Overview of Lower Extremity Blocks
The lumbosacral plexus is a network of nerves in the lower spine that controls the muscles in your lower body. It includes the nerve roots from the first lumbar vertebra to the fourth sacral vertebra. Unlike the similar network in the upper body, you can’t numb it fully with just one injection. For a long time, the preferred method to numb the lower body was a neuraxial block. But with more outpatient, or day surgeries, due to improved technology, this method has become less popular.
The introduction of ultrasound-guided methods has allowed doctors to locate nerves more accurately and do a better job of numbing the lower body. While it usually requires several injections, it’s still a good choice for day surgery cases. Use of this numbing technique for the lower body have grown, particularly in surgeries or treatments where the lower body needs to be numb.
Numbing individual nerves is a crucial part of managing pain after orthopedic surgeries. These methods are important parts of a pain management plan that includes several types of treatments. The femoral nerve block, a type of this method, was first used in 1952. Since then, advancements, especially those involving ultrasound, have significantly improved how nerve blocks are used in surgeries involving the upper body. Using a nerve block instead of general anesthesia can lower some risks associated with major surgery.
At first, these types of nerve blocks weren’t widely used in the lower body because neuraxial anesthesia was more common and seemed more straightforward. A neuraxial block only required one injection and relied on the body’s structure to guide the needle. On the other hand, nerve blocks in the lower body require more knowledge about the lumbosacral plexus and need multiple nerves to be blocked at different depths.
However, recent improvements in ultrasound technology have allowed doctors to place nerve blocks more accurately, so there’s been renewed interest in this method. This is partly due to efforts to combat the opioid crisis and rising healthcare costs in the United States. Nerve blocks can help reduce the need for opioid painkillers after surgery and have been studied extensively in hip and knee surgeries. One analysis of knee surgery cases found that numbing multiple nerves, especially with a combined femoral and sciatic nerve block, led to the best results in terms of pain relief, reduced opioid use, and improved range of motion. While more research is needed on the use of nerve blocks in arthroscopic hip surgeries, they can potentially reduce pain, lower morphine use, and shorten hospital stays.
Improved pain management through nerve blocks can increase patient satisfaction, make healthcare more cost-effective, speed up recovery, and facilitate outpatient surgeries while reducing complications.
Anatomy and Physiology of Lower Extremity Blocks
The lumbosacral plexus, a network of intersecting nerves in the lower back, splits into a few major nerves. These include the femoral, lateral femoral cutaneous, obturator, and sciatic nerves. These nerves are responsible for feeling and movement in the entire leg.
The femoral nerve provides feeling and aids movement to the front part of the thigh. This nerve continues as the saphenous nerve, which provides sensation to the inside of the same-side leg and foot and part of the corresponding big toe. The LFCN gives sensation to the outside of the thigh. The obturator nerve provides feeling to the inside of the thigh and powers the muscles that pull the thigh inward.
Neither the lateral femoral cutaneous nor the obturator nerve affect feeling or movement in the leg below the knee. The sciatic nerve, in conjunction with the posterior cutaneous nerve of the thigh, provides sensation and movement to the back part of the thigh. The sciatic nerve continues to the back and splits into the tibial and common peroneal nerves, just above the hollow at the back of the knee. These nerves are responsible for sensation and movement in the front, outer, and back parts of the lower leg.
Five nerves help with feeling and movement in the foot. The saphenous nerve is responsible for sensation in the inner side of the foot and part of the big toe. The deep peroneal nerve provides sensation between the big and second toes. The superficial peroneal nerve covers most of the top of the foot and toes, while the sural nerve provides sensation to the outer side of the foot and part of the fifth (or ‘little’) toe. Lastly, the posterior tibial nerve splits into the medial and lateral plantar nerves and provides sensation and motor control for the sole and underneath part of the toes.
Why do People Need Lower Extremity Blocks
Lower extremity blocks are a type of anesthesia that specifically numbs the hip, knee, ankle, or foot. These are especially useful for patients who can’t have general or neuraxial anesthesia, which is a type of anesthesia that numbs the entire body or a large part of it. Using such targeted anesthesia can help control pain after surgery, reduces the need for opioids – a strong type of pain medicine – and helps in restoring mobility to the patients earlier. In fact, being able to move earlier can prevent other complications like blood clots in the veins and bed sores, and helps in physical therapy progress.
Lower extremity blocks can either be the main anesthesia or be used together with general or neuraxial anesthesia. They effectively control pain and have less side effect such as blocking muscle movements. Some common types of lower extremity blocks are FNB, fascia iliaca block, SNB, saphenous nerve block, adductor canal block, iPACK block, ankle block, and LPB.
