bluuebunny/crossref_metadata_2025 huggingface dataset:
Strain rate and mineral content in fracture models of bone
Authors: Currey J. D.
Published: February 2005

I reanalysed data from my previous work to determine the extent to which a model for the loading‐rate dependence of the fracture of cortical bone, put forward by Carter and Caler, fits this independently derived data set. In particular, the extent to which the generality of the model is vitiated by its ignoring the effect of mineralisation on strength was tested. The model was rather strongly corroborated. In addition, the reanalysed data show that yield strain is strongly strain‐rate dependent, but that Young's modulus is rather unvarying over physiological strain rates. The implication of this for hypotheses concerning fracture of bone are discussed.
Kinetic effects of adriamycin and bleomycin on two osteosarcoma models
Authors: Bell D. F. , Bell R. S. , Mankin H. J. , Gebhardt M. C. , Weltie F. , O'Brien T.
Published: February 2005

Although chemotherapeutic drugs are frequently administered to patient with osteosarcoma, there has been little research into the effect of cytotoxic drugs on osteosarcoma cell biology. The effect of two drugs (Adriamycin and bleomycin) on cell cycle kinetics was investigated in vitro in an established line of human osteosarcoma cells and in vivo using the Dunn osteosarcoma model. The cell cycle changes were consistent with G2 arrest for both drugs in vivo and in vitro. The alteration in cell cycle distribution was correlated with inhibition of 3H‐thymidine incorporation in vitro. In vivo, the greater change in cell cycle distribution caused by Adriamycin was reflected in the increased inhibition of tumor growth found with this drug.
Viability of ligaments after freezing: An experimental study in a rabbit model
Authors: Frank C. , Edwards P. , McDonald D. , Bodie D. , Sabiston P.
Published: February 2005

Our purpose in this study was to assess ligament fibroblast viability after freezing by quantifying the subsequent ability of fibroblasts to synthesize collagen in vitro. Both medial collateral ligament (MCL) complexes from 40 adolescent rabbits were studied. Collagen production was determined by in vitro incubation of ligaments in 3H‐proline (a collagen precursor) and subsequent analysis of 3H‐hydroxyproline (a marker of newly synthesized collagen). Autoradiographs determined the distributions of ligament cell activity. All right MCL complexes served as fresh controls, providing a baseline of collagen production. Each left MCL was assigned to an experimental group and was either incubated fresh (10 animals); “killed” by drying, multiple freeze thawing, or cycloheximide (six animals); or slowly frozen at −70°C without cryoprotection (24 animals). Collagen production of rapidly thawed ligaments was studied by proline incubation at 1 day, 9 days, or 6 weeks after freezing and was compared with that of contralateral fresh controls. Results demonstrate that some cells in the substance of these rabbit ligaments retained the ability to synthesize collagen in vitro after being frozen for up to 6 weeks. Mean collagen production of frozen ligaments was decreased, but tests of mean and median values as well as ratios were statistically similar to fresh contralateral ligaments in all animals. This postfreezing ligament cell survival and collagen production after −70°C storage may have implications for ligament transplantation.
Pressure recording in the subacromial bursa
Authors: Sigholm Göran , Styf Jorma , Körner Lars , Herberts Peter
Published: February 2005

The microcapillary infusion (MCI) technique was evaluated in monitoring pressure in the subacromial bursa in 30 shoulders in healthy volunteers. The total pressure in the bursa was studied as the volunteers held their arms at rest and as they lifted their arms and held them lifted with or without a weight of 1 kg in the hands. The pressure in the bursae at rest averaged 8 mm Hg and was found stable during a 40‐min period. When the arms were lifted, the average bursa pressure increased from 8 to 39 mm Hg. As the arms were held up, the weights were put in the hands, and the average bursa pressure then further increased to 56 mm Hg. When the infusion catheters were repeatedly flushed, during a period of 5 min and with a total of 1.2 ml of saline, the average bursa pressure doubled regardless of arm position and load in the hands. The compliance of the bursae decreased from 0.09 to 0.04 ml/mm Hg when the arms were lifted and from 0.04 to 0.02 ml/mm Hg when the arms were lifted and the hands were loaded. The MCI method was found suitable for recording pressure in the subacromial bursa during exercise.
External ultrasound can generate microampere direct currents in vivo from implanted piezoelectric materials
Authors: Cochran George V. B. , Kadaba Murali P. , Palmieri Vincent R.
Published: February 2005

Under development is an internal fixation plate that incorporates a piezoelectric element to generate current when excited mechanically by either weight bearing or external application of ultrasound. The intent is to deliver this current to electrodes at a fracture or osteotomy site to aid in prevention or treatment of nonunion. The present study examines quantitatively the ability of external ultrasound to generate current from small piezoelectric ceramic elements implanted in tissue. An ultrasonic transducer (2.25 MHz, 10–20 V input, <10 mW/cm2 output) was employed to excite small test coupons of a piezoelectric ceramic in vitro and in vivo with various materials, including water, PVC gel, cortical bone, and living soft tissues, interposed. In all instances, it was possible to generate currents of up to 20 μA after rectification; currents up to 1 mA were achieved in some cases. The work indicates that external ultrasonic energy could effectively power small internal devices designed to stimulate bone healing, without the need for implanted batteries or percutaneous leads.
Effect of purified human interleukin‐1 on cartilage degradation
Authors: Hubbard John R. , Steinberg James J. , Bednar Michael S. , Sledge Clement B.
Published: February 2005

