bluuebunny/crossref_metadata_2025_split huggingface dataset:
Trochanteric transfer in total hip replacement: Effects on the moment arms and force‐generating capacities of the hip abductors
Authors: Free Scott A. , Delp Scott L. 
Published: February 2005

AbstractA three‐dimensional computer model of the pelvis, femur, gluteus medius, and gluteus minimus was used to evaluate the changes in muscle moment arms and force‐generating capacities caused by alterations in the location of the greater trochanter. In the first part of this study, the hip center and all other aspects of joint geometry remained unaltered, while we examined changes in abduction moment arms that resulted from transfer of the trochanteric fragment to a wide variety of positions on the femur. The largest increase in average abduction moment arm was 11% (0.5 cm), which occurred with an anterolateral transfer. Most transfers resulted in moment arm changes of less than 5%. In the second part of this study, the hip center was displaced 2 cm superiorly, and the effects of a distal trochanteric transfer on the moment arms and force‐generating capacities of the abductors were analyzed. The superior displacement caused a 13% decrease in the moment arm of the abductors and a 43% decrease in their force‐generating capacity. The moment arm was not restored by distal transfer of the greater trochanter; however, distal transfer had the major advantage of restoring muscle lengths and force‐generating capacities. These results suggest that trochanteric transfer should be considered primarily as a means to restore muscle length because it has limited potential to increase the moment arms of the two primary hip abductors.
Removal of surface bacteria by irrigation
Authors: Anglen Jeff , Apostoles Peter Steven , Christensen Gordon , Gainor Barry , Lane Joel 
Published: February 2005

AbstractWe examined the efficacy of various irrigation solutions delivered through a power irrigator to remove bacteria from three different surfaces. Titanium, stainless‐steel, and cortical bone surfaces were coated with three different bacterial species: Staphylococcus aureus, Pseudomonas aeruginosa, and Staphylococcus epidermidis. They were then irrigated with 1 L of fluid delivered by jet lavage. The fluids tested were normal saline and solutions of bacitracin, neomycin, and soap. One set of specimens was not irrigated, as a control. After irrigation, the specimens were sonicated to remove residual bacteria, and the sonicate was quantitatively cultured to allow evaluation of the amount of residual bacteria on the surface. The results showed that removal of bacteria reflects an interaction between bacterial species, surface characteristics, and irrigation solution. Fewer bacteria were present in all the irrigation groups than in the control. Soap solution was as good as or better than any other solution at removing all three types of bacteria from all three surfaces, although not all of the pairwise comparisons were statistically significant. There was a significant advantage to soap solution over antibiotic irrigant or saline alone in removing Staphylococcus epidermidis from metallic surfaces. The use of a soap solution for irrigation seems to improve the removal of some bacteria from some surfaces in this experimental model and may represent a better type of irrigation additive.
Porous ceramics as bone graft substitutes in long bone defects: A biomechanical, histological, and radiographic analysis
Authors: Johnson Kenneth D. , Frierson Kerek E. , Keller Tony S. , Cook Charles , Scheinberg Robert , Zerwekh Joseph , Meyers Laura , Sciadini Marcus F. 
Published: February 2005

AbstractThree porous ceramic bone graft materials were compared with regard to their ability to heal a 2.5 cm defect created surgically in a bilateral canine radius model. The ceramic materials were analyzed at 12 and 24 weeks after surgery and included tricalcium phosphate, hydroxyapatite, and collagen hydroxyapatite, which contained a mixture of 35% tricalcium phosphate and 65% hydroxyapatite with added collagen. Each material was evaluated alone and with added bone marrow aspirate. All the implants were compared with a graft of autogenous cancellous bone in the contralateral radius. Biomechanical testing and radiographic evauation revealed that the addition of bone marrow aspirate was essential for tricalcium phosphate and hydroxyapatite to achieve results comparable with those of cancellous bone. Collagen hydroxyapatite performed well without the addition of bone marrow, although the addition of marrow did have a positive effect. Further qualitative radiographic and histological analysis demonstrated that tricalcium phosphate was the only ceramic that showed any sign of degradation at 24 weeks. This observed degradation proved to be an important factor in evaluating radiographs because the radiodensity of collagen hydroxyapatite and hydroxyapatite interfered with the determination of radiographic union. At 24 weeks, tricalcium phosphate with bone marrow was the material that performed most like cancellous bone. In this study, the biomechanical and radiographic parameters of tricalcium phosphate with bone marrow were roughly comparable with those of cancellous bone at 12 and 24 weeks. Tricalcium phosphate was the only implant that showed significant evidence of degradation at 24 weeks by both histological and radiographic evaluations, and this degradation took place only after a degree of mechanical competence necessary for weight‐bearing was achieved.
Protective effect of hypothermia on contractile force in skeletal muscle
Authors: Bolognesi Michael P. , Chen Long‐en , Seaber Anthony V. , Urbaniak James R. 
Published: February 2005

