Hip resurfacings revised for inflammatory pseudotumour have a poor outcome

The Correlation of Serum Metal Ions with Functional Outcome Scores at Three-to-Six Years following Large Head Metal-on-Metal Hip Arthroplasty

Based on success of hip resurfacing, large head Metal on Metal (MoM) hip arthroplasty has gained significant popularity in recent years. There are growing concerns about metal ions related soft tissue abnormalities. The aim of this study was to define a correlation of metal ions with various functional outcome scores following large head MoM hip arthroplasty. Consecutive cohort of 70 patients (76 hips) with large head MoM hip arthroplasty using SL-Plus femoral stem and Cormet acetabular component were prospectively followed up. An independent observer assessed the patients which included serology for metal ion levels and collection of Oxford Hip, Harris hip, WOMAC, SF-36 & modified UCLA scores. Median serum cobalt and chromium levels were 3.10 μg/L (0.35–62.92) and 4.21 μg/L (0.73–69.27) with total of median 7.30 μg/L (2.38–132.19). The median Oxford, Harris, WOMAC, SF-36 and modified UCLA scores were 36 (6–48), 87 (21–100), 36 (24–110), 104 (10–125), and 3 (1–9), respectively. Seventeen patients had elevated serum cobalt and chromium levels ≥7 μg/L. There was no significant correlation between serum metal ion levels with any of these outcome scores. We recommend extreme caution during follow up of these patients with large head MoM arthroplasty.

Femoral neck fracture after Birmingham Hip Resurfacing Arthroplasty: prevalence, time to fracture, and outcome after revision

A consecutive cohort of 3076 Birmingham Hip Resurfacings from a single institution was analyzed. The prevalence of femoral neck fracture, the time to fracture, and the outcome after revision were investigated. Fractures occurred in 34 hips (prevalence, 1.1%). Median time to fracture was 0.27 year (range, 0.014-11.2 years). Mean operation time for revision was 59 minutes, and 71% underwent isolated femoral component revision. At a mean follow-up of 5.5 years since revision, 3 patients required re-revision (2 aseptic loosening, 1 for sepsis) giving a survival of 95.7% (confidence interval, 86.9%-100%) at 5 years for the revision. Median Oxford Hip Score was 12.5% (interquartile range, 3.2%-32.3%). There were no cases of radiologic failure during follow-up. Most fractures occur early after hip resurfacing and were straightforward to revise.

Do revised hip resurfacing arthroplasties lead to outcomes comparable to those of primary and revised total hip arthroplasties?

BACKGROUND

A theoretical clinical advantage of hip resurfacing (HR) is the preservation of femoral bone. HR femoral component revision reportedly yields postoperative function comparable to that of primary THA. However, few studies have looked at the outcome of both HR femoral and acetabular side revisions.

QUESTIONS/PURPOSES

We determined whether (1) patients undergoing HR revision to THA have perioperative measures and outcome scores comparable to those of patients undergoing primary THA or revision of primary THA and (2) patients undergoing HR revision of both components have perioperative measures and outcome scores comparable to those of patients undergoing HR revision of the femoral component only.

METHODS

We retrospectively reviewed and compared 22 patients undergoing revision HR to a THA to a matched (age, sex, BMI) group of 23 patients undergoing primary THA and 12 patients undergoing primary THA revision. Patients completed the WOMAC and SF-12 questionnaires before surgery and at latest followup (range, 24-84 months for HR revision, 28-48 months for primary THA, and 24-48 months for revision THA). Blood loss, days in hospital, complications, and outcome scores were compared among groups.

RESULTS

We observed no differences in SF-12 scores but observed lower WOMAC stiffness, function, and total scores in the HR revision group than in the primary THA group. Patients undergoing HR revision of both components had comparable SF-12 and WOMAC stiffness, function, and total scores but overall lower WOMAC pain scores compared to patients undergoing HR revision of the femoral side only. The HR revision group had greater intraoperative blood loss compared to the primary THA group but not the revision THA group.

CONCLUSIONS

The perioperative measures and outcome scores of HR revision are comparable to those of revision THA but not primary THA. Longer followup is required to determine whether these differences persist. Patients undergoing HR revision of one or both components can expect comparable stiffness and function.

LEVEL OF EVIDENCE

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

Metal-on-metal total hip arthroplasty: do symptoms correlate with MR imaging findings?

PURPOSE

To determine the prevalence of magnetic resonance (MR) imaging abnormalities after metal-on-metal total hip arthroplasty and to determine whether presence of symptoms correlates with findings at MR imaging.

MATERIALS AND METHODS

This HIPAA-compliant study was approved by the institutional review board, and informed consent was waived. MR imaging was performed with conventional sequences and a 1.5-T clinical imager in 192 hips (174 patients) evaluated during a 15-month period. Two observers retrospectively reviewed the images for the presence and size of pseudotumor, communication with the pseudocapsule, wall thickness, synovial hypertrophy, compartmentalization, solid components, foci of wall susceptibility, osteolysis, bone marrow edema, abductor muscle or tendon abnormality, and Anderson MR grade (normal, infection, or varying severity of metal-on-metal disease). These findings were compared between asymptomatic and symptomatic patients by using the Fisher exact test or the Wilcoxon-Mann-Whitney test, as appropriate.

RESULTS

Prevalence of pseudotumors per patient and per hip was 69% (120 of 174 patients, 132 of 192 hips). Bone marrow edema (present in six asymptomatic patients and 19 patients with pain, P < .01) and tendon tearing (present in five asymptomatic patients and 13 patients with pain, P < .05) were predictors of pain. Presence of symptoms was not correlated with presence (P = .4151) or size of pseudotumors. Anderson MR grade binarized into normal versus abnormal showed moderate agreement between readers (κ = 0.439) but was also not correlated with symptoms (P = .6648).

CONCLUSION

The presence of bone marrow edema and abductor tendon tears but not the presence or size of pseudotumor was associated with patient pain.

