Lower extremity nerve blocks: Techniques

INTRODUCTION — Peripheral nerve blocks of the lower extremity are used for operative anesthesia and/or postoperative analgesia for a variety of lower extremity surgeries.

This topic will discuss the innervation of the lower extremity, techniques and drugs used for lower extremity nerve blocks, and complications specific to these blocks. Where appropriate, the use of perineural catheters for continuous nerve block will be discussed. Indications, contraindications, comparison of techniques relevant to all peripheral nerve blocks, equipment, and complications common to all nerve blocks are discussed separately. (See "Overview of peripheral nerve blocks".)

INNERVATION: LOWER EXTREMITY — The lumbar plexus is formed by the ventral rami of the first three lumbar nerves (L1, L2, L3) and part of the fourth lumbar nerve (L4). A branch from the 12^th thoracic spinal nerve (T12) often joins the L1 nerve root (figure 1).

The lumbar plexus is located in the posterior third of the psoas muscle, anterior to the lumbar transverse processes. It gives rise to nerves that supply the muscular and cutaneous innervation to the lower extremity, including the iliohypogastric nerve, ilioinguinal nerve, genitofemoral nerve, femoral nerve, lateral femoral cutaneous nerve, and obturator nerve (figure 2).

The femoral nerve (L2 to L4) runs through the psoas muscle and emerges at the lower border between the psoas and iliacus muscles, beneath the inguinal ligament lateral to the common femoral artery. The femoral nerve innervates muscles involved with hip flexion and knee extension, and provides sensation to the anterior thigh, femur, knee joint, and medial leg (figure 3 and figure 4). The saphenous nerve is the terminal sensory branch of the femoral nerve.

The lateral femoral cutaneous nerve (also called the lateral cutaneous nerve of the thigh; L2 and L3) emerges from the lateral border of the psoas major muscle, crosses the iliacus, and ultimately runs behind or through the inguinal ligament and in front of or through the sartorius muscle into the thigh. The lateral femoral cutaneous nerve provides sensory innervation of the lateral thigh (figure 2 and figure 1 and figure 3).

The obturator nerve originates from the anterior divisions of the L2 to L4 nerves. It runs along the medial border of the psoas major muscle, passes through the obturator foramen, enters the medial thigh, and divides into anterior and posterior branches. The anterior branch is located between the adductor longus and brevis muscles, and the posterior branch is located between the adductor brevis and magnus muscles. The articular branch, which innervates a small area of the medial aspect of the knee, is derived from the posterior branch of the obturator nerve (figure 2 and figure 1 and figure 3).

The sciatic nerve is the largest nerve in the body; it is derived from the L4 through S3 spinal nerves and runs posteriorly down the thigh, continuing below the knee after dividing into the tibial and peroneal (common fibular) nerves. It supplies hip extensor muscles, knee flexor muscles, the motor function of the lower leg, and most of the sensory function of the lower extremity below the knee (figure 2 and figure 3).

Sensory innervation of the posterior thigh is provided by the posterior femoral cutaneous nerve (also called the posterior cutaneous nerve of the thigh), which is a branch of the sacral plexus (S1 to S3). It arises from the sacral nerve roots and runs through the greater sciatic foramen beneath the pyriformis muscle along with the sciatic nerve.

Sensory innervation of the foot includes one branch of the femoral nerve (ie, the saphenous nerve) and four branches of the sciatic nerve (ie, the superficial and deep peroneal, tibial, and sural nerves). The superficial and deep peroneal (fibular) nerves are branches of the peroneal (common fibular) nerve. The sural nerve is a branch of the tibial nerve (figure 2 and figure 5).

LUMBAR PLEXUS (PSOAS COMPARTMENT) BLOCK — A lumbar plexus block, also known as the psoas compartment block, is an advanced-level block and should only be performed by an experienced clinician. The psoas compartment block is usually used as a supplement to general anesthesia for lower extremity surgery and for management of postoperative pain. It may also be used as a primary regional anesthetic to avoid the sympathectomy and bilateral lower extremity block that would result from neuraxial anesthesia [1]. If anesthesia of the lower leg or posterior thigh is required for the procedure, the sacral nerve roots must be blocked separately, typically with a sciatic nerve block [2]. (See 'Sciatic nerve block' below.)

