bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanism of action of parathyroid hormone‐induced proteoglycan synthesis in the growth plate chondrocyte
Authors: Iannotti J. P. , Brighton C. T. , Iannotti V. , Ohishi T.
Published: February 2005

In the growth plate chondrocyte, parathyroid hormone (PTH) stimulates phosphoinositol 4, 5 bisphosphate (PIP2) degradation, which results in the rapid production of inositol (1,4,5) triphosphate (IP3). IP3 induced the release of calcium from an intracellular store, which caused a rapid increase in the cytosolic ionized calcium concentration. Parathyroid hormone also induced a 30–50% increase in proteoglycan synthesis. Phorbol esters, which pharmacologically activate protein kinase C, resulted in a 70–80% increase in proteoglycan synthesis. Treatment of the chondrocytes with retinoic acid (0.2 μM) inhibited the parathyroid hormone and phorbol ester‐induced increase in intracellular ionized calcium and the increase in proteoglycan synthesis. From this data we postulate that the stimulation of proteoglycan synthesis in growth plate chondrocytes by PTH is mediated by the breakdown of membrane phosphoinositides, which results in the production of IP3 and an increase in ionized intracellular calcium. It is suggested that the degradation of membrane phosphoinositides also results in production of diacylglycerol and, thereby, an activation of protein kinase C, which has a large stimulatory effect on proteoglycan synthesis. The increase in cytosolic calcium most likely acts synergetically with diacylglycerol to activate protein kinase C. Retinoic acid blocks the effect of PTH and phorbol ester‐induced proteoglycan synthesis and may act through the inhibition of protein kinase C. The overall effect of PTH on the growth plate chondrocyte appears to be a stimulation of proteoglycan synthesis that is mediated by the degradation products of membrane phosphoinositides.
Vertebral end‐plate failure in porcine‐and bovine models of spinal fracture instrumentation
Authors: Allan D. Gordon , Russell G. Gordon , Moreau Marc J. , Raso V. James , Budney David
Published: February 2005

The use of mature porcine and immature bovine spines as models for the assessment of spinal fracture instrumentation is commonplace. By comparing the load‐displacement characteristics of these spine segments and observing the fracture type, this study investigated the tendency of immature bovine spines to fail prematurely at the vertebral physis, disrupting biomechanical evaluation of spinal fracture fixation devices. Load to failure of the spines was determined using the Instron Universal Testing Machine and a specially designed endcap. In axial compression, the 10–16‐week‐old calf spines failed at 12,845 ± 1,466 N, compared with mature pig spines at 17,300 ± 5,170 N (p < 0.05). Axial compression with flexion caused consistent failure through an end‐plate in both species: 995 ± 156 N for the calf spines and 2,025 ± 575 N for the porcine spines (p < 0.005). It was concluded that the tendency for immature bovine spines to fail more readily at the cartilaginous end‐plate makes the calf spine a less desirable model.
Control of transmission of HIV and other bloodborne pathogens in biomechanical cadaveric testing
Authors: Cavanaugh John M. , King Albert I.
Published: February 2005

The Bioengineering Center at Wayne State University uses universal blood and body fluid precautions when handling human cadavers in bio‐mechanical testing. Our infection control protocol largely follows the precautions outlined by the Centers for Disease Control (CDC). In addition, we screen each cadaver for the human immunodeficiency virus (HIV) and the hepatitis B virus (HBV) before accepting a cadaver for biomechanical tests. This paper discusses acquired immunodeficiency syndrome (AIDS) and infection control guidelines by addressing the following: (a) what is AIDS? (b) How infectious is the HIV virus, which causes AIDS? (c) What precautions should be taken in cadaveric testing to safeguard against HIV and other bloodborne pathogens? The infection control procedures presented in this paper can be adapted to whole‐body cadaveric testing or to the testing of tissue specimens.
In situ cross‐linking of cartilage proteoglycans
Authors: Phillips Frank M. , Pottenger Lawrence A. , Hay Rick V.
Published: February 2005

Although the in vitro interactions between purified cartilage matrix components have been studied extensively, little is known about these interactions in situ. In this study, cartilage was treated with a cross‐linking reagent with a span of 1.2 nm between its reactive terminal groups in order to preserve the native relationships between closely associated matrix components throughout extraction, purification, and preparation for electron microscopy. After in situ cross‐linking, electron microscopy and gel chromatography revealed that about one‐half of the guanidine hydrochloride extractable proteoglycans were polymeric, usually with two to five proteoglycan subunits in each polymer. Cross‐linking consistently involved the thin segments of the proteoglycan subunits. Some of the proteoglycan polymers were capable of binding hyaluronic acid and were parts of aggregates under associative conditions. SDS–polyacrylamide gel electrophoresis revealed that link proteins were present within the polymers, and studies in which purified proteoglycans were cross‐linked in vitro confirmed that the link proteins increased the proportion of polymeric proteoglycans. These findings suggest that individual proteoglycans within cartilage have intimate associations with other proteoglycans that are mediated by link proteins.
Internal remodeling of periosteal new bone during fracture healing
Authors: Aro Hannu T. , Wippermann Burkhard W. , Hodgson Stephen F. , Chao Edmund Y. S.
Published: February 2005

