Dysfunctional paraspinal muscles in adult spinal deformity patients lead to increased spinal loading.

PURPOSE: Decreased spinal extensor muscle strength in adult spinal deformity (ASD) patients is well-known but poorly understood; thus, this study aimed to investigate the biomechanical and histopathological properties of paraspinal muscles from ASD patients and predict the effect of altered biomechanical properties on spine loading. METHODS: 68 muscle biopsies were collected from nine ASD patients at L4-L5 (bilateral multifidus and longissimus sampled). The biopsies were tested for muscle fiber and fiber bundle biomechanical properties and histopathology. The small sample size (due to COVID-19) precluded formal statistical analysis, but the properties were compared to literature data. Changes in spinal loading due to the measured properties were predicted by a lumbar spine musculoskeletal model. RESULTS: Single fiber passive elastic moduli were similar to literature values, but in contrast, the fiber bundle moduli exhibited a wide range beyond literature values, with 22% of 171 fiber bundles exhibiting very high elastic moduli, up to 20 times greater. Active contractile specific force was consistently less than literature, with notably 24% of samples exhibiting no contractile ability. Histological analysis of 28 biopsies revealed frequent fibro-fatty replacement with a range of muscle fiber abnormalities. Biomechanical modelling predicted that high muscle stiffness could increase the compressive loads in the spine by over 500%, particularly in flexed postures. DISCUSSION: The histopathological observations suggest diverse mechanisms of potential functional impairment. The large variations observed in muscle biomechanical properties can have a dramatic influence on spinal forces. These early findings highlight the potential key role of the paraspinal muscle in ASD.

Quantal biomechanical effects in speech postures of the lips.

The unique biomechanical and functional constraints on human speech make it a promising area for research investigating modular control of movement. The present article illustrates how a modular control approach to speech can provide insights relevant to understanding both motor control and observed variation across languages. We specifically explore the robust typological finding that languages produce different degrees of labial constriction using distinct muscle groupings and concomitantly distinct lip postures. Research has suggested that these lip postures exploit biomechanical regions of nonlinearity between neural activation and movement, also known as quantal regions, to allow movement goals to be realized despite variable activation signals. We present two sets of computer simulations showing that these labial postures can be generated under the assumption of modular control and that the corresponding modules are biomechanically robust: first to variation in the activation levels of participating muscles, and second to interference from surrounding muscles. These results provide support for the hypothesis that biomechanical robustness is an important factor in selecting the muscle groupings used for speech movements and provide insight into the neurological control of speech movements and how biomechanical and functional constraints govern the emergence of speech motor modules. We anticipate that future experimental work guided by biomechanical simulation results will provide new insights into the neural organization of speech movements.NEW & NOTEWORTHY This article provides additional evidence that speech motor control is organized in a modular fashion and that biomechanics constrain the kinds of motor modules that may emerge. It also suggests that speech can be a fruitful domain for the study of modularity and that a better understanding of speech motor modules will be useful for speech research. Finally, it suggests that biomechanical modeling can serve as a useful complement to experimental work when studying modularity.

Evidence that an internal schema adapts swallowing to upper airway requirements.

