Purpose: To compare biomechanical behaviour of the anterior root of the lateral meniscus (ARLM) after a transtibial repair (TTR) and after an in situ repair (ISR), discussing the reasons for the efficacy of the more advantageous technique. Methods: Eight cadaveric human knees were tested at flexion angles from 0° to 90° in four conditions of their ARLM: intact, detached, reinserted using TTR, and reinserted using ISR. Specimens were subjected to 1000 N of compression, and the contact area (CA), mean pressure (MP), and peak pressure (PP) on the tibial cartilage were computed. For the TTR, traction force on the sutures was registered. Results: ARLM detachment significantly altered contact biomechanics, mainly at shallow flexion. After ISR, differences compared to the healthy group persisted (extension, CA 22% smaller (p = 0.012); at 30°, CA 30% smaller (p = 0.012), MP 21%, and PP 32% higher (both p = 0.017); at 60°, CA 28% smaller (p = 0.012), MP 32%, and PP 49% higher (both p = 0.025). With TTR, alterations significantly decreased compared to the injured group, with no statistical differences from the intact ones observed, except for CA at extension (15% decrease, p = 0.012) and at 30° (12% decrease, p = 0.017). The suture tension after TTR, given as mean(SD), was 36.46(11.75)N, 44.32(11.71)N, 40.38(14.93)N, and 43.18(14.89)N for the four tested flexion angles. Conclusions: Alterations caused by ARLM detachment were partially restored with both ISR and TTR, with TTR showing better results on recovering CA, MP, and PP in the immediate postoperative period. The tensile force was far below the value reported to cause meniscal cut-out in porcine models.

This work studies the influence of loading velocity and previous cyclic loading history on the stiffness and strength of a multifilament coreless ultra-high-molecular-weight polyethylene (UHMWPE) surgical suture. Thread samples (n = 8) were subjected to a load-to-failure test at 0.1, 0.5, 1, 5, and 10 mm/s without previous loading history and after 10 cycles of loading at 1–10 N, 1–30 N, and 1–50 N. The experimental data were fitted to mathematical models to compute the stress–strain relation and the strength of the suture. The bilinear model involving two stress–strain ratios for low- and high-strain intervals was the best fit. The ratio in the low-strain range rose with loading speed, showing mean increases of 5.9%, 6.5%, 7.9%, and 7.3% between successive loading speeds. Without a previous loading history, this ratio was less than half than that at high strain. However, 10 cycles of 1–30 N or 1–50 N significantly increased the stress–strain ratio at a low strain level by 135% and 228%, respectively. The effect persisted after 2 min but vanished after 24 h. No influence was found on the suture strength. In conclusion, the stiffness of the studied suture was influenced by the strain level, loading velocity, and recent cyclic loading history. Conversely, the suture strength was not affected.

(1) Background: Image acquisition systems based on videogrammetry principles are widely used across various research fields, particularly in mechanics, with applications ranging from civil engineering to biomechanics and kinematic analysis. This study presents the design, development, and validation of a low-cost, two-camera 3D videogrammetry system for the kinematic analysis of human motion. (2) Materials and Methods: Built using commercially available components and custom MATLAB^® (version 2019b) software, the system captures synchronized video streams and extracts precise 3D coordinates of markers. Its performance was validated against the Vicon^® (Vicon Nexus 1.7.1) system, a gold standard in musculoskeletal motion analysis. Comparative tests were conducted under static and dynamic conditions at varying working distances and velocities. (3) Results: Results demonstrate that the proposed system achieves high accuracy, with maximum measurement errors below 0.3% relative to Vicon^®, and similar repeatability (SD of approximately 0.02 mm in static conditions). Compared to manual caliper measurements, both vision systems yielded similar results, with errors ranging between 0.01% and 0.82%. (4) Conclusions: A low-cost, two-camera videogrametric system was validated, offering full transparency, flexibility, and affordability, making it a practical alternative for both clinical and research settings in biomechanics and human movement analysis, with potential to be extended to general kinematic analysis.

Meniscal root repair is not routinely recommended for patients over 75 years old, yet surrogate age-unrestricted human or porcine models are used for its evaluation. This study assesses the suitability of older human or porcine meniscus models for in vitro testing of the sutured meniscal horn. Three groups of menisci underwent a load-to-failure test with continuous monitoring of the traction force and deformation around the suture: human < 75 years, human ≥ 75 years, and porcine. Both surrogate models were compared to the younger group. The porcine group exhibited a 172.1%-higher traction force before tearing (p < 0.001) and a 174.1%-higher ultimate force (p < 0.001), without there being differences between the human groups. At tissue level, the older group had a 28.7%-lower cut-out stress (p = 0.012) and the porcine group had a 57.2%-higher stress (p < 0.001). Regarding elasticity at the sutured area, a 48.1%-greater deformation rate was observed in the older group (p < 0.001), without difference for the porcine group. In conclusion, neither the porcine nor the older human model demonstrated a clear advantage as a surrogate model for young human sutured meniscal horns. The older human meniscus is preferable for resistance at the specimen level, while the porcine model better represents deformation in the sutured zone.

