Sonicate fluid inoculated into blood culture bottles does not improve diagnosis of periprosthetic joint infection caused by anaerobes. A retrospective analysis.

BACKGROUND: In microbiological diagnosis of periprosthetic joint infection (PJI) there is much controversial discussion about culture media and incubation time, especially if anaerobic bacteria are the causative agents. This retrospective analysis was conducted to compare the results obtained by inoculation of sonicate fluid from prosthetic components into BD Bactec blood culture bottles with those obtained by our culture method using sensitive supplemented growth media. METHODS: Twenty-eight cases were included in this study. For definition of PJI, the criteria of the Musculoskeletal Infection Society (MSIS) were considered. The quantity and time to positivity of anaerobes detected in sonicate fluid were monitored both from inoculated supplemented liver thioglycollate broth and anaerobic blood culture bottles. Furthermore, phenotypic testing was performed on the antimicrobial activity within the sonicate fluid. RESULTS: The most frequently isolated microbes were Cutibacterium species, followed by Finegoldia magna, Parvimonas micra, Robinsoniella peoriensis, Clostridium species, Peptoniphilus harei and Slackia exigua. In 24 cases, the microorganisms became detectable within five days (median time 3.2 days) when sonicate fluid was incubated in supplemented liver thioglycollate broth, regardless of whether the patients had taken antimicrobial agents prior to surgery. However, when sonicate fluid was inoculated into anaerobic Bactec bottles, the median time to positivity was 7.4 days and only 12 cases (43%) were correctly identified. Sixteen cases remained negative after 14 days of incubation. CONCLUSION: Depending on the pathogen, incubation of sonicate fluid using blood culture bottles can support diagnosis of PJI but compared with our culture medium it is less efficient if anaerobes are the suspected cause of infection. Microbiological expertise is therefore indispensable to ensure reliable detection of these microorganisms in PJI until a gold standard for laboratory handling of anaerobes has been established.

Progressive femoral cortical and cancellous bone density loss after uncemented tapered-design stem fixation.

BACKGROUND: Aseptic implant loosening and periprosthetic bone loss are major problems after total hip arthroplasty (THA). We present an in vivo method of computed tomography (CT) assisted osteodensitometry after THA that differentiates between cortical and cancellous bone density (BD) and area around the femoral component. METHOD: Cortical and cancellous periprosthetic femoral BD (mg CaHA/mL), area (mm(2)) and contact area between the prothesis and cortical bone were determined prospectively in 31 patients 10 days, 1 year, and 6 years after uncemented THA (mean age at implantation: 55 years) using CT-osteodensitometry. RESULTS: 6 years postoperatively, cancellous BD had decreased by as much as 41% and cortical BD by up to 27% at the metaphyseal portion of the femur; this decrease was progressive between the 1-year and 6-year examinations. Mild cortical hypertrophy was observed along the entire length of the diaphysis. No statistically significant changes in cortical BD were observed along the diaphysis of the stem. INTERPRETATION: Periprosthetic CT-assisted osteodensitometry has the technical ability to discriminate between cortical and cancellous bone structures with respect to strain-adapted remodeling. Continuous loss of cortical and cancellous BD at the femoral metaphysis, a homeostatic cortical strain configuration, and mild cortical hypertrophy along the diaphysis suggest a diaphyseal fixation of the implanted stem. CT-assisted osteodensitometry has the potential to become an effective instrument for quality control in THA by means of in vivo determination of periprosthetic BD, which may be a causal factor in implant loosening after THA.

