bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of donor cell and matrix survival in fresh articular cartilage allografts in a goat model
Authors: Jackson Douglas W. , Halbrecht Jeffery , Proctor Christopher , van Sickle David , Simon Timothy M.
Published: February 2005

The long‐term survival of allografts of articular cartilage has been proposed to be dependent on the survival of the cells that maintain the unique structural and material properties of the allograft. In this study, we assessed cell survival in 24 fresh articular cartilage allografts of the medial plateau in a Spanish‐goat model. A DNA‐probe technique was used to distinguish clearly between DNA from donor (allograft) and host cells. The intraarticular survival of viable allograft chondrocytes in the transplanted articular cartilage started to diminish as early as 3 weeks after transplantation; however, there was considerable variation in the amount of donor cell DNA detected in the allografts at 6 and 12 months following transplantation. This contrasts with our experience with fresh allografts of ligament, tendon, and meniscus, in which no donor DNA was detected 4 weeks after transplantation. DNA from host cells was present in all articular cartilage allografts, as evidenced by detectable unique host DNA patterns. Histological and histochemical assays showed that none of the transplants demonstrated normal structure and composition at 1 year after transplantation. The grafts in which large quantities of donor DNA were present appeared grossly superior to those with no or reduced remaining demonstrable donor DNA.
Effect of capacitive coupled electrical stimulation on regenerate bone
Authors: Pepper John R. , Herbert Morley A. , Anderson J. R. , Bobechko Walter P.
Published: February 2005

An in vivo study was carried out to determine if capacitive coupled electrical stimulation increased the rate of recovery of strength of regenerate bone produced as a result of lengthening by the Ilizarov technique. Thirty‐four adult male beagles underwent a right tibial mid‐diaphyseal corticotomy, followed by a 5‐day delay, and then 21 days of lengthening (1 mm/day). At the start of the post‐distraction period (day 27), stimulation (3–6.3 V peak to peak, 5–10 mA root‐mean‐square at 60 kHz) was applied for 28 days to one group. The nonstimulated group (n = 17) underwent a 28‐day period with no stimulation. From each group, four tibiae were prepared for histology; both ends of the remaining bones were embedded in polymethylmethacrylate and tested in torsion (internal rotation at 4.7°/sec) until failure. Statistically significant changes included a 37% lower maximum torque capacity and a 40% decrease in strain energy to failure in the stimulated group compared with the nonstimulated group. The findings are supported by measured trends to a lower modulus of rigidity (37% decrease) and a smaller percentage of active osteoid perimeter (20% decrease) for the stimulated group. The experimental data suggest that when this dose of capacitive coupled electrical stimulation is applied to the regenerating bone created during distraction osteogenesis, it delays the recovery of bone strength compared with an untreated control.
Basic fibroblast growth factor enhances bone‐graft incorporation: Dose and time dependence in rats
Authors: Wang Jian‐Sheng , Aspenberg Per
Published: February 2005

In a previous study, we found that basic fibroblast growth factor could stimulate bone‐graft incorporation. In the present study, the effects of different doses and implantation times were further studied, using the bone conduction chamber, in rats. Inside the chamber, the graft is isolated from the surrounding tissues except at one end, where small openings embedded in host bone allow ingrowth of tissue. The distance that new tissues had reached from the openings into the graft was measured on histological slides. Bone grafts were obtained from the proximal tibiae of donor rats, frozen at −70°C, and lipid‐extracted. Before implantation, they were soaked overnight in a hyaluronate gel with or without basic fibroblast growth factor and then were fitted into the chambers, which were implanted in the proximal tibiae of recipient rats. In a doseresponse experiment, grafts containing 0.3, 8, 40, 200, or 1,000 ng of basic fibroblast growth factor were compared with grafts treated with carrier gel only, after an implantation time of 6 weeks. Fibrous tissue always penetrated the grafts further than the ingrown bone; the distance that it reached from the ingrowth openings (total ingrowth distance) was increased by all of the doses except 0.3 ng per implant. The distance of bone ingrowth was increased by 8, 40, and 200 ng. The increased total ingrowth with 1,000 ng was due to an increased amount of fibrous tissue ahead of the bone, whereas with the lower doses the increase was due to more bone. Thus, the dose had an effect on the type of ingrown tissue found in the graft. In a time‐effect study, grafts treated with 40 ng of basic fibroblast growth factor had a higher uptake of [99mTc]MDP at 2 and 4 weeks and an increased bone ingrowth distance at 10 weeks. The radioactivity from [125I]basic fibroblast growth factor declined with a half‐life of 17 hours. The results suggest that basic fibroblast growth factor may be beneficial for the incorporation of contained bone grafts; studies using more clinically relevant models are required.
Differential effects of insulin‐like growth factor‐I on matrix and DNA synthesis in various regions and types of rabbit tendons
Authors: Abrahamsson Sven‐Olof , Lohmander Stefan
Published: February 2005

