bluuebunny/crossref_metadata_2025 huggingface dataset:
Fibroblast distribution in the anteromedial bundle of the human anterior cruciate ligament: The presence of α‐smooth muscle actin‐positive cells
Authors: Murray M. M. , Spector M.
Published: February 2005

The anterior cruciate ligament is a complex tissue composed of structural proteins, proteoglycans, and cells. The histology of the human anterior cruciate ligament is characterized by the specific distribution and density of the fibroblast phenotype as well as by the unique organization of the structural proteins. A notable finding of this study was the identification of three histologically different zones along the anteromedial bundle as it coursed from the femoral to the tibial attachment. Two of the zones, the fusiform and ovoid, were located in the proximal one‐quarter of the bundle; the third zone, the spheroid, occupied the distal three quarters of the bundle fascicles. The fusiform cell zone was characterized by a high number density of longitudinally oriented cells with a fusiform‐shaped nucleus, longitudinal blood vessels, and high crimp length. The cytoplasm of the cells in this zone appeared to be intimately attached to the extracellular collagen and followed the crimp waveform of the fibers. Fusiform cells were noted to stain positively for the α‐smooth muscle actin isoform in this region, particularly at areas of crimp disruption. The ovoid cell zone was characterized by a high number density of cells with an ovoid‐shaped nucleus, longitudinal vessels, and a high crimp length. In this zone as well, the cytoplasm of the cells appeared to follow the waveform of the adjacent collagen. Ovoid cells were noted to stain positively for the α‐smooth muscle actin isoform in this region. The spheroid cell zone was characterized by a low density of spheroid cells, few blood vessels, and short crimp length. Cells were noted within and among fascicles, as well as within lacunae. In selected areas, as many as 50% of the cells in this region stained positively for the α‐smooth muscle actin isoform. This is also the first report of cells expressing the α‐smooth muscle actin isoform in the intact human anterior cruciate ligament. This specific type of contractile actin, initially identified only in smooth‐muscle cells, pericytes, and myofibroblasts, was seen in cells with various morphologies and predominantly in cells located at areas of crimp disruption. Further work is necessary to elucidate the role of the various fibroblast phenotypes in the maintenance of the human anterior cruciate ligament.
Early expression of marker genes in the rabbit medial collateral and anterior cruciate ligaments: The use of different viral vectors and the effects of injury
Authors: Hildebrand Kevin A. , Deie Masataka , Allen Christina R. , Smith David W. , Georgescu Helga I. , Evans Christopher H. , Robbins Paul D. , Woo Savio L‐Y.
Published: February 2005

Gene therapy is a technique that may offer advantages over current methods of cytokine delivery to ligaments. To determine if implanted genes could be expressed in normal and injured knee ligaments, the medial collateral ligament and anterior cruciate ligament were studied in 18 rabbits. A retroviral ex vivo technique using allograft medial collateral ligament and anterior cruciate ligament fibroblasts and an adenoviral in vivo technique were compared as methods for delivering the LacZ marker gene to knee ligaments. Bilateral knee surgeries were performed, and the rabbits were equally divided into three groups. Group 1 received the retrovirus and the medial collateral ligament was ruptured, Group 2 received the adenovirus and the medial collateral ligament was ruptured, and Group 3 received the adenovirus and the medial collateral ligament was not injured. The anterior cruciate ligament was not injured in any group. The medial collateral and anterior cruciate ligaments of the right knees received 106 allografted, transduced ligament fibroblasts or 109 adenovirus particles, whereas the ligaments of the left knee received a similar volume of saline solution only. Equal numbers of rabbits were killed at 10 days. 3 weeks, and 6 weeks following the procedure. Ligament samples were stained with X‐gal to detect the expression of the LacZ gene product, β‐galactosidase. LacZ gene expression was evident in ruptured and uninjured medial collateral ligaments as well as in the anterior cruciate ligament. The expression lasted between 10 days and 3 weeks in the medial collateral and anterior cruciate ligaments with use of the retrovirus and between 3 and 6 weeks in the medial collateral ligament and at least 6 weeks in the anterior cruciate ligament with the adenovirus. The length of gene expression in the ruptured and uninjured medial collateral ligaments did not differ. These preliminary studies indicate that gene transfer to normal and injured knee ligaments is possible.
Gene therapy: Adenovirus‐mediated human bone morphogenetic protein‐2 gene transfer induces mesenchymal progenitor cell proliferation and differentiation in vitro and bone formation in vivo
Authors: Lou Jueren , Xu Fang , Merkel Kurt , Manske Paul
Published: February 2005

