Musculoskeletal Anatomy Research Articles

Three-Dimensional Magnetic Resonance Imaging in the Musculoskeletal System: Clinical Applications and Opportunities to Improve Imaging Speed and Resolution.

Although conventional 2-dimensional magnetic resonance (MR) sequences have traditionally comprised the foundational imaging strategy for visualization of musculoskeletal anatomy and pathology, the emergence of isotropic volumetric 3-dimensional sequences offers to advance musculoskeletal evaluation with comparatively similar image quality and diagnostic performance, shorter acquisition times, and the added advantages of improved spatial resolution and multiplanar reformation capability. The purpose of this review article is to summarize the available 3-dimensional MR sequences and their role in the management of patients with musculoskeletal disorders, including sports imaging, rheumatologic conditions, peripheral nerve imaging, bone and soft tissue tumor imaging, and whole-body MR imaging.

Anatomical insights into fish terrestrial locomotion: A study of barred mudskipper (Periophthalmus argentilineatus) fins based on μCT 3D reconstructions.

Mudskippers are a group of extant ray-finned fishes with an amphibious lifestyle and serve as exemplars for understanding the evolution of amphibious capabilities in teleosts. A comprehensive anatomical profile of both the soft and hard tissues within their propulsive fins is essential for advancing our understanding of terrestrial locomotor adaptations in fish. Despite the ecological significance of mudskippers, detailed data on their musculoskeletal anatomy remains limited. In the present research, we utilized contrast-enhanced high-resolution microcomputed tomography (μCT) imaging to investigate the barred mudskipper, Periophthalmus argentilineatus. This technique enabled detailed reconstruction and quantification of the morphological details of the pectoral, pelvic, and caudal fins of this terrestrial mudskipper, facilitating comparison with its aquatic relatives. Our findings reveal that P. argentilineatus has undergone complex musculoskeletal adaptations for terrestrial movement, including an increase in muscle complexity and muscle volume, as well as the development of specialized structures like aponeuroses for pectoral fin extension. Skeletal modifications are also evident, with features such as a reinforced shoulder-pelvic joint and thickened fin rays. These evolutionary modifications suggest biomechanically advanced fins capable of overcoming the gravitational challenges of terrestrial habitats, indicating a strong selective advantage for these features in land-based environments. The unique musculoskeletal modifications in the fins of mudskippers like P. argentilineatus, compared with their aquatic counterparts, mark a critical evolutionary shift toward terrestrial adaptations. This study not only sheds light on the specific anatomical changes facilitating this transition but also offers broader insights into the early evolutionary mechanisms of terrestrial locomotion, potentially mirroring the transformative journey from aquatic to terrestrial life in the lineage leading to tetrapods.

Development of interprofessional educational module for understanding the musculoskeletal basis of sports injury

ABSTRACT Context: Interprofessional education (IPE) is crucial in promoting a better understanding of collaborative practices within the healthcare system. Unfortunately, healthcare professionals are still working in isolation. To address this issue, a study was conducted to develop a module-based teaching and learning activity focusing on sports injuries and to promote IPE. Aims: The aim of the study was to develop, implement, and evaluate an IPE module. Settings and Design: An educational mixed-method study was conducted on 25 facilitators and 108 students. Methods, Materials and Statistical Analysis: The facilitators were interviewed for an assessment of the need for the IPE module. Qualitative analysis was done on the interview data. An interprofessional team was created to develop the sports injury prevention module (SIPM). The SIPM consisting of 11 objectives was developed and validated by experts. After the implementation of SIPM students’ performance was analysed with the help of pre and post-tests. The perception of students and facilitators about IP SIPM were recorded with the help of questionnaires. Results: Need assessment data showed that the facilitators were not very familiar with the concept of IPE. There was a significant increase in students’ performance with a P value ≤ 0.05 after learning with SIPM. Both facilitators and students agreed that module-based IPE increases students’ attentiveness and learning. Conclusions: For effective interprofessional educational collaboration for training students of the healthcare profession, there is a need for an interprofessional educational module. SIPM can enhance the learning of musculoskeletal anatomy and create awareness about sports injuries among students.

ChatGPT efficacy for answering musculoskeletal anatomy questions: a study evaluating quality and consistency between raters and timepoints.

