bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of the intrinsic properties of the anterior cruciate and medial collateral ligament cells: An in vitro cell culture study
Authors: Nagineni Chandrasekharam N. , Amiel David , Green Melvin H. , Berchuck Matthew , Akeson Wayne H.
Published: February 2005

The poor healing abilities of the anterior cruciate ligament (ACL) in contrast to those of the medial collateral ligament (MCL) are well known. Different intrinsic properties of the constituent cells of these ligaments have been proposed to be one of the factors in the differential repair mechanisms. To examine this hypothesis, we have established primary cell lines of ACL and MCL from the tissue explants of approximately similar dimensions and have studied their behavior in vitro. The outgrowth of cells from ACL explants was slower than from MCL explants, as shown by the size of the surrounding clusters of cells. Both ACL and MCL cultures exhibited typical fibroblastic morphology. No significant differences were observed in either attachment or growth of cells from the attached explants derived from various segments of ACL and MCL. Growth curves of ACL and MCL cultures at both passage numbers 2 and 6 showed a slower rate of proliferation of ACL cells than MCL cells (p < 0.005). DNA synthesis measured in terms of [3H]thymidine incorporation (CPM/103 cells) of both log phase (ACL = 607.5 ± 5.4 vs. MCL = 1356.4 ± 11.3) and confluent (ACL = 83.0 ± 3.6 vs. MCL = 189.8 ± 5.4) cultures, supports the conclusion that differential proliferation rates of these cells exist in culture. FITC‐phalloidin staining (for actin) of later passage cultures (P3‐P5) showed a spread‐out appearance of ACL cells and an elongated appearance of MCL cells. Relatively more stress fibers were seen within ACL cells. SDS‐PAGE and Western blot analysis of cellular proteins revealed higher actin (43 kDa) content in ACL cells than in MCL cells. In vitro wound closure assay was performed by creating a uniform wound of 0.6 mm width in the confluent layer of ACL and MCL cultures. By 48 h postwounding, cell‐free zones created in ACL cultures were occupied partially by single cells in a nonconfluent fashion. In contrast, the wounded zone in the MCL cultures was almost completely covered by the cells. Results presented in this report demonstrate a lower proliferation and migration potential of ACL cells in comparison with MCL cells. These differences in intrinsic properties of ACL and MCL cells that were observed in vitro might contribute to the differential healing potentials of these ligaments in vivo.
Correlating magnetic resonance imaging with the biochemical content of the normal human intervertebral disc
Authors: Weidenbaum M. , Foster R. J. , Best B. A. , Saed‐Nejad F. , Nickoloff E. , Newhouse J. , Ratcliffe A. , Mow V. C.
Published: February 2005

Magnetic resonance imaging was used to determine the T2 relaxation times of prepared proteoglycan solutions and of normal human intervertebral disc tissue from the annulus fibrosus (AF) and nucleus pulposus (NP). The collagen, proteoglycan, and water contents of the disc tissue samples were determined by biochemical assays after they were scanned. Correlations among 1/T2, collagen, proteoglycan, and water contents of the tissue samples and among 1/T2, water, and proteoglycan contents of the proteoglycan solutions were calculated. A moderate negative correlation between 1/T2 and water content was noted for the tissue samples, and a very high negative correlation was found between 1/T2 and water content for the proteoglycan solutions. The very high positive correlation between 1/T2 and proteoglycan content of the proteoglycan solutions is probably due to this negative correlation between 1/T2 and water content. There was no significant correlation between 1/T2 and proteoglycan content of the tissues. The moderate positive correlation between 1/T2 and collagen content is probably due to the high negative correlation between collagen content and water content. No significant correlation was found between the collagen and proteoglycan contents of the tissues. Thus it appears that the data confirm previous reports in the literature that the collagen of the disc tissue functions to control its water content.
Fibrillar collagen‐biphasic calcium phosphate composite as a bone graft substitute for spinal fusion
Authors: Zerwekh Joseph E. , Kourosh Sohrab , Scheinberg Robert , Kitano Tatsuro , Edwards Martin L. , Shin Deahwan , Selby David K.
Published: February 2005

The osteoconductive capacity of fibrillar collagen‐biphasic calcium phosphate composition was compared to autogenous bone in a canine spinal fusion model. All animals underwent a standard intervertebral body fusion (L2–L4) with rigid internal fixation and received either autogenous bone alone or a mixture of the ceramic and autogenous bone (3:1) as the graft material. Animals were followed for 12 months and the quality of fusion in each animal assessed by biomechanical testing and histological analysis. The fused L2–L4 segment of each dog was embedded in bone cement and mounted in a specially designed mechanical tester for testing in flexion, extension, and side bending. Overall, the mean rigidity of the fusion mass was not significantly different between the two groups [10.5 ± 4.1 (SD) for autogenous bone vs. 11.3 ± 1.7 for the ceramic plus autogenous bone, p > 0.05]. Similar findings were obtained for mean bending moment, compressive load, angular deformation, and energy absorbed for the two groups. Histological analysis was performed on transverse nondecalcified specimens. Quantitation of bone ingrowth using back‐scattered electron imaging disclosed no significant differences in the amount of new bone formed at the graft site between autogenous bone and the ceramic plus autogenous bone recipients (23.4 ± 10% vs. 25.8 ± 8.8%) when correction for the autogenous bone volumes was performed. Light microscopic analysis of toluidine blue‐stained transverse sections demonstrated new bone growth around and through the ceramic bone graft material. These results suggest that use of a collagen‐biphasic calcium phosphate ceramic and autogenous bone mixture (3:1) provides a suitable osteoconductive alternative to the use of autogenous bone and results in the formation of a mechanically competent fusion mass not significantly different from that obtained with autogenous bone alone.
Three‐Dimensional mechanical properties of the thoracolumbar junction
Authors: Oxland Thomas R. , Lin Ruey‐Mo , Panjabi Manohar M.
Published: February 2005

