Navicular bone fracture and severe deep digital flexor tendinopathy after palmar digital neurectomy in two horses.

Background: Navicular syndrome is a common cause of forelimb lameness in horses. Beyond changes to the navicular bone itself, horses with a clinical diagnosis of navicular syndrome often have pathology associated with other components of the navicular apparatus, including the navicular bursa, deep digital flexor (DDF) tendon, collateral sesamoidean ligaments, and impar ligament. Palmar digital neurectomy (PDN) is often used as a salvage procedure for horses diagnosed with navicular syndrome that become unresponsive to medical management. There are many potential complications associated with PDN, some of which are debilitating. Case Description: This report describes two cases of navicular bone fracture with severe DDF tendinopathy and distal interphalangeal joint subluxation/hyperextension that occurred 12 and 19 weeks after bilateral forelimb PDN. Conclusion: These two cases highlight the importance of proper patient selection before PDN due to the high incidence of undiagnosed soft tissue pathology in conjunction with radiographic evidence of navicular syndrome. Advanced imaging of the digit is recommended to identify and characterize any soft tissue pathology associated with the navicular apparatus before pursuing PDN to avoid disease progression and catastrophic injury.

Effect of perfusate volume on amikacin concentrations after saphenous intravenous regional limb perfusion in standing, sedated horses.

OBJECTIVE: To determine the influence of perfusate volume on synovial fluid amikacin concentrations in the joints of the hind limb after standing saphenous intravenous regional limb perfusion (IVRLP). STUDY DESIGN: Randomized crossover design. ANIMALS: Six adult horses. METHODS: Saphenous IVRLP was performed in 6 standing horses with 1 g of amikacin diluted with 0.9% NaCl to volumes of 10 ml, 60 ml, and 120 ml. Samples of synovial fluid from the tarsocrural, metatarsophalangeal, and hind limb distal interphalangeal joints were collected at 15 and 30 min after perfusate administration. Concentrations of 40 µg/ml and 160 µg/ml were considered therapeutic for susceptible and resistant pathogens, respectively. RESULTS: No difference in synovial fluid amikacin concentrations was detected between volumes in any joint (P = .4). All synovial fluid amikacin concentrations were higher at 30 min compared to 15 min (P = .003). All median synovial fluid amikacin concentrations at 30 min were > 40 µg/ml using the 60 ml and 120 ml volumes. Synovial fluid amikacin concentrations >40 µg/ml were only reached in the hind limb distal interphalangeal joint when the 10 ml volume was used. All median synovial fluid amikacin concentrations observed were < 160 µg/ml. CONCLUSIONS: Target concentrations for pathogens that were considered susceptible were consistently reached with perfusate volumes of 60 ml and 120 ml. However, median synovial fluid amikacin concentrations did not reach target levels for resistant pathogens. CLINICAL SIGNIFICANCE: Perfusate volumes of 60 ml or 120 ml are recommended to treat infections due to susceptible pathogens in the joints of the distal hind limb. These results justify investigation of saphenous IVRLP with different perfusate volumes using higher doses of amikacin.