Outcomes related to pseudotumours, metal ion levels in bilateral resurfacing among MoM hip arthroplasty research

GENEVA — “Metal-on-metal is still a problem that is worthwhile to be discussed in its own session,” Karl Knahr, MD, of Vienna, Austria, said during a free paper session he moderated at the 17th EFORT Congress, here.

The session included research results of the effects of elevated serum cobalt levels on patients’ visual pathways, which was presented by Timothy Unsworth-Smith, MD, and risk stratification strategies for patients after metal-on-metal (MoM) hip arthroplasty, which was presented by Henrik Malchau, MD, PhD.

Unsworth-Smith and colleagues identified a statistically significant disturbance of retinal electrophysiology among patients with Articular Surface Replacement (DePuy Synthes) hip replacement compared with two control groups.

Karl Knahr

Dimitris Dimitriou, MD, and colleagues used metal artifact reduction sequence (MARS) MRI for cross-sectional imaging of pseudotumours after MoM hip arthroplasty in 37 hips (32 patients) to determine the natural history of the tumours. The patients’ mean age was 56 years.

At a minimum follow-up of 4 years they found four type 2 pseudotumours with evidence on MRI of progression (11%).

“To date this is the largest longitudinal study regarding the natural history of pseudotumour in asymptomatic patients. Some pseudotumours do not progress,” Dimitriou said.

An increased cystic wall thickness and atypical fluid signals were present on MRI in the progressive tumours, he noted.

“The important message for this study is not all symptoms for type 1 pseudotumours require revision. It is important to systematically evaluate the MoM patients. A routine MRI follow-up may not be indicated in asymptomatic MoM patients with a low-grade pseudotumour and no further clinical changes,” Dimitriou said.

Gulraj S. Matharu, BSc, and colleagues studied bilateral hip arthroplasty with Birmingham Hip Resurfacing (Smith & Nephew) and Corail-Pinnacle (DePuy Synthes) MoM hips in 235 patients. They found significantly higher ion parameters in patients with adverse reactions to metal debris (ARMD) vs. patients without ARMD.

“This is the largest study we are aware of assessing limits for ion metal thresholds in bilateral hip patients,” Matharu said.

“Implant-specific thresholds were more effective for identifying ARMD than fixed thresholds and this is a clinically important finding,” he said. – by Susan M. Rapp

References:

Dimitriou D, et al. Paper #57. Matharu G, et al. Paper #633. Unsworth-Smith T, et al. Paper #3. All papers presented at: 17th EFORT Annual Congress—A combined programme in partnership with swiss orthopaedics; 1-3 June 2016; Geneva.

Dimitriou, D, et al. J Arthroplasty. 2016.doi:10.1016/j.arth.2016.02.070.

Disclosures: Dimitriou reports no relevant financial disclosures. Knahr reports he is a paid consultant to Mathys Ltd. and received IP royalties and research support from Zimmer Biomet. Matharu reports he received financial/material support for this research from Arthritis Research UK. Unsworth-Smith reports no relevant financial disclosures.