Metal-on-Metal Bearing: Is This the End of the Line? We Do Not Think So

BACKGROUND

Recent studies have recommended the discontinuation of metal-on-metal (MoM) components in total hip arthroplasty (THA) because of adverse effects reported with large-diameter MoM THA. This is despite favorable long-term results observed with 28 and 32 mm MoM bearings.

QUESTIONS/PURPOSES

The aim of this study was to assess the value of calls for an end to MoM bearings as THA components. Specifically, we wish to address the risks associated with MoM bearings including adverse soft tissue reactions, metal ion release, and carcinogenic risk.

METHODS

The study evaluates the arguments in the literature reporting on MoM (adverse soft tissue reactions, metal ion release, and carcinogenic risk) and the experience of the current authors who re-introduced these bearings in 1995. They are balanced by a benefit-risk review of the literature and the authors' experience with MoM use.

RESULTS

Adverse reactions to metallic debris as well as metal ion release are predictable and can be prevented by adequate design (arc of coverage, clearance), metallurgy (forged instead of cast alloy, high-carbide content), and appropriate component orientation. There is no scientific evidence that carcinogenicity is increased in subjects with MoM hip prostheses. MoM articulations appear to be attractive allowing safe hip resurfacing, decreasing the risk of THA revision in active patients, and providing secure THA fixation with cement in cages in severely deformed hips. MoM bearings in women of child-bearing age are controversial, but long-term data on metallic devices in adolescents undergoing spinal surgery seem reassuring.

DISCUSSION

Adequate selection of MoM articulations ensures their safe use. These articulations are sensitive to orientation. Fifteen years of safe experience with 28- and 32-mm bearings of forged alloy and high-carbide content is the main reason for retaining them in primary and revision THA.

Adoption of hip resurfacing arthroplasty at hospital for special surgery: a cohort study

BACKGROUND

Hip resurfacing arthroplasty (HRA) is an alternative to traditional total hip replacement (THR) that allows for the preservation of femoral bone. It is a more technically difficult procedure that has led some researchers to report an unsatisfactory learning curve (Berend et al., J Bone Joint Surg Am Suppl 2:89-92, 2011; Mont et al., Clin Orthop Relat Res 465:63-70, 2007).

PURPOSE

The purpose of this study was to investigate the adoption of HRA at our institution, examining the clinical results, revision rate, and modes of failure. Additionally, a comparison of three different implant systems was performed.

METHODS

A retrospective review of a consecutive series of HRA performed at our institution between the years 2004 and 2009 was carried out. A total of 820 HRA with a minimum of 2 years of follow-up were included in the study. The majority of included patients were males (70%), with osteoarthritis (92%). The average age was 49.8 years, and the mean BMI was 27.5 kg/m(2).

RESULTS

The average Harris hip score improved from 61 to 96.5 postoperatively. Thirteen revisions (1.6%) were performed for femoral neck fracture, femoral head osteonecrosis, acetabular loosening, metal reactivity/metallosis, and metal allergy. The overall Kaplan-Meier survival curve with revision surgery as an endpoint showed 98.5% survival at 5 years. There were no observable differences in clinical scores or revision rates between the different implant systems.

CONCLUSIONS

HRA can be successfully adopted with a low complication rate, given careful patient selection, specialized surgical training, and use of good implant design.

Evidence-based understanding of management perils for metal-on-metal hip arthroplasty patients

Adverse biological reactions causing failures of metal-on-metal (MoM) hip arthroplasty can be local or systemic. Both dose-dependent cytotoxicity of wear debris leading to subsequent necrosis of periprosthetic soft tissues and adaptive immunity may play an important role in pathogenesis in susceptible patients. There appears to be a spectrum of clinical presentations of adverse soft tissue reactions, reflecting a complex interplay of implant, surgical, and patient factors. A systematic treatment approach is helpful in optimizing evidence-based management of MoM patients. Although specialized tests such as metal ion levels are a useful diagnostic tool for evaluating MoM hip arthroplasty patients, overreliance on any single investigative tool in clinical decision-making process should be avoided. Future research focusing on diagnostic tools for detecting adverse periprosthetic soft tissue necrosis as well as optimization of MoM bearings and modular connections to further diminish wear and corrosion is warranted.

Common femoral vein thrombosis caused by a metal-on-metal hip arthroplasty-related pseudotumor

We present a case of a pseudotumor causing a deep femoral vein thrombosis 16 months after undergoing a metal-on-metal total hip arthroplasty. There is increasing concern over the effect of metal ions that are produced by wear in metal-on-metal hip arthroplasty systems. Recently, a number of articles have reported the development of an inflammatory pseudotumor causing a number of different problems early on in the lifespan of the implant necessitating revision surgery. This case reports the first presentation of a pseudotumor causing a serious venous thrombosis due to pressure effect and indicates further possible evidence for caution when considering metal-on-metal bearing hip arthroplasty.

Debonding of the acetabular porous coating of a hip resurfacing arthroplasty: a case report

We report an unusual case of loosening of the acetabular component of a hip resurfacing arthroplasty due to debonding of the titanium surface coating from the acetabular shell. A 41-year-old male scaffolder had bilateral hip resurfacings in 2006. These initially functioned well. At 54 months he was found to have migration of the acetabular component on the right side. This was subsequently revised to a cemented total hip arthroplasty. Debonding of the surface coating was suspected on radiographs prior to the revision procedure, and was confirmed intraoperatively.

Minimum 5-year follow-up after Cormet hip resurfacing. A single surgeon series of 234 hips

The performance of the Cormet hip resurfacing device was evaluated after a minimum of 5 years in 234 hips. The mean age of the patients was 54 years; there were 135 men and 80 women. The primary diagnosis was osteoarthritis in 78% of the patients. Outcome measures were the Harris Hip Score and implant survival. The overall survival rate was 94% with 12 revisions in women and 3 in men. There were 7 femoral and 5 acetabular failures and two revisions for groin pain. Cumulative survival rate in men and women was 98% and 89%, in patients with a femoral component larger than 44 mm and smaller than 44 mm 97% and 89% respectively. Patients with primary osteoarthritis had a 95% cumulative survival rate at 5 years. The risk of failure was 6.4 times higher in women than in men. Our results suggest that hip resurfacing with the Cormet device is an acceptable alternative for active patients with hip arthritis, but patient selection is crucial for good long-term results.

