Indications for Brace Treatment.

Brace treatment is restricted to immature children in an attempt to prevent curve progression during further skeletal growth. In general, bracing is indicated in growing adolescents (Risser grade 0, 1, or 2) who on initial evaluation have curves in the range of 30 to 45 degrees or who have documented progression exceeding 5 degrees in curves that initially measured 20 to 30 degrees. Those who are Risser grade 0 should be considered candidates for bracing when their curves reach 25 degrees. Patients should consider their existing deformities cosmetically acceptable and must be willing to wear the brace the prescribed amount of time. Low-profile braces (TLSOs) are the most commonly used orthoses today, but their use is restricted to patients whose curve apex is at T7 or below. Fortunately, this is the case with most curve patterns in adolescents with idiopathic scoliosis. In 2005 the Bracing Committee of the SRS made recommendations concerning inclusion criteria for future brace studies involving AIS. Optimal inclusion criteria are age 10 years and older when the orthosis is prescribed, Risser grade 0 to 2, primary curve magnitude of 25 to 40 degrees, no previous treatment, and if female, either premenarchal or less than 1 year postmenarchal.

Contraindications to Brace Treatment.

Brace treatment has several contraindications. First, most studies concur that large curves (>45 degrees) in a growing adolescent cannot be effectively controlled by a brace and that these patients need surgical treatment. Even if progression could be controlled with a brace, the cosmetic appearance associated with these large curves is often unacceptable because of excessive trunk shift and rib prominence. An exception to this general rule involves very immature adolescents with large curves (approximately 50 degrees) who have not yet reached their PHV. These patients may benefit from bracing to delay curve progression until greater maturity is reached; this may avoid the need for additional anterior spinal fusion to prevent the crankshaft phenomenon.

In addition, bracing is not indicated for patients who find wearing an orthosis to be emotionally intolerable, although appropriate psychological counseling may result in eventual acceptance of a brace by an adolescent. Extreme thoracic hypokyphosis precludes the use of an orthosis. In these cases, normal positioning of the pads within the brace could exacerbate the rib deformity. If the hypokyphosis is 20 degrees or less, corrective pads should be lateralized to eliminate any anteriorly directed derotation forces. Finally, skeletally mature adolescents (Risser grade 4 or 5 and, if female, 2 years postmenarchal) should not be treated with braces.

Relative contraindications to bracing include a high thoracic or cervicothoracic curve, which ordinarily does not respond to orthotic treatment, and male sex. A relative lack of effectiveness of bracing in boys has been documented, in part because of extremely poor compliance.

Comparison of Orthoses.

Numerous reports in the literature attest to the effectiveness of brace treatment. * ^a In most of these studies, bracing was considered effective if the curve remained within 5 to 6 degrees of its original magnitude on completion of treatment. Some of these studies included low-risk patients (Risser grades 3 to 5, curves <20 degrees), patients still undergoing treatment, patients who had previously undergone treatment, and children younger than 10 years. In some studies, patients were eliminated from the study population because of noncompliance. All these factors make comparisons among studies difficult, particularly when one is trying to assess the effectiveness of bracing in patients most at risk (Risser grade 0 or 1, premenarchal girls, 25- to 45-degree curves). Some of the more recent literature has been more consistent in focusing on the population at greatest risk. ^†a These studies, along with a 1997 meta-analysis of the bracing literature, strongly reinforce the idea that bracing is effective in controlling curve progression. Perhaps the most compelling evidence for this at present comes from a study by Katz and colleagues. In this study, braced patients had compliance objectively verified through the use of a heat sensor in the orthosis. The total number of hours of brace wear correlated with curve progression. This effect was most significant in patients who were at Risser stage 0 or 1 at the beginning of treatment. Curves did not progress in 82% of patients who wore the brace more than 12 hr/day, as opposed to only 31% of those who wore the brace less than 7 hr/day.

References .

†a References .

‡a References .

Boston Brace.

The Boston brace was introduced in 1971 by Hall and associates. Its design consists of a prefabricated, symmetric thoracolumbar-pelvic module with built-in lumbar flexion and areas of relief opposite areas of pressure ( Fig. 12-22 ). Braces are individually constructed by an orthotist by using a blueprint created from the patient’s full-length radiograph. This brace is the most commonly used TLSO today and is effective in controlling curve progression, including larger curves measuring 35 to 45 degrees. ^§a It has been reported that the Boston brace exerts derotational force on the scoliosis; however, a long-term study found no lasting improvement in derotation of the spine. The brace is effective in treating either single- or double-curve patterns in which the apex of the most cephalic curve is located at T7 or below.

A, Scoliosis deformity before brace application. B, Posterior view of the Boston brace. C, Correction of scoliosis with the patient in the brace.

§a References .

Providence Brace.

The Providence brace, like the Charleston brace, is used only at night ( Fig. 12-23 ). Made with computer-assisted design and manufacturing technology, it is reported to be effective. We now use this brace in place of the Charleston brace for the treatment of thoracolumbar or lumbar curves.

A and B, Patient with thoracolumbar scoliosis treated with a Providence brace.

Brace Treatment Protocols.

The number of hours per day that the brace needs to be worn remains uncertain. Originally, 20 to 22 hr/day was advocated for the Milwaukee brace in immature adolescents with progressive curves; the same recommendation applied to the lower-profile TLSOs. Understandably, this caused adolescents some emotional distress, and poor compliance with brace wear was common. As a result, the idea of part-time brace use evolved, with the goal of approximately 16 hr/day of bracing. Although several studies have reported that part-time use of orthoses appears to be as effective as full-time wear in controlling curve progression, other reports emphasize that the outcome is better when more hours per day are spent in the brace. This was confirmed by Katz and colleagues in a 2010 study that objectively assessed brace compliance by using heat sensors in the orthosis.

In an effort to form a consensus from the literature on the effectiveness of bracing (including whether part-time bracing controls curve progression as effectively as full-time bracing does), the Prevalence and Natural History Committee of the SRS conducted a meta-analysis on more than 1900 patients from 20 studies. It concluded that bracing (with TLSOs or the Milwaukee brace) is effective in controlling curve progression in individuals with idiopathic scoliosis and that full-time bracing (23 hr/day) is more effective than part-time bracing (8 to 16 hr/day). The latter finding is supported by more recent studies.

When brace treatment is chosen for a patient, certain general guidelines should be followed. Once the brace has been constructed and fitted to the patient by the orthotist, the patient should work up to the prescribed number of hours of wear per day. After 2 to 4 weeks the adolescent should return to the orthopaedist’s office for an initial brace evaluation. At that time, any problems (e.g., intolerable pressure points) will have been identified by the patient and can be addressed by the orthotist. Equally important, an in-brace radiograph should be obtained to verify the amount of curve correction being achieved. With the Boston brace, a minimum of 40% to 50% curve correction should be obtained in the brace. With the Charleston and Providence braces, the amount of in-brace correction should approach 90% for flexible curves and 70% for rigid curves. Regardless of the type of brace used, insufficient in-brace curve correction leads to an unsatisfactory outcome that differs little from the expected natural history. If proper correction cannot be obtained with brace use, orthotic treatment should be discontinued.

During brace management, follow-up visits are scheduled at 4-month intervals for rapidly growing adolescents with large curves. The interval may be extended to 6 months for patients nearing maturity whose curves have shown no recent changes. During these visits a single standing PA thoracolumbar radiograph is obtained with the patient out of the brace. Curve progression, if it has occurred, is readily identifiable, and appropriate adjustments to the treatment program can be made. Some physicians obtain radiographs with the patient wearing the brace to show the brace’s effect on both the curve and spinal balance. However, curve progression may be missed if the patient undergoes imaging while wearing the brace.

With female patients, if the brace has been successful in controlling curve progression, plans can be made to discontinue treatment when the girl is approximately 18 to 24 months postmenarchal and Risser grade 4 and when no further increase in her height has occurred ( Fig. 12-24 ). Rather than tapering use of the brace, we discontinue it completely at that time. In male patients, curves exceeding 25 degrees have a tendency to progress even when Risser grade 4 maturity has been reached. Therefore, in boys, bracing may need to be continued until Risser grade 5 is achieved. Frequently, this does not occur until the later teenage years, which makes compliance with brace wear a challenge.

