Integration of features in depictions as a function of size.
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Cues↗
Biomedical subjects
D L Butler
Publications and source records attributed to D L Butler.
Clinical significance of low levels of myeloperoxidase positivity in childhood acute nonlymphoblastic leukemia.
The clinical significance of a low percentage of myeloperoxidase-positive blast cells in childhood acute nonlymphoblastic leukemia was determined. Of 155 consecutive cases studied by cytochemical staining methods, 14 were characterized by 4% to 15% (median 6%) myeloperoxidase-positive blasts. All 14 cases showed reactivity to Sudan black B stain, and 7 had Auer rods. The morphological subtypes of leukemia were M1 (8 cases), M2 (3), M4 (1), and M5 (2). Immunological marker studies disclosed the lymphoid-associated T11 antigen on cells from 8 of the 11 cases tested. Other lymphoid-related findings in these 8 cases included the T3 antigen and E rosette formation in 1 case each. Among cases that were prospectively studied for the expression of lymphoid-associated markers, 6 of 8 with low levels of myeloperoxidase positivity compared with only 1 of 44 with higher levels (greater than 15%) possessed such features (P less than 0.001). We conclude that low levels of myeloperoxidase reactivity distinguish cases of acute leukemia in which the blast cells coexpress lymphoid (T11 antigen) and myeloid markers.
Acute Disease↗
Evaluation of fixation methods in cruciate ligament replacement.
Laboratory studies designed to simulate in vivo loading of a ligament graft and fixation method are affected by the age of the cadaveric donor, the types of tissue and fixation device employed, and the testing methods used. The use of older donors compromises the graft bone, underlying bone bed, and soft tissue. Staples, sutures, and screws all provide different fixation strengths depending on the tissue to be held. Cyclic testing of the graft better evaluates the performance of the composite during the activities of daily living, while high-speed failure tests indicate the replacement's ability to resist a traumatic injury. Several studies were examined in light of these factors. Each study had certain merits but also limitations. Further studies are required for careful evaluation of the cyclic response of cancellous screws of different sizes, barbed staples, and other methods of graft fixation. Only then can recommendations be made as to the best device to use for achieving the clinical goals of joint stability, adequate resistance to traumatic loads, and proper graft attachment healing.
Biomechanical Phenomena↗
Comparison of material properties in fascicle-bone units from human patellar tendon and knee ligaments.
The fascicle material properties in bone-fascicle-bone units were determined for the anterior and posterior cruciate ligaments (ACL, PCL), the lateral collateral ligament (LCL) and the patellar tendon (PT) from three young human donor knees. Groups of fascicles from each tissue were isolated with intact bone ends and failed at a high strain rate in a saline bath at 37 degrees C. In each knee tested the load related material properties (linear modulus, maximum stress and energy density to maximum stress) for the patellar tendon were significantly larger than corresponding values for the cruciate and collateral ligaments. Bundles from different ligaments in the same knee were similar to each other in their mechanical behavior. In addition, no significant differences were present in the maximum strains recorded for any of the four tissue types examined. The results presented have implications in studies of ligament injury. They are also important in the design and use of synthetic and biological ligament replacements and in tissue and whole knee modeling.
Adult↗
An exception to the 90 degrees corner bias.
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Cues↗
The relationship between crimp pattern and mechanical response of human patellar tendon-bone units.
The objectives of this study are twofold. First, to further develop the understanding of the relationship between the observed mechanical response and changes in the crimp pattern in human patellar tendon bone units. This is accomplished through the use of a specially constructed test frame and microscope system that permits observation and measurement of the crimp patterns as a function of load. Second, the results of the experimental study are used to develop a constitutive equation that includes spatial variation in the crimp pattern. The results of both the experimental and analytical study imply that local strain in the proximity of the attachment site is significantly larger than the strain in the central region of the tendon. The experimental and histological results are for specimens taken from four human bone-patellar tendon-bone units.
Adult↗
On the interpretation of our anterior cruciate ligament data.
Design of a synthetic replacement or selection of a biologic substitute requires detailed knowledge of the mechanical properties of the normal ligament. Femur-anterior cruciate ligament-tibia unit (ACL) data have been frequently used for this purpose, although not always properly. Mechanical properties of the human ACL-bone unit are reviewed. Ligament stiffness, elongation, and energy results are based on grip-to-grip motion and thus include ligament and limited bone deformations. Maximum bone-ligament-bone force in young donors (1730 +/- 66N) is higher than reported previously and represents only ligamentous failures. Methods for measuring tissue dimensions are provided and must be duplicated for obtaining accurate material property data. Bone-ligament-bone strain data are higher than those in reports where midsubstance collagen strains are measured and differ from data obtained on isolated ligaments. The authors have examined many factors that affect ligament-bone unit response. Increasing age weakens the tissue-bone preparation, and only when testing is performed at high rates will ligamentous failures predominate. Use of the authors' data in prosthetic ligament evaluation requires that the material be selected based on ligament bundle properties, the prosthesis be examined under similar testing conditions, and anticipated functional loads and margins of safety be determined.