The effect of cup orientation and coverage on contact mechanics and range of motion of metal-on-metal hip resurfacing arthroplasty

Implant malpositioning has been identified as a factor associated with clinical failures of metal-on-metal hip resurfacings (MoMHRs). This study investigated the effect of cup orientation and cup coverage on the contact mechanics (incidence of edge-loading) and range of motion (ROM) of MoMHR. Three generic MoMHRs with differing amounts of cup coverage were considered at various orientations. Contact area and contact pressure at the bearing surface were predicted for each design using finite element (FE) method. The ROM was determined based on the geometry overlap. Edge contact was found at lower angles of inclination (65°) for lower coverage cup designs; however, they also provided the greatest ROM. Conversely, cups with greater coverage did not exhibit edge contact until the cup was more steeply positioned (75°), however ROM was reduced. This study enables both sets of variable to be considered in the design of metal-on-metal bearings in hip.

MRI of aseptic lymphocytic vasculitis-associated lesions in metal-on-metal hip replacements

OBJECTIVE

The aim of this review is to describe the clinical, histopathologic, and MRI features of aseptic lymphocytic vasculitis-associated lesions in total hip replacements.

CONCLUSION

The introduction of modern metal-on-metal hip arthroplasty has been accompanied by a newly described disease, aseptic lymphocytic vasculitis-associated lesions, which is characterized histologically by bland necrosis and dense perivascular lymphocytic infiltrates. Conventional radiographic findings are often normal, but the typical MRI findings include periprosthetic fluid collections, soft-tissue masses, gluteal tendon avulsion, bone loss, periosteal stripping, neurovascular involvement, and periprosthetic fractures. The severity of the histologic and MRI appearances can be graded according to defined published criteria.

Bearing surfaces for total disc arthroplasty: metal-on-metal versus metal-on-polyethylene and other biomaterials

BACKGROUND CONTEXT

Concerns about the effect of metallic wear debris from metal-on-metal bearing surfaces in total hip arthroplasty have increased. Some spinal arthroplasty devices include metal-on-metal bearing surfaces.

PURPOSE

To review the literature for clinical reports of complications because of wear debris from metal-on-metal spinal arthroplasty devices. To review the biology of wear debris from metal-on-metal bearing surfaces drawn from the hip arthroplasty literature and place it in the context of global regulatory actions and clinical and laboratory studies.

STUDY DESIGN

Literature review.

METHODS

To identify clinical reports, the PubMed database from the United States National Library of Medicine was queried using Medical Subject Headings terms and additional keyword terms. In addition, experts from academia and regulatory agencies were questioned regarding their knowledge of reports, including experts who attended the US Food and Drug Administration roundtable in September 2010.

RESULTS

Three case reports and one case series including seven total cases were identified in which abnormal inflammatory reactions and soft-tissue masses after metal-on-metal disc replacements were consistent with pseudotumor and metal hypersensitivity. Spinal cases are present as pain and neurologic symptoms. On plain radiography, there is no clear periprosthetic osteolysis or loosening. On magnetic resonance imaging, there is increased magnetic susceptibility artifact because of metallic debris that renders images inadequate. Computed tomography myelography demonstrates a soft-tissue mass, which exhibits epidural extension surgically. Histologically, large areas of necrotic debris and exudates are interspersed with chronic inflammatory cells. Lymphocyte or macrophage predominance is determined by the rate of wear and the presence of gross, microscopic, or submicron metallic wear debris. The metallurgy of the involved devices is cobalt-chromium-molybdenum (CoCrMo) alloy, and the bearing surface is CoCrMo-on-CoCrMo.

CONCLUSIONS

Metal-on-metal spinal arthroplasty devices are subject to postoperative complications because of metallic wear debris with similar clinical, radiographic, histologic, gross anatomic, and device-related features to those found in metal-on-metal bearing surfaces in total hip arthroplasty.

The sensitivity, specificity and predictive values of raised plasma metal ion levels in the diagnosis of adverse reaction to metal debris in symptomatic patients with a metal-on-metal arthroplasty of the hip

Plasma levels of cobalt and chromium ions and Metal Artefact Reduction Sequence (MARS)-MRI scans were performed on patients with 209 consecutive, unilateral, symptomatic metal-on-metal (MoM) hip arthroplasties. There was wide variation in plasma cobalt and chromium levels, and MARS-MRI scans were positive for adverse reaction to metal debris (ARMD) in 84 hips (40%). There was a significant difference in the median plasma cobalt and chromium levels between those with positive and negative MARS-MRI scans (p < 0.001). Compared with MARS-MRI as the potential reference standard for the diagnosis of ARMD, the sensitivity of metal ion analysis for cobalt or chromium with a cut-off of > 7 µg/l was 57%. The specificity was 65%, positive predictive value was 52% and the negative predictive value was 69% in symptomatic patients. A lowered threshold of > 3.5 µg/l for cobalt and chromium ion levels improved the sensitivity and negative predictive value to 86% and 74% but at the expense of specificity (27%) and positive predictive value (44%).

Metal ion analysis is not recommended as a sole indirect screening test in the surveillance of symptomatic patients with a MoM arthroplasty. The investigating clinicians should have a low threshold for obtaining cross-sectional imaging in these patients, even in the presence of low plasma metal ion levels.

Risk of cancer with metal-on-metal hip replacements: population based study

OBJECTIVE

To assess the risk of cancer associated with modern primary metal-on-metal hip replacements.

DESIGN

Population based study.

