Displacement of popliteal sciatic nerve catheters after major foot and ankle surgery: a randomized controlled double-blinded magnetic resonance imaging study  R.W. Hauritz, E.M. Pedersen, F.S. Linde, K. Kibak, J. Børglum, S. Bjoern, T.F. Bendtsen  British Journal of Anaesthesia  Volume 117, Issue 2, Pages 220-227 (August 2016) DOI: 10.1093/bja/aew172 Copyright © 2016 The Author(s) Terms and Conditions

Fig 1 Ultrasound-guided popliteal sciatic nerve catheter insertion. The ultrasound transducer was held at all times to provide the short-axis view of the sciatic nerve (SN). The needle approach was out-of-plane (OOP) parallel to the the SN (SAX-OOP group). (a) The patient was placed in the left lateral decubitus position. The needle was inserted OOP, initially at a steep angle with an increasingly shallow angle, keeping the transducer immobile, until the needle tip was seen as a hyperechoic dot (green arrow), when it intersected the plane of the ultrasound beam in the subcutaneous tissue. At that point, the needle insertion was halted, followed by a cranial parallel shift of the transducer until the cross-sectional sonographic image of the needle disappeared. Then again, the transducer was kept immobile and the needle was advanced until the needle tip reappeared in the plane of the ultrasound beam. With such alternating subtle movements of transducer and needle, the needle tip was tracked sonographically until it was located proximal to the bifurcation of the SN, between the tibial and common peroneal nerve components. (b) Hydrolocation in the subparaneural space. The position of the needle tip is controlled with needle hub steering and verified by hydrolocation. (c) Nerve catheter inserted and adjusted by retraction of the catheter until appropriate tip location proximal to the SN bifurcation, verified by hydrolocation and perineural spread of saline. Hereafter, local anaesthetic is injected. Green asterisk, biceps femoris muscle; white asterisk, injected saline; magenta asterisk, local anaesthetic; red arrow, common peroneal nerve; orange arrow, tibial nerve; green arrow, tip of Tuohy needle; blue arrow, tip of nerve catheter; yellow dotted line, paraneural sheath. British Journal of Anaesthesia 2016 117, 220-227DOI: (10.1093/bja/aew172) Copyright © 2016 The Author(s) Terms and Conditions

Fig 2 Ultrasound-guided popliteal sciatic nerve catheter insertion. The ultrasound transducer was held at all times to provide the short-axis view of the sciatic nerve (SN). The needle approach was in-plane (IP), through the biceps femoris muscle perpendicular to the SN (SAX-IP group). (a) The patient was placed in the left lateral decubitus position. The needle was advanced with an IP approach, penetrating the long head of the biceps femoris muscle. (b) Hydrodissection inside the subparaneural space with saline, 1–3 ml. (c) Placement of the nerve catheter through the needle and hydrodissection. Green asterisk, biceps femoris muscle; white asterisk, injected saline; magenta asterisk, local anaesthetic; red arrow, common peroneal nerve; orange arrow, tibial nerve; green arrow, Tuohy needle; blue arrow, nerve catheter; yellow dotted line, paraneural sheath. British Journal of Anaesthesia 2016 117, 220-227DOI: (10.1093/bja/aew172) Copyright © 2016 The Author(s) Terms and Conditions

Fig 3 Magnetic resonance image from a patient with no clinical signs of nerve catheter displacement. This patient had a nerve catheter inserted parallel to the sciatic nerve after triple arthrodesis (SAX-OOP-group). (a) Transverse section distal to the sciatic bifurcation displays complete circumferential spread of contrast around the peripheral sciatic nerve branches, namely the tibial nerve and the common peroneal nerve. The paraneural sheath is distinctly visible. (b) Same picture as in (a), but with magnification of the area around the paraneural sheath. Red asterisk, vastus intermedius muscle; orange asterisk, biceps femoris muscle (short head); green asterisk, biceps femoris muscle (long head); blue asterisk, semimembranosus muscle; cyan asterisk, semitendinosus muscle; yellow asterisk, gracilis muscle; magenta asterisk, sartorius muscle; kharki asterisk, vastus medialis muscle; white asterisk, femur; orange arrow, tibial nerve; red arrow, common peroneal nerve; yellow dotted line, paraneural sheath. British Journal of Anaesthesia 2016 117, 220-227DOI: (10.1093/bja/aew172) Copyright © 2016 The Author(s) Terms and Conditions

Fig 4 Magnetic resonance image from a patient with clinical signs of catheter displacement. This patient had a nerve catheter inserted perpendicular to the sciatic nerve (SAX-IP group). (a) Nerve catheter displacement, with spread of contrast outside the biceps femoris muscle and subcutaneously (magenta arrows). (b) Nerve catheter displacement, with spread of contrast inside the short and long heads and between the deep fascia and muscle (green arrows) of the biceps femoris muscle. Orange arrow, tibial nerve; red arrow, common peroneal nerve. British Journal of Anaesthesia 2016 117, 220-227DOI: (10.1093/bja/aew172) Copyright © 2016 The Author(s) Terms and Conditions