Case 23 - Pulling Your Leg
Author: Angus Perks Reviewer: Nish Cherian/Nick Mani
A 2 year old male with known talipes was brought in in the early hours having slipped in his talipe-correction boots and twisted his left leg. He has a PMH of enlarged adenoids for which he is awaiting surgery. The left thigh was notably swollen and he was in considerable pain, unwilling to move from sitting nor have his left leg touched.
He received paracetamol and ibuprofen at triage. A gentle ultrasound of his left thigh showed the following: -
Clip Collection (Press right/Left to change the clips)
Left Mid-Tigh Transverse View
-
This demonstrates a break in the cortex of the femur with surrounding haematoma, confirming the suspected femoral shaft fracture.
-
This child needs analgesia at least until theatre in the morning.
After paracetamol and ibuprofen, options include:Opiate analgesia
Traction (which will require bridging analgesia/sedation)
Regional anaesthesia.
Given his adenoid/tonsillar enlargement, you feel that sedation overnight would not be appropriate and so you place LMX/LAT gel in his left femoral crease in preparation for a nerve block. 40 minutes later, after some intranasal fentanyl, you perform a femoral nerve block using 4.5ml 0.25% bupivacaine (images below).
Clip 2a & 2b- Femoral crease, transverse. Left to Right = Medial to Lateral
FV – Femoral Vein, FN – Femoral Nerve, FA – Femoral Artery, LA – Local Anaesthetic
(Click the right arrow for annotation)
15 minutes later the child is happy and comfortable transferring to X-ray and having his leg manipulated for imaging. This is later placed in skin traction and he is listed for theatre the following day.
Image 1- XRs of the left femur demonstrating the fracture
Ultrasound-Guided Femoral Nerve Block
Femoral Nerve Block (FNB) has long been a technique used for anaesthesia of femur fractures. Ultrasound-guided blocks have been shown to be faster and more efficacious than nerve-stimulator guided blocks [1,2] and are relatively simple to perform.
Below is a brief description of the technique, but there is an excellent summary by NYSORA [3].
The patient should be monitored and sterility observed throughout the procedure.
With the linear (high-frequency) ultrasound probe positioned transversely in the femoral crease, the femoral nerve is located lateral to the femoral artery. Tip: tilting the transducer cranially or caudally can help improve visualisation of the femoral nerve.
After anaesthetising the skin with lidocaine, a short-bevel, 20-22G needle is advanced in-line with the transducer from lateral to medial under direct visualisation. Passage through the fascia iliaca should be felt and the tip of the needle positioned just lateral to the femoral nerve.
An assistant then aspirates (ensuring no blood aspirate) and injects a small amount of local anaesthetic under direct US visualisation. There should be little resistance to injection. High resistance suggests intrafascicular or incorrect fascial plane position of the needle tip.
LA should displace the femoral nerve medially, away from the needle, or should disperse above/below the femoral nerve. 10-15ml of LA is required in an adult.
Image 2- Surface Anatomy of Different Hip/Pelvis Blocks
FICB (II)- Fascia Iliaca Compartent Blcok Infra-Inguinal, FICB (SI)- Fascia iliaca Compartment Block Supra-Inguinal, FN- Femoral Nerve Block, PENG- Peri-Capsular Nerve Group Block
Image 3- The Nerve Branches Blocked by Femoral Nerve Block (Anterior Pelvic Skeletal View)
ASIS- Anterior Superior Iliac Spine, LFCN- Lateral Femoral Cutaneous Nerve, FN- Femoral Nerve, ON- Obturator Nerve
Image 4- Ergonomicology/Safety
Patient, Performer, Assistant, Equipment, Monitoring, Check-list/Stop Before You Block
Note- the ultrasound machine is at the opposite side of the bed for this block
Image 5- Cartoon demonstration of Femoral Nerve Block (FNB) vs Fascia Iliaca Compartment Block (FICB) Infra-inguinal (II) In-Plane
SM- Sartorius Muscle, IPM- Iliopsoas Muscle, PM- Pectinous Muscle, FL- Fascia Lata, FI- Fascia Iliaca
FN- Femoral Nerve, FA- Femoral Artery, FV- Femoral Vein, ON- Obturator Nerve, LFC- Lateral Femoral Cutaneous Nerve
Femoral Nerve Block vs Fascia Iliaca Block
A few trials have compared FNB vs Fascia Iliaca Block (FIB) vs ‘3-in-1’ Block [1,4]. There is little convincing evidence to suggest that either of the three is superior, and that pain scores do not vary significantly between the different blocks.
There is a theoretically (albeit unproven) higher risk of vascular or nerve injury with FNB, although with US guidance this should not be significant with an experienced operator.
One advantage of FNB is that it requires a smaller volume of local anaesthetic and so should be considered if LA is required at other sites.
US-guided FIB has been added to the new RCEM Ultrasound Curriculum as of August 2021. The skills required and technique are easily transferable between FNB/FIB and many other nerve blocks, and familiarisation with ‘needling’ under US guidance is extremely useful for EM physicians. Early effective analgesia is a fundamental part of good Emergency Care and regional blocks are an excellent way to provide this.
CASE RESOLUTION
The use of ultrasound in these cases allows for effective analgesia for procedures & diagnostics in ED and analgesia may last many hours afterwards, avoiding need for sedation and side effects of systemic analgesics. In this case ultrasound facilitated diagnosis and nerve block prior to imaging, significantly improving patient comfort throughout their ED stay.
References: -
