Orthop Clin N Am 38 (2007) 531–540

Anterior and Thoracoscopic Scoliosis Surgeryfor Idiopathic Scoliosis

Vidyadhar V. Upasani, MDa, Peter O. Newton, MDb,*aDepartment of Orthopedic Surgery, University of California San Diego, 3020 Children’s Way,

MC5054, San Diego, CA 92123, USAbDepartment of Orthopedic Surgery, Rady Children’s Hospital San Diego, 3030 Children’s Way,

Suite 410, San Diego, CA 92123, USA

Orthopedic management of idiopathic scoliosisis based on knowledge of the natural history ofthis spinal disorder, identifying those patients

with a high likelihood of developing worseningdeformity. Long-term studies of untreated scolio-sis have associated severe deformity with poor

prognosis, increased morbidity and mortalityassociated with worsening cardiopulmonary com-promise, increased back pain, and psychosocial

issues related to the deformity [1,2]. Surgical treat-ment, with instrumentation and spinal arthrode-sis, was shown to achieve long-lasting deformityreduction at the cost of spinal flexibility [3,4]. Al-

though posterior spinal instrumentation and fu-sion continues to be the most commonly usedapproach in the surgical treatment of idiopathic

scoliosis, anterior procedures, both open andthoracoscopic, have proven to be a viable optionin selected patients.

Anterior scoliosis surgery

Open anterior surgical techniques for spinal

deformity correction were described first in thelate 1960s. Dwyer and colleagues [5] developeda vertebral screw and flexible cable system to

achieve coronal deformity correction by applyinga compressive force along the convexity of thespine. The Zielke system, developed in the 1970s,

replaced the Dwyer cable and used an anterior-threaded rod to treat short- and long-segment

* Corresponding author.

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

0030-5898/07/$ - see front matter � 2007 Elsevier Inc. All r

doi:10.1016/j.ocl.2007.05.003

deformities [6]. Since that time, open anteriorsurgical techniques and instrumentation have ad-vanced considerably. Current implant systems

use rigid, single- or dual-rod constructs to achievespinal realignment and stabilization.

During the early 1990s, anterior video-assisted

thoracoscopy was described by Regan and Mackand colleagues [7,8]. This technique provides analternate approach, through a limited chest wall

dissection, to achieve multilevel thoracic spinalrelease and instrumentation. Once mastered, thistechnically challenging approach theoreticallyaffords several advantages over the traditional

thoracotomy, including reduced pulmonary mor-bidity and postoperative pain, better visualization,and improved cosmesis.

The ultimate goals of all anterior spinal de-formity correction procedures remain the same.The primary concern is to visualize the spine and

obtain exposure that will allow spinal release andinstrumentation without damaging the surround-ing neurovascular structures. Secondarily, a thor-ough disc and ligamentous excision must be

performed to mobilize the spine maximally.Lastly, a solid interbody arthrodesis must beachieved after instrumentation and correction of

the spinal deformity. In general, surgical fusionsshould be as short as possible to minimize the lossof spinal flexibility, yet be long enough to ensure

optimal correction and lasting spinal balance.

Indications

Surgical indications for patients who haveadolescent idiopathic scoliosis are dependent on

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532 UPASANI & NEWTON

various factors. The risk for deformity progres-sion based on gender, bone age, and curvemagnitude plays a critical role when deciding

which patients need operative treatment [9–11].Studies of the natural history of this disease indi-cate that surgical treatment should be consideredin immature patients once the Cobb angle of their

major curve exceeds 40� to 45�, whereas more ma-ture patientsdwith a lower risk for curve progres-siondmay be observed until their major curve

exceeds 50� [1,2,12]. Curve pattern, trunk defor-mity (axial plane rotation), and balance alsoshould be considered when recommending surgi-

cal correction, because a single curve may creategreater trunk shift than a balanced double or tri-ple curve.

Combined anterior and posterior scoliosis pro-

cedures are primarily indicated in the treatmentof large (O75�) or rigid (bend correction !50�)spinal deformities. The anterior approaches (open

or thoracoscopic) enable maximal spinal mobili-zation before instrumentation, by allowing accessto the main anterior stabilizing structures of the

spine, including the annulus, the intervertebraldisc, and the anterior longitudinal ligament. Thedegree to which spinal flexibility can be increased

is dependent on the complete release of thesestabilizing structures. In the most severe cases,resection of the rib head and costovertebral jointmay be required to optimize spinal mobility.

