bluuebunny/crossref_metadata_2025 huggingface dataset:
Microvessel endothelial cells and pericytes increase proliferation and repress osteoblast phenotypic markers in rat calvarial bone cell cultures
Authors: Jones A. R. , Clark C. C. , Brighton C. T.
Published: February 2005

To investigate the influence of microvessel cells on osteoblasts, we exposed osteoblast‐enriched cultures of rat calvarial cells to cultured endothelial cells and pericytes using feeder‐layer co‐cultures, co‐culture dish inserts, and conditioned media experiments. When co‐cultured with growth‐arrested feeder‐layers of endothelial cells or pericytes for 10 days, bone cell cultures showed an increase in cell number and reduction in alkaline phosphatase activity. The response of bone cells to endothelial cells was nearly twice their response to pericytes. A similar response was demonstrated by exposure to microvessel cells in co‐culture dish inserts and by exposure to media conditioned by microvessel cells. In long‐term cultures of bone cells, the levels of osteocalcin and the number of mineralized nodules both were reduced by exposure to media conditioned by the microvessel cells. Transient exposure to conditioned media from the microvessel cell cultures for 3 days, during the period from initial plating to cell confluence, produced nearly the same effect on the cultures of bone cells as did continuous exposure to these conditioned media. The influence of isolated microvessel cells on osteoblast‐enriched calvarial cells was found to be primarily mitogenic, mediated by soluble factors, independent of cell contact, and a cause of prolonged reduction in the expression of early and late markers of the osteoblast phenotype.
Changes in innervation of long bones after insertion of an implant: Immunocytochemical study in goats with antibodies to calcitonin gene‐related peptide and B‐50/GAP‐43
Authors: Buma P. , Elmans L. , Oestreicher A. B.
Published: February 2005

In this study, we describe the distribution of fibres that contain calcitonin gene‐related peptide in normal bones and in bones that are remodeling after insertion of an implant. With routine histology and antibodies to calcitonin gene‐related peptide, small neural and free‐running fibres staining positively for calcitonin gene‐related peptide were found in the periosteum, endosteum, and cortical bone of the tibia in the goat. In many cases, the free‐running fibres were associated with blood vessels that entered the bone through Volkmann's canals. The endosteal blood supply was destroyed as a result of insertion of the implant. The necrotic bone was no longer innervated, as shown by the lack of staining for the antibodies. At 6 weeks, a repair phase started with revascularization and remodeling of the necrotic endosteal bone. During this repair phase, there was increased innervation with fibres containing calcitonin gene‐related peptide in the remodeling cavities at the interface between living and necrotic bone. These fibres ended blindly, with many large varicosities, and could be demonstrated by immunostaining with monoclonal antibodies to B‐50/growth associated protein‐43, an antibody to outgrowing neuronal fibres. The correlative occurrence between extensive sprouting of fibres containing calcitonin gene‐related peptide and the remodeling of necrotic endosteal bone suggests that sensory fibres with calcitonin gene‐related peptide have a regulatory role in the control of angiogenesis or of bone remodeling associated with the insertion of an implant, or with both processes.
Thermal response and torque resistance of five cortical half‐pins under simulated insertion technique
Authors: Wikenheiser Mark A. , Markel Mark D. , Lewallen David G. , Chao Edmund Y. S.
Published: February 2005

A model was developed that can quantitate heat generation during placement of half‐pins in cortical bone. Five half‐pins were tested to assess differences in insertion torque, heat generation, and microdamage at the pin‐bone interface. Thin thermocouple probes were placed 0.5 mm from the track of the pin and within the pin to measure its temperature during insertion. Scanning electron microscopy was used to view the pin‐bone interface to assess the microdamage during placement. The design of the tip of the pin influenced insertion torque and heat generation. Higher heat generation was measured when a thermocouple was placed within the pin itself and less was measured when thermocouple probes were placed within bone samples 0.5 mm from the impending pin track. Furthermore, insertion torque and thermal responses were related, but there were no significant differences in microdamage to bone when different pins and drilling/tapping techniques were used. Due to the significant heat generation at the pin‐bone interface, proper cooling with saline irrigation should be applied during pin insertion regardless of the design of the pin. The microdamage observed at the surface of the pin track may have significant implications with regard to loosening of pins, but such effects must be studied with in vivo models.
Effect of bone cylinder length on distraction osteogenesis in the rabbit tibia
Authors: Windhager R. , Tsuboyama T. , Siegl Helga , Groszschmidt K. , Seidl G. , Schneider B. , Plenk H.
Published: February 2005

