Controlled study of the prevalence of radiological osteoarthritis in clinically unrecognised juxta-articular Paget's disease

Background-Paget's disease of bone is common and often undiagnosed in the p opulation. The association of Paget's disease and osteoarthritis is well de scribed but only in cases ascertained in secondary and tertiary care centre s to which they have been referred largely because of pain. This study repr esents an attempt to confirm the association between Paget's disease and os teoarthritis in a population previously unknown to have Paget's disease. Methods-Radiographs of people over 55 years that included the entire pelvis , sacrum, femoral heads and lumbar spine (mostly plain abdominal radiograph s) were obtained from hospital records for the period 1993-95. Films were s creened by a trained observer and the positive films were reviewed by a con sultant radiologist who also examined a 1 in 10 sample of the negative film s. A subsample of 153 confirmed positive cases were matched for age and sex using cases without Paget's disease and these pairs were assessed by two o bservers working in tandem. The hip joints were scored 0-5 using a modifica tion of the original descriptive classification of Kellgren and Lawrence an d minimum joint space of the hip was also measured. Results-Not all cases were available for assessment. A total of 248 films w ere included (137 without Paget's, 89 with unilateral and 22 with bilateral disease). The mean age of the cases and controls was 78.4 years and 77.4 y ears respectively with 66/45 male/female cases and 78/59 male/female contro ls. One hundred and twenty nine affected hips were available for comparison with 352 unaffected hips. Median joint space narrowing for the affected hi p was 3 mm (range, 0-5 mm) and for the unaffected hip 4 mm (range, 0-6 mm, Mann-Whitney U test, p=0.00001). Median Kellgren and Lawrence grade for bot h groups was 0, with no statistical difference between the groups (Mann-Whi tney U test, p=0.74). In terms of severity of osteoarthritis, there were 19 instances of grades 2+ in the unaffected hips, and only five in the affect ed hips. Conclusions-Pagetic coxopathy is characterised by loss of joint space, whic h may represent a secondary chondropathy. Although joint failure may result from this secondary chondropathy progression may be dependent on non-Paget ic factors. It is also possible that the usual radiological features of ost eoarthritis may be modified or obscured by the Paget's disease.