Pain Management: A Patient's Guide to Piriformis Muscle Injections

Introduction

Piriformis muscle injections are commonly used to determine what is causing buttock and sciatica type pain. Piriformis muscle injections are both diagnostic injections and therapeutic injections, meaning that they help your doctor determine the cause of your back pain and may or may not provide you with relief from the pain. These injections eliminate pain temporarily by paralyzing the piriformis muscle and stopping spasm in the muscle. If the piriformis muscle is injected and your pain goes away for several days, then it is very likely that a portion of your pain is caused by piriformis syndrome. Once you and your doctor know what structure is causing your pain, you can begin to explore options for treating the condition.

This guide will help you understand

• where the injection is given
• what your doctor hopes to achieve
• what you need to do to prepare
• what you can expect from the injection
• what might go wrong

Anatomy

What parts of the body are involved?

The lower lumbar spinal nerves leave the spine and join to form the sciatic nerve. The sciatic nerve leaves the pelvis through an opening called the sciatic notch.

The piriformis muscle begins inside the pelvis. It connects to the sacrum, the triangular-shaped bone that sits between the pelvic bones at the base of the spine. The connection of the sacrum to the pelvis bones forms the sacroiliac joint. There is one sacroiliac joint on the left and one on the right of the low back. The other end of the piriformis muscle connects to the greater trochanter, the bump of bone on the top side of your hip.

The piriformis muscle is one of the external rotators of the hip and leg. This means that as the muscle works, it helps to turn the foot and leg outward. Problems in the
piriformis muscle can cause problems with the sciatic nerve. This is because the sciatic
nerve runs under (and sometimes through) the piriformis muscle on its way out of the
pelvis. The piriformis muscle can squeeze and irritate the sciatic nerve in this area,
leading to the symptoms of sciatica.

Related Document: A Patient's Guide to Lumbar Spine Anatomy

Rationale

What does my physician hope to achieve?

Your doctor is recommending a piriformis muscle injection to try and determine if piriformis muscle contractures are part of the cause of your pain. This type of injection is primarily a diagnostic injection. The injection may only help your pain temporarily, sometimes just for a few hours. Once your doctor is sure that it is the piriformis muscle causing your pain, other procedures may be recommended to reduce your pain for a longer period of time.

The large sciatic nerve travels through the pelvis and leaves the pelvis through an opening called the sciatic notch. The nerve then travels down the back of the leg where it branches many times to supply sensation and muscle power to all areas of the lower extremity.

The piriformis muscle and tendon run right over the top of the sciatic nerve as the nerve leaves the pelvis at the sciatic notch. Spasm in the piriformis muscle can cause pain by squeezing against the sciatic nerve. This causes the nerve to become irritated and inflamed - resulting in pain in the buttock and leg. If the spasm continues, the muscle may become contracted (shortened). This increases the pain and inflammation. To reverse the contracture, the muscle and tendon need to be stretched and lengthened back to normal. Paralyzing the muscle temporarily with an injection can make the stretching less painful, more effective, and speed up the process of lengthening the muscle and tendon.

Related Document: A Patient's Guide to Piriformis Syndrome

If the stretching program fails to correct the problem, surgery to lengthen the tendon is an option. Before considering surgery, it is necessary to confirm the diagnosis as best as possible, so the information from the injection is important. If the injection temporarily relieves your symptoms, then the surgeon is more comfortable that the surgery is indicated and has a good chance of helping your problem. If the injection does not help, then some other cause of your symptoms may need to be considered.

During a piriformis muscle injection, the medications that are normally injected include an anesthetic and cortisone. The anesthetic medication (such as novocaine, lidocaine or bupivicaine) is the same medication used to numb an area when you are having dental work or having a laceration sutured. The medication causes temporary paralysis of the piriformis muscle lasting one hour to six hours, depending on which type of anesthetic is used.

Cortisone is an extremely powerful anti-inflammatory medication. When this medication is injected into a painful, inflamed joint, it can reduce the inflammation and swelling. Reducing the inflammation reduces pain. If cortisone is also injected into the joint at the same time, you may get several weeks' worth of relief from your pain. This can allow you to get started in a physical therapy program, strengthening and stretching the piriformis muscle to reduce the contracture and the spasm in the muscle.

Preparation

How will I prepare for the procedure?

