One-Way Self-Expanding Rod for Early-Onset Scoliosis: A Prospective Observational Study of 20 Patients

Background: Progressive early-onset scoliosis (EOS) raises major challenges for surgeons, as growth must be preserved. With conventional growing rods, the need for repeated surgery for rod lengthening is associated with numerous complications, high costs, and a heavy psychosocial burden on the patient and family. We assessed the safety and efficacy of a new One-Way Self-Expanding Rod (OWSER). Methods: This prospective single-centre phase 2 study included two groups of children with progressive EOS treated by the OWSER in 2016-2017: ten received a unilateral construct to treat progressive non-neuromuscular curves and ten others a bilateral construct for neuromuscular scoliosis. Clinical and radiological data were assessed at surgery then 3, 6, 12, and 18 months later. The primary endpoint was success defined as absence of repeated surgery or Cobb angle progression <15° at 12 months. Findings: In the non-neuromuscular group, rod expansion occurred in 50% of patients [95CI, 19-81]; in the 5 other patients, rotational conflict at the flat part of the rod prevented rod expansion, 4 of them required surgery within the first 12 months. Rod expansion occurred spontaneously and during monthly traction sessions in all ten neuromuscular patients [95%CI, 69-100], without mechanical or device-related complications, and residual pelvic obliquity was improved by -3° [-6·0 to 9·5] at 18 months. Lung function improved in the non-neuromuscular group. Interpretation: Used in a bilateral construct, the OWSER seems safe and less aggressive than traditional growing rods. It should avoid further surgery and reduce the complication rate. The bilateral construct seemed effective in correcting EOS in our small sample. The OWSER may be the treatment of choice for progressive spinal deformities in skeletally immature children. Trial Registration: ClinicalTrials.gov: NCT02266667. Funding Statement: Euros Company, SAS. Declaration of Interests: LM received grant and research support from Euros Company SAS and is a co-designer of the device. All other authors declare that they have no conflicts of interest. Ethics Approval Statement: All parents or guardians provided written informed consent. The study protocol was sponsored by the Assistance Publique-Hopitaux de Paris and approved by the appropriate ethics committee (Comite de Protection des Personnes Ile-de France 2, n° 2014-06-10) and Agence Nationale de Securite du Medicament (ANSM, DMTCOS/DMCHIR/LAB/2014-A01043-44-A).