Muscle Attachment Points Research Articles

Finite element analysis of the Fibula's contribution to lower extremity torsional stiffness

AimsThe purpose of this article is to investigate the effects of the fibula on the torsional stiffness of the lower limb. A comprehensive model of the lower limb was constructed, including the resected femur, patella, tibia, fibula, and foot, with tendons and ligaments. Two configurations were developed, with and without the presence of the fibula, to evaluate the resulting stress state and consequently determine the contribution of the fibula to the torsional stiffness of the lower limb. MethodsThe finite element method was used to analyse how the fibula affects the stress distribution in the lower extremity under body weight loading and torsional forces. A detailed three-dimensional solid model of the lower extremity with and without the fibula was constructed. Loading conditions were imposed simulating an axial compressive load of 700 N applied to the upper extremity of the resected femur and a torsional load of 6000 Nmm applied to the proximal femur, and a fixed constraint was imposed on the foot. ResultsRemoving the fibula results in an increase in stress on all the tendons and ligaments tested. The increases ranged from 4 % (patellar tendon) to 21 % (lateral retinaculum). This suggests that the fibula plays a significant role in the distribution of mechanical stress in the lower extremity. The most affected structures are the lateral retinaculum and the posterior cruciate ligament, both with a 21 % increase in stress, suggesting that these structures may compensate more for the absence of the fibula. ConclusionThe fibula plays a critical role in maintaining the structural integrity and biomechanical function of the lower extremity. It acts as a lateral strut, contributing to the stability of the ankle and knee by providing an attachment point for several muscles and ligaments that are essential for coordinating complex movements and providing stability during dynamic activities.

Skeletotopic landmarks of the points of fixation of the quadriceps femoral muscle in representatives of canids

The article presents skeletotopic landmarks of the points of fixation of the quadriceps femoral muscle in representatives of Canidae (shalayka and domestic dog), which are absent in the available literature. Thus, it was revealed that the straight head in the distal part of the shalaika is attached to the base of the cranial surface of the kneecap by tendon fibers, and in the domestic dog its muscle-tendon fixation was found. The research was carried out at the Department of Anatomy and Histology of Animals named after Professor A. F. Klimov of the Moscow State Academy of Veterinary Medicine and Biotechnology – MBA named after K. I. Scriabin. The material for the research was sectional material - pelvic limbs (n=16), selected from adult dogs and canine hybrids (shalayka), without external signs of musculoskeletal system pathologies. The methods of fine macro- and microanatomic dissection under the control of a Micromed HR 350 S binocular magnifier were used, followed by functional analysis of the studied structures and skeletotopic projection of muscle attachment points on the kneecap. When studying the structures located on the kneecap, it was found that the cranial head of the tailor's muscle and the wide fascia of the thigh, covering the cranial surface of the kneecap, connects to the underlying organs through loose connective tissue. However, at the top of the cranial tubercle, they closely fuse with the tendon of the rectus femoris muscle, as well as directly with the periosteum of the cranial tubercle of the kneecap, and then, covering the rectus ligament of the kneecap, continue into the fascia of the lower leg.

Novel Baseline Facial Muscle Database Using Statistical Shape Modeling and In Silico Trials toward Decision Support for Facial Rehabilitation.

Backgrounds and Objective: Facial palsy is a complex pathophysiological condition affecting the personal and professional lives of the involved patients. Sudden muscle weakness or paralysis needs to be rehabilitated to recover a symmetric and expressive face. Computer-aided decision support systems for facial rehabilitation have been developed. However, there is a lack of facial muscle baseline data to evaluate the patient states and guide as well as optimize the rehabilitation strategy. In this present study, we aimed to develop a novel baseline facial muscle database (static and dynamic behaviors) using the coupling between statistical shape modeling and in-silico trial approaches. Methods: 10,000 virtual subjects (5000 males and 5000 females) were generated from a statistical shape modeling (SSM) head model. Skull and muscle networks were defined so that they statistically fit with the head shapes. Two standard mimics: smiling and kissing were generated. The muscle strains of the lengths in neutral and mimic positions were computed and recorded thanks to the muscle insertion and attachment points on the animated head and skull meshes. For validation, five head and skull meshes were reconstructed from the five computed tomography (CT) image sets. Skull and muscle networks were then predicted from the reconstructed head meshes. The predicted skull meshes were compared with the reconstructed skull meshes based on the mesh-to-mesh distance metrics. The predicted muscle lengths were also compared with those manually defined on the reconstructed head and skull meshes. Moreover, the computed muscle lengths and strains were compared with those in our previous studies and the literature. Results: The skull prediction's median deviations from the CT-based models were 2.2236 mm, 2.1371 mm, and 2.1277 mm for the skull shape, skull mesh, and muscle attachment point regions, respectively. The median deviation of the muscle lengths was 4.8940 mm. The computed muscle strains were compatible with the reported values in our previous Kinect-based method and the literature. Conclusions: The development of our novel facial muscle database opens new avenues to accurately evaluate the facial muscle states of facial palsy patients. Based on the evaluated results, specific types of facial mimic rehabilitation exercises can also be selected optimally to train the target muscles. In perspective, the database of the computed muscle lengths and strains will be integrated into our available clinical decision support system for automatically detecting malfunctioning muscles and proposing patient-specific rehabilitation serious games.

