bluuebunny/crossref_metadata_2025 huggingface dataset:
Venous drainage of the femur permits passage of 100‐μm particles
Authors: Janssen Herbert F. , Robertson William W. , Berlin Sueleal
Published: February 2005

Iatrogenic metastasis of bone tumor is reportedly increased if aggregates of tumor cells enter the circulation. The current study used a previously developed animal model to explore the movement of 25‐, 50‐, and 100‐μ‐diameter particles from an experimental femur biopsy site into the circulation. The results indicate that cell aggregate‐sized particles can enter the circulation from the femur at a rate similar to that of the 15‐μm particles used in previous studies. Arterial blood samples collected during and after the injection of particles contained no 50‐ or 100‐μm particles, suggesting that the lung is an effective filter for these larger particles.
Pulsed electromagnetic fields alter phenotypic expression in chondroblasts in tissue culture
Authors: Norton Louis A. , Witt Davis W. , Rovetti Leslie A.
Published: February 2005

We hypothesize that pulsed electromagnetic fields (PEMF) alter phenotypic expression of chondroblasts by promoting the production of alkaline phosphatase (AP) and altering the structure of proteoglycans. Chondroblasts from the hypertrophic zone of tibial epiphyses (HC), sternum (SC), and skin fibroblasts (F) were cultured from 16 day chick embryos. Cultures were randomly designated control (C) or experimental (E). E received PEMF for 24 h in a 6 h on. 6 h rest sequence. The controls were in the same incubator shielded by Mu metal. Assays for AP activity were performed and normalized to protein content. Proteoglycan synthesis assay involved labeling with 35S fractionating in a 5% to 20% surcrose gradient determining total protein and chondroitin sulfate content. PEMF showed no change of AP activity on F. A high AP basal activity was found in HC, but was not increased above the control. PEMF increased AP in the SC samples (E/C ratio). The sucrose gradient data showed a shift in peaks for SC only altering the ratio of carbohydrate to protein for the SC. Analysis of carbohydrate and protein indicated that the effect was decreased synthesis or degradation of protein. We conclude that PEMF alters the phenotypic expression of sternal chondroblasts in our in vitro system.
Inhibition of epiphyseal cartilage collagenase by tetracyclines in low phosphate rickets in rats
Authors: Greenwald Robert A. , Simonson Barry G. , Moak Susan A. , Rush Scott W. , Ramamurthy N. S. , Laskin Richard S. , Golub Lorne M.
Published: February 2005

Drugs in the tetracycline family can inhibit mammalian tissue collagenase both in vitro and in vivo by a mechanism that is independent of antibiotic action. The epiphyseal cartilages of rachitic rats contain extremely high levels of collagenase (CGase), and we have used this model to study further the phenomenon of tetracycline inhibition of tissue CGase. Rickets was induced in rats by phosphate/vitamin D deficiency and parameters of gross bone morphology, bone chemistry, and serum chemistry were evaluated in both rachitic and nonrachitic animals with and without treatment with oral tetracyclines (TETs). Minocycline (or doxycycline) partially suppressed the appearance of many of the expected changes in the rachitic animals, including gross bone hardness, growth plate widening, long bone length, suppression of weight gain, and decreased bone ash content. The effects were dose dependent and were associated with marked suppression of the enhanced CGase activity. Examination of collagen breakdown products by SDS‐PAGE documented that the rachitic enzyme behaved like other mammalian collagenases including in vitro inhibition with minocycline 10–20 μg/ml and with a nonantibiotic tetracycline. No evidence of TET osseous toxicity was noted, and, in fact, administration of TET to nonrachitic animals had a mildly favorable effect on growth and development. TET suppression of CGase can be demonstrated in a well defined model system and this form of pharmacologic enzyme inhibition can be a useful probe for delineating the role of the enzyme in connective tissue pathology.
Limb lengthening by diaphyseal corticotomy, callus distraction, and dynamic axial fixation. An experimental study in the ovine femur
Authors: Steen Harald , Fjeld Terje O. , Bjerkreim Ingjald , Tevik Asbjørn , Aldegheri Roberto , Trivella Giampaolo
Published: February 2005

Limb lengthening of the left femur was performed in 12 sheep, 7–8 months of age. After weakening of the cortex by drill holes, a controlled fracture was created in the diaphysis. The bone segments were fixed in reduced position using a unilateral external fixation device. The fixator was left in neutral position for 10 days postoperatively when lengthening started. By means of daily distraction at a rate of 1.0 mm once a day for 3 weeks, an average lengthening of 1.9 cm (11.9%) was obtained. Two weeks after distraction had been discontinued, distinct callus bridging of the lengthening zone was confirmed radiographically in all animals. At this time the rigid state of fixation was converted to a system allowing axial compression by loading in half the animals. The other half of the animals served as controls with the fixator remaining unchanged. The external device was left on until 5 weeks after the end of distraction. At this time the animals were killed. Both femora of all animals were tested mechanically in torsion. The average ultimate torsional strength of the elongated femur compared with control was 71% in the group with dynamic axial fixation and 65% in the control group. No significant difference in relative strength of the tested bones in the two groups was found. We conclude that intermittent axial compression by loading during consolidation had no significant effect on the bone‐healing process evaluated by radiography and mechanical testing.
Correlations between mechanical stress history and tissue differentiation in initial fracture healing
Authors: Carter D. R. , Blenman P. R. , Beaupré G. S.
Published: February 2005

