bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of immobilization on achilles tendon healing in a rat model
Authors: Murrell George A. C. , Lilly Edward G. , Goldner Richard D. , Seaber Anthony V. , Best Thomas M. 
Published: February 2005

AbstractThe aim of this study was to evaluate the effects of immobilization and mobilization on the functional and biomechanical recovery of injured Achilles tendons. Male Sprague‐Dawley rats were allocated randomly into four groups: (a) sham operation, (b) division only (surgical transection of the Achilles tendon without immobilization), (c) “dummy” external fixation (division of the Achilles tendon and application of Kirschner wires), and (d) rigid external fixation (division of the Achilles tendon and immobilization with Kirschner wires connected by two triangular frames). All procedures were performed on the right lower limb; the left, uninjured, lower limb served as an internal control. Kirschner wires and external fixators were removed on day 12. Functional performance was determined from measurements of hind pawprints of rats walking preoperatively and on postoperative days 1, 3, 5, 7, 9, 11, 13, and 15. On day 15, the animals were killed and biomechanical evaluations were performed on both the injured and the uninjured Achilles tendon constructs. No functional or mechanical deficits were observed in the sham‐operation group. Animals subjected to division of the Achilles tendon had an initial functional deficit that returned to near normal by day 15. The application of Kirschner wires was associated with an impairment of the functional performance of the rat as well as of the mechanical properties of the tendon‐bone constructs. Immobilization by connection of the Kirschner wires to an external frame had an additional, highly significant (p < 0.001) detrimental effect on the functional and mechanical recovery of Achilles tendon‐calcaneal complexes.
Effect of link protein and free hyaluronic acid binding region on spacing of proteoglycans in aggregates
Authors: Kahn Anthony , Taitz Ari D. , Pottenger Lawrence A. , Alberton Gregory M. 
Published: February 2005

AbstractAging of articular cartilage results in accumulation of aggrecan fragments of various sizes that retain their ability to aggregate even though they may have relatively few glycosaminoglycan chains. Residual binding of partially degraded aggrecan may prevent binding of newly synthesized aggrecan subunits that have greater numbers of glycosaminoglycan chains. This study was undertaken to determine the effects of various relative molar ratios of intact aggrecan, link proteins, and hyaluronic acid binding region fragments on the structure of reconstituted aggregates. High molar ratios of link proteins relative to aggrecan decreased the spacing between adjacent aggrecan subunits; low molar ratios of hyaluronic acid binding region relative to aggrecan (4:1 or less) had no significant effect on spacing, and high molar ratios resulted in an increase in the spacing and a decrease in the percentage of aggrecan subunits found in aggregates. These data suggest that the density of aggrecan subunits on the aggregate is determined primarily by steric hindrance of the glycosaminoglycan chains of the aggrecan subunits and that, to a limited extent, partial degradation of aggrecan in an aggregate allows attachment of more aggrecan subunits.
Elastic modulus of calcified cartilage is an order of magnitude less than that of subchondral bone
Authors: Mente P. L. , Lewis J. L. 
Published: February 2005

AbstractThe elastic moduli of calcified cartilage and subchondral bone tissues were measured experimentally with use of a three‐point bending test. Specimens were obtained from a bovine patella and the distal end of a bovine femur, from two different animals. Fifteen specimens were tested as “pure” subchondral bone beams, and 15 were tested as composite calcified cartilage/subchondral bone beams. A least‐squares optimization scheme was used to obtain modulus values from the composite beams. The elastic modulus for subchondral bone calculated from the “pure” subchondral bone beams was 2.3 ± 1.5 GPa (3.9 ± 1.5 GPa for specimens from the femur and 1.6 ± 0.7 GPa for specimens from the patella). The composite beam optimization resulted in a modulus for subchondral bone of 5.7 ± 1.9 GPa and a modulus for calcified cartilage of 0.32 ± 0.25 GPa. The modulus for the calcified cartilage was more than an order of magnitude lower than the modulus of the underlying subchondral bone. This supports the idea that the zone of calcified cartilage forms a transitional zone of intermediate stiffness between the articular cartilage and the subchondral bone.
Ingrowth reduces implant‐to‐bone relative displacements in canine acetabular prostheses
Authors: Heiner John P. , Manley Paul , Kohles Sean , Ulm Mark , Bogart Linda , Vanderby Ray 
Published: February 2005

