bluuebunny/crossref_metadata_2025 huggingface dataset:
Moderate running exercise augments glycosaminoglycans and thickness of articular cartilage in the knee joint of young beagle dogs
Authors: Kiviranta Ilkka , Tammi Markku , Jurvelin Jukka , Säämänen Anna‐Marja , Helminen Heikki J.
Published: February 2005

The local influences of physical exercise on thickness and glycosaminoglycan (GAG) content of canine articular cartilage were measured by microspectrophotometry of Safranin O‐ and periodic acid‐Schiff (PAS)‐stained tissue sections. Female Beagle dogs were housed in individual cages (bottom 0.9 × 1.2 m) and divided into runner (n = 6) and control (n = 8) groups. The trainig program started at the age of 15 weeks. During the subsequent 10 weeks, the dogs were accustomed to running on a treadmill inclined 15° uphill. Thereafter, the dogs ran 1 h daily, 5 days a week, at a speed of 4 km/h for 15 weeks. At the age of 40 weeks, the dogs were killed, and the samples for histology were taken from 11 different anatomical locations of the right knee (stifle) joint. The thickness of the uncalcified cartilage increased 19–23% on the lateral condyle and patellar surface of the femur, whereas the enhancement was smaller in other parts of the trained cartilage. The calcified cartilage did not show thickness alterations. Total GAGs were augmented by 28% in the summits on the femoral condyles, more on the medial than lateral side. The increased GAGs appeared to be predominantly chondroitin sulphates and were localized in the intermediate, deep, and even in the calcified zones, whereas the superficial zone did not show changes. There was a concomitant increase of non‐GAG oligosaccharides in the intermediate and deep zones, but not in the calcified cartilage. As judged from the enhanced GAG content and thickness, it is considered that moderate running exercise locally alters the biological properties of young articular cartilage at regions bearing the highest loading surplus.
Hydraulic resistance: A measure of vascular outflow obstruction in osteonecrosis
Authors: Downey Daniel J. , Simkin Peter A. , Lanzer William L. , Matsen Frederick A.
Published: February 2005

This study introduces hydraulic resistance (HR) as a new method to measure intraosseous vascular outflow resistance in the human proximal femur. HR is the standard measure of resistance to fluid flow in porous matrices and is derived from serial pressure/flow determinations. Eighteen hips were studied in 11 patients taken to surgery for core decompression therapy of presumable atraumatic osteonecrosis of the femoral head. HR was much higher in osteonecrotic (174 ± 29 mm Hg min/ml, SE) than in normal human cadaveric femora (14 ± 6) and was also higher in subcapital (253 ± 39) than intertrochanteric sites (78 ± 17). HR correlated highly with baseline intraosseous pressure (r = 0.74, p < 0.001). HR testing is a simple, practical method which quantifies outflow obstruction of the intraosseous circulation. We believe this test will be helpful in the diagnosis of atraumatic osteonecrosis and in the understanding of its underlying pathophysiology.
The influence of different degrees of stiffness of fixation plates on experimental bone healing
Authors: Terjesen Terje , Apalset Kristen
Published: February 2005

In order to throw some light on the controversial issue of the optimal stiffness in fracture fixation, the effects on bone healing of rabbit tibial osteotomies fixed by plates with four different degrees of stiffness were studied. The least stiff plate was made of glass fiber‐reinforced epoxy; the other three were made of stainless steel. The median bending stiffness in vitro of tibial osteotomies fixed with the various plates were 13%, 17%, 61%, and 74%, related to the stifness of intact tibiae. Transverse midshaft unilateral tibial osteotomies were fixed by the various plates, and the animals were killed after 6 weeks. The amount of periosteal callus was inversely related to the stiffness of the plates. A marked trend toward decreased strength and stiffness occurred in tibiae where the most rigid plate was used, compared with the values of those with the less rigid plates. This indicates that the stress‐protecting effect of very stiff plates begins early in the healing period and is pronounced even at 6 weeks and that a steel plate of lower stiffness is more appropriate for bone healing. However, too flexible plates involve increased risk of redislocation and mechanical failure.
Osteogenesis in rats with an inductive bovine composite
Authors: Nathan Ranga M. , Bentz Hanne , Armstrong Rosa M. , Piez Karl A. , Smestad Thomas L. , Ellingsworth Larry R. , McPherson John M. , Seyedin Saeid M.
Published: February 2005

Subcutaneous (S.C.) implantation of allogeneic demineralized bone matrix in rats results in endochondral bone formation. In contrast, implants of bovine demineralized bone matrix in rat S.C. tissue show inconsistent cartilage and bone formation, presumably due to an intense inflammatory reaction at the implant site. To overcome this response, a partially purified bone inducing extract was prepared from bovine bone by a series of steps that included demineralization, guanidine/HCI extraction, gel filtration, and cation exchange chromatography. To develop a carrier, the inactive guanidine/HCI‐extracted matrix was then trypsinized to remove the inflammatory and immunogenic components, thus yielding a predominantly collagenous matrix. Bovine composites were prepared by combining different amounts of the bone inducing extract with a carrier that consisted of the trypsinized bone matrix and purified soluble bovine dermal collagen. Subcutaneous implantation of the composite preparation resulted in dose‐dependent endochondral bone formation in rats. The inductive activity and the low‐level inflammatory response were comparable to allogeneic implants.
Canine osteoarthritis: Effects of endogenous neutral metalloproteoglycanases on articular cartilage proteoglycans
Authors: Pelletier J. P. , Martel‐Pelletier J. , Malemud C. J.
Published: February 2005

