bluuebunny/crossref_metadata_2025 huggingface dataset:
Buccal glands of adults of the lamprey Mordacia mordax, including comparisons with other species
Authors: Potter I. C. , Thomson G. J. , Cook R. D. , Cox J. M. , Macey D. J.
Published: February 2005

Mordacia mordax is one of the two anadromous parasitic lamprey species of the southern hemisphere family Mordaciidae. Its adults possess two lateral buccal glands and one central buccal gland. When the tongue‐like piston is retracted, the buccal glands occupy much of the opening of the oral cavity at the rear of the buccal cavity. The glands contain numerous tube‐like, ductless secretory units, which discharge directly into the buccal cavity. Their secretory epithelial cells contain numerous granules, some of which are zymogen‐like, while others have a beaded, spiralled appearance. The similarity of the latter to mast cell granules suggests that they may likewise produce an anticoagulant, which would be valuable to a presumed blood feeder such as M. mordax. The mucus produced by these cells could act as a carrier for the secretions and as an adhesive for promoting retention of t he secretions on the host's surface. When the young adults is transferred to salt water, the buccal glands increase their production and discharge of secretions. Since the glands are not enclosed in musculature, their secretions are probably discharged by mechanical pressure applied by the forward movement of the head of the tooth‐bearing piston into the buccal cavity. An account is given of the way in which the location, number, glandular organization, secretory granules, and type of secretion of the buccal glands of M. mordax, and thus presumably also their mode of function, differ markedly from those of members of the other lamprey family found in the southern hemisphere, and of all holarrctic lampreys. © 1995 Wiley‐Liss, Inc.
Measurement of mechanical properties of ligament substance from a bone‐ligament‐bone preparation
Authors: Woo S. L‐Y. , Gomez M. A. , Seguchi Y. , Endo C. M. , Akeson W. H.
Published: February 2005

This investigation presents a new approach in the measurement of the mechanical properties of the ligament substance from tensile testing of a bone‐ligament‐bone complex. Such basic information should be one of the necessary prerequisites in the evaluation of ligament repair as well as reconstruction by autogenous tissue grafts or artificial ligament implants. The use of a video system permits the determination of tensile strains of the mid‐medial collateral ligaments from the canine, swine, and rabbit without mechanically interfering with the ligament deformation during testing. This methodology further eliminates the difficulties of measuring the initial length of the entire medial collateral ligament, as its insertions to bones are ambiguous and cover a large area. It was found that the strain of the ligament substance is consistently and considerably less than specific deformation of the bone‐ligament‐bone complex. These data suggest that the ligament‐bone structure stretches nonuniformly with the highest deformation occurring near or at the ligament insertion sites to bone. Other interesting findings include the variation of tensile strains along the ligament substance for all animal species studied.
The origin of stress‐generated potentials in fluid‐saturated bone
Authors: Pienkowski D. , Pollack S. R.
Published: February 2005

The objective of this study was to determine the origin of stressgenerated potentials (SGPs) in fluid‐saturated bone. Stress‐generated potentials were studied as a function of the conductivity, NaCl concentration, and viscosity of the fluid contained within cortical human and bovine bone. Bone samples were soaked in solutions in which NaCl and sucrose concentrations were systematically varied. Macroscopic SGPs and their relaxation times were measured as a function of these properties. Stress‐generated potentials were also measured as a function of conductivity and NaCl concentration by using a microelectrode. The results of this study confirmed that the properties of the fluid in bone have a great influence on the magnitude and time dependence of the SGP. Especially notable was the observation that solutions of high NaCl concentration consistently reversed the polarity of the SGP. These results are consistent with streaming potential theory. Although fluid‐saturated bone may retain some piezoelectric properties, SGPs are predominantly caused by streaming potentials.
Comparison of mechanical work and metabolic energy consumption during normal gait
Authors: Burdett Ray G. , Skrinar Gary S. , Simon Sheldon R.
Published: February 2005

The validity of using mechanical measures of work to indicate the metabolic energy consumption during normal gait was examined. These mechanical measures were (a) mechanical work done on the center of mass per kilogram body mass per second (\documentclass{article}\pagestyle{empty}\begin{document}$ \dot W_{{\rm cm}} $\end{document}), calculated by integration of ground reaction forces measured by force platforms; (b) total body segmental work per kilogram body mass per second (\documentclass{article}\pagestyle{empty}\begin{document}$ \dot W_{{\rm seg}} $\end{document}), calculated from individual body segment energies measured by motion analysis; and (c) the sum of the normalized absolute moment impulses per second acting on the joints of the lower extremities (\documentclass{article}\pagestyle{empty}\begin{document}$ \dot M $\end{document}), calculated from both force and motion data. The metabolic energy consumption, determined by analysis of expired air, and the three mechanical measures of work were calculated for six normal subjects walking at five speeds. Each measure of mechanical work per second walked was highly correlated with metabolic energy consumption/kg · s (r = 0.89 for Wcm, r = 0.79 for \documentclass{article}\pagestyle{empty}\begin{document}$ \dot W_{{\rm seg}} $\end{document}, and r = 0.85 for M), but a poorer correlation was found between each measure of mechanical work per meter walked and net metabolic energy consumption/kg. m (r = 0.54 for Wcm, r = 0.28 for Wseg, and r = 0.03 for M). These mechanical parameters, particularly when measured per time, may be useful in comparing metabolic energy consumption between individuals or between different walking conditions for the same individual.
Comparative cost of walking in young and old adults
Authors: Waters Robert L. , Hislop Helen J. , Perry Jacquelin , Thomas Lynn , Campbell Joyce
Published: February 2005