SETTING

Nationwide retrospective comparative register.

PARTICIPANTS

10,728 patients who underwent metal-on-metal total hip arthroplasty and 18,235 patients who underwent conventional metal-on-polyethylene, ceramic-on-polyethylene, and ceramic-on-ceramic total hip arthroplasty (the non-metal-on-metal cohort) in the Finnish Arthroplasty Register 2001-10. Data on cancer cases up to 2010 for these cohorts were extracted from the Finnish Cancer Registry.

MAIN OUTCOME MEASURES

The relative risk of cancer was expressed as the ratio of observed to expected number of cases from the Finnish population--that is, the standardised incidence ratio. The relative risk of cancer in the metal-on-metal cohort compared with the non-metal-on-metal cohort was estimated with analyses of these ratios and Poisson regression.

RESULTS

The overall risk of cancer in patients with metal-on-metal hip implants was similar to that in the Finnish population (378 observed v 400 expected, standardised incidence ratio 0.95, 95% confidence interval 0.85 to 1.04). The overall risk of cancer in patients with metal-on-metal hip implants was also no higher than in patients who had received non-metal-on-metal hip implants (relative risk 0.92, 0.81 to 1.05).

CONCLUSIONS

Metal-on-metal hip replacements are not associated with an increased overall risk of cancer during a mean follow-up of four years.

Pseudotumors are common in well-positioned low-wearing metal-on-metal hips

BACKGROUND

Pseudotumors are sterile inflammatory lesions found in the soft tissues surrounding metal-on-metal (MOM) and metal-on-polyethylene hip arthroplasties. In patients with MOM hip arthroplasties, pseudotumors are thought to represent an adverse reaction to metal wear debris. However, the pathogenesis of these lesions remains unclear. Currently, there is inconsistent evidence regarding the influence of adverse cup position and increased wear in the formation of pseudotumors.

QUESTIONS/PURPOSES

We therefore determined whether pseudotumor formation was associated with (1) adverse cup position, (2) raised metal ion levels, and (3) increased wear rates of the retrieved components.

METHODS

We retrospectively reviewed all 352 patients for whom we had retrieved specimens from revisions of a current-generation MOM hip prosthesis between February 2008 and September 2010; of these, 105 met our inclusion criteria. We used multivariate logistic regression analysis to compare acetabular orientation, metal ion levels before revision, and component wear rates between patients with (n = 72) and without (n = 33) pseudotumors, according to findings on metal artifact reduction sequence MRI.

RESULTS

The proportion of patients demonstrating evidence of a pseudotumor in well-positioned hips was similar to those with adverse cup positions (67% and 66%, respectively). Patients revised with pseudotumors had similar whole-blood metal ion levels and component wear rates to those who were not revised.

CONCLUSIONS

Pseudotumors were not associated with increased wear or metal ion levels, suggesting patient susceptibility is likely to be more important.

Metal-on-metal total hip arthroplasty: causes and high incidence of early failure

Early failures of metal-on-metal total hip arthroplasty (THA) occur due to aseptic loosening, metal hypersensitivity reactions, pseudotumor formation, and component seizing. The purpose of this study was to investigate the timing, common modes of failure, clinical outcomes, and incidence of metal-on-metal THA revisions. A review was performed of 80 patients who underwent revision of a failed metal-on-metal THA for any reason. The most common reason for metal-on-metal failure was aseptic acetabular loosening, with a rate of 56.25% (45/80 patients). Early failure of metal-on-metal THAs was noted, with 78% of these revisions being performed within 2 years of the index operation and 92.5% within 3 years. Furthermore, 13% of patients experienced significant localized soft tissue reactions. Mean preoperative Harris Hip Score was 42.35 ± 14.24 and mean postoperative Harris Hip Score was 66.5 ± 23.2 (range, 9.55-95.4), with an average follow-up of 438 ± 492 days (range, 40-2141), or 1.2 years.It is imperative that clinicians be cognizant of the fact that the proposed advantages of metal-on-metal THA are not without potential detrimental sequelae. This article proposes an algorithm to aid in diagnosing the etiology of a painful metal-on-metal THA, as well as 2 classification schemes regarding metal-on-metal THA complications to help direct treatment.

Chinese experience with metal-on-metal hip resurfacing

The aim of this study was to study the actual clinical and laboratory results of metal-on-metal resurfacing hip arthroplasties by comparing with other implants. A total of 127 cases were operated on at the Department of Orthopaedics of Wuhan Union Hospital from 2005 to 2011. An important cause of failure is the fracture of the femoral neck. The chromium and cobalt levels of resurfacing hip arthroplasty and large-diameter head total hip arthroplasty (THA) are higher than those of a conventional metal-on-polyethylene total hip arthroplasty. There was a high ion level associated with an abduction angle of more than 45° and repetitive extreme hip motion in the 3 revision cases. The findings of this study are novel and quite controversial with that of the previously published literature.

Hip resurfacing arthroplasty: short-term survivorship of 4,401 hips from the Finnish Arthroplasty Register

BACKGROUND AND PURPOSE

Population-based registry data from the Nordic Arthroplasty Register Association (NARA) and from the National Joint Register of England and Wales have revealed that the outcome after hip resurfacing arthroplasty (HRA) is inferior to that of conventional total hip arthroplasty (THA). We analyzed the short-term survival of 4,401 HRAs in the Finnish Arthroplasty Register.

METHODS

We compared the revision risk of the 4,401 HRAs from the Register to that of 48,409 THAs performed during the same time period. The median follow-up time was 3.5 (0-9) years for HRAs and 3.9 (0-9) years for THAs.

RESULTS

There was no statistically significant difference in revision risk between HRAs and THAs (RR = 0.93, 95% CI: 0.78-1.10). Female patients had about double the revision risk of male patients (RR = 2.0, CI: 1.4-2.7). Hospitals that had performed 100 or more HRA procedures had a lower revision risk than those with less than 100 HRAs (RR = 0.6, CI: 0.4-0.9). Articular Surface Replacement (ASR, DePuy) had inferior outcome with higher revision risk than the Birmingham Hip Resurfacing implant (BHR, Smith & Nephew), the reference implant (RR = 1.8, CI: 1.2-2.7).

