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EQUINE VETERINARY EDUCATION / AE / OCTOBER 2014
a)
b)
c)
Fig 2: a) Plantar and b) proximoplantar images of the left hindlimb of Case 1 showing soft tissue swelling on the distal medial aspect of the tarsus (arrows). c) Plantar image of the left hindlimb of Case 2, showing soft tissue swelling on the distal medial aspect of the tarsus and proximal metatarsal region (arrows).
Two horses (Cases 1 and 2) had palpable oedematous soft
tissue swelling on the distal medial aspect of the tarsus, extending from the chestnut distally, in the hindlimb with injury of the accessory ligament of the suspensory ligament (Fig 2). There was localised heat but no pain on palpation. Only one horse showed detectable lameness in straight lines (Case 1) (grade 2 left hindlimb lameness and grade 2 right forelimb lameness). Proximal and distal limb flexion tests of the hindlimbs did not alter the gait in any horse. In 4 horses lameness was only apparent ridden. Going large around a 60 × 20m arena there was no consistent pattern of hindlimb lameness but in 10m diameter circles lameness was accentuated and horses were consistently lamer on the inside hindlimb (grade 3 or 4). Before local analgesia was performed, one horse had overt bilateral hindlimb lameness and unilateral forelimb lameness (Case 1), one had unilateral forelimb and unilateral hindlimb lameness (Case 2), one had unilateral hindlimb lameness and a bilaterally shortened cranial phase of the forelimb steps (Case 3), one had bilateral hindlimb lameness and a bilaterally shortened cranial phase of the forelimb steps (Case 4) and one had bilateral hindlimb lameness (Case 5). In 3 horses (Cases 1–3) the saddle consistently slipped to one side, despite fitting well. Saddle slip was abolished when lameness was eliminated using diagnostic analgesia. In one horse (Case 2) there was dynamic hyperextension of all 4 fetlocks.
© 2014 EVJ Ltd No horse showed improvement in lameness after
perineural analgesia of the plantar and plantar metatarsal nerves (a ‘low 4-point block’) of the lame limb(s). In 3 horses (Cases 2, 4 and 5) baseline hindlimb lameness when the horse was ridden was eliminated by perineural analgesia of the deep branch of the lateral plantar nerve (3 ml mepivacaine; response assessed at 10 min after injection); in 2 horses (Cases 1 and 3) there was improvement in lameness after perineural analgesia of the deep branch of the lateral plantar nerve but perineural analgesia of the tibial nerve (15 ml mepivacaine; response assessed at 15 min after injection) was required to abolish lameness in the hindlimb with injury of the accessory ligament of the suspensory ligament. Further improvement in the quality of the canter was achieved in the 2 horses (Cases 1 and 4) in which mepivacaine (2 × 12 ml; response assessed at 15 min after injection) was infiltrated around the sacroiliac joints. No improvement in lameness was seen after intra-articular analgesia of the tarsometatarsal joint (3 ml mepivacaine; response assessed 10 min after injection) in any horse. No significant radiological abnormality was seen in any
hindlimb. Proximal suspensory desmopathy was identified in all lame hindlimbs and characterised ultrasonographically by enlargement of the suspensory ligament, heterogeneous echogenicity and loss of long linear echoes in longitudinal
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