bluuebunny/crossref_metadata_2025 huggingface dataset:
Demonstration of HLA and ABH Antigens in Fresh and Frozen Human Menisci by Immunohistochemistry
Authors: Khoury Miguel A. , Goldberg Victor M. , Stevenson Sharon
Published: February 2005

The expression of HLA and ABH antigens in fresh, frozen, and twice‐frozen normal human meniscal tissue was evaluated with use of immunohistochemistry. A generalized expression of Class‐I and Class‐II HLA antigens was found in the endothelial and synovial cells of all three forms of tissue. Fibrochondrocytes were Class‐I positive and Class‐II negative. ABH antigens were expressed by endothelial cells in relationship to the blood group of the patient. Freezing preserved most of the HLA and ABH molecular structure. Although the normal meniscus consists of a relatively few chondrocytes embedded in an extracellular matrix, it also contains Class‐II and ABH‐positive endothelial cells and Class‐II‐positive synovial cells. These antigens are present at the moment of transplantation and could evoke an immune response in the host that would modulate the results of meniscal allografting.
Method for establishing and measuring in vivo forces in an anterior cruciate ligament composite graft: Response to differing levels of load sharing in a goat model
Authors: Lewis Jack L. , Poff Bradley C. , Smith Joel J. , Lindquist Conrad , Engebretsen Lars , Lew William D.
Published: February 2005

In order to determine the appropriate load history for optimal remodeling of an anterior cruciate ligament graft, methods for establishing and measuring graft forces in vivo are required. Our objectives with this study were to (a) develop a method in which the graft force due to an external load could be set to a preselected value in a living animal, (b) show that this force could be maintained after fixation, and (c) determine what happens to the forces after the animal has functioned for as long as 2 weeks postoperatively, when differing levels of load sharing between the segments had been set at surgery. The anterior cruciate ligament was reconstructed in 12 goats with use of a bone‐patellar tendon‐bone graft and a synthetic augmentation device. The forces in the graft segments were established, at the time of surgical fixation, with use of a force‐setting technique. In five animals, the tendon segment was set to carry 90% of the total graft force; in the remaining seven animals, the augmentation segment was set to share 90% of the total graft force. Graft forces were measured, with the use of buckle transducers mounted extra‐articularly over the anterior tibia, under a 67 N anterior tibial load at 60° of knee flexion before and after fixation and at 2 weeks postoperatively. When the tendon was the high force‐carrying member, the force in the tendon decreased by an average of 25% during the 2 weeks after surgical fixation, while the force in the augmentation segment showed a significant increase of 111%. When the augmentation segment was the high force‐carrying segment, the force in that segment decreased by an average of 10% during the 2 weeks and the tendon force increased by 47%. These data suggest that when the tendon was set to carry high force, it may have stretched, due to biological changes in the tissue, and that the augmentation segment was not as greatly affected over the 2 postoperative weeks when it was set to carry most of the total load. Because of the frictional effects of the graft segments passing around the osseous contours of the anterior tibia and the fact that the calibrations of the buckle transducer from surgery were used to reduce the data on force at 2 weeks postoperatively, there are uncertainties related to the measured graft segment forces in this study. However, if the animals had been killed and the buckle transducers calibrated immediately after the test at 2 weeks, these uncertainties would not exist.
Estimation of material properties in the equine metacarpus with use of quantitative computed tomography
Authors: Les C. M. , Keyak J. H. , Stover S. M. , Taylor K. T. , Kaneps A. J.
Published: February 2005

The purpose of this study was to investigate the relationships between data obtained from quantitative computed tomography and mechanical properties in the equine metacarpus, as measured in vitro in bone specimens. Three hundred and fifty‐five bone specimens from the metacarpi of 10 horses were machined into right cylinders aligned with the long axis of the bone. A computed tomographic scan of the specimens, along with a Cann‐Genant K2HPO4 calibration standard, was obtained. The specimens then were compressed to failure, and the elastic modulus, yield stress, yield strain, strain energy density at yield, ultimate stress, ultimate strain, and strain energy density at ultimate failure were calculated. The specimens were dried and ashed. Quantitative computed tomography‐derived K2HPO4 equivalent density proved to be an excellent estimator (r2 > 0.9) of elastic modulus, yield stress, ultimate stress, wet density, dry density, and ash density; a moderately good estimator (0.4 < r2 < 0.9) of strain energy density at yield and at ultimate failure; and a poor estimator (r2 < 0.2) of yield strain and ultimate strain. It was concluded that the relationships between quantitative computed tomography data and mechanical properties of the equine metacarpus were strong enough to justify the use of these data in automated finite element modeling.
Ion resonance electromagnetic field stimulation of fracture healing in rabbits with a fibular ostectomy
Authors: Deibert Mark C. , Mcleod Bruce R. , Smith Stephen D. , Liboff Abraham R.
Published: February 2005