Another indication for these combined ap-proaches is in the treatment of immature (Risser0 with an open triradiate cartilage) patients.

Unbalanced ablation of the posterior growthpotential, with continued anterior growth, isbelieved to cause a slowly progressive rotational

(‘‘crankshaft’’) deformity [13,14]. To prevent thisproblem, patients are treated often with an ante-rior release and fusion and a posterior instrumen-tation and fusion.

Combined procedures also are indicated inpatients who are at increased risk for pseudoarth-rosis formation, such as those with bone-healing

deficiency syndromes (eg, neurofibromatosis,Marfan syndrome) or a history of irradiation.An anterior discectomy provides a large surface

area of cancellous bone and allows for a circum-ferential fusion to increase the likelihood offorming a solid arthrodesis.

Anterior instrumentation has been associatedwith the potential to save one to three distal fusionlevels in the treatment of isolated major thoracic,thoracolumbar, or lumbar curves [15]. This proce-

dure also has been found to be kyphogenic and

ideally suited in the treatment of patients whohave a hypokyphotic or lordotic thoracic spine[16]; however, in the treatment of thoracolumbar/

lumbar curves, structural grafts are required tomaintain normal thoracolumbar sagittal align-ment. Double-rod, double-screw constructs alsomay allow additional control of the sagittal plane

in patients who have thoracolumbar curves [17].Anterior thoracoscopic techniques are more

amenable to the treatment of curves with certain

characteristics. For example, smaller curves (usu-ally !70�) with greater than 50% flexibility canbe treated appropriately with a single rod–screw

construct. Single structural thoracic curves andthose double or triple curves in which only thethoracic component is structural also are treatedmore readily with a single-rod anterior thoraco-

scopic procedure.

Contraindications

Impaired preoperative pulmonary function andthe presence of comorbidities associated with in-trathoracic or intra-abdominal visceral abnormal-

ities are two of the absolute contraindications toanterior scoliosis procedures. The pulmonary sta-tus of the patient must allow single-lung ventila-

tion; transthoracic and thoracoscopic approachesrequire selective deflation of one lung to allowadequate space within the chest cavity to exposeand instrument the spine. Vertebral body osteope-

nia, although rare in the adolescent idiopathicscoliosis population, is seen commonly in patientswho have neuromuscular disorders and may limit

anterior instrumentation options. Vertebral bodysize is another consideration; it may limit adequatefixation in small or underweight patients.

Obesity (O60–70 kg) may be another relativecontraindication to anterior thoracic instrumen-tation, because patients with an increased body

mass may be more prone to overstressing a single-rod anterior construct, resulting in implant failureor loss of deformity correction. Dual-rod anteriorconstructs may be more appropriate in obese

patients; they were shown to be more stiff bio-mechanically [18] and clinically equivalent [17] tosingle-rod instrumentation in achieving deformity

correction.Specific to anterior thoracoscopic surgery, the

existence of intrathoracic pleural adhesions from

prior thoracotomy procedures or pulmonaryinfections should be considered a relative contra-indication. Although minor adhesions can be

533ANTERIOR SURGERY FOR IDIOPATHIC SCOLIOSIS

divided, a near complete pleural symphysis be-tween the chest and lung can make adequate lungcollapse nearly impossible. In addition, althoughchildren weighing less than 30 kg have been

treated safely with the anterior thoracoscopicapproach, the relative benefit of this minimallyinvasive technique seems to be reduced in small

patients [19]. If visualization is inadequate at anypoint during the endoscopic procedure, conver-sion to an open approach must be considered. A

rigid spinal deformity or one that is too closely ap-proximated to the rib cage also is difficult to treatwith a thoracoscopic anterior procedure. Preoper-

ative radiographs should be reviewed to ensurea minimum working distance of 2 to 3 cm forthoracoscopic procedures.

Open anterior release and instrumentation

The thoracic spine is accessed most commonlythrough a single or double anterolateral thoracot-omy in patients who have idiopathic scoliosis.

