Abstract
Summary
162 patient cohort with serial Metal Artefact Reduction Sequence MRI scans. Patients with normal initial scans can be followed up at 1 year. Those with abnormal scans should be followed up at a shorter interval of 6 months.
Introduction
Cross-sectional imaging is a key investigation in the assessment and surveillance of patients with metal-on-metal (MoM) hip arthroplasty. We present our experience of Metal Artefact Reduction Sequence (MARS) MRI scanning in metal on metal hip arthroplasty. We aimed to investigate the natural history and radiological disease progression from Adverse Reactions to Metallic Debris.
Methods
A total cohort of 626 patients who had metal on metal arthroplasty underwent MARS MRI scanning with 162 patients having more than one MRI scan. A musculoskeletal radiologist reviewed and reported on all MRI scans. The findings were described as either normal or classified according to Hart et al. We then considered the patient's progression between groups on serial scans and the time intervals between them.
Results
65 patients had a normal first MRI, 38 (54%) remained normal on follow-up scan with a mean scanning interval of 14.6 months. The remaining 27 patients who progressed form normal to either Type 1/2/3 did so over a mean scan interval of 14 months. Of those 56 patients with a Type 1 (thin walled fluid collection) 28.5% of these progressed during interval scanning and 8.9% of Type 1 reactions returned to normal. Over half the patients with an abnormal initial MARS MRI scan 46/85 (54%), with either Type 1 or 2 abnormal soft tissue reaction, had progressed to more severe types following a mean interval scan time of 12.2 months.
Discussion
A safe interval for a follow-up MARS MRI scanning in a patient who has normal initial findings appears to be 12 months. We consider a 6-month scan appropriate for patients under surveillance who have initial abnormal cross-sectional imaging.
