B EYOND THE P SEUDOTUMOR – MARS MRI OF PAINFUL METAL - ON - METAL HIPS R. Sandhu, K. Satchithananda, A. Mitchell, A. Lewis, J. Henckel, E. Kew, S. Sabah, D. McRobbie, A. Papadakos, A. Hart Beyond The Pseudotumor - MARS MRI Of Painful Metal-On-Metal Hips 1 The following presentation was given at the Radiological Society of North America (RSNA) in 2011

MRI (Magnetic Resonance Imaging) is a crucial tool in the assessment of patients with metal on metal (MOM) hip replacements with postoperative hip pain. In a number of these patients, we have diagnosed clinically relevant pathology, which is not related to the presence of pseudotumors (sterile synovial based soft tissue lesions) around the prosthesis. These lesions are likely to have been missed by other imaging modalities such as focussed hip ultrasound. Beyond The Pseudotumor - MARS MRI Of Painful Metal-On-Metal Hips 2 INTRODUCTION

Reason for revision surgery Aseptic loosening32% Periprosthetic fracture25% Pain23% Other20% 1 million metal-on-metal (MOM) hips were implanted worldwide from 1997 – 2011 All regulatory agencies worldwide have guidelines on management of patients with painful MOM hips 1 type, the ASR, has been recalled after 100,000 implantations. It has a failure rate of upto 49% at 5 years. Beyond The Pseudotumor - MARS MRI Of Painful Metal-On-Metal Hips 3 EPIDEMIOLOGY INTRODUCTION “UNEXPLAINED” 43%

INTRODUCTION We are a tertiary referral centre for patients with painful MOM hips We run “painful MOM hip” clinics and have performed MARS MRI in over 200 patients We are linked to the London Implant Retrieval Centre which has collected over 900 explanted MOM hips from all over the world Beyond The Pseudotumor - MARS MRI Of Painful Metal-On-Metal Hips 4 OUR EXPERIENCE

We studied patients using MARS MRI imaging techniques to demonstrate lesions other than pseudotumours and will discuss their implications. Metal artefact-reduction sequences for MRI can produce diagnostic quality images of the periprosthetic tissues – Toms et al, Clin Radiol [2008], Hart et al, JBJS(Br) [2009] Beyond The Pseudotumor - MARS MRI Of Painful Metal-On-Metal Hips 5 METHODS

The ‘non-pseudotumor’ lesions found on the postoperative MOM hip replacement MARS MRI included: – massive muscle necrosis – periprosthetic fractures – a case of diffuse bony metastases – an exostosis – a case of clinically relevant genitourinary pathology Beyond The Pseudotumor - MARS MRI Of Painful Metal-On-Metal Hips 6 RESULTS

Beyond The Pseudotumor - MARS MRI Of Painful Metal-On-Metal Hips 7 MASSIVE OSTEOLYSIS COMPLICATIONS Axial T1W and Intraoperative image Patient went on to have a total hip replacement

Beyond The Pseudotumor - MARS MRI Of Painful Metal-On-Metal Hips 8 PERIPROSTHETIC FRACTURES COMPLICATIONS Axial T1W Patient went on to have a prosthesis revision to treat their pubic ramus fracture

Beyond The Pseudotumor - MARS MRI Of Painful Metal-On-Metal Hips 9 METASTATIC BONY DEPOSITS COMPLICATIONS Axial and Coronal T1W Patient went on to have chemotherapy and hormonal therapy

Beyond The Pseudotumor - MARS MRI Of Painful Metal-On-Metal Hips 10 AN EXOSTOSIS COMPLICATIONS Axial T1W This lesion would have been missed with a focussed left hip US

Beyond The Pseudotumor - MARS MRI Of Painful Metal-On-Metal Hips 11 CASE OF FIBROIDS COMPLICATIONS Axial T2W This patient went on to have a gynaecological referral

The demonstration of these ‘non-pseudotumor’ lesions highlights the importance of MRI when imaging MOM hip replacements for postoperative pain. Of equal importance is the demonstration of supplementary pathology which in some cases significantly alters the patient’s treatment. Moreover, a number of these lesions can only be demonstrated by MRI rather than focussed hip ultrasound because of its larger field of view enabling visualisation of the whole pelvis. Beyond The Pseudotumor - MARS MRI Of Painful Metal-On-Metal Hips 12 DISCUSSION

We aimed to show that when reporting a MARS MRI, it is not only the periprosthetic tissues that are important but also the evaluation of other structures. This includes pathology other than pseudotumors that has significant additional implications in patient management. Beyond The Pseudotumor - MARS MRI Of Painful Metal-On-Metal Hips 13 CONCLUSION