Rabbits with a fibular ostectomy were exposed for 28 days to magenetic fields that satsfied the ion resonance conditions for calcium or magnesium. The rabbits were exposed to whole body treatment for 1/2 hour, 3 hours, or 24 hours per day. The fibulae from the experimental and control animalas were removed surgically and were subjected to force‐deflection testing to establish the stiffness of the healed fracture. The fibulae from the rabbits exposed to the ion resonance magnetic fields were found to be 55‐299% (p < 0.01) more robust than the fibulae from the control animals.
Effect of static load on matrix synthesis rates in the intervertebral disc measured in vitro by a new perfusion technique
Authors: Ohshima Hiroshi , Urban J. P. G. , Bergel D. H.
Published: February 2005

The effect of static loading on matrix synthesis was measured in intact bovine coccygeal discs. The discs were maintained at 37°C in a humid atmosphere and were perfused across their upper and lower surfaces for as long as 8 hours with media containing radioisotopes (3H‐proline and 35S‐sulphate) via porous filter disks embedded in Perspex (Plexiglas) holders. Static loads were applied to the disc with use of weights. The activity of free, nonincorporated isotope in the centre of the disc was monitored continuously with a microdialysis probe. Incorporated tracer in different regions of the disc was determined at the end of each experiment from the activity of the nondialysable tracer. Free tracer activity rose steeply over the first 3–4 hours of perfusion, as tracer diffused into the disc, and reached a steady value after 5–6 hours, as expected from diffusion theory. The rate of tracer incorporation estimated from the integrated value of free tracer concentration was constant for as long as 8 hours. Incorporation rates varied across the disc: the highest rates were in the inner layer of the annulus fibrosus, and the lowest rates were in the outer layer of the annulus. The rates for both 35S‐sulphate and 3H‐proline varied with load. The rates were lowest in the nucleus pulposus and the inner layer of the annulus fibrosus with a 0.5 kg load, and they almost doubled as the load was increased to 5–10 kg. Heavier loads (15 kg) led to a decrease in incorporation. Hydration of the disc also varied with load; hydration decreased as load increased and was maintained near in vivo values with 5–10 kg of load (0.13–0.26 MN/m2). The effect of load on incorporation rates in the disc is compatible with the suggestion that rates are at a maximum at in vivo hydrations and decrease if the hydration decreases or if the disc swells.
Autogenous flexor tendon grafts: Fibroblast activity and matrix remodeling in dogs
Authors: Abrahamsson Sven‐Olof , Gelberman Richard H. , Amiel David , Winterton Paul , Harwood Fred
Published: February 2005

To investigate rates of cellular proliferation and matrix turnover in autogenous flexor tendon grafts, hindlimb intrasynovial (flexor digitorum profundus) and extrasynovial (peroneus longus) tendons were placed within the synovial sheaths of the medial and lateral forepaw digits of 18 dogs and treated with controlled early passive motion. After the dogs had been killed, short‐term culture and labeling in vitro were utilized to determine rates of DNA, proteoglycan, collagen, and noncollagen protein synthesis. Schiff base covalent collagen crosslink concentrations and total collagen and protein content also were evaluated at intervals through 6 weeks. Tendon grafts of extrasynovial origin showed greater rates of DNA synthesis and significantly elevated levels of proteoglycan, collagen, and noncollagen protein synthesis and Schiff base covalent collagen crosslink concentrations (dihydroxylysinonorleucine) compared with intrasynovial tendon grafts. It was not clear to what extent the increased activity in the extrasynovial graft was due to actual differences between the intrasynovial and extrasynovial tendons or to the responses of the connective tissue surrounding the extrasynovial tendon graft. Since both types of grafts demonstrated similar unaltered levels of collagen and protein content over time, these data suggest greater rates of matrix turnover in tendon grafts of extrasynovial origin than in those of intrasynovial origin. Coupled with previous findings showing increased cellular proliferation in extrasynovial tendon grafts, these data indicate that the process of translation to an intrasynovial environment necessitates a more active process of soft‐tissue repair and remodeling when extrasynovial donor tendons are used.
Preserving plantar flexion strength after surgical treatment for contracture of the triceps surae: A computer simulation study
Authors: Delp Scott L. , Statler Kimberly , Carroll Norris C.
Published: February 2005

Contractures of the triceps surae commonly are treated by surgical lengthening of the gastrocnemius aponeurosis or the Achilles tendon. Although these procedures generally relieve contractures, patients sometimes are left with dramatically decreased plantar flexion strength (i.e., decreased capacity to generate plantar flexion moment). The purpose of this study was to examine the trade‐off between restoring range of motion and maintaining plantar flexion strength after surgical treatment for contracture of the triceps surae. A computer model representing the normal moment‐generating characteristics of the triceps surae was altered to represent two conditions: isolated contracture of the gastrocnemius and contracture of both the gastrocnemius and the soleus. The effects of lengthening the gastrocnemius aponeurosis and the Achilles tendon were simulated for each condition. The simulations showed that nearly normal moment‐generating characteristics could be restored when isolated gastrocnemius contracture was treated with lengthening of the gastrocnemius aponeurosis. However, when isolated gastrocnemius contracture was treated with lengthening of the Achilles tendon, the moment‐generating capacity of the plantar flexors decreased greatly. This suggests that lengthening of the Achilles tendon should be avoided in persons with isolated gastrocnemius contracture. Our simulations also suggest that neither lengthening of the gastrocnemius aponeurosis nor lengthening of the Achilles tendon by itself is an effective treatment for combined contracture of the gastrocnemius and soleus. Lengthening the gastrocnemius aponeurosis did not decrease the excessive passive moment developed by the contracted soleus. Lengthening the Achilles tendon restored the normal passive range of motion but substantially decreased the active force‐generating capacity of the muscles. Our simulations indicate that independent lengthening of the contracted gastrocnemius and soleus, rather than lengthening of their common tendon, accounts for differences in the architecture of these muscles and may be a more effective means to restore range of motion and maintain plantar flexion strength when combined contracture of the gastrocnemius and soleus is present.
Patellar tracking measurement in the normal knee
Authors: Nagamine Ryuji , Otani Takuya , White Stephen E. , McCarthy Daniel S. , Whiteside Leo A.
Published: February 2005