Normative data that summarize the energy requirements and gait characteristics of level outdoor walking were determined in 111 normal subjects between the ages of 20 and 80 years. Subjects were divided into two age groups: young adults (20–59 years) and senior subjects (60–80 years). The mean rate of oxygen consumption for young adults and senior subjects did not significantly differ, averaging 11.9 ml/kg‐min for both groups. The data on heart rate paralleled the findings on oxygen consumption, averaging 100 and 103 beats/ min, respectively. The net oxygen cost per meter walked for senior subjects, 0.16 ml/kg‐m, was significantly greater (p < 0.0005) than the value for young adults, 0.15 ml/kg‐m, due to a decline in the average walking speed. The average gait velocity for senior subjects, 73 m/min, was statistically significantly less (p < 0.0005) than the values for the younger adults, 80 m/min.
Tissue response to carbon‐reinforced polyethylene
Authors: Groth Harry E. , Shilling Joel M.
Published: February 2005

There has been clinical concern about the gray discoloration in synovial tissue adjacent to carbon‐reinforced polyethylene total joint implants. To evaluate the pathologic response of the synovium to this material, synovial specimens from 11 total ankle cases with carbon‐reinforced tibial components and two synovial specimens from cases with standard polyethylene tibial components were studied by gross and histologic techniques. Polyethylene debris was found to produce a significant synovial reaction with histiocytes and foreign body giant cells. This was found in both the carbon‐reinforced cases and in those cases without carbon‐reinforced components. This reaction is also seen in revisions of total hips and total knees in which standard polyethylene components have been implanted. In contrast with this, carbon particles produced only a minimal reaction in the synovial tissue. Carbon appears to be an extremely benign implant material, and synovial discoloration from shed carbon fibrils does not appear to present a significant clinical problem.
An experimental polyarthritis associated with systemic antigen excess in immune rabbits
Authors: Kawai Kazuo , Scudamore R. Allan , Cooke T. Derek V.
Published: February 2005

Rabbits were immunized with bovine serum albumin and later challenged intraperitoneally with the same antigen. Polyarthritis, characterized by synovial lining layer hyperplasia and leukocyte infiltration, was conditional on animals having excess free serum antigen in the presence of circulating immune complexes (IC). Nonimmune controls did not develop polyarthritis following antigen challenge. Data are presented that strongly suggest that synovitis was triggered by deposition of IC in the synovia. During the chronic phase of polyarthritis the synovium was clear of antigen but there was marked retention within joint fibrocartilage, suggesting that antigen, immobilized locally, may maintain the chronic synovitis. Clinical relevance: There are several animal models in which experimental arthritis has been induced by antigenic challenge. The resemblance of the lesions to those of human rheumatoid arthritis has provided the rationale for studying the immune events associated with the onset of acute and maintenance of chronic phases of experimental arthritis.
Effects of increased systemic blood pressure on the tissue fluid pressure threshold of peripheral nerve
Authors: Szabo Robert M. , Gelberman Richard H. , Williamson Richard V. , Hargens Alan R.
Published: February 2005

This study was designed to evaluate the functional response of the median nerve at the wrist to various degrees of acute, local compression in hypertensive patients. After measuring resting tissue fluid pressure in the carpal tunnel of the nondominant hand of nine subjects (diastolic pressures of 90 mm Hg or greater), localized pressures of 50, 60, or 70 mm Hg were applied to the palmar aspect of the wrist. Motor and sensory latencies and amplitudes of the median nerve were evaluated before compression, during 30–240 min of compression, and during the postcompression recovery phase. Sensory responses were completely blocked at a threshold tissue fluid pressure of 60–70 mm Hg, measured by the wick catheter technique. This pressure threshold was greater than the 40–50 mm Hg previously found in normotensive subjects. The tissue pressure threshold of normotensive and hypertensive subjects was consistently 30 mm Hg below diastolic blood pressure (approximately 45 mm Hg below mean arterial blood pressure). These results support the concept that ischemia is the prime mechanism of conduction block in low pressure, nerve‐compression syndromes.
Blood flow and bone uptake of99mTc‐labeled methylene diphosphonate
Authors: Riggs Stanley A. , Wood Michael B. , Cooney William P. , Kelly Patrick J.
Published: February 2005