The aim of this study was to analyze the mechanisms by which neutral metalloproteoglycanases (NMPE) degrade proteoglycans (PGs) in the cartilage of an experimental model of osteoarthritis (OA). We demonstrated that chondrocytes in osteoarthritic cartilage synthesize PGs with the same functional characteristics as those found in normal cartilage. Osteoarthritic cartilage contains NMPE in both active and latent forms. Both forms can degrade newly synthesized and endogenous PG macromolecules, as indicated by the reduced hydrodynamic size found in the two PG populations of osteoarthritic cartilage. PG monomers, derived from the included fraction of Sepharose CL2B chromatography, were unable to form aggregates with hyaluronic acid. Reduction and alkylation showed that PG monomers from osteoarthritic cartilage had a small hydrodynamic size, especially after activation with aminophenylmercuric acetate. No significant differences were observed in the size of the chondroitin sulfate chain when normal cartilage was compared with its osteoarthritic equivalent. These results suggest that the proteolytic degradation of cartilage matrix PGs by NMPE occurs at both the hyaluronate‐binding region and at the chondroitin sulfate‐rich region of the core protein.
Antibiotic release from an experimental biodegradable bone cement
Authors: Gerhart T. N. , Roux R. D. , Horowitz G. , Miller R. L. , Hanff P. , Hayes W. C.
Published: February 2005

An experimental biodegradable bone cement [poly(propylene fumarate)‐methylmethacrylate] (PPF‐MMA) has been compared in vivo with polymethylmethacrylate (PMMA) as a carrier agent for local release of antibiotics. This approach is potentially applicable to the treatment of chronic osteomyelitis where the clinical goal is to achieve sustained high concentrations of antibiotics locally in the infected bone. In our experiments, gentamicin‐ and vancomycin‐impregnated cylindrical PMMA and PPF‐MMA cement specimens were implanted subcutaneously in rats, and blood and wound fluid samples were obtained over a 2‐week period. Antibiotic levels were determined using immunoassays, and microbiologic activity was confirmed with agar diffusion techniques. The biodegradable PPF‐MMA cement achieved and maintained considerably higher wound antibiotic levels than did PMMA cement. Vancomycin levels for the PPF‐MMA cement were greater than 20 times those for the PMMA cement at all sampling times from 24 h to 14 days. For both cements, the serum antibiotic concentrations remained safely below maximum levels recommended for parenteral therapy. Mechanical testing of the PPF‐MMA cement showed that admixture of 3% by weight of antibiotic did not adversely affect material properties. We conclude that this experimental biodegradable bone cement (PPF‐MMA) can be used as a carrier to achieve high sustained local levels and low serum levels of antibiotics. Because it is biodegradable and thus does not require a secondary procedure for removal, it has special potential for use in treatment of chronic osteomyelitis.
Predicting talocalcaneal joint orientations from talocalcaneal/talocrural joint orientations
Authors: Engsberg Jac R. , Grimston Susan K. , Wackwitz John H.
Published: February 2005

The purpose of this investigation was to determine the capacity of talocalcaneal/talocrural joint orientations to predict talocalcaneal (TC) joint orientations. A custom designed orientation‐loading fixture was used to position the calcaneus and shank with six degrees of freedom, and to apply loads in three orthogonal directions. Three reference pins were rigidly mounted in the calcaneus, talus, and shank segments to provide position data in 243 test situations. Test data were fitted to statistical models using analysis of variance. The models were then used to determine the capacity to predict talus positions from shank positions, both with respect to the calcaneus. Results indicated large between and within specimen variation and was attributed to individual joint morphology. It was concluded that (a) eversion‐inversion orientations of the TC/talocrural joint were not always accurate indicators of TC joint orientations. (b) abduction‐adduction orientations of the combined joint had the greatest overall influence on TC orientations (thus, monitoring eversion‐inversion and abduction‐adduction orientations of the combined joint would be more valuable in predicting pronation‐supination positions than monitoring only eversion‐inversion orientations), and (c) foot categories based on TC and TC/talocrural joint morphology should be developed. They would provide more accurate prediction for specimen foot orientations than prediction from overall average values.
Treatment of antigen‐induced arthritis in rabbits with dysprosium‐165–ferric hydroxide macroaggregates
Authors: Zuckerman Joseph D. , Sledge Clement B. , Shortkroff Sonya , Venkatesan Prasanna
Published: February 2005

