Idiopathic Scoliosis Treatment & Management

Updated: Nov 21, 2018
  • Author: Charles T Mehlman, DO, MPH; Chief Editor: Jeffrey A Goldstein, MD  more...
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Treatment

Approach Considerations

An extensive yet incomplete understanding of the natural history of idiopathic scoliosis remains a reality. Thus, more than a modicum of uncertainty remains associated with selection of recommended treatments for idiopathic scoliosis. The main treatment options for idiopathic scoliosis may be summarized as the three Os, as follows:

  • Observation
  • Orthosis
  • Operative intervention

When to choose each of these treatments is a complicated matter.

The risk of curve progression varies based on the idiopathic scoliosis group in which a patient belongs (ie, infantile, juvenile, adolescent).

The future of the understanding of idiopathic scoliosis will clearly be guided by human genome analysis. [84] The characterization of the structure and function of specific gene loci and eventual ability to regulate their expression will undoubtedly form the basis of scoliosis treatments of the future. Someday, clinicians may look back upon present mechanically based treatments of scoliosis and wonder how patients ever benefited.

Controversies exist at this time regarding several surgical tactics that may be used to treat similar curve types. Examples of this include anterior fusion and instrumentation versus posterior fusion and instrumentation for isolated thoracic curves. Both validated methods of curve classification and prospective, randomized, controlled studies comparing the surgical methods will be necessary before definitive answers can be embraced.

Future potential also exists in strategies for modulating spinal growth as a means of treating idiopathic scoliosis. This modulation may be genetic or mechanical in nature.

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Treatment Indications

Infantile idiopathic scoliosis

Although defined by a seemingly arbitrary age limit (< 3 years at the time of diagnosis), infantile idiopathic scoliosis demonstrates marked differences that distinguish it from the other two categories of idiopathic scoliosis.

Infantile idiopathic scoliosis is the only type of idiopathic scoliosis whose most common curve pattern is left thoracic. It is the only type of scoliosis that is more common in boys. It is more common in European patients or those of immediate European descent. In the past, infantile idiopathic scoliosis may have constituted up to 41% of all idiopathic scoliosis cases in parts of Europe, but the current rate would appear to be closer to 4%. This is still dramatically higher than the estimated 0.5% rate in North America. [85]

Infantile idiopathic scoliosis is also the only type of idiopathic scoliosis with any significant reputation for spontaneous resolution. Reported spontaneous resolution rates are in the range of 20-92%. [8, 86] Ceballos et al studied 113 Spanish patients with infantile idiopathic scoliosis. They found a 92% rate of associated plagiocephaly and an almost 25% rate of congenital hip dysplasia. [87] In addition, they found that nearly 74% of their patients' curves were of the resolving variety (mainly left thoracic curves) and the other 26% were progressive curves (mainly double primary type curves).

Prediction of curve progression in infantile idiopathic scoliosis has been tied to assessment of the rib vertebral angle difference (RVAD) originally described by Mehta in 1972. [88] As described by Mehta, this measurement is carried out at the apical vertebra of the curve. In instances in which the curves resolved spontaneously, the RVAD was less than 20° in about 80% of cases, and in those instances in which the curves were progressive, the RVAD exceeded 20° in about 80% of cases. Other authors have confirmed the prognostic value of the RVAD, as well as its reliable application. [87, 89]

Treatment indications

Nonoperative treatment of progressive infantile idiopathic scoliosis predominates and may involve the use of conventional thoracolumbosacral orthosis (TLSO)-type braces, Milwaukee-type braces, and even intermittent Risser casting. Some have questioned the value of bracing in infantile idiopathic scoliosis and have stated that "a curve that resolves in a brace would probably have resolved without treatment." [85]

If surgical treatment becomes necessary, anterior release and fusion followed by posterior spinal fusion with instrumentation is considered to be the functional treatment. Every effort should be made to delay such surgical intervention as long as possible to optimize spinal growth, but relentless curve progression should not be accepted or tolerated while some arbitrary chronologic age is awaited.

