bluuebunny/crossref_metadata_2025 huggingface dataset:
Matrix vesicle enzymes in human osteoarthritis
Authors: Einhorn Thomas A. , Gordon Stanley L. , Siegel Scott A. , Hummel Charles F. , Avitable Matthew J. , Carty Robert P.
Published: February 2005

The enzymatic activities and in vitro calcification properties of matrix vesicle fractions isolated from normal and osteoarthritic (OA) human articular cartilage were compared to determine the essential conditions for calcification in these tissues. Four groups of human cartilage were examined, I, normal articular cartilage from aged, nonOA joints; II, discolored or fibrillated cartilage from OA joints; III, osteophytic cartilage from OA joints; IV, loose body cartilage from OA joints. Fetal bovine growth plate cartilage was also studied. Both ATP‐ and 5′‐AMP‐dependent in vitro matrix vesicle calcification occurs in all cartilage groups examined and, for human articular cartilage, these activities increase progressively from Groups I to II to III. Calcification does not occur in the absence of either phosphate or pyrophosphate. Alkaline phosphatase, 5′‐AMPase, and ATP:pyrophosphohydrolase activities are increased in Groups III and IV cartilage compared with Group I and are detected at high levels in fetal bovine growth plate cartilage. Pyrophosphatase activity occurs in only those cartilage groups juxtaposed to areas of new bone formation (osteophytic, loose body, and bovine growth plate). These results suggest that OA, growth plate, and even normal articular cartilage all have the potential to undergo calcification as long as both phosphate and pyrophosphate ions can be generated at sufficiently high levels. However, the capacity for cartilage to deposit hydroxyapatite, as it does during bone formation, may depend on the presence of pyrophosphatase activity.
Antibiotic absorption from infected and normal joints using a rabbit knee joint model
Authors: Schurman David J. , Kajiyama Glen
Published: February 2005

An understanding of the absorption of antibiotics from joints was investigated comparing intraarticular (i.a.) absorption with intramuscular (i.m.) absorption in rabbit knee mode. The antibiotics investigated were methicillin, cephalothin, cefazolin, cefoxitin, amikacin, neomycin, kanamycin, and gentamicin. Absorption was measured both in animals in which the knee joint was infected with Staphylococcus aureus and in normal animals. The pattern of absorption from infected joints 37% slower than from an i.m. injection. In animals that are not infected i.a. antibiotics are actually absorbed 12% faster than i.m. anitbiotics. Thus, i.a. antibiotics are absorbed rapidly and similarly to i.m. injection and should be included in total dose calculations for antibiotic regimens, especially with regard to their potential toxicity.
Correlations of radiographic analysis of healing fractures with strength: A statistical analysis of experimental osteotomies
Authors: Panjabi Manohar M. , Walter Stephen D. , Karuda Mark , White Augustus A. , Lawson Jack P.
Published: February 2005

The assessment of fracture healing strength using routine roentgenograms is difficult and controversial. There are few experimental data that correlate radiographic appearance with the actual quantitative strength of healing fractures. However, this method is widely used in clinical practice. A study is presented in which transversely osteotomized rabbit tibiae were allowed to heal for 3 to 8 weeks. A pair of orthogonal roentgenograms was taken of each bone and the bones were tested for strength in a dynamic torsion testing machine. Statistical analyses were done to study the correlations between the roentgenographic and strength parameters. Cortical continuity was found to be the best single predictor of strength of a healing fracture (correlation coefficient r = 0.80). The least important predictor was the callus area (r = 0.17). Fracture displacement, callus thickness, and callus diameter had negative correlations. From these experimental findings in an animal model, we conclude that even under laboratory conditions the information gained from plain radiographs is not sufficient to accurately predict the strength of a healing fracture.
Ultrastructural aspects of nerves, bones, and vessels in hereditary sensory neuropathy
Authors: Teot L. , Arnal F. , Humeau C. , Pous J. G. , Dimeglio A.
Published: February 2005

This study concerns two children, from the same otherwise normal family, presenting progressive spontaneous amputations of the limbs, suggesting peripheral hereditary sensory neuropathy. Samples from the distal nerves and vessels and the distal tibial epiphyses were examined ultrastructurally. The nerves showed signs of degeneration, and a typical bone necrosis, without osteoclasts, was observed in the 2 cm margin of the samples. Simultaneous modifications of the vessels suggest a neurally initiated vascular reflex resulting in bone destruction. Theories that might explain the observations are discussed.
Effects of prosthetic acetabular replacement on strains in the pelvis
Authors: Lionberger D. , Walker P. S. , Granholm J.
Published: February 2005

The effects of cemented acetabular components on the strains in the pelvis were determined experimentally. Four components were tested: A plain metal hemisphere: a metal hemisphere with a triflange; a hemisphere with an iliac peg; and a hemisphere with a complete flange and a peg. Loading was carried out in neutral, flexion, and extension directions. The subchondral one was only slightly reamed, and extension directions. The subchondral bone was only slightly reamed, and components were cemented and tested successively. For the intact hip joint, the strains on the superior acetabular rim were much lower than those on the posterior rim. After placement of the components, the tensile strains on the rim decreased by 22–54% while the compressive strains increased by 0–25%. The bone on the medial inferior surface was subjected ot 65% less tensile strain and 48% more compressive strain in neutral and extension loading. There were no great differences between the four styles of acetabular component.
Evaluation of tibiofibular motion under load conditions by computed tomography
Authors: Jend H.‐H. , Ney R. , Heller M.
Published: February 2005

