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Surgical Management of High-Grade Dysplastic Spondylolisthesis
Summary of Key Points
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Dysplastic spondylolisthesis is a developmental disorder of the spine that is associated with significant pain and disability.
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Sacropelvic and spinopelvic balance are important determinants of the impact of spondylolisthesis on health status.
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Reduction of high-grade dysplastic spondylolisthesis is most useful in patients with sacropelvic and spinopelvic imbalance.
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Surgical techniques for reduction of high-grade dysplastic spondylolisthesis include posterior-only or combined anterior and posterior surgeries.
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Circumferential fusion using interbody or transosseous techniques is useful to improve fusion rates.
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Pelvic fixation is important to reduce strain on sacral screws and reduce rates of implant failure.
Spondylolisthesis is an important deformity that may cause significant pain, neural symptoms, and disability in the pediatric and adult patient. The lumbosacral spine is the transition between the mobile lumbar spine and the pelvic vertebra. The pelvis is the foundation of the spinal column, and pelvic parameters, including the pelvic incidence and sacral slope, have a high correlation with the lordosis of the lumbar spine that is required for alignment of the spinal column. , (See Chapter 10 for a detailed discussion of lumbopelvic alignment.) The alignment and morphology of the lumbopelvic junction determine the biomechanical stresses between L5 and S1 and are important factors in the development of both developmental and acquired spondylolisthesis. High-grade dysplastic spondylolisthesis is characterized by morphological deficiency of the L5–S1 articulation, as well as high shear forces created by a high pelvic incidence. , Small changes in the relationship between L5 and the subjacent sacrum have a major impact on global alignment of the spinal column and the health status of patients with spondylolisthesis. The purpose of this chapter is to review the clinical presentation of high-grade dysplastic spondylolisthesis and to provide an evidence-based approach to surgical management.
Clinical Presentation of High-Grade Dysplastic Spondylolisthesis
Spondylolisthesis in the child and the adult presents with a spectrum of severity regarding neural symptoms, deformity, pain, and disability. The term high-grade dysplastic spondylolisthesis is descriptive of both the severity and the etiology of the deformity. In 1938 Henry Meyerding from the Mayo Clinic developed a classification for spondylolisthesis based on the percentage of slippage of the vertebrae relative to each other. Low-grade olisthesis refers to a displacement of L5 less than 50% across the end plate of S1, and high-grade olisthesis refers to displacement of L5 greater than 50%. The sagittal alignment between L5 and S1 is important in the description of high-grade deformity. Boxall and Bradford et al. introduced the sagittal radiographic parameter of slip angle as the angle between the posterior border of the sacrum and the end plate of L5. Fig. 150.1 demonstrates slip angle and Meyerding grade. The authors demonstrated that the slip angle is an important variable associated with neural symptoms and progression of deformity, including after in situ fusion. Measuring the sagittal alignment between L5 and S1 as lumbosacral kyphosis is useful when the inferior end plate of L5 has significant dysplastic changes that may compromise the characterization of the inferior end plate of L5. Lumbosacral kyphosis is measured between the superior end plate of L5 and the posterior margin of the sacrum. The sagittal alignment of the lumbopelvic junction is an important parameter in determining the sacropelvic balance and spinopelvic balance, or global alignment of the spine.
Sagittal alignment of the lumbopelvic junction has an important and significant impact on the health status of patients. Mac-Thiong and Labelle proposed a classification of spondylolisthesis based upon sacropelvic and spinopelvic balance ( Fig. 150.2 ; Table 150.1 ). High-grade dysplastic spondylolisthesis is characterized as balanced when there is a high sacral slope and a low pelvic tilt. In contrast, unbalanced sacropelvic alignment is present with more severe deformity and compensatory retroversion of the sacrum with a high pelvic tilt, and correlating low pelvic tilt. Spinopelvic balance is measured by the relationship between C7 and the femoral heads and sacrum. In balanced spinopelvic alignment, the C7 plumbline falls between the femoral heads and the posterior margin of the sacrum. If the C7 plumbline falls beyond that stable zone, the spinopelvic alignment is unbalanced. The classification is valuable in capturing regional and global measures of spondylolisthesis.
