Browsing by Author "Guzmán, Rodrigo"
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Publication Biomechanical Cadaveric Evaluation of the Role of Medial Column Instability in Hallux Valgus Deformity(2022) Wagner, Emilio; Wagner, Pablo; Pacheco, Florencia; López, Mario; Palma, Felipe; Guzmán, Rodrigo; Berral, FranciscoBackground: Medial column instability is a frequent finding in patients with flatfeet and hallux valgus, within others. The etiology of hallux valgus is multifactorial, and medial ray axial rotation has been mentioned as having an individual role. Our objective was to design a novel cadaveric foot model where we could re-create through progressive medial column ligament damage some components of a hallux valgus deformity. Methods: Ten fresh-frozen lower leg specimens were used, and fluorescent markers were attached in a multisegment foot model. Constant axial load and cyclic tibial rotation (to simulate foot pronation) were applied, including pull on the flexor hallucis longus tendon (FHL). We first damaged the intercuneiform (C1-C2) ligaments, second the naviculocuneiform (NC) ligaments, and third the first tarsometatarsal ligaments, leaving the plantar ligaments unharmed. Bony axial and coronal alignment was measured after each ligament damage. Statistical analysis was performed. Results: A significant increase in pronation of multiple segments was observed after sectioning the NC ligaments. Damaging the tarsometatarsal ligament generated small supination and varus changes mainly in the medial ray. No significant change was observed in axial or frontal plane alignment after damaging the C1-C2 ligaments. The FHL pull exerted a small valgus change in segments of the first ray. Discussion: In this biomechanical cadaveric model, the naviculocuneiform joint was the most important one responsible for pronation of the medial column. Bone pronation occurs along the whole medial column, not isolated to a certain joint. Flexor hallucis longus pull appears to play some role in frontal plane alignment, but not in bone rotation. This model will be of great help to further study medial column instability as one of the factors influencing medial column pronation and its relevance in pathologies like hallux valgus. Clinical relevance: This cadaveric model suggests a possible influence of medial column instability in first metatarsal pronation. With a thorough understanding of a condition's origin, better treatment strategies can be developed.Item Biomechanical Evaluation of Circumtibial and Transmembranous Routes for Posterior Tibial Tendon Transfer for Dropfoot(2018) Wagner, Emilio; Wagner, Pablo; Zanolli, Diego; Radkievich, Rubén; Redenz, Gunther; Guzmán, RodrigoBackground: Tibialis posterior tendon transfer is performed when loss of dorsiflexion has to be compensated. We evaluated the circumtibial (CT), above-retinaculum transmembranous (TMAR), and under-retinaculum transmembranous (TMUR) transfer gliding resistance and foot kinematics in a cadaveric foot model during ankle range of motion (ROM). Methods: Eight cadaveric foot-ankle distal tibia specimens were dissected free of soft tissues on the proximal end, applying an equivalent force to 50% of the stance phase to every tendon, except for the Achilles tendon. Dorsiflexion was tested with all of the tibialis posterior tendon transfer methods (CT, TMAR, and TMUR) using a tension tensile machine. A 10-repetition cycle of dorsiflexion and plantarflexion was performed for each transfer. Foot motion and the force needed to achieve dorsiflexion were recorded. Results: The CT transfer showed the highest gliding resistance (P < .01). Regarding kinematics, all transfers decreased ankle ROM, with the CT transfer being the condition with less dorsiflexion compared with the control group (6.8 vs 15 degrees, P < .05). TMUR transfer did perform better than TMAR with regard to ankle dorsiflexion, but no difference was shown in gliding resistance. The CT produced a supination moment on the forefoot. Conclusion: The CT transfer had the highest tendon gliding resistance, achieved less dorsiflexion and had a supination moment. Clinical Relevance We suggest that the transmembranous tibialis posterior tendon transfer should be the transfer of choice. The potential bowstringing effect when performing a tibialis posterior tendon transfer subcutaneously (TMAR) could be avoided if the transfer is routed under the retinaculum, without significant compromise of the final function and even with a possible better ankle range of motion.Publication