intra-observer correlation for version measurement ranged from 0.74 to 0.94. Correlation for inclination varied between 0.94 and 0.97. Upper and lower limits of agreement in Bland-Altman plots for version measurements between observers ranged from 4.1 to 7.2 degrees and from -3.2 to -8.3 degrees, respectively. For inclination measurements the upper and lower limits ranged from 3.1 to 5.3 degrees and from -2.7 to -6.0 degrees. CONCLUSIONS: Mean errors, correlation coefficients and 95% limits of agreement were on an acceptable level. We believe that this method is applicable for clinical use.

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Hip resurfacings have been performed in our hospital since May 2001, and in this retrospective study, we analysed the clinical and radiological outcome of the first 144 prostheses (126 patients). One hundred and seven patients have visited our hospital for regular follow-up examination; 16 are not in regular follow-up and were sent a Harris Hip Score (HHS) questionnaire. Three patients live abroad. Mean follow-up was six years. One patient was lost during follow-up. Four prostheses have been revised. The six year cumulative survival rate was 96.7%. Two female patients required revision for aseptic lymphocyte-dominated vascular associated lesions (ALVAL) and two male patients due for femoral head necrosis. Both reoperated female patients had cup inclination > 60°. Mean HHS in the follow-up was 95.3, and mean patient satisfaction 2.53 on a scale 0-3. Neck thinning > 10% was seen in seven hips and impingement in 12 hips.

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BACKGROUND: Modern metal-on-metal hip resurfacing implants are being increasingly used for young and active patients, although the long-term outcome and failure mechanisms of these implants are still unknown. In this consecutive revision case series, early failures of femoral implants (at < 4 years) were studied. METHODS: 3 revisions were done due to a fracture of the femoral neck and 1 due to loosening and varus position of the femoral component. Femoral heads were removed en bloc 2-46 months after the primary operation, embedded in methylmethacrylate, sectioned, stained, and analyzed as whole-mount specimens in 4 55-62-year-old patients with osteoarthritis. RESULTS: Histopathology was characterized by new but also partly healed trabecular microfractures, bone demineralization, cysts, metallosis, and abnormal formation of new woven bone. All samples displayed signs of notching, osteoporosis, and aseptic necrosis, which seemed to have been the main reason for the subsequent development and symptoms of the patients and revision operations of the hips. INTERPRETATION: Based on these early revision cases, it appears that aseptic necrosis is a common cause of early loosening of resurfacing hip implants.

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BACKGROUND AND PURPOSE: Two-stage revision remains the gold standard in the treatment of infected knee arthroplasty. Lately, good long-term results of direct exchange arthroplasty have been reported. The purpose of this literature review is to compare the clinical outcome achieved with one-stage revision and two-stage revision with different types of spacers. METHODS: A thorough systematic review of literature was undertaken to idenepsy reports on the treatment alternatives. Papers written in English or including an English abstract, published from 1980 through 2005, and reporting either the success rate in eradication of infection or the clinical status achieved were reviewed. 31 original articles describing the results of 154 one-stage exchange arthoplasties and of 926 two-stage exchange arthoplasties were included. The depth of detail in the description of materials and methods varied markedly, making it impossible to perform a meta-analysis. Instead, a descriptive review of the results is presented. RESULTS: With a follow-up of 12-122 months, the overall success rate in eradication of infection was 73-100% after one-stage revisions and 82-100% after two-stage revisions. Reinfection rates were the lowest in series where articulating cement spacers were used, though the follow-up was relatively short. Studies using articulating spacers reported the highest average postoperative ranges of motion. Otherwise, no correlations were observed between the clinical outcome and the length of follow-up, the type of revision, or the type of spacer. The clinical outcome (knee scores and range of motion) of the one-stage revisions was no different from that of the two-stage revisions. INTERPRETATION: Two-stage exchange is an effective treatment. Mobile spacers may further improve the range of motion. More experience in one-stage revision is required in order to define its role in the management of infected knee arthroplasties.

