Femoral nerve block

Femoral Nerve Block

A femoral nerve block is a medical procedure that involves the injection of local anesthetics near the femoral nerve to provide analgesia for surgeries and pain management, particularly in the anterior thigh and knee. This technique is widely used in orthopedic and trauma surgeries, facilitating postoperative pain control and reducing the need for systemic opioids.

Indications

The primary indication for a femoral nerve block is pain management. It is particularly beneficial for surgeries involving the lower extremity, such as:

• Total knee arthroplasty
• Anterior cruciate ligament reconstruction
• Fractures of the femur
• Procedures on the knee and anterior thigh

In addition to surgical indications, femoral nerve blocks are used in emergency medicine for pain control in patients with hip fractures and in chronic pain management for conditions affecting the femoral nerve distribution area.

Anatomy

The femoral nerve is the largest branch of the lumbar plexus, originating from the dorsal divisions of the L2 to L4 nerve roots. It descends through the fibers of the psoas major muscle, emerges from its lower part, and passes beneath the inguinal ligament into the thigh. It provides motor innervation to the anterior compartment of the thigh and sensory innervation to the anterior thigh and medial aspect of the leg.

Technique

The femoral nerve block is performed using either landmark-based techniques or under ultrasound guidance, which has become the preferred method due to its higher success rates and safety profile.

1. 1. 1. Ultrasound-Guided Technique

1. The patient is placed in a supine position with the leg slightly externally rotated. 2. The ultrasound probe is placed below the inguinal ligament to visualize the femoral nerve, artery, and vein. 3. After identifying the femoral nerve, a needle is advanced in-plane or out-of-plane to the ultrasound probe towards the nerve. 4. Local anesthetic is injected around the nerve, ensuring proper spread without intravascular injection.

1. 1. 1. Landmark-Based Technique

1. The inguinal crease is identified, and a point 1-2 cm lateral to the pulse of the femoral artery is marked. 2. A needle is inserted at this point and advanced perpendicularly until a loss of resistance is felt or a paresthesia is elicited in the nerve distribution area. 3. Local anesthetic is then injected after negative aspiration for blood.

Complications

While generally safe, femoral nerve blocks can be associated with complications such as:

• Infection
• Hematoma
• Nerve damage
• Intravascular injection
• Local anesthetic systemic toxicity (LAST)

Contraindications

Absolute contraindications include patient refusal and infection at the injection site. Relative contraindications involve coagulopathy, pre-existing neurological deficits, and severe systemic infection.

Conclusion

Femoral nerve blocks are a valuable tool in pain management, offering significant benefits in terms of pain control and reduction in opioid consumption. With advancements in ultrasound technology, the safety and efficacy of this procedure have improved, making it a preferred choice for many clinical indications.