A prospective study concerning the relationship between metal allergy and post-operative pain following total hip and knee arthroplasty

Forgotten joint score associated with prosthesis weight in cementless total hip arthroplasty: a prospective clinical study

Background

This prospective study aimed to investigate the influence of weight difference between implanted prosthesis and removed bone in cementless total hip arthroplasty (THA) on hip awareness and patient-reported outcomes.

Methods

A total of 48 patients (56 hips) who underwent primary THA were prospectively enrolled. Implanted prosthesis and removed bone were weighed intraoperatively. Forgotten Joint Score (FJS) and Western Ontario and McMaster Universities (WOMAC) scores were obtained before and at 1 and 3 months after surgery. Patients were divided into groups A, B, and C according to the percentile of the weight difference.

Results

The mean weight difference of the implanted prosthesis and removed bone was 117.97 ± 47.35 g. A negative correlation was found among the weight differences of the three groups and 1- and 3-month postoperative FJS (correlation coefficients, -0.331 and -0.734, respectively). A positive correlation was found among the weight difference of the three groups and 3-month postoperative WOMAC (correlation coefficient, 0.403). A significant difference in 3-month postoperative FJS and WOMAC scores was found among the three groups. The mean 3-month postoperative FJS (79.00) of group C was significantly lower than that of group A (93.32) (P < 0.05). The mean WOMAC score (15.83) of group A was significantly lower than that of group C (23.67) (P < 0.05).

Conclusion

The implanted prosthesis is larger than the removed bone in cementless THA. The weight difference is negatively correlated with hip function. The weight difference should be minimized to achieve optimal hip joint awareness.

Understanding immune-mediated cobalt/chromium allergy to orthopaedic implants: a meta-synthetic review

BACKGROUND

The frequency of primary joint replacement surgery continues to increase worldwide. While largely considered biologically inert entities, an increasing body of evidence continues to validate a not insignificant incidence of allergic reactions to such implants. Little previous work has explored genuinely immune-mediated reactivity in this context. In the absence of a contemporary published summary on the topic, this paper explored the current state of understanding of cobalt/chromium allergy and proposes a patient management algorithm whereby such immune reactions are clinically suggested.

METHODS

A structured, systematic literature review was performed by following PRISMA search principles to provide an updated review of this area.

RESULTS

Thirty-six topic-related articles were identified, the majority reflecting lower tiers of scientific evidence with a lack of homogeneous quantitative data to facilitate valid cohort comparisons. Largely, the available literature represented small case series' or expert opinions.

CONCLUSIONS

Despite increasing clinical awareness and acknowledgement of true allergy to joint replacement components, this review highlighted that the evidence base underpinning the diagnosis and management of such patients is limited. Both patient-reported metal allergy or skin patch testing are grossly unreliable methods and show almost no correlation with true immune reactivity. Recent studies suggested a potential role for patient-specific in vitro cellular activation testing and/or targeted genetic testing when cobalt/chromium allergy is clinically suspected. However, while likely representing the contemporary "best available" approaches both can be costly undertakings, are not yet universally available, and still require broader validation in non-research settings before wider uptake can be championed.

The effect of Nickel hypersensitivity on the outcome of total knee arthroplasty and the value of skin patch testing: a systematic review

Background

To assess the Nickel sensitizing potential of total knee arthroplasty (TKA), explore the relationship between hypersensitivity and clinical outcomes, and evaluate the utility of skin patch testing pre- and/or postoperatively.

Materials and methods

A literature search was performed through EMBASE, Medline and PubMed databases. Articles were screened independently by two investigators. The level of evidence of studies was assessed using the Oxford Centre for Evidence-Based Medicine Criteria and the quality evaluated using the Methodological Index for Non-randomized Studies and Cochrane risk-of-bias tools.