Table 150.1
New Classification of Lumbosacral Spondylolisthesis
| Slip Grade | Sacropelvic Balance | Spinopelvic Balance a | Spondylolisthesis Type |
|---|---|---|---|
| Low-grade (<50%) | Low PI (<45 degrees) | – | 1 |
| Normal PI (45–60 degrees) | – | 2 | |
| High PI (≥50 degrees) | – | 3 | |
| High-grade (≥50%) | Balanced (high SS, low PT) | – | 4 |
| Unbalanced (low SS, high PT) | Balanced (C7 plumbline between femoral heads and sacrum) | 5 | |
| Unbalanced (C7 plumbline anterior to femoral heads or posterior to sacrum) | 6 |
PI , Pelvic incidence; PT , pelvic tilt; SS , sacral slope. From Labelle H, Mac-Thiong JM, Roussouly P. Spino-pelvic sagittal balance of spondylolisthesis: a review and classification. Eur Spine J . 2011;20 Suppl 5(Suppl 5):641-646. With permission.
a The spine is almost always balanced in patients with low- or high-grade spondylolisthesis with a balanced pelvis.
Health-related quality of life is highly correlated with spinopelvic and global alignment parameters in children and adults. Harroud et al. studied children and adolescents with low- and high-grade spondylolisthesis, and the authors demonstrated a significant correlation of sagittal malalignment and reduced health status on self-reported Scoliosis Research Society–22 scores. Tanguay et al. evaluated lumbosacral kyphosis and health status using Short Form–12v2 and demonstrated a significant correlation between the physical composite score and lumbopelvic kyphosis in adolescents with spondylolisthesis. , Gussous et al. demonstrated a similar high correlation between sagittal sacropelvic and global alignment parameters in adults with spondylolisthesis.
Management of High-Grade Dysplastic Spondylolisthesis
The surgical approach to spondylolisthesis is characterized by significant variability. High-grade deformity measured by radiographic parameters, including lumbosacral kyphosis, sacropelvic imbalance, and spinopelvic imbalance, is associated with significant reduction of self-reported health-related quality of life in children, adolescents, and adults. The evidence that reduction of spinopelvic parameters results in a reliable improvement of health status has been mixed.
Reduction of high-grade spondylolisthesis is associated with significant risk of neural injury and implant failure. Postoperative neural compromise with reduction of L5 onto the sacrum has been a significant complication of surgical reduction of high-grade olisthesis. Petraco et al. demonstrated a nonlinear relationship between L5 reduction and tension of the L5 nerve root, with more than 70% of the strain on the L5 root occurring when the reduction of L5 on S1 was more than 50%. Bradford et al. demonstrated the priority of reducing slip angle rather than slip grade, concluding that, in long-term follow-up, slip angle reduction was more important, and safer regarding neural injury, compared with complete reduction of slip grade. In a long-term follow-up study of adolescents fused in situ or fused with surgical reduction for high-grade spondylolisthesis, Poussa et al. recommended fusion in situ as the treatment of choice for severe spondylolisthesis. Patients treated with surgical reduction had lower Oswestry Disability Index scores, better Scoliosis Research Society scores, and less disc degeneration with in situ fusion compared with surgical reduction. However, surgical techniques used for internal fixation and pelvic fixation in the study were limited, and poor fixation techniques were likely to have contributed to compromised long-term outcomes in the reduction group. Subsequent publications demonstrated that patients treated with circumferential fusion had better outcomes than those treated with anterior or posterior fixation alone. Molinari et al. demonstrated significantly higher fusion rates in patients treated with circumferential fusion compared with in situ posterolateral fusion, and fusion was strongly associated with improved outcomes.
In contrast, there is significant literature that supports improved outcomes after surgical reduction of high-grade olisthesis. Boxall et al. demonstrated improved fusion and maintenance of correction in patients treated with surgical reduction compared with in situ fusion. Nahle et al. demonstrated that improvement of proximal femoral angle after surgical realignment of high-grade spondylolisthesis is correlated with improved outcome. Mac-Thiong et al. reported that a balanced pelvis postoperatively was the most significant predictor of patient satisfaction with surgery, self-image improvement, and improvement of other health status domains. Similarly, Alzakri et al. demonstrated improved quality-of-life metrics in patients who maintained or achieved a normal pelvic balance after a surgical reduction of high-grade spondylolisthesis. Overall, the evidence in the literature supports that patients with significant health status compromise related to deformity caused by high-grade dysplastic spondylolisthesis are most likely to improve with surgical reduction of deformity.
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