The bones of the lower back are usually aligned in an arc with respect to one another. Occasionally, the bones might be shifted, with the upper bone sliding forward on the bone below. This is known as a spondylolisthesis, which is translated from Greek as 'slippage of the bone'.
This slippage can be a cause of back pain, but can also cause pinching/irritation of the nerves, as the nerves travel in between the slipped bones. Shifting of the bones would then decrease the available space for the nerves to pass through this area; this results in low back pain, lower extremity pain, as possibly weakness of the lower extremities.
There are two major types of lumbar spondylolisthesis seen in adult patients. The most common type of spondylolisthesis is usually seen at the L4/L5 level and is present in patients over the age of 50. This is a result of 'wear and tear' arthritis (degenerative spondylolisthesis) and results in the 4th verbtebra slipping forward with respect to the 5th vertebra. It can cause lower back pain as well as causing pain into the buttocks, thighs, and lower legs from compression of the nerves in the area.
The second common type of spondylolisthesis is seen in younger as well as older patients and occurs at the L5/S1 level. This is usually due to a stress fracture of the L5 vertebra during the teenage years. The patient may or may not have been aware of the injury at the time it occurred, as it is usually a repetitive use injury. However, as a result of this injury, the L5 bone then slowly slides on top of the S1 bone, causing lower back pain and lower extremity pain from compression of the nerves in the area of the slippage. This type of slippage is known as an isthmic spondylolisthesis.
The treatment of the pain associated with either of these spondylolisthesis conditions can usually be addressed without surgery. Common treatment options include: oral medications, physical therapy, as well as epidural injections. These can help decrease pain in the lower back as well as lower extremity pain caused by an irritated/compressed nerve. Chiropractic adjustment and a battery of other alternative treatments - while unlikely to help - can be tried and are seldom harmful.
Due to the instability of the spine in patients with spondylolisthesis, only surgery can prevent the bones from slipping further away from each other and only surgery can create more room for any compressed nerves. However, it is used only as a last resort option, when all reasonable non-operative treatments have failed. It is also considered when a patient develops weakness in the lower extremity and/or the patient develops bowel/bladder problems; both of these are uncommon.
Surgery involves decompressing the pinched nerves as well as fixing the slipped bones together by fusing them. Fusion implies that one slipped bone will heal to the other slipped bone; if these two bones heal together to become one unified bone, then the pain caused by the movement between them will be gone. Until the fusion occurs and the bones heal together (a process that can take 6-12 months), the bones are held together with spinal instrumentation (rods, screws, plates, etc.).The spinal instrumentation functions as an internal brace/cast; it is not meant to hold the spine together forever, but rather over the 1-2 year period while the bones fuse to one another. This surgical procedure is commonly referred to as a lumbar laminectomy/fusion.
Please discuss any further questions about your specific situation with a fellowship-trained orthopedic spine surgeon.