Point of optimal kinematic error: Improvement of the instantaneous helical pivot method for locating centers of rotation

[EN] This paper proposes a variation of the instantaneous helical pivot technique for locating centers of rotation. The point of optimal kinematic error (POKE), which minimizes the velocity at the center of rotation, may be obtained by just adding a weighting factor equal to the square of angular velocity in Woltring's equation of the pivot of instantaneous helical axes (PIHA). Calculations are simplified with respect to the original method, since it is not necessary to make explicit calculations of the helical axis, and the effect of accidental errors is reduced. The improved performance of this method was validated by simulations based on a functional calibration task for the gleno-humeral joint center. Noisy data caused a systematic dislocation of the calculated center of rotation towards the center of the arm marker cluster. This error in PIHA could even exceed the effect of soft tissue artifacts associated to small and medium deformations, but it was successfully reduced by the POKE estimation.This work has been funded by the Spanish Government (Grants DPI2009-13830-C02-01, DPI2009-13830-CO2-02, DPI2010-20814-CO2-01, DPI2010-20814-CO2-02).De Rosario Martínez, H.; Page Del Pozo, AF.; Mata Amela, V. (2014). Point of optimal kinematic error: Improvement of the instantaneous helical pivot method for locating centers of rotation. Journal of Biomechanics. 47(7):1742-1747. doi:10.1016/j.jbiomech.2014.02.003S1742174747

Analytical study of the effects of soft tissue artefacts on functional techniques to define axes of rotation

[EN] The accurate location of the main axes of rotation (AoR) is a crucial step in many applications of human movement analysis. There are different formal methods to determine the direction and position of the AoR, whose performance varies across studies, depending on the pose and the source of errors. Most methods are based on minimizing squared differences between observed and modelled marker positions or rigid motion parameters, implicitly assuming independent and uncorrelated errors, but the largest error usually results from soft tissue artefacts (STA), which do not have such statistical properties and are not effectively cancelled out by such methods. However, with adequate methods it is possible to assume that STA only account for a small fraction of the observed motion and to obtain explicit formulas through differential analysis that relate STA components to the resulting errors in AoR parameters. In this paper such formulas are derived for three different functional calibration techniques (Geometric Fitting, mean Finite Helical Axis, and SARA), to explain why each technique behaves differently from the others, and to propose strategies to compensate for those errors. These techniques were tested with published data from a sit-to-stand activity, where the true axis was defined using bi-planar fluoroscopy. All the methods were able to estimate the direction of the AoR with an error of less than 5 degrees whereas there were errors in the location of the axis of 30-40 mm. Such location errors could be reduced to less than 17 mm by the methods based on equations that use rigid motion parameters (mean Finite Helical Axis, SARA) when the translation component was calculated using the three markers nearest to the axis. (C) 2017 Elsevier Ltd. All rights reserved.This work was funded by the Spanish Government and co-financed by EU FEDER funds (Grant DPI2013-44227-R). We would like to thank Prof. Tung-Wu Lu, Tsung-Yuan Tsai, Mei-Ying Kuo and Horn-Chaung Hsu from National Taiwan University for making the data from their studies available for further research on STA,, and Dr. Tecla Bonci from the Italian University of Sport and Movement 'Foro Italico' for providing the access to benchmark data.De Rosario Martínez, H.; Page Del Pozo, AF.; Besa Gonzálvez, AJ. (2017). Analytical study of the effects of soft tissue artefacts on functional techniques to define axes of rotation. Journal of Biomechanics. 62:60-67. https://doi.org/10.1016/j.jbiomech.2017.01.046S60676

Model of Soft Tissue Artifact Propagation to Joint Angles in Human Movement Analysis