Eleven fresh frozen cadaveric knee specimens were mounted in a knee kinematics test device, and normal patellar movements were evaluated with use of an external device for direct measurement of patellar movements. The effects of four different measurement conditions were assessed through alteration of one condition and determination of its effect on patellar kinematics with the use of six specimens. The four conditions included (a) change of the measuring axis from an axis parallel to the central axis of the femur (femoral axis) to one parallel to the central axis of the tibia (tibial axis), (b) rotation of the femoral axis internally 6°, (c) change of the direction of the quadriceps force from parallel to the mechanical line of the lower extremity to a direction parallel to the femoral shaft, and (d) increase of the magnitude of the quadriceps force from 111 to 500 N. During knee flexion, the patella shifted laterally after a slight initial medial shift, tilted laterally from midflexion to 90°, and gradually rotated medially. The patellar shift relative to the tibial axis appeared to be more medial than the shift measured relative to the femoral axis; the discrepancy was caused by the valgus position of the tibia relative to the femur. Changing the rotational angle of the femoral axis artifically changed the patellar position. Varying the direction of the quadriceps within the narrow range and increasing the quadriceps force did not affect patellar movements. It is likely that the anatomic configuration of the patella allows the patella to seat in a stable configuration so that it resists moderate changes in the load and direction of the quadriceps. Tibial rotation exerted a major influence on patellar shift and tilt in the early phase of knee flexion: the patella rotated medially when the tibia was externally rotated and rotated laterally when the tibia was internally rotated. These results indicate that the patella may be unstable in the first phase of knee flexion when the tibia is rotated.
Regional mitogenic response of the meniscus to platelet‐derived growth factor (PDGF‐AB)
Authors: Spindler K. P. , Mayes C. E. , Miller R. R. , Imro A. K. , Davidson J. M.
Published: February 2005

Since meniscal healing is region‐specific, we studied the regional (peripheral compared with central) response of meniscal explants to human, recombinant platelet‐derived growth factor‐AB. Mensical explants from the hindlimbs of both knees of mature sheep were sectioned and were cultured with variable doses of human, recombinant platelet‐derived growth factor‐AB, and incorporation of [3H]‐thymidine was measured. The mitogenic response was measured at different times in culture (48 or 96 hours) and by location (lateral or medial). In the absence of the growth factor, the peripheral third of both menisci incorporated 10‐fold more [3H]‐thymidine on a weight basis than did the central two‐thirds. Cellularity was equivalent in the two regions. Doses of less than 100 ng/ml of growth factor produced either no stimulation or a variable response. A dose of 100 ng/ml resulted in consistent, significant (p < 0.05) stimulation in all groups in the peripheral region, and a dose of 200 ng/ml provided more than a 2.5‐fold increase. Multiple‐factor analysis of variance demonstrated that there were no significant differences between experiments, times in culture, or menisci. The central region did not respond to stimulation with the growth factor at any of the doses tested. These data suggest that regional differences (peripheral compared with central) in responsiveness to human, recombinant platelet‐derived growth factor‐AB may reflect a different level of signal transduction machinery for growth factor receptors and distinct fibrochondrocyte populations. These findings are consistent with the variable healing capcity of the meniscal regions in vivo and suggest a pharmacological means to promote the repair of the peripheral meniscal region.
Fiber composition and fiber transformations in neck muscles of patients with dysfunction of the cervical spine
Authors: Uhlig Yvonne , Weber Barbara R. , Grob Dieter , Müntener Markus
Published: February 2005

Biopsies of ventral neck muscles (sternocleidomastoid, omohyoid, and longus colli) and dorsal neck muscles (rectus capitis posterior major, obliquus capitis inferior, splenius capitis, and trapezius) were taken from 64 patients who underwent spondylodesis for cervical dysfunction of different etiologies. The muscle fibers were classified histochemically as type I, IIA, IIB, or IIC (transitional or intermediate fibers) according to the pH lability of their myofibrillar ATPase. Signs of muscle fiber transformations were observed in all muscles investigated, as evidenced by an increased relative amount of type‐IIC fibers. The transformations occurred independently of (a) the type of muscle (i.e., more “postural” or more “phasic”), (b) the sex and age of the patient, (c) the type of condition, and (d) the presence of additional neurological deficits. Thus, the same pattern of muscular reaction was found in patients with rheumatoid arthritis as in patients with soft‐tissue injuries of the neck (e.g., “whiplash injury”). In the ventral muscles and the obliquus capitis inferior, the occurrence of transformations correlated strongly with the duration of symptoms; in the ventral muscles the vast majority of transformations were encountered in patients with a shorter history of symptoms, whereas in the obliquus capitis inferior the reverse occurred. In the other dorsal muscles, no correlation with the duration of symptoms was found. Muscles in which transformations had ceased displayed, on average, a significantly higher percentage of fast type‐IIB fibers than were found in muscles with ongoing transformations. This strongly indicates that the transformations proceeded in the direction from “slow oxidative” to “fast glycolytic”.
Clinical reproducibility of dual energy X‐ray absorptiometry
Authors: Williams‐Russo Pamela , Healey John H. , Szatrowski Ted P. , Schneider Robert , Paget Stephen , Ales Kathy , Schwartzberg Patricia
Published: February 2005