This study reports that recombinant adenovirus‐mediated human bone morphogenetic protein‐2 gene transfer can induce mesenchymal progenitor cell differentiation and bone formation. The recombinant adenovirus with the human bone morphogenetic protein‐2 gene was constructed, and mature human bone morphogenetic protein‐2 expression mediated by adenovirus gene transfer was detected by specific antibody. Under adenovirus‐mediated bone morphogenetic‐protein gene transfer, mesenchymal progenitor cell line C3H/10T 1/2 showed cell proliferation dependent on adenovirus bone morphogenetic‐protein dose. The C3H/10T 1/2 cells transduced by adenovirus bone morphogenetic protein also exhibited differentiation to osteoblast phenotype, which indicates alkaline phosphatase activity. Injection of the C3H/10T 1/2 cells into the thigh muscles of nude mice led to ossicle development detectable on radiographs. Histological analysis indicated that the new ossicles that developed in the thigh muscles of the mice had different osseous components including bone trabeculae, bone marrow, and chondrified tissue. The results of this study demonstrate the potential for gene therapy by adenovirus‐mediated bone morphogenetic‐protein gene transfer.
Intravertebral body reconstruction with an injectable in situ‐setting carbonated apatite: Biomechanical evaluation of a minimally invasive technique
Authors: Schildhauer T. A. , Bennett A. P. , Wright T. M. , Lane J. M. , O'Leary P. F.
Published: February 2005

The ability to mechanically reinforce an osteoporotic vertebral body could impede spinal compression fracture and the associated pain and complications. Previous studies have shown that reinforcement of fractured vertebrae with conventional acrylic cement can relieve symptoms and avoid further collapse. In this study, we explored the use of a carbonated apatite cement combined with a minimally invasive injection technique to improve the compressive mechanical properties of cadaveric vertebral bodies. After establishing the biomechanical characteristics of cement formulations intended to have appropriate viscosities, we evaluated the infiltration of the cements into thoracic vertebral bodies using a combined suction‐injection technique. The energy‐absorption capabilities of the reinforced vertebral bodies were then measured during axial compressive tests and compared with those of nonreinforced vertebrae. The ultimate compressive strength of the cement formulations averaged from 11.6 to 17.7 MPa, depending on curing conditions. The suction‐injection technique allowed from one‐half to two‐thirds of each vertebral body to be infiltrated with cement. Energy absorption was significantly higher (p < 0.05) between 25 and 70% collapse of the vertebral body in the specimens that received the apatite injection as compared with the controls. These results suggest that osteoporotic vertebral‐body augmentation with the injection of apatite cement could prevent further collapse after initial failure has occurred. The osteoconductive nature of the cement and its ability to be remodeled by bone, together with its compressive strength, which is higher than that of cancellous bone, could provide better clinical results than those of current treatments with acrylic cement.
Evaluation of blood flow within the subchondral bone of the femoral head: Use of the laser speckle method at surgery for osteonecrosis
Authors: Fukuoka Shinji , Hotokebuchi Takao , Jingushi Seiya , Fujii Hitoshi , Sugioka Yoichi , Iwamoto Yukihide
Published: February 2005

The laser speckle method is a new form of tissue flowmetry that can analyze the interference pattern that appears when tissue is illuminated with a laser beam. During surgery for 100 cases of osteonecrosis of the femoral head, we measured the blood flow within the subchondral bone using this method. We compared the flow maps (two‐dimensional distribution of the microcirculation) obtained this way with the necrotic area estimated by the preoperative magnetic resonance images and with the collapse seen during surgery. The laser speckle method was able to distinguish between the ischemic areas and the normal areas in 92 femoral heads, including five hips for which neither the magnetic resonance images nor the collapse observed during surgery demonstrated a distinct margin surrounding the necrotic area. We concluded that the laser speckle method is useful for defining the margin around a necrotic area.
Cytokine‐induced tendinitis: A preliminary study in rabbits
Authors: Stone David , Green Colleen , Rao Uma , Aizawa Harutaka , Yamaji Toomoo , Niyibizi Christopher , Carlin Greg , Woo Savio L‐Y.
Published: February 2005

This study was designed to determine the effects of a single injection of a species‐specific preparation of cytokines into rabbit patellar tendons and to compare the results with a known model of tendinitis, the collagenase‐injection model. New Zealand White rabbits were divided into two groups and two time periods (4 and 16 weeks) and injected in the midsubstance of the right patellar tendon with either cytokines or collagenase under ultrasound guidance to confirm intratendinous needle placement. The left patellar tendon was injected with 0.025 ml of saline solution and served as a control. The rabbits were returned to cage activity after injection. At death, two rabbits in each group underwent histological analysis; the remaining eight animals in each time frame were evaluated biomechanically and then biochemically with use of the patella/whole patellar tendon/tibia complex. Histologic results at 4 weeks in the tendons injected with cytokines demonstrated increased cellularity, which was resolving by 16 weeks. The matrix appeared unchanged. The tendons injected with collagenase demonstrated increased angiogenesis of the matrix, hypercellularity, and fibrosis around the tendon at 4 weeks. At 16 weeks, myxoid changes, focal fibrosis, and collagen‐bundle disarray with persistent increase in cellularity were noted. Biomechanically, a significant decrease in ultimate load at 16 weeks was seen in the tendons injected with cytokines but no change was seen in cross‐sectional area. The tendons injected with collagenase demonstrated a significant increase in cross‐sectional area at 4 and 16 weeks compared with those injected with cytokines. Biochemically, there was no significant difference in collagen content between the two groups at 4 or 16 weeks but the tendons injected with collagenase demonstrated a significant increase in crosslinking at 16 weeks. Our conclusion is that the tendons injected with the cytokine preparation represent a model of mild, seemingly reversible tendon injury. The cytokine preparation produces no matrix damage or evidence of collagen degradation and is species specific.
In vivo finger flexor tendon force while tapping on a keyswitch
Authors: Dennerlein Jack Tigh , Diao Edward , Mote C. D. , Rempel David M.
Published: February 2005