Este libro se ha elaborado como un recurso educativo introductorio a la biomecánica, principalmente destinado a estudiantes de Ingeniería de la Salud e Ingeniería Biomédica. En él, en primer lugar, se establecen unas bases para el entendimiento y la compresión de conceptos mecánicos aplicados al cuerpo humano, así como de los tipos de ensayos existentes en biomecánica y las estructuras presentes en el sistema musculoesquelético, tales como el hueso, los músculos, los tendones y ligamentos, y las articulaciones, y su forma de modelarlos mecánicamente. Posteriormente, en el segundo capítulo se exponen las diferentes magnitudes de interés en biomecánica, y los diferentes sensores que se pueden emplear para obtenerlas a través de los ensayos explicados en el primer capítulo.

La osteotomía tibial proximal de adición interna (OTPAI) es una cirugía para corregir la desalineación del eje longitudinal de la pierna mediante la apertura en la metáfisis tibial fijada mediante un sistema de tornillos y placa para mantener la apertura hasta la cicatrización del hueso. El sistema TomoFix® destaca por la estabilidad que ofrece a la apertura, habiéndose convertido en el patrón oro. Sin embargo, resulta incómodo por su voluminosidad y su disponibilidad es más limitada. El sistema de bloqueo de fracturas óseas AxSOS® presenta mayor aprovisionamiento, menor coste y produce menor protrusión por su reducida dimensión, pero no se ha comprobado la estabilidad y resistencia que ofrece su aplicación para la OTPAI. Por ello, se diseña un estudio comparativo de la aplicación del sistema AxSOS frente al de referencia, TomoFix. El montaje experimental incluye la alineación del eje de la tibia, previamente identificado mediante exploración radiológica previa con TAC, utilizando utillaje específicamente diseñado y fabricado por impresión 3D. El ensayo trata de replicar las cargas típicas del período de rehabilitación. Concretamente, los especímenes se sometieron a 3 etapas de compresión cíclica a 1 Hz: S1: 500 ciclos, [150,900]N; S2: 1000 ciclos, [150,1200]N; S3: 2000 ciclos, [150,1400]N. Para monitorizar los desplazamientos del extremo óseo proximal respecto al distal se emplean tres sensores láseres. Con estos desplazamientos medidos se computa la evolución la apertura de la cuña y del ángulo girado entre los extremos óseos en los planos sagital y frontal. En cada subciclo se calcula la variación de amplitud del movimiento y el valor residual acumulado El objetivo del presente trabajo es la comprobación del diseño experimental en especímenes cadavéricos y la determinación del tamaño muestral mínimo necesario para establecer diferencias entre los dos sistemas de fijación de OTPAI. Para ello, se realizó un estudio piloto con 8 especímenes de tibia cadavérica a las que se les realizó una OTPAI biplanar de 7mm. Posteriormente, se asignaron de forma aleatoria a un grupo de estudio (N=4) en función del sistema de fijación: AxSOS® (Stryker Iberia) o TomoFix® (DePuy Synthes). Todos los sistemas se fijaron al hueso con 6 tornillos de bloqueo con apoyo bicortical. Se consideró como fallo el colapso del fulcro de la cuña o una pérdida de corrección superior a 2º en cualquier plano. El tamaño muestral mínimo se estableció como el necesario para detectar una variación de inclinación residual en los planos anatómicos de 1º. Los valores medios de todos los parámetros calculados fueron muy similares en ambos grupos. El cálculo a partir de los valores estadísticos de las variables de interés obtenidas en este estudio pilota, arrojó un valor de N=7. El colapso de la cortical lateral fue el fallo predominante. Ningún espécimen superó S3. En el grupo AxSOS, 4 superaron S1 y 2 S2; en el grupo TomoFix, 3 S1 y 2 S2. De confirmarse estos resultados, la estabilidad de la corrección, en términos de amplitud cíclica y de pérdida permanente de la alineación, son similares cuando se fija la osteotomía con el sistema AxSOS o con el sistema de referencia TomoFix, antes de la cicatrización tras la cirugía de OTPAI.