There is increasing interest in the use of digital platforms such as ChatGPT for anatomy education. This study aims to evaluate the efficacy of ChatGPT in providing accurate and consistent responses to questions focusing on musculoskeletal anatomy across various time points (hours and days). A selection of 6 Anatomy-related questions were asked to ChatGPT 3.5 in 4 different timepoints. All answers were rated blindly by 3 expert raters for quality according to a 5 -point Likert Scale. Difference of 0 or 1 points in Likert scale scores between raters was considered as agreement and between different timepoints was considered as consistent indicating good reproducibility. There was significant variation in the quality of the answers ranging from extremely good to very poor quality. There was also variation of consistency levels between different timepoints. Answers were rated as good quality (≥ 3 in Likert scale) in 50% of cases (3/6) and as consistent in 66.6% (4/6) of cases. In the low-quality answers, significant mistakes, conflicting data or lack of information were encountered. As of the time of this article, the quality and consistency of the ChatGPT v3.5 answers is variable, thus limiting its utility as independent and reliable resource of learning musculoskeletal anatomy. Validating information by reviewing the anatomical literature is highly recommended.

Recent developments in computational modelling of the knee

ObjectiveModel calculations of knee joint loading range from an assumption of perfectly rigid articular surfaces to more realistic simulations of cartilage and meniscal deformation. Rigid-body musculoskeletal models simulate knee contact mechanics using the ‘bed of springs’ method from elastic foundation theory whereas finite-element models discretise each structure into a series of interconnected elements and ascribe material properties to each element. This mini-review describes some of the most recent developments in computational modelling of knee contact mechanics and suggests possible avenues for future improvements. DesignNarrative mini-review. ResultsMuscle and joint contact forces can be calculated synchronously at a reasonable computational cost (typically a few hours of CPU time) using rigid-body models and elastic foundation theory whereas similar calculations using fully deformable finite-element models can take several days and even weeks. The main computational expense incurred in finite-element musculoskeletal modelling is the solution of a muscle-force optimization problem. ConclusionCalculation of muscle and joint contact forces within the framework of a finite-element musculoskeletal model remains challenging. Integrating biomechanical data from human motion experiments with fully deformable finite-element models to simulate knee contact mechanics during dynamic activity is an evolving science. Future work should explore the use of efficient methods such as direct collocation to perform muscle-driven dynamic optimization simulations of movement using finite-element musculoskeletal models. Dynamic optimization may be combined with finite-element modelling to enable predictive simulations of movement so that the effects of changes in musculoskeletal anatomy on knee contact mechanics can be studied more systematically.

Yoga as a Didactic Tool for Musculoskeletal Anatomy for First Year Medical Students

Yoga as a Didactic Tool for Musculoskeletal Anatomy for First Year Medical Students

The effects of supplemental instruction derived from peer leaders on student outcomes in undergraduate human anatomy.

Supplemental instruction (SI) confers student success, as represented by grades, knowledge retention, and student engagement. However, studies often report professional, not undergraduate, program findings. To measure these effects, students studying human anatomy at a university in Ontario, Canada, attended structured (peer-assisted) or unstructured (nonpeer-assisted) SI sessions and completed a pre-/post-survey. Fifty-eight learners (39 systems (SYS) and 19 musculoskeletal (MSK) anatomy) completed both surveys and had responses analyzed. Both cohorts, maintained initial perceptions across pre-/post-analyses (MSK p = 0.1376 and SYS p = 0.3521). Resource usage was similar across both cohorts with discrepancies in skeletal model and textbook use. No MSK learner ranked any labresourcesas "not at all useful." MSK learners felt more prepared to write a graded assessment (p = 0.0269), whereas SYS learners did not (p = 0.0680). Stratification of learners in MSK and SYS revealed learners spending between 30 and 60 min in SI sessions during the study period had the highest grades compared to students who spent less than 30 (p = 0.0286) or more than 60 (p = 0.0286) min attending SI sessions, respectively. Most learners in MSK (89.4%) and SYS (66%) concluded that they preferred structured over unstructured SI. Sentiment/thematic analysis using a generative AI-driven large language model revealed learners held positive perceptions of SI, emphasizing structured learning, resources, personalized learning, and support offered as the most prevalent themes surrounding SI. Ultimately, this study provides evidence that supports SI for improving student outcomes related to perceived preparedness for completing assessments and preferred teaching/learning styles in undergraduate human anatomy.