Tendon healing and integration of tendon grafts may be site or donor specific. To determine if differences exist in sensitivity to growth factors that have the potential to influence tendon repair, we compared the effects of recombinant human insulin‐like growth factor‐I on various types of tendon segments. The dose response effects on proteoglycan, collagen, noncollagen protein, and DNA synthesis were investigated in short‐term explant cultures of intrasynovial intermediate and proximal segments of deep flexor tendons, extrasynovial segments of deep flexor tendons, and Achilles tendons of rabbits. The four different types of tendon segments cultured in media without recombinant human insulin‐like growth factor‐I synthesized similar amounts of each of the matrix components. Intrasynovial proximal segments synthesized 15 times less DNA than other tendon segments. Recombinant human insulin‐like growth factor‐I stimulated matrix and DNA synthesis of all tendon segments in a dose‐dependent manner in intervals from 10 to 1,000 ng/ml. The potency (LogED50) of the stimulation did not differ between the segments. The estimated maximal stimulation (Emax) of proteoglycan synthesis by recombinant human insulin‐like growth factor‐I was higher, and of collagen and noncollagen protein synthesis was lower, in intrasynovial proximal segments as compared with that of the other types of segments. In contrast, the estimated maximal stimulation of DNA synthesis by recombinant human insulin‐like growth factor‐I was 6‐fold higher than controls in all types of tendons. These findings demonstrate differences in mitotic capacity between anatomical regions of tendons during culture without recombinant human insulin‐like growth factor‐I and in matrix synthesis after stimulation with it.
Distribution of cellular repopulation and collagen synthesis in a canine anterior cruciate ligament autograft
Authors: Spindler Kurt P. , Andrish Jack T. , Miller Raymond R. , Tsujimoto Kazuo , Diz Debra I.
Published: February 2005

Whether the central core of an anterior cruciate ligament autograft reconstruction is nutritionally compromised at a time when revascularization is known to be complete has not been determined by methods that detect matrix synthesis. In a canine model of anterior cruciate ligament reconstruction with patellar tendon autograft, the adequacy of the supply of metabolites for cellular matrix synthesis was determined by autoradiographic analysis. Total collagen synthesis and cellularity were also quantified. Total collagen synthesis was found to be significantly elevated (p = 0.014 by analysis of variance) in the ligament reconstructions as compared with normal anterior cruciate ligaments or patellar tendons, but cellularity was not (p = 0.13 by analysis of variance). Autoradiography demonstrated even distribution of [3H]proline incorporation throughout the graft and normal tissue. When revascularization was complete, there was an adequate supply of metabolites for cellular synthesis of protein macromolecules within all regions of the ligament reconstruction. At 3 months after reconstruction, the grafts were found to be actively remodeling their collagen matrix. Since the long‐term function of an anterior cruciate ligament autograft is dependent on viable fibroblasts to maintain the collagen matrix, the canine anterior cruciate ligament reconstruction contains living cells that are able to remodel the matrix under appropriate conditions.
Swelling and fibronectin accumulation in articular cartilage explants after cyclical impact
Authors: Farquhar T. , Xia Y. , Mann K. , Bertram J. , Burton‐Wurster N. , Jelinski L. , Lust G.
Published: February 2005

The objective of this study was to determine if repeated impact could damage living cartilage and lead to osteoarthritis‐like changes in its biology. Canine cartilage explants were subjected to impacts of as much as 50 MPa once every 5 seconds for 30 minutes. On each impact cycle, the loading rate was 100 MPa/sec to the assigned peak stress, which was held for 1 second. After impact testing, the cartilage was kept in defined culture for as long as 10 days. Radiosulfate incorporation in the region that received direct impact varied with load 0–4 hours after impact, but it did not vary with load at 20–24 hours after impact. Even so, most explants were visibly damaged by 20 or 50 MPa, and there was subtle evidence of damage from impacts of 5 or 10 MPa. For example, ion‐induced swelling in 0.01MNaCl was increased, suggesting that the physical integrity of the matrix was reduced relative to controls. Self‐diffusion of water, measured by proton magnetic resonance imaging, was also increased in the deeper zones of the explant, consistent with changes in structure at the molecular level. Ten days after impact, the water content and the fibronectin content of the loaded region of the explant were both increased. In combination, these osteoarthritis‐like changes suggested that the physical strength of normal cartilage limits its ability to withstand cyclical impact.
Influence of biomaterial surface texture on bone ingrowth in the rabbit femur
Authors: Friedman Richard J. , An Yuehuei H. , Ming Jing , Draughn Robert A. , Bauer Thomas W.
Published: February 2005

