Biomedical subjects

K N An

Publications and source records attributed to K N An.

At least 19 recordsLinked to original sources

PubMed1992

Biochemically discrete zones of canine flexor tendon: evaluation of properties with a new photographic method.

We describe a photographic method that we have found useful for studying small strain fields within a larger zone of interest. We have used this method to document differences in material properties which correlate with zones of different biochemical makeup in the canine flexor digitorum profundus tendon. This method may be useful in analysis of experimental injury and wound healing in this model and may have application in evaluating material properties of soft tissue in other models as well.

Animals↗

PubMed1992

Origin of the medial ulnar collateral ligament.

The anatomic features of the origin of the anterior medial collateral ligament of the elbow were studied in 10 cadaver elbows to determine the percentage of the medial epicondyle that can be removed without violating the ligament, and whether or not this ligament attaches to the condyle as well as to the epicondyle. In all specimens the anterior medial collateral ligament originated exclusively from the anteroinferior surface of medial epicondyle and had no attachment to the condyle. Only 20% of the width of the medial epicondyle in the coronal plane can be removed without violating a portion of the origin of the anterior medial collateral ligament, an essential stabilizer of the elbow. Excision of the entire epicondyle for ulnar neuropathy would completely detach this ligament from its origin and might therefore potentiate instability. Since the ligament originates on the anteroinferior surface of the epicondyle, more bone can be removed with less violation of the anterior medial collateral ligament origin if the plane of the osteotomy lies between the sagittal and coronal planes.

Cadaver↗

PubMed1992

The relationship between wrist position, grasp size, and grip strength.

In the first part of this study, the position assumed by a normal wrist during unconstrained maximal grip and the relationship between wrist position and grip strength were investigated in 20 healthy subjects. Grip strength and wrist position were recorded in the self-selected position and then again while the subjects voluntarily deviated the wrist randomly into flexion, extension, or radial or ulnar deviation of 10 to 15 degrees. The self-selected position was 35 degrees of extension and 7 degrees of ulnar deviation. Grip strength was significantly less in any position of deviation from this self-selected position, even after accounting for fatigue. With the wrist in only 15 degrees of extension or in neutral radio-ulnar deviation, grip strength was reduced to two thirds to three fourths of normal. Sex did not affect wrist position. The dominant wrists were within 5 degrees of the nondominant ones but were relatively less extended and in more ulnar deviation. Grip strength is significantly reduced when wrist position deviates from this self-selected optimum position. In the second part of the study, the effect of grasp size on this self-selected position was studied in 21 subjects. The degree of wrist extension was inversely and linearly related to how large a setting on the Jamar dynamometer was used. This was true regardless of hand size, although the effect was more significant for smaller hands. Radial and ulnar deviations were not affected by handle position. A minimum of 25 degrees of wrist extension was required for optimum grip strength.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1992

Changes in wrist and forearm configuration with grasp and isometric contraction of elbow flexors.

The purpose of this study was to determine the changes in wrist and forearm configuration with grasp and elbow flexor contraction by analysis of resting and grasping x-ray films of 15 normal adults and forearm scanograms of 10 other normal subjects. With grasp, a significant proximal migration of the radius (averaging 0.9 mm), a decrease in the carpal height ratio, and an increase in the lunate uncovering index were observed. With flexor contraction, there was a significant decrease in the forearm interosseous space.

Adult↗

PubMed1992

Comparative flexor tendon excursion after passive mobilization: an in vitro study.

Two experimental studies were conducted to investigate flexor tendon excursions. In the first study, tendon excursions due to passive joint motion in various loading condition were evaluated. In the second study, the efficacy of a new technique that used synergistic wrist motion (S-splint) was compared with the traditional dorsal splinting methods: the Kleinert splint (K-splint) and the Brooke Army Hospital/Walter Reed modified Kleinert splint with a palmar bar (P-splint). The results of these studies question the anticipated tendon excursion associated with postoperative splinting. They demonstrated that the measured tendon excursion under a condition of low tendon tension was almost half that of theoretically predicted values. In zone II, the magnitude of excursion introduced by the three mobilization methods were in descending order: S-splint, P-splint, K-splint (p less than 0.05). Differential tendon excursion between the flexor digitorum profundus and the flexor digitorum superficialis had a mean value of 3 mm and was not significantly different among the three methods. Passive proximal interphalangeal joint motion was the most effective means of providing increased amplitude of tendon gliding in zone II. Passive distal interphalangeal joint motion did not increase excursion in zone II as much as had been predicted.

Cadaver↗

PubMed1992

Flexor tendon forces: in vivo measurements.

S-shaped force transducers were developed for measurement of the forces along intact tendons. After calibration, the transducers were applied to the flexor pollicis longus and flexor digitorum superficialis and profundus tendons of the index finger in five patients operated on for treatment of carpal tunnel syndrome. The tendon forces generated during passive and active motion of the wrist and fingers were recorded. For pinch function, the amount of the applied load was measured with a special pinch meter. Tendon forces in the range of 0.1 to 0.6 kgf were measured during passive mobilization of the wrist. Tendon forces up to 0.9 kgf were present during passive mobilization of the fingers. Tendon forces up to 3.5 kgf were present during active unresisted finger motion. Tendon forces up to 12.0 kgf were recorded during tip pinch, with a mean applied pinch force of 3.5 kgf. These results have potential application in determining the amount of force that a tendon repair would have to resist during passive as well as active postsurgical mobilizations.