AbstractThe clinical success of limb replantation and tissue transfer is partly dependent on the duration of ischemia experienced by the amputated part. This study focused primarily on the damage that occurs during this ischemic period. An experimental system was implemented that allowed the observation of contractile function in totally isolated skeletal muscle after ischemia. Contractile function was selected as an indicator of ischemic damage because normal function is the ultimate goal of replantation. All experiments were performed on the rat extensor digitorum longus. The muscles were subjected to ischemic periods of 1.5, 3.0, and 5.0 hours and were stored in either a hypothermic (4°C) or a room‐temperature (23°C) environment during the ischemic interval. After the ischemic period, all muscles were transferred to a tissue bath and were subjected to contractility testing, followed by fatigue testing. In both groups, muscle function decreased as the ischemic interval was increased. A significant difference in function between the normal control and the muscles of both ischemic group implied that ischemic injury had occurred in the hypothermic and room‐temperature muscles, even with the relatively short 1.5‐hour ischemic interval. After each ischemic interval, however, the hypothermic muscles produced significantly greater contractile force than the room‐temperature muscles in both the contractility and the fatigue tests. After 1.5 hours of ischemia, the contractile force in the hypothenic group was about three times as great as that observed in the room‐temperature group. These results indicated that muscle function after a period of totally isolated ischemia is protected by hypothermic preservation. They also support the advisability of storage of amputated parts and free muscle flaps in hypothermic environments before replantation, even after relatively brief intervals of ischemia.
Proteoglycans of human rotator cuff tendons
Authors: Berenson Matthew C. , Blevins Field T. , Plaas Anna H. K. , Vogel Kathryn G. 
Published: February 2005

AbstractRotator cuff and biceps tendons that appeared grossly normal were procured from adult cadavers without a history of shoulder problems. These tendons were analyzed for the amount and type of glycosaminoglycan, type of proteoglycan, and histology. When compared with the distal/tensional region of biceps tendon, the glycosaminoglycan content of supraspinatus, infraspinatus, and subscapularis tendons was 2.5‐fold higher and the glycosaminoglycan content of the proximal/compressed region of biceps tendon was 3‐fold higher. The ratio of hyaluronic acid to chondroitin sulfate/dermatan sulfate in all three cuff tendons was approximately 1. Rotator cuff tendons contained large proteoglycan similar to aggrecan, as demonstrated by sodium dodecyl sulfate‐polyacrylamide gel migration, elution from Sepharose CL‐4B, and content of both chondroitin sulfate and keratan sulfate chains. Both decorin and biglycan were also present, as demonstrated by migration in sodium dodecyl sulfate‐polyacrylamide gels and core protein immunoreactivity. In contrast, decorin was the only proteoglycan prominent in distal/tensional regions of biceps tendon. Histological analysis showed layers of loosely organized, alcian blue‐stained material running between the longitudinal collagen fiber bundles. The proteoglycan content of rotator cuff tendons was similar to fibrocartilage in tendons that have been subjected to compressive loads in situ. This suggests that cells of normal adult rotator cuff tendons have adapted to loads distinct from pure tension. However, the histological organization did not resemble mature fibrocartilage. The increased amount of proteoglycan in rotator cuff tendons may serve to separate and lubricate collagen bundles as they move relative to each other during normal shoulder motion.
Comparison of functional deficits in the rabbit tibialis anterior following tourniquet ischemia and tourniquet compression
Authors: Ohara William M. , Pedowitz Robert A. , Oyama Brian K. , Gershuni David H. 
Published: February 2005