Distinct temporospatial expression patterns of glycolysis-related proteins in human hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) represents the sixth most frequent human cancer worldwide and is characterized by rapid progression as well as resistance to systemic chemotherapy. Recently, glycolysis has emerged as a potent driving force of tumor growth and therapy failure. The precise role of glycolysis for the pathogenesis of human HCC has not been elucidated thus far. Therefore, we have conducted a comprehensive analysis of the expression patterns of central glycolysis-related factors [glucose transporter-1 and -2 (Glut-1 and Glut-2), phosphoglycerate kinase-1 (PGK-1) and hypoxia-inducible factor-1alpha (HIF-1alpha)] in a large cohort of benign and malignant human liver samples. PGK-1 protein and gene expression was scant in normal liver, elevated in cirrhotic livers and most intense in HCC. Strong immunoreactivity of Glut-2 was noted in cirrhotic livers, whereas in HCC it was only expressed in 50% of examined cases. Strikingly, PGK-1 as well as Glut-2 protein expression was indicative of poor patient prognosis. Glut-1 protein was absent in neoplastic hepatocytes but prominent in tumor-associated endothelial cells. Specific nuclear staining of HIF-1alpha was noted in only 12% of HCC samples. Our data point toward a tumor-promoting function of glycolysis in HCC and establish PGK-1 as an independent prognostic parameter. Furthermore, the endothelial-specific expression of Glut-1 makes a special dependence of vessels on glucose reasonable to assume. In summary, we believe our analysis warrants the validation of glycolytic inhibitors as innovative treatment approaches of human HCC.

Assessment of plantar pressure in forefoot relief shoes of different designs.

BACKGROUND: After reconstructive forefoot surgery, patients require complete or partial forefoot relief, which can be obtained with a variety of shoe designs. The aim of this study was to evaluate the effectiveness of two different types of forefoot-relief shoes frequently used after surgery, especially their safety against unintentional forefoot load. METHODS: Ten healthy volunteers were asked to perform five trials on a treadmill at self-selected speeds. In the first trial, mean peak pressure values in mass-produced shoes and insoles were evaluated and considered as 100%. Two different shoe designs (short heel-short sole, ii: short heel-complete sole) were compared in two trials each with appropriate and inappropriate use (attempting to put weight on the forefoot) gait pattern. Plantar pressure values were obtained using the Pedar cable system (Novel Inc., Munich, Germany). For analysis, pedobarographic pictures were subdivided into midfoot (31% to 60% of the total insole length) and forefoot (61% to 100% of the total insole length). ANOVA was used for statistical analysis, and p values less than 0.01 were considered significant. RESULTS: With the short-soled shoe, forefoot and midfoot relief was 100% in both compliant and in noncompliant use. With wearing a complete sole, compliant use led to a significant reduction (p < 0.01) of mean peak pressure under the forefoot (34 +/- 13% remaining) and midfoot (47 +/- 13% remaining). Noncompliant use of the complete-sole shoe produced mean peak pressure values significantly higher (p < 0.01) than normal gait in mass produced shoes under the forefoot, but not under the midfoot. CONCLUSIONS: Forefoot-relief shoes are effective in reducing both mean and peak plantar pressures. Shoes with a nonsupported midfoot and forefoot may be safer with inappropriate use than shoes with a complete sole. The kind of forefoot shoe should be carefully chosen to regulate weightbearing after reconstructive forefoot surgery.

[The influence of laser irradiation of low-power density on an experimental cartilage damage in rabbit knee-joints: an in vivo investigation considering macroscopic, histological and immunohistochemical changes]. / Der Einfluss von Laserlichtbestrahlung niedriger Leistungsdichte auf einen experimentellen Knorpelschaden im Kniegelenk des Kaninchens: eine in vivo-Untersuchung unter Berücksichtigung makroskopischer, histologischer und immunhistochemischer Veränderungen.

In a total of 45 rabbits, knee-joint arthrosis was induced according to the Hulth & Telhag model. Depending on the post-operative survival time, the cartilage was investigated macroscopically, histologically and immunohistochemically (within a period of 10 days to 8 months). Thereafter, the influence of laser irradiation at a wavelength of 692.6 nm and energy densities of 1 and 4 J/cm2 on the cartilage morphology seven days following the exposure was examined. After joint instability surgery it was found out that the cartilage changes in the main stress area (MSA) and in regions outside the main stress area (ROMSA) progressed differently. Various qualitative and semi-quantitative changes were found for collagens I, II, IV and V, and for the glycoproteins fibronectin and tenascin. Immunohistochemically, there was a growing expression of collagen I in the apical layers, collagen II showed a stronger pericellular expression, and collagen IV showed, after an initial growth of the pericellular expression, a reduced territorial expression and a stronger apical-interterritorial expression in the osteoarthrotic cartilage. For fibronectin, the cellular expression turned out to grow in the ROMSA. In the MSA it decreased, but at the same time the interterritorial expression grew. For Tanascin, there was a decrease of the interterritorial expression in the radial zone while the pericellular and interterritorial expression of the apical layers of the osteoarthrotic cartilage grew. Lasing proved to significantly influence the osteoarthrotically changed cartilage when applied at an energy density of 1 J/cm2, i.e., the morphological changes had not yet progressed to the extent the control group had. Both the chondrocyte density and the glucosaminoglycan content turned out to be higher. When lasing was applied at higher energy densities, no significant difference among the control groups was found. Thus, it could be demonstrated in vivo that an arthrotic process decelerates through the influence of laser light of low-energy densities.