[EN] This work describes the kinematic laws that govern the transmission of soft tissue artifact errors to kinematic variables in the analysis of human movements. Artifacts are described as relative translations and rotations of the marker cluster over the bone, and a set of explicit expressions is defined to account for the effect of that relative motion on different representations of rotations: the rotation around the screw axis, or rotation vector, and three Euler angle sequences (XY0Z, YX0Y00, ZX0 Y00). Although the error transmission is nonlinear in all cases, the effect of artifacts is greater on Euler sequences than on the rotation vector. Specifically, there are crosstalk effects in Euler sequences that amplify the errors near singular configurations. This fact is an additional source of variability in studies that describe artifacts by comparing the Euler angles obtained from skin markers, with the angles of an artifact-free gold standard. The transmission of errors to rotation vector coordinates is less variable or dependent on the type of motion. This model has been tested in an experiment with a deformable mechanical model with a spherical joint.This work has been funded by the Spanish Government and co-financed by EU FEDER funds (Grants DPI2009-13830-C02-01 and DPI2009-13830-C02-02).Page Del Pozo, AF.; De Rosario Martínez, H.; Mata Amela, V.; Besa Gonzálvez, AJ. (2014). Model of Soft Tissue Artifact Propagation to Joint Angles in Human Movement Analysis. Journal of Biomechanical Engineering. 136:1-7. doi:10.1115/1.4026226S1713

Representation of planar motion of complex joints by means of rolling pairs. Application to neck motion

[EN] We propose to model planar movements between two human segments by means of rolling-without-slipping kinematic pairs. We compute the path traced by the instantaneous center of rotation (ICR) as seen from the proximal and distal segments, thus obtaining the fixed and moving centrodes, respectively. The joint motion is then represented by the rolling-without-slipping of one centrode on the other. The resulting joint kinematic model is based on the real movement and accounts for nonfixed axes of rotation; therefore it could improve current models based on revolute pairs in those cases where joint movement implies displacement of the ICR. Previous authors have used the ICR to characterize human joint motion, but they only considered the fixed centrode. Such an approach is not adequate for reproducing motion because the fixed centrode by itself does not convey information about body position. The combination of the fixed and moving centrodes gathers the kinematic information needed to reproduce the position and velocities of moving bodies. To illustrate our method, we applied it to the flexion-extension movement of the head relative to the thorax. The model provides a good estimation of motion both for position variables (mean R pos=0.995) and for velocities (mean R vel=0.958). This approach is more realistic than other models of neck motion based on revolute pairs, such as the dual-pivot model. The geometry of the centrodes can provide some information about the nature of the movement. For instance, the ascending and descending curves of the fixed centrode suggest a sequential movement of the cervical vertebrae. © 2010 Elsevier Ltd.This work was funded by the Spanish Government and co-financed by EU FEDER funds (Grants DPI2006-14722-C02-01, DPI2006-14722-C02-02, DPI2009-13830-C02-01, DPI2009-13830-C02-02 and Ramon y Cajal contract to JAG).Page Del Pozo, AF.; De Rosario Martínez, H.; Galvez Griso, JA.; Mata Amela, V. (2011). Representation of planar motion of complex joints by means of rolling pairs. Application to neck motion. Journal of Biomechanics. 44(4):747-750. https://doi.org/10.1016/j.jbiomech.2010.11.019S74775044

Kinematic description of soft tissue artifacts: quantifying rigid versus deformation components and their relation with bone motion