Force may be a risk factor for musculoskeletal disorders of the upper extremity associated with typing and keying. However, the internal finger flexor tendon forces and their relationship to fingertip forces during rapid tapping on a keyswitch have not yet been measured in vivo. During the open carpal tunnel release surgery of five human subjects, a tendon‐force transducer was inserted on the flexor digitorum superficialis of the long finger. During surgery, subjects tapped with the long finger on a computer keyswitch, instrumented with a keycap load cell. The average tendon maximum forces during a keystroke ranged from 8.3 to 16.6 N (mean = 12.9 N, SD = 3.3 N) for the subjects, four to seven times larger than the maximum forces observed at the fingertrip. Tendon forces estimated from an isometric tendon‐force model were only one to two times larger than tip force, significantly less than the observed tendon forces (p = 0.001). The force histories of the tendon during a keystroke were not proportional to fingertip force. First, the tendon‐force histories did not contain the high‐frequency fingertip force components observed as the tip impacts with the end of key travel. Instead, tendon tension during a keystroke continued to increase throughout the impact. Second, following the maximum keycap force, tendon tension during a keystroke decreased more slowly than fingertip force, remaining elevated approximately twice as long as the fingertip force. The prolonged elevation of tendon forces may be the result of residual eccentric muscle contraction or passive muscle forces, or both, which are additive to increasing extensor activity during the release phase of the keystroke.
Immunohistochemical analysis of type X‐collagen expression in osteoarthritis of the hip joint
Authors: Boos Norbert , Nerlich Andreas G. , Wiest Irmagard , von der Mark Klaus , Ganz Reinhold , Aebi Max
Published: February 2005

Conflicting data have been reported on the spatial distribution of type X‐collagen expression in osteoarthritis, and no concise data exist on a possible correlation between type X‐collagen expression and clinical and radiological alterations. Well defined clinical and radiological data were compared with histopathological and immunohistochemical findings to investigate the expression of type‐X collagen in osteoarthritis of the hip joint. Femoral heads were obtained in toto from 11 patients undergoing routine hip arthroplasty for femoral neck fractures (n = 3) or osteoarthritis (n = 8) and from 13 patients (age: 12 days to 69 years) without any evidence of hip‐joint pathology. Whole coronal sections from the femoral head were decalcified for routine histology and immunohistochemical analysis with use of type‐specific monoclonal antibodies to type‐X collagen. Our results demonstrate that type‐X collagen is consistently found in osteoarthritic cartilage and is absent from normal adult cartilage (including the region of calcified cartilage). Except for the occurrence of type‐X collagen in the middle zone of articular cartilage in advanced stages of osteoarthritis, there is no specific change in the staining pattern or intensity for the collagen during osteoarthritis, particularly when the staining is related to clinical and radiological parameters. Hardly more than 20% of the extracellular matrix stained for type‐X collagen; therefore, we suggest that, in most cases, this type of collagen may not play a direct biomechanical role in the weakening of osteoarthritic cartilage but rather may contribute indirectly to a disturbance of the disc biomechanics by altering matrix‐molecule interaction. However, expression of type‐X collagen may indicate a change in chondrocyte phenotype that consistently coincides with the formation of chondrocyte clusters, one of the first alterations in osteoarthritis visible on histologic examination.
Muscle regeneration and fiber‐type transformation during distraction osteogenesis
Authors: De Deyne Patrick G. , Hayatsu Kazunori , Meyer Rick , Paley Dror , Herzenberg John E.
Published: February 2005

The successful outcome of distraction osteogenesis depends in part on the adequate adaptation of the surrounding soft tissue. We characterized the adaptation of the tibialis anterior during distraction osteogenesis at different rates (0.7 and 1.4 mm/day) and amounts (15 and 30%) of lengthening. We documented the increased expression of neonatal and slow myosin heavy chain in the tibialis anterior of skeletally immature rabbits. There was neither expression of neonatal myosin heavy chain in the experimental soleus or in the slow muscle fibers of the tibialis anterior nor increased expression of slow myosin heavy chain in the soleus or gastrocnemius. The increased amount of neonatal myosin heavy chain was concentrated in the distal half of the muscle, whereas the increase in the number of fibers that were labeled with antibodies to slow myosin occurred to the same extent throughout the tibialis anterior. Electrophysiological methods showed that the tibialis anterior was functionally intact during and after distraction osteogenesis. We concluded that in the tibialis anterior of young, skeletally immature animals, distraction osteogenesis seems to induce a recapitulation of the developmental process without leading to functional changes. In addition, during distraction osteogenesis, a fiber‐type transformation occurs similar to that observed in models of muscle overloading.
Late‐preconditioning protection is evident in the microcirculation of denervated skeletal muscle
Authors: Wang Wei Z. , Tsai Tsu‐Min , Anderson Gary L.
Published: February 2005

