How to Choose the Surgical Approach for the Treatment of De Novo Scoliosis

CHAPTER PREVIEW

CHAPTER SYNOPSIS:

The management of degenerative, or de novo, scoliosis requires a surgeon to individualize the surgical treatment according to the patient’s symptoms, deformity, and confounding factors. A detailed plan of the surgical approach and method of reconstruction should be considered with the goals of improving function, restoring alignment, and reducing pain for the patient. A variety of surgical options is available to help address the pathology, from decompression alone to circumferential procedures.

IMPORTANT POINTS:

Surgical Indications

•

Axial symptoms that do not respond to conservative treatment
•

Progressive neurologic symptoms
•

Progression of the deformity

Surgical Techniques

•

Decompression alone
•

Decompression with posterior fusion
•

Combined anterior and posterior approaches
•

Staged procedures
•

Posterior osteotomies

CLINICAL/SURGICAL PEARLS:

•

Fusion is most commonly performed with instrumentation to improve the fusion results.
•

In an elderly patient with osteoporosis, fusion with bone grafting alone may be sufficient.
•

Posterior interbody techniques may be useful to achieve stable three-column support while avoiding an anterior approach.
•

In cases of deformity, anterior procedures are almost always combined with posterior procedures.
•

If stages of anterior and posterior procedures are considered, the second stage should be performed at the earliest time allowed by the patient’s condition.
•

Osteotomies are increasingly more popular ways to restore sagittal balance with a posterior correction of kyphosis.

CLINICAL/SURGICAL PITFALLS:

•

Decompression alone should be considered with caution in the setting of deformity.
•

Limitations of combined procedures include increased operative time and added morbidity from the anterior approach.
•

If long fusions extend to the sacrum, additional pelvic fixation or anterior column support, or both, is advocated.

VIDEO AVAILABLE:

N/A

“De novo” scoliosis, or degenerative scoliosis, occurs in patients who had a relatively straight spine earlier in life and later develop deformity. This is generally related to degeneration itself, but there may also have been antecedent destabilizing factors such as surgery, trauma, infection, or other variables. Nonetheless, the specific factors predisposing to such deformity are often not completely clear.

Initial disc degeneration and facet arthropathy are associated with instability en route to stabilization of the lumbar spine during more advanced degeneration, as described by Kirkaldy-Willis and Farfan. Settling of the degenerative segments can lead to scoliosis in the coronal plane, spondylolisthesis in the sagittal plane, and rotational listhesis in the axial plane. In addition to focal deformity, degenerative scoliosis may be associated with alterations in overall balance. As with the other deformities noted earlier, this can be in any plane; however, loss of normal lordosis or frank kyphosis is the most commonly observed direction of decompensation.

When a patient presents with such deformity in adult life, this may be difficult to differentiate from adult idiopathic scoliosis. However, degenerative scoliosis is generally more focal to the less stabilized lumbar spine and is associated with lesser rotational components than idiopathic scoliosis. Because of the degeneration associated with degenerative scoliosis, a significant degree of disc degeneration, ligamentum flavum hypertrophy, and facet hypertrophy also occur, which are often associated with central or foraminal stenosis, or both.

Reports of the prevalence of degenerative scoliosis have varied from 6% to 33%, a variability that may be somewhat confounded by the aging population. Lateral osteophytes more than 5 mm asymmetric between sides or an asymmetric disc space collapse of more than 20% has been reported to be independent predictors of developing degenerative scoliosis. The average age at presentation is in the late 60s. A Cobb angle of 30 degrees or more, lateral vertebral translation of 6 mm or more, variations in the depth of L5 relative to the intercrestal line, and grade 3 apical rotation have been found to be important radiographic predictors of curve progression.

PATIENT EVALUATION

Clinical Presentation

Patients with degenerative scoliosis may have axial symptoms, neurogenic symptoms, and/or complaints of progressive imbalance. Although lateral listhesis, L3 and L4 end plate obliquity, and thoracolumbar kyphosis have been correlated with axial pain on presentation, Cobb angle, age, level of listhesis, and plumbline offset were not directly related. Classic complaints of neurogenic claudication with or without radicular symptoms from the concavity of curvature may be present. Progression of curvature or decompensation can be suggested by subjective changes in stance or changes noted in the fit or lay of clothing.

