bluuebunny/crossref_metadata_2025 huggingface dataset:
Localized, tumor‐associated osteolysis involves the recruitment and activation of osteoclasts
Authors: Clohisy Denis R. , Ogilvie Christian M. , Carpenter Randall J. , Ramnaraine Margaret L. R.
Published: February 2005

The cellular and biochemical mechanisms that direct destruction of bone at the site of tumor osteolysis are unknown. In order to understand this process better, a murine model designed for the study of tumor osteolysis was developed and the influence of osteolytic and nonosteolytic tumors on bone was investigated. Tumors developed following femoral intramedullary injection of sarcoma (2472) and melanoma (G3.26) cell lines: however, only tumors from the 2472 cell line caused osteolysis. It was determined that 2472 tumor‐induced osteolysis commenced 6 days after the femora had been inoculated with 2472 cells. There were more osteoclasts per millimeter of bone surface in 2472 tumor‐bearing limbs (16.7 ± 5.0) than in sham‐injected limbs (3.8 ± 0.9) (p < 0.015). In addition, an increase in the osteoclast size (area) was detected in 2472 tumor‐bearing limbs: 412 ± 65 μm2 compared with 187 ± 17 μm2 (p < 0.01). In vitro bone resorption experiments indicated that 2472 tumor cells had a limited ability to destroy bone in comparison with macrophages and osteoclasts. Taken in total, these findings define a model that is useful for the study of tumor osteolysis, and the data from analyses of the model demonstrate that the cellular mechanisms responsible for 2472 tumor‐induced osteolysis include both an increase in the number of osteoclasts and activation of mature osteoclasts.
Role of tumor necrosis factor alpha in particulate‐induced bone resorption
Authors: Algan Sheila M. , Purdon Marie , Horowitz Stephen M.
Published: February 2005

The purpose of this study was to determine the role of tumor necrosis factor alpha in bone resorption secondary to mediator release from macrophages exposed to cement particles. The J774 mouse macrophage cell line was exposed to polymethylmethacrylate particles for 24 hours and the resulting conditioned medium was analyzed for prostaglandin E2, tumor necrosis factor alpha, interleukin‐1 alpha and beta, and the ability to stimulate release of prostaglandin E2 and 45Ca from radiolabeled mouse calvaria. Macrophage exposure to polymethylmethacrylate particles led to a 9‐fold increase in release of tumor necrosis factor alpha (p < 0.01), but did not lead to a significant increase in release of prostaglandin E2, interleukin‐1 alpha, or interleukin‐1 beta when compared to unexposed cells. Exposure of the macrophages to polymethylmethacrylate particles over a time course from 30 minutes to 96 hours led to an increase in the release of tumor necrosis factor alpha that was initially detected at 30 minutes and was maximum at 48 hours. Incubation of the macrophage‐polymethylmethacrylate conditioned medium with rat calvaria significantly increased the release of 45Ca and prostaglandin E2 from the bone. To study the role of release of tumor necrosis factor alpha in bone resorption, the macrophage‐polymethylmethacrylate conditioned medium was then preincubated with anti‐tumor necrosis factor alpha antibody prior to exposure of the conditioned medium to the calvaria. This preincubation was successful in significantly inhibiting 45Ca release by calvaria (p < 0.01) to levels that were not significantly different from the levels of release by unexposed calvaria. Tumor necrosis factor alpha appears to play a critical role in initiating particulate‐induced bone resorption. Exposure of macrophages to polymethylmethacrylate particles leads to a significant release of tumor necrosis factor alpha in a time‐dependent fashion. This macrophage‐polymethylmethacrylate conditioned medium stimulated release of prostaglandin E2 and bone resorption in bone organ culture. The addition of anti‐tumor necrosis factor alpha antibody to this in vitro system inhibited the bone resorption stimulated by the macrophage‐polymethylmethacrylate conditioned medium and partially suppressed the production of prostaglandin E2. The sequence of events in this model for particulate‐induced bone resorption appears to be initiated by the production of tumor necrosis factor alpha by the macrophage, followed by production of prostaglandin E2 by cells in bone, and then by bone resorption.
Equal effectiveness of electrical and volitional strength training for quadriceps femoris muscles after anterior cruciate ligament surgery
Authors: Lieber R. L. , Silva P. D. , Daniel D. M.
Published: February 2005

Neuromuscular electrical stimulation and voluntary muscle contraction are two exercise modes widely used in rehabilitation to strengthen skeletal muscle. Since there is debate as to which mode is most effective, we compared electrical stimulation with voluntary contraction performed at matched intensities following reconstructive surgery of the anterior cruciate ligament. Forty men and women, aged 15–44, were randomly assigned to either an electrical stimulation or a voluntary contraction group. None of the subjects had a previous history of neuromuscular injury. The subjects received treatment for 30 minutes a day, 5 days a week, for 4 weeks. Knee extension torque was monitored during treatment to try to match the absolute muscular tensions (quantified as “activity”) achieved during therapy. To match the activity of the subjects in the electrical stimulation group, who were treated at the highest stimulation intensity they could tolerate, the subjects in the voluntary contraction group were paced at progressively increasing intensities corresponding to 15, 25, 35, and 45% of the injured limb's maximum voluntary torque during weeks 1, 2, 3, and 4, respectively. We found no significant difference between the groups in terms of maximum voluntary knee extension torque throughout the study period. In addition, 1 year after surgery, there was still no significant difference between groups with regard to knee extension torque (p > 0.4). These data suggest that neuromuscular electrical stimulation and voluntary muscle contraction treatments, when performed at the same intensity, are equally effective in strengthening skeletal muscle that has been weakened by surgical repair of the anterior cruciate ligament.
Hamstrings and psoas lengths during normal and crouch gait: Implications for muscle‐tendon surgery
Authors: Delp Scott L. , Arnold Allison S. , Speers Rosemary A. , Moore Carolyn A.
Published: February 2005