Although convex spinal epiphysiodesis (which has been shown to be quite effective in the management of congenital scoliosis) is intuitively attractive, it has not been shown to be as reliable in the setting of infantile idiopathic scoliosis. [90] Addition of some type of posterior instrumentation may improve the results of epiphysiodesis. [91]

A treatment outline for infantile idiopathic scoliosis may be as follows:

  • Curves less than 25° with an RVAD less than 20° are preferentially observed and monitored with spinal radiographs at regular intervals
  • Curves exceeding these parameters are typically braced, with some consideration given to the value of intermittent Risser casting
  • Surgery is considered for curves not adequately controlled with nonoperative measures

Juvenile idiopathic scoliosis

Juvenile idiopathic scoliosis most closely mimics the epidemiology and demographics of the adolescent version of the disease. It is more common in females, and its most common curve pattern is a right thoracic curve. [9] In fact, given its demographic similarities, high rate of progression, and need for surgery, juvenile idiopathic scoliosis might be considered to be a malignant subtype of adolescent idiopathic scoliosis.

Robinson and McMaster studied 109 patients with juvenile idiopathic scoliosis in Scotland and found that 95% (104 of 109 patients) demonstrated curve progression and 64% (70 of 109 patients) progressed to require a spinal fusion. [9] This spinal fusion rate is similar to that reported by James 15 years earlier. [92]

A study from Washington University found a 50% rate of neural axis abnormalities in young children (< 10 years) with idiopathic scoliosis. [93] These findings included Chiari type I malformations and dural ectasia. At least one case report also exists in which a spinal intraosseous arteriovenous malformation was found in association with juvenile scoliosis. [94]

Treatment indications

One potential treatment algorithm for juvenile idiopathic scoliosis is as follows:

  • Observation for curves less than 25° with follow-up radiographs at regular intervals
  • Bracing for curves that range from 25º to 40° and at least consideration of bracing (based on curve flexibility) for curves from 40º to 50°
  • Bracing for smaller curves that demonstrate rapid progression to the 20-25° range
  • Surgical intervention for inflexible curves that exceed 40° or virtually any curve that exceeds 50°.

Bracing and casting may be used outside the above-mentioned parameters in an effort to help control a large curve in a young child for whom the surgeon is attempting to optimize spinal growth. Similar recommendations exist regarding the value of MRI in juvenile idiopathic scoliosis due to a significant rate of neural axis abnormalities. [93]

Adolescent idiopathic scoliosis

Adolescent idiopathic scoliosis is the most common type of idiopathic scoliosis and the most common type of scoliosis overall. Progressive curvature may be predicted by a combination of physiologic and skeletal maturity factors and curve magnitude. Small curves in more mature patients have a substantially lower risk of progression (~2%) than larger curves in more immature patients, in whom the risk is much higher (approaching or exceeding 70%).

Lenke classification

Currently, the Lenke classification system is commonly used to categorize adolescent idiopathic scoliosis. This system, first published in 2001, includes the following three components [95] :

  • Curve type (1, 2, 3, 4, 5, or 6)
  • Lumbar spine modifier (A, B, or C)
  • Sagittal thoracic modifier (–, N, or +)

On coronal and sagittal radiographs, the six types specified by Lenke et al have specific characteristics that distinguish structural and nonstructural curves in the proximal thoracic (PT), main thoracic (MT), thoracolumbar (TL), and lumbar (L) regions. [95] Regional curves are measured, the major curve is identified, and a determination is made as to whether the minor curve is structural. The curve is then assigned to the appropriate numeric type (1 through 6).

The lumbar spine modifier is based on the relation of the center sacral vertical line (CSVL) to the apex of the curve. If the CSVL passes between pedicles of apical lumbar vertebrae, the modifier A is assigned; if it touches a pedicle, the modifier B is assigned; and if it does not touch apical lumbar vertebrae, the modifier C is assigned.

The sagittal thoracic modifier is based on the sagittal Cobb angle from T5 to T12. If the angle is less than 10º (hypokyphotic), the modifier – is assigned; if it is 10-40º (normal), the modifier N is assigned; and if it exceeds 40º (hyperkyphotic), the modifier + is assigned.

Treatment indications

Treatment recommendations for adolescent idiopathic scoliosis are driven almost totally by curve magnitude (the only caveat being that brace treatment is thought to be effective only in patients who are still growing). It is thus somewhat ironic to note that stated recommendations urge observation for curves less than 30°, bracing of curves that reach the 30-40° range, and consideration of surgery for curves that exceed 40°. This amounts to a 10° window between observation and major spinal surgery. It is even more ironic to note that 10° is a commonly discussed margin of error for measuring such scoliotic curves.