Radiographic findings with brace wear. A, Initially, this premenarchal girl aged 12 years 7 months had a 30-degree thoracic curve and was Risser grade 0. B, Treatment in a Boston brace was begun, with in-brace correction to 18 degrees. C, Brace wear was continued until the patient was 2 years postmenarchal and Risser grade 4. D, Thirty months later, the curve remained stable at 26 degrees.

Curve Patterns

King Classification System.

In 1983, King and colleagues introduced a radiographic classification system for AIS in which five different thoracic curve types were described ( Fig. 12-25 ). This system provided useful recommendations for surgical intervention with Harrington implants; however, with the evolution of multiple hook or screw implant systems in the late 1980s, which allowed increased three-dimensional curve correction, several shortcomings in the descriptions and recommendations of the King system became evident. The one King curve pattern that is not better described in other systems is type IV, a thoracic curve in which the L4 vertebra is tilted into the curve. This curve pattern requires instrumentation to a more distal segment into the lumbar curve, generally the vertebra last touched by the center sacral vertical line (CSVL).

Diagrammatic representation of the King classification of idiopathic scoliosis, which consists of five distinct curve patterns. This classification continues to be used regularly, although its reliability and reproducibility have been questioned.

(Redrawn from King HA, Moe JH, Bradford DS, et al: The selection of fusion levels in thoracic idiopathic scoliosis, J Bone Joint Surg Am 1983;65:1302, with permission from The Journal of Bone and Joint Surgery, Inc.)

Lenke Classification System.

Lenke and co-workers developed a new classification system for AIS in 1997 that recognized the important contributions already made by King and colleagues. Specific goals for the new classification system were to allow more acceptable comparisons among the various types of operative treatment available, to support a treatment-based approach by determining which of a patient’s scoliotic curves should be included in the instrumentation and fusion, to encourage three-dimensional analysis of scoliosis, and to achieve greater intraobserver and interobserver reliability. The Lenke classification system is dependent on curve measurements in both the frontal and sagittal planes. It is comprehensive (42 different curve patterns can be derived) yet is fairly easy for surgeons to learn quickly. The three main variables requiring evaluation are curve type ( Table 12-3 ), lumbar spine modifiers, and thoracic sagittal modifiers ( Fig. 12-26 ).

Table 12-3

Lenke Curve Types

Curve Type	Description	Characteristic Curve Patterns			Structural Region
		Proximal Thoracic	Main Thoracic	Thoracolumbar or Lumbar
1	Main thoracic	Nonstructural	Structural (major) Cobb angle: ≥25° on side-bending radiographs Kyphosis: +20° between T10 and L2	Nonstructural	Main thoracic
2	Double thoracic	Structural Cobb angle: ≥25° on side-bending radiographs Kyphosis: +20° between T2 and T5	Structural (major) Cobb angle: ≥25° on side-bending radiographs Kyphosis: +20° between T10 and L2	Nonstructural	Proximal thoracic, main thoracic
3	Double major	Nonstructural	Structural (major) Cobb angle: ≥25° on side-bending radiographs Kyphosis: +20° between T10 and L2	Structural Cobb angle: ≥25° on side-bending radiographs Kyphosis: +20° between T10 and L2	Main thoracic, thoracolumbar, or lumbar
4	Triple major	Structural Cobb angle: ≥25° on side-bending radiographs Kyphosis: +20° between T2 and T5	Structural (major) * Cobb angle: ≥25° on side-bending radiographs Kyphosis: +20° between T10 and L2	Structural (major) * Cobb angle: ≥25° on side-bending radiographs Kyphosis: +20° between T10 and L2	Proximal thoracic, main thoracic, thoracolumbar, or lumbar
5	Thoracolumbar or lumbar	Nonstructural	Nonstructural	Structural (major) Cobb angle: ≥25° on side-bending radiographs Kyphosis: +20° between T10 and L2	Thoracolumbar or lumbar
6	Thoracolumbar or lumbar, main thoracic	Nonstructural	Structural Cobb angle: ≥25° on side-bending radiographs Kyphosis: +20° between T10 and L2	Structural (major) Cobb angle: ≥25° on side-bending radiographs Kyphosis: +20° between T10 and L2	Thoracolumbar or lumbar, main thoracic

 

Modified from Lenke LG, Betz RR, Harms J, et al: Adolescent idiopathic scoliosis: a new classification to determine extent of spinal arthrodesis, J Bone Joint Surg Am 83:1169, 2001, with permission from The Journal of Bone and Joint Surgery, Inc.

* Either the main thoracic curve or the thoracolumbar or lumbar curve can be the major curve.

Schematic drawings of the curve types, lumbar modifiers, and sagittal structural criteria that determine specific curve patterns. MT, main thoracic; PT, proximal thoracic; TL, thoracolumbar; TL/L, thoracolumbar/lumbar.

(Redrawn from Lenke LG, Betz RR, Harms J, et al: Adolescent idiopathic scoliosis: a new classification to determine extent of spinal arthrodesis, J Bone Joint Surg Am 83:1169, 2001, with permission from The Journal of Bone and Joint Surgery, Inc.)

Using standard-size projection-type slides of photographs of premeasured radiographs, the developers of the Lenke classification system found both interobserver and intraobserver reliability to be excellent. However, in clinical practice, physicians vary significantly both in their selection of end vertebrae and in their angular measurements of curves in individuals with idiopathic scoliosis. Because scoliosis surgeons rarely have access to premeasured radiographs when they evaluate patients and formulate surgical plans, the reliability of the Lenke classification system is less impressive when tested with unmarked radiographs. When all three of the main variables are combined, its overall reliability is fair. When each variable is reviewed separately, its reliability improves. Despite this limitation, the Lenke classification system offers a more comprehensive preoperative radiographic evaluation of patients with AIS than was available with previous systems and appears to correlate with surgical treatment of structural regions of the spine.

The first parameter to identify in the Lenke classification system is curve type (see Fig. 12-26 ), which is determined by first identifying the largest curve. The other curves are then deemed structural by magnitudes that are greater than 25 degrees on the supine best-bend radiograph or if junctional kyphosis (measured between T2 and T5 for the proximal and main thoracic curves and between T10 and L2 for the main thoracic and thoracolumbar/lumbar curves) is greater than 20 degrees. Once the type of curve is identified, the second main variable, the lumbar spine modifier, is assessed ( Fig. 12-27 ). The CSVL (vertical line drawn upward from the center of the sacrum) is drawn, and its position relative to the concave pedicle of the apical lumbar vertebra determines the lumbar modifier. The final main variable, the thoracic sagittal modifier (T5-12), is then assessed to gain a better understanding of the three-dimensional deformity. The sagittal modifier is hypokyphotic (<10 degrees), normal (10 to 40 degrees), or hyperkyphotic (>40 degrees). In addition to radiographic characterization, the clinical appearance is critical to determine curves requiring surgical treatment. A comparison of right and left shoulder height is important to determine when inclusion of the proximal thoracic curve is necessary, waistline asymmetry helps determine when inclusion of the lumbar curve is necessary, and the axial plane rotational deformities are critical when deciding which curves are structural.

Rules and definitions for determining the lumbar spine modifiers A, B, and C. A, Steps required to determine the stable vertebra. B, Description of lumbar modifiers A, B, and C. CSVL, Center sacral vertical line; SRS, Scoliosis Research Society.

(Redrawn from Lenke LG, Betz RR, Harms J, et al: Adolescent idiopathic scoliosis: a new classification to determine extent of spinal arthrodesis, J Bone Joint Surg Am 83:1169, 2001, with permission from The Journal of Bone and Joint Surgery, Inc.)

Construct Selection.

Three major trends with respect to surgical treatment of scoliosis have occurred: first, the posterior approach has had greater use than the anterior approach for nearly all curves, including Lenke 5 and 6 thoracolumbar and lumbar curves; second, pedicle screws have been used in all regions, including the thoracic spine, in place of hooks and hybrids ; and third, because of greater use of posterior releases and more powerful posterior implants, use of an anterior release has declined.

