Overview of Superficial Peroneal Nerve Block
The superficial peroneal nerve (also known as the superficial fibular nerve) is a type of nerve that both receives and sends signals. This nerve is responsible for sensation in the front and side portion of your lower leg and most of the top of your foot (excluding the space between your first two toes).
It’s not uncommon for the superficial peroneal nerve to get trapped, causing discomfort and possibly a tingling sensation in the areas that the nerve services. To relieve these symptoms, a nerve block can be applied. This procedure involves numbing the nerve, which also makes it useful for surgeries on the top of the foot.
Using ultrasound during this procedure can help the doctor avoid injuring nearby structures like blood vessels and can also make the numbing process more effective.
Anatomy and Physiology of Superficial Peroneal Nerve Block
The superficial peroneal nerve is one of two main branches that stem from a common peroneal nerve. It starts around the narrow part of the fibula (the calf bone), in roughly 81% of people. In about 9% of people, it starts between the calf bone and the knee. For the remaining 10%, it begins above the knee.
Once it originates, the nerve moves down the upper part of the fibula (calf bone) and goes deep into a muscle called the peroneus longus. Then, it travels through this muscle and runs between it and another muscle called the peroneus brevis. The nerve continues its journey going down between the peroneus brevis and a third muscle, the extensor digitorum longus, sitting closer to the surface.
The nerve then goes through a dense band of connective tissue (the deep fascia), becoming more superficial and passing through a tunnel in the peroneal region, located at the upper two-thirds and lower one-third junction, roughly 12 cm above the ankle.
As it travels through the body, the superficial peroneal nerve performs two main tasks. Firstly, it supplies motor nerves to the peroneus longus and brevis muscles, which helps control movement. Secondly, it sends sensory information from the front and outside part of the lower leg, as well as most of the top of the foot (excluding the area between the first and second toe).
Why do People Need Superficial Peroneal Nerve Block
There are certain activities and injuries that can result in pain in the superficial peroneal nerve, a nerve in your leg. These include running, playing football, and ballet dancing. These activities can cause the muscles in your leg to enlarge, which then squeezes the nerve. Wearing tight boots and socks can also cause similar problems.
Accidental injuries can also cause this nerve pain. A hard hit to the leg while playing sports, a twisted ankle, or a broken bone in your lower leg can all put strain or pressure on the nerve. Sometimes, this nerve pain happens after a surgery. This is common when an incision is made in the leg to relieve pressure from a condition called compartment syndrome.
Complex Regional Pain Syndrome (CRPS) of the Ankle and Foot is another condition that can cause this nerve pain. CRPS usually develops after an injury, surgery, stroke or heart attack. The pain is out of proportion to the severity of the initial injury.
Sometimes, this nerve is numbed during certain surgical procedures. This might be done when managing fractures and dislocations in the ankle or during operations on the top of the foot. These surgeries might include draining an abscess, fixing a toenail, or removing a foreign object.
When a Person Should Avoid Superficial Peroneal Nerve Block
There are several reasons why a patient might not be able to undergo a certain medical procedure. These include:
– If the patient decides not to go through with the medical procedure.
– If the patient is allergic to the substance (injectant) that would be introduced into their body during the process.
– If the patient has a local infection, which means there’s an infection in a specific area of their body.
– If the patient has local malignancies, which are uncontrolled and abnormal growths or cancers in a specific area of the body.
– Coagulopathy is another reason a patient might not undergo a procedure. Coagulopathy is a condition affecting how the blood clots, which can make a procedure risky because of potential excessive bleeding.
– If the patient has superficial peroneal neuropathy because of an underlying illness such as diabetes mellitus. Superficial peroneal neuropathy is a condition that affects the peripheral nerves in the legs, leading to numbness, tingling, and muscle weakness.
Equipment used for Superficial Peroneal Nerve Block
These items are typically used for a medical procedure, they help to keep things clean and to do the procedure accurately:
- Povidone iodine solution or chlorhexidine – these are cleaning solutions used to disinfect the skin before the procedure.
- Sterile towels and gauze – these are used to keep the area clean during the procedure.
- Sterile gloves – worn by the doctor to protect you against infections.
- A gown – It’s necessary when the procedure involves the placement of a catheter for a continuous block, which is a type of pain relief method.
- In case the doctor uses an ultrasound to guide the procedure, they’ll use a high-frequency ultrasound probe (a tool used to create images of the inside of your body), with a sterile cover and gel to ensure clear images and cleanliness.
- A control syringe is used to draw out any fluid from the area before injecting the local anesthetic (a drug that numbs a particular area) during a landmark-based technique (a method used to locate the correct place for the injection).
- Needles are used for drawing up the anesthetic and for injecting it into the body.
- The anesthetic used to numb the area can be on its own or mixed with drugs like epinephrine (a drug that constricts blood vessels to limit bleeding) and/or other additives, like dexamethasone (a steroid that can reduce inflammation and pain)
Who is needed to perform Superficial Peroneal Nerve Block?
Doctors who are skilled in methods like using clear physical signs on the body, or using ultrasound guidance for locating nerves, have the ability to carry out nerve block procedures. These procedures might involve the use of anesthesia and could be performed by anesthesiologists (doctors who specialize in pain management during surgeries) or physiatrists (doctors who specialize in physical medicine and rehabilitation).
Preparing for Superficial Peroneal Nerve Block
When you go to the hospital for a medical procedure, it’s important to understand every step of the process. The first thing your doctor will do is explain why you need to have an injection and tell you about what will take place, what’s in the injection, any possible side effects you might experience, and what the likely outcomes are. This way, you have all the necessary information to make an informed decision about your treatment.
