Elongation Patterns Research Articles

Elongation Patterns of the Posterior Cruciate Ligament after Total Knee Arthroplasty.

This study aimed to understand the ability of fixed-bearing posterior cruciate ligament (PCL)-retaining implants to maintain functionality of the PCL in vivo. To achieve this, elongation of the PCL was examined in six subjects with good clinical and functional outcomes using 3D kinematics reconstructed from video-fluoroscopy, together with multibody modelling of the knee. Here, length-change patterns of the ligament bundles were tracked throughout complete cycles of level walking and stair descent. Throughout both activities, elongation of the anterolateral bundle exhibited a flexion-dependent pattern with more stretching during swing than stance phase (e.g., at 40° flexion, anterolateral bundle experienced 3.9% strain during stance and 9.1% during swing phase of stair descent). The posteromedial bundle remained shorter than its reference length (defined at heel strike of the level gait cycle) during both activities. Compared with loading patterns of the healthy ligament, postoperative elongation patterns indicate a slackening of the ligament at early flexion followed by peak ligament lengths at considerably smaller flexion angles. The reported data provide a novel insight into in vivo PCL function during activities of daily living that has not been captured previously. The findings support previous investigations reporting difficulties in achieving a balanced tension in the retained PCL.

Modelling time variations of root diameter and elongation rate as related to assimilate supply and demand.

In a given root system, individual roots usually exhibit a rather homogeneous tip structure although highly different diameters and growth patterns, and this diversity is of prime importance in the definition of the whole root system architecture and foraging characteristics. In order to represent and predict this diversity, we built a simple and generic model at root tip level combining structural and functional knowledge on root elongation. The tip diameter, reflecting meristem size, is used as a driving variable of elongation. It varies, in response to the fluctuations of photo-assimilate availability, between two limits (minimal and maximal diameter). The elongation rate is assumed to be dependent on the transient value of the diameter. Elongation stops when the tip reaches the minimal diameter. The model could satisfactorily reproduce patterns of root elongation and tip diameter changes observed in various species at different scales. Although continuous, the model could generate divergent root classes as classically observed within populations of lateral roots. This model should help interpret the large plasticity of root elongation patterns which can be obtained in response to different combinations of endogenous and exogenous factors. The parameters could be used in phenotyping the root system.

Length-Change Patterns of the Collateral Ligaments During Functional Activities After Total Knee Arthroplasty

This study aimed to quantify the elongation patterns of the collateral ligaments following TKA during functional activities of daily living. Using mobile video-fluoroscopy to capture radiographic images of the knee in a group of six patients, each with an ultra-congruent knee implant, tibiofemoral kinematics were reconstructed throughout complete cycles of level gait, downhill walking, stair descent, and squat activities. Kinematic data were then used to drive subject-specific multibody knee models to estimate length-change patterns of the LCL as well as three bundles of the MCL. In addition, a sensitivity analysis examined the role of the attachment site in the elongation patterns. Our data indicate a slackening of the LCL but non-uniform length-change patterns across the MCL bundles (ranging from lengthening of the anterior fibers to shortening of the posterior fibers) with increasing knee flexion angle. Near-isometric behavior of the intermediate fibers was observed throughout the entire cycle of the studied activities. These length-change patterns were found to be largely consistent across different activities. Importantly, length-change patterns were critically sensitive to the location of the femoral attachment points relative to the femoral component. Thus, in TKA with ultra-congruent implants, implantation of the femoral component may critically govern post-operative ligament function.

Pseudophacopteron longicaudatum (Hemiptera) induces intralaminar leaf galls on Aspidosperma tomentosum (Apocynaceae): a qualitative and quantitative structural overview.

The structural complexity of galls depends on species-specific interaction driven by the galling taxa. However, the host plant and environment stressors can impose limits on gall developmental patterns and impact the establishment of gall morphology. Herein, we employed qualitative and quantitative approaches in order to elucidate how cell divisions, elongation patterns, and tissue organization are determinant for the development of intralaminar gall morphology induced by Pseudophacopteron longicaudatum Malenovský, Burckhardt, Queiroz, Isaias & Oliveira (Hemiptera: Psylloidea: Phacopteronidae) on leaves of Aspidosperma tomentosum Mart. (Apocynaceae). In addition, we aimed to determine which anatomical process can discriminate the stages of gall development, plus, examine the histochemical and cytological profiles of the galls. The differentiated structures, mainly abaxial epidermis and spongy parenchyma, are associated with gall closure, with hyperplastic events concentrated in the young phase of the galls. Thus, epidermis and spongy parenchyma hypertrophy and are responsible for the determination of the nymphal chamber formation and gall shape. The mature galls do not differentiate into a typical nutritive cells and do not develop a histochemical gradient in their tissues. The cytological features of galls such as plastoglobules and multivesicular bodies are related to ROS scavenging mechanisms due the high oxidative stress.

