The Effect of Proximal Anchor Choice During Distraction-based Surgeries for Patients With Nonidiopathic Early-onset Scoliosis: A Retrospective Multicenter Study.

BACKGROUND: It is unclear whether the type of proximal anchor affects the spine length achieved with distraction-based surgeries in patients with nonidiopathic early-onset scoliosis (EOS). Since distraction may produce kyphosis, spine length should be assessed in the sagittal plane using the sagittal spine length (SSL-curved arc length of the spine in the sagittal plane). Our purpose was to determine if the type of proximal anchor in distraction-based surgeries will affect final spine length. METHODS: Patients with nonidiopathic EOS treated with distraction-based systems (minimum 5 y follow-up, 5 lengthenings) were identified from 2 EOS registries. Radiographic analysis preoperative, postimplant (L1), and after each lengthening (L2-L5, L6-L10, L11-L15) was performed with the primary outcome of T1-S1 SSL. RESULTS: We identified 126 patients-70 had rib-based implants (52 congenital, 9 syndromic, 9 neuromuscular) and 56 had spine-based implants (15 congenital, 29 syndromic, 12 neuromuscular) with preoperative age 4.6 years, scoliosis 75 degrees, and kyphosis 48 degrees. After initial correction (P<0.05), scoliosis remained constant [58 degrees (13 to 104 degrees) at L11-L15] and kyphosis increased over time [38 degrees (9 to 108 degrees) at L1 to 60 degrees (17 to 134 degrees) at L11-L15] (P<0.05). Preoperative SSL was higher in the spine-based group (29.6 cm) when compared with the rib-based group (25.2 cm) (P<0.05). This difference was maintained after initial implantation (spine-based: 32.2 cm vs. rib-based: 26.7 cm, P<0.05) and at final follow-up (spine-based: 37.0 cm vs. rib-based: 34.4 cm, P<0.05). As preoperative SSL differed between groups, maximum SSL gains per interval were also normalized to preoperative SSL. There was no statistically significant difference between groups at L1, L2-L5, and L6-L10. However, at L11-L15, the rib-based group achieved a more relative increase in spine length compared with the spine-based group (45% vs. 31%, P<0.05). CONCLUSION: At minimum 5 year follow-up, distraction-based surgeries increased spine length for patients with nonidiopathic EOS; regardless of proximal anchor type.

Distraction-based surgeries increase thoracic sagittal spine length after ten lengthening surgeries for patients with idiopathic early-onset scoliosis.

STUDY DESIGN: Retrospective, comparative, multicenter. OBJECTIVES: To determine if the choice of proximal anchor affects thoracic sagittal spine length (SSL) for children with idiopathic early-onset scoliosis (EOS). Debate exists as to whether spine growth is maintained during treatment for EOS. As rib- (RB) and spine-based (SB) distraction procedures may be kyphogenic, the traditional measurement of spine growth on coronal radiographs may not identify out-of-plane increase in spine length. A measure of SSL, along the spine's sagittal arc of curvature, has been validated to reliably assess the length of the thoracic spine. METHODS: Patients with idiopathic EOS treated with distraction-based systems (minimum 5-year follow-up, five lengthening surgeries) with radiographic analysis preoperatively, postimplant (L1), and during lengthening periods (L2-L5, L6-L10) were evaluated with primary outcome of T1-T12 SSL. RESULTS: We identified 34 patients (14 RB, 20 SB) with preoperative age 4.9 years (4.2 RB vs. 5.4 SB), scoliosis 72° (60° RB vs. 77° SB; p < 0.05), kyphosis 39° (50° RB vs. 34° SB; p < 0.05), and SSL 17.8 cm (15.5 RB vs. 18.5 SB; p < 0.05). After initial scoliosis correction from implantation, scoliosis remained constant over time. RB patients had greater kyphosis than SB patients: L1, 46° RB vs. 19° SB (p < 0.05); L2-L5, 50° RB vs. 27° SB (p < 0.05); L6-L10, 56° RB vs. 26° SB (p < 0.05). SSL increased for both groups from preoperative to the tenth lengthening (p < 0.05). As compared with RB patients, SB patients had higher SSL preoperatively and maintained this difference to the tenth lengthening (p < 0.05). After ten lengthening surgeries, when normalized to preoperative SSL, relative thoracic growth was greater for RB (27%) than for SB patients (19%) (p < 0.05). CONCLUSION: Regardless of proximal anchor choice, thoracic length continued to increase during the distraction phase of treatment for idiopathic EOS. LEVEL OF EVIDENCE: Level III.