Results

Twenty studies met the eligibility criteria, reporting on 1354 knee arthroplasties. Studies included patients undergoing primary or revision TKA, pre- and/or postoperatively, and used patch testing to identify Nickel hypersensitivity. Prevalence of Nickel hypersensitivity ranged from 0% to 87.5%. One study compared the prevalence of Nickel hypersensitivity in the same patient group before and after surgery and noted newly positive patch test reactions in three patients (4.2%). Three studies reported lower prevalence of Nickel hypersensitivity in postoperative patients compared to preoperative ones. Seven studies suggested that hypersensitivity might cause adverse clinical outcomes, but six did not support any relationship. Seven studies recommended preoperative patch testing in patients with history of metal allergy, and nine concluded that testing may be valuable postoperatively.

Conclusions

Patients undergoing TKA with no prior history of metal hypersensitivity do not seem to be at an increased risk of developing Nickel hypersensitivity, and there is conflicting evidence that patients with pre-existing hypersensitivity are more likely to experience adverse outcomes. Patch testing remains the most commonly used method for diagnosing hypersensitivity, and evidence suggests preoperative testing in patients with history of metal allergy to aid prosthesis selection, and postoperatively in patients with suspected hypersensitivity once common causes of implant failure have been excluded, since revision with hypoallergenic implants may alleviate symptoms.

Clinical Results of Revision TKA in Patients With Presumed Metal and Cement Allergy

BACKGROUND

Metal and cement allergy affects a small subset of patients, causing severe pain and often systemic reaction after total knee arthroplasty (TKA). Revision with ceramic-surfaced femoral components has been reported to resolve these symptoms of metal allergy, but no solution currently is available for patients with allergies to metal and bone cement.

METHODS

Five patients (5 knees) with documented metal allergy were revised with custom porous-coated ceramic femoral components (Magnesia-stabilized Zirconia) from January 2007 to January 2013. An additional 23 patients (23 knees) met inclusion criteria from 2007 to 2015, but because the ceramic implant was unavailable, they underwent different treatment based on their underlying allergy to metal, cement, or both. Inclusion criteria included the history of clinically documented severe metal allergy, severe pain, swelling, and effusion >1 year after TKA, negative workup for infection, loosening, and ligament imbalance. Knee Society scores were compared for each cohort.

RESULTS

Mean Knee Society scores for all 5 patients revised with custom cementless ceramic femoral components improved significantly for objective score (preoperative, 39 ± 5; most recent visit, 90 ± 2) and function score (preoperative, 33 ± 8; most recent visit 93 ± 4) (P < .0001). The 12 knees revised with off-the-shelf cemented ceramic-coated femoral components had similar results. The 7 unrevised knees (including 4 knees with allergy to metal and bone cement) and the 4 knees revised with standard CoCr femoral components did not improve and worsened over time.

CONCLUSION

Symptoms resolved in the 5 patients revised with custom ceramic implants and in the 12 patients revised with ceramic-coated components, but did not improve in the patients unrevised or revised with CoCr femoral components. Symptoms presumed to be associated with metal or cement allergy improve with the use of ceramic femoral surfaces, but patients who are allergic both to metals and bone cement would be candidates only for porous-coated ceramic implants fixed without bone cement.

Metal Hypersensitivity or Missed Periprosthetic Joint Infection? A Critical Review

The World Association Against Infection in Orthopedics And Trauma (W.A.I.O.T.) Study Group on Bone And Joint Infection Definitions Metal hypersensitivity (MHS) has been investigated by several authors as a possible reason for painful total joint arthroplasty, with controversial results. Periprosthetic joint infection (PJI) is another possible source of unexplained pain and implant failure that may be difficult to diagnose if not properly investigated. We performed this critical review to assess whether the current literature on MHS includes an adequate diagnostic workup to discern metal allergy from PJI. The results of this review highlight the importance of assessing patients for PJI before making a diagnosis of MHS and emphasize that the methods currently used to exclude PJI are substantially inadequate. Therefore, well-designed clinical trials with adequate diagnostic protocols and definitions of PJI that can differentiate MHS from low-grade PJI are needed. [Orthopedics. 2022;45(2):e73-e78.].

