Indications for fusion in the lumbar spine.

A wide variety of lumbar spinal conditions have been managed by spinal fusion. Results appear better when the diagnosis is specific and related to definable instability or deformity in patients with a stable psychologic state. Success rates are higher in isthmic spondylolisthesis, unstable spinal stenosis syndromes (degenerative spondylolisthesis, degenerative scoliosis), and in patients with objective segmental instability. Variable success rates are reported for disk-related low back pain conditions and in patients with failed previous surgery. Instrumentation appears to be beneficial in situations in which complex deformities or obvious instability are present.