The thoracolumbar junction region is a frequent site of spinal trauma. Accurate knowledge of the normal mechanical behavior of the intervertebral joints in this region is of importance to the clinician in treating the spinal injuries. The present study documented the complete three‐dimensional motions of levels T11–T12 and T12‐L1 in the thoracolumbar region. Pure moments of flexion/extension, bilateral axial torque, and bilateral lateral bending were applied to 11 three‐vertebrae human cadaveric specimens (T11‐L1) to a maximum of 7.5 Nm. Intervertebral motions were calculated using stereophotogrammetry and presented in the form of load‐displacement curves, each containing three rotations and three translations at one intervertebral level. Average ± SD flexion, extension, axial rotation, and lateral bending ranges of motion to one side were 2.7 ± 1.3°, 2.4 ± 1.3°, 1.8 ± 0.7°, and 3.5 ± 1.1°, respectively, at level T11–T12. The same ranges of motion at T12‐L1 were 2.9 ± 1.4°, 3.9 ± 1.4°, 1.2 ± 0.7°, and 3.7 ± 1.1°, respectively. The extension and axial rotation ranges of motion at level T11–T12 were found to be significantly different than the same motions at T12‐L1. The different geometry in the facet joints explains these observed differences in the mechanical behavior of T11–T12 and T12‐L1.
Immunohistochemical localization of β1‐integrins in anterior cruciate and medial collateral ligaments of human and rabbit
Authors: Gesink Dirk S. , Pacheco Hector O. , Kuiper Scott D. , Schreck Paul J. , Amiel David , Akeson Wayne H. , Woods Jr. Virgil L.
Published: February 2005

The integrins are a family of adhesion‐mediating cell surface receptors that play critical roles in cell‐extracellular matrix interactions and have been shown to be important in the healing response in several tissues. We have studied integrin expression in normal human and rabbit anterior cruciate (ACL) and medial collateral (MCL) ligaments of the knee as a preamble to studies of β1‐integrin expression in healing ligaments. Histologic sections of human and rabbit ACL and MCL were probed for integrin expression utilizing integrin‐specific monoclonal antibodies (mAbs) followed by immunoperoxidase detection. Staining of human specimens with mAbs revealed the presence of β1‐, α1‐, and α5‐integrin chains on the tissue fibroblasts of both ACL and MCL, while staining of rabbit specimens with rabbit integrin‐reactive monoclonals revealed the presence of β1‐ and α5‐integrin on these ligaments. Equivalent amounts of the integrins studied were present on normal ACL and MCL. We conclude that the rabbit is an appropriate model for analyzing the expression and functional role of integrins in ligament wound healing.
[99mTc]Diphosphonate uptake and hemodynamics in experimental arthritis: Effect of naproxen in the canine carrageenan injection model
Authors: Hansen Ebbe Stender , He Shu‐Zheng , Søballe Kjeld , Kjølseth Dorthe , Henriksen Tine Brink , Hjortdal Vibeke Elisabeth , Bünger Cody
Published: February 2005

The impact of naproxen treatment on juxta‐articular hemodynamics and bone metabolism in experimental juvenile arthritis was studied in the articular carrageenan injection model. Unilateral gonarthritis was induced for 12 weeks in eight dogs receiving naproxen (dosage, 2 mg/kg) and eight controls. Regional blood flow was assessed by the microsphere method, plasma volume by the distribution space of [125I]fibrinogen, and bone metabolism by the 2‐h uptake of [99mTc]diphosphonate ([99mTc]DPD). Synovial effusion was less prominent with naproxen treatment as judged by joint fluid volume and pressure. Naproxen reduced the arthritic capsular hyperemia, almost normalized a severe blood flow increase in patella and both juxta‐articular epiphyses, ameliorated an expansion of plasma volume in the patella and the distal femoral epiphysis, and normalized an increased [99mTc]DPD uptake in subchondral femoral bone and the tibial cortex. Significantly increased arteriovenous shunting in the arthritic extremity was unaffected by naproxen. The study suggests that long‐term cyclooxygenase inhibition offers protection against hemodynamic and metabolic changes in juxta‐articular bone secondary to synovial inflammation.
Effect of short‐term hypomagnesemia on the chemical and mechanical properties of rat bone
Authors: Boskey Adele L. , Rimnac Clare M. , Bansal Manjula , Federman Micheline , Lian Jane , Boyan Barbara D.
Published: February 2005

