Objective evaluation for analgesia of the distal interphalangeal joint, the navicular bursa and perineural analgesia in horses with naturally occurring forelimb lameness localised to the foot

Abstract

Background

The outcome and interpretation of intra-synovial diagnostic analgesia of the distal interphalangeal joint (DIPJ) and the navicular bursa (NB) remain in dispute, and no objective studies have been carried out to establish the percentage of improvement over time from these two analgesia techniques.

Objectives

To investigate the qualitative and time-dependent outcome of DIPJ-A and NB-A in naturally occurring forelimb lameness.

Study design

Case series.

Methods

Twenty-three clinical cases with forelimb lameness were evaluated objectively using a body mounted inertial sensor system (BMIS). Lameness was localised to the foot with a palmar digital nerve block and/or an abaxial sesamoidean nerve block on day 1, and analgesia of the DIPJ (DIPJ-A) and NB (NB-A) were performed on days 2 and 3. Improvement following perineural analgesia was measured after 10 min and intra-synovial blocks after 2-, 5- and 10-min. Horses with at least 70% improvement measured objectively after diagnostic analgesia were included in the study.

Results

There was no significant association between improvement following perineural analgesia and the DIPJ-A and NB-A. The mean improvement in the lameness differed between DIPJ-A and NB-A at 2 min (p < 0.001) and at 5 min (p = 0.04), and it was no longer observed after 10 min (p = 0.06). A positive NB-A produced a high degree of improvement that remained stable, whereas the DIPJ-A improved over time.

Main limitations

Perineural and intra-synovial analgesia were performed without contrast medium to assess the diffusion of mepivacaine.

Conclusions

Our results suggest that perineural analgesia is not reliable enough to differentiate pain originating from DIPJ and NB. Early evaluation of the DIPJ-A and NB-A can determine the origin of the pain. An improvement following NB-A was constant over time, but an improvement following DIPJ-A varied by up to 10 min.