bluuebunny/crossref_metadata_2025 huggingface dataset:
Prediction of long‐term polyethylene wear in total hip arthroplasty, based on early wear measurements made using digital image analysis
Authors: Pedersen Douglas R. , Brown Thomas D. , Hillis Stephen L. , Callaghan John J
Published: February 2005

The capability to reliably predict long‐term in vivo wear of polyethylene would be of great value for the early identification of problematic total hip designs. Formal quantitative estimates of long‐term polyethylene wear were made from a series of 197 patients who had a total hip arthroplasty and who were followed for a minimum of 10 years; the estimates were based on the wear that was apparent radiographically at nominally 2 years after the operation. A newly developed digital image‐analysis edge‐detection procedure was applied to 1,237 archived follow‐up radiographs. The edge‐detection measurements were analyzed with a robust regression random‐coefficients statistical formulation developed especially to address the distributions of wear rate observed across this population over time. Formal regression equations were reported, which can be used to estimate late‐wear depth for a patient radiographed at a 2‐year follow‐up visit. Series wide, the correlation between predicted and observed wear depths was 0.73 at 4 years, with a correlation decline of approximately 0.03 per additional year.
Bone ingrowth to implant surfaces in an inflammatory arthritis model
Authors: An Yuehuei H. , Friedman Richard J. , Jiang Ming , LaBreck Jacqueline C. , Draughn Robert A. , Butehorn Henry F. , Bauer Thomas W.
Published: February 2005

Many studies have shown enhanced bone apposition to implants coated with hydroxyapatite, but the optimum implant texture, especially in abnormal trabecular bone, is unclean The purpose of this project was to evaluate the histological and mechanical properties of cylindrical implants with three different surface textures that were placed in the cancellous bone of the distal femur of the rabbit after the production of an inflammatory knee arthritis. The three implant surfaces included a beaded surface (Group A), a beaded surface coated with hydroxyapatite (Group B), and a smooth surface coated with hydroxyapatite (Group C). The right knees of 36 rabbits were injected with carrageenan twice a week for 2 weeks. Then bilateral implantations were performed, with 12 rabbits in each group receiving identical implants in the right and left knees. The rabbits were killed 6 weeks after surgery. Mechanical (push‐out test) and histomorphometric analyses were performed to determine the quality and quantity of bone ingrowth. In Group A, there was virtually no direct contact (a 20–60‐μm clearance) between the bone and the beaded surfaces. Direct contact between the bone and the implant surfaces was seen in Groups B and C. The thickness and number of trabeculae were smaller on the arthritic side than on the control side for all groups but were not different between groups for either the control or the arthritic side. Mechanical testing showed that the shear strength of the interface was weaker on the arthritic side in all groups. The results suggest that inflammatory arthritis induced by carrageenan may influence the quality of local bone (osteopenic changes) and hence compromise the bone apposition and mechanical stability of the interface between the implant and bone.
Identification of sex hormone receptors in human and rabbit ligaments of the knee by reverse transcription‐polymerase chain reaction: Evidence that receptors are present in tissue from both male and female subjects
Authors: Sciore Paul , Frank Cyril B. , Hart David A.
Published: February 2005

Gender‐related factors have been attributed to observed differences in the rate of injury to ligaments (e.g., anterior cruciate ligament) between male and female subjects. These differences may be a result of unique regulatory mechanisms within the tissue in response to the sex hormones estrogen and progesterone. These hormones, when bound to specific intracellular receptors (estrogen receptor and progesterone receptor, respectively), modulate gene expression within hormone‐responsive tissue. The purpose of this study was to evaluate the expression of the estrogen and progesterone receptors in ligament tissue from male and female rabbits and humans by the sensitive molecular technique of reverse transcription‐polymerase chain reaction. Total RNA was extracted from human anterior cruciate ligament tissue and from medial cruciate ligament, anterior cruciate ligament, patellar tendon, and synovium tissue of the New Zealand White rabbit by the newly developed TRIspin method. The total RNA was reverse transcribed and analyzed by polymerase chain reaction to assess the expression of estrogen and progesterone receptors. Our results demonstrate that estrogen and progesterone receptor transcripts are expressed in ligament tissue of male and female rabbits and humans and that alterations in receptor expression occur in ligaments during pregnancy. In the human samples, only a small percentage of the estrogen receptor appeared to be a nonfunctional mRNA splice variant, and the predominant form contained the estrogen‐binding domain.
Effect of 25‐OH‐vitamin D on fracture healing in elderly rats
Authors: Delgado‐Martínez A. D. , Martínez M. E. , Carrascal M. T. , Rodríguez‐Avial M. , Munuera L.
Published: February 2005