Crouch gait, one of the most common movement abnormalities among children with cerebral palsy, is characterized by persistent flexion of the knee during the stance phase. Short hamstrings are thought to be the cause of crouch gait; thus, crouch gait is often treated by surgical lengthening of the hamstrings. In this study, a graphics‐based model of the lower extremity was used in conjunction with three‐dimensional kinematic data obtained from gait analysis to estimate the lengths of the hamstrings and psoas muscles during normal and crouch gaits. Only three of 14 subjects with crouch gait (four of 20 limbs with knee flexion of 20° or more through stance) had hamstrings that were shorter than normal by more than 1 SD during walking. Most (80%) of the subjects with crouch gait had hamstrings of normal length or longer, despite persistent knee flexion during stance. This occurred because the excessive knee flexion was typically accompanied by excessive hip flexion throughout the gait cycle. All of the subjects with crouch gait had a psoas that was shorter than normal by more than 1 SD during walking. These results emphasize the need to consider the geometry and kinematics of multiple joints before performing surgical procedures aimed at correcting crouch gait.
Proliferative and matrix synthesis response of canine anterior cruciate ligament fibroblasts submitted to combined growth factors
Authors: Desrosiers Eric A. , Yahia L'Hocine , Rivard Charles‐Hilaire
Published: February 2005

We investigated the effects of growth factors on the proliferation and matrix synthesis of anterior cruciate ligament fibroblasts. Fibroblasts from the anterior cruciate ligaments of dogs were transferred at the second passage in a defined medium. Epidermal growth factor, platelet‐derived growth factor‐AB, transforming growth factor‐β1, insulin‐like growth factor‐1, and insulin, combined two by two following a 5 × 5 logarithmic concentration matrix, were added. Tridimensional curves showing cell proliferation at 24 hours against the concentration of two effectors were obtained for each combination. Collagen and proteoglycan productions were quantified using [14 C]glycine and Na2[35S]O4. Ratios of type I:III collagen and hydrodynamic size distributions of proteoglycans were assayed, respectively, by sodium dodecyl sulfate‐polyacrylamidel gel electrophoresis and gel filtration chromatography. Epidermal growth factor had an effect nearly equivalent to that of platelet‐derived growth factor‐AB on cell proliferation. Both had a greater effect than insulin‐like growth factor‐1, which in turn had a greater effect than both the effect of insulin or the nearly equivalent effect of transforming growth factor‐β1. Neither platelet‐derived growth factor‐AB nor insulin has a significant effect by itself on collagen production. Epidermal growth factor slightly decreases collagen production as well as the type I:III collagen ratio: both transforming growth factor‐β1 and insulin‐like growth factor‐1 increase the same parameters. Epidermal growth factor inhibits the stimulation induced by transforming growth factor‐β1. Similarly, insulin decreases the response to insulin‐like growth factor‐1. Proteoglycan production was significantly increased by all growth factors in this study, with transforming growth factor‐β1 having the strongest effect, Small hydrodynamic size of proteoglycan was correlated to a high level of proteoglycan biosynthesis. The results may be readily applied to tissue engineering or provide a basis for in vivo investigations.
Medial collateral ligament healing one year after a concurrent medial collateral ligament and anterior cruciate ligament injury: An interdisciplinary study in rabbits
Authors: Yamaji Tomoo , Levine Rebecca E. , Woo Savio L‐Y. , Niyibizi Christopher , Kavalkovich Karl W. , Weaver‐Green Colleen M.
Published: February 2005

The optimal treatment for concurrent injuries to the medial collateral and anterior cruciate ligaments has not been determined, despite numerous clinical and laboratory studies. The objective of this study was to examine the effect of surgical repair of the medial collateral ligament on its biomechanical and biochemical properties 52 weeks after such injuries. In the left knee of 12 skeletally mature New Zealand White rabbits, the medial collateral ligament was torn and the anterior cruciate ligament was transected and then reconstructed. This is an experimental model previously developed in our laboratory. In six rabbits, the torn ends of the medial collateral ligament were repaired, and in the remaining six rabbits, the ligament was not repaired. Fifty‐two weeks after injury, we examined varus‐valgus and anterior‐posterior knee stability; structural properties of the femur‐medial collateral ligament‐tibia complex; and mechanical properties, collagen content, and mature collagen crosslinking of the medial collateral ligament. We could not detect significant differences between repair and nonrepair groups for any biomechanical or biochemical property. Our data support clinical findings that when the medial collateral and anterior cruciate ligaments are injured concurrently and the anterior cruciate ligament is reconstructed, conservative treatment of the ruptured medial collateral ligament can result in successful healing.
Lower limb alignment and foot angle are related to stance phase knee adduction in normal subjects: A critical analysis of the reliability of gait analysis data
Authors: Andrews Michelle , Noyes Frank R. , Hewett Timothy E. , Andriacchi Thomas P.
Published: February 2005