KEY POINTS: To swallow food and liquid safely, airway protection is essential. Upward and forward movements of the hyoid and larynx in the neck during swallowing vary in magnitude between individuals. In healthy human adults, hyoid and laryngeal movements during swallowing were scaled by differences in initial upper airway area before swallowing. Individuals increased laryngeal elevation during swallowing in response to increased airway opening before swallowing. We show that when upper airway protection requirements change, individuals use an internal sensorimotor scaling system to adapt movements to maintain swallow safety. ABSTRACT: Hyoid and laryngeal movements contribute to laryngeal vestibule closure and upper oesophageal sphincter opening during swallowing. Evidence of an internal sensorimotor scaling system allowing individuals to achieve these functional goals is lacking. In speech, speakers adjust their articulatory movement magnitude according to the movement distance required to reach an articulatory target for intelligible speech. We investigated if swallowing is similar in that movement amplitude may be scaled by the functional goal for airway protection during swallowing, rather than by head and neck size. We hypothesized that healthy individuals adapt to their own anatomy by adjusting hyo-laryngeal movements to achieve closure of the upper airway. We also investigated if individuals would automatically compensate for changes in their initial hyo-laryngeal positions and area when head position was changed prior to swallowing. Videofluoroscopy was performed in 31 healthy adults. Using frame-by-frame motion analysis, anterior and superior hyoid and laryngeal displacement, and hyo-laryngeal area were measured prior to and during swallowing. Kinematic measurements during swallowing were examined for relationships with pharyngeal neck length, and initial hyo-laryngeal positions, length and area before swallowing. During swallowing, individuals altered laryngeal elevation magnitude to exceed hyoid elevation based on hyo-laryngeal length before swallowing. Anterior laryngeal displacement was related to initial larynx distance from the spine, while hyoid elevation was predicted by pharyngeal neck length and initial hyoid distance from the mandible prior to the swallow. In conclusion, individuals automatically adapt hyo-laryngeal movement during swallowing based on targets required for closing the hyo-laryngeal area for safe swallowing.

Variability in muscle activation of simple speech motions: A biomechanical modeling approach.

Biomechanical models of the oropharynx facilitate the study of speech function by providing information that cannot be directly derived from imaging data, such as internal muscle forces and muscle activation patterns. Such models, when constructed and simulated based on anatomy and motion captured from individual speakers, enable the exploration of inter-subject variability of speech biomechanics. These models also allow one to answer questions, such as whether speakers produce similar sounds using essentially the same motor patterns with subtle differences, or vastly different motor equivalent patterns. Following this direction, this study uses speaker-specific modeling tools to investigate the muscle activation variability in two simple speech tasks that move the tongue forward (/ə-ɡis/) vs backward (/ə-suk/). Three dimensional tagged magnetic resonance imaging data were used to inversely drive the biomechanical models in four English speakers. Results show that the genioglossus is the workhorse muscle of the tongue, with activity levels of 10% in different subdivisions at different times. Jaw and hyoid positioners (inferior pterygoid and digastric) also show high activation during specific phonemes. Other muscles may be more involved in fine tuning the shapes. For example, slightly more activation of the anterior portion of the transverse is found during apical than laminal /s/, which would protrude the tongue tip to a greater extent for the apical /s/.

Role of muscle damage on loading at the level adjacent to a lumbar spine fusion: a biomechanical analysis.

PURPOSE: It is well established that posterior spinal surgery results in damage to the paraspinal musculature. The effects of such iatrogenic changes on spinal loading have not been previously investigated, particularly at levels adjacent to a spinal fusion. Therefore, the objective of this study was to investigate the effect of simulated muscle damage on post-operative spinal loading at the adjacent levels to a spinal fusion during upright postures using a mathematical model. METHODS: A musculoskeletal model of the spine using ArtiSynth with 210 muscle fascicles was used to predict spinal loading in an upright posture. The loading at L1-L2 and L5-S1 were estimated before and after simulated paraspinal muscle damage (i.e., removal of muscle attachments at L2-L5) along the lumbar spine, both with a spinal fusion at L2-L5 and without a spinal fusion. RESULTS: The axial compressive forces at the adjacent levels increased after simulated muscle damage, with the largest changes being at the rostral level (78 % increase in presence of spinal fusion; 73 % increase without spinal fusion) compared to the caudal level (41 % in presence of fusion and 32 % without fusion). Shear forces increased in a similar manner at both the rostral and caudal levels. These changes in loading were due to a redistribution of muscle activity from the local lumbar to the global spinal musculature. CONCLUSIONS: The results suggest that the paraspinal muscles of the lumbar spine play an important role in adjacent segment loading of a spinal fusion, independent of the presence of rigid spinal instrumentation.

Computational models and their applications in biomechanical analysis of mandibular reconstruction surgery.