[Analysis of the periprosthetic femoral bone reaction after uncemented total hip arthroplasty with computertomography assisted osteodensitometry in vivo: 6-year follow-up]. / Analyse der periprothetischen femoralen Knochenreaktion nach zementfreier Hüftendoprothetik mittels computertomographiegestützter Osteodensitometrie in vivo: 6-Jahres-Follow-up.

AIMS: We prospectively analyzed the cancellous and cortical periprosthetic femoral bone reaction after implantation of a cementless total hip arthroplasty with computertomography assisted osteodensitometry after a mean of 1 and 6 years. MATERIALS AND METHODS: Twenty-one patients (Ø age at implantation: 52 years) with osteoarthrits of the hip joint received 21 cementless hip prostheses with a three-dimensionally tapered design. All patients were analyzed clinically, with CT-osteodensitometry and plain radiography after a mean of 10 days, at 1 and 6 years postoperatively. Cancellous and cortical bone density was evaluated automatically using a special software tool. RESULTS: The proximal region of the stem showed progessive cortical (Ø -15% 1 year, -25% 6 years post-OP) and cancellous (Ø -26% 1 year, -49% 6 years post-OP) bone density loss. Cortical bone density loss was lower and non-progressive at the diaphysis (Ø -7% 1 year, -9% 6 years post-OP) and the distal region (Ø -6% 1 year, -4% 6 years post-OP) of the stem. All stems showed no signs of loosening on plain radiography and good clinical results according to the Harris hip score. CONCLUSION: Computertomography assisted osteodensitometry is the only method which allows discrimination between periprosthetic cortical and cancellous bone density changes in vivo. The analyzed uncemented stem fixates at the diaphysis and distal region. Due to the changed biomechanical loading after stem implantation, progressive proximal cancellous bone density loss was measured for the first time in vivo. Its role in the pathogenesis of implant loosening is still unknown and needs to be further elucidated.

Functional differences between growth plate apoptotic bodies and matrix vesicles.

UNLABELLED: Mineralization often occurs in areas of apoptotic changes. Our findings indicate that physiological mineralization is mediated by matrix vesicles. These matrix vesicles use mechanisms to induce mineralization that are different from the mechanisms used by apoptotic bodies released from apoptotic cells. Therefore, different therapeutic approaches must be chosen to inhibit pathological mineralization depending on the mechanism of mineralization (matrix vesicles versus apoptotic bodies). INTRODUCTION: Physiological mineralization in growth plate cartilage is restricted to regions of terminally differentiated and apoptotic chondrocytes. Pathological mineralization of tissues also often occurs in areas of apoptosis. We addressed the question of whether apoptotic changes control mineralization events or whether both events are regulated independently. METHODS: To induce mineralization, we treated growth plate chondrocytes with retinoic acid (RA); apoptosis in these cells was induced by treatment with staurosporine, anti-Fas, or TNFalpha. The degrees of mineralization and apoptosis were determined, and the structure and function of matrix vesicles and apoptotic bodies were compared. RESULTS: Release of matrix vesicles and mineralization in vivo in the growth plate occurs earlier than do apoptotic changes. To determine the functional relationship between apoptotic bodies and matrix vesicles, growth plate chondrocytes were treated with RA to induce matrix vesicle release and with staurosporine to induce release of apoptotic bodies. After 3 days, approximately 90% of staurosporine-treated chondrocytes were apoptotic, whereas only 2-4% of RA-treated cells showed apoptotic changes. RA- and staurosporine-treated chondrocyte cultures were mineralized after 3 days. Matrix vesicles isolated from RA-treated cultures and apoptotic bodies isolated from staurosporine-treated cultures were associated with calcium and phosphate. However, matrix vesicles were bigger than apoptotic bodies. Furthermore, matrix vesicles but not apoptotic bodies contained alkaline phosphatase and Ca2+ channel-forming annexins II, V, and VI. Consequently, matrix vesicles but not apoptotic bodies were able to take up Ca2+ and form the first mineral phase inside their lumen. Mineralization of RA-treated cultures was inhibited by antibodies specific for annexin V but not mineralization of staurosporine-treated cultures. CONCLUSION: Physiological mineralization of growth plate chondrocytes is initiated by specialized matrix vesicles and requires alkaline phosphatase and annexins. In contrast, mineral formation mediated by apoptotic bodies occurs by a default mechanism and does not require alkaline phosphatase and annexins.