Magnesium is known to have an essential role in determining the properties of bone, but the way in which Mg exerts its actions remains unclear. Although long‐term Mg deficiency is known to produce osteopenia, the effects of short‐term Mg deficiency have not been established. To test the hypothesis that Mg deficiency results in an altered pattern of initial mineralization and concomitant altered bone properties, the radiographic, histologic, chemical, and mechanical properties of the bones of rats given a Mg‐deficient diet were compared to those of rats pair‐fed the same diet supplemented with Mg. Short‐term Mg‐deficiency in the diet of growing rats produced a significant decrease in both the trabecular bone volume and the mineral content of the newly formed metaphysis, a significant increase in the Ca:P ratio, and a slight, but significant increase in hydroxyapatite crystallite size and/or perfection in the metaphysis. Comparable, but not significant, trends were found in the diaphyses. Metaphyseal bone osteocalcin levels were reduced in the Mg‐deficient rats and lipid was more easily extracted from their bones. No detectable alterations in radiographic microstructure were noted. Mechanically, a significant decrease in the maximum three‐point bend strength of the femurs of Mg‐deficient rats was observed. These data support the hypothesis that short‐term Mg deficiency affects the pattern of bone mineral formation.
Partial pressures of oxygen and carbon dioxide in bone and their correlation with bone‐blood flow: Effect of decreased arterial supply and venous congestion on intraosseous oxygen and carbon dioxide in an animal model
Authors: Kiær Thomas , Dahl Benny , Lausten Gunnar
Published: February 2005

Pathological changes in bone have been related to a preceding impediment of the arterial or venous bone circulation and hypoxia. In this study, we analyzed the feasibility of mass spectrometry in measuring intraosseous oxygen and carbon dioxide. The partial pressures were also measured in intraosseous blood samples, and blood flow in bone was measured with the radioactive microspheres technique. The average partial pressure of oxygen in the lateral femoral condyle was 34 ± 1.6 mm Hg when measured in intraosseous blood samples and 36.3 ± 2.3 mm Hg when measured with the on‐line mass spectrometer, with significant correlation between the methods. The absolute value of the partial pressure of carbon dioxide measured in situ with mass spectrometry was correlated with the value in the withdrawn blood. There was no significant difference in partial pressures of oxygen and carbon dioxide between the two sides or between repetitive measurements. Arterial occlusion resulted in severe hypoxia, whereas more moderate changes followed venous occlusion.
Failure of perfusion with oxygenated Krebs‐Ringer solution to preserve the eccrine function of the vascular endothelium in bone
Authors: Moran Christopher G. , Wood Michael B.
Published: February 2005

An ex vivo canine tibia preparation was perfused at a constant rate with aerated (95% O2‐5% CO2) Krebs‐Ringer solution for 24 h. Bolus injections of norepinephrine (0.125‐0.5 μg) were given and then acetylcholine (5 × 10−5 M) was used to stimulate endothelial production of smooth muscle relaxing factors. Following 1 h of perfusion the addition of acetylcholine resulted in significant attenuation of the response to norepinephrine (p < 0.001). After 4 h perfusion acetylcholine did not attenuate the norepinephrine response, but addition of I‐arginine (the precursor of endothelial‐derived relaxing factor) resulted in significant attenuation in the presence of acetylcholine (p < 0.005). At 6, 12, and 24 h the acetylcholine did not attenuate the norepinephrine response. It is concluded that normothermic, continuous perfusion with oxygenated Krebs‐Ringer solution results in normal endothelial eccrine activity up to 1 h. Following this period there is substrate depletion but endothelial eccrine function can be demonstrated for up to 4 h. At 6 h this function cannot be demonstrated, suggesting degradation of the functional integrity of the endothelium.
Rigid immobilization alters matrix organization in the injured rat medial collateral ligament
Authors: Padgett Larry R. , Dahners Laurence E.
Published: February 2005

The effects of mobilization on matrix reorganization and density after ligament injury were studied in rat medial collateral ligaments using scanning electron microscopy (SEM). Both medial collateral ligaments of 14 Sprague‐Dawley rats were sharply incised transversely at their midpoint. A 1.14‐mm threaded Kirschner wire was driven through the tibia and into the femur of the right leg (through the knee) to immobilize that knee at 90° of flexion. Four additional rats were used as controls. The right medial collateral ligament of the control rats was exposed in the same manner as the experimental rats and the wound closed without damaging the ligament. Rats were sacrificed on the 7th and 14th days postinjury and the ligaments evaluated by SEM. The electron micrographs from this study demonstrated that early on, the tissue at the injury site is disorganized on a gross scale with large bundles of poorly organized matrix. Large “defects” were present between bundles in the substance of the ligament and appeared as holes in the ligament around the injury site. As healing progressed, the matrix in the mobilized specimens appeared to bridge the injury site more rapidly and completely with fewer “defects” and thus higher density than the immobilized specimens.
Blood flow changes in the tibia during external loading
Authors: McDonald F. , Ford T. R. Pitt
Published: February 2005