AbstractThe purpose of this study was to measure the contractile properties of skeletal muscle after direct compression with a tourniquet and to compare these properties with those found after a similar period of tourniquet ischemia. A rabbit model of tourniquet compression of the tibialis anterior was developed and tested for this investigation. Fifty‐seven animals then were divided into four protocol groups: (a) thigh tourniquet (ischemia) at 350 mm Hg (46.7 kPa), (b) leg tourniquet (compression) at 350 mm Hg (46.7 kPa), (c) leg tourniquet at 125 mm Hg (16.7 kPa), and (d) controls. A significant decrease in maximum tetanic tension was demonstrated in all three experimental groups. Direct compression at 350 mm Hg resulted in the greatest decline in maximum tetanic tension (22.6% of control), followed by compression at 125 mm Hg (30.5% ) and ischemic injury (40.2% ). In addition, direct compression at 350 mm Hg resulted in a significantly greater loss of force‐generating capacity when compared with the ischemic group (p < 0.01). A similar pattern was noted for the rate of rise in maximum tetanic tension. Gross histologic examination of the tibialis anterior sections was consistent with the results of functional testing, with the more severe abnormalities noted in the compressed specimens. These results clearly demonstrate that tourniquet compression injury results in a more significant loss of functional strength and contractile speed than tourniquet ischemia. Further investigations on the safe limits of tourniquet use thus should be directed toward measuring the effect of the pneumatic tourniquet on the underlying soft tissues.
A mechanism for rotation restraints in the knee joint
Authors: Blankevoort L. , Huiskes R. 
Published: February 2005

AbstractLigament function in restraining axial rotation of the tibia relative to the femur cannot be revealed by analysis of ligament forces alone. The action of the articular surfaces should be taken into account as well. In this study, three‐dimensional mathematical models of four human knee joints were used to determine the limits of axial rotation between 0 and 90° of flexion, whereby the forces in the ligaments and articular contact were calculated, together with their contribution to the restraint moment that was required to counterbalance the applied axial moment of 3 Nm. In external rotation, the direct axial restraint was provided by the collateral ligaments. In internal rotation, when the cruciate ligaments and medial collateral ligament were predominantly loaded, the direct restraint moment resulting from the ligament forces was not sufficient to counterbalance the applied moment. The articular contact forces, which resulted from balancing the axial components of the ligament forces, contributed considerably to the restraint of internal rotation, Depending on the flexion angle, the contact forces provided approximately 50–50% of the internal restraint, whereas 95–100% of the external rotation restraint was accounted for by the ligament forces.
Relationship between bone growth rate and hypertrophic chondrocyte volume in new zealand white rabbits of varying ages
Authors: Kuhn Janet L. , Delacey Jonathan H. , Leenellett Elizabeth E. 
Published: February 2005

AbstractThe dynamics of longitudinal bone growth are very complex, and potential targets for control could be any one of a number of cells or physiologic processes. Previous studies have demonstrated a linear relationship between hypertrophic cell morphology and bone growth rate in various growth plates and animals. It is unclear whether this relationship varies with age or growth plate. This study tested for significant correlations between mean terminal hypertrophic cell volume and bone growth rate as a function of age and growth plate in the New Zealand White rabbit. Three male rabbits in each of five age groups (2, 3, 5, 8, and 12 weeks old) were used to analyze growth plates from the proximal femur, proximal tibia, and proximal and distal radius. With use of tetracycline labeling and stereological techniques, bone growth rates and hypertrophic chondrocyte volumes were measured. The data were stratified by age and growth plate location and were analyzed using linear regressions. Analyses of covariance were used to test for significant differences. First, there were significant differences due to age. Linear relationships between bone growth rate and hypertrophic chondrocyte volume existed only for the older age groups (all r2 > 0.8), not for the 2 or 3‐week‐old groups. Also, the slope of the relationship was significantly higher in 5‐week‐old rabbits than in the 8 and 12‐week‐old groups, Second, there were significant differences between species. A comparison of the rabbit data with pig and rat data in the literature showed significant differences between all three species. Third, significant differences between growth plates were found. Although hypertrophic chondrocyte volume plays an important role in bone growth, its function may be dependent on age, species, and location.
Effects of postmortem freezing on tensile failure properties of rabbit extensor digitorum longus muscle tendon complex
Authors: Leitschuh Paul H. , Doherty Tammy J. , Taylor Dean C. , Brooks Daniel E. , Ryan John B. 
Published: February 2005

