Osteoarthritis and Osteoporosis Assessed from Hand Radiographs : Prevalence , Determinants , and Associations with Morbidity and Mortality

Objectives Osteoarthritis (OA) is highly prevalent in hand joints and it may be an indicator of systemic OA. However, few studies have focused on hand OA as a predictor of mortality or disability. Osteoporosis (OP) has clinical and public health importance because of increased risk of fractures. To date, a case-finding strategy is recommended to target patients at high risk of fracture, and there is a need for simple and cheap measurement of bone mass. A number of previous studies have reported an inverse relationship between OA and OP, but limited studies are available on longitudinal changes in bone mineral mass in subjects with radiographic OA. Such studies are needed to design effective management for OA and OP. The aim of this study was to investigate OA and OP assessed from hand radiographs and their prevalence, determinants and associations with morbidity and mortality. Methods In 1978-80, a representative population sample of 8,000 Finns aged 30 or over were invited to a comprehensive health examination; 7,217 (90%) complied. Hand radiographs were taken from 3,595 subjects to diagnose OA in both hands and to determine the metacarpal cortical index (MCI), a proxy of cortical bone mineral mass. Work disability and mortality of the subjects were systematically followed from registers covering the whole population. Record linkage to the National Hospital Discharge Register identified subjects who had been hospitalised for primary treatment of hip fracture or myocardial infarction by the end of 1994. In 2000, calcaneal broadband ultrasound attenuation (BUA) was measured with the SAHARA sonometer, and clinical re-examination was carried out in 340 of the participants. Results The prevalence rates of OA of Kellgren’s grade 2 to 4 in any finger joint (finger OA) and in at least two symmetrical pairs of distal interphalangeal joints (symmetrical DIP OA) and thumb carpometacarpal joints (CMC-1 OA) were 44.8%, 16.0% and 11.0%, respectively. The subjects with body mass index (BMI) over 35 kg/m had a two-fold risk of hand OA of any type as compared to those with normal relative weight (body mass index 20.0 24.9 kg/m). Symmetrical DIP OA predicted total mortality in women (relative risk (RR) 1.23; 95% confidence interval (CI) 1.01-1.51), and finger OA predicted cardiovascular deaths in men (RR 1.42; 95% CI 1.05-1.92). It appeared that the risk of a new major coronary event was elevated among those with regular analgesic use at baseline (RR 1.51; 95% 1.08-2.10). None of the hand OA types predicted work disability or was associated with difficulties in performing ordinary daily activities. High age, low BMI, high stature and smoking showed, independently of each other, statistically significant associations with low MCI. The adjusted relative risk of hip fracture per increment of MCI by a standard deviation (0.1) was 0.69 (95% CI 0.55-0.86). Symmetrical DIP OA and CMC-1 OA showed a statistically significant association with low MCI in proportion to the radiological severity of OA. Symmetric DIP OA predicted low values of BUA at follow-up. Conclusions Obesity is a strong risk determinant of all forms of hand OA in both sexes. This indicates that overweight exerts a systemic influence on the risk of OA. The increased cardiovascular mortality in men with finger OA was not explained by the general risk factors of cardiovascular diseases, or by the regular use of analgesics. However, the regular use of analgesics at baseline predicted a major coronary event during follow-up. Even if hand OA is prevalent, its impact on disability in the general population is modest. MCI, easily determined at low cost, can be used to assess bone mineral status and future hip fracture risk. Patients with symmetrical DIP OA might be considered candidates for evaluation of osteoporosis over time. National Library of Medicine Classification: WE 348, WE 250 Medical Subject Headings: osteoarthritis; osteoarthritis/mortality; osteoarthritis/radiography; osteoporosis; hand joints/radiography; risk factors; hip fractures; bone density; obesity; longitudinal studies; Finland