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1
Content available remote Is a “movable hinge axis” used by the human stomatognathic system?
100%
Thieme K. M. , Kubein-Meesenburg D. , Ihlow D. , Nagerl H.
Acta of Bioengineering and Biomechanics
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2006
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tom Vol. 8, nr 1
13-25
EN
This treatise deals with sagittal in vivo motions of the human mandible. The concept of a “movable hinge axis”, which is commonly used in dentistry, was scrutinised theoretically and empirically. We wondered whether a “movable hinge axis”– or better a mandibularly fixed hinge axis (MFHA) – was actually used by subjects with sound temporomandibular joints. To answer this question we first showed that the assumptions of a MFHA would comprise that of the neuromuscular apparatus of the stomatognathic system piloting the mandible by solely two kinematical degrees of freedom (DOF). We spatially recorded in vivo motions of mandibles with high-precision ultrasonic devices. The subjects were asked to guide their mandibles in sagittal movements so that the lower incisal edges ran along the Posselt diagrams. The mathematical procedure is described in detail, hence a possible use of two DOF by a subject could quickly be puzzled out from a set of motions. These analyses revealed that the quasi-plane mandibular movements were approximately piloted by two kinematical DOF in subjects with sound temporomandibular joints. The grade of approximation was measured. Thus, the ensemble of possible positions of the moved body (mandible) can be described by a coordinate system, which is inherent in the stomatognathic system. Lacking precision and poor reproducibility in using only two variables for mandibular position control yield hints that the subject has clinical problems in his stomatognathic system.
2
Content available remote High-resolution in vivo measurement of biomechanical features of the periodontium
88%
Cronau M. , Kubein-Meesenburg D. , Ihlow D. , Nagerl H. , Fanghanel J.
Acta of Bioengineering and Biomechanics
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2006
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tom Vol. 8, nr 1
27-36
EN
Common models describing initial tooth movement mostly rest on the assumption of viscoelastic behaviour of the tooth. The periodontium is regarded as an elastic isotropic material following Hooke’s law for small displacements. These assumptions have been examined in vivo. The study is based on 22 cases with natural spacing between the teeth. An experimental device was designed for measuring small mesial and distal rotations of the crown following time-dependent torques. They were optically recorded with high accuracy (<0.001 deg resolution). The torques were produced by a digitallycontrolled rotary magnet motor and applied to the buccal side of mandibular premolars by means of a flexible Cardan shaft. Thresholds were found which had to be overcome by the applied torque to rotate the tooth about its centre of resistance. The data provided strong hints that the periodontium was a thixotropic substance and showed also shear thinning. These properties seemed to have a large interindividual variety.
3
Content available remote Physiological functions of the human finger
75%
Dumont C. , Burfeind H. , Kubein-Meesenburg D. , Hosten N. , Fanghanel J. , Gredes T. , Nagerl H.
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tom 59
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nr 5
69-74
4
Content available remote Mechanisms of circumduction and axial rotation of the carpometacarpal joint of the thumb
75%
Dumont C. , Perplies R. , Doerner J. , Fanghanel J. , Kubein-Meesenburg D. , Wachowski M. M. , Nagerl H.
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tom 60
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nr 8
65-68
5
Content available The thumb carpometacarpal joint: curvature morphology of the articulating surfaces, mathematical description and mechanical functioning
75%
Dathe H. , Dumont C. , Perplies R. , Fanghänel J. , Kubein-Meesenburg D. , Nagerl H. , Wachowski M. M.
Acta of Bioengineering and Biomechanics
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2016
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tom Vol. 18, no. 2
103--110
EN
Purpose: The purpose is to present a mathematical model of the function of the thumb carpometacarpal joint (TCMCJ) based on measurements of human joints. In the TCMCJ both articulating surfaces are saddle-shaped. The aim was to geometrically survey the shapes of the articulating surfaces using precise replicas of 28 TCMCJs. Methods: None of these 56 articulating surfaces did mathematically extend the differential geometrical neighbourhood around the main saddle point so that each surface could be characterised by three main parameters: the two extreme radii of curvature in the main saddle point and the angle between the saddles’ asymptotics (straight lines). Results: The articulating surfaces, when contacting at the respective main saddle points, are incongruent. Hence, the TCMCJ has functionally five kinematical degrees of freedom (DOF); two DOF belong to flexion/extension, two to ab-/adduction. These four DOF are controlled by the muscular apparatus. The fifth DOF, axial rotation, cannot be adjusted but stabilized by the muscular apparatus so that physiologically under compressive load axial rotation does not exceed an angle of approximately ±3°. Conclusions: The TCMCJ can be stimulated by the muscular apparatus to circumduct. The mechanisms are traced back to the curvature incongruity of the saddle surfaces. Hence we mathematically proved that none of the individual saddle surfaces can be described by a quadratic saddle surface as is often assumed in literature. We derived an algebraic formula with which the articulating surfaces in the TCMCJ can be quantitatively described. This formula can be used to shape the articulating surfaces in physiologically equivalent TCMCJ-prostheses.