Dual energy x‐ray absorptiometry is a technique advocated for the measurement of bone mass throughout the skeleton, and recently it has been used to measure changes in periprosthetic bone mass after joint replacement. The accuracy and precision of the method in clinical patient populations have not been firmly established. This study sought to establish the short‐term reproductibility of measurements made with dual energy x‐ray absorptiometry of multiple sites in a large sample of elderly patients with rheumatic disease. Reproductibility was assessed in the lumbar spine and in three femoral sites in 69 patients participating in a longitudinal clinical trial. In each patient, absorptiometry was performed twice in the same day at as many as five time points over a 2‐year period. The mean (±SD) baseline bone density was 0.783 ± 0.128 g/cm2 for the femoral neck and 1.015 ± 0.218 g/cm2 for the lumbar spine. The correlations between the duplicate baseline measurements of the spine were excellent (r = 0.9936, p < 0.001) and were stable over the 2‐year period; the mean difference between the duplicate baseline measurements was 1.82 ± 1.54% and the mean coefficient of variation was 1.29%. Measurements in the femur were much less precise: these values were 3.61 ± 3.14% and 2.55% in the femoral neck, 3.66 ± 4.35% and 2.59% in the greater trochanter, and 5.28 ± 5.61% and 3.73% in Ward's triangle. This study evaluated the short‐term reproductibility of dual energy x‐ray absorptiometry in a clinical population. The reproductibility of a technique must be taken into account when it is applied longitudinally to follow patients over time. The reproductibility of bone densitometry of the spine in large clinical populations with orthopaedic and rheumatic disease was similar to that reported for in vitro measurements and for very small sample studies of healthy normal subjects. However, the reproductibility of densitometry of femoral sites was much poorer than that for spinal sites. Reproducibility is a significant methodological issue for the use of dual energy x‐ray absorptiometry to assess the effect of osteoporosis therapies on the hip as well as the change in periprosthetic bone mass around a hip prosthesis. The poorer reproductibility of the measurements in the femoral sites suggests that a much wider margin of error is required in the interpretation of within‐patient change in bone mass over time.
Contaminated fractures of the tibia: A comparison of treatment modalities in an animal model
Authors: Curtis Mark J. , Brown Phillip R. , Dick James D. , Jinnah Riyaz H.
Published: February 2005

External fixation is the current standard treatment for skeletal stabilization of open tibial fractures, but intramedullary fixation techniques have become increasingly popular. The aim of this study was to compare, in an animal model, the susceptibility to infection of contaminated fractures stabilized with external fixation with that of contaminated fractures fixed with intramedullary locking nails with or without reaming. A unilateral osteotomy of the tibia was performed in 15 goats under general anesthesia. Each osteotomy was stabilized with either (a) a unilateral biplanar external fixator, (b) an 8 mm diameter intramedullary rod inserted without reaming of the medullary cavity, or (c) a 10 mm diameter rod inserted after reaming. A standardized inoculum of Staphylococcus aureus, 103 colony forming units per milliliter, was placed at each osteotomy site on a piece of absorbable gelatin sponge, to simulate contamination of an open fracture. Antibiotics were not administered. The animals were allowed full activity after the procedure. Fourteen days postoperatively, the animals were killed, radiographs of the tibiae were taken, and the tibiae were harvested in a sterile manner. Multiple specimens for quantitative microbiological analysis were taken from the fracture site and from sites 3 cm distal and 6 cm proximal to the fracture. Additional specimens of bone were taken for histological study. Clinical, radiographic, and microbiological analysis demonstrated that, in this animal model, there were significantly fewer and less severe infections in fractures fixed with external fixation than in those fixed with an intramedullary nail with or without reaming. There was marked cortical necrosis in tibiae that had been fixed with nailing and reaming.
Closeness of fit of uncemented stems improves the strain distribution in the femur
Authors: Hua J. , Walker P. S.
Published: February 2005

