An ultrasound‐guided, tendon‐sparing, lateral approach to injection of the navicular bursa

Abstract

Navicular disease in the horse often requires injection of the navicular bursa. We have developed an ultrasound-guided, lateral needle approach to navicular bursocentesis, which avoids penetration of the deep digital flexor tendon (DDFT) and the need for radiographic control. To describe and evaluate the feasibility and efficacy of an ultrasound-guided, lateral bursocentesis technique. Cadaveric and in vivo experiments. The navicular bursa in 62 cadaveric forelimbs of 31 horses and in both forelimbs of 26 live horses, positioned with the foot flexed in a navicular block, were submitted to lateral, ultrasound-guided injection of 1.5 ml radiocontrast agent. Lateromedial radiographs were taken to locate the contrast. A second injection of 0.5 ml methylene blue was administered during needle withdrawal in cadaveric limbs to investigate the needle pathway during dissection. Contrast agent was successfully deposited in the navicular bursa in 104 of 114 (91%) limbs and in the navicular bursa alone in 89 of 114 (78%) limbs. Dissection showed no evidence of penetration of the DDFT in cadaver limbs. Failure to inject the navicular bursa was significantly associated with poor quality of the ultrasound image (P = 0.04) and resulted in aberrant injection of the distal interphalangeal joint in five of 114 (4%) limbs, the peribursal soft tissues in four of 114 (4%) limbs and the digital flexor tendon sheath in one of 114 (0.9%) limbs. Synovial fluid was observed at the needle hub in 58% of live horses. It is unknown whether injection results obtained in the limbs of horses without disease can be extrapolated to horses with clinical disease of the podotrochlear apparatus. The localisation of contrast medium on radiographs may not accurately reflect the behaviour of local anaesthetic solution or therapeutic medications injected in the navicular bursa. This lateral, ultrasound-guided technique for injecting the navicular bursa is effective, does not penetrate the DDFT and avoids exposure of personnel to radiation.