摘要:

AbstractThe relation between mechanical loading of cartilage and chondrocyte activity in vivo may be mediated by several physical transduction mechanisms including: cell deformation, hydrostatic pressure gradients, fluid flow, streaming currents, and physicochemical changes. We have developed an organ culture system designed to study chondrocyte biosynthetic response to such physical stimuli. This study focuses on the effects of static compression and physicochemical changes. Cartilage disks harvested from the reserve zone of the epiphyseal plate of 1–2‐week‐old calves were subjected to static compressive stresses of 0–3 MPa in unconfined compression and the incorporation of [35S]sulfate and [3H]proline was measured during the 12‐h loading period. Incorporation of both proline and sulfate decreased monotonically with increasing stress. Compressive loading also produces physicochemical changes including a decreased water content and increased matrix fixed‐charge density, with a concomitant increase in interstitial counterion concentrations (e.g., K+, H+) and decreased coion concentrations (e.g., SO42−). We therefore examined the possibility that specific changes in interstitial mobile ion concentrations may be linked to chondrocyte response to static compression by measuring biosynthesis in the absence of mechanical compression while independently altering the SO42−, K+, and H+composition of the bathing medium. We found that proline and sulfate incorporation were strongly dependent on pH, but independent of [SO42−]and [K+] in the range studied. These results suggest that compression‐induced changes in local, interstitial pH may account for the observed biosynthetic response to

ISSN:0736-0266    

DOI:10.1002/jor.1100060602

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractImmunohistochemical methods were employed to examine alterations in the cartilage extracellular matrix constituents associated with endochondral ossification in humans. The distributions of chondroitin 4‐ and 6‐ sulfate and keratan sulfate proteoglycan (PG) determinants. cartilage PG link protein. collagen types I and II. and fibronectin were determined in iliac crest growth‐plate specimens using the avidin‐biotin‐horseradish peroxidase system. Collagen type II was distributed throughout the growth plate, providing a framework within which chondrocytes divided and formed clusters of differentiating (hypertrophic) cells. The septa between these clusters and their subchondral extensions into underlying bone trabeculae were rich in PG. PG link protein, and collagen type II and resembled the extracellular matrix of reserve cartilage. The territorial matrix associated with the differentiating cells within the clusters contained reduced amounts of collagen type II, PG link protein, and possibly cartilage PG. Collagen type I and fibronectin were detected within the cytoplasm of the maturing and degenerating cells, and fibronectin localized intensely to the pericellular matrix envelopes of these cells. These alterations presumably facilitate the degradation of the matrix associated with the cell clusters by invading vascular tissue, while the septa. which retain the characteristics of more typical cartilage matrix, are not degraded and firmly anchor the cartilage to the subchon

ISSN:0736-0266    

DOI:10.1002/jor.1100060603

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractThe possible role of mechanical loading history in chondroosseous development at the ends of long bones is explored using two‐dimensional finite element models of chondroepiphyses. Loading histories are characterized in terms of discrete loading cases defined by joint contact pressure distributions and an associated number of loading cycles. An osteogenic stimulus throughout the chondroepiphyses is calculated following the theory that cyclic octahedral shear stresses promote endochondral ossification and cyclic compressive dilatational stresses inhibit ossification. The resulting distributions for the osteogenic stimulus predict the appearance of the secondary ossific nucleus and the shape of the developing bony epiphysis. The zone of Ranvier and the formation of articular cartilage and the growth plate are also predicted by the models. These findings are consistent with the hypothesis that tissue stress histories constitute an important influence during skeletal morphogenesis. Further study and testing of the concepts introduced in this study are appropriat

