Thoracoscopic Release and Fusion for Scoliosis

 

 

 

DEFINITION

Thoracoscopy provides the ability to gain access to the thoracic spine via small incisions (portals).

Anterior release includes removal of the annulus fibrosus, anterior longitudinal ligament, nucleus pulposus, and, if necessary, the rib head.

Scoliosis is a lateral curvature of the spine with axial plane rotation.

Fusion is the healing of two vertebral bodies together, usually fused by bone graft or bone graft substitute.

 

 

ANATOMY

 

The thoracic spine spans from the first thoracic vertebra (T1) to the 12th thoracic vertebra (T12).

 

The rib head attachment to the vertebral body is more anterior in the proximal thoracic spine than the distal thoracic spine.

 

The annulus fibrosus is the circumferential fibrous tissue that surrounds the nucleus pulposus, which is in the center of the disc.

 

The anterior longitudinal ligament, which runs on the anterior aspect of the vertebral body, is a strong fibrous tissue that is contiguous throughout the spine. The segmental arteries and veins originate from the aorta and vena cava, respectively, and traverse the vertebral body. The parietal pleura of the chest surrounds the thoracic spine, covering the segmental vessels and the disc and vertebral bodies. The anterior, middle, and posterior axillary lines run (in reference to the axilla) in the anterior, middle, and posterior aspects of the axilla. Scoliotic deformity in the thoracic spine is lateral curvature with axial plane rotation as well as hypokyphosis (idiopathic scoliosis).

 

The arch of the aorta and the arch of the azygos vein typically are located at the T4-T5 levels.

 

PATHOGENESIS

 

Scoliosis can be grouped into many categories based on pathogenesis.

 

The most common type of scoliosis seen is idiopathic, in which the etiology and pathogenesis are unknown.

 

Theories of pathogenesis include hormonal influences, growth disturbance, genetic factors, muscle imbalance, and proprioception and balance abnormalities.

 

Other types of scoliosis include the following:

 

 

Congenital: abnormal vertebra due to failure of formation or segmentation

 

 

Neuromuscular: for example, cerebral palsy, Duchenne muscular dystrophy, spinal muscular atrophy Neurogenic: for example, neurofibromatosis, spinal cord injury

NATURAL HISTORY

 

An idiopathic scoliosis curve may progress in two ways:

 

 

With continued spine growth

 

When curve magnitude is greater than 50 degrees at skeletal maturity

 

Curve progression can be rapid during spine growth or slow following skeletal maturity (approximately 1 degree per year).

 

 

Curve magnitudes above 80 to 90 degrees in the thoracic spine may result in symptomatic pulmonary issues. Large curves in adulthood can result in pain.

PATIENT HISTORY AND PHYSICAL FINDINGS

 

The examination for spine deformity should include standing visualization of the spine to look for shoulder height differences, waist asymmetry, overall trunk balance, or coronal head imbalance (FIG 1).

 

Further information is obtained as to the character of the pain (eg, sharp, dull, aching), when the pain occurs (eg, during activity, while attempting to sleep, pain waking from sleep), and the location of the pain (eg, upper, middle, lower back) as well as whether it radiates into the lower extremities.

 

Other history should include any information on other neurologic symptoms such as bowel or bladder incontinence.

 

Sensory symptoms should be elicited, especially with hyperesthesias along the chest wall or upper or lower extremities.

 

Cutaneous manifestations of dysraphism should be analyzed.

 

 

 

FIG 1 • A,B. This 9-year-old boy has a left-sided large thoracic scoliosis but no evidence of neural axis abnormalities on preoperative MRI.

 

 

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The neurologic examination should include motor strength and a sensory examination of the upper and lower extremities.

 

The abdominal reflexes are the most important neurologic assessment. They are assessed by stroking the skin adjacent to the umbilicus on the left and right and upper and lower quadrants and should be symmetrically absent or present. When asymmetric, magnetic resonance imaging (MRI) is necessary to evaluate for neural axis abnormalities.