Differences in the cross‐sectional shapes of intramedullary stems are expected to affect the strains in the femur, a close proximal fit being proposed as particularly advantageous. We compared uncemented femoral stems of different designs, as well as a cemented stem, using the intact femur as a control. The collarless stems were custom‐made, standard asymmetric, symmetric (i.e., neutral), and cemented symmetric. These different types of stem were inserted in sequence into eight cadaver femurs. A photoelastic coating technique was used to give a measure of the shear strains over the bone surface. The mean reductions of maximum shear strains in the upper 30 mm of the proximal‐medial regions for the custom, asymmetric, symmetric, and cemented stems were 11, 24, 6, and 75%, respectively. The strains for the symmetric stem were concentrated in the proximal‐medial region just below the neck resection line and then decreased rapidly below that level. For the asymmetric stems, the relative strains in the proximal‐anterior and proximal‐medial regions were dependent on the tightness of fit in the anterior‐posterior and medial‐lateral directions. The custom stems consistently produced a pattern of strain distribution that, overall, was closer to normal than that of the other stems; extremes at the anterior and medial regions were avoided. The strains down the entire medial side of the cemented stem were significantly less than for the intact femur or for the uncemented stems.
Evaluation of vascular compliance and vasoconstrictive reactions in amputated hindlimbs of rats
Authors: Ono Hiroshi , Nakagawa Yoji , Mizumoto Shigeru , Tomita Naohide , Tamai Susumu
Published: February 2005

The vascular compliance and the contractility of vascular smooth muscle of preserved, amputated hindlimbs of rats were evaluated using a fresh blood extracorporeal circulatory system. Vascular compliance was measured under physiologic circulatory conditions (blood pressure of the amputated limb was maintained at 80–150 mm Hg [10–20 kPa]) and found not to differ significantly from that of freshly amputated limbs after storage at 4°C for 12 hours. However, after more than 24 hours of storage at 4°C, the vascular compliance decreased significantly (p < 0.01). To evaluate the contractility of vascular smooth muscle, the arterial blood pressure in the amputated limbs was transiently increased with injections of norepinephrine. The contractility could be preserved for at least 12 hours at 4°C; however, it decreased markedly after more than 24 hours. The vascular compliance and vasoconstrictive reactions of the amputated limbs were maintained for at least 12 hours at 4°C.
Osteoarthritis in cynomolgus macaques II. Detection of modulated proteoglycan epitopes in cartilage and synovial fluid
Authors: Carlson Cathy S. , Loeser Richard F. , Johnstone Brian , Tulli Hermina M. , Dobson Denene B. , Caterson Bruce
Published: February 2005

The purpose of the present study was to determine the usefulness of the monoclonal antibodies 7‐D‐4 and 3‐B‐3 as biomarkers of severity of naturally occurring osteoarthritis in the knee joints of adult cynomolgus macaques. The antibodies were used to immunolocate chondroitin sulfate proteoglycan epitopes in articular cartilage or synovial fluid from knee joints with a range in severity of osteoarthritis. The joints were examined radiographically, grossly, microradiographically, and histologically to characterize the severity of disease, and the results of three different methods of proteoglycan analysis (immunohistochemistry, enzyme‐linked immunosorbent assay, and Western blot analysis) were compared. Subjectively, the degree of positive immunostaining for 7‐D‐4 was minimal in normal sites and increased as damage to articular cartilage increased. The scores for 7‐D‐4 immunostaining in the medial tibial plateau (the site most severely involved in this model) were correlated significantly with severity of damage to articular cartilage (p < 0.05, r2 = 0.50), thus supporting the subjective observations. The ratio of 7‐D‐4 to sulfated glycosaminoglycans in synovial fluid also was correlated with the score for 7‐D‐4 immunostaining in the medial tibial plateau (p < 0.05, r2 = 0.54) and with the score for 3‐B‐3 immunostaining in the medial femoral condyle (p < 0.05, r2 = 0.65). There were no significant correlations among scores for 3‐B‐3 immunostaining, severity scores, and the ratios of 3‐B‐3 to sulfated glycosaminoglycans in the synovial fluid. By Western blot analysis, both epitopes were sensitive markers of early cartilage damage in young adult monkeys but were less sensitive in older monkeys. This work provides evidence that measurement of the epitope recognized by 7‐D‐4 in synovial fluid or, by immunohistochemical or Western blot methods, in articular cartilage has potential use as a marker of severity of naturally occurring osteoarthritis.
Influence of short‐term hydrostatic pressure on organization of stress fibers in cultured chondrocytes
Authors: Parkkinen Jyrki J. , Lammi Mikko J. , Inkinen Ritva , Jortikka Matti , Tammi Markku , Virtanen Ismo , Helminen Heikki J.
Published: February 2005

The present study describes changes in the organization of stress fibers that occur in articular cartilage chondrocytes subjected to hydrostatic pressure. Primary cultures of chondrocytes from bovine articular cartilage, grown on coverslips, were subjected to 5, 15, or 30 MPa hydrostatic pressure at 37°C. The pressure was applied continuously or cyclically at two frequencies: 0.125 Hz (4 seconds of pressure and 4 seconds of no pressure) or 0.05 Hz (1 second of pressure and 19 seconds of no pressure) for a period of 2 hours. Control chondrocytes showed a polygonal form with prominent stress fibers extending across the cells. The exposure of cells to 30 MPa pressure caused a nearly total disappearance of stress fibers and retraction of the cells from each other. With pressure at 15 MPa or cyclic pressure, the number of cells with stress fibers was decreased. In cells subjected to 5 MPa pressure, the stress fibers resembled those in control chondrocytes. The pressure effects were reversible after 2 hours. Pressure had no effect on the staining pattern of vinculin, which suggests that microfilaments are more vulnerable to pressure than vinculin. The results indicate that cytoskeletal changes may be an integral part of the response of chondrocytes to hydrostatic pressure.
Proposal for the regulatory mechanism of Wolff's law
Authors: Mullender M. G. , Huiskes R.
Published: February 2005

