Spinal Decompression

Spinal Fusion

Spinal Decompression

Diseases and conditions of the spinal column can occur on many levels. In adults and particularly with aging, some of the most common back problems involve disc problems or nerve irritation (dysfunction) leading to symptoms such as leg pain, numbness, tingling, weakness, back pain, unsteadiness and fatigue. In severe cases nerve dysfunction at the level of the spine can lead to severe disabling pain and paralysis.

To understand the vulnerability of the spinal cord and nerves at the level of the spine, one must closely examine the anatomy of the normal and the diseased spines. A healthy spinal column consists of vertebral bones stacked upon one another in smooth alignment. The spinal canal sits within the spinal column and houses the spinal cord and spinal nerves that send signals to and from the brain. This spinal canal offers excellent protection to the neurologic structures from injury due to the bony aspects surrounding the canal. Despite this protection, the spinal column remains mobile permitting displacement and adaptation to stress and load. In order to fulfill this function, the linkages between the vertebrae are not rigid (with a disc in the front, and ligaments in the back).

When all goes well, the spine can function beautifully through the vigorous demands of daily living, work, and recreational activity. However, the spine is vulnerable to injury and to degeneration (gradual failure with aging and wear/tear). The structures most vulnerable to degeneration are the soft tissues, namely the intervertebral discs, the ligaments and cartilage of the facet joints. Even with normal aging the discs gradually collapse, the facet joints thicken and ligaments lose their elasticity and stabilizing ability. These various gradual changes in the spine lead to a loss of space for the nerve elements (spinal stenosis) since degeneration has a tendency to lead to settling between vertebrae (sometimes also shifting, such as in spondylolisthesis) and thereby narrowing of the spinal canal and neuroforamen at the affected levels (usually lower lumbar spine).

As outlined above, it is clear that many people suffering from spinal problems suffer from insufficient space for neurologic structures. One of the most common surgical procedures performed on the spine thus involves freeing up the compressed nerves, and this is called " spinal decompression". There are many different techniques that surgeons use to perform a decompression yet the common goal is to ensure a careful freeing up of the affected nerves by removal of bone, disc and facet capsule (whichever may be the specific case at hand).

The principal elements that lead to nerve compression (spinal stenosis) involve the disc, the facet joints and ligaments (ligamentum flavum, posterior longitudinal ligament). Surgical treatment for patients suffering from spinal stenosis must be tailored to the particular element(s) causing the most trouble in that particular case. The common procedures include: Discectomy (for a herniated disc), Laminotomy (to open up more space posteriorly in the spinal canal), Laminectomy (to unroof the spinal canal posteriorly), and Foramenotomy (to open up the neuroforamen). In many cases a combination of techniques are used to ensure a proper decompression of the nerve elements.

Spinal Fusion

Diseases and conditions of the spinal column can occur on many levels. A healthy spinal column consists of vertebral bones stacked upon one another in smooth alignment. The spinal canal sits within the spinal column and houses the spinal cord and spinal nerves that send signals to and from the brain. This spinal canal offers excellent protection to the neurologic structures from injury due to the bony aspects surrounding the canal. Despite this protection, the spinal column remains mobile permitting displacement and adaptation to stress and load. In order to fulfill this function, the linkages between the vertebrae are soft (with a disc in the front, and ligaments in the back).

When all goes well, the spine can function beautifully through the vigorous demands of daily living, work, and recreational activity. However, the spine is vulnerable to injury and to degeneration (gradual failure with aging and wear/tear). The structures most vulnerable to degeneration are the soft tissues, namely the intervertebral discs, the ligaments and cartilage of the facet joints. Even with normal aging the discs gradually collapse, the facet joints thicken and ligaments lose their elasticity and stabilizing ability.

