Version May 2024
INTRODUCTION — Quadratus lumborum (QL) blocks are fascial plane blocks performed by injecting local anesthetic (LA) in planes defined by the thoracolumbar fascia around the QL muscle. QL blocks provide analgesia for abdominal and hip surgery.
This topic will discuss anatomy, ultrasound imaging, and injection techniques for the three most common approaches to QL blocks. General considerations common to all peripheral nerve blocks, including patient preparation and monitoring, use of aseptic technique, drug choices, contraindications, and complications are discussed separately. (See "Overview of peripheral nerve blocks".)
Ultrasound imaging for peripheral nerve blocks is also discussed in detail separately. (See "Ultrasound for peripheral nerve blocks".)
ANATOMY
●Muscles, fascia, and planes – The QL muscle is a posterior abdominal wall muscle. It extends between the posteromedial iliac crest, the medial border of the 12th rib, and transverse processes of L1 to L4 (figure 1). The lateral border of the QL muscle runs from medial to lateral in a cranial to caudal direction. The psoas muscle lies medial and anterior to the QL muscle.
The QL muscle is surrounded by the thoracolumbar fascia, which is made up of multiple layers of fascia and aponeuroses. The thoracolumbar fascia has three layers (figure 2) [1]:
•The anterior thoracolumbar fascia encases the anterior aspect of the QL and psoas muscles and continues laterally as the transversalis fascia.
•The middle thoracolumbar fascia encases the posterior aspect of the QL muscle.
•The posterior thoracolumbar fascial layer surrounds the erector spinae group of muscles.
Where the QL muscle passes beneath the diaphragm, the anterior thoracolumbar fascia divides into two layers; one continues as the endothoracic fascia, and the other joins the diaphragm as the arcuate ligament. Caudally, the anterior thoracolumbar fascia continues as the fascia iliaca [2-5]. The continuity of these fascial planes in the abdomen provides a potential path for local anesthetic (LA) to spread from the abdomen into the thorax and paravertebral space. (See 'Clinical anatomic correlation' below.)
●Nerves – Nerves in the vicinity of QL block injection include the following:
•The lumbar plexus forms from the T12 to L4 nerve roots, which emerge from the intervertebral foramina and enter the body of the psoas muscle in which the plexus forms anterior to the lumbar transverse processes. The branches of the lumbar plexus then emerge from the psoas muscle at various locations.
•The iliohypogastric and ilioinguinal nerves (L1, possibly T12, L2 and L3) run posterior to the psoas muscle and then lie between the ventral surface of the QL muscle and the transversalis fascia (figure 1) [6,7].
•The lateral femoral cutaneous, obturator, and femoral nerves run behind or through the psoas muscle, emerging from its lateral border more caudally than the ilioinguinal and iliohypogastric nerves to run between the QL muscle and the transversalis fascia.
•The dorsal rami of spinal nerves run posterior to the QL muscle and then pierce the erector spinae muscles.
●Blood vessels – Branches of the lumbar arteries may run laterally from the aorta posterior to the QL muscle, though the muscle, or anterior to it [8].
CLINICAL ANATOMIC CORRELATION
●Clinical uses – QL blocks are used for postoperative analgesia; they do not reliably provide complete anesthesia for surgery. They are used for analgesia after hip and abdominal surgery, including cesarean delivery [9-12]. In contrast with transversus abdominis plane block, which is commonly used for analgesia after abdominal surgery, QL blocks may provide visceral as well as somatic analgesia.
Anterior QL blocks are more appropriate for analgesia after hip surgery, possibly due to spread of local anesthetic (LA) to the lumbar plexus, as described below. Posterior and lateral QL blocks are used for abdominal surgery.
●Mechanism of action – The mechanism of action of QL blocks is uncertain, with two likely explanations, as follows [13]:
•LA may spread through the diaphragm to reach the paravertebral space via the endothoracic pathway. This would result in blockade of somatic (cutaneous) nerves of the abdominal wall and lower thoracic sympathetic trunk. This latter effect could potentially explain the visceral analgesia demonstrated with the QL block [13].
•LA may spread directly to the lumbar plexus and its branches, and to the dorsal rami of spinal nerves (see 'Anatomy' above). This is most likely to be the case with an anterior QL block.