Advanced head and neck cancers involving the mandible often require surgical removal of the diseased parts and replacement with donor bone or prosthesis to recreate the form and function of the premorbid mandible. The degree to which this reconstruction successfully replicates key geometric features of the original bone critically affects the cosmetic and functional outcomes of speaking, chewing, and breathing. With advancements in computational power, biomechanical modeling has emerged as a prevalent tool for predicting the functional outcomes of the masticatory system and evaluating the effectiveness of reconstruction procedures in patients undergoing mandibular reconstruction surgery. These models offer cost-effective and patient-specific treatment tailored to the needs of individuals. To underscore the significance of biomechanical modeling, we conducted a review of 66 studies that utilized computational models in the biomechanical analysis of mandibular reconstruction surgery. The majority of these studies employed finite element method (FEM) in their approach; therefore, a detailed investigation of FEM has also been provided. Additionally, we categorized these studies based on the main components analyzed, including bone flaps, plates/screws, and prostheses, as well as their design and material composition.

To what extent can mastication functionality be restored following mandibular reconstruction surgery? A computer modeling approach.

STATEMENT OF PROBLEM: Advanced cases of head and neck cancer involving the mandible often require surgical removal of diseased sections and subsequent replacement with donor bone. During the procedure, the surgeon must make decisions regarding which bones or tissues to resect. This requires balancing tradeoffs related to issues such as surgical access and post-operative function; however, the latter is often difficult to predict, especially given that long-term functionality also depends on the impact of post-operative rehabilitation programs. PURPOSE: To assist in surgical decision-making, we present an approach for estimating the effects of reconstruction on key aspects of post-operative mandible function. MATERIAL AND METHODS: We develop dynamic biomechanical models of the reconstructed mandible considering different defect types and validate them using literature data. We use these models to estimate the degree of functionality that might be achieved following post-operative rehabilitation. RESULTS: We find significant potential for restoring mandibular functionality, even in cases involving large defects. This entails an average trajectory error below 2 mm, bite force comparable to a healthy individual, improved condyle mobility, and a muscle activation change capped at a maximum of 20%. CONCLUSION: These results suggest significant potential for adaptability in the masticatory system and improved post-operative rehabilitation, leading to greater restoration of jaw function.

Estimating tongue deformation during laryngoscopy using a hybrid FEM-multibody model and intraoperative tracking - a cadaver study.

Throat tumour margin control remains difficult due to the tight, enclosed space of the oral and throat regions and the tissue deformation resulting from placement of retractors and scopes during surgery. Intraoperative imaging can help with better localization but is hindered by non-image-compatible surgical instruments, cost, and unavailability. We propose a novel method of using instrument tracking and FEM-multibody modelling to simulate soft tissue deformation in the intraoperative setting, without requiring intraoperative imaging, to improve surgical guidance accuracy. We report our first empirical study, based on four trials of a cadaveric head specimen with full neck anatomy, yields a mean TLE of 10.8 ± 5.5 mm, demonstrating methodological feasibility.

All Obstructive Sleep Apnea Events Are Not Created Equal: The Relationship between Event-related Hypoxemia and Physiologic Response.

Rationale: Obstructive sleep apnea (OSA) severity is typically assessed by the apnea-hypopnea index (AHI), a frequency-based metric that allocates equal weight to all respiratory events. However, more severe events may have a greater physiologic impact. Objectives: The purpose of this study was to determine whether the degree of event-related hypoxemia would be associated with the postevent physiologic response. Methods: Patients with OSA (AHI, ⩾5/h) from the multicenter Canadian Sleep and Circadian Network cohort were studied. Using mixed-effect linear regression, we examined associations between event-related hypoxic burden (HBev) assessed by the area under the event-related oxygen saturation recording with heart rate changes (ΔHRev), vasoconstriction (vasoconstriction burden [VCBev] assessed with photoplethysmography), and electroencephalographic responses (power ratio before and after events). Results: Polysomnographic recordings from 658 patients (median [interquartile range] age, 55.00 [45.00, 64.00] yr; AHI, 27.15 [14.90, 64.05] events/h; 42% female) were included in the analyses. HBev was associated with an increase in all physiologic responses after controlling for age, sex, body mass index, sleep stage, total sleep time, and study centers; for example, 1 standard deviation increase in HBev was associated with 0.21 [95% confidence interval, 0.2, 0.22], 0.08 [0.08, 0.09], and 0.22 [0.21, 0.23] standard deviation increases in ΔHRev, VCBev, and ß-power ratio, respectively. Conclusions: Increased event-related hypoxic burden was associated with greater responses across a broad range of physiologic signals. Future metrics that incorporate information about the variability of these physiologic responses may have promise in providing a more nuanced assessment of OSA severity.