A closed fracture model of the rat tibia was employed to study internal remodeling of periosteal new bone during fracture repair. Static histomorphometric parameters of osteoid surface (or perimeter) and eroded surface (resorption surface) were used as indicators of appositional bone formation and resorption of bone trabeculae, respectively. Intracortical remodeling at the fracture site was evaluated using quantitative tetracycline histology and microradiography. The extents of osteoid and eroded bone surfaces did not differ significantly in the periosteal woven new bone in the early phases of fracture healing. Later on, the periosteal new bone had significantly more osteoid surface than eroded surface (p < 0.001). The number of osteoclasts also decreased significantly over time during fracture healing (p = 0.028). Cortical bone showed a continuous increase of porosity (p < 0.01) between 1 and 6 weeks after fracture. These results suggest that there is a time‐related change in the balance of periosteal bone formation and resorption during the progress of fracture repair. We hypothesize that this change was related to the restoration of bony continuity. Further studies are, however, needed to indicate the histomorphometric features of periosteal new bone in fracture nonunions.
Magnetic resonance imaging of meniscal degeneration in asymptomatic knees
Authors: Negendank William G. , Fernandez‐Madrid Felix R. , Heilbrun Lance K. , Teitge Robert A.
Published: February 2005

Histopathological studies have suggested that spontaneous degeneration of knee menisci predisposes to symptomatic tears. We used magnetic resonance (MR) imaging to study noninvasively 20 patients with documented meniscal tears in one knee but asymptomatic contralateral knees, 18 normal controls, and 15 patients with symptomatic nonmeniscal knee disorders. A scoring system for MR signal changes was developed, and differences between the three groups were tested for significance by a multivariate analysis of covariance. MR signal changes in the menisci begin at around 30 years of age, progress with age, occur in both men and women, and occur in subjects who are inactive as well as those who undergo habitual knee stress exercises. Most subjects with documented meniscal tears in one knee have MR signals in the asymptomatic contralateral knee that reflect a more advanced degree of meniscal degeneration than in age‐comparable normal controls or patients with nonmeniscal knee disorders. After adjustment for potential confounding variables, weight, and sex, the mean scores in the asymptomatic knee of patients with meniscal disease are significantly higher than those of normal controls (p = 0.021) and nonmeniscal disease patients (p = 0.019). These results document the occurrence of age‐dependent degeneration within knee menisci, and support the hypothesis that a segment of the population has pre‐existing meniscal degeneration predisposing them to traumatic or spontaneous meniscal tears.
Measurement of lower extremity kinematics during level walking
Authors: Kadaba M. P. , Ramakrishnan H. K. , Wootten M. E.
Published: February 2005

A simple external marker system and algorithms for computing lower extremity joint angle motion during level walking were developed and implemented on a computer‐aided video motion analysis system (VICON). The concept of embedded axes and Euler rotation angles was used to define the three‐dimensional joint angle motion based on a set of body surface markers. Gait analysis was peformed on 40 normal young adults three times on three different test days at least 1 Week apart using the marker system. Angular motion of the hip, knee, and ankle joints and of the pelvis were obtained throughout a gait cycle utilizing the three‐dimensional trajectories of markers. The effect of uncertainties in defining the embedded axis on joint angles was demonstrated using sensitivity analysis. The errors in the estimation of joint angle motion were quantified with respect to the degree of error in the construction of embedded axes. The limitations of the model and the marker system in evaluating pathologic gait are discussed. The relatively small number of body surface markers used in the system render it easy to implement for use in routine clinical gait evaluations. Additionally, data presented in this paper should be a useful reference for describing and comparing pathologic gait patterns.
The effects of contact pressure elevations and aseptic necrosis on the long‐term outcome of congenital hip dislocation
Authors: Hadley Nancy A. , Brown Thomas D. , Weinstein Stuart L.
Published: February 2005

The relationship between excessive articular contact pressure, aseptic necrosis, and the long‐term outcome with unilateral congenital dislocation of the hip (CDH) was studied in a series of 84 patients treated by closed reduction and followed for an average of 29.2 years. Contact stress was estimated from archived radiographs taken at the time of maturity and at several follow‐up visits. At a recent review, each patient was rated both clinically for pain and function and radiographically for deformity, degeneration, and aseptic necrosis. For each of 431 films, articular contact stress (force/area) was estimated mathematically, based upon a frontal plane equilibrium (force) analysis and a landmark‐based inference of three‐dimensional head surface (area). Good correlation with final deformity (Spearman ρ = 0.78) was obtained when the hips were ranked in terms of a new cumulative overpressure index P̂, defined as a time‐pressure product involving years of pressure exposure beyond a 2 MPa pressure damage level. An unsatisfactory outcome occurred in 90.4% of the hips experiencing P̂ > 10 MPa‐years (most of which had aseptic necrosis involvement), whereas the outcome was satisfactory in 80.9% of hips with P̂ < 10 MPa‐years.
Anterior cruciate ligament replacements: A mechanical study of femoral attachment location, flexion angle at tensioning, and initial tension
Authors: Bylski‐Austrow D. I. , Grood E. S. , Hefzy M. S. , Holden J. P. , Butler D. L.
Published: February 2005

