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Biomedical subjects

D A Sonstegard

Publications and source records attributed to D A Sonstegard.

16 recordsLinked to original sources
PubMed1983

The mechanical properties of human tibial trabecular bone as a function of metaphyseal location.

Experimental determination of the elastic modulus and ultimate strength of human tibial trabecular bone as a function of metaphyseal location is presented. A 1 cm cubic matrix with planes parallel to the subchondral plate was defined on five fresh frozen cadaver tibias. Approximately 400, 7 mm X 10 mm cylindrical bone plugs were cut from the locations defined by the matrix and tested in uniaxial compressive stress at a strain rate of 0.1%S-1. Results of the study indicate that the trabecular bone properties vary as much as two orders of magnitude from one location to another. As might be predicted from Wolff's law, and noted by previous investigators, concentrations of strength arise from the medial and lateral metaphyseal cortices toward the major medial and lateral contact regions. These results may be valuable for improved analytical modeling and optimal prosthetic design.

Aged↗
PubMed1982

The effect on supination-pronation of angular malalignment of fractures of both bones of the forearm.

UNLABELLED: Ten fresh human upper-extremity cadaver specimens were tested for the effect of residual angulation from simulated fractures of both bones of the forearm on the potential for range of rotation of the forearm and for limitations of pronation and supination specifically. Ten and 20-degree angulations for the radius and ulna, such as might be encountered in all reasonable clinical situations, were tested. Little significant loss of forearm rotation resulted from angulations of 10 degrees in any direction. With 20 degrees of angulation, there was statistically significant and functionally important loss of forearm rotation. CLINICAL RELEVANCE: A residual angulation of 10 degrees in mid-shaft fractures of the radius, ulna, or both bones of the forearm will not limit forearm rotation anatomically. Loss in the range of rotation can be expected with residual angeles of 20 degrees or more.

Forearm↗
PubMed1977

The effect of biopsy-hole shape and size on bone strength.

Investigation in cadaver femora of the relationship between the shape or size of a hole made in the cortex and the breaking strength of the bone revealed that of the shapes studied, an oblong hole with rounded ends afforded the greatest residual strength. Furthermore, we found that increasing the width of the hole caused a significant reduction in strength, while increasing the length did not.

Biopsy↗
PubMed1977

The spherocentric knee: biomechanical testing and clinical trial.

The spherocentric knee is a non-hinged, intrinsically stable knee-joint prosthesis which allows controlled triaxial rotation and was designed specifically for use in severely deformed or grossly unstable knees. Biomechanical evaluation of the prosthesis implanted in fresh human cadaver limbs demonstrated highly favorable motion, stability, strength, deflection, and energy absorption characterists for the spherocentric prosthesis-bone assembly as compared with control cadaver knees. After an average follow-up of 25.5 months after the first twenty-five spherocentric arthroplasties, the clinical results were highly satisfactory and suggested that the spherocentric knee may be relatively resistant to the problems of wear debris, loosening, and breakage which have plagued other intrinsically stable knee-joint prostheses.

Aged↗
PubMed1977

Carpal tunnel syndrome: contribution of flexor tendons.

Tension in flexor tendons during wrist flexion may play a role in otherwise unexplained instances of the carpal tunnel syndrome. As the wrist is flexed, the median nerve in the tunnel bends around the taut flexor retinaculum. At the same time, the nerve is subject to compression against this ligament by tensed overlying flexor tendons that also bend around the ligament. Experimental data to support this possibility have been collected from cadaver hands. A pressure transducer has been substituted for the median nerve in the tunnel and registered sizable pressures when tension was applied to the flexor digitorum profundus tendons of the second and third digits during varying degrees of wrist flexion. If the profundus tendons are not tensed, pressure in the tunnel remains negligible until wrist flexion reaches its extreme. Thus, repetitive hand activities involving pinch or grasp during wrist flexion may be a contributing factor in some instances of the carpal tunnel syndrome.

Biomechanical Phenomena↗
PubMed1975

Experimental fixation of fractures of the femur with methylmethacrylate.

Use of a simple method for injection of cooled methylmethacrylate into the distal part of the femur through the canal of a Küntscher rod to stabilize distal femoral-shaft fractures proved experimentally to greatly increase the torsional stability at the fracture site. This method may allow rapid ambulation of debilitated patients and prevent the complications of extended bed rest.

Biomechanical Phenomena↗
PubMed1975

Rotational control of unstable subcapital fractures. An experimental study.

An experimental evaluation of the stability of rotational fixation of unstable, subcapital femoral-neck fractures as provided by either the multiple pin and side-plated Deyerle device or the heavy duty Jewett triflanged nail showed no significant difference between the two devices. The determination of moment versus deformation behavior included study of two torsional axis orientations and superposition of simulated body-weight and muscular-force impaction loadings.

Body Weight↗