Relative Energy Deficiency in Sport (REDs) and knee injuries: current concepts for female athletes

In athletes, a mismatch between caloric intake and energy expended in exercise can eventually lead to Relative Energy Deficiency in Sport (REDs), where the athlete suffers from physiological derangements and decreased sport performance. The prevalence of REDs is higher in females than males. Females are already at a higher risk of knee injuries, which has been attributed to a multitude of factors such as hormonal influences, differences in musculoskeletal anatomy and neuromuscular control compared to males. The literature demonstrates an even higher risk of knee injuries in female athletes with symptoms of REDs. We propose the various factors that influence this risk. A reduction in anabolic hormones can affect muscle development and tendon repair. A relationship between poor neuromuscular control and knee injury has been established, and this can be further worsened in patients with menstrual dysfunction. Chronic deficiency in nutrients such as collagen and vitamin D can result in poorer recovery from microtrauma in tendons and ligaments. All these factors may contribute to increasing the risk of knee injuries, which may include anterior cruciate ligament tears, patella tendinopathy and patellofemoral pain syndrome. This review aims to educate sports clinicians to have a high index of suspicion when treating knee injuries in females; to screen and then manage for REDs if present, for holistic patient care.

Optimizing shoulder elevation assist rate in exoskeletal rehabilitation based on muscular activity indices: a clinical feasibility study

BackgroundRestoring shoulder function is critical for upper-extremity rehabilitation following a stroke. The complex musculoskeletal anatomy of the shoulder presents a challenge for safely assisting elevation movements through robotic interventions. The level of shoulder elevation assistance in rehabilitation is often based on clinical judgment. There is no standardized method for deriving an optimal level of assistance, underscoring the importance of addressing abnormal movements during shoulder elevation, such as abnormal synergies and compensatory actions. This study aimed to investigate the effectiveness and safety of a newly developed shoulder elevation exoskeleton robot by applying a novel optimization technique derived from the muscle synergy index.MethodsTwelve chronic stroke participants underwent an intervention consisting of 100 robot-assisted shoulder elevation exercises (10 × 10 times, approximately 40 min) for 10 days (4–5 times/week). The optimal robot assist rate was derived by detecting the change points using the co-contraction index, calculated from electromyogram (EMG) data obtained from the anterior deltoid and biceps brachii muscles during shoulder elevation at the initial evaluation. The primary outcomes were the Fugl–Meyer assessment-upper extremity (FMA-UE) shoulder/elbow/forearm score, kinematic outcomes (maximum angle of voluntary shoulder flexion and elbow flexion ratio during shoulder elevation), and shoulder pain outcomes (pain-free passive shoulder flexion range of motion [ROM] and visual analogue scale for pain severity during shoulder flexion). The effectiveness and safety of robotic therapy were examined using the Wilcoxon signed-rank sum test.ResultsAll 12 patients completed the procedure without any adverse events. Two participants were excluded from the analysis because the EMG of the biceps brachii was not obtained. Ten participants (five men and five women; mean age: 57.0 [5.5] years; mean FMA-UE total score: 18.7 [10.5] points) showed significant improvement in the FMA-UE shoulder/elbow/forearm score, kinematic outcomes, and pain-free passive shoulder flexion ROM (P < 0.05). The shoulder pain outcomes remained unchanged or improved in all patients.ConclusionsThe study presents a method for deriving the optimal robotic assist rate. Rehabilitation using a shoulder robot based on this derived optimal assist rate showed the possibility of safely improving the upper-extremity function in patients with severe stroke in the chronic phase.

Junior and senior students possess differential preferences towards multimodal digital anatomy resources.

