Decision of Posterior Fixation Level by Load-Sharing Classification in Thoracolumbar and Lumbar Burst Fracture

Abstract

Study Design : Retrospective study on 54 thoracolumbar and lumbar burst fractures treated with pedicle screw instrumentation. Objectives : To decide the optimal level of fusion in thoracolumbar and lumbar burst fractures treated with pedicle screw instrumentation by load sharing concept. Summary of Literature Review : Short segment pedicle screw fixation is condemned with frequent failure in maintenance of reduction. The type of posterior fixation construct that is most desirable is less well defined. Materials and Methods : Using the Load-Sharing classification, Group I consisted of 24 cases with fractures totaling 6 points or less underwent surgery which was subdivided into two subgroups(A : 1 level above and below including fractured vertebra, B : long segment fixation). Group II consisted of 30 cases with fractures totaling 7 points or more underwent surgery which was subdivided into three subgroups(C : 1 level above and below including fractured vertebra, D : 2 levels above, 1 level below including fractured vertebra, E : 2 levels above and below the fractured vertebra). Change of segmental kyphosis, inter-screw angle, upper disc height, lower disc height and anterior body height were measured using post-operative and follow-up lateral radiographs. Results : Comparing two subgroups in group I(A Vs. B), group A showed definitely more loss of upper disc height than group B but the others were not significantly different. Comparing three subgroups in group II(C, D, E), group C showed definitely more loss of reduction than two other groups but loss of anterior body height was not significantly different. There were no significant differences between group D and E. C o n c l u s i o n s : For fracture totaling 6 points or less, the long segment fixation(2 level above and 1 level below including fractured vertebra) is a successful method at thoracolumbar junction and short segment fixation to preserve motion segment at lumbar spine. For fracture totaling 7 points or more, short segment fixation is inappropriate and long segment pedicle screw fixation (2 level above and 1 level below including fractured vertebra) could effectively treat burst fractures of thoracolumbar and lumbar spine.