bluuebunny/crossref_metadata_2025_split huggingface dataset:
An investigation of a compliant interface for press‐fit joint replacement
Authors: Walker P. S. , Rodger R. F. , Miegel R. E. , Schiller A. L. , Deland J. T. , Robertson D. D. 
Published: February 2005

AbstractEarlier in vitro studies showed that a compliant layer between a metal surface and trabecular bone improved the load distribution. In this study, the behavior of a compliant layer of Dacron velour was investigated in vivo using a patella resurfacing in a sheep as a model. Bilateral cases were used to compare the velour interface with a direct metal‐to‐bone interface. For the metal patellas, a fibrous layer developed adjacent to the metal while the underlying bone formed a new subchondral‐like layer. With the velour interface, fibrous tissue invaded the velour, followed later by bone, which sometimes reached the metal surface. For follow‐ups of 8 months or more, the load across the interface was transferred over localised patches, for both the press‐fit and velour interfaces. There was no significant difference in the areas of contact. There was evidence that this was due to the irregularity of the bony surface beneath the fibrous layer, or to bone nodules actually growing up to the metal. It was concluded that in this in vivo model, the velour layer did not retain a more uniform load distribution compared with the press‐fit joint, due to the nature of the bone and fibrous tissue that formed at the interfaces.
Factors affecting graft force in surgical reconstruction of the anterior cruciate ligament
Authors: Lewis Jack L. , Lew William D. , Engebretsen Lars , Hunter Robert E. , Kowalczyk Curtis 
Published: February 2005

AbstractThe effect of the maximum unloaded graft length (Lo) and femoral fixation hole location on graft force with the knee under anteriorly directed tibial loads was measured in five fresh cadaver knees with a reconstruction of the anterior cruciate ligament (ACL). The reconstruction was performed using a composite graft consisting of the semitendinosus and gracilis tendons augmented with the Kennedy ligament augmentation device (LAD). Buckle transducers were used to measure ligament and graft forces. The total graft force was adjusted to match the intact ACL at 30° flexion using a force‐setting method so that a standardized reference configuration could be repeatedly obtained. The graft force was highly sensitive to L0, typically changing by 50% with a change in L0 of 3 mm. Variation in femoral hole location of 5 mm anterior, posterior, proximal, and distal to the anatomic position produced changes in graft force, particularly at 60° and 90° flexion; however, these changes were not statistically significant. The effect of femoral hole location varied considerably between knees. This variability makes predicting proper hole placement difficult, and suggests the need to adjust each knee at surgery to account for this variable femoral hole position sensitivity.
The effect of a brain lesion on bone healing
Authors: Spencer R. F. , Bullock R. , Cooper K. , Norman R. J. , Becker P. J. 
Published: February 2005

AbstractUsing a feline model, the effects of stereotaxic brain lesions producing unilateral spasticity on bilateral fibular osteotomies were observed. Healing in spastic limbs occurred with more new bone formation than on the contralateral (control) side. Union appeared to be slightly faster in spastic limbs. Histomorphometric analysis of resected fibular specimens following union revealed little difference between spastic and non‐spastic limbs. When these brain‐lesioned animals were compared with a group with identical osteotomies but no brain lesions in respect of various systemic biochemical and endocrine parameters, no differences were found.
Morphometric and anisotropic symmetries of the canine distal femur
Authors: Kuhn J. L. , Goulet R. W. , Pappas M. , Goldstein S. A. 
Published: February 2005

AbstractThe purpose of this study was to investigate the homotypical variation in morphologic and anisotropic properties of trabecular bone from paired canine distal femurs. A microcomputed tomography system was used to produce three‐dimensional digital reconstructions of the trabecular bone structures. The results showed that the mean bilateral differences in all bone morphology variables were < 5%. Differences in measures of degree of anisotropy were also < 5% between matched sites from left and right sides. In general, the bilateral difference in angle of orientation was < 15%. These data are valuable for calculating the appropriate sample size to use in experiments using the contralateral canine femur as a control. The results and general approach of the study may have significance for the future use of other contralateral trabecular bone sites as controls.
Muscle activities during asymmetric trunk angular accelerations
Authors: Marras W. S. , Mirka G. A. 
Published: February 2005