Evaluation of tibiofibular motion in vivo has been possible only by invasive methods. A new nonivasive method has been developed that uses computed tomography (CT). A special device was constructed for use on the CT table to study fibular motion with load placed across the ankle. From dorsal to plantar flexion the fibula moved 1.1 ± 0.4 mm medially with an accompanying nonsignificant ventral shift and medial rotation. Application of load across the ankle did not significantly alter these findings. In a subgroup of predominantly females, plantar flexion of the ankle provoked a dorsal fibular motion of 0.7 ± 0.8 mm. In this subgroup application of load across the ankle reduced the medial and dorsal motion during the accompanying plantar flexion. The mechanism of these different movements can be deduced from the morphology of the ankle joint and its ligamentous and muscular guidance mechanism. The variable axis of joint movement and the insertion of the lateral ligament forced the fibula anterior in plantar flexion. When external talar rotation is present, the normal fibular motion is prevented unless load is applied across the ankle. The new investigative procedure permits study of the sequelae of traumatic and iatrogenic injuries to the fibula.
Effect of EHDP on fracture healing in dogs
Authors: Lenehan Timothy M. , Balligand Marc , Nunamaker David M. , Wood Frederick E.
Published: February 2005

Ethane‐1‐hydroxy‐1, 1‐diphosphonate (EHDP) was administered subcutaneously to mature beagle dogs at dose levels of 0.1, 0.5, and 5.0 mg/kg/day for a 20 week period to determine the drug's effects healing. Uniform, transverse fractures of the midshaft radius were created in one limb and treated by external splintage. Drug‐induced effects on fracture healing were monitored radiographically, histologically, and histomorphometrically; mechanical properties of the healing bones were determined in 4‐point bending tests. At a dose of 0.1 mg/kg/day, ultimate load at failure and flexural rigidity of the fractured limbs equated or exceeded that of saline control animals, and radiographic healing was normal. At a dose of 0.5 mg/kg/day ultimate load at failure and flexural rigidity of the fractured limbs proved inferior to saline control values, and radiographic healing appeared delayed. At a dosage of 5.0 mg/kg/day, there was obvious radiographic nonunion, and the callus of fractured radii had little inherent flexural rigidity or strength. Histomorphometrically, no differences were noted between control animals and the 0.1 or 0.5 mg/kg/day group; however, mineralization activity activity appeared totally disrupted at the higher dosage level (5.0 mg/kg/day). In the 5.0 mg/kg/day group, EHDP‐induced effects proved reversible with mineralization evident as early as 3 weeks following drug withdrawal. In mature beagle dogs EHDP proved to have dose‐dependent and reversible inhibitory effects on secondary fracture healing.
Ultrastructure of electrically induced osteogenesis in the rabbit medullary canal
Authors: Brighton Carl T. , Hunt Robert M.
Published: February 2005

The ultrastructural changes in the medullary canal of the adult male New Zealand white rabbit associated with the trauma of the insertion of an inactive cathode were compared to that associated with electrically induced osteogenesis from an active cathode delivering 20 μA constant direct current. In the vicinity of both an inactive and an active cathode, the medullary canal cellular content was replaced first by polymorphic cells and later by osteoblastic new bone formation. The polymorphic cells always appeared in the immediate vicinity of a capillary or other blood vessel. With time, the new bone formation in the medullary canal surrounding the inactive cathode disappeared, while new formation surrounding the active cathode progressively increased in amount. When the new bone formation in the medullary canal surrounding an inactive cathode disappeared, it was replaced by a network of polymorphic cells. When direct current was then applied to such an inactive electrode, the polymorphic cells were again rapidly replaced by bone. The close association of polymorphic cells with osteoblasts suggests that the former may be a precursor cell of the latter.
Mechanical factors in electrode‐induced osteogenesis
Authors: Spadaro J. A. , Mino D. E. , Chase S. E. , Werner F. W. , Murray D. G.
Published: February 2005

Previous experiments have suggested that mechanical activity of electrode implants may contribute to the observed bone formation that has been attributed to the electrical currents. This was tested by implanting movable and stationary wires in the medullary canal of the rabbit femora or tibiae. The moving implants uniformly showed significant medullary bone formation at the wire, whereas the stationary ones did not. This bone persisted for as long as 8 weeks and was mostly resorbed by 12 weeks as the implants became fixed. The new trabecular bone closely resembled that typically seen at electrically active implants. Implant motion may have a more important role in electrically induced osteogenesis than previously thought.
In vivo versus in vitro polymerization of acrylic bone cement: Effect on material properties
Authors: Bargar W. L. , Brown S. A. , Paul H. A. , Voegli T. , Hseih Y. , Sharkey N.
Published: February 2005

