MIS Treatment of Spondylolisthesis

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About Spondylolisthesis

Spondylolisthesis is a spinal disorder in which one vertebra slips forward over the vertebra below.  It usually affects the low back or lumbar spine. The condition may be classified as congenital, degenerative, or isthmic. Congenital means a disorder present at birth, degenerative is often age-related, and isthmic spondylolisthesis occurs when there is a defect or fracture of the pars interarticularis. The pars interarticularis is a bone connecting the upper and lower facet joints.

Diagnosis and Slip Severity

Important to a proper diagnosis is the patient’s medical history, physical and neurological examination, and imaging studies.

  • Medical history includes symptoms, their severity, and treatments already tried.
  • Physical and neurological examination includes evaluating movement limitations, balance problems, pain, extremity reflexes, muscle weakness, and sensation. The exam may include a series of movements such as bending sideways, forward and backward at the waist, and walking.
  • Imaging studies may include standing x-rays (front/back, side).  In addition, if necessary, a CT scan, or MRI is performed.

Using the patient’s x-ray, CT scan, or MRI studies, the severity of the slip is graded using the Meyerding Grading System to classify the degree of vertebral slippage. This system is easy to understand. Slips are graded on the basis of the percentage that one vertebral body has slipped forward over the vertebral body below. While every spondylolisthesis does not require surgery, the degree of slip is important to surgical treatment considerations.

Grade I:  1-24%

Grade II: 25-49%

Grade III: 50-74%

Grade IV: 75%-99%

Grade V: 100%, spondyloptosis

When Minimally Invasive Surgery (MIS)  is Recommended

Besides the severity of the slip, there are other considerations before surgery is recommended, if at all. Although the indications for surgery vary between adults and children, MIS may be recommended if:

  • Pain and other symptoms worsen and are unresponsive to nonoperative treatment
  • Neurologic problems develop, such as bowel or bladder dysfunction
  • Imaging tests, such as x-ray or MRI, demonstrate spinal instability or slip progression

Goals of Minimally Invasive Surgery

Surgical goals include:

  • Decompression of spinal nerves (relieve pressure)
  • Stabilization of the spine to prevent slip progression and further nerve compression

Surgery may include combined procedures such as repair of the pars interarticularis, decompression, spinal fusion and instrumentation, and deformity correction.

  • Repair of the pars may involve removal of the bone combined with spinal fusion and instrumentation.
  • Decompression procedures relieve pressure on spinal nerves.  Discectomy (disc removal), laminotomy, laminectomy, and foraminotomy are common procedures.  Laminotomy (partial removal) and laminectomy (complete removal) involve removing the vertebral body’s lamina to increase the size of the spinal canal.  The lamina is a section of bone near each facet joint covering access to the spinal canal.  Foraminotomy expands the foramen or spinal nerve passageways.
  • Spinal fusion uses bone graft to fuse or join two or more vertebrae.  Fusion is often combined with instrumentation, such as interbody devices (i.e. cage), pedicle screws and rods, to immediately stabilize the spine and stop slip progression until the construct fuses.
  • Deformity correction involves restoring the spine to a more normal alignment and fixing the spine in position using fusion and instrumentation.

MIS Treatment

Minimally spine surgery procedures approach the spine from the front (anterior), back (posterior), side (lateral), or back and side (posterolateral).  Procedures such as those listed below share the same surgical goals:

  • Anterior Lumbar Interbody Fusion (ALIF)
  • Direct Lateral Interbody Fusion (DLIF)
  • Guided Interbody Lumbar Fusion (GILF)
  • Posterior Lumbar Interbody Fusion (PLIF)
  • Transforaminal Lumbar Interbody Fusion (TLIF)
  • Extreme Lateral Interbody Fusion (XLIF)

The interbody device, such as a titanium cage or PolyEtherEther Ketone (PEEK) spacer, is implanted into the disc space. Bone graft is packed into and around the device to stimulate spinal fusion.

  • ALIF provides access to the spine and disc through the abdomen. This procedure is often combined with posterior fusion and instrumentation for better spinal fixation.
  • DLIF provides access to the spine through the side of the body. This procedure involves a transpsoas approach, which means the surgeon accesses the spine through the psoas muscle; a long muscle on both sides of the lumbar spine.
  • GLIF provides lateral (side) access to the spine and with unique medical instrumentation allows the physician to perform an interbody lumbar fusion without repositioning the patient during the surgery. This is a new, state-of-the-art procedure.
  • PLIF provides access to the disc through the back (posterior) of the spine. Besides implantation of the interbody device, posterior instrumentation, such as screws and rods are included for stabilization.
  • TLIF provides access to both sides of the disc through the intervertebral foramina, small passageways through which nerves exit the spinal canal.  An interbody device, such as a cage or spacer is implanted into the disc space from one side of the spine.  Pedicle screws and rods, with additional bone graft, secure the back (posterior) section of the spine.  TLIF fuses the front and back sections of the spine.
  • XLIF accesses the spine through small posterior incisions between the ribs and hip. This procedure treats L1 to L5 and is not effective for L5-S1.  Because XLIF does not affect supporting spinal structures, such as the ligaments, posterior instrumentation may not be needed.

Risks and Complications

Although the potential risks and complications of MIS are similar to the potential risks and complications of open surgery, MIS may offer significant benefits to the patient. Benefits may include:

  • Less postoperative pain
  • Quicker recovery
  • Reduced blood loss
  • Minimized tissue damage
  • Smaller surgical incisions (more cosmetically appealing)
  • Less scarring
  • Improved function

Of course, no patients are identical and risk and complications vary. The surgeon is the best source of information with respect to the possible risks and benefits of an individual’s MIS procedure.