Scintigraphic tracking of mesenchymal stem cells after intravenous regional limb perfusion and subcutaneous administration in the standing horse.

OBJECTIVE: To assess distribution, uptake, and persistence of radiolabeled mesenchymal stem cells (MSC) using scintigraphy after intravenous regional limb perfusion (RLP) and subcutaneous injections in standing, sedated horses. STUDY DESIGN: Experimental study. ANIMALS: Horses (n = 12). METHODS: Six horses had RLP performed through the cephalic vein on 1 limb and subcutaneous injection in the metacarpal area in the opposite limb. The other 6 horses had RLP performed through the lateral palmar digital vein and subcutaneous injection in the coronary band. A pneumatic tourniquet was used for the RLP. MSC were labeled with technetium-HMPAO. Scintigraphic images were obtained at the time of injection, 1, 6, and 24 hours later. Results of RLP were compared with results from previous studies where similar injections were performed in anesthetized horses. RESULTS: Both RLP techniques led to greater variability, lower uptake, lower persistence, and poorer distribution when compared to results previously reported for horses under general anesthesia. The subcutaneous injections in the metacarpal area and coronary band resulted in MSC loss to the general circulation but no evidence of local migration. CONCLUSION: Due to partial or complete failure of the tourniquet, RLP performed in the standing horse as described is less efficient than performed under general anesthesia. Further work is needed to optimize the use of tourniquets to perform RLP for MSC administration in standing patients. The subcutaneous injections did not result in local migration in these normal horses.

Comparison of radiography, nuclear scintigraphy, and magnetic resonance imaging for detection of specific conditions of the distal tarsal bones of horses: 20 cases (2006-2010).

OBJECTIVE: To describe pathological findings identified with MRI in the distal tarsal bones of horses with unilateral hind limb lameness attributable to tarsal pain and to compare the usefulness of MRI with that of radiography and nuclear scintigraphy in evaluation of this region. DESIGN: Retrospective case series. ANIMALS: 20 lame horses. PROCEDURES: In all horses, MRI, radiography (4 standard projections), and nuclear scintigraphy of the tarsus had been performed. Horses were excluded if the results of all 3 imaging modalities were not available or if lameness was detected in more than 1 limb. Pathological changes identified with MRI were cross-referenced with the findings determined with other imaging modalities. RESULTS: Compared with MRI findings, the following lesions were identified with radiography: medullary and subchondral bone sclerosis in 9 of 16 horses, pathological changes related to osseous hyperintensity in 0 of 10 horses, and osteoarthritis in 5 of 8 horses. Standard radiographic projections did not aid in the identification of fracture of the distal tarsal bones (3 horses). Location of increased radiopharmaceutical uptake with nuclear scintigraphy corresponded with the location of pathological changes detected with MRI in all horses. The intensity of the radiopharmaceutical uptake on nuclear scintigraphic images did not correspond with the severity of the pathological changes identified with MRI. CONCLUSIONS AND CLINICAL RELEVANCE: Radiography was unreliable for the detection of pathological changes related to osseous hyperintensity identified with MRI, fracture, and subchondral bone sclerosis in the equine tarsus. Nuclear scintigraphy was effective in localizing pathological changes, but MRI provided superior anatomic detail.

Computed tomographic appearance of osteochondritis dissecans-like lesions of the proximal articular surface of the proximal phalanx in a horse.

A 6-year-old Thoroughbred gelding presented with a left forelimb lameness. The results of lameness examination, radiography, nuclear scintigraphy, and computed tomography are presented. Based on the diagnostic imaging, subchondral fractures and osteochondritis dissecans lesions of the proximal articular surface of the proximal phalanx were diagnosed. A brief discussion of osteochondritis dissecans is presented.