Anatomic and mechanical factors that affect loading in the knee joint can contribute to pathologic changes seen at the knee in degenerative joint disease and should be considered in treatment planning. The objectives of this study were to quantify the relationships between the alignment of the bones of the lower extremity, foot progression angle, and knee adduction moment, and to determine the reliability of our gait measurements. Gait analysis and complete radiographic evaluation of the lower extremity were performed on 11 healthy subjects. The gait measurements were recorded with an optoelectronic digitizer and a multicomponent force plate. The subjects who had radiographic measurements indicative of varus alignment of the lower extremity had statistically higher peaks in knee adduction moment in early stance. Conversely, those with valgus alignment of the lower extremity had statistically lower peaks in knee adduction moment in early stance. The subjects who had a large toe‐out angle and low ankle inversion moment peaks in late stance had significantly lower peaks in knee adduction moment in late stance. These significant (low to moderate) correlations suggest that the limbs with more valgus alignment and those with a toe‐out gait exhibited a reduced peak adduction moment at the knee. To verify the reproducibility of the data, gait analysis testing was performed on each lower limb on 2 separate days for each subject. Analysis of variance showed that there was no significant difference between test limbs or test days for each subject. Our results suggest that the alignment of the lower limb and the foot progression angle, which can be readily measured in a clinical setting, can serve as predictors of knee joint loading in healthy individuals. These findings may have important implications for both surgical and nonsurgical treatment of abnormalities of the knee joint.
Intraosseous infusion of prostaglandin E2 prevents disuse‐induced bone loss in the tibia
Authors: Welch R. D. , Ashman R. B. , Baker K. J. , Browne R. H.
Published: February 2005

We investigated whether intraosseous injection of prostaglandin E2 would preserve tibial bone mass in the skeletally unloaded limb of a large animal model. Skeletal unloading of one rear limb was produced by unilateral Achilles tenectomy in the goat. Prostaglandin E2 was injected at 0.5 or 1.0 mg (1 ml of volume) twice daily, beginning on day 7 and continuing for 10 days, through an implant that had been surgically placed in the proximal tibial metaphysis. Thirty‐five days after surgery, the tibiae were harvested for measurement of static and dynamic bone parameters and mechanical characteristics using transmission ultrasound. Prostaglandin E2 produced a dose‐dependent increase in the formation of woven new bone at all bone envelopes. The 1.0 mg dosage prevented and partially reversed the effects of skeletal unloading and added new bone (p < 0.05) compared with the unloaded tibiae. Because prostaglandin E2 increased both bone formation and resorption and the new bone produced was primarily woven bone, the material properties of the tibiae infused with prostaglandin E2 did not increase significantly during the study compared with the unloaded and weight‐bearing tibiae.
Functional degradation of the rabbit sciatic nerve during noncompressive segmental ischemia
Authors: Kanaya Fuminori , Breidenbach Warren C. , Firrell John C.
Published: February 2005

The purpose of this study was to evaluate functional degradation in a nerve with a local ischemic segment created without a direct compression effect. Ischemia of one segment of a rabbit sciatic nerve was induced by stripping the nerve's extrinsic blood supply along 15 cm. Blood flow of both in situ and ischemic nerves was quantitatively measured with radioactive microspheres in six serial segments in seven animals. The flow in one middle segment of the stripped nerve was significantly reduced to 0.1 ml/min per 100 g (p = 0.006). In another eight animals, both in situ and stripped nerves were metabolically challenged with repetitive stimuli (200 Hz). Conduction velocity and peak amplitude were measured before stimuli, after 30 and 60 minutes of stimuli, and after a 30‐minute recovery period. Conduction velocity was reduced in both nonischemic and stripped nerves during prolonged repetitive stimulation. Peak amplitude was reduced slightly in the nonischemic group and markedly in the stripped group. Normal or higher values were seen again in both groups during the recovery period. It was demonstrated, therefore, that conduction properties of the nerve, especially amplitude, can be affected by localized ischemia in one segment.
Chondrocyte survival in cryopreserved osteochondral articular cartilage
Authors: Ohlendorf Christian , Tomford William W. , Mankin Henry J.
Published: February 2005

Fluorescent staining techniques were used in combination with confocal and conventional fluorescent microscopy to determine the location of viable chondrocytes in frozen and thawed osteochondral articular cartilage. The results showed that cell survival was confined to the superficial layer of the cartilage matrix. The addition of a cryopreservative agent (dimethyl sulfoxide) increased chondrocyte survival but only in the same layer. There was no evidence of cell survival in the middle or deep layers of the cartilage with or without the use of dimethyl sulfoxide. Under the conditions employed in this study, chondrocyte survival in a cryopreserved osteochondral allograft appears to be limited to the superficial layer of the articula cartilage.
In vitro activation of human fibroblasts by retrieved titanium alloy wear debris
Authors: Manlapaz Mariel , Maloney William J. , Smith R. Lane
Published: February 2005