Positioning — The patient is placed in the lateral decubitus position, operative side up, with the operative leg flexed at the hip and knee. The iliac crests and the spinous processes of the lumbar spine are palpated and identified (figure 6).

Ultrasound-guided lumbar plexus block — This technique uses ultrasound to identify the transverse process and psoas muscle and to determine the depth of needle insertion [3]. The curved, low-frequency ultrasound transducer is placed longitudinally adjacent to the spine at the second to third lumbar (L2 to L3) level (picture 1) to image the vertebral transverse processes (image 1). Injection can be performed in this orientation. Alternatively, the transducer may be turned 90 degrees (picture 2) to obtain a transverse view of the psoas major muscle, which should appear lateral to the vertebral body and deep to the quadratus lumborum and erector spinae muscles.

The lumbar plexus lies deep within the posterior one-third of the psoas major muscle, though it is not usually visualized directly with ultrasound. The peritoneum can also be visualized and used as a landmark to avoid bowel puncture.

The needle is inserted at the cephalad edge (medial edge in transverse orientation) of the ultrasound transducer using an in-plane technique (picture 3). The full length of the needle should be seen as it approaches the target structure, which is the posterior third of the psoas major muscle. After negative aspiration, local anesthetic (LA) is injected in 5 mL increments, with gentle aspiration between injections. Because the psoas compartment is a large, loosely compacted space, a large volume of LA (eg, up to 0.5 mL/kg) is required. Spread of LA within the muscle should be observed.

Nerve stimulator-guided lumbar plexus block — There are two methods for psoas compartment block using a nerve stimulator (figure 6):

●A line is drawn from the iliac crest to the spinous process of the fourth lumbar vertebra (figure 6). An insulated needle is inserted on that line, 4 cm lateral to the midline.

Or

●A line (line 1 in the figure) is drawn between the two iliac crests (figure 6). A second line (line 3 in the figure) is drawn, connecting the lumbar spinous processes. A third line (line 2 in the figure) is drawn through the posterior superior iliac spine (PSIS) parallel to the second line. A final line (line 4) is drawn perpendicular to lines 2 and 3 at the level of L4 and divided into thirds. The needle is inserted 1 cm cephalad to line 4, at the junction of the lateral and middle thirds of line 4.

When using either method, the insulated needle is inserted perpendicular to the skin and advanced until quadriceps muscle stimulation is elicited or bony contact occurs. If bone (presumably the L4 transverse process) is encountered, the needle is withdrawn and directed caudad. The needle is then "walked off" the bone until quadriceps stimulation is obtained with current between 0.5 and 1 mA, although higher current levels can be used. Intraneural injection in this region can result in intrathecal injection (ie, spinal anesthesia). After negative aspiration for blood or cerebrospinal fluid (CSF), 20 to 30 mL of LA is injected in 5 mL increments, with gentle aspiration between injections.

Perineural catheter lumbar plexus block — Indwelling perineural catheters may be placed for continuous psoas compartment block for prolonged postoperative analgesia after hip, femur, or knee surgery. The technique for placing catheters is the same as for single-shot injections, using ultrasound guidance or nerve stimulation. An 18 or 19 gauge Tuohy needle is used rather than a block needle, with the bevel oriented laterally to direct the catheter toward the plexus. A 20 or 19 gauge single- or multi-orifice epidural catheter is threaded just far enough to allow the orifice (or orifices) to emerge beyond the needle tip. If resistance is encountered or pain occurs, the needle position should be reassessed.

Some anesthesiologists prefer to perform the nerve block via the catheter instead of via the needle, in order to confirm proper placement of the catheter tip. This is particularly important when a nerve stimulator technique is used. When ultrasound guidance is used, after removal of the needle, the location of the catheter can be confirmed by visualization of the catheter and spread of LA. We inject several mL of LA through the needle under ultrasound guidance to confirm placement and inject the rest of the bolus through the catheter while visualizing spread of LA.

The catheter is secured to the skin with a sterile dressing after applying a sterile surgical glue.