To investigate the effect of 25‐OH‐vitamin D supplements (calcidiol) on fracture healing in the elderly, an experimental model with 15 18‐month‐old female Wistar rats was designed. An experimental fracture in the middle third of both femora of each rat was made. Then the rats were randomly assigned to two groups: one group was subcutaneously treated with 25‐OH‐vitamin D during all healing processes, and the other group (the control group) was not. After 5 weeks of healing, the animals were killed and both femora were extracted. Blood samples were collected before fracture and at death to determine the levels of 25‐OH‐vitamin D. All bones that were extracted were subjected to a torsion test to assess healing; a significantly greater maximum shear force before failure was supported in the treated group (p < 0.01). Moreover, a positive correlation (p < 0.01; r = 0.55) was found between blood levels of 25‐OH‐vitamin D at death and the mechanical strength of the callus. Thus, the administration of 25‐OH‐vitamin D after the experimental fracture significantly improved the mechanical strength of the fractured bone. If similar results are found in the human, then treatment with 25‐OH‐vitamin D after the occurrence of a fracture would be a good way to improve fracture healing in the elderly.
Single local injection of recombinant fibroblast growth factor‐2 stimulates healing of segmental bone defects in rabbits
Authors: Kato Takashi , Kawaguchi Hiroshi , Hanada Keigo , Aoyama Ikuo , Hiyama Yoshiyuki , Nakamura Toshiyuki , Kuzutani Kazuya , Tamura Makoto , Kurokawa Takahide , Nakamura Kozo
Published: February 2005

The effects of a single local injection of recombinant human fibroblast growth factor‐2 on the healing of segmental bone defects were evaluated in rabbits. One month after the external fixator originally designed for this experiment was installed in the tibia of the rabbit, a 3‐mm bone defect was created by an osteotomy in the middle of the tibia and 0, 50, 100, 200, or 400 μg of fibroblast growth factor‐2 in 100 μg of saline solution was injected into the defect. Injection of the growth factor increased the volume and mineral content of newly made bone at the defect in a dose‐dependent manner with significant effects at Concentrations of 100 μg or greater. These significant effects were observed at 5 weeks and later. One hundred micro‐grams of the growth factor increased the volume and mineral content of newly made bone by 95 and 36%, respectively, at 5 weeks. These results indicate that a single local injection of fibroblast growth factor‐2 stimulates the healing of segmental defects. We speculate that such an injection could be clinically useful for the healing of fractures even when the fracture gap is rather large.
Adhesion and reliability of interfaces in cemented total joint arthroplasties
Authors: Ohashi K. L. , Romero A. C. , McGowan P. D. , Maloney W. J. , Dauskardt R. H.
Published: February 2005

Debonding of the prosihctielpolymelhylmcthacrylate interface has been implicated in the initial failure process of cemented total hip arthroplasties. However, little quantitative understanding of the debonding process, as well as of the optimum interface morphology for enhanced resistance to debonding, exists. Accordingly, a fracture‐mechanics approach has been used in which adhesion at the interface is characterized in terms of the interface fracture energy. G (J/m2), and shown to be a strong function of the morphology, debonding length, and loading mode of the interface. Double‐cantilever‐beam and four‐point‐flexure fracture‐mechanics samples containing four clinically relevant prosthetic surface preparations were prepared to survey a range of interface roughness and loading modes. Adhesion at the interface could not be characterized with a single‐valueu material property but was found to exhibit resistance‐curve behavior in which resistance to debonding increased with both the initialdebond extension and the roughness of the interface. Values of debonding. initiation. Go, were relatively insensitive to the roughness of the surface and the loading mode, whereas steady‐state fracture resistance of the interface. Gss, increased significantly with the roughness and shear loading of the interface. These quantitative results suggest that debonding of the prosthetic/polymethyl methacrylate interface may be primarily attributed to surface interactions such as interlocking and the pullout of rough asperities thai occur behind the debond tip. A simple mechanics analysis of such interactions was performed and revealed increases in the fracture resistance of the interface that were consistent with experimentally measured values.
Response of chondrocyte subpopulations cultured within unloaded and loaded agarose
Authors: Lee David A. , Noguchi Takashi , Knight Martin M. , O'donnell Liam , Bentley George , Bader Dan L.
Published: February 2005

Although it is well known that the metabolism of chondrocytes can be altered by the application of mechanical strain, it is unclear whether chondrocytes from the superficial and deep zones of cartilage respond in a similar manner. In this study, chondrocytes from the uppermost 15‐20% (superficial cells) and the remaining tissue (deep cells) from bovine articular cartilage were isolated separately and cultured in agarose constructs. Cell deformation on application of a 15% static compressive strain was identical for both subpopulations after 24 and 72 hours in culture. The constructs were incubated under static and dynamic (0.3,1, and 3 Hz) strains of 15% amplitude. Glycosaminoglycan synthesis by deep cells was unaffected by static strain or 3 Hz dynamic strain, whereas 0.3 Hz produced a significant reduction and 1 Hz induced a highly significant 50% stimulation of glycosaminoglycan synthesis (p < 0.001). Superficial cells exhibited a general inhibition of glycosaminoglycan synthesis. By contrast, proliferation of superficial cells was stimulated by dynamic strain whereas deep cells were not influenced. It has been suggested previously that mechanotransduction‐induced controls of glycosaminoglycan synthesis and proliferation in chondrocytes embedded in agarose are uncoupled. Data presented in this study demonstrate that the two processes do, in fact, occur in different sub‐populations of chondrocytes within the full‐depth cell isolate.
Transport of tissue inhibitor of metalloproteinases‐1 through cartilage: Contributions of fluid flow and electrical migration
Authors: Garcia A Minerva , Lark Michael W. , Trippel Stephen B. , Grodzinsky Alan J.
Published: February 2005

