Outcomes in patients with tether rupture after anterior vertebral tethering for adolescent idiopathic scoliosis: the good, the bad, and the ugly.

introductionThough multiple studies have reported tether rupture rates after anterior vertebral tethering (AVT) as high as 50%, few have adequately analyzed the clinical significance of tether rupture and factors that potentially increase the likelihood of revision surgery. We reviewed 262 consecutive adolescent idiopathic scoliosis (AIS) patients after AVT with the goal of identifying early and late tether ruptures and categorizing these tether ruptures as inconsequential, consequential, problematic, or beneficial. Our hypothesis was that the tether rupture rate after AVT for AIS would be significant but only a small percentage of patients would require revision surgery.

methodsCharts, radiographs, and CT scans were reviewed for tether rupture in 262 consecutive AIS patients treated with AVT for thoracic and thoracolumbar/lumbar curves 33-77°. Early tether rupture occurred < 2 years and late tether rupture ≥ 2 years postoperatively. Tether rupture was further categorized as inconsequential (final curve < 40° and no pain), consequential (curve ≥ 40° and/or convex back pain), problematic (revision surgery required), or beneficial (improvement of overcorrection) at follow-up.

resultsOf 262 consecutive AIS patients status post AVT (106 thoracic curves, 53 thoracolumbar curves, and 103 double curves), tether rupture was found in 45 patients with 66 curves (34 thoracic and 32 thoracolumbar/lumbar) treated at age 14.5 years and at Risser 2.6 and Sanders 4.7. Curves with tether rupture corrected from 50.3° preoperatively to 20.8° postoperatively, but lost 7.2° of correction with tether rupture settling at 28.0° final at 2.6 years (0-11 years). Early tether rupture occurred in 12/133 (9%) and late tether rupture in 33/129 (26%) patients with 2-11 year follow-up. Tether rupture was inconsequential in 67% (30/45) of patients, consequential in 13% (6/45), problematic in 16% (7/45), and beneficial in 4% (2/45). In those patients with tether rupture, 69% occurred in a thoracolumbar/lumbar curve and 47% demonstrated a rupture at L2,3. Revision surgery for a thoracolumbar/lumbar tether rupture involved tether replacement alone in 4 patients and thoracic fusion in 2 additional patients, 1 requiring thoracic fusion alone, and 1 requiring thoracic fusion with thoracolumbar/lumbar tether replacement (hybrid). Revision surgery for a thoracic tether rupture involved 1 tether replacement and 1 thoracic fusion. Revision surgery was unrelated to curve correction or loss of correction, but was related to multiple tether ruptures and convex back pain (p < 0.005).

conclusionThis study demonstrated an early tether rupture rate of 9% and late tether rupture rate of 26% in a large series of patients treated with AVT for AIS over 14 years. While the majority of patients had inconsequential tether rupture (67%), with 7.2° loss of correction, a final curve < 40°, and no pain, a number of patients had consequential (13%) or problematic tether rupture (16%). These adversely affected patients had a final curve ≥ 40°, convex back pain, or required revision surgery. Additionally, a small number of patients (4%) actually benefitted from tether rupture by improvement in an area of impending overcorrection. LEVEL OF EVIDENCE: IV.