Purpose: The purpose of this study is to compare biomechanical characteristics of tension band wiring using Kirschner wires (TBWKW), cannulated screws (TBWCS), and ring pins (TBWRP) for transverse fracture of the patella. Methods: A total of 48 polyurethane synthetic patellae were biomechanically tested. All patellae were osteotomized to create a transverse fracture. Each TBWKW, TBWCS, and TBWRP fixed 16 broken patellae. A specially designed fixation board simulated a knee with 90° flexion. Ten static tests and six dynamic tests were performed on each method. The static test is measuring maximum strength ( N) during traction until breakage of the fixation. The dynamic test consisted of measuring the fracture gap (mm) after 10,000 repetitive loading cycles between 100 N and 300 N that simulated actual daily activity. A gap of 2 mm or more was defined as a failure in both tests. Result: The failure load was 438.6 ± 138.6 N, 422.2 ± 72.7 N, and 1106.8 ± 230.3 N for TBWKW, TBWRP, and TBWCS, respectively. TBWCS showed a statistically significant difference compared to TBWKW and TBWRP in the static test ( p < 0.001). All the groups had no failure in the dynamic test. The mean fracture gap after completion of the dynamic test was 0.3267 ± 0.3395 mm, 0.2938 ± 0.2165 mm, and 0.0360 ± 0.0570 mm for TBWKW, TBWRP, and TBWCS, respectively ( p = 0.044). The mean values in the dynamic test showed no statistical difference. There was a significant difference between TBWRP and TBWCS ( p = 0.009), but others showed no difference with statistical significance. Conclusion: All three methods have sufficient stability at a daily activity. TBWCS showed a better failure load compared with TBWKW and TBWRP. TBWRP showed compatible mechanical characteristics with traditional tension band wiring. TBWRP could be an alternative method for TBWKW.

Background: Although preventing triceps fragment displacement is essential for treating an olecranon fracture, we frequently encounter situations in which only a few screws can be fixed to the triceps fragment. The aim of this study was to compare the stability of double-plate fixation and posterior plate fixation for olecranon fractures when the triceps fragment was small and only 2 screws could be inserted. Methods: A composite ulna model was used to simulate olecranon fracture. Four groups were formed consisting of double-plate and posterior plates with cortical and locking screws. The cyclic loading test was conducted for 500 cyclic loads of 5 to 50 N on a specimen to measure micromotion and displacement of the gap caused by light exercise. The load-to-failure test was performed by applying a load until fixation loss, defined as when the fracture gap increased by 2 mm or more or catastrophic failure occurred, to measure the maximum load. Results: Eight samples per group were tested through the pilot study. All groups were stable with a micromotion of <0.5 mm. However, the mean micromotion showed significant differences between the 4 groups ( P < .001, Table 1 Table 1 Mean gapping and displacement in the cyclic loading test. Displacement after the test Group Gapping during the test (range) Anterior cortex (range) Posterior cortex (range) Double-cortical 0.42 ± 0.11 (0.25–0.58) ∗ 0.02 ± 0.18 (−0.78–0.31) 0.14 ± 0.14 (−0.13–0.16) † Double-locking 0.17 ± 0.03 (0.12–0.21) ∗ 0.05 ± 0.10 (−0.16–0.16) 0.08 ± 0.14 (−0.17–0.11) Posterior-cortical 0.09 ± 0.02 (0.05–0.12) ∗ 0.03 ± 0.13 (−0.37–0.22) 0.03 ± 0.19 (−0.14–0.28) Posterior-locking 0.12 ± 0.04 (0.07–0.17) ∗ 0.04 ± 0.10 (−0.12–0.22) −0.03 ± 0.22 (−0.44–0.20) ). In the mean micromotion during exercise, posterior plating with cortical screws was the most stable (0.09 ± 0.02 mm) while double-plating with cortical screws was the most unstable (0.42 ± 0.11 mm). At the maximum load, posterior plating with locking screws was the strongest (205.3 ± 2.8 N) while double-plating with cortical screws was the weakest (143.3 ± 27.1 N). There was no significant difference in displacement after light exercise between the groups. Conclusions: This study...