RESUMEN
We tested pull-out strength and linear stiffness of meniscal repair using bioabsorbable arrows and vertical and horizontal loop sutures in fresh-frozen bovine lateral menisci. In phase I, menisci repaired either with 2-0 Ti-Cron vertical or horizontal loop suture, or 10-, 13-, or 16-mm Meniscus Arrows were loaded to failure at 12.5 mm/sec. In phase II, we examined the number of barbs engaged and angle of insertion using 10- and 13-mm arrows. Pull-out strengths of both suture repair groups were significantly higher than those of the arrow groups. Vertical loop sutures were significantly stiffer than horizontal sutures and 10-mm arrows. In phase II, the mean ultimate load to failure for the 10-mm arrows was 35.1 N, significantly stronger than in phase I (18.5 N); however, stiffness remained low (7.9 N/mm). Five arrows in the 13-mm group were inserted parallel to the tibial surface and showed no significant difference from phase I. Five arrows were inserted at more than a 30 degrees angle. This group was significantly weaker than in phase I. Single vertical loop suture showed the highest overall pull-out strength. Although weaker than sutures, arrows should provide sufficient stability for meniscal healing. The number of barbs engaged and angle of insertion are critical.
Asunto(s)
Implantes Absorbibles , Meniscos Tibiales/cirugía , Dispositivos de Fijación Ortopédica , Suturas , Análisis de Varianza , Animales , Bovinos , Elasticidad , Diseño de Equipo , Falla de Equipo , Ácido Láctico/química , Meniscos Tibiales/patología , Poliésteres , Polímeros/química , Estrés Mecánico , Propiedades de Superficie , Técnicas de Sutura , Lesiones de Menisco TibialRESUMEN
OBJECTIVE: To evaluate effects of age (immature vs adult) and location along the trachea on the biomechanical properties (via a tensile stress relaxation test) and biochemical properties (Water content and total proteoglycan content) of canine tracheal ring cartilage. SAMPLE POPULATION: Entire trachea from 8 immature and 8 adult dogs. PROCEDURE: A section of each tracheal ring from 8 immature dogs (6 months old) and 8 adult dogs (2 to 3 years old) was tested biomechanically (maximal stress, equilibrium stress, equilibrium modulus, and percentage of relaxation) and processed for biochemical analysis (water content and total proteoglycan content). Two rings from each trachea were prepared for histologic analysis (H&E or safranin-O staining). RESULTS: Biomechanical and biochemical parameters were not different between cervical and thoracic rings of either age group. Mean maximal stress, equilibrium stress, and equilibrium modulus were significantly higher for adult, compared with immature, dogs. However, percentage of relaxation for adult dogs was significantly lower. Tracheal rings of adult dogs had a significantly higher proteoglycan content and a significantly lower water content than did those of immature dogs. Water content and biomechanical parameters were significantly correlated, and proteoglycan content and biomechanical properties were significantly but weakly correlated. On histologic sectioning, a qualitative decrease in safranin-O staining in the rings of immature dogs also was observed. CONCLUSIONS AND CLINICAL RELEVANCE: Biomechanical and biochemical properties of the canine tracheal ring cartilage are altered with age. However, location of the ring along the trachea did not affect these properties for either age group. Results lend support to the theory that proteoglycan content has some effect on tensile properties of tracheal rings and may explain increased compliance observed in rings from dogs with collapsed trachea.