Implementation and validation of a 1D fluid model for collapsible channels.

A 1D fluid model is implemented for the purpose of fluid-structure interaction (FSI) simulations in complex and completely collapsible geometries, particularly targeting the case of obstructive sleep apnea (OSA). The fluid mechanics are solved separately from any solid mechanics, making possible the use of a highly complex and/or black-box solver for the solid mechanics. The fluid model is temporally discretized with a second-order scheme and spatially discretized with an asymmetrical fourth-order scheme that is robust in highly uneven geometries. A completely collapsing and reopening geometry is handled smoothly using a modified area function. The numerical implementation is tested with two driven-geometry cases: (1) an inviscid analytical solution and (2) a completely closing geometry with viscous flow. Three-dimensional fluid simulations in static geometries are performed to examine the assumptions of the 1D model, and with a well-defined pressure-recovery constant the 1D model agrees well with 3D models. The model is very fast computationally, is robust, and is recommended for OSA simulations where the bulk flow pressure is primarily of interest.

Sociotechnical challenges and progress in using social media for health.

Social media tools that connect patients, caregivers, and health providers offer great potential for helping people access health advice, receive and give social support, manage or cope with chronic conditions, and make day-to-day health decisions. These systems have seen widespread adoption, but often fail to support the goals as fully as designers and users would like. Through Ackerman's lens of the "sociotechnical gap" and computer supported cooperative work (CSCW) as a science of the artificial, we review contemporary sociotechnical challenges and progress for using social media to support health. These challenges include a tension between privacy and sharing, policy information credibility, accessibility, and tailoring in social spaces. Those studying, building, deploying, and using social media systems to further health goals will benefit from approaching this work by borrowing from Ackerman's framing of CSCW. In particular, this requires acknowledgment that technical systems will not fully meet our social goals, and then adopting design and educational approaches that are appropriate to fill this gap, building less-nuanced systems as partial solutions and tools for advancing our understanding, and by working with the CSCW research community to develop and pursue key lines of inquiry.

A user-centred methodology for designing an online social network to motivate health behaviour change.

Positive health behaviour is critical to preventing illness and managing chronic conditions. A user-centred methodology was employed to design an online social network to motivate health behaviour change. The methodology was augmented by utilizing the Appeal, Belonging, Commitment (ABC) Framework, which is based on theoretical models for health behaviour change and use of online social networks. The user-centred methodology included four phases: 1) initial user inquiry on health behaviour and use of online social networks; 2) interview feedback on paper prototypes; 2) laboratory study on medium fidelity prototype; and 4) a field study on the high fidelity prototype. The points of inquiry through these phases were based on the ABC Framework. This yielded an online social network system that linked to external third party databases to deploy to users via an interactive website.

Cortical control of posture in fine motor skills: evidence from inter-utterance rest position.

The vocal tract continuously employs tonic muscle activity in the maintenance of postural configurations. Gamma-band activity in the sensorimotor cortex underlies transient movements during speech production, yet little is known about the neural control of postural states in the vocal tract. Simultaneously, there is evidence that sensorimotor beta-band activations contribute to a system of inhibition and state maintenance that is integral to postural control in the body. Here we use electrocorticography to assess the contribution of sensorimotor beta-band activity during speech articulation and postural maintenance, and demonstrate that beta-band activity corresponds to the inhibition of discrete speech movements and the maintenance of tonic postural states in the vocal tract. Our findings identify consistencies between the neural control of posture in speech and what is previously reported in gross motor contexts, providing support for a unified theory of postural control across gross and fine motor skills.

