Automated hand functional analysis.
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Computer Graphics↗
Biomedical subjects
K N An
Publications and source records attributed to K N An.
Isometric elbow strength in normal individuals.
Isometric elbow strength was measured with torque cell dynamometers in a group of 104 normal subjects. Their mean age was 43 years (range, 21-79 years). Test functions included elbow flexion and extension, forearm pronation and supination, and grip. In general, the men were twice as strong as the women, and the dominant extremities were 6% stronger than the nondominant. The mean extension strength was 61% of that of flexion, and pronation was 86% of supination.
Adult↗
The early healing of tibial osteotomies stabilized by one-plane or two-plane external fixation.
The pattern of early healing of canine tibial osteotomies associated with two different types of external fixation devices was investigated. Two-plane fixation was significantly more rigid than one-plane fixation in three of the five loading conditions that were examined. The more rigid fixation allowed less lateral displacement at the site of the osteotomy, induced less formation of callus early in the healing process, permitted direct bridging by osteons more frequently, and provided healing that was more rigid early in the process of repair. In the later stages of healing there were no differences in the quantity of callus or in the strength of the healing bone. In this canine model, external fixation with higher rigidity resulted in rapid union that differed from the union that resulted after less rigid external fixation only with regard to porosity, torsional stiffness, and displacement at the site of the fracture.
Animals↗
Anatomic and kinematic analysis of the human forearm using high-speed computed tomography.
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Anthropometry↗
The effect of partial removal of proximal ulna on elbow constraint.
Accepted clinical practice allows the resection of up to 80% of the olecranon in comminuted fractures. Although this procedure is well-established, its effect on the static stability of the ulnohumeral joint has not been studied. An experiment was designed to study the amount of the greater sigmoid fossa of the ulna that can be removed before significant static ulnohumeral instability may occur. In eight fresh specimens, tested both in extension and at 90 degrees of flexion, changes in constraint were studied in four displacement, two torsional, and two axial modes. The constraint of the ulnohumeral joint appeared linearly proportional to the area of remaining articulation and was not provided solely by the distal 25%. The proximal portion of the olecranon has a greater effect on joint constraint than is generally appreciated.
Biomechanical Phenomena↗
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.
Acromioclavicular Joint↗
Dynamic splinting: a systematic approach to the selection of elastic traction.
Elastic traction is an important but occasionally misapplied component of upper-extremity dynamic splints. Information regarding a systematic approach for selection of elastic traction has been limited. A biomechanical analysis of dynamic splinting methods was done to identify factors that might help educate therapists in the proper application of elastic traction. Material properties of elastic traction were measured with a mechanical testing system capable of accurately identifying physical properties of various substances. Results of this analysis indicated that specific spring constant values for clinically used bands ranged from 134 to 531 g, original length values ranged from 0.7 to 3.2 in., the consistency of bands labeled as identical by the manufacturer was generally very good, and each band's ability to maintain its material properties with repeated elongation was similar from band to band and showed gradual diminution after several hundred repetitions. These data were combined with theoretical constructs of splint fabrication to devise a simple and logical method for analysis and determination of elastic traction requirements for various diagnostic applications. A goniometer, ruler, and spring scale are the only tools necessary to perform the analysis. Simple charts depicting forces and moments provide identification of the appropriate rubber band for application.
Arthritis, Rheumatoid↗
Forces in the normal and abnormal hand.
An analytic model for human hand force analysis was developed through anatomical study and measurement of multiple cadaveric specimens. A method of solution was developed to determine muscle and joint force distributions under various isometric hand functions. Applications of this model to abnormal conditions include studying the effects of tendon laceration, neuromuscular weakness, and surgical restoration by tendon transfer. Limitations and further applications of the model are discussed in detail.
Biomechanical Phenomena↗
Elbow joint contact study: comparison of techniques.
Elucidation of the contact areas between joint surfaces is important to both prosthetic design and the understanding of degeneration of articular cartilage. Numerous experimental methods are available to study joint contact, including cartilage staining, joint space casting, and pressure sensitive film techniques. This study attempts to compare the ability of each experimental technique to determine elbow joint contact. The silicone casting technique appears to be the best method to study joint contact area. The effects of magnitude and orientation of applied forces on the elbow joint contact patterns are studied.
Coloring Agents↗
Electromyographic analysis of the thumb: a study of isometric forces in pinch and grasp.