Flexural strength and molecular weight of polymethylmethacrylate bone cement were determined for cement polymerized in vivo in a canine total hip replacement and cement from the same batch polymerized in vitro. Both in vivo and in vitro samples showed a slight increase in flexural strength and modulus at 2 weeks, followed by a nearly equivalent decline at 8 weeks. In vitro and in vivo samples exhibit a comparable stress to failure, but the in vivo samples show a significantly increased strain and decreased modulus. Cement from the proximal region of the prosthesis has significantly decreased flexural strength, lower modulus, and lower molecular weight than cement from the distal region and plug, suggesting that failures in the proximal region of a prosthesis may be due to inferior physical and mechanical properties of the bone cement in that region.
Tensile properties of the medial collateral ligament as a function of age
Authors: Woo Savio L‐Y. , Orlando Carlo A. , Gomez Mark A. , Frank Cyril B. , Akeson Wayne H.
Published: February 2005

The biomechanical properties of the rabbit medial collateral ligament (MCL) as a function of maturation and age were investigated. Femur–MCL–tibia (F‐M‐T) preparations were obtained from rabbits of different age groups (open or closed epiphysis). Parallel increases in the animal body weight and ligament cross‐sectional area were recorded with age. Cyclic and tensile failure tests were performed to obtain the structural properties of the F‐M‐T complex and the mechanical properties of the MCL substance. There were significant increases in the load at failure, energy‐absorbing capability of the bone–ligament junction, and in the tensile strength of the ligament substance as a result of maturation and subsequent aging. Increases in the area of hysteresis obtained during cyclic loading–unloading were also documented. At the closing of the epiphysis, the mode of failure of the F‐M‐T structure progressed from tibial avulsion to failure in the midsubstance of the ligament. An asynchronous rate of maturation was observed between the structural properties of the bone–ligament complex and the mechanical properties of the ligament substance.
Tibial epiphyseal development: A cross‐sectional histologic and histomorphometric study in the New Zealand white rabbit
Authors: Masoud Ibrahim , Shapiro Frederic , Moses Alan
Published: February 2005

Sequential histomorphometric studies on the developing rabbit tibia from birth to skeletal maturity demonstrate that growth plate height lessens as longitudinal growth diminishes. Differing rates of development proximally and distally are documented. Distally, growth plate height, width, and area and total epiphyseal area peak or reach near maximum values by 3 weeks, whereas proximally, they do so by 8 weeks (except for height, which also peaks at 3 weeks). The distal growth plate is being obliterated by 16 weeks, at which time the proximal growth plate remains well structured and open. The distal tibia and fibula develop as one tissue mass. The articular cartilage and epiphyseal cartilage are continuous from birth, whereas a single ossification center and a single growth plate are present by 8 weeks. The data point to the presence of intrinsic growth plate, as well as systemic, control mechanisms affecting skeletal growth. Knowledge of temporal and quantitative features of epiphyseal and growth plate development will greatly aid in the elucidation of the underlying controls.
Biochemistry and antigenicity of osteoarthritic and rheumatoid cartilage
Authors: Schurman David J. , Palathumpat Marykutty V. , Desilva Anil , Kajiyama Glen , Smith R. Lane
Published: February 2005

The purpose of this study was to test whether cartilage serves as the source or repository of antigenic components active in the stimulation of inflammation in rheumatoid arthritis through an analysis of peripheral blood lymphocyte proliferation. Articular cartilage samples were obtained from patients with osteoarthritis, rheumatoid arthritis, and ankylosing spondylitis undergoing joint replacement surgery. Each sample was homogenized and characterized biochemically with respect to the content of proteoglycan, collagen, and immunoglobulin. Proteoglycan content of rheumatoid cartilage was reduced by 71% when compared to osteoarthritic cartilage; the proteoglycan content of ankylosing spondylitis cartilage was reduced by 40% when compared to osteoarthritic cartilage. Immunoglobulins were detectable in all cartilage samples when analyzed by ELISA or endoplate titration. Lymphocyte proliferation, quantified by uptake of 3H‐thymidine, was unaltered by addition of cartilage fragments, low (saline) and high salt extracts (2.0 M CaCl2), or cartilage residues. Both autologous and heterologous lymphocytes were tested against the cartilage samples with no difference in reactivity. Purified bovine articular proteoglycans and Type II collagen were also inactive. Although tetanus toxoid and phytohemaglutinin were effective stimulants of proliferation, lymphocytes from arthritis patients were suppressed relative to those of normal individuals. Analysis of arthritic articular cartilage by these techniques failed to demonstrate the presence of antigen(s) stimulating proliferation of peripheral blood lymphocytes.
Age‐related changes in the kinetics of release of proteoglycans from normal rabbit cartilage explants
Authors: Sandy John D. , Plaas Anna H. K.
Published: February 2005

The release of proteoglycans from explant cultures of articular cartilage from immature and mature rabbits has been studied with the following results. At both ages the tissue proteoglycan was released in two phases: an initial extensive release (day 0 to 3) and a period of slow release (day 4 to 15). The percentage released in the initial phase was, however, significantly greater for mature (55%) than immature (38%) explants. At both ages the newly synthesized proteoglycans (in vivo labeled) were also released in two kinetic pools. Thus, graphical analysis of release data readily resolved the disappearance curves into two linear components with in vitro half‐lives of 1 day and 22 days. Again, the percentage in the short half‐life pool was much greater for mature (70%) than immature (40%) explants. At both ages the initial release was largely chondrocyte‐mediated since freeze‐thawing the tissue before culture markedly reduced proteoglycan release. At both ages the released proteoglycans were smaller than equivalent preparations of extracted proteoglycans and they were much less capable of forming aggregates with hyaluronate. The results show that there are age‐dependent changes in rabbit articular cartilage that increase the proportion of proteoglycans, both total and newly synthesized, that are susceptible to rapid chondrocyte‐mediated catabolism in explant cultures.
Tensile properties of human knee joint cartilage: I. Influence of ionic conditions, weight bearing, and fibrillation on the tensile modulus
Authors: Akizuki Shaw , Mow Van C. , Müller Francisco , Pita Julio C. , Howell David S. , Manicourt Daniel H.
Published: February 2005