The purpose of this study was to examine both the histologic and the mechanical characteristics of bone apposition to an experimental surface, arc‐deposited titanium, in a rabbit model and to compare them with those of four previously studied surfaces: one layer of cobalt‐chromium beads, three layers of cobalt‐chromium beads, plasma‐sprayed cobalt‐chromium, and uncoated titanium alloy. Bilateral cylindrical implants were press‐fit into the lateral femoral condyles of 70 adult New Zealand White rabbits, which were allowed unrestricted activity and then killed at 6 or 12 weeks. The distal femora were harvested, radiographed, and prepared for either mechanical or histologic evaluation. All of the implants with coated surfaces had significantly greater shear strength than the implants of grit‐blasted titanium alloy after both 6 and 12 weeks. After 6 weeks, maximum bone apposition occurred in the beaded surfaces. After 12 weeks, the shear strengths and bone apposition of implants of arc‐deposited titanium and of one and three layers of cobalt‐chromium beads were significantly greater than those of implants of plasma‐sprayed cobalt‐chromium and grit‐blasted titanium alloy. The histologic studies correlated with the mechanical results. After 12 weeks, the bone apposition and mechanical stability of arc‐deposited titanium were similar to those of a single layer of beads. There appeared to be no advantage to multiple layers of beads, and the plasma‐sprayed cobalt‐chromium and gritblasted titanium surfaces showed lower shear strength and bone apposition than the other groups.
Bone formation and bone resorption in failed total joint arthroplasties: Histomorphometric analysis with histochemical and immunohistochemical technique
Authors: Kadoya Y. , Revell P. A. , Al‐Saffar N. , Kobayashi A. , Scott G. , Freeman M. A. R.
Published: February 2005

To elucidate the reactions of bone around aseptically loosened total joint arthroplasties, 24 interface tissues with adjacent bone were obtained in 17 revision operations (11 hips and six knees). The morphology of the bone surface next to the interface membrane was investigated with histochemical and immunohistochemical techniques and then histomorphometrically analysed. One‐third of the total bone surface, 32.69 ± 5.16% (mean ± SE) (n = 24), showed positive alkaline phosphatase activity. The bone surface in contact with the cells positive for CD11b (a macrophage marker) amounted to 19.33 ± 5.16% (n = 24). The proportion of the osteoclastic bone resorption estimated by vitronectin receptor expression was 7.67 ± 1.82% (n = 21). Tissues retrieved from the sites where radiographic evidence of osteolysis was present (n = 12) had a significantly larger extent of the bone surface in contact with CD11b‐positive cells than did the tissues from areas without osteolysis (n = 12, p = 0.0067, Mann‐Whitney U test), whereas no significant difference was observed in the extent of osteoclastic bone resorption. These data demonstrate that active bone formation, regarded as a repair process, is the most common feature even in revised cases. They also highlight the role played by macrophages, not as cells producing inflammatory mediators that could activate osteoclasts, but as cells primarily responsible for the bone loss in osteolytic lesions.
Curved beam model of the proximal femur for estimating stress using dual‐energy x‐ray absorptiometry derived structural geometry
Authors: Mourtada Firas A. , Beck Thomas J. , Hauser Diana L. , Ruff Christopher B. , Bao Gang
Published: February 2005

The investigation of individual differences in hip strength requires a method to measure structural geometry in vivo and a valid analytical approach to calculate mechanical stress. We developed a method for deriving structural geometry of the femur from the proximal shaft through the femoral neck, using data from dual energy x‐ray absorptiometry. The geometric properties are employed in a two‐dimensional curved beam model of the proximal femur to estimate stresses on the lateral and medial bone surfaces. Stresses calculated by this method are compared with those from the conventional flexure formula and with results produced from a cadaver femur with use of three‐dimensional finite element analysis of computed tomography data. Loading conditions simulating a one‐legged stance and a fall on the greater trochanter are employed. Stresses calculated by curved beam theory are in much better agreement with three‐dimensional finite element analysis than are those for which the conventional straight beam formula was used. In simulation of a fall on the greater trochanter, all three methods show peaks of stress at the femoral neck but only the curved beam and finite element analysis methods show an additional peak at the medial intertrochanteric margin. Both neck and trochanter regions correspond to common failure sites for hip fractures in the elderly. The curved beam treatment of hip structure derived from dual‐energy x‐ray absorptiometry provides an approach for the in vivo engineering analysis of hip structure that is not practical by other methods.
Type‐I collagen mutation compromises the post‐yield behavior of Mov13 long bone
Authors: Jepsen Karl J. , Goldstein Steven A. , Kuhn Janet L. , Schaffler Mitchell B. , Bonadio Jeffrey
Published: February 2005

Despite recent advances in our understanding of the molecular basis of skeletal fragility, little is known about how these molecular alterations lead to whole bone brittleness. In the current study, we investigated the relationship between a type‐I collagen mutation and post‐yield behavior of whole bone in Mov13 transgenic mice by considering tissue‐level organizational issues known to be important for normal bone fracture. Mechanical assays revealed that the post‐yield deflection of Mov13 femurs was reduced by 61% relative to littermate controls. Fractographic images revealed that lamellar interfaces, which were important for dissipating energy during the failure process of control femurs, were not effective in Mov13 mice. Further investigation revealed that a 22% reduction in bone collagen content, a 2‐fold increase in tissue porosity, and significant alterations in collagen organization interfered with normal energy dissipation mechanisms of Mov13 microstructure. Collectively, the results provided the first evidence that the reduced ductility associated with a type‐I collagen mutation was mediated by alterations in intermediate structures that normally contribute to the post‐yield behavior of cortical bone. The results suggest that, to better understand the pathogenesis of skeletal fragility, it is important to consider the effects of molecular alterations on higher‐level structures, particularly those structures that contribute to the failure mechanisms in normal bone.
Adenovirus‐mediated gene transfer into tendon and tendon sheath
Authors: Lou Jueren , Manske Paul R. , Aoki Mitsuhiro , Joyce Michael E.
Published: February 2005