The influence of external load on the blood flow of the rabbit tibia was assessed by laser Doppler flowmetry (LDF). Blood flow readings were obtained from three adolescent and three adult female New Zealand White rabbits whose tibiae previously had been pinned with modified orthopaedic pins. Readings were obtained from the exposed mid‐shaft of the tibia of each hind leg before, during, and after loading. The loading was either static or sinusoidal intermittent. The LDF resulted in a reading from the tibia which was consistent with the recordings of blood flow; the traces were similar to the pulsatile nature of pulse pressure recordings. After loading of the tibia, in both the adolescent and adult rabbits the effects were an increase in blood flow, as measured with LDF, on the tensile aspect, and a decrease in flow on the compressive side. These changes were statistically significant (p < 0.01) as measured by a Student t test. This change in flow reached a plateau with change in strain. Furthermore, the changes in flow produced by loading continued as long as the load was applied. A response similar to reactive hyperaemia occurred on the compressive aspect of the tibia; there was an increase of blood flow above the resting level after removal of the static load. The effect of a sinusoidal intermittent load was less than that of a static load, and the differences in flow between tensile and compressive aspects was not significant. The changes induced offer further insight into factors controlling bone remodelling.
A quantitative study of the routes of blood flow to the tibial diaphysis after an osteotomy
Authors: Triffitt Paul D. , Cieslak Catharine A. , Gregg Paul J.
Published: February 2005

Techniques of tissue exclusion have been used previously in qualitative investigations of the vascularity of long bones, after experimental fracture; we quantified their effects on bone blood flow in rabbits. Thirty‐six adult rabbits were divided into three groups in which flow was measured, with the microsphere technique, 1 and 2 weeks after osteotomy. In Group 1, osteotomy of the tibial shaft only was done; in Group 2, osteotomy was done with exclusion of the periosteum and muscle by a silicone rubber sheath; and in Group 3, osteotomy was done with exclusion of the marrow by reaming and insertion of an intramedullary nail. All involved limbs were immobilized in a cast. In Group 1, cortical flow increased but marrow flow did not change, which suggests that the changes in cortical flow were mediated by a supply paralleling that of the marrow. In Group 2, the changes in cortical flow were abolished, which implies that this parallel supply is from the periosteum and extraosseous tissues. In Group 3, cortical flow was not significantly reduced, which demonstrates reeruitment of this periosteal and extraosseous supply. These results lend support to the hypothesis that the blood supply to the healing diaphysis is principally from the periosteum and extraosseous tissues during the early peak period of blood flow.
The mechanical properties of skeletally mature rabbit anterior cruciate ligament and patellar tendon over a range of strain rates
Authors: Danto Michael I. , Woo Savio L‐Y.
Published: February 2005

The effect of strain rate on the mechanical properties of the rabbit anterior cruciate ligament (ACL) and patellar tendon (PT) was evaluated. The medial portion of the ACL was loaded to tensile failure at rates of 0.003, 0.3, and 113 mm/s, and the middle third of the PT was loaded at rates of 0.008, 0.8, and 113 mm/s. The load was recorded with a high‐speed measurement plotting system, and each test was videotaped for strain analysis. The nonlinear portion of the stress‐strain curve was curve‐fit to an exponential function having two nonlinear constants, representing the initial modulus, and rate of change of the modulus. The modulus of the rabbit PT was found to be 89% higher than that of the ACL. The initial modulus and rate of change of the modulus also were greater for the PT than for the ACL. The modulus of the PT was shown to be more sensitive to strain rate than that of the ACL; a 94% increase was observed for the PT, and a 31% increase was observed for the ACL; a 94% increase was observed for the PT, and a 31% increase was observed for the ACL. There was no effect of strain rate on the mode of failure of either the ACL or the PT; all but three of the specimens failed at the insertion site.
Double‐level cauda equina compression: An experimental study with continuous monitoring of intraneural blood flow in the porcine cauda equina
Authors: Takahashi Keisuke , Olmarker Kjell , Holm Sten , Porter Richard W. , Rydevik Björn
Published: February 2005

Compression of the spinal nerve roots may occur clinically at multiple levels at the same time; however, the basic pathophysiology of multilevel compression is largely unknown. In this study, the intraneural blood flow was analyzed continuously in the uncompressed segment between two compression balloons, with a pig used as an experimental model and a thermal diffusion method. At 10 mm Hg compression, there was a 64% reduction of total blood flow in the uncompressed segment compared with pre‐compression values. Total ischemia occurred at pressures 10‐20 mm Hg below the mean arterial blood pressure. After two‐level compression at 200 mm Hg for 10 min, there was a gradual recovery of the intraneural blood flow towards the baseline. Recovery was less rapid and less complete after 2 h of compression. Double‐level compression of the cauda equina can thus induce impairment of blood flow, not only at the compression sites, but also in the intermediate nerve segments located between two compression sites, even at very low pressures. These findings may have clinical importance in the understanding of the pathophysiology of multiple‐level cauda equina compression.
Torque history of electrically stimulated human quadriceps: Implications for stimulation therapy
Authors: Lieber Richard L. , Kelly M. Jeanne
Published: February 2005