The viability and osteogenic potential of bone cylinders for bone transport was investigated in one tibia of 18 mature male New Zealand rabbits. The length of the bone cylinder was equal to or twice that of the diameter of the tibia. The cylinder was cut subperiosteally with an externally cooled oscillating saw from a lateral approach, after a specific unilateral external fixator had been applied. To simulate bone transport, one end of the cylinder was fixed to the distal bone stump by a cerclage wire and healing and revascularization was prevented by an interposed expanded polytetrafluoroethylene membrane. The periosteum was readapted and sutured, and distraction began 10 days postoperatively at 0.25 mm/12 hours for 22 days. New bone formation in the distraction gap was quantified by dual energy x‐ray absorptiometry and by computer‐assisted histomorphometry of polyfluorochrome‐labeled undecalcified bone sections and corresponding microradiographs. In half of the animals with each size cylinder, osseous bridging occurred, so the findings on distraction osteogenesis are reported only for the remaining nine animals. Generally, centripetal mineralization of the gap with two distinct zones of ripening bone structures and a central radiolucent fibrocartilaginous zone could be distinguished. Neither absorptiometry nor histomorphometry showed significant differences in the overall amount of this new bone formation for the bone cylinders of two different lengths. However, osteogenesis was significantly greater at the proximal end than at the cylinder. New bone was formed predominantly from endosteal sites in the smaller cylinders and from periosteal sites in the larger cylinders. Histologically, there was complete necrosis of both sizes of cylinders, followed by revitalization through newly formed vascular channels. This process started earlier and was more pronounced with the smaller bone cylinders. It is concluded from these experiments that even careful subperiosteal osteotomy with an oscillating saw leads to necrosis of both small and large bone cylinders. However, distraction osteogenesis still can be achieved and is mediated mainly by the revitalized endosteum in the smaller cylinders and by the periosteum, which apparently can be better preserved, in the larger cylinders. These results demonstrate the feasibility of even extremely small bone cylinders for distraction osteogenesis; the minimum length is determined only by the possibility of stable fixation.
Ilizarov callus distraction produces systemic bone cell mitogens
Authors: Holbein Oliver , Neidlinger‐Wilke Cornelia , Suger Gebhard , Kinzl Lothar , Claes Lutz
Published: February 2005

We tested the hypothesis that the application of strain during callus distraction induces systemic osteoblast stimulating factors that enhance osteoblast activity both locally and systemically. To study the systemic occurrence of strain‐induced osteoblast stimulating factor during callus distraction, we investigated the mitogenic capacity of sera from 12 patients who had undergone callus distraction on the osteoblastic cell line SaOS‐2 (part I). Serum samples from six patients who had undergone rigidly fixed high tibial osteotomy (i.e., without distraction) served as controls. The sera were assayed for platelet‐derived growth factor and transforming growth factor‐beta. In part II of the study, the in vitro effects of mechanical strain were investigated in a simplified model by cyclic stimulation of osteoblast cultures isolated from cortical bone explants from the same patients; a specially developed apparatus was used for cell‐stretching. Sera taken during the third to fourth week of callus distraction demonstrated a significant increase in proliferation of SaOS‐2 cells (p < 0.005). In contrast, sera from patients who had had an osteotomy failed to induce or decreased the mitogenic capacity of SaOS‐2 cells. The concentration of platelet‐derived growth factor increased significantly (p < 0.01) in sera from both the patients who had undergone callus distraction and the controls who had had osteotomy. However, the level of transforming growth factor‐beta was increased (p < 0.05) in the sera from the patients who had distraction (sera that stimulated proliferation of SaOS‐2 cells), but the level was not increased in the sera from patients who had osteotomy. Cyclic stretching of osteoblasts in vitro stimulated proliferation (p < 0.05) and increased the cellular production of transforming growth factor‐beta significantly (p < 0.05). These findings suggest that mechanically stimulated osteoblasts have the potential to increase proliferation and to produce additional mitogens in response to cyclic strain. This study supports the notion that mechanically stimulated tissue induces systemic factors that enhance osteoblast activity and thus influence the formation of callus. Isolation and characterization of these factors potentially could lead to serum assays to predict osteogenesis during callus distraction.
Comparison of allograft/endoprosthetic composites with a step‐cut or transverse osteotomy configuration
Authors: Markel Mark D. , Wood Suzanne A. , Bogdanske John J. , Rapoff Andrew J. , Kalscheur Vicki L. , Bouvy Bernard M. , Rock Michael G. , Chao Edmund Y. S. , Vanderby Ray
Published: February 2005

This study was designed to compare the biomechanical and functional characteristics of allograft/endoprosthetic composites of the proximal 25% of the femur repaired with either a transverse or a step‐cut osteotomy, using a canine model (10 dogs, five with each type of osteotomy). Serial radiography and weight‐bearing studies were performed monthly, and mechanical testing was done 6 months after surgery. The femora were tested in torsion and compared with the contralateral control (insertion of a femoral component but no osteotomy). At 6 months, the composites with a step‐cut osteotomy had 36% greater structural stiffness than the composites with a transverse osteotomy (p < 0.005) and 121% greater maximum torque at failure than the controls (p < 0.005), without greater structural stiffness. Evaluation of peak vertical ground reaction forces revealed significantly greater weight‐bearing on the experimental limb in dogs with a transverse osteotomy. The results of this relatively short‐term study were mixed. Despite the increased structural stiffness of the allograft/endoprosthetic composite with a step‐cut osteotomy, the dogs with this type of reconstruction had decreased weight‐bearing throughout the course of the study. The step‐cut osteotomy may augment the stability of the allograft/endoprosthetic composite, allowing faster healing (as demonstrated by the results of mechanical testing), but in some way, not understood, may cause pain in the reconstructed limb. Longer term studies are needed to answer these questions and to determine whether alteration of the traditional transverse osteotomy has any advantage.
Osteosarcoma oncogene expression detected by in situ hybridization
Authors: Wang Humin , Rodgers William H. , Chmell Michael J. , Svitek Chris , Schwartz Herbert S.
Published: February 2005

