Effects of acepromazine and xylazine on subjective and objective assessments of forelimb lameness
The ability to localise lameness in horses using diagnostic analgesia is incredibly useful and forms the bedrock of a thorough lameness workup. However, anyone involved in the placement of nerve blocks will know how challenging, and at times dangerous, this can be. Historically the use of sedation to facilitate placement of nerve blocks was thought to affect the interpretation of the block through its analgesic effect. Equally, assessment of an excitable horse can be challenging and administration of sedation or tranquilisation may be necessary to allow safe and accurate assessment when trotted in hand. Morgan et al (Equine Vet J. doi: 10.1111/evj.13225) have compared the effect of xylazine (0.1–0.2 mg/kg intravenously (IV)), acepromazine (0.02 to 0.04 mg/kg IV) and IV saline when administered to six lame horses. Lameness was induced with set screws in a custom-made shoe and the study was a randomised crossover design. Horses were assessed at 10, 30, 45 and 60 minutes after treatment using both subjective assessment and inertia sensors. No significant difference was seen in the level of lameness, either objectively or subjectively, for any treatment group compared with the saline control. In addition, significant sedation-induced ataxia was not observed. A reduced stride rate was seen throughout the 60-minute period of the study following acepromazine administration; this was not seen with xylazine. In individual observers, acepromazine induced variable changes in subjective lameness grade. This manifested in a decrease in lameness grade after high-dose acepromazine was administered with one observer, and an increase in lameness grade following lowdose acepromazine administration with another observer. In conclusion, the study supports the use of low-dose acepromazine or xylazine to facilitate forelimb lameness evaluation. This should be considered both in calming an excitable horse, causing it to trot more consistently, and to reduce movement during placement of nerve blocks.
Nonsurgical and surgical management of metacarpo/metatarsophalangeal joint dorsal chip fracture in the Thoroughbred racehorse
Treatment of choice for osteochondral chip fractures of the dorsoproximal aspect of the proximal phalanx is considered to be arthroscopic removal. This is to prevent the continued release of inflammatory mediators that contribute to the development of degenerative joint disease. Ramzan and Wylie (Equine Vet J. doi:10.1111/evj.13185) have compared the clinical features, use of intraarticular medication and return to racing in Thoroughbreds when these chip fractures are conservatively or surgically managed. Horses ≥2years old were included, resulting in a total of 98 horses of which 70 were managed conservatively and 28 were managed surgically. Chip fractures predominantly involved the forelimb (94%) with the majority (71%) have a lameness grade of ≤2/5. Horses with large osteochondral fragments were more likely to undergo surgery, as were those with more than one fragment. Triamcinolone acetate was the most commonly used intra-articular treatment (64%) and there was no difference in the number of follow-up joint injections when comparing the post-diagnosis period in the conservatively managed with the post-surgical period in the surgically managed. There was no significant difference in the proportion of horses from each group that returned to racing following diagnosis. Neither did the size of number of fragments affect the likelihood for return to racing; indeed, all 6 conservatively managed horses with large osteochondral fragments raced following diagnosis. The median time to first start following conservative treatment (106 days) was significantly shorter compared to surgically managed horses (203 days). There was no evidence that nonsurgical management was associated with increased risk of associated ongoing orthopaedic problems during the study follow-up period. Although assumptions about long-term soundness cannot be made, horses remained under the care of the practice performing the study for a mean of >2 years. It is therefore unlikely that a significant number of horses developed orthopaedic problems attributable to the chip fracture beyond this 2-year period. In summary, non-surgical management was associated with a faster return to racing, without any recorded detriment. The authors recommend that management decisions in respect of this injury should be guided primarily by individual circumstances and clinical judgement.
A multi-centre cohort study investigating the outcome of synovial contamination or sepsis of the calcaneal bursae in horses treated by endoscopic lavage and debridement
Infection of the calcaneal bursae is a common sequela of wounds to the plantar aspect of the tarsus. Endoscopic treatment under general anaesthesia is considered the gold standard for all synovial infections, with a survival rate of 86%. Specific survival rates following infection of the calcaneal bursa have been poorly documented, with no studies detailing outcomes following endoscopic treatment. Isgren et al (Equine Vet J. doi:10.1111/evj.13180) performed a retrospective study involving 128 horses with sepsis of the calcaneal bursa. Overall survival to hospital discharge was 84%. Both administration of systemic antimicrobials and reduced time to referral were associated with lower mortality. Tendon damage (≥30% cross-sectional area), bone involvement, duration of general anaesthesia, postoperative synoviocentesis and postoperative wound dehiscence were all associated with increased mortality. Of the 57 horses for which follow-up was available, 91% returned to their previous or a higher level of work. This highlights the importance of early recognition and referral of horses with infection of the calcaneal bursa and the positive effect of early administration of broad-spectrum antibiotics.