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Biomedical subjects

K N An

Publications and source records attributed to K N An.

At least 289 records · Page 16Linked to original sources
PubMed1984

Determination of muscle and joint forces: a new technique to solve the indeterminate problem.

Analytic determination of muscle force across human joints encounters an indeterminate problem. A new optimization approach, based on minimizing the upper bound of muscle stress, is introduced to obtain a unique solution. Mathematical and physiological justification of this new approach distinguishes it from previously described methods. A complex joint, the elbow, was studied. The results of muscle forces in resisting the elbow flexion moment were obtained and compared with electromyographic observation, as well as with solution from other optimizing techniques. The resultant humero-ulnar joint forces at various elbow joint positions are calculated. In normal daily activities, resultant joint forces of 0.3-0.5 times body weight are commonly encountered.

Biomechanical Phenomena↗
PubMed1984

Reliability of isometric strength testing. Temporal factors and strength variation.

Isometric strength measurements of grip, pronation, supination, and elbow extension and flexion on dominant and nondominant sides were made on 40 normal subjects (age range, 40-70 years) to investigate the variability of isometric strength at different times of the day. Statistically significant differences were found in certain pronation, supination, and grip comparisons. No statistically significant difference was found in extension and flexion. Although significant, the absolute change in strength at different times of the day was small and showed no consistent trend. On the basis of these data, it appears that this variation can probably not be routinely detected in the normal clinical setting. However, the study further defines the reliability of isometric strength testing and should be considered in further attempts at more accurate measurement of elbow function. The small variations of strength, approximately 5%, that can be measured universally with sensitive testing equipment, are clinically relevant. However, when attempting to determine an impairment state in order not to place too much importance on small differences, care should be exercised in interpreting strength measurements. This investigation demonstrates how the application of sophisticated biomechanical techniques may be employed to provide useful objective information in the difficult clinical area of disability assessment. Disability judgments may be made more accurate as more is learned of the normal variables influencing objective measurement.

Adult↗
PubMed1983

Tendon excursion and moment arm of index finger muscles.

Tendon excursions during rotation of individual index finger were recorded continuously throughout the joints' ranges of motion. Both intrinsic and extrinsic muscles were studied during flexion--extension and abduction--adduction functions. Excursions and joint-displacement relationships were observed to not always be linear. Moment arms of tendons with respect to joint centers were further derived from excursion data. The significance of this information to tendon transfer techniques is discussed. These data are also important for theoretical modeling in muscle force determination.

Biomechanical Phenomena↗
PubMed1983

Objective evaluation of hand function in scleroderma patients to assess effectiveness of physical therapy.

A system was developed to evaluate the hand function of patients with scleroderma objectively in terms of joint contracture, range of movement, dexterity, strength, and skin compliance. Twelve patients with progressive systemic sclerosis were evaluated using this technique to determine the effectiveness of classic physical therapy methods. A statistically significant improvement in hand function was found after a single physical therapy treatment. This conservative mode of treatment may contribute to improved hand function in patients with scleroderma.

Biomechanical Phenomena↗
PubMed1982

Rigidity and stress analyses of external fracture fixation devices--a theoretical approach.

The rigidity and stresses in external fracture fixation devices were studied by means of the finite element method. Different geometries and material parameters were simulated using a beam element model. Axial, bending and torsional loads were applied through the bone ends and the displacement obtained at the fracture sites was used to calculate the fracture fixation stiffness. The key parameters which increased fixation rigidity were identified. High pin stresses were predicted under certain application conditions. Possible clinical implications for the use of such apparatus are discussed in the light of bone fracture healing. The present results are expected to have a significant impact on future design modifications and clinical applications of this popular instrument in orthopedic surgery and traumatology.

Biomechanical Phenomena↗
PubMed1981

A comparison of the effect of open intramedullary nailing and compression-plate fixation on fracture-site blood flow and fracture union.

UNLABELLED: We compared the effects of compression-plating and open intramedullary nailing after reaming on the vascular supply to a standard fracture site, on the rate of fracture union, and on the biomechanical quality of bone after union, and on the biomechanical quality of bone after union in dogs. The proper location of a compression plate in relation to the periosteum also was investigated. Bone blood flow reached higher levels and remained elevated longer in fractures that were fixed with a rod than in those fixed with a plate. Rod-fixed fractures healed by periosteal callus, whereas plate-fixed fractures healed by endosteal callus. The fracture gained mechanical strength more slowly in the rod-fixed group than in the plate-fixed group. Subperiosteal or extraperiosteal placement of a plate revealed similar effects on bone-healing. CLINICAL RELEVANCE: Decisions to use intramedullary rods or compression plates for internal fixation of fractures should be based on knowledge of the biological effects of these procedures on blood flow at the fracture site and on the mechanical strength of the healing fracture. This study defines in quantitative terms the advantages and disadvantages of intramedullary rods compared with compression plates in the internal fixation of fractures.

