Edmund Y. S. Chao

A biomechanical study of normal functional elbow motion.

UNLABELLED We studied thirty-three normal patients, eighteen women and fifteen men, for normal motion and the amount of elbow motion required for fifteen activities of daily living. The amounts of elbow flexion and forearm rotation (pronation and supination) were measured simultaneously by means of an electrogoniometer. Activities of dressing and hygiene require elbow positioning from about 140 degrees of flexion needed to reach the occiput to 15 degrees of flexion required to tie a shoe. Most of these activities are performed with the forearm in zero to 50 degrees of supination. Other activities of daily living (such as eating, using a telephone, or opening a door) are accomplished with arcs of motion of varying magnitudes. Most of the activities of daily living that were studied in this project can be accomplished with 100 degrees of elbow flexion (from 30 to 130 degrees) and 100 degrees of forearm rotation (50 degrees of pronation and 50 degrees of supination). CLINICAL RELEVANCE These data, not previously recorded, may be used to provide an objective basis for the determination of disability impairment, to determine the optimum position for elbow splinting or arthrodesis, and to assist in the design of elbow prostheses. The motion needed to perform essential daily activities is obtainable with a successful total elbow arthroplasty.

Normal axial alignment of the lower extremity and load-bearing distribution at the knee.

Based on a series of 120 normal subjects of different gender and age, the geometry of the knee joint was analyzed using a full-length weight-bearing roentgenogram of the lower extremity. A special computer program based on the theory of a rigid body spring model was applied to calculate the important anatomic and biomechanical factors of the knee joint. The tibiofemoral mechanical angle was 1.2 degrees varus. Hence, it is difficult to rationalize the 3 degree varus placement of the tibial component in total knee arthroplasty suggested by some authors. The distal femoral anatomic valgus (measured from the lower one-half of the femur) was 4.2 degrees in reference to its mechanical axis. This angle became 4.9 degrees when the full-length femoral anatomic axis was used. When simulating a one-legged weight-bearing stance by shifting the upper-body gravity closer to the knee joint, 75% of the knee joint load passed through the medial tibial plateau. The knee joint-line obliquity was more varus in male subjects. The female subjects had a higher peak joint pressure and a greater patello-tibial Q angle. Age had little effect on the factors relating to axial alignment of the lower extremity and load transmission through the knee joint.

Muscles across the elbow joint: A biomechanical analysis

Abstract In order to understand the mechanics of the human musculoskeletal system, quantitative data on the functional anatomy of the muscles related to the joint are necessary. Several important biomechanical parameters of the muscles controlling the elbow joint were determined. Serial cross-sectional anatomy analysis was used to obtain the centroid and thus the moment arms of each of the muscles along the upper arm and at the elbow joint. Muscle volume and true fiber length at the resting position were also measured. From these data, the physiological cross-sectional areas were calculated. The volume provided the information on the work capacity of the muscles. The physiological cross-sectional area provided the potential tension which the muscle can generate.

Biomechanical study of the ligamentous system of the acromioclavicular joint.

The ligamentous structures of the acromioclavicular joint were studied by gross examination and quantitative measurement in twelve human cadaver specimens. Distances between insertions at various extreme positions of the clavicle were studied with the biplane radiographic technique. Ligamentous contributions to joint constraint under displacements were determined by performing load-displacement tests along with sequential sectioning of the ligaments. Twelve modes of joint displacement were examined. The acromioclavicular ligament acted as a primary constraint for posterior displacement of the clavicle and posterior axial rotation. The conoid ligament appeared to be more important than has been previously described. That ligament played a primary role in constraining anterior and superior rotation as well as anterior and superior displacement of the clavicle. The trapezoid ligament contributed less constraint to movement of the clavicle in both the horizontal and the vertical plane except when the clavicle moved in axial compression toward the acromion process. The various contributions of different ligaments to constraint changed not only with the direction of joint displacement but also with the amount of loading and displacement. For many directions of displacement, the acromioclavicular joint contributed a greater amount to constraint at smaller degrees of displacement, while the coracoclavicular ligaments, primarily the conoid ligament, contributed a greater amount of constraint with larger amounts of displacement.

A survey of finite element analysis in orthopedic biomechanics: The first decade

The finite element method (FEM), an advanced computer technique of structural stress analysis developed in engineering mechanics, was introduced to orthopedic biomechanics in 1972 to evaluate stresses in human bones. Since then, this method has been applied with increasing frequency for stress analyses of bone and bone-prosthesis structures, fracture fixation devices and various kinds of tissues other than bone. The aims of these investigations were to assess relationship between load carrying functions and morphology of the tissues, and to optimize designs and fixation techniques of implants. Although the amounts of significant findings and useful concepts generated by the FEM during the first decade of its application in this field were limited, many publications have served to illustrate its capabilities and limitations. The method is now well established as a tool for basic research and for design analysis in orthopedic biomechanics, and the number of publications in which it is used is increasing rapidly. In the meantime, following developments in engineering mechanics, the capabilities of the method are augmented which, together with an increasing sophistication of computers, guarantees exciting possibilities for the future. However, the biological structures and the clinical problems concerned are complex. Scientific progress in this area requires a sound understanding of engineering mechanics on the one hand, and a profound appreciation of the complex reality on the other. These features were not always apparent in the FEM work reported during the first ten years. In the following survey, the developments of FEM applications in orthopedic biomechanics during the first decade are discussed. Special problem areas are indicated and future trends anticipated.

