A longitudinal study of MARS MRI scanning of soft-tissue lesions around metal-on-metal total hip arthroplasties and disease progression

Abstract

We investigated the changes seen on serial metal artefact reduction magnetic resonance imaging scans (MARS-MRI) of metal-on-metal total hip arthroplasties (MoM THAs). In total 155 THAs, in 35 male and 100 female patients (mean age 70.4 years, 42 to 91), underwent at least two MRI scans at a mean interval of 14.6 months (2.6 to 57.1), at a mean of 48.2 months (3.5 to 93.3) after primary hip surgery. Scans were graded using a modification of the Oxford classification. Progression of disease was defined as an increase in grade or a minimum 10% increase in fluid lesion volume at second scan. A total of 16 hips (30%) initially classified as 'normal' developed an abnormality on the second scan. Of those with 'isolated trochanteric fluid' 9 (47%) underwent disease progression, as did 7 (58%) of 'effusions'. A total of 54 (77%) of hips initially classified as showing adverse reactions to metal debris (ARMD) progressed, with higher rates of progression in higher grades. Disease progression was associated with high blood cobalt levels or an irregular pseudocapsule lining at the initial scan. There was no association with changes in functional scores. Adverse reactions to metal debris in MoM THAs may not be as benign as previous reports have suggested. Close radiological follow-up is recommended, particularly in high-risk groups.

Advances in MRI around metal

“…In the algorithmic approach to diagnosis and management of metal‐on‐metal arthroplasty published in 2012 by the hip society, imaging should include ultrasound or metal artifact reduction sequence MRI in addition to plain radiography . MARS sequences including VAT and SEMAC have been shown to be useful for detection, staging, and progression analyses of adverse local tissue reactions (ALTR) in the context of metal‐on‐metal hip prostheses . Several studies reported ALTR findings on MRI in up to a third of asymptomatic patients, and despite missing laboratory findings, there is no significant relation between MRI findings and pain or a priori risk factors, which underlines the importance of MRI .…”

Mid-term changes in blood metal ion levels after Articular Surface Replacement arthroplasty of the hip

“…29,30 It will also be important to correlate changes in the levels of metal ions with soft-tissue changes and revision. One study reported that progressive ALTR is correlated with the levels of metal ions, 31 while another found the opposite. 32 In conclusion, we found that the levels of Co and Cr ions in the blood increase from early to mid-term follow-up in patients with large head (> 40 mm) MoM arthroplasties.…”

What is appropriate surveillance for metal-on-metal hip arthroplasty patients?

“…By contrast, a study of 155 MoM THAs undergoing repeat MARS-MRI within a mean time of 15 months after the initial imaging observed that the risk of disease progression was high in patients with initially normal scans (30%), and in those with isolated trochanteric fluid (47%) and effusions (58%) on initial MARS-MRI (Briant-Evans et al. 2015 ). Disease progression on imaging was associated with high blood cobalt concentrations, or an irregular pseudocapsule lining at initial MARS-MRI (Briant-Evans et al.…”

“…The Modified Oxford Classification has been proposed more recently (Briant-Evans et al. 2015 ), which classifies MARS-MRI scans initially into 4 groups (normal, trochanteric fluid, effusion, ARMD), with the ARMD group subsequently classified according to others (Hauptfleisch et al. 2012 ).…”

“…Disease progression on imaging was associated with high blood cobalt concentrations, or an irregular pseudocapsule lining at initial MARS-MRI (Briant-Evans et al. 2015 ).…”