Ultrasound imaging of the infraorbital foramen and simulation of the ultrasound-guided infraorbital nerve block using a skull model.

PURPOSE: Infraorbital nerve block is used for intraoperative and postoperative analgesia in nasal and oral surgery procedures, as well as in the chronic pain settings. Ultrasound guidance has not been described in the literature. The aim of the study was to assess the quality of ultrasound imaging of the infraorbital foramen and develop an "in-plane" technique of the block using a skull model.
METHODS: The infraorbital foramina were assessed on five skull models immersed in the water bath. Ultrasound-guided simulation of an in-plane infraorbital nerve block was then performed. Slightly curved needle was placed close to the foramina and its visibility was recorded. Success rate and time to locate infraorbital foramina, success rate and time to insert the needle close to the foramina under ultrasound and correlation between the ultrasound and caliper measurements were evaluated and recorded. Data for the left and right foramen were compared.
RESULTS: The infraorbital foramina were successfully located using ultrasound in all 20 cases. Simulation of infraorbital nerve block was also successful in all measurements. The time difference between locating or simulating blockade of the left and right infraorbital foramina was not statistically significant. Correlation between ultrasound measurement and direct measurement using a caliper was satisfactory for the distances between the inferior orbital rim and the inferior margin of the infraorbital foramen but poor for the distances between the lower rim of the orbit and the superior margin of the foramen.
CONCLUSIONS: This experimental study suggests that the infraorbital foramen is easily located using ultrasound and an "in-plane" ultrasound-guided technique for infraorbital nerve blockade is feasible on the model.