Development of a non-fusion scoliosis correction device: designing and testing

If for some reason spinal development during adolescence malfunctions, a deformity such as scoliosis may develop. Scoliosis is a deformity of the spine, characterised by a lateral curvature and an axial rotation. Treatment of scoliosis includes non-surgical and surgical interventions. Current surgical treatment of scoliosis is unsatisfactory because it embraces the permanent immobilisation of several vertebrae, which results in a fused spine that is unable to flex and to develop normally in immature patients. Therefore, an improved method is required. This dissertation addresses the development of a new implant system that delivers a revolutionary surgical solution to a problem classified as ‘adolescent idiopathic scoliosis’ (AIS). This non-fusion correction system (XS LATOR) comprises two (separate) implants. One implant (XS TOR) is a torsion-generating element that applies a torque on the spine to correct the axial rotation of the vertebrae. The other implant (XS LAT) is a lateral bending element that applies a bending moment to correct the lateral curvature. The implants can be used together in such a way that an optimal configuration for each patient can be implemented. The system will be implanted in the adolescent during the growth phase and removed when the spine is fully grown, which means that the implants must be functional for a period of ten years. Unlike current fusion systems, the system is highly flexible thus fusion of the vertebrae will be avoided. Consequently, the imposed corrective moment and torque on the spine are small but remain present all the time and thus generate a gradual shape change as observed in orthodontic braces. Axial motion is possible due to U-loops at both ends of the devices The U-loops can slide into plain bearings. With axial motion three aspects are covered: spinal growth, variations in spinal lengths of the patients and axial motion due to daily activities.