Modes of periacetabular load transfer to cortical and cancellous bone after cemented versus uncemented total hip arthroplasty: a prospective study using computed tomography-assisted osteodensitometry.

Stress-shielding and periprosthetic bone loss after total hip arthroplasty (THA) may be clinically relevant for high-demand patients. Analysis of cortical and cancellous bone density (BD) changes in vivo after THA is of interest to basic science researchers and joint reconstruction surgeons. An insufficient periprosthetic bone stock may predispose to migration, early mechanical failure, and major problems in revision surgery. We used computed tomography (CT)-assisted osteodensitometry in two prospectively analyzed cohorts after cemented (n = 21) versus noncemented (n = 23) cup fixation. Periacetabular BD (mgCaHa/mL) was determined in five CT scans cranial and five CT scans at the level of the cup 10 days and 26 months postoperatively. For press-fit cups BD decreased significantly in all CT cans except in four out of the five scans of cortical bone cranial to the cup. The decrease was highest for cancellous bone ventral to the cup (-45 to -53%). After cemented cup fixation, significant cortical BD decrease was seen ventral to the cup (-11 to -20%). Cancellous BD decrased only ventral (-21 to -31%) and in two scans cranial (-11 and -12%) to the cup. The modes of load transfer between cemented and uncemented cups differ fundamentally. Cemented cups especially prevent the loss of cancellous bone of the acetabulum while also cortical BD loss was significantly lower in most CT scans surrounding the cemented cup compared to the press-fit component. Long-term results are required to prove whether third-generation cementing technique protects periprosthetic BD and thereby improve implant survival.

Role of hypoxia-inducible factor 1 alpha in the integrity of articular cartilage in murine knee joints.

INTRODUCTION: Chondrocytes have to withstand considerable hypoxic conditions within the avascular articular cartilage. The present study investigated the effects of inhibiting or stabilizing hypoxia-inducible factor (HIF)-1 alpha by 2-methoxyestradiol or dimethyloxaloylglycine on the progression of osteoarthritis in murine knee joints. METHODS: 2-Methoxyestradiol was injected six times over a period of 2 weeks into the left knee joint of Balb/C mice. Joints were assessed by histochemical and immunohistochemical methods, 3 weeks and 12 weeks following the first injection. Dimethyloxaloylglycine, an inhibitor of HIF-degrading prolyl-hydroxylases, was injected into the left knee joints of STR/ORT mice once a week over the entire period of 12 weeks. Right knee joints that received a saline solution served as controls. In addition, the effects of dimethyloxaloylglycine on HIF-1 target gene expression and on collagen metabolism were analyzed in vitro. RESULTS: Injection of 2-methoxyestradiol led to osteoarthritic changes in the treated knee joints of Balb/C mice. The first signs of osteophyte formation were observed in the knee joints after 3 weeks, followed by progressive destruction of the articular cartilage at 12 weeks that was not, however, accompanied by inflammatory reactions. Injection of dimethyloxaloylglycine could not prevent severe osteoarthritis that spontaneously developed in the knee joints of STR/ORT mice. In chondrocyte cultures, administration of dimethyloxaloylglycine resulted in an upregulation of Sox9 expression. Such a stimulatory effect was not observed, however, for the expression of type II collagen, which might be the indirect consequence of intracellular collagen retention observed by immunofluorescence or of increased expression of IL-1 beta and IL-6. CONCLUSIONS: Induction of osteoarthritis by 2-methoxyestradiol demonstrates the importance of HIF-1 in maintaining the integrity of hypoxic articular cartilage. Stabilization of HIF-1 by dimethyloxaloylglycine, however, was not of therapeutic value, since this nonselective prolyl-hydroxylase inhibitor also interferes with proper collagen metabolism and induces the expression of catabolic cytokines.