A general theory for the role of intermittently imposed stresses in the differentiation of mesenchymal tissue is presented and then applied to the process of fracture healing. Two‐dimensional finite element models of a healing osteotomy in a long bone were generated and the stress distributions were calculated throughout the early callus tissue under various loading conditions. These calculations were used in formulating theoretical predictions of tissue differentiation that were consistent with the biochemical and morphological observations of previous investigators. The results suggest that intermittent hydrosatic (dilatational) stresses may play an important role in influencing revascularization and tissue differentiation and determining the morphological patterns of initial fracture healing.
Mechanical and physicochemical determinants of the chondrocyte biosynthetic response
Authors: Gray Martha L. , Pizzanelli Angelina M. , Grodzinsky Alan J. , Lee Raphael C.
Published: February 2005

The relation between mechanical loading of cartilage and chondrocyte activity in vivo may be mediated by several physical transduction mechanisms including: cell deformation, hydrostatic pressure gradients, fluid flow, streaming currents, and physicochemical changes. We have developed an organ culture system designed to study chondrocyte biosynthetic response to such physical stimuli. This study focuses on the effects of static compression and physicochemical changes. Cartilage disks harvested from the reserve zone of the epiphyseal plate of 1–2‐week‐old calves were subjected to static compressive stresses of 0–3 MPa in unconfined compression and the incorporation of [35S]sulfate and [3H]proline was measured during the 12‐h loading period. Incorporation of both proline and sulfate decreased monotonically with increasing stress. Compressive loading also produces physicochemical changes including a decreased water content and increased matrix fixed‐charge density, with a concomitant increase in interstitial counterion concentrations (e.g., K+, H+) and decreased coion concentrations (e.g., SO42−). We therefore examined the possibility that specific changes in interstitial mobile ion concentrations may be linked to chondrocyte response to static compression by measuring biosynthesis in the absence of mechanical compression while independently altering the SO42−, K+, and H+ composition of the bathing medium. We found that proline and sulfate incorporation were strongly dependent on pH, but independent of [SO42−]and [K+] in the range studied. These results suggest that compression‐induced changes in local, interstitial pH may account for the observed biosynthetic response to static compression.
The role of mechanical loading histories in the development of diarthrodial joints
Authors: Carter Dennis R. , Wong Marcy
Published: February 2005

The possible role of mechanical loading history in chondroosseous development at the ends of long bones is explored using two‐dimensional finite element models of chondroepiphyses. Loading histories are characterized in terms of discrete loading cases defined by joint contact pressure distributions and an associated number of loading cycles. An osteogenic stimulus throughout the chondroepiphyses is calculated following the theory that cyclic octahedral shear stresses promote endochondral ossification and cyclic compressive dilatational stresses inhibit ossification. The resulting distributions for the osteogenic stimulus predict the appearance of the secondary ossific nucleus and the shape of the developing bony epiphysis. The zone of Ranvier and the formation of articular cartilage and the growth plate are also predicted by the models. These findings are consistent with the hypothesis that tissue stress histories constitute an important influence during skeletal morphogenesis. Further study and testing of the concepts introduced in this study are appropriate.
Contact stress aberrations following imprecise reduction of simple tibial plateau fractures
Authors: Brown Thomas D. , Anderson Donald D. , Nepola James V. , Singerman Robert J. , Pedersen Douglas R. , Brand Richard A.
Published: February 2005

Despite the well‐recognized association between poorly reduced intraarticular fractures and late degenerative changes, current guidelines regarding the reduction precision necessary to avoid excessive cartilage pressures are based largely on anecdotal clinical observations. To gain a quantitative appreciation of the relation between local pressure elevations and fracture reduction imprecision, a simplified laboratory cadaver model of minimally displaced tibial plateau fractures was developed. Cartilage contact stress distributions were measured as a function of depressed fragment malreduction in seven knees, using high‐resolution (100 pixels/mm2) digital image scans of Fuji‐film stain patterns. The contact stress data showed a general trend of increases of peak local pressure with increasing fracture site incongruity, and in a few isolated instances the effect was very pronounced. Across the whole series, however, statistically significant departures from anatomic pressure levels did not occur until the fragment stepoff was >1.5 mm. Even at the 3‐mm stepoff level, for which the depressed fragment usually no longer made contact with the femoral condyle, the peak local pressure values on the intact side of the fracture line averaged only ∼75% greater than those prevailing anatomically. Given the successful clinical outcomes normally achieved for conservatively managed simple tibial plateau fractures having stepoff magnitudes (5–10 mm) clearly sufficient to insure fragment articular noncontact, the present laboratory results suggest that nominally factor‐of‐two peak local pressure elevations, provided that they occur over only small portions of the cartilage surface, are probably within the long‐term overall tolerance range of an articular joint.
Reconstruction of the digital pulley in the monkey using biologic and nonbiologic materials
Authors: Kain Christopher C. , Manske Paul R. , Reinsel Tom E. , Rouse Andrew M. , Peterson William W.
Published: February 2005