The time course of knee extension torque was measured in human quadriceps muscles during 30 min of transcutaneous neuromuscular electrical stimulation (NMES). Ninety subjects were divided into six experimental groups (n = 15 per group), which received stimulation at one of the following frequency/duty cycle combinations: 10 Hz/50%, 30 Hz/50%, 50 Hz/50%, 10 Hz/70%, 30 Hz/70%, and 50 Hz/70%. Two‐way analysis of variance revealed that the magnitude of the relative torque decrease (the percentage of decrease in torque relative to the initial value) was significantly different between frequencies (p < 0.005) and duty cycles (p < 0.02), with no significant interaction (p > 0.6). Increasing either frequency or duty cycle caused a greater decrease in torque. In spite of this result, there was no significant difference between groups in the total activity (torque‐time integral) achieved during the 30 min treatment session. The magnitude of this activity corresponded to only about 7–14 maximum voluntary contractions. Finally, the average torque during the treatment session was significantly different among groups (p < 0.001), being greatest for the 50 Hz/50% group and least for the 10 Hz/70% group. Taken together, these data suggest that a smaller number of longer duration contractions produces the greatest muscle tension. They also suggest that the absolute torque levels achieved with NMES are relatively low compared with voluntary muscular activity.
Effects of solvent preservation with or without gamma irradiation on the material properties of canine tendon allografts
Authors: Maeda A. , Inoue M. , Shino K. , Nakata K. , Nakamura H. , Tanaka M. , Seguchi Y. , Ono K.
Published: February 2005

We studied the effects of solvent preservation with and without gamma irradiation on the material properties and morphology of canine tendons. Twenty‐four paired tendons were harvested from both hind limbs of eight dogs. The tendons from the right legs were divided into three treatment groups of eight tendons each. In the first group, the tendons were subjected to solvent preservation for sterilization and drying (solvent group). In the second group, the tendons were treated in the same manner and then were sterlized by gamma irradiation (solvent/gamma group). The same treatments were applied to the tendons in the third group but in reverse order (gamma/solvent group). Tendons from the contralateral left legs were frozen immediately for use as controls for each corresponding treatment group. Histologically, the tendons treated with solvent, with or without gamma irradiation, had a more prominent wavy pattern in the collagen fibers than the control tendons. Mechanically, the tangent moduli for the solvent, solvent/gamma, and gamma/solvent groups were 58.53, and 99%, respectively, of each contralateral control. The respective tensile strengths were 85, 39, and 86% of that of the contralateral control. The tendons in the solvent/gamma group underwent the most severe changes in material properties: the tendons in the gamma/solvent group changed the least. This suggests that gamma irradiation followed by solvent drying is the procedure of choice for the preservation of tendon allografts.
Immunolocalization of selected cytokines and proteases in canine articular cartilage after transarticular loading
Authors: Pickvance E. A. , Oegema Theodore R. , Thompson Roby C.
Published: February 2005

Cytokines and proteases are thought to play a role in the destruction of cartilage and the development of osteoarthritis. The purpose of this study was to document chronological involvement of interleukin‐1 beta (IL‐1β), tumor necrosis factor‐alpha (TNF‐α), stromelysin (MMP‐3), fibronectin, and alteration in the chondroitin sulphate sulfation pattern. Canine patellae underwent a closed‐joint impact to induce the development of osteoarthritis. The animals were killed at 2, 12, 24, and 52 weeks. The patellar damage included cracks in the superficial zone of cartilage and the zone of the calcified cartilage‐bone interface, vertical step‐off fractures in the zone of calcified cartilage, and loss of proteoglycan around the cracks in the deep and superficial zones of cartilage. With avidin‐biotin immunohistochemistry, these specimens were stained with antibodies to IL‐1β, TNF‐α, MMP‐3, fibronectin, and altered proteoglycan sulfate with the monoclonal antibody 3‐B‐3. Three of the four specimens obtained at 2 weeks demonstrated a strong cellular and weak matrix staining‐pattern for IL‐1β, TNF‐α, MMP‐3, and fibronectin around the cracks in the superficial and transitional zones of cartilage. No consistent staining pattern was noted in the cracks in the deep zone. None of the specimens obtained at 12, 24, or 52 weeks stained for these antibodies. No staining for the abnormal sulfation with the 3‐B‐3 antibody was evident in any specimen. The specimens obtained at 52 weeks showed healing of the step‐off fractures and a filling‐in of the proteoglycan loss. This model probably reflects the short‐term cartilaginous changes in the patella after trauma; thus, only transient elevations in the cytokines and proteases were evident.
The use of coccygeal discs to study intervertebral disc metabolism
Authors: Oshima H. , Ishihara H. , Urban J. P. G. , Tsuji H.
Published: February 2005

There have been very few studies on the metabolism of the intervertebral disc. One possible reason is that lumbar discs suitable for in vitro synthesis studies are difficult to obtain. We have examined some properties of coccygeal discs to see if those discs are a suitable alternative. The properties measured appear similar to those of lumbar discs, with collagen content lowest in the nucleus and highest in the outer annulus, while hydration and glycosaminoglycan content were highest in the nucleus and of a similar level to those of canine lumbar discs (approximately 83% water). The discs were under mechanical load in vivo, resulting in an equilibrium swelling pressure of 0.25–0.3 MPa. The 35S‐sulphate incorporation rate was 2–5 × 10−5 mmol/g dry weight per hour in the inner annulus and nucleus, in comparison with 2–3 × 10−5 mmol/g dry weight per hour in rabbit and canine lumbar discs. Coccygeal discs are a readily obtainable and cheap source of disc material, and they are easy to dissect out. Since the general properties of these discs are similar to those of lumbar discs, we suggest that they are a suitable model for the study of the metabolic and other properties of lumbar discs.
Effect of fetal thyroid hormone (RT3) on sarcoma cells in culture
Authors: Dutkowsky Joseph P. , Smith Richard A. , Calandruccio Rocco A. , Carnesale Peter G.
Published: February 2005

