The aim of this preliminary proof-of-concept study was to evaluate and compare the
success and complication rate of infiltration of the maxillary nerve of cadaver heads
using previously described surface landmarks, standard ultrasound and a novel needle
guidance positioning ultrasound system (SonixGPS).
Prospective, anatomical, method-comparison study.
Thirty-eight equine cadaver heads.
Twenty-six veterinary students performed the three methods consecutively on cadaver
heads using an 18 gauge, 8.9 cm spinal needle and 0.5 mL iodinated contrast medium.
Computed tomography was used to quantify success (deposition of contrast in contact
with the maxillary nerve) and complication rate (contrast identified within surrounding
vasculature or periorbital structures) associated with each method.
Perineural injection of the maxillary nerve was attempted 76 times, with an overall
success rate of 65.8% (50/76) and complication rate of 53.9% (41/76). Success rates
were 50% (13/26) with surface landmark, 65.4% (17/26) with standard ultrasound guidance
and 83.3% (20/24) with SonixGPS guidance approaches (Fisher's exact test, p=0.046). No significant difference in complication rate was found between the three
Ultrasound-guided maxillary nerve blocks were significantly more successful than surface
landmark approaches when performed by inexperienced operators, and the highest success
rate was achieved with guidance positioning system (GPS) needle guidance.
Local anaesthesia of the equine maxillary nerve in the fossa pterygopalatina is frequently
used for diagnostic and surgical procedures in the standing sedated horse. Due to
vague superficial landmarks with various approaches and the need for experience via
ultrasound guidance, this block remains challenging. GPS guidance may improve reliability
of maxillary and other nerve blocks, and allow a smaller volume of local anaesthetic
solution to be used, thereby improving specificity and reducing the potential for