Vascular distribution of contrast medium during intraosseous regional perfusion in the equine distal limb

Objective — To describe the vascular distribution pattern of contrast medium during intraosseous regional perfusion (IORP) of the distal portion of the forelimb in horses.

Sample Population — 13 cadaver forelimbs from 12 horses without vascular or orthopedic disease of the distal forelimb.

Procedure — Serial lateromedial radiographs were taken of 10 heparinized cadaver distal forelimbs at 0, 1, 2, 6, 15, and 30 minutes during IORP of the third metacarpal bone (MCIII) using iodinated contrast medium and a tourniquet placed over the proximal MCIII. Vascular regions of interest (ROI) were created for each radiograph. Reviewers identified presence or absence of contrast in each ROI. This information was summarized to identify vessel-filling patterns over time. Vessel identification was verified using computed tomography angiography and latex perfusion studies on separate cadaver distal forelimbs.

Results — During IORP, contrast medium filled the medullary cavity of the MCIII, exited via trans-cortical vessels and diffused distally to the remaining arteries and veins of the limb, distal to the tourniquet. Maximum vessel and soft tissue opacification occurred in most specimens at 6 and 30 minutes, respectively. Serial radiography vessel patterns matched those of CT images and dissected specimens.

Conclusions and Clinical Relevance — Intraosseous regional perfusion provides a repeatable pattern of vascular distribution in the distal portion of the equine forelimb. This is the first documentation of arterial perfusion using this technique. Previous reports indicate that IORP only delivers medications to the venous vessels of the perfused limb. Maximum soft tissue perfusion was observed at 30 minutes.