We examined three surgical variables that affect the ability of an anteior cruciate ligament replacement to restore the limit of anterior tibial translation. These were the placement site of the substitute on the femur, the initial tension applied to the replacement, and the flexion angle of the knee at the time of tensioning. An anterior load of 100 N was applied to the tibia. As the knee was flexed, we measured the tensile force in the substitute and the anteroposterior position of the femur relative to the tibia. Placement largely determined whether the force in the replacement increased or decreased with flexion. Placement also largely determined whether the tibia moved anteriorly or posteriorly with flexion compared to its position in the intact knee. The initial tension and the flexion angle at tensioning affected the magnitude of force in the substitute and the magnitude of the change in AP position. They did not affect how force and AP position changed with flexion. Greater increases in force and greater posterior shifts in tibial position were produced by changing the flexion angle at tensioning from 0° to 30° than by increasing the initial tension from 22 to 44 N.
Young's modulus, bending strength, and tissue physical properties of human compact bone
Authors: Keller T. S. , Mao Z. , Spengler D. M.
Published: February 2005

The Young's modulus, bending strength, apparent density, and ash content of 155 human compact bone bending specimens were determined. Both Young's modulus (E) and bending strength (S) were strongly correlated to tissue dry apparent density (ρa). Based upon the correlation coefficient (R) and the percent deviation of the data from the regression curve (% dev.), these correlations were best described by power law relationships: E∞ ρa1.54 (R2 = 0.79, % dev. = 2.4) and S∞ ρa2.18 (R2 = 0.80, % dev. = 6.4). Bending strength was related to Young's modulus raised to the 1.26 power, implying a nonlinear relationship for these variables. We found a weak correlation between ash content and the mechanical behavior of the compact bone specimens, particularly Young's modulus, but could not statistically justify formulation of a more complex multivariate power model incorporating both density and ash content. Regional variations in strength and stiffness along the femoral shaft and within the cortex were also noted and were attributed primarily to differences in apparent density. The relationships formulated for the mechanical behavior of human compact bone are discussed in terms of the results of previous investigations of the mechanical behavior of nonhuman compact bone and human cancellous bone.
Effects of calcium channel‐blocking agents on platelet–osteogenic sarcoma interaction: Platelet aggregation and electron microscopic findings
Authors: Mehta Paulette , Kimura Arthur , Lawson Daniel
Published: February 2005

A variety of tumors stimulate platelet activation. Because platelet activation may, in part, require calcium channel mobilization, we evaluated whether calcium channel blocking agents inhibit osteogenic sarcoma induced platelet aggregation. Platelet rich plasma (PRP) from normal subjects was incubated with one of four calcium channel‐blocking agents: nifedipine, diltiazem, verapamil, or amlodopine, all 0–25 μg/ml, or diluent. Osteogenic sarcoma cells (2 or 4 × 106/ml) were then added. Platelet aggregation was monitored by light transmission through PRP, and residual PRP was processed for electron microscopy. MG63 cells caused aggregation of PRP in most subjects (mean, 36+ 3%). Calcium channel‐blocking agents (nifedipine > diltiazem > amlodopine > verapamil) caused partial inhibition of osteogenic sarcoma‐induced platelet aggregation, at high concentrations only. Electron microscopy showed platelets aggregating to each other and to tumor cell membranes within 1–5 minutes. Changes in pattern of platelet clumping around tumor cells occurred when PRP was incubated with high concentration of diltiazem (50 μg). This study shows that calcium channel‐blocking agents inhibit osteogenic sarcoma‐induced platelet aggregation when used in high doses.
An approach for time‐dependent bone modeling and remodeling—application: A preliminary remodeling simulation
Authors: Beaupré G. S. , Orr T. E. , Carter D. R.
Published: February 2005

In a companion paper, we presented a time‐dependent theory for bone modeling and remodeling in response to a daily loading history. This paper represents a preliminary attempt to use the theory to determine the distribution of bone density within the adult proximal femur under an assumed normal loading history. Subsequent functional adaptation of the internal structure due to changes in the loading history are then determined. Throughout this preliminary study, the external geometry of the proximal femur is considered to be fixed, i.e., changes in the external shape are neither stimulated nor allowed. Linear and trilinear (dead‐zone nonlinearity) rate remodeling laws were compared. Computer emulations using two‐dimensional finite element models were successful in creating a normal‐appearing distribution of bone tissue when remodeling was initiated from a solid structure of homogeneous bone density. Subsequent reduction in the loading history caused regional bone atrophy. Reinstatement of the normal loading history caused a generalized increase in bone mass but resulted in a slightly different bone distribution than was calculated for a constant loading history. These results demonstrate the utility of the remodeling theory and are consistent with the hypothesis that similar stress‐related phenomena are responsible for both normal morphogenesis and functional adaptiation in response to changes in the bone loading.
An in vitro mechanical and histological study of acute stretching on rabbit tibial nerve
Authors: Rydevik Björn L. , Kwan Michael K. , Myers Robert R. , Brown Richard A. , Triggs Kevin J. , Woo Savio L‐Y. , Garfin Steven R.
Published: February 2005