The effects of highly purified human monocyte‐derived interleukin‐1 (IL‐1) on bovine nasal cartilage breakdown were investigated. Cartilage degradation was determined by quantifying the fraction of total proteoglycan released from cartilage during 8 days of culture. The response appeared to be chondrocyte‐dependent, for IL‐1 stimulated proteoglycan (PG) release from living but not from dead (frozen‐thawed) cartilage. IL‐1 action on living cartilage was heat labile and concentration dependent, with significant effect at 5 U/ml and maximal effect at 10–20 U/ml. Kinetic studies showed significant stimulation of PG release by 3 days of incubation with 10 U/ml IL‐1. Studies in which IL‐1 was removed on day 1 or day 4 showed that the cartilage‐degrading effect of this monokine was reversible. Although IL‐1 caused little change in the Sepharose CL‐2B chromatographic profile of released PGs using an associative elution buffer, a significant shift to lower mol wt was observed under dissociative conditions. To probe the mechanism of IL‐1 action, cartilage samples were incubated with IL‐1 in the presence of the protein synthesis inhibitor, cycloheximide, or the lysosomal membrane‐stabilizing steroid, hydrocortisone. Cycloheximide at 5–10 μg/ml completely blocked IL‐1–induced breakdown. On the other hand, 3 × 10−7 M hydrocortisone had little or no effect on IL‐1 action. IL‐1 was also shown to stimulate the degradation of human articular cartilage.
Model analysis of factors influencing the prediction of muscle forces at the knee
Authors: Mikosz R. P. , Andriacchi T. P. , Andersson G. B. J.
Published: February 2005

A three‐dimensional stochastic mathematical muscle model of the knee joint has been developed and applied to a study in which the influence of both mechanical and physiological factors were examined in relation to the prediction of muscular forces about the joint. The model includes a representation of the proximal portion of the tibia and distal portion of the femur along with a mathematical expression of the patellar mechanism and 13 muscles crossing the knee joint. The model accounts for the rolling and gliding movement of the tibial‐femoral articulation. The computational technique involves equilibrating three components of external moments at the knee joint to the internal moments generated by muscular forces and soft tissue. The variables contained in the moment equilibrium equation are randomly chosen based on the choice of the tibial‐femoral contact point. The randomness of the variables, reflected in the final solution, defines a stochastic process in the context of the present model. Studies with the model indicated that a very important mechanical aspect of the model was the capability to simulate the moving contact point between the tibia and femur. The moving contact point increased the mechanical advantage of the quadriceps muscles by 50%, which corresponded to in vivo EMG measurements. Muscle force predictions during normal gait have shown the capability of the model to determine the presence of synergistic and antagonistic muscle action.
Energy‐speed relationship of walking: Standard tables
Authors: Waters Robert L. , Lunsford Brenda Rae , Perry Jacquelin , Byrd Richard
Published: February 2005

The energy expenditure of level walking was measured in 260 normal male and female subjects walking around a 60.5m‐circular outdoor track. Subjects were divided into four age groups (children, 6–12 years; teens; young adults, 20–59 years; and senior adults, 60–80 years). Oxygen consumption was measured with a modified Douglas Bag technique during the fourth and fifth minutes of each trial. Standard tables according to age and sex were derived for the average energy expenditure (rate of oxygen uptake, energy cost per meter, and heart rate) and for the gait characteristics (speed, cadence, stride length) at the subjects' customary slow, normal, and fast walking speeds. Statistical analysis was performed to determine the energy–speed relationship for the different age groups to derive normative tables for the rate of oxygen uptake throughout the range of customary walking velocities.
Viscous isoamyl 2‐cyanoacrylate as an osseous adhesive in the repair of osteochondral osteotomies in rabbits
Authors: Harper Marion C.
Published: February 2005

An in vivo study of viscous isoamyl 2‐cyanoacrylate used in limited amounts as an osseous adhesive was performed to evaluate the ability of the monomer to maintain the reduction of an unstable intra‐articular osteochondral osteotomy as well as to allow for healing around the sites of adhesive placement. A histologic evaluation of any inflammatory reaction involving adjacent bone, cartilage, or synovium was also performed. Osteochondral fragments were created in 48 rabbit knees. In 24 knees, reduction of the fragment was secured with one small drop of adhesive at either end of the osteotomy surface. In 24 control knees, no adhesive was used. Ninety‐six percent of the osteotomies in the adhesive treated group healed versus 50% of the control group. This difference is statistically significant (p < 0.05). Osseous and cartilaginous healing was noted to proceed in an apparently unimpaired fashion around the sites of adhesive placement, and no inflammatory reaction involving adjacent viable tissue was evident.
Pulsed ultrasound doppler velocimetry in the assessment of microvascular hemodynamics
Authors: Blair William F. , Brown Thomas D. , Greene E. R.
Published: February 2005

