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Pseudotumor in metal-on-metal hip arthroplasty: a comparison study of three grading systems with MRI

C Smeekes1,2, B J M Schouten3, M Nix4

  • 1Department of Orthopaedics, Leiden University Medical Centre, 9600, 2300, RC, Leiden, The Netherlands. c.smeekes@lumc.nl.

Skeletal Radiology
|February 2, 2018
PubMed
Abstract

Insights

High-risk patients undergoing metal-on-metal total hip arthroplasty (MoM THA) have a high incidence of pseudotumors, while low-risk patients do not. Three MARS-MRI grading systems showed moderate interobserver reliability.

Area of Science:

  • Orthopedic Surgery
  • Radiology
  • Biomaterials Science

Background:

  • Pseudotumors are a known complication of metal-on-metal total hip arthroplasty (MoM THA).
  • Metal artifact-reducing sequences magnetic resonance imaging (MARS-MRI) effectively identifies these pseudotumors.
  • Existing MRI grading systems for pseudotumors lack validation in large clinical studies.

Purpose of the Study:

  • To classify pseudotumors in high- and low-risk MoM THA patients using three grading systems on MARS-MRI.
  • To evaluate the interobserver reliability of these pseudotumor grading systems.

Main Methods:

  • Retrospective analysis of 377 MoM THA patients (240 MRI scans) with M2a-38 and Taperloc stems.
  • Patients categorized into high-risk and low-risk groups based on established risk factors.
  • Two observers assessed pseudotumors using three distinct grading systems on MARS-MRI.

Main Results:

  • Pseudotumor prevalence was 59% in high-risk, 0% in low-risk, and 43% in control groups via MARS-MRI.
  • Elevated serum cobalt levels were observed in the high-risk group.
  • Interobserver reliability kappa values were 0.43 (Anderson), 0.44 (Hauptfleisch), and 0.49 (Matthies).

Conclusions:

  • High-risk MoM THA patients face a significant risk of pseudotumor development.
  • No pseudotumors were detected in low-risk patients.
  • All three grading systems demonstrated moderate interobserver agreement, with the Matthies system performing best.
Keywords:
ClassificationGrading systemInterobserver reliabilityMARS-MRIMoMPseudotumorTHA

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