Humans↗
Biomechanics of ligaments and tendons.
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Adrenal Cortex Hormones↗
Freeze dried anterior cruciate ligament allografts. Preliminary studies in a goat model.
One ACL in each of 11 mature goats was replaced with a freeze dried bone-ACL-bone allograft. One year following implantation the goats had their knees evaluated biomechanically and for microvascularity and histologic changes. The reconstructed knees had a significantly greater total AP laxity (3.8 +/- 0.6 mm) (mean and SEM) than the controls (1.0 +/- 0.1 mm). Differences in primary AP laxity were responsible for 81% of the difference in total laxity, with only a 0.4 mm difference in secondary laxity. Neutral stiffness in the reconstructive knee was 17% of control, while stiffness at 30 newtons (N) of anterior force was approximately 50% of controls. Ligament stiffness in the linear region for the ACL allograft was 35% of the control value of 686 N/mm. The maximum load of the allografts was 571 +/- 45 N, or 25% of the contralateral ACL control strength (2301 +/- 155 N). Five of the seven allografts failed at the femoral insertion. Both elongation (83%) and energy (21%) to maximum load were less for allografts than controls. Histologic evaluation of the allografts revealed the presence of a regular oriented dense connective tissue which resembled a normal ligament. Microangiography revealed a periligamentous and endoligamentous vascular pattern reminiscent of a normal ACL and complete revascularization of the bone plugs.
Animals↗
Cruciate reconstruction using freeze dried anterior cruciate ligament allograft and a ligament augmentation device (LAD). An experimental study in a goat model.
One ACL in each of 11 mature goats was replaced with a freeze dried bone-ACL-bone allograft and a ligament augmentation device (LAD). The LAD was released from its tibial fixation at 3 months postoperation. Biomechanical, microvascular, and histological changes were evaluated 1 year following implantation. The reconstructed knees had a significantly greater total AP translation (3.1 +/- 0.5 mm) (mean and SEM) than the contralateral controls (1.0 +/- 0.1 mm). Differences in primary AP translation were responsible for 59% of the difference in total translation, with only a 0.6 mm difference in secondary translation. Neutral stiffness in the reconstructive knee was 22% of control, while stiffness at 30 N of anterior force was approximately 35% of controls. Ligament stiffness in the linear region for the ACL allograft/LAD was 53% of the control value of 691 N/mm. The maximum load of the allograft/LADs was 1,052 +/- 145 N, or 43% of the contralateral ACL control strength (2,448 +/- 144 N). Five of the six allografts failed at the femoral insertion. Energy (39%) to maximum load was less for allograft/LADs than controls but elongation to maximum load was the same as control. Histologic evaluation of the allograft/LADs revealed soft tissue cellular ingrowth into the LAD in the extraarticular portions. No bony growth into the LAD was observed. The collagen fibers of the graft appear to be arranged in a longitudinal orientation although some areas show chaotic collagen fibers. Microangiography revealed a periligamentous and endoligamentous vascular pattern reminiscent of a normal ACL and complete revascularization of the bone plugs.
Animals↗
The effects of processing techniques on the mechanical properties of bone-anterior cruciate ligament-bone allografts. An experimental study in goats.
There has been a growing interest in the use of allografts as ACL substitutes. Allografts are often freeze dried to increase shelf storage time and sterilized with ethylene oxide. This study was conducted to determine the effect of a specific ethylene oxide sterilization procedure and freeze drying process on the initial mechanical properties of femur-ACL-tibia preparations. Twelve knees (stifle joints) from six mature goats were divided into two groups (one knee of pair to each group). Knees were cleaned of all soft tissue except for the anterior cruciate, posterior cruciate, and collateral ligaments. Group 1 was sterilized with ethylene oxide (simulating clean procurement) then freeze dried. Group 2 was freeze dried only (simulating sterile procurement). The knees were rehydrated and then tested in tension to failure to determine their structural mechanical properties. The ethylene oxide-freeze dried specimens (Group 1) had a mean maximum load before failure of 2059 +/- 273 newtons (N) (+/- SE) which was not statistically different than the maximum load of the freeze dried specimens (Group 2) of 2023 +/- 214 N. The average strength of Group 1 and 2 combined was not significantly different than a third group of 12 normal femur-ACL-tibia controls which had an average maximum force of 2403 +/- 133 N. No significant differences between the groups were observed for stiffness, energy to maximum strength, or elongation to maximum force. It appears the freeze dry processing, with or without ethylene oxide sterilization, using the procedure we used, has, at most, a small effect on the initial mechanical properties of the preparations.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