The preservation of the structure of articular cartilage depends on the availability of inhibitors of matrix‐degrading enzymes. Tissue inhibitor of metalloproteinases‐1 is thought to be an important contributor to the integrity of the matrix of articular cartilage, but the mechanisms that regulate its availability within the tissue are poorly understood. These studies elucidate the contributions of diffusion, fluid flow, and electrical migration to the transport of iodinated recombinant human tissue inhibitor of metalloproteinases‐1 through explants of adult bovine articular cartilage under conditions relevant to the loading of cartilage. With use of measured partition coefficients of the cartilage explants, the diffusivity of the inhibitor was 0.5‐1.6 × 10−7 cm2/sec. Fluid velocities that were induced by applying an electrical current across the cartilage disks increased the flux of the inhibitor by approximately 20 to more than 150‐fold compared with the effect of diffusion alone for the range of current densities that were applied. We examined the contribution of electrophoretic migration by titrating the charge on the inhibitor during measurements of flux and found that flux in the presence of the applied current decreased as the inhibitor became more negatively charged. Enhancements in the flux of the inhibitor were observed relative to the flux during diffusion alone even under conditions in which electrophoretic migration opposed the flux due to fluid flow, suggesting that of the transport mechanisms tested, fluid flow was dominant. These results suggest that the physical phenomena present during physiologic loading conditions (e.g., fluid flows and streaming currents) can affect the transport of tissue inhibitor of metalloproteinases‐1 through the matrix of cartilage.
Ultrahigh molecular weight polyethylene particles have direct effects on proliferation, differentiation, and local factor production of MG63 osteoblast‐like cells
Authors: Dean D. D. , Schwartz Z. , Blanchard C. R. , Liu Y. , Agrawal C. M. , Lohmann C. H. , Sylvia V. L. , Boyan B. D.
Published: February 2005

Small particles of ultrahigh molecular weight polyethylene stimulate formation of foreign‐body granulomas and bone resorption. Bone formation may also be affected by wear debris. To determine if wear debris directly affects osteoblasts, we characterized a commercial preparation of ultrahigh molecular weight polyethylene (GUR4150) particles and examined their effect on MG63 osteoblast‐like cells. In aliquots of the culture medium containing ultrahigh molecular weight polyethylene, 79% of the particles were less than 1 μm in diameter, indicating that the cells were exposed to particles of less than 1 μm. MG63 cell response to the particles was measured by assaying cell number. [3H]thymidine incorporation, alkaline phosphatase specific activity, osteocalcin production, [35S]sulfate incorporation, and production of prostaglandin E2 and transforming growth factor‐β. Cell number and [3H]thymidine incorporation were increased in a dose‐dependent manner. Alkaline phosphatase specific activity, a marker of cell differentiation for the cultures, was significantly decreased, but osteocalcin production was not affected. [35S]sulfate incorporation, a measure of extracellular matrix production, was reduced. Prostaglandin E2 release was increased, but transforming growth factor‐β production was decreased in a dose‐dependent manner. This shows that ultrahigh molecular weight polyethylene particles affect MG63 proliferation, differentiation, extracellular matrix synthesis, and local factor production. These effects were direct and dose dependent. The findings suggest that ultrahigh molecular weight polyethylene wear debris particles with an average size of approximately 1 μm may inhibit bone formation by inhibiting cell differentiation and reducing transforming growth factor‐β production and matrix synthesis. In addition, increases in prostaglandin E2 production may not only affect osteoblasts by an autocrine pathway but may also stimulate the proliferation and activation of cells in the monocytic lineage. These changes favor decreased bone formation and increased bone resorption as occur in osteolysis.
Growth potential of loose bodies: An immunohistochemical examination of primary and secondary synovial osteochondromatosis
Authors: Saotome Koichi , Tamai Kazuya , Koguchi Yasumori , Sakai Hiroya , Yamaguchi Takehiko
Published: February 2005

Histologic and immunohistochemical studies of growth potential were performed on 53 surgically removed loose bodies representing 10 cases of primary synovial osteochondromatosis, 37 bodies representing 12 cases of secondary synovial osteochondromatosis, and five bodies representing five cases of osteochondral fracture. Loose bodies in primary synovial osteochondromatosis were nodular, showing plump chondrocytes and irregular calcification, and all contained proliferative cell nuclear antigen‐positive chondrocytes (labeling index: 42.5%; range: 36.0–52.0%). Other markers stained less frequently. Loose bodies in secondary synovial osteochondromatosis showed uniform chondrocytes and annular calcification surrounding core tissue. Eighteen of 37 loose bodies showed proliferative cell nuclear antigen‐positive chondrocytes, mostly peripherally. Chondrocyte labeling indices were less than 5% for proliferative cell nuclear antigen and other markers, although some connective tissue cells in the outer layer were stained. Loose bodies from osteochondral fractures were composed of articular cartilage, subchondral bone, and connective tissue; cartilage was negative for markers, whereas connective tissue contained positive cells. One specimen showed cartilaginous metaplasia of connective tissue. These results suggest that loose bodies have the potential for slow growth by proliferation of chondrocytes in primary synovial osteochondromatosis and by metaplasia following proliferation of surrounding connective tissue in secondary synovial osteochondromatosis.
Immunodetection and partial cDNA sequence of the proteoglycan, superficial zone protein, synthesized by cells lining synovial joints
Authors: Schumacher Barbara L. , Hughes Clare E. , Kuettner Klaus E. , Caterson Bruce , Aydelotte Margaret B.
Published: February 2005