Fifteen archival human osteosarcoma specimens were examined by in situ hybridization for the expression of human and mouse transforming growth factor‐β (isoforms 1, 2, and 3), c‐fos, and metalloproteinase (stromelysin‐3 and matrilysin). Osteosarcoma subtypes were confirmed by review of patients' radiographs, histopathology, and age at diagnosis. The outcome and method of treatment were documented. The subtypes of osteosarcoma consisted of nine conventional osteosarcomas and two each of fibroblastic, telangiectatic, and post‐radiation osteosarcomas. Each specimen was histologically examined under light microscopy, and then adjacent paraffin sections were assayed with sense and anti‐sense RNA probes by in situ hybridization. The probes localized to the neoplastic cells, confirming the methodology of the technique. Human transforming growth factor‐β1 had the most uniform binding affinity to the osteosarcomas examined and was more specific in binding than mouse transforming growth factor‐β1. Specific mRNA encoding for the transforming growth factor‐βs, c‐fos, and metalloproteinases are detectable in patterns within osteosarcoma cells, and collectively, their expression parallels the different histopathologic subtypes. The less differentiated subtypes (telangiectatic and post‐radiation osteosarcomas) expressed the fewest molecular markers. Osteosarcoma is a heterogeneous tumor. Differential expression of matrilysin in osteosarcoma is the first reported detection of metalloproteinase activity in human skeletal sarcoma.
Incorporation of polylactide‐polyglycolide in a cortical defect: Neoangiogenesis and blood supply in a bone chamber
Authors: Winet H. , Hollinger J. O. , Stevanovic M.
Published: February 2005

Erodible polymers are an alternative to metals for fracture fixation (for example, in the malleolus) and for maxillofacial reconstruction. In this study, the vascular response to eroding polylactide‐polyglycolide copolymer threads was observed chronically in a bone chamber implant, with use of intravital microscopy. A bone chamber implant loaded with 100 μm thick polylactide‐polyglycolide threads was implanted into the right tibia in 15 mature female New Zealand White rabbits. Periodic intravital microscopic observations were performed from the third to the tenth or twelfth week after implantation. Vascularization, blood flow, and trabecular growth into the chambers from the medial cortex were recorded on videotape and analyzed using digital image processing. A statistically significant delay of neo‐osteogenesis in the presence of this copolymer was described in an earlier report. The present report describes the measures of neoangiogenesis and blood supply; there was a significant delay in neoangiogenesis. It is suggested that both delayed angiogenesis and osteogenesis were secondary consequences of the macrophage response to slowly eroding poly‐L‐lactide crystal nanoparticles and the influence of reduced nutrient exchange. The lesser effect on blood supply and vascular volume fraction was seen to be linked to the slowing down of angiogenesis, as the latter allowed vessels to mature, with a widening of their calibers. This homeostatic adjustment was interpreted as being only partially successful in restoring control levels of oxygen delivery, because resulting increases in vessel surface area did not reach control levels. Thus, in the presence of eroding polylactide‐polyglycolide, the oxygen supply and extravasation of other nutrients may be below normal during healing phases when the need is critical.
Hindlimb suspension diminishes femoral cross‐sectional growth in the rat
Authors: van der Meulen Marjolein C. H. , Morey‐Holton Emily R. , Carter Dennis R.
Published: February 2005

Growth, functional adaptation, and torsional strength were examined in the femora of 39‐day‐old male Sprague‐Dawley rats subjected to hindlimb suspension for 0, 1, 2, 3, or 4 weeks and were compared with measurements for age‐matched control animals. Our goal was to understand the effect of reduced loading on the normal age‐related changes in femoral properties during growth. The control animals exhibited growth‐related increases in all geometric and torsional properties of the femur. The mean body mass and femoral length of the hindlimb‐suspended rats were similar to those of the controls throughout the experiment. Over 4 weeks, the femoral cross‐sectional and torsional measurements from the hindlimb‐suspended rats demonstrated increases in comparison with the basal values (+33% cross‐sectional area, +64% polar moment of inertia, +67% ultimate torque, and +181% torsional rigidity), but the age‐matched controls showed significantly greater growth‐related increases (+71% cross‐sectional area, +136% polar moment of inertia, +127% ultimate torque, and +367% torsional rigidity). The differences in femoral structural strength between the hindlimb‐suspended animals and the age‐matched controls were attributable to differences in altered cross‐sectional geometry.
Cortical bone perfusion in plated fracutured sheep tibiae
Authors: Kregor Philip J. , Senft David , Parvin Dara , Campbell Colleen , Toomey Sean , Parker Colleen , Gillespy Thurman , Swiontkowski Marc F.
Published: February 2005

