Assessing periarticular bone mineral density in patients with early psoriatic arthritis or rheumatoid arthritis

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Assessing periarticular bone mineral density in patients with early

psoriatic arthritis or rheumatoid arthritis

B J on1, C E Hutchinson2, J 2, I N Bruce3 and A L Herrick4

Background: Periarticular osteoporosis is an early finding in the hands of

patients with rheumatoid arthritis (RA), due to release of bone resorbing

cytokines from the inflamed synovium. There has been disagreement as to

whether periarticular bone loss occurs in psoriatic arthritis (PsA). Bone

mineral density (BMD) can now be measured accurately using dual energy x ray

absorptiometry (DEXA). Recently, DEXA has been used to measure periarticular

BMD at predefined regions of interest (ROIs) around the joints.

Objectives: Firstly, to compare periarticular BMD around the finger joints

of patients with early RA or PsA. Secondly, to determine whether

periarticular bone loss is related to joint inflammation and radiological

erosions in RA and PsA.

Methods: Seventeen patients with RA and 15 with PsA were recruited, all with

disease duration of less than five years. All finger joints were examined by

one person for swelling, or tenderness, or both. Hand radiographs were

scored for the presence of erosions. Periarticular BMD was measured at 10

predetermined ROIs using a Hologic QDA-4500A fan-beam densitometer.

Results: Patients with PsA were less likely to be positive for rheumatoid

factor (RF) (13% v 94%) and more likely to be men (60% v 23%) than patients

with RA. There were no other clinical differences between patients with RA

or PsA. Patients with RA had significantly lower BMD at each of the ROIs

than those with PsA (p<0.05). However, these differences disappeared after

adjusting for age and sex. Among patients with RA, those with a higher total

number of swollen and/or tender hand joints had significantly lower

periarticular BMD at the metocarpophalangeal (MCP) and proximal

interphalangeal (PIP) joints. No such association was found for patients

with PsA.

Conclusions: In early disease, periarticular bone loss occurred both in

patients with RA and those with PsA. Among patients with RA, periarticular

osteoporosis was related to measures of joint inflammation. There was no

association between joint inflammation and periarticular bone loss in

patients with PsA, which lends support to the hypothesis that the primary

site of inflammation in PsA is extrasynovial.

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