Improved implants, patient selection and long-term data needed to assess true efficacy of anterior vertebral body tethering in skeletally immature patients

Paul Rushton

Anterior vertebral body tethering (AVBT) of skeletally immature patients is associated with satisfactory deformity correction in the majority of cases, new research has found. However, complication and revision rates suggest the need for improved implants and patient selection.

In addition, long-term follow-up “remain crucial to establish the true efficacy of this procedure”, say the researchers.

The prospective study of 112 cases, the findings of which were published by Paul Rushton (Great North Children’s Hospital, Newcastle Upon Tyne, UK) et al in the journal Spine, was designed to determine the efficacy of AVBT in skeletally immature patients.

The study included consecutive skeletally immature patients with idiopathic scoliosis who were treated with AVBT between 2012 and 2018 by one of two surgeons working at two independent centres and followed up for more than two years. Data were collected prospectively and supplemented retrospectively where necessary. Outcomes were measured preoperatively, at first erect radiograph (FE), one-year postoperatively and at most recent follow up (FU).

A total of 112 patients underwent 116 primary tethering procedures (108 thoracic and eight lumbar tethers). Four patients had primary tethering of both lumbar and thoracic curves.

At surgery mean age was 12.7 ± 1.4 years (8.2–16.7) and Risser 0.5 ± 0.9 (0–3). Follow up was mean 37 ± 9 months (15–64). Preoperative mean coronal Cobb angle of the 130 tethered curves was 50.8° ± 10.2 (31–81) and corrected significantly to 26.6° ± 10.1 (−3–61) at FE radiograph (p<0.001).

Further significant improvement was seen from FE to one-year, to mean 23.1° ± 12.4 (−37–57) (p<0.001). There was a small but significant increase between one-year and FU to 25.7° ± 16.3 (−32–58) (p<0.001), which appeared to reflect tether breakage.

Untethered minor curves were corrected from 31.0° ± 9.5 (3–57) to 20.3° ± 10.3 (0–52) at FU (p<0.001). Rib hump was corrected from 14.1 ± 4.8 (0–26) to 8.8° ± 5.4 (0–22) at FU (p<0.01).  In all 25 patients (22%) had 28 complications with 15 patients (13%) requiring 18 revision operations including six completed and one awaited fusions.

Speaking to Spinal News International, Rushton said: “The included cases were performed by the senior authors, one of whom I worked for as fellow. The study helps us learn a little more about AVBT. It suggests that AVBT is able to growth modulate in this immature patient cohort, a key premise of its adoption. The outcomes at this early time point appear reassuring with most patients having mild deformities and having not required fusion surgery. The results show some unpredictability in terms of growth modulation with both under and over correction seen often leading to revision surgery.

“Thus we could improve the tools used to select which patients may benefit from this technique and at what point to intervene. Also tether breakage was seen commonly after two- to three-year follow-up and typically associated with some loss of correction.

“The implications of tether breakage are not understood at this point, but it does raise questions about the effect of further tether breakage and loss of correction over follow-up. Fundamentally we need medium and long term follow-up to understand the potential worth of this technique.”



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