Dysprosium‐165–ferric hydroxide macroaggregates (165Dy‐FHMA) was used as an agent of radiation synovectomy in an antigen‐induced arthritis model in New Zealand white rabbits. Animals were killed up to 6 months after treatment. 165Dy‐FHMA was found to have a potent but temporary antiinflammatory effect on synovium for up to 3 months after treatment. Treated knees also showed significant preservation of articular cartilage architecture and proteoglycan content compared with untreated controls, but only during the first 3 months after treatment. In animals killed 3 and 6 months after treatment there were only minimal differences between the treated and untreated knees, indicating that the antiinflammatory effects on synovial tissue and articular cartilage preservation were not sustained.
Gain in mass density of bone following strenuous physical activity
Authors: Leichter Isaac , Simkin Ariel , Margulies Joseph Y. , Bivas Arye , Steinberg Raya , Giladi Michael , Milgrom Charles
Published: February 2005

A group of 223 military recruits aged 18–21 years underwent strenuous physical training for a period of 14 weeks. The absolute bone density of the distal tibia in both lower limbs was measured before the training period and at its end. The density was determined by the Compton scattering technique, which has been developed in our laboratory; this method provides the bone mass of all bone constituents per unit volume. The distribution curve of the bone density in both tibiae shifted to higher values at the end of the training period. The mean bone density in the right and left tibia increased significantly by 7.5%. This study indicates that following an intensive physical exercise regime, a significant increase in the mass density of bone can be obtained in young adults within a short period.
The mechanical and morphological properties of bone beneath internal fixation plates of differing rigidity
Authors: Claes L.
Published: February 2005

The internal fixation of diaphyseal fractures by bone plates is a well recognized treatment. The normal physiological stress of bone is reduced by plates that cause a negative balance of bone‐remodeling processes. Many investigators have shown that the degree of stress protection is dependent on the rigidity of the plates. It was the aim of this study to quantify mechanical and morphological changes at different locations in a plated diaphyseal bone as a function of differing plate rigidity. Two types of plates with the same size but different materials were used. The stainless steel plates had a modulus of elasticity and bending stiffness 3.2 times higher than the carbon fiber reinforced carbon plates. Both types of plates were applied to the intact right and left femora of six foxhounds for 6 months. The stiffer stainless steel plates led to a significantly higher bone loss and correspondingly greater loss of mechanical properties. These effects were greatest directly beneath the plate and less with increasing distance from the plate.
The repair of experimentally produced defects in rabbit articular cartilage by autologous chondrocyte transplantation
Authors: Grande Daniel A. , Pitman Mark I. , Peterson Lars , Menche David , Klein Michael
Published: February 2005

Using the knee joints of New Zealand White rabbits, a baseline study was made to determine the intrinsic capability of cartilage for healing defects that do not fracture the subchondral plate. A second experiment examined the effect of autologous chondrocytes grown in vitro on the healing rate of these defects. To determine whether any of the reconstituted cartilage resulted from the chondrocyte graft, a third experiment was conducted involving grafts with chondrocytes that had been labeled prior to grafting with a nuclear tracer. Results were evaluated using both qualitative and quantitative light microscopy. Macroscopic results from grafted specimens displayed a marked decrease in synovitis and other degenerative changes. In defects that had received transplants, a significant amount of cartilage was reconstituted (82%) compared to ungrafted controls (18%). Autoradiography on reconstituted cartilage showed that there were labeled cells incorporated into the repair matrix.
Role of mechanical loading in the progressive ossification of a fracture callus
Authors: Blenman Patricia R. , Carter Dennis R. , Beaupré Gary S.
Published: February 2005

The progressive ossification pattern in a fracture callus was predicted based on a theory that relates the local stimulus for ossification to the tissue mechanical loading history. Two‐dimensional finite element analyses of a fracture callus were considered at three different stages of ossification. The sites of callus ossification represented in the initial model were predicted by previous analyses relating mechanical stress and vascularity to the differentiation of mesenchymal tissue in the early callus. The zones of further ossification, bone bridging, and bone consolidation predicted in the present study were found to be similar to the ossification patterns that have been documented by other researchers. The approach used to predict fracture healing is identical to that of previous studies predicting joint morphogenesis, with the exception that fracture healing requires continuous, articulating skeletal elements.
Energy absorptive properties of human trabecular bone specimens during axial compression
Authors: Linde Frank , Hvid Ivan , Pongsoipetch Buntoeng
Published: February 2005

Human trabecular bone specimens (n = 121) from the proximal tibial epiphysis of nine macroscopically normal cadaver knees were tested nondestructively to a fixed strain (0.6%) for analysis of unloading energy and hysteresis energy followed by a destructive test for analysis of work to failure. All energy properties showed interindividual variation (p < 0.005). There was a strong positive correlation between unloading energy and both stress (r = 0.95) and stiffness (r = 0.89) determined at 0.6% strain. A less strong, but statistically significant, correlation was found between hysteresis energy and stress (r = 0.82) and stiffness (r = 0.76) at 0.6% strain. There was a negative correlation between the loss tangent and stiffness at 0.6% strain (r = −0.40, p < 0.001). Work to failure correlated positively with modulus of elasticity (r = 0.75), ultimate stress (r = 0.92), and ultimate strain (r = 0.51). There was a positive mutual correlation between all energy properties (p < 0.001).
Use of patellar tendon autograft for anterior cruciate ligament reconstruction in the rabbit: A long‐term histologic and biomechanical study
Authors: Ballock R. Tracy , Woo Savio L‐Y. , Lyon Roger M. , Hollis J. Marcus , Akeson Wayne H.
Published: February 2005