Hypoxia-inducible factor 1alpha mediates anoikis resistance via suppression of alpha5 integrin.

The transcription factor hypoxia-inducible factor 1 (HIF-1) alpha is abundantly expressed in the majority of human carcinomas and their metastases. HIF-1alpha controls central metastasis-associated pathways such as glycolysis, angiogenesis, and invasion. Functional inhibition of HIF-1alpha leads to impaired metastasis formation in murine tumor models. However, the precise molecular mechanisms underlying the metastasis-promoting role of HIF-1alpha have not been fully characterized. The ability of transformed epithelial cells to initiate the metastatic cascade relies on their ability to escape anoikis, a default program of apoptosis induction following loss of integrin anchoring to the extracellular matrix. Therefore, we addressed the function of HIF-1alpha in anoikis resistance and anchorage-independent growth. Inhibition of HIF-1alpha via RNA interference resulted in up-regulation of alpha5 integrin on the cell surface of human gastric cancer cells, whereas other integrins remained unaffected. Integrin alpha5 induction occurred at the level of transcription and was dependent on elevated intracellular superoxide in HIF-1alpha-knockdown cells. HIF-1alpha-deficient cells displayed significantly increased anoikis susceptibility due to up-regulated alpha5 integrin. Finally, colony formation in soft agar was shown to be dependent on HIF-1alpha as HIF-1alpha-deficient cells displayed a 70% reduction in anchorage-independent proliferation. Results obtained by RNA interference could be entirely confirmed by application of the pharmacologic HIF-1alpha-inhibitor 2-methoxyestradiol. Hence, our data argue for a pivotal role for HIF-1alpha in anoikis control via suppression of alpha5 integrin. HIF-1alpha-inhibiting drugs might therefore offer an innovative strategy for antimetastatic cancer therapy.

Hypoxia and osteoarthritis: how chondrocytes survive hypoxic environments.

PURPOSE OF REVIEW: This review summarizes the current knowledge about hypoxia and hypoxia-inducible factor-1 (HIF-1) for chondrocyte survival, energy generation and matrix synthesis of articular chondrocytes during cartilage homeostasis and disease. RECENT FINDINGS: In recent years increasing evidence of a pivotal role of hypoxia and the transcription factor HIF-1alpha in cartilaginous tissues has been published. Growth plates with functionally inactivated hypoxia-inducible factor-1alpha display great defects in their central areas caused by massive cell death. This very important observation indicates that hypoxia-inducible factor-1alpha is absolutely necessary for chondrocytes to survive extremely low oxygen tensions. Furthermore, hypoxia-inducible factor-1alpha has been shown to have very important functions for the regulation of glucose transport, anaerobic energy generation and matrix synthesis by articular chondrocytes. Besides hypoxia, other factors such as proinflammatory mediators and mechanical load have been shown to increase hypoxia-inducible factor-1alpha activity in articular chondrocytes. All these factors are known to be involved in the pathogenesis of osteoarthritis. Thus, a dependence of osteoarthritis chondrocytes on hypoxia-inducible factor-1alpha to survive and function properly is a reasonable assumption. SUMMARY: Low oxygen tensions and hypoxia-inducible factor-1alpha are important factors in articular chondrocyte behaviour during cartilage homeostasis and osteoarthritis. Hypoxia-inducible factor-1alpha is a highly conserved transcription factor that has key functions in controlling energy generation, cell survival and matrix synthesis by articular and growth-plate chondrocytes.

Acetabular cortical and cancellous bone density and radiolucent lines after cemented total hip arthroplasty: a prospective study using computed tomography and plain radiography.

