The Fate of The Broken Tether: How Do Curves Treated With Vertebral Body Tethering Behave After Tether Breakage?

Abstract

<h3>Study Design. </h3><p>Retrospective, multicenter.</p><h3>Objective. </h3><p>The aim of this study was to assess curve progression and occurrence of revision surgery following tether breakage after vertebral body tethering (VBT).</p><h3>Summary of Background Data. </h3><p>Tether breakage after VBT is common with rates up to 50% reported. In these cases, it remains unknown whether the curve will progress or remain stable.</p><h3>Materials and Methods. </h3><p>Adolescent and juvenile idiopathic scoliosis patients in a multicenter registry with ≥2-year-follow-up after VBT were reviewed. Broken tethers were listed as postoperative complications and identified by increased screw divergence of >5 degrees on serial radiographs. Revision procedures and curve magnitude at subsequent visits were recorded.</p><h3>Results. </h3><p>Of 186 patients who qualified for inclusion, 84 (45.2%) patients with tether breakage were identified with a mean age at VBT of 12.4±1.4 years and mean curve magnitude at index procedure of 51.8±8.1 degrees. Tether breakage occurred at a mean of 30.3±11.8 months and mean curve of 33.9±13.2 degrees. Twelve patients (12/84, 14.5%) underwent 13 revision procedures after tether breakage, including six tether revisions and seven conversions to fusion. All tether revisions occurred within 5 months of breakage identification. No patients with curves <35 degrees after breakage underwent revision. Revision rate was greatest in skeletally immature (Risser 0–3) patients with curves ≥35 degrees at time of breakage (Risser 0–3: 9/17, 53% <em>vs.</em> Risser 4–5: 3/23, 13%, <em>P</em>=0.01). Curves increased by 3.1 and 3.7 degrees in the first and second year, respectively. By 2 years, 15/30 (50%) progressed >5 degrees and 8/30 (26.7%) progressed >10 degrees. Overall, 66.7% (40/60) reached a curve magnitude >35 degrees at their latest follow-up, and 14/60 (23.3%) reached a curve magnitude >45 degrees. Skeletal maturity did not affect curve progression after tether breakage (<em>P</em>>0.26), but time to rupture did (<em>P</em>=0.048).</p><h3>Conclusions. </h3><p>While skeletal immaturity and curve magnitude were not independently associated with curve progression, skeletally immature patients with curves ≥35 degrees at time of rupture are most likely to undergo additional surgery. Most patients can expect progression at least 5 degrees in the first 2 years after tether breakage, though longer term behavior remains unknown.</p><h3>Level of Evidence. </h3><p>Level III.</p>