To assess the degree of success of anterior cruciate ligament (ACL) replacement using the patellar tendon (PT) autograft, 29 New Zealand white rabbits underwent ACL reconstruction using a medial one‐third PT autograft. The femur–ligament–tibia complexes were evaluated at 0, 6, 30, and 52 weeks postoperatively for gross and histologic appearances and tensile load to failure properties. Grossly, the autografts did not resemble the control ACLs. Histologically, the autografts progressed from being hypercellular with a random collagen fiber bundle organization to having a near normal cellularity with a more parallel collagen fiber bundle pattern. Anteroposterior knee laxity was more than two times that of the control knees 52 weeks after reconstruction. Biomechanically, the PT autografts plateaued at 30 weeks postoperatively. The ultimate load and stiffness were 15 ± 5% and 24 ± 6% of the control ACLs, respectively. At 52 weeks, the appearance of the PT autograft had some general histologic similarities as compared with the native ACL. However, these similarities did not extend to the functional properties of the autograft.
Effect of muscle flap coverage on bone blood flow following devascularization of a segment of tibia: An experimental investigation in the dog
Authors: Richards Robin R. , Schemitsch Emil H.
Published: February 2005

Severe tibial fractures may be associated with soft tissue loss, devascularization of cortical bone, and significant morbidity. Local rotational muscle flap coverage is used to obtain coverage of acute open tibial fractures and to treat chronic osteomyelitis of the tibia. The purpose of this study was to determine (a) the longitudinal and cross‐sectional regional blood flow characteristics of the canine tibia and (b) whether a muscle flap was superior to vascularized skin coverage in restoring blood flow to devascularized canine tibial cortex. A 2.5‐cm segment of tibia between two standardized osteotomies was devascularized. The segment was replaced anatomically and stabilized with a plate. The animals were divided into two experimental group: (a) skin coverage (n = 8), and (b) muscle flap coverage (n = 8). Thirty‐one days postoperatively Ce141 microspheres were injected to measure bone blood flow. The tibial diaphysis was divided into proximal, middle (devascularized), and distal segments. The unoperated leg was used as a control. In the control tibiae, the middle segment was less vascular than either the proximal or distal segment and no difference between anterior and posterior cortical blood flow was observed. Blood flow to the devascularized segment of tibia was significantly greater when it was covered with a muscle flap (p < 0.025). The most significant increase in bone blood flow in the muscle flap coverage group versus the skin coverage group occurred in the anterior cortex of the tibia (p < 0.005). This may be clinically important since the soft tissues over the anterior tibia are commonly deficient following open fractures. The rate of osteotomy union was increased in the experimental group with muscle flap coverage (p < 0.05). These findings indicate that muscle flap coverage enhances the restoration of blood flow to devascularized tibial cortex.
Heterotopic osteogenesis in porous ceramics induced by marrow cells
Authors: Ohgushi Hajime , Goldberg Victor M. , Caplan Arnold I.
Published: February 2005

When untreated porous calcium phosphate ceramics were transplanted into subcutaneous (s.c.) or intramuscular (i.m.) sites, fibrovascular tissue grew in the pore region without evidence of bone formation. However, when these same ceramics were combined with syngeneic marrow cells, osteogenesis was observed inside the pore region of the implanted ceramic. The osteogenesis began on the surface of the pore region at ∼3 weeks postimplantation by a process of intramembranous bone formation, with the de novo bone tissue observed directly interfacing with the ceramic surface. Infrequently, small isolated areas showed cartilage formation with no noticeable endochondral ossification. At 4 weeks postimplantation of the ceramic with marrow cells, the osteogenesis in the ceremic accompanied an observed increase in compressive strength, rigidity, and energy absorption of the ceramic. These results suggest that a combination of porous ceramics and marrow cells may be useful for clinical problems requiring osseous reconstruction.
The effect of ascorbic acid on the metabolism of rat calvarial bone cells in vitro
Authors: Spindler Kurt P. , Shapiro David B. , Gross Stephen B. , Brighton Carl T. , Clark Charles C.
Published: February 2005

Addition of 50 μg/ml sodium ascorbate to confluent cultures of isolated rat calvarium bone cells resulted in a 21% increase in DNA production, a 50–60% increase in incorporation of [14C]proline into collagenous and noncollagenous proteins, and a 200% increase in alkaline phosphatase activity; under identical conditions, [35S]sulfate incorporation into proteoglycans (glycosaminoglycans) was not affected. These results suggest that ascorbate may be important in maintaining or stimulating the osteogenic phenotype of normal bone cells.
Quantitative histologic study of the influence of spinal instrumentation on lumbar fusions: A canine model
Authors: Farey Ian D. , McAfee Paul C. , Gurr Kevin R. , Randolph Mark A.
Published: February 2005

