Spinal Instability
Spinal instability refers to an abnormal or excessive movement between adjacent vertebrae that exceeds the physiological range of normal spinal motion.
What is Spinal Instability?
Spinal instability refers to an abnormal or excessive movement between adjacent vertebrae that exceeds the physiological range of normal spinal motion. In a stable spine, each vertebral motion segment moves in a controlled, predictable way — guided by the intervertebral disc, facet joints, and surrounding ligaments working together. When these stabilising structures degenerate or are disrupted, abnormal movement can occur, causing pain and potentially compressing adjacent neural structures.
Spinal instability is an important but sometimes difficult-to-diagnose cause of back pain and related symptoms. It may be present in isolation or in combination with disc degeneration, spondylolisthesis, spinal stenosis, or post-surgical changes. At One Brain and Spine, our Melbourne neurosurgeons use clinical assessment combined with dynamic imaging to identify instability and direct appropriate management.
What Causes Spinal Instability?
- Intervertebral disc degeneration — as discs lose height and structural integrity, they no longer adequately resist shear and rotational forces, leading to increased segmental movement
- Facet joint degeneration — arthritic facet joints with lax capsules fail to appropriately limit vertebral movement
- Spondylolisthesis — forward slipping of one vertebra represents a form of translational instability
- Spondylolysis — a pars interarticularis defect (stress fracture) that disrupts the bony ring stabilising the posterior spine
- Post-surgical instability — following extensive laminectomy or discectomy, removal of stabilising posterior structures can create iatrogenic instability
- Traumatic ligamentous injury — disruption of the disc, facet joints, and ligaments following significant spinal trauma
- Inflammatory conditions — rheumatoid arthritis can cause atlantoaxial (upper cervical) instability through ligament laxity
Symptoms of Spinal Instability
The symptoms of lumbar spinal instability are variable and can overlap with other spinal conditions. Characteristic features include:
Back Pain
- Catching or giving way sensation in the back with certain movements
- Sharp, sudden episodes of severe back pain provoked by specific movements — often described as the back 'going out'
- Pain worsened by transition from sitting to standing or from standing to walking
- Relief of pain when the spine is supported — with a brace, or when lying down
- Morning stiffness that improves during the day
Nerve-Related Symptoms
Instability can cause intermittent compression of nerve roots — producing episodic leg pain, numbness, and weakness. Symptoms may be positional — worsened by certain movements and relieved by rest.
Neurogenic Claudication
When instability is associated with dynamic stenosis — spinal canal narrowing that worsens with specific postures — neurogenic claudication may develop.
How is Spinal Instability Diagnosed?
Spinal instability can be difficult to diagnose on standard MRI alone, as the imaging is performed with the patient lying still. Dynamic imaging — where the spine is imaged in different positions — is essential to capture abnormal movement.
Imaging Investigations
- Dynamic X-rays (flexion/extension views) — the most important investigation for detecting segmental instability. Excessive translation (>4mm) or angulation (>10°) between vertebrae on dynamic views confirms instability.
- MRI — demonstrates associated disc and facet joint degeneration, neural compression, and endplate changes consistent with instability
- CT scan — provides excellent bony detail and identifies pars defects or fractures contributing to instability
- EOS full-length standing X-ray — assesses overall spinal alignment and balance
Treatments
Non-Surgical Treatment Options
Conservative management is the first line of treatment for spinal instability:
- Core and paraspinal muscle rehabilitation — the primary non-surgical treatment. Strengthening the multifidus, transversus abdominis, and paraspinal muscles provides dynamic stabilisation of the unstable segment.
- Clinical Pilates — the gold-standard exercise approach for spinal stability rehabilitation
- Physiotherapy — functional rehabilitation and movement retraining
- Lumbar bracing — external support during the rehabilitation period or for acute exacerbations
- Activity modification — avoiding movements and activities that provoke instability symptoms
- Analgesic and anti-inflammatory medications
When is Surgery Required?
Surgery is recommended when instability causes severe, refractory pain that has not responded to sustained conservative management, or when there is associated progressive neurological deficit from nerve compression. The goal of surgery is to eliminate the abnormal movement at the unstable segment (fusion) while decompressing any compressed neural structures.
Surgical Treatment — Spinal Fusion
Spinal fusion is the definitive surgical treatment for spinal instability. By permanently joining the unstable vertebrae, fusion eliminates the abnormal movement and relieves both back pain and any associated nerve compression. At One Brain and Spine, minimally invasive fusion techniques — including robotic-assisted TLIF, ALIF, PLIF, and LLIF/PTP — are used to achieve stable, accurate fixation with reduced surgical morbidity.
Frequently Asked Questions — Spinal Instability Melbourne
How is spinal instability different from normal back pain?
Spinal instability causes characteristic mechanical back pain — sudden, sharp episodes provoked by specific movements, a giving way sensation, and pain that is relieved by support or lying down. It is diagnosed by dynamic X-rays showing excessive vertebral movement, distinguishing it from simple mechanical back pain.
Can spinal instability be treated without surgery?
Yes, for many patients. Core muscle rehabilitation — particularly clinical Pilates — is highly effective at providing muscular stabilisation of an unstable spinal segment, reducing pain and preventing deterioration. Surgery is reserved for severe, refractory cases or those with progressive neurological compromise.
Is spinal fusion the only surgical option for instability?
Spinal fusion is the definitive treatment for confirmed segmental instability, as it eliminates abnormal movement at the affected level. The type of fusion approach — TLIF, ALIF, PLIF, or LLIF/PTP — is selected based on the patient's anatomy and individual circumstances, and will be discussed in detail with your neurosurgeon at One Brain and Spine.
Why Choose One Brain and Spine for Spinal Instability in Melbourne?
One Brain and Spine is a specialist neurosurgical group practice in Melbourne, formed by three experienced neurosurgeons committed to the highest standard of spinal care. We offer the full spectrum of evidence-based treatments from conservative management through to the most advanced minimally invasive and endoscopic surgical techniques available in Australia.
- Specialist neurosurgeons — all fellowship-trained with subspecialty expertise in spinal surgery
- Latest surgical technology — robotic-assisted navigation, endoscopic techniques, and microsurgery
- Conservative-first approach — surgery recommended only when clearly indicated
- Multidisciplinary care — working with physiotherapists, pain specialists, and radiologists across Melbourne
- Transparent, patient-centred consultations — your diagnosis and all options explained clearly
- Privately insured patients welcome — all major health funds accepted