We have previously described a large proteoglycan named superficial zone protein that was isolated and purified from culture medium of superficial slices of bovine articular cartilage. Monoclonal antibodies were raised against superficial zone protein and used as probes in Western blot analyses for immunohistochemical studies both to determine precisely which cells within the joint synthesize the proteoglycan and to isolate a cDNA fragment from a bovine chondrocyte λgt11 library that encodes part of the proteoglycan. The cDNA fragment that was obtained with use of monoclonal antibody 6‐A‐1 encodes the 3′ end of the sequence for superficial zone protein. On Western blots, monoclonal antibody 3‐A‐4 recognized an epitope on native, but not reduced, superficial zone protein, whereas monoclonal antibody 6‐A‐1 reacted with both native and denatured antigen. The proteoglycan was immunolocalized with monoclonal antibody 3‐A‐4 in chondrocytes predominantly within the superficial zone of fetal and adult articular cartilage and in some cells of the synovial lining. However, the proteoglycan was not detected in chondrocytes deep in articular cartilage, in nasal septal cartilage, or in synovial stromal cells. The only matrix staining positively for superficial zone protein was at the articular surface bordering the synovial cavity in adult, but not fetal, joints. Isolated chondrocytes and synovial cells showed intracellular binding of monoclonal antibody 3‐A‐4, and flow‐cytometric analysis with the antibody gave the following percentages of immunopositive cells: 37.4, 52.5, 3.4, and 7.5 from chondrocytes from the full‐thickness, superficial, and deep zones and from synovial cells, respectively. Thus, both chondrocytes and synovial cells bordering the joint cavity synthesize superficial zone protein and substantiate its usefulness as a phenotypic marker of particular cellular species lining the articular cavity.
Mechanically modulated cartilage growth may regulate joint surface morphogenesis
Authors: Heegaard J. H. , Beaupré G. S. , Carter D. R.
Published: February 2005

The development of normal joints depends on mechanical function in utero. Experimental studies have shown that the normal surface topography of diarthrodial joints fails to form in paralyzed embryos. We implemented a mathematical model for joint morphogenesis that explores the hypothesis that the stress distribution created in a functional joint may modulate the growth of the cartilage anlagen and lead to the development of congruent articular surfaces. We simulated the morphogenesis of a human finger joint (proximal interphalangeal joint) between days 55 and 70 of fetal life. A baseline biological growth rate was defined to account for the intrinsic biological influences on the growth of the articulating ends of the anlagen. We assumed this rate to be proportional to the chondrocyte density in the growing tissue. Cyclic hydrostatic stress caused by joint motion was assumed to modulate the baseline biological growth, with compression slowing it and tension accelerating it. Changes in the overall shape of the joint resulted from spatial differences in growth rates throughout the developing chondroepiphyses. When only baseline biological growth was included, the two epiphyses increased in size but retained convex incongruent joint surfaces. The inclusion of mechanobiological‐based growth modulation in the chondroepiphyses led to one convex joint surface, which articulated with a locally concave surface. The articular surfaces became more congruent, and the anlagen exhibited an asymmetric sagittal profile similar to that observed in adult phalangeal bones. These results are consistent with the hypothesis that mechanobiological influences associated with normal function play an important role in the regulation of joint morphogenesis.
Size and position of a single condyle allograft influence knee kinematics
Authors: Elias John J. , DesJardins John D. , Faust Alfred F. , Lietman Steven A. , Chao Edmund Y. S.
Published: February 2005

An optimal match for size and shape between the donor femur and the host knee is considered a critical factor influencing the outcome of a knee allograft implantation. An in vitro allograft model was developed to determine the influence of the size and position of a lateral distal femoral condylar allograft on knee kinematics. Functional knee motion was simulated in a cadaver host knee in the intact state after removing and reimplanting the native lateral condyle of the distal femur and after serially replacing the native condyle with eight donor allografts. Each allograft was first tested in an optimal position and subsequently shifted 3 mm proximal and 3 mm distal to the joint line to quantify changes in joint kinematics due to the position of the allograft. The intact knee and the knee with the ideally implanted native allograft followed similar kinematic trends. Decreasing the width of the allograft increased the valgus knee orientation at full flexion, translated the tibia posteriorly at full extension, and externally rotated the tibia throughout knee flexion. The proximal shift in allograft position increased the valgus orientation at full extension, translated the tibia posteriorly at mid‐flexion, and externally rotated the tibia throughout flexion. The distal shift in position had the opposite effect on the kinematics of the proximal shift. These results indicate that improving techniques for preoperative size‐matching and intraoperative allograft placement may help to reduce biomechanical complications following implantation of the allograft.
Effects of isokinetic muscle activity on pressure in the supraspinatus muscle and shoulder torque
Authors: Sporrong Håkan , Styf Jorma
Published: February 2005

