|
Spondylolisthesis is the anterior or forward slipping of one vertebra or vertebral body on another. This can be caused by a spondylolysis, which is a defect in a posterior structure of the spine called the pars interarticularis. This allows motion of the vertebral body away from the posterior joint construct.
This may be caused by a dysplastic spondylolisthesis which is congenital in origin. This can also be an isthmic spondylolisthesis arising from a stress fracture of the pars. Degenerative spondylolisthesis occurs when the disc complex and posterior support structures become incompetent and can no longer maintain adequate alignment. Traumatic spondylolisthesis is caused by an acute fracture event disrupting the posterior neural arch. Finally, pathologic spondylolisthesis is created when a bone disease, like osteoporosis, or a tumor allow the anterior subluxation to occur.
Generally spondylolisthesis occurs at lower end of the spine above the pelvis at L5-S1 or L4-5. It will not usually happen above these levels except in the degenerative type. As noted above, causes are varied but the condition itself in most common cases is relatively benign. In fact there often is no pain except for mild pain with heavy activity or sports. When pain becomes a factor it often is cause by active progression of the deformity or instability which is made worse with bending and extension of the spine. There is a classification system which is based on anterior slip of the vertebra related to the adjacent one. Up to a 25 percent slip is Grade 1, up to 50 percent is Grade 2, up to 75 percent is Grade 3 and up to 100 percent is Grade 4. If the vertebral body is completely off the adjacent body this is classified as Grade 5 and is called a spondyloloptosis.
During an acute phase of pain, rest may be recommended as well as later physical therapy to strengthen the abdominal and back muscles. Anti inflammatory drugs can be helpful in controlling symptoms as well. Rarely will leg pain, motor weakness or leg paresthesias or tingling occur. If these do happen it is often the result of progressive deformity and surgery may be recommended. Almost never are bowel and bladder incontinence an issue.
During surgery, the spine is exposed over the posterior midline and the muscle and soft tissue removed. The bone is cleaned and prepared for fusion. Before any attempt at reduction of the slip, the nerve roots are decompressed to allow free egress of the nerves out their neural foramen or openings. Special pedicle reduction screws are place in the sacrum and involved vertebrae. Prior to reduction, disc tissue is often removed to free up the segment. Sometimes a sacral dome reshaping is performed to also allow the slipped vertebra more mobility towards reduction. Sometimes an anterior metal or ceramic cage is placed to help reestablish the normal disc height and bone graft is added to help in healing. The screws are attached to two metal rods and the slipped vertebra is slowly drawn backward by the reduction screws.
After the surgeon is satisfied with the alignment, bone graft is taken from the pelvis and possibly bone growth factors and bank bone may be added to achieve a solid bone fusion, which should stabilize the spondylolisthesis. During surgery spinal cord monitoring using sensory and motor potentials are utilized. This allows the surgeon to find out in real time if reduction of the spondylolisthesis is causing any neurologic problems. Sacral nerve roots which affect and control bowel and bladder function are often at higher risks during these procedures so great care is taken to preserve and protect all neural structures.
Patients are closely monitored for skin and incisional problems due to the usual lack of soft tissue coverage over the lower part of the pelvis. Patients generally go home in five (5) to seven (7) days wearing a soft lumbar corset for support and helping them to avoid excessive motion. Patients are usually very independent quickly and generally get good pain relief in the long term. Patients can usually resume normal activities once healed.
 |
|
 |
|
Severe spondylolisthesis L5-S1 Pre-Op, Note L5 in front of sacrum 1 |
Post-Op reduction of spondylolisthesis with posterior instrumentation and fusion with anterior cage |
For more information, click here.
return to top
|
