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Clinical Trial
. 2014 Aug;85(4):375-82.
doi: 10.3109/17453674.2014.908345. Epub 2014 Apr 3.

A comparison of the diagnostic accuracy of MARS MRI and ultrasound of the painful metal-on-metal hip arthroplasty

Imran A Siddiqui  1 , Shiraz A Sabah, Keshthra Satchithananda, Adrian K Lim, Suzie Cro, Johann Henckel, John A Skinner, Alister J Hart
Affiliations
Clinical Trial

A comparison of the diagnostic accuracy of MARS MRI and ultrasound of the painful metal-on-metal hip arthroplasty

Imran A Siddiqui et al. Acta Orthop. 2014 Aug.

Abstract

Background and purpose: Metal artifact reduction sequence (MARS) MRI and ultrasound scanning (USS) can both be used to detect pseudotumors, abductor muscle atrophy, and tendinous pathology in patients with painful metal-on-metal (MOM) hip arthroplasty. We wanted to determine the diagnostic test characteristics of USS using MARS MRI as a reference for detection of pseudotumors and muscle atrophy. PatienTS AND METHODS: We performed a prospective cohort study to compare MARS MRI and USS findings in 19 consecutive patients with unilateral MOM hips. Protocolized USS was performed by consultant musculoskeletal radiologists who were blinded regarding clinical details. Reports were independently compared with MARS MRI, the imaging gold standard, to calculate predictive values.

Results: The prevalence of pseudotumors on MARS MRI was 68% (95% CI: 43-87) and on USS it was 53% (CI: 29-76). The sensitivity of USS in detecting pseudotumors was 69% (CI 39-91) and the specificity was 83% (CI: 36-97). The sensitivity of detection of abductor muscle atrophy was 47% (CI: 24-71). In addition, joint effusion was detected in 10 cases by USS and none were seen by MARS MRI.

Interpretation: We found a poor agreement between USS and MARS MRI. USS was inferior to MARS MRI for detection of pseudotumors and muscle atrophy, but it was superior for detection of joint effusion and tendinous pathologies. MARS MRI is more advantageous than USS for practical reasons, including preoperative planning and longitudinal comparison.

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Figures

Figure 1.
Figure 1.
Case 1. MARS MRI, ultrasound, and intraoperative images of a pseudotumor and gluteal muscle atrophy. a. A coronal STIR sequence MARS MRI section showing a right anterior (type-IIa) and lateral (type-IIb) pseudotumor (white arrows). In addition, right-sided fatty atrophy of the gluteus medius and minimus muscles (grade 3) can be seen. b. Lateral longitudinal USS showing a large cystic pseudotumor (type 2) with a thickened wall and upper solid focal region (thick white arrow). c. Lateral longitudinal USS of the right gluteus medius and minimus muscle showing fatty atrophy (reported as grade 2). d. Photograph taken during revision surgery showing a florid inflammatory reaction to the right hip neocapsule (thick white arrow). GT: greater trochanter; Gmed: gluteus medius; Gmin: gluteus minimus. Pathology is indicated by white arrows.
Figure 2.
Figure 2.
Case 2. Radiography, MARS MRI, ultrasound, and intraoperative images of gluteal musculotendinous damage. a. A pelvic radiograph showing a left-sided MOM total hip replacement in situ and highlighting the absence of the greater trochanter region of the left proximal femoral bone. b. A T1-weighted MARS MRI image in coronal section showing left-sided fatty atrophy of the gluteus medius and gluteus minimus muscles (grade 3) and thinning of the gluteus minimus tendon. c. Left lateral USS over the greater trochanter showing thin and hypoechoic tendons for the gluteus medius and gluteus minimus muscles. d. Photograph taken during revision surgery showing erosion of the left greater trochanter and gluteus medius muscle. MOM GT: the MOM femoral component (greater trochanter region); Gmed: gluteus medius tendon. Pathology is indicated by white arrows.
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