Lumbar plexus catheters are used only for inpatients, because of the risk for fall due to lower extremity motor block and the potential risk of neuraxial spread of LA. We administer an infusion of 0.1% bupivacaine at 5 to 12 mL per hour.

Side effects and complications — Because of the deep nature of this block, this is an advanced-level block that should only be performed by experienced clinicians. The incidence of complications of psoas compartment block is low overall, but is higher than with other peripheral nerve blocks [2]. The most common complication is epidural spread of LA, leading to bilateral block. Other complications include falls due to motor block [4], total spinal anesthesia, renal injury, and retroperitoneal hematoma; extensive retroperitoneal hematoma has been reported after lumbar plexus block [5,6].

In contrast with many other peripheral nerve blocks, the American Society of Regional Anesthesia and Pain Medicine (ASRA) recommends that anticoagulation guidelines for neuraxial blocks be followed when performing lumbar plexus block [7]. (See "Neuraxial anesthesia/analgesia techniques in the patient receiving anticoagulant or antiplatelet medication".)

FEMORAL NERVE BLOCK — Femoral nerve block is used to provide anesthesia or postoperative analgesia for surgery of the anterior thigh and knee (eg, anterior cruciate ligament repair, patella surgery, quadriceps tendon repair) and medial portions of the lower leg.

Relevant anatomy and techniques for femoral nerve block are discussed in detail separately. (See "Femoral nerve block procedure guide".)

FASCIA ILIACA (LATERAL FEMORAL CUTANEOUS) BLOCK — The fascia iliaca block is an alternative to the femoral nerve block and may more reliably block the lateral femoral cutaneous nerve than the femoral block (figure 1) [8]. It blocks the sensory innervation of the lateral thigh. This block does not depend on deposition of local anesthetic (LA) near an individual nerve; instead, it works by spread of the LA in a fascial plane. Therefore, this block is not performed with nerve stimulation. It can be done using ultrasound guidance or with an anatomic approach.

Positioning — The patient is placed in the supine position.

Ultrasound-guided fascial iliaca block — A line is drawn between the anterior superior iliac spine (ASIS) and pubic tubercle and divided into thirds (figure 7). An ultrasound probe is placed transversely to the leg at the junction between the middle and lateral thirds (picture 4) to identify the fascia lata, iliacus muscle, and fascia iliaca (image 2). The needle is introduced in-plane (picture 3) inferior to the inguinal ligament and guided beneath the fascia iliaca, and after negative aspiration, 30 mL of LA is injected in 5 mL increments, with gentle aspiration between injections. Spread of LA in medial and lateral directions under the fascia iliaca is evidence of correct needle placement.

A suprainguinal approach has also been described [9]. The technique is the same as above but is performed cephalad to the inguinal ligament instead.

Landmark-based fascia iliaca block — An alternative approach to this block relies upon superficial anatomy and loss of resistance with the block needle. The line between the ASIS and pubic tubercle is drawn and trisected. At the border between the lateral and middle thirds, a perpendicular line 2 cm in length is drawn caudally. A blunt needle is inserted and directed cephalad at a 45 degree angle. Two distinct "pops" should be felt as the needle passes through the fascia lata, and then the fascia iliaca. After negative aspiration, 30 mL of LA is injected in 5 mL increments, with gentle aspiration between injections.

Ultrasound guidance has been shown to more successfully achieve femoral and obturator motor block and sensory block of the medial thigh than an anatomic, loss-of-resistance technique [10]. There may be more than two fascial planes in the inguinal area [10,11]. Therefore, the two "pops" felt using the loss-of-resistance technique do not reliably correlate with the fascia lata and fascia iliaca; LA may thus be placed incorrectly using this technique.

Perineural catheter fascia iliaca block — Continuous infusion fascia iliaca block can be used as part of a multimodal pain control protocol after hip fracture. The technique for placing catheters is the same as for single-shot injections, using ultrasound guidance or an anatomic approach. Continuous infusion of 0.1% bupivacaine is administered at 8 to 10 mL/hour. (See 'Perineural catheter lumbar plexus block' above.)

