Structural components of the arch of the foot analyzed by radiogrammetric and multivariate statistical methods

The structural component of the arches of the human foot were analyzed by a radiogrammetric method and multivariate statistical procedures. The right feet of 101 male university students were radiographed in the standing position from a lateromedial direction. 6 joint heights were measured directly on the radiographs. Factor analysis with varimax rotation showed 3 basic underlying factors for arch heights: (1) calcaneonavicular joint, cuneonavicular joint and first tarsometatarsal joint; (2) calcaneocuboidal joint and 5th tarsometatarsal joint and (3) subtalar joint. The first factor represented the medial longitudinal arch height, the second was associated with the lateral longitudinal arch height. No transverse factor indicating tarsometatarsal or transverse tarsal joints was found. Cluster analysis showed a similar configuration to that in factor analysis. Analysis suggested a key role of the subtalar joint which integrated both the medial and lateral longitudinal arch heights.     

Knee medial and lateral contact forces in a musculoskeletal model with subject-specific contact point trajectories

Contact point (CP) trajectory is a crucial parameter in estimating medial/lateral tibio-femoral contact forces from the musculoskeletal (MSK) models. The objective of the present study was to develop a method to incorporate the subject-specific CP trajectories into the MSK model. Ten healthy subjects performed 45 s treadmill gait trials. The subject-specific CP trajectories were constructed on the tibia and femur as a function of extension-flexion using low-dose bi-plane X-ray images during a quasi-static squat. At each extension-flexion position, the tibia and femur CPs were superimposed in the three directions on the medial side, and in the anterior-posterior and proximal-distal directions on the lateral side to form the five kinematic constraints of the knee joint. The Lagrange multipliers associated to these constraints directly yielded the medial/lateral contact forces. The results from the personalized CP trajectory model were compared against the linear CP trajectory and sphere-on-plane CP trajectory models which were adapted from the commonly used MSK models. Changing the CP trajectory had a remarkable impact on the knee kinematics and changed the medial and lateral contact forces by 1.03 BW and 0.65 BW respectively, in certain subjects. The direction and magnitude of the medial/lateral contact force were highly variable among the subjects and the medial-lateral shift of the CPs alone could not determine the increase/decrease pattern of the contact forces. The suggested kinematic constraints are adaptable to the CP trajectories derived from a variety of joint models and those experimentally measured from the 3D imaging techniques.     

Subject-specific knee joint geometry improves predictions of medial tibiofemoral contact forces

Estimating tibiofemoral joint contact forces is important for understanding the initiation and progression of knee osteoarthritis. However, tibiofemoral contact force predictions are influenced by many factors including muscle forces and anatomical representations of the knee joint. This study aimed to investigate the influence of subject-specific geometry and knee joint kinematics on the prediction of tibiofemoral contact forces using a calibrated EMG-driven neuromusculoskeletal model of the knee. One participant fitted with an instrumented total knee replacement walked at a self-selected speed while medial and lateral tibiofemoral contact forces, ground reaction forces, whole-body kinematics, and lower-limb muscle activity were simultaneously measured. The combination of generic and subject-specific knee joint geometry and kinematics resulted in four different OpenSim models used to estimate muscle–tendon lengths and moment arms. The subject-specific geometric model was created from CT scans and the subject-specific knee joint kinematics representing the translation of the tibia relative to the femur was obtained from fluoroscopy. The EMG-driven model was calibrated using one walking trial, but with three different cost functions that tracked the knee flexion/extension moments with and without constraint over the estimated joint contact forces. The calibrated models then predicted the medial and lateral tibiofemoral contact forces for five other different walking trials. The use of subject-specific models with minimization of the peak tibiofemoral contact forces improved the accuracy of medial contact forces by 47% and lateral contact forces by 7%, respectively compared with the use of generic musculoskeletal model.     

Muscle forces predicted using optimization methods are coordinate system dependent

Optimization methods are widely used to predict in vivo muscle forces in musculoskeletal joints. Moment equilibrium at the joint center (usually chosen as the origin of the joint coordinate system) has been used as a constraint condition for optimization procedures and the joint reaction moments were assumed zero. This study, through the use of a three-dimensional elbow model, investigated the effect of coordinate system origin (joint center) location on muscle forces predicted using a nonlinear static optimization method. The results demonstrated that moving the origin of the coordinate system medially and laterally along the flexion-extension axis caused dramatic variations in the predicted muscle forces. For example, moving the origin of the coordinate system from a position 5mm medial to 5mm lateral of the geometric elbow center caused the predicted biceps force to vary from 12% to 46% and the brachialis force to vary from 80% to 34% of the total muscle loading. The joint reaction force reduced by 24% with this medial to lateral variation of the coordinate system origin location. This data revealed that the muscle forces predicted using the optimization method are sensitive to the coordinate system origin location due to the zero joint reaction moment assumption in the moment constraint condition. For accurate prediction of muscle load distributions using optimization methods, it is necessary to determine the accurate coordinate system origin location where the condition of a zero joint reaction moment is satisfied.     

