Published: Oct 10, 2013 | Updated: Oct 10, 2013
By Nancy Walsh

Full Story:  http://www.medpagetoday.com/Rheumatology/Arthritis/42192

Erosive osteoarthritis (OA) of the hand is a severe form of radiographic hand OA, rather than a distinct clinical entity, and may be driven by the presence of metabolic abnormalities, researchers reported.

The pattern of joint involvement in erosive OA was similar to that seen in severe non-erosive disease, particularly for symmetry, with an adjusted odds ratio of 6.5 (95% CI 3-14.1) for involvement of the same joint in the opposite hand, according to Michelle Marshall, PhD, of Keele University in Staffordshire, England, and colleagues.

But individuals with erosive hand OA had more than twice the risk of metabolic syndrome (OR 2.7, 95% CI 1-7.1) and more than four times the risk of dyslipidemia (OR 4.7, 95% CI 2.1-10.6) compared with patients who had severe non-erosive OA, the researchers reported online in Annals of the Rheumatic Diseases.

Erosive hand OA differs from non-erosive disease in several ways. For instance, the onset of symptoms such as swelling, stiffness, and pain tends to be abrupt, and radiographs reveal “gull-wing” or “saw-tooth” deformities and collapse of the subchondral bone.

Following apparent widening of the joint space, remodeling occurs, resulting in the appearance of large osteophytes and an irregular subchondral plate.

And overall, worse clinical and radiographic outcomes — along with systemic risk factors — have been reported for erosive OA.

But the cause and pathogenic processes associated with erosive OA have not been fully established, and the European League Against Rheumatism has suggested that erosive disease may be a subset of generalized hand OA.

To determine whether erosive hand OA actually is a separate entity or part of a continuum of severity and to identify potential risk factors, Marshall and colleagues recruited patients from a clinical assessment study of hand OA and also from a study of knee OA to provide a larger, enriched sample.

All participants reported hand pain and stiffness for at least “a few” days within the past month.

X-rays of the hands were scored according to the Kellgren and Lawrence (KL) system, and the presence of erosive changes was evaluated according to the Verbruggen-Veys progression scale.

A total of 1,167 patients and 8,608 hand joints were included in the analysis.

On the KL grading scale, 1,754 joints were grades 2 or higher, indicating possible or definite osteophytes and narrowing of the joint space.

Moderate-to-severe KL scores of 3 or higher were found in 425 joints, indicating the presence of multiple osteophytes, joint space narrowing, sclerosis, and possible bone deformities.

Severe scores of 4, with large osteophytes, marked joint space narrowing, severe sclerosis, and definite bone deformities were found in 112 joints.

Erosive disease was identified in 207 joints in 80 patients.

The second distal interphalangeal joint was most often affected, and significant associations were found for the overall ranked order of involved joints in both erosive and non-erosive OA (r >0.95).

As with symmetry, the pattern of involvement across the joints of the same hand and the same finger was similar for both erosive and non-erosive disease.

Patients with erosive and non-erosive disease were similar in many characteristics, including age, sex, the presence of knee OA, a family history of arthritis, and body mass index. The main difference was in the presence of dyslipidemia and metabolic syndrome.

Among patients with non-erosive KL 3, a total of 6.2% had abnormal levels of cholesterol, as did 8.8% of those with non-erosive KL 4.

In contrast, 21.2% of those with erosive disease had lipid abnormalities.

And for patients with KL 3 and 4, rates of metabolic syndrome were 4.1% and 2.9%, respectively, while the rate was 11.2% for those with erosive disease.

The patterns of involvement in the hand joints suggest that there are “strong similarities” between erosive OA and moderate-to-severe non-erosive OA, and may represent an evolution mediated through metabolic pathways, the researchers explained.

“The exact mechanism is not yet known but osteoarthritis is believed to share similar biochemical and inflammatory pathways to metabolic disorders, and dyslipidemia may alter lipid metabolism in a number of joint tissues,” they wrote.

A limitation of the study was the relatively small number of patients with erosive disease.