Proponents of screws suggest they provide stronger fixation than hooks do, are safe when inserted by experienced surgeons, avoid placing metal within the canal, provide a stronger corrective force for three-dimensional curve correction, may obviate the need for anterior fusion to avoid the crankshaft phenomenon because of the strength of the construct, and may avoid the need to perform thoracoplasty. Those who question the routine use of pedicle screw placement for thoracic scoliosis cite the significant increase in cost with no documentation of measurable improvement in outcome studies, early reports of loss of thoracic kyphosis with screws, and the potential risk for injury to the spinal cord by surgeons inexperienced in the technique.

Fusion selection recommendations are based on correct identification of curve patterns and the clinical deformity in each patient. Some generalities on selection of the level can be taken into consideration when developing plans for fusion. The upper instrumented vertebra (UIV) is usually the proximal end vertebra for thoracic and thoracolumbar/lumbar curves and, most often, T2 when fusing a structural proximal thoracic curve. The lowest instrumented vertebra (LIV) for lumbar/thoracolumbar curves is usually the distal end vertebra when performing posterior instrumentation. When fusing vertebrae for idiopathic scoliosis via the anterior approach, they should generally be the UIV and LIV. In addition to these guidelines, each curve pattern has some specific rules to follow.

Lenke type 1A and 1B curves have single thoracic structural curves with nonstructural lumbar curves that do not cross the midline (CSVL). Clinically, trunk imbalance is more pronounced to the right in these patients than in those with double-curve patterns and responds nicely to surgical treatment. For posterior constructs the UIV is generally the proximal end vertebra or one proximal to it when it is significantly off midline. The rules for selection of the LIV are more varied, with three general rules: first, fusion to one or two levels proximal to the stable vertebra ; second, fusion to the vertebra that last touches the CSVL; and third, as reported by Suk and colleagues, rules based on the relative position of the neutral vertebra (the most proximal vertebra that has neutral axial plane rotation based on the position of the pedicles) and the position of the distal end vertebra. Preoperative planning for posterior instrumentation using only screws is shown in Figure 12-28 . Frequently, the implant is a hybrid, with screws used as an anchor at the bottom of the constructs and some combination of hooks, sublaminar wires, or tape and screws used above. For the King-Moe type IV curve (a Lenke 1A curve when L4 is tilted into the curve), the end vertebra may be chosen as the LIV, especially when the stable vertebra is L4, and posterior instrumentation can be stopped at L2 (two levels cephalic to the stable vertebra). Anterior instrumentation has shown that even more inferior motion segments can be preserved because the implant extends down to only the lowest vertebra included in the measured curve.

Construct planning for the use of all pedicle screws varies among surgeons, and no specific pattern has been fully adopted or studied. However, the most common scenario is to use pedicle screws at each level in a segmental fashion for the rod that is used for the main portion of the correction.

For the double major curve shown, the most common screw pattern is segmental screw fixation for the left rod, which is used to correct the coronal plane while maintaining the sagittal plane or correcting any junctional kyphosis between the main thoracic and lumbar curves. Typically, variable-angle or polyaxial screws can be used in the lumbar spine and fixed-angle screws in the thoracic spine. If a segmental screw pattern is not used, an alternative screw pattern on the left side should always include segmental fixation of the lumbar curve and a more typical hook–screw construct for the thoracic curve. However, to achieve maximal correction, segmental fixation with pedicle screws is generally used for the left rod.

The screw pattern on the right rod generally includes at least two screws in the distal segment of the lumbar spine to allow fine-tuning of the lowest instrumented vertebra to ensure that it is horizontal and neutral. L2 and L3 screws are used for complete fixation of the lumbar curve, and T11 and T12 screws are used for fine-tuning of the lumbar curve. Screws are used at the apex of the convexity of the thoracic curve to provide an opportunity to perform a convex apical derotation maneuver to correct the axial plane deformity in the thoracic spine. Two screws are then used at T4 and T5 to provide good fixation proximally.

Once the screws are placed on the left side, a rod rotation maneuver is performed to correct the coronal plane and sagittal plane deformity. The apical convex screws can then be used to derotate the apical thoracic spine after loosening the rod on the concave apical segments. Downward and lateral pressure on the convex screws with upward and medial pressure on the concave screws allows apical derotation. Following this, the right rod can be placed, and fine-tuning of the coronal and sagittal planes is performed.

Patients with Lenke type 1C curves have single thoracic structural curves with nonstructural lumbar curves, and the apical lumbar vertebra completely crosses the midline (i.e., is not in contact with the CSVL). In the late 1980s and 1990, use of “derotation” instrumentation for selective thoracic fusions often led to spinal imbalance manifested as a shift in the patient’s trunk or head (or both) to the left of midline—so-called decompensation. ^‖a

‖a References .

A, Preoperative anteroposterior radiographs of a Lenke 3C curve with an 80-degree right thoracic curve and a 63-degree left lumbar curve in a 13-year-old girl. B, Two years after surgery, the overall coronal plane correction is satisfactory. Greater implant density was used on the right side than in Figure 12-28 because of the large stiff nature of the curve.

When using this method of instrumentation for selective fusions in individuals with Lenke type 1C curves, the surgeon should keep in mind some principles that can minimize the chance of postoperative imbalance. First, the instrumentation should not extend beyond the stable vertebra; second, if using the rod rotation maneuver, incomplete rotation should occur to avoid overcorrection or excessive straightening of the thoracic curve; and third, other correction strategies such as apical translation with fixed proximal and distal anchors or a cantilever can be performed. Preoperative planning involving pedicle screw anchors for selective thoracic instrumentation and fusion of a Lenke type 1C curve is shown in Figure 12-30 .

Planning fusion for a Lenke 1 curve using an all-screw construct and preoperative, postoperative, and follow-up standing anteroposterior radiographs following posterior spinal fusion of a Lenke 1C pattern. A, Fusion selection in this case was to L1. For the left side, two distal screws provide a nice foundation to build the construct. To translate the apex medially and posteriorly, two (shown here) or three (for stiffer curves) apical screws are used. For stiff curves, one, two, or three screws may be reduction-type screws to allow gradual reduction of the apex to the left and posteriorly. Alternatively, some systems allow attachment to a regular polyaxial screw, which permits this translation to occur. Proximally, two screws provide excellent control of the proximal segments of the spine. For the right rod, a similar two-screw construct proximally and distally controls these segments of the spine; the three screws shown here provide excellent axial plane correction. Alternatively, two screws can be used at the apex on the convex side. B, Preoperative images of a Lenke 1C pattern in a 14-year-old demonstrating a main thoracic curve of 57 degrees and a lumbar curve measuring 46 degrees. C, Six weeks following selective thoracic fusion from T4 to T12, the patient has undergone shift of the trunk to the left, which is expected. D, At 6 months the lumbar curve has appropriately increased so that the patient has become nicely balanced.

Failure to properly distinguish Lenke type 1C or King type II curves from true double major curves (Lenke type 3C) may be responsible for some cases of postoperative imbalance following selective thoracic fusions. Useful guidelines have been developed to help differentiate these curve patterns. Relative ratios between the thoracic and lumbar curves with regard to their size, rotation, and deviation from midline can be assessed preoperatively on a standing radiograph. If thoracic curve parameter–lumbar curve parameter ratios are less than 1.0, both curves will require fusion. If the ratios are greater than 1.2 for curve size and deviation and greater than 1.0 for rotation, selective thoracic fusion can be performed safely. With true double major curves, both curves must be included in the posterior fusion to achieve a balanced spine with segmental fixation systems.

Selective anterior fusion on the convexity of the thoracic component in Lenke type 1C curves (using screws and either a threaded or a smooth rod) has been advocated. Reported advantages over posterior instrumentation include improved balance, correction of a hypokyphotic thoracic spine, and preservation of more inferior motion segments.

Preliminary studies have reported breakage of the threaded rod in 31% of patients, but this complication can be remedied by the use of a larger rod and thorough dis­kectomies and bone grafting. Thoracoscopically placed anterior instrumentation has become used less often but overall demonstrates comparable results to posterior fusion with inclusion of fewer fusion levels.

