I know I keep saying that this or that block is one of the ‘easy ones’, but this one really is another one of them. There are only a few simple essentials to identify on the image, and this block is also a good one to perform early as you are developing ultrasound skills and knowledge. Most of the time, adding ultrasound means learning a completely new needle orientation and entry site, but not with this block. There are several intermediate steps that can be taken along the way to help you as you learn to go to an ultasound block with all blocks in general. This block, because it can be done the same way as the classic approach and because it has a significant ‘tactile’ component, may allow you a short-cut to integrating ultrasound into your practice. That is, you can perform the classic block as usual, but have the probe on the patient to view what you are expecting to feel and then to view the injection of local.

     When I first started utilizing this block long ago, I used it primarily to help position elderly patients for a spinal who were presenting with a femur neck fracture for an ORIF of the hip. I would use the classic ‘2 pop’ technique with a single injection as soon as I got them in the holding room to give it time to set up for the procedure and to improve their analgesia. This made it much easier to position them without having to give them all the meds I was trying to avoid in the first place by doing a spinal.It won’t take all of their pain away, but it will do a great deal toward that end immediately and overnight with a single injection. This block for this indication is another good example of how the avoidance of opioids and their side-effects can be turned into not only a good patient experience, but also a way to optimize outcomes and minimize costs. There are a lot of unrecognized ‘soft costs’ that can be avoided when the elderly can avoid opioids.

     This block can be performed in a transverse or longitudinal orientation and as an in-plane or out of plane technique. I have found the longitudinal (probe beam going caudal to cranial) in-plane approach the quickest to identify and perform, so I use this approach the vast majority of the time. The transverse orientation is essentially like the Femoral Nerve Block (see tab above) described in another section but in a more cranial location. It is still the goal to deposit local anesthetic just deep to the fascia iliaca and above the iliacus muscle at this location just medial to the anterior superior iliac spine (ASIS).

     The cadaver image below identifies the ‘window’ in which the block is performed in either orientation. My finger is on the ASIS, and the sartorius muscle is at the tip of my finger extending down and to the left, passing the splitting femoral artery and femoral nerve on the medial aspect. The probe would sit just medial to this point going medially for the transverse approach, or it is turned ninety degrees to sit between the sartorius muscle and the femoral nerve. Deep to these structures is the ilium which is covered by our targets, the iliacus muscle and the overlying fascia iliaca.

      I usually just find the ASIS, and put the probe just medial to it and make quick scans up/down and left/right to confirm my position then perform the block. The first structure to quickly identify on ultrasound is the bright steep (up and down)appearance of the ilium with its bone shadow below. The muscle immediately superficial to it extending out of the pelvis is the the iliacus. Roll the probe slightly to view the fascia iliaca at its brightest angle. Note from the cadave image that a slice of the sartorius muscle may be overlying the iliacus on the caudal aspect and could be mistaken for the superficial aspect of the iliacus muscle. Move the probe slightly medially to get it out of the image. Similarly, the internal oblique muscle can sometimes appear overlying the cranial aspect od the iliacus muscle. You should be able to note that the muscular fibers are almost perpendicular and so should have a distinctly different appearance. Make sure the ilium is directly below such that when your needle comes in (right to left in the below image), the needle will be cranial to the ilium bone so that local will spread in that direction. The local must go cranial to the ilium to get the lateral femoral cutaneous and (hopefully) the obturator nerve.

     This is another advantage that I perceive with the longitudinal approach in that local is ‘driven’ cranially, and there should be enough spread medially and laterally.  This block requires a large volume of local to be successful as the multiple targets are a distance apart. Thirty to forty milliliters or more is not uncommon, and higher infusion rates will be necessary after the first day. Often, this block is for trauma, so the patient will not be ambulatory, and a higher concentration of local is fine. If this block is done for a total hip arthroplasty (similar results with fewer risks than a lumbar plexus block), consider limiting the local anesthetic concentration to optimize immediate physical therapy if it is planned for the day of surgery. Since I have my patients in a knee immobilizer with ambulation, I do not drop the concentration for our day of surgery physical therapy. Before injecting, make sure that neither the femoral artery or vein are seen in long axis as a dark pulsating or compressible (respectively) structure. Further, just lateral to these structures, the femoral nerve may be visualized as a bright and relatively thick band-like structure. Again, we are positioning the probe in the ‘window’ between the sartorius muscle and the femoral nerve and vessels.

     The long bright wavey lines at the top of this image represent subcutaneous fat. You can see the iliacus muscle extending out of the pelvis (going out toward the right) as it rolls over the bright appearing ilium. If we were to move the probe farther to the left, the internal oblique muscle would appear overlying the iliacus muscle. Moving even further, we would see a space open between those muscles, revealing the moving bowels. Sometimes, doing this is helpful to get fully oriented. I believe in the right upper area above the iliacus muscle is a sliver of the sartorius muscle. At least that is where it should appear.

     The dark local should pool under the fascia iliaca and flow cranially. Readjust your needle if it spills caudally on the other side of the ilium. This is one of the few blocks that I push in my catheter beyond the needle tip (particularly if it is a multi-orifice catheter) several centimeters. Be aware that pushing in too much can lead to knotting of the catheter especially if it is not a relatively stiff catheter.

     Some say that injecting local into the iliacus muscle superficially is OK since it will still track to the nerves. This will lead to a much slower onset though. To me, the reason I utilize ultrasound is primarily for that very problem. The difference between a classic technique and this one is the ability to differentiate between and perform an ‘adequate’ block and an ‘optimized’ block. What I mean is that if you note that you are within the muscle (or getting some spread above the fascia iliaca) or your spread is not heading cranially, you can redirect your needle to achieve this. Also, a slow set up leads to difficulty determining if the block was successful or not, especially in an elderly premedicated patient where the entire surgical site is not expected to be covered. (“Did I put it above the fascia or get fooled by the sartorius muscle and it should be replaced, or should I just keep waiting?”) This becomes even more of a challenge with post-operative patient evaluation.

Watch the video below to see a fascia iliaca scan and find even more helpful tips for performing this nerve block in the ‘Tips & Tricks’ section of this website :

See Also: Sartorius Muscle, Fascia Iliaca Tips, CPNB for AKA,Fascia Iliaca Tips #2,  Recognizing Appropriate Fascia Iliaca Spread: Watch this Video!