bluuebunny/crossref_metadata_2025 huggingface dataset:
Telemeterized in vivo hip joint force data: A report on two patients after total hip surgery
Authors: Kotzar G. M. , Davy D. T. , Goldberg V. M. , Heiple K. G. , Berilla J. , Heiple K. G. , Brown R. H. , Burstein A. H.
Published: February 2005

Two telemeterized femoral components were implanted in two patients as part of normal total hip replacement procedures. The two components were instrumented to measure the three force components directed along: (a) the neck axis, (b) transverse to the neck axis and in the plane of the prosthesis, and (c) transverse to the neck axis and perpendicular to the plane of the prosthesis. Data were collected at multiple sessions during the early postoperative period for a number of standard activities, including gait, stair climbing, rising from a chair, single leg stance, double leg stance, ipsilateral and contralateral straight leg lifts while supine, ipsilateral flexion and extension while standing, and ipsilateral abduction while standing and lying on the contralateral side. These data are summarized and compared with the published results from analytic studies and with the results from previous studies using instrumented femoral components. Peak loads for gait during the period of study were roughly 2.7 body weights (BW) when the patients walked at their normal pace. Contact forces at the hip during stationary single leg stance approximated the peak loads during gait with values ranging from 2.1 to 2.8 BW. The highest forces recorded reached values approaching 5.5 BW and occurred during periods of instability while the patient engaged in stationary single leg stance. Our in vivo data indicate that forces generated during the above activities increase in magnitude quite rapidly during the early postoperative period and that during this period the patients have the ability to perform the activities of daily living without generating the high amplitude joint contact forces suggested by the results of dynamic studies. Joint contact forces during gait were found to depend on speed, but the high absolute magnitudes predicted by model studies were not supported by the in vivo data.
Evaluation of orthogonal mechanical properties and density of human trabecular bone from the major metaphyseal regions with materials testing and computed tomography
Authors: Ciarelli M. J. , Goldstein S. A. , Kuhn J. L. , Cody D. D. , Brown M. B.
Published: February 2005

We evaluated the orthogonal mechanical properties of human trabecular bone from the major metaphyseal regions with materials testing and quantitative computed tomography (CT). The proximal tibia, distal femur, proximal femur, distal radius, and proximal humerus from fresh cadaver specimens between the ages of 55 and 70 years were excised and prepared for experimentation. The bones were embedded and scanned at 1 or 1.5 mm intervals on a Technicare HPS 1440 and GE 9800 CT scanner. After scanning, the bones were sectioned, producing 8‐mm cubes of trabecular bone which were mechanically tested in uniaxial compression at a strain rate of 1%/s. The testing sequence consisted of preyield tests in two of the three orthogonal directions and failure in the third. After testing, the cubes were evaluated for apparent density and ash weight. The results of the study show that the strength and stiffness of trabecular bone varies significantly within metaphyseal regions and from metaphysis to metaphysis. The power and significance of relationships between density and modulus varied as a function of metaphyseal location. Both linear and nonlinear models were significant, suggesting that trabecular deformation occurs in response to both axial and bending loads. Finally, the need for architectural measures of trabecular bone to predict mechanical properties is emphasized.
Electrokinetic behavior of intact wet bone: Compartmental model
Authors: Walsh W. R. , Guzelsu N.
Published: February 2005

Streaming potential experiments were performed on chemically‐treated intact wet bone plugs equilibrated in potential‐determining ion buffers. Comparison of calculated zeta (ζ) potentials from intact wet bone streaming potentials and bone particle electrophoresis indicates different values. Intact streaming potential experiments, where fluid is forced through the samples, represents flow, primarily through the vascular channel system, and contribution of the organically‐lined channels to the electrokinetic (ζ) potential. Bone particle electrophoresis represents mainly the electrokinetic contribution of exposed mineralized matrix. The organic linings present in the vascular chanel system limit potential‐determining ions' access to the mineralized matrix. These linings may have an important role in mineral homeostasis and control of ion fluxes between bone compartments.
Human carpal ligament recruitment and three‐dimensional carpal motion
Authors: Savelberg H. H. C. M. , Kooloos J. G. M. , De Lange A. , Huiskes R. , Kauer J. M. G.
Published: February 2005

In five fresh human cadaver wrist joints six carpal ligaments and seven carpal bones were marked with small, radio‐opaque pellets. Using a roentgenstereophotogrammetric measuring system, the ligamentous length changes and the kinematics of carpal bones were determined in different flexion and deviation positions of the hand. The data generated by this method differ significantly from lengthening data predicted by current concepts on carpal ligament functioning. The motions of carpal bones and the lengthening of the carpal ligaments were related to each other. It appeared that most carpal ligaments lengthen only during one half of a full movement cycle. Hence, ligaments seem to constrain either a dorsal‐ or a palmar‐directed motion of the hand, or an ulnar‐ or a radial‐directed motion of the hand. When the hand is in maximal radial deviation or maximal palmar flexion, none of the ligaments has a greater length than in the neutral situation. The tested parts of the lunatotriquetrum palmar ligament do not lengthen during any movement of the hand. Significant lengthening relative to the neutral situation was found for the radiocapitate palmar ligament (6.5% in maximal ulnar deviation and 11.7% in maximal dorsal flexion of the hand), and for the distal string of the radiolunate palmar ligament (6.4% in maximal ulnar deviation). It was confirmed that the carpals, apart from moving in the plane in which the hand motion takes place, also execute considerable out‐of‐plane motions during hand motions. The combination of these expermentally and simultaneously determined data on length change and on the movements of carpal bones are found to be necessary in order to give suitable explanations for the observed separate kinematical phenomena.
Ascorbic acid requirement for optimal flexor tendon repair in vitro
Authors: Russell Jean E. , Manske Paul R.
Published: February 2005

