Ultrasound is just as accurate as magnetic resonance imaging in identifying osteophytes in patients with hand osteoarthritis.
Ultrasound found even more moderate-to-large osteophytes than MRI, and trumped both conventional radiographs and clinical examination in identifying the bony spurs, Dr. Alexander Mathiessen and his colleagues wrote in the April 20 online edition of Annals of the Rheumatic Diseases.
"This is most likely due to the multiplanar imaging capability of ultrasound and the fact that posterior-anterior radiographs are only able to detect osteophytes tangentially to the beam, and therefore, mainly on the lateral and medial side of the joints," wrote Dr. Mathiessen of Diakonhjemmet Hospital, Oslo, and his colleagues.
They prospectively examined 127 patients (mean age, 69 years), of whom 116 were women. All the patients had hand osteoarthritis, with a mean disease duration of 18 years.
The investigators compared the sensitivity and specificity of osteophyte detection by ultrasound, MRI, radiographs, and clinical exam.
Ultrasonography was performed and interpreted by an experienced clinician and a trainee. Still ultrasound images representative of the different joint groups were collected into a unique reference atlas, which was also validated during the study. Clinical exams were performed by a single experienced rheumatologist. Almost 4,000 joints were imaged and clinically examined.
Ultrasound identified osteophytes in 53% of 3,771 joints examined.
In all, 851 patients had both MRI and ultrasound on 851 joints; ultrasound detected osteophytes in 75% and MRI in 87%.
A total of 117 patients had ultrasound, radiography, and clinical exam. Ultrasound detected osteophytes in 53% of the joints and radiography in 30% of them. Clinical exams revealed joint enlargement in 37%.
Ultrasound detected a median of 16 osteophytes/bony enlargements per patient – significantly more than the number detected by radiography (8) or clinical exam (11) (Ann. Rheum Dis. 2012 April 20 [doi: 10.1136/annrheumdis-2011-201195]).
Using MRI as the reference, the investigators found that ultrasound displayed a sensitivity of 83% and a specificity of 75%. The method actually identified more severe pathology than did MRI, finding 401 instances compared with 288.
"Ultrasound detected osteophytes in all joints in which MRI had scored 2-3 [on the Oslo Hand Osteoarthritis MRI scale], except for two joints in which the osteophytes were found by MRI in the lateral part of the joints," the authors noted. "Among 129 joints in which osteophytes were detected by MRI but not ultrasounds, 127 of the joints were scored as grade 1 on MRI. ... Conversely, [radiography] detected osteophytes in 41 joints without identified ultrasound pathology, and 37 of these joints had scored 1 by [radiography]."
The atlas of representative ultrasound images displayed "excellent intra- and inter-reader reliability for both readers and scoring sessions," with a greater than 88% rate of close reader agreement and a 100% rate of exact agreement."
Ultrasounds were performed only on the hands’ dorsal surfaces, which might have underestimated the total number of osteophytes identified. But because MRI demonstrated that most osteophytes occurred on the dorsal surface, "the current finding of high concordance between MRI and ultrasound suggests that it may be sufficient to perform ultrasound only on the dorsal sides of the finger joints," the authors said.
The study was sponsored by Abbott. The authors had no financial disclosures.