Aluminum-Allergen of the Year 2022

ABSTRACT

Exposure to elemental aluminum and its salts is unavoidable. Aluminum as a metal is present in transport, construction, packaging, and electronic equipment. Aluminum salts are present in consumer products, food items and drinking water, vaccines, drugs, and antiperspirants. Aluminum in vaccines and preparations for allergen-specific immunotherapy are the major sensitization sources. The predominent clinical manifestations of aluminum allergy are pruritic subcutaneous nodules and eczematous dermatitis. Patch testing shall be performed with aluminum chloride hexahydrate (ACH) in petrolatum. The preparation with ACH 10% detects substantially more aluminum allergy than ACH 2%. A patch test with elemental aluminum, for example, an empty Finn Chamber, is only positive when there is a strong aluminum allergy. A patch test reading should be performed 1 week after the application so as not to miss 15% to 20% of aluminum allergy. Aluminum should be included in any baseline patch test series for children and investigated for a possible inclusion in baseline series for adults. Aluminum test chambers can interfere with the testing resulting in both false-negative and false-positive patch test reactions to nonaluminum contact sensitizers.

Nickel hypersensitivity and skin patch testing in total hip replacement surgery: a systematic review

Approximately 60,000 cemented femoral stems are implanted in the UK each year with the majority being manufactured from stainless steel containing 10–15% nickel. Nickel hypersensitivity has been reported in up to 13% of the general population and there is a concern that nickel hypersensitivity might adversely affect the outcome of total hip replacement (THR). We reviewed the current literature on the potential link between nickel hypersensitivity and THR complications, and the usefulness of patch testing.

We conducted a literature search in PubMed, MEDLINE and EMBASE databases. The level of evidence and the quality of the selected studies were assessed using the Oxford Centre for Evidence-Based Medicine Criteria and the Methodological Index for Non-Randomised Studies tool, respectively.

Twenty-six studies met the inclusion criteria, reporting on 1852 patients who underwent primary or revision THR. All studies detailed skin patch testing and recorded prevalence of nickel hypersensitivity from 1.5% to 33.3%. Five studies reported a rise in Nickel hypersensitivity following THR, while four reported a decreased prevalence post-operatively. Eight studies concluded that metal hypersensitivity could have developed following THR, while seven studies did not support a link between metal hypersensitivity and THR complications. Four of the studies recommended routine patch testing pre-operatively, but three others concluded that routine patch testing was not indicated.

We have not identified a link between nickel hypersensitivity and THR complications, and the role of patch testing remains unclear. Further large-scale studies would be required to investigate this relationship and to clarify the role of patch testing in facilitating implant selection.

Cite this article: EFORT Open Rev 2021;6:825-838. DOI: 10.1302/2058-5241.6.210051

Metal allergy in primary and revision total knee arthroplasty : a scoping review and evidence-based practical approach

Aims

Metal allergy in knee arthroplasty patients is a controversial topic. We aimed to conduct a scoping review to clarify the management of metal allergy in primary and revision total knee arthroplasty (TKA).

Methods

Studies were identified by searching electronic databases: Cochrane Central Register of Controlled Trials, Ovid MEDLINE, and Embase, from their inception to November 2020, for studies evaluating TKA patients with metal hypersensitivity/allergy. All studies reporting on diagnosing or managing metal hypersensitivity in TKA were included. Data were extracted and summarized based on study design, study population, interventions and outcomes. A practical guide is then formulated based on the available evidence.