Internode elongation pattern, internode diameter and hormone changes in soybean (Glycine max) under different shading conditions

Internode length and diameter in soybean (Glycine max (L.) Merr.) are closely associated with lodging. The pattern of internode elongation and increase in internode diameter and factors involved were studied in two soybean cultivars, HN48 (tall-stem cultivar) and HN60 (dwarf cultivar), in the growing seasons of 2017 and 2018. Four treatments included natural lighting, shading of the apical meristem, covering of all internodes with aluminium foil, and whole-plant shading with plastic shading nets. When the number of internodes (N) on the main stem was >3, internode N began to elongate. Internode N – 1 exhibited the most rapid elongation, and internode N – 2 elongated slowly. Internode N – 3 stopped elongating, but the increase in internode diameter did not cease as internode elongation stopped. Shading the soybean apical meristem, the stem, and the whole plant all led to internode elongation. Different shading conditions did not alter the pattern of internode elongation. Soybean stem and apical meristem were both light-sensitive tissues. With an increase in shading, internode length increased, whereas internode diameter decreased. Contents of gibberellic acid (GA3) and salicylic acid in the stem also increased, but abscisic acid content decreased. Shading reduced the size of starch grains but increased the number of osmiophilic granules in the chloroplast. Elevated GA3 level was the main cause of the changes in internode length and diameter induced by shading. These results suggest that reduction in GA3 synthesis and enhancement in carbohydrates formation could a strategy for soybean plants to avoid lodging.

Elongation Patterns of the Collateral Ligaments After Total Knee Arthroplasty Are Dominated by the Knee Flexion Angle.

The primary aim of this study was to assess the effects of total knee arthroplasty (TKA) implant design on collateral ligament elongation patterns that occur during level walking, downhill walking, and stair descent. Using a moving fluoroscope, tibiofemoral kinematics were captured in three groups of patients with different TKA implant designs, including posterior stabilized, medial stabilized, and ultra-congruent. The 3D in vivo joint kinematics were then fed into multibody models of the replaced knees and elongation patterns of virtual bundles connecting origin and insertion points of the medial and lateral collateral ligaments (MCL and LCL) were determined throughout complete cycles of all activities. Regardless of the implant design and activity type, non-isometric behavior of the collateral ligaments was observed. The LCL shortened with increasing knee flexion, while the MCL elongation demonstrated regional variability, ranging from lengthening of the anterior bundle to slackening of the posterior bundle. The implant component design did not demonstrate statistically significant effects on the collateral elongation patterns and this was consistent between the studied activities. This study revealed that post-TKA collateral ligament elongation is primarily determined by the knee flexion angle. The different anterior translation and internal rotation that were induced by three distinctive implant designs had minimal impact on the length change patterns of the collateral ligaments.

Ginseng-derived patatin-related phospholipase PgpPLAIIIβ alters plant growth and lignification of xylem in hybrid poplars

Patatin-liked phospholipase A (pPLAs) are major lipid acyl hydrolases that participate in various biological functions in plant growth and development. Previously, a ginseng-derived pPLAIII homolog was reported to reduce lignin content in Arabidopsis. This led us to evaluate its possible usefulness as a biomass source in wood plant. Herein, we report that there are six members in the pPLAIII gene family in poplar. Overexpression of pPLAIIIβ derived from ginseng resulted in a reduced plant height with radially expanded stem growth in hybrid poplars. Compared with the wild type (WT), the chlorophyll content was increased in the overexpression poplar lines, whereas the leaf size was smaller. The secondary cell wall structure in overexpression lines was also altered, exhibiting reduced lignification in the xylem. Two transcription factors, MYB92 and MYB152, which control lignin biosynthesis, were downregulated in the overexpression lines. The middle xylem of the overexpression line showed heavy thickening, making it thicker than the other xylem parts and the WT xylem, which rather could have been contributed by the presence of more cellulose in the selected surface area. Taken together, the results suggest that PgpPLAIIIβ plays a role not only in cell elongation patterns, but also in determining the secondary cell wall composition.