A study on effect of virtual actuator in optimization calculation for muscle force estimation

The reserve actuators used in the Residual Reduction Algorithm of the musculoskeletal software OpenSim generate forces instead of muscles. In this study, we verified range of reserve actuator settings that can appropriately estimate muscle forces. A healthy adult man walked during the experiment. The results of the estimated lower limb muscle forces during walking indicated that the biarticular muscles, including rectus femoris and biceps femoris LH, and the monoarticular muscles which have many muscle attachment points, including gluteus maximus and psoas muscles, were not affected by the reserve actuators. While the monoarticular muscles, including soleus muscle, gastrocnemius muscle, tibialis anterior muscle, and biceps femoris SH, which have few muscle attachment points were easily affected by the reserve actuators.

Individualized 3D printing-assisted repair and reconstruction of neoplastic bone defects at irregular bone sites: exploration and practice in the treatment of scapular aneurysmal bone cysts

BackgroundThe irregular anatomical shape and complex structures of irregular bones make it more difficult to repair and reconstruct bone defects in irregular bones than in the long bones of the extremities. Three-dimensional (3D) printing technology can help to overcome the technical limitations of irregular bone repair by generating simulations that enable structural integration of the lesion area and bone structure of the donor site in all directions and at multiple angles. Thus, personalized and accurate treatment plans for restoring anatomical structure, muscle attachment points, and maximal function can be made. The present study aimed to investigate the ability of 3D printing technology to assist in the repair and reconstruction of scapular aneurysmal ABC defects.MethodsThe study included seven patients with ABCs of the scapula. Based on computed tomography (CT) data for the patient, the scapula (including the defect) and pelvis were reconstructed using Mimics Medical software. The reconstructed scapula model was printed using a 3D printer. Before the operation, the model was used to design the surgical approach and simulate the operation process, to determine the length and radius of the plate and the number and direction of screws, and to determine the bone mass of the ilium and develop reasonable strategies for segmentation and distribution. The operation time, amount of bleeding, length and radius of the plate, and direction and number of screws were recorded.ResultsThe average duration of follow-up was 25.6 months, and none of the seven patients experienced recurrence during the follow-up period. The surgical approach, the length and radius of internal fixation, and the number and direction of screws were consistent with the designed operation plan. Patients gradually recovered the anatomical structure of the scapula and function of the shoulder joint.ConclusionsIn the treatment of bone defects caused by irregular bone tumors, 3D printing technology combined with surgery has the advantages of less trauma, short operation time, less bleeding and reducing the difficulty of operation, which can reduce the waste of bone graft, and more complete reconstruction of the anatomical structure of the defective bone.

Relationship between sacral shape variation and phylogeny in Old World monkeys.

The sacrum, an essential skeletal element in the trunk, articulates with the ilium and lumbar and caudal vertebrae. While there are known morphological differences between hominoids and cercopithecoids (Old World monkeys), sacral morphological variations among cercopithecoids have rarely been studied outside of research on tail length variation. Increased knowledge regarding sacral variations in extant primates, however, could help in understanding and reconstructing their evolutionary development. Therefore, this study aimed to explore phylogenetic sacral shape variations among cercopithecoids. Geometric morphometric analyses were performed on 221 sacra from 39 different cercopithecoid species. Clear shape differences were observed among Colobinae, Cercopithecini, and Papionini, particularly in the spinous processes and sacral lateral mass. These parts function as muscle attachment points or skeletal joints, and variations in them seemed to reflect their required functions. However, the significance of the relationship between shape and function was not so great as to explain all the observed variation. According to recent genetic/developmental biological studies, shape variations may also be caused by the pleiotropic effects of some genes, such as posterior Hox genes. Therefore, while skeletal morphology has previously been considered to be directly connected to skeletal function, this study's results suggest that other factors influencing sacral shape require further research.