The FNB is usually used for surgeries on the front part of the thigh and inner part of the leg below the knee. It provides pain relief for knee surgeries and helps improve outcomes for patients. However, it can weaken leg muscles making patients more prone to falls.
The fascia iliaca block targets the femoral nerve and LFCN. It is often used for hip surgeries and provides fast pain relief. Injecting a local anesthetic under a tissue called the fascia iliaca does it.
The SNB is used for surgeries on the foot, ankle, and back of the knee. It provides a wide coverage for the lower part of the leg. It can, though, result in blocked muscle movement.
The saphenous nerve block is used for surgeries on the inner side of the knee, foot, and ankle. This block numbs the area without affecting the back part of the knee.
The adductor canal block targets two nerves playing a major role in sensation and movement. It is used for surgeries of the inner knee, foot, and ankle. Compared to the FNB, this block allows for early movement.
The iPACK block provides pain relief to the back part of the knee, often used along with the adductor canal block. It gives better pain control, reduces the need for opioids, and allows for early walking.
The ankle block is used for foot surgeries, it numbs the foot using surface landmarks and does not require ultrasound guidance.
The LPB is used for hip surgeries and can be done using ultrasound. It blocks three nerves – femoral, obturator, and LFCNs. Its use has decreased due to the use of the fascia iliaca block and other anesthesia techniques.
While these types of anesthesia are effective, they could potentially lead to complications like bleeding, infection, nerve damage, and muscle weakness. Therefore, it’s important that the choice of anesthesia type and its administration are carefully done based on each patient’s condition.
When a Person Should Avoid Lower Extremity Blocks
Lower leg nerve blocks, a type of procedure to numb your legs, usually have very few complications. However, there are some conditions that may make this procedure risky:
If a person’s blood clots more easily than normal, a condition known as a hypercoagulable state, the doctor may not notice the early signs of a deep vein clot. This is especially important in people who are at high risk for blood clots that can travel to the lungs, known as venous thromboembolism.
Individuals with low platelet count (thrombocytopenia) or those on blood thinners have a predisposition to bleed at the site of injection, leading to potential complications.
If there are already skin infections at the place where the needle will be inserted, it’s possible that the infection can be spread to the lower leg or the nerves, potentially causing a severe deep infection.
Lastly, if a patient is known to be allergic to the type of anesthesia that would be used for the procedure, a lower extremity nerve block should not be performed due to the risk of a severe allergic reaction, known as anaphylaxis, or other less severe allergic responses.
Equipment used for Lower Extremity Blocks
When doctors perform nerve blocks in the lower part of the body, they use various tools and substances. These include:
– Povidone iodine solution or chlorhexidine: These are antiseptic solutions used to clean the skin before the procedure to prevent infection.
– Sterile towels and gauze: These clean materials are used to wipe the skin and cover the wound after the procedure.
– Sterile gloves: The doctor wears these during the procedure to maintain cleanliness and prevent any potential infections.
– Sterile gown: This is a clean protective garment that the doctor might wear when they have to place a catheter (a thin tube to deliver medicine).
– Pre-injection aspiration control syringe: This is a special kind of syringe that the doctor uses to make sure they’re injecting the anesthetic in the right spot.
– Needles: There are several types of needles involved. The 18 or 20 Gauge (G) needles are used for preparing the anesthetic solution. The smaller, 25 G needle is used for the actual injection of the anesthetic.
– Local anesthetic with additives: The anesthetic, which temporarily numbs the area, might have additional substances mixed in. These could be epinephrine (which constricts blood vessels), dexamethasone or dexmedetomidine (substances that can enhance the anaesthetic’s effect).
Who is needed to perform Lower Extremity Blocks?
A lower extremity nerve block is a simple procedure that temporarily blocks nerve signals in your lower body. Although straightforward, this procedure could lead to serious complications. That’s why doctors carry it out in specifically designed areas equipped with standard American Society of Anesthesiologists monitors (machines that keep track of your vital signs like heart rate and blood pressure).
Also, they establish intravenous access (a way to give medications or fluids directly into your vein), and have emergency medication and equipment on hand, if needed. This includes a substance called Intralipid, used to treat specific types of drug overdose. This preparation ensures the procedure is as safe as possible, ready for any unexpected scenario.
How is Lower Extremity Blocks performed
Different levels of numbness are needed for different types of surgery on your legs. To achieve this, we can block different combinations of nerves in your leg. This ensures that the area of your leg being operated on doesn’t feel any pain.