In this study, we successfully transferred the Escherichia coli β‐galactosidase gene, LacZ, into the chicken tendon and tendon sheath by a recombinant adenovirus. The recombinant adenovirus Adv‐βgal that carried the E. coli LacZ gene was constructed by homologous recombination in 293 cells (human transformed embryonic kidney) between the expressing vector and the ClaI large fragment of adenovirus 5 genome. Each chicken received a 10 μl injection, containing 105 plaque‐forming units of recombinant virus Adv‐βgal, into the tendon sheath of the long toe. Samples of tendon and tendon sheath were harvested at 3, 30, and 75 days after the injection. The LacZ gene transfer was detected for its coding product β‐galactosidase by staining with X‐gal solution. The results showed that all tendon and tendon sheath samples from the three harvest times stained positive (blue). The tendon sheath samples were more extensively stained; staining of the tendon was limited to the epitenon layer. These data suggest that a functional exogenous gene can potentially be transferred into the tendon and tendon sheath by similar techniques; such techniques may be used to improve healing and reduce adhesion formation.
Age trends in remodeling of the femoral midshaft differ between the sexes
Authors: Feik S. A. , Thomas C. D. L. , Clement J. G.
Published: February 2005

Cross‐sectional area properties of the femoral midshaft from 203 individuals of known height and weight, 1–97 years of age, from a modern Australian population were quantified using automatic video image analysis. The aim of this study, taking height and weight into account, was to determine whether (a) age trends in remodeling differ between the sexes, (b) men are better able to compensate for bone loss with age, and (c) this protective mechanism is carried through into old age. Our findings indicated that during adulthood there are distinct gender differences in femoral remodeling. From around the third to the seventh decade, men showed a fairly uniform increase in subperiosteal area, polar moment of inertia, and medullary area. Women displayed two distinct phases during this period: relative stability until around the menopause and then a marked increase in all of the above variables. In old age, gender differences diminished, both sexes showing reduced periosteal apposition and increased endosteal resorption. The resultant decline in cortical area of approximately 4% in men and 15% in women from the third to the eighth decade was significant only in women. For a given height, men had larger, stiffer femoral shafts with a greater cortical width and area and maintained this advantage into old age. Diaphyseal bone was not immune from age‐related changes affecting other skeletal sites; however, due to compensatory remodeling, which was particularly evident in men, this was not reflected in increased fracture rates.
Local expression of human growth hormone in bone results in impaired mechanical integrity in the skeletal tissue of transgenic mice
Authors: Tseng Kuo‐Fung , Bonadio Jeffrey F. , Stewart Timothy A. , Baker Andrew R. , Goldstein Steven A.
Published: February 2005

The effect of local production of human growth hormone on murine cortical bone was investigated using a transgenic mouse model. Femora and humeri from human growth hormone transgenic mice and littermate control mice were obtained, and the geometrical, biomechanical, compositional, and histomorphometric properties of all specimens were determined. The goals were to investigate the effects of local expression of human growth hormone on skeletal integrity, including the functional geometry of long bone and its related structural and mechanical behavior, as well as tissue composition and integrity. As expected, local production of human growth hormone by osteoblasts indeed resulted in longer femora with significantly greater mid‐diaphyseal cross‐sectional geometry in the transgenic mice (16% increase in cross‐sectional area and 29% increase in bending moments of inertia). However, the significant increase in geometry was not associated with a proportional increase in bending stiffness and other structural properties, which suggested that the mechanical properties of the cortical bone tissue may have been inferior. Microspecimen bending tests verified this prediction, given that transgenic cortical bone tissue had significantly lower apparent elastic modulus and ultimate strength (52 and 68%, respectively, of control values). These defects in the whole bone structural and tissue mechanical properties of transgenic specimens were associated with a smaller fraction of ash, larger fractions of woven bone and cartilage islands, and greater porosity in the mid‐diaphyseal cortices. These results suggest that local production of human growth hormone by osteoblasts is indeed anabolic for bone, but at the expense of bone tissue integrity.
Endothelin induces vasoconstriction in the bone vasculature in vitro: An effect mediated by a single receptor population
Authors: Coessens B. C. , Miller V. M. , Wood M. B.
Published: February 2005