We investigated whether ischemic preconditioning induces microvascular protection in skeletal muscle at the late phase (after 24 hours) when the same muscles are subjected to prolonged warm global ischemia. The cremaster muscle of the male Sprague‐Dawley rat underwent vascular isolation and was subjected to 4 hours of ischemia and 60 minutes of reperfusion. Early preconditioning consisted of 45 minutes of ischemia followed by 15 minutes of reperfusion before prolonged ischemia/reperfusion; late preconditioning also consisted of 45 minutes of ischemia but was done 24 hours (24‐hour period of reperfusion) before the prolonged ischemia/reperfusion. Arteriole diameters and capillary perfusion were measured with use of intravital microscopy. Four groups were compared: rats that underwent early preconditioning, their controls, rats that underwent late preconditioning, and their controls. Early and late preconditioning significantly attenuated vasospasm and capillary no‐reflow compared with the controls for each. Average arteriole diameter was significantly larger in the rats that underwent late preconditioning than in any other rats; it was also significantly larger in the controls for late preconditioning than in those for early preconditioning. We introduce a model of the rat cremaster muscle that has been isolated from its vascular supply as a useful preparation to study the effects of late preconditioning on microcirculation in skeletal muscle. Late preconditioning provided better microvascular protection than did early preconditioning. The mechanism for this preconditioning protection is being investigated because it should provide a means for therapeutic intervention.
Effect of demineralized bone matrix on polymorphonuclear leukocyte degranulation
Authors: Kale Ashay A. , Clancy Robert , Leslie Michael P. , Di Cesare Paul E.
Published: February 2005

The potential use of allogenic demineralized bone matrix to augment or treat bone defects or nonunios in animals and humans is currently being investigated. Demineralized bone matrix induces osteogenesis by a multistep cascade of endochondral ossification that is mediated by bone‐induction factors. The migration and activation of polymorphonuclear leukocytes appear to be critical in the initiation of the cascade of osteogenesis induced by demineralized bone matrix. This study examined the effects of demineralized bone matrix on the degranulation of polymorphonuclear leukocytes. Demineralized bone matrix stimulated the release of polymorphonuclear leukocyte‐specific, but not azurophilic, granules in a time and dose‐dependent manner. The ability of the bone matrix to induce this degranulation was independent of its size and species. The mechanism by which this degranulation occurs is not completely understood; however, it is known that it does not occur by means of a receptor that requires guanidine triphosphate‐dependent regulatory proteins as does polymorphonuclear leukocyte degranulation induced by N‐formyl peptide. The factor that stimulates degranulation is not type‐I collagen but rather appears to be a cytokine that has a heparin‐binding domain and a molar mass of 10‐70 kDa. Loss of the ability of demineralized bone matrix to induce degranulation of polymorphonuclear leukocytes correlated positively with the loss of its ability to induce bone formation.
Elastic fibers of musculoskeletal tissues in bovine marfan syndrome: A morphometric study
Authors: Gigante A. , Chillemi C. , Potter K. A. , Bertoni‐Freddari C. , Greco F.
Published: February 2005

Bovine Marfan syndrome has all the major pathognomonic, clinical, and pathological features of the human syndrome. To further explore the alterations characterizing Marfan syndrome, musculoskeletal tissues from affected and healthy cattle were subjected to histochemical and histomorphometric analysis. Our findings demonstrated reduced elastic fiber content in the periosteum, capsule, interosseous ligament, and flexor tendons of the metatarsophalangeal joint of affected cattle. The elastic properties of a tissue are supplied by elastic fibers in the extracellular matrix; therefore, their reduced content in articular tissues suggests that these fibers could be functionally incompetent to withstand normal stress, causing a predisposition to joint laxity and dislocation. Moreover, perichondrial‐periosteal membrances, which are made of collagen and elastic fibers, are known to affect the growth process of the long bones. The decrease in the number of elastic fibers in these membranes could result in reduced restraint of skeletal growth and explain some skeletal abnormalities of Marfan syndrome (i.e., dolichostenomelic habitus).
P‐glycoprotein expression in osteosarcoma: A basis for risk‐adapted adjuvant chemotherapy
Authors: Baldini N. , Scotlandi K. , Serra M. , Picci P. , Bacci G. , Sottili S. , Campanacci M.
Published: February 2005

Previous reports on osteosarcomas treated with multi‐agent chemotherapy have shown that P‐glycoprotein expression is a reliable prognostic indicator. The current thinking is that, of the several agents used for the treatment of osteosarcoma, only doxorubicin is involved in drug resistance mediated by P‐glycoprotein. This study examines the relationship of P‐glycoprotein expression to clinical outcome in osteosarcomas, treated only with doxorubicin in addition to surgery, to determine if the prognostic significance of P‐glycoprotein expression reflects the ability of osteosarcoma to respond to this drug. The expression of P‐glycoprotein in tumor specimens was assessed by immunohistochemistry in 37 nonmetastatic, operable osteosarcomas treated at a single institution with doxorubicin as a single adjuvant drug. The P‐glycoprotein status was analysed in relation to the length of event‐free survival. A widespread pattern of P‐glycoprotein expression in tumor cells at diagnosis was significantly associated with a higher rate of systemic relapse (p < 0.001). On comparison of this group of patients with a similar series of 92 patients, all treated with multi‐agent chemotherapy plus surgery of the primary lesion and previously analysed for P‐glycoprotein status, only P‐glycoprotein‐positive, doxorubicin‐resistant tumors consistently benefited from the addition of drugs other than doxorubicin (p < 0.001). Osteosarcomas with different abilities to respond to adjuvant chemotherapy can be identified by the expression of P‐glycoprotein in tumor cells at the clinical onset. P‐glycoprotein status may serve as a basis for risk‐adapted, individualized therapeutic regimens. Standard programs are sufficient for P‐glycoprotein‐negative osteosarcomas, whereas P‐glycoprotein‐positive tumors may benefit from the use of more intensive therapeutic approaches.
Expression of osteocalcin and its transcriptional regulators core‐binding factor alpha 1 and MSX2 in osteoid‐forming tumours
Authors: Hopyan Sevan , Gokgoz Nalan , Bell Robert Stuart , Andrulis Irene Louise , Alman Benjamin Aaron , Wunder Jay Steven
Published: February 2005