In mature dogs with comparable levels of bone remodeling, we produced either increased (with adenosine triphosphate) or decreased (with epinephrine) blood flow to one hindlimb. In 13 dogs (five control, four with increased flow, and four with decreased flow), we compared uptake, at 3 h after injection of radiolabeled diphosphonate in the mid‐tibia, with blood flow as determined by microspheres. Blood flow was determined with 85Sr‐labeled microspheres, and determination of uptake of 99mTc methylene diphosphonate (99mTc‐MDP) was by a gamma detector. There was a linear relationship between changes in diphosphonate uptake and changes in blood flow at decreased and normal flows; however, at high flows the relationship was nonproportional, indicating a disproportionately slower increase in 99mTc‐MDP uptake with increasing blood flow. In six dogs an initial 1‐h uptake curve of 99mTc‐MDP was determined in both control and experimental limbs under states of increased and decreased blood flow. The 30‐min uptake value, 60‐min uptake value, area under the curve, and the slope of the curve were related to flow as determined by microspheres. The data are consistent with the hypothesis that deposition of bone‐concentrating isotopes such as 99mTc‐MDP is partly controlled by blood flow; at subnormal and normal flows tracer uptake is closely related to blood flow, but at supranormal flow rates it is not and appears to be diffusion limited.
Fracture of long bones: Rate effects under singular and combined loading states
Authors: Peterson D. L. , Skraba J. S. , Moran J. M. , Greenwald A. S.
Published: February 2005

This study was undertaken to determine the effect of loading rate on bone failure under singular and combined loading states. Using the entire loading range of an Instron Materials Testing Machine, 190 pairs of canine radii were tested. One bone of each pair was subjected to either torsional or a combination of axial and torsional loads, and compared with a control specimen. Compressive loads of 4.6 and 11.5 N were utilized. Torque to failure and energy data versus loading rate were plotted. As loading rate increased, the torque and energy values were found to increase, reach a peak, and then decline at higher rates. Fractures produced under the combined state of loading are representative of those clinically found in human trauma situations.
A study of factors influencing muscle activity about the knee joint
Authors: Andriacchi T. P. , Andersson G. B. J. , Örtengren R. , Mikosz R. P.
Published: February 2005

Several factors influencing the myoelectric activity of muscles surrounding the knee joint were studied using fine‐wire monopolar electrodes. The muscles studied included the vastus lateralis, vastus intermedius, rectus femoris, vastus medialis, gracilis, sartorius, biceps femoris, semimembranosus, semitendinosus, tensor fasciae latae, medial head of the gastrocnemius, and lateral head of the gastrocnemius. Muscle activity was measured in response to unidirectional loads tending to flex and extend the knee, and to combined loads of flexion‐adduction, flexion‐abduction, extension‐adduction, and extension‐abduction. Results indicate that the individual muscle responses are dependent upon the direction, magnitude, and combination of external moments, as well as on the flexion angle of the knee joint. Muscle response appeared to be influenced by certain intrinsic mechanical characteristics of the knee joint that tend to change the moment arms of the muscles as the knee moves. For example, the substantial changes in quadriceps myoelectric activity with knee flexion, with constant load applied, can be related to the movement of the tibial‐femoral contact changing the lever arm of the quadriceps mechanism. This study indicates that the mechanics of the knee joint must be taken into consideration while attempting to interpret or predict the load response of muscles crossing the knee joint.
Joint position sense in total knee arthroplasty
Authors: Skinner Harry B. , Barrack Robert L. , Cook Stephen D. , Haddad Ray J.
Published: February 2005

Seventeen postoperative total knee arthroplasty (TKA) patients were evaluated using two tests of knee joint position sense. Young controls and age‐matched controls underwent identical tests. The TKA patients also underwent gait analysis, including foot switch stride analysis, and clinical evaluation using a standard scoring system. Results showed statistically significant decreases in joint position sense from young controls to old controls, and further significant decreases with joint disease; however, no further worsening was noted as a result of TKA. The abnormal gait parameters seen in TKA patients correlated as well with position sense as with clinical score. Strongest correlations were seen when a combined clinical and proprioceptive score was compared with gait parameters. In spite of alleviation of pain and correction of deformity, normal gait and function are not typically achieved after total knee replacement. Irreversible loss of joint proprioceptive function due to the disease process may be a major factor in the discrepancy between clinical and functional outcomes of total joint arthroplasty. Furthermore, loss of proprioception and the resulting abnormal gait patterns may place increased stress on components and contribute to loosening. In addition, an association between degenerative joint disease and decline in proprioception is suggested.
Allogenic transplants of bone revascularized by microvascular anastomoses: A preliminary study
Authors: Moore J. Russell , Phillips Thomas W. , Weiland Andrew J. , Randolph Mark A.
Published: February 2005

