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Saini H, Klotz T, Röhrle O. Modelling motor units in 3D: influence on muscle contraction and joint force via a proof of concept simulation. Biomech Model Mechanobiol 2022; 22:593-610. [PMID: 36572787 PMCID: PMC10097764 DOI: 10.1007/s10237-022-01666-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Accepted: 12/02/2022] [Indexed: 12/28/2022]
Abstract
AbstractFunctional heterogeneity is a skeletal muscle’s ability to generate diverse force vectors through localised motor unit (MU) recruitment. Existing 3D macroscopic continuum-mechanical finite element (FE) muscle models neglect MU anatomy and recruit muscle volume simultaneously, making them unsuitable for studying functional heterogeneity. Here, we develop a method to incorporate MU anatomy and information in 3D models. Virtual fibres in the muscle are grouped into MUs via a novel “virtual innervation” technique, which can control the units’ size, shape, position, and overlap. The discrete MU anatomy is then mapped to the FE mesh via statistical averaging, resulting in a volumetric MU distribution. Mesh dependency is investigated using a 2D idealised model and revealed that the amount of MU overlap is inversely proportional to mesh dependency. Simultaneous recruitment of a MU’s volume implies that action potentials (AP) propagate instantaneously. A 3D idealised model is used to verify this assumption, revealing that neglecting AP propagation results in a slightly less-steady force, advanced in time by approximately 20 ms, at the tendons. Lastly, the method is applied to a 3D, anatomically realistic model of the masticatory system to demonstrate the functional heterogeneity of masseter muscles in producing bite force. We found that the MU anatomy significantly affected bite force direction compared to bite force magnitude. MU position was much more efficacious in bringing about bite force changes than MU overlap. These results highlight the relevance of MU anatomy to muscle function and joint force, particularly for muscles with complex neuromuscular architecture.
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Affiliation(s)
- Harnoor Saini
- Institute of Modelling and Simulation of Biomechanical Systems, University of Stuttgart, Pfaffenwaldring 5a, 70569 Stuttgart, BW Germany
| | - Thomas Klotz
- Institute of Modelling and Simulation of Biomechanical Systems, University of Stuttgart, Pfaffenwaldring 5a, 70569 Stuttgart, BW Germany
| | - Oliver Röhrle
- Institute of Modelling and Simulation of Biomechanical Systems, University of Stuttgart, Pfaffenwaldring 5a, 70569 Stuttgart, BW Germany
- Stuttgart Center for Simulation Technology (SC SimTech), University of Stuttgart, Pfaffenwaldring 5a, 70569 Stuttgart, BW Germany
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Saini H, Röhrle O. A biophysically guided constitutive law of the musculotendon-complex: modelling and numerical implementation in Abaqus. Comput Methods Programs Biomed 2022; 226:107152. [PMID: 36194967 DOI: 10.1016/j.cmpb.2022.107152] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 08/25/2022] [Accepted: 09/20/2022] [Indexed: 06/16/2023]
Abstract
BACKGROUND AND OBJECTIVE Many biomedical, clinical, and industrial applications may benefit from musculoskeletal simulations. Three-dimensional macroscopic muscle models (3D models) can more accurately represent muscle architecture than their 1D (line-segment) counterparts. Nevertheless, 3D models remain underutilised in academic, clinical, and commercial environments. Among the reasons for this is a lack of modelling and simulation standardisation, verification, and validation. Here, we strive towards a solution by providing an open-access, characterised, constitutive relation (CR) for 3D musculotendon models. METHODS The musculotendon complex is modelled following the state-of-the-art active stress approach and is treated as hyperelastic, transversely isotropic, and nearly incompressible. Furthermore, force-length and -velocity relationships are incorporated, and muscle activation is derived from motor-unit information. The CR was implemented within the commercial finite-element software package Abaqus as a user-subroutine. A masticatory system model with left and right masseters was used to demonstrate active and passive movement. RESULTS The CR was characterised by various experimental data sets and was able to capture a wide variety of passive and active behaviours. Furthermore, the masticatory simulations revealed that joint movement was sensitive to the muscle's in-fibre passive response. CONCLUSIONS This user-material provides a "plug and play" template for 3D neuro-musculoskeletal finite element modelling. We hope that this reduces modelling effort, fosters exchange, and contributes to the standardisation of such models.
