- Email: [email protected]
The displacement of the bony insertion of the anterior cruciate ligament during knee flexion
Abstracts
of the third meeting
of the European
Society of Biomechanics
799
The joint moments may be manipulated and the resulting body motion plotted at the terminal in stick figure format. By “exercising” the model a user can gain insights into the complexities of gait and could, for instance. study the compensations necessary if one moment was reduced as in pathological gait. Rejkrence
Onyshko, S. and Winter, D. A. (1980) A mathematical Biomechunics
model ‘for the dynamics
of human
locomotion.
J.
13, 361-368.
B. BIOMECHANICS THE DISPLACEMENT
OF JOINTS
OF THE BONY INSERTION OF THE ANTERIOR LIGAMENT DURING KNEE FLEXION
J. M. DORLOT (Ecole Polytechnique,
Montrlal,
CRUCIATE
Canada)
P. CHKISTE~ A. MEUNIER and J. WITVOET (Laboratoire de Recherches 10 avenue de Verdun, 75010 Paris, France)
Orthopddiques.
Measurements of the displacement of the tibia1 and femoral insertion sites of the antero-medial and postero-lateral bands of the ACL ligament were performed on six cadaver knees. The length of the AM band is maximum at full extension, decreases up to 45” flexion, and remains constant on further flexion. The length of the PL band is minimum at 45” flexion and increases in extension or in flexion from that position. Anterior and posterior drawer tests were done at 90” flexion. Sectioning the PL band did not effect the force-displacement relationship of the anterior drawer, but up to 200N applied force sectioning of the AM band had a similar effect to a complete cut of the ACL. In neither case was the posterior drawer modified. Neither band is taut when the knee is flexed at 90”, both are in tension at full extension and only the PL band is under tension in full tension.
BIOMECHANICAL
BEHAVIOUR OF THE HUMAN TARSUS RELATED TO A NEW RADIOLOGICAL INDEX
R. J. BENINK (Department of Anatomy and Embryology, University of Leiden, The Netherlands) Studying the relationship between the amount of supination of the human tarsus and the amount of laterorotation of the loaded tibia in skeletoligamentous preparations, we noticed considerable individual differences in input rotational forces. We registered in our test cage the input moment and the vertical tibia displacement as a function of the laterorotating angle of the tibia (axial load 380N), in 34 embalmed specimens and 2 fresh intact amputated legs. Soon it became clear that there is a significant relationship between tarsal morphology and form of the curves. Higharched feet and flat feet behaved as extremes at both sides totally different in comparison with a normal foot. This relationship could be expressed only with the aid of a new radiological criterium based on the positional interdependence between talus and calcaneus taken from a standardized X-ray picture, known as the tarsal index. The moment curve as well as the vertical tibia displacement curve can be expressed in one variable. These variables can be related and correlated with each other and the radiological tarsal index. TENDON C. W.
SPOOR
FORCES BALANCING (Department
of Anatomy,
A FORCE ON THE FINGERTIP University
of Leiden, The Netherlands)
A two-dimensional static force analysis of the human middle finger has been carried out. An external force. taken as unity, is exerted on the fingertip in various directions in the sagittal plane. Four equilibrium conditions with six unknown tendon forces are derived. Only one intrinsic muscle force is used. Geometrical data are treated as knowns. All possible non-negative solutions for the tendon forces are shown in a diagram. This also shows which forces are necessary for equilibrium. We calculated the directions of the external force for which equilibrium is possible without intrinsic force. This analysis is applied to geometrical finger data from the literature. We find that in some fingers equilibrium without an intrinsic muscle force is possible for every direction of the external force. In the other fingers it is possible for a certain region of dorsodistal directions only, IA’ 1/11/‘0 INVESTIGATIONS
ON THE MECHANICAL ILIOTIBIALIS
FUNCTION
OF THE TRACTUS
H. A. C. JACOB, A. H. HUGGLER and B. RCJTTIMANN(Biomechanics Laboratory of the Department of Orthopaedic Surgery (Balgrist), University of Zurich, Switzerland) It is often assumed that the equilibrating forces about the hip joint in one-legged stance are mainly exerted by the abductor muscles that insert in the greater trochanter. If a load bearing function is simultaneously attributed to
of the third meeting
of the European
Society of Biomechanics
799
The joint moments may be manipulated and the resulting body motion plotted at the terminal in stick figure format. By “exercising” the model a user can gain insights into the complexities of gait and could, for instance. study the compensations necessary if one moment was reduced as in pathological gait. Rejkrence
Onyshko, S. and Winter, D. A. (1980) A mathematical Biomechunics
model ‘for the dynamics
of human
locomotion.