INTRODUCTION: The aim of this prospective study was to evaluate load-transfer mechanisms and stress patterns of periacetabular cortical and cancellous bone after cemented total hip arthroplasty (THA) in vivo using computed tomography (CT) assisted osteodensitometry. In addition we analyzed the efficacy of CT in detecting radiolucent lines around the acetabular component compared to plain radiography. MATERIALS AND METHODS: Twenty-two cemented acetabular cups were investigated using conventional sequential axial CT scans (Ø 8 days and 26 months post-OP) and plain radiography (Ø 5 days and 40 months post-OP). CT assisted osteodensitometry was used to determine cancellous and cortical bone bone density (BD). Radiolucent lines were evaluated using both CT and plain radiography. RESULTS: Significant BD loss at the time of follow-up was only detectable ventral to the cup (cortical bone: -16%, P = 0.001; cancellous bone: -31%, P = 0.001). The BD changes dorsal and cranial to the cup were not significant. Postoperatively no radiolucent lines were observed in the cement-bone interface by CT, while on plain radiography acetabular lucent lines were seen in 12 out of 22 cases. CONCLUSION: CT-osteodensitometry has the technical ability to discriminate between cortical and cancellous bone structures with respect to strain-adapted remodeling: sufficient cancellous and cortical bone stock remained dorsal and cranial to the cup indicative of a balanced load transfer to these regions. CT-osteodensitometry has the potential to become an effective instrument for quality control in THA and the method of choice for in vivo determination of periprosthetic BD. In contrast, plain radiography is more suitable for the early detection of radiolucent lines compared to axial CT scans.

The role of HIF-1alpha in maintaining cartilage homeostasis and during the pathogenesis of osteoarthritis.

As a consequence of the avascular nature of cartilage the microenvironment in which chondrocytes must exist is characterized by hostile conditions, most prominently very low levels of oxygen (hypoxia). In recent years, a vast number of papers reporting on the role of hypoxia in cartilage development and disease has been published. It is well established today that the principal mediator of cellular adaptation to hypoxia, the transcription factor hypoxia inducible factor (HIF)-1, is of pivotal importance for survival and growth arrest of chondrocytes during cartilage development as well as energy generation and matrix synthesis of chondrocytes in healthy as well as osteoarthritic cartilage. With this commentary we aim to briefly discuss the recently published literature in this field.

Regulation of type II collagen synthesis during osteoarthritis by prolyl-4-hydroxylases: possible influence of low oxygen levels.

Osteoarthritic (OA) chondrocytes are metabolically active, displaying increased synthesis of type II collagen. Here, we show by immunohistochemistry and polymerase chain reaction that in comparison with healthy cartilage, OA articular chondrocytes exhibit increased in vivo synthesis of collagen prolyl-4-hydroxylase type II, a pivotal enzyme in collagen triple helix formation. Exposure of primary human articular chondrocytes to 1% oxygen enhanced accumulation of native type II collagen and stabilized hypoxia-inducible factor-1alpha (HIF-1alpha). This effect was abolished by addition of the HIF-1 inhibitor 2-methoxyestradiol. Real-time polymerase chain reaction analyses of mRNAs from these cultures revealed increased transcript levels of both alpha-subunits of prolyl-4-hydroxylase (P4HA1, approximately 2-fold; P4HA2, approximately 2.3-fold) and of classical HIF-1 target genes (glucosetransporter-1, approximately 2.1-fold; phosphoglyceratekinase-1, approximately 2.2-fold). Treatment of hypoxic chondrocytes with 2-methoxyestradiol reduced transcriptional activity of HIF-1 and synthesis of alpha(II), and to a lesser extent alpha(I), subunits of collagen prolyl-4-hydroxylases. mRNA levels of type II collagen (Col2A1) and the beta-subunit (P4HB) of prolyl-4-hydroxylase, however, displayed only modest changes at 1% oxygen. From these results and our in vivo data, we inferred that besides increased Col2A1 mRNA expression by OA chondrocytes, accelerated posttranslational modification processes might contribute to the increased synthesis and accumulation of type II collagen during OA and experimental hypoxia.

Periacetabular bone changes after uncemented total hip arthroplasty evaluated by quantitative computed tomography.