A‐2 pulleys were replaced in the hand of the nonhuman primate; on the long/little fingers the pulleys were reconstructed with a woven nylon fabric (Nitex), and on the ring/index fingers the pulleys were reconstructed with fascia lata. The opposite unoperated hand served as a control. At 2, 3, and 6 months postoperative, the animals were killed to compare the function of the reconstructed pulleys with the control pulleys of the opposite digit. Using a tensile testing machine, two parameters, work of flexion and tendon excursion, showed that both pulley reconstructions permitted minimal tendon bowstringing and had excellent gliding function. Both materials increased in strength over time to become stronger than the control pulley. Histologic examination showed no foreign body reaction to the Nitex; excellent fibrous ingrowth into the woven nylon was seen, which matured in time. The surface of the Nitex pulley facing the tendon developed and maintained a synovial‐like gliding surface. The Nitex pulley compared favorably with the fascial pulley biomechanically and histologically; both reconstructed pulleys functioned well compared with normal pulleys.
Sex differences in age‐related remodeling of the femur and tibia
Authors: Ruff Christopher B. , Hayes Wilson C.
Published: February 2005

Changes with age in cross‐sectional geometry of the lower limb bones were investigated in a large sample of cadaveric skeletal material from U.S. white adults. Section properties (areas and second moments of area) were determined at 11 locations by sectioning and direct measurement of 103 femora and 99 tibiae. All properties were standardized for body size differences by dividing by powers of bone length, and age trends were determined through linear regression analysis. Results indicate that while both men and women undergo endosteal resorption of bone and medullary expansion with aging, only men exhibit concurrent subperiosteal bone apposition and expansion. As a consequence, men show little change in cortical area and some increase in second moments of area with age, while women show decreases in both cortical area and second moments of area. Thus, only men appear to remodel bone in a way that would tend to compensate for loss of bone material strength with aging. In a previous study of a preindustrial sample with high activity levels, both men and women exhibited bone subperiosteal expansion and increase in second moments of area with aging. Together with observed differences in fracture incidence among living populations, these findings suggest that relatively low activity levels may not stimulate optimal bone remodeling throughout life and thus may contribute to higher risk of fracture in old age.
Prevention of ligament and meniscus atrophy by active joint motion in a non–weight‐bearing model
Authors: Klein Leroy , Heiple Kingsbury G. , Torzilli Peter A. , Goldberg Victor M. , Burstein Albert H.
Published: February 2005

This study describes the effect of active joint motion on the maintenance of ligament and meniscus mass in a non–weight‐bearing model of disuse. Denervation and fixation models of immobilization have shown that resorption of isotope and atrophy of mass occured for hard tissue (bone) and soft tissues (ligament, tendon, or meniscus). A unilateral ankle disarticulation model of disuse that maintains active knee motion without weight bearing was studied for 8 weeks in dogs that were chronically prelabeled with three different isotopes. The effects of non–weight‐bearing without denervation or fixation were analyzed for the resorption of isotopes, and net atrophy of bone mass (femur or tibia) and soft‐tissue mass (collateral or cruciate ligaments, menisci). A large and similar loss of all three isotopes, as well as collagen and calcium mass occurred for whole femur and tibia; this indicated that mass loss was equivalent to bone resorption and suggests little replacement with new bone. No loss of isotope or mass per whole tissue occurred for the collateral and cruciate ligaments or menisci. The strength of the femur–anterior cruciate ligament–tibia complex was analyzed by a tensile failure test when a fast rate of deformation was applied; the results did not differ qualitatively or quantitatively between control and experimental limbs. The absence of weight bearing for 8 weeks resulted in marked bone atrophy without resorption or atrophy of soft tissues, or decrease of the mechanical strength for the femurligament–tibia complex. With this model the amount of active joint motion remaining appears able to prevent ligament and meniscus atrophy even though marked bone atrophy occurred during this period.
Calcitonin and fracture healing. An experimental study on rats
Authors: Paavolainen Pekka , Taivainen Tomi , Michelsson Jan‐Erik , Lalla Martti , Penttinen Risto
Published: February 2005

The effects of systemically administered calcitonin (CT) on fracture healing were analyzed in an experimental study on rats. The healing of a fracture was followed from 3 days up to 9 weeks postoperatively. Half of the rats in each age group were given daily CT 10 MRC‐U/kg body wt s.c. Mechanical properties of the healing tibial fractures (tension strength) as well as various connective tissue components of the callus tissue were analzyed. No difference in the radiological or microscopical appearance of the fractures was detectable between the animals receiving CT and the controls. In the biochemical analysis matrix production as assessed from the concentrations of nitrogen, hexosamines, and hydroxyproline within the callus followed the usual lines of undistributed fracture union without any difference between the groups with and without CT. No differences could be detected in the mineralization of the callus between the specimens from animals receiving CT and those without. The tensile strength values of the fractures increased almost linearly up to 9 weeks. At 1 week the tensile strength values for fractures union in the animals without CT were ∼50% higher, but later on no differences could be detected between the groups. These results indicate that although in the early phases of long‐term CT therapy collagen synthesis may be impaired, there will be no effect on the net content of collagen or calcifying tissue in the callus or on the mechanical strength of healing fractures.
Transpedicular screw fixation
Authors: Moran James M. , Berg William S. , Berry James L. , Geiger Jack M. , Steffee Arthur D.
Published: February 2005