Work‐related shoulder pain is an increasing problem. Work in overhead positions, which causes high pressure in the supraspinatus muscle, has been shown to increase the shoulder load. It is not known how different types of muscle activity in the shoulder affect pressure in the muscle. The aim of this study was to investigate the difference between contraction modes. This has not been done before for shoulder muscles. The results are relevant from several aspects, both clinical and experimental. Pressure in the supraspinatus muscle and torque generation in the shoulder during isokinetic concentric and eccentric activity were measured in nine healthy human subjects. Torque and arm position were measured continuously with a computerized ergonometer. The contraction velocity was 60° per second, and the range of movement was 0–120° of abduction. Electromyographic measurements were recorded with a surface electrode above the supraspinatus muscle belly. Intramuscular pressure was recorded with a microcapillary infusion technique. Peak intramuscular pressure did not differ significantly between the two modes of contraction, but the peak was reached at 115° (SD = 15°) of abduction during concentric activity and at 6° (SD = 7°) of abduction during eccentric concentric activity and 2.3 mm Hg/Nm (0.31 kPa/Nm) during eccentric activity. The peak torque occurred at 44° of abduction during concentric muscle activity and at 74° of abduction during eccentric activity. Intramuscular pressure was higher during isometric contraction than during eccentric and concentric activity, and the torque was in between the two latter contraction modes. We conclude that the supraspinatus muscle is heavily loaded not only in high arm positions during concentric contraction but also during eccentric contraction in arm positions of 0‐30° of abduction.
Interleukin‐1 beta promotes functional recovery of crushed peripheral nerve
Authors: Korompilias Anastasios V. , Chen Long‐En , Seaber Anthony V. , Urbaniak James R.
Published: February 2005

This study was conducted to elucidate the role of the cytokine interleukin‐1 beta on peripheral nerve recovery following crush injuries of wo different magnitudes. Eighty‐eight female rats were divided into four groups. A 5‐mm segment of the right sciatic nerve was subjected to a 100‐g crush load for 2 hours in the rats in Groups A1 and B1 or to a 15,000‐g crush load for 10 minutes in the rats in Groups A2 and B2. The rats in Groups A1 and A2 received 10 μg/100 g body weight human recombinant interleukin‐1 beta intraperitoneally 48, 24, and 1 hours before the nerve injury. The rats in Groups B1 and B2 were treated with an equal volume of normal saline solution with identical schedule guidelines. Walking‐track tests (sciatic functional index) performed at intervals until 56 days after the crush and measurements of the contractile force of the extensor digitorum longus muscle made until 28 days were used to evaluate functional recovery of the nerve. During the second week after injury, the rats treated with interleukin‐1 beta (A1) had an earlier recovery on the walking track than did those treated with saline solution (B1); this difference reached significance (p < 0.05) at day 11. Although Group A2 demonstrated a trend toward earlier recovery compared with Group B2, there was no significant difference between the two groups. After low or high‐load crush injury, tetanic contractile forces were greater in the rats treated with human recombinant interleukin‐1 beta than in those treated with saline solution. The results suggest that treatment with human recombinant interleukin‐1 beta before crush injury can promote function in the peripheral nerve after the injury. However, the mechanisms that underlie the observed beneficial effects are not completely understood and only speculations can be made.
In situ forces in the human posterior cruciate ligament in response to muscle loads: A cadaveric study
Authors: Höher Jürgen , Vogrin Tracy M. , Woo Savio L‐Y. , Carlin Gregory J. , Årøen Asbjørn , Harner Christopher D.
Published: February 2005

The objectives of this study were to determine the effects of hamstrings and quadriceps muscle loads on knee kinematics and in situ forces in the posterior cruciate ligament of the knee and to evaluate how the effects of these muscle loads change with knee flexion. Nine human cadaveric knees were studied with a robotic manipulator/universal force‐moment sensor testing system. The knees were subjected to an isolated hamstrings load (40 N to both the biceps and the semimembranosus), a combined hamstrings and quadriceps load (the hamstrings load and a 200‐N quadriceps load), and an isolated quadriceps load of 200 N. Each load was applied with the knee at full extension and at 30, 60, 90, and 120° of flexion. Without muscle loads, in situ forces in the posterior cruciate ligament were small, ranging from 6 ± 5 N at 30° of flexion to 15 ± 3 N at 90°. Under an isolated hamstrings load, the in situ force in the posterior cruciate ligament increased significantly throughout all angles of knee flexion, from 13 ± 6 N at full extension to 86 ± 19 N at 90°. A posterior tibial translation ranging from 1.3 ± 0.6 to 2.5 ± 0.5 mm was also observed from full extension to 30° of flexion under the hamstrings load. With a combined hamstrings and quadriceps load, tibial translation was 2.2 ± 0.7 mm posteriorly at 120° of flexion but was as high as 4.6 ± 1.7 mm anteriorly at 30°. The in situ force in the posterior cruciate ligament decreased significantly under this loading condition compared with under an isolated hamstrings load, ranging from 6 ± 7 to 58 ± 13 N from 30 to 120° of flexion. With an isolated quadriceps load of 200 N, the in situ forces in the posterior cruciate ligament ranged from 4 ± 3 N at 60° of flexion to 34 ± 12 N at 120°. Our findings support the notion that, compared with an isolated hamstrings load, combined hamstrings and quadriceps loads significantly reduce the in situ force in the posterior cruciate ligament. These data are in direct contrast to those for the anterior cruciate ligament. Furthermore, we have demonstrated that the effects of muscle loads depend significantly on the angle of knee flexion.
Effects of increased in vivo excursion on digital range of motion and tendon strength following flexor tendon repair
Authors: Silva Matthew J. , Brodt Michael D. , Boyer Martin I. , Morris Timothy S. , Dinopoulos Haralambos , Amiel David , Gelberman Richard H.
Published: February 2005