Kinect-driven Patient-specific Head, Skull, and Muscle Network Modelling for Facial Palsy Patients

Background and ObjectiveFacial palsy negatively affects both professional and personal life qualities of involved patients. Classical facial rehabilitation strategies can recover facial mimics into their normal and symmetrical movements and appearances. However, there is a lack of objective, quantitative, and in-vivo facial texture and muscle activation bio-feedbacks for personalizing rehabilitation programs and diagnosing recovering progresses. Consequently, this study proposed a novel patient-specific modelling method for generating a full patient specific head model from a visual sensor and then computing the facial texture and muscle activation in real-time for further clinical decision making. MethodsThe modeling workflow includes (1) Kinect-to-head, (2) head-to-skull, and (3) muscle network definition & generation processes. In the Kinect-to-head process, subject-specific data acquired from a new user in neutral mimic were used for generating his/her geometrical head model with facial texture. In particular, a template head model was deformed to optimally fit with high-definition facial points acquired by the Kinect sensor. Moreover, the facial texture was also merged from his/her facial images in left, right, and center points of view. In the head-to-skull process, a generic skull model was deformed so that its shape was statistically fitted with his/her geometrical head model. In the muscle network definition & generation process, a muscle network was defined from the head and skull models for computing muscle strains during facial movements. Muscle insertion points and muscle attachment points were defined as vertex positions on the head model and the skull model respectively based on the standard facial anatomy. Three healthy subjects and two facial palsy patients were selected for validating the proposed method. In neutral positions, magnetic resonance imaging (MRI)-based head and skull models were compared with Kinect-based head and skull models. In mimic positions, infrared depth-based head models in smiling and [u]-pronouncing mimics were compared with appropriate animated Kinect-driven head models. The Hausdorff distance metric was used for these comparisons. Moreover, computed muscle lengths and strains in the tested facial mimics were validated with reported values in literature. ResultsWith the current hardware configuration, the patient-specific head model with skull and muscle network could be fast generated within 17.16±0.37s and animated in real-time with the framerate of 40 fps. In neutral positions, the best mean error was 1.91 mm for the head models and 3.21 mm for the skull models. On facial regions, the best mean errors were 1.53 mm and 2.82 mm for head and skull models respectively. On muscle insertion/attachment point regions, the best mean errors were 1.09 mm and 2.16 mm for head and skull models respectively. In mimic positions, these errors were 2.02 mm in smiling mimics and 2.00 mm in [u]-pronouncing mimics for the head models on facial regions. All above error values were computed on a one-time validation procedure. Facial muscles exhibited muscle shortening and muscle elongating for smiling and pronunciation of sound [u] respectively. Extracted muscle features (i.e. muscle length and strain) are in agreement with experimental and literature data. ConclusionsThis study proposed a novel modeling method for fast generating and animating patient-specific biomechanical head model with facial texture and muscle activation bio-feedbacks. The Kinect-driven muscle strains could be applied for further real-time muscle-oriented facial paralysis grading and other facial analysis applications.

Automated muscle elongation measurement during reverse shoulder arthroplasty planning

Adequate deltoid and rotator cuff elongation in reverse shoulder arthroplastyis crucial to maximize postoperative functional outcomes and to avoid complications. Measurements of deltoid and rotator cuff elongation during preoperative planning can support surgeons in selecting a suitable implant design and position. Therefore, this study presented and evaluated a fully automated method for measuring deltoid and rotator cuff elongation. Complete scapular and humeral models were extracted from computed tomography scans of 40 subjects. First, a statistical shape model of the complete humerus was created and evaluated to identify the muscle attachment points. Next, a muscle wrapping algorithm was developed to identify the muscle paths and to compute muscle lengths and elongations after reverse shoulder arthroplasty implantation. The accuracy of the muscle attachment points and the muscle elongation measurements was evaluated for the 40 subjects by use of both complete and artificially created partial humeral models. Additionally, the muscle elongation measurements were evaluated for a set of 50 arthritic shoulder joints. Finally, a sensitivity analysis was performed to evaluate the impact of implant positioning on deltoid and rotator cuff elongation. For the complete humeral models, all muscle attachment points were identified with a median error < 3.5 mm. For the partial humeral models, the errors on the deltoid attachment point largely increased. Furthermore, all muscle elongation measurements showed an error < 1 mm for 75% of the subjects for both the complete and partial humeral models. For the arthritic shoulder joints, the errors on the muscle elongation measurements were <2 mm for 75% of the subjects. Finally, the sensitivity analysis showed that muscle elongations were affected by implant positioning. This study presents an automated method for accurately measuring muscle elongations during preoperative planning of shoulder arthroplasty. The results show that the accuracy in measuring muscle elongations is higher than the accuracy in indicating the muscle attachment points. Hence, muscle elongation measurements are insensitive to the observed errors on the muscle attachment points. Related to this finding, muscle elongations can be accurately measured for both a complete humeral model and a partial humeral model. Because the presented method also showed accurate results for arthritic shoulder joints, it can be used during preoperative shoulder arthroplasty planning, in which typically only the proximal humerus is present in the scan and in which bone arthropathy can be present. As the muscle elongations are sensitive to implant positioning, surgeons can use the muscle elongation measurements to refine their surgical plan.