Digital technologies are changing how anatomy is taught tremendously. However, little is known about the effective integration of multimodal digital resources when concurrently provided in an anatomy course. To address this question, an array of digital anatomy resources including Augmented Reality (AR) and Virtual Reality (VR) anatomy resources were concurrently trialed by a total of 326 undergraduate and postgraduate students across three undergraduate (systemic anatomy, neuroanatomy, and regional anatomy) and one postgraduate anatomy (applied musculoskeletal anatomy) curricula in 2022. A five-point Likert scale learning and teaching survey was conducted to evaluate students' experiences, preferences, and perceptions. Most undergraduate (81% systemic anatomy, 76% neuroanatomy, and 87% regional anatomy) and postgraduate (97%) participants across the four cohorts felt confident in studying anatomy using digital resources and the majority (>80% undergraduate and >90% postgraduate) found the multimodal digital anatomy resources interactive and stimulating. The response showed that undergraduate (77% systemic anatomy, 81% neuroanatomy, and 97% regional anatomy) and postgraduate students (92%) consistently enjoyed their experience of using multimodal digital anatomy resources and thought that these resources enhanced their interest in studying anatomy. However, there are significant differences in ratings of specific digital resources among the junior (first-year undergraduates) and senior (third-year undergraduates and postgraduates) students. The virtual dissection table was uniformly preferred by the four cohorts of students across the board. Interestingly, however, VR anatomy and radiographic-based digital anatomy resources received diverse ratings. VR anatomy was valued most by junior undergraduate students (84%) who studied systemic anatomy compared to their senior counterparts (73%) who studied regional anatomy, whereas radiographic-based digital anatomy resources were more valued by the postgraduate students (93%) compared to undergraduates (65% systemic anatomy, 73% neuroanatomy, and 48% regional anatomy). This study identifies that while students uniformly appreciate the value of multimodal digital anatomy teaching, there is a clear difference in their perceptions towards individual resources, likely in a course-specific manner. We conclude that the selection and adoption of digital anatomy tools must be tailored as part of course design and that digital anatomy tools should be used in combination to provide an effective learning experience for students.

Comparing Peer-Taught Student Tutors to Faculty-Taught Student Tutors in Educating Medical Students on Musculoskeletal Ultrasound.

In recent years, medical education has witnessed a shift in the integration of ultrasound into the preclinical years of medical school. Given the exponential increase in accessibility to ultrasound technology, students now have the opportunity to create peer learning groups in which ultrasound concepts can be taught from peer to peer, empowering students to work together to integrate ultrasound concepts early in their preclinical education. This project investigates the efficacy of peer-taught student tutors (PTSTs) in imparting the fundamentals of basic ultrasound techniques to first-year medical students in the setting of identifying and labeling upper extremity musculoskeletal (MSK) anatomy. Methods: First-year medical students were instructed to identify volar forearm structures with an ultrasound probe. Students and instructors were given access to an ultrasound probe, ultrasound gel, an iPad, and a standardized patient. Students were taught either by an ultrasound instructor (UI) or PTST. After a hands-on demonstration by a UI or PTST, participating students were told to take screenshots and label their images as accurately as possible, identifying the aforementioned volar structures on a standardized patient without any feedback. The labeled screenshot images of volar structures were graded based on the ability to clearly visualize the intended structures. Results: The results of this study comparethe efficacy of PTSTs as educators of basic sonographic identification techniques with that of UI faculty members. A chi-square analysis was performed between the images obtained by the UI and PTST students, and there was no statistically significant difference in identification accuracy between the groups (p = 0.7538, 0.1977, 0.1812, 0.301). When using the Mann-Whitney U rank test, there remained no statistically significant difference between the accuracy of the students taught by STs compared to students taught by UIs (p = 0.7744, 0.09538, 0.07547, 0.1846). Another finding showed that students belonging to both teaching groups were generally not able to infer the pathology of volar wrist structures when given pathology identification questions regarding upper extremity ultrasound. Using chi-square with Yates correction, there is nosufficient evidence to justify an association between the ability to answer pathology-based ultrasound questions and instructor type (p = p = 0.6299, 0.8725). This study supports the interpretation that the capability of first-year medical students to learn novice MSKsonographic identification is independent of whether the educator is a PTST or UI. This interpretation reveals a promising avenue toward the integration of the fundamentals of ultrasound identification early in medical education with little to no concern for the exhaustion of institutional resources. Along with the other well-documented benefits of the utilization of STs in medical school, a peer tutoring system centered on ultrasound skills designed in the way this study describes can be an effective, resource-sparing system that enhances medical students' sonographic capabilities early in their preclinical years.

