Soft tissue composition, quadriceps strength, bone quality and bone mass in rheumatoid arthritis.

OBJECTIVES

To examine differences in soft tissue composition, bone quality, bone mass and quadriceps strength between women with rheumatoid arthritis (RA) and healthy controls.

METHODS

79 women with RA (median disease duration 10 yrs) were studied. Most were or had been on steroids. 67 healthy age-matched women served as controls. The lean tissue mass (LTM) and fat mass (FM) of the total body and of the major body subregions, as well as the bone mineral density (BMD, g/cm2) of the femoral neck, spine (L2-L4) and distal forearm were measured by dual energy x-ray absorptiometry (DXA). Bone quality expressed as the speed of sound (SOS m/sec), broadband ultrasound attenuation (BUA, dB/MHz) and stiffness was assessed by an Achilles ultrasound device, and isometric quadriceps strength by an isokinetic dynamometer.

RESULTS

No between-group differences were found for the body mass index (BMI, weight/height2), total or regional percentage fat, LTM and FM. However, women with RA had 20% lower quadriceps strength than controls. BMD at the femoral neck and distal forearm, and SOS, BUA and stiffness were significantly lower in patients than in controls. No difference was found for spine BMD. In the RA group, z-scores for SOS and stiffness were significantly more reduced than those for BMD. Multiple regression analyses indicated negative associations between ultrasound parameters and the cumulative steroid dose.

CONCLUSIONS

Reductions in BMD and muscle strength in RA were not accompanied by changes in soft tissue composition, Bone quality assessed by ultrasonography was compromised in RA and may be modified by steroids.