Peripheral nerves are often mechanically stretched in association with trauma to extremities, resulting in varying degrees of impairment of nerve function. However, little is known about the biomechanical properties of peripheral nerves and limits of stretching that the nerve may undergo before structural changes occur. Also, the injury pattern of nerves under stretching is poorly understood. In the present study, fresh rabbit tibial nerves (n = 18) were harvested. Nine nerves were stretched to failure in an INSTRON materials testing machine at a rate of 1 cm/min (strain rate of 0.5%/s). Loaddeformation and stress‐strain curves were determined. Histological examination by light microscopy of the stretched nerves as well as six normal control nerves and three clamped nonstretched control nerves was performed. The results show that the rabbit tibial nerves have an in situ strain of 11.0 + 1.5% and exhibit a nonlinear stress‐strain relationship. After 20% strain, the curve becomes linear up to failure. The ultimate strain and tensile strength of the nerves were 38.5 + 2.0% and 11.7 + 0.7 MPa, respectively. At failure, the load dropped suddenly, but the specimens remained grossly intact. Histological analysis of the stretched nerves showed multiple ruptures of perineurial sheaths when compared to controls.
Method for setting total graft force and load sharing in augmented ACL grafts
Authors: Lew William D. , Engebretsen Lars , Lewis Jack L. , Hunter Robert E. , Kowalczyk Curtis
Published: February 2005

The objective of this study was to develop a method for obtaining a controllable and reproducible immediate postoperative mechanical state in a knee with an anterior cruciate ligament (ACL) reconstruction. This method, called the force‐setting technique, was demonstrated using a composite graft consisting of the middle third of the patellar tendon with bone blocks (PT) and the ligament augmentation device (LAD). The total graft force was set to match the force in the intact ACL at 30° flexion with the knee under the same standardized external load, while at the same time the load sharing between the biologic and augmentation components was controlled. The total graft force was set to match the ACL force three separate times in each knee, with ratios of load sharing set at the following levels: 50% PT‐50% LAD, 25% PT‐75% LAD, and 75% PT‐25% LAD. ACL, PT, LAD, and collateral forces were measured using buckle transducers, and three‐dimensional knee motion was measured using an instrumented spatial linkage as 90 N anteriorly directed tibial loads were applied to eigth specimens at 0°, 30°, 60°, and 90° flexion with an intact ACL, an excised ACL, and the three load‐sharing reconstruction states. The total graft force could be consistently set to within an average of 2% of the intact ACL force at 30° flexion, and load sharing between the graft segments could be set to within an average of 5.1% of the desired ratio at 30°. The load sharing was maintained at the other flexion angles except 90° when the PT was to have carried 25 and 50% of the total graft force, and extension when the PT was to have carried 75% of the graft force. When averaged over all specimens and flexion angles, the total graft force was 15% greater than the force in the ACL, and this was not statistically significant.
Glucosaminidase, galactosaminidase, and glucuronidase in the growth plate
Authors: Gamble James G. , Haimson Robert , Smith R. Lane
Published: February 2005

The activities of glucosaminidase, galactosaminidase, and glucuronidase were determined in fractions of bovine growth plate cartilage. Glucosaminidase and galactosaminidase activities were lowest in the area corresponding to the reserve cartilage and increased from the upper to the lower portions of the hypertrophic zones of the growth plate, reaching a maximum in the calcifying cartilage. Glucuronidase activity showed a distinct spike of activity in the calcifying cartilage. The spatial distribution of these activities suggests a role in calcification and in the dissolution of the extracellular matrix at the chondro‐osseous junction of the growth plate.
A study of fracture callus material properties: Relationship to the torsional strength of bone
Authors: Markel Mark D. , Wikenheiser Mark A. , Chao Edmund Y. S.
Published: February 2005

This study was designed to quantitate the local material properties of fracture callus during gap healing and to relate these local properties to the torsional strength of bone in a canine model under external fixation. Bilateral tibial transverse osteotomies were performed in 32 dogs and stabilized using unilateral external skeletal fixators with a 2‐mm gap. Dogs were divided into four equal groups and euthanized at either 2, 4, 8, or 12 weeks. The torsional properties of one bone of each pair were determined. In both bones of each pair, the indentation stiffness, calcium content, and histomorphometric properties of six sites of periosteal callus, six sites of endosteal callus, four sites of cortical bone, and two sites of gap tissue were determined. Each of the four types of tissue had a specific structural or material property change during the study period. The indentation stiffness of periosteal callus increased up to 8 weeks and then plateaued. Endosteal callus stiffness peaked at 8 weeks and then decreased by 12 weeks. Gap tissue stiffness increased linearly over time. Cortical bone stiffness decreased over time. Indentation stiffness was significantly associated with the calcium content of periosteal callus (R2 = 0.50, p < 0.0001) and gap tissue (R2 = 0.66, p < 0.0001). The local stiffnesses of gap tissue and periosteal callus were significantly associated with the maximum torque (gap, R2 = 0.50, p < 0.0001; periosteal, R2 = 0.34, p < 0.05) and the torsional stiffness (gap, R2 = 0.44, p < 0.0001; periosteal, R2 = 0.65, p < 0.0001) of the bone. Changes in local material properties corresponded to histologic changes in new bone formation and porosity of the four tissues.
An animal model for the study of neuromuscular injury induced beneath and distal to a pneumatic tourniquet
Authors: Pedowitz Robert A. , Rydevik Bjorn L. , Gershuni David H. , Hargens Alan R.
Published: February 2005

