Apical Derotation for Deformity Correction in Adolescent Idiopathic Scoliosis Using the Pedicle...

Apical Derotation for Deformity Correction in AdolescentIdiopathic Scoliosis Using the Pedicle Screw-plate Spinal

System: Surgical Technique and Results

Pongsthorn Chanplakorn, MD, Wiwat Wajanavisit, MD, and Wichien Laohacharoensombat, MD

Summary: The treatment of adolescent idiopathic scoliosis has evolved

substantially over the last few decades. The Cotrel-Dubousste spinal

system has demonstrated excellent results in coronal and sagittal

deformity correction but remains inferior in rotational deformity control.

The evolution of pedicle screws in the modern spinal instrument system

allows 3-column fixation and allows true rotational correction of the

vertebral body by direct manipulation. However, the screws can cut into

the spinal canal, which can cause disastrous consequences. Since 1990,

the pedicle screw-plate system has been in the process of development

and has been used for the treatment of adolescent idiopathic scoliosis.

With our technique, indirect manipulation of the spinal deformity results

in gradual curve correction and in apical vertebral derotation as well. Our

results have been comparable to those of the direct derotation techniques

reported previously. In this article, the surgical planning and surgical

technique applied to our pedicle screw-plate system are demonstrated,

and the clinical results are presented.

Key Words: idiopathic scoliosis—derotation—pedicle screw-plate

system—surgical technique—short fusion.

(Tech Orthop 2011;26: 203–211)

Adolescent idiopathic scoliosis (AIS) is a 3-dimensionaldeformity of the spine, which consists of lateral curvature

plus rotation of the vertebral bodies. Nonoperative treatment isa widely accepted approach to control the progression of spinalcurvature in mild deformity at the early stage of the disease.However, there is still a lack of scientific evidence supportingthe effectiveness of such treatment, and surgical correction isoften necessary in several patients.1 The primary objectives ofsurgical treatment in AIS are as follows: (1) to arrestprogression; (2) to achieve maximum permanent correctionof the deformity in 3 dimensions; (3) to improve appearance bybalancing the trunk; and (4) to minimize short-term and long-term complications.

The revolutionary design and capability of spinalinstruments have drastically changed the principle of scoliosissurgical correction over the past 2 decades. The firstannouncement of the 90-degree rod rotation maneuverespoused by Cotrel and Dubousset in the early 1980s was an

excellent technique for coronal and sagittal realignment.However, in the axial plane, true vertebral rotation minimallyoccurred, whereas vertebral translation was essential, becausethe rotation took place by hooks rather than by vertebralbodies.2,3 This is of clinical interest, as vertebral rotation is amajor concern in scoliotic deformity correction.

Pedicle screw constructs were introduced at the beginningof the 1990s, followed by the report of superior outcome ofdeformity correction over the hook system in lumbar andthoracolumbar regions. These successes have led a number ofscoliosis surgeons to develop techniques for using pediclescrews in the thoracic region for deformity correction withsimilarly promising results.4–6 The advantages offered byscrew fixation include a secure 3-column fixation, superiorcontrol of the upper and lower instrumented vertebrae, and theability to manage large scoliosis deformities with a posterior-only approach.5,7 These advantages provide the possibility oftrue apical derotation for the first time in modern spinaldeformity surgery.

Many techniques have been described to accomplishperiapical derotation using pedicle screws. The derotationmaneuvers consist of either manipulating concave apical screwsby pushing in a lateral direction or by pushing convex periapicalscrews in a medial direction, or by bilateral screw rotationthrough a so-called “quadrilateral frame” described recently byChang and Lenke.8 However, from a safety perspective, thedirect derotation through either maneuver carries importantconsiderations such as screws cutting into the spinal canal orscrews displacing out of the vertebral body, which can possiblycause disastrous consequences. In terms of the length of fusion,the acceptable endpoints of fusions are the neutral vertebrae,6,9

which usually need longer fusion beyond the end vertebra (EV)and may jeopardize the lower spinal motion segments.

Since 1990, our group has been developing the pediclescrew-plate system (PSP) and it has been used for the treatmentof many spinal disorders and for the correction of spinaldeformities, particularly AIS. Our technique for scoliosiscorrection has been developed for its effectiveness andversatility and for the simplicity of the operation. Indirectmanipulation of the spinal deformity from gradual curvecorrection, so-called “dynamic derotation,” can be effectivelyperformed, as results from our series have shown that thedegree of spinal deformity correction is up to 70%. Further,regarding the degree of apical vertebral derotation, 44% ofapical vertebral rotation has been demonstrated in our results,10

which are comparable to the direct derotation techniquereported by Lee et al.6 More recently, the short fusion lessthan EV to EV technique has been developed and can beapplied in some particular curve patterns.11 This strategy cansave 1 or 2 lumbar motion segments, one of the major concernsin scoliosis surgical correction. In this study, our surgicalplanning and the surgical technique applied to our PSP systemare demonstrated, and clinical results are presented.

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Received for publication July 10, 2011; accepted July 17, 2011.From the Department of Orthopedics, Faculty of Medicine Ramathibodi

Hospital, Mahidol University, Bangkok, Thailand.The authors declare that they have nothing to disclose.Address correspondence and reprint requests to Wichien

Laohacharoensombat, MD, Department of Orthopedics, Faculty ofMedicine, Ramathibodi Hospital, Mahidol University, 240 Rama VI road,Payathai, Ratchathewi, Bangkok 10400, Thailand. E-mail: Rawlh@mahidol.ac.th.Copyright r 2011 by Lippincott Williams & WilkinsISSN: 0148-703/11/2603-0203

THE PSP: THE COMPONENT DESIGN ANDLOCKING MECHANISM

The PSP system (T.K.S. Methyl Works Co. Ltd,Bangkok, Thailand) consists of 4 main components: the screw,washer, nut, and spinal plate. The screw of the PSP is designedfor the periapical vertebral derotation maneuver. It has a longshank serving as a lever to rotate the vertebral body. Further, ithas a long-distance small-pitch thread that can obtain maximalpulling power. Moreover, between the shank and the screwthread, it has a large round-shaped flare for placement of thespinal plate, which also acts as a locking buttress between thescrew, plate, and washer (Fig. 1). The PSP spinal plate includes2 buttress square locking rods connected with small bridgesdesigned to increase the bending stiffness of the system. Thelocking mechanism of the PSP system is a fully constraineddesign. The washer is designed to constrain with the lockingrods through the identical thread that is forced to lock the PSPplate. The nut is used to press the washer down through theproximal screw thread to secure it against the PSP plate, whichis placed over the screw flare (Fig. 1A). When the screw istightly fixed to the plate with the washer and nut, it can beeasily removed by twisting in the same manner as turning thescrew into the pedicle.

When the function of the PSP spinal plate is comparedwith the rod, it is less versatile in adapting to the spinaldeformity in the coronal plane and to the rotational deformity.This feature provides some intrinsic corrective force. Bendingthe plate in the saggital plane will control the kyphotic-lordoticdeformities to some extent. The other unique property of theplate is its buttressing power on the lamino-spinous part of thespines involved in the scoliotic deformity. The peripheral endsof the plate on the concave side can be buttressed on the EV,1 to 2 levels beyond the screw segments, whereas on theconvex side the central part of the plate can be buttressed onthe unscrewed apical vertebral segments of the curve. These

contact points can be regarded as the fixation points, althoughno screw is involved. In general, the length of the plate on theconcave side is longer than that of the screw segments (Fig. 2).

SURGICAL TECHNIQUE AND DEFORMITYCORRECTION WITH THE PSP SYSTEM

Selection of Fusion SegmentsOur strategic approach for deformity correction in

scoliosis is to minimize the extent of fusion as much aspossible. In general, the guideline introduced by Lenke et al12

has been used for the selection of the proper fusion segments inour PSP system, with some modification. The principles are asfollows: (1) the major curve and the structural minor curve areincluded in the instrumentation and fusion; (2) nonstructuralminor curves are not considered in instrumented fusion but thelong spinal plate may be used for buttressing to improve thedeformity correction in the coronal plane; (3) in lumbarmodifier C curve pattern, the instrumented fusion will beconsidered only if the magnitude of the curve has aconsiderable effect on the coronal balance (Fig. 3).

Surgical Techniques

PositioningWe position our scoliosis patients prone on 2 dome-

shaped gel positioners to support the chest and pelvis over theradiolucent operating table. The abdomen should be hung freeto prevent any compression to the vena cava. We use the strapfor pulling the apical chest wall to reduce the deformity. Thetape strap should run under the patient across the surgical tableto the opposite side to keep the surgical area free of obstacles.

Surgical ExposureThrough the posterior midline incision, the spines are

subperiosteally exposed, keeping all the ligament and cartila-

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FIGURE 1. The component design of the pedicle screw-plate system (PSP) in lateral (A) and axial (B) views. The pedicle screw consists of3 main components: screw threads (a), flare (b), and shank (c). The long screw shank serves as a lever for the derotation maneuver. Thefully constrained lock of the PSP is shown in the dash circle. The nut is used to press the special design thread washer (d) through thesmall-pitch thread [over the screw flare (b)] against the identical buttress threads of the spinal plate (e).

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ginous tissue attached to the carefully retracted paraspinalmuscles. Exposure is extended until the proximal part of thetransverse process is visualized. Generally, both EV areincorporated in the fixation.

Placement of the Pedicle ScrewsOn the concave side, 4 or 5 screws are placed into the

pedicle of the adjacent apical vertebrae, with 1 optional screwin the lower EV (T12 or L1 in the common thoracic curve). Onthe convex side, 2 or 3 screws are placed in the upper adjacentvertebrae and 2 in the lower EV. If the curve is flexible, anoptional apical screw is also used (Fig. 4A). The position of allpedicle screws should be checked for any missing position byusing an image intensifier. At this step the spinal navigationsystem is very helpful to place the screws in the preciseposition.

Assembly of the PSP PlatesAs the screws are aligned according to the anatomic axis

of the pedicle, threading all the screws on each side of thespine into the contour plate demands some training experience.On the concave side, first thread in the 2 proximal screws, andthen gradually lever the adjacent distal screws one by one intothe slot of the plate. Guide both ends of the plate to stay on thesame side of the curve and push down the plate until it comesin contact with the lamina. Repeat the maneuver on the convexside. Starting with the 3 proximal screws, gradually thread inthe apical and distal screws. This maneuver needs bothlevering and twisting of the plate. Once all the screws are

threaded into the slot of the plate, some degree of rotationaldeformity correction is achieved (Fig. 4B).

Deformity CorrectionThe screws are then alternately and gradually tightened to

the plates. On the concave side, tightening the apical screwswill pull the spinal segments to move to contact thekyphotically contour plate. This spreads the EV away fromthe center (distraction) and derotates the apical vertebrae. Onthe contrary, tightening the periphery screws on the convexside will create compression force and reduce the hump by theeffect of buttressing the center of the relatively straight plate tothe apical vertebrae (Fig. 5). Thereafter, after the PSP platesare tightened, the sagittal deformity will be contoured by fineadjustment of the screws.

In patients with severe rigid deformity, disectomy, partialvertebral resection, or pars resection may be performed onperiapical vertebrae to reduce stiffness of the curve beforeassembly of the PSP spinal plate and deformity correctionmaneuver. However, in our viewpoint, the aim of treatment insuch patients is not total correction of deformity but onlysetting the balance of the spine and impeding the progressionof deformity (Fig. 6).

RESULTS

Clinical Results of the PSP System on IdiopathicScoliosis Deformity Correction

The clinical results of our surgical technique onidiopathic scoliosis (AIS) deformity correction using the PSP

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FIGURE 2. A radiographic illustration of 13-year-old girl in antero-posterior (AP) view (A) with adolescent idiopathic scoliosis, 60-degreethoracic and 47-degree lumbar curves, and normal thoracic kyphosis (Lenke 1BN). She underwent a posterior derotation and spinalfusion from T5 to T12 with the pedicle screw-plate system. The lumbar and proximal thoracic curves were also corrected by thebuttressing effect of the spinal plate (white arrows). The final follow-up x-ray 2 years after surgery, in AP view (B), revealed a well-balanced spine; however, a 15-degree thoracic curve remained, along with a minimal lumbar curve. CSVL, central sacral vertical line.

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system were analyzed. Forty-three patients (35 female and 8male) with a diagnosis of AIS were included in this study. Theaverage age of the patient was 14.6 years (range, 10 to 20.5 y).

The patients were divided into 3 groups according to thedegree of spinal deformity as measured by the Cobb method:group 1 or the small deformity group, in which the Cobb angle

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FIGURE 3. A radiographic illustration of a 15-year-old girl in antero-posterior (AP) view (A) and lateral view (B) with adolescentidiopathic scoliosis, 50-degree thoracic and 42-degree lumbar curves, and normal thoracic kyphosis (Lenke 1CN). She underwent aposterior derotation and spinal fusion from T4 to L1 with the PSP system, with correction of lumbar and proximal thoracic curves by thebuttressing effect of the spinal plate (white arrows in C and D). The final follow-up x-ray 1 year after surgery in AP (C) and lateral view(D) demonstrated a nearly straight spine and optimal sagittal alignment. Only a 10-degree thoracic curve remained.

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FIGURE 4. Illustrates the placement planning of the pedicle screws (A). Using more pedicle screws on the concave side of the apicalvertebrae is our preference for the gradual correction of spinal curvature. An optional screw (*) can be placed if the spine is flexible. ThePSP plates are contoured and assembled (B). Our spinal plate designs the multiple slots for threading the screws inside. The spinal plateon the concave side (a) is a more kyphotic contour and longer than the plate on the convex side (b). The peripheral end of the concaveside spinal plate will push the lamino-spinous part of the spine (arrow) and contour the proximal part of the deformity (buttress effect).After threading all screws into the spinal plates, some degree of deformity will be corrected.

FIGURE 5. Demonstrates the mechanisms of the deformity correction. On the concave side, when the pedicle screws are graduallytightened, the apical screws will pull the spine to the precontoured spinal plate (white arrow). The vertebrae will spread out from thecenter (black arrow), creating a distraction (A). The apical vertebrae will also derotate to the spinal plate by this maneuver (B). On theconvex side, as the screws are tightening, the vertebrae will compress to the center (black dash arrow).

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was < 45 degrees; group 2 or the large deformity group, inwhich the Cobb angle was between 45 and 89 degrees; andgroup 3 or the severe deformity group, in which the Cobbangle was > 90 degrees. As demonstrated in Table 1, we didfind that the Cobb angle significantly improved in both groupsafter surgery; nevertheless, the degree of correction was foundto be lowest in the severe deformity group (38.7%) whencompared with the large (53.6%) or small deformity group(51.0%). Conversely, all 3 groups demonstrated an increase in

kyphotic angle. However, in the large and severe deformitygroups, a slight increase in kyphotic angle was observed. Thesignificant improvement of the sagittal contour was demon-strated only in the small deformity group.

Results on Apical Vertebral DerotationWe conducted the analysis to evaluate the efficacy of our

PSP system on the deformity correction in idiopathic scoliosispatients by considering the magnitude of apical derotation. All

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FIGURE 6. Radiographic illustrations of a 12-year-old girl with severe scoliosis in antero-posterior (AP) view (A) and an 85-degreethoracic curve with hypokyphosis (Lenke 1A-). She underwent posterior derotation and spinal fusion from T5 to L1 with the pediclescrew-plate system. The final follow-up x-ray 1 year after surgery in AP view (B) revealed that the spinal balance was improved even witha 40-degree thoracic curve remaining.

TABLE 1. Clinical Results of Deformity Correction Grouped by the Degree of Spinal Deformity

Preoperative Cobb Angle (Degree)

Group 1 (<45 degrees) Group 2 (45-89 degrees) Group 3 (Z90 degrees)

Age at surgery (y) 14.8 (2.59) 14.8 (2.73) 13.5 (1.40)No. fusions (levels) 7.2 (2.66) 7.8 (2.89) 8.3 (3.20)

Cobb angle (degree)Preoperation 39.0 (4.07) 54.23 (8.23) 96.3 (8.46)Postoperation 18.7 (6.92) 25.12 (9.75) 58.9 (8.55)

Percentage correction* 48.0% 53.7% 38.8%P-valuew < 0.0001 < 0.0001 < 0.0001

Kyphotic angle (degree)Preoperation 10.4 (8.87) 13.9 (8.95) 20.8 (10.11)Postoperation 15.9 (7.83) 18.4 (8.76) 23.6 (6.71)

Percentage correction* 52.8% 32.3% 13.5%P-valuew < 0.01 < 0.05 0.425NS

Blood loss (mL) 402.7 (256.92) 573.52 (453.42) 843.75 (462.45)

Data are shown as means (SD). NS indicates not significant.*Calculated using the difference between preoperative and postoperative values and comparing with the preoperative value.wCalculated using the paired t test.

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patients included in this study were operated upon using ourtechnique. However, the juvenile scoliosis patients and thepatients who had severe spinal deformity, in whom the Cobbangle >100 degree, were excluded from this study. Aftersurgical correction, we found a significant apical vertebralrotation (Apex-S1 angle) from 26.7 degrees preoperatively to15.0 degrees postoperatively, a 43.8% correction. Moreover,the alignment index, which represents the overall segmentalvertebral rotation, was also significantly improved from 18.7degrees preoperatively to 9.1 degrees postoperatively, a 51%improvement (Fig. 7). Significant improvements in parameterswith regard to spinal balance were also demonstrated in thisstudy (Table 2).

Results of The Short Fusion Technique onIdiopathic Scoliosis Deformity Correction

We conducted this study to evaluate the result of our short

fusion technique on AIS deformity correction. Thirty-nine

patients were included in this study. The mean age of the

patients at the time of surgery was 14.7 years (range, 9 to 20 y).

The mean follow-up time was 2.1 years (range, 0.8 to 3 y).

Fusion level was designed on the basis of the pattern and

flexibility of the deformity as previously described and was

classified into 3 groups: the short fusion group (fusion less than

EV), the end-to-end fusion group (fusion limited to the EV),

and the classic fusion group (fusion beyond the EV). We found

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FIGURE 7. Preoperative and postoperative serial computerized topography scan at the upper end vertebra, the apex, the lower endvertebra, and the sacrum of the spinal curve demonstrating apical vertebral derotation after surgery (from Laohacharoensombat et al10).

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that the degree of correction among the 3 groups was 49% onaverage and did not demonstrate any statistical differencebetween groups (Table 3). However, the degree of correctionwas inferior to the results from our previous series in whichwas used EV-to-EV fusion (Table 2).

DISCUSSION

Our results showed that the PSP system can be used fordeformity correction in AIS. However, our PSP system hassome limitations. First, to assemble the PSP plates, threadingall the screws on each side of the deformed spine into the rigidcontour plate demands some training experience and flexibilityof the spine. Second, the ability to correct severe spinaldeformity is limited, especially in the sagittal plane. Third,through our design, the PSP plate cannot be contoured in thecoronal plane. Therefore, some difficulty is usually encounteredwhen using the PSP plate in severe rigid deformity correction.In our experiences, there are 2 alternatives to handle thisparticular situation. First, disectomy, partial vertebral resection,or pars resection may be performed to reduce stiffness of thecurve before assembling the PSP spinal plate. Second, the

number of screw fixations in the spinal curve can be reduced sothat the straight plate can be accommodated. However, thespinal curve should be partially corrected with this technique.

Again, our goal of treatment of AIS is not total correctionof the deformity. It is to just restore the balance of the spine andimpede progression of the deformity. Therefore, in terms ofselection of fusion levels, the instrumented fusions areconsidered only on the major curve to restore the spinal balanceboth in coronal and sagittal planes, whereas the small minorspinal curves are corrected by the buttressing effect with spinalplates as demonstrated in Figs. 2 and 3. This strategy can save 1or 2 lumbar motion segments. However, in a few cases we arefaced with progressive deformity out of the instrumented fusionregion and need revision surgery. This phenomenon, in ourexperience, is especially encountered when the surgery iscarried out in growing children with severe deformity.

CONCLUSIONS

The PSP system is one of the most effective implants thatcan be used to correct spinal deformity in AIS. Using ourtechnique, the spinal deformity of AIS can be successfullycorrected in 3 dimensions, coronal, sagittal, and axial rotation,as demonstrated in our results. In addition, the constrain lockdesign of the implant has an advantage in that it can be appliedfor gradual deformity correction. In our experience, thismechanism should be safer than direct manipulation of screws.Further, with the PSP system, short instrumented fusion can beperformed in selected patients. However, assembly of the PSPplates demands training experience, and additional proceduresmay be necessary to reduce stiffness of the curve in severerigid deformity correction.

REFERENCES

1. Weinstein SL, Dolan LA, Cheng JCY, et al. Adolescent idiopathic

scoliosis. Lancet. 2008;371:1527–1537.

2. Lenke LG, Bridwell KH, Baldus C, et al. Analysis of pulmonary

function and axis rotation in adolescent and young adult idiopathic

scoliosis patients treated with Cotrel-Dobousset instrumentation.

J Spinal Disord. 1992;5:16–25.

3. Wood KB, Transfeldt EE, Ogilvie JW, et al. Rotational changes of the

vertebral-pelvic axis following Cotrel-Dobousset instrumentation.

Spine. 1991;16:S404–S408.

4. Kim YJ, Lenke LG, Bridwell KH, et al. Free hand pedicle screw

placement in the thoracic spine: is it safe? Spine. 2004;29:333–342.

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TABLE 2. The Clinical Results of Deformity Correction Under the Gradual Derotation Technique Using the Instruments of the PedicleScrew-Plate System

Preoperative Postoperative Percentage Correction* Pw

Cobb angle 52.1 (12.1) 14.8 (7.3) 71.5% <0.0001Apex-S1 26.7 (10.7) 15.0 (7.6) 43.8% <0.0001Alignment index 18.7 (10.7) 8.78 (5.6) 53.0% <0.0001Kyphosis 22.0 (15.3) 24.3 (9.9) 10.5% 0.3946Rib hump (cm) 3.0 (1.5) 1.6 (0.9) 46.6% <0.0001Plump line shift (cm) 1.4 (0.9) 0.5 (0.7) 64.2% <0.0001

Data of the operative results of patients with a mean age of 14.9 years (range, 11 to 21 y) and a mean follow-up (F/U) time of 48.9 months(range, 25 to 60 mo); at last F/U the mean postoperative Cobb angle increased to 21.5 degrees (31% change). Data are means (SD) of angularmeasurement in degrees. The Rib hump and Plump line shift are measured in centimeters.

*Calculated using the difference between preoperative and postoperative values and compared with the preoperative value.wCalculated using the paired t test (adapted from Laohacharoensombat W et al. J Med Assoc Thai 2005;88).

TABLE 3. Results of Deformity Correction in Various Lengths ofSpinal Fusion

Cobb Angle Measurement(Degree)

Preoperative Postoperative Pw

Fusion less than EV 52.4 (18.85) 27.6 (15.55) <0.0001mean difference 24.8 (8.91) 48.9%

correction*Fusion from EV to EV 51.6 (20.06) 26.6 (12.36) <0.0001

mean difference 19.3 (11.37) 48.9%correction*

Fusion beyond EV 67.4 (34.70) 36.7 (26.48) 0.0014mean difference 30.0 (15.87) 48.9%

correction*

Data are shown as means (SD) EV indicates end vertebra.*Calculated as the difference between preoperative and post-

operative values and compared with the preoperative value. Nostatistically significant difference was observed between the 3 groups(one-way analysis of variance, P-value = 0.6369).

wCalculated using the paired t test. (adapted from Wajanavisitet al11).

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5. Kuklo TR, Lenke LG, O’Brien MF, et al. Accuracy and efficacy of

thoracic pedicle screws in curves more than 90 degree. Spine.

2005;30:222–226.

6. Lee SM, Suk S, Chung ER. Direct vertebral rotation: a new technique of

three-dimensional deformity correction with segmental pedicle screw

fixation in single thoracic idiopathic scoliosis. Spine. 2004;29:343–349.

7. Luhmann SJ, Lenke LG, Kim YJ, et al. Thoracic adolescent idiopathic

scoliosis curves between 70 and 100 degree: is anterior release

necessary? Spine. 2005;30:2061–2067.

8. Chang MS, Lenke LG. Vertebral derotation in adolescent idiopathic

scoliosis. Opre Tech Orthop. 2009;19:19–23.

9. Suk S, Lee SM, Chung ER, et al. Determination of distal fusion level

with segmental pedicle screw fixation in single thoracic idiopathic

scoliosis. Spine. 2003;28:484–491.

10. Laohacharoensombat W, Jaovisidha S, Wajanavisit W, et al. Apical

derotation in the treatment of idiopathic scoliosis. J Med Assoc Thai.

2005;88:S58–S64.

11. Wajanavisit W, Woratanarat P, Woratanarat T, et al. The evaluation of

short fusion in idiopathic scoliosis. IJO. 2010;44:28–34.

12. 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. 2001;83:1169–1181.

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