Anterolisthesis

Anterolisthesis, a form of spondylolisthesis, is a spinal condition that occurs when one of the spinal vertebrae slips forward over the underlying vertebrae. Spondylolisthesis is a broad group of conditions that also includes retrolisthesis, which occurs when a vertebra slips backwards over the underlying vertebrae. Most commonly, anterolisthesis affects the lower back, particularly the lumbar spine, and is common in young athletes and older individuals with degenerative spinal changes.

Anterolisthesis may occur when there is a defect or fracture of the pars interarticularis, which is the bony bridge that connects the superior and inferior facet joints of two contiguous vertebrae. Damage to the pars interarticularis, called spondylolysis, can cause the posterior part of the vertebral arch to separate from the rest of the vertebrae. If the defect is bilateral, the vertebrae can shift and slip anteriorly relative to the vertebrae below, resulting in anterolisthesis. For example, spondylolysis of L5 can cause the L5 vertebral body to slide anteriorly relative to the S1 vertebra.

In young individuals, anterolisthesis is typically caused by repetitive stress loads in sports that involve hyperextension or rotation of the lumbar spine, such as gymnastics or weightlifting. Other causes include congenital defects and traumatic injuries, such as falls from height or motor vehicle accidents. In older individuals, anterolisthesis is more commonly associated with degenerative changes of the spine, including arthritis of the facet joints and disc degeneration. As the intervertebral discs degenerate, there is a corresponding loss of disc height, leaving a disproportionate load on the posterior part of the spinal column that weakens the pars interarticularis. 

Symptoms of anterolisthesis can include lower back pain that radiates to the buttocks or legs, muscle spasms, and stiffness in the back. Usually, pain worsens with activity and improves when lying down as the affected vertebrae temporarily slip back into place. If sliding of the vertebrae continues, it can compress one or more of the spinal nerves traveling through openings in the spinal column, resulting in lower limb pain, difficulty walking, and tingling and numbness in one or both legs. 

Diagnosis of anterolisthesis typically involves a physical exam and imaging tests, such as X-rays, a CT scan, or an MRI of the spine. On a lateral or oblique view of the lumbar spine, X-rays can show a defect or fracture of the pars interarticularis with various degrees of vertebral sliding. A CT scan of the spine may be performed if there is a high suspicion of spondylolisthesis with normal X-rays, while an MRI can be helpful to determine if there’s spinal nerve or spinal cord compression in people with neurogenic claudication.

Spondylolisthesis can be graded based on the Meyerding classification, where grade I involves a sliding of less than 25% of the vertebral body, and grade V defines a sliding of the entire vertebral body over the underlying vertebrae. Most cases of spondylolisthesis are grade I or II on the Meyerding classification. 

Most people with anterolisthesis can be managed successfully without surgery. Conservative treatment options include rest and avoidance of activities that worsen the symptoms, physical therapy to strengthen the back muscles, and pain management with anti-inflammatory medications (e.g., ibuprofen, diclofenac, naproxen) or epidural steroid injections in some cases. 

In cases where there is persistent pain or compression of the spinal cord or spinal nerves producing neurologic deficits, surgery may be recommended. Surgery for spondylolisthesis may involve direct fixation by placing a screw or wire in the fractured pars interarticularis to prevent the vertebrae from sliding forward. Another technique is spinal decompression, which aims to relieve pressure on the spinal nerves to reduce pain and improve mobility. Finally, spinal fusion involves permanently joining together two or more vertebrae to correct the alignment of the vertebrae, prevent them from sliding further, and reduce the mobility of the spine.

Anterolisthesis is a common cause of lower back pain that occurs when one of the spinal vertebrae slips forward over the vertebrae below it. Common causes include congenital defects; degenerative changes; trauma; and repetitive stress, such as from gymnastics or weightlifting. Symptoms include lower back pain, stiffness, and numbness or tingling in the legs. Diagnosis is made based on imaging techniques, such as an X-ray or CT scan. Treatment may involve pain medications, physical therapy, or surgery, in some cases.