Factors influencing blood flow in the equine digit and their effect on uptake of 99m technetium methylene diphosphonate into bone

It was hypothesised that exercise may promote perfusion of the distal part of the limbs and enhance uptake of radiopharmaceutical into bone, but bandaging and lameness would have no effect. Two hundred and two horses undergoing routine nuclear scintigraphic examination for assessment of lameness or poor performance between November 1998 and November 1999 were assigned randomly to one of 4 groups: no bandages and no exercise (NB/NE); bandages and no exercise (B/NE); no bandages and exercise (NB/E); bandages and exercise (B/E). In the bandage groups, the distal forelimbs were bandaged for at least 16 h prior to injection of radiopharmaceutical. In the exercise groups, horses were lunged for 15 min at trot and canter prior to injection. Quantitative values for perfusion of the front feet and uptake of the radiopharmaceutical into the bones of the distal limb were obtained from scintigraphic measurements during the vascular and bone phases of radiopharmaceutical distribution. Perfusion of the front feet was classified as good in 60% of limbs, reduced in 21% and poor in 19%. There was a strong positive relationship between exercise and both perfusion of the front feet and uptake of the radiopharmaceutical into bone. Bandaging had no effect. There was a relationship between environmental temperature and both perfusion and uptake of the radiopharmaceutical into bone. Estimation of foot surface temperature using thermography was helpful in predicting perfusion of the distal limbs. There was no relationship between lameness and uptake of the radiopharmaceutical into bone. It is therefore recommended that, whenever possible, horses are exercised for 15 min prior to injection of radiopharmaceutical if nuclear scintigraphy of the distal parts of the limb is to be performed.