AbstractThe objective of this study was to characterize trunk muscle and intra‐abdominal pressure behavior during extensions of the trunk when angular trunk acceleration levels and trunk twist were varied during lifting exertions. Since force is related to acceleration, it was believed that changes in trunk acceleration would cause activity changes in the muscles and abdominal cavity pressurization mechanics that load the spine during manual materials handling tasks. The electromyographic activity of 10 trunk muscles and intra‐abdominal pressure were studied in 39 subjects as they moved their trunks under high, medium, and low constant angular acceleration conditions. The results indicated that almost all the muscles were affected by acceleration and asymmetry. Muscle activities of up to 50% of maximum were observed even though a minimal amount of torque was being produced by the back. Coactivation of muscles was also apparent. Muscles located at the greatest distances from the spine such as the latissimus dorsi and oblique groups, increased their activities the most as trunk acceleration increased. Muscles located farthest from the spine also played an important role as the trunk became more asymmetric. Intra‐abdominal pressure changed minimally over the test conditions. The nature of these responses and their impact on spine loading are discussed.
A quantitative assessment of cross‐sectional cortical bone remodeling in the femoral diaphysis following hip arthroplasty in elderly females
Authors: Torchia Michael E. , Ruff Christopher B. 
Published: February 2005

AbstractA quantitative assessment of cross‐sectional cortical bone remodeling in the femoral diaphysis following hip arthroplasty was made by direct in vitro measurements of cross‐sectional geometric properties. We obtained eight femora from four female cadavers ranging in age from 77 to 96 years. In three cases unilateral uncemented Austin Moore implants were used, and in one case a unilateral cemented Thompson prosthesis had been implanted. The time of implantation in the two specimens where this information could be obtained was greater than 40 months. Sections were made at 12 diaphyseal locations from the superior aspect of the lesser trochanter through the distal diaphysis. Section properties (areas and second moments of area, or area moments of inertia) were determined by tracing photographs of the cross‐sections with a digitizer. In this sample of prosthetic femora, we found reductions in both total subperiosteal area (TA) and endosteal area (ENDA) relative to the contralateral unoperated side in most sections distal to the lesser trochanter. The average pairwise reduction in ENDA for this region was 21.1 mm2, reaching statistical significance in one distal diaphyseal section. The average decline in TA in this region was 10.2 mm2. Because the reduction in endosteal dimensions was generally greater than the reduction in subperiosteal dimensions, cortical area (CA) was maintained or increased throughout the distal 80% of this region in prosthetic femora with an average increase in CA of 9.3 mm2, reaching statistical significance in one mid‐diaphyseal section. A completely different pattern of remodeling occurred in the two most proximal sections through the lesser trochanter and base of the femoral neck. Here, both endosteal and subperiosteal dimensions increased in the prosthetic femora, but ENDA increased more than TA, resulting in cortical thinning. The average pairwise increase in ENDA and TA, and loss in CA for these two sections was 59.8 mm2, 15.7 mm2, and 44.1 mm2, respectively, with a near‐significant increase in ENDA in one section and a significant loss of CA in the other. In comparisons between the methods of fixation, the three uncemented specimens demonstrated an increase in mediolateral bending rigidity (relative to the contralateral unoperated side) in the sections surrounding the stem tip, wherease the cemented specimen lost mediolateral bending rigidity in this region. Changes in cross‐sectional cortical bone geometry following prosthetic implantation throughout the entire femoral diaphysis, even well below the stem tip, have not been reported previously in the literature.
The influence of fixation peg design on the shear stability of prosthetic implants
Authors: Giori N. J. , Beaupré G. S. , Carter D. R. 
Published: February 2005