Osteosarcoma, fibrous dysplasia, and myositis ossificans contain osteoid‐producing cells that are not necessarily morphologically typical osteoblasts. Nevertheless, these pathologic cells may share differentiation steps with osteoblasts at the molecular level. Osteocalcin, a bone‐specific extracellular matrix protein, is a marker of mature osteoblasts. Osteocalcin is upregulated by the transcription factor core‐binding factor alpha 1, which is responsible for commitment to the osteoblastic lineage, and is downregulated by MSX2, a homeobox‐containing transcription factor expressed during the early proliferative phase of osteoblast differentiation. Semiquantitative reverse transcription‐polymerase chain reaction was used to compare expression levels of osteocalcin, core‐binding factor alpha 1, and MSX2 in 34 osteosarcoma, five fibrous dysplasia, and five myositis ossificans specimens, as well as in seven normal cortical bone samples. Despite normal or elevated levels of core‐binding factor alpha‐1 expression in most specimens, osteocalcin expression was low or undetectable in most cases of osteosarcoma (25 of 34) and myositis ossificans (4 of 5). Single‐strand conformation polymorphism and sequencing did not identify and mutations in the DNA‐binding domain of core‐binding factor alpha 1. However, a high level of MSX2 expression was demonstrated in these lesions, which may inhibit osteocalcin transcription. The presence of moderate levels of osteocalcin in fibrous dysplasia may contribute to the characteristic disconnected appearance of trabeculae in that entity because osteocalcin is a negative regulator of bone formation.
Carvedilol reduces ischaemic skeletal muscle necrosis
Authors: Hvaal K. , Mathisen S. R. , Svindland A. , Kirkeby O. J. , Skjeldal S.
Published: February 2005

Carvedilol is an alpha1 and nonselective beta‐adrenergic receptor antagonist with antioxidative properties known to protect against reperfusion injury in the heart, brain, and kidneys. The aim of this study was to test the hypothesis that carvedilol improves postischaemic reperfusion and tissue survival in skeletal muscle. Sixteen Wistar rats underwent tourniquet ischaemia of the left hindlimb for 3 hours and 15 minutes at 27°C, Single‐fiber laser Doppler probes were inserted in the left and right anterior tibial muscles, and microvascular perfusion was measured until 2 hours after removal of the tourniquet. Perfusion indices for each 15‐minute interval were calculated for the left hindlimb (tourniquet ischaemia) by dividing the postischaemic by the pre‐ischaemic laser Doppler flowmetry values, and the geometrical areas under the curves representing a plot of perfusion index relative to time, measured in arbitrary units, were compared. Laser Doppler flowmetry values for the right anterior tibial muscle were compared. Tissue damage was measured by histomorphometry of necrotic areas and no‐reflow zones in cross sections from the anterior tibial muscle 72 hours after ischaemia. Neutrophils were counted in the same sections. The treatment group received 1 mg carvedilol/kg body weight before ischaemia and 1 mg/kg immediately before removal of the tourniquets. The areas under the curves representing the plot of perfusion index relative to time were larger for the rats treated with carvedilol: 9.5 compared with 3.0 arbitrary units (p = 0.0003). Treatment did not change the laser Doppler flowmetry values for the right hindlimbs. The histomorphometric areas of necrosis in cross sections from the muscles were reduced from 88% (38‐96%) in the control animals to 41% (7‐85%) in those treated with carvedilol (p = 0.01), and the area of no‐reflow was reduced from 20% (2‐52%) to 0% (0‐7%) (p = 0.006). The number of neutrophils did not differ between groups. The study supports the hypothesis that carvedilol improves early reperfusion and protects skeletal muscle subjected to 3 hours and 15 minutes of ischaemia.
Interleukin‐4 inhibits granulocyte‐macrophage colony‐stimulating factor, interleukin‐6, and tumor necrosis factor‐alpha expression by human monocytes in response to polymethylmethacrylate particle challenge in vitro
Authors: Trindade Michael C. D. , Nakashima Yasuharu , Lind Martin , Sun Doo‐Hoon , Goodman Stuart B. , Maloney William J. , Schurman David J. , Lane Smith R.
Published: February 2005