INTERPRETATION

We found that HRA had comparable short-term survivorship to THA at a nationwide level. Implant design had an influence on revision rates. ASR had higher revision risk. Low hospital procedure volume worsened the outcome of HRA. Female patients had twice the revision risk of male patients.

Large-diameter modular metal-on-metal total hip arthroplasty: incidence of revision for adverse reaction to metallic debris

Large-diameter modular metal-on-metal (MOM) total hip arthroplasty (THA) may offer reduction in wear debris and improved stability. Four studies are summarized here that used a large-diameter modular MOM system. A total of 1076 THAs were performed. This article presents data from 779 of these THAs with minimum 2-year follow-up (mean, 4.2 years) or revision since index THA (21 hips, with 1 more pending). Overall survivorship at 2 years was 98.6%; at 5 years, it was 97.0%. Seven revisions for an adverse reaction to metallic debris (ARMED), and 1 additional pending revision for ARMED, showed marked variability in presenting symptoms and intraoperative and postoperative findings. Data show good clinical performance of the modular MOM system, but suggest that surgeons must be diligent in monitoring MOM THA patients and aggressive in diagnosing and revising patients with a potential ARMED.

A hierarchy of computationally derived surgical and patient influences on metal on metal press-fit acetabular cup failure

The impact of anatomical variation and surgical error on excessive wear and loosening of the acetabular component of large diameter metal-on-metal hip arthroplasties was measured using a multi-factorial analysis through 112 different simulations. Each surgical scenario was subject to eight different daily loading activities using finite element analysis. Excessive wear appears to be predominantly dependent on cup orientation, with inclination error having a higher influence than version error, according to the study findings. Acetabular cup loosening, as inferred from initial implant stability, appears to depend predominantly on factors concerning the area of cup-bone contact, specifically the level of cup seating achieved and the individual patient's anatomy. The extent of press fit obtained at time of surgery did not appear to influence either mechanism of failure in this study.

In vivo evaluation of edge-loading in metal-on-metal hip resurfacing patients with pseudotumours

Objectives

Pseudotumours (abnormal peri-prosthetic soft-tissue reactions) following metal-on-metal hip resurfacing arthroplasty (MoMHRA) have been associated with elevated metal ion levels, suggesting that excessive wear may occur due to edge-loading of these MoM implants. This study aimed to quantify in vivo edge-loading in MoMHRA patients with and without pseudotumours during functional activities.

Methods

The duration and magnitude of edge-loading in vivo was quantified during functional activities by combining the dynamic hip joint segment contact force calculated from the three-dimensional (3D) motion analysis system with the 3D reconstruction of orientation of the acetabular component and each patient’s specific hip joint centre, based on CT scans.

Results

Edge-loading in the hips with pseudotumours occurred with a four-fold increase in duration and magnitude of force compared with the hips without pseudotumours (p = 0.02).

Conclusions

The study provides the first in vivo evidence to support that edge-loading is an important mechanism that leads to localised excessive wear (edge-wear), with subsequent elevation of metal ion levels in MoMHRA patients with pseudotumours.

Ten-year clinical, radiological and metal ion analysis of the Birmingham Hip Resurfacing

We present the clinical results and survivorship of consecutive 100 Birmingham Hip Resurfacings in 90 patients at a minimum follow-up of ten years. All procedures were carried out by an independent surgeon who commenced a prospective study in 1998. Patients were assessed clinically using the Western Ontario and McMaster Universities osteoarthritis index, Short-Form 36, Harris hip score and University of California, Los Angeles activity score. Radiological analysis was performed by an independent observer and blood metal ion levels concentrations were measured at ten years post-operatively in 62 patients. The median acetabular component inclination was 46.2° (34° to 59°) and anteversion 11.0° (0° to 30°). The median chromium concentration in the unilateral group was 1.74 (0.41 to 15.23) and for the bilateral group was 2.98 (1.57 to 18.01). The equivalent values for cobalt were 1.67 (0.54 to 20.4) and 1.88 (1.38 to 19.32).

In total there were eight failures giving an overall survival at ten years of 92% (95% confidence interval (CI) 86.7 to 97.3). BHR in male patients had an improved survivorship of 94.6% (95% CI 89.4 to 100) compared with females at 84.6% (95% CI 70.7 to 98.5), but this did not reach statistical significance (p = 0.119). Four of the nine BHRs with a bearing diameter of 42 mm failed.

The overall results were consistent with data produced from other centres in that the clinical outcome of large male patients was extremely encouraging, whereas the survival of the smaller joints was less satisfactory.

Experimental evaluation of new concepts in hip arthroplasty

In this thesis we evaluated two different hip arthroplasty concepts trough in vitro studies and numerical analyses. The cortical strains in the femoral neck area were increased by 10 to 15 % after insertion of a resurfacing femoral component compared to values of the intact femur, shown in an in vitro study on human cadaver femurs. There is an increased risk of femoral neck fracture after hip resurfacing arthroplasty. An increase of 10 to 15 % in femoral neck strains is limited, and cannot alone explain these fractures. Together with patient specific and surgical factors, however, increased strain can contribute to increased risk of fracture. An in vitro study showed that increasing the neck length in combination with retroversion or reduced neck shaft angle on a standard cementless femoral stem does not compromise the stability of the stem. The strain pattern in the proximal femur increased significantly at several measuring sites when the version and length of neck were altered. However, the changes were probably too small to have clinical relevance. In a validation study we have shown that a subject specific finite element analysis is able to perform reasonable predictions of strains and stress shielding after insertion of a femoral stem in human cadaver femurs. The usage of finite element models can be a valuable supplement to in vitro tests of femoral strain pattern around hip arthroplasty. Finally, a patient case shows that bone resorption around an implant caused by stress shielding can in extreme cases lead to periprosthetic fracture.

