Early Outcomes of an Alternative Bearing Surface in Primary Total Knee Arthroplasty in Patients with Self-reported Metal Allergy

Existing and Novel Assessment Methods for Metal Sensitivity in Elective Lower-Limb Arthroplasty-A Scoping Review

Background

Metal sensitivity is a possible cause for revision in elective lower-limb arthroplasty. This scoping review aims to identify and evaluate all existing and novel assessment methods for metal sensitivity in elective lower-limb arthroplasty.

Methods

The Cochrane Central Register of Controlled Trials (CENTRAL), Ovid Medical Literature Analysis and Retrieval System Online (MEDLINE), PubMed, and Google Scholar databases were searched for studies published between January 1, 2000, and September 1, 2023. Studies evaluating one or more metal sensitivity assessment method preoperatively, perioperatively, or postoperatively were included. Studies were grouped based on the assessment methods reported and summarized based on the study design, outcome measure, results, and comments on the method's validity.

Results

A total of 1220 results were screened, with 39 results (15 retrospective cohort studies, 11 prospective cohort studies, 6 case reports, 5 randomized controlled trials, and 2 case control studies) included, identifying 12 assessment methods. The most used one was patch testing, featuring in 17 studies (43.6%). Lymphocyte transformation assay/testing featured in 12 studies (30.8%). Plasma/serum concentration of metal ions featured in 6 studies (15.4%). Patient history and serum cytokine testing featured in 7 (17.9%) and 4 (10.3%) studies each. Generalized serum inflammatory markers featured in 3 studies (7.7%). The remaining 6 methods each featured in one or 2 studies. Evidence of the reliability of most metrics was limited.

Conclusions

Several assessment methods were identified. However, evidence of any methods reliably predicting and diagnosing the occurrence of metal sensitivity was limited. There is a need for improved metrics of metal hypersensitivity.

Hypoallergenic Knee Implant Usage and Clinical Outcomes: Are They Safe and Effective?

Background

One of the most debated topics in modern total knee arthroplasty (TKA) is the impact of metal hypersensitivity (MH) as a potential cause of prosthesis failure. Implanting hypoallergenic prostheses to avoid potential problems in suspected cases of MH is one treatment option that can be used in such cases. However, their long-term clinical safety and efficacy are not well proven.

Methods

All literature relevant to modern hypoallergenic implants were reviewed and summarized to provide a comprehensive synopsis. In addition, a detailed literature search was performed on PUBMED, MEDLINE, and Google Scholar to identify all the clinical studies reporting outcomes for hypoallergenic knee implants. Our search was confined to those studies published as full manuscripts in the English language from July 2018 to July 2023.

Results

To minimize the risk of MH, new implant variants have been developed which are either under clinical evaluation or in routine clinical use. These include conventional metal implants with protective coatings (mono- or multilayer) and metal-free implants. However, there is insufficient clinical data to confirm the rationale and effectiveness of using these "hypoallergenic" TKA implants.

Conclusions

Published studies and arthroplasty registry data analyses indicate no significant differences between hypoallergenic and standard TKAs with overall good survival rates. In the future, further high-quality studies are needed to better understand the complexity of this subject.

Do Patients With Hypoallergenic Total Knee Arthroplasty Implants for Metal Allergy Do Worse? An Analysis of Health Care Utilizations and Patient-Reported Outcome Measures

BACKGROUND

Metal allergy is a rare and controversial cause of implant failure and poor outcomes following total knee arthroplasty (TKA). Few studies have investigated clinical and patient-reported outcome measures (PROMs) in patients treated with hypoallergenic implants. This investigation aimed to compare: (1) health care utilizations (eg, hospital length of stay, 90-day readmission rate, and incidence of nonhome discharge) and (2) 1-year PROMs between patients who received hypoallergenic and standard TKA implants.

METHODS

This was a retrospective review of prospectively collected data from patients who underwent primary TKA between 2018 and 2019. Propensity score matching (3:1) was used to compare standard TKA patients with those who received hypoallergenic TKA implants, respectively. Knee injury and Osteoarthritis Outcome Score (KOOS) pain, KOOS Physical function Shortform (PS), and Veterans RAND 12-Item Health Survey Mental Component Score were collected preoperatively and at 1-year. After matching, 190 hypoallergenic and 570 standard TKAs were analyzed.

RESULTS

No differences were observed in length of stay (P = .98), 90-day readmission (P = .89), and nonhome discharge (P = .82). Additionally, there was no significant difference in change from preoperative to 1-year PROMs (KOOS pain, P = .97; KOOS PS, P = .88; Veterans RAND 12-Item Health Survey Mental Component Score, P = .28). Patient-reported satisfaction was similar at 1-year (P = .23). Patients achieved similar rates of Patient Acceptable Symptom State (PASS) and minimal clinically important difference (MCID) for KOOS pain (PASS, P = .77; MCID, P = .33) and KOOS PS (PASS, P = .44; MCID, P = .65).

CONCLUSION

Patients treated with hypoallergenic TKA implants for suspected metal allergy had similar outcomes compared to patients who had standard implants and no metal allergy.

A comparison of clinical outcomes after total knee arthroplasty (TKA) in patients with preoperative nickel allergy receiving Cobalt-Chromium (CoCr) or Nickel-Free Implant

INTRODUCTION

The role of metal hypersensitivity reactions in total knee arthroplasty (TKA) failure is debated. There is no consensus on whether use of a more expensive nickel-free implant is indicated for patients who have pre-operative nickel allergy. The purpose of this study was to examine the outcome of patients who have pre-operative nickel allergy receiving nickel-free or cobalt chromium (CoCr) implants.

