# One Year Results of the Randomized BiPOWR Trial Comparing the Spring Distraction System (SDS) and the One Way Self-Expanding Rod (OWSER) for the Correction of Neuromuscular and Syndromic Early Onset Scoliosis

## TL;DR

A clinical trial compared two spinal implants for treating scoliosis in children with neuromuscular or syndromic conditions, finding similar curve correction but a much lower complication rate with one system.

## Contribution

The first randomized controlled trial comparing two growth-friendly spinal implants in neuromuscular early onset scoliosis.

## Key findings

- Both SDS and OWSER achieved 50% curve correction maintained at 1-year follow-up.
- SDS had a significantly lower adverse event rate (30% vs 78% per patient/year) compared to OWSER.
- Both systems provided excellent spinal growth without requiring repeated lengthening procedures.

## Abstract

Current “growth-friendly” implants for treatment of Early Onset Scoliosis (EOS) have limitations that reduce their efficacy and cost-effectiveness. Recently, two systems have been developed that mitigate many of these limitations, the Spring Distraction System (SDS) and the One Way Self-Expanding Rod (OWSER). The purpose of the multicenter BiPOWR trial was to compare 1-year efficacy and -safety of both strategies in the treatment of neuromuscular or syndromic EOS.

Non-ambulant, neuromuscular/syndromic EOS patients were included in three academic hospitals. They were randomized to treatment with SDS or OWSER and were blinded until after surgery. Outcomes were coronal curve, spinal growth and the occurrence of (serious) adverse events ((S)AEs). In addition, spinal growth and implant lengthening were calculated. Data were collected pre-operatively, immediately post-operatively, and at 1-, 3-, 6-, and 12-month follow-up.

Thirty patients were included. Two patients passed away during follow-up, and these patients were replaced. All collected data were used for analysis. Mean age at surgery was 9.0 years, and 20/30 patients were male. Mean coronal curve decreased from 74.9° pre-operatively, to 37.6° post-operatively, remaining stable at 37.7° at the 1-year follow-up, with no group differences. T1-T12 length increased by 18 mm/year for SDS and 9 mm/year for OWSER. For T1-S1 length, this was 26 mm/year (SDS) and 18 mm/year (OWSER). Five (S)AEs occurred in the SDS group and 11 (S)AEs in the OWSER group. Two SDS patients passed away, unrelated to the surgery or implant. One (S)AE in the SDS group and 6 (S)AEs in the OWSER group were implant-related.

The SDS and the OWSER achieved coronal curve correction of 50%, which was maintained at 1-year follow-up. Spinal length increase was excellent for both systems. The (S)AE rate was 30%/patient/year for SDS and 78%/patient/year for OWSER.

(1) The current study is the first RCT that compares two “growth-friendly” implants in a neuromuscular early onset scoliosis (EOS) population.(2) The Spring Distraction System (SDS) and the One Way Self-Expanding Rod (OWSER) both achieve around 50% curve correction which is maintained at 1 year follow-up.(3) Both systems achieve excellent T1-T12- and T1-S1 height increase, without the need for repetitive lengthenings.(4) The (S)AE rate of SDS was 30%/patient/year. For OWSER, the (S)AE rate was 78%/patient/year.

(1) The current study is the first RCT that compares two “growth-friendly” implants in a neuromuscular early onset scoliosis (EOS) population.

(2) The Spring Distraction System (SDS) and the One Way Self-Expanding Rod (OWSER) both achieve around 50% curve correction which is maintained at 1 year follow-up.

(3) Both systems achieve excellent T1-T12- and T1-S1 height increase, without the need for repetitive lengthenings.

(4) The (S)AE rate of SDS was 30%/patient/year. For OWSER, the (S)AE rate was 78%/patient/year.

RCT

Level 1