Additional patient factors may also influence some orthopedic surgeons to brace patients with curves measuring less than 30° or in excess of 40°. For instance, a rapidly progressive curve in a 12-year-old child that suddenly goes from 16º to 26° may easily prompt bracing.

When it comes to surgical considerations, patients with adolescent idiopathic scoliosis may be functionally subdivided into those patients in whom significant anterior spinal growth is a concern and those in whom it is not. This amounts to a quantification of risk of development of the complication known as crankshaft phenomenon. [96] This can have a major impact on the surgical treatment plan in that a child at significant risk for crankshaft phenomenon will require an anterior spinal fusion procedure.

Much effort has been devoted to predicting which patients may suffer from this continued anterior spinal growth that results in progressive angulation and rotation of the spine. [96, 97, 98, 99, 100] In fact, a hierarchy of risk can be constructed in which progressively more precise estimates can be made. In this hierarchy, the presence of a radiographic Risser sign and reaching menarche are somewhat predictive but less so than closure of the triradiate cartilage, and reaching one's peak height velocity is perhaps the most powerful predictor of being at rather low risk for the crankshaft phenomenon.

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Medical Therapy

Nonoperative management consists of either simple observation or orthosis use. Observation is watchful waiting with appropriate intermittent radiographs to check for the presence or absence of curve progression. Orthosis use for scoliosis is discussed extensively below.

No other treatments, including electrical muscle stimulation, physical therapy, spinal manipulation, and nutritional therapies, have been shown to be effective for managing the spinal deformity associated with idiopathic scoliosis. The lack of demonstrated effectiveness in this context means either that scientifically valid studies have been done that do not support the treatment or that no such studies have yet been published that would allow an evidence-based evaluation.

The first widely used scoliosis brace with proven effectiveness was the Milwaukee brace. This brace was developed by Walter Blount and Albert Schmitt and introduced at a meeting of the American Academy of Orthopaedic Surgeons in 1946. [101] It was originally designed to be used as part of the surgical treatment of scoliosis and only later evolved into a standalone nonoperative treatment.

Lonstein and Winter studied 1020 patients with adolescent idiopathic scoliosis treated with the Milwaukee brace. They reported that this orthosis was effective in preventing significant curve progression in patients with 20-39° curves. [102] These same authors recommended that adolescents with a curve of 25° and a Risser sign of 0 be braced immediately and not wait for evidence of curve progression. Other authors have shown that an average curve correction of 20% in the brace (Milwaukee brace) is associated with bracing success. [103, 104]

Rowe et al performed a meta-analysis aimed at evaluating the efficacy of nonoperative treatments for idiopathic scoliosis. [105] They calculated the weighted mean proportion of success for three nonoperative treatments: observation, electrical stimulation, and bracing. They were able to successfully combine data on 1910 patients from 20 different studies for purposes of meta-analysis and reported the following main results:

  • Observation, 49% success rate
  • Electrical stimulation, 39% success rate
  • Bracing 8 hr/day, 60% success rate
  • Bracing 16 hr/day, 62% success rate
  • Bracing 23 hr/day, 93% success rate

In a prospective multicenter study from the Scoliosis Research Society, Nachemson et al found brace treatment (an underarm plastic brace worn for at least 16 hr/day) to be successful 74% of the time (95% confidence interval [CI], 52-84%). [106] Some authors have not been able to identify a major difference between full-time bracing (23 hr/day) and part-time bracing (12-16 hr/day). [107]

The psychological stress associated with scoliosis has been documented, [108] and this does not improve compliance with brace wear. MacLean et al from Vanderbilt studied 31 adolescent and preadolescent females who were undergoing part-time brace treatment for their idiopathic scoliosis. [109] Part-time bracing was defined as 13-16 hr/day. The investigators noted that 84% of patients described the initial period of bracing in "stressful terms" and experienced lower levels of self-esteem. A reassuring finding was that no overt psychopathology was identified in this study.

Compliance with prescribed brace-wear regimens has been shown to be poor. DiRaimondo and Green found that on average, patients only wore their braces 65% of the prescribed amount of time. [110] Patients prescribed part-time (16 hr/day) bracing actually demonstrated worse compliance (58%) than those prescribed full-time (24 hr/day) bracing (71%). Overall, only 15% of patients demonstrated a highly compliant (≥90%) brace-wear routine.