Animals↗
PubMed1980

Standardization of a polyurethane elastomer for facial prostheses.

This study has shown that the polyester urethane elastomers are soft and flexible, characteristics which are desirable for simulating soft facial tissue. In addition, this material was found to have a larger resistance-to-tear when compared with othe materials. The physical and mechanical properties are very sensitive to the composition and the amount of catalyst added. Less influence on the elastomer properties was noticed for the range of temperatures at which it was polymerized. The range of curing time used in this study shows no significant statistical difference on the elastomer properties. Future studies will be directed toward the polymerization of the material at a wider range of times and temperatures to determine the effects at the low and high ends of the range.

Chemical Phenomena↗
PubMed1980

Electrogoniometer for the measurement of human elbow joint rotation.

Since the electrogoniometric method has been justified for the measurement of lower extremity joint motion, a similar device is developed for the measurement of elbow joint and forearm rotations. In this design, the axis of forearm rotation coincides with the anatomical axis which eliminates the cross talk existing in the regular triaxial goniometer. Although the axis of abduction-adduction is still offset from the elbow joint, special linkage arrangement was used to obtain equivalent motion. Experimental method was used to validate the accuracy of the device and model simulation was performed to emphasize the importance of accurate placement of the instrument on test subjects. Application of the present apparatus to normal subjects was studied to illustrate the range of elbow motion required in performing normal activities of daily living. This device is currently used in the functional evaluation of patients with elbow and forearm problems.

Activities of Daily Living↗
PubMed1980

Hand strength measurement instruments.

A set of instruments based on strain-gage application has been designed for hand strength measurement. The reduction in size, variation in position, and ease of calibration offer a wide range of functional evaluation without causing discomfort to the subjects being examined. The strength during the entire period of functional activity can be continuously monitored. The measurement signal from the device in analogue form makes computer-aided strength evaluation possible. Above all, the construction of the devices also allows easy adaptation to different hand deformities. The instruments can be useful tools for both research and clinical evaluation.

Hand Deformities, Acquired↗
PubMed1978

Physical and mechanical behavior of polyurethane elastomer formulations used for facial prostheses.

The initial results of this study of the physical and mechanical behavior of polyurethanes used for facial prostheses are presented. The parameters studied were surface hardness, modulus of elasticity (M), strength (S), percentage of elongation, and S/M ratio. Results showed that the physical and mechanical behavior of the polyurethanes can be altered by variations in the basic composition of the material accomplished through changes in the ratio of Part A to Part B and by the addition of catalysts. Properties of compositions with low quantities of Part B (isocyanate) and no catalyst reached or approximated those parameters proposed as ideal goals to simulate living tissue. When preparing polyurethane material, proper mixing is essential to avoid entrapment of air and phase separation of the catalyst. These conditions, which may render the prostheses less durable, are masked by the addition of colorants in the prearation of a sample for clinical application.

Chemical Phenomena↗
PubMedDate not supplied

Distal upper extremity function following proximal humeral resection and reconstruction for tumors: contralateral comparison.

BACKGROUND: Most functional analyses after limb salvage operations about the shoulder have focused on proximal function with the assumption that distal function is largely unaffected. This analysis examines distal function objectively. METHODS: Objective laboratory data regarding distal upper extremity strength after reconstructive procedures for tumors near the shoulder joint was collected over a 16-year period. Thirty-two patients were able to participate fully in the data collection at an average most recent follow-up duration of > 3.5 years. RESULTS: Statistically significant reductions on the involved side compared with the uninvolved side in grip, forearm pronation, forearm supination, elbow flexion, and elbow extension strength were documented (p < 0.05). The magnitude of reduction in strength diminishes distally, with the greatest effect in this group of patients being observed in elbow extension, followed by elbow flexion, forearm supination, and forearm pronation. Grip strength consistently showed the least amount of strength reduction compared with the uninvolved side, even within resection and reconstruction groups. Subjective patient rating of dexterity was no less than 3 of 5. Ninety percent of patients rated their dexterity 4 of 5 (52%) or 5 of 5 (38%). CONCLUSIONS: Despite the insistence of "normal" function in the distal upper extremity after limb salvage procedures, complete normality is not maintained. However, the degree of maintenance of distal function appears to be high, especially for grip strength and forearm pronation strength, and patient satisfaction is acceptable.

Adolescent↗