Minimum 5-year results of modular metal-on-metal total hip arthroplasty

This study reports minimum 5-year results of 95 hips implanted with a Pinnacle (DePuy, Warsaw, Ind) modular metal-on-metal acetabular prosthesis. Clinical scores such as the Harris Hip and Western Ontario and McMaster Universities Arthritis Index revealed excellent clinical outcomes at mean 6-year follow-up. With the use of large-diameter femoral heads, dislocation was rare, occurring in only 1 hip. Moreover, no acetabular and only 3 femoral osteolytic lesions were detected. Kaplan-Meier survivorship at 7 years after arthroplasty was 97.8% for the total hip arthroplasty construct and 100% for the acetabular shell. No unexplained pain or other complication attributable to wear debris or the metal-on-metal articulation was observed. These findings indicate that total hip arthroplasty with this specific modular metal-on-metal bearing performed well in a high-demand population at midterm follow-up.

Function and survival after revision of hip resurfacing

The purpose of this study was to compare functional outcome and survival of isolated acetabular, isolated femoral and both component revision after failure of primary Birmingham Hip Resurfacing. The Oswestry Outcome Centre prospectively collected data on 5000 hip resurfacing between 1997 and 2002. Of these, 182 hips were revised: 8% had revision of the acetabular component only, 42% had revision of the femoral component only to conventional stemmed prosthesis, and 50% had revision of both components to conventional total hip arthroplasty (THA). We used a postal questionnaire to assess function by Harris and Merle d'Aubigné and Postel hip scores and determined survival using re-revision as an endpoint. In patients with isolated acetabular revision, the median Harris hip score (HHS) was 74 at a mean of 4.5 years follow up. Isolated femoral revision had a median HHS of 82 at a mean of 3.8 years. When both components were revised, the median HHS was 85 at a mean of 4 years. We observed no difference in HHS between the groups. There was an average survival of 92% at 10 years. Survival was significantly lower for isolated acetabular revision (75%) than isolated femoral (93%) or both component revision (96%).

Inflammatory pseudotumor complicating metal-on-highly cross-linked polyethylene total hip arthroplasty

Inflammatory masses or cysts occurring in the pelvis, thigh, and gluteal regions, often mimicking infection, occasionally arise after total hip arthroplasty procedures. Inflammatory pseudotumors comprise a subgroup of these lesions. Pseudotumors have been associated with pain, rashes, instability, neuropathy, and premature loosening of prosthetic components, often leading to early and difficult revision surgery. The association between such pseudotumors and metal-on-metal bearings has led to questions regarding the performance of these bearings in hip arthroplasty. We present a case of pseudotumor requiring revision surgery, which occurred uniquely around a metal-on-highly cross-linked polyethylene bearing.

A MRI classification of periprosthetic soft tissue masses (pseudotumours) associated with metal-on-metal resurfacing hip arthroplasty

OBJECTIVE

Metal-on-metal hip resurfacing arthroplasty (MoMHRA) has become a popular option for young patients requiring hip replacement. A recognised complication is the formation of a symptomatic reactive periprosthetic soft tissue mass (pseudotumour). We present a radiological classification system for these reactive masses, dividing them into three groups: Type I are thin-walled cystic masses (cyst wall <3 mm), Type II are thick-walled cystic masses (cyst wall >3 mm, but less than the diameter of the cystic component) and Type III are predominantly solid masses.

MATERIALS AND METHODS

We reviewed all MRI performed over a 4-year period in patients with primary MoMHRA referred to our institution. In all cases the masses were assessed on MRI according to size, anatomical position, signal intensity and involvement of bone, muscle or neighbouring neurovascular bundles.

RESULTS

Periprosthetic masses were seen in 33 hips in 17 female (7 bilateral) and 8 male patients (1 bilateral). The Type I lesions were the most common and more likely to be posterior to the hip joint. The Type III masses were significantly larger than the cystic lesions and were more likely to be located anterior to the hip joint. To date 22 patients have undergone revision surgery with conversions to total hip replacement. Severity of symptoms and revision rates were lowest in the Type I group and highest in the Type III group.

CONCLUSION

Solid anterior pseudotumours were most likely to have the more severe symptoms and require revision surgery.

Metal-on-metal surface replacement: a triumph of hope over reason: opposes

Hip resurfacing has been performed for over a decade but still raises controversy as an alternative to traditional total hip arthroplasty (THA). Concerns exist about the potential complications of hip resurfacing, including femoral neck fracture and osteonecrosis of the femoral head. Recently, attention has been given to the metal-on-metal bearing of hip resurfacing with regard to production of metal ions, possible tissue necrosis, and rare instances of metal hypersensitivity. Given the success of the gold-standard THA, it is understandable why some surgeons believe metal-on-metal surface replacement to be "a triumph of hope over reason." However, this article opposes that viewpoint, demonstrating that data exist to justify the practice of preserving bone in younger patients. Hip resurfacing can maintain femoral bone without the expense of removing additional acetabular bone by using modern implants with incremental sizing. Furthermore, many of the problems cited with the bearing couple (such as excess metal production) have been due to poor implant designs, which have now been removed from the market. Finally, we now realize that the metal-on-metal articulation is more sensitive to malposition; thus, good surgical technique and experience can solve many of the problems that have been cited in the past. National registry results confirm that in a select population, hip resurfacing performs comparably to THA, while fulfilling the goal of bone preservation.

High revision rate at 5 years after hip resurfacing with the Durom implant

BACKGROUND/RATIONALE

There is growing evidence that different resurfacing implants are associated with variable survival and revision rates. A registry analysis indicated the Durom resurfacing implant had high revision rates at 5 years, whereas three original studies reported low revision rates at short-term followups. Thus, the revision rates appear controversial.