Spinal fixation employing transpedicular screws has recently been the focus of increased attention at various institutions throughout the world, but concerns about the safety and efficacy of transpedicular screws linger. This study was undertaken to address some of these concerns. The study included evaluation of the internal and external morphology of the vertebral pedicles, which revealed that adequate bone stock is generally available at T2, T7, T12, and L1–L5 spinal levels to accept screws in the 4–7‐mm diameter range. The pedicle was observed to be composed of abundant cancellous bone internally with relatively thick cortical walls. The method of pilot hole preparation for pedicle screws was also examined. Screws inserted in pilot holes prepared with a 3.4‐mm blunt probe (ganglion knife) resulted in higher pullout forces in eight of 10 trials as compared with those with pilot holes prepared using a 3.2‐mm drill. Furthermore, the probes afford greater control of hole depth and alignment. Fatigue studies on three screws designs revealed a graduation of strength between a 7.0‐mm pedicle screw, and a modified 6.5‐mm cancellous lag screw. The modified cancellous lag screw has an inherent stress riser that affected fatigue life. It was noted that extreme care must be exercised to prevent bending of the pedicle screws during implantation. If bending ocurs one can expect a 50% reduction in the number of cycles to failure.
Early histologic, metabolic, and vascular assessment of anterior cruciate ligament autografts
Authors: Kleiner Jeffery B. , Amiel David , Harwood Fred L. , Akeson Wayne H.
Published: February 2005

A rabbit model for anterior cruciate ligament (ACL) reconstruction using autogenous patellar tendon was utilized to study the early events of autograft cellular dynamics. Biochemical, autoradiographic, histological, and vascular injection techniques demostrated that the native autograft cell population rapidly necroses. This repopulation occurs without a vascular contribution; cells entering the autograft are reliant upon synovial fluid nutrition.
Partial restoration of immobilization‐induced softening of canine articular cartilage after remobilization of the knee (stifle) joint
Authors: Jurvelin J. , Kiviranta I. , Säämänen A.‐M. , Tammi M. , Helminen H. J.
Published: February 2005

The restoration of the biomechanical properties of articular cartilage was studied after 15 weeks of remobilization of the knee joint in beagles previously immobilized with a cast for 11 weeks. The shear moduli were determined with an indentation creep test immediately after load application and at equilibrium at six predefined test points of femoral, tibial, and patellar cartilages. Permeability of the cartilage was estimated from the creep measurements. The values were compared with nontreated, age‐matched (55 weeks) controls and with cartilage collected immediately after immobilization. Remobilization reduced the high creep rates created by immobilization and shifted the depressed equilibrium shear moduli towards those of the controls. However, in the femoral condylar cartilage, the equilibrium shear modulus remained at lower level (p < 0.05) and permeability at higher level (p < 0.05) as compared with the controls. We conclude that articular cartilage, showing signs of atrophy after long‐term immobilization, was capable of restoring its biomechanical properties during remobilization. This repair was not, however, completed in all parts of the knee joint by the end of the observation period.
Sensory innervation of soft tissues of the lumbar spine in the rat
Authors: Cavanaugh John M. , El‐Bohy Ashraf , Hardy Warren N. , Getchell Thomas V. , Getchell Marilyn L. , King Albert I.
Published: February 2005

The purpose of this study was to investigate neurophysiologically and anatomically the soft tissues of the dorsal compartment of the lumbar spine in order to understand better their possible role in low back pain. The focus was primarily on the lumbar facet joint and supraspinous ligament of the Sprague–Dawley rat. Microdissection of the dorsal ramus and electrophysiological and neuroanatomical studies of the dorsal ramus and its terminations in paravertebral tissue revealed that (a) there are mechanosensitive, slowly adapting fibers in the rat lumbar facet joint capsule; (b) there are slowly adapting, mechanosensitive units in the rat supraspinous ligaments that respond to tensile loading; both types of mechanosensitive units have high threshold; (c) mechanical stimulation of these tissues sometimes elicits afterdischarges lasting several minutes; (d) many extracellular recordings from the medial branch of the dorsal ramus appear to be reflex activity to mechanical stimulation; (e) silver impregnation of the rat joint capsule reveals individual axons, very few of which were encapsulated, suggesting that they terminate in free nerve endings; and (f) the nerves of the rat facet joint capsule contain 68, 160, and 200 kdalton polypeptide subunits of neurofilament protein (NFP). These results indicate that neurons of lumbar facet joint capsules and ligaments in the back are sensitive to mechanical strain and that the higher threshold neurons may serve a nociceptive (pain) function.
The effect of external fixation stiffness on early healing of transverse osteotomies
Authors: Gilbert Jerome A. , Dahners Laurence E. , Atkinson Melissa A.
Published: February 2005