Results

We included 38 heterogeneous studies (two randomized controlled trials, six comparative studies, 19 case series, and 11 case reports). The evidence indicates that metal hypersensitivity is a rare complication with some histopathological features leading to pain and dissatisfaction with no reliable screening tests preoperatively. Hypoallergenic implants are viable alternatives for patients with self-reported/confirmed metal hypersensitivity if declared preoperatively; however, concerns remain over their long-term outcomes with ceramic implants outperforming titanium nitride-coated implants and informed consent is paramount. For patients presenting with painful TKA, metal hypersensitivity is a diagnosis of exclusion where patch skin testing, lymphocyte transformation test, and synovial biopsies are useful adjuncts before revision surgery is undertaken to hypoallergenic implants with shared decision-making and informed consent.

Conclusion

Using the limited available evidence in the literature, we provide a practical approach to metal hypersensitivity in TKA patients. Future national/registry-based studies are needed to identify the scale of metal hypersensitivity, agreed diagnostic criteria, and management strategies.

Cite this article: Bone Jt Open 2021;2(10):785–795.

Patch Test Results and Outcome in Patients with Complications from Total Knee Arthroplasty: A Consecutive Case Series

The role of hypersensitivity in implant-related complications remains controversial. The objectives of our study were to (1) establish the prevalence of hypersensitivity to components of knee prostheses in patients referred to our contact dermatitis clinic, (2) determine if patients with post-surgery dermatitis have become sensitized, and (3) describe the outcome of patients with and without hypersensitivity. We reviewed the charts of patients referred from 2007 to 2018 and extracted demographic information, date, type, and site of implant, clinical presentation, and results of patch testing (PT) or lymphocyte transformation tests (LTT). We called most patients to gather data such as clinical outcome, nature, and timing of additional surgery. Statistical analysis included computation of conventional descriptive statistics. Because of the type of study design, only some categorical variables were tested for possible associations by analytical tools (cross-tabulation). Thirty-nine patients, 23 men (59.0%), and 16 women (41.0%), were included. Their mean age in years was 63.3 (95% confidence interval [CI]: 60.9-65.7) ranging from 39.0 to 79.0, (standard deviation) = 9.69, without statistically significant differences between males and females. Five patients had positive PT possibly relevant to their implant. Four patients had revision surgery and two improved. Of nine patients with dermatitis, one with relevant PT did not improve after revision, and the dermatitis was unrelated to TKA in eight. Of the 26 patients without dermatitis or relevant PT results, 9 had revisions because of incapacitating symptoms, and 5 improved. Hypersensitivity to implant components is a potential factor in the etiology of TKA complications. Patients with confirmed hypersensitivity may benefit from revision. Our study, however, did not detect statistically significant differences in outcome of revision surgery between patients with positive versus negative PT or LTT. In spite of this, we consider that patients with a history suggestive of metal, acrylate or aminoglycoside allergy should be tested preoperatively to avoid hypersensitivity-related postoperative complications. In the absence of hypersensitivity, some patients with incapacitating symptoms may also improve following revision.

Increased risk of eczema after joint replacement: A population-based retrospective cohort study

There are very few reports of eczema and other prosthetic-related allergic skin complications following arthroplasty. We aimed to assess the risk of eczema after joint replacement.We performed a retrospective population-based cohort study in 2024 joint replacement patients using the Longitudinal Health Insurance Database. For comparison, 8096 controls were selected, with 4 control subjects for each joint replacement patient matched for age, sex, and index year, to assess eczema risk. We examined 14-year cumulative eczema incidence associated with age, sex, immunity, disease history, and joint replacement location.Eczema rates in the joint replacement patients were 38% higher than in the control group (57.90 vs 41.84 per 1000 person-years, respectively). Compared with the control group, joint replacement patients showed a 1.35-fold increased risk of eczema according to the multivariable Cox model (95% Confidence interval [CI] = 1.23-1.49). Knee replacement patients had higher eczema risk compared with the control group (Hazard ratio [HR] = 1.45, 95% CI = 1.33-1.70). Stratified by study period, the joint replacement cohort had a higher eczema risk after the 3-month follow-up.Our study revealed that joint arthroplasty increased risk of eczema in this 14-year follow-up study, and this was not related to personal atopic history or gender.