Questions have also been raised regarding the consistency of strap tension in TLSO bracing. Using an instrumented load cell to measure strap tension, Aubin et al studied 34 of their patients with braces in Quebec. [111] They found marked variability in tension, with the greatest change occurring while patients were recumbent.

In part because of the aforementioned psychological and brace-wear compliance issues, new approaches to bracing are being developed. [112, 113] One such approach, developed by Coillard and Rivard of the St Justine Hospital in Montreal, is a dynamic bracing method known as the SpineCor Brace or as the St Justine Brace. [114] It involves elastic straps that are anchored on a pelvic corset, and based on curve morphology, these straps are tensioned to exert corrective forces. The brace is a radical departure from traditional plastic and metal orthoses.

Early results with the St Justine Brace are encouraging, with success rates comparable to those of traditional bracing. Continued follow-up of their growing international cohort of patients is necessary. A study by Gutman et al found the SpineCor brace to be less effective than the Boston brace for treatment of adolescent idiopathic scoliosis. [115]

Contraindications

Few, if any, absolute contraindications exist regarding scoliosis care, just as few, if any, absolute indications for intervention exist. Accepted contraindications for bracing include skeletal maturity and excessive curve magnitude. Thoracic lordosis and certain curve patterns such as double thoracic curves also have been offered as at least relative contraindications to bracing.

The main contraindication to posterior scoliosis surgery would be medical instability and inability to survive surgery. Anterior scoliosis surgery would also be contraindicated in these patients, as well as in those with a precarious pulmonary status.

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Surgical Therapy

Even in the setting of adequate correction and solid fusion, up to 38% of patients still have occasional back pain. [67, 116]

The primary goal of scoliosis surgery is to achieve a solid bony fusion. The surgical technique used to achieve such an arthrodesis is vastly more important than the instrumentation system that the surgeon needs to use, if any. [6, 117]

Modern instrumentation systems have been shown to allow adequate curve correction but to possess little or no ability to diminish associated rib humps. [118] Despite claims of certain instrumentation systems to derotate the spine, little actual derotation has been documented. Derotation of the instrumented curve also has been shown to possibly occur at the expense of creation of new rotation in uninstrumented portions of the spine. [119]

Previously, much attention was paid to the ability of certain spinal instrumentation systems (eg, Cotrel-Dubousset to derotate the spine during scoliosis correction. Jarvis and Greene showed that use of the Wisconsin segmental spinal instrumentation (a system traditionally thought to not be associated with significant spinal derotation) was associated with spinal derotation equal to or greater than that of the Cotrel-Dubousset–type systems. [120]

Since 1993, video-assisted thoracoscopic surgery (VATS) has been used in the anterior treatment of pediatric spinal deformity at Cincinnati Children's Hospital Medical Center. [121] This minimally invasive technique is aimed at decreasing operative morbidity and optimizing patient recovery from surgery. More than 100 of these procedures have been performed at this institution. Initial biomechanical studies in animal models correctly predicted what clinical practice has now borne out—that endoscopic anterior release and diskectomy is as effective as the open version of the operation. [122, 106, 123, 124] Endoscopic spinal instrumentation techniques have also been introduced and continue to evolve. [125]

Hoppenfeld described an ankle clonus test for intraoperative assessment of the integrity of the spinal cord during scoliosis surgery. In more than 1000 patients, the test was noted to have no false-negative results and three false-positive results. This translated into 100% sensitivity and 99.7% specificity. [126]

Preoperative considerations

Preoperative evaluation focuses on specifics of curve location, magnitude, and flexibility. These parameters are used in conjunction with patient maturity factors to determine optimal treatment choice, but definitive studies are not yet available that dictate specific surgical tactics. However, the scoliosis surgeon is aided by commonly applied clinical guidelines that have evolved over time. The goal is always to fuse as little of the spine as possible while adequately treating existing major curvature.

For a thoracic curve (with adequate flexibility) without any significant associated lumbar curvature, the most common surgical approach has not changed since the days of Paul Harrington: posterior spinal fusion with instrumentation. Surgeons may choose from a diverse array of anchors to secure large-diameter rods (usually in the 0.25-in. range) to the spine. These anchors include sublaminar hooks, pedicle hooks, transverse process hooks, sublaminar wires (Luque wires), spinous process wires (Drummond wires), and pedicle screws.

