摘要:

AbstractLaser ablation of acrylic bone cement is an alternative method of cement removal that can be used during revision arthroplasty of cemented implants. This study investigated the feasibility of using a continuous‐wave Argon ion laser (wavelength = 514 nm) with the addition of methylene blue or red dye no. 13 to enhance the ablation of two types of bone cements: polymethylmethacrylate and polybutylmethylmethacrylate. Six cement/dye combinations were studied while power (0.5, 0.75, and 1.0 W) and exposure times (30, 45, 60, and 90 seconds) were varied. The Argon laser was unable to ablafre undyed polymethylmethacrylate or polybutylmethylmethacrylate. However, ablation was shown for both cements with either dye. The red dye had a stronger absorption peak at 514 nm than did the blue dye. Statistically larger ablation areas were seen for red polymethylmethacrylate than for blue polymethylmethacrylate (p<0.013) at all levels tested. Ablation areas were larger in red than in blue polybutylmethylmethacrylate cement. Blue polybutylmethylmethacrylate cement produced larger ablation areas than did blue polymethylmethacrylate cements at all energy levels tested, with smaller surrounding damage areas. Red polybutylmethylmethacrylate cement also produced larger ablation areas than did red polymethylmethacrylate cement (at 0.75 and 1.0 W), again with smaller damage areas. Damage zones were smallest in red polybutylmethylmethacrylate cements at all test levels. These results suggest that, by using dyes to selectively alter the absorption characteristics of bone cement, laser ablation can be an effective method for cement removal. Changes in the chemical structure of the cement can also influence the response to laser treatment. Furthermore, the absorption spectra of the bone cement can be altered to maximize energy absorption at a wavelength that is not absorbed by bone tissue; this potentially minimizes damage to bone during revision surger

ISSN:0736-0266    

DOI:10.1002/jor.1100160112

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

年代:1998

数据来源: WILEY

摘要:

AbstractThis study was performed to investigate the potential utility of ofloxacin‐impregnated bioabsorbable polymers for osteomyelitis therapy.Pseudomonas aeruginosaosteomyelitis was induced in 48 New Zealand White rabbits Four weeks after infection, the animals were randomized to one of four treatment groups: drug‐free polymer, ofloxacin polymer, systemic ofloxacin, or ofloxacin polymer plus systemic ofloxacin. Twentyeight days later, radiographs were taken of the affected area, the animals were killed, and bone was obtained for histoloeic evaluation. culture. and determination of ofloxacin concentrations. The percentage of sterile bone cultures was 33, 83, 75, and 91 for the groups treated with drug‐free polymer, ofloxacin polymer, systemic ofloxacin, and ofloxacin polymer plus systemic ofloxacin, respectively. When compared with the drug‐free polymer, both the ofloxacin polymer and the ofloxacin polymer plus systemic ofloxacin significantly improved the rate of sterilization. The mean concentrations of the drug in bone for the groups treated with ofloxacin polymer, systemic ofloxacin, and ofloxacin polymer plus systemic ofloxacin were 34.9 (range: 2–160), 1.9 (range: 0.8–3), and 26.0 μg/g (range: 9–100 μg/g), respectively. These data suggest that the DL‐lactide:glycolide polymer studied is a suitable vehicle for the delivery of high local concentrations of ofloxacin and that these concentrations result in eradication of the bacterial pathogen in

ISSN:0736-0266    

DOI:10.1002/jor.1100160113

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

年代:1998

数据来源: WILEY

摘要:

AbstractThe characterization of stress and deformation fields that incorporate moving cyclic loads and nonlinear material response in ultra‐high molecular weight polyethylene components for total knee replacements is required to quantify mechanisms of surface damage. A simulation of stresses in polyethylene components for total knee replacement subjected to cyclic moving loads was performed with use of nonlinear finite element analysis. Convergence to a steady‐state cycle of stress and deformation was observed within five cycles of loading. Differential plastic deformation under the surface of the polyethylene led to horizontal residual stresses that were tensile at the surface and compressive in the subsurface. The magnitudes of the residual J stresses indicate their importance in surface failure mechanisms. Horizontal residual tensile stresses at the surface are consistent with the initiation and propagation of surface cracks that could cause pitting in polyethylene. Horizontal residual compressive stresses under the surface could cause such cracks to arrest or turn and thus limit damage to a region just beneath the surface. The results emphasize the importance of incorporating nonlinear effects to simulate long‐term stress fields associated with surface damage in polyeth

ISSN:0736-0266    

DOI:10.1002/jor.1100160114

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

年代:1998

数据来源: WILEY

摘要:

