The potential of spring distraction to dynamically correct complex spinal deformities in the growing child

Purpose Current treatment of progressive early onset scoliosis involves growth-friendly instrumentation if conservative treatment fails. These implants guide growth by passive sliding or repeated lengthenings. None of these techniques provide dynamic correction after implantation. We developed the spring distraction system (SDS), by using one or multiple compressed springs positioned around a standard sliding rod, to provide active continuous distraction of the spine to stimulate growth and further correction. The purpose of this study was to determine feasibility and proof of concept of the SDS. Methods We developed a versatile, dynamic spring distraction system for patients who would benefit from active continuous distraction. This prospective case series evaluates four patients with exceptional and progressive congenital spine deformities. Results Four patients had a mean age of 6.8 years at surgery with a mean follow-up of 36 months (range 25-45). The mean progressive thoracic lordosis, which was the reason for initiating surgical treatment in two patients, changed from 32 degrees lordosis preoperatively to 1 degrees kyphosis post-operatively. During follow-up, this further improved to 32 degrees thoracic kyphosis. In the two other patients, with cervicothorcacic scoliosis, the main coronal curve improved from 79 degrees pre-operatively to 56 degrees post-operatively and further improved to 42 degrees. The mean T1-S1 spine growth during follow-up for all patients was 1.3 cm/year. There was one reoperation because of skin problems and no device-failures. Conclusion These early results show the feasibility and the proof of concept of spring-based distraction as a dynamic growth-enhancing system with the potential of further correction of the deformity after implantation.