Usually, a single thoracotomy is adequate toaccess seven or fewer levels between T4 throughT12, whereas a double thoracotomy may be

required to achieve exposure when more thanseven levels are going to be fused. In idiopathicscoliosis, the spine usually is approached from the

convexity of the curve (a right-sided thoracot-omy). Typically, the thoracolumbar/lumbar spine(T10–L5) is approached through a thoracoabdo-minal incision. This incision should cross the

costochondral junction before turning obliquelyacross the abdominal wall toward the lateralborder of the rectus abdominis sheath. A low

thoracotomy, with a tenth-rib resection, canfacilitate access to the thoracic cavity, the thor-acolumbar spine, and the retroperitoneal space.

After exposure of the spine has been achieved,the discs to be resected, and, if indicated, thevertebrae to be instrumented are verified usingintraoperative fluoroscopy or portable radio-

graph. A thorough discectomy is performed ateach subsequent level, with excision of the annu-lus and the anterior longitudinal ligament. In-

complete disc resection has been associated withsuboptimal mobilization of the spine and anincreased incidence of implant failure and pseu-

doarthrosis formation. At times, visualization ofthe posterior disc may require resection of the ribhead down to the base of the transverse process.

The cartilaginous superior and inferior endplatesalso must be separated completely from theadjoining vertebral bodies, and the bony end-plates should be decorticated with sharp curettes.

Fixed-head vertebral body screws, rangingfrom 5 to 7 mm in diameter, are used commonlyin patients who have idiopathic scoliosis. Prior to

screw placement, the superior and inferior end-plates, the anterior cortex, and the anterior aspectof the spinal canal should be understood clearly

for each vertebral body. Biomechanically,pronged staples and bicortical screw fixationsignificantly increased construct stiffness during

single-screw anterior vertebral body instrumenta-tion [20]. In addition, juxta-endplate screws pro-vided better fixation than did screws placed inthe traditional midvertebral location [21]. This

screw position seems to increase fixation strengthby butting the screw threads up against the supe-rior (or inferior) endplate of the vertebral body.

For dual-rod constructs, a two-hole vertebralbody staple should be placed carefully to allowappropriate positioning and trajectory of both

screws (Fig. 1A). All screw tips should be palpatedon the concavity of the deformity to ensure that

Fig. 1. (A) A two-hole vertebral body staple is used to allow appropriate positioning and trajectory of dual-screw im-

plants. (B) Dual-rod construct after deformity correction and rod implantation has been achieved.

534 UPASANI & NEWTON

they are not excessively long and are not causinginjury to adjacent neurovascular or visceral struc-tures. After all screws have been placed, the single

or dual rods (Fig. 1B) are prebent to the desiredcoronal and sagittal contour of the spine, looselyanchored within the screw heads, and then rotatedinto position to correct scoliosis and to restore the

normal sagittal contour of the spine. Beginningdistally, the disc spaces are wedged open, andthe interspaces are packed with bone graft.

Many bone-grafting materials are available: struc-tural and nonstructural grafts, autologous grafts,fresh-frozen and freeze-dried allografts, deminer-

alized bone matrices, and various synthetic bonesubstitutes. Regardless of the material used, it isimportant to ensure that both bony endplatesare well decorticated and able to provide good

vascularity to the graft material. Because the ante-rior approach tends to be kyphogenic, a structuralgraft may be necessary in the thoracolumbar and

lumbar spine to preserve the natural lordosis.Derotation, translation, and compression ma-

neuvers may be used during rod insertion to

achieve deformity correction. Scoliosis correctioncan be achieved directly by cantilevering the rodinto the vertebral screws or by rolling the precon-

toured rod from scoliosis into the sagittal plane.After tightening the proximal screws, furthercoronal correction can be obtained by sequen-tially compressing between screws along the

convexity of the curve. After the instrumentationis complete, the patient’s neurologic functionshould be assessed with a wake-up test or spinal

cord monitoring. Intraoperative radiographs alsoshould be obtained to confirm screw placementand evaluate the initial deformity correction.