Numerous studies from our laboratory have defined aspects of the repair process in a lacerated flexor tendon model, both in vivo and in vitro. Inherent in the development of a viable tissue or cell culture model system is the definition of the optimal media environment. Since our laboratory investigations of in vitro flexor tendon repair encompass the formation of numerous extracellular matrix proteins, we have defined the optimal level of ascorbic acid with which to study the tendon wound healing process. The ascorbic acid requirement for proline and lysine hydroxylase activity during collagen biosynthesis is well known, and the importance of this vitamin for matrix proteoglycan synthesis more recently has been appreciated. This report describes the effect of several levels of ascorbic acid on 3H‐thymidine incorporation, collagen and noncollagen protein synthesis, and glucose utilization and lactate production. Profundus flexor tendon segments were obtained from young adult New Zealand white rabbits and maintained in organ culture for periods of 1, 2, or 3 weeks. Ascorbic acid concentrations ranged from 50 to 300 μg/ml and were added fresh at each 48‐h media change. Tendon protein synthesis, glucose metabolism, and cell permeability/viability were significantly correlated with the level of ascorbic acid in the culture medium. The results suggest that ascorbic acid levels in excess of the traditional 50 μg/ml are necessary to optimally maintain flexor tendons from adult animals in organ culture with 48‐h media and ascorbate changes. Additionally, it may be necessary to determine the precise ascorbic acid requirement for individual tissues, since the specific tissue/cell and species requirement for ascorbate may vary.
Alterations in femoral and acetabular bone strains immediately following cementless total hip arthroplasty: An in vitro canine study
Authors: Page Alexandra , Jasty Murali , Bragdon Charles , Ito Keita , Harris William H.
Published: February 2005

Alterations in strain patterns in both the femur and acetabulum of the dog, due to cementless total hip arthroplasty (THA), were evaluated by monitoring cortical bone strains before and immediately following implantation of components, using an accurate in vitro jig, simulating the loading of the canine hip in vivo. Femoral arthroplasty with straight stem, canal‐filling, femoral components, made of titanium‐based alloy, led to a statistically significant reduction of proximal femoral bone strains, with proximal medical compressive strains reduced, on average, to only 22% of intact strain magnitude (p < 0.01), even though the prostheses contained collars and were not fixed with cement. Strain alterations on the acetabulum, following cementless THA, were more complex and variable. Laterally, a significant decrease (p < 0.01) in periacetabular strains to between 20 and 60% of the intact state was observed, while medial wall strains varied inconsistently after arthroplasty. These strain alterations reflect major changes in mechanical loading of both the femur and acetabulum immediately following cementless THA, using components similar to those used clinically in humans. Major reductions in strains on the proximal femur occurred with cementless femoral components, while the change in strains on the acetabulum were variable, and could be a result of variations in fit and placement of components inherent even in well‐controlled implantation techniques. The physiologic in vitro loading of the canine femur with the pelvis, used to obtain these data, can be applied to future investigations exploring stress transfer around uncemented components and the relationship of stress transfer to morphological changes of bone, in the canine model.
Evidence of proteoglycan/proteoglycan interactions within aggregates
Authors: Kahn Anthony , Pottenger Lawrence A. , Phillips Frank M. , Viola Randall W.
Published: February 2005

Nonaggregated proteoglycan monomers, digested fragments of the monomers, as well as link proteins have been shown to self‐associate. These associations have not been shown to occur on the aggregate. However, previous reports, using the Kleinschmidt technique of monolayer electron microscopy, have noted proteoglycan subunits on the aggregate that appear to interact, either as branched proteoglycans or as proteoglycan subunits that appear to share the same attachment site on the hyaluronic acid chain. Branching and shared attachments were noted in all aggregates analyzed in this study. Increasing the average space between proteoglycan subunits on the reconstituted aggregated resulted in a significant decrease in branched proteoglycans, indicating either a weak association occurring on the aggregate, or an artifact created by a three‐dimensional structure being reduced to a two‐dimensional monolayer image. The shared attachments were independent of both the presence of link proteins and changes in spacing between proteoglycans, suggesting a proteoglycan—proteoglycan interaction occurring before aggregation. The interactions were not influenced by proteoglycan concentration at the time of aggregation. Link proteins, however, did increase the number of proteoglycans on the aggregate that could be cross‐linked with a bifunctional reagent, suggesting that link proteins facilitate proteoglycan—proteoglycan interactions.
Vascular assessment of the periarticular ligaments of the rabbit knee
Authors: Wallace C. Douglas , Amiel David
Published: February 2005