AbstractWe examined bone‐to‐implant relative displacements of acetabular prostheses acutely and after ingrowth in a canine model. Uncemented hemispherical acetabular cups with titanium mesh pads comprising approximately 26% of the surface of the cup were inserted in eight adult canine hemipelves ex vivo. The acetabular prostheses were fixed with 13 mm titanium screws. Zero, one, and two‐screw configurations were tested, with the order of testing randomly assigned. A load simulating 1,000 cycles of canine gait was applied to the acetabular component, and relative displacements were measured at three locations between imlant and bone to determine acute fixation. A repeated measures analysis of variance showed that two screws produced only 42% of the average relative displacement of one screw and 14% that of zero screws. Eight adult mixed‐breed dogs then underwent unilateral total hip arthroplasty. All acetabula were biologically fixed with two cancellous screws. The results at 4 months showed significantly less relative displacement between the implant and bone than was measured in ex vivo implantations (p = 0.014). Bone ingrowth filled 20 ± 6% (mean ± SD) of the available space. The relative displacements of these implants were small in all cases (12 ± 13 μm) and did not correlate with the amount of bone ingrowth. These data suggest that acetabular fixation with two screws can lead to bone ingrowth and reduced relative motion of the prosthesis under functional loading.
Malrotation of the humeral component of the capitellocondylar total elbow replacement is not the sole cause of dislocation
Authors: Itoi Eiji , King Graham J. W. , Niebur Glen L. , Morrey Bernard F. , An Kai‐Nan 
Published: February 2005

AbstractMalrotation of the humeral component of the capitellocondylar total elbow replacement is thought but not proved to be one of the major causes of postoperative dislocation. The purpose of this study was to quantitate the effect of malrotation of the humeral component on the kinematics and laxity of the capitellocondylar total elbow prosthesis. Eleven fresh previously frozen elbows were used. With the humeral component in optimal position, external rotation, or internal rotation, movements of the elbow with neutral, valgus, and varus loading were monitored with an electromagnetic tracking device. When the humeral component was positioned in external rotation, the ulna was more valgus and supinated than when the component was in optimal position, and when the component was in internal rotation the ulna was more valgus in extension and more supinated in flexion. Malrotation in external rotation decreased valgus‐varus laxity, and malrotation in internal rotation increased rotational laxity. Only one elbow became dislocated, despite constant severe maltracking between the components in all of the specimens. We concluded that although malrotation of the humeral component influences the laxity and causes maltracking, it is not the primary cause of postoperative dislocation. The contribution of other factors should be investigated.
Maturation‐related biochemical changes in swine anterior cruciate ligament and tibialis posterior tendon
Authors: Watanabe Masanobu , Nojima Motoo , Shibata Taihou , Hamada Minoru 
Published: February 2005

AbstractIn order to determine the differences between ligaments and tendons in terms of change in biochemical composition during maturation, the biochemical characteristics of the anterior cruciate ligament and tibialis posterior tendon of swine were studied. The collagen content of the tibialis posterior tendon was found to increase rapidly with growth of the body, reaching a plateau prior to maturation. In contrast, the rate of increase in the anterior cruciate ligament was slow, indicating that maturation of this tissue is delayed. The quantity of glycosaminoglycan in both the anterior cruciate ligament and the tibialis posterior tendon decreased with growth. In mature animals, glycosaminoglycans in the anterior cruciate ligament included chondroitin sulfate, hyaluronic acid, and dermatan sulfate, but only trace amounts of chondroitin sulfate were found in the tibialis posterior tendon. Although the ratio of dermatan sulfate to hyaluronic acid generally increased with growth, this increase was more conspicuous in the tibialis posterior tendon than in the anterior cruciate ligament. The anterior cruciate ligament and tibialis posterior tendon both contained collagen of types I, III, and V. In mature swine, type III was increased in the anterior cruciate ligament but not in the tibialis posterior tendon. These findings demonstrate slower maturaiton for ligament than for tendon with regard to the changes in biochemical constituents, especially those in collagen type and glycosaminoglycan, during the growth process, and also suggest that the composition of these tissues changes in accordance with their changing functional requirements.
Effects of different levels of direct current on early ligament healing in a rat model
Authors: Litke Diane S. , Dahners Laurence E. 
Published: February 2005

