Effects of various perineural analgesia techniques on decreasing experimentally-induced lameness of the equine metacarpophalangeal joint.

BACKGROUND

Recent evidence has shown that perineural analgesia may be less specific than previously thought.

AIMS/

OBJECTIVES

To compare the effects of four distal limb perineural analgesia techniques on resolving synovitis-induced lameness of the equine metacarpophalangeal joint (MCPJ).

METHODS

Nine horses had one MCPJ injected with 75 ng of recombinant equine interleukin-1β (reIL-1β). Ten hours later, horses underwent one of two blocking patterns: (1) a palmar digital (PDNB) followed by an abaxial sesamoidean (ASNB) nerve block or (2) a palmar metacarpal (PMNB) followed by a palmar (PaNB) nerve block. Skin sensitivity was evaluated four minutes post block. Lameness was assessed subjectively (Modified AAEP Grade 0-5) and objectively at five and ten minutes following each block. After a one-week washout period, lameness was induced in the opposite MCPJ, and the opposite blocking pattern was performed.

RESULTS

Mean subjective lameness post-reIL-1β injection was grade 3.2 and was not significantly improved following PDNBs or ASNBs. However, in two horses (2/9) lameness improved by ≥50 % five minutes post-PDNB. Mean subjective lameness significantly improved following PMNBs (grade 2.7 ± 0.8 at five and 2.2 ± 1.0 at ten minutes post-block; p < 0.03) and PaNBs (grade 1.5 ± 1.2 at five and 1.3 ± 1.3 at ten minutes post-block; p < 0.0001). Objective lameness scores followed a similar pattern, except the mean Q score did not significantly improve five minutes following the PMNB.

CONCLUSION

MCPJ lameness was most reliably improved following both PMNBs and PaNBs. In some instances, MCPJ pain was substantially improved following a PDNB.