Postoperative rehabilitation is an important factor in determining functional outcome following intrasynovial flexor tendon repair. We hypothesized that a rehabilitation protocol that produced increased in vivo excursion would lead to increased digital range of motion and tendon strength and decreased adhesion formation in a canine model. Ninety‐six flexor digitorum profundus tendons from 48 dogs were cut transversely and repaired by a multistrand suture technique. Postoperative rehabilitation was performed daily with a low excursion‐low force (1.7‐mm average excursion: < 10 N force) or a high excursion‐low force (3.6 mm excursion: < 10 N force) protocol. After death of the dogs at 10, 21, or 42 days, specimens were evaluated for digital range of motion, tensile mechanical properties, elongation of the repair site, and adhesion formation. Our data indicate that the range of motion of digits whose tendons were at low or high excursion was similar to that of controls. Increased in vivo tendon excursion due to synergistic wrist motion did not significantly affect ex vivo flexion of the distal and proximal interphalangeal joints or tendon displacement (p > 0.05). Similarly, tensile properties (ultimate load, repair site rigidity, and repair site strain at 20 N and at failure) and length of the gap at the repair site were not significantly affected by increased excursion (p > 0.05). Severity of adhesion formation was reduced slightly by increased excursion (p = 0.04). Our findings indicate that 1.7 mm of tendon excursion is sufficient to prevent adhesion formation following sharp transection of the canine flexor tendon and that additional excursion provides little added benefit.
Differences in mRNA expression patterns between patellar tendons and anterior cruciate ligaments of immature pigs
Authors: Yin C. , Wayne J. S. , Jiranek W. A. , Zuelzer W. A.
Published: February 2005

The patellar tendon is the most commonly used graft source in reconstruction of the anterior cruciate ligament. The performance of a patellar tendon graft in such a reconstruction is largely related to the structural and functional differences between patellar tendons and anterior cruciate ligaments. From a genetic point of view, the structural and functional differences are ultimately decided by the differential patterns of gene expression between the two tissues. In the present study, the genetic differences between normal patellar tendons and normal anterior cruciate ligaments were explored by screening a large number of mRNA species to detect the species unique to each tissue. Of the approximately 1,000 mRNAs screened, 20 differentially expressed mRNA species were detected. Eight were unique to patellar tendons, and 12 were unique to anterior cruciate ligaments. Of these 20 unique mRNA species, 12 did not match any of the known sequences in gene databases and were probably novel genes. Transcriptional control is a major step in the genetic pathway: therefore, the variations found between patellar tendons and anterior cruciate ligaments at this level of gene expression indicate that the differences between the two tissues are likely more extensive than previously thought. These differences probably influence the survival of patellar tendon autografts and should be explored further.
Histological and biochemical evaluation of perichondrial transplants in human articular cartilage defects
Authors: Bouwmeester Phianne , Kuijer Roel , Terwindt‐Rouwenhorst Els , van der Linden Ton , Bulstra Sjoerd
Published: February 2005

From 1986 to 1992, 88 patients with articular defects in the knee were treated with a perichondrial arthroplasty. In this study, we report on the results for 22 biopsies of grafted tissue with a mean follow‐up of 21 months. Biopsies were obtained at routine arthroscopy after approximately 1 year or at arthroscopy or arthrotomy at a later stage when patients were operated on again because of recurrent complaints. Biopsies were taken only when a partial failure was present or when there was a clear failure resulting in fibrocartilage, a loose flap, or a loose body. The biopsies were analyzed histologically, biochemically for the amount of type‐II collagen, and immunohistochemically with antibodies for types I, II, and X collagen. The well‐being of the patients was investigated with use of the Hospital for Special Surgery knee score. The biopsies from 6 patients contained more than 50% hyaline cartilage. At arthroscopy, the mean relative amount of type‐II collagen was 56% in the biopsies classified as good. The cartilage of the grafted area was macroscopically normal for eight of the 22 biopsies. Histological and biochemical analysis of biopsies from failed transplants showed fibrocartilage with mainly type‐I collagen. These tissues were retrieved primarily from patients with additional abnormalities in the knee joint. It was concluded that adult human perichondrium is able to form hyaline‐like cartilage in an isolated cartilage defect in an otherwise healthy knee.
Compositional and metabolic changes in damaged cartilage are peak‐stress, stress‐rate, and loading‐duration dependent
Authors: Chen Chih‐Tung , Burton‐Wurster Nancy , Lust George , Bank Ruud A. , Tekoppele Johan M.
Published: February 2005

