Background Among the main subsets of osteoarthritis of the hand (HOA): there are nodal OA (NOA) and erosive (EHOA). Although this last form affects most frequently middle-aged women only few data are still available on bone mineral density (BMD) of these patients.
Objectives To study the prevalence of low BMD in patients with EHOA and NOA, who consecutively underwent phalangeal radiographic absorptiometry (pRA) in our outpatient clinic, compared to matched healthy subjects.
Methods Two cohorts of subjects for a total of 76 patients fulfilling ACR criteria for hand OA were studied. Patients showing at least one erosion in interphalangeal (IP) joints were included in the EHOA group, while patients with erosions in the metacarpophalangeal joints were excluded. Patients were also evaluated for disease duration, number of affected active (swollen and painful or tender) joints (NAAC), radiographic in Kellgren & Lawrence score (RS), Body Mass Index (BMI) (kg/m2) was also calculated (Table 1). All the patients and 190 healthy subjects (N) (mean age 67.8±7.7 years) underwent pRA scanning at the 2nd, 3rd and 4th finger of the non-dominant hand by means of a monoenergetic X rays (60 kV) equipment (Alara Metriscan, Hayward, Ca, USA). BMD was estimated in the three middle phalanges and the average expressed as mineral mass/area (g/cm2). T and Z scores were also provided by the instrument using local reference data. The local Ethics Committee granted approval of the study protocol and all patients gave their informed consent.
Results A reduction of BMD fitting osteopenia was found in 35% of patients with EHOA, 21% with NOA, and 43% of N (p=0.03, EHOA vs NOA), while osteoporosis affected 20% with EHOA, 28% with NOA, and 20% N. BMD was higher in EHOA with respect to both the NOA and N groups (p=0.025 and p<0.05, respectively). T and Z scores were significantly higher in the EHOA vs the N population (T: p=0.01; Z: p<0.01). There were no statistically significant differences between NOA and healthy subjects.
Conclusions Phalangeal BMD was higher in EHOA patients with respect to both N and NOA subjects. Joint erosion and inflammation do not appear to determine sufficient phalangeal bone loss to discriminate EHOA vs NOA. To a certain extent, higher mineral density could be explained by more pronounced osteoreparative processes in EHOA than in NOA. This issue needs further investigation to better understand the relationship between osteoarthritis and local osteoporosis and the possible interferences with instrumental evaluation.
Disclosure of Interest None Declared