It is currently believed that the trabecular structure in bone is the result of a dynamic remodeling process controlled by mechanical loads. We propose a regulatory mechanism based on the hypothesis that osteocytes located within the bone sense mechanical signals and that these cells mediate osteoclasts and osteoblasts in their vicinity to adapt bone mass. A computer‐simulation model based on these assumptions was used to investigate if the adaptation of bone, in the sense of Wolff's law, and remodeling phenomena, as observed in reality, can be explained by such a local control process. The model produced structures resembling actual trabecular architectures. The architecture transformed after the external loads were changed, aligning the trabeculae with the actual principal stress orientation, in accordance with Wolff's trajectorial hypothesis. As in reality, the relative apparent density of the structure depended on the magnitude of the applied stresses. Osteocyte density influenced the remodeling rate, which also is consistent with experimental findings. Furthermore, the results indicated that the domain of influence of the osteocytes affects the refinement of the structure as represented by separation and thickness of the struts. We concluded that the trabecular adaptation to mechanical load, as described by Wolff, can be explained by a relatively simple regulatory model. The model is useful for investigating the effects of physiological parameters on the development, maintenance, and adaptation of bone.
Integrative repair of articular cartilage in vitro: Adhesive strength of the interface region
Authors: Reindel Eric S. , Ayroso Annamarie M. , Chen Albert C. , Chun Denise M. , Schinagl Robert M. , Sah Robert L.
Published: February 2005

The objective of this study was to quantify the strength of the repair tissue that forms at the interface between pairs of cartilage explants maintained in apposition in an in vitro culture system. Articular cartilage explants were harvested from calves and from adult bovine animals, dissected into uniform blocks, and incubated in pairs within a chamber that maintained a 4 × 5 mm area of tissue overlap. Following 1–3 weeks of incubation, integrative repair was assessed by testing samples in a tensile single‐lap configuration to estimate adhesive strength. After incubation in medium containing 20% fetal bovine serum, the adhesive strength between pairs of calf cartilage blocks and pairs of adult bovine cartilage blocks increased at a rate of 7.0 and 10.5 kPa/week, respectively. This repair process appeared to be dependent on viable cells, since lyophilization of adult bovine cartilage before incubation completely inhibited the development of an interface with a measurable adhesive strength. The repair process was dependent on serum components in the medium. Incubation of sample pairs for 3 weeks in medium supplemented with 20% fetal bovine serum resulted in a relatively high proteoglycan content as well as a relatively high adhesive strength (34 kPa), whereas incubation in basal medium with or without 0.1% bovine serum albumin resulted in a 54–70% lower proteoglycan content and a 65–88% lower adhesive strength. Samples incubated for 3 weeks with serum also had a 20% higher DNA content than samples maintained in basal medium. Histological analysis indicated some cell division at the free surfaces of the explant and also occasional cells within the interface region between explants.
Effects of basic fibroblast growth factor, transforming growth factor‐β1, insulin‐like growth factor‐1, and insulin on human osteoarthritic articular cartilage explants
Authors: Posever James , Phillips Frank M. , Pottenger Lawrence A.
Published: February 2005

This study evaluated the effects of basic fibroblast growth factor, transforming growth factor‐β1, insulin‐like growth factor‐1, and insulin on the incorporation of thymidine and sulfate in human osteoarthritic articular cartilage. Tissue explants were obtained from 11 patients undergoing total knee arthroplasty and were categorized as nonfibrillated or fibrillated cartilage. The explants were cultured for 22 days, with changes of medium and growth factor every 72 hours, and labeled with [3H]thymidine and [35S]sulfate. Growth factors were used in the following concentrations: basic fibroblast growth factor at 1, 10, and 100 ng/ml; transforming growth factor‐β1 at 0.5, 5, and 50 ng/ml; insulin‐like growth factor‐1 at 0.15, 1.5, and 15 ng/ml; and insulin at 0.05, 0.5, and 5 μg/ml. Basic fibroblast growth factor decreased thymidine incorporation to 70% and sulfate incorporation to less than 20% that of the growth factor‐free controls. Transforming growth factor‐β1 had no significant effect on thymidine incorporation, whereas the concentrations studied inhibited sulfate incorporation to approximately 40% that of the controls. At the concentrations tested, insulin‐like growth factor‐1 had no significant effect on incorporation of either thymidine or sulfate. In contrast, insulin significantly stimulated the incorporation of both. Compared with growth factor‐free controls, insulin maximally increased thymidine incorporation by a factor (± EM) of 2.36 ± 0.47 and 1.69 ± 0.19 in nonfibrillated and fibrillated explants, respectively; sulfate incorporation was maximally increased 1.60 ± 0.24 and 1.92 ± 0.29‐fold for nonfibrillated and fibrillated explants, respectively. Of the factors tested, insulin demonstrated the greatest promise for promoting a synthetic response that may contribute to the regeneration of osteoarthritic cartilage.
Torsional loads in the early postoperative period following total hip replacement
Authors: Kotzar G. M. , Davy D. T. , Berilla J. , Goldberg V. M.
Published: February 2005