Pulsed ultrasonic Doppler velocimetry (20 MHz) (PUDVM) has evolved considerably in the last 10 years. Engineering development has resulted in a computer‐controlled vessel‐scanning instrument whose backscattered frequency shift spectra are analyzed using fast Fourier transforms (FFT). Benchtop and theoretic studies indicate accurate (error <5%) velocity and volumetric flow rate measurements in vessels with a lumen diameter as small as 1.2 mm. Clinical application of the PUDVM has provided transcutaneous measurements of blood flow variables in normal human digital arteries. Experimental application to arteries 1.0–1.5 mm has provided information on the hemodynamic effects of topical vasodilators, standard microarteriorrhaphy, variations in microvascular technique, interpositional grafts, and early wound repair. With improving computer capabilities and technical modifications, the PUDVM will be an increasingly important tool in clinical and experimental microsurgery.
The mineral and mechanical properties of bone in chronic experimental diabetes
Authors: Einhorn Thomas A. , Boskey Adele L. , Gundberg Caren M. , Vigorita Vincent J. , Devlin Vincent J. , Beyer Monica M.
Published: February 2005

The long‐term effects of experimentally induced diabetes on bone were studied in eight male Lewis rats, intravenously (i.v.) injected with 65 mg/kg of streptozocin (STZ) and maintained for 12 months. Eight untreated age‐matched rats served as controls. In the STZ‐treated rats, experimentally induced diabetes was documented by the presence of hyperglycemia at 24 h and at 3 and 12 months. Significantly less weight was gained and less growth occurred in the STZ‐treated rats despite careful attention to feeding and hydration. Mineral alterations were detected in the bones of the animals with experimental diabetes. Decreased hydroxyapatite crystal perfection, decreased Ca/P of the ash, and decreased ash content in the tibial metaphyses with increased ash content in the tibial diaphyses, was noted relative to controls. Bone osteocalcin content was increased in the metaphyses of the STZ‐treated rats. While absolute measures of stiffness, torsional strength and energy absorption were decreased in the bones of the STZ‐treated animals, when torsional strength and stiffness were normalized for differences in both growth and geometry, the normalized stiffness values for the diabetic bones were increased. The results suggest that in experimental diabetes certain aspects of bone mineralization are adversely affected and lead to reduced strength‐related properties. However, a compensatory increase in stiffness occurs. The reason for this increase, although not known, may be related to changes in bone crystal structure.
Changes in bioelectric potentials on bone associated with direct current stimulation of osteogenesis
Authors: Rubinacci Alessandro , Black Jonathan , Brighton Carl T. , Friedenberg Zachary B.
Published: February 2005

This study was designed to determine whether changes occur in the bioelectric potentials on bone during and after bone stimulation with a 20‐μA direct current (DC) and whether the variations in bioelectric potentials are related to the variations in bone formation. The bioelectric potentials were recorded at different times on the rabbit distal tibial surface, during (current‐on state) and after (current‐off state) DC stimulation with a cathode implanted within the medullary canal. The new bone formed at the end of the experiment was quantitated and related to the bioelectric potentials recorded at current‐on and current‐off states, respectively. Direct current stimulation resulted in electronegative potential spike centered on the cathode tip while current was applied. After electrical stimulation was turned off, the residual potentials at the end of the experiment did not significantly differ from the initial values. Conversely, the time sequence of the changes was significantly different from the control to the experimental group. The variations in the induced potentials at current‐on state were significantly related to the variations in bone formation. This study suggests the existence of a relationship among bioelectric potentials, DC stimulation, and osteogenesis.
Strength reductions from metastatic cortical defects in long bones
Authors: McBroom R. J. , Cheal E. J. , Hayes W. C.
Published: February 2005

The purpose of this investigation was to measure the reduction in bone strength resulting from drill holes in diaphyseal bone and to compare this with finite element and theoretical predictions for stresses in a tubular structure. Fifty‐two pairs of canine femora were tested to failure in four‐point bending. One bone of each pair was used as the control; the other femora had holes of variable size drilled in the lateral cortex. At a ratio of drill hole diameter to bone diameter of 0.2, the bone retained only 62% of its expected strength. A linear regression between the area fraction (the ratio of the cross‐sectional area of the drilled specimen to the control specimen) and the percentage of expected strength yielded a strong positive correlation (R2 = 0.79). The average cross sectional properties were used as the basis for linear orthotropic and nonlinear elastic‐plastic finite element models of idealized geometry. The linear models proved insuifficient for prediction of failure loads. The nonlinear models, which accounted for both material plasticity and the stress concentration effects of the defect, yielded good correspondence with the experimental data. While the influence of irregular borders and adaptive remodeling of the bone adjacent to the defect requires further investigation, our results suggest the possibility of prediction of fracture risk based on geometric properties of metastatic lesions. Prophylactic fixation remains a matter of clinical judgement based on the functional demands and expected strength of the affected bones.
Stimulation of matrix formation in rabbit chondrocyte cultures by ascorbate. 1. Effect of ascorbate analogs and β‐aminopropionitrile
Authors: Wright George C. , Wei Xiqin , McDevitt Cahir A. , Lane Bernard P. , Sokoloff Leon
Published: February 2005