The limited contact dynamic compression plate and partial contact plate were designed to decrease contact with cortical bone in an attempt to decrease cortical ischemia, remodeling, and eventual porosis under the plate after use of standard dynamic compression plates. This study quantified cortical bone blood flow beneath the plate with these three different designs in a sheep tibia fracture model. In 18 skeletally immature sheep, the right tibia was fractured and then was internally fixed with an interfragmentary screw and a dynamic compression plate, limited contact dynamic compression plate, or partial contact plate. At 12 weeks, cortical bone perfusion was assessed with laser Doppler flowmetry in nine areas beneath the plate. The baseline (before fracture) cortical bone cell flux averaged 100 ± 60 mV. After fracture, this decreased to 60 ± 48 mV (p < 0.0003); immediately after plating, the perfusion averaged 29 ± 25 mV (p < 0.01). Cortical bone perfusion then increased to 106 ± 52, 165 ± 71, and 163 ± 71 mV at 2, 6, and 12 weeks after fracture (p < 0.001 for all when compared with values after plating). No significant differences in cortical perfusion were seen between the types of plate. Cortical porosity under the plate was assessed with digital density analysis of microradiographs of this region. No significant difference was seen between the types of plate in this analysis or in biomechanical and disulphine blue perfusion analysis. Thus, no significant advantage was seen for the new plate designs used in this model. This lack of advantage may be a result of the immature animals used in the study, the protocol for blood flow measurement, the invasive periosteal stripping employed to create the fracture, or all three. However, as advantages with the new plate designs have been seen in other studies, this area warrants further investigation.
Laxity characteristics of normal and pathological murine knee joints in vitro
Authors: van Osch Gerjo J. V. M. , Blankevoort Leendert , van der Kraan Peter M. , Janssen Bernard , Hekman Edsko , Huiskes Rik , van den Berg Wim B.
Published: February 2005

The aim of this study was to validate a device developed previously to measure laxity of murine knee joints and to investigate whether experimentally induced pathological conditions result in measurable laxity. The laxity characteristics of normal murine knee joints were derived from measurements of 25 left knees of normal mice. Reporducible, nonlinear s‐shaped load‐displacement curves were determined, and parameters of anterior‐posterior translation, varus‐valgus rotation, and compliance were calculated from the curves. No differences were found between the left and right knee joints of eight mice. The average displacement between 0.8 N of anterior force and 0.8 N of posterior force was 0.47 ± 0.10 mm. The endpoint compliances for anterior and posterior displacements were 0.16 ± 0.03 and 0.16 ± 0.04 mm/N, respectively. The average rotation between a 4 Nmm valgus moment and a 4 Nmm varus moment was 17.4 ± 3.3°. The endpoint compliances for varsus and valgus rotations were 1.1 ± 0.7 and 1.0 ± 0.3°/Nmm, respectively. Storage of the joints at −70°C had no effect on laxity. We also studied the parameters of laxity after pathology of the knee joint was induced. Zymosan‐induced or antigen‐induced arthritis did not increase laxity of the joint. In an osteoarthritis model induced by injection of collagenase, laxity was markedly increased. In conclusion, laxity in the knees of mice can be measured reproducibly, and changes in the characteristics of laxity due to pathological conditions can be quantified.
Role of muscles in lumbar spine stability in maximum extension efforts
Authors: Gardner‐Morse Mack , Stokes Ian A. F. , Laible Jeffrey P.
Published: February 2005

Many problems of the lumbar spine that cause pain are attributed to instability. The ligamentous spine (without muscles) is unstable at very low compressive loads. This study examined the hypothesis that instability of the lumbar spine is prevented under normal circumstances by the stiffness of spinal musculature, without active responses from the neuromuscular control system. The effect of muscle activity (force and stiffness) on the stability of the lumbar spine was analyzed for maximum voluntary extension efforts with different spinal postures in the sagittal plane. The analysis included realistic three‐dimensional representation of the muscular anatomy with muscles crossing several motion segments. The stiffness of motion segments was represented using in vitro measured properties. Under a range of conditions with maximum extension effort, active muscle stiffness was required to prevent the lumbar spine from buckling. The dimensionless value of the muscle stiffness parameter q as a function of activation and length had to be greater than a critical value in the range of 3.7–4.7 in order to stabilize the spine. Experimentally determined values of q ranged from 0.5 to 42. These analyses demonstrate how changes in motion segment stiffness, muscle activation strategy, or muscle stiffness (due to degenerative changes, injuries, fatigue, and so on) might lead to spinal instability and “self‐injury”.
Effects of fluid‐induced shear on articular chondrocyte morphology and metabolism in vitro
Authors: Smith R. Lane , Donlon B. S. , Gupta M. K. , Mohtai M. , Das P. , Carter D. R. , Cooke J. , Gibbons G. , Hutchinson N. , Schurman D. J.
Published: February 2005