The flow‐independent (intrinsic) tensile modulus of the extracellular matrix of human knee joint cartilage has been measured for normal, fibrillated, and osteoarthritic (removed from total knee joint replacements) cartilage. The modulus was determined in our isometric tensile apparatus and measured at equilibrium. We found a linear equilibrium stress‐strain behavior up to ∼15% strain. The modulus was measured for tissues from the high and low weight‐bearing areas of the joint surfaces, the medial femoral condyle and lateral patello femoral groove, and from different zones (surface, subsurface, middle, and middle‐deep) within the tissue. For all specimens, the intrinsic tensile modulus was always less than 30 MPa. Tissues from low weight‐bearing areas (LWA) are stiffer than those from high weight‐bearing areas (HWA). The tensile modulus of the ECM correlates strongly with the collagen/proteoglycan ratio; it is higher for LWA than for HWA. Osteoarthritic cartilage from total knee replacement procedures has a tensile stiffness less than 2 MPa.
Fibronectin and water content of articular cartilage explants after partial depletion of proteoglycans
Authors: Burton‐Wurster Nancy , Lust George
Published: February 2005

The aim of this study was to test the hypothesis that fibronectin in cartilage of osteoarthritic joints accumulates in increased quantities in response to a reduction in proteoglycan content in the matrix. We determined fibronectin content in an ELISA system, uptake of plasma 125I‐fibronectin from the medium, and glycosaminoglycan content by a dye method. The proteoglycan content of canine articular cartilage was reduced by co‐incubation of the cartilage with canine synovium, partially purified catabolin, or retinoic acid. Data suggested that proteoglycan loss alone was not sufficient to result in the increased fibronectin accumulation that has been reported in the deteriorating articular cartilage of osteoarthritic joints. Cartilage that lost as much as 75% of its proteoglycan content did not have increased fibronectin content and did not take up more fibronectin from the external medium. A related goal of this study was to evaluate the percentage of water in proteoglycan‐depleted but disease‐free cartilage, as the percentage of water is known to be elevated in osteoarthritic cartilage. Data indicated that the percentage of water in the depleted cartilage increased in proportion to the decrease in proteoglycan content, but the total amount of water in the cartilage did not increase; water content appeared to be unchanged. Under the conditions used, the proteoglycan content was reduced and the percentage of water was elevated, but fibronectin content was not increased. Thus, the cartilage incubated in vitro did not mimic osteoarthritic cartilage.
Antibiotic stability in an implantable pump
Authors: Perry Clayton R. , Ellington Lisa L. , Becker Annette , Vossen Mark K. , Burdge Robert E. , Greenberg Richard N.
Published: February 2005

We measured the stability of vancomycin, amikacin, netilmicin, tobramycin, gentamicin, clindamycin, and aztreonam in an implantable drug pump. Two pumps were filled with the antibiotic being tested and were incubated at 37° for 3 weeks. Samples were taken daily. At 3 weeks the pumps were disassembled and examined microscopically for signs of deterioration. If the pumps were intact, bioassays were used to quantitate the biologic activity of each daily antibiotic sample. Vancomycin degraded the pump. Amikacin, netilmicin, tobramycin, gentamicin, clindamycin, and aztreonam had no effect on the pump and maintained their biologic activity over the 3‐week period.
A comparison of various types of fixation devices for protection of the posterior cruciate ligament against a posterior drawer force
Authors: O'Meara Clifton B. , Tencer Allan F. , Ivey Frank M. , Woodard Peggy
Published: February 2005

We compared four different fixation devices to determine which offers the greatest relative protection to the posterior cruciate ligament (PCL) against elongation with an applied posterior drawer force. We designed a system to monitor and record the change in distance between an approximate origin and insertion of the PCL as known forces were applied posteriorly to the tibia with the femur fixed. Six fresh cadaver knees were used in this investigative series. They were first tested with the PCL intact, then with the PCL transected, and then with the various fixation devices applied. After comparing the results with transarticular pins and quadrilateral and anterior half‐frame external fixators, we found that transarticular fixation offers significantly greater protection to the PCL. This study may prove to be helpful to the orthopaedist when selecting ancillary fixation for posterior cruciate repair or reconstruction.
Load‐displacement behavior of sacroiliac joints
Authors: Miller J. A. A. , Schultz A. B. , Andersson G. B. J.
Published: February 2005