An area of experimental bone grafting that needs further study is the use of free vascularized allografts of bone. In 35 outbred mongrel dogs, the viability of vascularized bone allografts with and without azathioprine immunosuppression was compared to vascularized autogenous bone grafts. Viability was assessed by histologic techniques, fluorochrome bone labeling, and electron microscopy. Autogenous vascularized bone grafts remained viable, and it was concluded that microvascular technique was not the limiting factor in attaining survival of the grafts. The behavior of autogenous vascularized bone grafts with and without the influence of azathioprine was similar. Allogenic vascularized bone transplants uniformly failed at a period between 2 and 3 weeks. Immunosuppression with azathioprine did not appreciably affect survival of the osteocytes. However, the host response to the foreign tissue was slightly modified. The clinical ramifications of bone transplantations in humans are not analogous to the clinical situation of transplantation of other organs. If vascularized bone transplants are performed in humans, a relatively safe form of immunosuppression is necessary. This study suggests that azathioprine alone does not offer sufficient immunosuppression to insure viability of the vascularized transplant.
Effect of cement pressure and bone strength on polymethylmethacrylate fixation
Authors: Askew Michael J. , Steege John W. , Lewis Jack L. , Ranieri John R. , Wixson Richard L.
Published: February 2005

The effect of the quality of the bone and of the cement pressurization magnitude and duration on the fixation achieved with polymethylmethacrylate (PMMA) bone cement is studied in vitro. Seventy‐one cementbone interface specimens, prepared under various conditions of pressurization of low‐viscosity bone cement, are tested in tension. The load at failure and the maximum cement penetration are measured to assess the fixation achieved, and the quality of the bone is assessed by determining the compressive strength of each of the bone specimens. Statistical analysis of the data indicates that the pressure magnitude is the most influential of the factors considered in the cement penetration behavior and in the development of failure load capacity. The duration of the pressure does not appear to be a significant factor. The cement penetration is a decreasing function of the bone strength, reflecting a decrease in the porosity and an increase in the area fraction. Although not directly measured in these tests, these latter bone properties are indirectly measured by the bone compressive strength. The effect of increasing bone strength on the failure load is nonlinear. The development of adequate failure load capacity is the result of a balance between the cement penetration allowed by the porosity of the bone and the inherent strength of the cancellous bone itself. Weak bone, although adequately penetrated by cement, cannot provide strong fixation. Stronger, denser bone limits cement penetration, but pressurization enhances development of failure load capacity through more complete infusion and interlocking of the cement in the available pore space. The strength of the fixation achievable for any bone is limited by the intrinsic strength of the bone. An optimal depth of cement penetration of 4 mm and an optimal bone area fraction of 0.20 are suggested for the most effective fixation.
Effects of fat admixture on the strengths of conventional and low‐viscosity bone cements
Authors: Ferracane J. L. , Wixson R. L. , Lautenschlager E. P.
Published: February 2005

The diametral tensile and compressive strengths of both conventional doughy and low‐viscosity (LVC) bone cements were tested with sequential admixtures of up to 50% (by weight) liquified fat. The addition of as little as 5% (by weight) fat caused a significant reduction (p = 0.05) in the strengths of both cements. The LVC appeared to be affected to a greater degree by fat contaminations than did the conventional cement, although the strengths of the LVC were generally equal to or higher than those of the conventional cement. The enhanced effect of fat contamination on the LVC was thought to be due to the more fluid, tacky nature of this material during administration.
Dynamic radioisotope bone imaging as a noninvasive indicator of canine tibial blood flow
Authors: Nutton Richard W. , Fitzgerald Robert H. , Brown Manuel L. , Kelly Patrick J.
Published: February 2005

The relative values of dynamic and static bone imaging with hydroxymethylenediphosphonate technetium 99m (99mTc HDP) as an indicator of bone blood flow was investigated in the tibia of mature dogs. The dynamic bone scan consisted of 60 1‐s images formed after the intravenous injection of 99m Tc HDP, and the static bone scan was a 45‐min uptake image. Blood flow to the tibia was determined by using radioactively labeled microspheres. Studies were carried out in control dogs, in dogs in which blood flow was increased in one leg with ATP, and in dogs in which blood flow was decreased in one leg with norepinephrine. A significant (p < 0.001) linear relationship between the dynamic scan values and bone blood flow was found at a wide range of blood flow rates. When blood flow increased by more than 50%, the effects of “diffusion limitation” were seen in the static scans: increase in tracer uptake was disproportionately small for a significant increase in blood flow. There is no method currently available for estimating bone blood flow by a noninvasive technique. The method described here may be useful for providing a semiquantitative measure of bone blood flow. This improved versatility of bone imaging may have a role in the management of osteomyelitis or complicated fractures, or in assessing the viability of vascularized bone grafts.
Invalidity of single‐passage measurements of the extraction of bone‐seeking tracers in rats and rabbits
Authors: Tothill P. , Hooper G.
Published: February 2005

Single‐passage experiments in which bone‐seeking tracers are injected arterially at the same time as microspheres to determine an extraction ratio are only valid if the maximum transit time through bone is less than the minimum recirculation time. This validity was investigated by injecting various intravascular and more diffusible tracers into the hearts or aortas of rats and rabbits at different times before the rapid cessation of circulation. At no time between 4 and 60 s after injection did the bone concentration of any of the tracers fall to negligible values. Removal of unbound tracer is therefore not complete before recirculation starts, and the single‐passage technique is invalid. Measurements of bone blood flow based on the clearance of 18F cannot be substantiated, as its extraction is flow dependent.
Changes in long‐bone structural properties during the first 8 weeks of plate implantation
Authors: Carter D. R. , Shimaoka E. E. , Harris W. H. , Gates E. I. , Caler W. E. , McCarthy J. C.
Published: February 2005

