Metal-on-metal bearing surfaces

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.

Cutaneous and systemic hypersensitivity reactions to metallic implants

Cutaneous reactions to metal implants, orthopedic or otherwise, are well documented in the literature. The first case of a dermatitis reaction over a stainless steel fracture plate was described in 1966. Most skin reactions are eczematous and allergic in nature, although urticarial, bullous, and vasculitic eruptions may occur. Also, more complex immune reactions may develop around the implants, resulting in pain, inflammation, and loosening. Nickel, cobalt, and chromium are the three most common metals that elicit both cutaneous and extracutaneous allergic reactions from chronic internal exposure. However, other metal ions as well as bone cement components can cause such hypersensitivity reactions. To complicate things, patients may also develop delayed-type hypersensitivity reactions to metals (ie, in-stent restenosis, prosthesis loosening, inflammation, pain, or allergic contact dermatitis) following the insertion of intravascular stents, dental implants, cardiac pacemakers, or implanted gynecologic devices. Despite repeated attempts by researchers and clinicians to further understand this difficult area of medicine, the association between metal sensitivity and cutaneous allergic reactions remains to be fully understood. This review provides an update of the current knowledge in this field and should be valuable to health care providers who manage patients with conditions related to this field.

Perivascular lymphocytic infiltration is not limited to metal-on-metal bearings

BACKGROUND

Perivascular lymphocytic infiltration (PVLI) suggests an adaptive immune response. Metal hypersensitivity after THA is presumed associated with idiopathic pain and aseptic loosening, but its incidence and relationship to metallic wear leading to revision are unclear as are its presence and relevance in non-metal-on-metal arthroplasty.

QUESTIONS/PURPOSES

We compared (1) incidence and severity of PVLI in failed hip metal-on-metal (MoM) to non-MoM implants and TKA; (2) PVLI in MoM and non-MoM hip arthroplasty based on reason for revision; and (3) PVLI grade to diffuse lymphocytic infiltration (DLI) and tissue reaction to metal particles.

PATIENTS AND METHODS

We retrospectively examined incidence and severity of PVLI, DLI, and tissue reaction in periprosthetic tissue from 215 THA and 242 TKA revisions including 32 MoM hips.

RESULTS

Perivascular lymphocytic infiltration was present in more TKAs (40%) than overall hip arthroplasties (24%) without difference in severity. Compared to non-MoM hips, MoM bearings were more commonly associated with PVLI (59% versus 18%) and demonstrated increased severity (41% versus 3% greater than mild). Histologically, PVLI correlated (r = 0.51) with DLI, but not tissue reaction. In THA, PVLI was most commonly associated with idiopathic pain (70%) and aseptic loosening (54%) in MoM, and infection in all hip revisions (53%).

CONCLUSIONS

Perivascular lymphocytic infiltration is more extensive in revisions of MoM and in aseptic loosening, idiopathic pain, or infection but is also present in TKA, non-MoM, and different reasons for revision. It correlates with other signs of metal hypersensitivity, but not with histologic measures of metal particulate load.

LEVEL OF EVIDENCE

Level III, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Pragmatic approach to the clinical work-up of patients with putative allergic disease to metallic orthopaedic implants before and after surgery

Allergic complications following insertion of metallic orthopaedic implants include allergic dermatitis reactions but also extracutaneous complications. As metal-allergic patients and/or surgeons may ask dermatologists and allergologists for advice prior to planned orthopaedic implant surgery, and as surgeons may refer patients with complications following total joint arthroplasty for diagnostic work-up, there is a continuous need for updated guidelines. This review presents published evidence for patch testing prior to surgery and proposes tentative diagnostic criteria which clinicians can rely on in the work-up of patients with putative allergic complications following surgery. Few studies have investigated whether subjects with metal contact allergy have increased risk of developing complications following orthopaedic implant insertion. Metal allergy might in a minority increase the risk of complications caused by a delayed-type hypersensitivity reaction. At present, we do not know how to identify the subgroups of metal contact allergic patients with a potentially increased risk of complications following insertion of a metal implant. We recommend that clinicians should refrain from routine patch testing prior to surgery unless the patient has already had implant surgery with complications suspected to be allergic or has a history of clinical metal intolerance of sufficient magnitude to be of concern to the patient or a health provider. The clinical work-up of a patient suspected of having an allergic reaction to a metal implant should include patch testing and possibly in vitro testing. We propose diagnostic criteria for allergic dermatitis reactions as well as noneczematous complications caused by metal implants.

