Isthmic and Degenerative Lumbar Spondylolisthesis: Diagnosis and Treatment
AANS 2015 MEETING HIGHLIGHT
At the American Association of Neurological Surgeons 83rd Annual Scientific Meeting in Washington, DC, controversies in, as well as recent advances in the diagnosis and treatment of lumbar spondylolisthesis were the subjects of a moderated discussion in which John Matthew Caridi, MD, was a panelist. Dr. Caridi is Assistant Professor of Neurosurgery and Orthopedic Surgery at the Icahn School of Medicine at Mt. Sinai Medical Center, New York. “My goal with this presentation is to examine the history of this condition and show how far we have come, and how far we have to go,” Dr. Caridi said.
One of the main distinctions drawn by the classification and grading schemes put forward by Meyerding, Wiltse, Marchetti and Bartolozzi, and the Spinal Deformity Study Group, is that lumbar spondylolisthesis can be described as either isthmic or degenerative.
Isthmic spondylolisthesis involves L5-S1 in patients of any age, affecting the L5 nerve (85%-90%) with lysis and radiculopathy. The next most commonly affected level is L4. Pars defects and spina bifida occulta are strongly associated. Twenty-five percent of radiographically visualized spondylolysis is associated with spondylolisthesis. With one exception, a defect in pars has never been found at birth. Isthmic spondylolisthesis occurs in 3%-6% of Caucasians, with the highest incidence (26%) in Alaskan Eskimos and a low incidence in African Americans. Male-to-female ratio is 2–3:1.
Factors predisposing patients to elongation of the pars or lysis are:
- Congenital weakness of pars interarticularis
- Vertebral dysplasia (eg, spina bifida or facet aplasia)
- Connective tissue abnormality
- Growth plate abnormality
- Abnormal sacro-pelvic morphology
Environmental predisposing factors are:
- Erect posture and gait
- Repetitive loading of the lumbosacral spine
The syndrome consists of a circular pattern of:
- Postural changes due to pain of neurological origin
- Altered biomechanics at the center of gravity and in spinopelvic balance
- Growth plate remodeling
- Bony dysplasia
- Degeneration of discs and soft tissues
To characterize the natural history of isthmic spondylolisthesis, Fredrickson, beginning in 1984, prospectively studied 500 first graders from age 6 years to adulthood. He observed a 4.4% overall incidence at age 6 years, which rose to 5.2% by age 12 years and to 6.0% by adulthood. An increased incidence was found among family members. Rosenberg et al studied 143 adults who never walked, and found that none had pars defects on plain radiographs. Evidence of Fredrickson and Rosenberg supports the concept that a pars lesion results from repetitive stress to this region.
Degenerative spondylolisthesis involves L4-L5 in adults, and affects L5 with claudication and no lysis. Degenerative spondylolisthesis affects adults aged 40 years and older. The male-to-female ratio is 5:1. Hormonal factors play a role, as well as prior pregnancy. Disc pathology with lumbar lordosis is observed. In degenerative spondylolisthesis, disc integrity is observed, with ligamentous laxity (anterior and posterior longitudinal ligament). If the L4-L5 facets are in a sagittal orientation at >45 degrees, degenerative spondylolisthesis is 25 times more likely more likely than disc degeneration without spondylolisthesis. It is unknown if this is a causal relationship or may be secondary to remodeling.
Regarding natural history, as reported by Matsunaga in 2000, 10% of patients show clinical deterioration over 10–18 years of follow-up, with no correlation observed between slip progression and deterioration. Thirty percent of affected patients show slip progression, with no correlation with clinical symptoms. In cases of progression, disc narrowing, spur formation, subcartilaginous sclerosis, and ligamentous ossification are observed.
Patients with degenerative spondylolisthesis report mechanical rather then discogenic pain (extension vs flexion). Neurogenic claudication occurs, with pain in 94% (bilateral, non-dermatomal); numbness in 63%; and weakness in 43% of patients. Six to 14% of patients first present with radicular pain. On spinal canal cross-section, posture dependence is observed.
Degenerative spondylolisthesis treatment goals:
- Decompression of neural elements
- Stabilization of the spine
- Correction of kyphosis
- Reduction of slip angle
- Possible reduction of the Meyerding grade
Positive results were reported for surgical treatment in:
- Spinal Patients Outcomes Research Trial (SPORT), where operated patients maintained substantially greater pain relief and improvement in function for 4 years
- The 1991 Herkowitz/Kurz prospective trial, where patients who had concomitant arthrodesis experienced significantly better results with respect to relief of pain in the back and lower limbs
Consensus guidelines reflect the positive outcomes attained with surgery for degenerative spondylolisthesis. The 2013 Journal of Neurosurgery guideline update for fusion procedures for degenerative disease of the lumbar spine, states that achievement of a solid arthrodesis is associated with superior outcomes, and that efforts to maximize fusion potential should be considered.
Dr. Caridi asserted, “Spondylolisthesis can be an extremely debilitating condition for our patients. It is also one of the conditions most effectively treated by surgery. We can make a significant difference in these patients' lives and it is important for all neurosurgeons to be familiar with the treatment options. It is also important to realize that these treatment options are evolving as our understanding of the disease improves and as our techniques become more sophisticated.”
May 27, 2015