Some surgeons have advocated anterior spinal fusion and instrumentation for such isolated thoracic curves. These have included both open (thoracotomy) and limited-incision (thoracoscopic) techniques.

When the primary problem is a large, stiff thoracic curve (usually not bending less than 50°), a different surgical tactic is usually undertaken in which an anterior release (usually including diskectomy and bone grafting) is performed prior to posterior spinal fusion and instrumentation. Anterior spinal fusion and instrumentation has also been advocated in this situation, provided the patient does not have excessive kyphosis associated with a large thoracic curve.

Large curve patterns that include both thoracic and lumbar deformity continue to challenge scoliosis surgeons. If adequate flexibility and balancing of the lumbar spine is possible, then selective fusion of the thoracic curve is possible. When this is not the case, extensive fusion (at times down to the fourth lumbar segment) may become necessary.

The Scoliosis Research Society has a reasonably specific definition of thoracolumbar scoliosis: a curve whose apex lies at the body of T-12 or L-1 or at the T12-L1 interspace. These curves are most commonly left-sided curves, and they present one of the most common scenarios in which anterior spinal fusion and instrumentation is utilized.

Anterior approaches to this area of the spine were pioneered by Hodgson (Hong Kong), Dwyer (Australia), and Zielke (Germany). Current approaches represent further refinement of these original techniques, such as modern large rod-and-screw systems and the John Hall short anterior segment overcorrection technique. The value of such techniques lies in their ability to powerfully correct large thoracolumbar curvatures while minimizing fused segments within the lumbar spine.

There is little debate regarding the fixation of the rods used for anterior instrumentation. Large bone screws are almost always the anchor of choice. For posterior instrumentation procedures, the surgeon has more options. Multiple hooks are the most commonly used anchors. They offer simplicity, strength, and near complete visualization during insertion. Their main drawbacks relate to size mismatch between hooks and associated bony elements, as well as the absence of appropriate hook sites (such as might be the case in myelomeningocele, tumor cases, or revision surgeries).

Sublaminar wires offer the power of segmental fixation and firm bony purchase, but with the drawback of possible dural and/or spinal cord trauma. As a result, either very selective use of or no use at all of sublaminar wires is usually the case in the setting of idiopathic scoliosis. A reasonable compromise was achieved when Drummond introduced his spinous process wires (also known as Wisconsin wires). These devices still offer the power of segmental fixation with virtually none of the nerve injury risks of sublaminar wires.

Pedicle screws have also become a popular anchor for the rods used in posterior scoliosis fusion procedures. [127] They offer the potential advantage of increased strength (and possibly power of correction) while at the same time introducing added insertion-technique complexity and different neurologic complication risks. A very real and major increase in the overall cost of instrumentation constructs that include many pedicle screws is the case when they are compared to similar constructs that may include hooks and wires.

At this time, the available evidence in favor of a commensurate improvement in clinical outcomes is not sufficiently conclusive to support routine use of such pedicle screw constructs in the treatment of idiopathic scoliosis.

Pulmonary function testing is commonly used in the preoperative evaluation of patients with idiopathic scoliosis who are slated to undergo surgery. Such testing may influence the surgeon's enthusiasm for related procedures, such as costoplasty (thoracoplasty). Pulmonary function testing may also uncover previously unrecognized tobacco use (an independent risk factor for pseudarthrosis) or undiagnosed (subclinical) pulmonary disease.

Predonation of several units of donor-directed blood is considered standard for most patients. Certain commercially available intraoperative blood recovery devices may also be used at times.

Anatomic and technical details

Posterior approach

The major superficial muscles of the back are not often directly visualized during posterior surgical approaches for scoliosis, but they must not be forgotten. These muscles include the trapezius, the rhomboid major, the rhomboid minor, and the latissimus dorsi. Using an animal model, Kawaguchi et al showed that significant posterior muscle injury can be induced by the pressure exerted by surgical retractors. [128] This certainly makes a case for intermittent removal and replacement of such retractors during the course of posterior spinal surgery.

