IS METALLOSIS A CONTRIBUTING FACTOR TO PROSTHETIC JOINT INFECTIONS? A COMPARATIVE STUDY

Aim Metallosis is a rare but severe complication of arthroplasty. Prosthetic Joint Infections (PJI) may be observed in patients presenting metallosis. In this study, we aimed to assess characteristics of metallosis and to compare them to patients with PJI epidemiology, management and outcome. Methods A retrospective monocenter study including all consecutive cases of metallosis between 2019 and 2024 were included. Samples for microbiology and pathology are collected for all patients having surgery in our center. Demographic, clinical, pathology, microbiology, imaging, surgical treatment, and outcome data were collected. Diagnosis of metallosis was based on clinical signs and confirmed by pathology results. Metallosis data for patients with infection were compared to a group of 100 patients presenting PJI. Results Sixty-two patients with metallosis diagnosis were included. Mean age was 67.2 ± 9.5 yo, 30 (49.2%) patients were male, Charlson score was 3.00 [2.00, 4.00]. Site of metallosis included hip 27 (43.5%), knee 32 (51.6%), shoulder 2 (3.2%). Fifty patients (80.6%) had local signs of inflammation; median CRP was 26mg/L [18-36]. Among all patients, 23 cases of loosening (37.7%), 13 (21.3.%) instability, 3 (4.9%) prosthesis dislocation. Among 62 patients, 29 (46.8%) had a diagnosis of metallosis with infection. Clinical signs in this group showed 25 (86.2%) local inflammation, median CRP was 27mg/L [29-38], 9 (14.5%) fistula and 3 (4.8%) patients with fever. Median delay between clinical symptoms and surgery was 3.48 [2.73-4.14] months. Treatment consisted in surgery with one-stage exchange in 55 (88.7%) patients. A favorable outcome was found in 24 (82.8%) patients. Comparing patients with metallosis-infection to patients with PJI only, no difference was found for delay between clinical signs and surgery (p=0.74), clinical manifestations (p=0.35), treatment (p=0.42) and outcome (p=0.16). However, microbial epidemiology of metallosis-infection showed mainly coagulase negative staphylococci like S. epidermidis (n=19; 65.5%) (p=0.03) and C. acnes (n=8; 27.6%) (p=0.05) significantly different from species of PJI group involving more frequently S. aureus and streptococci species. Conclusions Our study reports that almost one half of patients with metallosis present an infection. Demography and clinical presentation of metallosis cases are very close to PJI explaining that its diagnosis may be challenging. Microbiology of metallosis-infection shows significant species differences but metallosis doesn't seem to be worsening clinical or surgical evolution.