scholarly journals Evaluation of S2 Alar and Traditional S1 Pedicle Fixation for Severe Lumbar Spondylolisthesis in Different Bone Mineral Densities: A Finite Element Analysis

2020 ◽  
Author(s):  
Juehan Wang ◽  
Wei Chen ◽  
Xi Yang ◽  
Ce Zhu ◽  
Tingxian Ling ◽  
...  
Keyword(s):  
Finite Element ◽  
Internal Fixation ◽  
Screw Fixation ◽  
Fixation Method ◽  
Common Disease ◽  
Model Parameters ◽  
Fixation Device ◽  
Internal Fixation Device ◽  
Computed Tomography Images ◽  
Lumbar Spondylolisthesis

Abstract Background: Lumbar spondylolisthesis is a common disease in older populations. The surgical treatment of spondylolisthesis has a history of more than 50 years, with L5-S1 screws widely used in clinical practice to reduce slippage and fusion. However, some patients with severe lumbar spondylolisthesis and osteoporosis could have complications, such as internal fixation rupture, S1 screw loosening, and incomplete slippage reduction. To better treat this kind of patient, sacral screw fixation is gradually becoming more common. Little is known about the biomechanical performance of L5-S2 alar internal fixation constructs after posterior lumbar interbody fusion. This study aimed to compare L5-S1 reduction and fixation methods and explore whether extending the fixation to include the S2 alar can significantly improve the stability of the internal fixation device. METHODS: Two kinds of validated finite element models of the L5-S1 segment were reconstructed via computed tomography images, including (1) the L5-S1 screw fixation model and (2) the L5-S2 alar fixation model. The inverse repair was performed using Geomagic software, the internal fixation device was drawn using Creo software, and the model parameters were set and analyzed using ANSYS Workbench software. Results: The average load of the L5-S2 alar internal fixation device was 86.9-111% higher than that of the L5-S1 fixation device when the internal bone of the S1 screw canal yielded. In the L5-S1 fixation model, the stress was concentrated in the tail of the S1 screw, and in the L5-S2 alar fixation model, the stress was concentrated in the titanium rod. In the L5-S2 alar fixation method, the internal deformation of the S1 screw track was scattered and uniform, while in the L5-S1 fixation method, local bone destruction in the front and back ends of the screw track was prone to occur due to the stress concentration. Conclusion: Extending fixation to the S2 wing can significantly improve internal fixation device stability and reduce the risk of intraoperative and postoperative fractures while avoiding injury to the sacroiliac joint, reducing the difficulty of surgery and the risk of injury to surrounding tissues. It is a reasonable plan for the treatment of moderate and severe lumbar spondylolisthesis with osteoporosis.

scholarly journals Evaluation of S2 alar and traditional S1 pedicle fixation for severe lumbar spondylolisthesis in different bone mineral densities: a finite element analysis

2020 ◽  
Author(s):  
Juehan Wang ◽  
Wei Chen ◽  
Xi Yang ◽  
Ce Zhu ◽  
Tingxian Ling ◽  
...  
Keyword(s):  
Finite Element ◽  
Internal Fixation ◽  
Posterior Lumbar Interbody Fusion ◽  
Normal Male ◽  
Model Parameters ◽  
Fixation Device ◽  
Element Analysis ◽  
Internal Fixation Device ◽  
Lumbar Spondylolisthesis ◽  
Yield Threshold

Abstract Purpose: Little is known about the biomechanical performance of L5-S2 alar internal fixation constructs after posterior lumbar interbody fusion. This study aimed to compare the biomechanical effect of L5-S1 internal fixation and L5-S2 alar internal fixation on severe lumbar spondylolisthesis. Methods: A normal male volunteer without a history of spinal disease was selected, lumbar CT data was collected. An intact L5-S2 three-dimensional finite element model was created by Mimics and Geomagic.Two kinds of fixation methods were reconstructed including (1) the L5-S1 screw fixation model and (2) the L5-S2 alar fixation model. The inverse repair was performed using Geomagic software, the internal fixation device was drawn using Creo software, and the model parameters were set and analyzed using ANSYS Workbench software. Results: The validity of the intact model shows that the ROM of the model is similar to that of a reported cadaveric study. The average stress of the L5-S2 alar internal fixation device was 86.9-111% higher(P＜0.001) than that of the L5-S1 fixation device when the bone of the S1 screw path reached the yield threshold. The maximal stress of the S1 screw in the L5-S2 alar fixation was significantly lower (P＜0.001) than it in the L5-S1 fixation when the stress exceeds the S1 bone yield threshold. When the S1 screw path bone yielded, the maximal deformation value of the S1 screw path was similar in both models (P>0.05), while the average deformation value of the S1 screw path in L5-S2 alar fixation was significantly higher (P＜0.01) than it in L5-S1 fixation. Conclusion: Extending fixation to the S2 wing can significantly improve internal fixation device stability and reduce the risk of intraoperative and postoperative fractures while avoiding injury to the sacroiliac joint, reducing the difficulty of surgery and the risk of injury to surrounding tissues. It is a reasonable plan for the treatment of moderate and severe lumbar spondylolisthesis with osteoporosis.