Modeling the future of shoulder arthroplasty

BackgroundIn patients with advanced shoulder pathology requiring arthroplasty, the goal is to restore optimal function and provide sustained pain relief. However, the capacity to select the ideal reconstruction of a specific patient’s shoulder and to predict the resulting functional outcome is limited. Computational modeling of the musculoskeletal system has the potential to expand our foundational knowledge of both the native and prosthetic shoulder joint. ObjectiveThe aim of this review is to describe how computational modeling enables more detailed analyses of the interactions between musculoskeletal anatomy and function and to suggest ways in which this approach may be used to optimize outcomes in patients undergoing shoulder arthroplasty. ResultsComputational modeling has been used to study shoulder joint biomechanics for more than 30 years. There are specific limitations that need to be addressed to realize the full potential of computational modeling in shoulder arthroplasty. First, more realistic, patient-specific models of the glenohumeral and scapulothoracic joints must be developed. Second, shoulder models must be coupled with accurate in vivo measurements of joint motion to perform more comprehensive analyses of muscle and joint function. Third, model predictions of shoulder biomechanics must be validated against experimental data. ConclusionPatient-specific musculoskeletal modeling of shoulder joint biomechanics can contribute significantly to predicting pathology and optimizing postoperative function.

3D Ultrasound Mosaic of the Whole Shoulder: A Feasibility Study

A protocol is proposed to acquire a tomographic ultrasound (US) scan of the musculoskeletal (MSK) anatomy in the rotator cuff region. Current clinical US imaging techniques are hindered by occlusions and a narrow field of view and require expert acquisition and interpretation. There is limited literature on 3D US image registration of the shoulder or volumetric reconstruction of the full shoulder complex. We believe that a clinically accurate US volume reconstruction of the entire shoulder can aid in pre-operative surgical planning and reduce the complexity of US interpretation. The protocol was used in generating data for deep learning model training to automatically register US mosaics in real-time. An in vivo 3D US tomographic reconstruction of the entire rotator cuff region was produced by registering 53 sequential 3D US volumes acquired by an MSK sonographer. Anatomical surface thicknesses and distances in the US mosaic were compared to their corresponding MRI measurements as the ground truth. The humeral head surface was marginally thicker in the reconstructed US mosaic than its original thickness observed in a single US volume by 0.65 mm. The humeral head diameter and acromiohumeral distance (ACHD) matched with their measured MRI distances with a reconstruction error of 0 mm and 1.2 mm, respectively. Furthermore, the demonstration of 20 relevant MSK structures was independently graded between 1 and 5 by two sonographers, with higher grades indicating poorer demonstration. The average demonstration grade for each anatomy was as follows: bones = 2, muscles = 3, tendons = 3, ligaments = 4–5 and labrum = 4–5. There was a substantial agreement between sonographers (Cohen’s Weighted kappa of 0.71) on the demonstration of the structures, and they both independently deemed the mosaic clinically acceptable for the visualisation of the bony anatomy. Ligaments and the labrum were poorly observed due to anatomy size, location and inaccessibility in a static scan, and artefact build-up from the registration and compounding approaches.

Neuropil Variation in the Prefrontal, Motor, and Visual Cortex of Six Felids

Introduction: Felids have evolved a specialized suite of morphological adaptations for obligate carnivory. Although the musculoskeletal anatomy of the Felidae has been studied extensively, the comparative neuroanatomy of felids is relatively unexplored. Little is known about how variation in the cerebral anatomy of felids relates to species-specific differences in sociality, hunting strategy, or activity patterns. Methods: We quantitatively analyzed neuropil variation in the prefrontal, primary motor, and primary visual cortices of six species of Felidae (Panthera leo, Panthera uncia, Panthera tigris, Panthera leopardus, Acinonyx jubatus, Felis sylvestris domesticus) to investigate relationships with brain size, neuronal cell parameters, and select behavioral and ecological factors. Neuropil is the dense, intricate network of axons, dendrites, and synapses in the brain, playing a critical role in information processing and communication between neurons. Results: There were significant species and regional differences in neuropil proportions, with African lion, cheetah, and tiger having more neuropil in all three cortical regions in comparison to the other species. Based on regression analyses, we find that the increased neuropil fraction in the prefrontal cortex supports social and behavioral flexibility, while in the primary motor cortex, this facilitates the neural activity needed for hunting movements. Greater neuropil fraction in the primary visual cortex may contribute to visual requirements associated with diel activity patterns. Conclusion: These results provide a cross-species comparison of neuropil fraction variation in the Felidae, particularly the understudied Panthera, and provide evidence for convergence of the neuroanatomy of Panthera and cheetahs.