OBTURATOR NERVE BLOCK — This block provides anesthesia of the medial distal thigh and can be used in combination with femoral, lateral femoral cutaneous, and sciatic blocks for procedures on the distal thigh and lower leg, and to prevent tourniquet pain during lower leg surgery (figure 3).

The obturator nerve is occasionally blocked to prevent stimulation of the adductor muscles of the hip, which may lead to complications during transurethral resection of lateral bladder wall lesions. The obturator nerve runs close to the lateral bladder wall, where direct stimulation with the resectoscope can result in adductor spasm, which can result in bladder perforation and other anatomic injuries.

Perineural catheter placement is not indicated with this block.

Positioning — The patient is placed in the supine position, with the leg externally rotated.

Ultrasound-guided obturator block — The ultrasound probe is placed in the inguinal crease (picture 5), and the femoral vein is identified. The probe is moved medially to visualize the pectineus and adductor longus muscles (image 3). The anterior branch of the obturator nerve is a hyperechoic structure found between the adductor longus (superficial) and brevis muscles. The posterior branch is a hyperechoic structure found between the adductor brevis (superficial) and magnus muscles. The needle is inserted in-plane or out-of-plane (picture 3) and is directed to the two intermuscular fascial planes described above. After negative aspiration, 5 to 10 mL of local anesthetic (LA) is injected into each of the intermuscular fascial planes while observing LA surrounding the hyperechoic nerve structures and distending the planes between the muscles.

Nerve stimulator-guided obturator block — The femoral artery is palpated and the tendon of the adductor muscle is identified at the pubic tubercle. This tendon is accentuated when the leg is externally rotated; it is the only tendon inserting on the pubic tubercle in the groin and medial thigh. In the inguinal crease, a line is drawn medially from the femoral artery to the adductor tendon. The insulated needle is inserted at the midpoint of this line, aimed cephalad at a 45 degree angle. The needle is advanced until stimulation of the adductor muscle is obtained (ie, posteromedial aspect of the thigh). After negative aspiration, 5 to 10 mL of LA is injected in 5 mL increments, with gentle aspiration between injections.

SAPHENOUS NERVE AND ADDUCTOR CANAL BLOCKS — The saphenous nerve is the terminal sensory branch of the femoral nerve. The saphenous nerve block is useful for ambulatory surgeries of the superficial, medial lower leg and provides analgesia of the medial ankle and foot. It can be blocked at the level of the tibial tuberosity below the knee.

The saphenous nerve can be blocked above the knee using the adductor canal block; adductor canal block is often used for analgesia after knee surgery. The saphenous nerve can also be blocked at the ankle as part of an ankle block. (See 'Ankle block' below.)

Adductor canal block — The saphenous nerve is blocked at the level of the mid-thigh with the adductor canal block (ACB) using ultrasound guidance. ACB technique is described in detail separately. (See "Adductor canal block procedure guide".)

Saphenous nerve block — The saphenous nerve can be blocked below the knee for surgery of the lower leg and ankle using an anatomic approach. Perineural catheters are not used for saphenous nerve block below the knee.

●Positioning – The patient is positioned supine, with the leg straight.

●Anatomic approach – Saphenous nerve block can be performed at the level of the tibial tuberosity, which is marked (figure 8). A subcutaneous wheal with 5 to 10 mL of LA is injected posterior to the medial tibial condyle, or, alternatively, LA can be injected around the saphenous vein if it is easily visualized [12].

Side effects and complications — The degree to which adductor canal blocks preserve the function of the quadriceps muscle, and therefore the ability to safely ambulate postoperatively, is controversial and is discussed separately. (See "Adductor canal block procedure guide", section on 'Motor block'.)

SCIATIC NERVE BLOCK — The sciatic nerve block provides complete anesthesia of the leg below the knee, with the exception of a strip of medial skin innervated by the saphenous nerve (figure 3). Combined with femoral or saphenous nerve block, it provides analgesia for surgery of the distal anterior thigh; anterior knee; and lateral calf, ankle, or foot. The sciatic nerve block can be performed using either an anterior or a posterior approach, with similar success rates for surgery below the knee [13].