ISSN:0736-0266    

DOI:10.1002/jor.1100060604

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractThe chondrocytes of the epiphyseal growth plate are the presumed target cells for hormones regulating skeletal growth. The somatomedins, a family of low molecular weight peptides, are thought to play a stimulatory role in this regulation. The cellular actions of the somatomedins are themselves determined by binding to specific receptors on target cells. Previous studies have characterized a specific receptor for somatomedin‐C (Sm‐C) or insulin‐like growth factor I (IGF‐I) on bovine growth plate chondrocytes (GPCs). We now report the characterization of a second type of somatomedin receptor on these cells that is more specific for another class of somatomedin represented by multiplication‐stimulating activity (MSA) or rat insulin‐like growth factor II (rIGF‐II). Binding of [125I]MSA/rIGF‐II to isolated GPCs was time dependent and saturable. Unlabeled Mr7.100 MSA/rIGF‐II and Sm‐C/IGF‐I were approximately equipotent in competing with [125I] MSA/rIGF‐II for binding. while Mr8,600 MSA/rIGF‐II was an order of magnitude less potent. Low levels of competition by insulin appeared in some studies at concentrations of 10−7M and higher. suggesting displacement of [125I]MSA/rIGF‐II binding. to the Sm‐C/IGF‐I receptor. In affinity‐labeling studies. [125I]Sm‐C/IGF‐I labeled a complex of Mr>300.000 (unreduced) and of Mr140.000 (reduced). consistent with a type I somatomedin receptor composed of disulfide‐linked subunits. [125I]MSA/rIGF‐II labeled a Mr240.000 moiety (unreduced) and Mr260.000 (reduced). consistent with a type II somatomedin receptor. Both affinity‐labeling and kinetic data revealed cross‐binding of MSA/rIGF‐II and insulin with the type I receptor and of Sm‐C/IGF‐I with the type II receptor. In contrast. the type II receptor did not recognize insulin. These data suggest a complex pattern of graded specificity of these receptors for their ligands. These data are consistent with the hypothesis that IGF‐II as well as Sm‐

ISSN:0736-0266    

DOI:10.1002/jor.1100060605

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractThe effects of polymethylmethacrylate (PMMA) exposure upon macrophage viability and function were studied in an attempt to determine what role these cells play in the loosening of cemented arthroplasties. P388D1 murine macrophage cell line was exposed to PMMA and polystyrene particles of similar size and concentration. DNA synthesis following exposure to PMMA or polystyrene was studied by [3H]thymidine incorporation. Macrophage function was studied by analyzing the ability of activated macrophages to kill mast cell targets following particle exposure. Our results demonstrate that exposure of macrophages to PMMA particles in vitro inhibits DNA synthesis and impairs their cytotoxic ability. Histologic examination revealed that macrophages phagocytose both PMMA and styrene particles, but the former eventually lyse these cells. Our studies suggest that the histologic appearance of macrophages and foreign body giant cells at the bone‐cement interface may be secondary to a repetitive cycle of PMMA particle phagocytosis and cell death, similar to that found in a foreign body granulomatous respons

ISSN:0736-0266    

DOI:10.1002/jor.1100060606

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractPostural control in single‐limb stance has previously been shown to be impaired among soccer players with functional instability (FI) of the ankle joint. The aim of the present study was to further study the role of the ankle in postural control. A dynamic method was used involving optoelectronic movement recordings of body segments and force‐plate recordings of the reaction ground force. Surface electromyography was recorded for the peroneus longus muscle. Thirty physically active men were selected. Fifteen of them had FI of the ankle chosen for recording. The results show that different patterns exist for maintaining equilibrium in single‐limb stance. The ankle has a central role for postural corrections. The position of center of pressure is highly correlated to the position of the ankle and peroneal muscle activity. When the body was in disequilibrium, corrections were made at the hip. It is proposed that a change from an inverted pendulum model to a multisegmental chain model takes place when adjustments at the ankle joint no longer suffice to maintain postural control. The men with FI showed impaired postural control associated with increased upper segmental correc