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Affiliation(s)
- Harnoor Saini
- Institute for Modelling and Simulation of Biomechanical Systems, University of Stuttgart, Pfaffenwalding 5a, 70569 Stuttgart, Germany.
| | - Oliver Röhrle
- Institute for Modelling and Simulation of Biomechanical Systems, University of Stuttgart, Pfaffenwalding 5a, 70569 Stuttgart, Germany; Stuttgart Center for Simulation Sciences (SC SimTech), Pfaffenwaldring 5a, 70569 Stuttgart, Germany
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Lapatki BG, Eiglsperger U, Schindler HJ, Radeke J, Holobar A, van Dijk JP. Three-dimensional amplitude characteristics of masseter motor units and representativeness of extracted motor unit samples. Clin Neurophysiol 2019; 130:388-395. [DOI: 10.1016/j.clinph.2018.12.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Revised: 11/06/2018] [Accepted: 12/09/2018] [Indexed: 12/22/2022]
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Malik B, Whittle T, Ogawa T, Murray GM. Reorganization of motor unit activity at different sites within the human masseter muscle during experimental masseter pain. Eur J Oral Sci 2018; 126:400-410. [PMID: 30059170 DOI: 10.1111/eos.12561] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/27/2018] [Indexed: 12/01/2022]
Abstract
The aims were to test the hypotheses that experimental masseter muscle pain leads to recruitment and/or derecruitment of motor units at different sites within the masseter and that the patterns of change in motor unit activity differ between sites. Single motor unit (SMU) activity was recorded at two sites within the right masseter [superior/anterior, inferior/posterior (IP)] during isometric biting tasks (ramp, step level) on an intraoral force transducer in 17 participants during three experimental blocks comprising no infusion (baseline), 5% hypertonic saline infusion (pain), or isotonic saline infusion (control). A visual analog scale (VAS) was used to score pain intensity. The VAS scores were statistically significantly greater during infusion of hypertonic saline than during infusion of isotonic saline. No significant differences in force levels and rates of force change were found between experimental blocks. In comparison with isotonic saline infusion, SMUs could be recruited and derecruited at both sites during hypertonic saline infusion. The frequency of recruitment or derecruitment, in comparison with no change, was statistically significantly greater at the IP site than at the superior/anterior site. Experimental noxious masseter stimulation results in a reorganization of motor unit activity throughout the muscle, and the pattern of reorganization may be different in different regions of the muscle.
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Affiliation(s)
- Bushra Malik
- Jaw Function and Orofacial Pain Research Unit, Faculty of Dentistry, Westmead Hospital Centre for Oral Health, University of Sydney, Westmead, Australia
| | - Terry Whittle
- Jaw Function and Orofacial Pain Research Unit, Faculty of Dentistry, Westmead Hospital Centre for Oral Health, University of Sydney, Westmead, Australia
| | - Toru Ogawa
- Division of Advanced Prosthetic Dentistry, Tohoku University Graduate School of Dentistry, Sendai, Japan
| | - Greg M Murray
- Jaw Function and Orofacial Pain Research Unit, Faculty of Dentistry, Westmead Hospital Centre for Oral Health, University of Sydney, Westmead, Australia
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van Dijk J, Eiglsperger U, Hellmann D, Giannakopoulos N, McGill K, Schindler H, Lapatki B. Motor unit activity within the depth of the masseter characterized by an adapted scanning EMG technique. Clin Neurophysiol 2016; 127:3198-3204. [DOI: 10.1016/j.clinph.2016.05.186] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Revised: 04/07/2016] [Accepted: 05/16/2016] [Indexed: 10/21/2022]
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Giannakopoulos NN, Katsikogianni EN, Hellmann D, Eberhard L, Leckel M, Schindler HJ, Schmitter M. Comparison of three different options for immediate treatment of painful temporomandibular disorders: a randomized, controlled pilot trial. Acta Odontol Scand 2016; 74:480-6. [PMID: 27410169 DOI: 10.1080/00016357.2016.1204558] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
OBJECTIVE The purpose of this study was to compare the short-term effectiveness of three different types of immediate, non-pharmacological intervention for alleviation of the painful symptoms of temporomandibular disorders (TMD). MATERIAL AND METHODS Thirty-six patients (mean age 41.6 ± 16.7 years, 25 females) diagnosed with non-dysfunctional painful TMD received counselling and subsequently were randomly allocated to three treatment groups: patients in Group A received prefabricated oral splints with water-filled elastic pads (Aqualizer(®)), those in Group B were provided with vacuum-formed co-polyester oral splints and those in Group C were given appointments to receive Michigan-type hard splints. Clinical examination was conducted, at baseline and after 2 weeks, by use of the RDC/TMD. Current pain intensity was determined by evaluation of graded chronic pain status (GCPS) on a numerical rating scale (NRS). Active maximum mouth opening without pain (AMMOP) was also measured. Paired sample t-tests and one-way analysis of variance with a significance level of p ≤ 0.05 were conducted. RESULTS After 2 weeks, overall mean current pain was reduced by 41.95% (p < 0.001). Current pain reduction was significant for Group B (66.6%, p < 0.001) but not for Groups A (37.88%, p = 0.56) and C (22.29%, p = 0.26). After 2 weeks, current pain level for Group B was significantly lower than that for Group C (p = 0.041). Overall, there was a statistically significant increase of AMMOP (p = 0.01). CONCLUSION All therapeutic options were pain-reducing. The results from this study suggest that cost-effective and time-effective intervention of counselling combined with use of a vacuum-formed splint is a favourable option for initial, short-term treatment of painful TMD.