An electromyographic study of thumb muscles was performed on eight subjects by means of integrated polyelectromyography and simultaneous recordings of isometric flexion-extension, abduction-adduction, and prehensile pinch and grasp of the thumb. The integrated electromyographic signal proved to be an excellent index of thumb muscle activity, with a linear relationship found at low to middle levels of muscle strength. To facilitate understanding of thumb function, thumb muscles can be classified as primary or secondary on the basis of electrical potential activity. In isometric flexion, the flexor pollicis longus (FPL) was primary, whereas in extension, the extensor pollicis longus (EPL) and abductor pollicis longus were primary. In adduction, the adductor pollicis and EPL were primary and the FPL was secondary. In abduction, the abductor pollicis brevis and opponens pollicis were primary. The adductor pollicis, and FPL were nearly equal during pinch and grasp, with significant electrical activity increasing with greater force requirements. The first dorsal interosseous and EPL contributed secondarily in both pinch and grasp. When surgeons consider tendon transfers for nonfunctioning thumb muscles, the primary muscles should be replaced first to best restore pinch and grasp strength.
Biomechanical Phenomena↗
Ligament stability of the metacarpophalangeal joint: a biomechanical study.
Capsuloligamentous contributions to metacarpophalangeal joint stability were obtained from load-displacement tests on the joints of 15 human cadavers. The contribution of each ligament to joint stability was obtained by measuring the reduction of load that induced a given joint displacement after sequential ligamentous sectioning. Four modes of joint displacement were examined: distal distraction, dorsopalmar dislocation, abduction-adduction rotations, and supination-pronation rotations. This study demonstrated that both radial and ulnar collateral ligaments play primary roles in stabilizing the metacarpophalangeal joint in all four modes of joint displacement. The accessory collateral ligaments contribute primarily to abduction-adduction rotational stability, but contribute little to stabilizing dorsopalmar dislocation or axial (supination-pronation) rotations. The palmar plate prevents dorsal dislocation only at full extension. The dorsal capsule has a moderate contribution to stability in distraction and supination-pronation rotations.
Adult↗
Rupture of the distal tendon of the biceps brachii. A biomechanical study.
In biomechanical studies on ten patients who had had a rupture of the distal tendon of the biceps brachii, we compared the results of immediate anatomical reattachment, delayed reattachment, and conservative treatment. When the tendon was simply attached to the brachialis muscle (one patient), there was nearly normal strength in elbow flexion but about 50 per cent loss of forearm supination. Late reinsertion (one patient) improved strength of both flexion and supination, but not to normal. Immediate reattachment (four patients) restored normal strength in flexion and supination at one year but not at four months (one patient). With conservative treatment (three patients) there was a mean loss of 40 per cent of supination strength and variable loss of flexion strength, averaging 30 per cent. These data suggest that immediate surgical reinsertion of the biceps tendon into the radial tuberosity, compared with other modes of treatment, restores more strength of flexion and supination.
Adult↗
Functional anatomy of the ligaments of the elbow.
Dissections of 10 fresh cadaver specimens revealed an important insertion of the posterior portion of the lateral collateral ligament to the ulna at the crista supinatoris. The humeral origin of the medial ligament attachments was found to lie posterior to the axis of elbow flexion; in this position a cam effect is created so that ligament tension varies with elbow flexion. The three-dimensional distance between the origin and the insertion of the anterior portion of the medial collateral ligament was found to increase slightly from extension to approximately 60 degrees of flexion; thereafter, it remained nearly constant. The distance of the posterior portion increased by about 9 mm from 60 degrees to 120 degrees of flexion. The flexion axis was shown to pass through the origin of the lateral collateral ligament, so the length of this structure was not changed during elbow flexion.
Aged↗
Ligamentous structures of the metacarpophalangeal joint: a quantitative anatomic study.
