摘要:

AbstractIt has been hypothesized that the electric fields associated with the dynamic loading of cartilage may affect its growth, remodeling, and biosynthesis. While the application of exogenous fields has been shown to modulate cartilage biosynthesis, it is not known what range of field magnitudes and frequencies can alter biosynthesis and how they relate to the magnitudes and frequencies of endogenous fields. Such information is necessary to understand and identify mechanisms by which fields may act on cartilage metabolism. In this study, incorporation of35S‐methionine was used as a marker for electric field‐induced changes in chondrocyte protein synthesis in disks of cartilage from the femoropatellar groove of 1 to 2‐week‐old calves. The cartilage was stimulated sinusoidally at 1, 10, 100, 103Hz with current densities of 10–30 mA/cm2. Incorporation was assessed in control disks maintained in the absence of applied current at 37, 41, and 43°C. The possibility that applied currents would induce synthesis of the same stress proteins that are caused by heating or other mechanisms was assessed by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis and examination of gel fluorographs. Total radiolabel incorporation in cartilage that had been stimulated relative to incorporation in the controls increased with current density magnitudes greater than 10 mA/cm2. The increase was greatest at 100 Hz and 1 kHz, and it depended on the position on the joint surface from which the cartilage samples were taken. Together, these results suggest that endogenous electric fields could affect cartilage biosynthesis. Stress proteins were not induced at any current density when the electrodes were electrically connected but chemically isolated from the media by agarose bridges. Stress proteins were observed for disks incubated at temperatures greater than 39°C (no field) and when the stimulating platinum electrodes were in direct contact with the media bathing the cartilage disks. Therefore, the increase in incorporation of35S‐methionine due to applied fields with the use of chemically isolated electrodes did not appear to be associated with

ISSN:0736-0266    

DOI:10.1002/jor.1100120202

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe recovery of articular cartilage from atrophy induced by joint immobilization was investigated in immature dogs. In a previous study, we showed that 11 weeks of immobilization of the knee (stifle) joint of young dogs reduced the concentration of articular cartilage glycosaminoglycans (GAGs) by 13–47%. In the present study, right hindlimbs from six female beagles were immobilized for 11 weeks, as in the previous study, and then were remobilized for 15 weeks. Cartilage from the knee joint was compared with cartilage from nonimmobilized knees of eight age‐matched control beagles. Histological samples taken from 11 different locations of the knee joint were stained with safranin O, and microspectrophotometry was used to demonstrate distribution of GAGs in the tissue. After remobilization, GAG concentration was restored in the patellofemoral region and tibial condyles. On the summits of the femoral condyles, and especially at the periphery of the femoral condyles, GAG concentration remained 8–26% less than the control values. On the summits, the thickness of the uncalcified cartilage was as much as 15% less than in the age‐matched controls. Consequently, the changes induced by unloading were reversible to a great extent, but a full restoration of articular cartilage was not obtained at all sites of the knee joint within the 15 weeks of remobilization. Immobilization of the skeletally immature joint therefore may affect the development of articular cartilage in such a way that very slow recovery or permanent alterations are

ISSN:0736-0266    

DOI:10.1002/jor.1100120203

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

年代:1994

数据来源: WILEY

摘要:

AbstractDegenerative joint disease was induced in the knee joints of mice by intraarticular injection of two different stimuli: iodoacetate and highly purified collagenase. Proteoglycan synthesis was measuredin vivoat different time points in four topographical areas of the knee joint (central and peripheral parts of the patella and central parts of the medial and lateral tibial plateaus) and was compared with histological observations of localized damage to the joint.In vitroincubation with iodoacetate had a direct effect on proteoglycan metabolism. Intra‐articular injection of iodoacetatein vivoinhibited the proteoglycan synthesis in cartilage from the central part of the patella. In the peripheral part of the patella, inhibition on day 1 was followed by stimulation of synthesis on days 3–30. Proteoglycan synthesis also was inhibited in the central parts of the medial and lateral tibial plateaus. The areas with inhibited synthesis had loss of safranin O staining on histology.In vitroincubation with collagenase did not have a direct effect on the proteoglycan metabolism of intact cartilage; this led to the assumption that osteoarthritis after injection of collagenase is caused by ligamentous injury, which leads to an unstable joint. Injection of collagenasein vivostimulated the proteoglycan synthesis in cartilage from the central and peripheral parts of the patella. In an early stage of the process, the cartilage from the tibial plateaus also was slightly stimulated. From 30 days after injection of collagenase, synthesis in the lateral tibial plateau decreased, whereas synthesis in the patella remained stimulated and synthesis in the medial tibial plateau remained normal. On histology, cartilage from the patella and the medial tibial plateau had a normal appearance, and there was loss of cartilage from the lateral tibial plateau. Our data indicate that the variation in response of cartilage from different anatomical areas of the knee joint depends on the stimulus used. This suggests that the location of cartilage damage depends on the etiological factor responsible for induction of the osteoarthritic proc