The effect of bending stiffness of external fixators on the early healing of transverse tibial osteotomies was studied in a canine model to determine whether there is a particular range of fixation stiffness where healing is poor. Five unilateral fixators with different stiffnesses were developed and employed along with a dynamic compression plate to fix experimental osteotomies of dog tibias and the contraiateral intact tibias served as controls. The six experimental fixation devices were: plate (P), stainless steel sidebar fixator (SS), stiff aluminum sidebar fixator (SA), intermediate aluminum sidebar fixator (IA), flexible aluminum sidebar fixator (FA), and Delrin sidebar fixator (D). Compared with human tibial fixation methods, the fixators ranged from a rigidity greater than a plate on a human tibia to a flexibility similar to a plaster cast on a human lower leg. Sixty‐four adult male mongrel dogs (29 ± 3 kg) underwent surgery and 52 completed the 9‐week study, leaving 7 to 10 dogs in each experimental group (P = 8, SS = 7, SA = 9, IA = 9, FA = 10, D = 9). After the 9‐week survival period the experimental tibias were radiographed and callus area was digitized. Both the experimental and control tibias were then tested to failure in four‐point bending, and failure moment, stiffness, and energy to failure were determined. Of the 52 osteotomies, only four developed nonunions: 3 of 10 in the FA group and 1 of 7 in the SS group. Using analysis of variance, no statistical differences were detected in failure force, stiffness, or energy to failure as a function of fixator groups. The mean callus area in the most flexible fixation group (D) was significantly greater than that in the P, SS, and IA groups.
Laser doppler flowmetry for bone blood flow measurements: Helium–neon laser light attenuation and depth of perfusion assessment
Authors: Nötzli Hubert P. , Swiontkowski Marc F. , Thaxter Steven T. , Carpenter George K. , Wyatt Robert
Published: February 2005

Laser Doppler flowmetry (LDF) has been successfully used in clinical and experimental settings to evaluate bone perfusion but unanswered questions regarding its capabilities and limitations still remain. This study was undertaken to determine absorption of He–Ne laser light (632.8 nm) and maximum depth for flow assessment (threshold thickness) under optimal conditions in bone. Light transmittance in bovine bone samples of femora and tibia was measured after each step of grinding and depth of penetration calculated. The threshold thickness was obtained by placing the same samples in a flow chamber where a solution of 2% latex circulated beneath; flow was detected by a laser Doppler probe resting on top of the sample. The results showed a significantly higher depth of penetration for trabecular than for cortical bone. A regression analysis showed a high correlation between the inorganic fraction of the bone and the depth of penetration. The maximum depth at which the laser Doppler probe can evaluate flow in bone conditions was found to be 2.9 ± 0.2 mm in cortical bone, 3.5 ± 0.3 mm in bone covered by 1 mm cartilage and 3.5 ± 0.2 mm in trabecular bone. The study showed the limitations of LDF in bone and their correlations to various bone properties.
Pressures in the distal radioulnar joint: Effect of surgical procedures used for kienbock's disease
Authors: Werner Frederick W. , Murphy Dennis J. , Palmer Andrew K.
Published: February 2005

Radial shortening and ulnar lengthening are two accepted surgical methods for treating Kienbock's disease. The effect of these procedures on the pressure within the distal radioulnar joint between the ulnar head and the sigmoid notch of the radius was experimentally evaluated in six fresh cadaver forearms. Radial shortening and ulnar lengthening led to increased pressure at the distal radioulnar articulation and caused shifting of the location of the center of pressure distally within the sigmoid notch. Radial displacement of the distal radial fragment at the time of radial shortening, however, decreased the peak pressures. Based on these experimental data, ulnar lengthening and radial shortening can be expected to alter the normal biomechanics of the distal radioulnar joint.
Kinetic and biochemical heterogeneity in vertebrate chondroepiphyseal regions during development
Authors: Diao Edward , Zaleske David J. , Avella Douglas , Trahan Carol , Armstrong Ann , Ehrlich Michael G. , Mankin Henry J.
Published: February 2005

The purpose of this study was to see if kinetic and biochemical heterogeneity could be documented in vertebrate chondroepiphyseal regions as they develop from mesenchymal condensations to cartilage. The kinetics of developing proximal and distal femoral chondroepiphyseal regions were studied from early limb bud stage to newborn animals in chicks, mice, and rabbits with thymidine autoradiography. Proteoglycan synthesis in the proximal femoral chondroepiphyseal region of the rabbit was studied with radioactive sulfate incorporation at 28 days of gestation and at 1 and 4 days after birth. The results indicated that these kinetic and biochemical characteristics of the developing chondroepiphyseal regions became heterogeneous very early in development. This early programming of populations of cells for division and for different biochemical functions existed during the fetal period when heterogeneity has been described histologically but has not been well documented.
A study of the mechanical strength of long bone defects treated with various bone autograft substitutes: An experimental investigation in the rabbit
Authors: Hopp Stanley G. , Dahners Laurence E. , Gilbert Jerome A.
Published: February 2005

This study was designed to determine which of several bone grafting materials would be the most efficacious substitute for autogenous bone graft in the treatment of segmental long bone defects. The experimental model was a 1‐cm defect in the rabbit ulna. The control group had nothing implanted in the defect. The six grafts tested were: (a) autogenous iliac crest bone, (b) autogenous cortical bone (ulna), (c) hydroxylapatite, (d) hydroxylapatite–demineralized bone matrix (allograft) composite graft, (e) freeze‐dried bone (allograft), and (f) demineralized bone matrix (allograft). At 6 weeks postoperatively, the ulnas were harvested, examined radiographically, and tested mechanically in torsion.

The radiographic examination proved to be of little value because some materials were radiodense at the time of implantation. The rates (percentage) of union, torques at failure, and energy to failure values were statistically significantly higher than control for all groups except hydroxylapatite.

We concluded that demineralized bone matrix and hydroxylapatite–demineralized bone matrix composite graft compare favorably with cortical replacement (autograft) in mechanical strength and rate of union and therefore may be satisfactory substitutes for bone grafting. Freeze‐dried bone did not appear to be as satisfactory because of its low mean energy to failure, but statistical analysis failed to confirm this opinion. Hydroxylapatite graft, when used alone, does not appear to be a suitable material for grafting segmental bone defects.
Effects of a scaphoid waist osteotomy on carpal kinematics
Authors: Smith D. K. , An K. N. , Cooney W. P. , Linscheid R. L. , Chao E. Y.
Published: February 2005

The effects of a scaphoid osteotomy on the kinematics of the carpal bones were determined in five cadaveric wrist specimens. Minute radiographic markers were inserted into the distal radius and selected carpal bones through limited arthrotomies between the intercarpal ligaments. Simultaneous biplanar radiographs were obtained in neutral and the extreme wrist positions of extension, flexion, radial deviation, and ulnar deviation, both before and after a scaphoid waist osteotomy. The positions of each of the carpal markers and their corresponding carpal bones were digitized for each wrist position, and a computer‐assisted motion analysis was performed for each specimen before and after transverse scaphoid waist osteotomy. Following the osteotomy, there was a tendency for the scaphoid osteotomy to collapse into a dorsally angulated or “humpback collapse” deformity during each extreme wrist position. There was also multiplanar osteotomy site motion as well as complex collapse deformities of the midcarpal joint associated with loss of the mechanical tie‐rod function of the scaphoid. These findings reveal the importance of the scaphoid in maintaining normal kinematics and the inherent instability of these fractures with loss of scaphoid integrity.
The evaluation of bone remodeling about orthopaedic implants with ultrasound
Authors: Zimmerman Mark C. , Meunier Alain , Katz J. Lawrence , Christel Pascal , Sedel Laurent
Published: February 2005

Total hip arthroplasty causes biomechanical changes in the normal femur, including a redistribution and concentration of stress. These mechanical alterations in the femur cause local remodeling and resorption that affect the geometry and mechanical properties of the bone. Two complementary ultrasonic techniques were used to study the local adaptive remodeling of bone due to prosthesis implantation. An ultrasonic wave propagation technique was used to determine elastic properties and a new scanning acoustic microscope (SAM) mapped the acoustic impedance profile of each section. The effects of the implantation of two types of hip prostheses, an uncemented bipolar prosthesis with an Austin‐Moore type stem and a cemented Charnley prosthesis, were investigated. Both prostheses had a detrimental effect on local elastic properties as determined by acoustic velocity measurements. The SAM system provided information about local inhomogeneities in bone properties not obtainable by any other means. The acoustic impedance maps highlighted bone resorption and bone remodeling on a microstructural level.
Proliferative and synthetic response of bovine growth plate chondrocytes to various capacitively coupled electrical fields
Authors: Brighton Carl T. , Jensen Loren , Pollack Solomon R. , Tolin Brad S. , Clark Charles C.
Published: February 2005

In vitro monolayer cultures of growth plate chondrocytes isolated from newborn calf costochondral junctions were subjected to capacitively coupled electrical fields for 48 h. In part A, the electrical signal was a 60‐kHz sine wave applied at different voltages so as to produce electrical fields at the pericellular level of 7, 20, 50, and 126 mV/cm. Incorporations of [3H]thymidine and [35S]sulfate were assayed to determine the effect of the above fields on cell proliferation and matrix synthesis, respectively. Proliferation was increased by 47% in the 20 mV/cm field whereas the same field decreased [35S]sulfate incorporation by 21%. These changes were significant at p < 0.05 in both instances. In part B, the 20 mV/cm field was applied in a pulsed fashion to produce daily duty cycles of 100. 25, 2, and 0.25%. Incorporation of [3H]thymidine, [35S]sulfate, and [14C]proline per DNA were assayed. Results indicated that the 100, 25, and 0.25% percent duty cycles showed significantly (p < 0.01–0.05) increased proliferation, whereas the 0.25% signal (5 ms on/495 ms off for 6 h/day) significantly decreased [14C]proline incorporation. We conclude that the biologic response of cells in vitro is signal specific, and that the total amount of electrical energy required to stimulate the growth plate chondrocyte to increased proliferation is very small since the total time the 0.25% duty cycle signal was only 3.6 min of a 24‐h period.
Drug‐induced inhibition of proteoglycanase activity in the hulth–telhag model
Authors: Ishizue Kenneth K. , Ehrlich Michael G. , Mankin Henry J.
Published: February 2005

Evidence has accumulated that there are increased degradative enzymes in osteoarthritis responsible for joint destruction. These enzymes are metal‐dependent, and inhibited by EDTA. EDTA was administered intraarticularly to rabbits in an experimental model of osteoarthritis. There was a 25% reduction in neutral proteoglycanase activity and 75% of the animals had a reduction in the severity of the arthritis as measured on a histologic‐histochemical grading system. It is suggested that future chemotherapeutic studies on arthritis might focus on enzyme inhibition.
Repeatability of kinematic, kinetic, and electromyographic data in normal adult gait
Authors: Kadaba M. P. , Ramakrishnan H. K. , Wootten M. E. , Gainey J. , Gorton G. , Cochran G. V. B.
Published: February 2005

The repeatability of gait variables is an important consideration in the clinical use of results of quantitative gait analysis. Statistical measures were used to evaluate repeatability of kinematic, kinetic, and electromyographic data waveforms and spatiotemporal parameters of 40 normal subjects. Subjects were evaluated three times on each test day and on three different test days while walking at their preferred or natural speed. Intrasubject repeatability was excellent for kinematic data in the sagittal plane both within a test day as well as between test days. For joint angle motion in the frontal and transverse planes, the repeatability was good within a test day and poor between test days. Poor between‐day repeatability of joint angle motion in the frontal and transverse planes was noted to be partly due to variabilities in the alignment of markers. Vertical reaction and fore–aft shear forces were more repeatable than the mediolateral shear force. Sagittal plane joint moments were more repeatable than frontal or transverse plane moments. For electromyographic data, repeatability within a day was slightly better than between test days. In general, the results demonstrate that with the subjects walking at their natural or preferred spped, the gait variables are quite repeatable. These observations suggest that it may be reasonable to base significant clinical decisions on the results of a single gait evaluation.
Effect of age on the abundance and fragmentation of link protein of the human intervertebral disc
Authors: Pearce R. H. , Mathieson J. M. , Mort J. S. , Roughley P. J.
Published: February 2005

The link proteins of the human intervertebral disc were studied in tissue extracts by sodium dodecyl sulfate/polyacrylamide gel electrophoresis (SDS/PAGE), followed by immunoblotting, using a specific monoclonal antibody. Three link proteins were detected, corresponding in electrophoretic mobility to those present in articular cartilage. As with articular cartilage, the largest link protein predominates in the young, whereas in the adult the smallest link protein is equally abundant and internal fragmentation of the link proteins occurs. Only in the newborn is the quantity of extractable link protein comparable to that from articular cartilage. In the adult, the disc contains much less link protein than is present in autologous articular cartilage. Neither the amount nor heterogeneity of the link protein differs among different levels within the lumbar spine, although the proportions of the three proteins can differ between the anulus fibrosus and nucleus pulposus. The anulus always contained more extractable link protein, relative to tissue wet weight than the nucleus, and the nuclear link protein, at least in adolescents, contained a greater proportion of the smallest link protein. Such changes in the quantity and structure of the disc link proteins may affect the properties of the proteoglycan aggregates and, thus, could influence disc function.
Cytochemical evidence for a proteoglycan‐associated filamentous network in ligament extracellular matrix
Authors: Bray D. F. , Frank C. B. , Bray R. C.
Published: February 2005

The purpose of this investigation was to examine the extracellular matrix of rabbit ligament before and after digestion with glycosaminoglycan degrading enzymes. In order to preserve and enhance the visibility of negatively charged tissue components, particularly the glycosaminoglycancontaining proteoglycans, the, cationic stains ruthenium red (RR) and ruthenium hexammine trichloride (RHT) were used. Cross‐sections of the midsubstance of 10‐month‐old (mature) rabbit medial collateral ligaments fixed using conventional procedures revealed a sparse population of stellate‐shaped cells that did not appear to be interconnected. Similar tissue fixed in either RR or RHT showed an extensive network of thin, electron‐dense “seams” that interconnected cells and appeared to irregularly subdivide the extracellular matrix (ECM). These seams mainly consisted of a meshwork of microfilaments throughout which small granules were dispersed. Numerous 14‐nm microfibrils, as well as mature elastic fibers were also present within the seams. The size and shape of the microfilaments, together with their threadlike, beaded appearance suggested that they could be Type VI collagen. The seam granules were easily removed with chondroitinase ABC, chondroitinase AC II, and mild (0.18 M) salt treatment. Only chondroitinase ABC succeeded in removing additional granules, tentatively identified as proteodermatan sulphate molecules, that were periodically located at d band sites along the Type I collagen fibrils. These results suggest that the seam granules are not dermatan sulphate containing proteoglycans, and further, that these proteoglycans may be sequestered into specific zones within the ECM through loose association with the seam microfilaments. While the functional significance of the seams remains unknown and their specific composition clearly requires further study, it is likely that they represent important functional (e.g., viscoelastic) or biological (e.g., nutritional) subdivisions of ligament substance.
Transplantation of the rabbit medial collateral ligament. I. Biomechanical evaluation of fresh autografts
Authors: Sabiston P. , Frank C. , Lam T. , Shrive N.
Published: February 2005

This investigation was designed to study the biomechanical recovery of a free bone‐ligament‐bone graft that was returned to its normal extraarticular position, with as little disturbance to its mechanical and biological environments as possible. Twenty‐five adult New Zealand white rabbits had their right bone‐medial collateral ligament (MCL)‐bone complex removed completely and replaced immediately using internal fixation. Animals were allowed unrestricted cage activity before sacrifice in groups of five at intervals of 3, 6, 12, 24, and 48 weeks posttransplantation. Contralateral legs served as internal controls and a separate series of normal animals served as external controls. All MCLs were tested biomechanically using a detailed testing protocol. Results showed early deterioration of 20–35% in autograft complex structural behavior, with weakening of both ligament substance and insertions. Viscoelastic behavior of these ligaments was also affected, showing increases in the amount of both cyclic load‐relaxation and static load‐relaxation at early healing intervals. These properties were statistically indistinguishable, however, from controls at 48 weeks. Failure behavior of autografts was even better preserved, reaching a low of 65% of control values at 24 weeks and recovering to within 10% of controls at 48 weeks. These results, plus the major changes in failure modes that occurred over that duration, suggest that autograft incorporation is a slow but dynamic process. These results further suggest that at least some connective tissue autografts, when placed under, as yet undefined, “proper biological and mechanical conditions,” can retain and recover a number of biomechanical properties over a period of 1 year. The longer‐term fate of these autografts and the exact nature of their similarities or differences from other graft alternatives (e.g., tendon for ligament), however, is unknown.
Stability of initial fixation of the tibial component in cementless total knee arthroplasty
Authors: Shimagaki Hitoshi , Bechtold Joan E. , Sherman Robert E. , Gustilo Ramon B.
Published: February 2005

This study measured the vertical displacement of three kinds of cementless tibial components [Porous Coated Anatomical (PCA), Tricon, and Whiteside], under eccentric loading up to 2,225 N. Displacement between the tibial tray and the proximal tibia was measured with linear variable differential transformers at the anterior and posterior side when anteriorly or posteriorly loaded, and at the medial and lateral side when medially or laterally loaded. The general pattern of motion was sinking at the loaded side and lift‐off at the opposite side and lift‐off at the opposite side. Lift‐off opposite the loaded side was fairly small for all components at all measurement sites. Among the three components, the Whiteside showed the smallest displacements. The Tricon (when anteriorly or posteriorly loaded), and the PCA (when medially or laterally loaded) showed sinking at the loaded side. Anterior screw fixation of the PCA was not effective in preventing anterior lift‐off. The tilting motion of the tibial components obseved in this study implies instability of the initial fixation, which could possibly compromise bony ingrowth. Furthermore, this tilting could cause uneven distribution of load, and potentially result in fracture of the underlying bone.
In vitro and in vivo effects of metal chelators on cartilage metabolism
Authors: Ehrlich Michael G. , Stefanich Ray , Ishizue Kenneth K. , Armstrong Ann L. , Mankin Henry J.
Published: February 2005

The effect of metallic chelating agents (EDTA, EGTA) on cartilage metabolism was studied both in vitro, on calf cartilage, and in vivo, in rabbits. The question asked was whether it was possible to affect neutral protease activity, and not also inhibit beneficial synthetic systems. In vitro, EDTA suppressed anabolic processes, while EGTA had no effect. However, EDTA in vivo did not suppress glycosaminoglycan or RNA production, but paradoxically stimulated them. At the same time, EDTA inhibited neutral protease activity in normal animals.
Quantitative analysis of cold stress performance after digital replantation
Authors: Nunley James A. , Penny Wade H. , Woodbury Max A. , Koman L. Andrew
Published: February 2005

Isolated cold stress testing (ICST) has been used to assess cold stress performance or digital thermoregulation, but statistical analysis of the results has been limited to visual comparisons of data. In this prospective study, 11 patients who underwent complete digital replantation were followed serially with ICST at 6 weeks, 3 months, 6 months, 1 year, and 2 years post‐operatively, and the results were analyzed quantitatively. For that analysis, we devised a mathematical method that provided a cooling and a warming coefficient to fit the data. Differences in these cooling and warming coefficients were then regressed against time after replantation, patient age, number of digits replanted, hand dominance, and clinical evidence of sensory recovery. There was a significant correlation between response to isolated cold stress testing (thermoregulation) and degree of sensory recovery (p ⩽ 0.02). This method for quantitative analysis of isolated cold stress testing data allows objective evaluation of digital blood flow patterns based on temperature, thereby providing a reliable and objective assessment of the recovery of thermoregulation in the replanted human digit.
Changes in the orientation of proteoglycans during the early development of natural murine osteoarthritis
Authors: Dunham Jane , Chambers M. G. , Jasani M. K. , Bitensky Lucille , Chayen J.
Published: February 2005

At least 80% of male STR/ORT mice naturally develop osteoarthritis that predominantly affects the medial tibial cartilage. Overt osteoarthritic changes, as judged by radiological and histological abnormalities, become apparent after 30 weeks of age. Consequently, mice < 30 weeks of age were used to investigate early changes in the cartilage matrix related to the natural development of osteoarthritis, without the need for experimental intervention to induce this condition. Quantitative Alcian blue staining showed little change in the total amount of proteoglycans in mice of this age. Polarized light microscopy of the birefringence induced by such staining demonstrated a progressive decline in the orientation of the proteoglycans in the medial cartilage of these mice. This decline was not found in CBA mice, which only very rarely develop osteoarthritis of this joint. Such progressive disorganization of the proteoglycans would be likely to permit the increased free water‐content characteristic of osteoarthritic cartilage.