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Thoracoscopic Anterior Instrumentation and Fusion for Idiopathic Scoliosis Daniel J.. Posterior segmental spinal in-strumentation was an advance over Harrington instrumentation because i

Thoracoscopic Anterior Instrumentation and Fusion for Idiopathic Scoliosis

Daniel J Sucato, MD, MS

Abstract

Surgical treatment for idiopathic

scolio-sis has changed rapidly in the last 20

years Posterior segmental spinal

in-strumentation was an advance over

Harrington instrumentation because

it improved correction in the sagittal

and coronal planes.1,2The single solid

rod used with anterior surgery was

an improvement over the Dwyer

ca-ble, especially for thoracolumbar and

lumbar curves, because it allowed

sur-geons to use a rotational maneuver

to correct both the sagittal and

coro-nal deformities.1,2Recently, the single

solid rod placed through an open

racotomy has been used to correct

tho-racic curves.3,4Anterior correction of

thoracic scoliosis offers the theoretic

advantage of better coronal correction

because it permits the surgeon to

per-form diskectomies, provides

improve-ment in the thoracic hypokyphosis seen

in idiopathic scoliosis, and saves

mo-tion segments In a prospective study,

Betz et al4demonstrated that anterior

surgery improved sagittal plane

align-ment while saving an average of 2.5

distal motion segments compared with

posterior surgery

In the last decade, indications have increased for endoscopic

approach-es to thoracic spine surgery Endos-copy was first used for biopsy and disk-ectomy as well as for anterior release and fusion, in combination with pos-terior spinal fusion and instrumenta-tion, to treat severe curves or when there was risk for the development of the crankshaft phenomenon.5-7The en-doscopic approach also has been used

to perform an anterior instrumen-tation, correction, and fusion Early results are encouraging, but the tech-nique requires further study and im-provement

Patient Selection and Preoperative Planning

The indications for anterior instrumen-tation and fusion include single tho-racic curves or thotho-racic curves with

a compensatory lumbar and/or up-per thoracic curve, that is, type IA, IB,

or IC curves using the Lenke classi-fication.8It is important to determine the curve type for preoperative

plan-ning so that the appropriate thoracic curve correction is achieved,

especial-ly in the setting of a so-called selec-tive thoracic fusion in the IC curve type The ideal patient for thoraco-scopic anterior instrumentation and fusion is one who has a relatively small curve size (50° to 65°) of relative flex-ibility (>50% flexflex-ibility index); is thin (40 to 60 kg), which makes placement and utilization of the portals easier; and is tall, because the sizable chest provides a greater working space and larger vertebral bodies for easier in-sertion of screws For surgeons with experience in the technique, the in-dications can include stiffer curves of

up to 75° The primary contraindica-tion for the procedure is poor pulmo-nary function, which limits the pa-tient’s ability to tolerate single-lung ventilation All patients should have preoperative pulmonary function tests

to assess their ability to tolerate the

Dr Sucato is Assistant Professor, Department of Orthopaedic Surgery, University of Texas at Southwestern, and Staff Orthopaedist, Texas Scot-tish Rite Hospital, Dallas, TX.

The author or the department or departments with which he is affiliated has received something of

val-ue from a commercial or other party related di-rectly or indidi-rectly to the subject of this article Reprint requests: Dr Sucato, 2222 Welborn Street, Dallas, TX 75219.

Copyright 2003 by the American Academy of Orthopaedic Surgeons.

Thoracoscopically assisted surgery is a new approach to access the anterior spine to

perform biopsies, anterior releases, diskectomies, and anterior instrumentation and

fusion for idiopathic thoracic scoliosis This approach compromises the chest wall

less than an open thoracotomy does because it uses several small portal incisions.

It has been suggested that this approach allows fusion of fewer motion segments

and better correction of curvature than does posterior spinal fusion and

instrumen-tation The technique, which is still evolving, is technically demanding, requiring

advanced training and special instrumentation and anesthesia techniques.