Titanium‐aluminum‐vanadium wear particles isolated from the soft‐tissue membrane of a failed total hip arthroplasty were added to human fibroblasts in cell culture. The cellular response to particle challenge was determined by assaying for levels of interleukin‐1β, interleukin‐6, tumor necrosis factor‐α, prostaglandin E2, basic fibroblast growth factor, platelet‐derived growth factor‐AB, and transforming growth factor‐β. Collagenase and gelatinase activities were analyzed by zymography and [3H]collagen degradation. Cell viability was assessed by measuring the uptake of [3H]thymidine. Over the range of particle concentrations tested, cell viability, as demonstrated by [3H]thymidine uptake, remained unaffected. Fibroblasts exhibited a dose‐dependent release of interleukin‐6 in response to exposure to titanium‐aluminum‐vanadium particles. At 6 and 48 hours, the highest concentration of titanium alloy particles (0.189% [vol/vol]) resulted in 7‐fold and 16‐fold increases in interleukin‐6 release, respectively, when compared with negative controls. Neither interleukin‐1β nor tumor necrosis factor‐α was detected in the culture medium at any particle concentration tested for both dermal and foreskin fibroblasts. The pattern of prostaglandin E2 release by fibroblasts mirrored the pattern of interleukin‐6 release. Fibroblasts exposed to the highest concentration of titanium alloy particles showed an increase in collagenase activity, starting at 12 hours. When medium samples were treated with amino phenylmercuric acetate to activate latent enzymes, a statistically significant increase in collagenase activity was observed as early as 6 hours (p < 0.001). Substrate gel analysis of medium from fibroblasts stimulated by high particle concentrations also showed an increase in gelatinolytic activity when compared with unstimulated controls. Analysis of medium samples for growth factors showed an increase in basic fibroblast growth factor at low particle concentrations, beginning at 12 hours. Levels of platelet‐derived growth factor‐AB and transforming growth factor‐β were not detectable in the controls or at any particle concentration tested. The results of this study showed that fibroblasts exposed to titanium alloy wear particles become activated and release proinflammatory mediators that influence bone metabolism. These data support the hypothesis that direct activation of fibroblasts by particulate wear may play a role in particle‐mediated osteolysis. Fibroblast activation coupled with the biologic response of macrophages to wear debris in the loosening membrane may have a synergistic effect on pathologic bone resorption.
Effect of transforming growth factor‐β and platelet‐derived growth factor‐BB on articular cartilage in rats
Authors: Hulth Anders , Johnell Olof , Miyazono Kohei , Lindberg Lisbeth , Heinegård Dick , Heldin Carl‐Henrik
Published: February 2005

The short‐term and long‐term effects on the growth zone in articular cartilage of transforming growth factor‐β1 and platelet‐derived growth factor‐BB injected intraarticularly into the knee joint of growing rats were investigated. The changes induced by five injections of 0.5 μg of transforming growth factor‐β1 included a rapid decrease in the size and number of hypertrophic cells and an enhanced subchondral bone formation. The changes were most marked in the patella but were also apparent in the tibia and femur. The proliferating cells became swollen and lost their normal organization. From the seventh day of the experiment to about 3 weeks, the matrix stained intensely with safranin O for proteoglycans. The alterations induced by transforming growth factor‐β also included synovial fibroplasia and synovitis, consisting predominantly of mononuclear cells. Localised necroses in the cartilage sometimes appeared after 21 days. In long‐term studies, destroyed cartilage was found in three of six rats and partial ossification of the joint cartilage was found in two after 90 and 180 days. Ossicles developed in the tendons in all six patellae. Injection of platelet‐derived growth factor‐BB resulted in an early and transitory minor increase in the osteogenic activity in the zone between cartilage and red bone marrow and later produced an ossicle in one of four tendons. None of the other changes noted after injection of transforming growth factor was observed.
Visualization by magnetic resonance imaging of focal cartilage lesions in the excised mini‐pig knee
Authors: Koh H. L. , Kshirsagar A. , Herrod N. J. , Carpenter T. A. , Hall L. D. , Hunziker E. B. , Tyler J. A.
Published: February 2005

This study showed that magnetic resonance imaging can be used to visualize partial thickness cartilage lesions, 0.7 × 10 mm in area and 0.5 mm in depth, surgically induced in the femur (femoropatellar compartment) of a mini‐pig knee joint. Formalin‐fixed joints, intact as well as disarticulated, were studied by high resolution imaging using a 2.35 T, 31 cm horizontal‐bore superconducting magnet. The two‐dimensional and three‐dimensional spatial resolutions achievable were as follows: 0.12 × 0.23 mm (two‐dimensional) and 0.35 × 0.35 × 0.35 mm (three‐dimensional) for the intact joint, and 0.08 × 0.08 mm (two‐dimensional) and 0.14 × 0.14 × 0.27 mm (three‐dimensional) for the disarticulated joint. These results demonstrate that magnetic resonance imaging, together with edge detection and volume rendering, can be used to visualize focal cartilage lesions.
Optimal normalization tests for shoulder muscle activation: An electromyographic study
Authors: Kelly Bryan T. , Kadrmas Warren R. , Kirkendall Donald T. , Speer Kevin P.
Published: February 2005