AbstractThe variety of fixation peg designs existing on prosthetic implants indicates uncertainty regarding the optimum design of fixation pegs for the reduction of stress and relative motion at the bone‐implant interface. Fixation pegs have a number of important functions on a prosthesis, one of which is to reduce shear stress and shear displacement at the bone‐implant interface. This is a parametric study intended to identify trends in the shear stability of prostheses incorporating a range of fixation peg designs. The parameters varied included the number of fixation pegs on a surface, the size of the pegs, and the aspect ratio (length/diameter) of the pegs. Mechanical tests were performed on urethane foam blocks with mechanical properties comparable to trabecular bone. The results indicated the following: (a) Fixation pegs act independently in resisting shearing force if they are spaced sufficiently far apart. (b) For any given shear displacement, smaller pegs generate a greater resistive shear force per unit of peg projected area in the direction of the applied load than larger pegs having the same aspect ratio. (c) Smaller diameter pegs cause the supporting material to yield at lower displacements. (d) Pegs with a high aspect ratio provide high shear stability with a minimum amount of bone removed, but may bend if the aspect ratio becomes excessive. (e) Smaller, slender pegs generate a greater resistive shear force at a given displacement per unit of peg volume than larger, lower aspect ratio pegs. The results of this study suggest that it may be possible to design prostheses with multiple smaller fixation pegs that conserve bone stock, distribute stress more uniformly to the supporting bone, and have stronger and stiffer shear fixation than prostheses with fewer larger pegs.
The effects of initial end contact on medial collateral ligament healing: A morphological and biomechanical study in a rabbit model
Authors: Chimich D. , Frank C. , Shrive N. , Dougall H. , Bray R. 
Published: February 2005

AbstractIn this investigation, the effect of initial end contact on medial collateral ligament (MCL) healing was studied in the rabbit model. Sixty‐eight 1‐year‐old New Zealand white rabbits were separated into two groups. In one group, a 4 mm saggital Z‐plasty was performed in the right MCL midsubstance (contact group), and in the other group, an analogous 4 mm midsubstance segment was removed (gap group). Left knees were unoperated to serve as internal contralateral MCL controls. Animals had unrestricted cage activity until sacrifice in groups of eight at 3, 6, 14, and 40 weeks postoperatively. Early results demonstrated that contact and gap injuries healed with what appeared to be scar tissue both morphologically and biomechanically. In both groups, laxities recovered to their contralateral values within 6 weeks and biomechanical viscoelastic behaviors recovered to 68–92% of contralaterals by 14–40 weeks. Despite these similarities, contacts showed morphological and biomechanical evidence of improved healing over gaps. Contact scars remodeled more quickly, recovered laxity more quickly, and were generally colser to contralaterals than gaps in terms of their structural strength, stiffness, and material behaviors, after 40 weeks of healing. With the exception of appearances and failure stress, all measured properties of contact healing MCLs were statistically indistinguishable from contralateral MCLs at 40 weeks of healing. These advantages of contact healing in this model support speculations that there are differences in the early rate and possibly in the later quality of ligament healing when cut rabbit MCL ends are in proximity. Longer‐term studies to define end points and mechanisms of healing are required.
Electromyographic activity of the abdominal and low back musculature during the generation of isometric and dynamic axial trunk torque: Implications for lumbar mechanics
Authors: McGill Stuart M. 
Published: February 2005

AbstractThis study focused on the electromyographic activity of the trunk musculature, given the well‐documented link between occupational twisting and the increased incidence of low back pain. Ten men and 15 women volunteered for this study, in which several aspects of muscle activity were examined. The first aspect assessed the myoelectric relationships during isometric exertions. There was great variability in this relationship between muscles and between subjects. Further, the myoelectric activity levels (normalized to maximal electrical activity) obtained from nontwist activities were not maximal despite maximal efforts to generate axial torque (e.g., rectus abdominis, maximum voluntary contraction; 22% external oblique, 52%; internal oblique, 55%; latissimus dorsi, 74%; upper erector spinae [T9], 61%; lower erector spinae [L3], 33%). In the second aspect of the study, muscle activity was examined during dynamic axial twist trials conducted at a velocity of 30 and 60°/s. The latissimus dorsi and external oblique appeared to be strongly involved in the generation of axial torque throughout the twist range and activity in the upper erector spinae displayed a strong link with axial torque and direction of twist, even though they have no mechanical potential to contribute axial torque, suggesting a stabilization role. The third aspect of the study was comprised of the formulation of a model consisting of a three‐dimensional pelvis, rib cage, and lumbar vertebrae and driven from kinematic measures of axial twist and muscle electromyograms. The relatively low levels of normalized myoelectric activity during maximal twisting efforts coupled with large levels of agonist–antagonist cocontraction caused the model to severely underpredict measured torques (e.g., 14 Nm predicted for 91 Nm measured). Such dominant coactivity suggests that stabilization of the joints during twisting is far more important to the iumbar spine than production of large levels of axial torque.
Interaction between active and passive knee stabilizers during level walking
Authors: Schipplein O. D. , Andriacchi T. P. 
Published: February 2005