While the rabbit is being extensively utilized in animal models for orthopaedic research, the vascular anatomy of the knee ligaments has not been thoroughly described in this species. This study demonstrates the blood supply to the infrapatellar fat pad, the cruciate ligaments, the medial collateral ligament (MCL), and the menisci, such that the effects of manipulating these tissue may be properly interpreted. Vascular injection with India ink and iodinated i.v. contrast dye was performed in 11 New Zealand white rabbits, and routine histology done on six. The large vessel anatomy is similar to that described for humans and dogs, with a descending geniculate artery, medial and lateral superior and inferior geniculate arteries, a posterior geniculate artery, and a recurrent anterior tibial artery. The microvascular anatomy is also similar in that the infrapatellar fat pad and synovial membrane are highly vascular, the menisci are vascularized from their periphery (being avascular centrally), and the medial collateral ligament is relatively well vascularized. A difference from dogs and humans is present in the anterior cruciate ligament (ACL), which is poorly vascularized, with a single artery on its anterior aspect. High magnification histologic evaluation reveals numerous capillaries in the substance of the MCL, while the ACL is nearly devoid of such vessels. The interspecies variation in vascular anatomy is a variable that must be taken into consideration in any surgical or traumatic animal model investigation of knee pathology.
Remodelling of bone around intramedullary stems in growing patients
Authors: Blunn Gordon W. , Wait Mary E.
Published: February 2005

The remodelling of bone around intramedullary cemented stems, used for the fixation of massive distal femoral replacements in young patients, has been studied. Several types of remodelling have been identif ed, and this is common to all of the retrieved specimens that have been in situ for periods of 6 to 18 months. Transection of cortical bone and the insertion of a massive prosthesis leads to (a) the formation of a pedicle of bone or bony bridge that grows from the transection site over the shaft of the prosthesis, (b) bone resorption at the transection site, (c) the development of an inner porotic cortex surrounding the intramedullary stem and subperiosteal bone formation, and (d) a shell of bone around the acrylic cement. The tibial component that allows continued growth of the proximal tibial physis consists of a press fit metallic plateau with a stem that slides into an ultra‐high‐molecular‐weight polyethylene sleeve inserted below the growth plate. A sclerotic layer of bone forms adjacent to a soft‐tissue interface around both the sleeve and the metallic component. Remodelling of bone around intramedullary stems is attributed either to a redeveloping blood supply or to load adaptive changes.
Changes in tibial bone mass after primary cementless and revision cementless total hip arthroplasty in canine models
Authors: Goethgen C. B. , Sumner D. R. , Platz C. , Turner T. M. , Galante J. O.
Published: February 2005

The purpose of this study was to examine right—left differences in tibial bone mass after unilateral (left) cementless total hip arthroplasty (THA). Of 39 dogs with THAs, 9 had primary cementless porous‐coated femoral stems for 6 months and 15 had similar stems for 2 years. Five dogs had aseptically failed cemented hips, and 10 had aseptically failed cemented hips that were revised with cementless porous‐coated femoral stems (5 without bone graft and 5 with autogenous bone graft). These animals were sacrificed 6 months after the revision surgery. The primary cementless dogs showed no right‐left difference in tibial bone mineral content (BMC) or cortical bone cross‐sectional geometry after 6 months, but after 2 years there was a distal right‐left difference in BMC of 6% caused by expansion of the medullary canal in the tibia of the operated limb. Tibial BMC was more than 20% lower in the operated limb of the failed cemented dogs, approximately 15% lower in the nongrafted group, and 7% lower in the grafted group. The right‐left tibial difference in BMC in the 2‐year primary cementless group is most probably because of subclinical disuse of the operated limb. Among the dogs with failed cemented stems, the lower right‐left difference in the two revised groups compared with the nonrevised group suggests that improved limb function after cementless revision THA may cause gain of previously lost bone.
In vivo flexion/extension of the normal cervical spine
Authors: Dvorak J. , Panjabi M. M. , Novotny J. E. , Antinnes J. A.
Published: February 2005

Twenty‐two women (age range 25—49 years, average 30.9 years) and twenty‐two men (age range 23—42 years, average 31.6 years), all healthy and asymptomatic, underwent passive flexion/extension examinations of the cervical spine. Functional x‐rays were taken and analyzed using a computer‐assisted method that quantified intervertebral rotations, translations, and locations of the centers of rotation for each level C1‐C2—C6‐C7. The aim of the study was to establish values for these parameters for a normal population as related to age and gender. In the process, a statistically significant difference was found in the average value of rotation between male and female groups at the C5‐C6 level. A new parameter, the ratio between translation and rotation, was also established and may prove useful for clinical diagnoses. This parameter has a smaller error associated with it than do pure translations and may aid the clinician by helping to account for the large variation in rotatory ranges of motion within the population. This translation/rotation ratio indicated highly significant differences in the lower segments of the cervical spine between gender groups.
Effects of indomethacin on demineralized bone‐induced heterotopic ossification in the rat
Authors: DiCesare Paul E. , Nimni Marcel E. , Peng Lynnus , Yazdi Mohamadreza , Cheung David T.
Published: February 2005