J Am Acad Orthop Surg 2003;11:221-227

procedure and to help predict the

post-operative course Pulmonary function

test findings below 60% of predicted

results are a relative contraindication

to anterior thoracic surgery

Preoperative assessment of the

pa-tient should include a physical

exam-ination to confirm radiographic

find-ings that the upper thoracic and lumbar

curves are compensatory without any

structural characteristics Imaging

should include standing lateral and

posteroanterior and supine bending

right and left radiographs The lateral

radiograph should be used to ensure

that excessive kyphosis (>40°) is not

present This is a contraindication for

anterior correction because, when

com-pression is used, anterior correction

can increase kyphosis.9Fusion levels

for the thoracic curve are determined

on the posteroanterior radiograph,

us-ing the superior and inferior end

ver-tebrae of the Cobb measurement as

the upper and lower end instrumented

vertebrae In a smaller patient or one

who has marked tilt of the upper end

instrumented vertebrae, a level

supe-rior to the end vertebra may be

cho-sen to provide greater fixation because

of the risk of cutout of the superior

screws Analysis of the lower end

ver-tebra may reveal that the disk

prox-imal to it is in fact neutral If so, the

more proximal level may be chosen

as the lower end instrumented

ver-tebra Supine bending radiographs are

important to confirm that the lumbar

and upper thoracic curves are truly

compensatory (bend to <25°)

Bend-ing radiographs are used to determine

the flexibility of the thoracic curve so

that a coronal bend may be placed in

the rod if the curve is stiff

Anesthesia Considerations

Maintaining a proper airway during

anesthesia is critical to the success of

thoracoscopic surgery To perform

an-terior instrumentation and fusion, the

lung on the convexity of the curve

must be deflated, and single-lung

ven-tilation techniques are used This is typically accomplished with a double-lumen endotracheal tube, which has

a bronchial lumen that sits in the de-pendent mainstem bronchus and a tra-cheal lumen that lies just proximal to the carina (Fig 1) The dependent lung

is ventilated through the bronchial lu-men, while the lung on the convex-ity of the curve becomes deflated when the tracheal lumen is occluded It is important to recheck tube placement after the patient is in the lateral de-cubitus position because, in up to 80%

of cases, the tube tends to move dis-tally.10

Patients undergoing single-lung ventilation are subjected to significant stresses from the right-to-left shunt through the dependent lung and from that lung’s decreased functional ca-pacity, the result of increased intra-abdominal pressure and compression from the weight of the mediastinal structures The high pressures that re-sult can lead to airway leaks or

trau-ma, which can cause pneumothorax

The so-called down lung syndrome, seen most frequently with lengthy surgeries, is characterized by absorp-tion atelectasis, accumulaabsorp-tion of se-cretions, and formation of transudate

in the dependent lung The anesthe-siologist needs to be skilled in the technique to minimize the chance of anesthetic complications.11,12

Patient Positioning and Operating Room Setup

The patient is positioned in the lat-eral decubitus position on a radio-lucent operating table with the con-vexity of the curve up (Fig 2) An absolutely lateral position is critical, especially during screw placement, and should be checked periodically

to ensure that it is maintained through-out the procedure The patient may

be secured using an inflatable radio-lucent beanbag or other positioning system Whatever method is used, the patient’s spine must be palpable

pos-teriorly, and the umbilicus visible an-teriorly, to allow orientation and ex-posure in case conversion to an open thoracotomy is necessary The thora-cotomy tray should be available in the operating suite The arm on the con-vexity of the curve can usually be po-sitioned out of the sterile field, espe-cially when the upper instrumented level is at T5 or below However, when the upper instrumented level is above T5, the arm may be incorporated into the sterile field to provide better con-trol of the patient’s arm and scapula, making proximal portal placement easier

One or two surgeons are positioned

on the posterior aspect and one on the anterior aspect of the patient The scrub assistant is usually anterior The video monitors should be at the head of the table on both sides of the patient to give the surgeons on each side a di-rect view The fluoroscopy C-arm unit

is brought in anteriorly when screws are placed, with the monitor at the foot

of the table

Although some surgeons perform the diskectomy on the posterior as-pect, the anterior position allows bet-ter control of posbet-terior penetration be-yond the posterior anulus fibrosus and

Figure 1 Correct positioning of the double-lumen endotracheal tube to ventilate the left lung The bronchial lumen should be just dis-tal to the carina and the tracheal lumen just proximal to the carina The tracheal lumen is occluded to allow for selective ventilation of the left lung.

posterior longitudinal ligament

Dur-ing screw placement and

instrumen-tation, the surgeon may be more

com-fortable at the posterior aspect of the

patient because leaning over the

op-erating room table is then

unneces-sary, and it is safer to direct the screws

slightly anteriorly

Surgical Procedure

Portal Placement

Accurate placement of the portals

is critical because they determine the

approach for the diskectomies and,

more important, the screw starting

points and directions Before the

pa-tient is prepared and draped, the

spi-nal levels to be instrumented are

lo-cated fluoroscopically in the coronal

and sagittal planes, and the skin is

marked In general, the incision for

the portals should be directly over the rib so that two portals (above and be-low the rib) can be used for each in-cision