The effect of meniscal tears and resultant partial meniscectomies on the knee contact stresses: a finite element analysis

Knee osteoarthritis (OA) is believed to result from high levels of contact stresses on the articular cartilage and meniscus after meniscal damage. This study investigated the effect of meniscal tears and partial meniscectomies on the peak compressive and shear stresses in the human knee joint. An elaborate three-dimensional finite element model of knee joint including bones, articular cartilages, menisci and main ligaments was developed from computed tomography and magnetic resonance imaging images. This model was used to model four types of meniscal tears and their resultant partial meniscectomies and analysed under an axial 1150 N load at 0° flexion. Three different conditions were compared: a healthy knee joint, a knee joint with medial meniscal tears and a knee joint following partial meniscectomies. The numerical results showed that each meniscal tear and its resultant partial meniscectomy led to an increase in the peak compressive and shear stresses on the articular cartilages and meniscus in the medial knee compartment, especially for partial meniscectomy. Among the four types of meniscal tears, the oblique tear resulted in the highest values of the peak compressive and shear stresses. For the four partial meniscectomies, longitudinal meniscectomy led to the largest increase in these two stresses. The lateral compartment was minimally affected by all the simulations. The results of this study demonstrate meniscal tear and its resultant partial meniscectomy has a positive impact on the maintenance of high levels of contact stresses, which may improve the progression of knee OA, especially for partial meniscectomy. Surgeons should adopt a prudent strategy to preserve the greatest amount of meniscus possible.     

A novel method for measuring medial compartment pressures within the knee joint in-vivo

A novel method for the measurement of knee joint forces in-vivo is described. A thin (0.2mm) flexible electronic pressure sensor was inserted through a narrow arthroscopic portal into the osteoarthritic medial compartment of the knee joint. The sensor partially covered the load bearing area. The surgery was performed under local anaesthetic during normal arthroscopic examination following patient consent. Results are presented for 11 patients. The method was used in a pilot study to assess the effects of four valgus knee braces on medial compartment forces. An analysis of variance could not detect un-loading by any brace although there were large variations in force output. These variations may be attributable to shifts in the sensor position. In-vivo measurement of joint force is technically feasible.     

Analysis of muscle activation patterns during transitions into and out of high knee flexion postures

Increased risk of medial tibiofemoral osteoarthritis (OA) is linked to occupations that require frequent transitions into and out of postures which require high knee flexion (>90°). Muscle forces are major contributors to joint loading, and an association between compressive forces due to muscle activations and the degeneration of joint cartilage has been suggested. The purpose of this study was to evaluate muscle activation patterns of muscles crossing the knee during transitions into and out of full-flexion kneeling and squatting, sitting in a low chair, and gait. Both net and co-activation were greater when transitioning out of high flexion postures, with maximum activation occurring at knee angles greater than 100°. Compared to gait, co-activation levels during high flexion transitions were up to approximately 3 times greater. Co-activation was significantly greater in the lateral muscle group compared to the medial group during transitions into and out of high flexion postures. These results suggest that compression due to activation of the medial musculature of the knee may not be the link between high knee flexion postures and increased medial knee OA observed in occupational settings. Further research on a larger subject group and workers with varying degrees of knee OA is necessary.     

Lectin-binding in normal and osteoarthrotic articular cartilage from STR/1N-mouse knee joints