Do ion levels in hip resurfacing differ from metal-on-metal THA at midterm?

BACKGROUND

Metal-on-metal Birmingham hip resurfacing (MOM-BHR) is an alternative to metal-on-metal total hip arthroplasty (MOM-THA), especially for young and/or active patients. However, wear resulting in increased serum ion levels is a concern.

QUESTIONS/PURPOSES

We asked whether (1) serum chromium (Cr), cobalt (Co), and molybdenum (Mo) concentrations would differ between patients with either MOM-BHR or MOM-THA at 5 years, (2) confounding factors such as gender would influence ion levels; and (3) ion levels would differ at 2 and 5 years for each implant type.

PATIENTS AND METHODS

Ions were measured in two groups with either MOM-BHR (n = 20) or MOM-THA (n = 35) and a mean 5-year followup, and two groups with either MOM-BHR (n = 15) or MOM-THA (n = 25) and a mean 2-year followup. Forty-eight healthy blood donors were recruited for reference values.

RESULTS

At 5 years, there were no differences in ion levels between patients with MOM-BHR or MOM-THA. Gender was a confounding factor, and in the MOM-BHR group at 5 years, Cr concentrations were greater in females compared with those of males. Mean ion levels were similar in patients with 2 and 5 years of followup for each implant type. Ion levels in patients were sevenfold to 10-fold higher than in controls.

CONCLUSIONS

As the metal ion concentrations in the serum at 5 years were in the range reported in the literature, we do not believe concerns regarding excessive metal ion levels after MOM-BHR are justified.

LEVEL OF EVIDENCE

Level III, therapeutic study. See the Guidelines for Authors for a complete description of level of evidence.

Resurfacing registers concern

We review the history and literature of hip resurfacing arthroplasty. Resurfacing and the science behind it continues to evolve. Recent results, particularly from the national arthroplasty registers, have spread disquiet among both surgeons and patients. A hip resurfacing arthroplasty is not a total hip replacement, but should perhaps be seen as a means of delaying it. The time when hip resurfacing is offered to a patient may be different from that for a total hip replacement. The same logic can apply to the timing of revision surgery. Consequently, the comparison of resurfacing with total hip replacement may be a false one. Nevertheless, the need for innovative solutions for young arthroplasty patients is clear. Total hip replacement can be usefully delayed in many of these patients by the use of hip resurfacing arthroplasty.

Effect of chromium and cobalt ions on the expression of antioxidant enzymes in human U937 macrophage-like cells

The main concern associated with metal-on-metal (MM) hip prosthesis is the presence of metal ions, mainly chromium (Cr) and cobalt (Co), which are found both systemically and locally in the organism of patients. Previous studies revealed that Cr(III) and Co(II) ions could induce damages to proteins in macrophage-like cells in vitro, probably through the formation of reactive oxygen species (ROS). We then hypothesized that these ions can modify the expression of antioxidant enzymes in these cells. Results showed that Cr(VI) induced the protein expression of Mn-superoxide dismutase, Cu/Zn-superoxide dismutase, catalase, glutathione peroxidase, and heme oxygenase-1 (HO-1) but had no effect of the expression of their mRNA. Cr(III) have no effect on the expression of all these antioxidant enzymes. Co(II) induced the expression of both protein and mRNA of HO-1 only. In conclusion, results showed that Cr(VI), Cr(III), and Co(II) had differential effects on the expression of antioxidant enzymes in macrophage-like cells in vitro.

Failed metal-on-metal hip arthroplasties: a spectrum of clinical presentations and operative findings

BACKGROUND

A number of recent reports have described novel failure mechanisms of metal-on-metal bearings in total and resurfacing hip arthroplasty. Hip arthroplasties with metal-on-metal articulations are also subject to the traditional methods of failure seen with different bearing couples. There is currently little information in the literature to help guide timely clinical evaluation and management of these patients.

QUESTIONS/PURPOSES

We therefore describe the (1) clinical presentations; (2) reasons for failure; (3) operative findings; and (4) histologic findings in patients with failed metal-on-metal hip arthroplasties.

