Ten to 30 per cent of spinal fusion surgeries fail. Patients get worse instead of better. The reasons for failure are many and varied. Broken screws or other broken hardware, spinal stenosis, and spinal instability top the list of causes.
In this study, surgeons report the results of at least two years of follow up for patients with poor results after instrumentation-augmented spinal surgery.
Tests done on 103 patients included myelography and CT scans. When these tests failed to find a reason for surgical failure, then electromyography (EMG) and nerve conduction velocity (NCV) tests were done.
When testing could show a specific cause of the symptoms, then revision surgery was done. In this study, pain and function after the second operation were measured for up to two years.
Patients who were helped the most by revision surgery had spinal stenosis or else instability in the lumbar segment above or below the previous fusion. With instability there can be forward slippage of the vertebra. This causes the size of the spinal canal to narrow putting pressure on the spinal nerve. This condition is called spinal stenosis. The patient has back and/or leg pain with spinal stenosis.
The authors conclude a correct diagnosis is needed before doing revision surgery for failed spinal fusion. Despite testing, 20 per cent of the patients have no known cause for fusion failure making the decision more difficult.