A Bioabsorbable Polymer for Collateral Ligament Repair in the Pig

1992 ◽  
Vol 05 (02) ◽  
pp. 80-84
Author(s):  
C. S. Patton ◽  
R. F. McConnel ◽  
R. Ross ◽  
G. M. H. Shires ◽  
Nancy Korenek
Keyword(s):  
Lactic Acid ◽  
Soft Tissue ◽  
Internal Fixation ◽  
Screw Fixation ◽  
Fixation Device ◽  
Collateral Ligament ◽  
Bioabsorbable Implants ◽  
Internal Fixation Device ◽  
Postsurgical Complications ◽  
Future Potential

SummaryA bioabsorbable internal fixation device of a poly-L-isomer of lactic acid (PLLA) was used to repair the proximal attachment of the medial femorotibial collateral ligament (MCL) in six miniature Yucatan pigs and compared with metal screw fixation in four pigs. Healing was evaluated by physical examination, gross dissection of surgical sites and histological evaluation of bone ligament interface. Chemical stress analysis of the tack was also evaluated.The absorbable PLLA tack induced minimal tissue reaction and maintained sufficient apposition for healing of the MCL in the miniature Yucatan pigs. No postsurgical complications were noted in the experimental or control groups. All surgical implant procedures were considered successful in maintaining MCL apposition. This study suggests future potential for utilization of the PLLA tack for bioabsorbable implants in soft tissue or bone.A bioabsorbable internal fixation device of a poly-L-isomer of lactic acid was used to repair the proximal attachment of the medial femorotibial collateral ligament in pigs, and compared with metal screw fixation. No postsurgical complications were noted in either group. All surgical implant procedures were successful. This study suggests future potential for utilization of the tack for bioabsorbable implants in soft tissue or bone.

MEASUREMENT OF INTERNAL FIXATION DEVICE SUPPORT IN EXPERIMENTALLY PRODUCED FRACTURES OF THE DORSOLUMBAR SPINE

Orthopedics ◽  
1979 ◽  
Vol 2 (1) ◽  
pp. 28-34
Author(s):  
Michael S Pinzur ◽  
Paul R Meyer ◽  
Eugene P Lautenschlager ◽  
John C Keller ◽  
William Dobozi ◽  
...  
Keyword(s):  
Internal Fixation ◽  
Fixation Device ◽  
Internal Fixation Device

scholarly journals Biomechanical evaluation of type p condylar head osteosynthesis using conventional small-fragment screws reinforced by a patient specific two-component plate

2020 ◽  
Vol 16 (1) ◽  
Author(s):  
Tetiana Pavlychuk ◽  
Denis Chernogorskyi ◽  
Yurii Chepurnyi ◽  
Andreas Neff ◽  
Andrii Kopchak
Keyword(s):  
Finite Element ◽  
Screw Fixation ◽  
Cortical Layer ◽  
Fixation Method ◽  
Patient Specific ◽  
Small Fragment ◽  
Element Analysis ◽  
Biomechanical Behavior ◽  
Condylar Head ◽  
Small Patient

Abstract Background The aim of this study was to evaluate via finite element analysis (FEA) the biomechanical behavior of conventional small-fragment screws reinforced by a patient-specific plate in type p condylar head. Methods A finite element model of the mandible was created using Mimics 12.1 software. A type p condylar head fracture was simulated in the right condyle, and the left condyle was used as a control. Two patterns of fixation were investigated: conventional two-screw fixation and the same fixation system reinforced with a small, patient-specific plate. Surface models were imported into the software Ansys 5.7for further volume mesh generation. Results The highest stress gradients were observed in the cortical layer of the lateral fragment, located near the screw. The conventional fixation method resulted in equivalent stresses 2 to 10 times greater than the reinforced method. Rigidity of fixation in the reinforced method increased up to 1.25–3 times compared to the conventional two-screw technique. Conclusion This study’s findings suggest significant benefits in unfavorable biomechanical conditions from reinforcement of the standard two-screw fixation of condylar head fractures with a small, patient-specific plate acting as a washer.

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