A single anterolateral portal is placed at the apex of the curve in the anterior-to-midaxillary line, and the thoracoscope is placed through this portal The thoracoscope consists of

a camera and a scope that is angled

at 30° or 45° Seen from the antero-lateral portal, the spine is horizontal

on the monitor; seen from the postero-lateral portal, the spine is vertical, giv-ing a good “pipeline” view (Fig 3) The scope should be oriented to see the disks straight on when the tho-racoscope is in the anterolateral por-tal This is best achieved by keeping the orientation light from the lens per-pendicular to the spine, with the scope handle at the 3-o’clock position when looking at the most cephalad disk (Fig

4, A) and at the 9-o’clock position when looking at the most caudad disk (Fig 4, B) This position allows visu-alization down the axis of the disk space and provides a true anteropos-terior view of the vertebral bodies The posterolateral portals are made under direct visualization The place-ment of the most cephalad portal is very important for proper instrumen-tation The skin mark initially made under fluoroscopic visualization is used to place a guide pin, which is then assessed using the camera in the anterolateral portal The ribs should

be counted to check the level of the

Figure 2 Operating room setup.

Figure 3 Thoracoscopic video images A, With the thoracoscope in the anterolateral portal,

the spine is horizontal on the monitor and provides a good assessment of the superior and

inferior extent of each vertebral body B, With the thoracoscope in one of the posterolateral

portals, the spine is more vertical on the monitor “pipeline” view, providing a good assess-ment of the anterior and posterior aspects of the spine The diaphragm is visible at the top

of the image.

guide pin If the pin is not

sufficient-ly superior or posterior to allow the

surgeon to place the proximal screw,

the pin is moved and the portal

in-serted The camera may then be placed

through that portal to check the

po-sition further

The remaining posterolateral

por-tals are then placed, with close

atten-tion paid to the distances between

portals and their positions in the

an-teroposterior and superoinferior

di-rections Positioning is assessed with

the thoracoscope in the anterior

por-tal to ensure that the porpor-tals are made

directly over the vertebral bodies A

typical portal configuration for a

seven- or eight-level instrumentation

is a single anterolateral portal and

four posterolateral portals (Fig 4, C)

Various portal configurations have

been described, including

posterolat-eral portals only or a combination of

three anterolateral with three

pos-terolateral portals

Disk Excision and Bone Grafting

Disk excision is the most important aspect of the procedure The surgeon incises the pleura in the midvertebral body, then coagulates the segmental vessels The pleura should be bluntly teased posteriorly past the rib heads and anteriorly around the front of the spine to allow access to the anterior longitudinal ligament and contralat-eral anulus Sharp incision of the disk can be made with a scalpel blade or harmonicscalpel.Diskshavers,rongeurs, and curettes are used to excise the disk

as completely as possible (Fig 5) An-imal studies comparing open thora-cotomy with thoracoscopic techniques havedemonstratedcomparableamounts

of diskectomy.13,14A quantitative anal-ysis of computed tomography (CT)

in 12 adolescent patients (mean age, 13.3 years) demonstrated that a mean

of 73% of the disk and end plate was removed, allowing correction from a mean of 55° to a mean of 9°.15

Autologous rib or iliac crest bone grafts can be used and probably are best placed immediately upon com-pletion of the diskectomy at each

lev-el Bone funnels are used to place the grafts and should start in the depths

Figure 4 A,Use of the thoracoscope in the anterolateral portal To view the proximal (cephalad) portion of the spine, the camera is po-sitioned parallel to the floor and the light source handle is at the 3-o’clock position The spine appears horizontal on the monitor (inset).

B,To view the distal (caudad) aspect of the spine, the camera is positioned parallel to the floor and the light source handle is at the 9-o’clock

position This keeps the spine horizontal on the monitor (inset) C, Portal placement for a typical thoracic idiopathic curve The anterolateral

portal is made in the anterior axillary line at the apex of the curve.

