A different approach to an ultrasound-guided saphenous nerve block

Comparison of infracondylar versus subsartorial approach to saphenous nerve block: A randomized controlled study

Background and Objectives:

Only a few different approaches are currently utilized for saphenous nerve block. Our study aimed to compare two different ultrasound (US)-guided saphenous nerve blocks and designed this study to test the hypothesis that the medial infracondylar approach has more success rate than the subsartorial approach applied in saphenous nerve blockage.

Methods:

The study included 76 patients (18–65 years old) with the American Society of Anesthesiologists physical status of I–III, who were scheduled for below-knee surgery by the orthopedics clinic. The patients who underwent US-guided saphenous nerve blockade were randomly divided into two groups: Group S (subsartorial approach) and Group M (medial infracondylar approach). For all patients who had a block procedure, the pinprick test was performed using a blunt needle on the saphenous nerve dermatome. Success rate, time of block performance (TBP), onset time of block (OTB), and duration of sensory blockade (DSB) were recorded using a patient follow-up form.

Results:

The US-guided saphenous nerve block success rate was similar (88% vs. 91%) or both techniques. The DSB values were 415.2 ± 65.3 min (95% confidence interval [CI]: 286.3–539.8) for Group S and 369.7 ± 52.2 min (95% CI: 265.6–467.8) for Group M (P = 0.04), and no significant differences in the TBP and OTB were observed between the groups.

Conclusion:

Both of the different anatomical approaches have equally high success rates. Although the DSB was found to be significantly longer in the subsartorial approach, this is clinically unimportant, and the medial infracondylar approach is still a viable alternative technique during saphenous nerve blockage.

Prospective randomized comparison between ultrasound-guided saphenous nerve block within and distal to the adductor canal with low volume of local anesthetic

Background and Aims:

The anatomic site and the volume of local anesthetic needed for an ultrasound-guided saphenous nerve block differ in the literature. The purpose of this study was to examine the effect of two different ultrasound-guided low volume injections of local anesthetic on saphenous and vastus medialis nerves.

Materials and Methods:

Recruited patients (N = 48) scheduled for orthopedic surgery were randomized in two groups; Group distal adductor canal (DAC): Ultrasound-guided injection (5 ml of local anesthetic) distal to the inferior foramina of the adductor canal. Group adductor canal (AC): Ultrasound-guided injection (5 ml local anesthetic) within the adductor canal. Following the injection of local anesthetic, block progression was monitored in 5 min intervals for 15 min in the sartorial branches of the saphenous nerve and vastus medialis nerve.

Results:

Twenty two patients in each group completed the study. Complete block of the saphenous nerve was observed in 55% and 59% in Group AC and DAC, respectively (P = 0.88). The proportion of patients with vastus medialis weakness at 15 min in Group AC, 36%, was significantly higher than in Group DAC (0/22), (P = 0.021).

Conclusions:

Low volume of local anesthetic injected within the adductor canal or distally its inferior foramina leads to moderate success rate of the saphenous nerve block, while only the injection within the adductor canal may result in vastus medialis nerve motor block.