Vertebral Slippage (Spondylolisthesis & Retrolisthesis)
What Exactly is Vertebral Slippage?
Vertebral Slippage describes the situation where one vertebra slides forward or backward upon its neighbour eventually causing symptoms. The condition is termed “Spondylolisthesis” and usually arises from disc degeneration and one vertebra slides forward on its neighbour. Where this is associated with childhood or congenital fractures in the back of the vertebral arch, it is termed “Spondylolytic Spondylolisthesis”. When one vertebra slides backwards on its neighbour then it is termed “Retrolisthesis”.
What Causes Vertebral Slippage?
As the disc degenerates the internal mass of the disc breaks up and leaves the body, the disc shrinks and looses height. The disc wall becomes slack and the vertebrae become freer to slide around. The direction of slide is controlled by the orientation of the facet joints behind and ligaments and muscles attached to the vertebrae. As the capsule of the facet joint stretches so the travel of slippage increases, the wall of the disc distorts and stretches and the boundaries of the exit canal (Foramen) consisting of the disc and overriding facets of the facet joint, distort. The slippage is arrested at a maximum override of 50%.
The cause of Spondylolytic Spondylolisthesis may centre upon the congenital orientation of the facet joints. If they are set in such a way that they are overloaded then whilst the bones are still soft in childhood, the supporting bone will fracture. Because the load persists and continuous movement takes place between the bone ends the fracture fails to heal leaving a defect held together by cartilage and fibrous scar. In later life either as a teenager or often in mid life, the disc degenerates the internal mass of the disc breaks up and leaves the body, the disc shrinks and looses height. The disc wall becomes slack and the vertebrae become freer to slide around and overriding increases. Here the facet joints have been separated from continuity with the vertebral body and can no longer control the direction or extent of travel and the unhealed fracture stretches and the boundaries of the exit canal (Foramen) consisting of the disc and overriding facets of the facet joint and fracture site, distort. The slippage usually arrests at an override of 50% in midlife presentations but in teenagers slippage can exceed 100%.
As the disc degenerates the internal mass of the disc breaks up and leaves the body, the disc shrinks and looses height. The disc wall becomes slack and the vertebrae become freer to slide around. In this situation the slide takes place in a backwards direction. This slide is in the main controlled by the orientation of the facet joints behind and ligaments and muscles attached to the vertebrae but the backwards direction may be directed by the natural overarching posture of the patient. As the capsule of the facet joint stretches so the travel of slippage increases, the wall of the disc distorts and stretches and the boundaries of the exit canal (Foramen) consisting of the disc and overriding facets of the facet joint, distort. The slippage usually arrests at an override of 5mm.
What causes pain in cases of Vertebral Slippage?
Vertebral Slippage is associated with various combinations of back, buttock and leg pain, numbness and muscle weakness. The back pain may arise from irritation within the disc wall but more commonly arises from the pinching of the trapped nerve in the exit doorway (Foramen) from the spinal column. The foramen is distorted and the nerve is tethered by years of scarring reaction to repetitive bruising, can not evade the pinching by the bulging distorted disc wall or overriding facet joints (or fracture margins in the case of Spondylolytic Spondylolisthesis). When advanced the compression causes numbness and weakness to develop.
Why is diagnosis difficult?
Unfortunately the patient may present with degeneration at more than one disc level. Until the advent of aware state surgical examination, the sources of Vertebral Slippage were hard to define and surgeons engaged in pre-operative ‘guesstimation’ based on the results of clinical examination, X-rays, MRI scans and CAT scans. The complexity of the spinal region means that a wide range of possible conditions exist to confound diagnosis. In the presence of back and leg pain and spondylolisthesis or retrolisthesis the surgeon will tend to focus upon this evident pathology and treat this. In our published studies the pain was arising at an adjacent level in almost 20% of cases. The patients body had adapted to the slippage and surgery at this level would not have modified the pain.
Can the sources of pain be pinpointed?
Aware state surgical examination enables the patient to give the surgeon feedback, guiding him or her to the point that is responsible for the pain. This ‘live’ approach allows the causal level of Vertebral Slippage to be accurately defined and then viewed using endoscopic instruments through a tiny incision. In this way, neural anomalies and strange nerve combinations can be detected and diagnostic errors regarding the disc level responsible for the pain, avoided. Thus, the surgeon is guided to the precise source of pain at that specified inter-vertebral point and the understanding of the actual mechanisms underlying the causation of Vertebral Slippage.
Is Accurately Targeted Treatment Possible?
Single targeted surgery enables Vertebral Slippage to be precisely treated with the minimum of damage to tissues, reduced patient risk and enhanced long-term outcome. This treatment, which is called ‘Foraminoplasty’ because it is carried out in the gaps or ‘Foramen’ between the vertebrae, allows the nerve to thoroughly liberated and the overriding joints or pointed fracture margins to be removed. This is only possible by the use of Endoscopic Minimally Invasive Spine Surgery where the full length of the exiting nerve can be explored and the points of irritation clearly demonstrated. In adult cases of Spondylolytic Spondylolisthesis for instance Endoscopic Lumbar Decompression & Foraminoplasty achieved a successful enduring outcome in 80% of cases. However in teenagers with rapidly progressing slippage of over 50% we recommend fusion and then treatment of residual symptoms with Endoscopic Lumbar Decompression & Foraminoplasty.
What is Wrong With Conventional Surgery?
This condition is usually treated by multi-level open surgery including decompression, solid or flexible fusion and is an ‘overkill’ with negative side-effects including blood loss, potential nerve and tissue damage, extended post-operative care and unnecessarily operating on pain-free levels. It is not as effective as Foraminoplasty in addressing and ameliorating the effects of Vertebral Slippage, rather it runs the risk of increased complications including recurrent disc bulging, infection, nerve damage and scarring round the nerve, implant failure, major vessel damage or sexual dysfunction.