Motor control similarity between speakers saying "a souk" using inverse atlas tongue modeling.

Finite element models (FEM) of the tongue have facilitated speech studies through analysis of internal muscle forces indirectly derived from imaging data. In this work, we build a uniform hexahedral FEM of a tongue atlas constructed from magnetic resonance imaging data of a healthy population. The FEM is driven by inverse internal tongue tissue kinematics of speakers temporally aligned and deformed into the same atlas space, while performing the speech task "a souk" allowing muscle activation predictions. This work aims to investigate the commonalities in tongue motor strategies in the articulation of "a souk" predicted by the inverse tongue atlas model. Our findings report variability among five speakers for estimated muscle activations with a similarity index using a dynamic time warp function. Two speakers show similarity index > 0.9 and two others < 0.7 with respect to a reference speaker for most tongue muscles. The relative motion tracking error of the model is less than 2% which is promising for speech study applications.

Association of alternative polysomnographic features with patient outcomes in obstructive sleep apnea: a systematic review.

STUDY OBJECTIVES: Polysomnograms (PSGs) collect a plethora of physiologic signals across the night. However, few of these PSG data are incorporated into standard reports, and hence, ultimately, under-utilized in clinical decision making. Recently, there has been substantial interest regarding novel alternative PSG metrics that may help to predict obstructive sleep apnea (OSA)-related outcomes better than standard PSG metrics such as the apnea-hypopnea index. We systematically review the recent literature for studies that examined the use of alternative PSG metrics in the context of OSA and their association with health outcomes. METHODS: We systematically searched EMBASE, MEDLINE, and the Cochrane Database of Systematic Reviews for studies published between 2000 and 2022 for those that reported alternative metrics derived from PSG in adults and related them to OSA-related outcomes. RESULTS: Of the 186 initial studies identified by the original search, data from 31 studies were ultimately included in the final analysis. Numerous metrics were identified that were significantly related to a broad range of outcomes. We categorized the outcomes into 2 main subgroups: (1) cardiovascular/metabolic outcomes and mortality and (2) cognitive function- and vigilance-related outcomes. Four general categories of alternative metrics were identified based on signals analyzed: autonomic/hemodynamic metrics, electroencephalographic metrics, oximetric metrics, and respiratory event-related metrics. CONCLUSIONS: We have summarized the current landscape of literature for alternative PSG metrics relating to risk prediction in OSA. Although promising, further prospective observational studies are needed to verify findings from other cohorts, and to assess the clinical utility of these metrics. CITATION: Hajipour M, Baumann B, Azarbarzin A, et al. Association of alternative polysomnographic features with patient outcomes in obstructive sleep apnea: a systematic review. J Clin Sleep Med. 2023;19(2):225-242.

Speech Audio Synthesis from Tagged MRI and Non-Negative Matrix Factorization via Plastic Transformer.

The tongue's intricate 3D structure, comprising localized functional units, plays a crucial role in the production of speech. When measured using tagged MRI, these functional units exhibit cohesive displacements and derived quantities that facilitate the complex process of speech production. Non-negative matrix factorization-based approaches have been shown to estimate the functional units through motion features, yielding a set of building blocks and a corresponding weighting map. Investigating the link between weighting maps and speech acoustics can offer significant insights into the intricate process of speech production. To this end, in this work, we utilize two-dimensional spectrograms as a proxy representation, and develop an end-to-end deep learning framework for translating weighting maps to their corresponding audio waveforms. Our proposed plastic light transformer (PLT) framework is based on directional product relative position bias and single-level spatial pyramid pooling, thus enabling flexible processing of weighting maps with variable size to fixed-size spectrograms, without input information loss or dimension expansion. Additionally, our PLT framework efficiently models the global correlation of wide matrix input. To improve the realism of our generated spectrograms with relatively limited training samples, we apply pair-wise utterance consistency with Maximum Mean Discrepancy constraint and adversarial training. Experimental results on a dataset of 29 subjects speaking two utterances demonstrated that our framework is able to synthesize speech audio waveforms from weighting maps, outperforming conventional convolution and transformer models.

