Isthmic spondylolisthesis results when a fracture gap at the pars interarticularis (the junction of the upper and lower lumbar spine joints of one vertebra) widens. Widening of the gap leads to the fifth lumbar vertebra shifting forward on the part of the pelvic bone called the sacrum; this is known as "slippage."
Degenerative spondylolisthesis results when wear and tear breaks down the pars interarticularis, causing slippage of one vertebra on another. This is more common in adults and most commonly occurs between the fourth and fifth lumbar vertebrae.
Post-treatment "maintenance" exercises like truncal core muscle strengthening (pilates or yoga) may be prescribed to condition the muscles and minimize reinjury.
If the pain, spasm, or slippage increases despite conservative management, then the surgeon may discuss spinal fusion with the patient:
Bones may be realigned depending on how much one vertebra has slipped forward on the other. The most important steps are restoring stability and making sure the nerves have no pressure on them.