The midplate structural rigidities of metal‐ and plastic‐plated intact canine femora were experimentally determined after initial plate application and 8 weeks after in vivo implantation. Composite beam theory significantly overestimated the bending rigidities of the metal‐plated bones. The rigidities of the plastic‐plated bones were nearly identical to that of the isolated bone, as composite beam theory predicted. Plating with either plate increased the intracortical porosity and caused the deposition of periosteal new bone, which was greater with plastic than with metal plates. The increased rigidities provided by the attachment of the metal plates and, hence, the degree of bone strain shielding were variable. Platings for 8 weeks which provided little strain shielding with either metal or plastic plates caused an increase in bone flexural rigidity (measured after plate removal) with respect to the contralateral control. Platings that provided increasing amounts of strain shielding caused a decreasing midplate bone rigidity (measured after plate removal) and increasing bone deposition at the outer screws. These findings suggest that the surgical implantation of any plate (metal or plastic) will provide a net stimulus to bone formation and consequently increased bone structural rigidity, even though intracortical porosity is increased. If the plate significantly reduces the normal loads borne by the bone, however, there is a net stimulus to remove bone, resulting in a loss of midplate structural rigidity within 8 weeks of implantation.
Partial purification and characterization of a proteoglycan‐degrading neutral protease from bovine epiphyseal cartilage
Authors: Ehrlich Michael G. , Armstrong Ann L. , Mankin Henry J.
Published: February 2005

Degradation of the proteoglycan matrix is considered an essential step in the process of calcification in the growth plate. This laboratory has just described the presence of a protease in human growth plate cartilage that degrades proteoglycan at neutral pH. We report here the isolation, partial purification, and characterization of these proteoglycan‐degrading neutral proteases of bovine epiphyseal cartilage. It appears that there is more than a single enzyme active at neutral pH. These enzymes are of low molecular weight (below 30,000), poorly charged, and inhibited by metal chelating agents. Activity is best restored in the presence of zinc. This represents the first characterization of this important enzyme group.
Spontaneous degenerative spinal disease in the laboratory rabbit
Authors: Green P. W. B. , Fox R. R. , Sokoloff L.
Published: February 2005

The spines of 35 rabbits (32 New Zealand white and 3 AC/J), ranging in age from 3 months to 8½ years, were investigated systematically for spontaneous degenerative changes. Three types of lesion were observed. (1) The nucleus pulposus underwent chondroid metaplasia throughout the length of the vertebral column by the age of 2 years. (2) Hydroxyapatite deposition was found in the nucleus pulposus in 12 of 20 animals examined roentgenographically. The lesion occurred principally in the distal thoracic segments and was first observed in 3‐month‐old rabbits. (3) Spondylosis occurred in each of four macerated spines from animals >24 months old. Portions of the spine spared by disc calcification were affected.
Response of amputated rat limbs to fetal nerve tissue implants and direct current
Authors: Sisken Betty F. , Fowler Ira , Romm Sharon
Published: February 2005

We have previously shown that implanted fetal nerve tissue stimulates the regeneration of amputated chick limbs. The purpose of this study was to determine whether a similar phenomenon would occur in amputated rat limbs and if addition of applied direct current (DC) would affect this process. Thus, fetal nerve tissue was implanted into amputated stumps of 3‐week‐old rats; variable tissue regeneration was induced that was dependent on the age of the donor implant and the presence of applied DC. Twelve or 14 day fetal neural implants induced new accessory bones containing epiphyseal plates and marrow cavities and occasionally formed joint‐like structures with the host humerus. Addition of DC to 12 day neural implants increased the number of new bones formed. Eighteen day neural tissue with applied DC did not induce new bone formation but stimulated the maximal elongation of the host humerus and outgrowth of nerve fibers to the cut surface. Implantation of fetal heart tissue or implantation of fetal neural tissue into unamputated limbs failed to induce new bone formation. Although true limb regeneration was not achieved, formation of new skeletal elements did occur and this effect was enhanced by applied DC.
In vitro contact stress distribution on the femoral condyles
Authors: Brown Thomas D. , Shaw Daniel T.
Published: February 2005

Contact stress distributions were measured across the tibiofemoral joints of 11 fresh‐frozen normal cadaver specimens. Local stress magnitudes were sensed by arrays of miniature piezoressistive transducers inset superficially in the cartilage of the femoral condyles. Knee joints were tested at 0, 10, 20, and 30° of flexion and later retested at 0° following medial and dual meniscectomies. For the intact joint, both the spatial mean and peak local contact stresses rose approximately linearly with the joint resultant, reaching levels of 2.6 and 8.0 MPa, respectively, at 3 kN of applied loading. Flexion angle variations in the range studied failed to cause significant changes in the major contact parameters. Although meniscectomies involved contact area reductions and consequent stress increases, such effects were more moderate than results previously seen for static loading of the tibial plateau.
Microinjury to the synovial membrane may cause disaggregation of proteoglycans in rabbit knee joint articular cartilage
Authors: Frost Linda , Ghosh Peter
Published: February 2005

