An analysis of implant failure after posterior long-segment instrumentation for thoracolumbar fracture

CHEN Yong-he; WANG Xiang; QU Dong-bin; JIANG Jian-ming

doi:10.3969/j.issn.2095-252X.2018.03.013

Abstract：Objective To analyze the reasons of implant failure after posterior long-segment instrumentation for thoracolumbar fracture, and to discuss the relationship between the imbalance of the spinal alignment and implant failure. Methods From January 2004 to January 2015, 70 patients with unstable thoracolumbar fracture were treated with posterior long-segment fixation in Nanfang Hospital, Southern Medical University. There were 41 males and 29 females with the mean age of ( 33.6 ± 10.4 ) years ( range: 18 - 57 years ). AO Spine fracture classification: type A3, A4, B and C. Fracture segments and AO fracture classification results were compared between the 2 groups. The distance of fractured vertebra shifting ( DFVS ), scoliosis and kyphotic Cobb's angle were measured on X-ray radiographs pre and post operatively. According to the spine coronal and sagittal alignment after the operation, we divided all patients into balanced group ( Group A, n = 49 ) and unbalanced group ( Group B, n = 21, 9 cases with the imbalanced sagittal alignment, 7 cases with the imbalanced coronal alignment, 5 cases with the imbalanced sagittal and coronal alignment ). The relationship between the unbalanced spine alignment and internal fixation failure was discussed.Results There were significant differences pre and post operation in DFVS[(11.1 ± 7.1)mm vs.(0.9 ± 1.3)mm],scoliosis Cobb's angle[(6.3 ± 7.3)°vs.(1.0 ± 1.3)°]and kyphotic Cobb's angle[(16.2 ± 9.9)°vs. ( 7.9 ± 8.2 ) ° ] in Group A ( P < 0.001 ). There were also significant differences pre and post operation in DFVS [ ( 9.2 ± 6.0)mm vs.(4.2 ± 3.6)mm]and kyphotic Cobb's angle[(17.8 ± 9.5)°vs.(7.7 ± 7.1)°]in Group B(P=0.001).But scoliosis Cobb's angle showed no differences in Group B. There were no significant differences in DFVS, scoliosis and kyphotic Cobb's angle between the 2 groups before the surgery ( P > 0.05 ). There were significant differences in DFVS and scoliosis Cobb's angle between the 2 groups 1 week after the surgery ( P < 0.001 ). There were significant differences in DFVS[(0.8 ± 1.4)mm vs.(4.2 ± 3.9)mm]and scoliosis Cobb's angle[(0.9 ± 1.2)°vs.(4.2 ± 6.1 ) ° ] between Group A and B at the final follow-up ( P < 0.001 ). Conclusions There are many reasons for implant failure after posterior long-segment instrumentation. The imbalance of coronal and sagittal alignment is an important factor leading to the failure of the internal fixation. In the process of fracture reduction, we should try to restore the balance of the spine alignment to reduce the risk of implant failure.