Indomethacin inhibits bone formation when treatment is initiated before the implantation of demineralized bone matrix (DBM). For the inhibition of bone induction to occur, indomethacin treatment had to be initiated 6 h or more before implantation of DBM. Initiating the drug treatment at or after the time of DBM implantation had no effects on the amounts of new bone formed. The inhibition by indomethacin is dose related over a range between 0.04 and 4 mg/kg body weight. Recovered day‐1 DBM implants, transplanted into indomethacin pre‐ and posttreated syngeneic rats, formed bone at the same rate as controls did. However, recovered day‐1 DBM implants lyophilized before transplantation showed decreased bone formation but significant dystrophic calcification as judged by a lower alkaline phosphatase activity and an elevated calcium content.
Regional blood flow and strontium‐85 incorporation rate in the rat hindlimb skeleton
Authors: Kirkeby Ole J. , Berg‐Larsen Trine
Published: February 2005

Regional distribution of radioactive microspheres and 85Sr incorporation rate in the os ilium, femur, and tibia were determined in 44 rats. In 15 additional animals, regional blood flow was measured with the reference sample technique. Highest numbers of microspheres were found in the distal femoral and proximal tibial metaphyses. Highest blood flow rates were found in the os ilium, the caput femoris, and distal femoral and proximal tibial metaphyses. The diaphyses and epiphyses of the femur and tibia had a relatively lower perfusion. The regional 85Sr incorporation rate was correlated (r = 0.67) to the regional distribution of the microspheres. The dispersion of the data was large and this was mainly due to biological variation. The results describe the regional distribution of blood flow in the rat hindlimb and demonstrate a close association between blood flow and mineral turnover in normal rat skeletal tissue as shown by the correlation between microsphere and 85Sr incorporation rate distribution.
Determination of fixed charge density in cartilage using nuclear magnetic resonance
Authors: Lesperance Leann M. , Gray Martha L. , Burstein Deborah
Published: February 2005

Many biomechanical and chemical properties of cartilage are dependent on the fixed charge density (FCD) of the extracellular matrix. In this study, nuclear magnetic resonance (NMR) spectroscopy was investigated as a nondestructive technique for determining FCD in cartilage. Sodium content was measured by NMR in cartilage explants and was compared with sodium content measured by inductively coupled plasma emission spectroscopy (ICP) in order to verify the total NMR visibility of sodium in cartilage. The ratio of NMR to ICP results was 1.02 ± 0.04 (calf, mean ± SD, n = 7) and 1.04 ± 0.11 (adult bovine, n = 8). Sodium concentration as measured by NMR was then used with ideal Donnan theory to compute estimates of FCD. For calf articular cartilage (AC) near physiological conditions, calculated FCD was −0.28 ± 0.03 M (n = 10). NMR measurements were then made for individual cartilage specimens sequentially equilibrated in baths of differing salt composition, pH, or ionic strength. For calf and adult AC, calculated FCD decreased dramatically between pH 3 and 2, with adult speciments becoming positively charged but calf tissue retaining a net negative charge. For calf AC equilibrated in 0.3–0.015 M NaCl, calculated FCD was observed to decrease slightly with decreasing bath ionic strength. For epiphyseal cartilage, FCD varied with the position of origin of the explant within the joint, ranging from − 0.19 to − 0.35 M in a manner that correlated with tissue glycosaminoglycan content. Preliminary NMR imaging experiments demonstrated similar variations of sodium concentration in intact ulnar epiphyseal cartilage. Collectively, these results demonstrate the ability of NMR to nondestructively follow FCD in cartilage. The technique is applicable to dynamic studies as well as to both in vitro and in vivo studies on living tissue.
Effect of hylan on cartilage and chondrocyte cultures
Authors: Larsen Nancy E. , Lombard Kathleen M. , Parent Edward G. , Balazs Endre A.
Published: February 2005

The protective role of hylan, a hyaluronan [hyaluronic acid (HA)] derivative, was studied in explanted bovine cartilage and isolated chondrocytes. Cartilage and chondrocytes were exposed to degradative enzymes (lysate from activated polymorphonuclear leukocytes), oxygen‐derived free radicals (ODFR), conditioned media from mononuclear cells (MCCM), and interleukin‐1 (IL‐1), in the presence and absence of hylan. The effect of HA was also studied. In cartilage explants susceptibility to pertubation was evaluated in terms of 35S release and proteoglycan depletion and was compared to control cultures; high viscosity hylan was found to reduce 35S release in cartilage explants caused by degradative enzymes, ODFR, MCCM, and IL‐1. The hylan effect was reversible and viscosity‐dependent. In chondrocyte cultures, high viscosity hylan was effective in reducing cell injury caused by degradative enzymes and ODFR. The data suggest that the glycosaminoglycan hylan, as well as native HA, may mediate exposure to and/or response to stimuli associated with initiation of degenerative processes in cartilage tissues.
S‐100 protein immunostaining identifies cells expressing a chondrocytic phenotype during articular cartilage repair
Authors: Wolff D. A. , Stevenson S. , Goldberg V. M.
Published: February 2005