Morpho-physiological Basis of Yield Performance of Early Maturing Rice Varieties in Bangladesh

A considerable progress in plant breeding for higher yield is attained mainly through selection of morpho-physiological attributes in rice. The field experiments were conducted at three different locations under sub-tropical conditions with four early maturing rice varieties viz., Binadhan-7, Binadhan-17, BRRI dhan33, and BRRI dhan39 during kharif-2 rice season (Aman; July-October) of 2016 to find out the natural variation in the morpho-physiological attributes contributing to higher grain yield in rice. Morphological parameters on plant height, root structure, tillering ontogeny, internode elongation pattern, flag leaf length, flag leaf width, flag leaf angle, number of primary & secondary rachis, branches and also physiological traits on chlorophyll content, photosynthesis rate, total dry mass, growth rate, number of vascular bundles, harvest index with yield and yield contributing characters were studied. Results indicated that plants having rapid growth and development at early growth stages showed higher chlorophyll content, photosynthesis rate, long flag leaf, number of vascular bundles in 1st internode and also exhibited the increase in the number of grains per panicle resulting higher grain yield. Among the test varieties, Binadhan-17 showed superiority in the most morpho-physiological criteria and higher number of vascular bundles manifesting in higher grain yield. This information may help breeders to identity and develop high yielding rice variety.

A Linear Model to Describe Branching and Allometry in Root Architecture.

Root architecture is a complex structure that comprises multiple traits of the root phenotype. Novel platforms and models have been developed to better understand root architecture. In this methods paper, we introduce a novel allometric model, named rhizochron index (m), which describes lateral root (LR) branching and elongation patterns across the primary root (PR). To test our model, we obtained data from 16 natural accessions of Arabidopsis thaliana at three stages of early root development to measure conventional traits of root architecture (e.g., PR and LR length), and extracted the rhizochron index (m). In addition, we tested previously published datasets to assess the utility of the rhizochron index (m) to distinguish mutants and environmental effects on root architecture. Our results indicate that rhizochron index (m) is useful to distinguish the natural variations of root architecture between A. thaliana accessions, but not across early stages of root development. Correlation analyses in these accessions showed that m is a novel trait that partially captures information from other root architecture traits such as total lateral root length, and the ratio between lateral root and primary root lengths. Moreover, we found that the rhizochron index was useful to distinguish ABA effect on root architecture, as well as the mutant pho1 phenotype. We propose the rhizochron index (m) as a new feature of the root architectural system to be considered, in addition to conventional traits in future investigations.

Elongation Patterns of the Anterior and Posterior Borders of the Anterolateral Ligament of the Knee

To compare the elongation patterns of the anterior and posterior borders of the anterolateral ligament (ALL) at varying knee flexion angles with the knee in a neutral position without any external forces and with external forces applied, including anterior-posterior translation, internal-external rotation, and varus-valgus angulation. Eight cadaveric knees were tested in a custom knee testing system. Elongation of the anterior and posterior borders of the ALL was measured using a MicroScribe 3DLX system at knee flexion angles of 0°, 30°, 60°, and 90° and after the application of internal-external rotation, anterior-posterior translation, and varus-valgus angulation. The anterior border showed a slight noncontinuous increase in percentage elongation (0.8% ± 2.2%) whereas the posterior border showed a continuous decrease in percentage elongation (-12.0% ± 2.8%) as knee flexion increased (P < .001). Apart from the elongation of the posterior border at 90° of knee flexion, internal rotation, varus angulation, and anterior translation resulted in a significant increase in the percentage elongation of the anterior and posterior borders at each flexion angle compared with external rotation, valgus angulation, and posterior translation, respectively. The ALL shows different elongation patterns between the anterior and posterior borders, with a continuous decrease in the percentage elongation of the posterior border as knee flexion increases. This study presents useful evidence to resolve the uncertainty regarding the change in length of the ALL at various degrees of knee flexion. This information may be helpful for deciding the optimal knee flexion angle during ALL graft fixation. The findings from this study suggest that graft fixation during ALL reconstructions should be performed at close to full extension of the knee.

The Complex Relationship Between In Vivo ACL Elongation and Knee Kinematics During Walking and Running.