To accurately compare electromyographic data from different muscles and different subjects, it is necessary to normalize the integrated data obtained from each muscle. The purpose of this study was to identify the manual muscle testing positions that elicit maximal neural activation (integrated electromyography) of three rotator cuff muscles (supraspinatus, infraspinatus, and subscapularis) and five shoulder synergists (pectoralis major, latissimus dorsi, and anterior, middle, and posterior deltoids). The electromyographic activity of these eight muscles was examined in the nondominant shoulders of nine subjects. Indwelling wire electrodes (supraspinatus, infraspinatus, and subscapularis) and surface adhesive electrodes (pectoralis major, latissimus dorsi, and anterior, middle, and posterior deltoids) were placed. Each subject performed a series of 27 isometric contractions, and optimal tests (maximal neural activation) were identified for each muscle. Four tests were identified that resulted in the maximal neural activation of all eight shoulder muscles: 90° of scapular elevation with −45° of humeral rotation for the supraspinatus, anterior deltoid, and middle deltoid; external rotation at 90° of scapular elevation and −45° of humeral rotation for the infraspinatus and posterior deltoid: internal rotation at 90° of scapular elevation and neutral humeral rotation for the subscapularis and latissimus dorsi: and internal rotation at 0° of elevation and neutral rotation for the pectoralis major. These results identify four standard testing positions that will provide reference values for normalization of maximal voluntary contraction for the eight muscles of the shoulder examined in this study. Standardization of these test positions offers normalization guidelines that can be used in future dynamic electromyography studies of the shoulder.
Alternative splicing of exon 12 of the COL2A1 gene interrupts the triple helix of type‐II collagen in the kniest form of spondyloepiphyseal dysplasia
Authors: Chen Luping , Yang Winnie , Cole William G.
Published: February 2005

An autosomal dominant mutation in the COL2A1 gene was identified in a child with the Kniest form of spondyloepiphyseal dysplasia. A C to T transition at nucleotide 35 of exon 12 changed the codon GCG for alanine 102 of the triple helical domain of α1 (II) chains of type‐II collagen to GTG for valine. The transition also introduced a GT dinucleotide into exon 12. Analysis of cDNA prepared from Kniest cartilage showed that in vivo the transition resulted in an alternatively spliced mRNA that lacked the 21 3′ nucleotides from exon 12. The cartilage cDNA contained approximately equal amounts of normal cDNA and shortened mutant cDNA. The deletion of 21 nucleotides from the mutant cDNA maintained the translational reading frame but resulted in the loss of alanine 102 to lysine 108, which interrupted the repetitive glycine‐X‐Y triplet sequence required for formation of the triple helix. Type‐II collagen molecules containing one or more mutant chains were expected, therefore, to contain interrupted triple helices with a short amino‐terminal helical domain A and a large carboxy‐terminal helical domain B. Kniest cartilage contained a reduced amount of pepsin‐solubilized type‐II collagen that consisted of overmodified α1 (II) chains. Peptide mapping showed that the overmodifications extended to the carboxy terminus of the α1(II) chains. Pepsin digestion also yielded shortened α1 (II) chains corresponding to helical domain B, Kniest chondrocytes cultured in alginate beads produced type‐II collagen that was not stably incorporated into the pericellular matrix. This study highlights the importance of dominant negative mutations of COL2A1 in producing Kniest dysplasia.
Regulation of proliferation and platelet‐derived growth factor expression in palmar fibromatosis (Dupuytren contracture) by mechanical strain
Authors: Alman Benjamin A. , Greel Debra A. , Ruby Leonard K. , Goldberg Michael J. , Wolfe Hubert J.
Published: February 2005

Palmar fibromatosis (Dupuytren contracture) causes fibrosis of specific palmar fascial bands. These bands are subjected to repetitive mechanical strain in situ. Primary cell cultures were derived from (a) palmar fibromatosis from eight patients, (b) uninvolved palmar fascia (Skoog's fibers) from four of these patients and (c) normal palmar fascia from four additional patients. The cells were plated onto collagen‐coated membranes either subjected to cyclic strain (25% maximal strain at 1 Hz) or without strain. Bromodeoxy uridine incorporation showed an increase in proliferation in all cultures subjected to strain. This increase was highest for palmar fibromatosis (10 to 40% nuclear incorporation, p = 0.02). Skoog's fibers and fascia from the normal individuals showed a trend (not significant) toward increase with strain (8 to 25%, p = 0.15 for Skoog's fibers, and 8 to 15%, p = 0.45 for normal fascia). Cyclic strain increased the expression of platelet derived growth factor‐A relative to glyceraldehyde‐3‐phosphate dehydrogenase in palmar fibromatosis (2.2 to 3.5, p = 0.05) and Skoog's fibers (0.8 to 2.0, p = 0.04). The expression of platelet‐derived growth factor‐B relative to glyceraldehyde‐3‐phosphate dehydrogenase was enhanced by cyclic strain only in the fibromatosis tissue (0.7 to 2.1, p = 0.04). The normal fascia did not express platelet‐derived growth factor. Platelet‐derived growth factor neutralizing antibody decreased bromodeoxyuridine incorporation in fibromatosis cultures subjected to cyclic strain to near levels for those grown in the absence of strain (38 to 16%, p = 0.05). Conditioned medium from fibromatosis cells grown under stain showed a trend toward increased proliferation in additional fibromatosis cultures compared with conditioned medium from fibromatosis cells grown without strain (9 to 15% nuclear incorporation, p = 0.20). The observed palmar fibromatosis contracture can be partially explained on the basis of the cell's response to cyclic strain, which may be mediated by plateletderived growth factor.
Gentamicin distribution from a collagen carrier
Authors: Mehta Sanjay , Humphrey J. Stewart , Schenkman Daniel I. , Seaber Anthony V. , Vail Thomas Parker
Published: February 2005

