Sciatica

Dr. WONG Yat Wa

Honorary Consultant in Orthopaedic Surgery

Specialist in Orthopaedics and Traumatology

Many people loosely use the term "sciatica" to describe any lower back, buttock, or thigh pain. However, the classical textbook definition of sciatica specifically refers to radicular pain originating from the nerve roots that form the sciatic nerve. Among these nerve roots, the L5 and S1 are most affected. Consequently, if the L5 nerve root is involved, pain, numbness, or a pins-and-needles sensation typically affects the lateral leg and the dorsum of the foot. Conversely, if the S1 nerve root is the cause, symptoms usually involve the posterior calf and the sole of the foot.

The sciatic nerve is composed of the L4, L5, S1, and S2 nerve roots. The distribution of symptoms such as pain or numbness depends on which nerve root is affected. For example, if the L5 nerve root is compressed, pain or numbness may radiate along the lateral thigh, lateral leg, and the dorsum of the foot. If the S1 nerve root is compressed, pain or numbness may extend from the posterior thigh to the posterior leg and the sole of the foot. There are many causes of sciatica. Mechanical compression of a nerve root by a prolapsed intervertebral disc, osteophyte, or hypertrophic ligamentum flavum are common causes. However, inflammation of nerve roots, compression by a neurogenic tumor, or epidural collection can also lead to sciatic symptoms. This article focuses on sciatica caused by acute disc prolapse and degenerative spinal diseases.

The lifetime incidence of sciatica ranges from 10-40% according to various epidemiological studies. Factors such as genetic predisposition leading to weaker structural integrity, degeneration, or any elements that accelerate lumbar degeneration—such as prolonged heavy manual labor, smoking, lack of physical exercise, and poor posture—can increase the likelihood of sciatica. Acute sciatica is commonly caused by acute intervertebral disc prolapse. The typical clinical presentation includes pain radiating from the lower back to the buttock and extending beyond the knee. It occurs more frequently in younger patients. Straight leg raising in the supine position is severely limited, and leg symptoms are aggravated immediately when patients ambulate. In contrast, sciatic symptoms due to degeneration (such as osteophyte or hypertrophic ligament compression of the nerve roots) have a more insidious onset and tend to affect older patients.

Most cases of sciatica are self-limiting. A short period of rest, appropriate drug treatments such as paracetamol, non-steroidal anti-inflammatory drugs, antiepileptic drugs such as pregabalin or gabapentin, or low-dose antidepressants such as amitriptyline, along with physiotherapy or acupuncture, can help control acute symptoms. Within four weeks, 70-80% of patients recover and return to normal life. Clinicians generally tailor holistic treatment programs based on the duration of symptoms, severity, and patient needs. In general, a combination of treatment modalities yields better outcomes. In principle, all non-surgical treatments should be maximized before considering surgery.

If sciatic pain persists or worsens, clinicians may adjust the drug dosage and recommend appropriate radiological investigations such as X-ray or MRI. Besides confirming the diagnosis, it is crucial to assess whether the imaging findings align with the patient's clinical picture. If non-invasive treatments fail, clinicians may consider an epidural injection of mixed steroids and analgesics. This can reduce inflammation around the nerve roots and support the diagnosis if pain relief occurs immediately after the injection. Once the patient's symptoms are under control, vigorous rehabilitation, especially core muscle mobilization and strengthening, is highly recommended to reduce the chance of recurrence.

Unless there is a neurological deficit, there is no need to immediately consider surgical intervention. It is worthwhile to try various non-operative treatments first. If non-operative treatments are ineffective, clinicians will base their decision on the exact diagnosis, patient preferences, pain severity, impact on daily activities, potential benefits of surgery, and the risks involved to determine whether surgery is worthwhile or feasible.

If a patient's sciatica is caused by nerve root compression due to a prolapsed intervertebral disc or other hypertrophic structures, surgeons can remove the compressing structure, such as the prolapsed disc, osteophyte, or hypertrophic ligament, through a small incision or endoscopically. Decompression of the nerves not only relieves symptoms but also reduces the risk of spinal nerve injury, which can potentially cause muscle weakness and atrophy or, in severe cases, cauda equina syndrome, where patients experience loss of urinary or bowel control. If there is associated lumbar spinal instability, spinal fusion may be necessary in addition to decompression. The surgical trauma of modern spinal decompression, with or without fusion, is not high, whether it is performed as open or minimally invasive surgery. Patients are advised to discuss the details with their surgeons to understand the pros and cons of various techniques.

There are many causes of sciatica. Apart from diseases of the vertebral column, inflammation of the nerve roots or autoimmune diseases can also cause sciatic-type pain. These patients will not benefit from surgery. Other poor surgical outcomes may result from inadequate decompression, spinal instability without proper fusion, or adhesions around the spinal nerves. Surgery may not always be indicated for failed non-operative treatment. An accurate diagnosis, a clinical picture that aligns with radiological findings, a clear surgical target, and patients' understanding of their own conditions are crucial for successful treatment.

Prevention is better than treatment. To prevent sciatica, it is essential to maintain a healthy spine. This includes engaging in appropriate core exercises and mobilization, maintaining proper posture, especially during heavy lifting, and quitting smoking.