The healing of articular surface defects has been studied with conventional histology, which relies on the staining of the extracellular matrix to identify the phenotype of the cells present. A chondrospecific cellular marker would be useful. S‐100 protein has been found in all chondroid tissues studied, and we evaluated its usefulness in the study of articular cartilage repair. Fullthickness rabbit femoral condylar defects were made, and the specimens were studied at serial time intervals. S‐100 protein staining positively showed chondroid cells in the 7‐ and 14‐day specimens, which were not identifiable by conventional techniques. At 30 and 60 days, an S‐100 positive band of cells separated a deep safranin‐O positive hypertrophic layer from a fibrocellular surface layer. At 120 days, the presence of S‐100 protein identified cells with chondrogenic potential, and the lack of S‐100 protein in other cells embedded in conventionally stained matrix suggested that these cells were no longer of a chondroid phenotype. The presence of S‐100 protein‐identified chondroid cells early in the repair process when the cells had not begun to synthesize conventionally stainable matrix and the lack of S‐100 protein in cells late in the repair positively identified a phenotypic change earlier than conventional histology.
Structural consequences of subchondral bone involvement in segmental osteonecrosis of the femoral head
Authors: Brown Thomas D. , Baker Kelly J. , Brand Richard A.
Published: February 2005

Appearance of a crescent sign usually marks the onset of necrotic femoral head collapse, but very little is known about which local factors contribute most critically to avoiding or postponing fracture of at‐risk juxtaarticular cancellous bone. A three‐dimensional finite element model was used to test the hypothesis that an initially mechanically uncompromised subchondral plate could provide a substantial degree of stress protection to a weakened underlying segmental infarction. The computational simulation of osteonecrosis showed that the principal stress distribution for an assumption of subchondral plate weakening (given also an underlying, comparably weakened segmental infarction) differed inappreciably from that of a normal femoral head. However, the tendency for local structural failure, as reflected in the ratio of stress to strength, was substantially higher in the former instance. If, instead, the mechanical integrity of the subchondral plate overlying the weakened segmental infarction was assumed to be preserved, computed stress levels in the at‐risk subjacent necrotic cancellous bone were still over 70% as high as for the weakened‐plate case. The data thus indicate that even a fully normal subchondral plate can provide only modest stress protection of a weakened underlying segmental infarction, whereas weakening of the necrotic cancellous bone throughout the infarction induces marked stress increase in the overlying subchondral plate. These findings suggest that the onset of collapse is probably dominated much more strongly by the degree of structural degradation of the cancellous bone within the main infarct body, than by the degree of structural degradation within the subchondral plate.
Effect of tension and placement of a prosthetic anterior cruciate ligament on the anteroposterior laxity of the knee
Authors: Fleming B. , Beynnon B. , Howe J. , McLeod W. , Pope M.
Published: February 2005

We wished to determine the optimal tensions required to restore normal joint laxity to anterior cruciate ligament (ACL)‐deficient knees using a braided polyethylene ACL prosthesis (PACL). In 10 cadaveric specimens, we measured the anteroposterior (AP) laxity of the intact knee at 10°, 30°, 60°, and 90° of flexion. The ACL was then removed and replaced with the PACL using tunnel‐tunnel (T‐T) and “over‐the‐top” (OTT) placement techniques. In both positions, the PACL was initially tensioned to 0, 9, 18, and 27 N with the knee flexed to 30°. AP joint laxity was then measured at each flexion angle. With an increase in initial tension, there was a corresponding decrease in AP laxity. At 30° and 90° of flexion, AP laxity was not significantly different from normal using T‐T placement and an initial tension of 0 N. At 90° of flexion, AP laxity was not signifincantly different from normal using OTT placement at 0 or 9 N of initial tension. For both positions, all other tension levels and flexion angles constrained AP laxity. No laxity differences were detected between the OTT and T‐T positions at any flexion angle. The variability in AP laxity of the T‐T position was significantly greater than OTT. With a 150‐N anterior shear force applied to the proximal tibia, the maximum tensions developed in the PACL were not significantly different between the two positions except at 90°. The results suggest that implantation of the PACL is best performed using OTT positioning with an initial tension of 0 N applied at 30° of knee flexion.
Trunk positioning accuracy in children 7‐18 years old
Authors: Ashton‐Miller James A. , McGlashen Kelly M. , Schultz Albert B.
Published: February 2005

Trunk proprioception was measured in 253 healthy children 7‐18 years of age using infrared markers placed on the back of the head and on the skin over the T1, T8, and S1 spinous processes. The children were tested for their accuracy in sensing return of the head and trunk to a centered, neutral position in the frontal plane. Whole‐body sway was also quantified during 10 s of relaxed standing by measuring mean amplitudes of trunk marker and foot center of pressure (CP) movements. The results show that trunk positioning accuracy improved significantly with age (p = 0.000). Subjects could position their trunk in the frontal plane to within a mean (±SD) of 2.5 (±1.1) and 0.9 (±0.6)± of the neutral position at ages 7 and 18 years, respectively. No statistically significant gender differences were found. At every age trunk positioning accuracy was diminished in the presence of a continuous external trunk moment (equivalent to 0.01 × body weight × height), although not significantly so. Neither mean trunk sway nor CP amplitudes were significantly correlated with age or sex. The overall results suggest that spine decompensation is only abnormal when it exceeds 20 mm in healthy children and adolescents.
Mechanical properties of microcallus in human cancellous bone
Authors: Blackburn Joanne , Hodgskinson Richard , Currey John D. , Mason Jennifer E.
Published: February 2005