Fetal thyroid hormone (RT3) is considered metabolically inactive and is present in high concentration in fetuses and in some patients with end‐stage malignant disease. In a virus‐induced erythroleukemia cell model, RT3 was found to stimulate the growth of the erythroleukemia cells in culture. The focus of this research was to test the effect of RT3, at several concentrations, on the growth of naturally occurring human sarcomas in cell culture. Cloned cell lines of Ewing sarcoma, rhabdomyosarcoma, and osteogenic sarcoma were grown in multiple flasks of serum‐free medium containing varying concentrations of RT3, ranging from 10−8 and 10−5 M. Cells grown in serum‐free medium containing no RT3 were used as a control. RT3 significantly increased the growth (total protein) of the rhabdomyosarcoma cell line in culture at concentrations between 10−8 and 10−6 M, with the maximum effect at 10−7 M. The growth of one cell line of Ewing sarcoma was not affected by RT3 for any of the concentrations tested. The growth of two Ewing sarcomas and one osteogenic sarcoma was significantly stimulated by RT3 but only at the highest concentration of 10−5 M. The growth of the other osteogenic sarcoma cell line was significantly increased at concentrations of 10−6 and 10−7 M. The stimulatory effect of RT3 on several sarcoma cell lines in culture suggests the presence of a specific receptor in the neoplastic cells and the possibility that RT3 may be useful as a model for new chemotherapeutic agents.
Energy cost of ambulation with different methods of foot and ankle immobilization
Authors: Fowler Patrick T. , Botte Michael J. , Mathewson James W. , Speth Steven R. , Byrne Thomas P. , Sutherland David H.
Published: February 2005

In order to measure the energy cost of immobilization of the foot and ankle during ambulation, 14 healthy male volunteers exercised while wearing various immobilization devices. Oxygen consumption, oxygen cost, cardiac output, minute ventilation, heart rate, stroke volume, stride length, and stride frequency were determined at a steady state of exercise as the subjects walked on a treadmill at 80 m/min (equivalent to the comfortable walking speed of approximately 3 mi/h). Each subject was tested with three different types of immobilization devices: a short leg walking cast, a prefabricated lower leg orthosis, and a rigid‐soled surgical shoe. The results were compared with those for the same men ambulating without an immobilization device. Ambulation with the short leg walking cast and the prefabricated lower leg orthosis required significantly more energy in comparison with control values (all p values ≤ 0.006) in terms of oxygen cost, cardiac index, oxygen consumption, and minute ventilation. However, when the rigid‐soled surgical shoe was worn, energy consumption as measured by all parameters was not significantly increased compared with control values. Comparison of the findings for the short leg walking cast and the prefabricated lower leg orthosis showed no significant differences in any parameter of energy consumption. Stride length, however, was significantly shorter in the short leg walking cast compared with all immobilizers tested.
Effects of prefracture irradiation on the biomechanical parameters of fracture healing
Authors: Widmann Roger F. , Pelker Richard R. , Friedlaender Gary E. , Panjabi Manohar M. , Peschel Richard E.
Published: February 2005

This study examined the effects on the biomechanical parameters of fracture healing of a single dose of 900 rad (the approximate single‐dose equivalent of 2,500 rad in 10 divided doses), given 1 day prior to closed fracture of the femur. The femurs were recovered at 2, 3, 4, 8, and 16 weeks after fracture and were mounted and tested to failure in torsion; the results were compared with those in nonirradiated controls from a previously published study. Prefracture irradiation delayed the progressive increase in biomechanical parameters of fracture healing. The delay was statistically significant up to 8 weeks after fracture. At 4 weeks, the normalized torque was 44% that of intact bone in the treated group compared with 75% for the control group. Sixteen weeks after fracture, the biomechanical and histological parameters of fracture healing of the irradiated femurs were no different from those of the nonirradiated controls. Within the treated group, the irradiated fractures remained significantly weaker than their contralateral intact bone at all time intervals, with a torque of only 79% that of intact bone at 16 weeks. Thus, femoral fractures in rats healed (or regained substantial strength) following palliative doses of radiation delivered 1 day prior to injury, but the repair process was delayed compared with that of nonirradiated controls.
A technique for the evaluation of the contributions of knee structures to knee mechanics in the knee that has a reconstructed anterior cruciate ligament
Authors: Feder Seth M. , Butler David L. , Holden John P.
Published: February 2005