AbstractThe tensile failures of extensor digitorum longus muscle tendon units from 16 male New Zealand White rabbits were studied in the fresh state (less than 30 minutes after death) and in the frozen/thawed state (frozen at −80°C for 28 days and then warmed to 38°C). Frozen/thawed extensor digitorum longus muscle tendon units had significantly lower values for load to failure (p < 0.01), energy absorbed to failure (p < 0.01), and strain at failure (p < 0.01), and they tended to fail at a different anatomic location (p < 0.01) (broadly at the fascia‐muscle interface as compared with horizontally at the musculotendinous junction) than fresh units. The results of this study suggest that freezing muscle tendon units significantly alters their tensile failure characteristics.
Subchondral plate thickness reflects tensile stress in the primate acetabulum
Authors: Dewire Peter , Simkin Peter A. 
Published: February 2005

AbstractTo evaluate possible relationships between body size and articular architecture, femoral head radius and subchondral plate thickness were assessed in skeletal hip joints from normal primates. The relative “contact pressure” on bearing surfaces was estimated from the measured radius and the normal body mass in species ranging from Cebuella pygmaea (0.1 kg) to Gorilla gorilla (170 kg). Subchondral plate thickness was evaluated by computed tomography in species ranging from Cercopithecus neglectus (4.0 kg) to Gorilla gorilla. Neither the “contact pressure” nor the thickness of the femoral subchondral plate varied substantially among species. In contrast, the acetabular subchondral plate thickened significantly (p = 0.01) as body size increased. This finding is interpreted as an osseous response to tensile acetabular stress, which can be expected to increase directly with the radius of curvature.
Prevention of bacterial adherence to implant surfaces with a crosslinked albumin coating in vitro
Authors: An Y. H. , Stuart G. W. , McDowell S. J. , McDaniel S. E. , Kang Q. , Friedman R. J. 
Published: February 2005

AbstractTitanium surfaces were coated with bovine serum albumin using carbodiimide, a crosslinking agent. The durability of the coated surfaces and the inhibitory effect of the albumin coating on bacterial adherence were tested in vitro for 20 consecutive days at 37°C in phosphate buffered saline, with intermittent agitation. The results showed that only 10% of the coated bovine serum albumin decayed off the surface during the 20‐day incubation period. The inhibition rate of the albumin coating on bacterial adherence remained high (greater than 85% ) throughout the experiment. The results suggested potential use of this crosslinked albumin coating to reduce bacterial adherence and thus the subsequent possibility of prosthetic or implant infection in vivo.
Role of different loading conditions on resorption of hydroxyapatite coating evaluated by histomorphometric and stereological methods
Authors: Overgaard S. , Søballe K. , Josephsen K. , Hansen E. S. , Bünger C. 
Published: February 2005

AbstractThe role of different loading conditions on resorption of plasma‐sprayed hydroxyapatite coating was investigated in an experimental study. Resorption of hydroxyapatite was quantified by histomorphometric and stereological methods on backscattered scanning electron images. Hydroxyapatite‐coated titanium implants were inserted unilaterally into the medial femoral condyle of the knee in 14 mature dogs. Initially, all implants were subjected to controlled micromotion of 150 μm. After 4 weeks, the dogs were randomly assigned either to have the implant surgically immobilized to prevent further micromovement or to have a sham operation. Sixteen weeks after the first operation, the implants were analyzed. Six noninserted implants served as controls. The surface area and volume of the hydroxyapatite coating were reduced on the immobilized implants by 53 and 67% (p < 0.05), respectively, and were further significantly reduced on the continuously loaded implants by 83 and 87%, respectively, compared with the control implants. The hydroxyapatite coating was significantly thinner on immobilized (15 μm) and continuously loaded (15 μm) implants as compared with control implants (23 μm), but no difference between the inserted implants was found. Areas not covered with hydroxyapatite had 29 and 24% bone coverage on the immobilized and continuously loaded implants (not significant). Resorption of hydroxyapatite coating did occur in vivo. Continuous loading of the implants accelerated resorption significantly compared with immobilization of the implants. It is suggested that completely resorbed hydroxyapatite was partly replaced by bone in direct contact with the metal implant surface.
Bone growth after osteotomy and internal fixation in young rabbits
Authors: Albanese Stephen A. , Spadaro Joseph A. , Chase Sharon E. , Geel Christoph W. 
Published: February 2005

