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


CONCLUSIONS
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.
Institute of Orthopedic and Musculoskeletal Science , University College London, the Royal National Orthopedic Hospital, Brockley Hill , Stanmore.
Imran A
IA
Siddiqui
Shiraz A
SA
Sabah
Keshthra
K
Satchithananda
Adrian K
AK
Lim
Suzie
S
Cro
Johann
J
Henckel
John A
JA
Skinner
Alister J
AJ
Hart
D000368:Aged; D018771:Arthralgia / Q000175:diagnosis* / Q000209:etiology; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D016477:Artifacts; D005260:Female; D005271:Femur Head Necrosis / Q000601:surgery; D006104:Granuloma, Plasma Cell / Q000175:diagnosis* / Q000209:etiology; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods / Q000592:standards*; D008297:Male; D008670:Metals / Q000009:adverse effects; D008875:Middle Aged; D009133:Muscular Atrophy / Q000175:diagnosis* / Q000209:etiology; D015207:Osteoarthritis, Hip / Q000601:surgery; D011183:Postoperative Complications / Q000175:diagnosis* / Q000209:etiology; D011446:Prospective Studies; D012086:Reoperation; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014463:Ultrasonography / Q000379:methods / Q000592:standards*
D008670:Metals