OBJECTIVE: To compare the reliability of quantitative measurement of minimum hip joint space with a qualitative global assessment of radiological features for estimating the prevalence of primary osteoarthritis (OA) of the hip in colon radiographs. METHODS: All colon radiographs from patients aged 35 or older, taken at three different radiographic departments in Iceland during the years 1990-96, were examined. A total of 3002 hips in 638 men and 863 women were analysed. Intraobserver and interobserver reliability was assessed by measuring 147 randomly selected radiographs (294 hips) twice by the same observer, and 87 and 98 randomly selected radiographs (174 and 196 hips) by two additional independent observers. Minimum hip joint space was measured with a millimetre ruler, and global assessment of radiological features by a published atlas. RESULTS: With a minimum joint space of 2.5 mm or less as definition for OA, 212 hips were defined as having OA. When the global Kellgren and Lawrence assessment with grade 2 (definite narrowing in the presence of definite osteophytes) or higher as definition for OA was used, 202 hips showed OA. However, only 166 hips were diagnosed as OA with both systems. With 2.0 or 3.0 mm minimum joint space as cut off point, the difference between the two methods increased. Both intrarater and interrater reliability was significantly higher with joint space measurement than with global assessment. CONCLUSIONS: Overall prevalence of radiological OA was similar with the two methods. However, the quantitative measurement of minimum hip joint space had a better within-observer and between-observer reliability than qualitative global assessment of radiographic features of hip OA. It is thus suggested that minimum joint space measurement is a preferable method in epidemiological studies of radiological hip OA.
We report the incidence of total hip replacements performed in Iceland between 1982 and 1996. During this period, 3,403 hip arthroplasties were done. The annual number of procedures increased from 94 hips in 1982 to 323 hips in 1996. Annual rates of total hip replacements due to primary osteoarthrosis per 10(5) inhabitants were 68 in 1982-1986, 90 in 1987-1991, and 114 in 1992-1996. In the years 1992-1996, the age-standardized incidence of total hip replacements for primary osteoarthrosis was 3/10(5) among patients younger than 39 years of age, while it was 621/10(5) among those 70-79 years of age. The mean age at surgery for primary osteoarthrosis was 69 years in both men and women. Incidence rates in various countries are difficult to compare, but by using age-standardized data and correction for differences in population structures between Iceland and Sweden, we find that the incidence of total hip replacement for primary osteoarthrosis of the hip is at least 50% higher in Iceland than in Sweden. This difference is consistent with the higher prevalence of hip osteoarthrosis observed in Iceland than in Sweden.
OBJECTIVE: To assess the prevalence of primary hip osteoarthritis (OA) in Iceland. To compare the prevalence of primary hip OA in Iceland with published rates of primary hip OA for related Scandinavian populations. METHODS: Roentgenographs were examined of 1530 Icelandic people 35 years or older (653 males, 877 females) subjected to colon radiography during the years 1990-1996. The radiographs examined represent approximately 40% of all colon radiographs taken in Iceland during this period. After exclusion of non-primary hip OA cases, the minimum hip joint space was measured with a mm ruler. Presence of hip OA was defined as a minimum joint space of 2.5 mm or less on an anteroposterior radiograph. Intraclass correlation coefficients for inter and intraobserver variability of assessment of mm joint space were 0.91 and 0.95, respectively. RESULTS: Of the 1517 people included, 227 hips in 165 patients (77 men, 88 women) were diagnosed as having radiological primary hip OA. The mean age at colon examination for these patients was 68 (35-89) years. The overall prevalence of coxarthrosis among all examined patients 35 years and older was 10.8% (12% for men, 10% for women), rising from 2% at 35-39 years to 35.4% for those 85 years or older. If the population structure (age and sex distribution) for those older than 35 years in Iceland was used to standardise prevalence for both Iceland and south Sweden (using previously published data for south Sweden), the age and sex standardised prevalence of hip OA for those older than 35 years in Iceland was 8%, compared with 1.2% for south Sweden. CONCLUSIONS: The prevalence of radiological primary hip OA is very high in Iceland, and in excess of fivefold higher than the prevalence found by using similar techniques in studies on related populations in southern Scandinavia. The rate difference is particularly notable for those younger than 70 years.