A technique to quantify the restraining action of specific knee structures during anterior/posterior (A/P) tibial displacement tests in the goat knee that has a reconstructed anterior cruciate ligament (ACL) is described. Joint specimens were mounted in an instrumented test stand to measure both the forces on, and resulting translations of, the tibia in the A/P direction. The intact grafted knee was tested first, after which structures were sequentially cut or removed, or both, and the test was repeated. The ACL graft remained intact in the joint during this process; therefore, subsequent axial failure testing was possible. Analysis of the resulting force‐displacement curves allowed the percentage contribution and anterior joint stiffness to be determined for each structure at a fixed anterior displacement in 12 goat knees 6 months after ACL allografting. The allografts were found to provide about 56% of the total restraining force, more than any other structure examined. Studies of this kind will be important in the documentation of the changing role of an autograft or allograft in a reconstructed knee over time.
Evaluation of bone‐grafting materials in a new canine segmental spinal fusion model
Authors: Muschler George F. , Huber Bryan , Ullman Thomas , Barth Richard , Easley Kirk , Otis James O. , Lane Joseph M.
Published: February 2005

This paper describes a new canine segmental spinal fusion model for the comparison of bone‐grafting materials. The test sites in the model are three separate posterior interfacet‐interlaminar fusion sites in the lumbar spine (L1‐2, L3‐4, and L5‐6). The outcome was assessed by scoring of the fusion sites for union and by mechanical testing of fused segments. The results from two experiments are presented. Autogenous cancellous bone was the most effective material tested and had a statistically superior score for union compared with all other materials (p = 0.01). The results with an osteoconductive matrix of collagen and ceramic alone were no better than those with the controls (no graft). However, addition of an extract of matrix‐derived proteins (15–30 kDa) to the collagen‐ceramic carrier appeared to improve the score for union. The inclusion of nonresorbed ceramic granules had no evident effect on the mechanical properties of fusions, with a comparable score for union. This model appears to be a sensitive and efficient method for the comparison of graft materials. Advantages over previously described models are discussed.
Posture affects motion coupling patterns of the upper cervical spine
Authors: Panjabi Manohar M. , Oda Takeori , Crisco Joseph J. , Dvorak Jiri , Grob Dieter
Published: February 2005

Measurements of motions of the cervical spine are used to help diagnose the problems of clinical instability due to degenerative changes and trauma. For a better interpretation of the three‐dimensional motions of the upper cervical spine, knowledge of the effects of posture on these motions is necessary. Seven fresh human cadaveric C0–C3 spinal specimens were utilized. Each specimen was put in three distinct sagital plane postures: full flexion, neutral, and full extension. At each posture, two load types were applied: left and right axial torques, and left and right lateral bending moments up to 1.5 Nm. The resulting three‐dimensional relative motions of C0–C1 and C1–C2 were measured, with use of nonconstraining stereophotogrammetry, in the form of load‐displacement curves. We found that the curves were nonlinear. The most dramatic change due to modification in posture was found in coupled sagittal plane rotation, which changed from extension at extended posture to flexion at flexed posture at both levels and in response to both load types. For the axial torque, the main axial rotation and coupled lateral bending changed little with posture. For the lateral bending moment, the main lateral bending rotation and coupled axial rotation decreased; the latter changed direction at C1–C2 as the spine was put into flexed posture. The motions for the right and left load applications generally were mirror images, except for the coupled sagittal plane rotations, which did not change with the direction of the load.
Laser doppler flowmetry for estimation of bone blood flow: Studies of reproducibility and correlation with microsphere technique
Authors: Lausten Gunnar Schwarz , Kiær Thomas , Dahl Benny
Published: February 2005

The blood flow in the femoral condyles of six pigs was measured by the microsphere technique and by laser Doppler flowmetry (LDF) before and after clamping of the external iliac artery. A significant decrease in the bone blood flow was found with both microsphere and LDF measurements, and a high correlation was found between the two methods. After release of the arterial clamp, the LDF values rapidly returned to approximately the same values as before clamping. In a second part of the study, the LDF output signal was studied in the intertrochanteric area of eight patients. The reproducibility of two LDF measurements at the same location was within 15%. The temporal variability of the LDF signal during 10 min of recording showed only slight variations. It is concluded that LDF is relative in nature and that the mean LDF output signal is suitable for monitoring dynamic responses of the bone blood flow to various stimuli. Several consecutive measurements have to be performed if the blood flow at different locations of a specific bone are to be compared with each other.
Effects of complete stress‐shielding on the mechanical properties and histology of in situ frozen patellar tendon
Authors: Ohno Kazunori , Yasuda Kazunori , Yamamoto Noritaka , Kaneda Kiyoshi , Hayashi Kozaburo
Published: February 2005

The effects of freezing and stress‐shielding on the mechanical properties and histology of the patellar tendon (PT) were studied with the use of 28 mature Japanese white rabbits. The PT was frozen in situ by liquid nitrogen to kill the fibroblasts and then, for stress‐shielding, a stainless‐steel wire, installed between the patella and the tibial tubercle, was stretched to release all tension in the PT. After being allowed unrestricted activity in their cages for 1, 2, 3, or 6 weeks, the animals were killed, and the PTs were excised for mechanical and histological study. The cross‐sectional area of the frozen and stress‐shielded PT started to increase significantly 1 week after the treatment and leveled off at 3 weeks. In contrast, the tensile strength and elastic modulus begar to decrease significantly at 1 week, falling to 15% of the control values at 6 weeks. Histologically, cells were absent until 2 weeks after freezing and stress‐shielding, although new cells appeared by 3 weeks. Splitting and fragmentation of collagen bundles were observed beginning at 2 weeks. These results indicate that complete stress‐shielding led to substantial changes in the mechanical properties of the once‐frozen PT, even in the absence of the tissue remodeling process by fibroblasts.
In vitro photodynamic therapy of musculoskeletal neoplasms
Authors: Hourigan A. J. , Kells A. F. , Schwartz H. S.
Published: February 2005