We measured the load‐displacement behavior of both single and paired sacroiliac (SI) joints in fresh cadaver specimens obtained from eight adults between the ages of 59 and 74 years. With both ilia fixed, static test loads were applied to the center of the sacrum along and about axes parallel and normal to the superior S1 endplate. Test forces up to 294 N were applied in the superior, inferior, anterior, posterior, and lateral directions. Moments up to 42 N‐m were applied in flexion, extension, lateral bending, and axial torsion. Displacement of the center of the sacrum were measured 60 s after each load increment was applied, using dial gauges and an optical lever system. The tests were then repeated with only one ilium fixed. Finally, the three‐dimensional location and overall geometry of each SI joint were measured. For an isolated left joint at the maximum test loads, the mean (SD) sacral displacements in the direction of the force ranged from 0.76 mm (1.41) in the medial to 2.74 mm (1.07) in the anterior direction. The mean rotations in the direction of the moments ranged from 1.40° (0.71) in right lateral bending to 6.21° (3.29) in clockwise axial torsion viewed from above. We also examined load‐displacement behavior under larger loads. Single sacroiliac joints resisted loads from 500 to 1440 N, and from 42 to 160 N‐m without over failure.
Porous hydroxyapatite as a bone graft substitute in diaphyseal defects: A histometric study
Authors: Holmes Ralph E. , Bucholz Robert W. , Mooney Vert
Published: February 2005

Porous hydroxyapatite (IP200), formed by conversion of the Poritidae porites exoskeleton, has pores averaging 230 μm and pore interconnections averaging 190 μm in diameter. In the distal radial diaphyses of 14 dogs, bilateral 7.5 × 20mm cortical windows were created and fitted with 5 × 7.5 × 20 mm blocks of IP200 implants and liiac autograft. Both implanted and contralateral grafted radius specimens were retrieved at 3, 6, 12, 24, and 48 months. Unstained undecalcified sections were examined by microradiography and UV epi‐illumination. Stained undecalcified sections were examined by light microscopy and quantitated by histometric methods. Implant specimens demonstrated good union and bone ingrowth at all time intervals. The implant specimens were composed of (mean ± SE) 10.6% ± 1.0% soft tissue, 51.2% ± 1.3% bone, and 38.2% ± 1.0% IP200. The graft specimens showed good union with little apparent ingrowth at 3 months, followed by progressive appositional closure of cancellous spaces. The graft specimens contained 21.9% ± 0.9% bone at 3 months with increases at each time interval to 73.1% ± 8.7% at 48 months. The volume fraction and mean width of IP200 did not change with time, confirming the absence of implant biodegradation. The volume fraction and mean width of bone remained stable in the implant but increased in the graft specimens, corresponding to graft neocortex formation. It is concluded that implants initially filled in with bone while grafts initially replaced much of their spongiosa and subsequently filled in with bone. Histometry of untreated defects and measurement of mechanical properties are suggested for further study.
Electron microscopic analysis of articular cartilage proteoglycan degradation by growth plate enzymes
Authors: Buckwalter Joseph A. , Ehrlich Michael G. , Armstrong Ann L. , Mankin Henry J.
Published: February 2005

To assess the effect of intracellular growth plate chondrocyte enzymes on proteoglycan structure, we examined enzyme‐treated articular cartilage proteoglycans and untreated articular cartilage proteoglycans with the electron microscopic monolayer technique. The untreated proteoglycan monomers ranged in length from less than 20 nm to more than 700 nm, with a mean length of 224.5 + 101.6 nm in one experiment and 224.6 + 95.7 nm in a second experiment. Incubation with growth plate enzymes reduced proteoglycan monomers to fragments with lengths that varied from less than 5 nm to 143 nm, increased the variability in monomer length, and destroyed proteoglycan aggregates. The enzyme treated monomers had an average length of 29.5 + 17.9 nm in one experiment and 35.2 + 17.0 nm in a second experiment. The smallest common fragments were 15 nm long and would be expected to contain about 15 glycosaminoglycan chains. This experiment demonstrates that enzymes extracted from growth plate chondrocytes can degrade the chondroitin sulfate‐rich region of proteoglycan monomer core proteins, produce a range of monomer fragment sizes with less than 20% of the fragments shorter than 5 nm or longer than 100 nm, increase the variability in monomer length, and degrade proteoglycan aggregates.
“Free” and “exchangeable” or “trapped” and “non‐exchangeable” water in cartilage
Authors: Maroudas A. , Schneiderman R.
Published: February 2005

We repeated some of our own previous experiments, as well as some of Torzilli's recent experiments (11) on which he bases his conclusions relating to a nonexchangeable “trapped water” in cartilage. We are unable to confirm Torzilli's findings. We observed partition coefficients for 3H.HO very close to unity. That both the extrafibrillar and most of the intrafibrillar water is freely exchangeable and behaves as available water towards small solutes has been independently shown (3) for other collagenous tissues. All the different permutations of partition experiments have yielded results that are fully consistent with our original picture of the very major fraction of cartilage water being free.
Magnetic resonance imaging of osteoarthritis: Correlation with gross pathology using an experimental model
Authors: Sabiston C. Paul , Adams Mark E. , Li David K. B.
Published: February 2005

Conventional radiography has several limitations in the study of osteoarthritis (OA): changes occur late, they are restricted to bone, and they do not correlate well with the patient's symptoms. Magnetic resonance imaging (MRI) can visualize with great detail the soft tissue changes in and around joints. We have obtained MR images of knees using an experimental model of OA in order to study the early changes of OA, to correlate the images with the gross patnology, and to compare MR images with radiographs. The changes on MRI correlated with the gross pathological changes as assessed by Kendall's rank correlation test as follows: meniscal changes, τ = 0.58 (p < 0.01); osteophytes, τ = 0.59 (p < 0.05); capsular fibrosis, τ = 0.55 (p < 0.05); and overall, τ = 0.68 (p < 0.001). Abnormalities were evident on MRI as early as 4 weeks after the onset of the disease, which is 8 weeks before they appear on radiographs. Thus, MRI can show changes in OA earlier than radiography can, and the images correlate with the gross pathology.
Mechanical consequences of rod contouring and residual scoliosis in sublaminar segmental instrumentation
Authors: Johnston Charles E. , Ashman Richard B. , Sherman Michael C. , Eberle Charles F. , Herndon William A. , Sullivan J. Andrew , King Andrew G. S. , Burke Stephen W.
Published: February 2005

