Modular taper junction corrosion and failure: how to approach a recalled total hip arthroplasty implant

Corrosion and Fretting of a Modular Hip System: A Retrieval Analysis of 60 Rejuvenate Stems

Femoral stems with dual-taper modularity were introduced to allow independent control of length, offset, and version. Corrosion and fretting related to micromotion at the neck-stem junction are thought to stimulate an adverse local tissue reaction (ALTR). Analysis of 60 consecutively retrieved modular-neck stem implants (Rejuvenate, Stryker) revised primarily for ALTR was done to determine the variables influencing corrosion and fretting patterns at the neck-stem interface. Taper damage evaluation was performed with stereomicrocopic analysis with two observers. Evidence of fretting and corrosion was seen at the neck-stem taper in all implants, including three implants revised for periprosthetic fractures within four weeks of the index surgery indicating that this process starts early. Femoral stems paired with the long overall neck lengths had significantly higher corrosion scores. Correlation of the corrosion severity at particular locations with the length of implantation suggests that the neck-stem junction experiences cyclic cantilever bending in vivo. The positive correlation between the length of implantation and fretting/corrosion scores bodes poorly for patients who still have this implant. Scanning electron microscopy on a subset of specimens was also performed to evaluate the black corrosion material. We strongly urge frequent follow-up exams for every patient with this particular modular hip stem.

A new universal, standardized implant database for product identification: a unique tool for arthroplasty registries

INTRODUCTION

Every joint registry aims to improve patient care by identifying implants that have an inferior performance. For this reason, each registry records the implant name that has been used in the individual patient. In most registries, a paper-based approach has been utilized for this purpose. However, in addition to being time-consuming, this approach does not account for the fact that failure patterns are not necessarily implant specific but can be associated with design features that are used in a number of implants. Therefore, we aimed to develop and evaluate an implant product library that allows both time saving barcode scanning on site in the hospital for the registration of the implant components and a detailed description of implant specifications.

MATERIALS AND METHODS

A task force consisting of representatives of the German Arthroplasty Registry, industry, and computer specialists agreed on a solution that allows barcode scanning of implant components and that also uses a detailed standardized classification describing arthroplasty components. The manufacturers classified all their components that are sold in Germany according to this classification. The implant database was analyzed regarding the completeness of components by algorithms and real-time data.

RESULTS

The implant library could be set up successfully. At this point, the implant database includes more than 38,000 items, of which all were classified by the manufacturers according to the predefined scheme. Using patient data from the German Arthroplasty Registry, several errors in the database were detected, all of which were corrected by the respective implant manufacturers.

CONCLUSIONS

The implant library that was developed for the German Arthroplasty Registry allows not only on-site barcode scanning for the registration of the implant components but also its classification tree allows a sophisticated analysis regarding implant characteristics, regardless of brand or manufacturer. The database is maintained by the implant manufacturers, thereby allowing registries to focus their resources on other areas of research. The database might represent a possible global model, which might encourage harmonization between joint replacement registries enabling comparisons between joint replacement registries.

Short-Term Metal Ion Trends Following Removal of Recalled Modular Neck Femoral Stems

Elevated serum metal ions have been well documented with the Rejuvenate modular neck femoral stem (Stryker, Mahwah, NJ); however, the rate at which ion levels decline following revision is less clear. This study included fifty-nine consecutive revisions of Rejuvenate stems for symptomatic ALTR. Blood tests prior to revision and postoperatively at 6weeks, 3months, 6months, and 1year measured serum cobalt and chromium concentrations, ESR, and CRP. At six weeks following revision of a unilateral Rejuvenate, cobalt and chromium levels dropped from preoperative levels by 67% and 42%, respectively. At three months, cobalt levels declined to 19% of preoperative values, but chromium levels remained stable. With this information, surgeons can set realistic expectations for serum metal ion levels following Rejuvenate stem revision.

Usefulness of ultrasonography for detection of pseudotumors after metal-on-metal total hip arthroplasty

We retrospectively analyzed 83 metal-on-metal total hip arthroplasties in 74 patients. Ultrasonography and magnetic resonance imaging (MRI) of each hip were performed to detect abnormal patterns and pseudotumors. We examined the reliability of ultrasonography for detecting pseudotumors in comparison with MRI. We also compared the acetabular component inclination between patients with and without pseudotumors. The mean positive and negative predictive values for pseudotumor detection by ultrasonography were 65% and 91%, respectively. The mean positive and negative likelihood ratios were 5.78 and 0.32, respectively. There was no clear association between pseudotumor presence and acetabular component inclination. We concluded that ultrasonography is a suitable technique to screen for the presence of pseudotumors. We also need to distinguish between bearing-related and taper junction corrosion-related complications.

Revision of Recalled Modular Neck Rejuvenate and ABG Femoral Implants

Modular neck femoral stems have been associated with adverse local tissue reactions (ALTR), leading to a voluntary recall, but these effects have not been well-characterized. A retrospective review of intraoperative findings and cobalt/chromium levels was performed in 103 hips undergoing revision for ALTR. The average preoperative serum cobalt level was 7.6 μg/L (range 1.1-23 μg/L) and chromium level was 1.8 μg/L (range 0.1-6.8 μg/L). Metallic sludge was noted in 100%, synovitis in 98%, pericapsular rind in 82%, and calcar erosion in 85%. An osteotomy was required for removal in 44%. We concluded that revision of modular neck femoral stems is associated with increased preoperative metal ion levels and stem-neck corrosion. Despite advanced stem explantation techniques, osteotomy was frequently required, leading to increased morbidity.