The aim of this study was to define the types of endothelin receptors present in the canine tibial vasculature. Endothelin receptor agonists and antagonists were used in two different models: isolated nutrient tibial arteries in organ bath and in vitro‐perfused canine tibial bones. In isolated nutrient tibial arteries, endothelin‐1 caused concentration‐dependent contractions of rings with and without endothelium. BQ‐123, a selective endothelin‐A antagonist, induced a significant rightward shift of endothelin‐1 concentration‐response curves. No contractions were observed with sarafotoxin S6c, a selective endothelin‐B agonist. The responses of endothelin‐1 were not affected by the presence of NG‐monomethyl‐L‐arginine acetate plus indomethacin or by removal of the endothelium. In perfused tibial bones, endothelin‐1 was more potent than endothelin‐3 in causing concentration‐dependent contractions. Neither endothelin‐1, endothelin‐3, nor sarafotoxin S6c caused relaxations. Neither the inhibition of nitric oxide nor the inhibition of prostaglandins significantly altered contractions to endothelin‐1. These concordant data indicate that endothelin is a vasoconstrictor in the bone vasculature, an effect that appears to be mediated only through endothelin‐A receptors.
Coloured microsphere assessment of blood flow to knee ligaments in adult rabbits: Effects of injury
Authors: Bray R. C. , Butterwick D. J. , Doschak M. R. , Tyberg J. V.
Published: February 2005

Coloured microspheres were used to determine standardized blood flow in an established model of medial collateral ligament injury in the adult rabbit knee. Resting blood flow in the ligament was ascertained to be on the order of 0.68 ± 0.08 ml/min/100 g (mean ± SEM) in normal rabbit knees, although errors in flow estimates of this magnitude may be quite high. In healing medial collateral ligament, however, flow had increased markedly 3 weeks after injury (21.45 ± 5.48 ml/min/100 g). Flows in sham‐operated control medial collateral ligaments were not significantly increased compared with those in control normal ligaments. Six weeks after injury, blood flow in the ligament remained elevated (16.90 ± 3.20 ml/min/100 g) and was similarly elevated in other neighbouring joint tissues (i.e., ipsilateral synovial fat pad). The increase in flow to ipsilateral noninjured articular tissues did not persist beyond 6 weeks, but flow in the healing medial collateral ligament scar tended to remain elevated after 17 weeks (4.20 ± 1.79 ml/min/100 g), although this did not achieve statistical significance. We conclude from these data that it is possible to measure the increase in blood flow in injured and healing articular tissues using the coloured microspheres technique and that ligament injury is a potent stimulus for increasing blood flow. Coloured microsphere measurements of blood flow to joint connective tissues may offer a valuable approach to future investigations of joint injury and arthritis.
Wrist joint motion simulator
Authors: Werner Frederick W. , Palmer Andrew K. , Somerset James H. , Tong Jason J. , Gillison Douglas B. , Fortino Maria D. , Short Walter H.
Published: February 2005

A computer controlled wrist joint motion simulator has been developed that actively moves forearms from cadavers through cyclic planar flexion‐extension motions, planar radial‐ulnar deviation motions, and combined motions such as circumduction. Hybrid position‐force feedback control algorithms are used to determine the wrist flexor and extensor tendon forces necessary to achieve the desired motions. The simulator was used in a series of 12 fresh cadaver forearms to produce both flexion‐extension and radial‐ulnar deviation motions and was found to cause repeatable, physiological movements. In these experiments, the extensor tendon forces were greater than those of the flexors, typically by a factor of two.
Relative effects of wound healing and mechanical stimulus on early bone response to porous‐coated implants
Authors: Hollister Scott J. , Guldberg Robert E. , Kuelske Cheryl L. , Caldwell Nancy J. , Richards Mark , Goldstein Steven A.
Published: February 2005

We hypothesized that early bone adaptation to well fixed porous‐coated implants is influenced more by wound healing than by mechanical loading. To test this hypothesis, two groups of dogs with identical, hydraulically controlled porous‐coated implants interference fit within distal femoral trabecular bone were used. One group had no load; the other had 35 N of load applied to the implants. At 5 weeks after surgery, the resulting adaptation of bone around the implants was quantified on a cellular basis by cytochemical analysis of type‐I procollagen synthesis and on a structural basis using three‐dimensional micro‐computed tomography imaging. The percentage of trabecular surfaces covered by osteoblasts expressing type‐I procollagen was significantly increased in bone surrounding the implant in both groups compared with contralateral control bone tissue. There was no difference between the groups with no load or 35 N of load. In addition, measures of trabecular bone structure did not differ significantly between the load and no‐load groups. Taken together, these results suggest that wound healing plays a much greater role in the early response of bone to well fixed porous‐coated implants than does mechanical stimulus.
Influence of bacterial strains on bone infection
Authors: Corder José , Munuera Luis , Folgueira María Dolores
Published: February 2005

Experiments were performed on 120 rabbits to compare the probability of infection after bone surgery without an implant, with polymethylmethacrylate, and with bone autografts. Staphylococcus aureus phage type 94/96. Isolated from a human osteomyelitis, was instilled into the intramedullar cavity after reaming of the femoral canal and before insertion of the implant. The different 50% infective doses were determined for each of the groups for comparative purposes. The bacterial concentrations required to produce infection in femora without an implant were two times less than those necessary in femora implanted with polymethylmethacrylate. The bone graft required bacterial concentrations nine times less than those necessary to infect femora containing polymethylmethacrylate and four times less than those required to infect femora without an implant. The results presented here confirm that the susceptibility to infection in orthopaedic surgery is not only material dependent but also bacteria dependent.
Influence of dosage and timing of application of platelet‐derived growth factor on early healing of the rat medial collateral ligament
Authors: Batten M. L. , Hansen J. C. , Dahners L. E.
Published: February 2005

