Tomosynthesis Effective in Diagnosing Knee Osteoarthritis

In the study, tomosynthesis identified more osteophytes (abnormal bony spurs) and subchondral cysts (small collection of fluid within the bone) in the knee joint than traditional X-ray imaging.

Daichi Hayashi, MD, PhD, research instructor at the Quantitative Imaging Center in the department of radiology at Boston University School of Medicine (BUSM; MA, USA), was the lead author of the study, which was published online March 25, 2012, in the journal Radiology. The research was led by Ali Guermazi, MD, PhD, professor of radiology at BUSM and chief of musculoskeletal radiology at Boston Medical Center.

Osteoarthritis, the most common form of arthritis, is characterized by a degeneration of cartilage and the underlying bone and other soft tissues in the joints, leading to pain and stiffness. According to the Centers for Disease Control and Prevention, osteoarthritis is the leading cause of disability in the United States, affecting approximately 26.9 million Americans.

Osteoarthritis can be diagnosed clinically, from symptoms and physical exams, or by capturing and assessing images. Whereas X-ray imaging has typically been used to diagnose the disease, recent research has shown, it is less accurate than magnetic resonance imaging (MRI). However, while MRI provides higher-quality images, it is much more costly than X-rays and cannot be regularly used in daily clinical practice. Computed tomography (CT) is another imaging modality that can provide detailed images of the joint, but it exposes patients to higher doses of radiation than X-rays. “Despite the known limitation of X-ray imaging, it is widely used to diagnosis knee osteoarthritis, both in terms of daily clinical practice and also for clinical research studies,” noted Dr. Hayashi.

Because of the limitations, Dr. Hayashi and the colleagues explored tomosynthesis to image the knee joint and determine its accuracy in detecting signs of osteoarthritis in the knee. Tomosynthesis utilizes an X-ray beam to take tomographic images (in slices similar to those from CT scans), which allows for better visualization than from a single X-ray image. The radiation exposure from tomosynthesis is similar to the traditional X-ray and much lower than CT. Also, it takes seconds to obtain images using tomosynthesis and can be performed while a person is standing up.

The investigators examined 40 participants (80 knees), all over the age of 40, who were recruited irrespective of knee pain or an X-ray diagnosis of osteoarthritis. The knees were imaged using X-ray, tomosynthesis and MRI. The presence of osteophytes and subchondral cysts were recorded, and knee pain was evaluated for each participant based on a questionnaire.

The study’s findings demonstrated that tomosynthesis, compared to X-ray, improves the detection of osteophytes in the knee joint in patients with or without osteoarthritis. The sensitivity for detecting osteophytes increased by five to 29% with tomosynthesis compared to X-ray. The sensitivity for detection of subchondral cysts in the knee joint increased by 11%-50% with tomosynthesis compared to X-ray. The study also concluded that individuals with tomosynthesis-detected osteophytes and cysts were more apt to feel pain than those without the lesions.

“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,” concluded Dr. Hayashi. “While tomosynthesis has not been widely used in imaging of bones and joints to date, the results of our study show that using tomosynthesis to detect knee osteoarthritis can be effective.”

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