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Biomedical subjects

K K Firoozbakhsh

Publications and source records attributed to K K Firoozbakhsh.

8 recordsLinked to original sources
PubMed1996

Internal fixation of oblique metacarpal fractures. A biomechanical evaluation by impact loading.

Internal fixation of oblique metacarpal fractures was studied in a cadaver model by impact loading. One hundred twenty fresh-frozen human metacarpals underwent compressive and bending impacts after oblique osteotomy and internal fixation. Dorsal plating with lag screws, 2 dorsal lag screws (2-screws), crossed Kirschner wire tension band (crossed K-wire), 5 stacked intramedullary Kirschner wire (5-rod), and paired intramedullary Kirschner wire (2-rod) were used. The failure occurred within 6 msec in the compressive impact and was almost immediate in the bending impact. The dorsal plate and the intramedullary rod fixations were the strongest and were not significantly different from the intact specimens in compressive impact; they were, however, 19% weaker in bending impact. The 2-screws was the weakest fixation in this group. This fixation was 59% weaker in compressive impact and 47% weaker in bending impact compared with the dorsal plating.

Biomechanical Phenomena↗
PubMed1996

Staple leg profile influence on pullout strength: a biomechanical study.

Bone staples have widespread applicability in orthopaedic surgery. Their use, however, is limited by inconsistent quality of fixation. Prior studies have shown potential for improvement in the reliability of staple fixation through a change in the design of the staple legs. To identify a superior leg cross section profile, pullout strength of 5 different newly designed staple leg cross sections were evaluated in fresh frozen human cadaveric bones before and after toggle loading. The tests were repeated in a synthetic bone model with variable but consistent densities. The curvilinear square profile had the highest pullout strength in both the cadaveric and synthetic bone, followed in descending order by square, circular, and triangular profiles. Controlling for density, the pullout strength of the curvilinear square profile was 8% higher than the square profile and 34% higher than the circular profile. The triangular profiles had the least resistance to pullout force before and after cyclic loading. The curvilinear square may be the best profile for the cross section of the staple leg for maximum pullout strength and may expand the clinical use of staples in bone fixation.

Adult↗
PubMed1994

Plain radiographic interpretation in trimalleolar ankle fractures poorly assesses posterior fragment size.

Twenty-five patients with trimalleolar ankle fractures were evaluated using both conventional radiography and computed tomography (CT) to determine the size of the posterior fragment along with other fracture characteristics. Plain radiograph measurements indicated very poor inter- and intraexaminer reliability. When compared to the CT scan measurement, 54% of the plain radiographic readings revealed > 25% error. Plain radiographic interpretations erred in most cases by overrating the size of the fragment, but major underestimations also occurred. The larger size fragments showed more error than the smaller ones. This information confirms our clinical suspicion that the lateral radiograph is unreliable in assessing the posterior fragment size.

Ankle Injuries↗
PubMed1993

Comparative fatigue strengths and stabilities of metacarpal internal fixation techniques.

To study quantitative differences in the fatigue strength and stability obtained with 5 types of internal fixation of metacarpal fractures, 105 preserved human metacarpals were cyclically tested in bending, torsion, and axial loading after oblique osteotomies of the metacarpal and internal fixation. The dorsal plate with lag screw was superior in all modes, followed by the two dorsal lag screws, crossed Kirschner wire tension banding, and intramedullary Kirschner wire fixation. The five intramedullary and the paired intramedullary Kirschner wire fixations were not statistically different. The fatigue life of the plate fixation was significantly larger in bending (1.5 times), torsion (1.6 times), and axial loading (2.5 times) than the second strongest fixation, two dorsal lag screws. Its initial rigidity was significantly higher in axial loading (1.5 times) but was not statistically different in bending and torsion.

Fracture Fixation, Internal↗
PubMed1993

Isokinetic dynamometric technique for spasticity assessment.

This study was conducted to determine the feasibility of quantifying spasticity by measuring the resistance to passive movement using an isokinetic dynamometer. A quantifiable method was developed by determining the summation of the four consecutive resisting torque amplitudes during flexion and extension of the knee at specified speeds and range of motion. A more rigorous assessment was made by finding the slope of the linear regression curve of torque-velocity data. Although the values of maximum torque were higher in the spastic group than in the normal group, the difference was statistically significant only when the sum of the torque amplitudes was considered (P < 0.0028). Values of the maximum torque as well as the sum of the torque amplitudes increased in a linear fashion (r > 0.75) with increasing velocity. The slopes of the torque-velocity curves were greater in spastic subjects than in normal subjects. The sensitivity to the rate of stretch was statistically greater (P < 0.0004) for the spastic group than normals only when the sum of torque amplitudes was considered. The corresponding data obtained during the flexion and extension of the knee were not statistically different (P > 0.05). Serial summation of torque amplitudes and measurement of slope in the torque-velocity curve are sensitive and repeatable methodologies for the measurement of spasticity assessment.

Adult↗
PubMed1992

Pullout strength of power- and hand-driven staples in synthetic bone: effect of design parameters.

The pullout strength of power-driven and hand-driven staples of different sizes and different leg profiles was investigated in a synthetic bone model. Consistent material properties were reflected in the relatively small standard deviation in pullout strength, which was less than 7% of the mean value for power-driven and less than 10% of the mean value for hand-driven staples. An approximate linear relationship was shown to exist between the mean value of pullout strength and foam density. In paired studies, the mean value of pullout strength was significantly (p less than 0.0005) greater for the power-driven staples than similar size hand-driven staples. It was also shown that a square cross section creates significantly (p less than 0.017) more resistance to pullout force than a circular section of similar or even larger area. Although the pullout strength was not a function of the staple's width, the staple's leg length contributed to its pullout strength in a nonlinear fashion. This study suggests that narrow, long, power-driven staples of rectangular cross section have the best pullout strength for similar cross-sectional area.

Bone Density↗