TERMINOLOGY — Three types of QL blocks have been described, each of which requires a different needle approach (picture 1). A 2021 consensus on nomenclature has defined a standard by which the QL blocks that have previously been called QL 1, 2 and 3 are now referred to as lateral, posterior, and anterior QL blocks, respectively, named for the relationship of the needle target to the QL muscle [14].
●Lateral QL (QL 1, posterior transversus abdominis plane block) – LA injected lateral to the QL muscle, between the aponeuroses of internal oblique and transversus abdominis muscles.
●Posterior QL (QL 2) – LA injected posterior to the QL muscle, in the plane between the QL and either the latissimus dorsi or erector spinae muscles.
●Anterior QL (QL 3, transmuscular QL) – Needle inserted through the QL muscle, and LA injected medial to the QL muscle, between the QL and psoas major muscles.
Variations of the anterior QL (eg, suprailiac and subcostal approaches) have been described, and are beyond the scope of this topic [15,16].
SINGLE-INJECTION QL BLOCK — QL blocks are performed using ultrasound guidance.
Patient positioning — Patients may be positioned lateral, supine with a lateral tilt, sitting, or prone, depending on the type of block, patient mobility, and clinician preference. For anterior and posterior QL blocks patients can be positioned lateral, prone, or sitting, to allow needle insertion medial to the edge of the ultrasound transducer (picture 1). For lateral QL blocks, we position patients supine, lateral, or supine with a lateral tilt.
Ultrasound equipment — Select a curvilinear low frequency (2 to 6 MHz) transducer, with the depth set appropriately for the patient's body habitus, typically at 6 to 10 cm.
Ultrasound imaging
●Place the transducer in a transverse orientation at the posterolateral abdominal wall between the iliac crest and the costal margin (L2 to L4 level).
●Move the transducer posteriorly, visualizing the following (picture 1):
•The QL muscle, which appears hypoechoic relative to the psoas muscle
•Taper of the external oblique (EO), internal oblique (IO), and transversus abdominis (TA) muscles to form their aponeuroses posterolateral to the QL muscle
•The psoas muscle, anteromedial to the QL
•A lumbar transverse process, which appears hyperechoic and curved
•The erector spinae muscle, medial to the transverse process
Tips:
●The "shamrock sign," can be helpful for identifying structures. The psoas, QL, and erector spinae muscles represent the leaves and the transverse process represents the stem of the shamrock.
●For a lateral or posterior approach, visualize the aponeuroses of the EO, IO and TA muscles along with the QL muscle (picture 1).
●Using a color Doppler with the final view prior to needle insertion may be beneficial to observe for any blood vessels that may be in the needle trajectory.
PERFORMING THE BLOCK — Single-injection approaches are performed with 20 to 22 gauge, 80 to 120 mm block needles. Place the needle tip as follows for the three types of QL block.
Anterior QL block
●Insert the needle in-plane to the transducer in a posterior (medial) to anterior (lateral) trajectory (picture 1).
●Advance the needle through the QL muscle.
●Place the needle tip within the anterior thoracolumbar fascia, medial to the QL muscle and between the QL and psoas muscles.
Note: Avoid advancing the needle past the thoracolumbar fascia into the retroperitoneal space to prevent bleeding or organ injury.
●After negative aspiration, inject 2 mL of saline to confirm correct needle tip placement.
●After another negative aspiration, inject 20 to 30 mL of local anesthetic (LA) in 5 mL increments, with gentle aspiration between injections. Visualize spread of LA, which should separate the QL and psoas muscles.
Lateral QL block
●Insert the needle in-plane to the transducer with an anterior (lateral) to posterior (medial) trajectory (picture 1).
●Advance the needle through the aponeurosis of the external oblique (EO), internal oblique (IO), and transversus abdominis (TA) muscle to place the tip at the lateral margin of the QL muscle, within the middle thoracolumbar fascia.
Note: Avoid advancing the needle past the thoracolumbar fascia into the retroperitoneal space, to prevent bleeding or organ injury.
●After negative aspiration, inject 2 mL of saline to confirm correct needle tip placement.
