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Category: Trauma; Ankle Introduction/Purpose: The importance of the deltoid ligament in the congruency of the tibiotalar joint is well known. The current trend is to repair it in cases of acute injuries in the context of ankle fractures, however, there is no information on how it should be reconstructed. The objective of this study was to compare different deltoid ligament repair types in an ankle fracture cadaveric model. Methods: 16 cadaveric foot-ankle-distal tibia specimens were used to conduct the study. All samples were prepared as a supination external rotation ankle fracture model. An axial load and cyclic axial rotations were applied on every specimen using a specifically designed frame. This test was performed without deltoid injury, with deltoid injury and finally with the ligament reconstructed. The reconstruction was performed in 4 different ways (anterior, posterior, middle, combined) using 4 specimens per group. Medial clear space (MCS) was measured for each condition on simulated weight-bearing and gravity stress radiographs. Reflective markers were utilized in tibia and talus, registering through a motion analysis system the kinematics, to record the tibiotalar uncoupling. Statistical analysis was performed using the SPSS software. Results: In all cases, the MCS increased significantly on gravity stress radiographs after damaging the deltoid ligament. There was no increase in the MCS on load radiographs. After repair, in all cases, the MCS was normalized. Kinematically, after damage the tibiotalar uncoupling increased significantly, decreasing after repair. All repairs significantly corrected the tibiotalar uncoupling, observing a significantly increased coupling effect (increased stiffness) with the combined repair. Conclusion: Our results show that deltoid repair recovers the tibiotalar coupling mechanism in an ankle fracture model. We suggest that the ideal repair should aim to repair the middle aspect of the deltoid ligament. The combined repair may lead to postoperative stiffness. Clinical studies are needed to prove these results and show clinically improved outcomes.

Category: Ankle, Basic Sciences/Biologics, Sports Introduction/Purpose: Peroneus brevis tendon tears are frequently diagnosed when ankle instability is present. No clear guideline exists as to when to repair or resect peroneal tendon tears, as most of the available literature uses Meyer’s work published in 1924 where a risk of spontaneous rupture would exist when less than 50% of the tendon remains undamaged. Our objective was to analyze the mechanical behavior of cadaveric peroneal tendons subjected to an artificially made damage, compromising 66% of its visible width and tested in a cyclic and failure phase. Our hypothesis was that no failure would be observed in the cyclic phase. Methods: 8 cadaveric foot- ankle – distal tibia specimens were included in this study. A longitudinal full thickness tendon defect was created, 3 cms in length, centered behind the tip of the fibula, compromising 66% of the visible width of the peroneal tendons as measured by a caliper. The peroneal retinaculum was kept intact. All specimens were mounted onto a special frame specifically designed for the study. All tendons were tested in a cyclic fashion using 100 repetitions between 50 N and 200 N. If no visual change or tendon failure was observed after the initial testing, a load to failure test was performed until tendon rupture or fixation failure was observed. Tendon stiffness and load to failure were registered. Statistical analysis was performed using the SPSS software. Results: No tendon failed during the cyclic testing. No defect lengthening was observed after the cyclic phase. On the failure phase, the mean load resisted by the peroneus brevis was 416 N, with a 95% confidence interval between 351 N -481 N. The mean load resisted by the peroneus longus was 723 N, with a 95% confidence interval between 578 N – 868 N. All failures were at the level of the defect created. The coefficient of variation was low for both tendons. Conclusion: A 33% of remaining peroneal tendon was able to resist very high tensile forces; therefore, it can be suggested that a 66% defect can be repaired and does not necessarily need a tenodesis as it has been historically recommended. The high resistance offered by the peroneus longus tendon offers the theoretical potential to use part of it as a free graft to repair peroneus brevis tears. The 50% rule, which determines when a peroneal tendon tear needs a tenodesis or repair, should be revisited.

Category: Bunion Introduction/Purpose: Hallux Rigidus (HR) is characterized initially by a decrease in Hallux metatarsophalangeal joint (MTPJ) dorsiflexion, decreasing the total range of motion. To be able to study different surgical treatment options, a cadaveric model has to be developed that recreates the limited range of motion. Our objective was to develop an Hallux Rigidus cadaveric model by shortening the plantar fascia (PF). Hallux MTPJ range of motion and joint stiffness were evaluated. Methods: 8 cadaveric foot- ankle – distal tibia specimens were prepared, identifying all extensor and flexor tendons proximally. The skin and subcutaneous tissue was kept intact. Each specimen was mounted on a special frame and luminous markers were attached to the skin (Oxford Foot Model). A dead weight equal to 50% of the stance phase force was applied to each tendon, except for the Achilles tendon and the posterior tibialis. 10 Hallux MTPJ dorsiflexion-plantarflexion cycles were performed by pulling the Extensor Hallucis longus tendon using an tensile testing machine (Kinetecnics). A Hallux Rigidus model was then developed by shortening the PF by 6 mm using a triple fiberwire suture technique. The same 10 cycles were repeated with a shortened PF. Each specimen served as its own control. Hallux metatarsophalangeal stiffness and kinematics were tested using a tensile testing machine and high definition cameras. Results: The group with a shortened PF significantly reduced the hallux dorsiflexion (18.6 degrees) compared to the native foot (23.7 degress) (p0.05). Conclusion: To create a HR model is vital to allow further understanding of the pathology. The cadaveric model should not alter the joint stability (intact periarticular soft tissues) but has to limit Hallux range of motion. The model we present successfully recreates HR by limiting MTPJ dorsiflexion. The absence of stiffness change shows that joint congruity and isometry were not modified. There are a few reports that state a PF shortening as the first stage in HR. This would lead to a hinge-like MTPJ dorsiflexion, creating a dorsal metatarsal head impingement that could evolve to a dorsal exostosis.