Asunto(s)
Envejecimiento/fisiología , Cartílago/fisiología , Análisis de Varianza , Animales , Cartílago/anatomía & histología , Cartílago/crecimiento & desarrollo , Perros , Técnicas In Vitro , Modelos Biológicos , Estrés Mecánico , Resistencia a la TracciónRESUMEN
The effect of laser energy on the length, stiffness, and structure of connective tissue was examined in a rabbit patellar tendon model. A holmium:yttrium-aluminum-garnet laser was used to deliver a calculated dose of laser energy (300 J/cm2) to one randomly selected patellar tendon in each of 13 adult New Zealand White rabbits. The contralateral patellar tendon was used as a control. Radiopaque markers were placed in the patella and tibial tuberosity to allow for patellar tendon length measurements (via standard lateral radiographs) before and after laser application and at 4 and 8 weeks. Limbs were not immobilized during the postoperative period. The tendons were harvested at 0 weeks (N = 7) and 8 weeks (N = 6) and evaluated for tensile, stiffness, cross-sectional area, histologic changes, and electron microscopic appearance. The results demonstrated significant tendon shrinkage (6.6% +/- 1.4%) after application of the calculated laser energy dose. However, tendon length had increased significantly beyond the immediate postlaser length at 4 weeks and beyond its original length by 8 weeks. At 8 weeks, the lased tendons were significantly less stiff with significantly greater cross-sectional areas than contralateral controls. There was generalized fibroblastic response throughout the entire lased tendon characterized by a marked increase in cellularity. There was also a change from the normal bimodal pattern of large- and small-diameter collagen fibers to a unimodal pattern with predominantly small-diameter fibers in the lased tendons. The tissue alterations seen in this study suggest that the biologic response of connective tissue to laser energy causes a further compromise in tissue integrity, beyond that attributed to the initial physical effects of the laser. These alterations must be taken into consideration when determining postoperative rehabilitation of laser-modified tissues.
Asunto(s)
Coagulación con Láser , Rótula/cirugía , Tendones/cirugía , Adulto , Análisis de Varianza , Animales , Artroscopía , Fenómenos Biomecánicos , Colágeno , Tejido Conectivo/patología , Humanos , Técnicas In Vitro , Conejos , Tendones/patología , Tendones/fisiologíaRESUMEN
In this study, cubes of trabecular bone with a wide range of structural properties were scanned on a micro-computed tomography system to produce complete three-dimensional digitizations from which morphological and architectural parameters could be measured in a nondestructive manner. The cubes were then mechanically tested in uniaxial compression in three orthogonal directions and to failure in one direction to find the orthogonal tangent elastic moduli and ultimate strengths. After testing, the cubes were weighed and ashed to determine the apparent and ash densities. A high correlation between the basic stereologic measurements was found, indicating that there is a relationship between the amount of bone and number of trabeculae in cancellous bone. Regression analysis was used to estimate the modulus and ultimate strength; these regressions accounted for 68-90% of the variance in these measures. These relationships were dependent on the metaphyseal type and donor, with the modulus also dependent on the direction of testing. This indicates that the properties of the individual trabeculae, as well as their amount and organization, may be important in predicting the mechanical properties of cancellous bone.
Asunto(s)
Huesos/anatomía & histología , Huesos/fisiología , Adulto , Anciano , Densidad Ósea , Elasticidad , Femenino , Fémur/anatomía & histología , Fémur/fisiología , Humanos , Húmero/anatomía & histología , Húmero/fisiología , Ilion/anatomía & histología , Ilion/fisiología , Vértebras Lumbares/anatomía & histología , Vértebras Lumbares/fisiología , Masculino , Microrradiografía , Persona de Mediana Edad , Modelos Biológicos , Intensificación de Imagen Radiográfica , Radio (Anatomía)/anatomía & histología , Radio (Anatomía)/fisiología , Estrés Mecánico , Tibia/anatomía & histología , Tibia/fisiología , Tomografía Computarizada por Rayos XRESUMEN
The purpose of this study was to test whether the menisci displace under joint compression combined with internal-external torques and anterior-posterior forces at fixed flexion angles. We further determined differences in displacements between the medial and lateral menisci. Loads were applied to the joint, and joint load and displacements were measured. Meniscal displacements were measured radiographically. With a joint compressive load of 1 kN, internal and external joint rotations caused the lateral meniscus to displace, on average, 0.37 mm deg-1 in the anterior-posterior direction, while the medial meniscus displaced 0.19 mm deg-1. Anterior and posterior joint translation, performed under 1 kN joint compression, caused the lateral meniscus to displace, on average, 0.66 mm mm-1 in the anterior-posterior direction, while the medial meniscus displaced 0.43 mm mm-1. Greater meniscal displacements were found at 15 and 30 degrees flexion than at 0 degrees for the lateral meniscus in internal rotation. Lateral meniscal displacements were larger than those of the medial with posterior tibial translation at full extension and with internal rotation.