●After another negative aspiration, inject 20 to 30 mL of LA in 5 mL increments, with gentle aspiration between injections. Visualize spread of LA, which will displace the QL muscle deeper.
Posterior QL block
●Insert the needle in-plane to the transducer with an anterior (lateral) to posterior (medial) trajectory (picture 1 and movie 1).
●Place the needle tip posterior to the QL muscle, within the middle thoracolumbar fascia, between the QL and the latissimus dorsi or erector spinae muscles, depending on how medially the block is placed.
●After negative aspiration, inject 2 mL of saline to confirm correct needle tip placement.
●After another negative aspiration, inject 20 to 30 mL of LA in 5 mL increments, with gentle aspiration between injections. Visualize spread of LA, which will displace the QL muscle deeper.
DRUG CHOICE AND DOSING
●Local anesthetics (LAs) – Long-acting LAs (eg, ropivacaine or levobupivacaine [outside the United States] 0.2 to 0.375%, or bupivacaine 0.25%) are used for QL blocks [17-19]. The total LA dose injected should be within the maximum allowable dose, including the dose used for the QL block and any other injections (eg, wound infiltration, other nerve blocks) (table 1). QL blocks can result in local anesthetic toxicity (LAST) due to the vascularity of the fascial planes and the high volumes of LA used. (See "Local anesthetic systemic toxicity".)
Liposomal bupivacaine has been used in a range of regional anesthetic techniques in an effort to prolong the duration of single-shot approaches. However, the evidence that a clinically important and cost-effective benefit to using liposomal bupivacaine is not convincing. (See "Clinical use of local anesthetics in anesthesia", section on 'Liposomal bupivacaine'.)
●Adjuvants – Although perineural adjuvants such as dexamethasone and dexmedetomidine have been shown to increase the duration of upper and lower extremity peripheral nerve blocks by several hours, there remains unclear evidence of benefit for QL blocks. The contributors do not routinely add adjuvants to local anesthetics for QL blocks. (See "Overview of peripheral nerve blocks", section on 'Adjuvants'.)
CONTINUOUS BLOCK — QL block catheters can provide prolonged analgesia beyond the duration of single-shot techniques.
●Catheter placement technique – Strict sterile technique must be used (including a sterile ultrasound transducer cover, full operating room table cover) for continuous block. The technique for continuous block is similar to a single-injection block. An 18 to 20 gauge Tuohy needle is used instead of a block needle. A single end hole or multiorifice catheter is inserted through the Tuohy needle, 3 to 6 cm beyond the needle tip.
We inject 2 to 3 mL of LA through the needle under ultrasound guidance to confirm correct placement of the needle tip, visualize insertion of the catheter, and then inject the rest of the bolus through the catheter in divided doses while visualizing spread of LA. Tunneling is generally not required, though the catheter should be well secured to the skin and covered with a clear sterile dressing.
●Infusion drug dose – After injecting a bolus of LA as described above for single-injection block, we start an infusion of 0.1 to 0.2% levobupivacaine or ropivacaine, or 0.125% bupivacaine, at 5 to 10 mL/hour. If available, programmed intermittent bolus of the same solution can be used at 8 mL every hour to 15 mL every three hours.
SIDE EFFECTS AND COMPLICATIONS — Side effects and complications from QL blocks are rare. They may be related to local anesthetic (LA) effects or needle trauma.
●QL block may result in LA distribution to the lumbar plexus and prolonged motor blockade, potentially delaying postoperative mobilization. Lower-limb weakness has been reported after both anterior and lateral QL blocks [20,21].
●Hypotension has been reported, which may be related to spread of LA to the paravertebral space resulting in presumed sympathetic blockade [22].
●Because of the doses used and the vascularity of the area, local anesthetic systemic toxicity (LAST) is a potential risk [23,24], although peak concentrations of LA are lower after QL blocks than transversus abdominis plane blocks [25].
●There is a risk of bleeding or organ injury if the needle is advanced beyond the thoracolumbar fascia into the retroperitoneal space, particularly with anterior or lateral QL blocks. Peritoneal puncture is unlikely with posterior QL block since the target is anterior to the QL muscle (figure 2). If a high (subcostal) anterior block is performed, there is risk of puncturing the pleura or kidney [13,26].