Figure 5 Axial CT scan of a thoracic disk space after diskectomy and bone grafting done as part of an anterior thoracoscopic in-strumentation and fusion Note the bone graft material (arrows) packed all the way to the opposite side of the disk space and posteri-orly The rod is seen on the right side of the vertebral body.

of the disk space to ensure that the

grafts are packed completely

Screw Placement

Before screws are placed, the

pa-tient’s position should be rechecked

toensureitisdirectlylateral.Thefluo-roscopic image should be at right

gles to the vertebral bodies in the

an-teroposterior projection and is used

to confirm that the screw is oriented

parallel to the end plate The

thora-coscope is placed in the anterior

por-tal initially to direct the guidewire

with respect to the superoinferior

starting point and orientation The

thoracoscope is then moved to a

pos-terolateral portal to check the

antero-posterior starting point and its

direc-tion The anteroposterior fluoroscopic

images are then used to fine-tune the

starting point in the superoinferior

di-rection

Screws are placed beginning at the

apex of the curve, with the starting

point of the screw just anterior to the

rib head The screws are directed

slightly anteriorly to avoid the spinal

canal and to be in the midaxial plane

of the rotated apical vertebral bodies

This screw orientation allows for

ro-tational correction during rod

inser-tion and compression As screws are

placed proximal and distal to the apex,

the starting holes move slightly more

anteriorly The cephalad screws are the

most difficult to place accurately with

good purchase because the vertebral

bodies are smaller, the rib heads

ob-scure more of the vertebral bodies, and

the proximal portals are often not

ide-ally placed The proximal screws must

be placed with great care and

atten-tion to anatomic landmarks to ensure

that these screws are not too

poste-rior, which could lead to spinal canal

penetration, but are posterior enough

to allow secure purchase in good bone

stock (Fig 6) It is often necessary to

remove the rib heads at T5 and T6 to

gain good access to the vertebral

bod-ies at these levels

Present instrumentation systems

are modifications of open anterior

strumentation systems, with all in-struments made to fit through a 10.5-mm–diameter portal Screws in sizes from 5.5 to 7.5 mm and rods in 4.0-, 4.5-, and 4.75-mm diameters are avail-able The proximity of the aorta to the vertebral bodies in the upper and midthoracic spine limits the amount

of bicortical screw purchase that can

be achieved16 (Fig 6) In the lower thoracic spine in a patient with idio-pathic scoliosis, the aorta is posi-tioned more anterior to the vertebral body Newer instruments allow the surgeon to place screws without the use of the guide wire, which can lead

to complications with inadvertent ad-vance across the vertebral body

Rod Insertion and Correction Maneuvers

The stiffness of the curve, the pur-chase of the most proximal screws, and whether maximum correction is desired (Lenke IA curve) will deter-mine whether a small coronal bend should be placed in the rod before in-serting it into the chest In taller pa-tients with smaller, more flexible curves and larger vertebral bodies, no coronal bend in the rod is necessary

In patients with a very lordotic tho-racic segment, a kyphotic bend can

be placed in the rod

The rod is inserted through the dis-tal or proximal posterolateral pordis-tal and grasped within the chest with a rod grabber so that it can be seated into the screws in one step The rod

is initially seated distally to help con-trol the length of rod that protrudes distal to the screw and prevent it from pushing against the diaphragm

Two correction maneuvers are per-formed: compression and cantilever

Because the rod is essentially straight

in the coronal plane, in contrast with the deformity, the rod can be seated only in the distal three or four screws

Initially, compression is performed across these screws, followed by can-tilevering the rod down into the re-maining proximal screws After the rod is captured in the proximal screw

heads, compression is then

complet-ed at these levels with care taken to avoid excessive force on the top screws The securing plugs are then tightened fully The surgeon must be sure to place the guide sleeve over the screw or grasp the rod to produce a countertorque to prevent screw mi-gration or “plowing.” Anteroposterior and lateral radiographs or

fluoroscop-ic images should be checked to en-sure that all screws are safely posi-tioned and that correction is adequate

in the coronal and sagittal planes

Pleural Closure and Chest Tube Insertion

The pleura can be closed to help decrease chest tube output, limit de-velopment of lung adhesions, and contain the bone graft in the disk space Diaphragmatic repair is incor-porated into the pleural closure when the instrumentation extends to T12 or L1 The pleura is closed with an En-dostitch device (US Surgical, Nor-walk, CT), running a suture begin-ning distally and another beginbegin-ning proximally, which then meet in the center so that they can then be tied easily A chest tube is placed through the incision of the most distal poste-rior portal skin incision Because of the single, small-diameter rod, all

pa-Figure 6 Axial CT scan of a thoracic ver-tebral body after anterior thoracoscopic in-strumentation and fusion The starting posi-tion of the screw is just anterior to the rib head The outline of the aorta is seen at approxi-mately 1 o’clock, just posterior to the left mainstem bronchus The screw has one to two threads engaging the opposite cortex; how-ever, the screw tip is close to the aorta.