The outcome of total joint arthroplasty is determined by biological events at the bone‐implant interface. Macrophages phagocytose implant or wear debris at the interface and release proinflammatory mediators such as interleukins 1 and 6, tumor necrosis factor‐alpha, and prostaglandin E2. These mediators are thought to contribute to the resorption of periprosthetic bone. Previous studies of tissues harvested from the bone‐implant interface of failed orthopaedic implants demonstrated a possible role for two other cytokines, granulocyte‐macrophage colony‐stimulating factor and interleukin‐4. The present study examined the effects of in vitro challenge with polymethylmethacrylate particles on the expression of granulocyte‐macrophage colony‐stimulating factor by primary human monocytes/macrophages and the role of interleukin‐4 in regulating this expression. The polymethylmethacrylate particles caused a dose‐dependent release of granulocyte‐macrophage colony‐stimulating factor at 48 hours. This release was accompanied by increased expression of interleukins 6 and 1beta and tumor necrosis factor‐alpha. Release of the lysosomal enzyme hexosaminidase also increased in response to the particles. Interleukin‐4 inhibited the expression of granulocyte‐macrophage colony‐stimulating factor, interleukin‐6, and tumor necrosis factor‐alpha at 48 hours in a dose‐dependent manner. The data presented in this study confirm the hypothesis that interleukin‐4 downregulates particle‐induced activation of macrophages, as demonstrated by the decreased release of proinflammatory mediators.
Reduced anterior tibial translation associated with adaptive changes in the anterior cruciate ligament‐deficient joint: Goat model
Authors: Jackson Douglas W. , Schreck Paul , Jacobson Scott , Simon Timothy M.
Published: February 2005

Adaptive changes in the menisci and adjacent posterior capsule were documented within anterior cruciate ligament‐deficient knee (stifle) joints in the goat model. These physical changes in the menisci and capsule developed over time and were associated with reduction in the initial (time zero) abnormal anterior tibial translation following transection of the anterior cruciate ligament. At 50 N of applied force, the normal goat knee joint has a total anterior‐posterior translation of 0.6 ± 0.1 mm (± SEM) at 45° of flexion and 0.3 ± 0.1 mm at 90°. The translation immediately after transection (time zero) with 50 N of force was 8.2 ± 0.5 mm at 45° and 4.9 ± 0.9 mm at 90°. Within 8 months after transection and at 50 N of force, the treated knees had reduced translation values of 5.3 ± 0.6 mm at 45° of flexion and 2.9 ± 0.5 mm at 90°, or 35 (p < 0.001) and 40% reductions, respectively, compared with the values at time zero. Magnetic resonance images of the ligament‐deficient stifle joints, as well as gross measurements and image analysis after dissection, consistently demonstrated increases in cross‐sectional area and volume of the menisci compared with the contralateral controls. These secondary changes were most pronounced in the posterior portion of the medial menisci, and histologic evaluation demonstrated hypercellularity with the accumulation of poorly organized collagen, reduced safranin O staining (proteoglycan matrix synthesis), a thickened capsule and capsule attachment, and increased vascularity at the meniscal capsule interface.
Hamstrings cocontraction reduces internal rotation, anterior translation, and anterior cruciate ligament load in weight‐bearing flexion
Authors: MacWilliams B. A. , Wilson D. R. , Desjardins J. D. , Romero J. , Chao E. Y. S.
Published: February 2005

Strengthening of the hamstrings is often recommended following injury and reconstruction of the anterior cruciate ligament. It has been suggested that hamstrings activity stabilizes the knee and reduces anterior cruciate ligament load during weight‐bearing flexion; however, the effects of hamstrings cocontraction on the kinematics and mechanics of the normal knee have not been assessed at physiological load levels. The aim of this study was to determine whether the addition of hamstrings force affects knee rotations, translations, and joint and quadriceps force during flexion with loads at physiological levels applied to the muscles and joints. Eight cadaveric knee specimens were tested with a servohydraulic mechanism capable of applying controlled dynamic loads to simulate quadriceps and hamstrings muscle forces throughout a physiological range of motion. A constant vertical load of physiologic magnitude was applied to the hip, and quadriceps force was varied to maintain equilibrium throughout flexion. Two conditions were tested: no hamstrings force and a constant hamstrings force equivalent to the vertical load. Hamstrings fore significantly reduced internal rotation (p < 0.0001) and anterior translation (p < 0.0001), increased quadriceps force (p < 0.0001) and normal resultant force on the tibia (p < 0.0001), and reversed the direction of the shear force on the tibia (p < 0.0001). These results suggest that hamstrings strengthening following anterior cruciate ligament injury may benefit anterior cruciate ligament‐deficient and reconstructed knees by reducing the load in the ligament; however, they also imply that this comes at the expense of efficiency and higher patellofemoral and joint forces.
Down‐regulation of chondrocyte aggrecan and type‐II Collagen gene expression correlates with increases in static compression magnitude and duration
Authors: Ragan Paula M. , Badger Alison M. , Cook Michael , Chin Vicki I. , Gowen Maxine , Grodzinsky Alan J. , Lark Michael W.
Published: February 2005

