A randomized prospective comparative study of nerve stimulator and ultrasonogram in popliteal sciatic nerve block for ankle and foot surgeries

Ramamoorthi Panneerselvam, Vijay Kanna, Rajamanoharan Akkayan


Background: Regional blocks in the field of anaesthesia were done traditionally with paraesthesia technique. To overcome the demerits with paraesthesia technique, nerve locator was applied for nerve blocks. Later, the application of ultrasonogram for regional blocks got the real time imaging of the nerves and drug administration. This resulted in publications of numerous studies with variable results. Therefore we planned to compare ultrasonogram and nerve locator in popliteal sciatic nerve block in our population.

Methods: A prospective, randomized, observer blinded study was planned to compare the nerve stimulator (Group N) and ultrasound (Group U) on duration of ‘block technique’, number of needle reinsertions in popliteal sciatic nerve block for ankle and foot surgeries. We included all consented patients aged ≥18 years of both genders belonging to ASA I to III and excluded pregnant mothers, diabetes mellitus, neuropathy, chronic opioid use, positioning difficulty, coagulopathy, nerve block contraindications, local anaesthetic allergic patients.

Results: The duration of block technique in Group U = 262.00 ± 108.36 Seconds and Group N = 715.16 ± 234.66 Seconds with statistically significant P value = 0.0001. The average number of needle reinsertions in Group N = 6.05 ± 2.31 and Group U = 2.46 ± 1.11 with statistically significant p value of 0.0001. Therefore the time taken to perform the block and the number of needle reinsertions in Group U is shorter than the Group N.

Conclusion: The duration of block technique and number of needle reinsertions are better with ultrasound. Though the onset of motor and sensory blockade were better with ultrasound success rate is not significantly different.



Regional anesthesia, Nerve blocks, Ultrasonogram, Motor blockade, Sensory blockade

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Irnich, W. The Chronaxie time and its practical importance. Pacing Clin Electrophysiol. 1980;3:292-301.

Manbachi A, Cobbold RSC. Development and application of piezoelectric materials for ultrasound generation and detection. Ultrasound. 2011;19(4):187-96.

Grechenig W, Clement HG, Peicha G, Klein A, Weiglein A. Ultrasound anatomy of the sciatic nerve of the thigh. Biomed Tech (Berl). 2000;45:298-303.

Soong J, Schafhalter-Zoppoth I, Gray AT. The importance of transducer angle to ultrasound visibility of the femoral nerve. Reg Anesth Pain Med. 2005;30:505.

Goldstein A. The effect of acoustic velocity on phantom measurements. Ultrasound Med Biol. 2000;26:1133-43.

Cheung S, Rohling R. Enhancement of needle visibility in ultrasound-guided percutaneous procedures. Ultrasound Med Biol. 2004;30:617-24.

Cohnen M, Saleh A, Luthen R, Bode J, Mödder U. Improvement of sonographic needle visibility in cirrhotic livers during trans jugular intrahepatic portosystemic stent-shunt procedures with use of real-time compound imaging. J Vasc Interv Radiol. 2003;14:103-6.

American Institute of Ultrasound in Medicine. Technical bulletin: Transducer manipulation. J Ultrasound Med. 1999;18:169-75.

Silvestri E, Martinoli C, Derchi LE, Bertolotto M, Chiaramondia M, Rosenberg I. et al. Echotexture of peripheral nerves: correlation between US and histologic findings and criteria to differentiate tendons. Radiology. 1995;197:291-6.

Fornage BD. Sonographically guided core-needle biopsy of breast masses: the “bayonet artefact”. AJR Am J Roentgenol. 1995;164:1022-3.

Bondestam S, Kreula J. Needle tip echogenicity: a study with real time ultrasound. Invest Radiol. 1989;24:555-60.

Vloka JD, Hadzic A, April E, Thys DM. The division of the sciatic nerve in the popliteal fossa: Anatomical implications for popliteal nerve blockade. Anesth Analg. 2001;92:215.

Benzon HT, Kim C, Benzon HP, Silverstein ME, Jericho B, Prillaman K, et al. Correlation between evoked motor response of the sciatic nerve and sensory blockade. Anesthesiology. 1997;87:547-52.

Zetlaoui PJ, Bouaziz H. Lateral approach to the sciatic nerve in the popliteal fossa. Anesth Analg. 1998;87:79.

Hadzic A, Vloka JD. A comparison of the posterior versus lateral approaches to the block of the sciatic nerve in the popliteal fossa. Anesthesiology. 1998;88:1480.