With aging, degeneration or injury a number of spinal problems can arise leading to loss of normal stability, loss of normal alignment or dysfunction of the nerves housed in the spinal canal. Although few patients suffering form such problems require surgical treatment, at times non-operative cares is not fully effective. When surgery is considered, a first consideration is to clearly identify the failed structure(s) and the source of pain or dysfunction. Patients requiring surgery are often found to suffer from some aspect of spinal instability, spinal compression or spinal deformity. It is thus understandable that many surgical procedures aim at restoring stability and proper spinal alignment, and this is achieved by creating what is called a spinal fusion.

In simplest terms a spinal fusion is a growing together of bone structures creating a solid bone bridge between vertebrae. There are many different methods that can be employed to create a fusion of the spine. The ideal technique in a particular patient will depend upon a number of factors including: level(s) to be fused, degree of instability or deformity, age of the patient, risk factors for non-union (failure to fuse properly), experience of the surgeon. Some of the common basic types of fusions are listed below.

Anterior Spinal Fusion

An anterior spinal fusion involves removal of the intervertebral disc between two levels (or more) and replacing this with pieces of bone. Over time the bone develops a firm bone bridge between the desired levels of the spine. In the cervical spine this approach is universally used for disc herniations with great success. In the lumbar spine anterior fusions without additional instrumentation or a posterior fusion are less successful. Although lone standing anterior fusions with devices such as cages may have the advantage of a minimally invasive procedure, they lack posterior stabilization and therefore may only give a short lasting or incomplete treatment of the spinal problem at hand (see figures 1,2).

Posterior Fusion without spinal instrumentation

Posterior (one incision through the back) spinal fusion with autologous (patients own bone) graft was the gold standard for a long period of time. Over the past years instrumentation systems have been developed that augment the immediate stability of the spine and the success rate of spinal fusion. Disadvantages of the posterior fusion without instrumentation include: the need to wear a brace or cast after surgery, the risk of incomplete or unsuccessful fusion (pseudarthrosis) (see figure 3).

Posterior Spinal Fusion with instrumentation

Posterior bilateral fusion with instrumentation (pedicular screws and rods or plates) has generally offers a high rate of successful spinal fusion. However these procedures require a large exposure that involve muscle stripping that may cause weakness, stiffness and prolonged recovery. Despite the development of advanced instrumentation systems, surgeons cannot guaranty a successful fusion and pain relief.

Circumferential Fusion (anterior and posterior)

Circumferential fusion is a combination of interbody and postero-lateral fusion. This technique is usually performed with instrumentation and the disc space can be filled with cages, bone allograft (from the bone bank) or bone autologous graft (from the patient). The instrumentation placed to stabilize the spine at the time of surgery may be one of several systems: pedicle screws and rods, screws and plates, hooks and screws, cables/wires and screws, facet screws. The ideal instrumentation and technique will depend upon the degree of instability, the amount of bone structure present and the experience of the surgeon. In general the circumferential fusion leads to a very high fusion rate. The disadvantage compared to anterior or posterior procedures alone is the invasiveness of the surgery (incisions in the front and back to access the spine).

Circumferential Fusion from posterior only PLIF, TLIF

A modification of the circumferential front and back surgery has been developed. This technique involves a circumferential fusion and interbody fusion but all through one incision in the back. There are two common versions: PLIF (posterior lumbar interbody fusion) and TLIF (transforaminal lumbar interbody fusion). In both techniques the disc is removed from the back by carefully passing around the nerve structures. Bone, or mesh cages are then packed into the disc space and posterior instrumentation and posterior bone graft are then placed. The success rate in terms of fusion and pain relief in carefully selected patients is excellent. Advantages of these techniques over the anterior/posterior circumferential includes avoidance of potential complications of the anterior approach, decreased operating time, decreased blood loss and reduced recovery time.

In performing a TLIF if the posterior laminae and facet joints are still intact it is possible to use a less invasive fixation than pedicle screws and rods (Magerl fixation technique). This consists of using small screws between two vertebrae which are already partially stabilized by the anterior interbody graft (see figure 6a,b,c).

See a presentation on the TLIF Procedure