QUESTIONS/PURPOSES

We therefore assessed (1) the survivorship including differences between women and men at a mean of 5 years after resurfacing with the Durom implant, and (2) clinical scores and radiographic parameters.

PATIENTS AND METHODS

We prospectively followed all 100 Durom hip resurfacings implanted in 91 patients (25 women and 66 men; mean age, 52 years) between 2003 and 2004. Survivorship analysis was performed with pending revision or revision for any reason as the endpoint. The minimum followup was 47 months (mean, 60 months; range, 47-72 months).

RESULTS

At a mean of 5 years, 11 hips were revised for various reasons. Cumulative survival was 88.2% for all patients and 81.5% for women. The mean Oxford (OHS) and Harris hip (HHS) scores were 14.6 and 94.7, respectively. The mean UCLA activity level was 7.9. Sclerotic changes around the short femoral stem (pedestal sign) were detected in 40% of the hips. We observed considerable femoral neck thinning with component-to-neck ratios of 0.85 preoperatively and 0.82 at 5 years.

CONCLUSIONS

Our study highlights a high revision rate 5 years after hip resurfacing with the Durom implant. This observation underlines previous findings from registry data and suggests that revision rates increase with time.

LEVEL OF EVIDENCE

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

Characterization of metal-wear nanoparticles in pseudotumor following metal-on-metal hip resurfacing

Biopsies from a typical case of pseudotumor following metal-on-metal hip resurfacing (MoMHR) were analyzed using light and transmission electron microscopy, backscatter scanning electron microscopy and energy dispersive x-ray spectrometry (EDS). Heavy macrophage infiltration was observed in all black pigmented specimens. Metal nanoparticles (NPs) were observed exclusively within phagosomes of living macrophages and fragments of dead macrophages. Although dead fibroblasts were found to be juxtaposed with dead and disintegrated macrophages, the NPs were not seen within either live or dead fibroblasts. Chromium (Cr) but not cobalt (Co) was the predominant component of the remaining wear NPs in tissue. The current study finding suggests that corrosion of Co in phagosomes of macrophages and resultant Co ion release lead to tissue necrosis and adverse soft tissue reactions (pseudotumors). Further studies are required to elucidate the precise mechanism of intracellular corrosion of metal NPs and the long-term toxicity of the Cr remaining in the peri-prosthetic tissues.

FROM THE CLINICAL EDITOR

In this study of metal-on-metal hip resurfacing-related tissue necrosis and pseudotumor formation, corrosion and decomposition of metallic cobalt in phagosomes of macrophages and resultant cobalt ion release were demonstrated to be the key elements of pathogenesis.

Metal-on-metal bearings: the evidence so far

Lately, concerns have arisen following the use of large metal-on-metal bearings in hip replacements owing to reports of catastrophic soft-tissue reactions resulting in implant failure and associated complications. This review examines the literature and contemporary presentations on current clinical dilemmas in metal-on-metal hip replacement.

Clinical experience of revision of metal on metal hip arthroplasty for aseptic lymphocyte dominated vasculitis associated lesions (ALVAL)

There has been growing concern regarding the systemic and local effects of metal ions released from metal-on-metal hip resurfacings and total hip replacements, including the development of aseptic lymphocyte dominated vasculitis associated lesions (ALVAL). We describe our experience of treating 13 patients with failed metal on metal bearing hip prostheses secondary to this condition. Hip revision occurred at mean of 45 months following primary surgery. Groin pain was present in all patients. Other common features included large bursal swelling and mechanical symptoms. 3 patients developed their symptoms immediately postoperatively. The mean time to presentation was 21 months. Radiographic abnormalities noted included 3 patients with cup loosening and 2 patients with neck thinning. The mean cup inclination was 52 degrees. Surgical findings included bursal swellings and creamy brown fluid. Osteolysis was rarely seen. 12 revisions were achieved with primary implants and all patients had immediate symptomatic improvement. One patient was left with a pseudoarthrosis due to extensive soft tissue destruction. Diagnosis of ALVAL was confirmed histologically. The diagnosis of ALVAL should be considered in patients with unexplained pain from a metal on metal bearing hip arthroplasty. Surgical findings are typical and symptoms tend to resolve reliably following conversion to an alternative bearing surface.

Survival of hard-on-hard bearings in total hip arthroplasty: a systematic review

BACKGROUND

Improvements in prosthetic materials, designs, and implant fixation for THA have led to bearing surface wear being the limitation of this technology. Hard-on-hard bearings promise decreased wear rates and increased survival. However, there may be different survival rates based on bearing materials, manufacturing technologies, and femoral component designs. Additionally, survival rate variability may be based on study design.

QUESTIONS/PURPOSES

We determined survival rates and study levels of evidence and quality for the following bearings: stemmed metal-on-metal THA, metal-on-metal hip resurfacing, ceramic-on-ceramic THA, and ceramic-on-metal THA.

METHODS

We performed a systematic review of the peer-reviewed literature addressing THA hard-on-hard bearings. Quality for Level I and II studies was assessed.

RESULTS

The four Level I or II second-generation stemmed metal-on-metal THA studies reported between 96% and 100% mean survival at 38 to 60 months. The two Level I hip resurfacing studies reported 94% and 98% mean survival at 56 and 33 months. The four Level I studies of ceramic-on-ceramic THA reported survival from 100% at mean 51 months to 96% at 8 years.

CONCLUSIONS

While hard-on-hard bearing survival rates have generally been variable with earlier designs, contemporary implants have demonstrated survival of 95% or greater at followup of between 3 and 10 years. Some variability in survival may be due to differences in surgical technique, component positioning, and implant designs. As bearing designs continue to improve with modified materials and manufacturing techniques, use will increase, especially in young and active patients, though concerns remain about the increased reports of adverse events after metal-on-metal bearings.