The posterior femoral cutaneous nerve (PFCN) may be blocked along with the sciatic nerve when the sciatic block is performed very proximally (eg, posterior approach or high anterior approach) [13,14]. PFCN block is required for surgery of the posterior thigh and knee and may provide analgesia for a thigh tourniquet. However, the need for this block for tourniquet pain is disputed [15].

The technique for sciatic nerve block is discussed in detail separately. (See "Sciatic blocks procedure guide".)

POPLITEAL BLOCK — The popliteal block anesthetizes the sciatic nerve in the popliteal fossa prior to its division into the tibial and the common fibular (peroneal) nerves, and can be used for anesthesia and analgesia for posterior knee, lateral ankle, and foot surgery (figure 2).

Relevant anatomy and techniques for popliteal nerve blocks are discussed separately. (See "Popliteal block procedure guide".)

INFILTRATION OF LOCAL ANESTHETIC BETWEEN THE POPLITEAL ARTERY AND CAPSULE OF THE KNEE (IPACK) BLOCK — The IPACK block is performed under ultrasound guidance to provide pain relief to the posterior aspect of the knee, without affecting motor function. The IPACK block targets the sensory articular branches originating from the sciatic, tibial, and common peroneal nerves, and the posterior division of the obturator nerve. It involves infiltration of local anesthetic (LA) between the posterior aspect of the femur and popliteal artery. The IPACK block is used for postoperative analgesia after total knee arthroplasty, anterior cruciate ligament repair, and procedures that involve the posterior capsule of the knee [16-18].

Positioning — The patient is placed in either supine or prone position with the knee slightly flexed or with the leg placed on a leg support.

Ultrasound-guided IPACK block — Either a posterior or a posteromedial ultrasound approach to IPACK block is used.

A low frequency curvilinear ultrasound transducer is placed transversely in the popliteal fossa crease, or at the posteromedial knee approximately 2 cm proximal to the proximal border of the patella. The popliteal artery and the distal femur are visualized. Color Doppler can be used to confirm the popliteal artery. If the femoral condyles are visualized, the transducer is moved proximally until the flat posterior surface of the distal shaft of the femur appears. The tibial and common peroneal nerves may be identified.

An 80 to 100 mm needle is inserted in-plane from medial to lateral, parallel to the posterior femur, in the space between the popliteal artery and the shaft of the femur. The needle is advanced until the tip is approximately 2 cm beyond the popliteal artery.

After negative aspiration, 1 to 2 mL of LA may be injected for hydrodissection to confirm location of the needle tip just posterior to the femur and in the space between femur and popliteal artery. A total of 20 mL of LA is then infiltrated in the tissue plane; LA is injected as the needle is withdrawn, in 3 to 5 mL increments, with gentle aspiration between injections and distributed evenly between the initial needle tip location (2 cm lateral to the popliteal artery) and the posteromedial border of the femur. The optimal dose for IPACK block has not been determined. A range of 10 to 30 mL has been used [19]; the authors use 20 mL of LA for this block.

ANKLE BLOCK — The ankle block consists of separate blocks of five nerves: four branches of the sciatic nerve (ie, superficial and deep peroneal [fibular] nerves, tibial nerve, and sural nerve) and one cutaneous branch of the femoral nerve (saphenous nerve) (figure 9 and figure 5). The ankle block is used for surgery on the foot and toes and is a purely sensory block (figure 3).

We perform ankle blocks with a landmark-based, anatomic technique. Ultrasound guidance can be used for the deep peroneal, tibial, and sural nerve blocks. In the experience of some other clinicians, ultrasound-guided ankle block may be more successful for nondiabetic patients than the use of a landmark-based technique.

Positioning — The patient is positioned supine, with the foot elevated and supported on blankets or pillows, and the ankle is rotated as necessary for needle placement.

Block of individual nerves

●Deep peroneal nerve block – The deep peroneal (fibular) nerve innervates the first web space of the foot and is blocked with an injection in the dorsum of the foot at the ankle (figure 9 and figure 5). This block can be performed using anatomic landmarks or with ultrasound guidance.

