The controversial relationship between osteoarthritis and osteoporosis: an update on hand subtypes.
To compare hand osteoarthritis (HOA) subtypes and to examine possible links with local bone mineral density (BMD). Fifty-five patients with erosive hand osteoarthritis (EHOA) and 21 patients with nodal hand osteoarthritis (NOA) fulfilling American College of Rheumatology criteria for HOA were evaluated. Subjects showing at least two erosions of the interphalangeal joints were assigned to the EHOA group; the others were considered NOA. Disease duration, number of active joints and radiological scores were assessed. All patients and 174 controls underwent phalangeal radiographic absorptiometry (pRA) of the middle phalanges of the non-dominant hand to assess BMD, T- and Z-scores. BMD was higher in EHOA with respect to NOA and controls (P = 0.05); T- and Z-scores were significantly higher in EHOA (P = 0.01 and P < 0.01). Values suggestive of osteopenia were found in 32% of EHOA and 22% of NOA patients, and in 44% of controls (P = 0.05 EHOA vs. NOA); a T-score < -2.5 standard deviations was present in 15% of EHOA and 28% of NOA patients, and in 21% of controls (P = 0.05 EHOA vs. NOA). Phalangeal BMD was higher in EHOA compared to NOA and controls. This characteristic could potentially be exploited to differentiate the two hand OA subtypes.