Case example 1

A 14-year-old girl who has a progressive sco-liotic deformity presented after failed treatment

with a brace. Preoperative posteroanterior (PA)(Fig. 2A) and lateral (Fig. 2B) radiographs re-vealed that she was Risser 3 and had a 43� thora-columbar curve with a 32� compensatory rightthoracic curve. One-year after a left open anteriorspinal fusion from T11 to L3 with dual-rod instru-mentation, PA (Fig. 2C) and lateral (Fig. 2D) ra-

diographs revealed a 15� thoracolumbar curveand an 11� thoracic curve.

Thoracoscopic anterior release

and instrumentation

Similar to open anterior procedures, the leftlateral decubitus position allows optimal access to

the right thoracic spine and enables greatercircumferential access to the vertebral bodiesand discs during the thoracoscopic approach.

Maintaining spatial orientation is more difficult

Fig. 2. A 14-year-old girl who had a progressive scoliotic deformity presented after failed treatment with a brace. Pre-

operative PA (A) and lateral (B) radiographs revealed that she was Risser 3 and had a 43� thoracolumbar curve with

a 32� compensatory right thoracic curve. One year after a left open anterior spinal fusion from T11 to L3 with dual-

rod instrumentation, PA (C) and lateral (D) radiographs revealed a 15� thoracolumbar curve and an 11� thoracic curve.

535ANTERIOR SURGERY FOR IDIOPATHIC SCOLIOSIS

during endoscopic spinal surgery. Positioning thesurgeon and the assistant anterior to the patientwith the video monitor properly aligned and

oriented behind the patient allows access to thespine from the most natural viewing perspective.

Single-lung ventilation with a double-lumenendotracheal tube is performed to deflate the right

lung selectively before port placement. The loca-tion of the ports is determined using anatomiclandmarks and fluoroscopic guidance to optimize

access to all motion segments planned to beinstrumented. The number of ports required de-pends on the type of deformity being treated and

the number of levels being instrumented. Gener-ally, three portals along the posterior axillary lineare used for instrumentation, and two portals

along the anterior axillary line are used forexposure and release of the anterior spine. Ante-rior axillary ports allow greater exposure of the

Fig. 3. A harmonic scalpel is used to create a longitudi-

nal opening of the pleura.

Fig. 4. The initial pleural opening is performed superfi-

cial to the segmental vessels. A segmental artery and vein

is seen crossing the midportion of the vertebral body.

concave aspects of the deformity during disc exci-

sion and retraction of the great vessels.Angled optics should be used to ensure that the

tip of the working instrument is visualized at all

times. A fan retractor is placed through one of theposterior axillary ports to retract and protect thedeflated lung. After confirming anatomic levelsusing intraoperative fluoroscopy, a harmonic scal-

pel is used to create a longitudinal opening of thepleura (Fig. 3). The initial pleural opening isperformed superficial to the segmental vessels

(Fig. 4). Limited exposure of the discs is accom-plished by retracting the pleura between the vessels.To broaden the exposure anteriorly, the segmental

vessels are coagulated and divided with the har-monic scalpel (Fig. 5). To achieve optimal hemosta-sis, the energy from the harmonic scalpel is applied

slowly over a 3- to 5-mm length of the vessel.

Fig. 5. The segmental vessels are coagulated and divided

with the harmonic scalpel to minimize bleeding while

broadening the exposure.

Fig. 6. A packing sponge is inserted between the ante-

rior spine and pleura to create a space and protect adja-

cent neurovascular structures.

536 UPASANI & NEWTON

After dividing the pleura, the loose areolartissue is divided, and a space is created betweenthe anterior spine and pleura using packing

sponges (Fig. 6). Directly lateral to the anteriorspine, the azygos vein and other great vesselscan be identified and must be avoided during thediscectomy procedure (Fig. 7). Circumferential ex-

posure of the spine and discs should be completedbefore excising the discs. Distal exposure to theT12–L1 disc space may require division of the di-

aphragm insertion. To accomplish this, the longi-tudinal pleural incision is extended onto theinferiorly retracted diaphragm, and blunt dissec-

tion is used to strip the diaphragm off the anterioraspect of the spine.