In previous studies, platelet‐derived growth factor has demonstrated beneficial in vivo effects on wound healing. We report the results of two studies of platelet‐derived growth factor in the rat medial collateral ligament injury model. Experimental injury sites were implanted with platelet‐derived growth factor, whereas contralateral controls received only collagen. Twelve days postoperatively, the femur‐medial collateral ligament‐tibia complex was tested mechanically. Our first study found a marked drop in the effectiveness of platelet‐derived growth factor when it was administered more than 24 hours after injury. Dose‐response testing showed maximum increases in strength (90% ) with 5.0 μg of platelet‐derived growth factor, but the 1.0 μg group showed similar strength increases, indicating a probable plateau effect in the response. These results indicate that platelet‐derived growth factor has promise for healing ligaments but that it must be administered in appropriate doses soon after injury.
Cement viscosity affects the bone‐cement interface in total hip arthroplasty
Authors: Stone James J‐S. , Rand James A. , Chiu Eric K. , Grabowski John J. , An Kai‐Nan
Published: February 2005

Quantitative information regarding the interface strength and degree of cement penetration associated with cement viscosity during total hip arthroplasty is limited. The aim of the present study was to determine the effect of the viscosity of bone cement at the time of implantation on the mechanical integrity of total hip arthroplasty. Cement that was injected at an early, less viscous stage produced greater failure strength in a push‐out test than its more viscous counterpart.
Osteoblast adhesion to orthopaedic implant alloys: Effects of cell adhesion molecules and diamond‐like carbon coating
Authors: Kornu Roger , Smith R. Lane , Maloney William J. , Kelly Michael A.
Published: February 2005

In total joint arthroplasty, long‐term outcomes depend in part on the biocompatibility of implant alloys. This study analyzed effects of surface finish and diamond‐like carbon coating on osteoblast cell adhesion to polished titanium‐aluminum‐vanadium and polished or grit‐blasted cobalt‐chromium‐molybdenum alloys. Osteoblast binding was tested in the presence and absence of the cell adhesion proteins fibronectin, laminin, fibrinogen, and vitronectin and was quantified by measurement of DNA content. Although adherence occurred in serum‐free medium, maximal osteoblast binding required serum and was similar for titanium and cobalt alloys at 2 and 12 hours. With the grit‐blasted cobalt alloy, cell binding was reduced 48% (p < 0.05) by 24 hours. Coating the alloys with diamond‐like carbon did not alter osteoblast adhesion, whereas fibronectin pretreatment increased cell binding 2.6‐fold (p < 0.05). In contrast, fibrinogen, vitronectin, and laminin did not enhance cell adhesion. These results support the hypothesis that cell adhesion proteins can modify cell binding to orthopaedic alloys. Although osteoblast binding was not affected by the presence of diamond‐like carbon, this coating substance may influence other longer term processes, such as bone formation, and deserves further study.
Differential growth by growth plates as a function of multiple parameters of chondrocytic kinetics
Authors: Wilsman Norman J. , Leiferman Ellen M. , Fry Michael , Farnum Cornelia E. , Barreto C.
Published: February 2005

Differential elongation of growth plates is the process by which growth‐plate chondrocytes translate the same sequence of gene regulation into the appropriate timing pattern for a given rate of elongation. While some of the parameters associated with differential growth are known, the purpose of this study was to test the hypothesis that eight independent variables are involved. We tested this hypothesis by considering four different growth plates in 28‐day‐old Long‐Evans rats. Temporal parameters were provided by means of oxytetracycline and bromodeoxyuridine labeling techniques. Stereological parameters were measured with standard techniques. For all four growth plates, the calculated number of new chondrocytes produced per day approximated the number of chondrocytes lost per day at the chondro‐osseous junction. This suggests that the proposed equations and associated variables represent a comprehensive set of variables defining differential growth. In absolute numbers, the proximal tibial growth plate produced about four times as many chondrocytes per day as the proximal radial growth plate (16,400 compared with 3,700). In the proximal tibia, 9% of growth is contributed by cellular division; 32%, by matrix synthesis throughout the growth plate: and 59%, by chondrocytic enlargement during hypertrophy. In the more slowly elongating growth plates, the relative contribution to elongation from cellular enlargement decreases from 59 to 44%, with a relative increase in contribution from matrix synthesis ranging from 32% in the proximal tibia to 49% in the proximal radius. This study suggests that differential growth is best depicted as a complex interplay among cellular division, matrix synthesis, and cellular enlargement during hypertrophy. Differential growth is best explained by considering a set of eight independent variables, seven of which vary from growth plate to growth plate. Thus, this study confirms the importance of cellular hypertrophy during elongation and adds to our understanding of the importance of locally mediated regulatory systems controlling growth‐plate activity.
Osteocyte density and histomorphometric parameters in cancellous bone of the proximal femur in five mammalian species
Authors: Mullender M. G. , Huiskes R. , Versleyen H. , Buma P.
Published: February 2005