The first objective of this study was to determine if the cumulative effects of impact or smoothly arising compression would damage the matrix of articular cartilage. Canine cartilage explants were subjected to repeated impacts or to smoothly arising compressions of as much as 20 MPa at 0.3 Hz for as long as 120 minutes. An increase in the water content of the loaded core compared with the surrounding ring was considered indicative of matrix damage. The results showed that damage to cartilage required repeated impacts with a peak stress of at least 2.5 MPa and a stress rate of at least 30 MPa/sec for 2 minutes or longer. This suggested that impact damage is cumulative and stress‐rate dependent. The second objective was to identify biosynthetic and compositional changes in impact‐damaged cartilage over a period of time after loading. Accordingly, canine cartilage explants were subjected to repetitive impacts of 5 MPa at 0.3 Hz for 2, 20, and 120 minutes. The loaded explants were then cultured for as long as 10 days. The increase in water content (1.9‐3.8%) in the core region relative to the surrounding ring persisted during the 10‐day culture. A significant increase in fibronectin synthesis (22‐47%) was found in the core region of impact‐damaged cartilage. Proteoglycan synthesis was increased by 41‐104%. An increase in denatured collagens (11‐70%) in the loaded cores substantiated damage to the collagen network. Denatured collagens stained with COL2‐3/4m monoclonal antibody were consistent with the compositional findings and were mainly located near the articular surface and in the deep zone. These changes were consistent with early osteoarthritis and suggested the induction of the initial stages of osteoarthritis in the impact‐damaged cartilage.
Heat shock‐induced necrosis and apoptosis in osteoblasts
Authors: Li Song , Chien Shu , Brånemark Per‐Ingvar
Published: February 2005

Damage to bone tissue due to heat shock is one of the main causes of the failure of osseointegration at the bone‐implant interface. To investigate the effect of heat shock on regeneration of bone tissue, osteoblasts were exposed to heat shock for 10 minutes at 42, 45, or 48°C or kept at 37°C as a control. After 10 minutes of heat shock, disruption of actin filaments was seen in the cells and the degree of disruption increased with the temperature. The cytoskeleton reassembled after a 12‐hour incubation at 37°C in the cells treated at 42 or 45°C, but this reversible recovery did not occur in the cells treated at 48°C. Flow cytometric analysis showed that heat shock at 48°C increased the number of necrotic cells to 15‐20% within minutes (p < 0.05 compared with 37°C). Apoptosis, evidenced by annexin V staining, DNA laddering, and caspase 3 activation, started after 6‐8 hours of incubation, reached a peak at 12 hours, and gradually declined (p < 0.05). Pretreatment with the antioxidant N‐acetyl‐L‐cysteine reduced the necrosis induced at 48°C of heat shock by one‐half (p < 0.05) but had no significant effect on caspase 3 activation induced by heat shock, suggesting that reactive oxygen species were critical in heat shock‐induced necrosis but not in apoptosis. Heat shock at 48°C induced a sustained translocation of p53 into the nucleus and a sustained activation of c‐jun N‐terminal kinase, whereas that at 42 and 45°C induced only transient p53 translocation and c‐jun N‐terminal kinase activation. These results suggest that the sustained activation of p53 and c‐jun N‐terminal kinase pathways may contribute to heat shock‐induced apoptosis. On the other hand, heat shock protein 70 increased dramatically in the cells treated at 45 or 48°C, suggesting that the protecting mechanism in the cells was also activated. Such protection was able to prevent apoptosis in cells treated at 45°C but not in those treated at 48°C.
Initial evidence for the involvement of bone morphogenetic protein‐2 early during periosteal chondrogenesis
Authors: Sanyal Arunik , Sarkar Gobinda , Saris Daniel B. F. , Fitzsimmons James S. , Bolander Mark E. , O'Driscoll Shawn W.
Published: February 2005

The potential of periosteum to form cartilage makes periosteal transplantation a viable approach to repairing defects in articular cartilage, which has a limited potential for repair. However, cartilage repair, including that by periosteal chondrogenesis, is poorly understood. Consequently, a thorough understanding of its molecular mechanisms will help to achieve the quality of neocartilage required for its clinical application in damaged joints. An in vitro model was used to study the early molecular events of periosteal chondrogenesis. During the search for the expression of transforming growth factor‐β‐related mRNAs in this model system, bone morphogenetic protein‐2 mRNA expression was found to be upregulated 20‐fold within the first 12 hours of culture. This stimulation was dependent on the explants being suspended in agarose and did not occur with explants cultured in liquid medium. The upregulation of bone morphogenetic protein‐2 mRNA expression was also enhanced by exogenously added transforming growth factor‐β in the presence of fetal calf serum. The upregulation, however, was not transient; rather, it persisted over a prolonged period in both transforming growth factor‐β‐treated and untreated explants. Further data indicate that this stimulation of bone morphogenetic protein‐2 mRNA expression was regulated at the transcriptional level and that no new protein synthesis was required for this. Bone morphogenetic protein‐2 is known to influence developmental chondrogenesis; therefore, these observations direct our attention toward an important potential role of it as a regulator of the early events in cartilage repair. Furthermore, because periosteum produces fracture (cartilage) callus, these findings may be important in defining the molecular mechanisms of fracture healing.
Relationship between body mass index and activity in hip or knee arthroplasty patients
Authors: McClung Christian D. , Zahiri Christopher A. , Higa Jerilyn K. , Amstutz Harlan C. , Schmalzried Thomas P.
Published: February 2005