The goal of this study was to examine the simultaneous effects of mechanical compression of chondrocytes on mRNA expression and macromolecular synthesis of aggrrecan and type‐II collagen. Bovine cartilage explants were exposed to different magnitudes and durations of applied mechanical compression, and levels of aggrecan and type‐IIa collagen mRNA normalized to glyceraldehyde‐3‐phosphate dehydrogenase were measured and quantified by Northern blot analysis. Synthesis of aggrecan and type‐II collagen protein was measured by radiolabel incorporation of [35S]sulfate and [3H]proline into macromolecules. The results showed a dose‐dependent decrease in mRNA levels for aggrecan and type‐II collagen, with increasing compression relative to physiological cut thickness applied for 24 hours. Radiolabel incorporation into glycosaminoglycans and collagen also decreased with increasing compression in a dose‐related manner similar to the changes seen in mRNA expression. The modulation of aggrecan and type‐II collagen mRNA and protein synthesis were dependent on the duration of the compression. Aggrecan and type‐II collagen mRNA expression increased during the initial 0.5 hours of static compression; however, 4‐24 hours after compression was applied total mRNA levels had significantly decreased. The synthesis of aggrecan and collagen protein decreased more rapidly than did mRNA levels after the application of a step compression. Together, these results suggest that mechanical compression rapidly alters chondrocyte aggrecan and type‐II collagen gene expression on application of load. However, our results indicate that the observed decreases in biosynthesis may not be related solely to changes in mRNA expression. The mechanisms by which mechanical forces affect different segments of the biosynthetic pathways remain to be determined.
Cytoindentation for obtaining cell biomechanical properties
Authors: Shin Daehwan , Athanasiou Kyriacos
Published: February 2005

A novel biomechanical testing methodology was developed to obtain the intrinsic material properties of an individual cell attached to a rigid substrate. With use of a newly designed cell‐indentation apparatus (cytoindenter), displacement‐controlled indentation tests were conducted on the surface of individual MG63 cells and the corresponding surface reaction force of each cell was measured. The cells were modeled with a linear elasticity solution of half‐space indentation and the linear biphasic theory on the assumption that the viscoelastic behavior of each cell was due to the interaction between the solid cytoskeletal matrix and the cytoplasmic fluid. To obtain the intrinsic material properties (aggregate modulus, Poisson's ratio, and permeability), the data for experimental surface reaction force and deformation were curve‐fitted with use of solutions predicted with a linear biphasic finite element code in conjunction with optimization routines. The MG63 osteoblast‐like cells had a compressive aggregate modulus of 2.05 ± 0.89 kPa, which is two to three orders of magnitude smaller than that of articular cartilage, six to seven orders smaller than that of compact bone, and quite similar to that of leukocytes. The peremeability was 1.18 ± 0.65 (×10‐10) m4/N‐s, which is four to six orders of magnitude larger than that of cartilage. The Poisson's ratio was 0.37 ± 0.03. The intrinsic material properties of the individual cell in this study can be useful in precisely quantifying mechanical stimuli acting on cells. This information is also needed for theories attempting to establish mechanotransductional relationships.
Inhibition of endochondral ossification during fracture repair in experimental hypothyroid rats
Authors: Urabe Ken , Hotokebuchi Takao , Oles Karl J. , Bronk James T. , Jingushi Seiya , Iwamoto Yukihide , Bolander Mark E.
Published: February 2005

Using a rat fracture model, we investigated the effects of a decrease in serum levels of thyroid hormone on the fracture‐repair process. Rats were divided into the following groups: (a) controls, (b) those treated with methimazole for the duration of the experiment, and (c) those treated with methimazole and L‐thyroxine, receiving both for the same duration. Three weeks after the initiation of pharmacologic treatment, closed femoral fractures were produced. The formation of cartilage tissue in the fracture callus in all rats was not obviously different on day 7 after fracture. In the rats treated with methimazole, differentiation from proliferating to hypertrophic chondrocytes in the fracture callus was less advanced and vascular invasion was clearly inhibited on day 12. Gene expression of alkaline phosphatase and osteocalcin in the callus was significantly lower in these rats than in the controls on days 10, 12, and 14. The mechanical properties of the fracture callus were also significantly weaker in these animals than in the controls on day 21, resulting in impaired fracture repair. These results demonstrate that hypothyroidism inhibits endochondral ossification, resulting in an impaired fracture‐repair process. L‐thyroxine replacement in the rats treated with methimazole caused the impaired repair process to revert to normal. These results indicate that thyroid hormone is one of the critical systemic factors for fracture repair.
Effect of age and sampling site on the chondro‐osteogenic potential of rabbit marrow‐derived mesenchymal progenitor cells
Authors: Huibregtse Barbara A. , Johnstone Brian , Goldberg Victor M. , Caplan Arnold I.
Published: February 2005

Four sequential bone‐marrow aspirations from the ipsilateral tibia and iliac crest of New Zealand White rabbits, aged 4 months or 1, 2, or 3 years, were assayed in vitro and in vivo for their chondroosteogenic potential. Nonhematopoietic cells from the samples of bone marrow were isolated and expanded in culture: their colony‐forming efficiency was determined, and second‐passage marrow‐derived cells, referred to as mesenchymal progenitor cells, were loaded into porous calcium‐phosphate ceramic cubes as carrier vehicles for an in vivo cartilage and bone‐formation assay. The cubes were placed subcutaneously in nude BALB/C mice for 3 and 6 weeks. On histological examination, the cubes were scored for the presence of bone and cartilage in their pores, and average values for age groups and location were compared. At aspiration, the samples from the iliac crest exhibited an overall reduction in cell concentration with increasing age, and at the first harvest time, they showed a decrease in colony‐forming efficiency and cube score with increasing age. This study demonstrated that repeated bone‐marrow aspirations may be performed and may have an enhancing effect on the osteochondral progenitor cells of older animals.
Changes in bone mineral density at the proximal tibia after total knee arthroplasty: A 2‐year follow‐up of 28 knees using dual energy x‐ray absorptiometry
Authors: Li Ming G. , Nilsson Kjell G.
Published: February 2005