The species‐specific relationships between trabecular morphology and osteocyte density were investigated in the femoral heads of 30 adult animals of five mammalian species (rat, rabbit, Rhesus monkey, pig, and cow). Our hypothesis is that osteocytes are mechanosensory cells and are involved in the regulation of bone remodeling. According to the predictions from a simulation model, this hypothesis implies that the influencing distance of osteocytes, together with the magnitude of the mechanical loads, determines the thickness of trabeculae and that the number of osteocytes primarily affects the rate of bone remodeling. The number of osteocytes per bone volume ranged from 93,200 mm−3in rat to 31,900 mm−3in bovine cancellous bone. Osteocyte density was inversely related to the size of the species. Since basal metabolic output is related to body mass, we speculate that osteocyte density may be related to metabolic rates. Trabecular thickness was larger in the cow than in the other species, but the range of variation between species was relatively small. This agrees with the hypothesis that trabecular thickness is limited by the domain that can be regulated by an osteocyte and that this domain is of similar size regardless of the species. Only in the rat was trabecular thickness considerably smaller than in the other species. This is probably due to the presence of the cartilaginous growth plate in the femoral head of the rat. The relationships with species are different for osteocyte density than for morphometric parameters. Hence, our data support our hypothesis that osteocyte density is not directly associated with the macroscopic trabecular architecture.
Effects of medial and lateral displacement calcaneal osteotomies on tibiotalar joint contact stresses
Authors: Steffensmeier S. J. , Berbaum K. S. , Brown T. D.
Published: February 2005

Translational calcaneal osteotomies are used clinically to realign the mechanical axis of the lower limb. In this study, the effects of medial and lateral displacements of the posteroinferior fragment on tibiotalar joint contact mechanics were assessed using pressure‐sensitive film. Eight osteotomized fresh‐frozen cadaver specimens were loaded in each of three testing positions: neutral position (no shift), 1 cm of lateral displacement of the inferior fragment with respect to the superior fragment, and 1 cm of medial displacement of the inferior fragment. For an applied load of 1.330 N, two times body weight, a 1 cm lateral displacement shifted the center of pressure an average of 1.06 mm laterally, whereas a 1 cm medial displacement shifted the center of pressure an average of 1.58 mm medially. While global contact parameters (contact area, spatial mean contact stress, and peak local contact stress) were not appreciably altered by osteotomy, regional contact parameters changed in a reproducible and statistically significant manner. Among four nominally equal‐sized, parasagittally bounded cartilage zones, lateral displacements consistently unloaded the most medial zone and increased loading of the most lateral zone; medial calcaneal displacements had the converse effect. These cadaver results suggest that translational calcaneal osteotomies may be used clinically to partially offload focal areas of cartilage along the medial and lateral borders of the tibiotalar joint.
Effect of growth factors on matrix synthesis by ligament fibroblasts
Authors: Marui Takashi , Niyibizi Christopher , Georgescu Helga I. , Cao Min , Kavalkovich Karl W. , Levine Rebecca E. , Woo Savio L‐Y.
Published: February 2005

Although it has been reported that several growth factors modulate soft‐tissue healing, the specific effects of growth factors on protein synthesis during ligament healing have not been widely investigated. In this study, we examined the effects of basic and acidic fibroblast growth factors, transforming growth factor β1, and epidermal growth factor on collagen and noncollagenous protein synthesis by cultured fibroblasts from medial collateral ligament and anterior cruciate ligament in vitro. Uptake of tritiated proline was used to measure synthesis of collagen and noncollagenous protein, and sodium dodecyl sulfate‐polyacrylamide gel electrophoresis was used to analyze the type of collagens synthesized. Our data showed that transforming growth factor β1 increased both collagen and noncollagenous protein synthesis by medial collateral and anterior cruciate ligament fibroblasts on a dose‐dependent basis. Collagen synthesis by cultured fibroblasts from the medial collateral and anterior cruciate ligaments was increased by treatment with transforming growth factor β1 by as much as approximately 1.5 times that of untreated controls. Although the response to transforming growth factor β1 by anterior cruciate ligament fibroblasts was equal to that by medial collateral ligament fibroblasts, the amounts of matrix proteins synthesized by anterior cruciate ligament fibroblasts were approximately half of that by medial collateral ligament fibroblasts. The increase was mostly in type‐I collagen. Treatment of anterior cruciate ligament fibroblasts with epidermal growth factor increased collagen synthesis by approximately 25% but had little effect on medial collateral ligament fibroblasts. Neither basic nor acidic fibroblast growth factor increased either collagen or noncollagenous protein synthesis. These findings suggest that topical application of transforming growth factor β1, alone or in combination with epidermal growth factor, may have the potential to strengthen the ligament by increasing matrix synthesis during its remodeling and healing processes.
Osteoarthritis: Differential expression of matrix metalloproteinase‐9 mRNA in nonfibrillated and fibrillated cartilage
Authors: Tsuchiya K. , Maloney W. J. , Vu T. , Hoffman A. R. , Huie P. , Sibley R. , Schurman D. J. , Smith R. L.
Published: February 2005