A case series of cementless revision total knee arthroplasty in patients with benzoyl peroxide allergy

PURPOSE

The contact allergens nickel, cobalt, and chromium are often discussed as possible triggers of allergic reactions to orthopedic implants. Additionally, acrylates and polymerization additives in bone cement (e.g., benzoyl peroxide (BPO)) have been implicated as triggers of eczema, wound healing disorders, and aseptic implant loosening. We report about six patients with aseptic loosening after total knee arthroplasty (TKA), who underwent revision surgery after testing positive for BPO hypersensitivity.

METHODS

After clarification of possible other causes of implant failure, epicutaneous testing had been performed and the implants were replaced in a two-stage procedure with cementless, diaphyseal anchoring, hypoallergenic (TiNb-coated) revision endoprostheses.

RESULTS

Epicutaneous testing revealed a BPO allergy in all six patients and an additional nickel allergy in three of the six patients. There was no histopathological or microbiological evidence for a periprosthetic infection. The clinical follow-up showed a low level of pain with good function, a stable knee joint, and proper implant position. The Knee Society Score (KSS) with its subscales Knee Score and Functional Score improved post-operatively from 43 to 70 points and from 47.5 to 68.3 points, respectively. Two implant-specific complications occurred: femoral stress shielding two years post-operatively with no further need for action and aseptic loosening of the tibial stem with the need of revision three years post-operatively.

CONCLUSIONS

The regression of complaints after replacement with cementless and nickel-free revision implants suggests allergic implant intolerance. Implantation of a cementless, hypoallergenic endoprosthesis might, therefore, be a surgical treatment strategy in patients with evidence of allergies.

Quality of life after total knee arthroplasty

Total knee arthroplasty (TKA) results in a high degree of patient satisfaction, as it provides patients with considerable medium- and long-term benefits in terms of quality of life, pain relief and function. Nevertheless, the literature reports that up to 30% of patients are dissatisfied. This dissatisfaction is directly related to the patients' quality of life, which they deem insufficient. Their quality of life depends on many physical, behavioural, social and psychological factors that are not taken into account by functional outcome scores. After describing the principles of quality of life evaluation after TKA, we will assess the effects of patient-related factors, the surgical technique and postoperative program through an exhaustive review of the literature. Patient expectations after TKA will then be outlined, particularly return to work and return to sports.

The Risk of Acute Infection Following Intra-articular Corticosteroid Injection Into a Pre-existing Total Knee Arthroplasty

BACKGROUND

No previous studies have investigated the risk of infection following intra-articular corticosteroid injection (IACI) into a pre-existing total knee arthroplasty (TKA). The aim of this study is to determine the risk of acute infection following IACI into a pre-existing TKA.

METHODS

A retrospective chart review identified all patients at a single institution between October 2009 and May 2015 that had an ipsilateral knee injection subsequent to a TKA. The risk of acute infection, as defined by development of an infection within 3 months of IACI, was determined via review of clinic notes, operative reports, laboratory records, and telephone interviews.

RESULTS

A total of 1845 injections in 736 patients met the inclusion criteria. In total, 101 (4.8%) patients were lost to follow-up. Three infections in 3 patients occurred within 3 months of IACI, yielding an infection rate of 0.16% per injection, or 1 infection in every 625 IACIs following TKA.

CONCLUSION

This study is the first to investigate the risk of acute infection following injection of corticosteroid into a pre-existing TKA. Given the dire consequences of infection following TKA, the routine use of IACI into a pre-existing TKA should be avoided, and a thorough workup should be performed in any patient with a painful TKA prior to consideration of IACI.