Experiencia de parto instrumental con vacuum en Hospital Público de Santiago de Chile(2024) Lopéz, Marcia; Espinosa, María; Guzmán, RodrigoIntroducción: El vacuum es el instrumento de elección para asistir el parto instrumental en países desarrollados. Objetivo: El objetivo del estudio es exponer los resultados maternos y fetales del uso del vacuum en población chilena y promover su disponibilidad y uso en nuestro país y Latinoamérica. Método: El estudio se realizó entre octubre de 2017 y diciembre de 2021, incluyendo a pacientes que tuvieron parto instrumental con vacuum en el Hospital San Juan de Dios de Chile. Se compararon los partos exitosos con vacuum y los partos en los que se requirió el uso de otro instrumento o una cesárea posterior al uso del instrumento. Resultados: Se realizaron 153 vacuum, correspondientes al 28,59% del total de partos instrumentales. El 79,74% tuvo éxito. El 5,88% no recibió anestesia o se aplicó anestesia local. Solo el 3,27% presentó desgarro perineal con compromiso del esfínter anal. El 91,5% de los recién nacidos no tuvieron complicaciones fetales. Un 20,3% requirió reanimación neonatal. Conclusiones: El estudio muestra que el vacuum es una opción segura y efectiva de parto instrumental en nuestra población. La correcta capacitación y protocolos adecuados son necesarios para garantizar resultados exitosos. Introduction: Vacuum extraction is the instrument of choice for assisting instrumental delivery in developed countries. Objective: The aim of the study is to present the maternal and fetal outcomes of vacuum use in the Chilean population and promote its availability and usage in our country and Latin America. Method: The study was performed between October 2017 and December 2021, including patients who underwent instrumental delivery with a vacuum extraction at the Hospital San Juan de Dios in Chile. Successful vacuum deliveries were compared with deliveries where another instrument was required, or a cesarean section was performed after instrument use. Results: A total of 153 vacuum deliveries were carried out, accounting for 28.59% of all instrumental deliveries. 79.74% were successful. 5.88% did not receive anesthesia or received local anesthesia. Only 3.27% experienced perineal tear with involvement of the anal sphincter. 91.5% of newborns had no fetal complications. 20.3% required neonatal resuscitation. Conclusions: The study demonstrates that the vacuum is a safe and effective option for instrumental delivery in our population. Proper training and appropriate protocols are necessary to ensure successful outcomesItem Proximal and Distal Failure Site Analysis in Percutaneous Achilles Tendon Rupture Repair(Sage, 2019-12) Wagner, Pablo; Wagner, Emilio; López, Mario; Etchevers, Gastón; Valencia, Oscar; Guzmán, RodrigoBackground: Different techniques have been described for percutaneous Achilles tendon rupture repair, but no biomechanical evaluation has been performed separately for proximal and distal suturing techniques. The purpose of this study was to biomechanically analyze proximal versus distal percutaneous Achilles suture configurations during cyclic loading and load to failure. Methods: A simulated, midsubstance rupture was created 6 cm proximal to the calcaneal insertion in fresh-frozen cadaveric Achilles tendons. Fifteen proximal specimens were divided into 3 groups: (A1) triple locking technique, (A2) Bunnell-type technique, and (A3) double Bunnell-type technique. Twelve distal specimens were divided into 2 groups: (B1) triple nonlocking technique and (B2) oblique technique. Repairs were subjected to cyclic testing and load to failure. Load to failure, cause of failure, and tendon elongation were evaluated. Results: None of the proximal specimens and 7/12 of the distal ones failed in cyclic testing. The proximal fixation groups demonstrated significantly more strength than the distal groups (P = .001), achieving up to 710 N of failure load in Group A3. Groups B1and B2 failed on average at 380 N with no difference between them (P > .05). The majority of all repairs failed in the suture-tendon interface. Distal groups had more elongation during cyclic testing (13.7 mm) than proximal groups (9.4 mm) (P = .02). Conclusion: The distal fixation site in this Achilles tendon repair was significantly weaker than the proximal fixation site. A proximal modified suture configuration increased resistance to cyclic loading and load to failure significantly. Clinical relevance: A modification can be suggested to improve strength of the Achilles repair.