In vivo anterior cruciate ligament (ACL) bundle (anteromedial bundle [AMB] and posterolateral bundle [PLB]) relative elongation during walking and running remain unknown. In this study, we aimed to investigate in vivo ACL relative elongation over the full gait cycle during walking and running. Ten healthy volunteers walked and ran at a self-selected pace on an instrumented treadmill while biplane radiographs of the knee were acquired at 100 Hz (walking) and 150 Hz (running). Tibiofemoral kinematics were determined using a validated model-based tracking process. The boundaries of ACL insertions were identified using high-resolution magnetic resonance imaging (MRI). The AMB and PLB centroid-to-centroid distances were calculated from the tracked bone motions, and these bundle lengths were normalized to their respective lengths on MRI to calculate relative elongation. Maximum AMB relative elongation during running (6.7 ± 2.1%) was significantly greater than walking (5.0 ± 1.7%, p = 0.043), whereas the maximum PLB relative elongation during running (1.1 ± 2.1%) was significantly smaller than walking (3.4 ± 2.3%, p = 0.014). During running, the maximum AMB relative elongation was significantly greater than the maximum PLB relative elongation (p < 0.001). ACL relative elongations were correlated with tibiofemoral six degree-of-freedom kinematics. The AMB and PLB demonstrate similar elongation patterns but different amounts of relative elongation during walking and running. The complex relationship observed between ACL relative elongation and knee kinematics indicates that ACL relative elongation is impacted by tibiofemoral kinematic parameters in addition to flexion/extension. These findings suggest that ACL strain is region-specific during walking and running. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1920-1928, 2019.

Properties and Function of the Medial Patellofemoral Ligament: A Systematic Review

Background: As the main passive structure preventing patellar lateral subluxation, accurate knowledge of the anatomy, material properties, and functional behavior of the medial patellofemoral ligament (MPFL) is critical for improving its reconstruction. Purpose: To provide a state-of-the-art understanding of the properties and function of the MPFL by undertaking a systematic review and statistical analysis of the literature. Study Design: Systematic review. Methods: On June 26, 2018, data for this systematic review were obtained by searching PubMed and Scopus. Articles containing numerical information regarding the anatomy, mechanical properties, and/or functional behavior of the MPFL that met the inclusion criteria were reviewed, recorded, and statistically evaluated. Results: A total of 55 articles met the inclusion criteria for this review. The MPFL presented as a fanlike structure spanning from the medial femoral epicondyle to the medial border of the patella. The reported data indicated ultimate failure loads from 72 N to 208 N, ultimate failure elongation from 8.4 mm to 26 mm, and stiffness values from 8.0 N/mm to 42.5 N/mm. In both cadaveric and in vivo studies, the average elongation pattern demonstrated close to isometric behavior of the ligament in the first 50° to 60° of knee flexion, followed by progressive shortening into deep flexion. Kinematic data suggested clear lateralization of the patella in the MPFL-deficient knee during early knee flexion under simulated muscle forces. Conclusion: A lack of knowledge regarding the morphology and attachment sites of the MPFL remains. The reported mechanical properties also lack consistency, thus requiring further investigations. However, the results regarding patellar tracking confirm that the lack of an MPFL leads to lateralization of the patella, followed by delayed engagement of the trochlear groove, plausibly leading to an increased risk of patellar dislocations. The observed isometric behavior up to 60° of knee flexion plausibly suggests that reconstruction of the ligament can occur at flexion angles below 60°, including the 30° and 60° range as recommended in previous studies.

In-vivo elongation of anterior and posterior cruciate ligament in bi-cruciate retaining total knee arthroplasty.

Anterior and posterior cruciate ligament (ACL and PCL) sacrifice in contemporary total knee arthroplasty (TKA) has been considered a potential factor leading to abnormal knee kinematics. Bi-cruciate retaining (BCR) TKA design allows retention of both ACL and PCL. However, there is a limited data on the ACL/PCL in-vivo elongation characteristics of BCR TKA. The study aimed to evaluate and compare the in-vivo elongation patterns of ACL/PCL between BCR TKA and contralateral non-implanted knee and to explore potential factors leading to the changed elongation patterns between limbs. ACL/PCL elongations of both knees during sit-to-stand were measured in 29 unilateral BCR TKA patients using a validated dual fluoroscopic tracking technique. Joint gap changes of the BCR TKA knees relative to the contralateral knee were quantified. BCR TKA and the contralateral non-implanted knee exhibited similar ACL elongation at extension and clinical anterior knee laxity. However, BCR TKA showed significantly greater PCL elongation during flexion than the non-implanted knee. Variation of changed elongation was observed for both ACL and PCL, suggesting a heterogeneous restoration of normal ACL/PCL functions. A significant correlation was found between extension joint gap change and the change of ACL elongation, highlighting the importance of precise joint line restoration and soft tissue balancing during BCR TKA surgery. Our findings suggest that BCR TKA did not fully restore "near-normal" cruciate ligament elongation patterns and anteroposterior stability. Considerable heterogeneity remains in the retained ligament elongation patterns and warrants further investigations of multifactorial factors to optimize ACL/PCL functions in BCR TKA. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:3239-3246, 2018.