The most consistent effects of 0.2 mM L‐ascorbate on monolayer cultures of rabbit articular chondrocytes were a diversion of incorporated radiosulfate into a pericellular matrix and enhancement of cell proliferation. Only with certain batches of fetal bovine serum (FBS) was there a cell‐for‐cell increase of proteoglycan synthesis. These actions increased as the cell inoculum rose from 0.5 to 2 × 105 cells/T25 flask. Maximal effects of ascorbate and D‐isoascorbate were found over a range of 0.05–0.02 mM. L‐Dehydroascorbic acid was less effective than either, and no stimulatory action was exerted by L‐cysteine, glutathione, dithiothreitol, methylene blue, or phenazine methosulfate. Ascorbate increased the hypro:pro ratio of newly synthesized proteins. β‐Aminopropionitrile (1 mM) reduced the proportion of [3H]hydroxyproline and [35S]O4‐proteoglycans in the ascorbate‐supplemented matrix 31 and 7%, respectively. In corresponding electronmicrographs, the number of pericellular filaments was reduced. We conclude: (a) Ascorbate has a general anabolic effect on chondrocytes in culture and enhances matrix assembly through mechanisms other than its redox function; (b) deposition of proteoglycans in the matrix is not simply the result of mechanical entrapment by allysine‐ or hydroxyallysine‐derived cross‐linking of collagen; and (c) contradictory reports on the subject result from variations in the serum employed, inoculum density, and concentration of ascorbate.
Resultant forces and angles of twist about the wrist after the ecrl to ecu tendon transfer
Authors: Berger Richard A. , Blair William F. , Andrews James G.
Published: February 2005

This paper describes an experimental investigation to determine the biomechanical efficacy of the extensor carpi radialis longus (ECRL) to extensor carpi ulnaris (ECU) tendon transfer procedure used in rheumatoid hand reconstruction. Six normal cadaver specimens were tested in an apparatus that measured (a) the forces acting on the hand to restrain it in seven characteristic wrist configurations, and (b) the amount of hand pronation/supination that occurred as a result of loads applied to the tendons of the six major wrist muscles. Each specimen was tested with the ECRL tendon intact, surgically released, and transferred to the insertion point of ECU. In the intact and transferred states, the ECRL tendon was loaded sequentially while the remaining five wrist tendons were subjected to equal constant loads. In all three experimental ECRL test states, forces were also applied to all intact wrist tendons in a manner designed to represent physiologic load sharing. When the ECRL tendon was loaded sequentially, the transfer resulted in the predictable increase in the radially directed restraining force and the predictable supination of the hand relative to the forearm. When all intact tendons were loaded physiologically, the transfer also resulted in an increase in the radially directed restraining force. Significant differences between test states occurred generally only between the intact and release states of the ECRL tendon and not between release and transferred states. The results confirm that the ECRL‐to‐ECU tendon transfer procedure leads to forces and displacements that tend to correct the undesired deformities commonly associated with advanced rheumatoid wrist disease; however, the similarity of results in release and transferred states indicates that the effectiveness of the procedure involves the loss of normal ECRL function rather than reinsertion into the ECU per se.
An apparatus to measure flexor tendon excursion and angular motion of the distal interphalangeal joint in a rabbit model
Authors: Younger Edward W. , Sharkey Neil A. , Szabo Robert M.
Published: February 2005

Investigators evaluating flexor tendon adhesions have utilized visual, histological, and gross mechanical methods in reporting their results. We have developed a device to measure tendon excursion and distal interphalangeal joint motion for a small animal model. The device was tested for accuracy and reproducibility using the rabbit hindfoot. There was no statistical difference between the right and the left in 30 paris of feet. This device provides an accurate method to quantify tendon excursion and relative adhesion formation in a rabbit model without destroying the specimen.
Stimulation of matrix formation in rabbit chondrocyte cultures by ascorbate. 2. Characterization of proteoglycans
Authors: McDevitt Cahir A. , Lipman Jack M. , Ruemer Robert J. , Sokoloff Leon
Published: February 2005

The effect of ascorbate on the proteoglycans synthesized by rabbit articular chondrocytes was studied in first‐ and third‐passage cultures for 12 and 26 days total duration, respectively. L‐Ascorbate (0.2 mM) was added daily to half of the flasks after attachment of the cells. The cultures were labeled with Na2[35S]O4 or [14C]‐glucosamine and [3H]‐proline. Proteoglycans were isolated from the media and pericellular matrices by dissociative extraction and associative density gradient centrifugation. There was a large decline in the amount of proteoglycan synthesized between early and late cultures. Ascorbate increased the DNA content, amount of radiosulfate incorporated into glycosaminoglycans per microgram of DNA, and the proportion of labeled proteoglycan in the percellular fraction of both short‐ and long‐term cultures. The proteoglycans of the media and matrices of all cultures, with and without ascorbate, eluted as aggregates under associative column chromatographic conditons. The proteoglycans of 26‐day cultures exhibited a higher degree of polydispersity in size than those of the short‐term culture and contained small amount of keratan (2–5%) and dermatan sulfate (4–8%) as assessed by keratanase and chondroitinase digestions, respectively. The effect of ascorbate, therefore, was to increase the amount of proteoglycan formed and to direct it into matrix deposition rather than to alter its quality.
The synovial production of collagenase and chondrocyte activating factors in response to cobalt
Authors: Ferguson Gary M. , Watanabe Shoji , Georgescu Helga I. , Evans Christopher H.
Published: February 2005