6
Content available remote A novel total knee replacement by rolling articulating surfaces. In vivo functional measurements and tests
75%
Nagerl H. , Frosch K. H. , Wachowski M. M. , Dumont C. , Abicht C. , Adam P. , Kubein-Messenburg D.
Acta of Bioengineering and Biomechanics
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2008
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tom Vol. 10, nr 1
55-60
EN
The purposes of the paper were as follows: to show the fundamental functional differences between the natural knee and common total knee replacements (TKR), to describe the ideas on how main properties of the natural knee can be adopted by a novel TKR and to present some main biomechanical functions of this TKR. By analyzing the morphology of the articulating surfaces and the kinematics of the natural knee the design of the novel TKR was developed. The use was made of the test procedures established in vitro and of lateral X-ray photographs as well as fluoroscopy in vivo. The function of the novel TKR is comparable to that of the natural knee joint in terms of kinematics (roll/slide behaviour), loads of the articulating surfaces (diminished shear loads), stability and leeway under external impacts, reduction of the load in the patellofemoral joint, and ligament balancing.
7
Content available remote Knee motion analysis of the non-loaded and loaded knee: a re-look at rolling and sliding
75%
Nagerl H. , Walters J. , Frosch K. H. , Dumont C. , Kubein-Meesenburg D. , Fanghanel J. , Wachowski M. M.
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tom 60
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nr 8
69-72
8
Content available remote Adjustable mechanical stability of the balanced tibiofemoral joint in flexion/extension: a novel measuring method in vitro
75%
Knosel M. , Kubein-Meeesenburg C. , Stuhmer H. , Nagerl H. , Mansour M. , Fanghänel J.
Acta of Bioengineering and Biomechanics
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2004
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tom Vol. 6, nr 2
3-15
EN
A number of muscles which pull over the tibiofemoral joint (possessing maximally four kinematic degrees of freedom) is larger than necessary in order to produce static equilibria in the physiologic positions of the tibiofemoral joint. Consequently, it should be possible to balance the knee in any arbitrary position by a set of combinations of isotonic muscular forces. The corresponding equilibria of the same flexional status should be differentiated by their degree of stability. Here, we describe a novel method which allows measuring the isotonic stability in flexion/extension in vitro for examining the above theses derived theoretically. By in vitro experiments we could show for the first time that not only a) the same position in flexion can be held in differing static equilibria by correspondingly differing combinations of muscular forces, but also b) the varying degree of stability ranges from stable and indifferent to unstable. These features were related a) to rotations of the resultant muscular force in the main functional plane and b) translations of its force line in parallel to this plane in the direction of abduction/adduction. By that we are able to present a hypothesis of how nature deals with an apparent antagonism of mechanically stable posture and mechanical instability of the joint demanded in the case of fast motion.
9
Content available remote Mandible, maxilla and cervical spine - a functional unit?
63%
Kubein-Meesenburg D. , Thieme K. M. , Weber S. , Fanghanel J. , Dumont C. , Spassov A. , Hahn W. , Ihlow D. , Nagerl H.
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tom 59
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nr 5
75-80
10
Content available The morphology of the articular surfaces of biological knee joints provides essential guidance for the construction of functional knee endoprostheses
63%
Nagerl H. , Dathe H. , Fiedler C. , Gowers L. , Kirsch S. , Kubein-Meesenburg D. , Dumont C. , Wachowski M. M.
Acta of Bioengineering and Biomechanics
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2015
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tom Vol. 17, no. 2
45--53
EN
Purpose: In comparative examinations of kinematics of the knees of humans and pigs in flexional/extensional motion under compressive loads, the significant differential geometric essentials of articular guidance are elaborated to criticise the shaping of the articular surfaces of conventional knee-endoprostheses and to suggest constructional outlines that allow the endoprosthesis to adopt natural knee kinematics. Implantation is discussed with regard to the remaining ligamentous apparatus. Methods: Twelve fresh pig knee joints and 19 preserved human knee joints were moved into several flexional/extensional positions. In each joint, the tibia and femur were repeatably caught by metal plates. After removing all ligaments, the tibia and femur were again caught in these positions, and their points of contact were marked on both articular surfaces. Along the marker points, a thin lead wire was glued onto each surface. The positions and shapes of the four contact lines were mapped by teleradiography. Results: All contact lines were found to be plane curves. The medial and lateral planes were parallel, thus defining the joint’s sagittal plane. In the human knee, as compared to the lateral, the medial femoral contact line was always shifted anteriorly by several millimetres. The tibial contact curve was laterally convex and medially concave. In the pig knees, the lateral and medial contact lines were asymmetrically placed. Both tibial curves were convex. Conclusions: Both knees represent cam mechanisms (with one degree of freedom) that produce rolling of the articular surfaces during the stance phase. Implantation requires preservation of the anterior cruciate ligament, and ligamentous balancing is disadvantageous.
11
Content available remote Axial rotation in the lumbar spine following axial force wrench
63%
Wachowski M. M. , Hubert J. , Hawellek T. , Mansour M. , Dorner J. , Kubein-Meesenburg D. , Fanghanel J. , Raab B. W. , Dumont B. C. , Nagerl H.
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tom 60
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nr 8
61-64
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