Silent soft tissue pathology is common with a modern metal-on-metal hip arthroplasty

BACKGROUND AND PURPOSE

Adverse reactions to metal debris have been reported to be a cause of pain in metal-on-metal hip arthroplasty. We assessed the incidence of both symptomatic and asymptomatic adverse reactions in a consecutive series of patients with a modern large-head metal-on-metal hip arthroplasty.

METHODS

We studied the early clinical results and results of routine metal artifact-reduction MRI screening in a series of 79 large-head metal-on-metal hip arthroplasties (ASR; DePuy, Leeds, UK) in 68 patients. 75 hips were MRI scanned at mean 31 (12-52) months after surgery.

RESULTS

27 of 75 hips had MRI-detected metal debris-related abnormalities, of which 5 were mild, 18 moderate, and 4 severe. 8 of these hips have been revised, 6 of which were revised for an adverse reaction to metal debris, diagnosed preoperatively with MRI and confirmed histologically. The mean Oxford hip score (OHS) for the whole cohort was 21. It was mean 23 for patients with no MRI-based evidence of adverse reactions and 19 for those with adverse reactions detected by MRI. 6 of 12 patients with a best possible OHS of 12 had MRI-based evidence of an adverse reaction.

INTERPRETATION

We have found a high early revision rate with a modern, large-head metal-on-metal hip arthroplasty. MRI-detected adverse rections to metal debris was common and often clinically "silent". We recommend that patients with this implant should be closely followed up and undergo routine metal artifact-reduction MRI screening.

"Asymptomatic" pseudotumors after metal-on-metal hip resurfacing arthroplasty: prevalence and metal ion study

Symptomatic abnormal periprosthetic soft-tissue reactions ("pseudotumors") have been reported after metal-on-metal hip resurfacing arthroplasty (MoMHRA). The aims of this study were (1) to determine the prevalence of asymptomatic pseudotumors after MoMHRA and (2) to measure metal ion levels in these patients. A total of 201 hips in 158 patients were evaluated at a mean follow-up of 61 months (range, 36-88) using ultrasound/magnetic resonance imaging and serum/hip aspirate cobalt and chromium measurements. Pseudotumors found in 7 patients (4%) were associated with significantly higher cobalt and chromium levels and inferior functional scores. Elevated levels of cobalt and chromium ions suggest that pseudotumors are associated with increased wear generated from metal-on-metal articulations. Clinicians need to be aware of pseudotumors as a differential diagnosis during clinical evaluation of MoMHRA patients, and further imaging such as ultrasound or magnetic resonance imaging is recommended to confirm the diagnosis.

Reducing metal ion release following hip resurfacing arthroplasty

Recent guidelines have suggested that routine postoperative care of patients with metal-on-metal hip prostheses should involve metal ion analysis. This study sought to investigate the relationship between bearing surface wear rates of metal components and serum metal ion analysis and also to quantify the incidence of excessive increases in serum metal ion concentrations post-hip resurfacing arthroplasty.

Revisions of metal-on-metal hip resurfacing: lessons learned and improved outcome

This retrospective, consecutive case series of a single surgeon performed between 2001 and 2010 assesses the outcome following revision of metal-on-metal hip resurfacing arthroplasties (N = 113). Mean time to revision was 31 months (0-101) after primary hip resurfacing. Malpositioning of the components with associated wear-induced soft tissue fluid collections was the most frequent factor leading to failure of a hip resurfacing arthroplasty. The mid-term outcome of the revisions was satisfactory; complications occurred in 11 patients (9.7%). Six of these patients underwent a re-revision.

Complications after metal-on-metal hip resurfacing arthroplasty

This article determines the incidence and cause of the complications commonly associated with metal-on-metal hip resurfacing implants and the proposed methods to prevent these complications. The literature available in PubMed was reviewed. Complication rates after hip resurfacing are low, and the procedure has shown both safety and efficacy in the hands of surgeons trained in specialized centers. Proper surgical technique can further reduce the incidence of femoral neck fracture, component loosening, and abnormal wear of the prosthesis. A more systematic detection of adverse local tissue reactions is needed to provide accurate assessments of their prevalence.

Metal-on-metal hip resurfacing: a critical review

In this article, a concise review of the current literature on metal-on-metal hip resurfacing (MoMHR) is given. In contrast to conventional total hip arthroplasty, older age, female sex and small femoral head sizes predispose to failure. Neck fracture and metal wear-related complications account for the most frequent reasons for re-operations. Although the long-term consequences of metal ion release remain unknown, the increasing prevalence of soft tissue related problems with potentially devastating functional consequences in this younger patient group are of concern. Outcome after revision for metal wear related failure of MoMHR is poor. In our opinion, patients with this device should be managed in dedicated centers with facilities for data collection and monitoring. The majority of proposed advantages of MoMHR cannot be supported by the published evidence.

The relationship between head-neck ratio and pseudotumour formation in metal-on-metal resurfacing arthroplasty of the hip

Pseudotumour is a rare but important complication of metal-on-metal hip resurfacing that occurs much more commonly in women than in men. We examined the relationship between head-neck ratio (HNR) and pseudotumour formation in 18 resurfaced hips (18 patients) revised for pseudotumour and 42 asymptomatic control resurfaced hips (42 patients). Patients in whom pseudotumour formation had occurred had higher pre-operative HNR than the control patients (mean 1.37 (sd 0.10) vs mean 1.30 (sd 0.08) p = 0.001). At operation the patients with pseudotumours had a greater reduction in the size of their femoral heads (p = 0.035) and subsequently had greater neck narrowing (mean 10.1% (sd 7.2) vs mean 3.8% (sd 3.2) p < 0.001). No female patient with a pre-operative HNR ≤ 1.3 developed a pseudotumour. We suggest that reducing the size of the femoral head, made possible by a high pre-operative HNR, increases the risk of impingement and edge loading, and may contribute to high wear and pseudotumour formation. As the incidence of pseudotumour is low in men, it appears safe to perform resurfacing in men. However, this study suggests that it is also reasonable to resurface in women with a pre-operative HNR ≤ 1.3.