Spinal surgery explained: fusion vs motion-preserving procedures

Spinal surgery isn’t one-size-fits-all. A Mediclinic orthopaedic surgeon explains spinal fusion, motion-retaining surgery and disc replacement, and how doctors choose the best option for each patient.

Spinal fusion procedures

Spinal fusion is a good option for spinal deformity or instability, says Dr Phillip van Sittert, an orthopaedic surgeon at Mediclinic Welkom. “Spinal surgery today commonly uses pedicle screws in the thoracic and lumbar spine – these are titanium or stainless-steel implants used to stabilise the spine. They’re inserted from the posterior (back of the spine), along with replacement cages filled with bone graft in both the lumbar (lower spine) and cervical (upper spine) regions,” he explains.

Pedicle screws are placed posteriorly and linked with rods to reduce movement between the vertebrae. Small spacer devices, called cages, are then placed between the vertebrae. These cages are filled with bone graft to help keep the spine stable and encourage the bones to grow together. Depending on the approach, the cages can be inserted from the back or the front of the spine to give added support and help the area heal.

However, a disadvantage of spinal fusion is loss of motion at the point of fusion. It also means more pressure is placed on the motion segment just below and above the fusion, explains Dr Van Sittert.

“As a result, these areas tend to ‘go’ within 5-8 years, causing trouble again, and potentially leading to an extended fusion,” he says. “Fusions come with potential problems, so we must weigh up the pros and cons of doing this surgery. Sometimes we don’t have an option if there is instability or a fracture, but fusions are not the answer to simple back pain.”

Motion-retaining procedures

Motion-retaining procedures were first made popular in Europe, but Dr Van Sittert says they’re rarely performed in South Africa today. The approach involves placing pedicle screws into the lower back vertebrae (L3, L4 and L5) and linking them with a flexible rod. Made from a non-metallic material, the rod allows limited movement – more than a full fusion, but less than before surgery.

The pedicle screws are screwed into the bone to  provide extra support, stability and strength to a spinal fusion while it heals and are placed above  and below the fused vertebrae. “The idea of having a flexible rod is to allow a bit of motion in the spine, but not too much,” explains Dr Van Sittert.

Disc replacements

A patient with lower back pain may be considered for a disc replacement, he says, but this is a major operation that requires careful planning and two surgeons. The procedure starts with a general surgeon performing open abdominal surgery to gently move the aorta and inferior vena cava – the body's two largest blood vessels running along the spine. This creates access for the orthopaedic surgeon to remove and replace the damaged disc.

“The disc replacement surgery itself isn’t difficult,” says Dr Van Sittert, noting that it can be very effective for patients with single- or double-level disc disease where there is no instability at that level. “Still, a disc replacement is major surgery. This procedure seems to work well, and motion is retained. Very seldom does a lumbar disc replacement go to a fusion.”

Cervical disc replacements

Cervical disc replacement for the neck is easier for an orthopaedic surgeon to perform, though it   comes with risk, as does every operation.

The benefits of cervical disc replacement include maintaining movement in the area for at least a year, and patients don’t need to wear a brace for the first six weeks after leaving the hospital, unlike with spinal fusion. “Patients usually return to work within two weeks, and their pain typically goes away quickly,” says Dr Van Sittert.

Most patients will see a big improvement in pain after cervical disc replacement, he adds. “The downside is that about 80% of these patients will develop auto-fusion within two years, where bone grows around the replaced disc between the vertebrae. However, for the remaining 20% who keep their movement, they can expect to have a normal neck afterwards. For these patients, it’s a simple solution to their neck issues.”