Expression of nonconscious knowledge via ideomotor actions.

Ideomotor actions are behaviours that are unconsciously initiated and express a thought rather than a response to a sensory stimulus. The question examined here is whether ideomotor actions can also express nonconscious knowledge. We investigated this via the use of implicit long-term semantic memory, which is not available to conscious recall. We compared accuracy of answers to yes/no questions using both volitional report and ideomotor response (Ouija board response). Results show that when participants believed they knew the answer, responses in the two modalities were similar. But when they believed they were guessing, accuracy was at chance for volitional report (50%), but significantly higher for Ouija response (65%). These results indicate that implicit semantic memory can be expressed through ideomotor actions. They also suggest that this approach can provide an interesting new methodology for studying implicit processes in cognition.

Three-dimensional reconstruction of soft palate modeling from subject-specific magnetic resonance imaging data.

PURPOSE: The objectives of this study were to extract a computational three-dimensional (3D) soft palate model from a set of magnetic resonance imaging (MRI) data and to identify an approach that generates a patient-specific model in a computerized visual platform. METHODS: Multiple MRI slices of the head and neck region of a young, non-overweight Caucasian male volunteer were taken in the supine position with a passive oral appliance in place. The DICOM (Digital Imaging and Communications) MRI slices were registered into a high-resolution volumetric data set for manually segmentation to generate a surface mesh and, with additional editing, a volume mesh. For biomechanical dynamic simulation and for physical simulation of the anatomical structures, the volume mesh format and multiple landmarks of each muscle were imported into ArtiSynth, a 3D biomechanical modeling toolkit. RESULTS: The segmented soft palate complex consisted of five groups of muscles: levator veli palatini, tensor veli palatini, palatoglossus, palatopharyngeous and musculus uvulae. The palatine tonsil between the pharyngopalatine and glossopalatine arches was included in the segmentation. CONCLUSIONS: The same procedure was used to build up a generic reference model of the dentition, tongue, mandible and airway from a mixture of medical records (CT and dental casts) of the same subject. This manual segmentation method eliminated the common errors that occur from an automatic segmentation although it was more time-consuming. It remains a fundamental process for analyzing the dynamic interaction between anatomical components in the oral, pharyngeal, and laryngeal areas.

Biomechanical modeling of English /r/ variants.

This study reports an investigation of the well-known context-dependent variation in English /r/ using a biomechanical tongue-jaw-hyoid model. The simulation results show that preferred /r/ variants require less volume displacement, relative strain, and relative muscle stress than variants that are not preferred. This study also uncovers a previously unknown mechanism in tongue biomechanics for /r/ production: Torque in the sagittal plane about the mental spine. This torque enables raising of the tongue anterior for retroflexed [Symbol: see text] by activation of hyoglossus and relaxation of anterior genioglossus. The results provide a deeper understanding of the articulatory factors that govern contextual phonetic variation.

A Unified Representation of Control Logic in Human-Ultrasound Machine Interaction.

Advances in human-computer interaction (HCI) technologies have granted sonographers and radiologists a much improved user experience when operating different ultrasound (US) machines. Continued HCI improvements in US would benefit from a systematic study of the HCI control logic used in this domain. Such a study has not been presented previously and is the subject of this paper. We surveyed sonographers to determine the most frequently used controls in US machines. We standardized the representation of the US machine HCI control logic by using the unified modelling language (UML). We used UML diagrams to analyze the HCI control logic of 10 different cart-based US machines from several major manufacturers, and we discovered that the control logic for the most frequently used functions are identical. While this control logic does not follow an established standard, it has been commonly adopted. Using the UML for the visualization and formulation of control logic, we can target logically optimal interactions (whose operation steps cannot be further reduced), e.g., adjustment of B-mode gain, frequency and depth, and can derive methods to simplify logically sub-optimal interactions, e.g., the pointing and selecting operation, as well as image measurements.Our study provides insights into existing HCI approaches used in US machines and establishes a rigorous UML-based framework for future US machine design to improve interoperability, efficiency and ease-of-use.