Proteoglycans (PGs) isolated from articular cartilage (AC) of mature rabbits subjected to two or more consecutive intraarticular (IA) injections of sterile saline 24 h apart showed an aggregation defect in the presence of excess hyaluronic acid (HA). Although the PG contents of experimental and control cartilages were indistinguishable, a higher proportion of PGs were extractable from the 3 × IA tissues, as assessed by uronic acid analysis. Proteoglycans from experimental and control cartilages when examined by Sepharose CL‐2B chromatography showed two subunit populations, the smaller (KAV = 0.70) containing more ketatan sulphate than the larger (KAV = 0.31). Cultures of AC from IA joints released more 35SO4‐labelled PGs into the media over 72 h than control tissues and consisted mainly of PG degradation products although 20% could aggregate in the presence of HA. Examination of PG aggregation 2 weeks after 2 × IA or 3 × IA injections showed that the defect initiated was still present; however, cartilage of immature rabbits was not affected by the 2 × IA procedure.
Pathogenesis of chronic inflammation in experimental ferritin‐induced arthritis. V. Electron microscopic localization of specific antibodies in the synovial membrane
Authors: Sakata Toshiro , Ohno Osamu , Ishikawa Hitoshi , Hirohata Kazushi , Cooke T. D. V.
Published: February 2005

Antibody synthesis by the arthritic synovium of rabbits with antigen‐induced arthritis has been demonstrated, but knowledge of the details of the specific localization of antibody in the membrane is limited. Specific antibody in the synovium of ferritin‐induced arthritis was detected by electron microscopic observation of bound ferritin. The specific antibodies were localized in the cisternae of the endoplasmic reticulum and perinuclear spaces within plasma cells. In the extracellular matrix, specific antibody was found distributed as a network within collagen bundles and in the basement membrane of the subsynovial small blood vessels.
Biomechanics of bipolar hip endoprostheses
Authors: Krein S. W. , Chao E. Y. S.
Published: February 2005

The bipolar endoprosthesis was designed to alleviate problems encountered with conventional hip endoprostheses. Recent designs have advocated the use of offset centers of rotation between the inner and outer jointbearing surfaces to generate a valgus‐producing moment on loading (antivarus head dynamics). This study was undertaken to justify this biomechanical feature by performing (a) cyclic loading of the bipolar head in the varus position, (b) analysis of motion between the inner and outer bearing surfaces, and (c) evaluation of antivarus head dynamic function. Four endoprosthetic designs were studied: the Bateman UPF, Osteonics UHR, Giliberty II, and Bi‐Centric. Significant plastic deformation occurred in the UPF and UHR prostheses when loaded in an extreme varus position. Theoretically, motion is most likely to occur at the inner bearing if the frictional coefficients are equal at both surfaces. The UHR prosthesis with eccentric offset of bearing centers can provide the antivarus effect in laboratory conditions. Whether the antivarus effect and/or the dominant inner bearing motion will occur in vivo awaits careful clinical study.
Stress analysis of a partially slotted intramedullary nail
Authors: Beaupré Gary S. , Schneider Erich , Perren Stephan M.
Published: February 2005

A finite element analysis of the Arbeitsgemeinschaft für Osteosynthesefragen/Association for the Study of Internal Fixation (AO/ASIF) intramedullary femoral nail was performed to study the failure of the nail from circumferential cracking near the slot tip. These failures are evidently the result of a stress‐concentrating effect owing to the partially slotted nail design. Several finite element models were created of the proximal one‐fourth of the nail. One model of the nail incorporated the cloverleaf profile as it is presently manufactured, and one had a circular cross section. An additional three models were created with alternative slot‐tip geometries: a narrowed slot, a tapered slot, and a widened slot. Antero‐posterior (AP) and medio‐lateral (ML) bending loads and torsion loads were applied in two fundamentally different loading modes: (1) loads that were applied on both sides of the slot tip (spanned); and (2) loads that were self‐equilibrating distal to the slot tip (non‐spanned). For the load cases studied, for all models, the stresses predicted from the finite element models were locally highest at the junction between the open and closed cross sections. Alternative slot‐tip shapes had a marked effect on the predicted stresses, in one case reducing maximum stress by 40%. However, no alternative slot tip shape was uniformly superior for all load cases. Therefore, until the in vivo loading modes are known more precisely, an alternative slot‐tip shape cannot be proposed.
Fatigue performance of external fixator pins
Authors: Kasman Roberta A. , Chao Edmund Y. S.
Published: February 2005

The fatigue performance of several types of commonly used external fixator pins was examined. The pins were tested under a cyclic bending mode. A strength reduction factor (SRF) was defined to quantify the effect of stress concentration caused by the pin threads as compared with the smooth portion of the pin. The half pins tested had much higher SRF values than the corresponding full pins because of the smaller root diameter of the threaded regions. The use of finer threads and a cold rolling process appeared to increase the pin fatigue strength. In some pins, the depth markers on the smooth portion and the self‐tapping fluted region were sites of significant stress concentration. When certain half pins are severely loaded under clinical conditions, they may fracture because of fatigue.
Radiation sterilization and the wear rate of polyethylene
Authors: Rose R. M. , Goldfarb E. V. , Ellis E. , Crugnola A. N.
Published: February 2005

