Erosive hand osteoarthritis ‘a distinct phenotype’

By Ingrid Grasmo, MedWire Reporter

There may be an underlying systemic cause for erosive hand osteoarthritis (EOA), suggest study findings showing more inflammatory signs in erosive joints relative to non-erosive joints.

"Whether EOA is a separate disease entity or a severe stage of hand osteoarthritis (HOA) has been unclear until now," say Marion Kortekaas (Leiden University Medical Center, the Netherlands) and colleagues.

The researchers assessed 55 HOA patients, with an average symptom duration of 5 years, for EOA using radiography and Verbruggen-Veys anatomical phase scores.

In total, 28 patients had EOA, as defined by the presence of at least one joint in the E or R phase. EOA and non-EOA patients were compared for ultrasound features; and effusion, synovial thickening, and power Doppler signal (PDS) were scored on a 4‑point scale.

Compared with HOA patients, those with EOA were significantly older (58 vs 65 years) and experienced more pain (Australian Canadian osteoarthritis hand index [AUSCAN] score of 8 vs 12).

Of the total 94 interphalangeal joints (IPJs) presenting erosive features, 12 were in the E phase and 82 in the R phase. IPJs were significantly more painful on palpitation and more often showed soft tissue swelling in patients with EOA.

Assessment of inflammatory signs by ultrasound revealed synovial thickening, effusion, and PDS in 13%, 50%, and 15% of the 94 joints showing erosion compared with 10%, 26%, and 8% for the 896 non-erosive HOA joints.

Summated joint scores of PDS revealed that effusion was significantly higher among EOA compared with HOA joints, at 3.0 vs 1.0.

When the researchers investigated the association of ultrasound features with anatomical phases of the Verbruggen-Veys score, they found that synovial thickening was significantly more frequent in the S, J, E, and R phases compared with the N phase.

Compared with the N phase, synovial thickening showed the strongest association with the J phase (odds ratio [OR]=10.6), effusion was most strongly associated with the R phase (OR=8.8), and PDS was most strongly associated with the E phase (OR=5.3).

Non-erosive joints in EOA patients demonstrated 3.2-fold more PDS and 2.2-fold more effusion compared with joints in non-EOA patients. The team says the findings suggest that inflammatory signs might be implicated in erosive evolution, and that EOA is a phenotype affecting all IPJs in such patients.

"Further longitudinal studies are needed to elucidate the role of inflammation in the development of erosiveness," conclude the researchers in the Annals of Rheumatic Diseases.

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