Integration of features in depictions as a function of size.
Explore the source record for details and available documents.
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.
Explore the source record for details and available documents.
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↗
Effects of structure and strain measurement technique on the material properties of young human tendons and fascia.
It is generally recognized that the organization of collagen bundles in soft tissues strongly influences their material properties. To study this, sixty failure tests were conducted on double-layered fascia lata, 'isolated' parallel-bundled tendons (gracilis and semitendinosus) and parallel-bundled bone-patellar tendon-bone units taken from about the knees of eighteen young human donors (mean age of 26 yr). Surprisingly, most material parameters for the two-layered fascia lata did not differ significantly from corresponding values for the isolated tendons and tendon-bone preparations, suggesting their longitudinal fibers predominated during loading. Differences were present however between the gracilis tendon and all other tissues for both modulus and maximum stress. The large variations in reported maximum and failure strains for tendons, fascia and other collagenous tissues prompted the other phase of the study. During 15 of the 60 failure tests, surface markers were simultaneously filmed to determine; differences between local surface strains and grip to grip values; the amount of tissue slippage and/or failure occurring in the grips; and the effect of strain measurement technique on tissue moduli and failure energy densities. Maximum local strains were found to be 25-30% of grip strains for all tissues tested. Some slippage and/or failure could be seen in all isolated tissues which were gripped directly although their maximum grip strains were similar to values for tendon-bone units. For all tissues, two to three fold differences were also found in moduli and failure energy densities between grip and midregion measurements.
Adult↗
Strain topography of human tendon and fascia.
Discretized surface strains for human tendon and fascia were photogrammetrically determined with high-speed cinematography and were displayed topographically using three-dimensional computer graphics. Substantial differences were found between estimates of tissue strain measured from grip motion versus discretized strain estimates from high-speed films. The computer-generated contour maps also provide a useful technique for analyzing the nonhomogeneity of tendon and fascial strains during high rate tests.
Adult↗
Advances in the understanding of knee ligament injury, repair, and rehabilitation.
Knee injuries continue to present a complex set of clinical problems. The answers to these problems have recently been redefined by the application of sophisticated biomechanical research methods to the study of knee ligaments and joint function. This manuscript reviews contributions which our laboratory has made to the understanding of knee injury, highlighting those research findings which form the basis for our clinical treatment of knee ligament injuries. High strain-rate techniques for studying knee ligament failure have replaced the previous low strain-rate methods and distinguish the failure mechanism of ligaments from that of bone. Ligament function is now further defined by measuring the restraining force provided by specific ligaments, adding to the information provided by cutting studies. The development of the 6-degrees-of-freedom concept and the instrumented kinematic chain now permit precise analysis of joint position, motion, and laxity. Biomechanical evaluation of intra-articular anterior cruciate ligament substitution has emphasized the importance of selection of a high-strength graft material, meticulous surgical technique with attention to graft vascularity, precise location of graft fixation sites, judicious adjustment of graft tension, post-operative protection during tissue remodelling, and a carefully conceived rehabilitation program. Newer biomechanical research methods have provided a sound scientific foundation on which to base clinical decisions concerning the care of knee ligament injuries.
Adrenal Cortex Hormones↗
Biomechanical analysis of human ligament grafts used in knee-ligament repairs and reconstructions.
Virtually all types of collagenous tissues have been transferred in and around the knee joint for intra-articular and extra-articular ligament reconstructions. However, the mechanical properties (in particular, strength) of such grafts have not been determined in tissues from young adult donors, where age and disuse-related effects have been excluded. To provide this information, we subjected ligament graft tissues to high-strain-rate failure tests to determine their strength and elongation properties. The results were compared with the mechanical properties of anterior cruciate ligaments from a similar young-adult donor population. The study indicated that some graft tissues used in ligament reconstructions are markedly weak and therefore are at risk for elongation and failure at low forces. Grafts utilizing prepatellar retinacular tissues (as in certain anterior-cruciate reconstructions) and others in which a somewhat narrow width of fascia lata or distal iliotibial tract is utilized are included in this at-risk group. Wider grafts from the iliotibial tract or fascia lata would of course proportionally increase ultimate strength. The semitendinosus and gracilis tendons are stronger, having 70 and 49 per cent, respectively, of the initial strength of anterior cruciate ligaments. The bone-patellar tendon-bone graft (fourteen to fifteen millimeters wide, medial or central portion) was the strongest, with a mean strength of 159 to 168 per cent of that of anterior cruciate ligaments. Patellar tendon-bone units, based on grip-to-grip motions, were found to be three to four times stiffer than similarly gripped anterior cruciate ligaments, while gracilis and semitendinosus tendon preparations had values that were nearly identical to those of anterior cruciate ligaments.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Biomechanics of the knee-extension exercise. Effect of cutting the anterior cruciate ligament.