Severe Wear and Pseudotumor Formation Due to Taper Mismatch in a Total Hip Arthroplasty: A Case Report

CASE

We describe the case of a seventy-six-year-old woman who had undergone bilateral total hip arthroplasty with Zweymüller-Metasul prostheses in 1996. After a fall sixteen years after the index procedures, radiographs suggested a taper fracture of the left total hip arthroplasty. However, revision surgery showed pseudotumor formation, with no evidence of taper fracture. Analysis of the prosthesis showed massive wear of the male stem taper caused by a mismatch between the stem taper and the head taper.

CONCLUSION

This case vividly demonstrates how taper size mismatch can cause dramatic metal wear and increased release of metal ions, resulting in pseudotumor formation.

Adverse reactions to metal debris in metal-on-polyethylene total hip arthroplasty using a titanium-molybdenum-zirconium-iron alloy stem

We report a series of three patients who underwent uncemented total hip arthroplasty with a modular titanium-molybdenum-zirconium-iron stem and a cobalt-chrome-molybdenum head on an ultra-high molecular weight highly cross-linked polyethylene liner bearing. All three cases subsequently developed pain and adverse reaction to metal debris, leading to revision of the implants within thirty-six months. They were subsequently found to have hypersensitivity to cobalt or chromium. However where tested, blood metal ion levels were within MHRA guideline limits. Corrosion was noted at the taper-trunnion junction. It is possible, that the multi alloy head-neck combination may lead to corrosion. Hypersensitivity to metal ions may result to ARMD at lower metal ion levels. The use of ceramic heads may help avoid this risk.

Risk stratification algorithm for management of patients with dual modular taper total hip arthroplasty: consensus statement of the American Association of Hip and Knee Surgeons, the American Academy of Orthopaedic Surgeons and the Hip Society

Although 'dual taper' modular stems with interchangeable modular necks have the potential to optimize hip biomechanical parameters, there is increasing concern regarding the occurrence of adverse local tissue reactions from mechanically assisted crevice corrosion at the neck-stem taper junction. A systematic treatment approach (risk stratification algorithm) based on the currently available data is recommended to optimize patient management. While specialized tests such as metal ion analysis and MARS MRI are useful modalities in evaluating for adverse tissue reactions, over-reliance on any single investigative tool in the clinical decision-making process should be avoided. There should be a low threshold to perform a systematic evaluation of patients with dual taper stem total hip arthroplasty as early recognition and diagnosis will facilitate the initiation of appropriate treatment.

Adverse clinical outcomes in a primary modular neck/stem system

We report our experience with 215 recalled neck modular stems due to corrosion. Among the 195 hips with 2 years follow-up, 56% had no clinical symptoms, 26% had groin pain (typical of corrosion), and 17% had other symptoms. Cobalt levels were comparable between asymptomatic (3.4 μg/L, range 0.7-7.3 μg/L) and symptomatic patients (4.0 μg/L range 0-13.2 μg/L). Abnormal imaging findings were seen in 46% of symptomatic and 11% of asymptomatic hips (P=0.001). Twenty-six hips (13%) have either undergone revision surgery or have been scheduled. Evidence of corrosion was seen at revision surgery in all patients. Despite modest elevations in serum cobalt levels, abnormal imaging studies were seen in 36%, clinical symptoms were seen in 44%, and revision for corrosion was undertaken or scheduled in 13% of the hips.

Dealing with recalled components

It is often difficult for orthopedic surgeons to react to a situation where a particular implant that they have been using for many years is suddenly recalled from the market by either the manufacturer or the United States Food and Drug Administration. This report briefly summarizes some of the issues that may arise when such a circumstance occurs. We briefly outline what an implant recall is, what measures the orthopedic surgeon should take when an implant is permanently recalled, what litigation issues may arise, and describe the resources available to the orthopedic surgeon for the evaluation of these patients. It is important to understand that the manufacturer and the insurance companies often bear the burden of the financial loss, although the anguish, time loss for patients, and the effect on clinical practice are issues which are largely inevitable. Nevertheless, it is essential for the orthopedic community to be aware and be prepared for these unlikely situations should they occur, so that we will remain the patient's best advocate at all times.

Cross-sectional imaging in evaluation of soft tissue reactions secondary to metal debris

An integral component of systematic treatment algorithms to optimize evaluation and management of patients with MoM hip arthroplasty recommend the use of cross-sectional imaging to diagnose the presence of adverse local tissue reactions. Cross-sectional imaging studies such as ultrasound is a useful screening tool to detect the presence of a soft-tissue mass adjacent to a MoM implant. MARS MRI is a useful diagnostic test for assessing MoM hip arthroplasty and modular taper corrosion for adverse tissue reactions. Each cross-sectional imaging modality has unique utility and limitations. As metal artifact reduction technique continues to be refined, the utility of MARS MRI in evaluating patients with MoM hip arthroplasty and modular taper corrosion is likely to have an increased role in the clinical decision making process. However, over-reliance on any single investigative tool in the clinical decision-making process should be avoided.