Fluorescein-isothiocyanate (FITC) labeled lectins were used to study the distribution pattern of specific binding-sites in histological sections of normal and osteoarthrotic articular cartilage from the mouse knee joint. Male inbred mice of the STR/1N-strain develop spontaneous arthrotic articular cartilage lesions on the medial condyle of tibia and femur. The varus-deformity of the knee joint leads to a recurrent medial patellar luxation with osteoarthrotic defects on the medial part of the facies patellaris femoris. It was demonstrated that the lectin staining pattern of osteoarthrotic articular cartilage, especially on the facies patellaris femoris, was different from that of normal articular cartilage. The differences in lectin staining corresponded to those observed between normal and fibrillated articular cartilage from human patellae. The normal articular cartilage of the mouse knee joint possessed lectin binding-sites for Concanavalin A (ConA) and wheat germ agglutinin (WGA), but not for Ulex europaeus agglutinin (UEA), soy bean agglutinin (SBA) and peanut agglutinin (PNA). In addition to the completely changed distribution pattern of ConA and WGA in osteoarthrotic cartilage, SBA, PNA and UEA developed distinct staining patterns particular to the fibrillated areas of arthrotic cartilage. The increased lectin-binding to arthrotic articular cartilage may be due to unmasking of sugars in the course of bondage breakdown in fibrillated cartilage or the production of pathological glycoproteins. It is evident that lectins can demonstrate minute differences between normal and arthrotic cartilage and it is concluded, therefore, that lectins are sensitive and specific tools for the study of degenerative joint diseases.     

Studies in Osteoarthritis of the Hip: Part I, * Classification

A definition and classification of primary OA hip is presented based on radiological criteria. Most cases of unilateral idiopathic OA hip remain unilateral over the years and the majority of these show a distinct radiological pattern with articular cartilage loss in the superolateral area of the joint. In contrast, OA hip with loss of cartilage in the medial area is usually bilateral. A supermedial form appears to be an intermediate type, but is less well defined.It is suggested that superolateral and medial forms of OA hip are fundamentally different in nature. Leg-length disparity, to be discussed in a subsequent section, is related to the superolateral type.     

Neuronal organization of the periamygdaloid cortex in the cat brain

Neuronal organization of the fields Pmm, Pml2, Pe and epm of the periamygdaloid cortex of the cat brain has been studied by means of Golgi and Nissl methods. The field Pmm essentially differs from other fields of this cortex by primitiveness of its cytoarchitectonic an neuronal organization (two layers uniform by the composition of their neurons are distinguished, the structure of the latter is relatively primitive). In the medial part of this field long axonal rarely branching short dendritic, and in the lateral part--poorly differentiating pyramidal and spindle-like cells predominate. The field Pmm can be considered as a transitional formation between the subcortex (the medial nucleus of the amygdaloid body) and other fields of the periamygdaloid cortex. The fields Pml2, Pe and epm are built more complexly: the cells are organized in 4 layers, more complexly differentiated by their form and size than in the field Pmm and correspondingly more various (long axonal densely branching cells are observed: pyramidal and spindle-like--of the cortical type and bushy--of the subcortical type, as well as long axonal rarely branching reticular cells). The short axonal cells in the fields Pml2, Pe and epm are rather variable in their form, size and direction of axons; in the field Pmm they are less numerous. The field Pmm and the complex of the fields Pml2, Pe and epm are perhaps different in their function, this is evident from different projection of their neurons. Axons of the cells in the field Pmm get into less differentiated and the most ancient medial nucleus of the amygdaloid body and into the ancient system of connections of the latter--terminal strip, and neurons of the fields Pml2, Pe and epm are projected into the basolateral part of the amygdaloid body and into the external capsule--phylogenetically younger structures. Besides, poverty of the axonal collateralies in the long axonal neurons and a small amount and uniformity of the forms of the short axonal cells in the field Pmm and contrary, rich collateralies and variety of short axonal cells in the composition of other fields demonstrate more complex internal integrative function, performing in that composition.     

The naso-frontal joint in snakes as revealed by high-resolution X-ray computed tomography of intact and complete skulls

The naso-frontal joint of snakes is described on the basis of high-resolution X-ray computed tomography scans of single individuals of spirit-preserved snake specimens. The suspension of the snout unit from the braincase at the naso-frontal joint shows some broad evolutionary trends among snakes with potential phylogenetic implications, such as sutured or fused medial frontal flanges formed by the medial frontal pillars and the frontal subolfactory processes (in alethinophidians), the restriction of the usually extended dorsoventral contact of the medial nasal flange with the medial frontal flanges to a dorsal or ventral contact (in macrostomatans), and the transfer of the main element of snout suspension from the nasal to the septomaxilla (in colubroids). Some phylogenetic implications of the morphological characters identified in this study are outlined and discussed.     