The Evaluation of Variations of The Hyoid Bone with Multidetector Computerized Tomography

The hyoid is a U shaped bone with a backward concavity. Locates at the lower edge of the mandible and lies parallel to the floor — functions as an attachment point for muscles and soft tissues of head and neck. The aim is to examine the variations and ossification of the hyoid. This study was performed retrospectively in 2010 - 2013 on 200 CT images. 3D volume rendering images of pure hyoid bone created from the axial CT images in 1 mm slice thickness. The morphological variation count was 23; ossification variations were 9 cases. No difference observed by gender, but there are differences between the age groups for ossification. Ossification rates were found as; partial 34 %, unilateral 33%, complete 22%, early 11%. Most of the morphologic variation were belong to minor horn (57%), variations of major horn were 30%. The clinical importance of hyoid bone has realized in recent years. Due to the close relationship of this bone with the muscles, ligaments, fascias, sternum, clavicles, its dysfunction can lead to general problems. Studies about the variations of hyoid bone found to be quite low, and we believe that our research will contribute to the content of literature.

An experimental study on the induction of Graves′ hyperthyroidism with Graves′ ophthalmopathy in BALB/c mice by TSHR gene immunization

Objective To construct a model of Graves′ disease(GD) with (or) Graves′ ophthalmopathy(GO) in BALB/c mice by immunization with pcDNA3.1/TSHR289. Methods pcDNA3.1/TSHR289 was injected into the bilateral gastrocnemius muscle of 35 model mice and electroporation was immediately performed. 10 control mice were injected with sterile saline and electroporated, while 5 blank mice were injected with sterile saline only. Each group of mice was immunized at 1, 4, 7, and 10 weeks, respectively. Serum total T4, TSH, TSAb, and TSBAb were measured before immunization, 2 weeks after each immunization, as well as 5 and 8 weeks after the last immunization. CT scan was used to evaluate the morphological changes of the eyes of the mice.99mTcO4- imaging was used to measure the thyroid uptake function, and the pathological changes of the thyroid and orbital tissues were evaluated by HE staining. Results After the 2nd time immunization, the serum concentrations of TT4, TSAb and TSBAb in GD mice were significantly higher than those of control and blank groups(F=13.781, 31.435, 36.112, P<0.01, respectively). The TSH continued to be significantly lower than that of control and blank groups(F=13.966, P<0.01). After the 4th time immunizations, the ability of uptaking99mTcO4- in GD mice thyroid was significantly enhanced compared with the control group. The thyroid goiter with a large amount of lymphocyte infiltration, and the thyroid follicle was thin. CT scan of GO mice showed thickening and swelling of the extraocular muscles, and no abnormalities in tendon and muscle attachment points. HE staining showed thickening of extraocular muscle fibers, lymphocyte infiltration of extraocular muscles and orbital tissue, increased hyaluronic acid, and infiltration of fat cells. Conclusion GD or GO model can be successfully induced by multiple intramuscular injection of pcDNA3.1/TSHR289 in BALB/c mice. Key words: Graves′ disease; Graves ophthalmopathy; TSHR; Mice models; Electroporation

Analyzing Moment Arm Profiles in a Full-Muscle Rat Hindlimb Model.

Understanding the kinematics of a hindlimb model is a fundamental aspect of modeling coordinated locomotion. This work describes the development process of a rat hindlimb model that contains a complete muscular system and incorporates physiological walking data to examine realistic muscle movements during a step cycle. Moment arm profiles for selected muscles are analyzed and presented as the first steps to calculating torque generation at hindlimb joints. A technique for calculating muscle moment arms from muscle attachment points in a three-dimensional (3D) space has been established. This model accounts for the configuration of adjacent joints, a critical aspect of biarticular moment arm analysis that must be considered when calculating joint torque. Moment arm profiles from isolated muscle motions are compared to two existing models. The dependence of biarticular muscle’s moment arms on the configuration of the adjacent joint is a critical aspect of moment arm analysis that must be considered when calculating joint torque. The variability in moment arm profiles suggests changes in muscle function during a step.