Histomorphometric and microradiographic studies were performed on 28 beagle hounds 1 year of age, followed up for 6 months after an L5–L6 anterior and posterior spinal destabilization procedure—Group I (n = 7),destabilizedsurgical controls, Group II (n = 7),posterolateral bone graftingafter destabilization; Group III (n = 7),Harrington rodinstrumentation and posterolateral bone grafting after destabilization; and Group IV (n = 7),Luque instrumentation, and bone grafting after destabilization. Six months postoperatively, device‐related osteoporosis occurred in spines treated with spinal instrumentation. Within the L5 vertebral body the mean trabecular width was less for the two groups with instrumentation (Groups III and IV) compared with the two groups without instrumentation (Groups I and II) (p < 0.001). The bone formation rate [mm3/(mm3× year)] × 103, which is based on the mean distance between sequenced fluorochrome labels, for Group I (destabilized, nonfused, noninstrumented dogs) was more than twice that of the other three groups, which were all equivalent (p < 0.05).Clinical relevance: Stress shielding, or more correctly, device‐related osteoporosis, probably can occur within vertebrae in response to rigid spinal instrumentation. However, the overall mechanical properties of vertebrae underlying spinal instrumentation are probably not at increased risk of fracture because the increase in cross‐sectional area of the vertebra and incorporated fusion mass more than compensate for the loss of volumetric bone density.
Biomechanics of the rabbit cervical spine as a function of component transection
Authors: Wetzel F. Todd , Panjabi Manohar M. , Pelker Richard R.
Published: February 2005

The rabbit cervical spine in the form of the functiona spinal unit was tested in a manner analogous to that used to study human functional spinal units. Anatomies and biomechanical similarities and differences with the human were demonstrated. The rabbit cervical spine failed abruptly after a welldefined series of anterior or posterior segmental injuries. However, up to the failure point, the rabbit cervical spine exhibited an increased range of motion after each segmental injury. The results of this study were used to develop an in vivo model for the study of spinal injury in subsequent projects.
Hardness, an indicator of the mechanical competence of cancellous bone
Authors: Hodgskinson R. , Currey J. D. , Evans G. P.
Published: February 2005

Hardness and calcium content in compact bone are strongly related. Variation in Young's modulus is produced mainly by variations in mineralisation. Therefore, there should be a relationship between hardness and Young's modulus. We demonstrate this. The calcium content of cancellous bone and adjacent compact bone in several species shows little difference, the cancellous bone having ∼10% less calcium. The hardness of cancellous bone in Bos is ∼12% less than that of adjacent compact bone, and the calcium is ∼2% less. These lines of evidence make it unlikely that the Young modulus of cancellous bone material is much different from that of compact bone. Similar evidence suggests that the yield stress of cancellous bone is similar to that of adjacent compact bone.
Material properties of the normal medial bovine meniscus
Authors: Proctor C. S. , Schmidt M. B. , Whipple R. R. , Kelly M. A. , Mow V. C.
Published: February 2005

The intrinsic compressive and tensile properties of normal bovine medial menisci were measured, and the variations in these properties with respect to the structural organization of the tissue and test specimen location were examined. Using a confined compression experiment, the compressive aggregate modulus and permeability of the meniscus were determined. The permeability of the tissue was also compared with the permeability as measured experimentally using a direct permeation experiment. Deep posterior specimens are significantly stiffer in compression than deep anterior and central‐anterior specimens, while deep anterior specimens are significantly less stiff than deep posterior and central‐posterior sepcimens. Posterior specimens have a significantly higher average water content. In addition, the permeability of the bovine meniscus was found to be about one‐tenth that of bovine articular cartilage. The tensile stiffness of meniscal tissue was determined from constant strain rate uniaxial tension tests. To asses the directional variations in the tensile properties, specimens were obtained from the circumferential and radial orientations. The results indicate that the femoral surface of the meniscus is isotropic in tension, while specimens from within the meniscus are anisotropic—the circumferential specimens are much stiffer than the radial specimens. Furthermore, circumferential posterior specimens from the interior of the meniscus are significantly stiffer than similar anterior specimens. Layer inhomogeneities in the tensile properties with respect to distance from the femoral surface are also present.
Transplantation of the rabbit medial collateral ligament. II. Biomechanical evaluation of frozen/thawed allografts
Authors: Sabiston P. , Frank C. , Lam T. , Shrive N.
Published: February 2005

This study was designed to test the mechanical behavior of a frozen/thawed bone‐medial collateral ligament (MCL)‐bone allograft in a rabbit model and to compare allograft behavior with contralateral unoperated ligaments as well as a group of normal bone‐ligament‐bone preparations prior to freezing. Twenty‐five mature rabbits received similarly frozen bone‐MCL‐bone allografts and were subsequently allowed to heal without immobilization in groups of five for 3, 6, 12, 24, or 48 weeks after transplantation. A series of biomechanical tests was performed on each allograft, contralateral, and external normal control ligament. Results demonstrated that allografts were significantly tighter than controls at 3 weeks and they remained tight over time. All allografts, however, had inferior structural and material behaviors as compared with controls. Allograft insertional bone and substance deteriorated to about 60% of contralateral strength at 12 and 48 weeks. Bony insertions became the most common site of graft weakness. Both stress at failure and the elastic modulus of allograft substance similarly reached a plateau at those intervals, but at about 30% of contralateral controls. Cyclic and load relaxation properties of allografts, on the other hand, did not deteriorate and were, in fact, indistinguishable from contralateral and normal values at 48 weeks. Comparison with a series of fresh autografts suggests that, with the exception of this viscoelastic recovery, allografts were mechanically inferior to autografts in their healing at the intervals tested. Collectively, these results suggest that allograft MCL healing in this composite model is dynamic but slow, featuring changes in bone and soft tissue over the first year after transplantation. Although “viable” and vascular, allografts have not normalized mechanically and, in fact, appear to have reached a new equilibrium whereby properties are neither improving nor deteriorating. Despite this apparent equilibrium, the trend for some viscoelastic recovery provides hope that allografts may have further potential for improvement. Longer‐term studies of MCL allograft mechanical behaviors are clearly required.
Excursion of the flexor digitorum profundus tendon: A kinematic study of the human and canine digits
Authors: Horibe S. , Woo S. L‐Y. , Spiegelman J. J. , Marcin J. P. , Gelberman R. H.
Published: February 2005

