What is Inferior Gluteal Nerve Injury?
The inferior gluteal nerve comes from a network of nerves in the lower back, specifically the fibers from the L5, S1, and S2 nerves. This nerve is responsible for controlling the gluteus maximus muscle, which is a large muscle in your buttocks that helps you extend, or straighten, your hip and rotate your hip outward. This specific nerve only controls the movement of this muscle and doesn’t provide any sensitivity or feeling.
Here’s how the inferior gluteal nerve works: it is a branch of another network of nerves known as the sciatic plexus. It begins its journey in front of a muscle in the pelvis called the piriformis muscle. It then leaves the pelvis through an opening known as the greater sciatic foramen, just below the piriformis muscle. Here, it splits into several branches. These branches move back and enter the gluteus maximus muscle from its deeper surface. The inferior gluteal nerve travels 5 to 6 cm from specific landmarks in your hip, the tip of the greater trochanter and the posterior superior iliac spine (PSIS), and enters into the lower part of the muscle. The inferior gluteal nerve is always found close to a blood vessel called the inferior gluteal artery.
The main purpose of the inferior gluteal nerve is to control the gluteus maximus. Thus, it plays a significant role in straightening your body from a bent forward position and straightening your hip when you go from sitting to standing, climb stairs, or stand up from a squat.
What Causes Inferior Gluteal Nerve Injury?
The inferior gluteal nerve can get injured in a variety of ways, but most commonly it happens as a result of medical procedures – what we call ‘iatrogenic injury’. The main surgical procedure that puts this nerve at risk is total hip replacement, but other things, like trauma, entrapment of the nerve, and pressure or lack of blood flow to the nerve can also cause injury. With all these types of injury, typically they result in an unusual walking pattern called a ‘gluteus maximus lurch’.
Total hip replacement is often done through an approach from the back of the hip; this approach carries the highest risk to the inferior gluteal nerve. This is because in this approach, the nerve often can’t be seen, and no clear path between the nerves is apparent. The risk of injuring the inferior gluteal nerve is highest when the surgeon has to make a cut through the gluteus maximus muscle. The nerve can be damaged in several ways: direct injury from sharp cutting, cutting off the blood supply to the nerve, or stretching or crushing the nerve from surgical instruments. Depending on if branches of the nerve or the whole nerve get injured, the damage can be partial or complete.
Two other typical causes of inferior gluteal nerve injury are entrapment (in a condition called ‘piriformis syndrome’) and surgery in the area around the sacrum. In piriformis syndrome, the foramen (a natural hole or passage) under the piriformis muscle can squeeze any nerve passing through it, leading to symptoms of inferior gluteal nerve entrapment. If this keeps up, the muscle on the same side (ipsilateral) as the nerve entrapment can start to waste away (atrophy). Surgery in the area of the sacrum, especially when removing tumors, can be tricky. Surgeons need to know exactly where they’re going to avoid damaging both the superior and inferior gluteal nerves and arteries. Ligaments near the sacrum can be used as landmarks to assist in identifying these important structures. It’s ideal to keep as much of the muscle as can be safely done in order to preserve as much function as possible.
Even though we often think of the inferior gluteal nerve as one whole nerve that only controls muscle action, a recent study has found that it typically actually gives out 1 to 2 branches that also have sensation duties like carrying feelings from the skin over a bony part of the thigh called the greater trochanter. This is really crucial information for orthopedic surgeons performing hip surgery, and pain specialists treating patients with gluteal pain syndromes.
Risk Factors and Frequency for Inferior Gluteal Nerve Injury
Currently, there aren’t any available statistics on how often injuries to the inferior gluteal nerve occur.
Signs and Symptoms of Inferior Gluteal Nerve Injury
Injury to the inferior gluteal nerve can lead to the loss of function in the gluteus maximus muscle, which is a condition often called ‘gluteus maximus lurch.’ This condition arises when the muscle on one side of the hip becomes weak or non-functional. Patients may notice their affected buttock losing its shape as the muscle wastes away.
Normally, during walking, the gluteus maximus muscle contracts when the heel of your foot touches the ground, which helps extend your hip. When the inferior gluteal nerve is damaged, this motion can be compromised. To compensate for this, patients often lean their upper body backwards when the affected heel strikes the ground during walking, a movement that is characteristic of the ‘gluteus maximus lurch.’ This backward lean is maintained throughout the walking cycle and helps to keep the hip locked in an extended position. In some cases, the hamstring muscles can adapt to help out to some degree.
It’s worth noting that, the gluteus maximus muscle doesn’t really help with maintaining a standing posture – it’s relaxed when you’re standing up straight and doesn’t play a big role in basic walking. But, it’s crucial for high-intensity actions like running, climbing, and getting up from a sitting or crouching position. It’s also needed to control the motion of the hip when one sits down.