Addition of CoCl2 solutions to the culture media of confluent monolayers of lapine or human synoviocytes stimulated their production of the neutral proteinases collagenase, gelatinase, and caseinase. With lapine cells, maximum stimulation occurred at 10−7 M CoCl2, while human cells required 10−4–10−5 M CoCl2 to achieve a maximum stimulation. Production of prostaglandin E2 by lapine cells was enhanced some 30–40% by concentrations of CoCl2 that maximally stimulated synthesis of the neutral proteinases, whereas all concentrations of CoCl2 slightly depressed the productio of prostaglandin E2 by human celis. Lapine synovial cells that had been stimulated by CoCl2 also produced a substance, or substances, that provoked the synthesis of collagenase, gelatinase, caseinase, and prostaglandin E2 by monolayers of articular chondrocytes. Chondrocytes themselves, however, resisted activation by CoCl2. These findings may be relevant to the aseptic loosening of joint prostheses.
Wound healing in the bone chamber 1. Neoosteogenesis during transition from the repair to the regenerative phase in the rabbit tibial cortex
Authors: Winet H. , Albrektsson T.
Published: February 2005

The optical bone chamber technique that includes intravital microscopy is described and is then applied to measuring primary wound healing neoostogenesis in rabbit tibia cortical bone during the period when fibrovascular tissue is being replaced by regenerating osteovascular tissue. The small population of rabbits sampled allowed only tentative conclusions. The quantitative measurements, a direct form of histomorphometry, are applied to determine the consistency of observations, with the hypothesis that healing into the bone chamber slit‐gap follows the pattern of primary bone regeneration established as “characteristic” by other studies. The results supported the hypothesis and showed that bony ingrowth started during the third postoperative‐week (W3) with a maximum linear growth rate of 85.5 μm/day for a bone front. Evidence for remodeling by W6 was also obtained. While the bone chamber environment for tissue ingrowth is artificial, it can generate quantitative data that may provide a statistically valid basis for modeling pathophysiologic processes associated with bone wound healing.
In vitro studies of fretting corrosion of orthopaedic materials
Authors: Brown Stanley A. , Hughes Paula J. , Merritt Katharine
Published: February 2005

Two models were used to study fretting corrosion of surgical alloys. In the first, the amount of load and motion between plates and screws was controlled, and corrosion rates of stainless steel and MP35N were determined by measurements of component weight loss and metal ion concentration in the test solutions. Stainless steel had the higher rate of fretting corrosion. The addition of 10% serum to saline resulted in a significant reduction of the corrosion rate of stainless steel and MP35N. The use of stainless steel screws in a mixed‐metal combination with MP35N and titanium plates showed minimal effects on the performance of the stainless steel screws but an increase in fretting corrosion of the MP35N plates. In the second model, plates were applied to glass fiber‐reinforced plastic tubes as bone analogues and subjected to cyclic axial loads. These results demonstrated a reduction in fretting corrosion rates associated with an increase in screw torque and a decrease in axial load. Corrosion rates were minimal with intact tubes simulating healed fractures and greatest with an oblique‐cut fracture simulation. These models have proven useful for the evaluation of fretting corrosion rates of different alloys and for evaluation of variables such as fracture stability.
A quantitative analysis of donor site morbidity after vascularized fibula transfer
Authors: Youdas James W. , Wood Michael B. , Cahalan Thomas D. , Chao Edmund Y. S.
Published: February 2005

Eleven patients with free vascularized fibula graft transplants to the upper extremity were studied for donor‐side morbidity effects. Based on their surgical follow‐up times, the patients were divided into either group 1 (5 ± 2 months) or group 2 (21 ± 8 months) to examine the effects of surgical trauma more closely. Gait evaluation was performed using two walkways containing different ground conditions. Knee and ankle‐foot motion was measured using a three‐dimensional electrogoniometer. Basic temporodistance factors and ground reactions were obtained from foot switches, instrumented floor mats, and a force plate. A modified Cybex II isokinetic dynamometer was used to quantitate ankle‐foot strengths. Moderate knee and ankle‐foot motion changes were seen while walking on the level, sideslope, and ramp in patients evaluated less than 10 months after their surgical procedure. Minimal joint motion effects were discovered in patients with follow‐up times longer than 10 months. Muscle strengths were significantly impaired in both groups, especially foot inversion and eversion. An inverse relationship existed between the length of resected fibula and ankle evertor muscle strength. Donor side morbidity does not appear to be caused by surgical soft‐tissue trauma exclusively. These patients need to be studied for several more years to determine the long‐term functional effects of free vascularized fibular graft transfer.
Biomechanics of fascia lata ligament replacements: Early postoperative changes in the goat
Authors: Holden John P. , Grood Edward S. , Butler David L. , Noyes Frank R. , Mendenhall H. Vincent , Van Kampen Craig L. , Neidich Robert L.
Published: February 2005

