Spinal fusion is an operation to permanently join two or more vertebrae together, eliminating movement between them. It is performed for spinal instability, severe disc degeneration, spondylolisthesis, or as part of deformity correction.
An incision is made in the back (posterior) and sometimes also the front (anterior). Screws are inserted into the vertebrae (pedicle screws) and connected with rods. A cage filled with bone graft material is placed in the disc space to promote fusion. Bone graft (from the patient or synthetic) is packed around the instrumentation. Over the following months, the bones grow together. The operation takes two to four hours depending on the number of levels.
Fusion may be recommended for spondylolisthesis (where one vertebra has slipped forward), spinal instability, recurrent disc herniations, severe disc degeneration causing back pain, spinal fractures, or deformity. It is also sometimes combined with decompression when the spine is unstable.
Physiotherapy and core strengthening, pain management, corticosteroid injections, bracing, and activity modification. Spinal fusion for back pain is a significant operation, and non-operative options should be fully explored.
Thorough pre-assessment. CT and MRI scans for planning. Smoking cessation is critical — smoking dramatically reduces fusion rates. Optimise weight and fitness before surgery.
The aim is to stabilise the spine, relieve pain, and protect the nerves. Most patients with instability or spondylolisthesis experience significant improvement. For degenerative back pain, results are more variable.
The fused segment will not move. This is usually compensated by adjacent levels.
Stiffness is common, particularly in the early months.
Not all patients achieve complete pain relief.
The bones may fail to fuse. Risk is approximately 5–15% and is much higher in smokers.
Increased stress on levels above and below the fusion may cause new problems over time.
Risk to nerve roots during screw placement.
Wound or deep infection around the metalwork. Approximately 2–5%.
Screws may loosen or rods may break.
More significant than simpler spinal procedures. Transfusion may be required.
Tear in the membrane covering the nerves.
General anaesthesia. Neuromonitoring may be used during surgery to monitor nerve function.
Hospital stay of two to five days. A brace may be worn for several weeks. Walking is encouraged early. Avoid bending, lifting, and twisting for six to twelve weeks. Return to desk work at four to eight weeks. Manual work at three to six months. Full fusion takes six to twelve months. Physiotherapy is important.
Regular follow-up with X-rays at six weeks, three months, six months, and one year to monitor fusion progress.
The fused segment will be rigid, but most patients adapt well. Fusion of one or two levels causes minimal functional limitation for most daily activities.
Nicotine significantly impairs bone healing. Smokers have a much higher risk of non-union (failure to fuse). Stopping smoking is one of the most important things you can do to improve outcomes.
Solid bony fusion typically takes six to twelve months.