The weight of patients has not been demonstrated to have a consistent effect on the rate of polyethylene wear in clinical studies of total joint replacement. For this reason, we analyzed the relationship beetween quantitative activity, measured with a pedometer, and body mass index, a measure of obesity. Data were acquired for 209 individuals, 22‐82 years of age; all were independent community walkers. One hundred and fifty‐one had a well functioning total hip or knee replacement. Analysis of variance was used to evaluate the relationship between activity and body mass index, with adjustments for confounding variables. The 58 individuals with no total joint prosthesis averaged 7,781 steps per day, which was higher (p < 0.01) than those with a total hip (5,869 steps per day) or knee (4,597 steps per day) replacement. The subjects with no total joint prosthesis were, however, younger than the patients with a prosthesis (p < 0.01), and the body mass index of the patients with a total knee replacement was higher than that of the patients with a hip replacement and that of the subjects with no prosthesis (p < 0.01). After adjustment for differences in age, gender, and Charnley class, a higher body mass index (greater obesity) was associated with lower activity (p = 0.05). With regard to the rate of polyethylene wear, decreased ambulatory activity may counterbalance increased weight, which could, at least in part, explain why weight has not had a consistent effect on polyethylene wear in clinical studies. Wear is a function of use, not time. The effect of obesity on activity should be considered in radiographic studies of wear and other outcome assessments of total joint replacements.
Microstructural properties of the distal growth plate of the rabbit radius and ulna: Biomechanical, biochemical, and morphological studies
Authors: Fujii Toshiyuki , Takai Shinro , Arai Yoshiyuki , Kim Wookcheol , Amiel David , Hirasawa Yasusuke
Published: February 2005

The purposes of this study were to define the tensile properties of each zone of the rabbit growth plate and to correlate them with the microarchitecture and biochemical composition of the zones. The epiphysis‐growth plate‐metaphysis complex was obtained from the radius and ulna of 20 8‐week‐old rabbits. Four dye markers were placed on the growth plate. The complex was loaded to failure with a tensile testing machine, and the strain behavior was recorded simultaneously with a microscope, a charge‐coupled device camera, and a video dimension‐analyzer system. The collagenous fiber architecture of each zone was examined with a microscope, and the collagen content of each zone was also determined. The tangent modulus of the resting zone was 75% stiffer than that of the other two zones. The highest values for strain at failure and energy absorbed to failure were observed in the hypertrophic zone, and the total collagen content was highest in the proliferating zone. The collagen fibers were more randomly aligned in the resting zone than in the other two zones. The diversity observed in the microarchitecture of the rabbit growth plate correlates with the zone‐dependent differences in its mechanical properties.
Efficiency of systematic sampling in histomorphometric bone research illustrated by hydroxyapatite‐coated implants: Optimizing the stereological vertical‐section design
Authors: Overgaard SøRen , Søballe Kjeld , Gundersen Hans Jørgen G.
Published: February 2005

The sampling efficiency of the unbiased stereological vertical‐section method was analyzed in five hydroxyapatite‐coated implants. They were inserted into humans and harvested after 1 year. To find an optimal sampling design for histomorphometric analyses, sampling efficiency was estimated by variance analyses at different sampling levels (humans, sections, fields of view, and number of counting items) and intensities. Only minor changes in variance were observed when the initial scheme was reduced to include just one of the two possible implant sides, every third field of view, and half the density of the probe; this reduced the total workload at the microscope to less than 10% for all sections. In addition, the number of sections for analysis could be reduced to every fourth section per implant (three to four sections for evaluation) without significantly increasing variance. The study demonstrated that biological variation contributed to the majority of the total observed variance. Optimizing the sampling design could significantly reduce the workload at the hard‐tissue microtome and the microscope without reducing the quality of the data that were unbiased and that had low sampling variance as compared with the true biological variation.
Vertebral trabecular bone microscopic tissue elastic modulus and hardness do not change in ovariectomized rats
Authors: Guo X. Edward , Goldstein Steven A.
Published: February 2005

Ovariectomized rats have been used extensively and have received substantial acceptance as animal models for postmenopausal osteoporosis. However, little is known about the microscopic tissue properties of rat vertebral bone, especially during osteoporosis caused by estrogen depletion. This study applied a new nanoindentation technique to quantify the microscopic mechanical properties of vertebral trabecular bone tissue in ovariectomized rats. Seventeen‐week‐old Sprague‐Dawley rats underwent an ovariectomy. After death at 37 weeks, the fraction of the trabecular bone area of the lumbar vertebrae (L4) was measured with scanning electron microscopy and the elastic modulus and hardness were determined with the nanoindentation technique. The bone area fraction was reduced significantly after the ovariectomy. However, the elastic modulus and hardness did not change significantly at the microscopic level. The results indicate that estrogen‐dependent osteoporosis in rats manifests in a loss of bone mass whereas the elastic and hardness properties of the surviving bone tissue remain relatively unchanged.