The resistance to sliding wear was measured in bovine serum for two polyethylenes with molecular weights of about 105 and 106 that had been irradiated in air and nitrogen with γ‐ray dosages up to 20 Mrad. Molecular weight measurements were performed after irradiation as well. Wear generally increased with dosage and contact stress, becoming measurable in many cases only after a critical dose (or stress) was exceeded. The most significant effect noted was that the irradiation changed the pressure dependence of the wear rate. Thus, whether or not a sterilizing (or resterilizing) dose will measurably increase the wear depends on the contact stress and, therefore, on the specific application. The increase in wear rate appeared to be due to a combination of scission and oxidation, suggesting the practical advisability of radiation sterilization under an inert atmosphere, as confirmed by comparative measurements at the higher dosages.
Interrupted and continuous microarteriorrhaphy techniques: A hemodynamic comparison
Authors: Blair William F. , Pedersen Douglas R. , Joos Karen , Bondi David
Published: February 2005

The purpose of this study was to compare interrupted and continuous suturing techniques in laboratory microarteriorrhaphy. The comparison was based on rat femoral artery hemodynamic variables, including blood velocities, lumen diameters, and calculated blood flow. These variables were calculated by an offline computer from Doppler frequency shifts that were measured by a 20‐MHz pulsed ultrasonic Doppler velocity meter. No statistical difference was noted postoperatively between the interrupted and continuous techniques relative to any hemodynamic variable. Average blood flow after the interrupted (n = 12) and continuous (n = 12) techniques was 6.59 ± 1.12 and 6.74 ± 1.20 ml/min, respectively. The two microarteriorrhaphy techniques result in equal postoperative vessel hemodynamics in a laboratory model.
Topographical variations in the morphology and biochemistry of adult canine tibial plateau articular cartilage
Authors: Bullough Peter G. , Yawitz Peter S. , Tafra Lorraine , Boskey Adele L.
Published: February 2005

Topographically, there are both morphological and biochemical differences in the articular cartilage of the tibial plateau of normal adult dogs when the cartilage covered by the meniscus is compared with that more centrally placed and not covered by meniscus. Histologically, differences are present in the surface morphology, in intra‐ and extracellular lipid content, and in the morphology of the mineralization front. Electron microscopy shows, in the covered cartilage, variability in collagen fiber size, with evenly spaced fibers apparently randomly distributed and an orderly relationship between the proteoglycans and collagen, whereas in the uncovered area, the collagen is aggregated into bundles and appears to be dissociated in large part from the proteoglycans. The most striking feature in the biochemistry of the two regions is an increased water content in the uncovered cartilage, as compared with the covered. In addition, there is an increased amount of proteoglycans that can be extracted in the uncovered cartilage. The heterogeneity of the cartilage on the tibial plateau should be taken into account when considering both the histologic and biochemical variations found in osteoarthritic cartilage; and when reflecting on the pathogenesis of osteoarthritis.
Determination of callus quantity in 4‐ week‐old fractures of the rat tibia
Authors: Aro H. , Eerola E. , Aho A. J.
Published: February 2005

In clinical practice the quantity of fracture callus is usually estimated on the basis of radiographs. In experimental studies on fracture healing, more exact chemical measurements (total protein, DNA, and mineral contents) have been used to quantitate the amount of callus. It is not known, however, how these two parameters correlate with each other. In this study we used different (radiographic, histomorphometric, and chemical) methods to evaluate the quantity of fracture callus in 4‐week‐old tibial fractures of rats stabilized by intramedullary nailing. The wet and dry weights and the nitrogen, collagen, calcium, phosphorus, and DNA contents of the calluses showed no correlation with the radiographic size of the calluses. There was a strong correlation (p < 0.001), however, between radiographic and histomorphometric callus sizes. The mass of callus and the chemically defined parameters of callus production thus indicate different properties of the healing bone.
Binding sites in fetal and growth plate cartilage
Authors: Cruess Richard L.
Published: February 2005

In addition to genetic and nutritional factors, linear growth during the prenatal and postnatal periods is controlled by peptide, steroid, and thyroid hormones interacting with the receptors present on the membrane or in the cytosol and nuclei of growth plate cartilage. Using standard procedures, insulin and “nonsuppressible insulin‐like activity” (a somatomedin) showed significant binding in 600, 15,000 and 105,000 g membrane fractions of epiphyseal cartilage of immature animals. The binding of growth hormone and prolactin was small and probably not significant. Specific uptake of glucocorticoid was demonstrated in viable canine chondrocytes, but not of androgen, estrogen, or vitamin D3 metabolite. A triiodothyronine receptor was present in nuclei from dog epiphyseal cartilage. Hormones that lack binding may affect cartilage only indirectly. Hormone receptors were studied in those portions of fetal growth cartilage that will later evolve into an ossification center, articular cartilage, and epiphyseal cartilage. Cytosol fractions contained a receptor for glucocorticoid but not for androgen or estrogen. Zonal analysis showed a higher level in the peripheral and central sections than in the palisade section. Triiodothyronine binding was also detected in nuclei prepared from whole fetal cartilage. Heterogeneity of cell function was obvious in fetal cartilage. Cell division was high in the central and peripheral zones as well as the upper half of the palisade zone, but low in the lower palisade section. Proline and sulfate incorporation predominated in the palisade section compared with the central and peripheral sections. Disease states with changes of metabolic activities in the cartilage may perhaps be better understood with a clearer knowledge of receptor levels and interactions.
Reliability after repeated use of a torque screwdriver employed for halo pin fixation
Authors: Garfin Steven R. , Botte Michael J. , Woo Savio L.‐Y. , Nickel Vernon L.
Published: February 2005