AbstractElectrical stimulation has been shown to enhance the repair of biological tissues such as bone and tendon. The objective of this study was to determine whether low level direct current enhances the early healing of injured medial collateral ligaments. Eighty‐seven rats were divided into three groups on the basis of the level of current delivered. All underwent transection of the medial collateral ligament bilaterally. The experimental medial collateral ligaments received current (which varied by group), while the contralateral medial collateral ligaments (the controls), with identical electrodes, received no current. After 12 days, each ligament was tested biomechanically with use of a hydraulic materials testing machine. Group 1 (8.6 ± 5.9 μA) showed statistically significant improvements in maximum rupture force, energy absorbed, stiffness, and laxity. The groups that had received lower levels of current did not show significant improvements. In this study, stimulation of 1–20 μA was the most effective level of direct current for the enhancement of early healing of the medial collateral ligament.
The entire rotator cuff contributes to elevation of the arm
Authors: Sharkey Neil A. , Marder Richard A. , Hanson Peter B. 
Published: February 2005

AbstractThe function of the infraspinatus, teres minor, and subscapularis during elevation of the arm remains poorly defined. These muscles may generate moments that contribute to abduction of the arm, although they frequently are classified as humeral depressors. The purposes of this study were to measure the contributions to abduction made by the more inferiorly positioned rotator cuff muscles relative to the contributions of the supraspinatus and to determine the range of motion at which the muscles are most effective. Five fresh cadaveric shoulder girdles were mounted in an apparatus designed to simulate contraction of the deltoid and rotator cuff while maintaining the normal relationship between glenohumeral and scapulothoracic motions. The deltoid force required for elevation was measured without simulated contraction of the rotator cuff and with simulated contraction of the entire rotator cuff, of the supraspinatus only, and of the infraspinatus‐teres minor and subscapularis only. A significant reduction in deltoid force when other muscle activity was added indicated that the additions contributed significantly to abduction. The deltoid force required with concurrent contraction of the entire rotator cuff averaged 41% less than with the deltoid alone but was not significantly different than with the deltoid and supraspinatus or with the deltoid, infraspinatus‐teres minor, and subscapularis. Concurrent application of forces to the supraspinatus or the infraspinatusteres minro and subscapularis significantly reduced the required deltoid force over the range of motion studied by an average of 28 and 36%, respectively. The contributions of the rotator cuff muscles to abduction of the arm were greatest at low abduction angles (30 and 60°) and were insignificant by 120°. The infraspinatus‐teres minor and subscapularis contribute significantly to abduction: their contibution was equal to that of the supraspinatus and, like the supraspinatus, they are most effective during the first 90° of abduction.
Comparison of antibiotic release from polymethylmethacrylate beads and sponge collagen
Authors: Becker Paul L. , Smith Richard A. , Williams Robert S. , Dutkowsky Joseph P. 
Published: February 2005

AbstractThe rates of elution of tobramycin in vitro were compared for polymethylmethacrylate beads impregnated with the powder form and an alternative biodegradable substance, sponge collagen. The impregnated polymethylmethacrylate beads initially had a lower zone of inhibition, but the rate of release was slow in comparison with that of the impregnated sponge collagen. The sponge collagen delivered a higher dose faster and with a shorter duration than the polymethylmethacrylate beads with the same antibiotic concentration in vitro, but the beads delivered a therapeutic concentration for longer periods. Because it deteriorates rapidly, sponge collagen may be unsatisfactory as an agent of antibiotic delivery in patients who have chronic osteomyelitis; however, it may be useful for patients who have acute trauma with highly contaminated bone or soft tissue, or during hemiarthroplasty revision, to deliver a high local concentration of antibiotic for a short period of time.
Muscle pathology and clinical measures of disability in children with cerebral palsy
Authors: Rose Jessica , Haskell William L. , Gamble James G. , Hamilton Ronald L. , Brown Daniel A. , Rinsky Larry 
Published: February 2005