Mechanical properties of fascia lata autografts used to replace the anterior cruciate ligament (ACL) in the goat were measured at 0, 2, 4, and 8 weeks after surgery. The ACL was replaced in the right knee of 50 animals divided equally into two groups according to graft fixation technique: (a) two smooth staples at each end, with the tissue pulled back toward the joint over the first staple and (b) reinforced fixation with a spiked bushing placed through the tissue and a 3‐cm‐long flat polypropylene braid sutured to each end of the graft. Eleven unoperated contralateral knees were tested as controls. All statistically significant effects of the reinforced versus staple fixation were observed at 0 weeks, with the reinforced group showing less anteroposterior (AP) translation of the joint and greater maximum force and stiffness of the femurgraft‐tibia units. The reinforced group had increased AP translation and decreased strength and stiffness by 2 weeks after surgery. Increased AP translation resulted primarily from increases in the low‐stiffness region of the forcedisplacement curve (primary AP translation) and to a lesser extent from increased translation in the high‐stiffness region (secondary anterior translation). Failures at 0 weeks with the reinforced fixation occurred at the bushing or end of the reinforcing braid, while all but one of the later failures occurred in the tissue mid‐substance. In the staple group, maximum force was greater at 8 weeks than at 0 weeks, as the failure locations changed from the fixation to the tissue mid‐substance. The failure mechanisms and maximum force values in the reinforced fixation group suggest that the remodeling tissue weakened rapidly after surgery.
Quantitation of glycocalyx production in coagulase‐negative Staphylococcus
Authors: Tsai Ching‐Lin , Schurman David J. , Smith R. Lane
Published: February 2005

The purpose of this study was to develop sensitive and accurate methods of quantitating bacterial glycocalyx. Coagulase‐negative staphylococci were cultured in trypticase soy broth. Quantitation of slime production was evaluated using various methods of fixation and staining. The amount of dye associated with bacterial slime was assessed spectrophotometrically following solubilization of the dye‐biofilm complex by 0.2 M NaOH at 85°C for 1 h. Carnoy's solution was optimal for fixation of the slime, and toluidine blue staining was most reproducible. Fifteen strains of Staphylococcus epidermidis showed a gradation in biofilm production ranging from high, medium, to low that was strain stable. Irrespective of the technique used, high, medium, and low producers of bacterial slime remained in the same category and always showed significantly different optical density reading (p < 0.05). In our experiments, solubilization of a toluidine blue‐bacterial biofilm complex was a direct, simple, and efficient method for reproducibly quantitating glycocalyx. This method provides a useful means of rapid quantitation of biofilm production to assess its role in the infection process and in the response to antibiotic therapy.
A biomechanical assessment of plate fixation, with insufficient bony support
Authors: Beaupré Gary S. , Carter Dennis R. , Dueland Rudolph T. , Caler William E. , Spengler Dan M.
Published: February 2005

The use of an internal fixation plate in the presence of a bone defect was studied using a theoretical model of an idealized long bone having a circular cross section and loaded using a combination of axial and bending loads. The analysis showed that the “bending‐open” loading mode does not occur if, in the normal unplated bone, the line of action of the resultant axial load passes within the outer cortex at the location where the plate is to be applied. In this situation the fracture will deform in a “bending‐closed” mode regardless of whether the plate is attached to the tension or the compression side. If bony contact cannot be achieved, lower plate stress is always encountered when the plate is attached to the compression side instead of the tension side. In vivo verification of the model was addressed in a pilot experiment using instrumented metal plates applied bilaterally to the femora of one dog. Bilateral bone defects were created in the midfemoral canine diaphysis. On one leg the plate was applied to the lateral aspect (“tension” side), and on the other leg the plate was applied to the medial aspect (“compression” side). The plate attached to the lateral aspect deformed plastically in the bending‐closed mode. The contralateral plate that was attached to the medial aspect (compression side) of the femur did not show signs of plastic deformation. Furthermore, the plate strains were lower in the plate attached to the medial aspect than those in the plate attached to the lateral aspect. The results and analysis of this study suggest that when applying plates to diaphyseal fractures where bony stability cannot be achieved, it may be acceptable or even desirable to attach the plate to the compression side of the bone.
Water content and equilibrium water partition in immature cartilage
Authors: Torzilli Peter A.
Published: February 2005

The water content, equilibrium water partition, and total thickness for immature bovine articular cartilage were determined and compared to previously determined values for mature tissue. The bulk equilibrium water partition and thickness were significantly greater in immature tissue as compared to mature tissue, while the bulk water content was similar. Spatial differences were noted in each physical parameter.
Effects of polymethylmethacrylate exposure upon macrophages
Authors: Horowitz Stephen M. , Frondoza Carmelita G. , Lennox Dennis W.
Published: February 2005

The effects of polymethylmethacrylate (PMMA) exposure upon macrophage viability and function were studied in an attempt to determine what role these cells play in the loosening of cemented arthroplasties. P388D1 murine macrophage cell line was exposed to PMMA and polystyrene particles of similar size and concentration. DNA synthesis following exposure to PMMA or polystyrene was studied by [3H]thymidine incorporation. Macrophage function was studied by analyzing the ability of activated macrophages to kill mast cell targets following particle exposure. Our results demonstrate that exposure of macrophages to PMMA particles in vitro inhibits DNA synthesis and impairs their cytotoxic ability. Histologic examination revealed that macrophages phagocytose both PMMA and styrene particles, but the former eventually lyse these cells. Our studies suggest that the histologic appearance of macrophages and foreign body giant cells at the bone‐cement interface may be secondary to a repetitive cycle of PMMA particle phagocytosis and cell death, similar to that found in a foreign body granulomatous response.
Cellular events associated with the induction of bone by demineralized bone
Authors: Bernick Sol , Paule Wendelin , Ertl Delia , Nishimoto Satoru K. , Nimni Marcel E.
Published: February 2005

