Background
Blockade of the lumbar plexus can be attained through an anterior approach described by Winnie [1] or through a posterior approach (psoas compartment block). The simplicity of completing the Winnie technique, well known as the 3-in-1 block, has made the technique much more popular than the posterior approach.
Controversy exists as to whether the anterior approach indeed covers the 3 target nerves: the femoral, obturator, and the lateral femoral. A meta-analysis found that more success is achieved with the obturator nerve block with the psoas compartment block when compared to the Winnie technique. [2] The obturator nerve provides innervation to the hip joint as well as the knee joint and, therefore, the degree of covering the nerve by the block results in better pain control and patient satisfaction.
Indications
Blockade of the lumbar plexus in combination with the sciatic nerve can provide anesthesia and high-quality analgesia for the whole lower extremity, with the advantage of more hemodynamic stability when compared to epidural analgesia. [3, 4, 5, 6] When a surgical block of the lower extremity is indicated, the psoas compartment block is favored over the Winnie technique. A surgical block may be considered for lower extremity amputation cases as well as orthopedic surgery cases in debilitated patients who may not tolerate the hemodynamic effects of general anesthesia.
The block may be done in conjunction with an IV opioid PCA instead of combining it with the sciatic nerve block for postoperative pain control. The use of the block is not only limited to the adult population but also extends to the pediatric population. Psoas compartment block was found to be a better technique for postoperative analgesia after hip and femoral surgery when compared to epidural block in children. [7, 8]
In a prospective single-blind study performed with 30 patients, Turker et al concluded that, when compared to epidural analgesia, lumbar plexus catheters are better tolerated for providing intraoperative and postoperative analgesia to hip fracture patients and for partial hip replacement surgery patients. [9] When combined with T12-L1 and sciatic nerve block, psoas compartment block can also be used in high-risk patients as the anesthetic technique for femoropopliteal bypass surgery. [10]
Contraindications
See the list below:
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Patient’s refusal or lack of understanding of the benefits and adverse effects of the procedure
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Anticoagulated and coagulopathy patients: Psoas compartment block is a paravertebral block. Although considered as an alternative for an epidural block in anticoagulated patients, this is no longer the case. The same American Society of Anesthesiology’s anticoagulation guidelines apply to paravertebral blocks. [11]
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Localized and systemic infection
Anatomy
The lumbar plexus is formed within the substance of the psoas major muscle by the anterior rami of spinal nerves L1 through L4 and some fibers from T12. These nerve roots enter the psoas muscle within a confined compartment; they then divide into anterior divisions (forming the lumbar plexus) and posterior divisions.
The plexus is about 3 cm anterior to the plane of the lumbar transverse process. Under ultrasound guidance, it appears as a hyperechoic structure that lies within the hypoechoic psoas major muscle (see the image below). The plexus is responsible for the innervation of lower abdomen and anterior and medial portion of the lower extremities. The branches of the lumbar plexus include the iliohypogastric, ilioinguinal, genitofemoral, lateral femoral cutaneous nerve, femoral nerve, and the obturator nerve. [12]
Ultrasound guided View of the Transverse process. The probe is placed parallel to the spinous processes S. sacrum, TP. Transverse process, LP. Lumbar Plexus
The block is approached at the L4 level in a sagittal plane that corresponds to the lateral end of the lumbar L4 transverse process. Completing the block at this level decreases the probability of puncturing the ipsilateral kidney.
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Patient in a lateral decubitus position.
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Ultrasound guided View of the Transverse process. The probe is placed parallel to the spinous processes S. sacrum, TP. Transverse process, LP. Lumbar Plexus