This study tested the effects of fluid‐induced shear on high density monolayer cultures of adult articular chondrocytes. Fluid‐induced shear (1.6 Pa) was applied by cone viscometer to normal human and bovine articular chondrocytes for periods of 24, 48, and 72 hours. At 48 and 72 hours, fluid‐induced shear caused individual chondrocytes to elongate and align tangential to the direction of cone rotation. Fluid‐induced shear stimulated glycosaminoglycan synthesis by 2‐fold (p < 0.05) and increased the length of newly synthesized chains in human and bovine chondrocytes. In human chondrocytes, the hydrodynamic size of newly synthesized proteoglycans also was increased. After 48 hours of fluid‐induced shear, the release of prostaglandin E2 from the chondrocytes was increased 10 to 20‐fold. In human chondrocytes, mRNA signal levels for tissue inhibitor of metalloproteinase increased 9‐fold in response to shear compared with the controls. In contrast, mRNA signal levels for the neutral metalloproteinases, collagenase, stromelysin, and 72 kD gelatinase, did not show such major changes. This study demonstrated that articular chondrocyte metabolism responds directly to physical stimulation in vitro and suggests that mechanical loading may directly influence cartilage homeostasis in vivo.
Biomechanical properties of third carpal articular cartilage in exercised and nonexercised horses
Authors: Palmer J. L. , Bertone A. L. , Mansour J. , Carter B. G. , Malemud C. J.
Published: February 2005

The relevance of site and exercise on the biomechanical properties of the articular cartilage from the equine third carpal bone were assessed by creep indentation testing. Six horses were exercised for 30 minutes three times weekly. Another six horses were housed in box stalls and were not exercised. At the conclusion of the study, one third carpal bone from each horse was harvested and the KLM biphasic material properties of cartilage were determined at 12 sites. There was a significant (p < 0.01) effect of site but not exercise on the cartilage aggregate modulus, which was significantly lower for sites on the dorsal aspect of the radial facet and for all sites on the intermediate facet as compared with sites on the palmar aspect of the radial facet of the third carpal bone. Exercise significantly increased the permeability constant at all sites when compared with the nonexercised group, but there was no difference between sites within groups. Exercise also significantly increased Poisson's ratio, but only at sites located on the palmar aspect of the radial facet. In general, both site and exercise influence the biomechanical behavior of third carpal articular cartilage. Inherent differences in cartilage biomechanical properties within a joint correlate with the location specificity of cartilaginous lesions in the equine midcarpal joint.
Force attenuation in trochanteric soft tissues during impact from a fall
Authors: Robinovitch Stephen N. , McMahon Thomas A. , Hayes Wilson C.
Published: February 2005

The risk for hip fracture from a fall is known to decrease with increased body mass index (weight/height2), a relative measure of obesity. To explore whether this reduced risk is due to the protective effect of increased soft‐tissue cushioning in obese individuals, we used an impact pendulum and surrogate human pelvis to conduct simulated fall impact experiments on trochanteric soft tissues harvested from the cadavers of nine elderly individuals. For each impact, the total applied energy was 140 J. Peak forces ranged from 4,050 to 6,420 N, and tissue energy absorption ranged from 8.4 to 81.6 J. Increased tissue thickness correlated strongly with both decreased peak force (r2 = 0.91) and increased tissue energy absorption (r2 = 0.76). However, peak forces in all cases were within 1 SD of previously reported average fracture forces forces elderly cadaveric femora. This suggests that force attenuation in trochanteric soft tissues alone is insufficient to prevent hip fracture in falls in which an elderly person lands directly on the hip. In such falls, additional energy‐absorbing mechanisms, such as breaking the fall with an outstretched hand and eccentric contraction of the quadriceps during descent, are likely to be involved if fracture does not occur.
Imaging of immature articular cartilage using ultrasound backscatter microscopy at 50 MHz
Authors: Kim H. K. W. , Babyn Paul S. , Harasiewicz K. A. , Gahunia H. K. , Pritzker K. P. H. , Foster F. S.
Published: February 2005

A high frequency sonographic technique–ultrasound backscatter microscopy–was used to visualize the subsurface structure of immature porcine articular cartilage from the knee joint. In 20‐week‐old pigs, all parts that were scanned, except the weight‐bearing regions of the femoral condyles, demonstrated heterogeneous ultrasound backscatter characteristics within the articular cartilage. A trilaminar pattern consisting of hypoechoic, hyperechoic, and anechoic layers ranging from superficial to deep generally was observed, except in the weight‐bearing regions of the femoral condyles, where a homogeneous anechoic pattern was seen. In the younger pigs (6 and 10 weeks old), the trilaminar backscatter pattern was not observed. Small, highly echogenic structures that correlated with vascular channels in histologic assessment were observed frequently in the cartilage of younger pigs, but they were seldom present in the cartilage of 20‐week‐old pigs. Structural details, such as disruption of the subchondral bone and presence of a thickened fibrous layer on the articular surface at the chondrosynovial junction, also were detected with the ultrasound backscatter microscope. We concluded that high frequency ultrasound can be used to visualize the subsurface structure of immature articular cartilage and some of its developmental changes. Further research is required to explain the mechanism underlying the observed backscatter characteristics of immature articular cartilage and to study its potential for the imaging of pathologic changes.
Late changes in bone mineral density of the proximal tibia following total or partial medial meniscectomy: A randomized study
Authors: Petersen Michael Mørk , Olsen Claus , Lauritzen Jes Bruun , Lund Bjarne , Hede Adam
Published: February 2005