The mechanical performance of contoured Luque rods in a neuromuscular model of spine deformity was examined to define an upper limit of deformity above which rod stresses would exceed the endurance limit for 316L stainless steel and therefore predict fatigue. Bovine constructs varying from 0–120° scoliosis were loaded axially, with strain recordings obtained at the apex of the curve. Relatively low loads produced enough tensile stress to contemplate implant fatigue in all except the nondeformed (0°) construct. Construct stiffness was found to decrease rapidly in spines with greater than 38° deformity. In addition, data on patients who had suffered rod fracture from four different centers were found to compare favorably with experimental observations. We conclude that the vulnerability of Luque rod constructs to implant failure, from a mechanical standpoint, is greater than is generally assumed. Cross‐linking of rods was found to increase stiffness. Methods to decrease tensile stresses in the implants and increase stiffness include external immobilization, larger diameter rods, and procedures to enhance correction.
Trauma type, age, and gender as determinants of hip fracture
Authors: Hedlund Rune , Lindgren Urban
Published: February 2005

We determined the trauma type of femoral neck and trochanteric fractures in men and women aged >20 years in 19, 128 fractures reported to a computerized medical information register during 1972–1981. We found that the earlier known exponential increase of fracture incidence by age started in early adulthood rather than during middle age. An age‐related increase was found for each type of injury as well, although the incidence of fractures resulting from severe trauma increased less than that of fractures associated with moderate trauma. The incidence of low‐energy fractures in men as well as in women displayed a constant increase rate with age from young adulthood on, impugning the widely held belief that the menopause is a significant risk factor for fractures. The dominating risk factor for proximal femoral fracture in adults appears to be age, irrespective of the cause of injury, with a chronological decline in bone strength as the most likely cause of the exponential increase in the fracture incidence during adult life.
Bone ingrowth into ploymer coated porous synthetic coralline hydroxyapatite
Authors: Tencer A. F. , Woodard P. L. , Swenson J. , Brown K. L.
Published: February 2005

Porous hydroxyapatite, converted hydrothermally from the calcium carbon exoskeleton of the coral genus Goniopora (CHAG), has been shown to be effective as a scaffold for bone ingrowth (2,3,5–7,9). However, the large pores in the material resulted in low compressive strengths. In a previous study, we found that microcoating the interal surfaces of CHAG with dilactic‐polylactic acid (DL‐PLA) improved significantly its compressive properties. The objective of this study was to determine the effect of PLA microcoating on bone ingrowth into CHAG plugs. Plugs of thick‐(3:1 chloroform to DL‐PLA by weight), medium‐ (10:1), and thin‐ (30:1) coated as well as uncoated CHAG were implanted transcortically in the proximal third of the diaphysis of the rabbit tibia. Specimens were harvested at 3, 12, and 24 weeks for mechanical testing and contralaterally for histological and histomorphometric assessment. At 12 weeks, uncoated CHAG plugs developed an average ultimate interface shear stress of 26.7 MPa, compared with 17 MPa for 30:1 and 8 MPa for 10:1 and 3:1 coated specimens. At 24 weeks, there were no significant difference in shear stress among any of the specimens. Histomorphometric assessments showed that the ratio of area fractions of new bone to area fractions of new bone and void space increased from 68–70% for 3:1 and 10:1 coated specimens at 3 weeks, and to 85.5–89.5% at 24 weeks. In comparison, uncoated and 30:1 specimens had area fraction ratios of about 82% at 3 weeks and 93% at 24 weeks. Histologic sections demonstrated direct apposition of new bone to both the coating and the hydroxyapatite as well as degradation of the coating.
Lumbar trunk muscle use in standing isometric heavy exertions
Authors: Schultz Albert , Cromwell Ronita , Warwick David , Andersson Gunnar
Published: February 2005

A study was conducted to see whether a biomechanical model previously validated for predicting the lumbar spine internal loads imposed by the performance of easy and moderately strenuous physical tasks was also adequate for predicting loads imposed by heavy exertions. Lumbar trunk muscle myoelectric activities were measured in 10 healthy young adult men performing a variety of less strenuous and more strenuous tasks while standing upright, and these were compared to the lumbar muscle contraction magnitudes predicted by the model. For the less strenuous tasks, measured activities and predicted forces showed strong linear correlations, confirming the validity of the model at those load levels. Model predictions for the more strenuous tasks were often found to be inadequate. Contrary to model‐incorporated assumptions, substantial antagonistic muscle contractions sometimes occurred, intraabdominal pressurization may sometimes have contributed substantially to the maintenance of structural equilibrium, and the ligamentous tissues of the trunk seemed sometimes to develop substantial passive resistances to bending and twisting moments.
The response of the canine intervertebral disc to immobilization produced by spinal arthrodesis is dependent on constitutional factors
Authors: Cole Tak‐Chun , Ghosh Peter , Hannan Neil J. , Taylor Thomas K. F. , Bellenger Christopher R.
Published: February 2005

