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The effect of screw thread length on initial stability of Schatzker type 1 tibial plateau fracture fixation: a biomechanical study

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ABSTRACT

Background: This study compares the cyclic loading properties and failure loads of two screw combinations on a synthetic Schatzker type 1 tibia fracture model. Our hypothesis was that after adequate compression with first a partially threaded screw, addition of a fully threaded screw would provide more stability than an addition of a second partially threaded screw.

Methods: The Schatzker type 1 tibial plateau fracture model was created. Fixation was obtained in group A (n = 10) with two partially threaded screws and in group B (n = 10) with one fully threaded screw and one partially threaded screw. Load-displacement evaluation was made at each 1000-cycle interval up to 10,000 cycles. Failure load was identified as the load creating a 2-mm displacement. Two-factor (groups and periods) repeated measurement analysis of variance and independent sample t tests were used.

Results: According to the two-factor repeated analysis, there was no significant difference for periods (p = 0.29) and time-period interaction (p = 0.59) (Wilk’s Lambda F value, 1.507 and 0.871, respectively). In the test of between-subject effects, there was no significant difference between groups in terms of cyclic loadings (p = 0.06, F = 4.065). However, in the t test for each 1000-cycle interval, the value of mean displacement in group B was significantly lower than that in group A in the initial, 1000-, 2000-, and 3000-cycle intervals (p = 0.023, 0.031, 0.025, 0.043, respectively). The mean displacement and standard deviations increased with the number of cycles. The mean range of displacement initially was 0.66 mm for group A and 0.36 mm for group B. The mean range of displacement after 10,000 cycles was 0.79 mm for group A and 0.44 mm for group B. The mean failure load value was 682 ± 234 N for group A and 835 ± 245 N for group B. In independent sample t tests, there were no significant differences between the two groups in terms of failure load (p > 0.05).

Conclusions: Obtaining fixation with one partially and one fully threaded screw can minimize displacement at the fracture site at early cyclic loadings.

No MeSH data available.


Experiment setup with two cameras pointed towards the bone model. The figure on the right is the close-up of the model
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Fig3: Experiment setup with two cameras pointed towards the bone model. The figure on the right is the close-up of the model

Mentions: The material test device (MTS 858 Mini Bionix™ II) was set up in such a way as to have direct loading on the fracture fragment (Fig. 3). This simulated the action shearing forces on the tibial plateau in full knee extension. We chose this position because it creates the greatest shearing forces on the tibiofemoral joint [15]. A rectangular-shaped piece of rubber was fixed on the fragment of the bone to distribute the load on a greater joint surface. Grid stickers were pasted on both sides of the fracture line on the anterior surface of the tibia. The stickers were registered digitally, and their movements were analyzed using two high-tech cameras that were able to do a 3D analysis (Vic3D 3D Digital Imaging Correlation (DIC), Correlated Solutions Inc.), although we only had a coronal plan analysis of displacement. We defined displacement as 2 mm of movement along any axis in the space on the basis that intra-articular fractures are usually treated operatively if there is more than 2 mm of articular step off. Pictures were taken as four frames per second for each 1000-cycle interval and load to failure test.Fig. 3


The effect of screw thread length on initial stability of Schatzker type 1 tibial plateau fracture fixation: a biomechanical study
Experiment setup with two cameras pointed towards the bone model. The figure on the right is the close-up of the model
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5120498&req=5

Fig3: Experiment setup with two cameras pointed towards the bone model. The figure on the right is the close-up of the model
Mentions: The material test device (MTS 858 Mini Bionix™ II) was set up in such a way as to have direct loading on the fracture fragment (Fig. 3). This simulated the action shearing forces on the tibial plateau in full knee extension. We chose this position because it creates the greatest shearing forces on the tibiofemoral joint [15]. A rectangular-shaped piece of rubber was fixed on the fragment of the bone to distribute the load on a greater joint surface. Grid stickers were pasted on both sides of the fracture line on the anterior surface of the tibia. The stickers were registered digitally, and their movements were analyzed using two high-tech cameras that were able to do a 3D analysis (Vic3D 3D Digital Imaging Correlation (DIC), Correlated Solutions Inc.), although we only had a coronal plan analysis of displacement. We defined displacement as 2 mm of movement along any axis in the space on the basis that intra-articular fractures are usually treated operatively if there is more than 2 mm of articular step off. Pictures were taken as four frames per second for each 1000-cycle interval and load to failure test.Fig. 3

View Article: PubMed Central - PubMed

ABSTRACT

Background: This study compares the cyclic loading properties and failure loads of two screw combinations on a synthetic Schatzker type 1 tibia fracture model. Our hypothesis was that after adequate compression with first a partially threaded screw, addition of a fully threaded screw would provide more stability than an addition of a second partially threaded screw.

Methods: The Schatzker type 1 tibial plateau fracture model was created. Fixation was obtained in group A (n = 10) with two partially threaded screws and in group B (n = 10) with one fully threaded screw and one partially threaded screw. Load-displacement evaluation was made at each 1000-cycle interval up to 10,000 cycles. Failure load was identified as the load creating a 2-mm displacement. Two-factor (groups and periods) repeated measurement analysis of variance and independent sample t tests were used.

Results: According to the two-factor repeated analysis, there was no significant difference for periods (p = 0.29) and time-period interaction (p = 0.59) (Wilk’s Lambda F value, 1.507 and 0.871, respectively). In the test of between-subject effects, there was no significant difference between groups in terms of cyclic loadings (p = 0.06, F = 4.065). However, in the t test for each 1000-cycle interval, the value of mean displacement in group B was significantly lower than that in group A in the initial, 1000-, 2000-, and 3000-cycle intervals (p = 0.023, 0.031, 0.025, 0.043, respectively). The mean displacement and standard deviations increased with the number of cycles. The mean range of displacement initially was 0.66 mm for group A and 0.36 mm for group B. The mean range of displacement after 10,000 cycles was 0.79 mm for group A and 0.44 mm for group B. The mean failure load value was 682 ± 234 N for group A and 835 ± 245 N for group B. In independent sample t tests, there were no significant differences between the two groups in terms of failure load (p > 0.05).

Conclusions: Obtaining fixation with one partially and one fully threaded screw can minimize displacement at the fracture site at early cyclic loadings.

No MeSH data available.