Testing for Inferior Gluteal Nerve Injury
To diagnose a lower buttock nerve injury, your doctor will ask you about your symptoms and medical history and perform a physical examination. This process is typically enough to determine if you have this kind of injury.
However, in some cases, your doctor might use imaging tests – like x-rays, CT scans, ultrasound, or MRI – to rule out other possible causes for your symptoms. These tests can provide detailed pictures of structures inside your body, helping your doctor to make a correct diagnosis.
On top of that, your doctor may use neuroconductive studies. These are tests that measure the speed and degree of electrical activity in your nerves. They can provide additional information that supports the findings from your physical examination, making it easier for your doctor to confirm the diagnosis of a lower buttock nerve injury.
Treatment Options for Inferior Gluteal Nerve Injury
Peripheral nerve injuries can happen in various ways and vary in seriousness. They commonly occur due to stretching, cutting, or crushing. A physician named Seddon categorized these injuries based on how severe they are. The three categories are neuropraxia, caused by nerve compression; axonotmesis, where the nerve’s axon is damaged but the outer layer of the nerve is intact; and neurotmesis, which involves total damage to the nerve.
This classification was further expanded by a physician named Sunderland, who suggested three types of axonotmesis. Grade I axonotmesis occurs when the axon is damaged, but the inside of the nerve is still intact, which is the best scenario for healing. Grade II axonotmesis involves damage to the axon and the inside of the nerve, but the outer part and bundles of nerve fibers are intact. Grade III axonotmesis, the most severe, affects the axon, inside and outside of the nerve, and the bundle of nerve fibers.
How a peripheral nerve injury is treated depends on the type and severity of the injury. If the injury is open, it might need surgery to determine the level of damage to the nerve. If the nerve is cleanly cut, for example during hip replacement surgery, it should ideally be repaired within 72 hours to prevent the ends of the nerve from retracting, and early repair often leads to better outcomes. Cut nerve injuries caused by crushing or blunt force usually have delayed surgery within 2-3 weeks so the ends of the nerve can scar over. The scared nerve ends can then be removed and the remaining nerve ends can be repaired, sometimes with a nerve graft. Injuries that are open but have not severed the nerve can be managed without surgery. Doctors use various tests and examinations over time to monitor the injury.
In general, injuries that are not open are managed without surgery at first, as the nerves often stay connected. If a nerve injury is suspected to be neuropraxia or axonotmesis, the injury is monitored using regular examinations, nerve function diagnostics, and radiological tests. If there are no signs of the nerve beginning to work again 3 to 4 months after the injury, this suggests a serious injury called neurotmesis, which usually requires surgery and the use of tests during the operation to monitor nerve function.
Physiotherapy and rehabilitation therapy can also help patients recover from peripheral nerve injuries.
What else can Inferior Gluteal Nerve Injury be?
Most of the time, damage happens to the inferior gluteal nerve during a surgical procedure called total hip arthroplasty (THA). However, there are other things that could cause this type of problem, such as problems with blood vessels, tumors, situations where a nerve is trapped, or infections. A detailed medical history and physical examination can help figure out the real cause.
If a person feels less sensation or numbness in the lower part of their buttock, or shows signs of damage to the inferior gluteal nerve, these could be early signs of recurring colorectal cancer.
Now, doctors know that they can perform a type of surgery to enhance the buttock muscle (intramuscular augmentation gluteoplasty) at a superficial level. This prevents any injury to the inferior gluteal nerve, which is located deep within the gluteus maximus muscle.
It was previously believed that damage to the inferior gluteal nerve during a procedure called sacrospinous ligament fixation could cause postoperative gluteal pain. However, the pain after this surgery is now believed to be possibly because of damage to nerve branches coming from the S3/S4 nerves.
What to expect with Inferior Gluteal Nerve Injury
Currently, there’s no available data in existing medical literature about the likely outcomes or prognosis of injuries to the inferior gluteal nerve.
Possible Complications When Diagnosed with Inferior Gluteal Nerve Injury
If the inferior gluteal nerve is damaged, it can lead to a couple of major problems. Firstly, it can change your walking pattern, which is known as the “gluteus maximus ‘lurch'”. Secondly, it can cause the gluteus maximus muscle, which is located in your buttock, to shrink. This can cause that side of your buttock to lose its shape. These changes can affect both your physical and mental health, not just in the short term, but over a long period as well.
Major Problems:
- Change in walking pattern
- Gluteus maximus muscle shrinking
- Loss of buttock shape
- Negative effects on physical and mental health
Preventing Inferior Gluteal Nerve Injury
Before going through any surgery that might put a certain nerve at risk, it’s important for doctors to explain to their patients what risks are involved. This conversation should happen before the patient agrees to the surgery. This way, they are fully aware of what may happen and can make an informed decision.