UNLABELLED: We conducted this study to determine the effective moment arm of the knee extensor mechanism and the conditions under which the anterior cruciate ligament is loaded during knee-extension exercises. The moment arm was calculated from measurement of the quadriceps force required to extend the knee with and without resistive weights placed at the foot, the leg weight, and the location of its center of gravity. Changes in three-dimensional joint motion after the anterior cruciate ligament was removed were considered to be an indication that the ligament was loaded. The quadriceps force rose during the initial phase of knee extension and remained nearly constant at an average value of 177 newtons between 50 and 15 degrees. With extension past 15 degrees it rose rapidly, reaching an average of 350 newtons at zero degrees of extension, and continued to increase with hyperextension. The addition of thirty-one newtons (seven pounds) at the foot approximately doubled the quadriceps force that was required to extend the knee. The effective moment arm of the extensor mechanism increased with knee extension, peaked at approximately 20 degrees, and rapidly decreased with further extension. No change was found in the quadriceps force or its effective moment arm when the anterior cruciate ligament was sectioned except in hyperextension, where the quadriceps force decreased in two of five specimens. There was, however, an increased anterior tibial displacement in the range of 30 degrees to full extension, suggesting that the anterior cruciate ligament is loaded in that flexion arc. CLINICAL RELEVANCE: This study demonstrates that very large quadriceps forces are required to accomplish the last 15 degrees of extension during leg-raising exercises, typically twice those required to reach 30 degrees of flexion. The large forces that are required to obtain full extension explain why an extensor lag occurs with quadriceps weakness even though a full passive range of motion is possible. Since thirty-one newtons (seven pounds) of resistive weight added at the foot approximately doubles the quadriceps forces required to extend the leg alone, using such weights can produce very large quadriceps forces and concurrent patellofemoral and tibiofemoral contact forces. Because the quadriceps force increases little as the leg is extended from 50 to 15 degrees, in patients with patellofemoral chondroses for whom a full range of joint motion is not desired, quadriceps exercises can be limited to the amount of extension without decreasing quadriceps force.(ABSTRACT TRUNCATED AT 400 WORDS)
Biomechanical Phenomena↗
Error analysis of a system for measuring three-dimensional joint motion.
In the past ten years there has been increased use of six-degree-of-freedom instrumented spatial linkages for the measurement of biological joint motions. In spite of the increased popularity, little information has been reported on the accuracy of these devices. In this paper, we present a two-part investigation of the accuracy of the instrumented spatial linkage when used to measure knee joint kinematics. In the first part, we present the results of a theoretical analysis and an experimental determination of the errors associated with spatial linkage systems. In the second part, we describe the errors associated with a bi-planar X-ray system used to obtain the coordinate transformation between the linkage ends and coordinate systems located in the bones comprising the joint. We found that the theoretical error analysis consistently overestimated the actual measurement error, thus providing an unreliable estimate of errors. The experimental study of both the linkage system and the bi-planar X-ray system demonstrated that the accuracy of displacement measurement is insensitive to large systematic errors in position measurement.
Biomechanical Phenomena↗
Tension-torsion characteristics of the canine anterior cruciate ligament--Part I: Theoretical framework.
It has been observed that the fascicles in the canine anterior cruciate ligament do not follow a straight line path between the tibial and femoral attachment sites, but rather their path is approximately helical about the ligament axis. Thus, a mathematical model for the mechanical response of a ligament was developed from the observed geometrical configuration of the fascicle. The principal result of the model indicated that a torque must always accompany the force during elongation of a ligament. The relationships between the ligament and fascicle variables are also examined in detail.
Animals↗
Tension-torsion characteristics of the canine anterior cruciate ligament--Part II: Experimental observations.
An experimental program was devised to determine whether the canine anterior cruciate ligament (ACL), with an apparent helical twist of its component fiber bundles, could support a torque during axial loading to failure. At the point of first significant failure, the anterior cruciate was found to develop an average maximum torque of 122 +/- 26 N-mm (mean +/- SEM) for the nine tension-torsion tests performed. A nearly linear axial force-torque curve was also observed where the average slope of all tests was 5.2 +/- 0.2 mm-1 (mean +/- SEM). The experimental axial force data was then used to determine material parameters in the constitutive equation for the fascicle and underlying bone. A nonlinear ligament model based on this response was found to reproduce the axial force data adequately and to reasonably predict the observed ligament torque over the entire subfailure loading range. The presence of a ligament torque during axial loading has implications in the design and selection of a ligament substitute. Such a substitute has already been examined in the canine in another study. The results also suggest more refined experiments which could relate the mechanical properties of a ligament to its detailed macrostructure and insertion site geometries.
Animals↗
The symptomatic anterior cruciate-deficient knee. Part I: the long-term functional disability in athletically active individuals.
Explore the source record for details and available documents.
Adolescent↗
Influence of line context on power function parameters.
Stimuli in experiments in which line-lengths are judged are typically single lines. In studies in which area and volume are judged, the stimuli are typically more complex. An experiment with 22 college undergraduates investigated whether differences in context (single lines versus lines in depicted boxes) influenced the exponent or scaling factor of the power function of length judgments. The scaling factor of the power function was significantly affected by context, but the exponent of the power function was not.
Discrimination Learning↗
Effect of orientation on judgments of line length.
This study investigated how the parameters of the power function of line judgments by 68 college undergraduates were affected by orientation of line. Exponents of the power functions did not vary as a function of orientation, but the scaling factors varied substantially. These results suggest that the horizontal-vertical illusion is best described as about a 12% illusion. Also, results are inconsistent with the hypothesis that the horizontal-vertical illusion affects the exponent of power functions for judgments of area and volume.
Adult↗