BACKGROUND: There are few dual X-ray absorptiometry (DXA) studies on periacetabular bone density changes after cup implantation. This study was designed to analyze the load-transfer mechanism and stress pattern of periacetabular cortical and cancellous bone after implantation of a ihemispherical titanium alloy press-fit cup with alumina-alumina pairing in vivo. We introduced a novel method of computed tomography (CT)-assisted osteodensitometry. METHOD: We investigated 26 hips (26 patients) with osteoarthritis using conventional sequential CT examinations performed within the first 10 days after implantation, and after a mean period of 1.1 years postoperatively. Bone density of full, cancellous and cortical bone (mgCaHA/mL) was measured. RESULTS: At the time of follow-up, the mean bone density values of the cortical bone cranial to the cup increased by 3.6% (p = 0.03) while the cancellous bone density decreased by 18%. Cancellous bone loss was greater in the region ventral to the cup (-35%) than in the dorsal region (-30%). Cortical bone density decreased ventral to the cup (-6.4%). All these changes were statistically significant. The bone density changes in the dorsal cortical region were not significant. INTERPRETATION: The method presented is an excellent tool for detailed measurement of bone density changes around the cup after total hip arthroplasty, and allows a thorough assessment of stress shielding phenomena in vivo. The hemispherical titanium alloy press-fit cup is a rigid implant which stress shields cancellous bone and enhances load transfer to the cranial cortical bone. Further investigations will demonstrate the impact these factors have on the long-term results of the implant, and may allow a type-related predictable prognosis of the longevity of the prosthesis.

Ultrasound-guided spinal fracture repositioning, ligamentotaxis, and remodeling after thoracolumbar burst fractures.

STUDY DESIGN: Computed tomography aided evaluation of spinal decompression by ultrasound-guided spinal fracture repositioning, ligamentotaxis, and remodeling after thoracolumbar burst fractures. OBJECTIVES: To determine the necessity of spinal canal widening by ultrasound-guided fracture repositioning for fractures with and without neurologic deficit. SUMMARY OF BACKGROUND DATA: Ultrasound-guided spinal fracture repositioning is an alternative new approach. Reports have varied concerning ligamentotaxis and remodeling. METHODS: Computed tomography aided planimetry of the spinal canal (64 consecutive burst fractures) and neurologic evaluation by Frankel grades. RESULTS: Ultrasound-guided spinal fracture repositioning (n = 37) reduced the stenosis of the spinal canal area from 45% before surgery to 20% after surgery of the estimated original area. Fifteen patients had a primary neurologic deficit, which improved markedly in 11 cases after treatment. Patients with neurologic symptoms had a greater preoperative spinal stenosis than those without. No correlation was seen between the degree of pretreatment spinal stenosis, fracture type, and severity of the neurologic deficit. Ligamentotaxis (n = 27) reduced the stenosis from 30% before surgery to 18% after surgery and remodeling (n = 11) from 25% after surgery to 13% after metal removal. CONCLUSION: Ultrasound-guided fracture repositioning is an efficient method for spinal canal decompression of burst fractures with neurologic symptoms. The marked degree of widening of the spinal canal due to the effects of ligamentotaxis and remodeling may render the reposition of retropulsed fragments unnecessary in cases of fractures without a neurologic deficit.

Hypoxia and HIF-1alpha in osteoarthritis.

We have previously shown that functional inactivation of hypoxia-inducible factor-1alpha (HIF-1alpha) in growth-plate chondrocytes will dramatically inhibit anaerobic energy generation and matrix synthesis. Using immunohistochemistry, we have now analyzed the spatial distribution of HIF-1alpha and its target genes in normal cartilage and in cartilage from knee joints with osteoarthritis. We detected HIF-1alpha and its target genes in both types of cartilage. In cartilage from joints with osteoarthritis, the number of HIF-1alpha-, Glut-1-, and PGK-1-stained chondrocytes increased with the severity of osteoarthritis. Activated matrix synthesis and strongly decreased oxygen levels are hallmarks of osteoarthritic cartilage. Thus, we assume that chondrocytes are depending on the adaptive functions of HIF-1alpha in order to maintain ATP levels and thereby matrix synthesis during the course of osteoarthritis.

