Understanding Lumbar Spinal Stenosis and Its Treatment

Dr. KO, Joshua

Honorary Consultant in Orthopaedic Surgery

Specialist in Orthopaedics & Traumatology

The human lumbar spine consists of a series of vertebral bodies, separated by intervertebral discs and connected at the back by facet joints. The primary functions of the lumbar spine are to control body movement, support body weight, and protect spinal nerves. The spinal nerves, enclosed within the spinal canal (commonly referred to as the "canal"), extend from the brain down to the lower limbs. Along the way, nerve roots branch out through openings between the vertebrae, controlling movements and sensations.

When the space inside the spinal canal becomes too narrow, the spinal nerves and nerve roots may get compressed, and just like blood clots in coronary arteries, impede blood circulation. This condition, known as lumbar spinal stenosis, also disrupts normal transmission of nerve signals and causes neurological symptoms such as numbness, tingling, or pain, significantly impacting daily life. Compression of the cauda equina nerves, which extend from the base of the spine to the lower limbs, may also affect leg function and bladder or bowel control.

Lumbar Degenerative Tissue Proliferation and Central Spinal Stenosis

As we age, the intervertebral discs degenerate over time and spinal joints endure continuous pressure, friction on cartilage and ligaments intensifies. This can lead to bone spurs, thickening of the yellow ligament, or disc herniation, causing the spinal canal to narrow and compress the nerves and nerve roots within. Medically, this is known as "lumbar spinal stenosis," primarily central stenosis, where the central canal narrows.

Some individuals are born with a naturally narrower spinal canal, making them more prone to lumbar spinal stenosis in middle age due to disc issues, a condition called "developmental stenosis." In severe cases, the degenerated disc fails to provide support, and movements like bending forward or backward can significantly irritate the nerves.

Leg Numbness, Pain, and Walking Difficulty

Typically, pain radiates from the lower back through the hips to the thighs and calves. In cases of mild spinal canal narrowing, symptoms may not be noticeable when one starts walking at first. As the narrowing worsens, symptoms like leg soreness, numbness, weakness and fatigue may appear earlier while walking. Patients may need to rest more often, and can walk less and less when the condition deteriorates.

The severity of canal narrowing and pain is closely associated with the posture. With the same walking distance, patients may feel more at ease while walking uphill than downhill as the lumbar spine leans slightly forward and widens the spinal canal.

Surgical "Decompression": Posterior Laminectomy

Before treatment, doctors will begin with a clinical examination, followed by X-rays to check for lumbar degeneration or misalignment. Once the problem area is identified, an MRI is arranged to assess the condition of lumbar tissues as well as the extent of nerve compression.

Treatment usually starts with physical and muscle therapy, which leverages the spine’s mobility to reduce canal narrowing. Slouching or standing for extended periods can overstress the lumbar spine, causing the thoracic spine to hunch and the lumbar spine to tilt backward, tightening muscles and worsening canal narrowing. Physical and muscle therapy helps relax these muscles and build up endurance, enabling patients to maintain an upright posture. Mild numbness may gradually subside over time.

If patients still cannot walk for 10 minutes after therapy, possibly due to severe central narrowing of the spinal canal, "posterior laminectomy decompression surgery" (commonly called "decompression surgery") may be needed. This procedure involves removal of “obstacles” such as bone spurs, thickened yellow ligaments, and herniated discs from the spinal canal, thereby relieving pressure on the nerves and nerve roots while addressing disc herniation.

Nowadays, most decompression surgeries are minimally invasive, using a "unilateral approach, bilateral spinal decompression" technique. With the patient under general anaesthesia, a surgeon will insert a 4–8 mm endoscope through a small back incision to access the spinal canal. Through another tiny incision, precise instruments will separate muscles on one side and remove part of the lamina, clearing bone spurs, ligaments, and discs that compress the nerves on both sides. A water flow is maintained throughout the surgery to flush out any debris and blood and reduce infection risk. Radiofrequency energy is also applied to tighten the joint capsule, thereby minimising friction and preserving the surrounding tissues and muscles.

Compared to microscopic decompression, endoscopic surgery can achieve higher precision with a clearer, more detailed view. Surgeons can decompress the canal without removing excess bone or tissues, thereby maintaining joint and muscle integrity and stability. Minimally invasive surgery involves smaller incisions, less bleeding, and faster recovery, and patients can be discharged the day after surgery. To prevent complications, elderly patients should avoid large movements like bending for two to three weeks post-surgery, especially if they have osteoporosis. Maintaining proper posture daily can further improve outcomes.

If the nerves are irritated by frequent disc movement and the proliferative structures are not well-developed or stable yet, an X-ray is needed to determine if fusion surgery is required. Fusion surgery carries risks, especially for elderly patients with fragile bones. It also requires longer recovery and may pose higher complication risks. For mildly unstable joints, endoscopic surgery can preserve the joint capsule and muscles at the affected site, using radiofrequency to tighten the capsule.

If physical therapy fails and severe pain persists, patients with developmental stenosis may opt for an epidural steroid injection ("nerve block") to control disc inflammation. 70% of patients can resume muscle therapy after injection. If a disc tear is found, percutaneous endoscopic discectomy may be performed with radiofrequency treatment. Fusion surgery is considered only if other treatments are ineffective.

As the saying goes, "The earlier the treatment, the better the outcome." Patients with mild stenosis symptoms should seek medical advice promptly. If leg pain prevents walking for 15 minutes or worsens even with slower walking, surgery should be considered.

Posture is a key factor in the rate of lumbar degeneration. Whether sitting or standing, maintain a proper upright posture. Regular exercise can strengthen the core, lower back, and intercostal muscles. Others like hip joint stretching practice deep breathing can also help reduce lumbar stress and friction, slow down degeneration, and improve or delay the progression of spinal stenosis.