ISSN:0736-0266    

DOI:10.1002/jor.1100060607

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractThe pelvis, a major load carrying component of the musculoskeletal system, is sometimes suspected as a site of mechanically provoked low back pain. Thus, studies of its basic biomechanics seem warranted. This study used biomechanical model simulations to examine how pelvic geometry and joint soft tissue properties influence relative motions among its bones and internal loadings of its joints. A biomechanical model of a pelvis was loaded by forces of up to 1000 N and moments of up to 25 Nm. Its resulting motions and joint loadings were determined. The effects on these responses due to pelvic geometry changes of 20% in lengths and 10° in angles, and soft tissue stiffness changes, most of which were 25%, were also examined. For all situations examined, model pelvis relative displacements were at most a few mm, and relative rotations were at most a few degrees. Internal forces and moments were always less than 530 N and 30 Nm, respectively

ISSN:0736-0266    

DOI:10.1002/jor.1100060608

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractDespite the well‐recognized association between poorly reduced intraarticular fractures and late degenerative changes, current guidelines regarding the reduction precision necessary to avoid excessive cartilage pressures are based largely on anecdotal clinical observations. To gain a quantitative appreciation of the relation between local pressure elevations and fracture reduction imprecision, a simplified laboratory cadaver model of minimally displaced tibial plateau fractures was developed. Cartilage contact stress distributions were measured as a function of depressed fragment malreduction in seven knees, using high‐resolution (100 pixels/mm2) digital image scans of Fuji‐film stain patterns. The contact stress data showed a general trend of increases of peak local pressure with increasing fracture site incongruity, and in a few isolated instances the effect was very pronounced. Across the whole series, however, statistically significant departures from anatomic pressure levels did not occur until the fragment stepoff was>1.5 mm. Even at the 3‐mm stepoff level, for which the depressed fragment usually no longer made contact with the femoral condyle, the peak local pressure values on the intact side of the fracture line averaged only ∼75% greater than those prevailing anatomically. Given the successful clinical outcomes normally achieved for conservatively managed simple tibial plateau fractures having stepoff magnitudes (5–10 mm) clearly sufficient to insure fragment articular noncontact, the present laboratory results suggest that nominally factor‐of‐two peak local pressure elevations, provided that they occur over only small portions of the cartilage surface, are probably within the long‐term overall tolerance range of a

ISSN:0736-0266    

DOI:10.1002/jor.1100060609

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractSeventeen female and 24 male subjects had varus and valgus and apparent rotations measured using a standardized mechanical testing device that cyclically applied a 20‐Nm moment in each direction. Five parameters‐apparent varus rotation, apparent valgus rotation, apparent overall rotation, varus stiffness, and valgus stiffness showed intersubject variations approaching 40%. Right‐left variations in the same subject averaged 12%, with no significant right‐left differences overall. Female knees rotated 66% more than male knees and were 35% less stiff. The ratio of apparent valgus rotation to apparent varus rotation averaged 0.775, and the ratio of valgus stiffness to varus stiffness averaged 1.23 for all knees. Stiffness and rotation parameters were highly correlated for both genders in the valgus phase of testing. Results suggest that although magnitudes of measured parameters vary considerably from subject, common relationships between parameters from the same normal kne

ISSN:0736-0266    

DOI:10.1002/jor.1100060610

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractA‐2 pulleys were replaced in the hand of the nonhuman primate; on the long/little fingers the pulleys were reconstructed with a woven nylon fabric (Nitex), and on the ring/index fingers the pulleys were reconstructed with fascia lata. The opposite unoperated hand served as a control. At 2, 3, and 6 months postoperative, the animals were killed to compare the function of the reconstructed pulleys with the control pulleys of the opposite digit. Using a tensile testing machine, two parameters, work of flexion and tendon excursion, showed that both pulley reconstructions permitted minimal tendon bowstringing and had excellent gliding function. Both materials increased in strength over time to become stronger than the control pulley. Histologic examination showed no foreign body reaction to the Nitex; excellent fibrous ingrowth into the woven nylon was seen, which matured in time. The surface of the Nitex pulley facing the tendon developed and maintained a synovial‐like gliding surface. The Nitex pulley compared favorably with the fascial pulley biomechanically and histologically; both reconstructed pulleys functioned well compared with normal pull

ISSN:0736-0266    

DOI:10.1002/jor.1100060611

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY