Spine Deformity 1 (2013) 46e50www.spine-deformity.org

Maintenance of Thoracic Kyphosis in the 3D Correction of ThoracicAdolescent Idiopathic Scoliosis Using Direct Vertebral Derotation

Satoru Demura, MDa,c, Burt Yaszay, MDa, Joseph H. Carreau, MDb,Vidyadhar V. Upasani, MDb, Tracey P. Bastrom, MAa, Carrie E. Bartley, MAa,

Peter O. Newton, MDa,*aDepartment of Orthopedics, Rady Children’s Hospital, 3030 Children’s Way, San Diego, CA 92123, USA

bDepartment of Orthopedic Surgery, University of California San Diego, 200 West Arbor Drive, San Diego, CA 92103, USAcDepartment of Orthopedic Surgery, Kanazawa University, 13-1 Takaramachi, Kanazawa, 920-8641, Japan

Received 10 March 2012; revised 21 June 2012; accepted 25 June 2012

Abstract

Objectives: Through a review of prospectively collected data, we sought to analyze the outcomes related to 3-dimensional correction ofadolescent idiopathic scoliosis (AIS) after posterior spinal fusion (PSF) and instrumentation using an aggressive combination of correctionstrategies.Background Summary: New techniques have been used to address sagittal plane deformity while maximizing coronal and axialcorrection, including Ponte osteotomy, differential rod over-contouring, and direct vertebral rotation with uniplanar screws.Methods: This is a consecutive single-center series of AIS patients with thoracic curves (Lenke 1 and 2) with 2-year follow-up whounderwent PSF and instrumentation with the use of the following correction strategies: segmental uniplanar screws, ultra high-strength 5.5mm steel rods, aggressive differential rod contouring, periapical Ponte osteotomies, and segmental direct vertebral derotation. ScoliosisResearch Society (SRS)-22, radiographic and clinical parameters were evaluated at preoperative and 2-year time points.Results: Twenty-six patientswere included (mean age 13.6� 1.5 years). Preoperative thoracic Cobbmeasured 52� 9�, which improved to 17�4� at 2-year follow-up, resulting in 68� 9%correction. The average thoracic kyphosis fromT5-T12 did not significantly change (21� 10� to 22�5� at 2 years); however, in patients with kyphosis less than 20� preoperatively (avg. 13� 5�) kyphosis increased significantly at 2-year follow-up(avg. 20� 4�, p!.05). Preoperatively, axial rotation was more than 13� in 21 of 26 cases. At 2-year follow-up, axial rotation remainedmore than13� in 4 of 26 cases (p!.01). Rib hump prominence was 17 � 5� preoperatively, which improved significantly to 10 � 4� at 2-year follow-up(p!.05). Postoperative SRSdomain scores significantly improved inpain (4.3 to4.7), self-image (3.7 to 4.3), and satisfaction (3.3 to 4.6) (p!.05).Conclusion: A high degree of coronal correction can be achieved in association with vertebral derotation without sacrificing sagittal planealignment. High-strength rods aggressively bent to create kyphosis allow both restoration of kyphosis and axial plane derotation in thoracicidiopathic scoliosis.� 2013 Scoliosis Research Society.

Keywords: Adolescent idiopathic scoliosis; Sagittal alignment; Uniplanar screw; Ponte osteotomy

Author disclosures: DS (none); BY (consulting for K2M, Synthes,

Ellipse; research support to institution from KCI, DePuy, K2M, Ellipse;

speaking fees from DePuy; royalties from Orthopediatrics); JHC (none);

VVU (none); TPB (none); CEB (none); PON (consulting for DePuy and

Stanford University; expert testimony; research support to instituion from

NIH, OREF, POSNA, SRS, Harms Study Group Foundation, DePuy, Axial

Biotech, and Biospace Med/EOS Imaging; speaking frees from DePuy;

patents with DePuy; royalties from DePuy and Thieme Publishing; devel-

opment of educational presentations from DePuy; stock from Nuvasive).

This work is supported in part by a grant from JJKK Medical Company,

a Division of DePuy Spine, Japan and in part by a grant to the Harms Study

Group Foundation from Depuy Spine.

*Corresponding author. Department of Orthopedics, Rady Children’s

Hospital, 3030 Children’s Way, Suite 410, San Diego, CA 92123, USA.

Tel.: (858) 966-6789; fax: (858) 966-7494.

E-mail address: pnewton@rchsd.org (P.O. Newton).

2212-134X/$ - see front matter � 2013 Scoliosis Research Society.

http://dx.doi.org/10.1016/j.jspd.2012.06.001

47S. Demura et al. / Spine Deformity 1 (2013) 46e50

Introduction

In the past several years, excellent coronal correctionhas been reported using segmental pedicle screw fixationin the treatment of adolescent idiopathic scoliosis (AIS)[1-9]. However, many of these same studies have de-monstrated an associated loss of thoracic kyphosis. One ofthe goals of AIS treatment is to maximize coronal andaxial plane correction while restoring thoracic kyphosis.Recently, uniplanar screws were developed to provide thebenefits seen with polyaxial screws in the sagittal plane inmaintaining thoracic kyphosis, while maintaining theadvantages of a fixed angle screw in the coronal and axialplanes. The purpose of this study was to analyze the3-dimensional correction after posterior instrumentationand fusion with the combined use of uniplanar screws,Ponte osteotomy, differential rod contour, and directvertebral rotation.

Materials and Methods

A retrospective review of prospectively collected data ofa single center from a larger multi-center study was con-ducted. Patients with AIS, Lenke type 1 or type 2 curveswho underwent posterior spinal fusion and instrumentationat a single institution from 2006 to 2008 by a singlesurgeon were included. Uniplanar screws, ultra high-strength 5.5 mm steel rods, Ponte osteotomies, differen-tial rod contouring, and direct vertebral rotation were usedin all cases. Patients who underwent an anterior releasewere excluded.

All cases followed the same procedure. After exposureof the posterior elements, soft tissue release and Ponteosteotomies were performed, and then followed by theinsertion of segmental uniplanar screws. To avoid violationof the facet joint and to minimize the incision, down-goingtransverse process hooks were used at the most proximalinstrumented vertebra. Deformity correction was done firstby placement of a hyperkyphotic ultra high-strength

Fig. 1. A 14-year-old female pre-operatively with a 48� right thoracic curve andcurve and 24� of kyphosis from T5-T12.

contoured rod on the concave side, followed by cantileverreduction of the thoracic hump with an under-contouredconvex rod. The coronal and sagittal corrections were finetuned with compression and distraction. Segmental directvertebral rotation was done to maximize axial correction.Ultra-strength (200 KSI) stainless steel rods (5.5 mm) wereused in all cases (Fig. 1).

Radiographic evaluations were performed at preopera-tive, 1-year, and 2-year postoperative time periods. Coronalmeasurements included Cobb angle of the proximalthoracic curve, major thoracic curve, thoracolumbar/lumbarcurve, and coronal balance (from C7 to the central sacralvertical line). Sagittal measurements included thoracickyphosis (T2eT12, T5eT12), lumbar lordosis (T12eS1),thoracolumbar junction (T10eL2), distal junctionalkyphosis, proximal junctional kyphosis, and sagittalbalance (from C7eS1). Axial radiographic evaluation wasperformed by measurement of vertebral rotation describedby Perdriolle [10] preoperatively and grading of apicalvertebral rotation by Upasani et al. [11] postoperatively.Angle of trunk rotation (rib hump, lumbar prominence),trunk shift, and shoulder height difference were alsoassessed. Patient-reported Scoliosis Research Society(SRS) 22 data were collected and analyzed at preoperativeand 2-year follow-up.

Statistical data were analyzed using SPSS (SPSS Inc.,Chicago, IL). For comparison of paired values, repeated-measures analysis of variance was used followed by theScheffe post-hoc test. A p value less than .05 was consi-dered significant.

Results

There were 26 patients (23 female, 3 male) with a meanage at the time of surgery of 13.6�1.5 years (11-17 years).There were 16 Lenke type 1 curves and 10 type 2 curves.The lumbar modifier was type A in 11 patients, type B in 6,and type C in 9. Preoperatively, 21 out of 26 patients had

a sagittal profile from T5-T12 of 5� (left), and postoperatively with a 14�

Table 1

Coronal radiographic parameters. The values represent mean � SD with ranges in parentheses.

Preop. (N526) 1-year (N525) 2-year (N526) Difference between

Pre and 1 yr, 2 yr

Proximal thoracic curve 29.1�8.8 � (15-51) 10.9 ��4.4 � (1-19) 11.5 ��5.7 � (2-22) p!.01, p!.01

% correction � 60.3�18.1 (14-93) 60.7�16.1 (24-89)

Main thoracic curve 52.4 ��8.8 � (40-70) 15.0 ��5.6 � (8-25) 16.5 ��3.9 � (10-25) p!.01, p!.01

% correction � 70.3�11.5 (47-88) 67.5�9.5 (44-82)

Thoracolumbar-lumbar curve 33.0 ��10.8 � (12-53) 13.4 ��8.2 � (3-32) 13.7 ��8.5 � (2-32) p!.01, p!.01

% correction � 58.5� 9.2 (29-94) 59.2�0.1 (33-93)

Coronal balance (cm)

(C7 translation from CSVL, absolute value)

1.5�1.1 (0.1-3.7) 1.1�0.9 (0-4.0) 1.0�0.7 (0-3.0) p5.274, p5.061

Abbreviation: CSVL, central sacral vertical line.

48 S. Demura et al. / Spine Deformity 1 (2013) 46e50

a sagittal profile in the ‘‘normal’’ range (T5eT12 10�-40�),5 patients were hypokyphotic (T5eT12 !10�), and nonewere hyperkyphotic (T5eT12 O40�), according to theLenke Classification system.

The mean operative time was 202�40 min (range132-291 min) with a mean blood loss of 562�254 cc(100-1000 cc). The number of levels fused was 10�2vertebrae on average (range 7-15). The upper instrumentedvertebra ranged from T2eT5, and lower instrumentedvertebra ranged from T11eL4. In this series, Ponte osteot-omies were done at 5�1 interspaces at the region of thethoracic apical hypokyphosis or lordosis (range 3-9 osteot-omies). The mean anchor density was 1.88�0.1 anchorsper level.

The coronal radiographic parameters and correctionrates are described in Table 1. The proximal thoracic, mainthoracic, and lumbar curves all showed significantimprovement from preoperative to 1- and 2-year post-operative (p!.001). The change in coronal balance trendedtoward significant correction (p5.06), with patients morebalanced postoperatively.

The sagittal parameters are shown in Table 2. Theaverage thoracic kyphosis (both T5eT12 and T2eT12) wassimilar from preoperative to postoperative (pO.05).However, when patients were divided into groups based onthe magnitude of their preoperative kyphosis, a significantdifference was found in kyphosis correction from preop-erative to postoperative (Fig. 2, Table 3).

Patients with kyphosis less than or equal to 20� pre-operatively had a significant increase in T5eT12 kyphosisfrom 13��5� (range, 6�-20�) preoperative to 20��4�

Table 2

Sagittal radiographic parameters. The values represent mean � SD with ranges

Preop. (N526) 1-y

Thoracic kyphosis (T2eT12) 28.5 ��11.0 � (8-50) 30

Thoracic kyphosis (T5e12) 20.7 ��10.4 � (6-40) 23

Thoracolumbar junction (T10eL2) �0.5 ��9.4 � (�17-14) 0

Lumbar lordosis (T12eS1) 54.8 ��12.0 � (32-81) 57

Proximal junctional kyphosis 4.1 ��3.4 � (�3-10) 4

Distal junctional kyphosis �3.6 ��7.6 � (�18-8) �1

Sagittal balance (cm) (C7 translation from S1) 0.0�3.6 (�7.2-6.6) �2

(range, 13�-25�) at 2 years (p!.01). In those patients withkyphosis greater than 20� preoperatively, T5eT12 kyphosisdecreased from 30��7� (range 22�-40�) to 24��5� (range,17�-32�) at 2 years (p!.05). The change in lumbarlordosis, thoracolumbar junction, proximal junctionalkyphosis, and distal junctional kyphosis were not signifi-cantly different.

Preoperatively, axial rotation greater than 13� by Per-driolle was observed in 21 out of 26 cases. At 2 years, axialrotation greater than 13� was found in only 4 of the 26cases (p!.01), (Table 4).

Rib hump prominence was 17��5� (range 10�-30�)preoperatively, which improved significantly to 10��4�

(range, 3�-16�) at 2-year follow-up (p!.01). Lumbarprominencewas 7��5� (range, 0�-18�) preoperatively, whichimproved significantly to 2��3� (range, 0�-8�) at 2-yearfollow-up (p!.01). Postoperative SRS domain scoressignificantly improved in pain (4.4-4.7), self-image (3.7-4.3),satisfaction (3.4-4.6), and total score (4.1-4.4) (p!.05). Nosignificant differences were found in SRS domains of func-tion and mental health (pO.05). The mean improvement forthe pain domain was 0.3 and 0.6 for appearance (self-image),which for self-image is below the minimally clinicallyimportant difference for this domain [12].

Discussion

The achievement and maintenance of high degrees ofcoronal correction in the surgical treatment of AIS usingsegmental pedicle screw fixation is well documented in theliterature, dating back to the work of Suk et al. in 1995,

in parentheses.

ear (N525) 2-year (N526) Difference Between

(Pre and 1 yr, 2 yr)

.8 ��7.2 � (19-43) 29.9 ��7.5 � (15-43) p5.210, p5.537

.3 ��5.1 � (12-36) 22.0 ��4.6 � (13-32) p5.246, p5.674

.8 ��10.9 � (�25-31) 0.3 ��10.3 � (�22-28) p5.715, p5.893

.2 ��10.8 � (38-78) 57.3 ��11.8 � (37-82) p5.518, p5.493

.8 ��4.4 � (�5-14) 5.2 ��3.9 � (�2-12) p5.731, p5.456

.4 ��7.7 � (�14-20) �1.8 ��8.6 � (�17-22) p5.192, p5.335

.3�3.9 (�7.6-5.6) �2.9�3.4 (�9.0-4.6) p5.078, p5.018

Fig. 2. Distribution of T5-T12 kyphosis pre-operatively and at 2-years

postoperatively.

Table 4

Axial radiographic parameters.

Perdriolle’s method

5 � 10 � 15 � 20 � 25 � 30 �

Pre-op (N) 2 3 6 7 7 1

Upasani’s grade

Grade 0

(0 �-8 �)Grade 1

(9 �-12 �)Grade 2

(>13 �)

2-year (N) 6 16 4

49S. Demura et al. / Spine Deformity 1 (2013) 46e50

which described the efficacy of pedicle screw fixationcompared with all hook constructs [1]. Since that time,numerous studies have reported on the effectiveness ofpedicle screws in achieving coronal correction [1-8]. Leh-man et al., for example, reported a coronal major curvecorrection of 72.1% with the use of segmental pediclescrews [5]. Lonner et al. compared major curve correctionwith the use of monoaxial screws (69%) to polyaxial screws(68%), and found there was not a significant differencebetween the two groups [6]. Similarly, Kim et al. reportedon the superiority of all screw constructs [9]. In the currentstudy, the use of uniplanar screws resulted in similarcorrection in the coronal plane compared with theliterature.

Although some studies have shown maintenance ofthoracic kyphosis [2,3], most recent studies have demon-strated a trend of hypokyphosis of the thoracic spine aftercorrection with all pedicle screw constructs. Lowensteinreported hypokyphotic tendencies with thoracic pediclescrew constructs compared with hybrid instrumentation [4].Lehman et al. also described a decrease in thoracickyphosis with the use of monoaxial screws [5]. Further-more, Lonner et al. compared the results using hybridinstrumentation, polyaxial, and monoaxial segmental screwfixation and found that the polyaxial constructs were able tobest maintain thoracic kyphosis [6]. The authors speculated

Table 3

Sagittal parameters by kyphosis group. The values represent mean � SD with ra

Preop. 1-year

Under 20 � group

T2eT12 kyphosis 20.4 ��7.0 � (8-31) 26.4 ��5.9 � (19-34)

T5eT12 kyphosis 12.9 ��5.3 � (6-20) 21.1 ��4.7 � (12-30)

Over 20 � group

T2eT12 kyphosis 37.9 ��6.2 � (28-50) 36.4 ��4.4 � (27-43)

T5eT12 kyphosis 29.8 ��6.5 � (22-40) 26.0 ��4.4 � (19-36)

that various factors affect postoperative thoracic kyphosis,such as implant density, derotation maneuver through theconvex monoaxial screws, and rod diameter. Our resultsshowed that the use of uniplanar screws in combinationwith ultra high-strength 5.5 mm steel rods maintainedthoracic kyphosis similar to that which has been reportedwith polyaxial screws. One possible reason for this mightbe the ability of uniplanar screws to angulate in the sagittaldirection similar to polyaxial screws.

In this series, Ponte osteotomies, which is a procedurecommonly used in the treatment of Scheuermann’skyphosis, were performed in all cases [13,14]. However, inthis series, the osteotomies were done to gain and/ormaintain kyphosis in most cases, rather than to reducekyphosis as in Scheuermann’s. To preserve thoracickyphosis in the treatment of AIS, it has been suggested thatone must attempt to lengthen the posterior column [15]. Byremoving the facets and soft tissues of posterior elementsincluding the supraspinous ligaments, interspinous liga-ments, ligamentum flavum, and facet joint capsule, we haveeffectively detethered the posterior elements allowing theposterior column to lengthen. In this series, we placedgreater kyphosis in the rods, especially the correctiveconcave rod. It is challenging to estimate the unique effectof each of the techniques or strategies on the sagittalprofile, as they were used in combination. In the currentstudy, there was a 3� gain in thoracic kyphosis in the entireseries and approximately 7� gain in patients with kyphosisless than 20� preoperatively. This significant increase inT5eT12 kyphosis was not seen in previous studies on allpedicle screw constructs.

To evaluate radiographic spinal deformity in the axialplane, Kuklo et al. reported on apical rib hump prominence,apical vertebral body-rib ratio, and apical rib spread

nges in parentheses.

2-year Difference Between Pre and 1 yr, 2 yr

26.9 ��7.9 � (15-43) p!.01, p!.01

20.2 ��3.9 � (13-25) p!.01, p!.01

33.5 ��5.2 � (26-41) p5.600, p5.025

24.1 ��4.7 � (17-32) p5.136, p5.013

50 S. Demura et al. / Spine Deformity 1 (2013) 46e50

difference [3]. This study used a more direct measurementof axial deformity based on direct vertebral measures [11].In this series, 22 out of 26 cases had less than 13� ofrotation (Upasani grade 0 or 1), which was similar to theresults of 210 cases that compared vertebral rotationbetween uniplanar and polyaxial screws [16]. A recentreport by Lonner et al. showed that improvement of angleof trunk rotation (ATR) was around 50% after surgeryutilizing pedicle screws [6]. However, their preoperativethoracic ATR was 13.0� to 14.8� on average, which wasa relatively modest rib prominence compared with thecurrent study (17��5�). We believe there is residual ribdeformity (altered rib shape) that is not correctedcompletely despite axial vertebral correction, and that thecurrent results indicate excellent correction of axial defor-mity without thoracoplasty.

Several strategies were consistently used in this fairlytypical series of patients with thoracic idiopathic scoliosiswith the goals of achieving high degrees of 3-dimensionalbalance and spinal deformity correction. These methodslargely allowed the goals to be achieved, particularlywith regard to the sagittal plane, which has been mostproblematic, particularly when surgeons have focused oncoronal and axial correction. Unfortunately, this seriesoffers little in determining if all the techniques are impor-tant, and if so, what each contributes to the 3D correction.

Restoring the relative length of the posterior column ofthe thoracic spine appears to be an important feature of idealAIS correction. Shortening the anterior column or length-ening the posterior column (or both) are the options. Inlarger, stiffer deformities, both may be required; however, inthe magnitude of scoliosis treated in this series of patients,the posterior lengthening approach was effective. Ultra-strength steel rods with aggressive rod contouring alsoallowed greater force application to the spine; however, thelimit of the bone-screw interface strength must also berecognized when attempting to maximize correction forces.

Conclusion

This study shows that excellent coronal and axialcorrection can be achieved without sacrificing thoracickyphosis. Several strategies were employed: multi-levelPonte osteotomies, differential rod over-contouring, uni-planar screws and ultra-strength 5.5 mm steel rods. Thiscombination offers a solution to the commonly seenproblem of induced hypokyphosis associated with pediclescrew constructs and direct vertebral rotation used in thecorrection of thoracic AIS.

References

[1] Suk SI, Lee SM, Kim WJ, et al. Segmental pedicle screw fixation in

the treatment of thoracic idiopathic scoliosis. Spine (Phila Pa 1976)

1995;20:1399e405.

[2] Suk SI, Lee SM, Chung ER, et al. Selective thoracic fusion with

segmental pedicle screw fixation in the treatment of thoracic idio-

pathic scoliosis: more than 5-year follow-up. Spine (Phila Pa 1976)

2005;30:1602e9.

[3] Kuklo TR, Potter BK, Polly Jr DW, et al. Monaxial versus multiaxial

thoracic pedicle screws in the correction of adolescent idiopathic

scoliosis. Spine (Phila Pa 1976) 2005;30:2113e20.[4] Lowenstein JE, Matsumoto H, Vitale MG, et al. Coronal and sagittal

plane correction in adolescent idiopathic scoliosis: a comparison

between all pedicle screw versus hybrid thoracic hook lumbar screw

constructs. Spine (Phila Pa 1976) 2007;32:448e52.

[5] Lehman Jr RA, Lenke LG, Keeler KA, et al. Operative treatment of

adolescent idiopathic scoliosis with posterior pedicle screw-only

constructs: minimum three-year follow-up of one hundred fourteen

cases. Spine (Phila Pa 1976) 2008;33:1598e604.

[6] Lonner BS, Auerbach JD, Boachie-Adjei O, et al. Treatment of

thoracic scoliosis: are monoaxial thoracic pedicle screws the best form

of fixation for correction? Spine (Phila Pa 1976) 2009;34:845e51.[7] Quan GM, Gibson MJ. Correction of main thoracic adolescent idio-

pathic scoliosis using pedicle screw instrumentation: does higher

implant density improve correction? Spine (Phila Pa 1976)

2010;35:562e7.

[8] Fu G, Kawakami N, Goto M, et al. Comparison of vertebral rotation

corrected by different techniques and anchors in surgical treatment of

adolescent thoracic idiopathic scoliosis. J Spinal Disord Tech

2009;22:182e9.

[9] Kim YJ, Lenke LG, Cho SK, et al. Comparative analysis of pedicle

screw versus hook instrumentation in posterior spinal fusion of adoles-

cent idiopathic scoliosis. Spine (Phila Pa 1976) 2004;29:2040e8.[10] Perdriolle R, Vidal J. Thoracic idiopathic scoliosis curve evolution

and prognosis. Spine (Phila Pa 1976) 1985;10:785e91.

[11] Upasani VV, Chambers RC, Dalal AH, et al. Grading apical vertebral

rotation without a computed tomography scan: a clinically relevant

system based on the radiographic appearance of bilateral pedicle

screws. Spine (Phila Pa 1976) 2009;34:1855e62.

[12] Carreon LY, Sanders JO, Diab M, et al. The minimum clinically

important difference in Scoliosis Research Society-22 appearance,

activity, and pain domains after surgical correction of adolescent

idiopathic scoliosis. Spine (Phila Pa 1976) 2010;35:2079e83.

[13] Geck MJ, Macagno A, Ponte A, et al. The Ponte procedure: posterior

only treatment of Scheuermann’s kyphosis using segmental posterior

shortening and pedicle screw instrumentation. J Spinal Disord Tech

2007;20:586e93.

[14] Lonner BS, Newton P, Betz R, et al. Operative management of

Scheuermann’s kyphosis in 78 patients: radiographic outcomes,

complications, and technique. Spine (Phila Pa 1976) 2007;32:

2644e52.

[15] Newton PO, Yaszay B, Upasani VV, et al. Preservation of thoracic

kyphosis is critical to maintain lumbar lordosis in the surgical treat-

ment of adolescent idiopathic scoliosis. Spine (Phila Pa 1976)

2010;35:1365e70.[16] Dalal A, Upasani VV, Bastrom TP, et al. Apical vertebral rotation in

adolescent idiopathic scoliosis: comparison of uniplanar and polyax-

ial pedicle screws. J Spinal Disord Tech 2011;24:251e7.