Effects of intra-articular anesthesia of the tarsometatarsal joint on skin sensation of the distal limb in horses.

Objective: To determine with mechanical nociceptive threshold (MNT) testing whether distal limb skin sensation is affected by intra-articular anesthesia of the tarsometatarsal joint (TMTJ).

Animals and procedure: This was a prospective cohort study. Ten client-owned horses that had intra-articular TMTJ anesthesia were included in the study. The MNT was measured at 6 sites on the distal limb at 3 time points: before anesthesia (T0) and at 10 min (T10) and 30 min (T30) post-injection. Linear mixed-model analyses were done, with the significance level set at P < 0.05.

Results: There was an increase in MNT (P = 0.001) across combined testing points between T0 and T30, indicating loss of skin sensation in the distal limb 30 min after TMTJ anesthesia. Regarding individual MNT sites, there were increases at the lateral proximal sesamoid bone (P = 0.002) and dorsal coronary band (P = 0.037) at T30 compared to T0.

Conclusion: Intra-articular anesthesia of the TMTJ significantly increased the combined MNT of the skin of the distal limb at 30 min, indicating decreased skin sensation.

Clinical relevance: Diagnostic anesthesia of the distal hind limb should be performed before TMTJ block. However, if patient compliance prevents this, lameness evaluation 10 min after blocking may enhance the reliability of interpretation.