Patients with Lenke type 2 curves have double thoracic structural curves with nonstructural lumbar curves. The first thoracic vertebra is tilted into the upper curve, with junctional kyphosis between the proximal and main thoracic curves. The patient’s shoulder on the side of the convexity of the upper curve is nearly always elevated. The upper curve and the shoulder elevation may worsen if only the lower main thoracic component is instrumented. Therefore, most Lenke type 2 curves require posterior instrumentation of both thoracic curves. Selective main thoracic fusion using anterior instrumentation has been successful when the proximal thoracic curve is sufficiently flexible. The posterior instrumentation should extend up to the second thoracic vertebra if T1 is tilted into the upper curve and the shoulder is elevated on the convex side of the upper curve, if the upper curve is greater than 30 degrees with limited flexibility, or if the transitional vertebra between the curves is located at T6 or below. Lenke type 3 curves represent double major structural curve patterns in which both the thoracic and lumbar components require instrumentation. Preoperative planning for instrumentation of double major curves is shown in Figure 12-31 , with LIV selection principally to the distal end vertebra. Curve characteristics that allow stopping short of the end vertebra include thoracolumbar or lumbar curves smaller than 55 degrees, flexible curves, and apex of the thoracolumbar or lumbar curves that is two or more levels proximal to the intended LIV. Lenke type 4 curves are triple major curve patterns in which both thoracic curves, in addition to the lumbar curve, are structural. All three curves require posterior instrumentation.

Planning fusion for a Lenke type 3C (double major) curve using a hook–screw construct.

• 1.
  

  The hook sites used for the thoracic component of the deformity are almost identical to those used for selective thoracic fusion.

  
  
• 2.
  

  For the lumbar component, the instrumentation usually extends to L3. Fusion to L4 should be considered only if the L3 vertebral body deviates significantly from the midline and if the L3-4 disk space remains wedged open on the side of the convexity. Fusion to L5 for idiopathic scoliosis is almost never indicated.

  
  
• 3.
  

  The convexity of the lumbar curve is approached first. Pedicle screws are placed at every level (in this example, from T12 through L3) ( A ). This provides firm fixation and allows correction (and compression) across the entire convexity of the lumbar curve.

  
  
• 4.
  

  On the concavity of the lumbar curve, a pedicle screw is placed at T12 and L3 ( B ). Another pedicle screw may be added at L2 if desired.

In Lenke type 5 curves, only the thoracolumbar or lumbar curve is structural. The anterior approach has traditionally been used for these curves with excellent three-dimensional correction. However, the use of posterior instrumentation with aggressive release techniques provides a viable alternative to the anterior approach. Proponents of the posterior approach suggest that the same number of levels are fused (proximal end vertebra to distal end vertebra), coronal plane correction is the same, surgical time is shorter, no chest tube is necessary, and intensive care unit and hospital stay is shorter. Advocates of the anterior approach suggest that not all curve patterns will allow similar fusion levels and the axial plane correction is less because the disk and soft tissues are still intact with the posterior approach. Anterior spine surgery for these curves has always had challenges in achieving fusion; however, constructs using one or two solid rods were developed and resulted in a decreased incidence of pseudarthrosis, better maintenance of restored sagittal lordosis, and elimination of postoperative brace immobilization. Preoperative planning for anterior or posterior instrumentation of a thoracolumbar curve is shown in Figure 12-32 .

Planning posterior instrumentation of a Lenke type 5C thoracolumbar curve and a case example. A, Generally, screws in each pedicle from end vertebra to end vertebra are used. B, Preoperative radiographs of a Lenke 5C curve with a 24-degree right thoracic curve and a 48-degree lumbar curve in a 14-year-old girl. C, Two years following posterior spinal fusion and instrumentation from T11 to L3.

Lenke type 6 curves represent double curve patterns, with the primary thoracolumbar or lumbar curve accompanied by a smaller but structural main thoracic curve. Selective fusion of the thoracolumbar or lumbar curve will not yield similar results as selective thoracic fusion because the thoracic curve will not respond to maintain balance. Posterior fusion and instrumentation are necessary in this circumstance.

Preoperative Curve Flexibility.

Preoperative curve flexibility can be assessed by a number of different techniques, including supine best-effort, side-bending radiographs; the fulcrum bend test; or a supine resting radiograph. We use supine best-bend radiographs because they realistically reflect the amount of curve correction that can be achieved posteriorly and determine flexibility of the spine with the newer generation of instrumentation systems. These radiographs are used to determine the flexibility of the remaining curves to provide a Lenke classification. They can also be used to help determine or confirm the LIV for isolated thoracolumbar or lumbar curves. For left thoracolumbar or lumbar curves, a right-bend film should demonstrate that the proposed LIV is centered over the sacrum and, on the left-bend film, should demonstrate “reversal” of the disk above the intended LIV. Large curves (>75 degrees) are best analyzed with traction films because the mechanics of the bend films is minimized for these large and stiff curves. The push-prone radiograph was shown to be the best preoperative indicator of flexibility for predicting the final lumbar curve measurement in patients undergoing selective thoracic fusion for Lenke type 1B and 1C curves. Significant study using the fulcrum bend test has demonstrated that for the thoracic curve, this test best predicts the status of the thoracic curve following posterior spinal fusion and instrumentation.

Neurologic Status.

If a subtle neurologic abnormality (e.g., asymmetric abdominal reflexes) is detected in an otherwise normal individual, MRI of the entire spinal canal should be considered to rule out syrinx, cord tethering, or diastematomyelia. Preoperative MRI should also be performed in patients with left thoracic curves and in those in whom the typical apical lordotic sagittal deformity is absent because of the association with intracanal abnormalities. The MRI study can be ordered when surgery is scheduled. Studies have demonstrated that excessive rotation or kyphosis in the thoracic spine is an indication to perform MRI.

Rib Deformities.

The rotational deformity inherent in AIS is often seen most by families and is generally mild to moderate with rare occurrence of the razorback deformity (it is more common in nonidiopathic conditions such as neurofibromatosis). Suggested indications for thoracoplasty include a preoperative rib prominence exceeding 10 degrees (measured from a tangential radiograph with the patient bent forward 90 degrees), preoperative curves greater than 60 degrees, and flexibility less than 20%. Surgeon preference and experience play a large role in determining the indications for thoracoplasty; however, the general trend has been less use of this procedure because of improved methods for direct vertebral rotation (DVR). Nonetheless, Professor Suk, the developer of the DVR technique, continues to perform thoracoplasty in all patients with AIS. In addition to improving the patient’s cosmetic appearance, partial resection of three to five apical ribs provides bone graft in amounts sufficient to obviate an iliac crest graft. A percutaneous thoracoplasty technique has resulted in excellent correction but some loss of coronal plane correction. Because some studies report a decline in pulmonary function following thoracoplasty, this technique is contraindicated in patients with compromised preoperative pulmonary or cardiac status. More recent studies have demonstrated an early decline in pulmonary function test results without long-lasting effects when compared with a cohort that did not undergo thoracoplasty.

Future Growth Potential.

Correction of scoliosis by posterior spinal instrumentation and fusion is usually maintained over time and is not adversely affected by any remaining anterior spinal growth; however, the crankshaft phenomenon (resumption of the curve secondary to anterior growth in patients with posterior fusion) can still occur. Dubousset coined the term when he observed that the entire spine and trunk gradually rotated and deformed as the anterior portion of the spine continued to grow and twist around the axis of the fusion mass (in a manner similar to an automobile crankshaft) ( Fig. 12-33 ). Methods to prevent this phenomenon include careful assessment of the growth remaining, the use of anterior fusion when appropriate, and greater use of and correction with pedicle screw fixation. Although its severity is difficult to quantify, the crankshaft phenomenon can best be appreciated by examining serial clinical photographs that demonstrate progressive changes in rib deformities, narrowing of the chest, and imbalance in the thoracic and lumbar spine. Radiographs can also demonstrate progressive changes over time, such as alterations in curve size, rotation, and rib–vertebral angle difference; translation of the apical vertebra toward the chest wall on the convexity; and changes in the vertical inclination of the instrumentation. Radiographic changes of more than 10 degrees in curve size, apical vertebral rotation, and the rib–vertebral angle difference are all thought to reflect progression of the deformity secondary to the crankshaft phenomenon. However, during the first 6 to 12 months after surgery, it is important to not automatically assume that changes in radiographic measurements are a result of the crankshaft phenomenon; these changes are often due to stress relaxation of the spine, gradual maturation of the fusion mass, and realignment of the curve.

Crankshaft phenomenon in an 11-year-old girl 1 year after undergoing posterior spinal fusion with instrumentation consisting of all pedicle screws. She grew 7 cm since surgery and has had a trunk shift to the right with a significantly worse clinical rotational deformity as shown here.