Justification of triaxial goniometer for the measurement of joint rotation

Abstract The modified triaxial goniometer was designed based on the gyroscopic concept. This device is capable of measuring the joint three-dimensional angular motion corresponding to a specific set of Eulerian angles. Since the angular measurement by this device is not sequence dependent, it is convenient to provide unique motion patterns of the joint from one position to another. The joint rotational axes are oriented based on identifiable bony landmarks which provide a convenient visualization of the anatomical motion involved. The error caused by the exoskeletal attachment of the instrument can be theoretically corrected. Considering all factors in joint functional evaluation, the triaxial goniometer is a useful and effective method to provide simple real time three-dimensional angular motion measurements.

Functional ranges of motion of the wrist joint.

We have examined 40 normal subjects (20 men and 20 women) to determine the ideal range of motion required to perform activities of daily living. The amount of wrist flexion and extension, as well as radial and ulnar deviation, was measured simultaneously by means of a biaxial wrist electrogoniometer. The entire battery of evaluated tasks could be achieved with 60 degrees of extension, 54 degrees of flexion, 40 degrees of ulnar deviation, and 17 degrees of radial deviation, which reflects the maximum wrist motion required for daily activities. The majority of the hand placement and range of motion tasks that were studied in this project could be accomplished with 70 percent of the maximal range of wrist motion. This converts to 40 degrees each of wrist flexion and extension, and 40 degrees of combined radial-ulnar deviation. This study provides normal standards for the functional range of motion of the wrist.

Comparison of tibiofemoral joint forces during open-kinetic-chain and closed-kinetic-chain exercises.

The purpose of this study was to analyze forces at the tibiofemoral joint during open and closed-kinetic-chain exercises. Five healthy subjects performed maximum isometric contractions at 30, 60, and 90 degrees of knee flexion during open-kinetic-chain extension, open-kinetic-chain flexion, and closed-kinetic-chain exercises. Electromyographic activity of the quadriceps and hamstrings, as well as load and torque-cell data, were recorded. Tibiofemoral shear and compression forces were calculated with use of a two-dimensional biomechanical model. The results showed that, during the open-kinetic-chain extension exercise, maximum posterior shear forces (the resisting forces to anterior drawer) of 285 +/- 120 newtons (mean and standard deviation) occurred at 30 degrees of knee flexion and maximum anterior shear forces (the resisting forces to posterior drawer) of 1780 +/- 699 newtons occurred at 90 degrees of knee flexion. The closed-kinetic-chain exercise produced significantly less posterior shear force at all angles when compared with the open-kinetic-chain extension exercise. In addition, the closed-kinetic-chain exercise produced significantly less anterior shear force at all angles except 30 degrees when compared with the open-kinetic-chain flexion exercise (p < 0.05). Analysis of tibiofemoral compression forces and electromyographic recruitment patterns revealed that the closed-kinetic-chain exercise produced significantly greater compression forces and increased muscular co-contraction at the same angles at which the open-kinetic-chain exercises produced maximum shear forces and minimum muscular co-contraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Three-dimensional force analysis of finger joints in selected isometric hand functions

Abstract Three-dimensional constraint forces of the finger tendons and joints in isometric hand functions were determined. The joint and tendon orientations were defined from biplanar X-ray films. Coordinate systems at each joint were used to define the constraint forces and moments. Four index fingers, one long finger, and one little finger were analyzed. Through free-body analysis, a statically indeterminate problem was derived. The method of systematic elimination of redundant unknown tendon forces was applied. Constraint conditions based on EMG and physiologic assessments were used to obtain admissible solutions. The findings are important in understanding the functional anatomy and pathologic deformities involving the hand and the basic requirements on prosthetic design of finger joints.

Application of a magnetic tracking device to kinesiologic studies

A magnetic position and orientation tracking system is currently available for the determination of the position and orientation of a sensor relative to a source by utilizing the principle of low-frequency magnetic field technology. The application of this system for biomechanical analysis of human movement is examined in this study. Studies of both planar particle motion and spatial rigid body motion based on Eulerian angle description and screw displacement axis description have been performed. The system has been found to be quite accurate and easy to use, and it would be a useful tool in kinesiologic research.