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

Abstract

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-1&#x3b2; (reIL-1&#x3b2;). 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-1&#x3b2; injection was grade 3.2 and was not significantly improved following PDNBs or ASNBs. However, in two horses (2/9) lameness improved by &#x2265;50 % five minutes post-PDNB. Mean subjective lameness significantly improved following PMNBs (grade 2.7 &#xb1; 0.8 at five and 2.2 &#xb1; 1.0 at ten minutes post-block; p < 0.03) and PaNBs (grade 1.5 &#xb1; 1.2 at five and 1.3 &#xb1; 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.