The route for exposure of the posterior spinal elements passes through the cartilaginous apophyses of the spinous processes. These structures, often referred to as the cartilaginous caps, are systematically split in the midline to allow sequential subperiosteal dissection of the spinous processes, laminae, facet joints, and transverse processes.

The laminae of the thoracic vertebrae spread out from the midline like wings and flow upwards (cranially) in the direction of the transverse processes. The facet joints of the thoracic spine are shingled in a coronal plane in such a way that the inferior facet that contributes to each joint is located posteriorly and the superior facet is located anteriorly. The thickness of the interior and superior facets of the thoracic spine is in the range of 3-5 mm. [129] The thoracic facet joints are located a mere 7-11 mm from the midline of the posterior spine.

Progressing from the thoracic to the lumbar spine, important differences are noted. The V-shaped laminae of the thoracic spine give way to the butterfly-shaped laminae of the lumbar spine. This orientation change is important for the surgeon to remember when exposing these bony elements. The facet joints of the thoracic spine, which are oriented in more of a coronal plane, transition into the more sagittally oriented facet joints of the lumbar spine. The transverse processes of the thoracic spine, which seem to flow directly up and away from the laminae, change significantly in the lumbar spine so that they are no longer in close proximity to the laminae and are located anterior and inferior to the lumbar facet joints.

The ribs are also obviously absent in the lumbar vertebrae. What some consider a rib remnant does persist and is referred to as a mammillary body or mammillary process. It is most pronounced near the thoracolumbar junction but may be identified on nearly all of the lumbar segments. In the sagittal plane, one must also appreciate that the normal gentle kyphosis of the thoracic spine reaches its apex at about the T7-9 region. Below this, a rather definite transition to lumbar lordosis occurs, with an apex around the L3 level.

Thoracic kyphosis is typically in the range of 20-40° (Cobb measurements usually taken from the top of T3 to the bottom of T12). Some authors have stated that up to 50° of thoracic kyphosis should be considered normal. [130] Normal lumbar lordosis is considered by some to range from 35º to 55° (Cobb measurements usually taken from the top of L1 to the top of L5).

Anterior approach

Anterior scoliosis surgery involves three main strategies, as follows:

  • Anterior lumbar or thoracolumbar surgery through a retroperitoneal approach that may or may not involve a diaphragmatic incision
  • Anterior thoracic surgery via traditional open thoracotomy
  • Anterior thoracic surgery via VATS

Various factors relative to skeletal maturity, curve location, and curve flexibility help determine which (if any) of these anterior surgeries may be appropriate.

The most common reason to use the retroperitoneal approach is for an instrumented anterior thoracolumbar spinal fusion. The most common curve pattern in that particular type of scoliosis is an apex left curve pattern; accordingly, the patient is usually positioned lying on the right side. This position is advantageous in that it provides the best access to the scoliotic spine and also places the thick-walled aorta closer to the surgical field (as opposed to the thin-walled inferior vena cava).

After superficial muscle dissection, the surgeon approach proceeds through the bed of the rib that corresponds with the highest vertebra in which instrumentation is planned. This is often either the ninth or tenth rib, with the rib itself being harvested for later use as a bone graft.

Careful dissection is then performed to mobilize the peritoneum (with its contents) in an anterior direction; it is peeled off of the undersurface of the diaphragm. Posterior division of the diaphragm (leaving about a 2-cm cuff for repair) helps to avoid damage to the phrenic nerve. Diaphragmatic division begins with splitting of the costal cartilage and proceeds in a posterior direction with intermittently placed tagging sutures to aid in closure.

The remainder of the retroperitoneal approach to the thoracolumbar spine requires careful superior retraction of the lung, anterior retraction of the peritoneum (with associated aorta and ureter), and posterior retraction of the iliopsoas musculature. Careful identification and division of the segmental vessels (overlying the vertebral bodies) is carried out with either electrocautery or ligatures.

Small sympathetic nerve branches in this same area are sacrificed during this stage of the exposure. This results in at least a transient period in which the left foot (for a left-side approach) will be both pinker and warmer than the contralateral foot. At times, this may result in nursing personnel notifying the surgeon that the contralateral foot is pale and cold, but in reality, it is the foot ipsilateral to the exposure that has changed.