 

The lower extremities should be carefully examined for asymmetry with respect to size and strength of the legs as well as foot deformities (eg, cavovarus foot deformities) as an indication for the presence of neural axis abnormalities.

 

Deep tendon reflexes and the Babinski reflex should be investigated.

 

IMAGING AND OTHER DIAGNOSTIC STUDIES

 

Plain radiography should include a standing posteroanterior (PA) and lateral radiograph of the spine to include the cervical spine to the pelvis and hips.

 

The PA radiograph (FIG 2A) should be evaluated for the following:

 

 

 

Coronal plane deformities using the Cobb method The C7-center sacral vertebral line (CSVL) placement

 

A trunk shift using Floman method (the distance between the CSVL and the mid-distance between the lateral rib margins)

 

 

Evaluation for any congenital abnormalities (eg, hemivertebra, congenital bar) The Risser stage (0 through 5)

 

The status of the triradiate cartilage (open or closed)

 

The lateral radiographs (FIG 2B) should be analyzed to determine the following:

 

 

Thoracic kyphosis and lumbar lordosis

 

Presence of associated spondylolisthesis or spondylolysis

 

Sagittal balance (distance between C7 plumb line and the posterior edge of the first sacral vertebral body)

 

 

 

FIG 2 • A,B. Preoperative anteroposterior (AP) and lateral radiographs demonstrate a 93-degree left thoracic scoliosis with a large trunk shift and open triradiate cartilage in the patient shown in FIG 1.

 

 

The Stagnara view is an oblique view to the patient, but an orthogonal view to the coronal curve that is used in severe spinal deformities to better visualize the spine.

 

Indications for MRI include neurologic abnormalities, significant back pain associated with scoliosis, atypical curve patterns such as a left thoracic curve, very young age, congenital scoliosis, neurofibromatosis, Marfan disease.

 

Computed tomography (CT) scanning may be useful to fully define the osseous anatomy, especially for extremely large curves and congenital curves.

 

DIFFERENTIAL DIAGNOSIS

Idiopathic scoliosis Congenital scoliosis Neurofibromatosis

Scoliosis associated with Marfan disease

 

 

NONOPERATIVE MANAGEMENT

 

Nonoperative management has little or no role for severe deformity.

 

Patients who are very young with moderate deformity may be treated with a brace to buy time to allow the patient to grow.

 

 

Bracing can be effective to prevent curve progression for smaller idiopathic curves (ie, 25 to 40 degrees).

 

SURGICAL MANAGEMENT

 

Anterior thoracoscopic release for spinal deformity has many technical considerations, which are discussed later in this chapter.

 

Indications for an anterior release/fusion

 

 

Severe spinal deformity: scoliosis greater than 80 to 90 degrees with significant rotational deformity or kyphosis greater than 100 degrees with flexibility index less than 50%

 

Skeletal immaturity, to avoid the crankshaft phenomenon. Usually performed for children younger than 10 years of age with open triradiate cartilage and Risser grade 0. Thoracoscopy has been shown to be safe in children less than 20 kg weight.

 

Deficient posterior elements, so that a posterior fusion may be difficult. Such deficiencies occur secondary to previous surgery with laminectomies for tumors or the treatment of neural axis abnormalities.

 

Preoperative Planning

 

Each patient should be carefully analyzed with respect to those curves that will undergo an anterior release.

 

The radiograph should be viewed to determine preoperatively which levels should be released. Release always includes the apical levels and usually includes all of the levels within the Cobb measurement.

 

For severe curves, traction in the operating room may be helpful in assisting curve correction.

 

Positioning and Approach

Lateral Position

 

Advantages

 

 

 

More familiar and traditional approach Conversion to open procedure is easy.