Expression of matrix metalloproteinase‐9 mRNA in osteoarthritic and normal cartilage was analyzed using reverse transcription polymerase chain reaction and in situ hybridization. Fifty‐four osteoarthritic cartilage samples were obtained from 24 patients undergoing total knee arthroplasty. Sixteen normal cartilage samples were obtained from non‐osteoarthritic knees of four autopsy cases. With normal cartilage, reverse transcription‐polymerase chain reaction analysis for matrix metalloproteinase‐9 mRNA showed that chondrocytes exhibited only a trace signal. In analysis of osteoarthritic cartilage, chondrocytes of moderately and severely fibrillated cartilage exhibited a 73‐fold and 110‐fold increase in matrix metalloproteinase‐9 mRNA signal, respectively, relative to normal cartilage. Chondrocytes of nonfibrillated osteoarthritic cartilage exhibited a 6‐fold increase (p < 0.02) in matrix metalloproteinase‐9 mRNA signal relative to normal cartilage. Analysis of matrix metalloproteinase‐9 mRNA expression in fresh‐frozen sections of normal and osteoarthritic cartilage by in situ hybridization confirmed these results. This study showed that reverse transcriptionpolymerase chain reaction provides a sensitive index of mRNA levels in normal and osteoarthritic cartilage samples and suggests that increased expression of matrix metalloproteinase‐9 precedes fibrillation of cartilage in the development of osteoarthritis.
Systematic and random errors in compression testing of trabecular bone
Authors: Keaveny Tony M. , Pinilla Tania P. , Crawford R. Paul , Kopperdahl David L. , Lou Albert
Published: February 2005

We sought to quantify the systematic and random errors associated with‐artifacts in the platens compression test for trabecular bone. Our hypothesis was that while errors may depend on anatomic site, they do not depend on apparent density and therefore have substantial random components. Trabecular bone specimens were first tested nondestructively using newly developed accurate protocols and then were tested again using the platens compression test. Percentage differences in modulus between the techniques (bovine) proximal tibia [n = 18] and humerus [n = 17] and human lumbar spine, [n = 9] were in the range of 4‐86%. These differences did not depend on anatomic site (p = 0.21) and were only weakly dependent on apparent density and specimen aspect ratio (r2 < 0.10). The mean percentage difference in modulus was 32.6% representing the systematic component of the end‐artifact error. Neglecting the minor variations explained by density and specimen size (approximately 10%), an upper bound on the random error from end‐artifacts in this experiment was taken as the SD of the modulus difference (±18.2%). Based on a synthesis of data taken from this study and from the literature, we concluded that the systematic underestimation error in the platens compression test can be only approximated and is in the range of 20‐40%; the substantial random error (±12.5%) confounds correction, particularly when the sample size is small. These errors should be considered when interpreting results from the platens test, and more accurate testing techniques should be used when such errors are not acceptable.
Effects of different estrogen and progestin regimens on the mechanical properties of rat femur
Authors: Kasra M. , Vanin C. M. , MacLusky N. J. , Casper R. F. , Grynpas M. D.
Published: February 2005

The purpose of this study was to examine the effects of estrogen replacement, in concert with three different progestin regimens. On the mechanical properties of rat femoral cortical bone. Ninety‐two 11‐month‐old female Sprague‐Dawley rats were randomly divided into six groups and were treated for a duration of 6 months. Group‐1 rats were intact controls. group‐2 rats were ovariectomized controls, and groups 3‐6 were Ovariectomized and given continuous doses of estrogen with 5% estradiol 17B silicone‐rubber implants. Groups 4, 5, and 6 were also given different doses of progestin (norethindrone): group 4 received a continuous dose of 3 μg per animal per day, group 5 received a cyclic dose of 6 μ per animal per day for 14 days of a 28‐day cycle, and group 6 received an interrupted dose of 3 μ per animal day for 3 days of a 6‐day cycle. Femurs from each group were mechanically tested. Bending stiffness was measured by nondestructive three‐point bending tests and maximum torque capacity, by destructive torsion tests. Geometrical properties and apparent density of cortical bone were also measured. The Significant differences were: the increases in elastic modulus (measured from the three‐point bending stiffness) of group 5 (cyclic norethindrone) compared with those of group 2 (ovariectomized controls) and group 3 (estrogen only); the increases in the size represented by the moment of inertia, the moment of the area, and medial‐lateral width of group 2 compared with those of group 5; and the increases in apparent density and decreases in moment of inertia of group 6 (interrupted norethindrone) compared with those of group2. Cyclic or interrupted treatment of progestin along with continuous treatment of estrogen after ovariectomy likely improves material properties of cortical bone, increases its density, and reduces the size of the bone compared with ovariectomized rats.