Open thoracotomy might be performed either for anterior thoracic spine release followed by posterior fusion or for anterior thoracic spine fusion with instrumentation. The most common curve pattern to address with this approach would be a right thoracic curve; accordingly, the patient would be positioned with the right side upward.

A similar rib selection and resection technique may be used if desired. From the interior of the chest, the intercostalis musculature (located between each of the ribs) can be seen. Identification of the azygos vein (anteriorly oriented along the vertebral bodies) is necessary. Further medial (ie, central) and running parallel to the azygos vein is the thoracic duct. Several portions of the sympathetic chain may be sacrificed as the segmental vessels overlying the thoracic vertebral bodies are divided and mobilized anteriorly and posteriorly. Blood flow changes similar to those noted in the retroperitoneal approach may be noted in the right foot (for a right thoracotomy).

In addition to this, thoracic surgical dissection carries with it the possibility of sacrificing branches to the greater splanchnic nerve, which would theoretically decrease the visceral referred pain that one might feel from an inflamed gallbladder or similar condition.

Thoracoscopic appreciation of the anatomy of the thoracic spine is becoming more common as endoscopic anterior release and fusion is rapidly moving from being considered an innovation to standard practice. Just as arthroscopic knee surgeons enjoyed an expansion in visualized anatomy in comparison with that visible in knee arthrotomies, the endoscopic spine surgeon benefits from much greater intrathoracic latitude. Most VATS procedures also involve the right thoracic cavity, and this discussion focusses on that particular side.

Proper rib counting and visualization of the superior intercostal vein (formed by the confluence of the second, third, and fourth intercostal veins) as it empties into the azygos vein are necessary steps to orient the surgeon. Beyond this, one also notes the mounds and valleys of the thoracic spine, with the mounds being the disks and the valleys being the vertebral bodies with the segmental vessels that overly them. [122]

The same anatomy outlined in the thoracotomy discussion still clearly applies, but further endoscopic fine points are needed. Specifically, the thoracic spine may be considered to be composed of three separate fields, with important anatomic nuances. [131] The upper field may be considered to be T2-5, the middle field may be considered to be T6-9, and the lower field may be considered to be T10-L1.

The upper field is dominated by the superior intercostal vein, and it is characterized by the fact that the rib heads tend to completely span their respective disk spaces and articulate with two vertebral bodies. This results in a rib such as the third rib coming directly into the region of the T2-3 disk space so that it will articulate with both the T2 and T3 vertebral bodies.

In the middle field, the rib head once again comes directly in toward the disk space, but now, it firmly attaches itself only to the disk space proper.

In the lower field, the rib head articulates directly with its corresponding vertebral body. Thus, in the lower field, the 11th rib is traced to its corresponding vertebral body and then moves directly cephalad to reach the T10-11 disk or directly caudad to reach the T11-12 disk. Once the vertebral bodies have been exposed in a skeletally immature patient, the growth cartilage of the vertebral endplate can be visualized. It has an odd tendency to appear green in color (a quirk of endoscopic optics) and is colloquially referred to as a Wolf line, in honor of Randall K Wolf.

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Postoperative Care

Postoperative patient management involves close monitoring, which often occurs initially in an intensive care unit setting. Patients have monitoring devices, such as arterial lines, and closed suction devices, such as chest tubes, that also require special nursing attention. The use of certain special spine-specific hospital beds, such as the Stryker frame, may also aid in patient care and comfort (change from supine to prone position) during the initial postoperative period.

The use of postoperative bracing varies from surgeon to surgeon. As noted (see Overview, Background), the roots of scoliosis surgery involved immobilization in a body cast. After the development of initial instrumentation systems (eg, Harrington instrumentation), external immobilization was still used routinely.

With the advent of large-rod multiple-hook constructs, such as the Cotrel-Dubousset system and its direct decendents, bracing has been deemphasized a bit. Thus, a patient now is almost as likely not to receive a postoperative brace as to receive one, whereas previously, bracing was much more widespread. In certain specific circumstances, such as anterior thoracic or thoracolumbar instrumentation procedures or surprisingly weak bone stock, postoperative bracing is still almost always used.

When a brace is used, it is typically to be worn full-time for at least 6 weeks, followed by a period in which the brace may be taken off for bathing, with subsequent progressive weaning. As a rule of thumb, patients may also miss up to 6 weeks of school (if their procedure is done during this part of the year), and up to 6 months may be required before they resume most of their normal activities. Vigorous sports may be restricted for at least a year, or in some instances permanently (depending on the outcomes of on risk-versus-benefit discussions between patients, families, and surgeons).

