ROME (FRONTLINE MEDICAL NEWS)Erosive hand osteoarthritis (OA) is probably a more severe form of the disease, rather than a separate clinical entity, a team of Norwegian researchers has suggested.

Dr. Alexander Mathiessen and associates from Diakonhjemmet Hospital in Oslo found that synovial inflammation was more common in patients with erosive disease. However, when they stratified the 293 patients studied according to the degree of structural joint damage, they found that the differences disappeared.

“Modern imaging techniques such as MRI and ultrasound have shown high prevalence of synovitis in hand osteoarthritis,” they explained in a poster presentation at the European Congress of Rheumatology.

Although erosive hand OA is often considered a more inflammatory phenotype, with more pain and disability and a more aggressive disease course, “it has been debated whether erosive hand OA is an inflammatory subset with more synovitis than conventional OA, or just a severe form of the disease” they observed.

Although a recent study ( Ann. Rheum. Dis. 2013;72:930-4 ) had found a higher frequency of inflammation in patients with erosive hand OA versus nonerosive hand OA, the study had not adjusted for the severity of structural damage. Dr. Mathiessen and coworkers therefore set out to examine whether the higher prevalence of synovitis that had been seen in patients with erosive hand OA was linked to the extent of joint disease according to the Kellgren-Lawrence (KL) scale .

The team used data from the Musculoskeletal Pain in Ullensaker Study (MUST) cohort ( BMC Musculoskelet. Disord. 2013;14:201 ), an observational study comprising 630 participants with self-reported OA. Their analysis used data on 293 patients who reported having hand OA and who fulfilled American College of Rheumatology criteria, with no other inflammatory joint disease.

The majority (76%) of patients with hand OA studied were women, with a mean age of 64.9 years. There were over 4,000 joints examined using both ultrasonography and radiography of which 359 (7.9%) were erosive.

“We focused mainly on the proximal and distal interphalangeal joints, since radiographic erosions occur in these joints mainly,” the researchers said.

Just fewer than 30% (n = 86) participants had at least one erosive interphalangeal joint. The median number of these finger joints involved was five, ranging from 0 to 15.

Grey scale (GS) and power Doppler (PD) synovitis was seen in 18.9% and 1.8% of patients with erosive hand OA and 11.1% and 0.4% of those with nonerosive hand OA, respectively (P < .001 for both comparisons).

Patients with erosive disease were more likely to have greater joint damage on the KL scale than patients with nonerosive disease, with 41.7% versus 4.5%, respectively, having a KL grade of 3-4 and 26.7% versus 64% having a KL grade of 0­-1.

The team reported that the prevalence of both GS and PD synovitis increases with more structural joint damage irrespective of erosive status and that there was a similar level of joint inflammation when data were stratified according to KL grade.

Somewhat paradoxically, they said, “erosive joints actually have less inflammation than nonerosive joints.”

The investigators did not report having any disclosures.