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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.


AP and lateral X-rays of the bone model after screw fixation
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Fig2: AP and lateral X-rays of the bone model after screw fixation

Mentions: After a model was osteotomized, the fragment was repositioned and fixed with combinations of two group screws. All screws were 75 mm in length and 6.5 mm in diameter. Two partially threaded cancellous screws were used for group A and one partially threaded screw and one fully threaded screw was for group B (Tasarımmed®, Istanbul, Turkey). The partially threaded screws in group B were always placed in the posterior hole, and the fully threaded screws were always placed in the anterior hole. Before the screws were placed, the screw path was tapped and they were tightened with screwdrivers at a torque limit of 1.5 N. This limit was chosen to make sure that all the screws were tightened with the same amount, and the screwdriver with 1.5-N limits is used routinely in our daily practice. Tibia specimens were cut perpendicularly to the long axis of the bone at 13 cm of the distance from the proximal end. Each sample was embedded in a plastic cylinder, which was 5 cm in diameter and 5 cm in length, using polyester steel putty. This was done so that the distal end of the tibia would be suitable for adapting on a testing machine. X-rays of the specimen are shown in Fig. 2.Fig. 2


The effect of screw thread length on initial stability of Schatzker type 1 tibial plateau fracture fixation: a biomechanical study
AP and lateral X-rays of the bone model after screw fixation
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig2: AP and lateral X-rays of the bone model after screw fixation
Mentions: After a model was osteotomized, the fragment was repositioned and fixed with combinations of two group screws. All screws were 75 mm in length and 6.5 mm in diameter. Two partially threaded cancellous screws were used for group A and one partially threaded screw and one fully threaded screw was for group B (Tasarımmed®, Istanbul, Turkey). The partially threaded screws in group B were always placed in the posterior hole, and the fully threaded screws were always placed in the anterior hole. Before the screws were placed, the screw path was tapped and they were tightened with screwdrivers at a torque limit of 1.5 N. This limit was chosen to make sure that all the screws were tightened with the same amount, and the screwdriver with 1.5-N limits is used routinely in our daily practice. Tibia specimens were cut perpendicularly to the long axis of the bone at 13 cm of the distance from the proximal end. Each sample was embedded in a plastic cylinder, which was 5 cm in diameter and 5 cm in length, using polyester steel putty. This was done so that the distal end of the tibia would be suitable for adapting on a testing machine. X-rays of the specimen are shown in Fig. 2.Fig. 2

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.