Posterior lumbar spinal fusion was performed on five mature greyhounds. Two months prior to death, all of the surgical and five age‐matched control greyhounds were given Na235SO4(1.0mCi/kg) intravenously. All fusion animals were killed 6 months postoperation, and discs beneath the fusion mass as well as those adjacent to it (parafusion discs) were sampled separately and dissected into the nuclei pulposi and annuli fibrosi (AF). Proteoglycans (PGs) were extracted with 4.0M GuHCI and then purified by CsCI density gradient ultracentrifugation. These PG monomers were subjected to Sepharose CL‐2B chromatography, and their hydrodynamic size and ability to aggregate were determined. The level, extractability, and hydrodynamic size of PGs in the AF of fusion discs were found to be greater than those in control discs, as were the keratan sulfate core protein complexes prepared by chondroitin ABC lyase digestion. The ability of the 60‐day‐old PG subunit populations, isolated from fusion discs, to aggregate was also higher than controls. There was, however, no difference between the galactosamine/glucosamine, galactosamine/protein, glucosamine/protein, or hexuronate/protein ratios of PGs in fusion and control discs.
Electromyographic analysis of muscles across the elbow joint
Authors: Funk D. A. , An K. N. , Morrey B. F. , Daube J. R.
Published: February 2005

An electromyographic (EMG) technique was developed to study simultaneously the eight major elbow muscles in five normal subjects. Recordings of EMG activity in elbow muscles were obtained while the elbow joint was subjected to resisted flexion, extension, abduction, and adduction functions. The results indicate that activity in the the major elbow muscles is determined by the size of the resultant flexion and extension moments created about the elbow joint, but not by varus and valgus moments. These results support the hypothesis that determination of muscle force about a joint depends on joint constraint, namely, the degree of freedom, the resultant joint forces and moments due to externally applied load, and also the function of the muscle, i.e., the line of action of the muscle that crosses the joint. The data may be used to further refine the calculation of muscle force distribution across the elbow joint.
Contact finite element stress analysis of porous ingrowth acetabular cup implantation, ingrowth, and loosening
Authors: Rapperport D. J. , Carter D. R. , Schurman D. J.
Published: February 2005

Two‐dimensional linear and contact finite element analyses were conducted of total hip arthroplasty using metal‐backed, porous ingrowth acetabular components. The stress transmission characteristics from the component to the surrounding bone were given special attention. Resultant loads of 20 and 40° medial of vertical were studied, and the influence of adding a metal flange to the rim of the cup was evaluated. The results indicated that when a conventional metal‐backed component (without a flange) is initially implanted and subjected to normal loading, these components may experience distraction between the component and the surrounding bone at inferior sites. Compressive stresses in the superior dome cancellous bone, however, will be substantial. If complete porous ingrowth is achieved, the superior dome compressive stresses will be reduced and substantial shear stresses created. In addition, high local bone stresses were found at the component rim. If bone ingrowth is achieved only in specific locations, stress transmission will be dictated by those locations and may differ markedly from the case of complete bone ingrowth. In the event that no porous ingrowth is achieved and a fibrous layer forms around the component, the interface stresses will be similar to those calculated for the natural hip. The addition of a flange to the rim of the cup will reduce the magnitude of the radial stresses transmitted to the cancellous bone superiorly and medially by directly transferring some of the load to the lateral wall of the pelvis. The flange will also help to relieve the high local stresses that are found at the component rim.
Effect of peripheral nerve on limb development
Authors: Dietz Frederick R.
Published: February 2005

The effect of peripheral nerve on limb growth and maturation has received little attention after the limb differentiation stage. This study used an amphibian model (Rana pipiens) to examine the effect of temporary denervation on the development of limb muscle and bone tissues. Quantitative microscopic techniques were employed to evaluate bone and muscle size and cellularity between denervated and control limbs. A 15% decrease in tibial length and a 17% decrease in cross‐sectional area were foound in the temporarily denervated limbs as compared with the control limbs during the growing period studied. A 26% increase in tibial osteocyte density was found in the denervated limbs, although total osteocyte number was the same. The same differences were found on comparing less and more mature limbs from normal animals. Gastrocnemius muscle from temporarily denervated limbs had a 46% lesser cross‐sectional surface area and a 66% greater muscle fiber density as compared with control limbs. Total muscle fiber number was the same. Similar findings were observed comparing limbs of different maturities from normal unoperated animals. This study suggests that the absence of peripheral nerves decreases the rate of bone maturation, which effect may be responsible for the diminished size of denervated limbs. This work demonstrates a model for regional growth disturbances that may aid in understanding such disorders as idiopathic leg length discrepancy, hemihypertrophy, clubfoot, and the limb deformities created by paralytic diseases.
Bone mineral in the castrated rat model of osteopenia
Authors: Grynpas M. D. , Simmons E. D. , Carnes D. , Gundberg C. , Pritzker K. P. H.
Published: February 2005