Hypothalamo-amygdaloid connections of cat's brain]

Under study were the afferent connections of the cat's amygdala nuclei with the hypothalamus (Nauta's method) in parallel with studying geometrical parameters of the afferent fibre endings in these nuclei by the Golgi method. It has been shown that the medial hypothalamus gives the beginning to a small amount of fibres running to the medial group of the amygdala nuclei; dissipated solitary fibres run to the large- and small-cellular parts of the basal nucleus. A considerable amount of fibres run from the lateral hypothalamus to the amygdala, mainly to the medial group of its nuclei and the anterior amygdalar area, only solitary fibres were followed in the basal nuclei. We failed to observe degenerated fibres from the medial preoptical area to the amygdale. The geometry of branches of these fibre systems in the amygdala nuclei was established: they all terminate as a compact but rarely branching brush.     

浙江天童常绿阔叶演替过程凋落物数量及分解动态

 浙江天童常绿阔叶林演替过程森林凋落物量呈增长趋势,其中：乔木叶比例最大,其它器官组分在不同演替阶段的比例不一致,灌木叶和草本、树皮比例随着演替进程而呈减少趋势,树枝和繁殖器官则呈增大趋势。以分解袋法测得凋落物年失重率和指数方程模拟的分解系数K在演替过程中均呈增长趋势,这与年凋落物数量变化趋势相似。可见,随着演替进程,生物循环加快,群落自肥能力增强。     

浙江天童常绿阔叶林演替过程凋落物数量及分解动态

浙江天童常绿阔叶林演替过程森林凋落物量呈增长趋势,其中：乔木叶比例最大,其它器官组分在不同演替阶段的比例不一致,灌木叶和草本、树皮比例随着演替进程而呈减少趋势,树枝和繁殖器官则呈增大趋势。以分解袋法测得凋落物年失重率和指数方程模拟的分解系数Ｋ在演替过程中均呈增长趋势,这与年凋落物数量变化趋势相似。可见,随着演替进程,生物循环加快,群落自肥能力增强。     

The effect of salicylate on prostaglandin levels in rabbit knees following inducement of osteoarthritic changes

Surgical inducement of medial instability in the right knee of rabbits was used to produce joint changes which resemble those observed in human osteoarthritis. Ordinary tap water was supplied to half of the rabbits and tap water plus sodium salicylate to the others. Determinations of prostaglandin were made on the synovial fluid and cartilage from all rabbits five months after surgery. In both groups, the concentration of prostaglandin in synovial fluid was lower in the operated knees, but the total amount of prostaglandin was found to be approximately equal to that in the unoperated knees. The development of degenerative joint changes therefore was not accompanied by increases in prostaglandin content. Salicylate treatment did not alter this observation, however, it did reduce overall prostaglandin levels. These results suggest that prostaglandin interaction is not involved in osteoarthritic joint degeneration.     

Body size and joint posture in primates

Body mass has been shown in experimental and comparative morphological studies to have a significant effect on joint posture in major limb joints. The generalizability of experimental studies is limited by their use of small sample sizes and limited size ranges. In contrast, while comparative morphological studies often have increased sample sizes, the connection between joint posture and morphological variables is often indirect. The current study infers joint postures for a large sample of primates using an experimentally validated method, and tests whether larger primates use more extended joint postures than smaller species. Postures are inferred through the analysis of patterns of subchondral bone apparent density on the medial femoral condyle. Femora from 94 adult wild‐shot individuals of 28 species were included. Apparent density measurements were obtained from CT scans using AMIRA software, and the angular position of the anterior‐most extent of the region of maximum apparent density on the medial femoral condyle was recorded. In general, the hypothesis that larger‐bodied primates use more extended knee posture was supported, but it should be noted that considerable variation exists, particularly at small body sizes. This indicates that smaller species are less constrained by their body size, and their patterns of apparent density are consistent with a wide range of knee postures. The size‐related increase in inferred joint posture was observed in most major groups of primates, and this observation attests to the generalizability of Biewener's model that relates body size and joint posture. Am J Phys Anthropol, 2009. © 2009 Wiley‐Liss, Inc.     

Globographic visualisation of three dimensional joint angles

Three different methods for describing three dimensional joint angles are commonly used in biomechanics. The joint coordinate system and Cardan/Euler angles are conceptually quite different but are known to represent the same underlying mathematics. More recently the globographic method has been suggested as an alternative and this has proved particularly attractive for the shoulder joint. All three methods can be implemented in a number of ways leading to a choice of angle definitions. Very recently Rab has demonstrated that the globographic method is equivalent to one implementation of the joint coordinate system. This paper presents a rigorous analysis of the three different methods and proves their mathematical equivalence. The well known sequence dependence of Cardan/Euler is presented as equivalent to configuration dependence of the joint coordinate system and orientation dependence of globographic angles. The precise definition of different angle sets can be easily visualised using the globographic method using analogues of longitude, latitude and surface bearings with which most users will already be familiar. The method implicitly requires one axis of the moving segment to be identified as its principal axis and this can be extremely useful in helping define the most appropriate angle set to describe the orientation of any particular joint. Using this technique different angle sets are considered to be most appropriate for different joints and examples of this for the hip, knee, ankle, pelvis and axial skeleton are outlined.     