Next, you’ll be asked to sign a form called ‘informed consent’, in accordance with hospital rules. Signing this means you understand and agree to the procedure that’s going to happen. The medical team will then make sure there’s enough light in the room, and position you comfortably on your back. Sometimes, they may need to turn you to your side to better access the injection site.
The person giving the injection will position themselves in a way that won’t strain their neck or back. Then, they’ll make sure your leg (or the part of your body where you’re getting the injection) is exposed in the right way.
Before the injection takes place, the area on your body where you’ll receive the injection will be cleaned thoroughly to remove any germs – this is called sterilization. It’s a very important step that ensures the procedure is safe and prevents infections.
Your doctor will then prepare the injection, which usually contains a local anesthetic. This is a drug that numbs a small area of your body, so you won’t feel any pain during the procedure. Sometimes, they may also add a drug called epinephrine or some steroids.
If your injection is being guided by an ultrasound (a device that uses sound waves to create pictures of the inside of your body), the medical team will adjust the settings on the ultrasound machine. This helps them to get a clear picture of the specific area where the needle will be injected.
How is Superficial Peroneal Nerve Block performed
Here’s how a doctor conducts an anesthetic procedure to numb a section of your leg, using either guiding landmarks on your body, or ultrasound technology:
With the guiding landmarks method, the doctor tries to numb an upper area of your leg by giving you a shot with 6 to 10 ml of the numbing medicine. The injection goes into the most tender spot, found along the front, outer side of your leg. This spot is usually 10 to 15 cm above the little bony bump on the outside of your ankle.
If a lower area of your leg needs to be numbed, the doctor injects 6 ml of the numbing medicine. This time, the shot is given just in front of the bony bump on the outer side of your ankle.
In both of these methods, the doctor puts the needle into your skin from lower to upper, or from the outer to inner side of your leg.
In the ultrasound-guided technique, the doctor uses an ultrasound machine. It works like this:
- First, the doctor puts a handheld device called a probe onto your skin. The probe sends ultrasound waves into your body, which bounce off your tissues and return to create an image on a screen. The doctor then moves the probe from the starting point of the nerve down to the little bony bump on the outside of your ankle. This helps the doctor find the exact spot where the nerve is trapped, see if you have any unusual anatomical features, and locate the small vein that accompanies the nerve.
- Next, the doctor targets the nerve at the site where it’s trapped, based on the ultrasound images. Depending on this, the injection can go into various spots around certain muscles, into a certain tunnel in your leg, or into the skin above the bony bump on the outer side of your ankle.
The doctor inserts the needle into your skin from the outer to the inner side using the ‘in-plane approach’, meaning it goes in parallel to the surface of your skin. Then, 3 to 5 ml of the numbing medicine is injected, aiming for the short (width) aspect of the nerve.
For the ultrasound-guided catheter technique, the doctor places the ultrasound probe on the back outer side of your leg, about 12 cm below your knee. Low-strength nerve stimulation is used to reproduce your pain, and a catheter, or thin, flexible tube, is inserted in the spot under ultrasound guidance. Again, using the ‘in-plane approach’, the catheter targets the short, or width, aspect of the nerve. Finally, 15 ml of the numbing medicine is provided through the catheter.
The benefits of using ultrasound guidance are that it helps to avoid injuring nearby vessels and lower the risk of nerve damage related to the procedure. It also allows for precise placement of the numbing medicine around the targeted nerve, leading to better control of pain. Lastly, using ultrasound guidance requires smaller amounts of local anesthetics to achieve the desired pain relief.
Possible Complications of Superficial Peroneal Nerve Block
If you’re having a medical procedure where a substance is injected into your body, there are a few potential risks you should know about. One risk is having an allergic reaction to the substance being injected. You might also get an infection, or there could be bleeding. One of the blood vessels near the injection site could get damaged, or the superficial peroneal nerve, a nerve near the surface of your leg, could get injured.
A more severe complication could be systemic toxicity, where the local anesthetics – the drugs used to numb a specific area of your body – affect your whole system. This could have effects on both your nervous system and your heart. You might taste metal, notice changes in your hearing, feel numb around your mouth, have blurred vision, feel restless, or even have seizures. Heart-related effects could include low blood pressure, abnormal heart contractions, irregular heartbeats, complete heart block which is a type of abnormal heart rhythm, and cardiovascular collapse, a serious condition where the blood circulation fails due to a failure of the heart to effectively pump blood.
What Else Should I Know About Superficial Peroneal Nerve Block?
The superficial peroneal nerve is responsible for sensations you feel on the front and outer side of your leg and the majority of the top of your foot (except for the space between your first two toes). This nerve can become trapped or pinched in various places because of its long pathway in your leg – such as between the long bone in your leg and an adjacent muscle, within some other muscles in your leg, or in some other spots along its course.
When this nerve gets trapped, people experience symptoms like pain, tingling, or a sensation of pins and needles on the front and outer side of their legs and most of their foot. It’s important for doctors to identify if these symptoms are coming from this specific trapped nerve or if they’re due to other conditions, like issues with the sciatic nerve or low blood flow.
To relieve the pain and other uncomfortable symptoms, doctors can perform a procedure where they block or numb the superficial peroneal nerve. This procedure is also helpful before doing surgeries on the top of the foot to make it pain-free. This nerve blocking procedure guided by an ultrasound, a type of imaging technology, is preferred as it gives better outcomes and has fewer risks compared to traditional method of using physical landmarks to find the nerve.