Quantitative Characterization of Cadaveric Pronator Muscles Using 3D Modeling

The pronator muscles of the upper limb, pronator teres (PT) and pronator quadratus (PQ), work together to rotate the radius around the ulna along an axis parallel to the central bands of the interosseous membrane while stabilizing the involved joints. Anatomical variations that affect the rotational efficiency of the PT have been described. Previously, we have described an aberrant PQ with a possible flexor function, and also defined 4 types of anatomical variations in PQ, based on the number of bellies present, and whether it occurred unilaterally or bilaterally, suggesting that PQ is more variable than appreciated. The PT typically has 2 distinct heads of origin (ulnar and humeral) and inserts onto the lateral radius. However, several anatomical variations have been reported, including the number of heads, locations of origin and insertion points, anomalous fiber orientations, and the presence of fibrous bridges and/or arches. In the current study, we sought to determine if there are patterns of anatomical variations in the PT, and whether any such variations occurred in relationship to those of the PQ. Sixteen forearms from 8 embalmed cadavers (4F,4M ages 64–93, mean 82) were dissected, and the PT and PQ muscles observed for muscle shape, fascicle orientation, and attachment points. PT and PQ heads was described, and PT tendon length, width, and distance from the radial head and styloid process measured. Our data revealed that the PT existed as only a single muscle head (humeral), bilaterally, in 25% of the cadavers examined, while exhibiting the traditional two muscle heads (humeral, ulnar) bilaterally in 75% of cadavers. Interestingly, the PT variant with a single humeral head occurred in conjunction with Type II PQ muscles bilaterally (i.e., the presence of 2 muscle bellies). Of the six cadavers with both humeral and ulnar heads of PT, 33.3% had an occurred with Type I PQ (1 head, bilateral), 33.3% with Type II PQ (2 heads, unilateral), and 33.3% with Type III PQ (2–3 heads, bilaterally). Our data suggests that there may be a relationship between the patterns of anatomical variations between PT and PQ muscles, which may provide new insight into the biomechanical relationship between these 2 muscles. The inclusion of additional cadaveric specimens, as well as quantitative comparisons between PT and PQ muscles, including cross sectional area, volume, and line of action, will help to elucidate the potential relationship between PT and PQ muscles.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Effects of phylogeny and locomotor style on the allometry of body mass and pelvic dimensions in birds.

The pelvic girdle provides physical support and attachment for the hind limb musculature. In birds there is variability in pelvic morphology across different orders and this has been used as evidence for various types of locomotion. However, the morphological variation of pelvic bones has yet to be studied systematically in birds. Therefore, we investigated basic allometric relationships among female body mass (as a size proxy) and various pelvic measurements in a phylogenetic context. We also examined in detail the inter-relationships among various pelvic measurements. Also considered were the effects of broader taxonomic relationships at the level of order, with further examination of the influence of style of terrestrial locomotion on the allometric relationships. Positive relationships were initially found among all pelvic linear measurements and female body mass (FBM). The relationships among measures of pelvic width and FBM were isometric, whereas those between pelvic length and FBM showed positive allometry. Also, FBM explained more of the variance in pelvic length than in width. Similarly, the angle of the pelvis had a significant negative relationship, but FBM only explained a very low proportion of the variation in pelvic angles. In general terms, ancova showed that the effect of FBM was smaller than the effect of locomotor style in this species set. Both the synsacrum and pelvic girdle play roles in weight support and therefore scale in proportion to body weight accordingly. All three parts of the pelvis (ilium, ischium and pubis) are attached around the acetabulum and also provide muscle attachment points, so it might be expected for them to scale in a similar manner. Increased angulation of the pelvis is linked to orders which employ their hind limbs in feeding, perching and running, although FBM also explains a very low proportion of the variation in pelvic angle. Muscle attachment and the confines on morphology presented by locomotion explain much of the variation exhibited by the relationships among pelvic measurements.

Cervical Spine Muscle-Tendon Unit Length Differences Between Neutral and Forward Head Postures: Biomechanical Study Using Human Cadaveric Specimens.

Forward head posture (FHP) may be associated with neck pain and poor health-related quality of life. Literature describes only qualitative muscle length changes associated with FHP. The purpose of this study was to quantify how muscle-tendon unit lengths are altered when human cadaveric specimens are placed in alignments representing different severities of FHP. This biomechanical study used 13 fresh-frozen cadaveric cervical spine specimens (Occiput-T1, 54±15y). Specimens' postural changes simulating increasing FHP severity while maintaining horizontal gaze were assessed. Specimen-specific anatomic models derived from computed tomography-based anatomic data were combined with postural data and specimen-specific anatomy of muscle attachment points to estimate the muscle length changes associated with FHP. Forward head posture was associated with flexion of the mid-lower cervical spine and extension of the upper cervical (sub-occipital) spine. Muscles that insert on the cervical spine and function as flexors (termed "cervical flexors") as well as muscles that insert on the cranium and function as extensors ("occipital extensors") shortened in FHP when compared to neutral posture. In contrast, muscles that insert on the cervical spine and function as extensors ("cervical extensors") as well as muscles that insert on the cranium and function as flexors ("occipital flexors") lengthened. The greatest shortening was seen in the major and minor rectus capitis posterior muscles. These muscles cross the Occiput-C2 segments, which exhibited extension to maintain horizontal gaze. The greatest lengthening was seen in posterior muscles crossing the C4-C6 segments, which exhibited the most flexion. This cadaver study did not incorporate the biomechanical influence of active musculature. This study offers a novel way to quantify postural alignment and muscle length changes associated with FHP. Model predictions are consistent with qualitative descriptions in the literature.