A well‐controlled animal model is presented for the study of neuromuscular injury induced by a pneumatic tourniquet. This model comprises a curved tourniquet surrounded by a stiff exterior shell, both of which were specifically designed to fit the conical and oblong shape of the rabbit hindlimb. Computed tomographic imaging was used to assess transverse tissue displacement induced by tourniquet compression. The curved tourniquet/shell configuration occluded the distal arterial blood flow to the extremity at a significantly lower cuff inflation pressure than a straight tourniquet of equal width. The magnitude and distribution of tissue pressures in the subcutaneous and deep tissues beneath the tourniquet were similar to those recorded in previous human cadaver studies of tourniquet compression. This animal model will facilitate the quantitation and analysis of tissue injury induced beneath and distal to a pneumatic tourniquet. Such data can help define the critical pressure and time limits for the safe use of pneumatic tourniquets in extremity surgery.
Rerouting peripheral nerves for spinal cord lesions
Authors: Romano Victor M. , Blair Sidney J. , Wurster Robert D.
Published: February 2005

To provide control of paralyzed limb muscles following spinal cord lesions, peripheral nerves containing motor axons from motoneurons located above a spinal cord lesion could potentially be rerouted to nerves containing motor axons located below the spinal cord lesion. To test this hypothesis in rats, the distal end of a cut tibial nerve, innervted by the L4–6 spinal level, was anastomosed or rerouted to the central end of the cut femoral nerve, innervated by the L3–4 spinal level. Appropriate controls were used. Recovery of lower hind limb motor function was followed at regular intervals, measuring the twitch tension of toe flexion (innervated by the tibial nerve) induced by transcutaneous stimulation of nerve rootlets exiting the spinal cord. After 4–6 months, 54% of motor function returned in the experimental group. Retrograde transport of horseradish peroxidase from the gastrocnemius muscles to spinal motoneuron cell bodies confirmed that the innervation of this group was at a higher level. Furthermore, after an L4 spinal transection, twitch tension responses to spinal cord outlet stimulation remained only in the experimental group. Therefore, a peripheral nerve containing motor axons from above the lesion was rerouted to a distal peripheral nerve to control muscles that would have otherwise been denervated.
Role of interfragmentary strain in fracture healing: Ovine model of a healing osteotomy
Authors: Cheal E. J. , Mansmann K. A. , Digioia A. M. , Hayes W. C. , Perren S. M.
Published: February 2005

It has been hypothesized that the histological pattern of fracture healing is controlled at least in part by the local mechanical strains in the interfragmentary region. To test this “interfragmentary strain hypothesis,” we applied cyclic bending deformations to tibial osteotomies in 11 sheep. An instrumented flexible plate spanning a 1‐mm osteotomy gap was deformed to create a gradient of tissue elongation from 10% under the plate to 100% at the opposite cortex. The cyclic deformations were applied three times per minute, 24 h per day, for 1–5 weeks. However, as a result of tissue differentiation, the bone‐plate complex increased in stiffness with healing time, resulting in a marked reduction of the gap deformation at approximately 4 weeks. Fracture healing was evaluated using vascular injection of India ink and conventional histology. A nonlinear three‐dimensional finite element model of the interfragmentary tissue at the initial stage of healing was used to predict the complex tissue strains. The ingrowth of vascularized soft tissue into the interfragmentary gap, as well as the subsequent differentiation of this tissue, occurred earlier and to a greater degree in regions of lower strain. In contrast, the proliferation of callus tissue was greatest at the periosteal and endosteal surfaces of the cortex opposite the plate. Direct comparison of the finite element predictions with the histology demonstrated that the spatial distribution of bone resorption at the fracture fragment ends directly corresponded to the locations of elevated tissue strain and stress. However, there was no consistent numerical relationship between the magnitude of these local peak strains and the corresponding volume of cortical bone resorption over the bone cross section.
Effect of circumferential bands on cortical vascularity and viability
Authors: Kirby Barbara M. , Wilson James W.
Published: February 2005

Wire cerclage devices do not restrict cortical vascularity; however, bands, because they are flat and wide, have been implicated as the cause of fracture nonunion by disruption of cortical vascularity. This experiment evaluated the effect of cerclage bands on the cortical vascularity of bones that had not been fractured. Stainless‐stell bands of four sizes (2.5, 5.0, 7.5, and 10.0 mm wide) and nylon bands of five sizes (2.5, 3.6, 4.8, 7.6, and 9.0 mm wide) were applied 1 cm apart to both femoral diaphyses of four mature dogs. In two additional dogs, 18‐gauge cerclage wires were applied 5 mm apart on one femur and nylon bands were applied immediately adjacent to one another on the other femur to cover 3 cm of the length of each femoral diaphysis. These six dogs were euthanatized and perfused 7 days postoperatively and specimens were studied by microangiography and correlated histology. Two additional dogs were studied 4 and 15 weeks after application of nylon and metal bands. There was no evidence of complete cortical devascularization under any size or type of cerclage appliance at any time interval. Numerous examples of vessels traversing the cortex directly beneath all the cerclage appliances were observed. Cerclage devices, even when flat and wide, do not restrict cortical vascularity when applied to intact bones.
Hemiepiphyseal reconstruction using tissue donated from fetal limbs in a murine model
Authors: Wolohan Michael J. , Zaleske David J.
Published: February 2005

