Clinical and force plate evaluation of the effect of a high plantar nerve block in lameness caused by induced mid-metatarsal tendinitis.

The researchers explored whether a high plantar nerve block could differentiate between two types of lameness in horses: one caused by flexor tendon issues, and the other by suspensory ligament issues. They used a collagenase model to induce lameness, but found that while the nerve block had clear effects, it did not provide clear differentiation between the two types of lameness.

Research Methodology

• The study was performed on five Standardbred horses in two trials, with the lameness condition induced using collagenase, an enzyme that breaks down collagen in the animals’ tendons or ligaments. This technique allowed the researchers to simulate the conditions of flexor tendon and suspensory ligament lameness.
• Clinical assessments, ground reaction force (GRF) measurements, and ultrasonographic checks were made before inducing lameness, as well as on the fourth (D4) and fourteenth day (D14) after lameness induction.
• Clinical evaluations and GRF measurements were also made on D4 and D14 after employing a high plantar nerve block, a form of local anesthesia used in horses to numb the lower part of the limb.
• The GRF measurements were analysed, and multiple variables were selected and compared with the clinical lameness scores given by the researchers.

Results

• The findings showed that the horses were significantly lame on D4, but by D14 the lameness had decreased. The GRF measurements corroborated these clinical observations.
• In the flexor tendon group, a high plantar nerve block resulted in either soundness or lameness in the other hind limb. The effects were less consistent in the suspensory ligament group.
• The clinical lameness scores given by the researchers showed moderate to high correlation with several objectively-measured GRF variables.
• The study underlines the utility of the collagenase model in studying the effects of a high plantar nerve block on lameness resulting from induced tendon or ligament damage.

Conclusion

• The most significant finding of the research is that while a high plantar nerve block can impact lameness in horses, it cannot unfailingly differentiate lameness caused by flexor tendon issues from that caused by suspensory ligament problems.
• This suggests a limitation in the diagnostic use of high plantar nerve blocks for specific types of equine lameness.