Implantation of demineralized bone (DB) in the form of powder or intact segments in extra skeletal sites stimulates new bone formation. Urist and co‐workers presented substantial evidence that there is a noncollagenous protein that has the ability to induce bone formation. One aim of this study was to trace the process of bone formation when DB, in the form of perforated rectangular plates, is implanted subcutaneously in 2‐month‐old rats. A second objective was to determine whether cartilage cells play a role in the formation of bone in this model. Various DB plates with 0.25 mm diameter holes were implanted subcutaneously for 1–4 weeks in rats. One week after implantation, DB plates were covered by vascularized connective tissue that invaded the perforations. Aggregates of chondrocytes were observed within the holes and on periosteal surfaces in only a few specimens. Further cartilage proliferation was not observed, and by the 2nd week there was no evidence of endochondral bone formation. Where these cartilage‐like cells were present, a thin layer of mineral was deposited around them; resorption and fibrous tissue infiltration followed. This aborted form of endochondral calcification was not followed spatially by bone formation. Patent vascularized channels were invaded by alkaline phosphatase‐positive mononuclear cells and fibroblasts, and became enlarged by the enzymatic action of macrophages. The next step involved the calcification of DB plates adjacent to the wide spaces. Osteoclasts now appeared leading to the resorption of this recalcified matrix. The eroded and now enlarged lacunar surfaces were lined by newly formed bone and osteoblasts. This process continued so that, at the end of 4 weeks following implantation, the original DB plates were replaced by trabecular bone. Biochemical data on calcium and alkaline phosphatase levels in the implants paralleled the morphological observations.
Growth hormone stimulates insulin‐like growth factor I actions on adult articular chondrocytes
Authors: Smith R. Lane , Palathumpat Marykutty V. , Ku Christine W. , Hintz Raymond L.
Published: February 2005

We report effects of adding insulin‐like growth factor I (IGF‐I) and methionyl human growth hormone (GH), alone or in combination, to adult bovine articular chondrocytes plated at high density. Purified human and synthetic IGF‐I stimulated chondrocyte DNA and proteoglycan synthesis. GH had no effect on either process. However, GH added in combination with IGF‐I increased proteoglycan, cell‐associated proteoglycan, and keratan sulfate synthesis over levels observed with IGF‐I alone. IGF‐I and GH did not alter the hydrodynamic size of proteoglycans or synthesis of collagen. Our results show that GH and IGF‐I act together to stimulate adult chondrocyte extracellular matrix synthesis.
An ultrastructural study of slipped capital femoral epiphysis: Pathogenetic considerations
Authors: Ippolito E. , Bellocci M. , Farsetti P. , Tudisco C. , Perugia D.
Published: February 2005

Two normal proximal femoral growth plates and core biopsies from six patients with slipped capital femoral epiphysis (SCFE) were studied by electron microscopy. In these SCFE patients, chondrocytes from all the zones of the plate were frequently smaller than normal, more irregular in shape, and many of them were degenerating, with formation of matrix vesicles and cellular debris. Floccular electron‐dense material, most likely abnormal proteoglycan, was present in the hypertrophic rough‐surfaced endoplasmic reticulum and Golgi apparatus as well as in the extracellular matrix, intermingled with collagen fibrils thinner than normal and lossely arranged. Mineralization of the abnormal matrix of the longitudinal septa of the degenerating zone was either scanty or absent, with scanty formation of irregular and thin bone trabeculae. The‐abnormalities observed in SCFE seem to be caused by a change in chondrocyte metabolism with consequent altered synthesis and/or extracellular aggregation of both collagen and proteoglycan, and scanty mineralization of the abnormal cartilage matrix.
Altered structural and functional properties of myosins, from platelets of idiopathic scoliosis patients
Authors: Peleg Itzhak , Eldor Amiram , Kahane Itzhak , Muhlrad Andras , Liebergall Meir , Floman Yizhar
Published: February 2005

Platelets of patients with idiopathic scoliosis (IS) have been shown to have decreased capacity to aggregate and secrete in response to certain agonists. Similarities between the contractile protein system of platelets and muscle have made the platelets a popular model for muscle disease. We attempted to characterize the function and structure of myosin in platelets of IS patients. Blood was obtained from seven IS patients and seven matched nonscoliotic healthy controls. The mean Cobb angle measurement of the IS patients was 35.4° with a mean Risser sign of 2.2. Washed platelets were isolated from the blood, and the contractile proteins from the membrane and the cytosol compartments were isolated and analyzed by two‐dimensional peptide mapping. As previously reported (J Biol Chem 258:9290, 1983), peptide maps of normal platelets revealed that the heavy chain of myosin located in the platelet membrane lacks one major spot relative to the cytoplasmic myosin. In IS patients the cytoplasmic myosin lacks the same peptide that is missing in the membrane myosin of normal individuals. In addition, the ATPase specific activity of the cytoplasmic myosin from IS platelets was significantly lower compared with the activity of the cytoplasmic myosin from normal platelets. These results suggest the presence of a fundamental abnormality of IS platelet contractile proteins.
The influence of chair height on lower limb mechanics during rising
Authors: Rodosky Mark W. , Andriacchi Thomas P. , Andersson Gunnar B. J.
Published: February 2005

