The different applications of Vertebral Body Tethering - Narrative review and clinical experience

Abstract

Background: Vertebral body tethering (VBT) has been originally developed as a growth modulation technique for the surgical management of skeletally immature patients with adolescent idiopathic scoliosis (AIS). Given the positive results obtained in this setting, the use of VBT is gradually expanding to other patient categories, such as those with no or limited remaining growth or with non-idiopathic scoliosis. Aim of this manuscript is to offer an overview over the current applications of VBT, along with imaging and comments derived from the clinical experience. The work was based on a literature search conducted in January 2023 on Pubmed, Scopus and Web of Science databases. Following keywords were used for the search: vertebral body tethering, adolescent idiopathic scoliosis, early onset scoliosis, neuromuscular scoliosis, syndromic scoliosis.

Results: Three patient categories in which VBT has been applied have been highlighted: VBT for growth modulation in AIS, VBT as anterior scoliosis correction in AIS and VBT for non-idiopathic curves or early-onset scoliosis.

Conclusion: While growth modulation in AIS still represents the most widespread use of VBT, the use of this technique has yielded positive results in different settings as well, such as scoliosis correction in AIS or temporary or definitive curve management in non-AIS curves. While long-term results are lacking, patient selection seems to play a central role to reduce the complication rate and ensure predictable and stable results.

Keywords: AIS; Anterior scoliosis correction; EOS; Growth modulation; Scoliosis; VBT; VBT-ASC.

Fig. 1

Example of a 12 year-old girl, Risser 0, with a Lenke 1A curve. One year after VBT, the curve is well corrected and the patient is Risser 4.

Fig. 2

Example of a 14-year-old boy (Risser 0) with a Lenke 5C curve measuring 52° at index surgery. At the last, 2-year follow-up the curve measured 12° and the patient was Risser 4. The sagittal parameters remained stable and, in particular, the lumbar lordosis was not affected by the use of an anterior instrumentation.

Fig. 3

Schematic representation of the per-operative correction needed in relationship to the remaining growth modulation. The more growth is expected, the smaller the intraoperative correction required – also to limit the risk of overcorrection. However, in more mature patients with limited or no growth potential, a higher amount of intraoperative correction is required as a further improvement after surgery will likely not occur or be very limited.

Fig. 4

Example of a 14 years-old patient (Risser 4) with a Lenke 1A curve measuring 41° at index surgery. At the 2-year follow-up, the curve is well corrected and the compensatory lumbar curve is completely straightened.

Fig. 5

Schematic representation of the different treatment options for scoliosis based on the skeletal maturity of the patients and their curve magnitude. The blue lines represent the Duval-Beaupère evolution of three different evolutive curve patterns, while the thick dotted black line represents the start of growth spurts. The ideal VBT curve is the one already severe (<40°) at Risser 0. Other patients have slower-evolving curves that are not severe enough at Risser 0, but will cross the 40–45° threshold later. These patients will require either PSF or ASC, depending on curve type and flexibility.

Fig. 6

Example 12-years old patient affected by Williams-Beuren syndrome. At index surgery the TRC were open and the patient presented a 65° Lenke 2B curve. At the last, 4-year follow up, both the main thoracic and the compensatory curve are stable and, if necessary, thoracic fusion could still be performed at skeletal maturity.

Fig. 7

Example of a 14-years-old patient (Risser 0, closed TRC) affected by a genetic disorder and with a progressing 65° lumbar curve. At the last, 3-year follow-up, the lumbar curve is controlled and, while there is a slight overcorrection at the thoracolumbar junction, this allows for a better coronal balance. As the patient is almost non-ambulant, a maintained coronal alignment is of particular significance as it facilitates sitting.