Carpal Tunnel Syndrome↗

PubMed1992

Force distribution across wrist joint: application of pressure-sensitive conductive rubber.

A new pressure-sensitive conductive rubber sensor was used for investigation of the pressure distribution through the radio-ulno-carpal joint. Twelve of these transducers were placed in the radio-ulno-carpal joint. Pressure was measured in seven different wrist positions under loads incrementally increasing from 0 to 12 kg. Half of the sensors showed less than 0.5 MPa, even at maximum load, while a high-pressure area was located palmary in each fossa. The peak pressure measured in the wrist neutral position was 2.4 MPa on the scaphoid fossa, 1.5 MPa on the lunate fossa, and 1.1 MPa on the triangular fibrocartilage with a 10 kg load. The peak pressure ratio between the scaphoid and the lunate was 1.7 in the neutral wrist position. This increased in radial deviation to 2.9 and decreased in ulnar deviation to 0.8. The force-transmission ratio was 50% through the scaphoid fossa, 35% through the lunate fossa, and 15% through the triangular fibrocartilage in the neutral position. The advantage of this sensor is that it is thin and flexible and provides reliable reproducible quasi-instantaneous measurements.

Biophysical Phenomena↗

PubMed1992

Healing of canine tendon in zones subjected to different mechanical forces.

The effect of external force environment on the healing of a partial thickness injury to canine flexor tendon was studied. A 50% laceration was made in either the fibrocartilaginous (compressive) zone or in the tendinous (tensile) zone of canine flexor digitorum profundus tendons. After three or six weeks, the tendons were harvested. An optical method for determining zone-specific material properties showed that, in response to injury, the structural stiffness decreased in the tensile zone of the tendon but increased in the compressive zone. The mechanical properties and failure mechanism of canine tendon and their changes in response to injury vary according to tendon zone, and differences in the healing process in mechanically specialised zones of the flexor tendon are discussed.

Animals↗

PubMed1992

Kinematics of semi-constrained total elbow arthroplasty.

We used 11 cadaver elbows and a three-dimensional electromagnetic tracking device to record elbow movements before and after implantation of a 'loose-hinged' elbow prosthesis (modified Coonrad). During simulated active motion there was a maximum of 2.7 degrees (+/- 1.5 degrees) varus/valgus laxity in the cadaver joints. This increased slightly after total elbow arthroplasty to 3.8 degrees (+/- 1.4 degrees). These values are lower than those recorded for the cadaver joints and for the prostheses at the limits of their varus/valgus displacements, indicating that both behave as 'semi-constrained' joints under physiological conditions. They suggest that the muscles absorb some of the forces and moments that in a constrained prosthesis would be transferred to the prosthesis-bone interface.

Biomechanical Phenomena↗

PubMed1992

A normal data base of posteroanterior roentgenographic measurements of the wrist.

In 120 adults, we measured the dominant wrist on posteroanterior roentgenograms in order to determine the normal dimensions and variations according to age and sex. Men and women were equally represented as were two age-groups (twenty-five to forty years and forty-one to sixty years). The roentgenograms were made, with standard exposure and development techniques, with the wrist and forearm in a neutral position and the x-ray tube aligned vertical to the radial styloid. The roentgenogram that was made with the wrist in the mid-coronal plane was digitized and was used to measure distances between specified landmarks. The mean ulnar variance was -0.9 millimeter (normal range, -4.2 to 2.3 millimeters). The average carpal height ratio was 53 per cent (normal range, 46 to 61 per cent). The mean radial inclination was 24 degrees (range, 19 to 29 degrees). The carpal-radial and carpal-ulnar ratios were smaller in women. The width of the distal radio-ulnar joint was reduced in the older subjects. There was a significant positive relationship (p < 0.0001) between the maximum force reached and the length of the third metacarpal. We believe that information concerning the normal roentgenographic measurements and relationship between the bones of the wrist can be used (1) to follow the progression of carpal instabilities, osteonecrosis, osteoarthrosis, or rheumatoid arthritis; (2) in clinical research; and (3) in the design of wrist implants.

Aged↗

PubMed1992

Compensatory motion in the upper extremity after elbow arthrodesis.

Ten healthy male subjects were asked to complete a series of tasks that represent normal elbow function. They were then fitted with a custom adjustable brace that simulated elbow arthrodesis at 50 degrees, 70 degrees, 90 degrees, and 110 degrees flexion and asked to repeat the tasks. The 3 Space Isotrak system was used to measure shoulder motion; a triaxial wrist goniometer was used to measure wrist compensation; and all subjects were videotaped to qualitatively observe other compensatory motion. Unlike other joints, elbow arthrodesis at any angle results in a significant impairment, since the adjacent shoulder and wrist joints cannot compensate to allow completion of activities.

