As is described in the section on spine disorders, sciatica is the medical term for pain radiating down the leg due to a trapped nerve. The surgery is, therefore, designed to decompress the nerve within the spinal canal by removing whatever is pressing on the nerve. This can either be a disc prolapse (disc bulge, disc rupture, disc herniation) or thickening of the facet joints and ligament lying near the nerve root. In both cases, the operation is similar in that it involves a midline incision in the lower lumbar spine. The precise position of the incision is based on intra-operative x-ray marking of the appropriate level. The midline incision is centred over the area of the relevant nerve root. The underlying muscle is then stripped away from the spinous process and lamina of the vertebra to expose the ligament that spans the space between the 2 lamina (ligament flavum). This is then opened (fenestrated) to enter into the spinal canal. In the case of a disc prolapse, the disc is lying on the far side of the nerve root, in other words in front of it. The surgeon gently retracts the nerve root to expose the lump of disc and physically removes it.
As is explained in the anatomy of the spine, the disc consists of an annulus (annulus fibrosus) and a nucleus (nucleus pulposus). It is the nucleus that has ruptured and a piece of this is pressing on the nerve root and it is this that is removed. In order to try and prevent a recurrence, the surgeon will then remove as much of the remaining nucleus within the disc space. It is commonly asked whether the entire disc is removed and usually it is not the case and the surgeon simply removes the herniated bit of nucleus and attempts to clear out the central bit. Therefore, the annulus of the disc remains to provide some structural integrity.
The procedure that has just been described is for a disc prolapse. Sometimes the cause of the sciatica is not a disc prolapse but a more generalised narrowing of the spinal canal due to thickening (hypertrophy) of the facet joints and of the ligamentum flavum. If this is the case, then rather than remove the disc prolapse, the surgeon will remove the relevant areas of thickened ligament and may do a partial nibbling of the thickened facet joint (undercutting facetectomy). In both cases (discectomy or flavectomy) the purpose of the surgery is for the surgeon to ensure that at the end of the operation, the nerve root is fully decompressed and this is usually associated with post-operative relief of the sciatica. After this operation, the patient can usually mobilise on the same day and at the very least the day after the operation and is home within a day to two of the surgery. We generally advise 6 weeks off work but it is recognised that many people have busy jobs and are unable to take such a period of time off work and the precise duration of time off will be the subject of a discussion with your surgeon.