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Complications

Complications are of great concern to parents, patients, and surgeons. Thankfully, complications are rare with modern scoliosis surgery, despite the magnitude of these spinal deformity procedures. [57, 132] Several important intraoperative, early postoperative, and late postoperative complications are discussed here.

McKie and Herzenberg described coagulopathy as a complication of intraoperative blood salvage during scoliosis surgery. [133] These authors suggested that thrombin and Gelfoam that may have been aspirated along with salvaged blood may have contributed to the disseminated intravascular coagulation experienced by their 17-year-old patient. This effect of the thrombin and Gelfoam would have been in addition to that of hemodilution (hemodilution-induced platelet and leukocyte activation syndrome).

The importance of appropriate intraoperative spinal cord monitoring during scoliosis surgery is hardly debatable. Such monitoring can allow early recognition and treatment of spinal cord dysfunction. [134] Somatosensory and motor evoked potentials are commonly used to monitor spinal cord function. A Stagnara wake-up test may also still be employed if the surgeon desires. Current efforts at monitoring have helped achieve and maintain a very low rate of spinal cord injury (less than one half of one percent).

Some concern exists regarding postoperative activity level and the possible hazards of trauma. Neyt and Weinstein reported a case of lumbar spine fracture dislocation in a teenage boy 3 years after successful scoliosis surgery. [135] The boy's fusion extended from the second thoracic vertebra to the first lumbar vertebra, and his subsequent fracture dislocation occurred at the L2-3 level.

Delayed infections following posterior spinal fusion with Texas Scottish Rite Hospital instrumentation has been reported. Richards described 10 such patients who presented with infections at an average of about 2 years after successful spinal fusion. [136] Low-virulence organisms such as Propionibacterium acnes were the main cause, and instrumentation removal was successful in eradicating the infections. Richards hypothesized that the infections might be related to the amount of hardware (eg, hooks, rods) used and suggested that efforts at minimizing such hardware might help prevent such infections.

Much has been written regarding a particular complication called crankshaft phenomenon, which may occur after posterior spinal fusion of idiopathic scoliosis in patients who have significant anterior spinal growth remaining. Sanders et al reported that the risk of the crankshaft phenomenon was highest in patients younger than 10 years and in patients with a Risser sign of 0 with an open triradiate cartilage. [137]

Significant concern exists regarding the inferior (caudad) extent of a patient's spinal fusion and its potential relationship with future low back pain. [138] Connolly led a group of researchers at the Toronto Hospital for Sick Children who studied this question in 83 patients fused with Harrington instrumentation to the second, third, fourth, or fifth lumbar vertebra. At an average of 12 years (range, 10-16 years) after surgical treatment, these patients were found to have a statistically higher rate (76%) of low back pain than a control group (50%).

Connolly's patients were from an era in which the predominant instrumentation system was noncontoured Harrington rods, which were notoriously associated with low back pain when applied to the lumbar spine. [138] The results of this study almost certainly cannot be generalized to current scoliosis patients, who are treated with very different instrumentation systems.

At an average of 21 years after posterior spinal fusion with Harrington instrumentation (performed by Paul Harrington himself), about 21% of patients experienced significant interscapular pain. [139]

Some complications have been associated with particular surgical approaches to scoliosis. For instance, chylothorax and tension pneumothorax have both been reported in association with VATS procedures. [140, 141]

Pseudarthrosis is a complication that represents a basic failure of the central intention of scoliosis surgery: bone fusion. Luckily, pseudarthrosis is very rare in modern scoliosis surgery. This is in small part due to excellent stable internal fixation (scoliosis instrumentation systems) and in large part due to proper attention to fusion technique.

Pseudarthrosis may be suggested by persistent pain, progressive deformity, or broken hardware. Previously, tomographic plain x-rays (tomograms) were commonly used to image suspected pseudarthrosis. This is no longer the case; such tomography equipment is on the endangered species list of imaging devices. Computed tomography (CT) may be helpful, but clinical suspicion and fusion mass exploration (a rare case for modern-day exploratory surgery) remain the cornerstones of pseudarthrosis diagnosis and treatment.

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