Sexual dimorphism in striped dolphin (Stenella coeruleoalba) crania from South Africa

AbstractThis study assessed the extent of sexual dimorphism in striped dolphin (Stenella coeruleoalba) cranial size and shape off the South African coast. Dorsal and ventral features of 60 striped dolphin crania from both the western and eastern coasts of South Africa were analyzed using landmark‐based geometric morphometrics. Although there was no evidence of dimorphism in cranial size, evidence for small, but significant, variation in both dorsal and ventral cranial shape was found between the sexes. The observed dimorphism was partly associated with changes in shape around the temporal fossa, occipital condyle and supraoccipital bone, the nasal bone, and the paraoccipital process and basiocciptal. The temporal fossa serves as an attachment point for the temporal muscle, which functions to close the lower jaw, and the occipital area serves as the anterior insertion of the epaxial muscles, which power the upstroke of the flukes during swimming. Both the paraoccipital process and basiocciptal are associated with the functioning of the hyoid apparatus, which serves as an attachment point for muscles and ligaments involved in feeding and sound production. These findings suggest the possibility of differences in diet, foraging behavior, vocalizations, and locomotion between the sexes of this species.

Muscle moment arms and sensitivity analysis of a mouse hindlimb musculoskeletal model.

Musculoskeletal modelling has become a valuable tool with which to understand how neural, muscular, skeletal and other tissues are integrated to produce movement. Most musculoskeletal modelling work has to date focused on humans or their close relatives, with few examples of quadrupedal animal limb models. A musculoskeletal model of the mouse hindlimb could have broad utility for questions in medicine, genetics, locomotion and neuroscience. This is due to this species’ position as a premier model of human disease, having an array of genetic tools for manipulation of the animal in vivo, and being a small quadruped, a category for which few models exist. Here, the methods used to develop the first three‐dimensional (3D) model of a mouse hindlimb and pelvis are described. The model, which represents bones, joints and 39 musculotendon units, was created through a combination of previously gathered muscle architecture data from microdissections, contrast‐enhanced micro‐computed tomography (CT) scanning and digital segmentation. The model allowed muscle moment arms as well as muscle forces to be estimated for each musculotendon unit throughout a range of joint rotations. Moment arm analysis supported the reliability of musculotendon unit placement within the model, and comparison to a previously published rat hindlimb model further supported the model's reliability. A sensitivity analysis performed on both the force‐generating parameters and muscle's attachment points of the model indicated that the maximal isometric muscle moment is generally most sensitive to changes in either tendon slack length or the coordinates of insertion, although the degree to which the moment is affected depends on several factors. This model represents the first step in the creation of a fully dynamic 3D computer model of the mouse hindlimb and pelvis that has application to neuromuscular disease, comparative biomechanics and the neuromechanical basis of movement. Capturing the morphology and dynamics of the limb, it enables future dissection of the complex interactions between the nervous and musculoskeletal systems as well as the environment.

Finger muscle attachments for an OpenSim upper-extremity model.

We determined muscle attachment points for the index, middle, ring and little fingers in an OpenSim upper-extremity model. Attachment points were selected to match both experimentally measured locations and mechanical function (moment arms). Although experimental measurements of finger muscle attachments have been made, models differ from specimens in many respects such as bone segment ratio, joint kinematics and coordinate system. Likewise, moment arms are not available for all intrinsic finger muscles. Therefore, it was necessary to scale and translate muscle attachments from one experimental or model environment to another while preserving mechanical function. We used a two-step process. First, we estimated muscle function by calculating moment arms for all intrinsic and extrinsic muscles using the partial velocity method. Second, optimization using Simulated Annealing and Hooke-Jeeves algorithms found muscle-tendon paths that minimized root mean square (RMS) differences between experimental and modeled moment arms. The partial velocity method resulted in variance accounted for (VAF) between measured and calculated moment arms of 75.5% on average (range from 48.5% to 99.5%) for intrinsic and extrinsic index finger muscles where measured data were available. RMS error between experimental and optimized values was within one standard deviation (S.D) of measured moment arm (mean RMS error = 1.5 mm < measured S.D = 2.5 mm). Validation of both steps of the technique allowed for estimation of muscle attachment points for muscles whose moment arms have not been measured. Differences between modeled and experimentally measured muscle attachments, averaged over all finger joints, were less than 4.9 mm (within 7.1% of the average length of the muscle-tendon paths). The resulting non-proprietary musculoskeletal model of the human fingers could be useful for many applications, including better understanding of complex multi-touch and gestural movements.