 

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FIG 3 • Lateral positioning. The patient is positioned in the lateral decubitus position with the surgical side

up (left in this case). An axillary roll was placed and the patient is in the direct lateral position to assist in surgeon orientation. Proximal is to the right and distal is to the left. A single anterior portal and four posterolateral portals are planned.

 

 

All thoracic levels can be accessed.

 

One can effectively obtain access to the T1-T5 levels, which are not accessible when the patient is in the prone position.

 

Disadvantages

 

 

 

Repositioning is necessary for the posterior approach. Single-lung ventilation is required.

 

Approach

 

 

Single-lung ventilation is achieved with a double-lumen endotracheal tube or a Univent tube.

 

 

 

 

FIG 4 • Prone positioning. A. Close-up view of the patient who has a left thoracic scoliosis. The left flank and spine have been prepared. B. The position of the monitor on the opposite side of the patient is shown. C,D. Surgical setup for a prone endoscopic release. C. View from behind the surgeons. The surgical assistant is on the opposite side of the operating table along with the monitor. The surgeon and first assistant are on the convex side of the patient—in this case, the left side. D. View from the opposite side: The surgeons are viewing the monitor. The primary surgeon and two assistants are operating.

 

 

Position the patient in the lateral decubitus position.

 

 

Check the endotracheal tube position and the single-lung ventilation status. Prepare and drape the chest and side (FIG 3).

 

Place four portals in the anterior axillary line.

 

Prone Position

 

Advantages

 

 

 

Not necessary to reposition patient for the posterior procedure No need for single-lung ventilation

 

Significantly decreased respiratory complications. Single double-lung ventilation is used.

 

Disadvantages

 

 

 

Difficult to obtain an anterior release proximal to T5. Conversion to open procedure is difficult.

 

Approach

 

 

Placement of regular endotracheal tube

 

Double-lung ventilation with decreased tidal volumes (about 50% to 60% of normal) and increased ventilatory rate which allows the lung to fall away from the spine

 

 

Place prone on a spine frame (FIG 4A,B) Ensure access to the flank and chest.

 

Prepare and drape the back and the chest and flank (FIG 4C,D).

 

 

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TECHNIQUES

• Thoracoscopic Release and Fusion for Scoliosis

Placement of Portals and Visualization

Place portals as anteriorly as possible, usually in the midaxillary line (TECH FIG 1A,B). Insert the camera into the initial portal with the lens directed posteriorly (TECH FIG 1C).

Find a clear space between the posterior chest wall and the lung and advance the thoracoscope.

Place a small, blunt-tipped cottonoid to retract the lung to identify the spine and other anatomic structures.

Place a fan retractor to fully retract the lung, if necessary (TECH FIG 1D). Place suction into the chest.

Place working portal.

Visualize the spine in the horizontal plane with the segmental vessels intact (TECH FIG 1E).

 

 

 

 

TECH FIG 1 • Prone anterior release. A. Skin markings are made to identify the left scapula and the four lateral portals. To the left is proximal. The most proximal portal usually gains access to the T5-T6 disc when it is in the midscapular region, as shown. B. Following placement of the four portals, the thoracoscope is placed in the most proximal working portal with an electrocautery in the second portal, suction is in the third portal, and the fan retractor in the fourth portal. C. The first portal is placed first, as shown; in this illustration, it is the most proximal portal, to the left. The secondary portal is then placed approximately two fingerbreadths distally and in line with the first. D. A fan retractor is placed to gently push down on the atelectatic lung. Visualized here is the superior most aspect of the chest. E. The spine is visualized in the horizontal plane. The segmental vessels are easily seen.

Exposure and Disc Removal

 

Incise the pleura along the midvertebral body line (TECH FIG 2A).

 

 

Spare the segmental blood vessels to preserve perfusion to the spinal cord. Bluntly retract the pleura anteriorly and posteriorly (TECH FIG 2B).

 

Incise the annulus fibrosus with the scalpel blade circumferentially from lateral rib head to near-opposite rib head (TECH FIG 2C).

