Positron emission tomography using 18F-fluorodeoxyglucose reveals digital perfusion deficits associated with...

To characterize healthy foot perfusion patterns under static weight-bearing load using 18F-fluorodeoxyglucose (18F-FDG) PET.

In 8 healthy adult light-breed horses (from May 2021 through September 2024), 18F-FDG was injected while horses stood continuously weight-bearing (CWB) for a 20-minute scan period. A repeat scan was then performed after 20 minutes of ambulation. On a separate occasion, scans were performed with ambulation allowed between injection and scanning (Amb_Control). 18F-fluorodeoxyglucose uptake was quantified via metabolic volume and standardized uptake values for coronary band, lamellae, and sole and compared using Friedman analyses.

Discrete 18F-FDG uptake deficits of varying size were present in CWB scans, most commonly medially in both the sole (8 of 8) and quarter lamellae (7 of 8), reflected in reduced median metabolic volume (cubic centimeters) in the medial sole (14.5 CWB [IQR, 9.0 to 19.6] vs 22.2 Amb_Control [IQR, 20 to 22.8]) and medial lamellae (23.4 CWB [IQR, 19.6 to 26.3] vs 26.8 Amb_Control [IQR, 24.7 to 28.1]). The lamellar standardized uptake value mean was also reduced in CWB (1.35; IQR, 1.26 to 1.53) vs Amb_Control (1.58; IQR, 1.4 to 1.77). Uptake deficits partially resolved in the rescan and were absent in Amb_Control scans.

In healthy limbs scanned under static weight-bearing conditions, discrete regions of the medial sole and lamellae were devoid of 18F-FDG uptake, consistent with weight-bearing-associated perfusion deficits. The size and nature of these perfusion deficits varied between individuals, but they consistently resolved upon ambulation.

The role of weight-bearing-related perfusion deficits (detectable using PET) in the development of supporting-limb laminitis warrants further investigation in clinical patients.