AbstractThe factors leading to overgrowth following fixation of long‐bone fractures in children have never been clearly understood. The amount of trauma and the type of fixation may play a role. A rabbit model was used to investigate the influence of a femoral osteotomy and plate fixation on subsequent growth. Unilateral midshaft femoral osteotomy was performed in 6‐week‐old rabbits, and the bone was fixed internally with a plate and screws. End‐to‐end reduction was performed either at full length or with a segment removed. Bone length measurements at the end of growth revealed no significant difference in growth between the control femur and the femur that had undergone osteotomy and plate fixation. Shortened plated femora also showed no tendency to grow longer or faster than full‐length fixed femora or controls. Interestingly, in the ipsilateral tibia a small but statistically significant length increase, equivalent to about 2% increase in additional growth, was observed, whereas technetium‐99 methylene diphosphonate uptake was reduced in the tibial physes. In the context of the rabbit experimental model chosen, these results suggest that significant femoral overgrowth does not occur following femoral osteotomy and plate fixation.
Human anterior and posterior cervical longitudinal ligaments possess similar tensile properties
Authors: Przybylski Gregory J. , Carlin Gregory J. , Patel Prakash R. , Woo Savio L‐Y. 
Published: February 2005

AbstractOne hundred bone‐ligament‐bone complexes were isolated from the cervical spines of 20 fresh‐frozen human cadavers and mechanically tested in uniaxial tension. Load‐elongation curves representing the structural properties of the complex were obtained, and stiffness, ultimate load, energy at failure, and elongation were determined from the curves. Stress‐strain curves representing the mechanical properties of the ligament substance were also obtained, and elastic modulus was determined from these curves. Comparisons were made between anterior and posterior longitudinal ligaments and among cervical levels. The cross‐sectional area of the anterior ligament was smaller at the C2‐C3 level than at subaxial levels. There was a trend toward less stiffness but more energy at failure and greater elastic modulus for the anterior compared with the posterior ligaments at subaxial levels, although the differences were not statistically significant (p > 0.05).
Muscle activation at the human knee during isometric flexion‐extension and varus‐valgus loads
Authors: Buchanan Thomas S. , Lloyd David G. 
Published: February 2005

AbstractWe examined the role of muscles in counteracting static loads in the transverse plane at the knee to determine if (a) knee muscles are activated to counteract isometric varus or valgus loads, (b) muscle activity during varus and valgus loads changes with the angle of knee flexion, and (c) the direction of a muscle's activation can be predicted by its moment arm orientations. For seven subjects, muscle activity was recorded during isometric tasks using surface and intramuscular electrodes from 10 muscles that span the knee. A six‐degree‐of‐freedom load cell was rigidly attached to each subjects lower leg just above the ankle, and the subjects were instructed to push against the load cell so as to produce moments in the flexion‐extension‐varus‐valgus plane at the knee. Moments in this plane were all of equal magnitude and varied in direction the full 360° in 20° increments. Most muscles were not activated to stabilize the knee against varus‐valgus loads, but the sartorius, gracilis, and tensor fasciae latae showed substantial electromyographic activation in these directions. The load directions where muscles were principally active were observed to be dependent on joint angle for some muscles. In particular, the principal directions of activation for these three muscles changed as the angle of knee flexion changed. Similarly, a muscle's moment arm orientation was a good predictor of direction of activation for some muscles and a poor one for others. These results suggest that different muscles may play different roles in providing joint stability and that these roles are complex functions of muscle moment arm orientations, joint angles, external load directions possibly and other undetermined parameters.