A comparison of the influence of global functional loads vs. local contact anatomy on articular cartilage thickness at the knee

Cartilage contact geometry, along with joint loading, can play an important role in determining local articular cartilage tissue stress. Thus individual variations in cartilage thickness can be associated with both individual variations in joint loading associated with activities of daily living as well as individual differences in the anatomy of the contacting surfaces of the joint. The purpose of this study was to isolate the relationship between cartilage thickness predicted by individual variations in contact surface geometry based on the radii of the femur and tibia vs. cartilage thickness predicted by individual variations in joint loading. Knee magnetic resonance (MR) images and the peak knee adduction moments during walking were obtained from 11 young healthy male subjects (age 30.5+/-5.1 years). The cartilage thicknesses and surface radii of the femoral and tibial cartilage were measured in the weight-bearing regions of the medial and lateral compartments of three-dimensional models from the MR images. The ratio of contact pressure between the medial and lateral compartments was calculated from the radii of tibiofemoral contact surface geometries. The results showed that the medial to lateral pressure ratios were not correlated with the medial to lateral cartilage thickness ratios. However, in general, pressure was higher in the lateral than medial compartments and cartilage was thicker in the lateral than medial compartments. The peak knee adduction moment showed a significant positive linear correlation with medial to lateral thickness ratio in both femur (R(2)=0.43,P<0.01) and tibia (R(2)=0.32,P<0.01). The results of this study suggest that the dynamics of walking is an important factor to describe individual differences in cartilage thickness for normal subjects.     

Quantitative proteomics at different depths in human articular cartilage reveals unique patterns of protein distribution

The articular cartilage of synovial joints ensures friction-free mobility and attenuates mechanical impact on the joint during movement. These functions are mediated by the complex network of extracellular molecules characteristic for articular cartilage. Zonal differences in the extracellular matrix (ECM) are well recognized. However, knowledge about the precise molecular composition in the different zones remains limited. In the present study, we investigated the distribution of ECM molecules along the surface-to-bone axis, using quantitative non-targeted as well as targeted proteomics.\In a discovery approach, iTRAQ mass spectrometry was used to identify all extractable ECM proteins in the different layers of a human lateral tibial plateau full thickness cartilage sample. A targeted MRM mass spectrometry approach was then applied to verify these findings and to extend the analysis to four medial tibial plateau samples.In the lateral tibial plateau sample, the unique distribution patterns of 70 ECM proteins were identified, revealing groups of proteins with a preferential distribution to the superficial, intermediate or deep regions of articular cartilage. The detailed analysis of selected 29 proteins confirmed these findings and revealed similar distribution patterns in the four medial tibial plateau samples.The results of this study allow, for the first time, an overview of the zonal distribution of a broad range of cartilage ECM proteins and open up further investigations of the functional roles of matrix proteins in the different zones of articular cartilage in health and disease.     

Ultrastructure of synapses in the nucleus of the trapezoid body of the bat]

The subsynaptic structure of the synapses in the medial nucleus of the trapezoid body was studied in the bat Myotis oxygnatus. The synaptic endings in the nucleus are represented by large-cup-shaped and small loop-shaped terminations. The cup-shaped terminations are formed of large branches originating from a thick myelinated fibre after loss of myelin from it. Each branch forms a series of contacts alternating with vast enlargements of extracellular space, on the body of the cell and its processes. Large branches are filled with synaptic vesicles, neurofilaments and neurotubules, mitochondria; all these components are distributed rather regularly along the branch diameter. In fine branches of the cup the synaptic vesicles are the main and often the only component. The pattern of the cup branch changes as the distance from the main fibre increases, namely the amount of neurofilaments and neurotubules diminishes up to their disappearance, while the amount and the density of synaptic vesicles increases. The small loop-shaped treminals are different from the cup-shaped ones by the composition of the synaptic vesicles and the structure of the contact zone. In addition to agranular vesicles there are also granular ones. Both types of terminations--cup-shaped and loop-shaped ones -- are found both on the bodies and dendrites. On distal portions of dendrites the terminations are disposed in nests.