For female adolescents in need of surgery who have not yet reached their PHV, who are premenarchal, and whose triradiate cartilage remains open, strong consideration should be given to combining anterior and posterior fusion to prevent the crankshaft phenomenon. For anterior spinal fusion, a conventional open thoracotomy approach has been compared with the newer, less invasive video-assisted thoracoscopic surgery (VATS). Advantages of VATS include muscle sparing, improved cosmetic results (less scarring), greater access to the entire length of the thoracic spine, and less effect on pulmonary function than with open thoracotomy. Instruments are used through multiple intercostal portals to resect disk material, perform anterior release, and insert bone graft. However, surgeons require extensive training in the VATS technique.

Some reports suggest that stiff posterior constructs, particularly when screws are used at nearly every level in the segment fused, may be strong enough to prevent the crankshaft phenomenon in immature patients, thus avoiding the need for anterior fusion. More research is needed to prove the effectiveness of this approach.

Transfusion Requirements.

Several procedures are available to reduce the need for homologous blood transfusions in patients undergoing posterior spinal instrumentation for scoliosis, including controlled hypotensive anesthesia, autologous blood predonation of 1 or 2 units, acute normovolemic hemodilution, intraoperative and postoperative salvage of lost blood, intraoperative use of antifibrinolytics, and transfusion decisions based on clinical judgment rather than on a predetermined hemoglobin value.

Various combinations of these methods have been shown to significantly reduce exposure of patients to homologous blood products during scoliosis surgery. ^¶a The combination of predonated autologous blood, hypotensive anesthesia, and intraoperative salvage of lost blood is probably the one used most frequently for healthy individuals with idiopathic scoliosis. Intraoperative salvage of lost blood, the most expensive of the available techniques, is most effective when blood loss is expected to exceed 1000 mL. Acute normovolemic hemodilution appears to be a satisfactory alternative to the use of predonated autologous blood.

¶a References .

Bone Grafting.

The primary goal of scoliosis surgery is to achieve a solid arthrodesis, which is enhanced by meticulous cleaning of soft tissue from the spine, facetectomies, decortication, and adequate bone grafting. Although autogenous iliac crest bone grafting has previously been the standard, significant postoperative pain at the donor site persists and remains the greatest problem with the use of autogenous grafting. Because of these postoperative symptoms, alternative bone graft substitutes have been sought. Numerous studies of successful fusions using allografts of frozen, bank-stored bone as a substitute for autogenous bone have been reported without an increase in pseudarthrosis rates.

To minimize the risk of transmitting human immunodeficiency virus, hepatitis virus, and any other potential viral pathogens, the donor blood and tissue are tested at the site of recovery, and testing is usually continued throughout the harvesting process. Freeze-dried cancellous bone is usually exposed to low-dose gamma radiation to sterilize all nonsystemic bacterial and fungal contaminants. Bone morphogenetic protein has become popular for use in single-level lumbar spinal fusions but has yet to become cost-effective for routine use in multisegment scoliosis fusions. The authors’ preferred technique is to perform thorough stripping of the spine, followed by aggressive facetectomies, decortications of the spine, and the use of allograft bone, without any pseudarthrosis in individuals with AIS being documented in the past 8 years.

Spinal Cord Monitoring.

Spinal cord monitoring using both spinal somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs) is the standard of care during scoliosis surgery and is critical to the safety of any spine deformity surgery. SSEPs record the sensory function of the spinal cord and provide continuous monitoring throughout the procedure. ^#a This test may, however, be adversely affected by changes in anesthetic level and perfusion, and critical changes tend to lag behind MEPs. With impending neurologic deficit, MEPs are used to monitor the anterior spinal cord motor tracts and are ideally performed by applying a stimulus to the motor cortex of the brain (transcranial MEPs [tcMEPs]). This provides direct stimulation of the motor cortex, which then travels through the anterior column tracts with responses noted in the upper and lower extremity musculature ( Fig. 12-34 ). When MEPs are used in conjunction with SSEPs, the chance of unrecognized injury to the spinal cord is minimized. A large multicenter study of 1121 patients demonstrated that 38 (3.4%) had a critical change on monitoring when tcMEPs and SSEPs were used. Hypotension was responsible for nine changes (corrected by elevating blood pressure), whereas three were due to segmental vessel ligation. The tcMEP/SSEP combination did not miss any patient with a transient motor or sensory deficit. Similar studies have demonstrated excellent results with combined multimodal intraoperative neuromonitoring during AIS surgery. Although total intravenous anesthesia with propofol is necessary to obtain good tcMEP data, other techniques to assist in obtaining good monitoring data have been evaluated. The current increase in the use of thoracic pedicle screws for fixation points has led some surgeons to use triggered electromyographic (EMG) monitoring; however, this has been relatively unreliable in the thoracic region without clearly identified thresholds to indicate when medial screw penetration is seen.

Output of a typical response when using transcranial motor evoked potentials (tcMEPs). The left extremities ( left ) and right extremities ( right ) are shown. The red response is the baseline data, whereas the green notes the latest output from the most recent “run” of tcMEPs. The muscle group in the upper extremity is the abductor pollicis brevis, and the lower extremities are evaluated with three muscle groups—the tibialis anterior ( LTA and RTA ), the soleus ( LSOL and RSOL ), and the abductor hallucis ( LAH and RAH ). Note that the most recent amplitudes ( green ) are the same as the baseline ( red ) in all muscle groups demonstrating good responses.

#a References .

Postoperative Pain Management.

Patient-controlled analgesia (PCA) and epidural analgesia are the two methods used regularly for the management of postoperative pain. PCA provides safe and effective analgesia in children as young as 5 years. It allows the patient to self-administer small, preprogrammed doses of opioids via a pump connected to the patient’s intravenous tubing. This enables the patient to titrate an opioid blood level in direct response to the changing intensity of pain. The built-in safety mechanism of PCA systems prevents oversedation. In addition, PCA devices can deliver a continuous infusion so that therapeutic levels of analgesia are maintained during sleep.

The use of epidural analgesia for scoliosis surgery has become increasingly popular because it provides excellent pain relief; however, meticulous attention to detail is required. * ^b At the end of the surgical procedure but before closure, the surgeon inserts an epidural catheter. The catheter is tunneled lateral to the incision and is usually left in place for 48 to 72 hours. Low-dose opioids are infused to provide effective analgesia, usually under the direction of pain management teams experienced in this technique. Close monitoring of the patient’s respiratory status and the use of pulse oximetry are necessary for 24 hours after the infusion has been discontinued. Postoperative pulmonary toileting is optimized with this technique.

References .

Antibiotic Prophylaxis for Dental Procedures.

Antibiotic prophylaxis for dental procedures in patients with spinal instrumentation is a controversial issue. Currently, no scientific evidence supports the position that antibiotics should be given during routine dental care. Streptococcus viridans , the predominant bacterium in normal human oral flora and the most common organism isolated from blood after dental procedures, has not been reported in delayed deep wound infections following spinal instrumentation. In those in whom early postoperative wound infections develop, Staphylococcus aureus is the predominant organism. Yet S. aureus accounts for only 0.005% of the normal oral flora and is rarely isolated after dental procedures.

Guidelines similar to those provided in the advisory statement issued by the AAOS regarding antibiotic prophylaxis for dental patients with total joint replacement should be used for those who have undergone spinal instrumentation. If antibiotic prophylaxis is given, the following regimen is recommended: patients who are not allergic to penicillin can be treated with cephalexin, cephradine, or amoxicillin, 2 g orally 1 hour before the dental procedure; patients who are allergic to penicillin should receive clindamycin, 600 mg orally 1 hour before the dental procedure.

Harrington Instrumentation.

Harrington developed his technique in the late 1950s and first reported it in 1962. In this system, hooks apply distraction forces to the concave side of the spinal curve via a ratchet mechanism. Compression force is applied to the convex side of the thoracic curve at the base of the transverse processes, with the amount of force adjusted by tightening nuts on a threaded rod.

Long-term follow-up studies have reported that approximately 30% to 40% of curve correction is maintained through the years with Harrington instrumentation. ^†b However, minimal, three-dimensional correction of the spine was achieved because distraction forces flattened the spine and the implants provided insufficient stability to allow brace-free postoperative mobilization. The technique is detailed in the second edition of Tachdjian’s Pediatric Orthopaedics .