tients should wear a brace during the

day (when not sleeping) for the first

3 months

Early Results

In one series of 28 girls (average age,

12.1 years) with a mean preoperative

curve of 55° (range, 46° to 78°), the

mean postoperative curve at 1 year

was 14° (74.5% correction)15(Fig 7)

Complications included six proximal

screws that partially pulled from the

vertebral body at the time of

compres-sion in four patients; two screws that

cut out at the time of insertion because

of small vertebral bodies in two

pa-tients; guidewire migration into the

spinal canal in one patient, with

re-sultant dural leak without neurologic

sequelae; and asymptomatic

pseudar-throsis in one patient who underwent

a posterior spinal fusion.15

Picetti and Bueff17reported

follow-ups over 2 years on 50 patients (mean

age, 12.7 years) with a mean

preop-erative curve of 58° Improvements in

techniques resulted in enhanced

cor-rection and fewer complications over the course of this series Mean curve correction was 50.1% in the first 10 pa-tients and 68.6% in the last 10 Sur-gical time improved from a mean of

6 hours 6 minutes in the initial 30

cas-es to 3 hours 58 minutcas-es in the last

10 cases Mean blood loss was 266

mL The chest tube was in place for

a mean of 2.25 days (range, 1 day to

5 days), and hospital stay averaged 2.9 days (range, 2 to 7 days)

Report-ed complications includReport-ed one screw pullout, three patients with chest wall numbness, five mucous plugs, one wound revision, and two rod frac-tures A demineralized bone matrix product was used in the initial pa-tients, resulting in a high incidence

of pseudarthrosis; however, only 1 patient of the remaining 35 had a pseudarthrosis when autologous rib graft was used.17

Complications

There are no published series of pa-tients who have had thoracoscopic

in-strumentation and fusion for idio-pathic scoliosis, so the prevalence of complications is not known How-ever, complications that have been presented and discussed at scientific meetings can be categorized as anesthesia-related and surgical The anesthesia-related complications in-clude the down lung syndrome, with significant atelectasis present on the initial chest radiograph; inability to tolerate single-lung ventilation and conversion to an open technique or posterior spinal fusion; inability to ob-tain single-lung ventilation because

of difficulty in tube placement; and pneumothorax secondary to high air-way pressures.12Because this proce-dure is new and technically demand-ing, the incidence of complications can be high, especially early in the surgeon’s experience Complications that can occur during surgery include blood vessel injury, lymphatic injury with resultant chylothorax, guide-pin migration into the opposite side of the chest with resultant pneumothorax,18 distal migration or plowing of the screw when the rod is seated

prox-Figure 7 Preoperative anteroposterior (A) and lateral (B) radiographs of a 13-year-old girl with a 56° right thoracic idiopathic curve with

a notable trunk shift to the right and hypokyphosis (panel B) Anteroposterior (C) and lateral (D) radiographs 1 year after anterior

tho-racoscopic instrumentation from T5 to T12, with near-complete correction of the coronal plane deformity and restoration of the normal sag-ittal profile.

imally or is compressed, and screw

cutout at the time of screw insertion

Summary

The endoscopic approach to curve

cor-rection, instrumentation, and fusion

for spinal deformity is a new technique

that promises improved patient care

because it limits the surgical incision

and chest wall compromise, improves

postoperative pain and pulmonary

function, and enhances cosmesis

Compared with posterior

instrumen-tation, anterior instrumentation by ei-ther open or thoracoscopic approach can save fusion levels while improv-ing three-dimensional correction

However, no studies have directly compared thoracoscopic instrumen-tation and fusion with open anterior and/or posterior procedures, making any conclusive statements impossible

A multicenter prospective study may

be needed to fully elucidate the ad-vantages this technique may have and

to help define the exact indications for

a thoracoscopic approach to treat scoliosis

Several important issues must be kept in mind First, the proposed ad-vantages have not been confirmed through scientific study Second, the technique continues to evolve to de-crease the duration of surgery while maintaining the safety of the proce-dure Third, screw migration and proximity of screws to important soft-tissue structures need further study Finally, this is a technically demand-ing procedure with a steep learndemand-ing curve and may not be appropriate for all surgeons who treat spinal defor-mity

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