Fixation strength of biocomposite wedge interference screw in ACL reconstruction: effect of screw length and tunnel/screw ratio. A controlled laboratory study

<p>Abstract</p> <p>Background</p> <p>Primary stability of the graft is essential in anterior cruciate ligament surgery. An optimal method of fixation should be easy to insert and provide great resistance against pull-out forces.</p> <p>A controlled laboratory study was designed to test the primary stability of ACL tendinous grafts in the tibial tunnel. The correlation between resistance to traction forces and the cross-section and length of the screw was studied.</p> <p>Methods</p> <p>The tibial phase of ACL reconstruction was performed in forty porcine tibias using digital flexor tendons of the same animal. An 8 mm tunnel was drilled in each specimen and two looped tendons placed as graft. Specimens were divided in five groups according to the diameter and length of the screw used for fixation. Wedge interference screws were used. Longitudinal traction was applied to the graft with a Servohydraulic Fatigue System. Load and displacement were controlled and analyzed.</p> <p>Results</p> <p>The mean loads to failure for each group were 295,44 N (Group 1; 9 × 23 screw), 564,05 N (Group 2; 9 × 28), 614,95 N (Group 3; 9 × 35), 651,14 N (Group 4; 10 × 28) and 664,99 (Group 5; 10 × 35). No slippage of the graft was observed in groups 3, 4 and 5. There were significant differences in the load to failure among groups (ANOVA/P < 0.001).</p> <p>Conclusions</p> <p>Longer and wider interference screws provide better fixation in tibial ACL graft fixation. Short screws (23 mm) do not achieve optimal fixation and should be implanted only with special requirements.</p

Shu 書 (documents) repertoire in argument-based texts from guodian: the case of cheng zhi 成之 (things brought to completion)

Cheng zhi 成之 (short for Cheng zhi wen zhi 成之聞之) from tomb no. 1, Guodian, has been widely understood as an early example of a text that sets out to explain the Shangshu. This claim is problematic because it relies on unfounded assumptions of canonicity. Going beyond this canon-centred, exegetical paradigm, this article provides a form analysis of argument construction in Cheng zhi, to demonstrate that conceptual communities during the Warring States draw on traditions of Shu 書 (Documents) as cultural capital to pursue their own socio-political and philosophical agendas. Rather than dominant interpretations that insist on Shu as an entity of stable and fixed texts, as well as on a singular engagement with the Shangshu 尚書 in Cheng zhi, I identify four textual voices in the Guodian text which in dialogic form articulate an integral position on good rule. They are what I call “explicit” and “silent authorial voices”, as well as two “external” voices. One is from the Shu traditions; the other is attributed to a constructed persona of moral integrity named “gentleman” (junzi). I show how the various voices consolidate the text’s argument by creating a reference structure that determines the way an argument is made in Cheng zhi. In this way, the Guodian text is shown to rework old cultural capital into new argument space to produce normative claims. This article concludes that while the Shu emerged as loosely textualised traditions during the Warring States period (ca. 453–222 bce), they nonetheless framed the expectations of conceptual text communities, casting light on these traditions as something dynamic, yet authoritative. </p