The change in bone mineral density at the proximal tibia during 2 years after total knee arthroplasty was studied in 28 knees (28 patients: 10 men and 18 women; median age: 71 years) with dual energy x‐ray absorptiometry. Bone mineral density was measured at the proximal tibia at nine regions of interest below the tibial component within 1 week after the operation (baseline); measurements were repeated at 3, 6, 12, and 24 months. All but one knee was malaligned before the operation, and all but three were corrected to within the normal range of alignment after it. The mean bone mineral density of all nine regions of interest at the proximal tibia temporarily decreased by 13% (p = 0.001) during the initial 3 months, probably due to a general metabolic reaction of the skeleton to the operative trauma combined with the effect of the postoperative immobilization, and then the initial level was regained for as long as 2 years. The overall changes in mean bone mineral density to 2 years were insignificant (p > 0.05); however, a great variation (43.9% decrease to 98.0% increase) was observed on an individual basis. This change over time was significantly associated (R2 = 0.36, p = 0.002) with the level of the baseline bone mineral density, which in turn was partly related (R2 = 0.24, p = 0.009) to the amount of malalignment of the knee before the operation. Knees with high baseline levels (n = 14: 11 with varus and three with valgus alignment) displayed a decrease of 10.0 ± 14.0% (mean ± SD, p > 0.05) for as long as 2 years, whereas those with low baseline levels (n = 14: seven with varus and six with valgus alignment and one neutrally alignment and one neutrally aligned) had an increase of 19.1 ± 38.2% (p = 0.038). In both groups, the mean bone mineral density converged to a level of 0.75–0.95 g/cm2 at 2 years.
Controlling the motion of total knee replacements using intercondylar guide surfaces
Authors: Walker Peter S. , Sathasivam Shivani
Published: February 2005

Total knee replacements using intercondylar cams, such as posterior stabilized types, have been in use for many years. In a previous study, software was written to analyze an alternative shape of the intercondylar cams. The goal of the current study was to investigate in a more general way the potential of intercondylar cams, or guide surfaces, for reproducing the anterior‐posterior motion of the natural knee throughout the flexion range. Typical sagittal outlines for the femoral and tibial bearing surfaces were defined, and a parametrized shape for the femoral guide surface was defined to produce a wide range of shapes. Software was written in which the femoral component was flexed in increments, with the posterior translation defined as a function of the flexion angle. The shape of the tibial guide surface was derived from the locus of the femoral guide surface at its multiple flexion positions. By iterating methodically through possible shapes of femoral guide surfaces, several types of total knee replacement components in common use today were identified, as well as other configurations of potential interest. For quantification of a given design, the software calculated the anterior and posterior laxity at each flexion angle. Laxity was defined as the motion before the femoral guide surface impacted the tibial guide surface or until the contact point of the bearing surfaces reached a specified slope. Convex femoral and concave saddle‐shaped tibial guide surfaces produced small laxities in both directions over most of the flexion range. A saddle design with small laxities in the first half of flexion, combined with a posterior stabilized feature, was an interesting combination. Potential improvements to the currently used designs were shown in this study and new shapes of intercondylar guide surfaces were derived that could be considered for application.
Hamstrings and iliotibial band forces affect knee kinematics and contact pattern
Authors: Kwak S. D. , Ahmad C. S. , Gardner T. R. , Grelsamer R. P. , Henry J. H. , Blankevoort L. , Ateshian G. A. , Mow V. C.
Published: February 2005

Many clinical studies have emphasized the role of the hamstrings and the iliotibial band on knee mechanics, although few biomechanical studies have investigated it. This study therefore examined two hypotheses: (a) with loading of the hamstrings, the tibia translates posteriorly and rotates externally and the tibial contact pattern shifts anteriorly; furthermore, the changes in tibial kinematics alter patellar kinematics and contact; and (b) loading the iliotibial band alters the kinematics and contact pattern of the tibiofemoral joint similarly to loading the hamstrings, and loading the iliotibial band laterally translates the patella and its contact location. Five cadaveric knee specimens were tested with a specially designed knee‐joint testing machine in an open‐chain configuration. At various flexion angles, the knees were tested always with a quadriceps force but with and without a hamstrings force and with and without an iliotibial band force. The results support the first hypothesis. Hence, the hamstrings may be important anterior and rotational stabilizers of the tibia, a role similar to that of the anterior cruciate ligament. The results also support the second hypothesis, although the iliotibial band force had a smaller effect on the tibia than did the hamstrings force. Both forces also changed patellar kinematics and contact, demonstrating that these structures should also be considered during the clinical management of patellar disorders.