METHODS

We retrospectively identified all 37 patients (37 hips) with metal on metal total hip or resurfacing arthroplasties who underwent revision over the past 3 years at our institution. Relevant clinical, radiographic, laboratory, intraoperative, and histopathologic findings were analyzed for all patients.

RESULTS

Of the 37 patients, 10 were revised for presumed hypersensitivity specific to the metal-on-metal articulation. This group included eight patients with tissue histology confirming chronic inflammation with lymphocytic infiltration, eight with aseptic loosening of a monoblock screwless uncemented acetabular component, two with iliopsoas impingement associated with a large-diameter femoral head, and three with femoral neck fracture after resurfacing arthroplasty; the remainder of the patients were revised for infection, instability, component malposition, and periprosthetic fracture.

CONCLUSIONS

Increased awareness of the modes of failure will bring to light the potential complications particular to metal-on-metal articulations while placing these complications into the context of failures associated with all hip arthroplasties. This novel clinical information should be valuable for the practicing surgeon faced with this patient population.

LEVEL OF EVIDENCE

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

Cup loosening after cemented Metasul® total hip replacement: a retrieval analysis

Small-diameter cemented Metasul® cups have been previously identified to be at high risk of early loosening. We asked whether this particular mode of failure was associated with a specific histological feature. Periprosthetic tissues were obtained at the time of revision of two aseptically loose cemented Metasul® cups. Each tissue sample was processed for routine histological analysis. A slight metallosis was visible microscopically in all tissue samples. Metallic wear-debris particles were present both extracellularly and within the cytoplasm of macrophages. We noted a perivascular infiltration of lymphocytes accompanied by mature plasma cells. Our observations are compatible with the hypersensitivity-like reaction previously reported, described as an aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL). Although wear was within normal reported range limits, this tissue reaction appeared as a consequence of continuous release of metallic ions from the prosthetic articulation. We hypothesise that ALVAL was involved in acetabular component failure, although acetabular loosening may have been initiated by high mechanical stress.

Metal allergy--a review on exposures, penetration, genetics, prevalence, and clinical implications

The prevalence of metal allergy is high in the general population, and it is estimated that up to 17% of women and 3% of men are allergic to nickel and that 1-3% are allergic to cobalt and chromium. Among dermatitis patients, the prevalence of metal allergy is even higher. Metal allergy is mainly an environmental disorder although null mutations in the filaggrin gene complex were recently found to be associated with nickel allergy and dermatitis. Environmental metal exposures include jewelry, buttons, clothing fasteners, dental restorations, mobile phones, and leather. Although consumer exposure is responsible for most cases of metal allergy, the importance of occupational metal exposure remains present and should always be taken into consideration when one interprets allergic patch test reactions to metals. Traditionally, nickel, cobalt, and chromium have been the most important contact allergens. However, recently, gold and palladium have drawn much attention as the prevalence of contact allergy to these metals is high. Palladium allergy is mainly a result of cross-sensitization to nickel, whereas gold allergy is rarely clinically relevant when one takes its high prevalence into account. The epidemiology of metal allergy has recently changed in Europe as nickel allergy among ear-pierced Danish women has decreased following regulatory intervention on nickel release from consumer products. In the United States, the prevalence of nickel allergy is still increasing, which may be explained by the absence of regulation. The prevalence of chromium allergy is increasing in the United States, Singapore, and Denmark among dermatitis patients. This increase is significantly associated with leather exposure in Denmark. Metal allergy may result in allergic contact dermatitis and systemic allergic (contact) dermatitis. Furthermore, metal allergy has been associated with device failure following insertion of intracoronary stents, hip and knee prostheses, as well as other implants. This area is in need of more research.

Large diameter metal-on-metal total hip arthroplasty for Crowe IV developmental dysplasia of the hip

The short-term results of middle-aged patients with severe developmental dysplasia of the hip treated with subtrochanteric femoral shortening and cementless large diameter metal-on-metal total hip arthroplasty were retrospectively evaluated. Clinical and radiological results of 15 hips of 13 patients with Crowe IV developmental dysplasia of the hip were enrolled in this study. The average follow-up period was 49 months (36-62 months). The average age of patients at the time of surgery was 45.5 years (range, 36-65 years). Radiographs were evaluated for component position, subsidence, loosening, and osteolysis. Intraoperatively, two patients had a small proximal femoral shaft split that was held with a cable wire. The average preoperative Harris hip score was 58; at 3 years, 82. Trendelenburg sign was negative in 11 hips at the last assessment. Loosening, subsidence, infection, dislocation, hypersensitivity and neurovascular complications were not observed. One hip had to be revised 1 year after surgery because of nonunion at the osteotomy site. Our study shows that large diameter metal-on-metal total hip arthroplasty, incorporating subtrochanteric femoral shortening, decreases dislocation rate and provides excellent results for the completely dislocated hip.