The ligamentous structure of the metacarpophalangeal (MCP) joint of the index finger in human cadavers was studied by gross examination and quantitative measurement. Anatomically, the collateral ligament is separable into two layers, with the precise origin arising from the metacarpal head and inserting on the proximal phalanx. Quantitatively, the change in length of the collateral ligament was studied with biplanar radiographic techniques. The distance between the origin and insertion of the collateral ligament changed in different portions of the ligament when the joint was moved from a position of hyperextension to that of flexion. When the MCP joint was flexed from 0 degree to 80 degrees, the dorsal portions of both the radial and ulnar collateral ligaments were lengthened (3-4 mm). The middle portions of both ligaments were slightly elongated (0.4-1.0 mm), and the volar portions of the ligaments were shortened (1-2 mm). When the MCP joint extended into hyperextension, the dorsal portions of the ligaments shortened 2-3 mm, the middle thirds of the ligaments shortened slightly, and the volar thirds of the ligaments lengthened. The results of this study suggest that the dorsal and volar portions of the collateral ligament provide MCP joint constraint at the flexed and extended positions, respectively.
Biomechanical Phenomena↗
Carrying angle of the human elbow joint.
Previous elbow kinematic studies have created some controversy because of conflicting and contradictory results. The lack of consistent results may be traced to the limitations and definitions of the specific measurement techniques, as well as individual variations in the specimens. To resolve this issue, a rigorous theoretical analysis of elbow kinematics was performed based on available anatomic and geometric data of the skeleton with consideration of anthropometric variations. Three definitions have been adopted previously for the measurement of the carrying angle of the elbow joint. The relationships of these three definitions of the carrying angle as a function of the elbow joint flexion angle were evaluated. Clinically, the dynamic change of carrying angle may have little practical significance. However, the variation is reflected in differences in design criteria of the resurfacing and semiconstrained elbow replacement implants.
Anthropometry↗
Kinematic analysis of human movement.
Understanding the kinematics of human movement is of both a basic and an applied value in medicine and biology. Motion measurement can be used to evaluate functional performance of limbs under normal and abnormal conditions. Kinematic knowledge is also essential for proper diagnosis and surgical treatment of joint disease and the design of prosthetic devices to restore function. In general, kinematic analysis of human movement can be categorized into two main areas: 1) Gross movement of the limb segments interconnected by joints, where the relative three-dimensional joint rotation is described by adopting the Eulerian angle system. With proper selection of axes of rotation between two bone segments, the associated finite rotation is sequence independent. This concept is particularly useful, since it matches precisely the clinical definition of joint motion. 2) Detailed analysis of joint articulating surface motion, where generalized three-dimensional, unconstrained rotation and translation are described utilizing the concept of the screw displacement axis. Knowing the surface geometry and soft-tissue constraints, the movement of an articulating joint can be analyzed to provide basic information for lubrication and wear studies. In addition, with appropriate numerical differentiation, velocity and acceleration can be obtained from the displacement information described by the above two methods. Currently available measurement techniques of human movement can be classified into three categories: 1) electrical linkage methods; 2) stereometric methods and biplanar roentgenographic methods; and 3) accelerometric methods. Each system has its unique advantages and limitations in terms of the operational principle, instruments required, data reduction, and type of information produced. Representative analyses of human upper and lower extremity movement will be included as illustrative examples.
Biomechanical Phenomena↗
Opposition of the thumb: an anatomic and biomechanical study of tendon transfers.
Tendon transfers for opposition of the thumb were anatomically and biomechanically studied to help determine the optimal criteria for selecting the best motor unit for a transfer. Forearm and hand muscle volume, mean fiber length, and cross-sectional area were measured in eight fresh specimens of the upper extremity to determine which muscles best replace lost thenar muscle strength. In a separate group of 18 specimens, the effective moment arms for abduction and flexion of the first metacarpal were calculated in vitro and from biplanar radiographic techniques to determine the effect of eight different opposition transfers on thumb abduction, rotation, and strength. Results of these studies demonstrate that the transfers of flexor digitorum superficialis (FDS) of the long finger and extensor carpi ulnaris best replaced lost thenar muscle strength and provided maximal abduction and near full thumb rotation. The transfers of the extensor carpi radialis longus and the FDS of the ring finger replaced 60% and 40% of required thenar muscle strength, respectively. The palmaris longus was the least effective transfer, having good abduction but weak flexion and opposition. Motion, balance, and strength of tendon transfers must be considered for effective thumb opposition.
Forearm↗
Determination of muscle orientations and moment arms.
In muscle force analysis, orientations and moment arms of the muscles about a joint provide essential coefficients in the equilibrium equations. For the determination of these parameters, several experimental techniques, including geometric measurement, tendon-joint displacement measurement and direct load measurement, are available. Advantages and disadvantages associated with each of the techniques are reviewed and compared based on our extensive experience.
Arm↗