 

 

Break up the disc with disc shavers (TECH FIG 2D). Remove the disc material with a rongeur (TECH FIG 2E).

 

Take down the endplate with a curved curette (TECH FIG 2F).

 

 

Place Surgicel (Ethicon, Inc., Somerville, NJ) or other thrombotic agent. Remove the disc from all levels planned.

 

Place bone graft if desired (TECH FIG 2G).

 

Close the pleura using the Endostitch device (US Surgical, Warsaw, IN), running one suture from proximal and one from distal (TECH FIG 2H-J).

 

 

Place a chest tube (TECH FIG 2K). Close the portal incisions.

 

 

 

TECH FIG 2 • A. Using a curved electrocautery blade, the pleura is incised in the longitudinal fashion, sparing the segmental vessels. B. The parietal pleura is retracted anteriorly, as shown, to allow for complete access to the anterior longitudinal ligament as well as the opposite annulus. The posterior pleura is also retracted. (continued)

 

 

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TECH FIG 2 • (continued) C. The annulus is incised parallel to the disc. D. Disc shavers are used to

break up the disc material. E. The disc material is removed with a rongeur. F. The endplate is taken

down to bone with an angled curette. G. Bone graft is placed. H-J. The pleura is closed with an Endostitch device. H. Closure is started distally with a running suture. I. Final closure of the pleura, in which the proximal suture is brought to the distal suture. J. The pleura is closed nicely with a running suture. K. Placement of the chest tube at the completion of the procedure, from distal to proximal. The lung is still deflated. The pleura, seen in the background, has been closed previously.

 

 

Portal placement

• Placement of portals is key for visualization and achieving good

  discectomy.

• Place the skin incision for the portal over a rib to allow the portal to be placed above and below the rib (two portals per skin incision).

• Ensure that portals are neither too posterior nor too anterior.

Preservation of

segmental blood vessels

• Incise the pleura in a longitudinal fashion, staying superficial to the

  segmental vessels.

• Use a curved harmonic scalpel or electrocautery.

• Incise any adventitial tissue adherent to the pleura over the disc to free up the parietal pleura.

• Bluntly retract the pleura to gain access to the disc.

Complete removal of

the disc

• Develop the same sequence for disc removal:

• Incise the disc with a scalpel blade.

• Break up disc material with shavers.

• Remove loosened disc material.

• Take down the endplates of the vertebral bodies with a curved curette.

• Remove excess endplate material.

Pleural closure

• Use the Endostitch device with 2-0 Vicryl suture.

• Use two sutures: The first begins in the proximal aspect and is run distally, and the second is started distally and is run proximally.

 

PEARLS AND PITFALLS

 

 

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POSTOPERATIVE CARE

 

Chest tube management

 

 

 

Connect chest tube to wall suction. Obtain daily chest radiographs.

 

The chest tube may be removed when drainage is less than 80 mL over 12 hours and serous color returns (with good pleural closure, removal usually is done on the first day).

 

Mobilize the patient to chair on postoperative day 1.

 

 

Mobilize the patient to ambulation when the chest tube is removed (usually postoperative day 2). Serial hemoglobin and hematocrit on postoperative days 1 and 2

 

Advance activities as tolerated to daily activities in the initial 6 weeks.

 

For the following 6 weeks, physical activities are advanced, depending on posterior constructs.

 

OUTCOMES

 

The addition of a thoracoscopic anterior release and fusion results in a decrease in pulmonary function in the first 6 weeks; however, at 1 to 2 years, it is 30% to 45% above baseline. Thoracoscopy has been shown to have less effect on pulmonary function compared to thoracoplasty.

 

 

 

FIG 5 • The 2-year postoperative AP (A) and lateral (B) radiographs of the patient shown in FIGS 1 and 2 demonstrated outstanding coronal and sagittal plane correction after prone thoracoscopic anterior release and fusion followed by a posterior spinal fusion and instrumentation from T2 to L2.