Total hip replacement in patients with multiple epiphyseal dysplasia with a mean follow-up of 15 years and survival analysis

The hip joint is commonly involved in multiple epiphyseal dysplasia and patients may require total hip replacement before the age of 30 years.

We retrospectively reviewed nine patients (16 hips) from four families. The diagnosis of multiple epiphyseal dysplasia was based on a family history, genetic counselling, clinical features and radiological findings. The mean age at surgery was 32 years (17 to 63), with a mean follow-up of 15.9 years (5.5 to 24).

Of the 16 hips, ten required revision at a mean of 12.5 years (5 to 15) consisting of complete revision of the acetabular component in three hips and isolated exchange of the liner in seven. No femoral component has loosened or required revision during the period of follow-up.

With revision for any reason, the 15-year survival was only 11.4% (95% confidence interval 1.4 to 21.4). However, when considering revision of the acetabular shell in isolation the survival at ten years was 93.7% (95% confidence interval 87.7 to 99.7), reducing to 76.7% (95% confidence interval 87.7 to 98.7) at 15 and 20 years, respectively.

Micro-Structural Alterations in MoM Hip Implants

Since the introduction of CoCrMo alloy metal-on-metal hip replacements have shown a great clinical performance. Metal-on-metal couplings produce a much lower wear rate and volume than e.g. metal-on-polyethylene. However, the particle size is significantly smaller within a nm-range. To evaluate the formation of nano-size wear particles in metal-on-metal hip replacements it is essential to understand the micro-structural changes in the sub-surface region of the CoCrMo alloy. For this study a MoM hip implant was analyzed by means of TEM. The results revealed that the good wear performance of this CoCrMo alloy is linked to a strain induced fcc  hcp phase transformation and in-situ re-crystallization under high shear stresses. The result is a nano-crystalline surface zone of ~200 to 400 nm thickness which undergoes an ongoing process of mechanical intermixing with componants of the interfacial fluid. The incorporation of organic carbon from proteins in between the nano-crystals could be visualised by EFTEM and EDS. This mechanically mixed nc-zone must be the origin of the wear particle detachment. An earlier study by Catelas et. al confirms the hypothesis of the location of wear particle detachment by analyzing the shape and chemical composition of emitted wear particles which exhibits the same size and shape of crystals observed in the nc-zone of the implant analyzed in this study.

The association between metal allergy, total hip arthroplasty, and revision

BACKGROUND AND PURPOSE

It has been speculated that the prevalence of metal allergy may be higher in patients with implant failure. We compared the prevalence and cause of revisions following total hip arthroplasty (THA) in dermatitis patients suspected to have contact allergy and in patients in general with THA. Furthermore, we compared the prevalence of metal allergy in dermatitis patients with and without THA.

MATERIALS AND METHODS

The Danish Hip Arthroplasty Registry (DHAR) contained detailed information on 90,697 operations. The Gentofte patch-test database contained test results for patients suspected of having allergic contact dermatitis (n = 18,794). Cases (n = 356) were defined as patch-tested dermatitis patients who also had primary THA performed. Two age- and sex-matched controls (n = 712) from the patch-test database were sought for each case.

RESULTS

The prevalence of revision was similar in cases (12%) and in patients from the DHAR (13%). The prevalence of metal allergy was similar in cases and controls. However, the prevalence of metal allergy was lower in cases who were patch-tested after operation (6%) than in those who were patch-tested before operation (16%) (OR = 2.9; 95% CI = 1-8).

INTERPRETATION

We found that the risk of surgical revision was not increased in patients with metal allergies and that the risk of metal allergy was not increased in cases who were operated, in comparison to controls. Despite some important study limitations, our observations add to the evidence that the risk of complications in metal allergic patients seems limited.