Muscle anatomy is reflected in the spatial organization of the spinal motoneuron pools

Neural circuits embed limb dynamics for motor control and sensorimotor integration. The somatotopic organization of motoneuron pools in the spinal cord may support these computations. Here, we tested if the spatial organization of motoneurons is related to the musculoskeletal anatomy. We created a 3D model of motoneuron locations within macaque spinal cord and compared the spatial distribution of motoneurons to the anatomical organization of the muscles they innervate. We demonstrated that the spatial distribution of motoneuron pools innervating the upper limb and the anatomical relationships between the muscles they innervate were similar between macaque and human species. Using comparative analysis, we found that the distances between motoneuron pools innervating synergistic muscles were the shortest, followed by those innervating antagonistic muscles. Such spatial organization can support the co-activation of synergistic muscles and reciprocal inhibition of antagonistic muscles. The spatial distribution of motoneurons may play an important role in embedding musculoskeletal dynamics.

Computational Approaches and Observer Variation in the 3D Musculoskeletal Modeling of the Heads of Anolis.

High-resolution imaging, 3D modeling, and quantitative analyses are equipping evolutionary biologists with new approaches to understanding the variation and evolution of the musculoskeletal system. However, challenges with interpreting DiceCT data and higher order use of modeled muscles have not yet been fully explored, and the error in and accuracy of some digital methods remain unclear. West Indian Anolis lizards are a model clade for exploring patterns in functional adaptation, ecomorphology, and sexual size dimorphism in vertebrates. These lizards possess numerous jaw muscles with potentially different anatomies that sculpt the adductor chamber of the skull. Here we test approaches to quantifying the musculoskeletal shape of the heads of two species of Anolis: A. pulchellus and A. sagrei. We employ comparative approaches such as DiceCT segmentation of jaw muscles, 3D surface attachment mapping, and 3D landmarking with the aim of exploring muscle volumes, 3D muscle fiber architecture, and sexual dimorphism of the skull. We then compare sources of measurement error in these 3D analyses while also presenting new 3D musculoskeletal data from the Anolis feeding apparatus. These findings demonstrate the accessibility and repeatability of these emerging techniques as well as provide details regarding the musculoskeletal anatomy of the heads of A. pulchellus and A. sagrei which show potential for further research of comparative biomechanics and evolution in the clade.

Inadequacies in Undergraduate Musculoskeletal Education-A Survey of Nationally Accredited Allopathic Medical Programs in Canada.

The aim of the study is to document the current state of musculoskeletal (MSK) medicine education across nationally accredited undergraduate medical programs. A cross-sectional survey design was used to gather curricular data on the following three musculoskeletal themes: (1) anatomy education, (2) preclinical education, and (3) clerkship education. The survey had a 100% response rate with all 14 English-language medical schools in Canada responding. The mean time spent teaching musculoskeletal anatomy was 29.8 hrs (SD ± 13.7, range = 12-60), with all but one program using some form of cadaveric-based instruction. Musculoskeletal preclinical curricula averaged 58.0 hrs (SD ± 53.4, range = 6-204), with didactic lectures, case-based learning, and small group tutorials being the most common modes of instruction. Curricular content varied greatly, with only 25% of "core or must-know" musculoskeletal topics being covered in detail by all programs. Musculoskeletal training in clerkship was required by only 50% of programs, most commonly being 2 wks in duration. Results document the large variability and curricular inadequacies that exist in musculoskeletal education across nationally accredited allopathic programs and highlight the need for the identification and implementation of more consistent musculoskeletal curricular content and educational standards by all nationally accredited medical programs.