†b References .

Multiple-Hook Segmental Instrumentation.

The CD instrumentation system was developed in France by Cotrel and Dubousset and was introduced in the United States in the mid-1980s ( Fig. 12-35 ). The system revolutionized posterior instrumentation for idiopathic scoliosis by enhancing the surgeon’s ability to improve the three-dimensional orientation of the spine. This was accomplished through the “derotation maneuver” popularized by Dubousset, whereby the contoured rod is secured to the spine with various hooks and rotated 90 degrees to bring the concave spine posterior and medial for correction. This maneuver, which continues to be used today, improves the sagittal contour, achieves significant curve correction, and improves the rotation or translation of the spine. The second rod increases the construct’s strength and torsional stability, particularly when rigidly united to the first rod via a rod-connecting device.

Cotrel-Dubousset (CD) instrumentation. The first contoured rod is secured to the concave side of the spine with multiple hooks and is rotated 90 degrees. This maneuver improves the sagittal contour and achieves significant correction of the curve. Placement of the second rod increases the construct’s strength. CD instrumentation uses numerous hooks but no sublaminar wires.

Numerous reports have documenteded significant improvement in the correction of idiopathic scoliosis with CD instrumentation. Rib deformities were reduced, curve correction in the range of 48% to 69% was achieved and maintained, and nearly normal sagittal alignment was restored. ^‡b The ability to preserve lumbar lordosis in curves requiring long fusion to L3 or L4 avoided the long-term “flat back” problems that occurred with Harrington distraction instrumentation.

‡b References .

Pedicle Screws.

The use of pedicle screws has dramatically changed the operative treatment of all spinal deformity, including AIS. The use of pedicle screw fixation for correction of deformity was first described in the lumbar spine in the mid-1990s. These studies demonstrated that pedicle screws provide greater ability to obtain and maintain coronal plane correction of the thoracolumbar or lumbar curves in individuals with double major idiopathic scoliosis. When compared with hooks, initial correction was 72% versus 60% with hooks, and less loss of correction occurred at follow-up (5% versus 13%). Significant improvement in LIV tilt (82% versus 50%) and translation (50% versus 23%) was seen when compared with hooks.

Pedicle screws placed in the lumbar spine for pediatric spinal deformity have a very good track record, with few complications. The improved correction of deformity and maintenance of the correction achieved with lumbar pedicle screws led to their use in the thoracic spine ( Fig. 12-36 ). Suk and coauthors first reported the routine use of pedicle screws in the thoracic spine for spinal deformity surgery in 1995 and achieved improved coronal plane correction in the screw group (72%) versus hooks (55%) and hybrids (66%). The initial reports of their safety demonstrated overall good results, with a pedicle screw breech rate of between 1.5% and 15% and few neurologic complications. The learning curve is steep, and greater surgeon experience leads to improved accuracy. Reports of improved correction of spinal deformity have led to fairly enthusiastic adoption of the technique by surgeons, with overall improved radiographic correction when compared with more traditional hook constructs. ^§b The improved coronal plane correction achieved with pedicle screw fixation can be attributed to several factors. First, surgeons generally place pedicle screws at more levels than when hooks or other anchors are used; second, the three-column fixation of the spine provides better “grip” of the vertebrae, so correction maneuvers yield greater improvement in the spinal deformity; third, the use of procedures to mobilize the spine has expanded and included greater use of Ponte-style or Smith-Petersen osteotomies, concave and convex rib osteotomies, and for very severe curves, use of the VCR procedure; and finally, with improved fixation, the surgeon can use a number of correction strategies, including the traditional rod rotation maneuver, segmental distraction or compression, and segmental in situ bending. Fixation of each vertebra in the instrumented segment may be an important factor when coronal plane correction with thoracic pedicle screws is analyzed. However, the appropriate screw “density” (the number of pedicles filled with pedicle screws relative to the total number that are available) is not well known, and early studies demonstrated conflicting results, with some showing a positive effect with improved coronal correction and others demonstrating no difference between high and low screw density. In North America, longer-term follow-up has demonstrated maintenance of correction with nearly 70% coronal plane correction.

Thoracic pedicle screw fixation. A, Preoperative posteroanterior ( left ) and lateral ( right ) radiographs of a 13-year-old girl with a double thoracic (Lenke type 2A) curve pattern. The main thoracic curve measures 62 degrees, and the upper thoracic curve measures 40 degrees. B, Supine-bending radiographs to the left ( left ) and to the right ( right ) demonstrate improvement of the main thoracic curve to 37 degrees and the upper thoracic curve to 36 degrees. C, Postoperative posteroanterior ( left ) and lateral ( right ) radiographs demonstrate excellent coronal correction and maintenance of the sagittal profile.

§b References .

Surgical treatment of spinal deformity has three main aspects. The first is to grab onto the spine with anchors strategically placed on the spine, typically with pedicle screws today. The second is to mobilize the spine when necessary through a variety of techniques, including intraoperative traction, multiple Ponte-style osteotomies, or even resection procedures. Finally, once the anchor points are placed and the spine is flexible (either inherently so or following mobilization techniques), a variety of surgical techniques can be used to improve the spinal deformity.

Thoracic pedicle screws can be placed in several ways, but generally two main methods are used: freehand, in which the screws are placed without the use of fluoroscopic guidance, and image guided, in which the screws are inserted under the guidance of some radiographic imaging modality.

Posterior Mobilization Techniques.

Removal of the inferior facet at all instrumented levels has been the standard technique to achieve fusion when performing surgery to correct spinal deformity. The opportunity for greater three-dimensional spine correction with the use of pedicle screws has been accentuated by a trend toward performing more aggressive spine mobilization procedures, thereby providing an opportunity to gain greater correction of deformity. Beyond standard facetectomies, the gradual resection of more posterior structures provides greater spine mobility in the following order: complete facetectomies/ligamentum release (Ponte or Smith-Petersen osteotomies), concave or convex rib resections (or both), vertebral body decancellation with wedge resection of the vertebra, pedicle subtraction osteotomy, and finally, complete VCR.

A Ponte-style osteotomy generally refers to complete removal of both the superior and inferior facets at all levels, typically in the setting of Scheuermann kyphosis. However, this nomenclature has been applied to the scoliotic spine deformity as well, especially when the anterior column is unfused. The Smith-Petersen osteotomy, in contrast, typically refers to performance of these complete facetectomies in the setting of a fully or partially arthrodesed anterior column. The ability to achieve correction with Ponte or Smith-Petersen osteotomies for AIS was characterized well for thoracolumbar and lumbar curves when it was first done on the convex spine, with overall 80% correction of these curves. Correction of thoracic curves with these osteotomies is most likely less than that seen in the lumbar spine because the ribs and chest wall limit correction and blood loss and operative time can be higher. However, bilateral complete facetectomies allow one to lengthen the posterior column to restore thoracic kyphosis while also “untethering” the concave spine to allow shortening and correction of the coronal plane deformity. Following complete removal of the inferior facet, the ligamentum flavum is removed with a large Leksell rongeur in the midline until epidural fat is seen, and completion of the flavectomy is then performed with a Kerrison rongeur ( Fig. 12-37 ). The superior facet on the convex side can be largely removed with a small Leksell rongeur because the dural sac is positioned closer to the concave spine. Care is taken to limit the depth of penetration of the rongeurs on the convex spine because the epidural veins are more prominent on this side. The concave superior facet is more safely removed with Kerrison rongeurs because the dural sac is in close proximity and care must be taken to remain directly on the bone when resection is performed. Subtle SSEP changes may be seen following these osteotomies.

Ponte osteotomy. A Kerrison rongeur is completing removal of the posterior elements of the spine. Epidural fat is seen.

The next level of posterior release would be rib resections on the concave side of the spine to allow lateral and posterior translation of the spine. Three to five ribs are resected by first performing subperiosteal dissection, typically beginning a couple of centimeters lateral to the transverse process and continuing for 3 to 5 cm. Because the ribs are close to the anterior aspect of the chest, small tears in the parietal pleura tend to occur and should be recognized at the time of surgery; placement of a chest tube may be required to prevent pneumothorax. The authors do not generally perform these resections because experience has shown limited appreciable correction and the risk for postoperative pulmonary issues and pneumothorax is high.

