Blind Versus Ultrasound-Guided Low-Volume Perineural Injection of Tibial and Fibular Nerves in Equine Cadaver Limbs.

The study compares two methods of administering local anesthesia to horse limbs: the traditional “blind” technique and an ultrasound-guided technique. The findings suggest that while both methods are equally effective, the ultrasound-guided technique uses less anesthesia and has a lower rate of diffusion, making it potentially a better option for certain situations.

Objectives of the study

• The research aims to compare two methods of administering local anesthesia to the tibial and superficial and deep fibular nerves in horses: the blind method, where the anesthesia is injected without visual guidance, and an ultrasound-guided method.
• The goal was to determine which technique is more efficient, by evaluating the diffusion and presence of an injected solution (comprising of radiopaque contrast, saline and food dye) around the nerves. The researchers considered the presence of the dye directly adjacent to the nerves as an indication of successful perineural injection.

Methodology

• 15 equine cadaver hindlimbs were used in the experiment and were divided into two groups, for blind injection and ultrasound-guided injection.
• In the blind group, 15 mL of the injectate was used for the tibial nerve and 10 mL for each fibular nerve. Meanwhile, in the ultrasound-guided group, only 3 mL was used for the tibial nerve and 1.5 mL for each fibular nerve.
• Radiographs were taken immediately after the injections, and the limbs were dissected to evaluate how the solution had diffused and to visually ascertain if it had reached the desired nerves.

Findings

• The results showed no statistically significant difference in success rates between the two methods, meaning both techniques effectively delivered the anesthesia to the target nerves.
• However, the ultrasound-guided technique used significantly less volume of the injectate and resulted in lesser diffusion following perineural injection of both the tibial and fibular nerves. This means the ultrasound-guided injections were more precise and wasted less of the injectate.
• Despite the evident benefits of the ultrasound-guided method, the research concludes that the choice between the two techniques would still depend on the veterinarian’s preference.