Smart implant rods for scoliosis treatment

Scoliosis is a spinal deformity caused by lateral curve on the frontal plane of the spine. Development and the treatment of the deformity varies with respect to the age. Scoliosis in patients with on going growth show rather more alteration compared to the adults. Because of the growth of the spine, the fixed segments need to be prolonged by surgical operation at periodic time intervals. Although posterior stabilization systems have been developed to facilitate lengthening for pediatric scoliosis, the treatment process is adversely affected because the correct time for elongation procedures can not be determined. With the smart implant rods produced within the scope of the thesis, stress and load between the two fixed vertebral segments in the treatment process can be tracked. First, sensors with the desired precision are produced and integrated into the bars. Smart implant rods were first subjected to mechanical tests individually according to the relevant standards of ASTM, and then vertebralctomy models were established for mechanical verification of the system and frequency values were measured by testing compression, tension, lateral bending and torsion tests. Frequency measurements were conducted under varying soft tissue thickness and effects were evaluated. Moreover, in order to determine the fatigue performances of the sensors, cyclic loads were applied and frequency measurements were recorded. System was tested on cadaviers under compression and tension tests. After mechanical modelling, animal model experiements were conducted. During the animal model experiments, transpedicular screws were inserted and attached with two rods on 15 sheeps. Sheeps were observed for a period of 6 months after the operation and frequency measurements were held once in a month from the sensors placed on the rods. In vertebrctomy models and cadaver tests, it was found that the increase in load under compression and lateral bending tests, increased the dielectric constant and capacitance, leading to an increase in frequency. Decrease in frequency was determined as the load was increased in tension tests. It has been shown that soft tissue thickness effects the measurements by the tests conducted. As a result of the measurements made after the cyclic loads, it has been revealed that the system is not affected by dynamic loading conditions. As a result of frequency measurements taken in living animal experiments, it was determined that the change between frequency values gradually decreased with the realization of fusion. Consequently, the developed system can reliably determine, whether the fusion has ben realised and prospective complications were seen caused by the increased stress on the rods. Thereof, revision surgeries, which are performed regularly in pediatric cases and independently of the development of the patient, can be performed as many and when needed. In addition, the use of these smart implant rods will make it possible to spot problems that can not be easily understood from the patient's x-ray, such as screw loosening, adjusting screw (nut) dissolving, and enable necessary intervention. As a result of the experiments, the measurements obtained through posterior fixation elements (smart implant rod), which deals with the treatment process in screw-rod systems commonly used in scoliosis surgeon, is introduced to the literatüre for the first time.