HIF-1alpha controls extracellular matrix synthesis by epiphyseal chondrocytes.

The transcription factor HIF-1alpha plays a crucial role in modifying gene expression during low oxygen tension. In a previous study, we demonstrated that HIF-1alpha is essential for chondrocyte growth arrest and survival in vivo. To explore further the role of HIF-1alpha in cartilage biology, we undertook studies with primary epiphyseal chondrocytes with a targeted deletion of HIF-1alpha. In this study, we show that HIF-1alpha is necessary for regulating glycolysis under aerobic and anaerobic conditions. HIF-1alpha-null chondrocytes were unable to maintain ATP levels in hypoxic microenvironments, indicating a fundamental requirement for this factor for the regulation of chondrocyte metabolism. Synthesis of the angiogenic factor vascular endothelial growth factor was also significantly induced by hypoxia, and this increase is lost in HIF-1alpha-null mutant cells. Under hypoxic conditions, aggrecan mRNA and protein levels were significantly reduced in chondrocytes lacking the HIF-1alpha transcription factor. Interestingly, strongly increased type-II collagen protein levels were detected in wild-type cells after 44 hours of hypoxia. In addition, type-II collagen mRNA and protein levels were strongly decreased under low oxygen in chondrocytes lacking HIF-1alpha. In summary, our results clearly demonstrate the importance of HIF-1alpha in maintenance of anaerobic glycolysis, and thereby extracellular matrix synthesis, of epiphyseal chondrocytes.

Hepatocyte growth factor and c-Met expression in rat and human liver fibrosis.

BACKGROUND: Hepatocyte growth factor (HGF) is a potent mitogen for hepatocytes in vitro. AIMS: Substitution of HGF was suggested for human liver disease on the basis of animal experiments. The cellular sources of HGF and its receptor, c-Met, in liver disease in vivo are not well defined. METHODS: We characterised HGF and c-Met expression in normal and cirrhotic human livers and rat livers at various time points after CCl4 administration by in situ hybridisation and immunohistology. HGF transcripts were restricted to resting and activated stellate cells in rat and human liver. RESULTS: In rat liver, HGF showed peak levels 6-12 h following acute intoxication, and remained increased after repeated CCl4 injury. HGF transcript levels were very low in normal human liver, but excessively raised in fibrosis/cirrhosis. In contrast, HGF immunoreactivity was found not only in perisinusoidal/periductular cells but also in cholangiocytes of proliferating ductules. c-Met RNA and protein was expressed in hepatocytes, cholangiocytes, and arteriolar endothelial cells. CONCLUSIONS: The HGF-specific immunostaining of proliferating cholangioles in the absence of HGF RNA suggests c-Met-mediated uptake of HGF and paracrine stimulation of cholangiocellular proliferation. Mitogenic effects of HGF on hepatocytes may therefore be accompanied by undesired cholangiogenesis and angiogenesis limiting its therapeutic value in chronic liver disease.

Deletion of Vhlh in chondrocytes reduces cell proliferation and increases matrix deposition during growth plate development.

The von Hippel Lindau tumor suppressor protein (pVHL) is a component of a ubiquitin ligase that promotes proteolysis of the transcription factor hypoxia-inducible-factor 1alpha (HIF1alpha), the key molecule in the hypoxic response. We have used conditional inactivation of murine VHL (Vhlh) in all cartilaginous elements to investigate its role in endochondral bone development. Mice lacking Vhlh in cartilage are viable, but grow slower than control littermates and develop a severe dwarfism. Morphologically, Vhlh null growth plates display a significantly reduced chondrocyte proliferation rate, increased extracellular matrix, and presence of atypical large cells within the resting zone. Furthermore, stabilization of the transcription factor HIF1alpha leads to increased expression levels of HIF1alpha target genes in Vhlh null growth plates. Lastly, newborns lacking both Vhlh and Hif1a genes in growth plate chondrocytes display essentially the same phenotype as Hif1a null single mutant mice suggesting that the Vhlh null phenotype could result, at least in part, from increased activity of accumulated HIF1alpha. This is the first study reporting the novel and intriguing findings that pVHL has a crucial role in endochondral bone development and is necessary for normal chondrocyte proliferation in vivo.