[Adverse reactions to metal orthopedic implants after knee arthroplasty]

Based on several clinical examples, the range of adverse or hypersensitive reactions to metal implants especially after total knee replacement are presented. In general, we found the patients to generally be women who present with pain, swelling, and local or generalized eczema. Some also present with early aseptic loosening mainly in the first 4 years after implantation. For these patients, a detailed allergy-specific history should be taken and a patch test should be performed; if necessary, blood ion levels should be evaluated to exclude cobaltism. Before revision surgery and exchange of the implant we always perform arthroscopic inspection to obtain biopsies for microbiology and histopathology. Using the Consensus Classification a good evaluation for planning revision with the different implant options is possible.

Allergy in Total Knee Replacement. Does It Exist?: Review Article

BACKGROUND

There is little data on whether preexisting allergies to implant materials and bone cement have an impact on the outcome of TKA.

QUESTIONS/PURPOSES

This review article analyzes the current literature to evaluate the prevalence and importance of metal and cement allergies for patients undergoing total knee arthroplasty.

METHODS

A review of the literature was performed using the following search criteria: "knee," "arthroplasty," and "allergy" as well as "knee," "arthroplasty," and "hypersensitivity."

RESULTS

One hundred sixteen articles were identified on PubMed, Seventy articles could be excluded by reviewing the title and abstract leaving 46 articles to be included for this review. The majority of the studies cited patch testing as the gold standard for screening and diagnosis of hypersensitivity following TKA. There is consensus that patients with self-reported allergies against metals or bone cement and positive patch test should be treated with hypoallergenic materials or cementless TKA. Treatment options include the following: coated titanium or cobalt-chromium implants, ceramic, or zirconium oxide implants.

CONCLUSION

Allergies against implant materials and bone cement are rare. Patch testing is recommended for patients with self-reported allergies. The use of special implants is recommended for patients with a confirmed allergy.

[The Berlin diagnostic algorithm for painful knee TKA]

BACKGROUND

Approximately 20% of patients are unsatisfied with their postoperative results after total knee arthroplasty (TKA). Main causes for revision surgery are periprosthetic infection, aseptic loosing, instability and malalignment. In rare cases secondary progression of osteoarthritis of the patella, periprosthetic fractures, extensor mechanism insufficiency, polyethylene wear and arthrofibrosis can cause the necessity for a reintervention. Identifying the reason for a painful knee arthroplasty can be very difficult, but is a prerequisite for a successful therapy.

AIM

The aim of this article is to provide an efficient analysis of the painful TKA by using a reproducible algorithm.

DISCUSSION

Basic building blocks are the medical history with the core issues of pain character and the time curve of pain concerning surgery. This is followed by the basic diagnostics, including clinical, radiological, and infectiological investigations. Unique failures like periprosthetic infection or aseptic loosening can thereby be diagnosed in the majority of cases. If the cause of pain is not clearly attributable using the basic diagnostics tool, further infectiological investigation or diagnostic imaging are necessary. If the findings are inconsistent, uncommon causes of symptoms, such as extra-articular pathologies, causalgia or arthrofibrosis, have to be considered. In cases of ongoing unexplained pain, a revision is not indicated. These patients should be re-evaluated after a period of time.

Allergy in total knee arthroplasty: a review of the facts

We explored the literature surrounding whether allergy and hypersensitivity has a clinical basis for implant selection in total knee arthroplasty (TKA). In error, the terms hypersensitivity and allergy are often used synonymously. Although a relationship is present, we could not find any evidence of implant failure due to allergy. There is however increasing basic science that suggests a link between loosening and metal ion production. This is not an allergic response but is a potential problem. With a lack of evidence logically there can be no justification to use 'hypoallergenic' implants in patients who have pre-existing skin sensitivity to the metals used in TKA.

Allergic reactions in arthroplasty: myth or serious problem?

PURPOSE

The purpose of this study was to determine the prevalence of sensitisation to chromium, cobalt, nickel, or a cement component in patients who received endoprosthetic surgery at our institution. Also, we aimed to assess the portion related to allergic reactions in endoprosthetic revisions and to follow-up those patients after allergic reaction related revisions.