AbstractThe gait of normal subjects and patients with varus deformities at the knee was studied by analyzing the interaction between the dynamic (muscular) and passive (ligamentous) restraints affecting lateral stability of the knee. A statically determinant model predicted that the midstance‐phase adducting moment during normal gait would cause lateral knee joint opening if either antagonistic muscle force and/or pretension in the lateral soft tissues were not present at the knee. The patient group tended to compensate for a high midstance‐phase adducting moment by walking with a style of gait that demanded more muscle force (greater flexion‐extension moments). This walking style reduced the chance of lateral joint opening. It can be speculated that this style of gait would help to maintain equilibrium at the knee. The higher muscle force would aid in resisting the adducting moment, keeping the joint closed laterally and thus increasing the stability of the knee.
The impact response of the seated subject
Authors: Broman Holger , Pope Malcolm H. , Benda Michal , Svensson Magnus , Ottosson Charlotte , Hansson Tommy 
Published: February 2005

AbstractAn impact method for establishing the dynamic response of the seated subject is introduced. The method employs a pendulum to apply the impact to the suspended seat. Pins are placed in the spinous process at L3. Highly reproducible results are obtained. The results were not affected by the amplitude of impact, implying a linear system. A marked peak of transmissibility is found in the 4–5 Hz range and an attenuation peak is found close to 8 Hz. Both muscle contraction and postural changes affect the dynamic response. A relaxed posture shows greater gain and attenuation peaks. A valsalva stiffens the system and reduces the effective damping. The vertical response of the body probably shows in the 5–6 Hz peak, while the rotational response is probably encompassed in the 8 Hz attenuation peak.
Age‐related changes in the human femoral cortex
Authors: Simmons E. D. , Pritzker K. P. H. , Grynpas M. D. 
Published: February 2005

AbstractBone undergoes structural changes with aging, but the nature of qualitative changes remains to be established. Blocks of midshaft femur were taken at autopsy from men of four different age groups: 20–25 years, 40–45 years, 60–65 years, and 80–85 years. Each femoral specimen was analyzed by density fractionation, a technique that allows the separation of bone by extent of mineralization and maturity. In the 20–25 group, lower density bone predominates. The 40–45 group is characterized by more highly mineralized bone with an increase in the 2.1–2.2 g/cc fraction. At 60–65 years, an increase in the lower density fraction was found, indicating an increase in new bone formation. At 80–85 years, there is an increase in the highest density bone (2.2–2.3 g/cc), which may represent regions of interstitial bone not properly removed through remodeling processes. Chemical studies did not reveal any change in Ca, P, Ca + PO4, or Ca/P molar ratio with respect to age. X‐ray diffraction studies show no changes in apatite crystal size with respect to age or degree of mineralization. Morphological studies documented increased remodeling activity and endosteal trabecularization in the older age groups, as well as increased intracortical porosity. An increase in the highest density fraction with aging may represent a pool of bone mineral that is less accessible to remodeling, which may be the interstitial bone.
Heterogeneity of blood flow in tibial cortical bone: An experimental investigation using microspheres
Authors: Willans S. M. , McCarthy I. D. 
Published: February 2005

