Anodizing of Self-Passivating W xTi1- x Precursors for W xTi1- xO n Oxide Alloys with Tailored Stability

Serum Metal Ion Levels in Modular Dual Mobility Liners after Total Hip Arthroplasty: A Comparison by Years and Implant Manufacturers

INTRODUCTION

Modular dual mobility (DM) liners are commonly used in total hip arthroplasty (THA) to decrease the risk of instability. However, there are concerns about accelerated wear, corrosion, and metal ion release in modular DM constructs. This study aimed to investigate serum metal ion levels over time after THA and evaluate any differences between implant manufacturers.

METHODS

This retrospective study enrolled 165 patients who underwent THA with a modular DM liner. Serum cobalt (Co), chromium (Cr), and zirconium (Zr) levels were assessed via a one-time blood draw. Patients were grouped into time cohorts of one to two, two to five, five to eight, and eight plus years based on years since DM placement. The primary outcome was serum Co, Cr, and Zr levels. Reference values of < 1.5 mcg/L for Co and < 1.2 mcg/L for Cr were considered within normal limits.

RESULTS

Median Co and Cr levels were 0.3 (range, 0.2 to seven) and 0.3 (range, zero to 3.1) mcg/L, respectively. There were 13 patients (7.9%) who had abnormally elevated metal ion levels; 10 received Implant A (13%), two received Implant B (4%), and one received Implant C (3%). The Zr levels were undetectable in all patients. Median Co levels (0.4 mcg/L) were higher within two years of DM implantation and had a greater range of values than other time periods (P < 0.001). Successive time periods displayed a decreased range of Co values over time.

CONCLUSION

There was a greater range of Co levels within two years of implantation, which reduced in variability over successive time periods. Although this could suggest an initial "settling-in" period of DM constructs, sequential blood draws from individual patients over time are needed to confirm such trends. Longitudinal tracking of metal ion levels over time in modular DM implants is recommended.

Metallosis in Total Hip Arthroplasty

» Metallosis is a rare but significant complication that can occur after total hip arthroplasty (THA) for a variety of reasons but most commonly in patients with metal-on-metal implants.» It is characterized by the visible staining, necrosis, and fibrosis of the periprosthetic soft tissues, along with the variable presence of aseptic cysts and solid soft tissue masses called pseudotumors secondary to the corrosion and deposition of metal debris.» Metallosis can present with a spectrum of complications ranging from pain and inflammation to more severe symptoms such as osteolysis, soft tissue damage, and pseudotumor formation.» Workup of metallosis includes a clinical evaluation of the patient's symptoms, imaging studies, serum metal-ion levels, and intraoperative visualization of the staining of tissues. Inflammatory markers such as erythrocyte sedimentation rate and C-reactive protein along with intraoperative frozen slice analysis may be useful in certain cases to rule out concurrent periprosthetic joint infection.» Management depends on the severity and extent of the condition; however, revision THA is often required to prevent rapid progression of bone loss and tissue necrosis.