The fascia iliaca block is a regional anesthesia technique where local anesthetic is placed underneath the fascia of the iliacus muscle, effectively blocking the femoral, lateral femoral cutaneous, and obturator nerves (1).  This block is most known for analgesia following hip fractures (1), although it can also be applied to a variety of lower extremity vascular procedures and proximal lower extremity amputations.  Regional anesthesia for hip fractures is associated with decreased mortality, opioid requirements, altered mental status, adverse cardiovascular events, and pulmonary complications (2). The American Society of Orthopaedic Surgeons recommends regional anesthesia for hip fractures in the elderly with strong evidence (3).  Similarly, the International Fragility Fracture Network Delphi consensus statement on the principles of anaesthesia for patients with hip fracture recommends that nerve blocks are offered to patients with hip fractures in addition to either general or regional anaesthesia (4). 

A suprainguinal approach to this block is recommended since a more proximal approach is likely to block the articular branches of the nerves (5).  The infrainguinal approach only consistently blocks the femoral nerve, occasionally blocks the lateral femoral cutaneous nerve, and rarely blocks the obturator nerve (5).  The suprainguinal fascia iliaca (SIFI) block results in a more complete sensory blockade, more consistent spread in a cranial direction under the fascia iliaca, reduced pain scores, reduced opioid consumption, and better patient satisfaction compared to the infrainguinal approach (6).

Although the suprainguinal approach is more effective than infrainguinal at blocking all three nerves, it may be more challenging to perform.   In this session, we’ll review tips and tricks for success with your SIFI blocks.

Start with a linear probe in the sagittal orientation over the anterior superior iliac spine (Figure 1).  Next move the probe slightly medial and tilt back lateral to identify the SIFI sonoanatomy (Figure 2).  Above the iliacus muscle we see the internal oblique muscle cephalad and sartorius muscle caudad.  This view is described as looking like a “bow tie” (Figure 3).   For those unfamiliar with ultrasound imaging at the anterior superior iliac spine (ASIS) but are familiar with groin sonoanatomy for vascular access, an alternative approach is to start with the probe in the transverse orientation at the inguinal crease, similar to an ultrasound view for femoral vascular access or a femoral nerve block (Figure 4).  Next, move the probe lateral until the sartorius muscle is identified above the iliopsoas muscle (Figure 5).  Once the sartorius and iliopsoas muscles are identified and centered, turn the probe 90 degrees to the sagittal orientation (Figure 6).  Scan cephalad in this orientation to the level of the ASIS (Figure 7).  Here you will identify the internal oblique and sartorius muscles forming a “bow tie” above the iliacus muscle.

I have found increased first pass success rate with SIFI block and minimal needle redirecting with a caudal to cranial approach aiming first for the fascial plane between the sartorius and iliacus muscles or the peak of the iliacus muscle.  Once we reach the correct fascial plane as evidenced by the sartorius and iliacus muscles “unzippering” (Figure 8), we can then hydro-dissect cephalad to the internal oblique and iliacus fascial plane to ensure that our local anesthetic is placed as proximal as possible (Figure 9).  As with all procedures, improved ergonomics allows for greater proceduralist comfort and effectiveness.  It is usually easiest to needle with your dominant hand, and so I recommend that you position yourself so that your dominant hand is needling in a caudal to cranial direction.  For example, if the physician is right-handed and performing a left-sided fascia iliaca block, he or she would stand on the right side of the patient and reach over to the left so that the block needle is in the right dominant hand and advanced in a caudal to cranial direction (Figure 10). 

At times it can be challenging to identify the correct fascial plane, especially in frail patients with extensive muscle atrophy.  The deep circumflex iliac artery (DCIA) is seen in the fascial plane between the internal oblique and iliacus muscles.  Identifying this artery can help with orientation to the relevant sonoanatomy (Figure 11).  Occasionally the common iliac artery is seen in long axis above the iliacus muscle (Figure 12).  In this case, sliding the probe slightly medially usually removes the artery from the needle trajectory. If a window cannot be identified without the artery in the needle path, an infrainguinal approach or alternative block should be considered.

