Definition

The term ‘keyhole surgery’ was initially used for operations in the abdomen (laparoscopy), for example for the removal of a gallbladder, and for exploration or surgery of large joints (arthroscopy), for example knees. It is now more widely used to describe operations through a small skin incision. In spinal surgery, the term Minimal Invasive Spine Surgery (MISS) is usually used.

General Points 

There are advantages and disadvantages of minimal invasive surgery. The most important point is that the goal of surgery (for example the removal of a slipped disc) is achieved and not that the scar is small! The idea or reason why minimal invasive techniques were developed was to minimise injury to the structures, which normally have to be cut to gain access to the area of surgery, for example skin and muscles in the spine. This often means a quicker recovery and less post-operative pain.

Special training of the surgeon is often required to learn these techniques.

Types of Minimal Invasive Spine Surgery

Microdiscectomy is an operation where an operating microscope is used during a discectomy. This gives much better visualisation of the nerves and allows the surgeon to operate through a very small incision. In my opinion, all discectomies should nowadays be done as a microdiscectomy.

Endoscopic surgery means using a rigid or flexible telescope and the picture is projected onto a screen. This technique allows a very small access incision but needs special instruments for the operation. In some cases the surgeon uses the endoscope to have a better view or a look around the corner with a flexible endoscope (endoscopic assisted surgery). For lumbar discectomies, there is no evidence that endoscopic surgery is better than a microdiscectomy.

Percutaneous techniques have been developed in the last few years. A ‘percutaneus’ operation means insertion of the screws and bolts trough stab-like incisions. In contrast to the usual open techniques, there is very little injury to the muscles and recovery is much quicker. However, the purely percutaneous operations are usually limited to a few indications as it is not possible to do a bone graft. It is important to remember that any metal work only supports the spine until the bone graft, which is used around the vertebral bodies or in the disc space, has fused. The main indications are fractures or TB of the spine, where it is expected that the bone will heal in time or in spinal metastases, where the patients life expectancy is in most cases limited. This is in particular an advantage in patients who has radiotherapy to a spinal metastasis. The radiotherapy has a negative effect on wound healing and a percutaneous technique can minimise the risk of post-operative wound problems.

Vertebroplasty and kyphoplasty and Percudyn are purely percutaneous operations.

In Minimal Access  or Mini-Open Spine  Surgery special retractors and instruments are used to minimise the incision. A bone graft can be used at the same time. Some surgeons use a percutaneous technique for one side and a mini-open technique for the other combining the benefits of both.