AbstractWe performed a histologic and morphometric study of spastic muscle from 10 children with diplegic cerebral palsy, comparing muscle structure with the gait parameters of energy expenditure index and dynamic electromyography. Variations in fiber area within and between fiber types were increased significantly in children with cerebral palsy. In each of the control subjects, the combined coefficient of variation for type‐1 and type‐2 fiber area was less than 25% and the average was 17%; in the subjects with cerebral palsy, the combined coefficient of variation was more than 25% and the average was 36% (p ≤ 0.004). The average difference between the mean area of type‐1 and type‐2 fibers was 26.7 ± 18.9% for subjects with cerebral palsy and 4.2 ± 2.4% for control subjects (p ≤ 0.004). There was a 67% predominance of one fiber type in the subjects with cerebral palsy compared with a 55% predominance in the control subjects (p ≤ 0.03). The difference between the total area of type‐1 and type‐2 fibers was 57% in the subjects with cerebral palsy and 17% in the control subjects (p ≤ 0.002). There was a significant correlation between the combined coefficient of variation of fiber area and the energy expenditure index (r = 0.77, p ≤ 0.03). The difference between the mean area of type‐1 and type‐2 fibers correlated with prolongation of electromyographic activity (r = 0.69, p ≤ 0.05). No abnormalities in fiber ultrastructure were found in the subjects with cerebral palsy. Children with cerebral palsy had abnormal variation in the size of muscle fibers and altered distribution of fiber types. The values for variation in fiber area correlated with the energy expenditure index and with prolongation of electromyographic activity during walking.
Compressive stress‐relaxation behavior of bovine growth plate may be described by the nonlinear biphasic theory
Authors: Cohen Boaz , Chorney Gail S. , Phillips Donna P. , Dick Harold M. , Mow Van C. 
Published: February 2005

AbstractThe compressive behavior of the bovine distal femoral growth plate was studied in vitro. Strain‐rate controlled, compression stress‐relaxation experiments were performed on cylindrical bone‐growth plate‐bone specimens from the interior and periphery of the growth plate. The questions addressed in this study were (a) Can the nonlinear biphasic theory, one with strain‐dependent permeability, be used to represent the compressive stress‐relaxation behavior of bovine growth plate? (b) How do different assumptions concerning the permeabilities of the chondro‐osseous interfaces influence the inferred material properties of the growth plate? and (c) Are there any differences in these properties between the periphery and the interior of the growth plate? Intrinsic biphasic material properties–aggregate modulus (HA), Poisson's ratio (v), and nonlinear strain‐dependent permeability coefficients (ko and M)–were calculated from the compression stress‐relaxation data with use of a finite element model and a least squares curve‐fitting procedure. To verify this constitutive model for the growth plate, an independent set of finite element analyses was performed with use of the determined intrinsic biphasic properties, and comparisons were made between these finite element predictions and two additional sets of experimental data subsequently obtained for the same specimens with use of two slower rates of compression. Excellent agreement was achieved between these finite element predictions and the latter two sets of data. The aggregate modulus was found to be insensitive to the permeability of the chondro‐osseous interface. The permeability coefficients were very sensitive to, and the Poisson's ratio was only slightly sensitive to the interface permeability condition. Therefore, the periphery of the growth plate is more compliant and permeable than the interior.
Substance P‐immunoreactive and protein gene product 9.5‐immunoreactive nerve fibres in bone marrow of rat coccygeal vertebrae
Authors: Imai Shinji , Hukuda Sinsuke , Maeda Toshihiro 
Published: February 2005

