Vertebral Body Tethering Surgery: Study Showing No Decrease in Coronal Curve Magnitude After First Postoperative...

Much enthusiasm has been generated around vertebral body tethering (VBT) as an alternative to fusion treatment. However, the majority of studies have shown little difference between coronal curve magnitude on the first postoperative erect radiograph and that at final follow-up, suggesting that VBT is not consistently modulating spine growth in a manner that substantially affects coronal curve magnitude.

All patients with adolescent idiopathic scoliosis (AIS) who underwent VBT between December 2013 and June 2020 and subsequently had at least 2 years of follow-up in a multicenter registry were reviewed. The change in coronal curve magnitude was calculated by subtracting the magnitude at the time of final follow-up from that on the first postoperative erect radiograph. A change of <5° was considered to be within normal measurement variability.

One hundred and ten patients met the inclusion criteria (racial breakdown: 94 White, 6 Black/African American, 3 Asian, 2 Middle Eastern, 1 mixed race, and 4 uncertain/unspecified; ethnicity: 87 not Hispanic or Latino, 1 Hispanic/Latino, and 22 did not report their ethnicity). Their mean age was 12.9 years (standard deviation [SD], 1.3 years) and the mean follow-up was 3.7 years (range, 2.0 to 6.9 years). A mean of 6.6 levels were tethered. The preoperative mean coronal curve magnitude was 51.0° (range, 32° to 75°), which corrected to a mean of 27.3° (range, 10° to 53°) on the first postoperative erect radiograph. At the time of final follow-up, the mean coronal curve magnitude was 30.9° (range, -50° to 69°), and 49.1% (54) of the 110 curves were stable (the coronal curve magnitude at final follow-up was within 5° of that on the first postoperative erect radiograph). A total of 42.7% (47) had >5° of increase in coronal curve magnitude following the initial postoperative erect radiograph, whereas 8.2% (9) showed a >5° increase during the follow-up period. Five of the 9 patients (4.5% of the series) had a >10° decrease, with 2 of the 5 having overcorrection, ending up with 31° and 50° curves in the opposite direction.

Although VBT holds promise and many (49.1%) of the 110 curves in this series remained stable from the first postoperative erect to the final follow-up radiograph, only 9 demonstrated a decrease in coronal curve magnitude over time, including 2 that overcorrected. Further research is needed to identify the factors differentiating among patients who had curve progression, did not have progression, or had overcorrection to determine which patients are more likely to benefit from VBT.

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.