Torques generated in one subject during the early postoperative period were measured with a telemeterized total hip component. The patient was examined during gait, stair ascent, rising from a chair, and single‐limb stance. The torques were plotted against both the resultant joint contact force and the force component directed along the stem axis. During gait, the maximum torque was 35 Nm, recorded at a walking velocity of 1.7 m/sec. The peak torques during stair ascent and during rising from a seated position were found to be 23 and 15 Nm, respectively. The maximum value for torque measured in this study was 37 Nm during one attempt at single‐limb stance. Comparison of plots for torque versus stem‐axis component for the four activities shows that the torque increased more rapidly for chair exits than for gait up to resultant contact force values of as much as 1,000 N. For stair ascent, the same was true to values of 1,400 N. Within any given activity, the relationship between stem torque and resultant or stem‐axis force showed considerable variability. These results indicate that experiments evaluating the stability of femoral components in total hip arthroplasty should incorporate a component directed along the stem axis, as well as a component normal to the plane of the prosthesis. The results also suggest that theoretical stress analysis models should consider the broad variability in the orientation of the joint force at the hip.
Restoration of function of the thumb flexor apparatus requires repair of the oblique and one adjacent flexor tendon pulley
Authors: Esplin V. S. , Tencer A. F. , Hanel D. P. , Cosio M. Q.
Published: February 2005

Damage to the pulleys of the thumb flexor apparatus may cause bow‐stringing of the tendon and affect muscle function. An experiment using the hands and distal forearms of cadavers was designed to determine which damaged pulleys increase excursion length of the flexor tendon with constant tendon and resisting loads. Each specimen was mounted to a loading frame with a dead weight pinned to the tip of the thumb. The thumb flexor tendon was clamped to an actuator that applied a fixed load and measured excursion of the tendon. Ranges of motion of the thumb joint were also measured. The thumb flexor apparatus of each specimen was tested intact first, with the hand in flexed, neutral, and extended positions; then it was tested with progressive sectioning of pulleys from proximal to distal in one group and from distal to proximal in a second group. The length of excursion increased significantly with all pulleys cut but there was no effect on on overall range of motion of the thumb. With proximal to distal sectioning, no change in tendon excursion occurred when the flexor retinaculum and the first annular pulleys were cut, until the oblique pulley was sectioned, leadving only the second annular pulley intact (range, 1.17–1.31 times that of intact excursion, dependent on position of the hand). With distal to proximal sectioning, tendon excursion was not affected when the second annular and oblique pulleys were cut but did increase when the first annular pulley was sectioned, leaving only the flexor retinaculum intact (range, 1.28–1.36 times that of intact excursion). Dependent on the location of damage, therefore, an intact oblique or first annular pulley can maintain normal excursion of the tendon.
Development of a musculoskeletal extremity health status instrument: The musculoskeletal function assessment instrument
Authors: Martin Diane P. , Engelberg Ruth , Agel Julie , Snapp Deborah , Swiontkowski Marc F.
Published: February 2005

Despite an increasing reliance on the use of health status measures to assess and evaluate medical care, no single instrument is currently available for use with the broad range of patients with musculoskeletal disorders of the extremities that is commonly seen in clinical practice. In this paper, we report on the development of the Musculoskeletal Function Assessment instrument, a 100‐item self reported health status instrument that is designed to meet this need. The instrument was developed in two phases During the first phase, items were selected on the basis of interviews with 135 patients and 12 clinicians and from reviews of existing health status instruments. The items then were grouped into categories. During the second phase, the instrument was tested for reliability and content validity using a sample of 327 patients with one of five musculoskeletal disorders of the upper and lower extremities (fractures, soft‐tissue injuries, repetitive motion disorders, osteoarthritis, and rheumatoid arthritis). The patients were selected from both community and academic sites. The Musculoskeletal Function Assessment instrument met standards for test‐retest reliability and internal consistency. Content validity also was demonstrated, based on a review of item selection procedures, expert opinion, and the distribution of scores on the instrument.
Trochanteric transfer in total hip replacement: Effects on the moment arms and force‐generating capacities of the hip abductors
Authors: Free Scott A. , Delp Scott L.
Published: February 2005

A three‐dimensional computer model of the pelvis, femur, gluteus medius, and gluteus minimus was used to evaluate the changes in muscle moment arms and force‐generating capacities caused by alterations in the location of the greater trochanter. In the first part of this study, the hip center and all other aspects of joint geometry remained unaltered, while we examined changes in abduction moment arms that resulted from transfer of the trochanteric fragment to a wide variety of positions on the femur. The largest increase in average abduction moment arm was 11% (0.5 cm), which occurred with an anterolateral transfer. Most transfers resulted in moment arm changes of less than 5%. In the second part of this study, the hip center was displaced 2 cm superiorly, and the effects of a distal trochanteric transfer on the moment arms and force‐generating capacities of the abductors were analyzed. The superior displacement caused a 13% decrease in the moment arm of the abductors and a 43% decrease in their force‐generating capacity. The moment arm was not restored by distal transfer of the greater trochanter; however, distal transfer had the major advantage of restoring muscle lengths and force‐generating capacities. These results suggest that trochanteric transfer should be considered primarily as a means to restore muscle length because it has limited potential to increase the moment arms of the two primary hip abductors.
Removal of surface bacteria by irrigation
Authors: Anglen Jeff , Apostoles Peter Steven , Christensen Gordon , Gainor Barry , Lane Joel
Published: February 2005