It has been recommended that halo torque screwdrivers be used only once. To determine if this advice is justified on biomechanical grounds, five commercially available torque screwdrivers were cycled 1,600 times each in an Instron testing machine over a 7‐day period. The screwdrivers displayed an initial error from the dial reading at both 6 and 10 in‐lb of only ± 0.3 in‐lb. After cyclic loading and retesting, the percent deviation from original calibration was 8% at both 6 and 10 in‐lb. These data demonstrate the accuracy and dependability of the torque screwdrivers and imply that repeated use of these devices should be safe.
Structure of newly synthesised (35S)‐proteoglycans and (35s)‐proteoglycan turnover products of cartilage explant cultures from dogs with experimental osteoarthritis
Authors: Carney Stephen L. , Billingham Michael E. J. , Muir Helen , Sandy John D.
Published: February 2005

The structure of newly synthesised proteoglycans from explant cultures of cartilage from joints subjected to transection of the anterior cruciate ligament (osteoarthritic) and from normal (non‐ or sham‐operated) joints was examined. The structure of the products of proteoglycan turnover was also examined using explants of normal and osteoarthritic cartilage maintained in culture for a 48 h chase period. The findings were as follows: (a) Newly synthesised (35S)‐proteoglycans extracted from cartilage explants from osteoarthitic joints whether examined 3 weeks, 3 months, or 6 months after surgery were larger than those from corresponding normal cartilage. This can be explained by the synthesis in osteoarthritic cartilage of abnormally long chondroitin sulphate chains on newly synthesised proteoglycans. (b) The extracts also contained a newly formed small proteoglycan species that was unable to interact with hyaluronic acid. The porportion of thei species was higher in osteoarthritic cartilage compared with normal, examined 3 weeks after surgery, but was generally absent from cartilage obtained 3 and 6 months after surgery. (c) Compared with controls, a smaller proportion of the (35S)‐ proteoglycans released into the maintenance medium of explant cultures of osteoarthritic cartilage during a 48 h chase period was able to interact with hyaluronic acid. However, although furnished with longer (35S)‐glycosaminoglycan chains, these proteoglycans were smaller than those from control explants.
Evidence for different sources of stress‐generated potentials in wet and dry bone
Authors: Otter M. , Shoenung J. , Williams W. S.
Published: February 2005

Physiologically moist bone and dry bone behave differently when tested for electrical response to cantilever bending. To characterize this difference more precisely, voltages were generated in the same specimen in each of the two states via the same testing procedure—changing the electrode‐to‐force distance by moving the electrodes and holding the force position constant. In the dry state, a nonsystematic pattern of voltages versus electrode position was generated. In the wet state, a linear relationship was found. Furtive on wetting the specimen. The implication is that different electromechanical transduction mechanisms are involved in the wet dry cases. The dominant mechanism in the wet case is taken to be the streaming potential rather than piezoelectricity.
Stress analyses of joint arthroplasty in the proximal humerus
Authors: Orr T. E. , Carter D. R.
Published: February 2005

Finite element stress analyses were performed on the proximal humerus before and after the simulated implantation of stemmed, metallic prosthetic components with porous sintered surfaces for direct bony attachment. Design geometries with surfaces at the prosthetic head/bone interface that were (a) convex, (b) flat, and (c) concave were studies. Analyses for each of the three geometries were conducted to reflect (a) bone ingrowth on all the prosthesis/bone surfaces and (b) bone ingrowth only along the underside of the prosthetic humeral head (assuming the stem was not coated with a porous material). Three loading conditions were used to model various degrees of abduction of the arm. Results indicated that in the normal humerus the compressive joint forces are transmitted from the articular surface through cancellous bone to the inferior cortical shell. Concentration of the rotator cuff muscles created tensile stresses in the superolateral cancellous bone and the superior cortical shell of the humerus. Results of the implanted numeral component models indicated that the use of a prosthesis with bone ingrowth along the stem would cause marked stress shielding proximally whereas the use of implants with porous ingrowth only on the underside of the humeral head replacement produced stress fields more similar to the normal humerus. The convex, flat, and concave surfaces provided similar load transfer from the component to the underlying bone in all loading cases. Other prosthetic head designs that may offer better initial stability produced stress fields similar to those of existing prostheses.