The adaptive bone remodeling in the proximal tibia following medial meniscectomy was measured quantitatively by dual photon absorptiometry. Thirty‐three patients who had undergone a meniscectomy (randomized to either total [n = 19] or partial [n = 14] meniscectomy) performed by open joint surgery approximately 12 years earlier were included in the study. Bone mineral density was measured in the previously injured legs and in the healthy contralateral legs in areas located medially and laterally in the cortical bone of the subchondral plates and below in the trabecular bone of the medial and lateral tibial condyles. The distribution of bone mineral within the proximal tibia showed a characteristic and significant pattern. In the trabecular bone of the healthy contralateral knees, bone mineral density was 15% higher in the medial tibial condyles compared with the values laterally: a total or partial meniscectomy increased this difference to 25%. With regard to the cortical bone of the subchondral plates, the bone mineral density in the healthy knees was 24.8–29.4% higher medially than laterally, whereas after total and partial meniscectomy the differences were, respectively, 37.7 and 41.4%. No significant differences in the distribution of bone mineral density, at either cortical or trabecular measuring sites, were found between totally and partially meniscectomized knees.
In vitro stimulation of articular chondrocyte mRNA and extracellular matrix synthesis by hydrostatic pressure
Authors: Smith R. Lane , Rusk S. F. , Ellison B. E. , Wessells P. , Tsuchiya K. , Carter D. R. , Caler W. E. , Sandell L. J. , Schurman D. J.
Published: February 2005

This study tested the effects of hydrostatic pressure (10 MPa) on adult articular chondrocyte mRNA and extracellular matrix synthesis in vitro. High density primary cultures of bovine chondrocytes were exposed to hydrostatic pressure applied intermittently at 1 Hz or constantly for 4 hours in serum‐free medium or in medium containing 1% fetal bovine serum, mRNAs for aggrecan, types I and II collagen, and β‐actin were analyzed by Northern blots and quantified by slot blots. Proteoglycan synthesis was quantified by 35SO4 uptake into cetylpyridinium chloride‐precipitable glycosaminoglycans, and cell‐associated aggrecan and type‐II collagen were detected by immunohistochemical techniques. In serum‐free medium, intermittent pressure increased aggrecan mRNA signal by 14% and constant pressure decreased type‐II collagen mRNA signal by 16% (p < 0.05). In the presence of 1% fetal bovine serum, intermittent pressure increased aggrecan and type‐II collagen mRNA signals by 31% (p < 0.01) and 36% (p < 0.001), respectively, whereas constant pressure had no effect on either mRNA. Intermittent and constant pressure stimulated glycosaminoglycan synthesis 65% (p < 0.001) and 32% (p < 0.05), respectively. Immunohistochemical detection of cell‐associated aggrecan and type‐II collagen was increased in response to both intermittent and constant pressure. These data support the hypothesis that physiologic hydrostatic pressure directly influences the extracellular matrix metabolism of articular chondrocytes.
Enhanced denaturation of the α1(II) chains of type‐II collagen in normal adult human intervertebral discs compared with femoral articular cartilage
Authors: Hollander Anthony P. , Heathfield Terrence F. , Liu Jane J. , Pidoux Isabelle , Roughley Peter J. , Mort John S. , Poole A. Robin
Published: February 2005

The mechanical strength of connective tissues is dependent on the integrity of their fibrillar collagen frameworks. The objective of the present study was to assess type‐II collagen damage (denaturation) in the adult human intervertebral disc compared with articular cartilage, in order to determine whether damage to this molecule may vary in different anatomical sites in the same person. A new immunochemical assay was used to measure the amounts of denatured and total type‐II collagen in the annulus fibrosus and nucleus pulposus of the L5‐S1 disc and in cartilage from the femoral condyles of the same individuals (n = 7). Denaturation of type‐II collagen was significantly higher in both the annulus fibrosus and the nucleus pulposus than in articular cartilage. Such increased damage to type‐II collagen in the adult disc may have relevance to the more pronounced degenerative changes observed in this tissue compared with articular cartilage.
Effect of alendronate on fracture healing and bone remodeling in dogs
Authors: Peter C. P. , Cook William O. , Nunamaker David M. , Provost Michael T. , Seedor J. Gregory , Rodan Gideon A.
Published: February 2005

To examine the effect of alendronate (4‐amino‐1‐hydroxybutylidene bisphosphonate) on fracture repair, the drug was given to mature beagle dogs orogastrically at 2 mg/kg/day for 9 weeks preceding fracture, 16 weeks after fracture, or both before and after fracture (25 weeks). A transverse mid‐diaphyseal fracture of the right radius was surgically induced and was stabilized by external coaptation splinting. Fracture healing and bone remodeling were evaluated by radiography, gross and histological examination, and bone histomorphometry. The mechanical properties of the fracture callus were determined by a four‐point bending test. Radiographs and gross and microscopic examination demonstrated normal bone healing at the fracture site in all dogs. In dogs that received alendronate during the fracture healing period, at 16 weeks the calluses were approximately 2–3 times larger than those in dogs that received a placebo during the healing period. This is consistent with slower callus bone remodeling, an expected pharmacological effect of the compound. Bone histomorphometry demonstrated that treatment with alendronate did not inhibit bone formation or mineralization. Mechanical testing showed that the ultimate load at failure and the flexural rigidity of both the fractured and contralateral intact bone were unaffected by treatment with alendronate. Therefore, in this study, treatment with alendronate before or during fracture healing, or both, resulted in no adverse effects on the union, strength, or mineralization of bone in mature beagle dogs.
Qualitative and quantitative analysis of orthotopic bone regeneration by marrow
Authors: Werntz Joanne R. , Lane Joseph M. , Burstein Albert H. , Justin Robert , Klein Robert , Tomin Emre
Published: February 2005