Disc excision is initiated by performing a cir-cumferential annulotomy using the ultrasonic

blade. An up-biting rongeur is used first to removethe most anterior and concave aspect of theannulus. A complete discectomy requires optimal

visualization deep into the disc space, ensuringthat the integrity of the posterior longitudinalligament is maintained and that the neural ele-

ments are protected. The superior and inferiorcartilage endplates are dissected sharply, and anangled curette or rongeur is used to decorticate

the bone. An endplate shaver inserted into eachintervertebral space may be used to ensure thatcomplete disc excision has been performed andthat the spine is mobile (Fig. 8). Hemostasis is

maintained by placing an oxidized cellulose agentin each intervertebral space.

To prepare for screw/rod implantation, a

15-mm port is placed between the ribs throughthe skin incisions along the posterior axillary line(Fig. 9). Each screw should be started in the mid-

aspect of the vertebral body just anterior to the rib

head articulation (Fig. 10). An awl is used first todetermine the screw path. Then, the vertebral

body is tapped, and a ball-tipped calibrated probeis used to determine screw length. The screwsshould achieve bicortical purchase; however, ex-

cessive screw penetration should be avoided toprotect adjacent neurovascular structures (aorta).After insertion of all of the screws, the fixed-angle

screw heads are aligned for rod insertion, and theintervertebral spaces are packed with bone graftusing a tubular plunger device.

Deformity correction is accomplished by can-

tilevering a precontoured rod into position(Fig. 11), and segmental compression is per-formed using an endoscopic compressing device

(Fig. 12). Following rod insertion, the pleura is re-approximated and closed over the instrumenta-tion using the EndoStitch device. Beginning

distally, the suture needle is passed through bothsides of the cut pleura or diaphragm, and an

Fig. 7. The contralateral segmental vessels and azygos

vein can be identified directly under the anterior spine.

Fig. 8. (A) An endplate shaver is inserted into each intervertebral space to ensure that a complete discectomy has been

performed and that the spine is optimally mobilized. (B) The posterior longitudinal ligament can be visualized by open-

ing the disc space to ensure that the spinal cord is protected.

537ANTERIOR SURGERY FOR IDIOPATHIC SCOLIOSIS

externally tied knot is slid down securely intoplace. The suturing device allows a double-endedneedle to be passed from one jaw to the other,

and a simple running closure of the pleura is per-formed (Fig. 13).

Case example 2

A 12-year-old girl who had adolescent idio-

pathic scoliosis and a progressive deformity pre-sented with preoperative PA (Fig. 14A) andlateral (Fig. 14B) radiographs that revealed she

was Risser 0, had a 43� thoracic curve, and hada 28� thoracolumbar curve. One year after an an-terior thoracoscopic release, T6 to T12 single-rodinstrumentation, and fusion with iliac crest bone

graft, PA (Fig. 14C) and lateral (Fig. 14D) radio-graphs revealed a 19� thoracic curve and a 10�

thoracolumbar curve.

Fig. 9. A 15-mm port is placed between the ribs through

skin incisions along the posterior axillary line to prepare

for instrumentation.

Fig. 10. A tap is used to ensure that the vertebral body

screw insertion is juxta-endplate to provide for superior

fixation.

Complications

The incidence of major complications, includ-ing death, paraplegia, or deep wound infections

after open or thoracoscopic procedures to in-strument the anterior thoracic/thoracolumbarspine, are less than 1% [22]. As would be ex-

pected, pulmonary complications account formore than 50% of the morbidity associated withthese procedures [23,24]. Most of time, these pul-

monary issues are related to postoperative pleuraleffusions, pneumothorax, atelectasis, or excessivechest tube drainage. Preoperative pulmonary

function studies can be obtained to prevent orplan for postoperative respiratory issues. An eval-uation of pulmonary function after open versusthoracoscopic anterior procedures revealed that

pulmonary function recovered more quickly afterthe less invasive procedure; this difference wasmaintained at the 2-year follow-up [25]. Other

Fig. 11. The precontoured rod is cantilevered into posi-

tion to obtain deformity correction.

Fig. 12. Segmental compression is performed to obtain

coronal plane deformity correction.

538 UPASANI &

infrequently reported complications after anteriorscoliosis surgery include injury to the great vessels,

ureter, or spinal cord and development of a retro-peritoneal hematoma or fibrosis.