•Anatomic approach – For deep peroneal block, the dorsalis pedis artery is palpated between the flexor hallucis longus and extensor digitorum longus tendons, which are identified by having the patient flex the great toe. The nerve lies just lateral to the artery. At the mid-tarsal portion of the foot, the needle is inserted just lateral to the artery and advanced until bone is encountered. As the needle is withdrawn, 2 to 3 mL of local anesthetic (LA) is injected.

•Ultrasound guidance – The ultrasound probe is placed in a transverse orientation on the dorsum of the foot at the level of the extensor retinaculum. The nerve should appear lateral to the anterior tibial artery, lying on the tibia. The flexor hallucis longus tendon adjacent to the neurovascular structures may be mistaken for the nerve. Flexion and extension of the great toe moves the tendon, thereby differentiating it from the nerve. The needle is inserted in-plane (picture 3); the tip is identified near the nerve; and after gentle aspiration, 2 to 3 mL of LA is injected.

●Superficial peroneal nerve block – The superficial peroneal (fibular) nerve innervates the dorsum of the foot and is blocked by subcutaneous infiltration of LA (figure 9 and figure 5). The needle is inserted at the injection site for deep peroneal nerve block as above. A total of 5 to 10 mL of LA is injected subcutaneously over the dorsum of the foot medially and then laterally from the site of needle insertion to the level of the malleoli.

●Tibial nerve block – The distal tibial nerve provides sensation to the calcaneus and plantar surface (sole) of the foot and is blocked at the level of the medial malleolus (figure 9 and figure 5). This block can be performed using anatomic landmarks or with ultrasound guidance:

•Anatomic approach – The posterior tibial artery is palpated behind the medial malleolus. The needle is inserted posterior to the artery, aimed towards the malleolus at a 45-degree angle, and advanced until contact with bone. As the needle is withdrawn, 2 to 3 mL of LA is injected. An additional 1 to 2 mL of LA is injected using a fan technique, medially and laterally, to increase the success rate of the block.

•Ultrasound guidance – The ultrasound transducer is placed in a transverse orientation posterior to the medial malleolus, and the nerve is identified posterior to the posterior tibial artery. The needle is inserted either in-plane or out-of-plane; the tip is positioned adjacent to the nerve; and after negative aspiration, 3 to 5 mL of LA is injected. Circumferential spread of the LA around the nerve is predictive of a successful block [20].

●Sural nerve block – The sural nerve innervates the lateral ankle and foot, as well as the fifth toe. It runs within the subcutaneous tissues behind the lateral malleolus (figure 9 and figure 5). Sural nerve block is usually performed using anatomic landmarks but can be performed with ultrasound guidance:

•Anatomic approach – The nerve is blocked by injecting 2 to 3 mL of LA behind the lateral malleolus as a subcutaneous wheal.

•Ultrasound guidance – The ultrasound probe is held in a transverse orientation just proximal to the lateral malleolus of the ankle. The nerve appears as a small, hyperechoic structure next to the lesser saphenous vein. Five mL of LA is injected around the vein; the LA should be observed spreading completely around the lesser saphenous vein.

●Saphenous nerve block – The saphenous nerve innervates the medial aspect of the ankle and foot. It is blocked at the ankle using anatomic landmarks (figure 9). The needle is inserted medial and superior to the medial malleolus and directed posteriorly towards the Achilles tendon. After negative aspiration, a wheal of 3 to 5 mL of LA is injected around the great saphenous vein.

DIGITAL NERVE BLOCK (TOE) — Digital nerve block is discussed in detail elsewhere. (See "Digital nerve block".)

DRUG CHOICES — Local anesthetics (LAs) are chosen according to the goal of the block (surgical anesthesia or analgesia) and the desired duration of the effect of the block (table 1). LAs and adjuvant drugs used for peripheral nerve blocks are discussed separately. (See "Overview of peripheral nerve blocks", section on 'Drugs'.)

