Biomechanical Comparison of Different Treatment Strategies for Thoracolumbar Burst Fracture: A Finite Element Study.

OBJECTIVE: The aim of this study was to compare the biomechanical performance of 6 pedicle screw internal fixation strategies for the treatment of burst fractures of the thoracolumbar spine using finite element (FE) analysis. METHODS: A finite element model of the T11-L3 thoracolumbar segment was established to simulate L1 vertebral burst fractures, and 6 models were conducted under multidirectional loading conditions: P2-D2, P1-D1, P2-D1,P1-D, P1-BF-D1, and P1-UF-D1. The range of motion (ROM) in the T12-L2 region and the von Mises stresses of pedicle screws and rods under the 6 internal fixation models were mainly analyzed. RESULTS: The maximum ROM and von Mises stress were obtained under flexion motion in all models. The P1-BF-D1 model had the least ROM and screw stress. However, when the injured vertebra was not nailed bilaterally, the P1-UF-D1 model had the smallest ROM; the maximum von Mises stress on the screw and rod was remarkably higher than that recorded in the other models. Moreover, the P2-D1 model had a ROM similar to that of the P1-D2 model, but with lower screw stress. The 2 models outperformed the P1-D1 model in all 6 conditions. The P2-D2 model had a similar ROM with the P2-D1 model; nevertheless, the maximum von Mises stress was not substantially reduced. CONCLUSIONS: The P1-BF-D1 model exhibited better stability and less von Mises stress on the pedicle screws and rods, thereby reducing the risk of screw loosening and fracture. The P2-D1 internal fixation approach is recommended when the fractured vertebrae are not nailed bilaterally.

Sagittal Spinopelvic Alignment in the Standing and Prone Positions of Patients with Old Traumatic Thoracolumbar Kyphosis: Relationship with Immediately Postoperative Parameters.

OBJECTIVE: The aim of this study was to investigate the changes in spine-pelvis sagittal parameters from the standing position to the prone position and to study the relationship between sagittal parameters and immediately postoperative parameters. METHODS: Thirty-six patients with old traumatic spinal fracture combined with kyphosis were enrolled. The preoperative standing position, prone position, and postoperative sagittal parameters of the spine and pelvis, including the local kyphosis Cobb angle (LKCA), thoracic kyphosis angle (TKA), lumbar lordosis angle (LLA), sacral slope (SS), pelvic tilt (PT), pelvic incidence minus lumbar lordosis angle (PI-LLA), and sagittal vertebral axis (SVA), were measured. The data of kyphotic flexibility and correction rate werecollected and analyzed. The parameters of the preoperative standing position, prone position and postoperative sagittal position were analyzed statistically. Correlation analysis and regression analysis of the preoperative standing and prone sagittal parameters and postoperative parameters were conducted. RESULTS: There were significant differences in the preoperative standing position, prone position, and postoperative LKCA and TK. Correlation analysis showed that preoperative sagittal parameters of the standing position and prone position were all correlated with postoperative homogeneity. Flexibility was not related to the correction rate. Regression analysis showed preoperative standing, prone LKCA, and TK were linear with postoperative standing. CONCLUSIONS: The LKCA and TK of old traumatic kyphosis obviously changed from the standing position to the prone position, which were linear with postoperative LKCA and TK and can be used to predict postoperative sagittal parameters. This change should be taken into account in the surgical strategy.

Preoperative standing to prone spinal-pelvic sagittal parameter changes in old traumatic spinal fractures with kyphosis / 中国修复重建外科杂志

OBJECTIVE@#To investigate the changes in spinal-pelvic sagittal parameters from preoperative standing to prone position in old traumatic spinal fractures with kyphosis.@*METHODS@#The clinical data of 36 patients admitted between December 2016 and June 2021 for surgical treatment of old traumatic spinal fractures with kyphosis, including 7 males and 29 females, aged from 50 to 79 years (mean, 63.9 years), were retrospectively analyzed. Lesion segments included 2 cases of T 11, 12 cases of T 12, 2 cases of T 11, 12, 4 cases of T 12 and L 1, 12 cases of L 1, 2 cases of L 2, 1 case of L 2, 3, and 1 case of L 3. The disease duration ranged from 4 to 120 months, with an average of 19.6 months. Surgical procedures included Smith-Petersen osteotomy in 4 cases, Ponte osteotomy in 6 cases, pedicle subtraction osteotomy in 2 cases, and improved fourth level osteotomy in 18 cases; the remaining 6 cases were not osteotomized. The bone mineral density ranged from -3.0 to 0.5 T, with a mean of -1.62 T. The spinal-pelvic sagittal parameters from preoperative standing to prone positions were measured, including local kyphosis Cobb angle (LKCA), thoracic kyphosis (TK), lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT), and PI and LL mismatch (PI-LL). The kyphotic flexibility=(preoperative standing LKCA-preoperative prone LKCA)/preoperative standing LKCA×100%. Spinal-pelvic sagittal parameters were compared between standing position and prone position before operation, and Pearson correlation was used to judge the correlation between the parameters of standing position and prone position before operation.@*RESULTS@#When the position changed from standing to prone, LKCA and TK decreased significantly ( P<0.05), while SS, LL, PT, and PI-LL had no significant difference ( P>0.05). Pearson correlation analysis showed that LL was significantly correlated with SS and PI-LL in both standing and prone positions ( P<0.05), and the correlation strength between LL and SS in prone position was higher than that in standing position. In the standing position, LKCA was significantly correlated with SS and PT ( P<0.05). However, when the position changed from standing to prone, the correlation between LKCA and SS and PT disappeared, while PT and PI-LL was positive correlation ( P<0.05). The kyphotic flexibility was 25.13%-78.79%, with an average of 33.85%.@*CONCLUSION@#For the patients of old traumatic spinal fractures with kyphosis, the preoperative LKCA and TK decrease significantly from standing position to prone position, and the correlation between spinal and pelvic parameters also changed, which should be taken into account in the formulation of preoperative surgical plan.