The most common problem following primary flexor tendon repair is the failure of the tendon apparatus to glide, secondary to the formation of adhesions. Early motion following tendon repair has been shown to be effective in reducing adhesions between the tendon and the surrounding sheath. Therefore, it is important to determine the amount of flexor tendon excursion along the digit during joint motion. In this study, the excursion between the flexor digitorum profundus (FDP) tendon and the sheath was examined in both human and canine digits. Based on roentgenographic measurements and joint kinematic analysis, the motion of the bones, the FDP tendon, and the sheath were measured with respect to joint rotations. It was found that the canine flexor tendon apparatus behaved similarly to that of the human for the motions studied. The amount of tendon excursion was very small in regions distal to the joint in motion (approximately 0.1 mm/10° of joint rotation). There was little displacement of the sheath (0.2–0.3 mm), except at the metacarpal joint region during metacarpophalangeal (MCP) joint motion and at the proximal interphalangeal (PIP) joint region during PIP joint motion. Tendon excursion relative to the tendon sheath was the largest in zone II during PIP joint rotation (1.7 mm/10° of joint rotation). These results suggest that PIP joint motion may be most effective in reducing adhesions following tendon repair in zone II.
Vasoactive substances in subchondral bone of the dog knee
Authors: Holm Ida Elisabeth , Ewald Henrik , Bülow Jens , Bünger Cody
Published: February 2005

The purpose of the present study was to investigate regulatory mechanisms for subchondral bone blood flow. A model including elevation of joint cavity pressure in the immature dog knee was applied. The role of prostaglandins in bone blood flow regulation was indirectly examined by indomethacin blockade. In six puppies, both venous tamponade of the joint cavity [50% of the mean arterial blood pressure(MAP)] and arterial tamponade (150% of MAP) resulted in a significant increase in the intraosseous pressure of the distal femoral epiphyses (p < 0.05). During venous tamponade no changes were registered in pO2, pCO2, pH, potassium, and lactate in blood withdrawn from the distal femoral epiphyses. Arterial tamponade resulted in hypoxia, a decrease in pH, and increased lactate. Inhibition of the prostaglandin synthesis did not alter this response pattern. Thus, the present study suggests the presence of a regulatory mechanism for subchondral bone blood flow since venous tamponade did not significantly alter intraosseous gas tensions, pH, lactate, or potassium in spite of elevated venous outlet resistance. The study does not allow any conclusion as to the exact nature of the regulatory mechanism, but local metabolic regulation is likely to be involved as indicated by accumulation of vasoactive substances at higher tamponade levels. Prostaglandins are probably of minor importance in this regulation.
Effects of proteoglycan extraction on the tensile behavior of articular cartilage
Authors: Schmidt Mary Beth , Mow Van C. , Chun Lawrence E. , Eyre David R.
Published: February 2005

We undertook an interdisciplinary biomechanical and biochemical study to explore the extent and manner in which the total pool of proteoglycans influences the kinetic and static behavior of bovine articular cartilage in tension. Two biomechanical tests were used: (a) the viscoelastic creep test and (b) a slow constant‐rate uniaxial tension test; and two enzymatic proteoglycan extraction procedures were used: (a) chondroitinase ABC treatment and (b) a sequential enzymatic treatment with chondroitinase ABC, trypsin, and Streptomyces hyaluronidase. We found that the viscoelastic creep response of all cartilage specimens may be divided into two distinct phases: an initial phase (< 15 s), characterized by a rapid increase in strain following load application, and a late phase (15 s < t < 25,000 s), characterized by a more gradual increase in strain. A major finding of this study is that the kinetics of the creep response is greatly influenced by the glycosaminoglycan content of the tissue. For untreated and control specimens, the initial response comprises about 50% of the total strain, while for chondroitinase ABC and sequentially extracted specimens, the initial response comprises up to 83% of the total strain. Furthermore, most untreated and control specimens did not reach equilibrium within the 25,000 s test period, while enzymatically digested specimens often reached equilibrium in less than 100 s. Thus, we conclude that through their physical restraints on collagen, the bulk of proteoglycan present in the tissue acts to retard fibrillar reorganization and alignment under tensile loading, thereby effectively preventing sudden extension of the collagen network. In contrast, the results of our slow constant‐rate uniaxial tension experiment show that essentially complete extraction of proteoglycan glycosaminoglycans does not affect the intrinsic tensile stiffness and strength of cartialge specimens or the collagen network in a significant manner. Hence, an important function of the bulk proteoglycans (i.e., the large aggregating type) in cartilage is to retard the rate of stretch and alignment when a tensile load is suddenly applied. This mechanism may be useful in protecting the cartilage collagen network during physiological situations, where sudden impact forces are imposed on a joint.
Acidic fibroblast growth factor (aFGF) injection stimulates cartilage enlargement and inhibits cartilage gene expression in rat fracture healing
Authors: Jingushi S. , Heydemann A. , Kana S. K. , Macey L. R. , Bolander M. E.
Published: February 2005

