Background Bone scintigraphy using ^99mTechnetium methylene diphosphonate (^99mTc MDP) has been shown to be sensitive in detecting subclinical synovitis¹ but lacks specificity for the aetiology of the articular disease. ^99mTc MDP scans may therefore have a role to play in identifyinginflammatory polyarthritis (IP) in selected patients, although it isrecognised that they cannot accurately differentiate between differentdegrees of activity in rheumatoid arthritis.²

Objectives To assess the value of ^99mTc MDP scans in inflammatory polyarthritis.

Methods All requests for bone scans for IP by the rheumatology department at the University Hospital of Wales over a 2¹/₂ year period were retrospectively assessed. The indications for the bone scan and the results were recorded. Degenerative changes on bone scan, confirmed on plain xrays, were considered negative for IP.

Results 94 bone scans were performed in total, of which 68 scans were done looking for possible IP. Of these, 17 (25%) confirmed a pattern of uptake consistent with IP, 6 (9%) were equivocal (possible IP) and 45 (66%) revealed no evidence of IP. 1 patient with a negative ^99mTc MDP scan subsequently developed psoriatic arthritis with erosions on plain films. In the subgroup of 45 patients with high ESR values, 9 (20%) bone scans suggested an IP, 6 (13%) were equivocal and 30 (67%) were negative. ^99m Tc MDP scans were requested regarding activity of arthritis in 7 patients with known rheumatoid arthritis, of which none were helpful in terms of altering management. 7 patients with seronegative arthritis underwent bone scintigraphy looking for evidence of peripheral joint involvement, which was demonstrated in 3 (43%) patients.

Conclusion These results suggest that ^99mTc MDP bone scans may be helpful in patients with normal clinical examination if there is a pattern of uptake suggestive of IP. Negative bone scans can also be helpful in patients with polyarthralgia and elevated inflammatory parameters on blood tests, although it should be stressed that the diagnosis of rheumatoid arthritis remains a clinical one. It is not possible to comment on the degree of activity of arthritis on ^99mTc MDP scans, and these should therefore not be requested for this.

References

1. Shearman J, Esdaile J, Hawkins D, Rosenthal L. Arthritis Rheum. 1982;25:83–6

2. De Bois MHW, Arndt JW, Van der Velde EA, Pauwels EKJ, Breedeveld FC. Br J Rheumatol. 1994;33:67–73