Researchers have confirmed that rheumatoid arthritis (RA) accelerates bone loss in the hand and that the degree of loss predicts inflammation and skeletal degeneration at other sites.
Several studies have demonstrated associations between RA and peripheral bone loss, particularly in the hands, say Helmut Franck (Schwerpunktspraxis für Rheumatologie/Endokrinologie, Bonn, Germany) and Jurgen Gottwalt (Rheumazentrum Oberammergau, Oberammergau, Germany). However, they point out that "few studies have used dual X-ray absorptiometry (DXA) for detailed measurement around the finger joints in small groups."
To quantify the degree of hand bone loss associated with RA and determine whether this predicts bone loss elsewhere, or other symptoms of rheumatic disease such as inflammation, Franck and Gottwalt used DXA to study the skeletons of 421 individuals with RA and 98 generally healthy volunteers. Average age for patients and volunteers was ranged from 56 to 58 years.
As expected, bone mineral density (BMD) of the carpus was significantly lower in those with RA (0.405 g/cm2) than in volunteers (0.421 g/cm2). There were also significant differences in BMD between patients and volunteers at the metacarpal joint II (0.318 vs 0.344) and the metacarpal joint III regions (0.325 vs. 0.340 g/cm2).
Although the reduced hand BMD at specific joints in RA patients was not accompanied by significant differences in BMD at the lumbar spine or hip, BMD measured over the entire hand region, did significantly predict bone loss at the forearm and hip.
Interestingly, BMD at the carpus, metacarpal joint II region, and metacarpal joint III region, were significantly and positively related to inflammation status, giving relationship co-efficients of 0.191, 0.190, and 0.204, respectively. Inflammation and overall hand BMD was also found to be significantly greater in those taking glucocorticoids.
The researchers conclude in the journal Rheumatology International, that their study supports the use of DXA to measure hand and sub-regional bone density and accurately and reproducibly determine juxta-articular bone loss.
Such analysis also, "detects bone loss in patients with RA even if standard DXA measurement of the spine and hip are normal, especially in conditions of increased inflammatory activities or treatment with glucocorticoid," write the investigators.
They add: "Peripheral DXA measurement should be accessible to patients, since it is associated with little exposure of radiation."