The fascia of the iliacus muscle is very tough, and it is not unusual to advance through the fascial plane target on first pass into the iliacus muscle.  Intramuscular injection will have a mottled, shreddy appearance rather than the unzippering appearance of two muscles peeling apart in a true fascial plane (Figure 13).  If you overshoot or undershoot, make small adjustments to your needle position until you are directly underneath the fascia of the iliacus muscle and above the muscle.  When local anesthetic is deposited in this location, the fascial plane expands and contracts with injection.  In adults we’ll inject 30 to 40 mL of dilute local anesthetic while keeping in mind the maximum safe dose of local that may be administered (Figure 14).

After block completion, we can visualize the spread of local anesthetic distally by scanning the femoral, lateral femoral cutaneous, and obturator nerves.  To scan the femoral nerve, start the probe in the transverse orientation in the inguinal crease.  Local anesthetic should be apparent under the femoral nerve and above the iliopsoas muscle (Figure 15).  Next slide the probe laterally until the sartorius muscle and a small fat pad just lateral to the muscle are identified.  Move the probe 1-2 centimeters distal from here and a branch of the lateral femoral cutaneous nerve should be seen in this fat pad surrounded with local anesthetic (Figure 16).  To scan the obturator nerves, move the probe back to the groin and visualize the femoral nerve and vessels in the transverse orientation.  Slide the probe medial and identify the pectineus muscle.  Continue to slide medial until the adductor muscles are seen just medial to the pectineus muscle.  The anterior branch of the obturator nerve is seen between adductor longus and brevis muscles.  The posterior branch of the obturator nerve is seen between adductor brevis and magnus muscles.  After successful completion of the SIFI block, local anesthetic will be seen surrounding both branches of the obturator nerve (Figure 17).

References

1.     O'Reilly N, Desmet M, Kearns R. Fascia iliaca compartment block. BJA Educ. 2019 Jun;19(6):191-197. doi: 10.1016/j.bjae.2019.03.001. Epub 2019 Apr 24. PMID: 33456890; PMCID: PMC7808109.

2.     Pedersen S, Borgbjerg F, Schousboe B, et al. A comprehensive hip fracture program reduces complication rates and mortality. J Am Geriatr Soc. 2008;56(10):1831-1838. 

3.     American Academy of Orthopaedic Surgeons Management of Hip Fractures in Older Adults Evidence-Based Clinical Practice Guideline. https://www.aaos.org/hipfxcpg.pdf  Published December 3, 2021.

4.     White SM, Altermatt F, Barry J, Ben-David B, Coburn M, Coluzzi F, Degoli M, Dillane D, Foss NB, Gelmanas A, Griffiths R, Karpetas G, Kim JH, Kluger M, Lau PW, Matot I, McBrien M, McManus S, Montoya-Pelaez LF, Moppett IK, Parker M, Porrill O, Sanders RD, Shelton C, Sieber F, Trikha A, Xuebing X. International Fragility Fracture Network Delphi consensus statement on the principles of anaesthesia for patients with hip fracture. Anaesthesia. 2018 Jul;73(7):863-874. doi: 10.1111/anae.14225. Epub 2018 Mar 6. PMID: 29508382.

5.     Vermeylen K, Desmet M, Leunen I, Soetens F, Neyrinck A, Carens D, Caerts B, Seynaeve P, Hadzic A, Van de Velde M. Supra-inguinal injection for fascia iliaca compartment block results in more consistent spread towards the lumbar plexus than an infra-inguinal injection: a volunteer study. Reg Anesth Pain Med. 2019 Feb 22:rapm-2018-100092. doi: 10.1136/rapm-2018-100092. Epub ahead of print. PMID: 30798268.

6.     Bansal K, Sharma N, Singh MR, Sharma A, Roy R, Sethi S. Comparison of suprainguinal approach with infrainguinal approach of fascia iliaca compartment block for postoperative analgesia. Indian J Anaesth. 2022 Oct;66(Suppl 6):S294-S299. doi: 10.4103/ija.ija_823_21. Epub 2022 Oct 12. PMID: 36425915; PMCID: PMC9680722.