Diagnostic Imaging

Initially, persistent lumbar-related symptoms are generally evaluated with dedicated lumbar imaging. Nonetheless, full-length, upright, posteroanterior, and lateral scoliosis films are essential for the analysis of coronal and sagittal balance if a significant deformity is noted.

If a significant neurologic component accompanies a patient’s symptoms and/or if symptoms persist despite conservative treatment measures, magnetic resonance imaging is important to define compression of the neural elements and rule out other unexpected findings. A computed tomographic scan is often considered if surgery is contemplated to better define the bony anatomy. This can also be combined with a myelogram to better resolve the bony anatomy and neuroanatomy concurrently.

If surgery is planned, bending films are also commonly obtained to assess the flexibility of a curvature in the planes of interest. This may become an important variable in the surgical decision-making process. These images are often taken supine with voluntary or fulcrum bending.

NONSURGICAL TREATMENT

Although mixed evidence has been reported for the efficacy of most conservative treatment options for symptoms associated with degenerative scoliosis, this is generally tried as a first line of treatment. Nonsteroidal anti-inflammatory medications and physical therapy are common measures that may be associated with improvement as with other degenerative spinal conditions. Epidural or facet injections, or both, may be considered as minimally invasive treatment options. Spinal orthoses can also provide the pain relief; however, this potential benefit should be weighed against the potential of trunk muscle deconditioning.

SURGICAL TREATMENT

If a patient has axial or neurologic symptoms despite conservative measures, progression of deformity, or both, surgical intervention may be considered. If this is the case, a number of factors must be considered, including the patient’s presenting complaint, degree and nature of the deformity, patient age, and confounding medical and surgical histories.

De novo scoliosis is a condition for which the risks and benefits of different surgical options must be weighed carefully against the patient’s priorities. Although large reconstructive procedures may be appropriate for younger, healthier, and more active patients, lesser procedures may be much more appropriate for more elderly patients with greater comorbidities. These considerations should lead to discussion with patients regarding surgical options and recommendations that match individual patient priorities whereas minimizing the risk for future problems.

Surgical options range from decompression alone to combined anterior and posterior reconstructions with many options in-between. The advent of newer surgical techniques and more advanced spinal instrumentation has greatly improved the ability to correct and stabilize such deformities, whereas certain technologies strive to minimize trauma to surrounding tissues.

Decompression Alone

Decompression alone may be considered to alleviate neurologic compression and corresponding complaints of radicular and neurologic claudication symptoms. In fact, this is the most direct intervention for alleviating such neurologic complaints.

Nonetheless, decompression alone should be considered only with caution in the setting of deformity for several reasons. First of all, a deformity itself may contribute to compression of the neural elements, making it difficult to fully alleviate central or foraminal stenosis without partial restoration of alignment (which could be achieved with instrumentation). Furthermore, concern exists that decompression alone will lead to progression of the underlying deformity and potentially recurrence of neural element compression and related symptoms.

Decompression alone is mostly considered in patients with degenerative scoliosis that is relatively mild in nature. Empirically, this would pose a lesser risk for accentuating deformity after decompression. This option might also be considered in elderly patients with more significant comorbidities for whom larger surgery might be associated with significantly greater risks.

It has been hypothesized that this potential for decompression may be most limited for shorter decompressions, or if minimal resection of native bone or ligaments, or both, has to be resected. For example, if this intervention is considered, potentially multiple laminotomies or minimally invasive techniques with lesser tissue dissection may be warranted over formal open laminectomies, which might be more destabilizing.

Other variables may also play into this decision. For example, a spine with advanced disc collapse and significant osteophytes may have less risk for progression of an underlying deformity than a spine with tall discs or decompensated alignment.

As with any spine surgery, decompression alone would not be expected to lead to improvement of axial symptoms. Overall, decompression alone should be considered with caution in the setting of deformity. This may be an appropriate option in the older, sicker patient with lesser deformity. However, as the deformity becomes of greater magnitude in more healthy patients, the risk/benefit ratio shifts toward including fusion in the surgical plan.

Decompression with Posterior Fusion

In patients who have a scoliotic curve of a slightly larger magnitude, lateral listhesis, anterolisthesis, significant residual disk space height, axial symptoms, and/or are healthy enough to tolerate a slightly greater intervention, fusion is often considered with decompression. Such fusions can be performed without instrumentation. For example, if a patient is elderly and has osteoporosis, and the goal is decreasing motion at the segment, but without necessarily relying on a solid fusion, an in situ fusion using bone graft alone may be sufficient ( Fig. 25-1 ).