An unstable spine, whether due to trauma, birth defect, tumours, infection or degenerative disease can lead to severe back pain as well as pain and weakness in the legs. Till now, the treatment involved fusing the spine through large incisions. The heavy retraction on the spinal muscles to expose the spine meant that there was significant trauma to the muscles. With the development of various technologies and surgical technique, the same result can be achieved in a minimally invasive way. This minimally access spine surgery significantly reduces the pain, blood loss, and recovery time.

Case study: This 45 years old lady presented with severe backache for five years and a progressively worsening leg pain set off by standing and walking. This severely compromised her daily activities. X-rays of her spine showed excessive movement between L4 and L5 (Fig 1,2). MRI revealed a tight and narrow canal at the same level due to thickened ligaments and joints.

She was advised surgery. The plan was to expose the right side of the spine using a specially designed tubular retractor. Through this screws would be inserted into the pedicles, an interbody fusion performed and the spinal canal widened. The fixation on the left side would be done by another set of specially designed instruments, called the Sextant, which allowed percutaneous screw and rod fixation

Operative procedure: The retraction system is conceptually very simple. After precisely identifying the L4-5 disc space on fluoroscopy, a 2.5-3 cm incision was made on the skin. The underlying muscle was sequential dilated with larger and larger tubes (Fig 3) till finally a 26 mm tube shaped retractor was inserted down to the bone (Fig 4). This tube retractor consists of two halves. These two halves can be widened apart so that while the skin exposure remains the same the exposure in the depth is 4 cm. This wide exposure in the depth is necessary to expose the facet joint and the two adjoining pedicles of the spine into which pedicle screws are tightened. Through the same exposure a TLIF (Transfacetal Lumbar Interbody Fusion) was performed using the help of an operating microscope. The facet joint of the spine was removed to expose the disc space. The disc was removed and the bone exposed on the opposing surfaces of the vertebral body. A cage made of titanium, carbon fibre or plastic was then filled with bone harvested from the facet joint and this was firmly positioned in the disc space. A rod was then tightened on to the head of each screw to give the fixation. Next, the spinal canal was widened not only on the same exposed side, but across the midline to the opposite side to provide space for the nerves.

On the opposite side, pedicle screws were tightened into the L4 and L5 pedicles through two separate 1cm puncture wounds. A rod was then connected to the heads of the two screws with a separate small incision through the sextant, which works on the principle of a common arch (Fig 5).

This allows the entire procedure to be performed with three 10 mm incisions and one 25 mm incision (Fig 6).