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Giannakopoulos NN, Corteville F, Kappel S, Rammelsberg P, Schindler HJ, Eberhard L. Functional adaptation of the masticatory system to implant-supported mandibular overdentures. Clin Oral Implants Res 2016; 28:529-534. [PMID: 27001374 DOI: 10.1111/clr.12830] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/27/2016] [Indexed: 12/26/2022]
Abstract
OBJECTIVES The purpose of this study was to investigate the adaptation behavior of the stomatognathic system after immediate loading (24 to 72 h after surgery) of two implants supporting mandibular overdentures, assessed on insertion and three months later. The study hypothesis was that insertion of the overdentures would significantly change masticatory performance and muscle activity at both times. MATERIAL AND METHODS Thirty subjects (nine female, mean age 69.64 ± 11.81 years; 21 male, mean age 68.67 ± 7.41 years) who participated in a randomized clinical trial were included in the study. Each patient was examined three times: (i) at baseline, after already having worn new dentures for three months (T1); (ii) immediately after insertion of the overdentures on the implants (T2); and (iii) after an adaptation period of three months (T3). Examination comprised assessment of masticatory performance with artificial test food (Optocal), and simultaneous bilateral surface EMG recording of the masseter and anterior temporalis muscles. Particle-size distribution (representative value X50 ), maximum muscle contraction (MVC), and total muscle work (TMW; area under the curve) were compared by use of repeated-measures analysis of variance (ANOVA). RESULTS At T3, all measured variables (i.e., masticatory performance and muscle activity) were significantly different from those at T1. At T2, no significant changes were observed. The study hypothesis had to be rejected for T2 but accepted for T3. CONCLUSION Functional rehabilitation (in terms of masticatory performance and masticatory muscle activity) does not occur immediately after immediate loading of two implants with mandibular overdentures, but requires a significant time for functional improvement.
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Affiliation(s)
| | | | - Stefanie Kappel
- Department of Prosthodontics, University of Heidelberg, Heidelberg, Germany
| | - Peter Rammelsberg
- Department of Prosthodontics, University of Heidelberg, Heidelberg, Germany
| | | | - Lydia Eberhard
- Department of Prosthodontics, University of Heidelberg, Heidelberg, Germany
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Terebesi S, Giannakopoulos NN, Brüstle F, Hellmann D, Türp JC, Schindler HJ. Small vertical changes in jaw relation affect motor unit recruitment in the masseter. J Oral Rehabil 2015; 43:259-68. [PMID: 26707515 DOI: 10.1111/joor.12375] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/17/2015] [Indexed: 12/21/2022]
Abstract
Strategies for recruitment of masseter muscle motor units (MUs), provoked by constant bite force, for different vertical jaw relations have not previously been investigated. The objective of this study was to analyse the effect of small changes in vertical jaw relation on MU recruitment behaviour in different regions of the masseter during feedback-controlled submaximum biting tasks. Twenty healthy subjects (mean age: 24·6 ± 2·4 years) were involved in the investigation. Intra-muscular electromyographic (EMG) activity of the right masseter was recorded in different regions of the muscle. MUs were identified by the use of decomposition software, and root-mean-square (RMS) values were calculated for each experimental condition. Six hundred and eleven decomposed MUs with significantly (P < 0·001) different jaw relation-specific recruitment behaviour were organised into localised MU task groups. MUs with different task specificity in seven examined tasks were observed. The RMS EMG values obtained from the different recording sites were also significantly (P < 0·01) different between tasks. Overall MU recruitment was significantly (P < 0·05) greater in the deep masseter than in the superficial muscle. The number of recruited MUs and the RMS EMG values decreased significantly (P < 0·01) with increasing jaw separation. This investigation revealed differential MU recruitment behaviour in discrete subvolumes of the masseter in response to small changes in vertical jaw relations. These fine-motor skills might be responsible for its excellent functional adaptability and might also explain the successful management of temporomandibular disorder patients by somatic intervention, in particular by the use of oral splints.