The VCR procedure is the most aggressive technique for achieving correction of the spine because it removes one or more vertebral segments at the apex of the deformity. It was initially described for severe spine deformity and trunk shift and used an anterior and posterior approach to the spine, with overall outstanding radiographic and clinical results. Bradford and Tribus reported on 24 patients with severe curves in which greater than 80% correction of the coronal and sagittal plane translation was achieved along with 50% correction of the curves. Despite complications in 14 of the patients, the overall satisfaction rate in patients was extremely high. Suk and co-workers described the posterior-only approach for the VCR procedure and reported 62% correction in the coronal plane and 45 degrees of correction in the sagittal plane in 70 patients with severe deformity from kyphoscoliosis, postinfectious kyphosis, and adult scoliosis. Similar to previous reports, the complication rate was relatively high, with 24 patients having complications, including 2 with postoperative spinal cord deficits who had neurologic deficits preoperatively. Lenke and coauthors reported their experience in performing posterior VCR for pediatric spinal deformity in 35 consecutive patients. The patients were divided into five diagnostic categories, including severe scoliosis, global kyphosis, angular kyphosis, kyphoscoliosis, and congenital scoliosis, with reported correction of 51%, 55%, 58%, 54%, and 60%, respectively. No spinal cord–related complications were reported; however, two patients lost intraoperative neuromonitoring data during correction with return of baseline monitoring, which resulted in prompt surgical intervention. The authors’ experience is similar in 32 consecutive VCR procedures: 4 were done via an anterior/posterior approach and the remainder via a posterior-only approach, with coronal plane correction from 122 degrees to 53 degrees and an average increase in T1 to T12 height of 6.1 cm associated with improvement in pulmonary function. The incidence of intraoperative changes in neuromonitoring parameters during surgery was 35%, with two patients waking with a decline in neurologic function, which returned to baseline.

The indications for posterior VCR are not fully defined for AIS; however, given its significant neurologic risk and long operative times with associated potential for significant blood loss and pulmonary complications, this procedure should be chosen as the technique of last resort. The authors generally use this procedure in individuals with very severe deformity—angular scoliosis or kyphosis—especially when previous fusion has been performed. This procedure should be performed only by the most skilled and experienced surgeons who have worked their way up the learning curve by performing less arduous spine mobilization procedures. A multicenter study of 147 pediatric VCR procedures performed by senior surgeons reported complications in 59% of patients, including 27% who had an intraoperative neurologic event without paraplegia. The posterior approach to the VCR procedure begins with rigid fixation of the spine with pedicle screws proximal and distal to the planned resection levels ( Fig. 12-38, A ). Typically, long-tabbed reduction screws are placed distal to the planned resection levels. The ribs associated with the resected levels are removed entirely, including the rib heads. A laminectomy is next performed to identify the neural elements. The authors prefer to ligate the nerve roots on the convex side first and to remove the pedicle or pedicles to the level of the floor of the spinal canal ( Fig. 12-38, B ). A provisional rod is then placed on the convex side and the concave osseous elements are removed, including the pedicle and the concave side of the vertebral body after the concave nerve roots have been ligated and transected. The concave pedicle and floor of the canal are very difficult to remove because the dural sac and spinal cord are tightly adherent to these structures and the cancellous channel to the concave pedicle is limited. Following complete resection of the concave bone, a second provisional rod is secured so that two provisional rods (one on the concave and one on the convex side) are in place ( Fig. 12-38, C ). The remainder of the convex bony anatomy can be removed with both rods in place because the convex bone is anterior to the convex rod. Following complete resection, exchange of the provisional rods for the final rods is accomplished. The authors typically remove the convex provisional rod and replace it with an undercontoured final rod that is seated in the proximal screws and secured firmly and then partially seated in the tips of the first two reduction screws distal to the resected area ( Fig. 12-38, D ). The final concave rod is placed similarly. The distal aspects of the two final rods are then pushed anteriorly to unhinge them from the set screws on the reduction screws while still providing some guidance to the spine segments. The spine can then be manually compressed without jeopardizing the screw–bone interface. Before this manipulation an anterior cage is placed in the resected area to maintain the length of the spine and to avoid kinking of the dura and potential neurologic deficits ( Fig. 12-38, D ). Sequential reduction of the distal aspect of the rod to the remaining screws is performed, compression is subsequently applied to achieve the final correction, and the rib grafts initially harvested at the time of resection are placed over the exposed dura ( Fig. 12-38, E ).

Vertebral column resection. A, Proximal ( right ) and distal fixation are seen with the planned removal of thoracic vertebrae 6 and 7 uninstrumented. B, A provisional right rod is in place and the seventh thoracic nerve root on the left convex side is being isolated and ligated. C, At completion of the resection, two provisional rods are in place and the spinal cord is completely free. A metal suction tip is seen anterior to the spinal cord. D, The spine has been reduced with the anterior cage in place to maintain overall length of the spine and prevent shortening with kinking of the spinal cord. E, Final intraoperative photo with the rib grafts in place spanning the resected segment and protecting the exposed spinal cord.

The choice of spine mobilization procedure is dependent on several factors related to the spine deformity, including its severity, flexibility, amount of previous fusion, and experience of the surgeon. The major risk is neurologic deficit, which occurs more commonly with more aggressive release procedures. The most recent review of the SRS database demonstrated an overall 0.9% incidence of neurologic deficits for all AIS surgery; however, the incidence increased when a Smith-Petersen osteotomy was performed (1.1%) and was greatest when VCR was performed (7.3%).

Anterior Mobilization Techniques.

Anterior release including discectomy, and possibly rib head resection when necessary, can be performed through an open thoracotomy or through a thoracoscopic approach. The thoracoscopic approach has some advantage over the open thoracotomy because smaller incisions are used with less chest wall disruption and less detrimental impact on pulmonary function, especially when it is performed in the prone position with double lung ventilation using a regular single-lumen endotracheal tube ( Video 12-1 ). The combined thoracoscopic release in the prone position and posterior instrumented fusion has resulted in overall excellent radiographic and clinical results.

Complications of Posterior Instrumentation and Fusion for Adolescent Idiopathic Scoliosis.

The primary complications associated with posterior surgery and instrumentation include infection, pseudarthrosis, neurologic deficit, and implant-related problems such as prominence, discomfort, and implant failure associated with pseudarthrosis. The overall incidence of reoperation after posterior instrumentation and fusion varies but is below 10% in more recent series. A 1% to 10% incidence of delayed wound infection has been reported, presumably related either to the increased amount of hardware or to the multiple hook–rod connections. * ^c Some of these episodes of delayed drainage were culture negative and attributed to micromotion at the hook–rod interface. Micromotion causes metallic debris, which leads to a foreign body reaction, formation of a false membrane and fluid, and finally loosening of the implant. Rather than representing an aseptic process, it is more likely that these delayed infections result from low-virulence organisms that are seeded at the time of surgery and remain quiescent over an extended period.

References .

The most feared complication in spine deformity surgery is neurologic deficit, whose incidence has remained steady through the years and is still below 1%. Reames and coauthors reported the most recent analysis of the SRS database, which found a 0.8% incidence of neurologic deficit at the time of surgery for AIS. The likelihood of complete or partial recovery of neurologic deficits is high in all series. The incidence of neurologic deficit is generally regarded to be higher with combined anterior/posterior surgery and when osteotomies are performed and is generally thought to be of vascular origin.

Anterior Approach to Thoracolumbar and Lumbar Curves.

The anterior approach to thoracolumbar and lumbar curves has been successful in correcting deformity and preventing curve progression. However, its use for these curves has diminished with greater use of pedicle screws and spine mobilization procedures. Shufflebarger and associates reported 80% correction of these curves with a posterior approach that involved the use of segmental pedicle screws at each level with wide Ponte-style osteotomies and convex compression. Comparison studies between the posterior and anterior approaches have demonstrated similar levels of instrumentation with similar correction of deformity; however, the posterior approach is associated with a shorter operative time and hospital stay without the need for a chest tube or a general surgeon to perform the surgical approach. In general, we treat all thoracolumbar and lumbar curves via a posterior approach except when the planned LIV is significantly translated from the CSVL, in which case the anterior approach with complete diskectomies and powerful derotation of the spine may allow better correction of the three-dimensional deformity of the spine.