Until now, the mechanical properties of the microcalluses that form in human cancellous bone have been unexplained. We measured the micro‐hardnesses of microcalluses in cancellous bone, of the trabeculae within the microcalluses, of the trabeculae adjacent to microcalluses, and of trabeculae lacking microcalluses in a human tibia and femur. We observed no important differences between materials at the four different sites. Because the microhardness of bone is very closely related to its stiffness, this finding indicates that microcalluses are likely to stiffen the trabeculae in which they are formed, even though they may surround unhealed fractures of the cancellous trabeculae.
Comparison of asymmetrical and symmetrical pulse waveforms in electromagnetic stimulation
Authors: Pienkowski D. , Pollack S. R. , Brighton C. T. , Griffith N. J.
Published: February 2005

Pulsing electromagnetic field (PEMF) stimulation is a noninvasive therapeutic modality that has been successfully used to stimulate healing of surgically resistant human bone fracture nonunions. Asymmetry of the stimulaus pulse waveform was thought to be necessary for therapeutic effectiveness, but asymmetrical pulses require significant electrical energy that constrains clinical delivery systems to suboptimal designs. Development of low‐energy consuming stimuli will enable clinical device improvements and may provide additional information about the interaction of electromagnetic fields with tissues. The objectives of this study were (a) to determine if asymmetry of the stimulus pulse waveform is needed for efficacy and (b) to determine if symmetrical pulse waveform stimuli also can produce a beneficial therapeutic response. The rabbit fibular osteotomy model was used to answer these questions and to identify which components of the clinically used asymmetrical PEMF produce the therapeutic response. The results suggest that assymmetry is not necessary and that a narrow pulse width, symmetrical square wave signal can also stimulate stiffness increases in this model. The data also suggest that the high‐amplitude, narrow‐pulse portion of the asymmetrical PEMF is the principal component of the signal pulse that is responsible for the clinical therapeutic effect.
The microstructural tensile properties and biochemical composition of the bovine distal femoral growth plate
Authors: Cohen B. , Chorney G. S. , Phillips D. P. , Dick H. M. , Buckwalter J. A. , Ratcliffe A. , Mow V. C.
Published: February 2005

The tensile properties of distal femoral growth plates from 12‐month‐old cows were determined on uniformily prepared straight bone‐growth plate‐bone specimens (7 × 7 mm2 in cross‐section) from predetermined anatomical sites on the physis. Each specimen was distracted to failure using a computer‐controlled servo‐hydraulic testing machine at a strain rate of 0.004 s−1. It was found that the exponential constitutive law, using finite deformation formulation for strain, provides an excellent description of the stress‐strain behavior of all the specimens up to the point of failure. The ultimate stress and both tangent moduli (i.e., the toe region tangent modulus and the tangent modulus calculated at 75% of ultimate strain) varied with anatomical site. The anterior region was the strongest, followed by the posterior/lateral. The anterior and posterior/lateral regions were also the stiffest, whereas the posterior/medial and center regions were the weakest and most compliant. The bone‐growth plate‐bone specimen exhibited a low ultimate strain (13.8% ± 6%) that did not vary significantly throughout the growth plate. This result suggests that disruption of the physis may occur in vivo even at the lower distractions currently recommended for the clinical chondrodiatasis procedure for leg lengthening. The biochemical composition of the growth plate in the anatomical regions correlated well with the tensile properties. There was a greater collagen content in the regions that were the stiffest and strongest. The gross morphology of the growth plate of the bovine distal femur is also described in this study. There is a regular pattern to the undulations of the physis at several dimensional levels. Histologic findings showed that orientation of the hypertrophic cell columns and transphyseal septa are aligned nearly parallel to the longitudinal axis of the diaphyseal shaft. This column orientation is not affected by the undulation of the primary contour of the physis, which at certain locations may be inclined as much as 60° relative to the diaphyseal axis. The orientation of the hypertrophic cell columns appears to be one of the dominant microstructural features influencing the tensile behavior of the bone‐growth plate‐bone specimens.
Treatment of proteoglycan aggregates with physeal enzymes reduces their ability to inhibit hydroxyapatite proliferation in a gelatin gel
Authors: Boskey A. L. , Maresca M. , Armstrong A. L. , Ehrlich M. G.
Published: February 2005

In vitro, cartilage proteoglycans (PGs) are effective inhibitors of hydroxyapatite formation and growth. Their inhibitory ability decreases with decreasing PG size and charge density. It has been suggested that the enzyme‐mediated alteration in the size and conformation of PGs in the growth plate may similarly facilitate the calcification process. In this study, a gelatin gel system was used to monitor hydroxyapatite formation and growth in the presence of proteoglycan aggregates, before and after enzyme treatment. To reproduce the physeal degradation cascade, an enzyme preparation was used that contained all of the growth plate enzymes. At a concentration of 500 μg/ml, the untreated proteoglycan aggregates reduced the amount of mineral formed by 30%. When the aggregates were treated with the heat‐inactivated enzyme, the same extent of inhibition was found. In contrast, treating the aggregates with the crude growth plate enzyme preparation removed all the inhibitory ability, such that 500 μg/ml of proteoglycan preparation yielded 10% more mineral than the controls. Treatment of the aggregates with chondroitinase ABC and trypsin, similarly removed all the inhibitory ability. These data, suggest that enzymatic degradation of proteoglycans may contribute to the regulation of growth plate calcification.
Increased release of matrix components from articular cartilage in experimental canine osteoarthritis
Authors: Ratcliffe Anthony , Billingham Michael E. J. , Saed‐Nejad Fatemeh , Muir Helen , Hardingham Timothy E.
Published: February 2005