The effect of the administration of acidic fibroblast growth factor (aFGF) on normal fracture healing was examined in a rat fracture model. One microgram of aFGF was injected into the fracture site between the first and the ninth day after fracture either every other day or every day. aFGF‐injected calluses were significantly larger than control calluses, although this does not imply an increased mechanical strength of the callus. Histology showed a marked increase in the size of the cartilaginous soft callus. Total DNA and collagen content in the cartilaginous portion of the aFGF‐injected calluses were greater than those of controls, although the collagen content/DNA content ratio was not different between the aFGF‐injected and control calluses. Fracture calluses injected with aFGF remained larger than controls until 4 weeks after fracture. The enlarged cartilaginous portion of the aFGF‐injected calluses seen at 10 days after fracture was replaced by trabecular bone at 3 and 4 weeks. Northern blot analysis of total cellular RNA extracted separately from the cartilaginous soft callus and the bony hard callus showed decreased expression of type II procollagen and proteoglycan core protein mRNA in the aFGF‐injected calluses when compared with controls. A slight decrease in types I and III procollagen mRNA expression was also observed. We concluded that aFGF injections induced cartilage enlargement and decreased mRNA expression for type II procollagen and proteoglycan core protein.
The three‐dimensional tracking pattern of the human patella
Authors: van Kampen A. , Huiskes R.
Published: February 2005

A study was undertaken to provide data on the three‐dimensional tracking pattern of the patella, relative to the femur, in human knee‐joint specimens. For this purpose, a highly accurate roentgen stereophotogrammetric analysis (RSA) method was applied. The three‐dimensional motion patterns of the tibia and the patella were measured and represented in terms of three translations and three rotations each, during knee flexion in neutral (unloaded), endorotated, and exorotated pathways. We found that the patella displays complex but consistent three‐dimensional motion patterns during flexion, which include flexion rotation, medial rotation, wavering tilt, and a lateral shift relative to the femur. The motion patterns are very much affected by tibial rotations accompanying flexion.
Measuring the volume fraction of bone ingrowth: A comparison of three techniques
Authors: Sumner Dale R. , Bryan James M. , Urban Robert M. , Kuszak Jerome R.
Published: February 2005

The need for quick, accurate, and reproducible methods to measure the amount of bone within porous metals has increased as the use of these materials has become more common within orthopedics. The purpose of this paper is to compare measrements of bone ingrowth using microradiography, stained histology, and backscattered electron imaging–scanning electron microscopy (BEI–SEM) in cementless, porous‐coated acetabular components retrived from human patients. BEI–SEM of bone ingrowth into porous metal provided excellent images for quantitative analysis. The stained sections and BEI–SEM images provided very comparable results, while microradiography consistently understimated the porosity of the porous coating and overestimated the amount of bone ingrowth.
Effect of fracture fixation on cortical bone blood flow
Authors: Smith Stephen R. , Bronk James T. , Kelly Patrick J.
Published: February 2005

Because internal and external fixation devices alter blood flow, and thus the transport of nutrients to the cortical bone of a healing fracture, we studied the effects of a fluted intrameduilary rod (IMR), a half‐frame external fixator (EF), and a compression plate (PL) on the cortical bone directly adjacent to the fracture site at 4 and 48 h and 14 and 90 days after fixation. Three specific areas of cortical bone were studied: endosteal cortex, periosteal cortex, and subplate cortex (cortical bone under the compression plate). The fractures fixed with IMR had the lowest blood flow at all time periods studied. At 4 h, the difference between IMR and PL or EF was statistically significant in the endosteal cortex (p < 0.01 or p < 0.05, respectively); also, the difference between the IMR and EF in the subplate cortical bone region was significant (p < 0.05). At 14 days, the blood flow to the endosteal cortex was still significantly lower with IMR than with EF (p < 0.025). At 90 days, the blood flow to the subplate region of cortical bone was significantly (p < 0.02) higher with PL than with IMR but there was no significant difference in bone remodeling with the different fixation devices.
An electron microscopic study of local anesthetic‐induced skeletal muscle fiber degeneration and regeneration in the monkey
Authors: Komorowski Thomas E. , Shepard Beverly , Økland Steinar , Carlson Bruce M.
Published: February 2005