Developing, Testing and Optimising a Mouse Hindlimb Musculoskeletal Model

Stability during locomotion arises from many complex interactions which are not yet fully understood. Studies into how sensory feedback from muscle spindles contributes to this have used neuromechanical simulations, however their accuracy is limited due to the lack of available physiological data. This presentation outlines the methods used to develop a musculoskeletal model of the mouse hindlimb, which will be used to predict responses to perturbations which occur with or without sensory feedback.The 3D musculoskeletal model, which represents bones, joints and 39 muscles of the mouse hindlimb, was created using SIMM (Musculographics, USA) through a combination of muscle architecture data and I2KI enhanced microCT scanning. Architecture data, such as muscle mass, pennation angle and fibre length were gathered from microdissections, while muscle geometry was determined using I2KI microCT scanning, a non‐destructive method of determining muscle paths and attachment points. Muscle moment arms predicted by the model were found to agree with measured data from previous studies.In future work, in vivo optogenetics will be used to characterise changes in gait and muscle forces which occur in free running mice in response to induced neural and mechanical perturbations with or without sensory feedback from hindlimb muscles. These physiological data will be used to update and refine the musculoskeletal model.

Lumbar Intervertebral Joint Loads as Determined by Patient Specific Musculoskeletal Modeling for Two Types of Sagittal Spino-Pelvic Alignment with Different Occurrence of Symptomatic Adjacent Segment Degeneration

Introduction Biomechanical consequences of fusion leading to adjacent segment degeneration (ASD) have been investigated in different studies, and adverse consequences of sagittal alignment on intervertebral disk (IVD) loads have been proposed as a potential cause. This study investigates IVD loading by means of patient-specific musculoskeletal modeling of potential anatomical factors that may predispose to ASD as recently identified in a retrospective clinical study.1 The current study thus attempts to quantify the reaction forces in the prospective adjacent IVDs as a consequence of spino-pelvic alignment in nonfused spines. Materials and Methods A publicly available model for the human lumbar spine2 was employed and slightly modified for this study. Most notable alterations were adjustments to muscle attachment points, scaling, and changes in the vertebral and sacral reference systems. Joint centers were maintained and length-dependent muscle properties were scaled to maintain the original muscle characteristics. For each patient from the clinical study,1 important landmark coordinates (positions of endplates T12-S1 and acetabulum) were extracted from a digital lumbar spine sagittal radiograph and models were created. Three subjects were excluded due to insufficiently clear radiographs. The models were grouped according to the anatomical relationship between lumbar lordosis (LL) and pelvic incidence (PI) (δPILL = PI-LL). Models above a threshold for ▵PILL, which clinically corresponded to patients having had revision surgery, were assigned to group ASD + ( n = 25); whereas models below the threshold and without symptomatic ASD were assigned to a control group (CTRL-, n = 34). To study only the effect of sagittal alignment, the height of the lumbar spine was normalized and segmental weights and center of mass positions were kept the same for all models. Simulations for static postures of neutral upright standing, 30° and 60° flexion and 15° extension were performed. Joint reaction loads between groups were compared in MATLAB with a Wilcoxon rank sum test. Results Computation of sagittal parameters LL and PI based on extracted landmarks matched well with measures determined in Reference1 and led to the same categorization of subjects. Validation of compression forces was performed with in vivo measurements3 (291N in our model vs. experimental values between 191 and 365N). Reported shear forces4 (L5-S1: 134N, L4-L5: 15N) were compared against those predicted by our model (L5-S1: 103N, L4-L5: 25N). Furthermore, load tendency for different postures were compared to intradiscal pressure values from the literature5,6, both normalized to neutral standing. Good agreement was achieved for flexion (239% vs. 220 and 260%, respectively) and extension (160 vs. 120% for both). Comparison of joint reaction loads for the two groups showed the most prominent differences in shear force and joint moments at the L3-L4 IVD joint level (Fig. 1). Significantly higher shear forces were observed in the ASD + group for flexed postures, while differences in neutral position were not significant. Flexion moments were significantly different among the two groups for all postures, while magnitudes were higher for the ASD + group for 60 degrees flexed postures only. (Fig. 1 shear force and flexion moments at the IVD joint L3-L4 for both groups) Conclusion The simulations showed that the IVDs at the third lumbar level of patients who needed revision surgery due to development of symptomatic ASD were exposed to significantly higher loading regimes before fusion in flexed postures. This might be an indication that not only the biomechanical effect of a fusion, but already a difference in disk loading history prior to fusion could affect the risk of ASD. Simulations of fusion for the two groups will show if the predictive capability of Reference1 can be supported by mechanical consequences on the loading of the IVD. I confirm having declared any potential conflict of interest for all authors listed on this abstract Yes Disclosure of Interest None declared Rothenfluh et al. Spino-pelvic malalignment predisposes to adjacent segment disease after lumbar spinal fusion(submitted). Christophy et al. A Musculoskeletal model for the lumbar spine. Biomech Model Mechanobiol 2011 Rohlmann et al. Loads on internal spinal fixators measured in different body positions. European Spine Journal, 1999. Arjmand et al. Comparison of trunk muscle forces and spinal loads estimated by two biomechanical models. Clinical Biomechanics 2009. Wilke et al. New in vivo measurements of pressures in the intervertebral disk in daily life Spine 1999. Sato et al. In vivo intradiscal pressure measurement in healthy individuals and in patients with ongoing back problems Spine 1999.