Epiphyseal reconstruction in the immature skeleton could have great clinical significance. Hemiepiphyseal reconstruction was performed in a murine model by transplanting fetal tissue to surgically created defects in postnatal mice. Reconstruction is facilitated by the existence of inbred strains. While the reconstruction as performed here did not completely restore the growth characteristics of the epiphysis, the model represents a potentially fruitful interface between basic and clinical biology.
Radiographic assessment of longitudinal growth of the rabbit femoral physes
Authors: Thomsen Erik , Drummond Denis S. , Robertson William W. , Christofersen Mark R.
Published: February 2005

Using surgically implanted metal markers, serial radiographs of 17 immature femurs were evaluated for growth of the entire femur and of the distal femoral physis in rabbits 20 to 100 days of age. From these data the rate of longitudinal growth was plotted. The most rapid growth during the study period was from 20 to 40 days. Growth rates reached a plateau at 100 days of age. The increases in length for unit of time were compared for the entire femur and the distal physis. The distal physis was responsible for ∼65–70% of the femoral growth for the study period. As an internal control of reproducibility of measurement two means of determining distal femoral growth rates were compared. Their best fit curves proved to be almost identical. The model of evaluation of femoral growth is reproducible and can serve as a control against which variables in growth can be compared.
Large compressive preloads decrease lumbar motion segment flexibility
Authors: Janevic J. , Ashton‐Miller J. A. , Schultz A. B.
Published: February 2005

The bending, shear, and torsion flexibilities of 13 intact adult lumbar motion segments (from 11 men, two women, 48–83 years of age) were compared under three different compressive preloads, 0, 2,200, and 4,400 N. Test forces and moments up to 160 N and 16 Nm were applied at the center of the upper end plate of the intact disc. A compressive preload of 2,200 N resulted in a significant decrease in motion segment flexibilities in all seven test directions (p < 0.06) when compared with results obtained with no preload; the preload decreased flexibility 2.6, 4.5, and 6.1 times in bending, axial torsion, and shear, respectively. These results suggest that studies of internal trunk load‐sharing between active and passive tissues during strenuous tasks, which engender large spine compressive loads, should take these changes in spine passive resistance into consideration.
Variation of collagen fiber alignment in a joint surface: A scanning electron microscope study of the tibial plateau in dog, rabbit, and man
Authors: Clark John M.
Published: February 2005

To determine if articular cartilage collagen fiber organization differs with location on the tibial plateau, specimens from dogs, humans, and rabbits were studied by scanning electron microscopy. Joint surfaces were fixed, dehydrated, and fractured radially so that the periphery could be compared with the center on single specimens. Generally, fibers were more tightly packed in the lateral side than in the medial and in the periphery as compared with the center, where the cartilage was consistently thicker and the radial zone was dominant and composed of straight vertical fibers. In the periphery, the tangential and transitional zones were better developed and contributed up to 50% of the cartilage depth in comparison to only 5% centrally. The soft, dull, malacic appearance of the center results from lack of a true surface layer of tangential collagen fibers.
Physeal reconstruction using tissue donated from early postnatal limbs in a murine model
Authors: Cundy Peter J. , Jofe Michael , Zaleske David J. , Ehrlich Michael G. , Mankin Henry J.
Published: February 2005

Physeal reconstruction was performed in a murine model by transplanting corresponding postanatal tissue from 4‐day‐old C57B mice to resection defects. The site of the reconstruction, the murine distal femoral epiphysis, is completely cartilaginous and avascular at this stage of development. The tissue transplanted into the defect was demonstrated to have high kinetic activity by its incorporation of titriated thymidine. The physeal reconstruction as performed restored only 25% of normal growth. While transplanting cell populations is feasible, the method will require a great deal of work before clinical application.
The influence of ibuprofen on fracture repair: Biomechanical, biochemical, histologic, and histomorphometric parameters in rats
Authors: Huo Michael H. , Troiano Nancy W. , Pelker Richard R. , Gundberg Caren M. , Friedlaender Gary E.
Published: February 2005

Ibuprofen is a widely used cyclo‐oxygenase inhibitor in clinical practice. It has been demonstrated by others to have an inhibitory effect on fracture repair in animals. In the present study, we were unable to demonstrate any significant alterations in fracture biomechanics as measured by torsion testing and fracture stage in mature Sprague‐Dawley rats treated with 30 mg/kg/day oral dose of ibuprofen, starting 3 days following fracture, over a 12‐week time interval. Fracture histology and serum osteocalcin levels were no different in treated animals than control animals. Furthermore, histomorphometric parameters of bone remodeling, including bone volume and bone formation rate in the intact tail vertebrae of these animals with unilateral femur fractures, were no different between treated and control animals.
Synthesis and characterization of magnetically responsive albumin microspheres containing cis‐hydroxyproline for scar inhibition
Authors: Iannotti J. P. , Baradet T. C. , Tobin M. , Alavi A. , Staum M.
Published: February 2005