[EN] This paper proposes a kinematic approach for describing soft tissue artifacts (STA) in human movement analysis. Artifacts are represented as the field of relative displacements of markers with respect to the bone. This field has two components: deformation component (symmetric field) and rigid motion (skew-symmetric field). Only the skew-symmetric component propagates as an error to the joint variables, whereas the deformation component is filtered in the kinematic analysis process. Finally, a simple technique is proposed for analyzing the sources of variability to determine which part of the artifact may be modeled as an effect of the motion, and which part is due to other sources. This method has been applied to the analysis of the shank movement induced by vertical vibration in 10 subjects. The results show that the cluster deformation is very small with respect to the rigid component. Moreover, both components show a strong relationship with the movement of the tibia. These results suggest that artifacts can be modeled effectively as a systematic relative rigid movement of the marker cluster with respect to the underlying bone. This may be useful for assessing the potential effectiveness of the usual strategies for compensating for STA. © 2012 International Federation for Medical and Biological Engineering.This work has been funded by the Spanish Government and co-financed by EU FEDER funds (Grants DPI2009-13830-C02-01, DPI2009-13830-C02-02 and IMPIVA IMDEEA/2012/79 and IMDEEA/2012/80).De Rosario Martínez, H.; Page Del Pozo, AF.; Besa Gonzálvez, AJ.; Mata Amela, V.; Conejero Navarro, E. (2012). Kinematic description of soft tissue artifacts: quantifying rigid versus deformation components and their relation with bone motion. Medical & Biological Engineering & Computing. 50(11):1173-1181. https://doi.org/10.1007/s11517-012-0978-5S117311815011Akbarshahi M, Schache AG, Fernandez JW, Baker R, Banks S, Pandy MG (2010) Non-invasive assessment of soft-tissue artifact and its effect on knee joint kinematics during functional activity. J Biomech 43:1292–1301Alexander EJ, Andriacchi TP (2001) Correcting for deformation in skin-based marker systems. J Biomech 34:355–361Andersen MS, Benoit DL, Damsgaard M, Ramsey DK, Rasmussen J (2010) Do kinematic models reduce the effects of soft tissue artefacts in skin marker-based motion analysis? An in vivo study of knee kinematics. J Biomech 43:268–273Andriacchi TP, Alexander EJ, Toney MK, Dyrby C, Sum J (1998) A point cluster method for in vivo motion analysis: applied to a study of knee kinematics. J Biomech Eng 120:743–749Benoit DL, Ramsey DK, Lamontagne M, Xu L, Wretenberg P, Renström P (2006) Effect of skin movement artifact on knee kinematics during gait and cutting motions measured in vivo. Gait Posture 24:152–164Camomilla V, Donati M, Stagni R, Cappozzo A (2009) Non-invasive assessment of superficial soft tissue local displacement during movement: a feasibility study. J Biomech 42:931–937Cappello A, Cappozzo A, La Palombara PF, Lucchetti L, Leardini A (1997) Multiple anatomical landmark calibration for optimal bone pose estimation. Hum Mov Sci 16:259–274Cappello A, Stagni R, Fantozzi S, Leardini A (2005) Soft tissue artifact compensation in knee kinematics by double anatomical landmark calibration: performance of a novel method during select motor tasks. IEEE Trans Biomed Eng 52:992–998Cappozzo A, Della Croce U, Leardini A, Chiari L (2005) Human movement analysis using stereophotogrammetry: part 1: theoretical background. Gait Posture 21:186–196Chèze L, Fregly BJ, Dimnet J (1995) A solidification procedure to facilitate kinematic analyses based on video system data. J Biomech 28:879–884Dumas R, Cheze L (2009) Soft tissue artifact compensation by linear 3D interpolation and approximation methods. J Biomech 42:2214–2217Ehrig RM, Taylor WR, Duda GN, Heller MO (2006) A survey of formal methods