An electron microscopic study was done on abductor pollicis brevis muscles of 18 Rhesus monkeys after intramuscular injections of 0.75% bupivacaine, 2% mepivacaine, or 2% lidocaine + epinephrine. The muscles were examined for from 2 h to 28 days. Severe muscle fiber damage, consisting of breakdown of sarcolemma and myofibrils, was seen as early as 2 h. Phagocyte‐mediated fragmentation of the degenerating muscle fibers was at its peak during the third and fourth days. Myoblasts were abundant during the fourth day. Early myotubes appeared on the fifth and sixth days, and they matured during the second week. Satellite cells appeared alongside mature myotubes. Overall, the local anesthetic‐induced breakdown and regeneration of skeletal muscle fibers in the monkey followed a course quite similar to that seen in the rat.
Differential effects of androgens on cortical bone histomorphometry in gonadectomized male and female rats
Authors: Turner Russell T. , Wakley Glenn K. , Hannon Kathleen S.
Published: February 2005

The physiological role of gonadal androgens in regulating bone metabolism is not established. To determine if androgens antagonize the changes in cortical bone after gonadectomy, we treated orchiectomized (ORX) rats with testosterone (T) and 5α‐dihydrotestosterone (DHT), and ovariectomized (OVX) rats with the afore‐mentioned androgens, as well as the synthetic androgen fluoxymesterone (FI) and the nonsteroidal estrogen diethylstilbestrol (DES). OVX resulted in a rapid, sustained increase in periosteal bone formation at the tibial diaphysis, whereas ORX resulted in decreased bone formation. Androgen treatment stimulated bone formation in ORX rats and suppressed bone formation in OVX rats. A large dose of DES suppressed bone formation in OVX rats to values below the intact controls. The results of these studies demonstrate that androgens counteract the changes in cortical bone formation after gonadectomy in females as well as males, and thereby reestablish the sex difference observed in intact rats.
Measurement of blood flow to the tibial diaphysis using 11‐μm radioactive microspheres. A comparative study in the adult rabbit
Authors: Triffitt Paul D. , Gregg Paul J.
Published: February 2005

The commonly used size of microsphere for bone blood flow estimation is 15 μm, because it has appeard to be the smallest size that is not subject to significant nonentrapment in bone. Soft‐tissue studies suggest that it is microspheres of 9‐10 μm or less that pass through peripheral tissues and give low calculated flows, whereas many vessels passing into and within cortical bone are < 15 μm in diameter. We have therefore performed a comparison between microspheres approximately 15 and 11 μm in average size. Blood flows to the cortex and marrow of the tibial diaphysis, and to the skeletal muscle of the anterior compartment, were obtained in six adult New Zealand White rabbits by the reference sample technique, injecting microspheres of 16.5+ 0.1 μm and 11.3+ 0.1 μm simultaneously. The calculated cortical flows averaged 2.07 and 2.51 ml/min/100 g, respectively, and the marrow flows 26.63 and 24.92 ml/min/100 g. Mean skeletal muscle flows were 15.57 and 14.54 ml/min/100 g, respectively. There were no significant differences between the calculated flows for the two sizes of microsphere. Thus, the smaller microspheres do not appear by this method to be subject to significant nonentrapment, and they are therefore suitable for blood flow measurement in these tissues.
The influence of support conditions in the loading fixture on failure mechanisms in the push‐out test: A finite element study
Authors: Harrigan T. P. , Kareh J. , Harris W. H.
Published: February 2005

The usefulness of the push‐out test as an indicator of interface strength was evaluated using finite element models of intact and partially failed cylindrical push‐out specimens loaded against a rigid annular support. The irregular stress distributions that were found in intact specimens depended more on interface conditions at the loading fixture than on a 35% increase in interface area. The maximum stress at the interface was a tensile stress. Critical energy release rates for interface failure were calculated for flawed specimens in which flaw size was either 10 or 100 μm, and for boundary conditions at the loading fixture that were either fixed or slipping in the radial direction. The critical energy release rates depended heavily on the support boundary conditions. Thus, the results of parametric push‐out tests can be reasonably compared only for specimens that are very similar in geometry and that are loaded in very carefully controlled fixtures.
The effects of strain rate on the properties of the medial collateral ligament in skeletally immature and mature rabbits: A biomechanical and histological study
Authors: Woo Savio L‐Y. , Peterson Robert H. , Ohland Karen J. , Sites Terry J. , Danto Michael I.
Published: February 2005

The effects of strain rate on the structural properties of the femurmedial collateral ligament‐tibia complex (FMTC) and on the mechanical (material) properties of the medial collateral ligament (MCL) of skeletally immature and skeletally mature rabbits were studied. The FMTCs were tested in tension to failure, at five extension rates (0.008 mm/s‐113 mm/s). For the FMTCs from the skeletally immature animals, values of load, elongation, and energy absorbed at failure increased substantially with extension rates. Such increases also existed for skeletally mature animals, but they were much less in magnitude. All samples from the skeletally immature animals failed by tibial avulsion, whereas samples from the skeletally mature animals failed within the ligament substance. The mechanical properties of the ligament substance were minimally strain‐rate sensitive for both groups. Histological sections of the ligament substance and insertion sites from the failed samples were examined, and these observations were correlated with the biomechanical findings. For the rabbit model used in this study, we conclude that skeletal maturity has more influence on the biomechanical properties of the MCL than does strain rate.