Solid-Rod Anterior Instrumentation.

TSRH instrumentation extended the concepts of Zielke by using a stiff, smooth, solid rod as the longitudinal connection between vertebral screws ( Fig. 12-40 ). The resulting stiffer, fatigue-resistant construct enhances the maintenance of correction and the likelihood of arthrodesis without postoperative external immobilization in most cases. Deformity is corrected by rotation of a 6.4-mm rod that is precontoured for lordosis (similar to the CD instrumentation principles for thoracic curves posteriorly, but in reverse). Because correction of deformity is achieved by gradual rod rotation, corrective forces are evenly distributed all along the construct simultaneously rather than applied acutely or gradually at a single segment.

A , A 14-year-old female with 56 degrees thoracolumbar idiopathic scoliosis. She underwent anterior instrumentation between T10 and L3, with autogenous bone graft and spacers between L1-L2 and L2-L3. At 2 years postoperative, she had a balanced spine and solid fusion ( B and C ).

The early results of anterior single-rod treatment of thoracolumbar and lumbar curves included a high incidence of pseudarthrosis, which improved with rib strut grafts. The addition of anterior interbody structural support in the form of a titanium cage or femoral ring allograft significantly increased the flexion–extension stiffness of the construct when using single-rod implants, and it appears to increase the likelihood of fusion. It is important to place the structural interbody support in the most anterior aspect of the intervertebral disk space to obtain optimal load sharing and in the concavity of the curve to aid in coronal plane correction. The concept of dual-rod constructs for anterior scoliosis surgery was popularized by Kaneda as a method of increasing the stiffness of the single-rod construct while maintaining coronal and sagittal plane correction and preventing pseudarthrosis. The stiffness of dual-rod systems is better than that of single-rod systems in flexion, extension, and torsion, with no increase in lateral-bending stiffness. The addition of anterior structural support to a dual-rod system increases overall construct stiffness in flexion but not in other loading conditions.

The surgical technique for dual-rod systems is to initially place two screws in each vertebra, with the posterior screw traversing along the posterior cortex of the vertebral body and the anterior screw directed in an anterior-to-posterior direction to provide increased pullout and plow resistance (see Plate 12-4 , I-M on page 306 .) A staple is similarly used to capture both screws. A contoured rod with the desired lordosis is placed into the posterior screws, and a rod rotation maneuver is performed in a similar manner as a single-rod technique to correct the scoliosis and restore or maintain lordosis. Anterior structural support in the form of a titanium mesh cage filled with the autologous rib graft harvested during the surgical approach is next placed to help maintain lordosis and assist in achieving correction of scoliosis. The second rod is then placed and slight compression is applied to lock in the anterior structural support. Kaneda and associates reported their results with Kaneda’s dual-rod system without anterior structural support in 25 patients (20 with idiopathic scoliosis and 5 others) with thoracolumbar or lumbar curves; they demonstrated average coronal correction of 83%, restoration of 9 degrees of lordosis (7 degrees of preoperative kyphosis), and no cases of pseudarthrosis. Others have demonstrated excellent correction and maintenance of correction with a dual-rod system. The Halm-Zielke system is composed of a lid plate fixed to the lateral aspect of the vertebral body with two screws—a screw sunk anteriorly and a second ventral derotation spondylodesis screw posteriorly. This low-profile system has yielded excellent correction with few complications. The dual-rod systems emphasize the importance of construct stiffness and the stability provided by the second rod.

Fusion levels for thoracolumbar and lumbar scoliosis are generally from the proximal end vertebra to the distal end vertebra, as assessed on the preoperative PA radiograph. Deciding on the distal fusion level is challenging because of the relatively common occurrence of a postoperative oblique disk (which opens into the convexity of the curve) below the fusion levels. This problem is more likely to occur when the disk below the distal end vertebra is parallel and the LIV is closer to the apex of the curve on the preoperative radiograph. Despite these challenges, relatively good success has been achieved with the so-called short-segment anterior fusion for mild to moderate curves that are relatively flexible. The fusion levels are based on the level of the apex of the deformity: when a disk is the apex, fusion should be two levels above and two levels below the disk; when the apex is a vertebra, fusion is one level above and one below the apex. The success of this surgical strategy is dependent on achieving overcorrection of the instrumented segments to translate the spine and balance the patient.

Anterior Instrumentation for Thoracic Deformity.

Dwyer and colleagues proposed this technique in the 1960s but found that correction was unsatisfactory with the cable systems. Since then, use of anterior instrumentation for thoracic deformity has reemerged. In 1988, Harms began repopularizing the idea after conjecturing that anterior correction without a posterior derotation maneuver of the thoracic curve in King type II deformities would prevent the lumbar curve from decompensating, as had been described following selective posterior instrumentation.

The technique of anterior spinal fusion and instrumentation (ASFI) of thoracic curves achieves excellent coronal curve correction and restoration of thoracic kyphosis, and the lumbar curve responds nicely in selected thoracic fusion situations. Advantages of the anterior approach over the posterior approach include the ability to save motion segments, no stripping of the paraspinal muscles and thus avoidance of scarring and perhaps subsequent pain, limited development of late operative site pain (seen with posterior implants), and a lower incidence of infection. Betz and colleagues, in a comparison of anterior and posterior approaches for thoracic scoliosis, found 58% correction of the coronal curve and an average of 2.5 levels that were saved with the use of anterior surgery; however, a high incidence (31%) of rod fracture occurred when a small-diameter rod (3.2 mm) was used. More recent studies using rods 4.0, 5.0, or 5.5 mm in diameter showed 47% curve correction, but pseudarthrosis developed in 7% of patients. A lower incidence of pseudarthrosis is seen with dual rods, but the challenge of placing two screws in the thoracic spine may prevent widespread use of this technique.

When placing anterior instrumentation in the thoracic spine it is necessary to understand the anatomic landmarks, including the relationship between the rib head and the vertebral body. The correct starting point for the screw must be identified to avoid the spinal canal. On the contralateral side of the chest, the aorta is positioned more laterally and posteriorly than is the case with a straight, normal spine. This exposes the aorta to a higher risk for injury when placing anterior screws. Transvertebral anterior screws should penetrate the far cortex only slightly to avoid injuring these important soft tissue structures.

The traditional surgical approach for ASFI of the thoracic spine was through an open thoracotomy incision ( Fig. 12-41 ). Thoracoscopic ASFI was first introduced in the mid-1990s following experience with thoracoscopy for anterior release and fusion in conjunction with posterior spinal fusion and instrumentation. Advantages of the thoracoscopic technique include smaller incisions, which results in improved cosmesis, and less chest wall dissection, which results in both less postoperative pain and improved pulmonary function. The disadvantage of the technique is that it is technically demanding, which results in a fairly steep learning curve, long operative times, and a relatively high pseudarthrosis rate.

Anterior thoracic instrumentation. A threaded rod is attached to vertebral body screws on the convexity of the thoracic curve. A shorter segment of thoracic fusion can be accomplished with this system than with posterior instrumentation.

Ideal patients for thoracoscopic ASFI include those with good pulmonary function; active patients with high bone mineral density for good screw purchase; tall, thin patients to allow easy portal placement and manipulation; and those with thoracic curves that have a coronal magnitude of less than 70 degrees and a flexibility index greater than 50%. Follow-up has demonstrated that the results of thoracoscopic AFSI are similar to those of open ASFI, with 55% coronal plane correction and a pseudarthrosis rate of 6%. When compared directly with a posterior approach, thoracoscopic ASFI is associated with similar coronal plane correction and less intraoperative blood loss but longer surgical times ( Fig. 12-42 ).

Thoracoscopic anterior spinal fusion and instrumentation for a thoracic curve. A, Preoperative posteroanterior ( left ) and lateral ( right ) radiographs demonstrate a 58-degree right thoracic curve with the end vertebra at L2 and the stable vertebra at L4. B, Posteroanterior (left ) and lateral ( right ) radiographs following thoracoscopic anterior spinal fusion and instrumentation from T7 to T12. Anterior correction mechanics allowed the fusion to stop at L2 in this case despite significant translation from the center sacral line.