The release rates of specific components of the proteoglycan aggregates (G1 domain, the chondroitin sulfate and keratan sulfate containing portion of the protein core, and link protein) of the articular cartilage of mature beagles were studied at early stages of canine experimental osteoarthritis (OA), generated by transection of the anterior cruciate ligament. Analysis of cartilage explants and synovial fluids indicates that at early stages of experimental OA, there is increased release of the proteoglycan aggregates of the articular cartilage. This involves a release from the tissue of the components of the proteoglycan that are specifically involved with aggregation together with the glycosaminoglycans of the proteoglycan. These components were detected at elevated levels in the media of explants of cartilage from the operated joint, and in the synovial fluids of the operated joints.
Effects of β‐adrenergic blockade in an osteoblast‐like cell line
Authors: Majeska R. J. , Minkowitz B. , Bastian W. , Einhorn T. A.
Published: February 2005

The β‐adrenergic blocking agent propranolol was shown in previous studies to increase orthotopic bone formation in rats. To understand the cellular mechanisms underlying this observation, propranolol was tested for its effects on osteoblastic cells, which posses adenylate cyclase‐coupled β‐adrenergic receptors. The ability of propranolol to modulate parathyroid hormone (PTH) and isoproterenol effects on adenylate cyclase activity and on alkaline phosphatase expression was studied in the osteoblast‐like rat osteosarcoma cell line ROS 17/2.8. At concentrations between 0.1 and 10 μM, DL‐propranolol specifically inhibited adenylate cyclase stimulation by the β‐adrenergic agonist isoproterenol, but did not alter either basal or PTH‐stimulated activity. At these concentrations, propranolol also blunted the inhibition of alkaline phosphatase activity by isoproterenol but not PTH. Propranolol alone had minimal effects on ROS alkaline phosphatase activity at low concentrations (0.1–1 μM), but became inhibitory at high concentrations (10–100 μM). Thus, the direct effects of physiologically relevant propranolol concentrations on osteoblastic cells can be attributed principally to β‐adrenergic blockade. These findings further suggest that propranolol may enhance bone formation by preserving osteoblastic activity in the face of inhibition by β‐adrenergic agonists.
Role of loads and prosthesis material properties on the mechanics of the proximal femur after total hip arthroplasty
Authors: Cheal Edward J. , Spector Myron , Hayes Wilson C.
Published: February 2005

The objective of this study was to establish the role of loads and prosthesis material properties on the mechanics of the proximal femur after total hip arthroplasty. We developed a three‐dimensional finite element model of an intact human femur and the same femur with a conventional collared straight‐stem femoral component. Using published data, we defined two sets of loading conditions: one that represented three phases of gait, and one that represented four different extreme loads. The four extreme loads were based on the peak joint contact forces that occur during stair ascent and isometric contraction of various muscle groups. The model was analyzed with three different material properties for the prosthesis, including cobalt‐chromium alloy, titanium alloy, and a carbon fiber‐reinforced polymer (CFRP) laminate. We assumed that the implant was stable, with rigid bonding, collar contact, and no cement. To address femoral component loosening, we examined the shear stresses at the implant‐bone interface; to address adaptive bone remodeling, we examined the principal stresses in the supporting cortical bone relative to those in the intact femur. Our analyses of the various loading conditions demonstrated large out‐of‐plane bending moments and torsional moments, especially for the load representing stair ascent. Based on stepwise multiple regressions, the maximum shear stresses at the implant‐bone interface in the distal region were dependent on the total applied axial force and torsion; the maximum shear stresses in the proximal region were dependent on the axial component of the joint contact force alone. Reduction in the prosthesis stiffness, by substitution of the CFRP material properties, resulted in lower interface shear stresses at the distal end of the stem and higher interface shear stresses at the more proximal sections, consistent with the findings of others. We fit equations, based on composite beam theory, to the maximum implant‐bone interface shear stresses and the cortical bone principal stresses as a function of the axial modulus of the prosthesis. These equations can be used to estimate the maximum stresses at the interface and in the cortical bone that would be predicted by similar models, for the same prosthesis constructed of alternative materials, relative to the stresses in the intact femur. The nonlinear nature of these relationships was such that the cortical bone stresses changed more rapidly, as a function of the prosthesis modulus, for lower values of elastic modulus, especially in the more proximal sections.
The axes of rotation of the thumb carpometacarpal joint
Authors: Hollister Anne , Buford William L. , Myers Loyd M. , Giurintano David J. , Novick Andrew
Published: February 2005