Moving beyond Vesalius: Why anatomy needs a mapping update

The improvement of the human condition is the driver behind a vast amount of ongoing research and naturally employs the most up-to-date methods in its endeavours. It has contributed greatly to our understanding of the body and benefitted our healthcare systems in remarkable ways, but there is a problem. The mapping of anatomy to its physiological functions is essentially derived from the work of Vesalius and traditionally favoured mobility over stability, and as a consequence has allowed the entrenched and simplifying assumptions of the musculoskeletal duality to persist to the present day, despite advances in technology.The lever model of motion, for example, assumes that the body is an intrinsically unstable system that requires an external controller (e.g. neural) to provide the necessary ‘catch-up’ stability for transient muscular latencies, and it is likely that the vulnerabilities inherent within such a mechanism would severely compromise living tissues. The foundational biomechanical assumptions of steady-state forces and kinematics has meant that the disproportionate and potentially damaging consequences of transient peak loadings have been largely overlooked, and which added to the long healing times required for post-traumatic recovery, suggests that such a mechanism would lead to material fatigue and destructive tissue failure.The musculoskeletal duality, however, was not always so dominant but conceptually rivalled in the 17th and 18th centuries by Hooke’s ‘cells’ and Malpighi’s ‘cellular tissues’, both of which have been largely forgotten but now deserve a re-evaluation. The definition of the term ‘cell’ as a small compartment within a larger structure had quite different connotations then than it does today, but this compartmental aspect of connective tissue anatomy gradually faded and is now only recognized for its pathological significance.This paper examines musculoskeletal anatomy from both historical and more recent viewpoints and highlights the concept of the fascial system as a distinct and intrinsically stable functional entity. It is a perspective that enables every anatomical ‘part’ to be included within a ‘cellular’ framework that differs substantially from the mobility-driven machine model: a tensioned fibrous network encompassing a complex heterarchy of regionally specialized compartments under compression, each of which has its own physical and parenchyma-driven characteristics that contribute to the functional whole. In other words, an updated fascia-centric interpretation of architectural anatomy that maps muscles and bones in a substantially different way from traditional models, renders the term musculoskeletal obsolete and greatly expands the meaning of compartment syndrome.

Motoneuron-driven computational muscle modelling with motor unit resolution and subject-specific musculoskeletal anatomy.

The computational simulation of human voluntary muscle contraction is possible with EMG-driven Hill-type models of whole muscles. Despite impactful applications in numerous fields, the neuromechanical information and the physiological accuracy such models provide remain limited because of multiscale simplifications that limit comprehensive description of muscle internal dynamics during contraction. We addressed this limitation by developing a novel motoneuron-driven neuromuscular model, that describes the force-generating dynamics of a population of individual motor units, each of which was described with a Hill-type actuator and controlled by a dedicated experimentally derived motoneuronal control. In forward simulation of human voluntary muscle contraction, the model transforms a vector of motoneuron spike trains decoded from high-density EMG signals into a vector of motor unit forces that sum into the predicted whole muscle force. The motoneuronal control provides comprehensive and separate descriptions of the dynamics of motor unit recruitment and discharge and decodes the subject's intention. The neuromuscular model is subject-specific, muscle-specific, includes an advanced and physiological description of motor unit activation dynamics, and is validated against an experimental muscle force. Accurate force predictions were obtained when the vector of experimental neural controls was representative of the discharge activity of the complete motor unit pool. This was achieved with large and dense grids of EMG electrodes during medium-force contractions or with computational methods that physiologically estimate the discharge activity of the motor units that were not identified experimentally. This neuromuscular model advances the state-of-the-art of neuromuscular modelling, bringing together the fields of motor control and musculoskeletal modelling, and finding applications in neuromuscular control and human-machine interfacing research.

Looking back over the shoulder: New insights on the unique scapular anatomy of the tapir (Perissodactyla: Tapiridae).

The musculoskeletal anatomy of the shoulder of many ungulates has been inferred from veterinary model taxa, with uniformity in muscle arrangements and attachment sites often assumed. In this study, I investigated the muscular and osteological anatomy of tapirs and their relatives (Perissodactyla: Tapiroidea), using a combination of gross dissection and digital imaging (photography and laser surface scanning). Dissections of three modern tapir species revealed that the m. infraspinatus originates from both supraspinous and infraspinous fossae for all species, lying on both sides of the distal scapular spine. The epimysial border between the m. supraspinatus and m. infraspinatus origin sites are marked in all species by an ossified ridge, sometimes extending the length of the scapular spine. This "supraspinous ridge" is clearly visible on the scapular surface of both modern and extinct Tapirus scapulae; however, the ridge does not appear present in any non-Tapirus tapiroids examined (e.g., Helaletes, Nexuotapirus), nor in other perissodactyls or artiodactyls. Moreover, the ridge exhibits a clearly distinct morphology in Tapirus indicus compared to all other Tapirus species examined. Combined, these findings indicate that the presence and position of the "supraspinous ridge" may represent a robust phylogenetic character for reconstructing relationships within tapiroids. Unfortunately, any functional locomotor outcomes or benefits of the m. infraspinatus straddling the scapular spine remains elusive. This study represents a firm reminder for anatomists, veterinarians, and paleontologists to (where possible) look beyond veterinary model systems when inferring musculoskeletal form or function in non-model organisms.