ISSN:0736-0266    

DOI:10.1002/jor.1100120204

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

年代:1994

数据来源: WILEY

摘要:

AbstractAlthough collagen fibers are arranged predominantly in the circumferential direction in the knee meniscus, there is evidence for radially oriented fibers within human menisci. A bovine medial meniscus model was used to study the hypothesis that radial fibers alter the radial tensile properties of the meniscus. The architecture of the collagen network and tensile properties of the bovine medial meniscus were examined; attention was given to large “radial tie fibers” and their regional variation. Menisci were sectioned serially into slices 400 μm thick. Polarized light microscopy showed that the distribution of radial tie fibers varied greatly among the anterior, central, and posterior regions. These radial tie fibers were larger and more frequent in the posterior region. Radial fibers persisted over many adjacent sections with similar architecture, which led to our hypothesis that they may be arranged in continuous sheets in which the morphology varies by region. Radially oriented specimens for tensile testing were grouped according to the number of radial tie fibers (full, partial, and no fiber) and region (anterior, central, and posterior). Uniaxial tensile testing was performed on a testing machine at a strain rate of 0.00017 sec−1until failure. The tensile modulus, ultimate tensile stress, and ultimate tensile strain were determined. The presence of radial tie fibers in the specimen had a significant effect on the tensile modulus and ultimate tensile stress. Specimens containing full radial tie fibers were stiffest and failed at the lowest strains; in specimens from the posterior region, the tensile modulus was 392%, the ultimate tensile stress was 314%, and the ultimate tensile strain was 68% that of the specimens with no radial fibers. In no‐fiber specimens, the tensile modulus in the posterior region was 225% of the modulus in the anterior region, and the ultimate tensile strain in the posterior region was 68% that of the strain in the anterior region. The abundance of radial tie fibers in the posterior region seems to contribute to the increased stiffness of this region. The preferential stiffening of the posterior region by these radial fibrous sheets may be well suited to the manner in which the bovine medial meniscus functions in load

ISSN:0736-0266    

DOI:10.1002/jor.1100120205

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe innervation of the human intervertebral disc was investigated by immunochemical methods. Immunoreactivity to the general nerve marker protein gene product (PGP 9.5) was found in the outer annulus fibrosus of 11 of 12 discs removed during anterior arthrodesis for back pain. PGP 9.5‐immunoreactive fibres ran between and across the collagenous lamellae, both in association with blood vessels and distant from them, and extended at least 3 mm into the disc. No innervation was observed in the nucleus pulposus. Fine fibres (<1 μm in diameter) immunoreactive to calcitonin gene‐related peptide and substance P (neuropeptides located in sensory and possibly nociceptive nerves) were identified in eight and four of the annuli fibrosi, respectively. Nerve fibres immunoreactive to vasoactive intestinal peptide and to the c‐flanking peptide of neuropeptide Y were found in the majority of specimens of annulus fibrosus that were ex

ISSN:0736-0266    

DOI:10.1002/jor.1100120206

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

年代:1994

数据来源: WILEY

摘要:

AbstractAdaptation of skeletal muscle during limb lengthening was assessed by measurement of the length of sarcomeresin situ. An external fixator was applied to the rabbit radius and ulna to elongate the forelimb by 3.5 mm, while allowing all the joints to be free. At regular intervals after the operation, the extensor digitorum lateralis muscle of the fifth digit was exposedin situand the length of the sarcomeres was measured by a laser diffraction technique. The sarcomeres, which had stretched to 3.51 μm immediately after elongation of the bone, became shorter with the passage of time. On postoperative day 9, the length was 3.10 μm, which was similar to the length of the unstretched muscle. These results indicated structural adaptation of the muscle to a new length and could explain why the efficiency of muscle function is maintained after limb lengthening. When these findings are combined with our previous results, it appears that stretch‐induced changes in sarcomere length are common in immobilized and nonimmobilized musc

ISSN:0736-0266    

DOI:10.1002/jor.1100120207

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

年代:1994

数据来源: WILEY

摘要:

AbstractMotion of the trapeziometacarpal joint was studied in 12 hands from fresh human cadavera. By use of a magnetic tracking system, a full range of motion of the first metacarpal was analyzed with respect to a defined trapezial coordinate system. The traces of the reference points on the head and base of the first metacarpal were monitored, and the instantaneous centers of rotation were calculated. During circumduction, the reference points on the head and base followed elliptical paths but in opposite directions. The average instantaneous center of circumduction was at approximately the center of the trapezial joint surface. In flexion‐extension, the axis of rotation was located within the trapezium, and the path of the head was identical to the path of the base. In abduction‐adduction, the axis of rotation was located distal to the trapezium within the base of the first metacarpal, and the base and head moved in opposite directions. There was no single center of rotation: rather, instantaneous motion occurred reciprocally between these centers of rotation within the trapezium and metacarpal base in the normal thumb. This changing instantaneous center of rotation results in a unique pattern of motion which is related to congruent, tightly constrained joint surfaces of two reciprocal saddle joints and to precisely positioned extraarticular ligame

ISSN:0736-0266    

DOI:10.1002/jor.1100120208

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

年代:1994

数据来源: WILEY

摘要:

AbstractThis study was designed to examine the roles of ligaments in the maintenance of the articular kinematics of the trapeziometacarpal joint. Circumduction of the trapeziometacarpal joint was studied in 12 hands from fresh human cadavera. With use of a magnetic tracking system, changes in the motion of the base of the first metacarpal after ligament sectioning were analyzed and compared with those of the normal joint. Two sets of ligaments were sectioned: (a) the anterior oblique and ulnar collateral ligaments and (b) the first intermetacarpal ligament and the ulnar joint capsule. Sectioning of the anterior oblique and ulnar collateral ligaments resulted in a significant dorsal‐ulnar shift in the path of the base of the first metacarpal. However, sectioning of the first intermetacarpal ligament did not affect the movement pattern of the center of the base. The anterior oblique and ulnar collateral ligaments provided constraint of the trapeziometacarpal joint during circumduction of the thum

ISSN:0736-0266    

DOI:10.1002/jor.1100120209

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

年代:1994

数据来源: WILEY

摘要:

AbstractFractures of the distal radius are common, especially in postmenopausal women, and their prevalence increases with age. Knowledge of the factors that increase the risk of fracture in this metaphyseal region would have predictive and therapeutic implications. Of particular interest in this study were (a) the relative contributions of cortical and trabecular bone to the strength of the distal radius and (b) the best radiographic features to use as strength indicators. In 21 forearms from fresh cadavera (median age at the time of death, 75 years), single photon absorptiometry and quantitative computed tomography were used to determine bone mineral content (BMC), density (BMC/W), and cross‐sectional properties of the radius at distal and midshaft sites. Mechanical testing of the forearms then was used to determine the ultimate force and energy to cause the type of fracture that might be caused by a fall on the outstretched hand. Twelve of the 17 tested specimens sustained a fracture of the distal radius, and five sustained a fracture of the scaphoid. In the group of fractures of the distal radius, we found the cross‐sectional area and moment of inertia of the cortical shell at the metaphyseal site to be better correlates of strength than the trabecular area and trabecular moment. In contrast, strength correlated much better with trabecular density than with cortical density. Overall, the best correlates of strength were the BMC and BMC/W at either the distal or proximal site. On balance, these results suggest that the thin cortical shell contributes substantially more to the mechanical strength of the distal radius than has been commonly apprecia

ISSN:0736-0266    

DOI:10.1002/jor.1100120210

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

年代:1994

数据来源: WILEY

摘要:

AbstractDecreased dynamic stability of the knee joint associated with functional disability is a feature of anterior cruciate ligament deficiency (ACLD). The purposes of this study were to examine the between‐limbs difference in reflex contraction latency of the hamstring muscles in patients with unilateral ACLD and to investigate its relationship with instability and function. Fifty patients with arthroscopically diagnosed unilateral ACLD were measured bilaterally for reflex hamstring contraction latency (RHCL), and 20 normal volunteers were similarly tested. The subjects were measured in a position of single‐limb full weight‐bearing with the knee flexed 30°. An anteriorly directed shear force was applied to the tibia, and surface electromyographs (EMGs) recorded the activity of the hamstrings in response to the applied force. The latency of contraction was defined as the time from initial tibial movement, identified by accelerometry, to the onset of increased hamstring EMG activity. Both legs were tested and a between‐limbs difference was computed. A significant difference in RHCL wasfound between the limb with ACLD and the control limb. The mean RHCL of the limb with ACLD was nearly double that of the unaffected limb, for a significant mean between‐limbs difference (p<0.05). The mean between‐limbs difference for the control subjects was not statistically significant. The conclusion is that patients with ACLD have an increased RHCL of the injured leg. As the RHCL is dependent on proprioceptive activity around the joint, it can be used as a measure of proprioceptive ability. The loss of the neurophysiological protective reflex involving the anterior cruciate ligament and hamstrings in patients with ACLD is likely to be a contributory factor in the decreased joint stability experienced by th

ISSN:0736-0266    

DOI:10.1002/jor.1100120211

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

年代:1994

数据来源: WILEY