21 Surgical Treatment of Syndromic Scoliosis
A multitude of syndromic conditions are associated with the development of spinal deformity in young children. The curve characteristics, soft tissue, and bone structure vary grossly depending on the specific condition; therefore, stacking these quite different conditions in the same section may appear somewhat simplistic. However, because of the rarity of the conditions, similarities in management strategies, and stark differences between syndromic and idiopathic scoliosis, a discussion under a common heading is justified.
21.1 General Considerations
The spine deformities associated with syndromic conditions typically do not respond to conservative measures as much as idiopathic deformities do, and a detailed discussion of nonoperative management is provided in Chapter 22. Casting and bracing are rarely successful. Casting may not be even tolerable or feasible in some patients with multiple comorbidities. Because of the associated abnormalities, the treatment goals in these children also need to be tailored accordingly. As an example, a noticeable residual cosmetic deformity, but a stable spine, is considered a very good result in a patient with syndromic scoliosis if this has been achieved without major complications. Intraoperative problems, such as excessive bleeding and anesthesia-related issues, are more common in this group. Because of the inherent abnormalities of the soft tissues and bone as well as the nervous system, spontaneous correction from the levels that are not included in the fusion mass may not be as dependable as in idiopathic deformity. Junctional deformity is more common in certain conditions, possibly because of the combination of these factors.
For these reasons, a longer fusion, which is attempted to be avoided in idiopathic deformity, may not be undesirable in patients with syndromic scoliosis. Given that the functional demand on the spine will be less in most patients with syndromic scoliosis, a long fusion probably is not as negative as it would be in a patient with idiopathic deformity. Therefore, selective and short fusion should be reserved for the rare patients with good muscle tone, neural control, mental acuity, and bone of good quality. Poor bone quality and a high rate of fixation failure justify longer fusions with the use of more anchors.
In a certain group of patients with syndromic scoliosis, postoperative external supports, most commonly in the form of thoracolumbosacral orthoses (TLSOs), should be considered. Decreased truncal control in some of these children, in addition to poor bone quality, may compromise the internal fixation before bony fusion occurs. There is evidence suggesting that pseudarthrosis and junctional kyphotic deformities may be more common in patients with syndromic scoliosis following posterior instrumentation procedures. Therefore, it is a safe approach to use external bracing in some cases, especially if the neurologic or cognitive status is compromised.
Because of the multitude of comorbidities typically seen in these patients, a multidisciplinary approach is warranted that begins at the first preoperative visit and continues all through the postoperative course. The surgeon should be familiar with the various syndromes and meticulous about noting the patient’s associated medical problems. Consequently, the relevant specialties should be consulted and involved in the preoperative care and preparation. Most commonly, cardiac, pulmonary, gastrointestinal, and neurology / neurosurgery consultations may be necessary. Involving a geneticist may ensure the diagnosis and help with the overall treatment plan. The medical management of patients with syndromic conditions is discussed in Chapter 20.
The surgical plan should include the type of approach and the implant type, size, and material. The bone quality, size and stiffness of the deformity, and desired degree of correction are important factors when an implant is chosen. Smaller implants should be made available because normal-size implants may not fit the dysplastic bones of these children. Preoperative radiographs should be well studied, and a computed tomographic (CT) scan should be acquired if there are any questions about structural anomalies, such as dysplastic or absent pedicles and underdeveloped posterior elements, that may alter the surgical plan. In the presence of positive neural findings or suggestive signs, magnetic resonance (MR) images of the whole neural axis should be acquired. Additionally, in complex deformities and syndromes with connective tissue involvement, MR imaging will prove useful for showing anomalies such as dural ectasia and intraspinal abnormalities that may alter the surgical plan. Specifically, it is wise to avoid canal-occupying implants like hooks, wires, or polyester tape in patients who have conditions associated with dural ectasia (e.g., connective tissue disorders, neurofibromatosis).
Transcranial motor evoked potentials (Tc-MEPs) and somatosensory evoked potentials (SSEPs) are routinely used to monitor all neurologically intact patients during spinal surgeries. Preoperative blood typing and crossmatching are mandatory because a higher rate of bleeding may be encountered, especially in patients with connective tissue disorders. The surgeon must involve the patient’s family at every step of the management. It is very important that the family and the child understand the treatment goals and plans. The parents should be well informed about the potential complications and the possible need for revision procedures, as well as the care and rehabilitation that will be required in the postoperative period.
21.2 Specific Syndromes
The complete list of syndromic conditions is exhaustive, and the reader is directed to Chapter 16 for a discussion of the natural history of the spine in some of the various conditions associated with scoliosis. However, this section provides an overview of the authors’ approach to the treatment of the most common syndromic conditions associated with early onset scoliosis. The treatment of thoracic insufficiency syndrome is not discussed here because it is covered in Chapter 4.
21.2.1 Marfan Syndrome
Early onset scoliosis that progresses despite bracing is the typical spinal deformity in Marfan syndrome. Dural ectasia is common finding (up to 95% of cases), and preoperative MR imaging of the whole spine should be done before these children undergo surgery. Possible dural tears and the need for repair should be included in the preoperative planning. Pedicle fixation is the preferred method because the laminae are often thin in children with dural ectasia. The pedicles are also affected by dural ectasia and therefore are thinner. The anatomy should be studied on the preoperative MR images or CT scans so that the instrumentation plan can be plotted. Growing rods can be used successfully to delay fusion in children with Marfan syndrome. The rates of junctional kyphosis and implant failure may be high. Current evidence shows that although the curve patterns are similar to those of idiopathic curves, selective fusion results in a high rate of progression in the spared secondary curve. Therefore, when definitive fusion is considered, all curves should be instrumented and fused.
The sagittal plane also requires attention because thoracolumbar kyphosis is not uncommon. Poor bone quality is another consideration; however, pedicle fixation has proved to provide sufficient anchor strength. Intraoperative bleeding is typically greater than in idiopathic deformity, and this must be considered in the preoperative planning.
21.2.2 Ehlers–Danlos Syndrome
One specific type of this connective tissue disorder is especially associated with the severe and early onset of kyphoscoliosis (Fig. 21.1). Because of the ligamentous laxity and low muscle tone, the deformity progresses early and quickly, and surgical treatment is often necessary.
One of the major intraoperative concerns is vascular friability. Anterior surgery should be avoided because of the high risk for injury to the major vessels. All correction can and should be achieved posteriorly. Dural ectasia is another common finding, and the surgeon should be prepared for potential dural tears. As in all collagen disorders, wound healing may be problematic, and the utmost care should be taken for a meticulous and minimally traumatic closure. Postoperatively, patients should be closely monitored for junctional issues because low muscle tone and hyperelasticity may predispose them to junctional deformity above and below the last instrumented level.
Loeys–Dietz syndrome and Beals syndrome are characterized by connective tissue abnormalities in association with early onset scoliosis. The spinal abnormalities and deformities are similar to those of Marfan syndrome. The rate of dural ectasia has been reported to be as high as 67% in patients with Loeys–Dietz syndrome. A surgical approach and precautions similar to those appropriate for Marfan syndrome are also valid for these conditions. The cervical spine requires attention in connective tissue disorders and should be evaluated for instability.
We recommend caution when halo traction is used in patients who have disorders associated with ligamentous laxity because there has been at least one report of the development of iatrogenic cervical kyphosis after halo traction in a patient with Marfan syndrome.
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