Local delivery of antibiotics by a degradable carrier has the potential for high local antibiotic levels and avoids systemic toxicity. Intravenous access, renal function monitoring, and subsequent surgical removal may not be required when degradable local delivery modalities are used. This study examined the in vivo elution of gentamicin from processed bovine collagen (type I) in 66 adult White rabbits. Collagen impregnated with gentamicin (3 mg/kg) was implanted into the vastus lateralis, and data were collected from 15 minutes to 28 days after implantation. Local tissue biopsies were taken a minimum of 2 mm from the implantation site. The gentamicin was released into the local tissue and averaged more than 3,800 μg/ml during the initial 4 hours after implantation. Local levels fell to 6.90 ± 5.22 μg/ml at 24 hours and subse‐quently were 2.70 ± 1.75. μg/ml or more through day 28. Serum levels reached an average peak of 4.04 ± 1.75 μg/ml at 5 hours after implantation, decreased after the initial 24 hours, and subsequently were less than 0.41 ± 0.20 μg/ml through day 28. Collagen impregnated with gentamicin proved to be an effective degradable carrier of gentamicin in the healthy rabbit; it provided local tissue concentrations above the minimum inhibitory concentration and serum concentrations below levels associated with systemic toxicity for 28 days after implantation.
Calculated stress‐shielding in the distal femur after total knee replacement corresponds to the reported location of bone loss
Authors: Tissakht M. , Ahmed A. M. , Chan K. C.
Published: February 2005

This study sought to determine the similarities between features of calculated stress‐shielding and observed bone loss in the distal femur after total knee replacement. Stress‐shielding was determined by comparing the magnitudes and distributions of strain energy density, calculated using three‐dimensional finite element models of the intact bone, the bone after total knee replacement with bonding assumed at all prosthesis‐bone interfaces, and the bone after total knee replacement with bonding assumed only at the distal interface. The loading condition simulated static lifting with the knee flexed at 45°, producing tibiofemoral and patellofemoral joint reactions of 900 and 450 N, respectively. The maximum magnitudes of strain energy density calculated using the total knee replacement models were less than 15% of the corresponding magnitudes from the intact bone model. The greatest difference was found to occur at the anterior distal corner of the femur, suggesting this location as the one most vulnerable to stress‐shielding. Clinically observed bone loss after total knee replacement frequently occurs at this location. At the anterior distal corner, the calculated magnitudes for the two total knee replacement models were similar, suggesting that stress‐shielding at this location was not reduced by limiting fixation only to the distal interface. Although the study corresponded to one loading condition and one geometry of the total knee replacement femoral component with the inherent limitations of model calculations, the results suggest a possible scenario for stress‐shielding.
Augmentation of femoral neck fracture fixation with an injectable calcium‐phosphate bone mineral cement
Authors: Stankewich C. J. , Swiontkowski Marc F. , Tencer Allan F. , Yetkinler Duran N. , Poser Robert D.
Published: February 2005

The first goal of this study was to determine if augmentation with an injectable, in situ setting, calcium‐phosphate cement that is capable of being remodeled and was designed to mimic bone mineral significantly improved the strength and stiffness of fixation in a cadaveric femoral neck fracture model. The second goal was to determine if greater increases in fixation strength were achieved as the bone density of the specimen decreased. Sixteen pairs of fresh cadaveric human femora with a mean age of 70.9 years (SD = 17.2 years) were utilized. The bone density of the femoral neck was measured with dual‐energy x‐ray absorptiometry. The femoral head was impacted vertically with the femoral shaft fixed in 12° of adduction using a materials testing machine to create a fully displaced fracture. Following fracture, 30% inferior comminution was created in each specimen. One randomly chosen femur from each pair underwent anatomic reduction and fixation with three cannulated cancellous bone screws, 7 mm in diameter, in an inverted triangle configuration. The contralateral femur underwent the same fixation augmented with calcium‐phosphate cement. Specimens were preconditioned followed by 1,000 cycles to one body weight (611.6 N) at 0.5 Hz to simulate single‐limb stance loading. The stiffness in the first cycle was observed to be significantly greater in cement‐augmented specimens compared with unaugmented controls (p < 0.05). After cycling, each specimen was loaded at 10 mm/min until complete displacement of the fracture surface and failure of fixation occurred. Specimens augmented with bone mineral cement failed at a mean of 4,573 N (SD = 1,243 N); this was significantly greater (p < 0.01) than the mean for controls (3,092 N, SD = 1,258 N). The relative improvement in fixation strength (augmented/control × 100% ) was not inversely correlated to femoral neck bone density (p = 0.25, R2 = 0.09), was weakly correlated to the volume of cement injected (p = 0.07, R2 = 0.22), and was inversely related to the fixation failure load of the control specimen (p = 0.001, R2 = 0.54). There was a mean relative improvement in fixation strength of 169.6% (SD = 77.5). These findings suggest that calcium‐phosphate cement provides initial beneficial augmentation to fixation of femoral neck fractures.
Distribution of elastic fiber types in the epiphyseal region
Authors: Gigante A. , Greco F. , Specchia N. , Nori S.
Published: February 2005