The effect of ACL deficiency on the end-to-end distances of the tibiofemoral ACL attachment during in vivo dynamic activity

PurposeTo evaluate the effect of ACL deficiency on the in vivo changes in end-to-end distances and to determine appropriate graft fixation angles for commonly used tunnel positions in contemporary ACL reconstruction techniques. MethodsTwenty-one patients with unilateral ACL-deficient and intact contralateral knees were included. Each knee was studied using a combined magnetic resonance and dual fluoroscopic imaging technique while the patients performed a dynamic step-up motion (~50° of flexion to extension). The end-to-end distances of the centers of the anatomic anteromedial (AM), posterolateral (PL) and single-bundle ACL reconstruction (SB-anatomic) tunnel positions were simulated and analyzed. Comparisons were made between the elongation patterns between the intact and ACL-deficient knees. Additionally, a maximum graft length change of 6% was used to calculate the deepest flexion fixation angle. ResultsACL-deficient knees had significantly longer graft lengths when compared with the intact knees for all studied tunnel positions (p < 0.01). The end-to-end distances for the AM, PL and SB-anatomic grafts were significantly longer between 0-30° of flexion when compared with the intact knee by p < 0.05 for all. Six percent length change occurred with fixation of the AM bundle at 30° of flexion, PL bundle at 10° and the SB-anatomic graft at 20°. ConclusionsACL-deficient knees had significantly longer in vivo end-to-end distances between 0°-30° of flexion for grafts at the AM, PL and SB-anatomic tunnel positions when compared with the intact knees. Graft fixation angles of <30° for the AM, <10° for the PL, and <20° for the SB-anatomic grafts may prevent permanent graft stretch.

OsPIN2, which encodes a member of the auxin efflux carrier proteins, is involved in root elongation growth and lateral root formation patterns via the regulation of auxin distribution in rice.

Auxin flow is important for different root developmental processes such as root formation, emergence, elongation and gravitropism. However, the detailed information about the mechanisms regulating the auxin flow is less well understood in rice. We characterized the auxin transport-related mutants, Ospin-formed2-1 (Ospin2-1) and Ospin2-2, which exhibited curly root phenotypes and altered lateral root formation patterns in rice. The OsPIN2 gene encodes a member of the auxin efflux carrier proteins that possibly regulates the basipetal auxin flow from the root tip toward the root elongation zone. According to DR5-driven GUS expression, there is an asymmetric auxin distribution in the mutants that corresponded with the asymmetric cell elongation pattern in the mutant root tip. Auxin transport inhibitor, N-1-naphthylphthalamic acid and Ospin2-1 Osiaa13 double mutant rescued the curly root phenotype indicating that this phenotype results from a defect in proper auxin distribution. The typical curly root phenotype was not observed when Ospin2-1 was grown in distilled water as an alternative to tap water, although higher auxin levels were found at the root tip region of the mutant than that of the wild-type. Therefore, the lateral root formation zone in the mutant was shifted basipetally compared with the wild-type. These results reflect that an altered auxin flow in the root tip region is responsible for root elongation growth and lateral root formation patterns in rice.

Состояние экспериментальных культур сосны скрученной в Республике Коми

Изложены результаты исследования четырех участков экспериментальных культур сосныскрученной в Республике Коми. В эксперименте представлено шесть происхождений сосны скрученной, выращенных из семян, заготовленных на лесосеменных плантациях Швеции, которые заложены по географическому принципу семенными потомствами плюсовых деревьев, отобранных в Канаде. Вкачестве контроля использовали семена сосны обыкновенной местного происхождения. Сосна скрученная превосходила сосну обыкновенную по объему ствола, однако доля стволов с дефектами у нее была выше. Установлена взаимосвязь показателей роста и качества ствола сосны скрученной с географической широтой происхождения материнских плюсовых деревьев в Канаде.

Pathway analysis identifies altered mitochondrial metabolism, neurotransmission, structural pathways and complement cascade in retina/RPE/ choroid in chick model of form-deprivation myopia.