Magnetically responsive albumin microspheres containing the proline analog, cis‐hydroxyproline, were synthesized and their in‐vitro physical properties were characterized. These microspheres have an average size of 1.1 ± 0.3 pm with 94% of the microspheres <2.0 pm. They are uniformly spherical and contain 67% albumin, 22% magnetite, and 8% cis‐hydroxyproline. The cis‐hydroxyproline is releasable during a 72‐h period and demonstrates a slow, releasable pool that constitutes approximately 50% of the incorporated drug. cis‐Hydroxyproline is neither chemically nor biologically altered during its incorporation into the microsphere. cis‐Hydroxyproline release from microspheres results in the in vitro inhibition of collagen secretion, which is indistinguishable from unincorporated cis‐hydroxyproline. In a rat‐tail animal model these microspheres were selectively targeted using an external magnetic field applied to a 1.5–2.0‐cm target site. Fifty to 80% of the infused microspheres were localized to this site, whereas without a magnetic field only 15–20% of the microspheres are localized to this site. cis‐Hydroxyproline microspheres resulted in a 16% decrease in collagen content in a scar model when compared with untreated animals (p < 0.05). With further refinement of this method of drug delivery, clinically useful inhibition of scar formation may result.
Culture‐expanded human periosteal‐derived cells exhibit osteochondral potential in vivo
Authors: Nakahara Haruhiko , Goldberg Victor M. , Caplan Arnold I.
Published: February 2005

Periosteal cells were enzymatically liberated from human rib periostea obtained from autopsies of 37 donors with an age distribution ranging from 25 weeks of gestation to 88 years old. These cells were introduced into cell culture and subcultured when they reached confluence. After subculture, the adherent periosteal‐derived cells showed a nondescript, fibroblast‐like morphology in cell culture. The cells from various passages of each donor were tested for in vivo osteochondrogenic potential with three different assay methods in athymic mice: (a) inoculation assay—the cells were directly inoculated into a subcutaneous site, (b) porous ceramics assay—the cells were combined with porous calcium phosphate ceramics, and this composite graft was implanted into a subcutaneous site, and (c) diffusion chamber assay—the cells were loaded into diffusion chambers and cultured in the peritoneal cavity. Frozen‐preserved and recultured periosteal‐derived cells were also assayed in the same way. In cases of donors younger than 19 years old, cultured, periosteal‐derived cells from up to several passages consistently formed bone and/or cartilage in each of the three assays. Frozen‐preserved and recultured cells from these donors also formed bone and/or cartilage after introduction into the three in vivo assays. In cases of donors older than 22 years of age, cultured, periosteal‐derived cells formed neither bone nor cartilage in vivo. Cultured muscle fibroblasts from some of the same donors did not form bone or cartilage when assayed in vivo under identical conditions. These results suggest that periosteal cells with osteochondrogenic potentials can be liberated from the periosteum of a rib of human donors up to a certain age. Importantly, this potential is retained after enzymatic liberation, cell culture, subculturing, and freeze preservation. The present results suggest that culture‐expanded human periosteal‐derived cells from young donors may be useful in the repair of skeletal defects to foster cell‐mediated regeneration of skeletal tissues, and that this methodology can be used to elucidate cellular, molecular, and genetic disorders in various metabolic bone diseases and skeletal dysplasias.
Localization of type X collagen in canine growth plate and adult canine articular cartilage
Authors: Gannon James M. , Walker Gordon , Fischer Mark , Carpenter Randy , Thompson Roby C. , Oegema Theodore R.
Published: February 2005

Type X collagen was extracted from ends of canine growth plates by pepsin digestion after 4 M guanidine hydrochloride extraction, purified by stepwise salt precipitation (2.0 M NaCl in 0.5 M acetic acid), and chromatographed on a Bio‐Gel A1.5 M column in 1.0 MCaCl2. Without reduction on sodium dodecyl sulfate (SDS) polyacrylamide gels, the preparation yielded a single, high‐molecular‐weight (mol wt) band; after reduction, a single band of relative mol wt 5.0 × 104 was found. Polyclonal sera were raised against the purified collagen and used in the immunolocalization of canine type X collagen. As expected, indirect immunoperoxidase (IP) or indirect immunofluorescent staining with the polyclonal sera demonstrated that most of the immunoreactivity was localized in the zone of provisional calcification of the growth plate and in cartilage remnants in the metaphyseal region of the physis. A progressive decrease in staining toward the diaphysis of the fetal canine long bone was apparent as the trabecular structures were remodeled to bone. Unexpectedly, type X collagen was also detected in the zone of calcified, mature articular cartilage. It was concentrated in the pericellular matrix of the chondrocytes, appeared at or just above the tidemark, and was expressed immediately before mineralization. Identification of type X collagen in both the canine growth plate and the zone of calcified articular cartilage suggests that cells in the deep layer of cartilage and in the zone of calcified cartilage in the adult animal retain some characteristics of a growth plate and may be involved in regulation of mineralization at this critical interface. The expression of growth plate‐like properties would allow the deep chondrocytes of mature articular cartilage to play a role in remodeling of the joint with age and in the pathogenesis of osteoarthritis.
Recombinant human insulin‐like growth factor‐I stimulates in vitro matrix synthesis and cell proliferation in rabbit flexor tendon
Authors: Abrahamsson Sven‐Olof , Lundborg Göran , Lohmander L. Stefan
Published: February 2005