Lumbar Intervertebral Joint Loads as Determined by Patient Specific Musculoskeletal Modeling for Two Types of Sagittal Spino-Pelvic Alignment with Different Occurrence of Symptomatic Adjacent Segment Degeneration

IntroductionBiomechanical consequences of fusion leading to adjacent segment degeneration (ASD) have been investigated in different studies, and adverse consequences of sagittal alignment on intervertebral disk (IVD) loads have been proposed as a potential cause. This study investigates IVD loading by means of patient-specific musculoskeletal modeling of potential anatomical factors that may predispose to ASD as recently identified in a retrospective clinical study.1 The current study thus attempts to quantify the reaction forces in the prospective adjacent IVDs as a consequence of spino-pelvic alignment in nonfused spines. Materials and MethodsA publicly available model for the human lumbar spine2 was employed and slightly modified for this study. Most notable alterations were adjustments to muscle attachment points, scaling, and changes in the vertebral and sacral reference systems. Joint centers were maintained and length-dependent muscle properties were scaled to maintain the original muscle characteristics. For each patient from the clinical study,1 important landmark coordinates (positions of endplates T12-S1 and acetabulum) were extracted from a digital lumbar spine sagittal radiograph and models were created. Three subjects were excluded due to insufficiently clear radiographs. The models were grouped according to the anatomical relationship between lumbar lordosis (LL) and pelvic incidence (PI) (δPILL = PI-LL). Models above a threshold for ▵PILL, which clinically corresponded to patients having had revision surgery, were assigned to group ASD + (n = 25); whereas models below the threshold and without symptomatic ASD were assigned to a control group (CTRL-,n = 34). To study only the effect of sagittal alignment, the height of the lumbar spine was normalized and segmental weights and center of mass positions were kept the same for all models. Simulations for static postures of neutral upright standing, 30° and 60° flexion and 15° extension were performed. Joint reaction loads between groups were compared in MATLAB with a Wilcoxon rank sum test. ResultsComputation of sagittal parameters LL and PI based on extracted landmarks matched well with measures determined in Reference1 and led to the same categorization of subjects. Validation of compression forces was performed with in vivo measurements3 (291N in our model vs. experimental values between 191 and 365N). Reported shear forces4 (L5-S1: 134N, L4-L5: 15N) were compared against those predicted by our model (L5-S1: 103N, L4-L5: 25N). Furthermore, load tendency for different postures were compared to intradiscal pressure values from the literature5,6, both normalized to neutral standing. Good agreement was achieved for flexion (239% vs. 220 and 260%, respectively) and extension (160 vs. 120% for both). Comparison of joint reaction loads for the two groups showed the most prominent differences in shear force and joint moments at the L3-L4 IVD joint level (Fig. 1). Significantly higher shear forces were observed in the ASD + group for flexed postures, while differences in neutral position were not significant. Flexion moments were significantly different among the two groups for all postures, while magnitudes were higher for the ASD + group for 60 degrees flexed postures only. (Fig. 1 shear force and flexion moments at the IVD joint L3-L4 for both groups) ConclusionThe simulations showed that the IVDs at the third lumbar level of patients who needed revision surgery due to development of symptomatic ASD were exposed to significantly higher loading regimes before fusion in flexed postures. This might be an indication that not only the biomechanical effect of a fusion, but already a difference in disk loading history prior to fusion could affect the risk of ASD. Simulations of fusion for the two groups will show if the predictive capability of Reference1 can be supported by mechanical consequences on the loading of the IVD.I confirm having declared any potential conflict of interest for all authors listed on this abstractYesDisclosure of InterestNone declaredRothenfluh et al. Spino-pelvic malalignment predisposes to adjacent segment disease after lumbar spinal fusion(submitted).Christophy et al. A Musculoskeletal model for the lumbar spine. Biomech Model Mechanobiol 2011Rohlmann et al. Loads on internal spinal fixators measured in different body positions. European Spine Journal, 1999.Arjmand et al. Comparison of trunk muscle forces and spinal loads estimated by two biomechanical models. Clinical Biomechanics 2009.Wilke et al. New in vivo measurements of pressures in the intervertebral disk in daily life Spine 1999.Sato et al. In vivo intradiscal pressure measurement in healthy individuals and in patients with ongoing back problems Spine 1999.