Your doctor may tell you to be NPO for a certain amount of time before the procedure. This means that you should not eat or drink anything for the amount of time before your procedure. This means no water, no coffee, no tea - not anything. You may receive special instructions to take your usual medications with a small amount of water. Check with your doctor if you are unsure what to do.

You should tell your doctor if you are taking any medications that thin your blood or interfere with blood clotting. The most common blood thinner is coumadin. Other medications also slow down blood clotting. Aspirin, ibuprofen, and nearly all of the anti-inflammatory medications affect blood clotting. Medications used to prevent strokes, such as Plavix, can also affect blood clotting. These medications usually need to be stopped seven days prior to the injection. Be sure to let your doctor know if you are on any of these medications.

Procedure

What happens during the procedure?

When you are ready to have the injection, you will be taken into the procedure area and an IV will be started. The IV allows the nurse or doctor to give you any medications that may be needed during the procedure. The IV is for your safety because it allows a very rapid response if you have a problem during the procedure, such as an allergic reaction to any of the medications injected. If you are in pain or anxious, you may also be given medications through the IV for sedation during the procedure.

Piriformis muscle injections are done with the help of fluoroscopic guidance. The fluorscope is an x-ray machine that allows the doctor to actually see an x-ray image while doing the procedure. This allows the doctor to watch where the needle goes as it is inserted. This makes the injection much safer and much more accurate. Once the needle is in the right location, a small amount of radiographic dye is injected. This liquid dye shows up on the x-ray image, and the doctor can watch where it goes. The anesthetic medication and the cortisone will go in the same place. The doctor wants to make sure the injection will put the medication where it can do the most good. Once the correct position is confirmed, the anesthetic and cortisone are injected, and the needle is removed.

You will then be taken out of the procedure room to the recovery area. You will remain in the recovery area until the nurse is sure that you are stable and you do not have any allergic reaction to the medications.

Your doctor will be interested in how much the pain is reduced while the anesthetic (numbing medication) is working. You may be given a pain diary to record what you feel for the next several hours. This is important for making decisions, so keep track of your pain.

The anesthetic may cause some temporary numbness and weakness. You will be free to go when these symptoms have resolved.

Complications

What might go wrong?

There are several complications that may occur during or after the piriformis muscle injection. Injection procedures are safe and unlikely to result in a complication, but no procedure is 100% foolproof. This document doesn't provide a complete list of the possible complications, but it does highlight some of the most common problems. Complications are uncommon, but you should know what to watch for if they occur.

Allergic reaction

Like most procedures where medications are injected, there is always a risk of allergic reaction. The medications that are commonly injected include lidocaine, bupivicaine, radiographic dye, and cortisone. Allergic reactions can be as simple as developing hives or a rash. They can also be life threatening and restrict breathing. Most allergic reactions will happen immediately while you are in the procedure room so that help is available immediately. Most reactions are treated and cause no permanent harm. You should alert your doctor if you have known allergies to any of these medications.

Infection

Several types of infections are possible complications of piriformis injections. Any time a needle is inserted through the skin, there is a possibility of infection. Before any injection is done, the skin is cleansed with a disinfectant and the health care provider doing the injection uses what is called sterile technique. This means that the needle and the area where the needle is inserted remains untouched by anything that is not sterile. The provider may also use sterile gloves.

Infections can occur just underneath the skin, in a muscle, or in the deep tissues of the buttock. You should watch for signs of increasing redness, swelling, pain, and fever. Almost all infections will need to be treated with antibiotics. If an abcess forms, then a surgical procedure may be necessary to drain the pus in the abcess. Antibiotics will also be necessary to treat the infection.

Increased pain

Not all injections work as expected. Sometimes, injections cause more pain. This may be due to increased spasm in the muscles around the injection. The increased pain is usually temporary, lasting a few hours or a few days. Once the medication has a chance to work, the injection may actually perform as expected and reduce your pain. Increased pain that begins several days after the injection may be a sign of infection. You should alert your doctor if this occurs.

After Care

What happens after the procedure?

If everything goes as planned, you will be able to go home soon after the injection, probably within one hour. There are no restrictions on diet or activity after the piriformis muscle injection. You can return to physical therapy or chiropractic care as soon as you like.

Most doctors will arrange a followup appointment, or phone consult, within one or two weeks after the procedure to see how you are doing and what effect the procedure had on your symptoms.

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