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33rd Annual Scientific Meeting proceedings

Stream: LA   |   Session: Orthopaedic Short Communications
Date/Time: 07-07-2023 (12:00 - 12:15)   |   Location: Theatre Hall
Radiographic assessment of the variable length of hindlimb splint bones to determine the risk of iatrogenic penetration of the metatarsophalangeal joint while performing a low 6 point nerve block.
Jiménez C1, Jansson J3, Berka N1, Fogarty U2, Vasey JR4, Hennessy S*1
1Anglesey Lodge Equine Hospital, Kildare, Ireland, 2Irish Equine Center, Naas, Ireland, 3Lisadell Equine Hospital, Follistown, Ireland, 4Avenel Equine Hospital, Ferguson, Australia.

Variable lengths of the second and fourth metatarsal (Mt2 and MT4) bones exist between horses. Varying effusion of the metatarsophalangeal (MTP) joint occurs with osteoarthritic change. The authors hypothesised that performing the plantar metatarsal nerve block poses a risk for MTP joint penetration in horses with long splint bones and joint effusion.

Material and Methods
Two groups of thoroughbred horses (> 3years old) were assessed.

Group1; 30 randomly selected cadaver hindlimbs had MTP joint maximal distension performed with iodinated contrast. Percentage 3rd metatarsal bone (Mt3) length occupied by proximal extension of the MTP joint was measured using radiography. Percentage Mt3 length occupied by Mt2 and Mt4 was determined radiographically.

Group2; percentage Mt3 length occupied by Mt2 and Mt4 was evaluated radiographically in 100 live horses.

Incidence of overlap of Mt2, Mt4 and the MTP joint was evaluated by comparison of mean percentage Mt3 lengths, and a Student-t test and Shapiro Wilks test compared the groups.

Group1; MTP joint proximal extension was a mean 31.1%(24.4-35.3%) Mt3 length. Overlap of the proximal MTP joint with Mt2 and Mt4 occurred in 56.67% of cases. Group2; Mt2 and Mt4 lengths extended a mean 68.5%(59-79.6%) Mt3 length. The groups were statistically comparable, and so an overlap of Mt2 and Mt4 with the MTP joint was anticipated in 55% of horses in group 2.

Discussion/ Conclusion
In conclusion, there is a risk of puncture the MTP joint during the low-6-point nerve block when MTP joint effusion is present in horses with long splint bones.

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