Spondylolisthesis

Spondylolisthesis is classified into several types based on its underlying cause:

Isthmic (Lytic) Spondylolisthesis

Caused by a fracture or defect in the pars interarticularis — a small bridge of bone connecting the front and back of the vertebra. These pars defects destabilise the neural arch, allowing the vertebral body to slip forward. Isthmic spondylolisthesis is more common in younger people and athletes, particularly those involved in sports with repetitive lumbar extension (gymnastics, fast bowling, weightlifting).

Degenerative Spondylolisthesis

The most common type seen in neurosurgical practice in Melbourne. Occurs due to age-related degeneration of the intervertebral disc, facet joints, and spinal ligaments — causing progressive instability and forward slipping of one vertebra. Predominantly affects adults over 50, and is more common in women. L4/5 is the most frequently affected level.

Other Types

• Dysplastic — rare congenital defect of the neural arch, often associated with spina bifida
• Traumatic — unstable fracture causing acute vertebral slippage
• Pathological — bone destruction from tumour, infection, or metabolic disease
• Iatrogenic — following spinal surgery (e.g. extensive laminectomy) that has destabilised the spine

Grading of Spondylolisthesis

The degree of slip is graded on X-ray:

• Grade I — less than 25% slip
• Grade II — 25 to 50% slip
• Grade III — 50 to 75% slip
• Grade IV — 75% to complete slip

Symptoms depend on the degree of slip, the presence of instability, and whether neural structures are compressed:

Back Pain

Lower back pain is the most common symptom. In unstable spondylolisthesis, pain is typically worsened by activities that load the spine — bending forward, lifting, and prolonged standing — and may be relieved by rest. The pain may arise from the unstable motion segment itself, adjacent disc degeneration, or compensatory facet joint stress.

Leg Pain (Sciatica and Radiculopathy)

Forward slipping of one vertebra on another uncovers and compresses the disc between them, and narrows the exit channels for spinal nerve roots. This causes leg pain, numbness, and weakness in the distribution of the compressed nerve roots. Neurogenic claudication — leg pain worsened by walking and standing — develops when canal stenosis coexists.

Neurogenic Claudication

Particularly in degenerative spondylolisthesis, associated lumbar canal stenosis causes neurogenic claudication — pain, heaviness, and weakness in the legs that comes on with walking and is relieved by sitting or bending forward.

Red Flag Symptoms

Seek urgent neurosurgical assessment if spondylolisthesis is associated with rapidly progressive leg weakness, or loss of bladder or bowel control — these may indicate cauda equina syndrome, a surgical emergency.

Imaging Investigations

• X-ray (standing, including flexion/extension dynamic views) — demonstrates the degree of vertebral slip, pars defects, and any dynamic instability (movement with bending)
• MRI — demonstrates associated disc degeneration, neural compression, and spinal canal stenosis
• CT scan — provides excellent detail of bony anatomy and pars defects; essential for surgical planning
• Bone scan (SPECT CT) — useful for identifying metabolically active pars defects in younger patients

Non-Surgical Treatment Options

Asymptomatic spondylolisthesis does not require surgery and is managed with observation and preventive measures. For symptomatic patients, conservative management is always the first approach:

• Physiotherapy — core strengthening and paraspinal muscle rehabilitation to improve spinal stability and reduce load on the unstable segment
• Clinical Pilates — highly effective for developing the deep stabilising muscles of the lumbar spine
• Activity modification — avoiding heavy lifting and high-impact activities that stress the unstable segment
• Analgesic and anti-inflammatory medications — for back pain management
• Bracing — lumbar bracing may provide symptomatic relief in selected patients, particularly during acute flare-ups
• Epidural steroid injections — for concurrent nerve root compression causing leg pain
• Weight management — reducing BMI decreases spinal loading

When is Surgery Required?

Surgery is indicated when symptoms are severe, significantly limiting quality of life, and have not responded to adequate conservative management. Surgery is also indicated for progressive neurological deficit, or cauda equina syndrome which requires emergency treatment.

Surgical Treatment Options

The primary goals of surgery for spondylolisthesis are: to decompress compressed neural structures, to stabilise the unstable spinal segment, and to restore normal spinal alignment. At One Brain and Spine, our Melbourne neurosurgeons offer minimally invasive and robotic-assisted approaches to achieve these goals with reduced surgical morbidity.

Decompression Alone

In selected patients with small, stable degenerative spondylolisthesis and predominantly leg symptoms from canal stenosis, decompression alone (laminectomy or minimally invasive decompression) may be appropriate. However, in most patients with spondylolisthesis, stabilisation with fusion is also recommended to prevent worsening of the slip.

Spinal Fusion

Spinal fusion stabilises the slipped vertebra, decompresses neural structures, and restores spinal alignment. Multiple fusion approaches are available at One Brain and Spine, tailored to individual anatomy and the degree of slip:

• TLIF (Transforaminal Lumbar Interbody Fusion) — a minimally invasive posterior approach combining nerve decompression and disc replacement with a cage, stabilised with screws and rods
• ALIF (Anterior Lumbar Interbody Fusion) — an anterior approach through a small abdominal incision; achieves excellent disc height restoration and slip correction.  May be supplemented by posterior pedicle screw fixation
• PLIF (Posterior Lumbar Interbody Fusion) — a posterior approach suitable for selected patients
• LLIF/PTP (Lateral Lumbar Interbody Fusion) — a lateral approach providing excellent access to the spine from a lateral and posterior approach at the same time.  An excellent option for spondylolisthesis above L4/5.
• Robotic-assisted surgery — One Brain and Spine utilises robotic navigation for highly accurate screw placement, minimising surgical risk