Photodynamic therapy is a tumoricidal modality that utilizes an inactive pharmacologic agent that becomes activated on exposure to visible light. Neoplasms selectively retain and accumulate photosensitizers at levels generally higher than surrounding non‐neoplastic tissues. The purpose of this study was to establish a testing method for in vitro investigation of the effects of photodynamic therapy on human musculoskeletal neoplasms by examination of the sensitivity of these tumors to photoactivation. Three human musculoskeletal neoplasms were cultured, exposed to the photosensitizer Photofrin, and then studied for their response to photodynamic therapy after laser activation. Giant‐cell tumor, dedifferentiated chondrosarcoma, and osteosarcoma were examined with use of strict experimental controls. The photoradiation conditions during photodynamic therapy were kept constant. Cell viability was determined as a function of energy dose. We concluded that the three musculoskeletal tumors were susceptible to in vitro photodynamic therapy and the test system was reproducible. The optimal in vitro nontoxic incubation concentration of Photofrin was 3 μg/ml. A differential cytotoxic response to photodynamic therapy was exhibited by the musculoskeletal neoplasms as a function of increased dosages of energy.
Effect of ischemic storage on endothelium in canine bone
Authors: Roorda Jan , Wood Michael B.
Published: February 2005

The limits of room temperature (24°C) and hypothermic (4°C) storage for preservation of endothelial eccrine function were investigated with use of an ex vivo perfusion apparatus model of the cannulated canine tibia. Norepinephrine‐induced contraction of smooth muscles in both the presence and absence of acetylcholine was compared, with and without selective blockade of endothelial‐derived relaxing factor (EDRF). At room temperature, release of EDRF deteriorated after 24 h and was absent after 48 h of storage. At 4°C, endothelial eccrine activity appeared unimpaired for as long as 72 h of storage. From 96–192 h of storage at 4°C, release of EDRF was suggested, but with an attenuation of its effect on smooth muscle. At 216 and 504 h of storage at 4°C, no endothelial eccrine activity was demonstrated.
Stem curvature and load angle influence the initial relative bone‐implant motion of cementless femoral stems
Authors: Berzins Aivars , Sumner Dale R. , Andriacchi Thomas P. , Galante Jorge O.
Published: February 2005

A 6 df measurement system was used to investigate the initial relative bone‐implant motion of two types of cementless total hip replacement femoral components—a straight stem and a curved stem. Five pairs of fresh frozen femurs from human cadavers were tested with loads applied to the femoral head at angles characteristic of level walking, stair‐climbing, and rising from a chair. The most important findings were that (a) the resultant proximal translations were twice as high with the straight stem as with the curved stem at load angles encountered in stair‐climbing and rising from a chair, (b) both stem types had more motion at load angles encountered in stair‐climbing and rising from a chair than in level walking, with the increases ranging from 3 to 14‐fold, (c) there was as much as 66‐fold more motion distally than proximally, and (d) the amount of interface motion varied by 5‐fold between the medial and lateral surfaces of the distal part of the implant because of the combined effects of translation and rotation. The amount of initial bone‐implant motion of the femoral component was found to be particularly sensitive to off‐axis loading; this suggests that stair‐climbing and rising from a chair should be avoided in the early postoperative period when a cementless porous‐coated femoral stem has been used.
Effects of local compression on peroneal nerve function in humans
Authors: Hargens Alan R. , Botte Michael J. , Swenson Michael R. , Gelberman Richard H. , Rhoades Charles E. , Akeson Wayne H.
Published: February 2005

A new apparatus was developed to compress the anterior compartment selectively and reproducibly in humans. Thirty‐five normal volunteers were studied to determine short‐term thresholds of local tissue pressure that produce significant neuromuscular dysfunction. Local tissue fluid pressure adjacent to the deep peroneal nerve was elevated by the compression apparatus and continuously monitored for 2–3 h by the slit catheter technique. Elevation of tissue fluid pressure to within 35–40 mm Hg of diastolic blood pressure (∼40 mm Hg of in situ pressure in our subjects) elicited a consistent progression of neuromuscular deterioration including, in order, (a) gradual loss of sensation, as assessed by Semmes‐Weinstein monofilaments, (b) subjective complaints, (c) reduced nerve conduction velocity, (d) decreased action potential amplitude of the extensor digitorum brevis muscle, and (e) motor weakness of muscles within the anterior compartment. Generally, higher intracompartmental pressures caused more rapid deterioration of neuromuscular function. In two subjects, when in situ compression levels were 0 and 30 mm Hg, normal neuromuscular function was maintained for 3 h. Threshold pressures for significant dysfunction were not always the same for each functional parameter studied, and the magnitudes of each functional deficit did not always correlate with compression level. This variable tolerance to elevated pressure emphasizes the need to monitor clinical signs and symptoms carefully in the diagnosis of compartment syndromes. The nature of the present studies was short term; longer term compression of myoneural tissues may result in dysfunction at lower pressure thresholds.