The effects of castration on cortical bone structure and chemistry were studied in male Wistar rats of two age groups, 8 and 24 months. Some rats were castrated and some were sham operated (control) in each group. All animals were killed after 4 months. Although no changes in serum chemistry, bone chemistry, or bone histology could be found, the young castrated animals versus controls showed less density of bone mineral as determined by the density fractionation technique and smaller crystallite size of mineral particles as determined by x‐ray diffraction line‐broadening analysis. These changes, indicative of less mature bone formation, were not observed in mature castrated or control rats despite a decreased amount of bone compared with young rats. In this model, castration appears to affect bone mineral quality in young but not in old animals.
Apparent absence of local response to bone screws in guinea pigs with contact sensitivity
Authors: Lewin J. , Lindgren J. U. , Wahlberg J. E.
Published: February 2005

Guinea pigs sensitized to nickel, cobalt, or chromium were used to study if impaired fixation occurred as a result of allergy against metal implants in bone. Screws made from stainless‐steel (ASTM F55, F138–139) or cobalt chromium (ASTM F75–76) were inserted in the right and left proximal tibiae, and the mechanical strength of the fixation to the bone was evaluated after 4 months. In addition, we studied the histology on decalcified sections of the implant bone interface from the distal femur where the same type of screws had been inserted. To see if changes in bone density occurred in the proximal tibia as a result of allergy, the amount of ash was determined. Although the animals maintained their contact sensitivity throughout the experimental period, there were no differences between allergic and control animals for any of the parameters studied. All screws were well fixed in the tibia at the end of the experiment, and histologically we did not find any significant differences between allergic and control animals by qualitative examination. The experiment supports our earlier results from a 6‐week experiment and indicates that contact allergy may be unimportant for the fate of orthopedic implants.
The effect of cryopreservation on canine menisci: A biochemical, morphologic, and biomechanical evaluation
Authors: Arnoczky Steven P. , McDevitt Cahir A. , Schmidt Mary Beth , Mow Van C. , Warren Russell F.
Published: February 2005

This study evaluated the effect of cryopreservation on the structural organization, biosynthetic activity, and material properties of canine menisci. The menisci were cryopreserved by incubating them in a 4% solution of dimethyl sulfoxide (DMSO) in physiologic media and freezing them to −100°C using a controlled rate freezing system. The menisci were then stored for varying periods of time from zero to 12 weeks in liquid nitrogen (−196°C). Following rapid thawing, changes in the histological appearance and biosynthetic activity of the menisci were evaluated as functions of storage time. In addition, the effects of the cryopreservation process on the tensile strength and modulus of the meniscal tissue were assessed. Although cryopreservation and short‐term storage did not appear to affect the morphological appearance or biomechanical character of the menisci, biosynthetic activity, as determined by Na2S35SO4 incorporation, was diminished to <50% of normal control values immediately following cryopreservation and thawing. Autoradiographic examination of these tissues revealed that only ∼ 10% of the meniscal cells were metabolically active, however, indicating that a marked increase in the metabolic activity of individual cells occurs following the freeze‐thaw cycle. Total metabolic activity continued to decline with storage time.
Serum‐free culture of rabbit meniscal fibrochondrocytes: Proliferative response
Authors: Webber Richard J. , Zitaglio Teresa , Hough Aubrey J.
Published: February 2005

We have formulated a serum‐free medium capable of supporting DNA synthesis in rabbit meniscal fibrochondrocytes at a level equivalent to 10% fetal bovine serum (FBS). The medium consists of a 1:1 mixture of Dulbecco's Modified Eagle's Medium and Ham's F‐12 medium supplemented with transferrin (1 μg/ml), selenium (1 pg/ml), trace metal mix (1:100), dexamethasone (100 ng/ml), insulin‐like growth factors I and II (50 ng/ml each), pituitary fibroblast growth factor (100 ng/ml), and lactalbumin hydrolysate (2 μg/ml). Endothelial cell growth supplement could be substituted for lactalbumin hydrolysate to obtain similar results. Ventrex PC‐1, a commercially available, low‐protein, serum‐free medium, was found to support proliferation of fibrochondrocytes but not as well as 10% FBS or our medium formulation. Lipid supplements, which are known to support the serum‐free growth of hyaline chondrocytes, were found to be either of no value or antagonistic for the culture of fibrochondrocytes. Likewise, vitamin E alone, progesterone, putrescine, and hydrocortisone were also without benefit in our culture system. Thecells had a more chondrocytic morphology when grown in defined medium as opposed to 10% FBS. The results of this study should now make it possible to identify and quantitate those factors necessary to affect meniscal repair by utilizing further techniques in vitro.
Degradative pathways in cultured synovial fibroblasts: Selective effects of pulsed electromagnetic fields
Authors: Murray J. Clifford , Lacy Margaret , Jackson Sylvia Fitton
Published: February 2005

A cell culture model for studying the cytokine‐mediated degradation of connective tissue was exposed to clinically applied, low‐frequency pulsed electromagnetic fields (PEMF), and levels of collagenolytic activity, two lysosomal hydrolases, and prostaglandin E2 were measured. PEMFs reduced the release of two lysosomal enzymes by cultured rabbit synovial fibroblasts but did not affect their response to mononuclear‐cell–conditioned medium. PEMF did not alter levels of cytokine activity produced by a mixed mononuclear cell population, nor did they affect the cytokine‐mediated release of collagenase or prostaglandin E2 by synovial fibroblasts. The relevance of these findings to the clinical application of PEMF to soft‐and hard‐tissue injuries is discussed.