Radiology: Tomosynthesis trumps x-ray in diagnosing knee osteoarthritis

Tomosynthesis image shows an osteophyte in the right lateral femur. Source: Radiology

Tomosynthesis has been shown to detect more abnormal bony spurs and subchondral cysts than conventional x-ray, demonstrating that tomosynthesis may be more beneficial in diagnosing knee osteoarthritis, according to a study published in the April issue of Radiology.

“Tomosynthesis itself is not a new technology, but its ability to provide three-dimensional information at a lower dose and potentially lower cost than computed tomography has aroused interest…However, its application to imaging of bones and joints has been limited,” wrote researchers at Boston University School of Medicine (BUSM), led by Ali Guermazi, MD, PhD.

While osteoarthritis can be diagnosed clinically, x-ray imaging is the standard for radiographic diagnosis. Recent research has shown MRI to be more accurate, though its high cost means it cannot be used routinely in daily clinical practice. Using MRI as a reference, the authors sought to evaluate the diagnostic performance of tomosynthesis in depicting osteophytes and subchondral cysts, compared with conventional radiography.

Forty subjects older than 40 years were recruited to the study irrespective of knee pain or an x-ray diagnosis of osteoarthritis. All 80 knees were imaged with tomosynthesis, radiography and MRI and knee pain was assessed for each participant based on a questionnaire.

Results showed the sensitivity for detecting osteophytes increased by 5 to 29 percent with tomosynthesis compared with x-ray. Sensitivity for detection of subchondral cysts in the knee joint increased 11 to 50 percent with tomosynthesis compared to x-ray.

Statistical significance was reached for osteophytes but not for subchondral cysts. Both radiography and tomosynthesis had high specificity in depiction of the lesions when MRI was used as the reference standard, but the authors suggested the use of tomosynthesis may increase the detection rate of osteoarthritis as it is defined by the presence of osteophytes.

Subjects with tomosynthesis-detected osteophytes and cysts were more likely to feel pain than those without the lesions, but radiography-depicted osteophytes seemed more strongly associated with pain. This implies that radiographically occult osteophytes might have less clinical importance, according to the authors.

“This study shows that the images obtained through tomosynthesis are significantly better than those from x-rays and could potentially be a better diagnostic tool for knee osteoarthritis in patients with knee pain,” Daichi Hayashi, MD, PhD, of the department of radiology at BUSM, said in a statement.