J.
13, 361-368.
B. BIOMECHANICS THE DISPLACEMENT
OF JOINTS
OF THE BONY INSERTION OF THE ANTERIOR LIGAMENT DURING KNEE FLEXION
J. M. DORLOT (Ecole Polytechnique,
Montrlal,
CRUCIATE
Canada)
P. CHKISTE~ A. MEUNIER and J. WITVOET (Laboratoire de Recherches 10 avenue de Verdun, 75010 Paris, France)
Orthopddiques.
Measurements of the displacement of the tibia1 and femoral insertion sites of the antero-medial and postero-lateral bands of the ACL ligament were performed on six cadaver knees. The length of the AM band is maximum at full extension, decreases up to 45” flexion, and remains constant on further flexion. The length of the PL band is minimum at 45” flexion and increases in extension or in flexion from that position. Anterior and posterior drawer tests were done at 90” flexion. Sectioning the PL band did not effect the force-displacement relationship of the anterior drawer, but up to 200N applied force sectioning of the AM band had a similar effect to a complete cut of the ACL. In neither case was the posterior drawer modified. Neither band is taut when the knee is flexed at 90”, both are in tension at full extension and only the PL band is under tension in full tension.
BIOMECHANICAL
BEHAVIOUR OF THE HUMAN TARSUS RELATED TO A NEW RADIOLOGICAL INDEX
R. J. BENINK (Department of Anatomy and Embryology, University of Leiden, The Netherlands) Studying the relationship between the amount of supination of the human tarsus and the amount of laterorotation of the loaded tibia in skeletoligamentous preparations, we noticed considerable individual differences in input rotational forces. We registered in our test cage the input moment and the vertical tibia displacement as a function of the laterorotating angle of the tibia (axial load 380N), in 34 embalmed specimens and 2 fresh intact amputated legs. Soon it became clear that there is a significant relationship between tarsal morphology and form of the curves. Higharched feet and flat feet behaved as extremes at both sides totally different in comparison with a normal foot. This relationship could be expressed only with the aid of a new radiological criterium based on the positional interdependence between talus and calcaneus taken from a standardized X-ray picture, known as the tarsal index. The moment curve as well as the vertical tibia displacement curve can be expressed in one variable. These variables can be related and correlated with each other and the radiological tarsal index. TENDON C. W.
SPOOR
FORCES BALANCING (Department
of Anatomy,
A FORCE ON THE FINGERTIP University
of Leiden, The Netherlands)
A two-dimensional static force analysis of the human middle finger has been carried out. An external force. taken as unity, is exerted on the fingertip in various directions in the sagittal plane. Four equilibrium conditions with six unknown tendon forces are derived. Only one intrinsic muscle force is used. Geometrical data are treated as knowns. All possible non-negative solutions for the tendon forces are shown in a diagram. This also shows which forces are necessary for equilibrium. We calculated the directions of the external force for which equilibrium is possible without intrinsic force. This analysis is applied to geometrical finger data from the literature. We find that in some fingers equilibrium without an intrinsic muscle force is possible for every direction of the external force. In the other fingers it is possible for a certain region of dorsodistal directions only, IA’ 1/11/‘0 INVESTIGATIONS
ON THE MECHANICAL ILIOTIBIALIS
FUNCTION
OF THE TRACTUS
H. A. C. JACOB, A. H. HUGGLER and B. RCJTTIMANN(Biomechanics Laboratory of the Department of Orthopaedic Surgery (Balgrist), University of Zurich, Switzerland) It is often assumed that the equilibrating forces about the hip joint in one-legged stance are mainly exerted by the abductor muscles that insert in the greater trochanter. If a load bearing function is simultaneously attributed to