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Affiliation(s)
- S Terebesi
- Department of Prosthodontics, Dental School, University of Heidelberg, Heidelberg, Germany
| | - N N Giannakopoulos
- Department of Prosthodontics, Dental School, University of Heidelberg, Heidelberg, Germany
| | - F Brüstle
- Department of Prosthodontics, Dental School, University of Heidelberg, Heidelberg, Germany
| | - D Hellmann
- Department of Prosthodontics, Dental School, University of Heidelberg, Heidelberg, Germany
| | - J C Türp
- Department of Reconstructive Dentistry and Temporomandibular Disorders, Dental School, University of Basel, Basel, Switzerland
| | - H J Schindler
- Research Group Biomechanics, Institute for Mechanics, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
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Hellmann D, Brüstle F, Terebesi S, Giannakopoulos NN, Eberhard L, Rammelsberg P, Schindler HJ. Static balancing behaviour of the mandible. Eur J Oral Sci 2015; 123:439-46. [PMID: 26446049 DOI: 10.1111/eos.12223] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/01/2015] [Indexed: 11/28/2022]
Abstract
The objective of this study was to investigate the mechanisms of physiological control of the craniomandibular system during force-controlled biting: in intercuspation, restricted by predetermined anatomic-geometrical conditions [i.e. biting in intercuspation (BIC)]; and on a hydrostatic system [i.e. auto-balanced static equilibrium of the mandible (BAL)], in which the mandible is balanced under unrestricted occlusal conditions. For 20 healthy subjects, the spatial positions of the condyles, the lower molars, and the incisal point were measured, and the electromyographic (EMG) activity of the musculus masseter and musculus temporalis anterior were recorded bilaterally, during force-controlled biting (50, 75, 100 N) on a hydrostatic device. The results were compared with those obtained during BIC. During BAL, the neuromuscular system stabilizes one condyle, so it behaves as a virtual fulcrum, and all available biomechanical degrees of freedom of the opposite side are used to achieve a bilaterally equal vertical distance between the upper and lower dental arches. The variability of the positions of the molars was significantly smaller than for the condyles. The EMG co-contraction ratios calculated for homonymous muscle regions revealed significant differences between BIC and BAL, specifically, greater symmetry during BAL with substantial asymmetry of approximately 25% remaining. In conclusion, the results revealed precise neuromuscular control of the position of the lower dental arch; this information might form the basis for interference-free tracking of the mandible in intercuspation under different conditions.
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Affiliation(s)
- Daniel Hellmann
- Department of Prosthodontics, Dental School, University of Heidelberg, Heidelberg, Germany
| | - Fabian Brüstle
- Department of Prosthodontics, Dental School, University of Heidelberg, Heidelberg, Germany
| | - Sophia Terebesi
- Department of Prosthodontics, Dental School, University of Heidelberg, Heidelberg, Germany
| | | | - Lydia Eberhard
- Department of Prosthodontics, Dental School, University of Heidelberg, Heidelberg, Germany
| | - Peter Rammelsberg
- Department of Prosthodontics, Dental School, University of Heidelberg, Heidelberg, Germany
| | - Hans J Schindler
- Department of Prosthodontics, Dental School, University of Heidelberg, Heidelberg, Germany.,Research Group Biomechanics, Institute for Mechanics, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
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