Our choices for LA for lower extremity blocks are as follows:

●Postoperative analgesia – 0.25 to 0.5% bupivacaine or 0.5% ropivacaine

●Surgical anesthesia – 2% lidocaine, 1.5% mepivacaine, 0.5% bupivacaine, 0.5% ropivacaine

●Perineural catheter infusion:

•Inpatient – 0.1% bupivacaine, 5 to 10 mL/hour

•Ambulatory surgery – 0.2% ropivacaine, 5 to 10 mL/hour

INTRAVENOUS REGIONAL ANESTHESIA — Intravenous regional anesthesia may be performed for surgical procedures on the foot and ankle, and is discussed separately. (See "Upper extremity nerve blocks: Techniques", section on 'Intravenous regional anesthesia (Bier block)'.)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Local and regional anesthesia" and "Society guideline links: Local anesthetic systemic toxicity".)

SUMMARY AND RECOMMENDATIONS

●Lumbar plexus block – The lumbar plexus block, also known as the psoas compartment block, is a deep, advanced-level block that is usually used to supplement general anesthesia for lower extremity surgery and for management of postoperative pain. It may also be used as a primary regional anesthetic to avoid the sympathectomy and bilateral lower extremity block that would result from neuraxial anesthesia. If anesthesia of the lower leg or posterior thigh is required, the sacral nerve roots must be blocked separately, typically with a sciatic nerve block. (See 'Lumbar plexus (psoas compartment) block' above.)

●Sciatic block – Proximal sciatic nerve block achieves anesthesia of the leg below the knee, with the exception of a strip of medial skin innervated by the saphenous nerve, as well as the posterior thigh and knee. Combined with femoral or saphenous nerve block, it provides analgesia for surgery of the distal thigh, knee, calf, ankle, or foot. It will also provide analgesia when a thigh tourniquet is required, if the posterior femoral cutaneous nerve is blocked. (See "Sciatic blocks procedure guide".)

●Popliteal block – The popliteal nerve block is a sciatic nerve block that is performed in the popliteal fossa to achieve anesthesia below the knee. (See 'Popliteal block' above and "Popliteal block procedure guide".)

●Femoral block – The femoral nerve block is used to provide anesthesia or postoperative analgesia for surgery on the anterior thigh and knee. (See "Femoral nerve block procedure guide".)

●Fascia iliaca block – The fascia iliaca block is an alternative to the femoral nerve block and may more reliably block the lateral femoral cutaneous nerve to achieve analgesia of the lateral thigh. (See 'Fascia iliaca (lateral femoral cutaneous) block' above.)

●Obturator block – The obturator nerve block provides anesthesia of the medial distal thigh and can be used in combination with femoral, lateral femoral cutaneous, and sciatic blocks for procedures on the distal thigh and lower leg, as well as to prevent tourniquet pain during lower leg surgery. This block is occasionally performed to prevent stimulation of the adductor muscles of the hip in order to avoid complications during transurethral resection of lateral bladder wall lesions. (See 'Obturator nerve block' above.)

●Adductor canal and distal saphenous nerve blocks – The saphenous nerve can be blocked at the level of the tibial tuberosity below the knee, or above the knee using the adductor canal block. The saphenous nerve block is useful for surgeries of the superficial, medial lower leg and provides analgesia of the medial ankle and foot. (See 'Saphenous nerve and adductor canal blocks' above and "Adductor canal block procedure guide".)

●Infiltration of local anesthetic between the popliteal artery and capsule of the knee (IPACK) block – This block involves injection of local anesthetic (LA) between the posterior shaft of the femur and popliteal artery. It provides analgesia for the posterior aspect of the knee, and is used for analgesia after total knee arthroplasty, anterior cruciate ligament repair, and procedures that involve the posterior capsule of the knee. (See 'Infiltration of local anesthetic between the popliteal artery and capsule of the knee (IPACK) block' above.)

●Ankle block – The ankle block is a purely sensory block that consists of separate blocks of five nerves: the superficial and deep peroneal, tibial, sural, and saphenous nerves. It provides anesthesia of the entire foot for procedures on the foot and toes. (See 'Ankle block' above.)

●Continuous block – Perineural catheters may be placed for continuous infusion of local anesthetic (LA) for postoperative pain using lumbar plexus, femoral nerve, fascia iliaca, sciatic, popliteal, and adductor canal blocks. (See 'Perineural catheter lumbar plexus block' above and 'Perineural catheter fascia iliaca block' above and "Femoral nerve block procedure guide", section on 'Continuous femoral nerve block'.)