AbstractThe distribution of tibial blood flow was measured by injecting approximately (600–1000) X 103 15 μ microspheres, labelled with either tin‐113 (113Sn) or cobalt‐57 (57Co) into femoral arteries of five mature greyhounds. The diaphyseal cortex, stripped of periosteum and devoid of marrow, was sawn into 40 pieces (10 transverse sections X 4 anatomical quarters/section). Relative deposition densities of the 113Sn microspheres in 40 pieces of cortex were found. These values, together with their associated masses, proved, from a statistical point of view, that flow rate heterogeneity was substantial in the diaphysis. In particular, for the diaphyseal cortex, distribution of relative deposition densities (flow rates) in six bones was found to be positively‐skewed with a relative dispersion ((SD/mean) x 100) of ∼40%.
Effects of gamma irradiation on the initial mechanical and material properties of goat bone‐patellar tendon‐bone allografts
Authors: Gibbons M. J. , Butler D. L. , Grood E. S. , Bylski‐Austrow D. I. , Levy M. S. , Noyes F. R. 
Published: February 2005

AbstractThe effects of 60Co gamma irradiation on the initial mechanical properties of the composite bone‐patellar tendon‐bone unit (CU) and the tendon midsubstance (TM) were studied. Frozen specimens were exposed to either 2 or 3 Mrad of gamma irradiation. Paired frozen specimens served as intraanimal controls. Treatment effects on the CU were assessed using four mechanical parameters. Effects on the TM were assessed using four material parameters measured using an optical surface‐strain analysis system. The maximum force and strain energy to maximum force of the composite unit were significantly reduced 27% and 40%, respectively, after 3 Mrad of irradiation (p < .05). Mechanical properties of the CU were not significantly altered, however, following 2 Mrad of irradiation. Based on individual paired contrasts between treatment and control, significant differences were also found in the material properties of the tendon midsubstance. The maximum stress, maximum strain, and strain energy density to maximum stress were significantly reduced following 3 Mrad, but not 2 Mrad, of irradiation. The results provide important “time zero” material property data, which will be useful for later anterior cruciate ligament reconstruction studies using irradiated allograft patellar tendons in the goat model and other animal models as well.
Cell patterns in the surface of rabbit articular cartilage revealed by the backscatter mode of scanning electron microscopy
Authors: Clark John M. , Rudd Eric 
Published: February 2005

AbstractTo study the distribution of cells in the surface layer of articular cartilage, rabbit hip and knee specimens were stained with silver and studied by scanning electron microscopy (SEM). The cartilage was treated en bloc using the Gomori methenamine silver technique, which stains the nuclei of exposed cells with reduced silver. The intact surface was then studied with a binocular microscope and SEM in the backscatter mode Only those cells within 30 μm of the surface stained, permitting that population to be imaged selectively. Depressions in the surface were related to groups of cells in clusters or rows bounded by collagen fibers. This study demonstrates the effectiveness of backscatter imaging in the study of chondrocytes. The relationship between surface contours and underlying cells is more complex than previously described.
Cartilage synthesizes the serine protease inhibitor PAI‐1: Support for the involvement of serine proteases in cartilage remodeling
Authors: Treadwell Benjamin V. , Pavia Michele , Towle Christine A. , Cooley Vernon J. , Mankin Henry J. 
Published: February 2005

AbstractThe work described here demonstrates the synthesis by human articular cartilage of plasminogen activator inhibitor‐1 (PAI‐1), a potent inhibitor of the serine protease tissue plasminogen activator (tPA). We also present data demonstrating an increase in PAI‐1 messenger ribonucleic acid (mRNA) in chondrocytes exposed to the cytokine interleukin‐1 (IL‐1). Interestingly, this elevation of steady‐state mRNA levels does not appear to result in an increase in synthesis of PAI‐1 protein. Northern blot analysis reveals that of the two mRNA species (3.4 kb, 2.4 kb) previously reported for PAI‐1, only the larger species (3.4 kb) appears to be synthesized by chrondrocytes. Our data demonstrate the IL‐1‐stimulated production by cartilage of tissue plasminogen activator. We also show evidence for the presence of plasminogen in cartilage. A scheme is presented indicating the probable importance of the serine proteases (tPA and plasminogen) and PAI‐1 in cartilage degradation.