Flexor tendons have an intrinsic ability for repair, with a capacity to metabolize matrix components and to proliferate. To identify factors with the potential of affecting those abilities, the effects of recombinant human insulinlike growth factor (rhIGF‐I), insulin and fetal calf serum (FCS) on the synthesis of proteoglycan, collagen, and non‐collagen protein and cell proliferation were investigated in short‐term explant cultures of the deep flexor tendon of the rabbit. Matrix synthesis and cell proliferation were stimulated dose dependently by rhIGF‐I at doses between 10 and 250 and at 10‐100 ng/ml, respectively, by insulin at 250–5,000 ng/ml, and by FCS at 2–15%. Estimated maximal stimulation (Emax) of up to three times the control value was observed with rhIGF‐I at 250 ng/ml. Maximal stimulation was observed at 5,000 ng/ml with insulin, and FCS at 15%. rhIGF‐I was more potent than insulin in stimulating protein synthesis and cell proliferation. The Emax of stimulation of proteoglycan and collagen synthesis by rhIGF‐I were two times that of FCS, and the Emax of cell proliferation by FCS was twice that of rhIGF‐I. Growth factors thus have the ability to stimulate matrix synthesis and cell proliferation in rabbit flexor tendon. This provides a rationale for further studies on the role of growth factors in flexor tendon healing in humans.
Effects of osteochondral defect size on cartilage contact stress
Authors: Brown Thomas D. , Pope David F. , Hale Joseph E. , Buckwalter Joseph A. , Brand Richard A.
Published: February 2005

Contact stress distributions were studied in vitro for 13 dog knees, with full‐thickness osteochondral defects drilled in the weight‐bearing area of both femoral condyles. Diameters of the circular defects were concentrically enlarged from 1 to 7 mm. Digitally‐imaged Fuji film was used to record cartilage contact stress distribution on femoral condyles for each increment of defect diameter. All specimens showed at least some tendency for contact stress concentration at the rim of the defects. However, detailed distributions had large interspecimen variability and, within a given specimen, contact stress distributions became progressively more nonuniform around the defect rim as the diameter was enlarged. Averaged over the full series of 26 condyles, circumferential mean cartilage contact stress around the defect rim was only moderately higher (by 10–30%) than intact surface's peak local contact stress [series average = 6.2 mega pascals (MPa)]. Maximal rim stress concentration occurred for 2 mm defects, there being a consistent trend toward mild rim stress decrease with further defect enlargement. Such modest contact stress elevations, per se, are probably insufficient to inhibit defect repair or to cause degeneration of surrounding cartilage. However, near the defect rim (for all diameters), the radial component of the gradient of contact stress (i.e., radialdirection variation of contact stress) was consistently elevated by an order of magnitude above that for intact, condyle articular cartilage.
Pattern of bone loss of the proximal femur: A radiologic, densitometric, and histomorphometric study
Authors: Kawashima Tadashi , Uhthoff Hans K.
Published: February 2005

The pattern of bone loss in the proximal femur was studied in 141 cadaveric femora from 36 women and 39 men ranging from 27 to 89 years of age. Bone mineral density (BMD) of the femoral neck, greater trochanter, Ward's triangle, and tensile and compressive stress regions were measured by dual photon absorptiometry. Radiographs were graded by Singh's method. Histomorphometry of tensile and compressive trabecular areas was performed on ground midsection of the methylmethacrylate‐embedded whole proximal femur. Although Singh index had some correlation with BMD of the femoral neck, the various BMD measurements showed that all regions lost bone to the same extent; in particular, no selective bone loss was found at low stress regions (tensile trabeculae or Ward's triangle). Histomorphometry revealed that most of the trabecular bone loss of the proximal femur is attributable to a decrease in thickness of individual trabeculae.
Mesenchymal stem cells
Authors: Caplan Arnold I.
Published: February 2005

Bone and cartilage formation in the embryo and repair and turnover in the adult involve the progeny of a small number of cells called mesenchymal stem cells. These cells divide, and their progeny become committed to a specific and distinctive phenotypic pathway, a lineage with discrete steps and, finally, end‐stage cells involved with fabrication of a unique tissue type, e.g., cartilage or bone. Local cuing (extrinsic factors) and the genomic potential (intrinsic factors) interact at each lineage step to control the rate and characteristic phenotype of the cells in the emerging tissue. The study of these mesenchymal stem cells, whether isolated from embryos or adults, provides the basis for the emergence of a new therapeutic technology of self‐cell repair. The isolation, mitotic expansion, and site‐directed delivery of autologous stem cells can govern the rapid and specific repair of skeletal tissues.
The effects of frequency and duration of controlled passive mobilization on tendon healing
Authors: Takai Shinro , Woo Savio L‐Y. , Horibe Shuji , Tung David K‐L. , Gelberman Richard H.
Published: February 2005

This study was designed to determine the effects of frequency and duration of controlled passive motion on the healing flexor tendon following primary repair. Adult mongrel dogs were divided into two groups based on frequency of controlled passive motion. In one group, motion was applied manually at a frequency of 12 cycles/min for 5 min/day; in the other group, a continuous passive motion machine was used to apply motion at a lower frequency of 1 cycle/min for 60 min/day, making the number of cycles each day for both groups identical. Gliding function and tensile properties of repaired tendons were evaluated biomechanically at 3 and 6 weeks postoperatively. Results showed that gliding function in both groups was similar, but tensile properties, as represented by linear slope, ultimate load, and energy absorption, were significantly improved in the higher frequency group. It was concluded that frequency of controlled passive motion rehabilitation is a significant factor in accelerating the healing response following tendon repair, and higher frequency‐controlled passive motion has a beneficial effect.