One of these procedures is known as the lumbar plexus block (LPB). This targets several nerves inside your hip and leg. A needle is placed near specific points in your lower back, with the help of an ultrasound or nerve stimulation to guide the needle into the correct spot. This procedure has been found to help reduce pain after hip surgery, but it does have a risk of causing falls, spinal anesthesia, and other complications.
Another method is called the ‘3-in-1 block’, which also targets several nerves but approaches them slightly differently. Anesthetic is injected just below your hip bone near your groin, and pressure is applied to ensure the anesthetic reaches all the targets. This method requires the use of more anesthetic and has been effective in relieving pain after hip surgery.
When it comes to nerve blocks for knee surgery, a femoral nerve block (FNB) has been shown to be really effective. The nerve can be blocked in different ways, but the best method seems to be just below your hip bone, about 2 inches away from your groin. This procedure uses either an ultrasound or nerve stimulation to help the surgeon guide the needle. FNB can result in lower pain and nausea after surgery and even improve your satisfaction. There are few downsides, though patients have reported falls and nerve pain.
Certain specific nerves like the saphenous nerve can be targeted at their locations such as the middle of your thigh. This type of nerve block is popular because it blocks pain without affecting movement—great for physical therapy and rehabilitation.
The adductor canal block (ACB) is a method primarily used to provide numbness after knee surgery. This technique preserves your thigh muscle strength, making it advantageous for walking surgeries and early postoperative mobilization. You’ll lay on your back with your leg slightly turned out to allow access to the thigh’s inner part. A needle is introduced through the skin under ultrasound guidance, and advanced towards the saphenous nerve, usually located next to the main leg artery.
Finally, a proximal nerve block (SNB), which provides numbness to the lower leg, foot, and ankle, can be achieved through various approaches. The classic approach is often called the Labat approach. This approach involves blocking the main nerve in the buttock between the bony points you can feel on your side and pelvis, below the surface muscles but above the deeper thigh muscle.
Accurate positioning of the needle is crucial in all these procedures to ensure the anesthesia works properly and to avoid any potential side effects. These techniques significantly reduce pain after surgery and can help you recover faster, but like all procedures, they can have side effects that your doctor will discuss with you.
Possible Complications of Lower Extremity Blocks
If you get an injection, you might experience some problems around the area where the needle went in, like:
* A hematoma, which is a swollen area filled with blood.
* Infection.
* An injury to the nerve around the injection site.
* Nearby areas becoming numb due to the anesthetic.
* The anesthetic not working properly, causing the injection to fail.
There can also be problems throughout your whole body from the anesthetic, not just at the injection site. This is known as local anesthetic systemic toxicity. You might experience symptoms like:
* Feeling dizzy or lightheaded.
* Vision becoming blurry.
* Hearing ringing or buzzing in your ears.
* Tasting metal in your mouth.
* Feeling numb or tingling around your mouth, fingers, or toes.
* Feeling sleepy or confused.
* In the worst-case scenario, having seizures or a heart attack.
What Else Should I Know About Lower Extremity Blocks?
When used properly, most lower leg nerve blocks (medicine injected to block pain signals) last between 6 to 24 hours. However, the amount of time they can provide numbness or pain relief may vary. There are other alternatives for pain relief and anaesthesia (medicine given to prevent pain) in the lower leg, including spinal and epidural anesthesia.
Recent studies indicate that lower leg nerve blocks have some significant benefits over general anesthesia—particularly for surgeries in the lower legs. These benefits include reduced pain, faster recovery times, and fewer side effects that are often associated with general anesthesia.
Two recent comprehensive assessments support this claim—both show that nerve blocks may be better than general anesthesia for surgeries on our lower legs. In one case, the research analyzed patients who had undergone amputations of their lower extremities. It found that patients who had been given a local or regional anesthetic (nerve blocks) ended up with better outcomes: fewer complications and improved pain management compared to those who had been given general anesthesia. This suggests that nerve blocks could be the better choice for lower leg amputations.
Another similar review looked at local or regional anesthesia vs. general anesthesia for surgeries aimed at improving blood flow to the lower leg. Similar to the first study, it found that patients treated with regional anesthesia showed improvement and had fewer problems after surgery. This strengthens the argument for using nerve blocks in lower leg surgery.
The above studies highlight the potential benefits of nerve blocks in lower leg surgery. Compared to general anesthesia, nerve blocks can help reduce the risk of complications after surgery, provide better pain management, and help patients recovery faster. However, it is always crucial to consider each patient’s unique situation, including their overall health, surgical risk, and preferences. Plus, while the studies do support the use of nerve blocks, successfully administering them does require special training and expertise. That means it’s really important to ensure that health professionals have proper training with these techniques to maximize their benefits and minimize potential risks.