●The risks of bleeding complications for QL blocks overall and the relative risks for the different types of QL blocks have yet to be determined. The posterior and lateral QL block approaches use a fascial plane that may contain the abdominal branches of lumbar arteries. (See 'Anatomy' above.)
Whether to avoid QL blocks in patients who are anticoagulated or who have bleeding disorders is controversial. We consider anticoagulation a relative contraindication to QL block due to the deep and noncompressible location of the block targets, particularly for anterior QL block. Deep blocks in non-compressible locations may increase the risk of hematoma. As a result, guidelines from the American Society of Regional Anesthesia and Pain Medicine recommend following the same principles in anticoagulated patients for deep blocks that would be used for neuraxial anesthesia [27]. These guidelines are discussed in detail separately. (See "Neuraxial anesthesia/analgesia techniques in the patient receiving anticoagulant or antiplatelet medication".)
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".)
SUMMARY AND RECOMMENDATIONS
●Anatomy – The quadratus lumborum (QL) block is a fascial plane block that involves injection of high-volume local anesthetic (LA) anterior, lateral, or posterior to the QL muscle to provide analgesia to the abdomen and hips (figure 1 and figure 2). (See 'Anatomy' above.)
●Terminology – We use nomenclature by which the QL blocks that have previously been called QL 1, 2, and 3 are referred to as lateral, posterior, and anterior QL blocks, respectively, named for the relationship of the needle target to the QL muscle. (See 'Terminology' above.)
●Single-injection QL block – QL blocks are performed with ultrasound guidance as follows, with further explanation above. (See 'Single-injection QL block' above.)
•Use a curvilinear low frequency (2 to 6 MHz) ultrasound transducer, and a 20 to22 gauge, 80 to 120 mm block needle.
•Place the transducer in a transverse orientation at the posterolateral abdominal wall between the iliac crest and the costal margin (picture 1).
•Needle placement (figure 2 and picture 1):
-For anterior QL block, place the needle through the QL muscle, with the tip medial to the QL muscle, between the QL and psoas major muscles. (See 'Anterior QL block' above.)
-For lateral QL block, place the needle tip lateral to the QL muscle, between the aponeuroses of internal oblique and transversus abdominis muscles. (See 'Lateral QL block' above.)
-For posterior QL block, place the needle tip posterior to the QL muscle, in the plane between the QL and erector spinae muscles. (movie 1) (See 'Posterior QL block' above.)
•For all blocks, after negative aspiration, inject 20 to 30 mL of LA in 5 mL increments, with gentle aspiration between injections, visualizing spread of LA.
●Continuous QL block – Continuous block is performed as described for single-injection block, using a Touhy needle with a 19 or 20 gauge catheter inserted through it and 3 to 6 cm beyond the needle tip. (See 'Continuous block' above.)
●Drug choice – Long-acting LAs (eg, ropivacaine or levobupivacaine [outside the United States], or bupivacaine) are used for QL blocks. Total dose must remain within maximum allowable dose, including any other LA injections. (See 'Drug choice and dosing' above.)
•For single-injection block – Levobupivacaine or ropivacaine 0.2 to 0.375%, or bupivacaine 0.25%.
•For continuous block – Bolus injection as for single-injection block, followed by continuous infusion of 0.1 to 0.2% levobupivacaine or ropivacaine, or 0.125% bupivacaine, at 5 to 10 mL per hour. If available, programmed intermittent bolus can be used at 8 mL every hour to 15 mL every three hours.
●Side effects and complications – Side effects and complications of QL blocks are rare. (See 'Side effects and complications' above.)
•Hypotension and motor block due to spread of LA, and needle trauma of surrounding structures (eg, pleura, kidney) are possible.
•Local anesthetic systemic toxicity (LAST) is a concern, due to the large volume of LA used for the block and vascularity of the block space.
•Whether to avoid QL blocks in patients who are at risk for bleeding (eg, anticoagulated or with a bleeding disorder) is controversial. We consider anticoagulation a relative contraindication to QL blocks.
•If the needle tip is advanced beyond the target space, there is risk of bleeding or organ trauma, particularly for anterior and possibly for lateral QL blocks.
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