Response of Charcot's arthropathy to contact casting: assessment by quantitative techniques

Aims/hypothesis. This study used two different methods of quantitative bone scanning to study the relation between activity of Charcot's arthropathy a nd clinical variables over 12 months. Methods. Skin temperature of affected and unaffected feet was measured at b aseline and every 3 months for 12 months in 17 subjects. Eight subjects und erwent a three-phase quantitative bone scan at baseline and 3 monthly for 1 2 months. Bone isotope uptake in a standard rectangular area over the foot and tibia was analysed by the bilateral scan method (the ratio of isotope u ptake of affected and unaffected feet) and the unilateral scan method (the ratio of isotope uptake of affected foot and ipsilateral tibia). The affect ed foot was placed in a contact cast for an average of 8 months. Results. At presentation the affected foot was hotter than the unaffected f oot but the temperature became progressively cooler over 12 months. Median isotope uptake in the affected foot was 2.1% of the injected dose (interqua rtile range, IQR 1.9-3.0). In both scanning methods the ratio of uptake dec reased after casting but at 12 months the affected foot still had more isot ope uptake. There was a strong correlation between temperature difference a nd the ratio of uptake in the bilateral scan method (r = 0.90; p < 0.0001) but when using the unilateral scan method this relation was not significant (r = 0.1; p = 0.6). A strong relation existed between perfusion of the aff ected foot in the dynamic phase and isotope uptake in the delayed phase of the scans (r = 0.92; p < 0.0001). Conclusion/interpretation. Bone activity and skin temperature of Charcot's arthropathy can be measured quantitatively and both improve over 12 months with contact casting. There is a strong relation between perfusion and dise ase activity in this condition.