A rat model of a femoral segmental defect was used to specifically test the hypothesis that autogenous marrow has the osteogenic capability to heal a bone defect. The variables analyzed included the ratio of the marrow volume to the defect, implantation of live or dead marrow, and remodeling of established nonunions by implantation of live marrow. The uniqueness of this model allows biomechanical evaluation of the new bone formed by the implant. When live marrow was implanted, woven bone formed at 3 weeks, progressing to early lamellar bone at 6 weeks, with subsequent remodeling for as long as 12 weeks in a volumetric fashion (p < 0.05). Bone marrow, when placed in a fresh femoral defect and given in sufficient amounts, produced a rate of union comparable with that of autologous bone grafts. Mature lamellar bone formed by marrow was evaluated biomechanically: the results were statistically comparable with those of cancellous bone grafts at 12 weeks. Significant bone formation occurred when marrow was percutaneously injected in femoral nonunions, although union and remodeling did not take place in this rat model. Implantation of dead marrow resulted in rare cellular infiltration and minimal bone formation in a manner comparable with that of autogenous cancellous bone grafts. These results indicate that bone marrow can lead to structurally functional bone regeneration in an orthotopic location.
Uniaxial tension inhibits tendon collagen degradation by collagenase in vitro
Authors: Nabeshima Y. , Grood E. S. , Sakurai A. , Herman J. H.
Published: February 2005

Tendon structure is governed largely by factors regulating the anabolic and catabolic phases of tenocyte metabolism. Little is known about the mechanisms that regulate the synthesis, activation, and action of metalloproteinases, which are key enzymes in a multifactorial cascade controlling homeostasis of the extracellular matrix. In the present study, we investigated the effect of tension on collagenase‐induced degradation of the tendon in vitro by assessing changes in structural and material properties measured during tensile failure tests. Devitalized right‐left pairs of rabbit patella‐patellar tendon‐tibia units were maintained under culture conditions in the presence of 60 U/ml highly purified collagenase for 20 hours. One randomly selected unit from each animal was subjected to a tension that produced a constant 4% elongation or strain (n = 10); the contralateral unit served as a slack comparison (n = 10). In one series of experiments (immediate, n = 5), the tension was applied immediately prior to collagenase exposure. In a second series (delayed, n = 5), it was delayed for 4 hours to allow time for the collagenase to diffuse into the tendon. Additional devitalized and nonincubated units (n = 6) were used as normal controls. Collagenase exposure caused large decreases in stiffness and elongation to failure in slack units. This resulted in greater than 80% reductions in both maximum failure force and energy to failure. In contrast, the loaded unit in both experimental protocols had significantly greater stiffness than control units. In both the immediate and the delayed protocols, the loaded tendons had significantly higher stiffness and failed at significantly higher elongations and maximum forces than the slack tendons. Diffusion studies with and without tension showed the tension did not inhibit diffusion of collagenase into the tendon but did significantly decrease the water content from 64.6 to 57.8%. The data suggest that stresses and strains of the extracellular matrix may modify the kinetics of the bacterial collagenase‐collagen interaction. Matrix stress and strain may be an important and overlooked factor that modulates the susceptibility of collagen to proteolytic degradation.
Reproducibility of isometric trunk extension torque, trunk extensor endurance, and related electromyographic parameters in the context of their clinical applicability
Authors: van Dieën Jaap H. , Heijblom P.
Published: February 2005

Testing the capacity of the trunk extensor muscles may be useful in the diagnosis of low back pain. In the present study, the reproducibility of measurements of maximum trunk extension force, trunk extension endurance, and related electromyographic parameters was investigated. Intraclass correlations indicated that the reproducibility of maximum force and endurance time was satisfactory. Nevertheless, the smallest difference in these parameters that could be attributed, with 95% confidence, to a change in the condition of a patient was, in general, more than 20%. On the electromyograms, the slopes of amplitude and frequency content appeared to be related to endurance time. The reproducibility of these parameters in terms of the intraclass correlation was again satisfactory; however, the smallest detectable difference generally exceeded 50%. The clinical applicability of the parameters studied is severely limited by a lack of reproducibility.
Mechanical properties of the anterior cruciate ligament chronically relaxed by elevation of the tibial insertion
Authors: Keira Motoharu , Yasuda Kazunori , Kaneda Kiyoshi , Yamamoto Noritaka , Hayashi Kozaburo
Published: February 2005

