Figure 36–1. Relevant anatomy for the 3-in-1 block on sagittal T2-weighted MRI. (A, Anterior; P, posterior; IFV, left femoral vein; UB, urinary bladder.)

Figure 36–2. MRI image after administration of local anesthetic on sagittal T2-weighted MRI. (A, Anterior; P, posterior; IFV, left femoral vein; LA, local anesthetic; UB, urinary bladder.)

Indications & Contraindications

The following are indications for using 3-in-l block:

The following are contraindications to 3-in-l nerve block:

Functional Anatomy

The femoral, lateral femoral cutaneous, and obturator nerves are formed by the ventral roots of the lumbar plexus from the 12th thoracic nerve (T12) to the 4th lumbar nerve (L4). The femoral nerve (L1/2-L4) is the largest of the three nerves from the lumbar plexus, and its position cephalad to the inguinal ligament is inside the greater psoas muscle and more distal between the greater psoas and the iliac muscles (Figure 36-3). The femoral nerve enters the thigh at the level of the inguinal ligament lateral to the femoral artery, where the iliopectineal arch (a deep layer of the inguinal ligament) and the fascia iliaca separate the two structures from each other (Figure 36-4). The femoral nerve divides slightly distal to the inguinal ligament in several branches, which is the rationale for the nerve block needle to be inserted close to the distal ligament when performing the 3-in-1 block. The femoral nerve supplies motor branches to the quadriceps femoris, sartorius, and pectineus muscles, and its sensory branch (saphenous nerve) innervates the anterior-medial side of the lower leg down to the medial ankle (Figures 36–5 and 36–6).

        Both the obturator and the lateral femoral cutaneous nerves divide at variable levels from the femoral nerve. The obturator nerve enters through the craniomedial part of the obturator foramen on the medial side of the thigh and divides in an anterior branch, which lies between the adductor brevis, obturator externus, adductor longus, and pectineus muscles, and a posterior branch, which pierces the obturator externus muscle and lies above the adductor magnus and brevis muscles. The obturator nerve supplies motor branches to all the mentioned muscles and also to the gracilis muscle. An accessory obturator nerve may divide from the lumbar plexus at the L3/4 level and supply a muscular branch of the pectineus muscle, then enter the hip joint.

Figure 36–3. Anatomy of the inguinal region.

The lateral femoral cutaneous nerve enters the thigh slightly medial to the anterior superior iliac spine and is a purely sensory nerve.

Figure 36–4. Anatomy of the inguinal region. Shown are the femoral artery (A) and vein (V), fascia lata (1), and femoral nerve (2).

Figure 36–5. Sensory surface innervation of the lower extremity.

Distribution of Anesthesia

Figure 36-5 illustrates the anesthetic distribution of the femoral, lateral femoral cutaneous, and obturator nerves. It is important to notice that the sensory area of the anterior branch of the obturator nerve is inconsistent at the medial side of the thigh and that the posterior branch of the obturator nerve innervates a sensory area at the popliteal fold, which is never anesthetized by a 3-in-l block. Also important to notice is that the most proximal parts of the thigh are sensory-innervated by nerves from the abdominal wall (femoral branch of the genitofemoral nerve) and therefore also not anesthetized by a 3-in-l block. Innervation of the lower-extremity osteotomes are illustrated in Figure 36-6.

Landmarks

The landmarks for the 3-in-l block are the anterior superior iliac spine, which is usually easy to palpate, and the inguinal ligament, an abdominal fascial layer fixed at the anterior superior iliac spine (Figure 36-7). In obese patients, identification of the inguinal ligament may be difficult. Below the inguinal ligament (or the femoral crease), the pulsation of the femoral artery is detectable, and the needle insertion site for the 3-in-1 block lies in the area between the inguinal ligament and lateral to the femoral artery (1–2 cm distal the ligament). In the inguinal area, it is useful to think of the mnemonic term NAVEL to remember the position of the femoral nerve and vascular components. From lateral to medial: N = femoral nerve; A = femoral artery; V = femoral nerve; E = empty space; L = lacunar ligament.