for determining the centre of rotation of ball joints. J Biomech 39:2798–2809Ehrig RM, Taylor WR, Duda GN, Heller MO (2007) A survey of formal methods for determining functional joint axes. J Biomech 40:2150–2157Fuller J, Liu LJ, Murphy MC, Mann RW (1997) A comparison of lower-extremity skeletal kinematics measured using skin- and pin-mounted markers. Hum Mov Sci 16:219–242Gao B, Zheng N (2008) Investigation of soft tissue movement during level walking: translations and rotations of skin markers. J Biomech 41:3189–3195Holden JP, Orsini JA, Siegel KL, Kepple TM, Gerber LH, Stanhope SJ (1997) Surface movement errors in shank kinematics and knee kinetics during gait. Gait Posture 5:217–227Leardini A, Chiari L, Della Croce U, Cappozzo A (2005) Human movement analysis using stereo photogrammetry: part 3. Soft tissue artifact assessment and compensation. Gait Posture 21:212–225Lucchetti L, Cappozzo A, Cappello A, Della Croce U (1998) Skin movement artefact assessment and compensation in the estimation of knee-joint kinematics. J Biomech 31:977–984Nester C, Jones RK, Liu A, Howard D, Lundberg A, Arndt A, Lundgren P, Stacoff A, Wolf P (2007) Foot kinematics during walking measured using bone and surface mounted markers. J Biomech 40:3412–3423Page A, de Rosario H, Mata V, Hoyos JV, Porcar R (2006) Effect of marker cluster design on the accuracy of human movement analysis using stereophotogrammetry. Med Biol Eng Comput 4:1113–1119Page A, de Rosario H, Mata V, Atienza C (2009) Experimental Analysis of Rigid Body Motion. A Vector Method to Determine Finite and Infinitesimal Displacements From Point Coordinates. J Mech Des 131: 031005Page A, Galvez JA, de Rosario H, Mata V, Prat J (2010) Optimal average path of the instantaneous helical axis in planar motions with one functional degree of freedom. J Biomech 43:375–378Peters A, Galna B, Sangeux M, Morris M, Baker R (2010) Quantification of soft tissue artifact in lower limb human motion analysis: a systematic review. Gait Posture 31:1–8Reinschmidt C, van den Bogert AJ, Lundberg A, Nigg BM, Murphy N, Stacoff A, Stano A (1997) Tibiofemoral and tibiocalcaneal motion during walking: external vs. skeletal markers. Gait Posture 6:98–109Ryu T, Choi HS, Chung MK (2009) Soft tissue artifact compensation using displacement dependency between anatomical landmarks and skin markers- a preliminary study. Int J Ind Ergon 39:152–158Sangeux M, Marin F, Charleux F, Dürselen L, Ho Ba Tho MC (2006) Quantification of the 3D relative movement of external marker sets vs. bones based on magnetic resonance imaging. Clin Biomech 21:984–991Sati M, de Guise JA, Larouche S, Drouin G (1996) Quantitative assessment of skin-bone movement at the knee. Knee 3(3):121–138Stagni R, Fantozzi S (2009) Can cluster deformation be an indicator of soft tissue artefact? Gait Posture 30(Suppl 1):S55Stagni R, Fantozzi S, Cappello A, Leardini A (2005) Quantification of soft tissue artefact in motion analysis by combining 3D fluoroscopy and stereophotogrammetry: a study on two subjects. Clin Biomech 20(3):320–329Stagni R, Fantozzi S, Cappello A (2009) Double calibration vs global optimization: performance and effectiveness for clinical application. Gait Posture 29:119–122Taylor WR, Ehrig RM, Duda GN, Schell H, Seebeck P, Heller MO (2005) On the influence of soft tissue coverage in the determination of bone kinematics using skin markers. J Orthop Res 23(4):726–734Tranberg R, Karlsson D (1998) The relative skin movement of the foot: a 2-D roentgen photogrammetry study. Clin Biomech 13(1):71–76Tsai T-Y, Lu Tung-Wu, Kuo M-Y, Lin C–C (2011) Effects of soft tissue artifacts on the calculated kinematics and kinetics of the knee during stair-ascent. J Biomech 44(6):1182–1188Woltring HJ, Long K, Osterbauer PJ, Fuhr AW (1994) Instantaneous helical axis estimation from 3-D video data in neck kinematics for whiplash diagnostics. J Biomech 27(12):1415–143

