The timing of tether breakage influences clinical results after VBT

Abstract

Introduction Tether breakage is a frequent mechanical complications after vertebral body tethering (VBT), but not all patients with a breakage show loss of correction. The reason of this clinical finding has not yet been clarified. We hypothesized that the integrity of the tether is relevant only in the early stages after VBT, when it drives growth modulation and tissue remodelling. After these mechanisms have taken place, the tether loses its function and a breakage will not alter the new shape of the spine. Thus, tether breakage would have a greater clinical relevance when occurring shortly after surgery. Methods All consecutive patients who underwent VBT and had a min. 2-year follow-up were included. The difference in curve magnitude between the 1st standing x-ray and the last follow-up was calculated (ΔCobb). For each curve, the presence and timing of tether breakage were recorded. The curves were grouped according to if and when the breakage was observed (no breakage, breakage at 0–6 months, 6–12 months, > 12 months). The ΔCobb was compared among these groups with the analysis of variance (ANOVA). Results Data from 152 curves were available: 68 with no breakage, 12 with a breakage at 0–6 months, 37 at 6–12 months and 35 > 12 months. The ANOVA found significant difference in the ΔCobb among the groups (Sum of square 2553.59; degree of freedom 3; mean of square 851.1; Fisher test 13.8; P < 0.0001). Patients with no breakage or breakage at > 12 months had similar ΔCobb (mean 4.8° and 7.8°, respectively, P = 0.3), smaller than the 0–6 or 6–12 groups (15.8° and 13.8°, respectively). Conclusion Tether breakage leads to a consistent loss of correction when occurring within the first 12 months, while it has limited clinical relevance when occurring later on.

Vertebral body tethering: An alternative to posterior spinal fusion in idiopathic scoliosis?

“…The aforementioned findings support the fact that a tether plays a fundamental role during the first year and once remodeling process terminates the spine holds its new shape and tether functions is lost ( 30 , 32 ). Even though, TB is associated with decreased curve correction, it is not associated with clinical success of the procedure or with reduction in quality-of-life post-surgery, nor is it an indication for reoperation ( 30 , 32 ).…”

“…The aforementioned findings support the fact that a tether plays a fundamental role during the first year and once remodeling process terminates the spine holds its new shape and tether functions is lost ( 30 , 32 ). Even though, TB is associated with decreased curve correction, it is not associated with clinical success of the procedure or with reduction in quality-of-life post-surgery, nor is it an indication for reoperation ( 30 , 32 ). Surgical revision is indicated in case of significant loss of correction resulting in dissatisfied patient with a curve >40° and include release of tether, extension or replacement with a new tether or switching to PSF ( 29 , 31 ).…”

“…6 of these patients lost correction and 2 had scoliosis progression requiring revision surgery. Baroncini et al then investigated the influence of timing of TB on clinical results and found that patients with no TB or TB >12 months had similar improvement in Cobb's angle but better than that seen in patients with early TB within 6 and 12 months (4.8°/7.8° vs. 15.8°/13.8°) ( 32 ). Another study by Shankar et al reported 27% (18/69) TB at 2-years follow-up, mostly occurring in major compared to minor curves and in thoracolumbar compared to thoracic tethers ( 33 ).…”

Inter-screw index as a novel diagnostic indicator of tether breakage

“…the VBT that may significantly influence the surgical outcome, accurate diagnosis of it becomes essential [6,7].…”

Incidence of Tether Breakage in Anterior Vertebral Body Tethering

“…1,[5][6][7][8][9][10][11][12] The tether tends to fail between levels 3 and failure can be identified radiographically. [1][2][3][6][7][8]11,[13][14][15] An example of a patient with suspected tether breakage is shown in Fig. 1.…”