Asunto(s)
Articulación de la Rodilla/fisiología , Meniscos Tibiales/fisiología , Tibia/fisiología , Fémur/fisiología , Humanos , Modelos Lineales , Meniscos Tibiales/anatomía & histología , Rotación , Estrés MecánicoRESUMEN
We evaluated the orthogonal mechanical properties of human trabecular bone from the major metaphyseal regions with materials testing and quantitative computed tomography (CT). The proximal tibia, distal femur, proximal femur, distal radius, and proximal humerus from fresh cadaver specimens between the ages of 55 and 70 years were excised and prepared for experimentation. The bones were embedded and scanned at 1 or 1.5 mm intervals on a Technicare HPS 1440 and GE 9800 CT scanner. After scanning, the bones were sectioned, producing 8-mm cubes of trabecular bone which were mechanically tested in uniaxial compression at a strain rate of 1%. The testing sequence consisted of preyield tests in two of the three orthogonal directions and failure in the third. After testing, the cubes were evaluated for apparent density and ash weight. The results of the study show that the strength and stiffness of trabecular bone varies significantly within metaphyseal regions and from metaphysis to metaphysis. The power and significance of relationships between density and modulus varied as a function of metaphyseal location. Both linear and nonlinear models were significant, suggesting that trabecular deformation occurs in response to both axial and bending loads. Finally, the need for architectural measures of trabecular bone to predict mechanical properties is emphasized.
Asunto(s)
Densidad Ósea , Huesos/fisiología , Anciano , Fenómenos Biomecánicos , Huesos/diagnóstico por imagen , Huesos/metabolismo , Humanos , Masculino , Persona de Mediana Edad , Tomografía Computarizada por Rayos XRESUMEN
The elastic moduli of human subchondral, trabecular, and cortical bone tissue from a proximal tibia were experimentally determined using three-point bending tests on a microstructural level. The mean modulus of subchondral specimens was 1.15 GPa, and those of trabecular and cortical specimens was 4.59 GPa and 5.44 GPa respectively. Significant differences were found in the modulus values between bone tissues, which may have mainly resulted from the differences in the microstructures of each bone tissue rather than in the mineral density. Furthermore, the size-dependency of the modulus was examined using eight different sizes of cortical specimens (heights h = 100-1000 microns). While the modulus values for relatively large specimens (h greater than 500 microns) remained fairly constant (approximately 15 GPa), the values decreased as the specimens became smaller. A significant correlation was found between the modulus and specimen size. The surface area to volume ratio proved to be a key variable to explain the size-dependency.
Asunto(s)
Huesos/fisiología , Densidad Ósea/fisiología , Huesos/anatomía & histología , Huesos/ultraestructura , Elasticidad , Humanos , Masculino , Microscopía , Microscopía Electrónica de Rastreo , Persona de Mediana Edad , Modelos Biológicos , Estrés Mecánico , TibiaRESUMEN
Distal canine femurs were sectioned into 8 mm cubic specimens. Orthogonal compression tests were performed to preyield in two or three directions and to failure in a third. Apparent density and ash weight density were measured for a subset of specimens. The results were compared to the human distal femur results of Ciarelli et al. (Transactions of the 32nd Annual Meeting of the Orthopaedic Research Society, Vol. 11, p. 42, 1986). Quantitative similarities existed in the fraction of components comprising the trabecular tissue of the two species. Qualitative similarities were seen in the positional and anisotropic variation of the mechanical properties, and also in the form and strength of the relationships between the mean modulus and bone density, ultimate stress and density, and ultimate stress and modulus. However, significantly different regression equations resulted for the mean modulus-density, and ultimate stress modulus relationships, indicating that for the same density, canine trabecular bone displays a lower modulus than human, and may achieve greater compressive strains before failure.