Outcomes

When evaluating anterior thoracoscopic re-

lease procedures, several animal studies reportedthe ability to achieve similar amounts of spinalmobilization compared with open techniques

Fig. 13. The EndoStitch device is used to suture the

pleura over the instrumentation.

[26–28]. A radiographic analysis also demon-strated a similar ability to achieve coronal andsagittal plane correction when comparing the

two techniques [29]; however, the thoracoscopicprocedure is technically challenging, and the steeplearning curve described by Newton and col-leagues [30] must be overcome to perform this

procedure safely and efficaciously. A series of112 consecutive cases of thoracoscopic anteriorrelease and fusion with more than 2-years of fol-

low-up revealed that clinical failures were exceed-ingly rare and that the primary goals of increasingspinal flexibility and achieving a solid arthrodesis

occurred in most cases [31].Several studies evaluated surgical outcomes in

patients who had idiopathic scoliosis by compar-ing anterior and posterior instrumentation

methods. In 1999, Lenke and colleagues [32] re-ported a greater main thoracic curve and sponta-neous thoracolumbar/lumbar curve correction

following selective anterior fusion comparedwith posterior instrumentation. Multiple investi-gators confirmed these findings and demonstrated

the ability of anterior instrumentation to achievesuperior radiographic results with the fusion offewer vertebral levels [33–35]; however, these early

studies compared anterior instrumentation tech-niques with posterior hook or hybrid constructs.

NEWTON

Fig. 14. A 12-year-old girl who had adolescent idiopathic scoliosis and a progressive deformity presented with preop-

erative PA (A) and lateral (B) radiographs that revealed she was Risser 0, had a 43� thoracic curve, and a 28� thoraco-lumbar curve. One year after an anterior thoracoscopic release, T6 to T12 single-rod instrumentation, and fusion with

iliac crest bone graft, PA (C) and lateral (D) radiographs revealed a 19� thoracic curve and a 10� thoracolumbar curve.

539ANTERIOR SURGERY FOR IDIOPATHIC SCOLIOSIS

In 2005, Potter and colleagues [36] evaluatedposterior instrumentation with thoracic pediclescrews; in some cases, posterior surgery providedbetter coronal and axial correction compared

with thoracic anterior instrumentation. Anteriorscoliosis procedures with single-rod constructsalso have been associated with an increased rate

of pseudoarthrosis and an increased rate of im-plant failure compared with posterior instrumen-tation [37]. Dual-rod constructs were developed

to provide more rigid fixation and were found toincrease mechanical stiffness [17,18]; however, ver-tebral body size restrictions make it difficult to

place these implants in the adolescent thoracicspine.

Two-year follow-up has been reported forthoracoscopic anterior instrumentation. In a series

of 50 consecutive patients [38], curve correctionaveraged 60%, with an average operating timeof 5.8 hours. This initial series of patients sug-

gested that thoracoscopic instrumentation wasa viable option in the treatment of adolescent idi-opathic scoliosis; however, success remained de-

pendent on patient selection and the surgeon’stechnical ability. Eighteen of the first 20 consecu-tive patients of this series now have more than

5-year follow-up; deformity correction and abso-lute pulmonary function have been maintained,and successful bony fusion has occurred at 92%of the motion segments (unpublished data).

Summary

The anterior surgical treatments for idiopathic

scoliosis continue to evolve and provide advan-tages over posterior procedures in specific in-stances. Open and thoracoscopic anterior

approaches allow direct access to the anteriorstabilizing structures of the spine, enable mobili-zation of a rigid deformity, and provide a large

surface area for arthrodesis; however, these pro-cedures are associated with increased rates ofpulmonary compromise, and long-term studieshave not been completed to determine their ability

to maintain deformity correction relative to mod-ern posterior segmental pedicle screw constructs.

Thoracoscopic procedures are technically de-

manding and surgeon experience must be consid-ered before recommending this procedure tocarefully selected patients; however, they do pro-

vide a more cosmetically appealing alternative toa large midline posterior or anterolateral thora-cotomy scar. Although the indications and

contraindications for anterior versus posteriorsurgical intervention (for thoracic and thoraco-lumbar curve patterns) have been defined to somedegree, there remains appropriate flexibility in the

decision-making process, allowing the surgeon tomake an optimal recommendation for each pa-tient based on surgeon experience and patient

needs.

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