Ultrasound-guided injection of the cranial tibial artery for stem cell administration in horses.

BACKGROUND: A technique for intra-arterial injection of mesenchymal stem cells (MSC) has been established for front limbs with the use of the median artery. This approach has been proposed for treatment of soft tissue injuries of the equine distal limb. A technique has not been validated yet for hindlimb injection. OBJECTIVES: To assess the feasibility of injection of the cranial tibial artery in horses, and to evaluate the distribution and persistence of MSC after injection. STUDY DESIGN: In vivo experiment. METHODS: In a first phase, the cranial tibial arteries of both hindlimbs of three research horses were catheterised with ultrasound guidance under general anaesthesia and injected with iodinated contrast. In the second phase, iodinated contrast was injected in three standing sedated horses with ultrasound guidance. In the final phase, 99m Technetium-HMPAO labelled allogenic bone marrow derived equine MSC were injected under standing sedation with the same technique in three other horses. Scintigraphy was used to assess MSC distribution and persistence for 24 h. Ultrasound was performed 24 h after injection to assess vessel impairment. RESULTS: Arterial injection was achieved in all 18 limbs without any significant complications. Mild partial periarterial injection was observed in four limbs. Scintigraphic images demonstrated diffuse MSC distribution from the tarsal area to the foot. Persistence decreased over time but signal was still present at 24 h. MAIN LIMITATIONS: Limited retention of the radiolabel in the MSC. CONCLUSIONS: Ultrasound-guided injection of the cranial tibial artery can be performed both under general anaesthesia and standing sedation in horses. This technique could be used for MSC treatment of equine proximal suspensory desmopathy or other injuries in the distal hindlimb.

18 F-sodium fluoride positron emission tomography of the racing Thoroughbred fetlock: Validation and comparison with other imaging modalities in nine horses.

BACKGROUND: Early and accurate detection of stress remodelling in racehorses is of utmost importance to prevent catastrophic injuries. Current imaging techniques have limitations in assessing early changes predisposing to catastrophic breakdowns. Positron emission tomography (PET) using 18 F-sodium fluoride (18 F-NaF) is a sensitive method for the detection of early bone turnover and may improve early recognition of subtle injuries. OBJECTIVES: To validate the clinical use of 18 F-NaF PET in Thoroughbred racehorses, to assess the value of PET in the detection of bone lesions and to compare PET results with findings of other advanced imaging modalities, clinical examination and pathology. STUDY DESIGN: Experimental exploratory study. METHODS: Twenty fetlocks from nine Thoroughbred racehorses were imaged using 18 F-NaF PET, computed tomography (CT) and scintigraphy. Five fetlocks were also imaged with magnetic resonance imaging and four fetlocks were also examined histologically. Imaging findings were independently reviewed by three board certified radiologists. Imaging, clinical and histopathological findings were correlated. RESULTS: PET imaging was well-tolerated by all horses. PET detected focal areas of 18 F-NaF uptake in instances where other imaging modalities did not identify abnormalities, in particular in the proximal sesamoid bones. Maximal standardised uptake values could be measured to quantify the activity of lesions. Areas of 18 F-NaF uptake corresponded to regions of increased vascularity and increased osteoblastic activity. MAIN LIMITATIONS: Limited number of cases. CONCLUSIONS: 18 F-NaF PET imaging of the Thoroughbred fetlock is feasible and compares favourably with other imaging modalities in detecting stress remodelling in Thoroughbred racehorses. PET appears to be a beneficial imaging modality when used for early detection of stress remodelling in an effort to prevent catastrophic musculoskeletal injuries in this population of horses.