METHODS

This was a retrospective review of 17,798 patients who underwent 20,324 unilateral primary TKAs between 2016 and 2020. Presence of pre-operative nickel allergy was determined (n=282). Patients were divided into 2 cohorts: those receiving (1) nickel-free or (2) CoCr implants. Clinical outcome scores and revision rates were assessed.

RESULTS

243 received a nickel-free implant and 39 received a CoCr implant. There was no significant difference in revision rate between the cohorts. Survivorship free of revision was 94% in the CoCr implant cohort and 98% in the nickel-free implant cohort (P=0.9). When comparing clinical outcome scores between cohorts, there was no difference in preoperative, 6-week or 1-year Knee Osteoarthritis Outcome Score Joint Replacement (KOOS JR.), Visual Analog Scale (VAS), Lower Extremity Activity Scale (LEAS), Patient-Reported Outcomes Measurement Information System (PROMIS), and Veterans RAND 12-item (VR12) scores between cohorts.

CONCLUSIONS

In this retrospective cohort study, there was no difference in revision rates or clinical outcomes in patients who had a nickel allergy undergoing primary TKA with CoCr or nickel-free implants. Further studies are needed to determine if nickel allergy is an independent risk factor for worse TKA outcomes in general.

Poor Correlation Among Metal Hypersensitivity Testing Modalities and Inferior Patient-Reported Outcomes After Primary and Revision Total Knee Arthroplasties

Background

Metal allergy testing may influence clinical decision-making for patients undergoing a total knee arthroplasty (TKA). Limited data were found to examine the consistency of available testing modalities. This study compares different metal allergy test results and clinical outcomes after primary and revision TKAs in patients with and without metal hypersensitivity.

Methods

Primary (n = 28) and revision (n = 20) TKA patients receiving hypoallergenic implants for metal allergies diagnosed by skin patch testing (SPT), lymphocyte proliferation testing (LPT), or lymphocyte transformation testing (LTT) were retrospectively reviewed. The agreement between tests was assessed by percentage and kappa statistic within patients who used multiple testing modalities. Postoperative clinical outcomes of these patients were compared to those of patients without metal hypersensitivity matched by age (±5 years), body mass index (±5), gender, and follow-up duration (±2 years).

Results

SPT and LPT showed weak agreement for nickel and minimal agreement for cobalt. SPT and LTT showed minimal agreement for nickel; weak agreement for titanium, bone cement, vanadium, and zirconium; but strong agreement for chromium and cobalt. LPT and LTT agreement was weak. Compared to matched controls, metal hypersensitivity patients undergoing primary TKAs with hypoallergenic implants experienced less improvement in Knee Society Scores, Veterans RAND 12 physical component scores, and range of motion. Patients undergoing revision TKAs for multiple indications including metal hypersensitivity had worse clinical outcomes with significantly worse improvements in Knee Society functional scores compared to matched controls.

Conclusions

Metal allergy tests produce conflicting results. Hypersensitivity patients may experience inferior clinical outcomes even with hypoallergenic implants. Clinician awareness may influence the choice of testing and improve preoperative counseling of this patient population.

High early failure rate for a new unicondylar knee system

Background

This single-center retrospective study evaluated early failure rates for an unicompartmental knee arthroplasty (UKA) system with an anti-allergic surface.

Methods

We studied 87 consecutive joints received an UKA at a single center between 2017 and 2020. All patients received a fully cemented anti-allergic Univation-Aesculap partial knee replacement implant with a corundum blasting surface. All joints had precise indication of unicompartmental arthroplasty according to the current criteria of this procedure. The current series was restricted to patients undergoing medial cemented UKA. Medial compartment osteoarthritis was the main indication.

Results

We found early failure (aseptic loosening) was documented in 20 of the 87 joints (23%). The time to failure ranged from 7 weeks to 3 years, for an estimated 33% (15-46%) cumulative hazard rate for implant loosening over three years. No cases of periprosthetic joint infection were found. On average, the patients began complaining about first symptoms during the third month after surgery. In most cases (66.66%), the cement remained fixed to the bone.

Conclusions

Based on these early results, the manufacturer of this implant stopped all further distribution. Continued efforts should be made to understand the clinical and radiographic outcomes of alternative and anti-allergic surface coatings in knee arthroplasty.

Bone Cement Hypersensitivity in Patients With a Painful Total Knee Arthroplasty: A Case Series of Revision Using Custom Cementless Implants

Little is known about patients with bone cement hypersenstivity after total knee arthroplasty (TKA). We present 7 patients implanted with 8 TKAs with clinical failure and a cement hypersensitivity diagnosis. All demonstrated hypersensitivity to bone cement via skin patch and/or lymphocyte transformation testing. All 7 patients also showed hypersensitivity to metal, most commonly nickel. Patients underwent custom cementless TKA revision. Prerevision and postrevision outcome measures, radiographs, intraoperative findings, and postrevision complications are reported. Functional scores improved after revision except Veterans RAND-12 mental component scores, which declined. Four patients continue to exhibit symptoms postoperatively, while one patient has had 3 additional surgical procedures. Patients presenting with bone cement hypersensitivity after TKA are particularly challenging. Evidence-based guidelines are lacking, and revision surgery may not relieve the presenting symptoms.