The effects of stress deprivation on the mechanical properties of the anterior cruciate ligament were studied in a canine model. Fifty‐eight mature mongrel dogs were divided into two groups. In the relaxed group (n = 30), the tibial insertion of the anterior cruciate ligament in each right knee was surgically elevated proximally 3 mm from the tibia: the elevation was anatomically reduced in the sham group (n = 28). In order to obtain control data, the left knee in each dog was left untreated. A femur‐anterior cruciate ligament‐tibia complex was excised from each knee for biomechanical tests at 6 or 12 weeks after surgery. To simplify data analysis, the treat/nontreat ratio (the ratio of the data obtained from the treated knee to that from the nontreated knee) was used. The cross‐sectional area of the ligament increased significantly in both groups; the area in the relaxed group (average treat/nontreat ratio = 1.37) was significantly larger than that in the sham group (1.16) at 6 weeks but not at 12 weeks. The treat/nontreat ratio of tensile strength in the relaxed group significantly decreased to 0.67 and 0.58 at 6 and 12 weeks, respectively: in the sham group, it significantly decreased to 0.79 at 6 weeks but subsequently increased to 0.87 at 12 weeks. Only at 12 weeks was a significant difference observed between the two groups. This study demonstrated that, in the anterior cruciate ligament, stress deprivation results in a rapid increase in the cross‐sectional area, although this effect disappears by 12 weeks, and in a decrease in mechanical strength, although a relatively long period of more than 6 weeks is required for the deterioration.
Nerve regeneration during patellar tendon autograft remodelling after anterior cruciate ligament reconstruction: An experimental and clinical study
Authors: Aune Arne Kristian , Hukkanen Mika , Madsen Jan Erik , Polak Julia M. , Nordsletten Lars
Published: February 2005

The innervation of the rat and human anterior cruciate ligament, patellar tendon, and patellar tendon autograft after reconstruction of the anterior cruciate ligament was investigated by immunohistochemical and histological methods. A rat model of reconstruction with patellar tendon autograft was evaluated during active graft remodelling (2–16 weeks) and compared with normal ligament and tendon. The knees of 10 patients who had undergone reconstruction with patellar tendon autograft were examined 5–37 months postoperatively (remodelling fully completed) with arthroscopy and biopsy. As a control, biopsies from normal ligament and tendon were obtained from four patients. Nerve fibers were identified using antisera for protein gene product 9.5, a general neural marker. Neuronal regeneration was assessed by the expression of growth‐associated protein 43/B‐50. The sensory type of innervation was characterized by assessing the distribution of nerves containing the sensory neuropeptides calcitonin gene related peptide and substance P. Immunoreactivity for all neural markers was found in both rat and human anterior cruciate ligament and patellar tendon. Two weeks after reconstruction, the rat autograft was acellular and no innervation could be identified. After 4 weeks, the grafts were viable, and immunoreactivity for protein gene product 9.5, growth associated protein 43/B‐50, and calcitonin gene‐related peptide was found until the 16th week postoperatively. Immunoreactivity for substance P was found in rat autografts at 4 weeks postoperatively only. All biopsies of human patellar tendon autograft showed signs of the remodelling process being fully completed, with revascularization and a sinusoidal collagen pattern with fibroblast repopulation. Neuropeptide immunoreactivity, however, was not found. The presence of immunoreactivity to sensory neuropeptides in the anterior cruciate ligament and patellar tendon may indicate a nociceptive and neuromodulatory function of these structures. The expression of sensory neuropeptides in the rat patellar tendon autograft suggests a possible involvement of sensory innervation during healing of the graft.
Intraoperative force‐setting did not improve the mechanical properties of an augmented bone‐tendon‐bone anterior cruciate ligament graft in a goat model
Authors: Smith Joel J. , Lewis Jack L. , Mente Peter L. , Lindquist Conrad M. , Poff Bradley C. , Lew William D.
Published: February 2005

It has been hypothesized that load affects the mechanical properties of an anterior cruciate ligament graft while it remodels. The goal of this study was to use an existing goat model to evaluate the effect of intraoperative set force on the postoperative mechanical properties of an autograft that had been augmented with a synthetic segment. The following questions were addressed. Do augmented autografts set with a high force intraoperatively have improved structural and material graft properties and lower anterior‐posterior knee laxity at 3 months after surgery, compared with autografts set with a low intraoperative force? How do the structural and material properties of these implanted autografts compare with the mechanical properties of an intact anterior cruciate ligament or an unimplanted control autograft? The anterior cruciate ligament was reconstructed in seven goats with use of a composite graft consisting of a bone‐patellar tendon‐bone autograft and a synthetic augmentation device. A force‐setting technique was used intraoperatively to establish the load‐sharing between the autograft and augmentation segments such that the autograft carried either a high (16.5 N in four animals) or low (1.5 N in three animals) level of force, while the total force in the composite graft remained constant. Tensile testing was performed at 3 months after surgery to determine the material and structural properties of the autograft, the intact anterior cruciate ligament from the normal contralateral knee, and a control bone‐patellar tendon‐bone graft of similar size that was harvested from the contralateral knee at the time of necropsy and had never been implanted in the joint. The structural and material properties of the autografts initially set to high or low loads at surgery were not significantly different after 3 months of implantation. The strength and stiffness of the implanted tendons were an average of 24 and 20% of the strength and stiffness of the normal anterior cruciate ligament and 31 and 62% of the control tendons, respectively. Intraoperative set force in an augmented anterior cruciate ligament graft at the levels chosen in this study did not significantly affect weakening of the autograft at 3 months.