METHODS

We selected patients with a pre-operative known sensitisation to chromium, cobalt, nickel, or a cement component for a post-operative allergic reaction. All patients who received revision surgery because of a potential allergic reaction were followed up post revision surgery.

RESULTS

Eight hundred fifty-five patients were pre-operative known to have a sensitisation to chromium, cobalt, nickel, or a cement component. Six hundred eighty-two patients (79.8 %) received a primary arthroplasty, and 173 patients (20.2 %) received a revision surgery. Seventeen patients (2.0 %) were revised because of allergic reactions. Allergic reactions were the cause for approximately 0.2 % of all endoprosthetic revisions and for 9.8 % of revisions in patients with sensitisation to one of the reviewed components. Potential allergens were strictly avoided in the replaced prosthesis. Outcome scores improved post-operatively.

CONCLUSIONS

The allergic patient should be thoroughly informed about potential reactions resulting from implant choice. Our study can serve as risk assessments by quantifying the incidence of allergic reactions due to endoprosthetic treatment.

The association between metal allergy, total knee arthroplasty, and revision: study based on the Danish Knee Arthroplasty Register

BACKGROUND AND PURPOSE

It is unclear whether delayed-type hypersensitivity reactions against implanted metals play a role in the etiopathogenesis of malfunctioning total knee arthroplasties. We therefore evaluated the association between metal allergy, defined as a positive patch test reaction to common metal allergens, and revision surgery in patients who underwent knee arthroplasty.

PATIENTS AND METHODS

The nationwide Danish Knee Arthroplasty Register, including all knee-implanted patients and revisions in Denmark after 1997 (n = 46,407), was crosslinked with a contact allergy patch test database from the greater Copenhagen area (n = 27,020).

RESULTS

327 patients were registered in both databases. The prevalence of contact allergy to nickel, chromium, and cobalt was comparable in patients with and without revision surgery. However, in patients with 2 or more episodes of revision surgery, the prevalence of cobalt and chromium allergy was markedly higher. Metal allergy that was diagnosed before implant surgery appeared not to increase the risk of implant failure and revision surgery.

INTERPRETATION

While we could not confirm that a positive patch test reaction to common metals is associated with complications and revision surgery after knee arthroplasty, metal allergy may be a contributor to the multifactorial pathogenesis of implant failure in some cases. In cases with multiple revisions, cobalt and chromium allergies appear to be more frequent.

Large fixed-size metal-on-metal total hip arthroplasty: higher serum metal ion levels in patients with pain

PURPOSE

Recently, concerns have arisen about metal-on-metal (MoM) total hip arthroplasty (THA). Therefore, the purpose of this cross-sectional cohort study was to describe the incidence of pain, pseudotumours, revisions and the relation between elevated metal ion levels, functional outcome and quality of life after MoM THA.

METHODS

In 351 patients, 377 MoM THA with a fixed-size 38-mm head were evaluated with a mean follow-up of 30 months (range 11-58). Evaluation included pain, serum metal ions, patient-reported questionnaires (Short Form-36 [SF-36], Hip disability and Osteoarthritis Outcome Score [HOOS] and the Oxford Hip Score [OHS]) and radiological imaging. Sixteen patients did not participate in the screening.

RESULTS

One hundred and eighteen (35 %) patients reported pain and showed significantly higher cobalt and chromium levels compared to patients without pain. Median serum cobalt levels were 4.4 μg/l (interquartile range [IQR] 6.6) and chromium levels were 3.6 μg/l (IQR 4.8). Patients with cobalt levels of ≤5 μg/l reported significantly better outcome on the SF-36 and HOOS. Fifty-seven pseudotumours were identified in 227 THAs. A revision rate of 19 % was observed.

CONCLUSIONS

In conclusion, 35 % of the patients experienced pain after MoM THA. These patients showed significantly higher serum metal ion levels. The patient-reported questionnaires indicated significantly better outcome in patients with cobalt levels ≤5 μg/l.