AbstractPrevious investigations have focused mainly on the nerve terminals in soft tissues surrounding the vertebrae to determine the source of spinal pain. Our study on rat coccygeal vertebrae compared intramedullary immunostaining for substance P with that of a more generally distributed neural marker, protein gene product 9.5, to suggest another source of spinal pain. Free intramedullary fibres staining for protein gene product 9.5 were rare compared with the abundant staining associated with intramedullary vessels. Shortly after entering the marrow with the nutrient vessels, substance P‐immunoreactive fibres parted from the vessels and then proceeded longitudinally and terminated on the end‐plates. Other (although fewer) substance P‐immunoreactive fibres entered the marrow at enthetic aspects of the vertebrae. The presence of free substance P‐immunoreactive fibres innervating endplates and penetrating entheses suggests that they may represent a novel source of spinal pain.
Superior displacement of the hip in total joint replacement: Effects of prosthetic neck length, neck‐stem angle, and anteversion angle on the moment‐generating capacity of the muscles
Authors: Delp Scott L. , Komattu Abraham V. , Wixson Richard L. 
Published: February 2005

AbstractThe purpose of this study was to determine the effects of superior displacement of the hip center and changes in three prosthetic parameters (neck length, neck‐stem angle, and anteversion angle) on the capacity of muscles to generate force and moment about the hip. A three‐dimensional model that calculates the maximum isometric forces and moments generated by 25 muscles crossing the hip over a wide range of body positions was used to evaluate the effects of a 2 cm elevation of the hip center and changes in the prosthetic parameters. After superior displacement of the hip center, the neck length was increased from 0 to 3 cm, the neck‐stem angle was varied between 110 and 150°, and the anteversion angle was varied between 0 and 40°. Our analysis showed that a 2 cm superior displacement of the hip center would decrease the moment‐generating capacity of the four muscle groups studied (abductors, adductors, flexors, and extensors) if neck length were not increased to compensate for decreased muscle length. In the computer model of an adult man that we used, a 2 cm increase in neck length restored the moment‐generating capacity of the muscles by increasing muscle length and force‐generating capacity. However, a 3 cm increase in neck length increased passive muscle forces substantially, which potentially could limit joint motion. An increased neck‐stem angle (i.e., a valgus neck) decreased the abduction moment arm but increased the moment‐generating capacity of the other muscle groups. A change in the anteversion angle from 0 to 40° had a relatively small effect on the isometric moment‐generating capacity of the muscles studied.
Effects ofcis‐diamminedichloroplatinum II released from d, l‐polyalactic acid implanted adjacent to cortical allografts in dogs
Authors: Straw Rodney C. , Withrow Stephen J. , Douple Evan B. , Brekke John H. , Cooper Mary F. , Schwarz Peter D. , Greco Deborah S. , Powers Barbara E. 
Published: February 2005

AbstractThis study was performed to determine the pharmacokinetics and local and systemic effects ofcis‐diamminedichloroplatinum II (cisplatin) released from an open‐cell polylactic acid polymer when the drug delivery device was placed adjacent to a cortical allograft. Bilateral intercalary femoral allografts were implanted in six normal beagles. The polymer containing cisplatin was implanted adjacent to the allograft in one femur, and the polymer without cisplatin was implanted adjacent to the allograft in the contralateral femur. Systemic toxicity was evaluated clinically by hematologic and serum biochemistry tests and urinalysis. Healing of the allograft was monitored radiographically. The femora were evaluated biomechanically, histologically, and histomorphometrically 7.5 months after surgery. Total serum platinum levels were measured by atomic absorption spectrophotometry, and pharmacokinetic parameters were calculated. Healing was impaired slightly by the presence of the polymer with cisplatin, and systemic and local toxicity was mild and transient. After implantation of the polymer with cisplatin, the mean peak total serum platinum concentration was low (1.71 ± 0.19 μg/ml). However, the area under the curve for total serum platinum concentration versus time for the first 21 days was large (27,050 ± 3,201 μg.min/ml). When cisplatin was given as an intravenous bolus at a dose of 70 mg/m2to six other beagles, the mean peak total platinum concentration was 8.80 ± 2.1 μg/ml and the area under the curve was 940.3 ± 256.7 μg.min/ml. These results indicate that a sustained release of cisplatin can be delivered safely from an open‐cell polylactic acid polymer. This device may be useful in the treatment of solid tumors.