The radiological and epidemiological data from the Copenhagen Osteoarthritis Study (COS) were analysed in order to assess the prevalence of osteoarthritis (OA) of the first carpometacarpal joint (CMCJ). Another aim of the study was to analyse relationships between radiologic CMCJ OA and self-reported pain. The third aim was to analyse if additional information could be obtained applying a new method of correlating individual radiological features to self-reported pain, compared to Kellgren and Lawrence's (K-L's) radiologic OA classification.
Between 1992 and 1994 standardised radiographs of both hands were recorded in 3,355 participants of the COS cohort. Subjects with known rheumatoid arthritis, other inflammatory arthritis or earlier fractures of the hand were excluded. OA of the CMCJ was assessed according to K-L's radiologic classification by two senior radiologists at our institution. The radiologists further evaluated individual radiologic features of CMCJ OA as recommended by K-L according to the text attached to each picture in their radiologic atlas of OA. To estimate inter- and intraobserver reproducibility a subset of 100 radiographs was reread.
Our analyses demonstrated that the K-L method was not able to classify all X-rays. In 608 (18.1%) cases, combinations of joint space width (JSW) measurements, the graduation of osteofytes, sclerosis and cysts fell outside the classification. The radiological evaluation of individual features of OA demonstrated an acceptable reproducibility, intrapersonal (kappa=0.79) as well as interpersonal (kappa=0.65). The prevalence of each radiological feature increased after the fifth decade, progressively more so among women (P<0.001), with the highest prevalence (36.0%) of grades 3 and 4 JSW reduction among women>80 years. A significant correlation was found between signs of radiologic degeneration and self-reported pain (P<0.001); however, different combinations of OA features had different relations to symptoms. Logistic regression analyses revealed sclerosis to have an independent influence on pain in the thumb compared with the presence of osteofytes, cysts and diminished JSW. Body mass index (BMI) was positively related to radiological changes. In logistic regression analyses BMI did not demonstrate an independent positive relation to OA.
Radiological degenerative changes in the CMCJ by age especially among women are quite common. However, it is demonstrated that global radiologic classifications of OA of the CMCJ have serious limitations in epidemiological studies. Not all cases fit into classification based on the K-L-atlas. Among the radiological features, subchondral sclerosis is significantly related to self-reported pain. Specific radiologic data should be incorporated in epidemiological studies on hand OA.