Figure 36–6. Osteotomal innervation of the lower extremity.

Equipment

The following items are used for 3-in-l blockade:

Techniques

Winnie described the paresthesia technique of the 3-in-l block in 1973. Currently, only two techniques are used, the nerve stimulator and the ultrasonographic guidance techniques.

Nerve Stimulator-Guided Technique

The position of the patient is supine with both legs extended and the leg to be blocked with 15–30 degrees lateral rotation. After standard preparation (monitoring, intravenous access, sterile preparation of the needle insertion area, and skin anesthesia), the nerve stimulation needle is connected to a nerve stimulator. The needle insertion site is 1–2 cm distal to the inguinal ligament with an angle of30–45 degrees and a cephalad direction (Figure 36-8). On the way to the femoral nerve, a twofold resistance loss can often be appreciated as the needle pierces the fascia lata and the fascia iliaca. Usually, the nerve is at a depth of 12 ± 4 mm. Once a distal motor response of the quadriceps femoris muscle (patella twitch) at a current intensity of 0.3 mA (0.1 msec) or less is observed and a negative aspiration test is obtained, the local anesthetic may be inj ected according to Winnie’s “immobile needle” technique.¹⁰

Figure 36–7. Landmarks for the 3-in-1 block. 1, Anterior superior iliac spine; 2, pubic bone; 3, femoral crease. Inguinal ligament stretches between 1 and 2. Femoral vein, artery, and nerve are represented as blue, red, and yellow lines, respectively.

Figure 36–8. Nerve stimulator-guided 3-in-1 block technique.

Ultrasound-Guided Technique

Significantly faster sensory onset times and improved quality of blocks can be obtained with ultrasound guided technique when compared with the conventional nerve stimulator technique.¹¹ In addition, significantly reduced amount of local anesthetics can be used, illustrating that the quality of peripheral nerve blockade can be influenced by direct visualization of the spread of local anesthetic.¹² This can be particularly important in elderly patients and those with cardiovascular compromise, as well as in patients who require combined nerve blocks.¹³

        Because of the superficial position of the femoral nerve, a high-frequency linear ultrasonographic probe can be used for the 3-in-l block (Figure 36-9). Inguinal vessels are easily visualized (Figure 36-10); the femoral nerve can be imaged slightly distal to the inguinal ligament in a cross-sectional view (Figure 36-10) in which a 4-cm needle with a blunt tip is placed below the iliopectineal arch, and approximately 5 mL (for a single femoral nerve block) or 20 mL (for a 3-in-1 block ) of local anesthetic is injected. It is not necessary to visualize the lateral femoral cutaneous and obturator nerves by ultrasonography. Both nerves are small, and the anterior branch of the obturator nerve is particularly difficult to visualize by ultrasound because of its position between the adductor brevis and longus muscles. Similar technique can be used to insert a catheter for continuous blockade (Figure 36-11 ).

Figure 36–9. Ultrasound-guided 3-in-l blocktechnique with the linear probe relative to the stimulating needle to achieve a crosssectional view.

Figure 36–10. Cross-sectional ultrasonographic view of the inguinal region. Femoral vein, artery, and nerve are labeled as VAN, respectively.

Volume & Choice of Local Anesthetics

Twenty milliliters is the adequate volume of local anesthetic for the 3-in-l block, although much larger volumes are described in the literature. The appropriate technique significantly influences the success of the block.¹² A single femoral nerve block can be performed with as little as 5–10 mL local anesthesia.

Figure 36–11. Ultrasound-guided placement of a 3-in-1 catheter.

Related posts:

Regional Anesthesia in the Patient with Preexisting Neurologic Disease. The History of Local Anesthesia. Stimulating Catheters. Diagnosis & Management of Intraspinal, Epidural, & Peripheral Nerve Hematoma. Histology of Peripheral Nerves. Supraclavicular Brachial Plexus Block.

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