PurposeRNA sequencing analysis has demonstrated bidirectional changes in metabolism, structural and immune pathways during early induction of defocus induced myopia. Thus, the aim of this study was to investigate whether similar gene pathways are also related to the more excessive axial growth, ultrastructural and elemental microanalytic changes seen during the induction and recovery from form-deprivation myopia (FDM) in chicks and predicted by the RIDE model of myopia.MethodsArchived genomic transcriptome data from the first three days of induction of monocularly occluded form deprived myopia (FDMI) in chicks was obtained from the GEO database (accession # GSE6543) while data from chicks monocularly occluded for 10 days and then given up to 24 h of normal visual recovery (FDMR) were collected. Gene set enrichment analysis (GSEA) software was used to determine enriched pathways during the induction (FDMI) and recovery (FDMR) from FD. Curated gene-sets were obtained from open access sources.ResultsClusters of significant changes in mitochondrial energy metabolism, neurotransmission, ion channel transport, G protein coupled receptor signalling, complement cascades and neuron structure and growth were identified during the 10 days of induction of profound myopia and were found to correlate well with change in axial dimensions. Bile acid and bile salt metabolism pathways (cholesterol/lipid metabolism and sodium channel activation) were significantly upregulated during the first 24 h of recovery from 10 days of FDM.ConclusionsThe gene pathways altered during induction of FDM are similar to those reported in defocus induced myopia and are established indicators of oxidative stress, osmoregulatory and associated structural changes. These findings are also consistent with the choroidal thinning, axial elongation and hyperosmotic ion distribution patterns across the retina and choroid previously reported in FDM and predicted by RIDE.

ダイズ品種における節間伸長の規則性 : エンレイと東山 69 号の比較

ダイズ品種における節間伸長の規則性 : エンレイと東山 69 号の比較

Patrón de alargamiento del brote terminal en un ensayo de procedencias de Pinus greggii Engelm. en la Sierra de Arteaga, Coahuila

El patrón de alargamiento del brote terminal determina el tipo de crecimiento en altura de una especie dada y poco se conoce sobre su variación entre procedencias, por lo que el objetivo de este estudio fue evaluar la variación en el patrón de crecimiento del brote terminal de árboles juveniles en un ensayo de tres procedencias de Pinus greggii establecido en Los Lirios, Arteaga, Coahuila. El crecimiento del brote terminal se midió cada 15 días durante dos años (2007 y 2008), con dichas mediciones se estimó el crecimiento parcial y acumulado. Los resultados indican que el periodo de mayor crecimiento en las tres procedencias fue de junio a agosto con aproximadamente 54% del crecimiento total en 2007 y de finales de mayo a julio con 72.5 % del crecimiento total en 2008. La mayor tasa de crecimiento fue de 0.28 cm día-1 en mayo en 2007 y de 0.33 cm día-1 en junio en 2008. En 2007, se encontraron diferencias estadísticamente significativas (P ≤ 0.05) entre procedencias para el crecimiento acumulado solamente en ocho fechas de evaluación, mientras que en 2008 no se presentaron diferencias significativas entre procedencias para el crecimiento acumulado ni en el crecimiento parcial. La temporada de alargamiento del brote terminal, inicio y conclusión en los árboles juveniles de P. greggii, ocurrió en el transcurso de 145 días y 197 días para 2007 y 2008, respectivamente; representando 90% del crecimiento total, lo cual ocurrió en condiciones de temperatura y fotoperiodo del verano en Arteaga, Coahuila.

In-vivo Elongation Patterns of the Anteromedial and Posterolateral Bundles of the ACL at Low Flexion Angles

The kinematics of the anteromedial (AM) and posterolateral (PL) bundles of the anterior cruciate ligament (ACL) in hyperextension was not well understood. This study investigated elongations of the two bundles in hyperextended knee. Twenty living knees were CT-scanned and fluoroscopy-imaged during a weight-bearing flexion–extension cycle from hyperextension to maximal flexion. The knee positions and the relative elongations of the two bundles were reproduced along the motion path using a combined fluoroscopic imaging and CT modeling technique. Results showed the elongation patterns of the two bundles were distinctively different (p < 0.01). The elongation of the PL bundle was slightly higher than that of the AM bundle at hyperextension and then decreased sharply with flexion. The elongation of the AM bundle was highest between the full extension and 10° flexion, and then decreased gradually with flexion angles. In every 10° from hyperextension to 30° flexion, the increasing rates of the PL bundle elongation were significantly higher than those of the AM bundle (p < 0.01). These data may provide important implications for selection of knee flexion angles for fixation of the AM and PL graft bundles in an anatomic ACL reconstruction that can help prevent over-stretching of the graft and reduce the risk of graft failure.