High Incidence of Pseudotumours after Hip Resurfacing Even in Low Risk Patients; Results from an Intensified MRI Screening Protocol

Abstract

We intensified our screening protocol for the presence of pseudotumours in a consecutive series of patients with a hip resurfacing arthroplasty (HRA), to establish whether we should be alert to the presence of 'silent' pseudotumours. Patients categorised with high risk (11 hips) and low risk (10 hips) for pseudotumour development and a control group (23 hips) were screened with metal artefact reduction sequence (MARS) magnetic resonance imaging (MRI). The Anderson classification to grade any metal-on-metal (MoM) disease present on MARS-MRI images was used. In 15 out of 44 MRI scans pseudotumours were observed (34.1%), of which six were graded with mild (13.6%), eight with moderate (18.2%) and one with severe MoM disease (2.3%). Twelve pseudotumours were present in asymptomatic patients (27.3%). Metal ion levels were normal in 80% of the MARS-MRI screened patients. As a consequence of our intensified screening protocol, one patient was revised for pseudotumour formation and another patient was scheduled for revision. Silent pseudotumours were observed in all three groups. Before our intensified screening protocol was initiated, no pseudotumours were encountered in our cohort of 289 HRAs. We concluded that clinical outcomes and plain radiographs for screening MoM patients underestimates the presence of pseudotumours in MoM patients. The true clinical relevance of these pseudotumours is still unclear.

The Natural History of Inflammatory Pseudotumors in Asymptomatic Patients After Metal-on-metal Hip Arthroplasty

“…Authors raised concerns regarding elevated serum metal ions and their systemic side effects [4,17,19,26,30,38,40]. Local reactive soft tissue masses termed pseudotumors or lymphocyte-dominated vasculitis-associated lesions started to appear in the literature [7,10,11,14,22,32,34,39]. It was proposed by some that these lesions represented a form of hypersensitivity reaction to local metal debris [8,20,35].…”

“…This eventually led to the recalls of specific metal-on-metal implants [15,43]. Several authors have reported on the prevalence of these pseudotumor masses in both symptomatic and asymptomatic patients after either large-diameter femoral head THA or hip resurfacing arthroplasty [23,27,39,42]. Hart et al [23] compared the prevalence of MRI-detected pseudotumors in a group of 30 patients with painful large head metal-on-metal hip arthroplasty and a control group of 28 well-functioning patients and found a similar prevalence of pseudotumor of 57% and 61% in the respective groups.…”

What Is the Natural History of Asymptomatic Pseudotumors in Metal-on-metal THAs at Mid-term Followup?

“…Also, no patient who had a negative first ultrasound was included in the followup period. Several other authors have documented the frequency with which pseudotumors after MoM THA [14,16,25,27]. However, the natural history of asymptomatic pseudotumors in large-head MoM hip replacements remains unclear.…”

The young osteoarthritic hip

“…however, the high midterm failure rates were not limited exclusively to this implant and a high number of serious side effects were seen in several designs. the local metal ion debris, which is generated by these implants can cause severe local problems with a high incidence of so-called pseudotumors (Pandit et al 2008, Van der Weegen et al 2013. in addition to local effects, these metal ions have shown to disseminate to other parts of the body by spreading to the lymph nodes, spleen, liver, and kidneys before being excreted in urine (Case et al 1994).…”