Three types of elastic fibers have been described: mature elastic fibers, elaunin fibers, and oxytalan fibers. To our knowledge, their location in the immature epiphysis has never been previously reported. The aim of the present study was to use histochemistry, immunohistochemistry, and electron microscopy to demonstrate the distribution of each type of elastic fiber in the epiphyseal region of growing humans and rabbits. Histological samples were collected from the knees of 10 immature New Zealand White rabbits and four children of various ages. The Weigert resorcin‐fuchsin, Gomori aldehyde‐fuchsin, Verhoeff iron haematoxylin, and Fullmer‐Lillie methods were used for histochemistry; anti‐elastin monoclonal antibodies, for immunohistochemistry; and tannic acid, uranyl acetate, and lead citrate stain, for transmission electron microscopy analysis. Elastic fibers were detected in the perichondrium, the epiphyseal vessels, and the outer and middle zones of Ranvier's groove. Their orientation was longitudinal in the outer zone and circumferential in the middle zone of the groove. Oxytalan fibrils (i.e., bundles of filaments of 10–12 nm in diameter that do not contain elastin) and elaunin fibers (i.e., filaments that cross discontinuous aggregates of elastin) were more plentiful in the middle zone and decreased with age, whereas mature fibers were more numerous in the outer zone and increased with age. This organization of elastic fibers seems to indicate an age‐related process of maturation of the elastic network. The contribution of these fibers to the mechanical properties of the epiphyseal plate and to the growth process remains to be determined.
Protective effect of 21‐aminosteroid pretreatment in peripheral nerve low‐load crush injury in mature and immature rats
Authors: Nasser Rima M. , Chen Long‐En , Seaber Anthony V. , Urbaniak James R.
Published: February 2005

The effects of U‐74006F (tirilazad mesylate), a 21‐aminosterold antioxidant, on injured peripheral nerve were studied. Twenty‐two immature and 44 mature rats were divided equally into two groups. The experimental group received two injections of 3 mg/kg of U‐74006F at a 2 hour interval. The control group received the same volumes of a citrate buffer. A 5 mm segment of the sciatic nerve was subjected to a crush load of 100 g for 2 hours. Motor function (sciatic functional index) was assessed to day 48 postoperatively. There was total paralysis of the crushed limb in all rats the first week after crushing. The experimental group had a statistically significant improvement in motor function compared with the controls on days 14, 21, 25, and 28 for the mature rats and on days 11 and 14 for the immature rats. The mature controls attained complete recovery on day 42 and had a significantly slower recovery rate than the immature controls, which had recovered fully by day 25. The recovery rates were almost similar among mature and immature groups pretreated with U‐74006F, both of which had fully recovered motor function by day 28. The results indicate that pretreatment with U‐74006F can significantly promote peripheral nerve function after low‐load crush injury and that the age of the animal influences the rate of peripheral nerve recovery.
Tensile properties of the interosseous membrane of the human forearm
Authors: Pfaeffle H. James , Tomaino Matthew M. , Grewal Rupinder , Xu Jiangming , Boardman N. Douglas , Woo Savio L‐Y. , Herndon James H.
Published: February 2005

The interosseous membrane is a structure deep in the forearm that joins the radius and the ulna. It is made up of membranous and ligamentous regions. Two main ligamentous structures have been described: a prominent central fiber group, the “central band,” and a smaller proximal fibrous band, the “oblique cord.” Many authors believe that the central band plays a biomechanical role in the normal and fractured forearm and that it may function much like a ligament. The objective of this study was to determine the tensile properties of the central band. Eighteen fresh frozen forearms from cadavers (45–70 years of age, both sexes) were used. A fiber bundle of the central band was subjected to a uniaxial tensile test to failure in a materials testing machine, and its tensile properties were calculated. Stiffness, ultimate load, and energy absorbed to failure were expressed as a function of specimen width. The central band structure had a stiffness of 13.1 ± 3.0 N/mm per mm width and an ultimate load of 56.6 ± 15.1 N per mm width (mean ± SD). The tissue of the central band displayed a modulus of 608.1 ± 160.2 MPa, ultimate tensile strength of 45.1 ± 10.3 MPa, and strain at failure of 9.0 ± 2.0%. This study demonstrated that the central band is comprised of strong tissue. The material properties of the central band compare with those of patellar tendon: modulus is 120% and ultimate tensile strength is 84% that of patellar tendon. As a structure, the interosseous membrane is stiff and capable of bearing high loads. Although load distribution across the central band is unknown, a 1.7 cm wide, evenly loaded homogenous portion of the central band would possess a stiffness comparable with that of the anterior cruciate ligament. The results of this study provide a basis for future analyses of radioulnar stability and load transfer.
Expression of collagen and matrix metalloproteinases in ruptured human anterior cruciate ligament: An in situ hybridization study
Authors: Spindler K. P. , Clark S. W. , Nanney L. B. , Davidson J. M.
Published: February 2005