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BACKGROUND: As revision total knee arthroplasty surgery is becoming more common, it is necessary to evaluate how individual revision prosthesis systems perform in degenerative and inflammatory arthritides. In this study, results of the use of the Total Condylar III (TC III) system in osteoarthritis (55 knees) were compared to results of its use in inflammatory arthritis (16). METHODS: Patients were followed radiographically for 5.9 (3.0-10.2) years and clinically for 3.0 (0.2-6.8) years, using re-revision as the endpoint. RESULTS: At 1 year after revision and at final follow-up, the total Knee Society knee score, function score and range of motion had improved (p < 0.001) with no differences between osteoarthritis and inflammatory arthritis. No knee had definite component loosening, although 23 knees had asymptomatic radiolucent lines. Complications comprised 4 infections, 1 patellar pain syndrome and 1 rupture of the patellar tendon. Using any re-revision of the prosthesis as the endpoint, 5-year survival was 95% and 8-year survival was 94%. INTERPRETATION: Concentration of demanding revision knee arthroplasties to a few hands led to good or excellent knee joint knee score results in four-fifths of the patients, and showed good outcome with the TCIII system. In spite of ligamentous laxity, propensity to develop infections, bone destruction and poor general health, patients with inflammatory arthritis had results similar to those with osteoarthritis.

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BACKGROUND: National and regional arthroplasty registries have been used to study the results of primary total knee arthroplasties. The purpose of this paper was to present the results of revision total knee replacements and describe predictors of survival of those replacements, with repeat revision as the end point. METHODS: The nationwide Finnish Arthroplasty Registry included 2637 revision total knee arthroplasties from 1990 through 2002. Survivorship of the revision total knee arthroplasties was analyzed, with repeat revision as the end point. The survivorship analyses comprised evaluations of the proportional hazards assumption followed by calculations of univariate and multivariate statistics and model diagnostics as appropriate. RESULTS: The survival rate following the revision total knee arthroplasties was 95% (95% confidence interval, 94% to 96%) at two years (1874 knees), 89% (95% confidence interval, 88% to 90%) at five years (944 knees), and 79% (95% confidence interval, 78% to 81%) at ten years (141 knees). Multivariate regression analysis showed the most significant predictors of prosthetic survival to be the age of the patient and the life in service of the primary total knee replacement (that is, the time between the primary total knee replacement and the revision). Survivorship was also significantly predicted by the year of the first revision total knee arthroplasty and the reason for the revision. CONCLUSIONS: An age greater than seventy years, revision five years or more after the primary arthroplasty, and absence of patellar subluxation are positive indicators of survival of a revision total knee replacement. We believe that normal aging as well as the deconditioning effect of disease (osteoarthritis and rheumatoid arthritis) and its treatment (primary total knee replacement) may lead to a reduced activity level, which, together with a presumed reluctance to operate on elderly patients, protects against repeat revisions. LEVEL OF EVIDENCE: Prognostic Level II. See Instructions to Authors for a complete description of levels of evidence.

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BACKGROUND: It has been suggested that a hip fracture as a primary diagnosis for arthroplasty is a risk factor for periprosthetic fracture. PATIENTS AND METHODS: We compared 16 patients with late periprosthetic fracture of the femur to 48 controls. The primary diagnosis for all patients was hip fracture. The date of operation for hip fracture was used to select the control group of patients, all of whom were operated at the same time and in the same hospital district. No other selection criteria were used. Complications at the time of index operation, type of prosthesis, age, sex, BMI, patient's diseases, medication, and surgeon's experience were compared using conditional logistic regression. RESULTS: We found that low age at the time of the hip fracture operation increased the risk of periprosthetic fracture (OR = 4.9, CI = 1.2-20). The polished wedge type of prosthesis was associated with a higher risk of periprosthetic fracture than were other designs (OR = 11, CI = 1.2-97). INTERPRETATION: These findings of risk factors for periprosthetic fracture are new and should be confirmed by further studies using larger numbers of patients.

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