AbstractThe capacity of isolated chondrocytes to join separate masses of cartilage matrix was investigated with composites implanted in subcutaneous pouches in nude mice. Slices of articular cartilage were harvested from lambs and were devitalized by cyclic freezing and thawing. The slices were then either co‐cultured with viable allogeneic lamb chondrocytes (experimental) or cultured without such chondrocytes (control). Composites of three slices were constructed with use of fibrin glue and were implanted in nude mice for periods ranging from 7 to 42 days. Bonding of the experimental matrices with viable chondrocytes was achieved at 28 and 42 days, as assessed by direct examination, histology, thymidine uptake, and fluorescence. No bonding occurred in the control composites without viable chondrocytes. We conclude that devitalized cartilage matrix is a scaffold to which isolated chondrocytes can attach and begin to repopulat

ISSN:0736-0266    

DOI:10.1002/jor.1100160115

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

年代:1998

数据来源: WILEY

摘要:

AbstractType‐VI collagen is an integral part of the extracellular cartilage matrix. However, the exact amounts of type‐VI collagen in normal and osteoarthritic human cartilage still are not known. In this study, we describe an inhibition enzyme‐linked immunosorbent assay that was developed to quantitate type‐VI collagen epitopes found in guanidinium chloride extracts from normal and osteoarthritic human cartilage. In 31 cartilage samples from various localizations of healthy adult human knees, type‐VI collagen epitopes accounted for approximately 0.40% of the total collagen content. Interestingly, type‐VI collagen epitopes increased about 4‐fold in osteoarthritic cartilage. A statistically significant increase of type‐VI collagen epitopes was found during early stages of the disease, with only a superficial roughening of the cartilage surface and a loss of proteoglycans. Thus, these findings indicate that type‐VI collagen is a minor component of normal human articular cartilage and that the amount of type‐VI collagen epitopes increases significantly during early stage

ISSN:0736-0266    

DOI:10.1002/jor.1100160116

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

年代:1998

数据来源: WILEY

摘要:

AbstractHyaluronan is an integral component of proteoglycan‐rich extracellular matrices such as hyaline cartilage. Hyaluronan is commonly found in embryonic tissue and is important in the formation of hydrated matrices that allow cellular expansion and migration. Cell surface hyaluronan‐binding proteins such as CD44 are presumed to be important in the cellular interactions with hyaluronan in both of these processes. The primary aim of this study was to document the spatial and temporal expressions of CD44 isoforms during the development and growth of the diarthrodial joints of rat limbs. With use ofin situhybridization and immunohistochemistry, the CD44s isoform is selectively identified as localized to a single cell layer on opposing sides of the joint at the first appearance of joint cavitation (on the 18th day of gestation). After joint formation in the neonate, the expression of the CD44s isoform in the cells at the joint surface is lost. These findings suggest that the CD44s isoform has a role in the development of the diarthrodial joint, presumably through interaction with hyaluro

ISSN:0736-0266    

DOI:10.1002/jor.1100160117

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

年代:1998

数据来源: WILEY

摘要:

AbstractSlices of lapine meniscus produced large amounts of nitric oxide after stimulation with interleukin‐1, tumor necrosis factor α, or a mixture of lapine synovial cytokines known as chondrocyte‐activating factors. Monolayer cultures of meniscal cells produced from the proteolysis of meniscal tissue contained a mixed population of chondrocytic and fibroblastic cells. These cultures also produced large amounts of nitric oxide in response to cytokines. Monolayer cultures of meniscal cells produced by the explant method, in contrast, were uniformly fibroblastic and did not produce nitric oxide in response to cytokines. We conclude that menisci contain two populations of cells, one fibroblastic and the other chondrocytic. The chondrocytic cells are responsible for generating most of the nitric oxide in response to cytokines. Endogenously generated nitric oxide suppressed the synthesis of collagen and proteoglycan by menisci but protected proteoglycan from the catabolic effects of interleukin‐1. The inhibitory effect of nitric oxide on collagen synthesis occurred without greatly altering the abundance of mRNAs encoding the various collagen α chains. During further investigation, arginine was unexpectedly found to stimulate the synthesis of collagen and, to a lesser degree, of noncollagenous proteins but not of proteoglycans. Fragments of meniscus, but not meniscal cells in monolayer culture, increased their production of matrix metalloproteinases. lactate, and, especially, prostaglandin E2in response to interleukin‐1. Inhibition of nitric oxide production with NG‐monomethyl‐L‐arginine enhanced production of matrix metalloproteinases but had little effect on the synthesis of lactate or p

ISSN:0736-0266    

DOI:10.1002/jor.1100160118

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

年代:1998

数据来源: WILEY

摘要:

AbstractCarpal tunnel syndrome may be caused by repeated or sustained elevated carpal tunnel pressure. This study examined the relationship between carpal tunnel pressure, posture, and fingertip load. In 20 healthy individuals, carpal tunnel pressure was measured with a catheter inserted into the carpal tunnel of the dominant hand and connected to a pressure transducer. With the wrist in a pressure‐neutral position, the subjects pressed on a force transducer with the index finger to levels of 0, 5, 10, and 15 N. They then pinched the transducer at the same levels of force. For both fingertip‐loading postures, the carpal tunnel pressure increased with increasing fingertip load. Carpal tunnel pressures were significantly greater (p<0.015) for the pinching task (14.2, 29.9, 41.9, and 49.7 mm Hg [1.89, 3.99, 5.59, and 6.63 kPa] for 0, 5, 10, and 15 N force levels, respectively) than for simple finger pressing (7.8, 14.1, 20.0, and 33.8 mm Hg [1.04, 1.88, 2.67, and 4.51 kPa]). This study indicates that although the external load on the finger remained constant between the two tasks, the internal loading, as measured by carpal tunnel pressure, experienced a near 2‐fold increase by using a pinch grip. These findings should be given consideration in designing work tasks and tools because relatively low fingertip forces, especially in a pinch grip, elevate carpal tunnel pressures to levels that, if prolonged, may lead to the development or exacerbation of carpal tunnel syn

ISSN:0736-0266    

DOI:10.1002/jor.1100160119

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

年代:1998

数据来源: WILEY

摘要:

AbstractA Bankart repair is performed to reduce abnormal translations of the humeral head on the glenoid due to a Bankart lesion, a separation of the capsulolabral complex from the glenoid rim. However, this is often accompanied by a loss of rotational range of motion that may lead to decreased function and osteoarthritis. This loss of rotation, coupled to the goal of reducing humeral translations, may be a result of the amount of imbrication of the capsule during repair. To determine the effects of capsular imbrication, we investigated how two Bankart repairs (2.5 and 5.0 mm of capsular imbrication) and a Bankart lesion altered the translations and rotations of the human glenohumeral jointin vitro. Coupled moments were applied to the unconstrained humerus in abduction‐adduction, in flexion‐extension, and to simulate the cocked phase of throwing. Motion was measured with an electromagnetic system. There were no differences in the kinematics betweenthe intact specimens and those with a Bankart lesion or between normal specimens and the first (2.5 mm) Bankart repair. The first repair significantly reduced external rotation for the cocked phase of throwing compared with the Bankart lesion: from 46.8 ± 23.6° to 32.4 ± 14.2° (±SD). The second (5.0 mm) Bankart repair produced significantly different posterior translation (‐4.7 ± 3.9 mm) of the humeral head relative to the glenoid compared with normal (5.1 ± 4.7 mm anterior) and the first repair (6.1 ± 8.3 mm anterior), as the humerus moved from full flexion to full extension. Differences were also found for all rotations in the cocked phase of throwing. For the second repair, the humerus extended 24.3° and externally rotated 18.6° less than normal and was abducted 15.4° more. These results indicate that both Bankart repairs do little to affect humeral translations with unconstrained moment loading but that rotations are affected during the cocked phase of throwing, with significant losses of external and ext

ISSN:0736-0266    

DOI:10.1002/jor.1100160120

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

年代:1998

数据来源: WILEY

摘要:

AbstractThis study investigated the impact of a combination of axial compressive and anterior‐posterior tibial loads on thein situforces in the anterior cruciate ligament. An axial compressive load is believed to contribute to increased stability of the knee joint; however, its effect onin situforces in the anterior cruciate ligament has not been clearly defined, to our knowledge. It was hypothesized that the application of an axial compressive load, when combined with an anterior tibial load, would result in largerin situforces in the anterior cruciate ligament than those caused by an isolated anterior tibial load. With use of a porcine knee model, the results confirmed this hypothesis; the addition of a 200 N axial compressive load to a 100 N anterior tibial load increased knee stability by reducing anterior‐posterior tibial translation and internal‐external tibial rotation and also caused a significant increase inin situforces in the anterior cruciate ligament (p<0.05). Specifically, there was a 34% increase in thein situforce at 30° of flexion, a 68% increase at 60° of flexion, and an 84% increase at 90° of flexion compared with those for an isolated anterior tibial load of 100 N. Additionally, there was a statistically significant increase of thein situforces in the anterior cruciate ligament at 60 and 90° as compared with those at 30°. These results suggest that axial compressive loads on the knee may play a role in injury of the anterior cruciate ligament when the knee

ISSN:0736-0266    

DOI:10.1002/jor.1100160121

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

年代:1998

数据来源: WILEY