The biological basis for failure of the human anterior cruciate ligament to heal after rupture is unknown. Since this failure could be influenced by abnormalities in matrix protein production or degradation, or both, several diverse matrix protein markers were utilized to survey the state of these extracellular proteins in intrinsic anterior cruciate ligament fibroblasts. Matrix gene expression was visualized by in situ hybridization 9 to 365 days after rupture using probes for type‐I collagen, collagenase, 72kDa‐gelatinase, and tissue inhibitor of metalloproteinase. Remnants of anterior cruciate ligament were biopsied arthroscopically from 20 patients at reconstruction, fixed in 4% paraformaldehyde, and processed with cDNA probes for the aforementioned mRNAs, mRNA expression of type‐I collagen was detected in all specimens, was equally distributed throughout the remnants, and remained evident even at 1 year after injury. Neither of the matrix‐degrading enzymes nor their inhibitor (tissue inhibitor of metalloproteinase) was expressed at substantial levels at any time point. Collagen expression within the anterior cruciate ligament confirmed the viability of the ligament remnants for as long as 1 year after rupture. The lack of significant expression of the two matrix‐degrading metalloproteinases by the fibroblasts is not consistent with an autodegradation of the remaining ruptured ligament tissue, and whether the lack of matrix remodelling may account, at least in part, for the poor healing response of the anterior cruciate ligament remains to be determined. This initial investigation by in situ hybridization techniques provides a descriptive profile of matrix gene expression in the damaged human anterior cruciate ligament.
Response of human osteoblasts to implant materials: Integrin‐mediated adhesion
Authors: Gronowicz G. , McCarthy M. B.
Published: February 2005

The initial interaction of the human osteoblast‐like cell line Saos‐2 with orthopaedic implant materials was analyzed to determine the mechanism by which these cells adhere to implant surfaces. Saos‐2 cells were allowed to attach to disks composed of the orthopaedic implant materials Tivanium (Ti6A14V) and Zimaloy (CoCrMo) and to control disks of glass and plastic. Serum had no effect on the number of cells that attached to Tivanium and Zimaloy at 4 or 24 hours but did increase the number of cells that attached to glass at 24 hours. Collagen synthesis was determined by [3H]proline incorporation into collagenase‐digestible protein and noncollagen protein. A significant increase of 19% was found for collagen synthesized in cells cultured on Zimaloy for 24 hours compared with glass, with no differences on Tivanium and plastic. However, collagenase‐digestible protein and noncollagen protein were increased the most (204 and 198%, respectively) on Tivanium compared with glass. To determine if integrins were involved in cell attachment to implant materials, the peptide GRGDSP (Gly‐Arg‐Gly‐Asp‐Ser‐Pro), which blocks integrin receptors through the Arg‐Gly‐Asp sequence, was added to the cells in serum‐free medium. This peptide inhibited cell adhesion by 28% on Tivanium and 40% on Zimaloy but had no effect on glass and plastic. The control peptide GRADSP (Gly‐Arg‐Ala‐Asp‐Ser‐Pro) had no effect on adhesion. Inhibition of protein synthesis and enzymatic removal of surface proteins did not affect the ability of Arg‐Gly‐Asp peptides to inhibit cell attachment to the implant materials. These results suggest that integrins are able to bind directly to Tivanium and Zimaloy. Western blot analysis of integrin protein demonstrated changes in many integrin subunits, depending on the substrate to which cells affached. In particular, the β1 integrin subunit was increased 3.8 to 9.5‐fold at 24 hours. To determine specifically which integrins may be involved in adhesion, antibodies to integrins were added. An antibody to the fibronectin receptor. α5β1, significantly inhibited binding of cells to Tivanium by 63% and to Zimaloy by 49% and had no effect on glass. The vitronectin receptor antibody, αvβ3/β5, did not alter cell adhesion. In conclusion, osteoblast‐like cells appear to be capable of attaching directly to implant materials through integrins. The type of substrate determines which integrins and extracellular matrix proteins are expressed by osteoblasts. These data provide information on how implant materials may affect osteoblast differentiation and bone growth.
Effect of noninvasive low intensity ultrasound on bone growth into porous‐coated implants
Authors: Tanzer M. , Harvey E. , Kay A. , Morton P. , Bobyn J. D.
Published: February 2005

Noninvasive low intensity ultrasound has been shown to be an effective means of accelerating bone fracture healing in both animal and clinical studies. An in vivo canine study was designed to determine if noninvasive low intensity ultrasound could influence the rate and extent of bone growth into porous‐coated implants. Twenty‐two pairs of fully porous transcortical implants were inserted bilaterally into the femora of 12 dogs. In each dog, one femur served as a control and the other was subjected to daily ultrasound stimulation for 2, 3, or 4 weeks. Overall, the ultrasound‐stimulated implants demonstrated an 18% increase in bone ingrowth compared with their contralateral controls (p = 0.02). Noninvasive low intensity ultrasound had its greatest effect in the first 2–3 weeks of stimulation. At 2 and 3 weeks, the ultrasound‐stimulated implants showed 21 and 16% more ingrowth than their respective contralateral controls. Because noninvasive low intensity ultrasound had a positive effect on bone ingrowth in this experimental investigation, further research is suggested to assess the clinical potential for application to noncemented porous‐coated total joint replacements.