Two axes of rotation of the carpometacarpal (CMC) joint of seven cadaver thumbs were located using an axis finder. The flexion‐extension axis is located in the trapezium and the abduction‐adduction axis is in the first metacarpal. These axes are fixed, are not perpendicular to each other or to the bones, and do not intersect. Motion of the first metacarpal on the trapezium can be defined by these two axes. Understanding of the movements of the basal joint of the thumb is essential to the study of its function and reconstruction.
Development of vascularization in the chondroepiphysis of the rabbit
Authors: Ganey Timothy M. , Love Sheila M. , Ogden John A.
Published: February 2005

Although numerous studies have addressed the presence of cartilage canals within developing epiphyses, the chronology of their appearance and their vascular contribution to the developing chondroepiphysis remain to be studied. We have selected a model, similar to the developing human skeletal system, in which extensive cartilage canal development precedes the subsequent secondary ossification process. In the rabbit proximal tibia, both chondroepiphyseal and vascular (cartilage canals) development were quantified from the first evidence of vessels until the formation of the secondary center of ossification. The volume of hyaline cartilage increased 25 times after intraepiphyseal vessels were initially observed. The blood supply, measured in cartilage canal volume, increased 400‐fold over the same period. Three distinct cartilage canal morphologies were identifiable before the formation of the secondary center of ossification: (a) an early phase, in which the canals appeared as infoldings derived from the perichondrium; (b) a reactive phase, occurring simultaneously with chondrocyte hypertrophy and characterized by a very large increase in mesenchymal cells within the cartilage canal; and (c) a vascular phase, coincident with mineralization of the matrix, in which the familiar, unitary canal morphology was replaced by that of a vascular plexus. While matrix mineralization and the formation of bone seem dependent on critical cellular events, notably chondrocyte hypertrophy, the role that the vascular supply plays in developing sufficient biological inertia for the ossifying transition must not be underestimated.
Contact characteristics of the subtalar joint: The effect of talar neck misalignment
Authors: Sangeorzan Bruce J. , Wagner Ulrich A. , Harrington Richard M. , Tencer Allan F.
Published: February 2005

In this study we determined the effects of misalignment of the talar neck on the contact characteristics of the subtalar joint. Each of seven fresh cadaver lower extremities was mounted in a loading jig and a vertical load was applied, 90% of which was directed through the tibia and 10% through the fibula. The foot was allowed to displace freely in the horizontal plane so that relative rotations, known to occur in the subtalar joint, would not be prevented. Pressure‐sensitive film, inserted into the posterior and anterior/middle articulations, was used to quantify changes in contact characteristics. After testing in the normal condition, the talar neck was osteotomized and stabilized with internal and external skeletal fixation. Contact characteristics were then determined in each of the following stages: anatomic realignment, or with 2‐mm displacement of the talar neck either dorsally, medially, laterally, or complex (dorsal and varus) with respect to the body of the talus. Measurements showed no significant changes in overall contact area or high pressure area in the posterior facet, although four of the seven specimens demonstrated increased localization of the contact area into two discrete regions. The combined anterior/middle facet, on the other hand, was significantly unloaded by all but medial displacement of the talar neck. An extraarticular load path and/or increased loading directly on the talonavicular joint was presumed to account for the loss of load transfer in the talocalcaneal joint.
The effects of fluoridated water on bone strength
Authors: Turner Charles H. , Akhter M. P. , Heaney Robert P.
Published: February 2005

Fluoride from fluoridated water accumulates not only in the enamel of teeth but also in the skeleton. The effects of fluoridated water on the skeleton are not well understood, yet there is some evidence that fluoridated water consumption increases the incidence of fractures. In the present study, femoral bending strength was measured in rats on fluoride intakes that ranged from low levels to levels well above natural high fluoride drinking water. Bone strength followed a biphasic relationship with bone fluoride content. Fluoride had a positive effect on bone strength for lower fluoride intakes and a negative influence on bone strength for higher fluoride intakes. The vertebral fluoride content at which femoral strength was maximum was between 1,100 and 1,500 ppm. The increase in femoral strength at this fluoride level was not accompanied by an increase in femoral bone density. The optimal fluoride content is within the range of bone fluoride contents found in persons living in regions with fluoridated water (1 ppm) for > 10 years.
The dermatan sulfate proteoglycans of the adult human meniscus
Authors: Roughley Peter J. , White Robert J.
Published: February 2005

The dermatan sulfate proteoglycans decorin and biglycan were extracted from pooled adult human menisci with 4 M guanidinium chloride and purified by successive cesium chloride density gradient centrifugation, ion exchange chromatography, and gel filtration. A final yield of about 2 mg of dermatan sulfate proteoglycan per gram of wet tissue was obtained. The proteoglycan is predominantly decorin with some biglycan, and the dermatan sulfate chains contain about 70% of their uronic acid residues as iduronate and possess about three times as much 4‐sulfation as 6‐sulfation of their N‐acetylgalactosamine residues. On gel filtration under associative conditions, about half of the proteoglycan exhibits self‐association. This includes most of the biglycan but also a substantial proportion of decorin. The molecules that show self‐association appear to have longer dermatan sulfate chains, though there is no apparent difference in their overall composition. The predominance of decorin in the adult meniscus and its ability to interact both with itself and collagen fibrils is compatible with a role in maintaining tissue integrity and strength.