ABSTRACT
Transpedicular screw failure with new segmental fixation was described in the literature with a varying incidences in degenerative lumbar conditions, spondylolisthesis and fractures of dorsal and lumbar spine,3'4'5'6'7 but little, if any, was written on this subject regarding scoliosis. May be because till recently FDA did not yet approve its use in scoliosis. The aim of this study was to detect the patterns of implant failure in idiopathic adolescent scoliosis with different types of transpedicular screw fixation and the possible factors that may be responsible for such pattern of failure. Material and methods: 69 cases of idiopathic scoliosis of more than 3 years follow up were examined. Sixteen cases had shown 21 screws failure. The patients included 15 girls and one boy. The average age was 13.06 years The systems used for fixation in those cases of implant failure were TSRH in 7 cases, Claris in 8 cases and Isola in one case. Main results Claris system had the highest incidence of implant failure [38.1%] followed by TSRH [28%] and the least was Isola system [4.3%]. The average number of screws and number of vertebrae fixed with the three system were nearly equal. The main mode of failure with Claris system was due to looseness of the connector screw interface that occurred in 70% of cases. This mode of failure represented 50% of cases with TSRH while the other modes were pulling out of the screw [30%] and screw breakage [20%]. The failed case in Isola system was due to looseness of the screw connector interface. The Lower end of the curve contains two thirds of the cases of failure and the main mode of failure in this area was due to looseness of the connector screw interface [71.4%]. In the upper end of curve failure occurs mainly due to pulling out of the screws. The main modes of failure, however, in the intermediate portion of the curve were both pulling out and looseness of the connector. The mode of failure did not show evident change with the two methods of curve correction [Cephalo-caudal compression-distraction and derotation]. Also the mean percent of correction of the curve was not different in the different mode of failures