The mechanics of the lower limb were analyzed in young, adult normal subjects when rising from a seated position. Limb mechanics were described in terms of flexion–extension motion and moments at the hip, knee and ankle while rising from four seat heights corresponding to 65, 80, 100, and 115% of the subject's knee joint height. The results indicate that the maximum moment tending to flex the hip joint was higher than that occurring at the knee or ankle. The magnitude of the maximum flexion moment at the hip was not substantially influenced by chair height, changing by < 12% between the highest and lowest chair heights. Conversely, the maximum knee flexion moments were found to be highly dependent on chair height and nearly doubled from the highest to the lowest position. The magnitude of the moments at the ankle did not change with chair height and were significantly lower than the magnitude of the moments found during normal walking. The magnitude of motion and moments at the hip were greater during chair‐rising than during stair‐climbing or walking. The range of motion required at the knee for the lower chair heights was also greater than was reported during stair‐climbing studies. Thus, the combination of moments in joint angles during chair‐rising are unique among common activities of daily living and should be considered in chair selection as well as in the guidelines for prosthetic devices.
Biochemical changes in articular cartilage after joint immobilization by casting or external fixation
Authors: Behrens Fred , Kraft Ellen L. , Oegema Theodore R.
Published: February 2005

Knees of mature dogs were immobilized for 6 weeks by long‐leg casts allowing 8°–15° of motion, a model studied by others, or with external fixators, a new, more severe model that kept the joints rigid. Some animals were allowed to recover for 1 week after the immobilization period. Articular cartilage was examined histologically and biochemically. After 6 weeks of immobilization, water increased 7% in both casted and fixator‐immobilized joints compared with normal knee cartilage, while hexuronic acid was 23 and 28% lower, respectively. The limited motion permitted by the casts resulted in a smaller depression of proteoglycan synthesis and less proteoglycan loss during immobilization than occurred in the rigid external fixator group. The protective effect of limited motion was shown clearly during the recovery period: as measured by hexuronic acid content. cartilage from the casted joints had almost recovered within 1 week, whereas the external fixator group experienced little or no recovery during the week after treatment. In contrast to previous studies by others with casted joints, both newly synthesized [35S]sulfate‐labeled and accumulated unlabeled proteoglycans from both casted and fixator‐immobilized cartilages were able to form complexes with exogenous hyaluronic acid to the same extent as those from control cartilage. Thus, in immobilized cartilage, failure of the newly synthesized proteoglycan to bind to hyaluronate is not a mechanism of accelerated proteoglycan loss. The accelerated proteoglycan turnover appears to be caused by a combination of decreased synthesis and increased proteolysis of the secreted proteoglycans. Clinically external fixators used to immobilize joint injuries should be applied for the shortest time possible and if possible should be mechanically modified to allow up to 10° of joint motion.
Neuropathology with spinal instrumentation
Authors: Coe Jeffrey D. , Becker P. Scott , McAfee Paul C. , Gurr Kevin R.
Published: February 2005

Neurohistologic examination of the spinal cord and cauda equina were compared for 28 beagles undergoing anterior and posterior spinal destabilization procedures—Group I (n = 7), destabilized operative controls; Group II (n = 7), posterolateral bone grafting; Group III (n = 7), Harrington distraction instrumentation and posterolateral fusion; and Group IV (n = 7), Luque rectangular instrumentation and posterolateral fusion. All dogs had appeared neurologically intact upon repeated examinations prior to death. Neurohistological abnormalities (Wallerian degeneration of the dorsal columns, corticospinal tracts, and nerve roots, focal cystic degeneration, and intraspinal central cavitation) occurred in only 1 of the 14 animals (7%) in Groups I and II (noninstrumented) and in 9 of the 14 animals (64%) in Groups III and IV (instrumented). This result is statistically significant (p < 0.001). Transient sensory disturbances and radicular paresthesias have been described in clinical reports of spinal instrumentation. It is probable that subclinical neurologic injuries, such as intraspinal and nerve root infarction in posterior neural tissue, can occur with the use of sublaminar hooks or wires. The chondrodystrophic beagle spinal model in this study should be considered a “worst case situation,” and the clinical incidence of neurohistologic changes is expected to be lower.
Recovery of the dog quadriceps after 10 weeks of immobilization followed by 4 weeks of remobilization
Authors: Lieber Richard L. , McKee‐Woodburn Thalia , Gershuni David H.
Published: February 2005

Skeletal muscle fiber areas were measured in three heads of the dog quadriceps after 10 weeks of immobilization followed by 4 weeks of remobilization. Two‐way analysis of variance demonstrated a significant decrease in both type 1 (p < 0.005) and type 2 (p < 0.001) fiber area. However, there was no significant difference among the three heads of the quadriceps (p > 0.2). Although muscle fiber areas had not returned to control levels following remobilization, the area fraction of perimysial and epimysial connective tissue was not significantly different from control values (p > 0.15). These data suggest that although the degree of muscle atrophy following 10 weeks of immobilization is severe and muscle specific, following 4 weeks of remobilization, muscles uniformly recover to about 70% of control values.