We examined the efficacy of various irrigation solutions delivered through a power irrigator to remove bacteria from three different surfaces. Titanium, stainless‐steel, and cortical bone surfaces were coated with three different bacterial species: Staphylococcus aureus, Pseudomonas aeruginosa, and Staphylococcus epidermidis. They were then irrigated with 1 L of fluid delivered by jet lavage. The fluids tested were normal saline and solutions of bacitracin, neomycin, and soap. One set of specimens was not irrigated, as a control. After irrigation, the specimens were sonicated to remove residual bacteria, and the sonicate was quantitatively cultured to allow evaluation of the amount of residual bacteria on the surface. The results showed that removal of bacteria reflects an interaction between bacterial species, surface characteristics, and irrigation solution. Fewer bacteria were present in all the irrigation groups than in the control. Soap solution was as good as or better than any other solution at removing all three types of bacteria from all three surfaces, although not all of the pairwise comparisons were statistically significant. There was a significant advantage to soap solution over antibiotic irrigant or saline alone in removing Staphylococcus epidermidis from metallic surfaces. The use of a soap solution for irrigation seems to improve the removal of some bacteria from some surfaces in this experimental model and may represent a better type of irrigation additive.
Porous ceramics as bone graft substitutes in long bone defects: A biomechanical, histological, and radiographic analysis
Authors: Johnson Kenneth D. , Frierson Kerek E. , Keller Tony S. , Cook Charles , Scheinberg Robert , Zerwekh Joseph , Meyers Laura , Sciadini Marcus F.
Published: February 2005

Three porous ceramic bone graft materials were compared with regard to their ability to heal a 2.5 cm defect created surgically in a bilateral canine radius model. The ceramic materials were analyzed at 12 and 24 weeks after surgery and included tricalcium phosphate, hydroxyapatite, and collagen hydroxyapatite, which contained a mixture of 35% tricalcium phosphate and 65% hydroxyapatite with added collagen. Each material was evaluated alone and with added bone marrow aspirate. All the implants were compared with a graft of autogenous cancellous bone in the contralateral radius. Biomechanical testing and radiographic evauation revealed that the addition of bone marrow aspirate was essential for tricalcium phosphate and hydroxyapatite to achieve results comparable with those of cancellous bone. Collagen hydroxyapatite performed well without the addition of bone marrow, although the addition of marrow did have a positive effect. Further qualitative radiographic and histological analysis demonstrated that tricalcium phosphate was the only ceramic that showed any sign of degradation at 24 weeks. This observed degradation proved to be an important factor in evaluating radiographs because the radiodensity of collagen hydroxyapatite and hydroxyapatite interfered with the determination of radiographic union. At 24 weeks, tricalcium phosphate with bone marrow was the material that performed most like cancellous bone. In this study, the biomechanical and radiographic parameters of tricalcium phosphate with bone marrow were roughly comparable with those of cancellous bone at 12 and 24 weeks. Tricalcium phosphate was the only implant that showed significant evidence of degradation at 24 weeks by both histological and radiographic evaluations, and this degradation took place only after a degree of mechanical competence necessary for weight‐bearing was achieved.
Protective effect of hypothermia on contractile force in skeletal muscle
Authors: Bolognesi Michael P. , Chen Long‐en , Seaber Anthony V. , Urbaniak James R.
Published: February 2005

The clinical success of limb replantation and tissue transfer is partly dependent on the duration of ischemia experienced by the amputated part. This study focused primarily on the damage that occurs during this ischemic period. An experimental system was implemented that allowed the observation of contractile function in totally isolated skeletal muscle after ischemia. Contractile function was selected as an indicator of ischemic damage because normal function is the ultimate goal of replantation. All experiments were performed on the rat extensor digitorum longus. The muscles were subjected to ischemic periods of 1.5, 3.0, and 5.0 hours and were stored in either a hypothermic (4°C) or a room‐temperature (23°C) environment during the ischemic interval. After the ischemic period, all muscles were transferred to a tissue bath and were subjected to contractility testing, followed by fatigue testing. In both groups, muscle function decreased as the ischemic interval was increased. A significant difference in function between the normal control and the muscles of both ischemic group implied that ischemic injury had occurred in the hypothermic and room‐temperature muscles, even with the relatively short 1.5‐hour ischemic interval. After each ischemic interval, however, the hypothermic muscles produced significantly greater contractile force than the room‐temperature muscles in both the contractility and the fatigue tests. After 1.5 hours of ischemia, the contractile force in the hypothenic group was about three times as great as that observed in the room‐temperature group. These results indicated that muscle function after a period of totally isolated ischemia is protected by hypothermic preservation. They also support the advisability of storage of amputated parts and free muscle flaps in hypothermic environments before replantation, even after relatively brief intervals of ischemia.