Femoral nerve block

Overview

A femoral nerve block involves injecting medication near the femoral nerve to provide brief pain relief, often known as analgesia, or regional anesthesia during knee and thigh procedures. This medication can be administered either continuously or as a single injection. In emergency situations such as hip or femur fractures, healthcare providers in the emergency room may also perform a femoral nerve block.

The femoral nerve, a significant nerve in the body, controls motor functions for movement in the legs, hips, ankles, and feet. It also plays a role in sensory functions, including touch, pain perception, and sensitivity to temperature changes. However, while the medication is effective, it may temporarily affect the function of hip and thigh muscles.

A femoral nerve block is given by healthcare providers through injection into the area of the mid-upper thigh, close to the pelvis. The lumbar plexus, a group of nerves that occur from the lumbar (lower back) area of the spinal cord, is where the femoral nerve originates.

Reasons for undergoing the procedure

Healthcare providers primarily use femoral nerve blocks for specific surgical procedures and to relieve acute pain resulting from sudden and severe injuries.

  • Regional anesthesia for surgeries: Femoral nerve blocks are used by surgeons to provide regional anesthesia for a number of procedures, such as:
    • Repair of quadriceps muscle tears and tendon ruptures.
    • Drainage of a knee hematoma following total knee replacement surgery (arthroplasty).
    • Surgery on the patella (kneecap), such as fracture repairs.
    • Quadriceps muscle biopsies.
    • Long saphenous vein stripping (removal or ligation of the saphenous vein).

Depending on the type of surgery being performed, surgeons may combine femoral nerve blocks with other nerve blocks, such as an obturator or sciatic block. Occasionally, they might also choose to use general anesthesia.

Femoral nerve blocks are also used by surgeons to control pain after significant femur (thigh bone) and knee procedures, such as total knee replacements. This usually involved administering the nerve block continuously.

  • Pain relief (analgesia): Healthcare providers may administer femoral nerve blocks to alleviate pain following severe injuries such as:
    • Femur fractures.
    • Hip fractures.
    • Femoral neck fractures.
    • Patellar injuries.

Emergency rooms are the usual settings for the administration of these nerve blocks. They also help with pain management in the event that healthcare providers need to execute treatments such as manipulation or closed reduction on displaced fractures. They improve patient comfort during physical examinations and X-rays.

Risk

Although they are uncommon, femoral nerve block risks can include:

  • Nerve injury that may be temporary or permanent.
  • Allergic reactions to the medication.
  • Hematoma (accumulation of blood outside of blood vessels).
  • Infection at the injection site.
  • Local anesthetic systemic toxicity, an uncommon but serious reaction to local anesthesia that, should it arise, needs to be treated right away by your healthcare team.

Because of potential quadriceps muscle weakness, a femoral nerve block could heighten the risk of falls during hospital recovery after surgery. Your healthcare provider will discuss this concern with you and provide guidance on fall prevention strategies.

Before the procedure

In most cases, there is no additional preparation required if you are having a femoral nerve block for acute injury pain treatment.

Your healthcare provider will provide you with particular instructions if you are having a femoral nerve block for surgery. You might be required to stop taking certain medications and fast (eat or drink nothing but water) before to the procedure.

During the procedure

Depending on whether a femoral nerve block is being performed for surgery or acute pain, the procedure may change slightly. It may also differ depending on whether a continuous catheter flow or a single injection is used.

Following a femoral nerve block, you can anticipate the following:

  • Lying on the procedure table on your back.
  • A mild sedative may be administered through an IV line in to help you relax.
  • During the procedure, healthcare providers will monitor vital signs such as blood oxygen levels using a pulse oximeter, heart health with an EKG, and blood pressure.
  • The healthcare provider may utilize imaging techniques such as ultrasound to accurately locate your femoral nerve and determine the precise injection site.
  • Also, they may employ a nerve stimulator, which involves inserting a needle connected to a stimulator machine into your nerve. The stimulator emits electrical signals, and the healthcare provider identifies the correct nerve location by observing twitching in your patella.
  • To numb the area where the nerve block will be given, the healthcare provider will inject a local anesthetic. As the needle pierces your skin, you can still feel a pinch or some minor discomfort.
  • If only one injection is required, the medication will be injected as close to the affected nerve or nerves as possible. If the medication is administered continuously, a catheter—a small, flexible tube—will be inserted close to your nerve and taped to your skin with medical tape.

After the procedure

A femoral nerve block offers effective pain relief for surgeries and acute injuries, potentially reducing the need for opioid medications. This approach helps mitigate the risks associated with opioid use, such as addiction, and facilitates earlier hospital discharge compared to opioid reliance alone.

Outcome

Femoral nerve blocks are typically highly effective for providing temporary pain relief. The choice of anesthetic type, strength, and dosage administered by your healthcare provider influences the onset, duration, and area of pain relief. Your provider will provide tailored information based on your specific situation to help you understand what to expect.

If the nerve block does not achieve the desired pain relief, your healthcare team will discuss alternative options with you. It’s important to promptly notify your healthcare provider if you experience any new symptoms or complications from the femoral nerve block, such as infection or nerve-related issues like burning pain, weakness, or tingling.