Activities of Daily Living↗

PubMed1992

Functional anatomy and biomechanics of the thumb.

The thumb is a mechanical unit consisting of strong ligaments and dynamic muscles, providing the resistance to the fingers and palm during pinch and grip. Each thumb joint has a mechanical equivalent that helps explain elements of thumb stability. The trapeziometacarpal joint is potentially the most unstable but has adapted to its unique position by special joint geometry and, in particular, a combination of support ligaments that permit a wide range of motion yet stability. New anatomic and mechanical studies demonstrate the key support structures that must be duplicated by reconstructive surgical procedures if thumb stability is to be maintained.

Biomechanical Phenomena↗

PubMed1992

Elbow subluxation and dislocation. A spectrum of instability.

After sequential releases of the ligaments and capsules of 13 fresh autopsy specimen elbows, external rotation and valgus moments with axial forces resulted in posterior dislocations in 12 of the 13 with the anterior medical collateral ligament (AMCL) intact. Kinematic displacements measured with a three-dimensional electromagnetic tracking device showed that dislocation involved posterolateral rotation of 34 degrees-50 degrees and 5 degrees-23 degrees valgus at about 80 degrees flexion. Dislocation is the final of three sequential stages of elbow instability resulting from posterolateral rotation, with soft-tissue disruption progressing from lateral to medial. In each stage, the pathoanatomy correlated with the pattern and degree of instability. Testing for valgus stability of the elbow during simulated active flexion revealed no significant increase (-0.3 degrees-2.4 degrees) in valgus laxity after reduction compared with the intact specimens (p greater than 0.05, beta = 0.1, delta = 2.5 degrees). In no case did the digitized AMCL origin-to-insertion distance increase beyond normal during the dislocation (p less than 0.01). The mechanism of dislocation during a fall on the outstretched hand would involve the body "rotating internally" on the elbow, which experiences an external rotation/valgus moment as it flexes. Posterior dislocations should therefore be reduced in supination. If valgus stability in pronation is demonstrated, the AMCL can be assumed to be intact, and rehabilitation in a hinged cast-brace with the elbow in full pronation can be commenced immediately.

Autopsy↗

PubMed1992

Intersegmental elbow joint load during pushup.

Intersegmental loading pattern on the elbow joint during a push-up exercise was investigated. Electromagnetic motion sensors and a piezoelectric force plate were used to simultaneously record upper extremity motion and forces on nine healthy male subjects during push-ups in six different hand positions. Peak axial forces exerted on the elbow joint averaged 45 percent of the body weight. Peak torque to produce elbow flexion was 2305.9 N-cm, or 56 percent of maximal isometric extensor torque. The results of this analysis give insight to the biomechanics of a normal elbow and to its load carrying capacity.

Adult↗

PubMed1991

Three-dimensional kinematics of glenohumeral elevation.

To help resolve longstanding uncertainties about kinematics of the shoulder, we studied three-dimensional glenohumeral joint motion during arm elevation. A magnetic tracking system was used to monitor the three-dimensional orientation of the humerus with respect to the scapula. Appropriate coordinate transformations were then performed for the calculation of glenohumeral joint rotation based on the defined Eulerian angle. The effects of the plane of elevation and the humeral rotation on the magnitude of arm elevation were documented. The maximum humeral elevation at the glenohumeral joint took place in a plane anterior to the scapular plane. Maximum elevation in all planes anterior to the scapular plane required external axial rotation of the humerus. Conversely, internal axial rotation was necessary for maximum elevation posterior to the scapular plane. Quantifying the obligatory axial rotation explains the relationship of internal and external rotation with maximum elevation.

Biomechanical Phenomena↗

PubMed1991

Correlation of physiological cross-sectional areas of muscle and tendon.

Muscle physiological cross-sectional area, as defined and measured by dividing the volume of the muscle by its fibre length, is proportional to the maximum strength of the muscle. It is one of the important parameters when considering muscle mechanics in sports science and, clinically in tendon transfer procedures. This study reports that tendon cross-sectional area correlated well with the physiological cross-sectional area of associated muscles.

Adult↗

PubMed1991

Physiological prediction of muscle forces--II. Application to isokinetic exercise.

The successful application of a physiological model of the musculoskeletal system capable of accounting for nonequilibrium dynamic loading and predicting individual muscle forces in the knee is presented. The model incorporates rigid-body mechanics and musculoskeletal physiology. Unknown muscle and joint contact forces outnumber the equilibrium equations resulting in an indeterminant problem. Mathematical optimization is utilized to resolve the indeterminacy. The model is used to estimate individual muscle forces during isokinetic exercise. Five subjects were tested at speeds of 60 degrees/s and 180 degrees/s. A newly proposed optimal criterion, minimizing muscular activation, results in muscle force predictions which have significantly higher correlations with myoelectric activity than other linear and nonlinear optimal criteria. The results demonstrate that properly constrained linear programming methods do not limit the number of active muscles and allow for uniform recruitment of the active muscles.

Adult↗

PubMed1991

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.

Activities of Daily Living↗