Propagation of Artifact Errors on Kinematic Variables. Effect on Euler Angles

This work has been funded by the Spanish Government and co-financed by EU FEDER funds (Grants DPI2009-13830-C02-01, DPI2009-13830- C02-02 and IMPIVA IMIDIC/2010/84)De Rosario Martínez, H.; Page Del Pozo, AF.; Mata Amela, V.; Besa Gonzálvez, AJ.; Moreno Cano, R. (2012). PROPAGATION OF ARTIFACT ERRORS ON KINEMATIC VARIABLES. EFFECT ON EULER ANGLES. Journal of Biomechanics. 45:293-293. doi:10.1016/S0021-9290(12)70294-4S2932934

Synergistic Action of Actinoporin Isoforms from the Same Sea Anemone Species Assembled into Functionally Active Heteropores

Among the toxic polypeptides secreted in the venom of sea anemones, actinoporins are the pore-forming toxins whose toxic activity relies on the formation of oligomeric pores within biological membranes. Intriguingly, actinoporins appear as multigene families that give rise to many protein isoforms in the same individual displaying high sequence identities but large functional differences. However, the evolutionary advantage of producing such similar isotoxins is not fully understood. Here,using sticholysins I and II (StnI and StnII) from the sea anemone Stichodactyla helianthus, it is shown that actinoporin isoforms can potentiate each other’s activity. Through hemolysis and calcein releasing assays, it is revealed that mixtures of StnI and StnII are more lytic than equivalent preparations of the corresponding isolated isoforms. It is then proposed that this synergy is due to the assembly of heteropores because (i) StnI and StnII can be chemically cross-linked at the membrane and (ii) the affinity of sticholysin mixtures for the membrane is increased with respect to any of them acting in isolation, as revealed by isothermal titration calorimetry experiments. These results help us understand the multigene nature of actinoporins and may be extended to other families of toxins that require oligomerization to exert toxicity

Relationship between neck motion and self-reported pain in patients with whiplash associated disorders during the acute phase

[EN] Background: Biomechanical measures quantify motor control and functional deficits in Whiplash Associated Disorders (WAD), but few studies relate those measures to the clinical scales that are routinely used to assess patients. Most studies are limited to chronic neck pain, and report poor to moderate correlations. Objective: To define a statistical model that relates measures of neck kinematics with clinical scales of neck pain, in WAD patients during the rehabilitation process in the acute phase (less than 3 months since the accident). Methods: 96 WAD patients self-assessed their pain using VAS and NPQ, and passed neck motion tests as part of their rehabilitation program. Four regression models were fitted to analyze the effects of the measured kinematic parameters and subject-specific characteristics on VAS and NPQ. Model errors were compared to minimal clinically significant differences. Results: Multiple correlation coefficients of the models were between 0.74 and 0.90. More than 66% of that correlation was accounted for by subject-specific factors, and most of the other half by the measured kinematic parameters. Range of motion of flexion-extension and axial rotation, and harmonicity of flexion-extension, where the variables most consistently related to the decrease of pain. The error of the models was within the MCSD in more than 50% of the observations. Conclusions: Part of the individual progression of pain and pain-related disability in acute WAD patients, as rated by NPQ and VAS, can be mapped to objective kinematic parameters of neck mobility tests, like ranges of motion, velocities, repeatability and harmonicity of movements.This work was supported by funding from European Union Horizon 2020 Research and Innovation Program, under grant agreement No. 777090.De Rosario Martínez, H.; Vivas Broseta, MJ.; Sinovas, I.; Page Del Pozo, AF. (2018). Relationship between neck motion and self-reported pain in patients with whiplash associated disorders during the acute phase. Musculoskeletal Science and Practice (Online). 38:23-29. https://doi.org/10.1016/j.msksp.2018.09.004S23293

Dorotea Barnés González (1904-2003): Una química española en la encrucijada de la espectroscopía y el estudio de los aminoácidos

Spanish chemist who, in collaboration with two other American scientists, published in 1930 an article on the chemical and spectroscopic characteristics of cystine. She was a true pioneer because this article is considered the first international scientific contribution made by a Spanish woman in the field of Biochemistry. However, her scientific career was cut short by her marriage (“My husband retired me from science”, she declared at the age of 92), and by the Spanish Civil War, which led to her exile and subsequent academic disqualification.Química española que, en colaboración con otras dos científicas estadounidenses, publicó en 1930 un artículo sobre las características químicas y espectroscópicas de la cistina. Fue una auténtica pionera porque este artículo es considerado como la primera contribución científica internacional hecha por una mujer española en el campo de la Bioquímica. Sin embargo, su carrera científica quedó truncada por su matrimonio (“A mí me retiró de la ciencia mi marido”, declaró a los 92 años), y por la Guerra Civil española, que la llevó al exilio y a la posterior inhabilitación académica