Alternatives to Spinal Fusion Surgery in Pediatric Deformity

Randal R. Betz, MD; M. Darryl Antonacci, MD; Laury A. Cuddihy, MD

Disclosures

Curr Orthop Pract. 2018;29(5):430-435. 

In This Article

Vertebral Body Tethering (VBT) and Anterior Scoliosis Correction (ASC)

Extensive preclinical data have been published on VBT including both animal and biomechanical studies.[25–30] At this time, several case reports and clinical papers outlining the efficacy of VBT in humans have been published or presented at international meetings.[31–38]

VBT and ASC Indications

Most surgeons consider candidates for VBT to include skeletally immature patients with thoracic scoliosis measuring between 35 and 60 degrees (generally Risser 0–2, Sanders digital score ≤4). Flexibility also is important, and curves need to bend to less than 30 degrees. Extremely young, immature patients (<11 yr of age) may experience overcorrection, and it might be worth delaying VBT to minimize this risk. However, this delay may allow for trunk deformity to increase, and it is better to intervene earlier and anticipate lengthening the cord. The Cobb angle can always be corrected; the rib deformity usually improves only minimally (Figure 1A–I).

Figure 1.

Posteroanterior (A) side-bend (B), and lateral radiographs (C) of a 12-year-old girl with a 49-degree curve. She was premenarche, Risser 0, Sanders 3. Her angle of trunk rotation was 15 degrees thoracic, 6 degrees lumbar. Her trunk rotation rib deformity was significantly worsening over the last 6 mo, which precipitated doing the surgery immediately knowing there would be another planned surgery for overcorrection. (D) The patient had an anterior scoliosis correction T5-T12 (she has 11 ribs) by author MDA. First erect posteroanterior radiograph 12 days postoperatively showed a planned residual curve measuring 21 degrees. (E) Posteroanterior radiograph 15 mo postoperatively with curve measuring -10 degrees. She was still Risser 0, Sanders 4. The -10 degrees is the authors' preferred amount of overcorrection that can be allowed before recommending a lengthening procedure. (F) Fluoroscopy anteroposterior image: a correction procedure 15 mo after index procedure. An entirely new cord was replaced using the same screws. The surgeon (MDA) is pulling up on the center of the curve to determine that it can only return to maximum of +15 to 20 degrees. This is done to prevent recurrence of an original curve severity but allow room for additional growth. (G) First erect posteroanterior after second surgery 3 days later. (H and I) Most recent erect posteroanterior and lateral radiographs at 34 mo after the index procedure and 20 mo after the second surgery. The patient is now 14 yr and 3 mo of age, post menarche, Risser 5, Sanders 7. (Courtesy M. Darryl Antonacci, MD).

Patients with thoracolumbar or lumbar curves or those with large, stiff thoracic curves are generally not considered candidates for VBT. The authors of this article have therefore used combined principles of growth modulation and tissue remodeling to treat these issues through advanced anterior scoliosis correction (ASC) techniques. Hence, the indications are broadened to include the vast majority of thoracic, thoracolumbar, and lumbar curves in immature as well as more mature patients (Sanders > 4) with small to large curves (35 to > 95 degrees) and stiff curves (those not bending below 30 degrees). Unlike VBT, which is traditionally a thoracoscopic thoracic approach, ASC is a mini-open muscle sparing approach to thoracic, thoracolumbar, or lumbar curves and, unlike VBT, incorporates anterior longitudinal ligament and disc annulus-releasing techniques. These releasing procedures allow significant segmental derotation to obtain correction, by "de-tethering" the stiff and large scoliotic spine in the sagittal, axial, and coronal planes. Another advantage of the mini-open ASC approach is that many of the segmental vessels are often able to be spared.

VBT and ASC Complications

Pahys et al.[37] reported a series of 100 consecutive patients treated with VBT. The mean operative time and estimated blood loss (EBL) decreased significantly with increasing surgeon experience; surgical time averaged under 200 min, and EBL was approximately 150 mL for the most recent 25 patients who underwent this procedure. There were no major neurologic or instrumentation-related complications or infection. Intraoperatively, two patients were converted to an open approach after inability to tolerate single-lung ventilation (one patient) and uncontrolled segmental vessel bleeding (one patient). One patient had a transient partial decrease in neuromonitoring that resolved by raising the mean blood pressure prior to closure. Minor postoperative complications included one patient with prolonged atelectasis requiring bronchoscopy, five patients with transient thigh pain or numbness, and one patient with intercostal neuralgia.

One of the benefits of VBT/ASC is that it does not limit a future posterior spinal fusion or any other treatment if necessary. Some literature suggests that the anterior thoracoscopic approach may impact pulmonary function.[39,40] However, several authors reported minimal to no decline in pulmonary function after anterior spine surgery, with thoracoscopic and mini-open approaches having the least effect.[41,42]

The possibility for overcorrection is a known potential problem. Too much skeletal growth can create a scoliotic curve in the opposite direction. In patients with significant growth remaining (open triradiate cartilage, Risser 0, etc.), it is important to tell the family that a second, minor lengthening procedure may be necessary.

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