 

 

Anterior release increases the flexibility of the spine and allows for great coronal, axial plane, and sagittal plane correction.

 

With good surgical technique, an outstanding anterior release can be achieved and will allow for exceptional three-dimensional correction of the spine with posterior instrumentation and fusion (FIG 5).

 

 

 

COMPLICATIONS

Single-lung ventilation

Intraoperative complications: inability to ventilate adequately secondary to ventilation-perfusion mismatches, high airway pressures and barotrauma, and underlying pulmonary issues

Postoperative complications: atelectasis secondary to barotrauma or mucous plugs Continuous chest tube drainage, especially when the parietal pleura has not been closed

Pneumothorax following chest tube removal

Intraoperative injury to the segmental blood vessels or the great vessels

Intraoperative injury to the thoracic duct, which usually occurs on the right side at the T11-T12 area. This can be avoided by dissection deep to the parietal pleura.

Chylothorax is treated with total parenteral nutrition and avoidance of a fatty diet.

Intraoperative excessive bleeding secondary to inadvertent segmental vessel injury. Strategies to coagulate the vessel are used.

Long-term complications secondary to a thoracoscopic anterior release and fusion are limited.

 

SUGGESTED READINGS

1. Al-Sayyad MJ, Crawford AH, Wolf RK. Video-assisted thoracoscopic surgery: the Cincinnati experience. Clin Orthop Relat Res 2005; (434):61-70.

    

    

2. Cheung KM, Wu JP, Cheng QH, et al. Treatment of stiff thoracic scoliosis by thoracoscopic anterior release combined with posterior instrumentation and fusion. J Orthop Surg Res 2007;2:16.

    

    

3. Crawford AH. Anterior surgery in the thoracic and lumbar spine: endoscopic techniques in children. Instr Course Lect 2005;54:567-576.

    

    

4. Huang EY, Acosta JM, Gardocki RJ, et al. Thoracoscopic anterior spinal release and fusion: evolution of a faster, improved approach. J Pediatr Surg 2002;37:1732-1735.

    

    

5. Lefevre Y, Ilharreborde B, Huot O, et al. Thoracoscopy in children less than 20 kg for the management of spinal disorders: efficacy of long-term follow-up. J Pediatr Orthop 2011;31:170-179.

    

    

6. Newton PO, Cardelia JM, Farnsworth CL, et al. A biomechanical comparison of open and thoracoscopic anterior spinal release in a goat model. Spine 1998;23:530-535.

    

    

7. Newton P, Shea K, Granlund K. Defining the pediatric spinal thoracoscopy learning curve: sixty-five consecutive cases. Spine 2000;25: 1028-1035.

    

    

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8. Niemeyer T, Freeman BJ, Grevitt MP, et al. Anterior thoracoscopic surgery followed by posterior

   instrumentation and fusion in spinal deformity. Eur Spine J 2000;9:499-504.

    

    

9. Picetti GD III, Pang D, Bueff HU. Thoracoscopic techniques for the treatment of scoliosis: early results in procedure development. Neurosurgery 2002;51:978-984.

    

    

10. Sucato DJ, Elerson E. A comparison between the prone and lateral position for performing a thoracoscopic anterior release and fusion for pediatric spinal deformity. Spine 2003;28:2176-2180.

     

     

11. Sucato DJ, Erken YH, Davis S, et al. Prone thoracoscopic release does not adversely affect pulmonary function when added to a posterior spinal fusion for severe spinal deformity. Spine 2009;34:771-778.

     

     

12. Sucato DJ, Welch RD, Pierce B, et al. Thoracoscopic discectomy and fusion in an animal model: safe and effective when segmental blood vessels are spared. Spine 2002;27:880-886.

     

     

13. Verma K, Lonner BS, Kean KE, et al. Maximal pulmonary recovery after spinal fusion for adolescent idiopathic scoliosis: how do anterior approaches compare? Spine 2011;36:1086-1095.