Introduction

Enhanced angiogenesis and osteogenesis may provide new strategies for the treatment of osteonecrosis.

Introduction

Osteonecrosis of the femoral head is a devastating disease in young patients and remains a challenge for clinicians and researchers alike. To increase understanding of the disease and produce effective treatments that preserve a patient's native hip, an animal model that mimics the disease process in humans, including collapse of the femoral head, is essential. Our goal was to create such a bipedal model by surgically inducing osteonecrosis in the femoral heads of chickens.

Purpose: Comorbidities in patients undergoing total joint arthroplasty continue to be a challenging problem. Retrospective studies have demonstrated that co-morbidities affect outcomes of revision total knee arthroplasty (RTKA). However, the relationship between the outcomes of RTKA and co-morbidities has not been well established. This prospective randomized study was undertaken to investigate these relationships.

Method: A prospective cohort study (the North America Knee Arthroplasty Revision Study) was conducted to examine factors that predict outcomes after RTKA. 308 subjects met inclusion/exclusion criteria. Subjects were followed from the time of the index surgery for a minimum of two years to monitor outcomes and complications. Validated quality of life instruments, including SF-36, WOMAC, Knee Society Score, and an activity scale were used. The rates of improvement from 0 to 12 and 12 to 24 months were analyzed.

Results: There were 145 males and 163 females. The mean age was 68.7 years. Mean time from primary procedure to RTKA was 7.9 years. Arthroplasty failure was classified as aseptic in 82% and septic in 18% of the cases. Hypertension was seen in 62.4%, back pain in 50%, heart disease in 25.9%, diabetes mellitus in 23.9%, gastric ulcers in 17.9%, and rheumatoid arthritis in 16.6%. Less frequent co-morbidities included anemia, cancer, kidney disease, lung disease and liver disease.

Conclusion: Analyses showed that the number of reported co-morbidities was the most significant predictor of outcomes, consistently forecasting poorer functional improvement on all measures. The results indicated that ultimate treatment of co-morbidities before and after surgery may improve outcomes of RTKA. Comorbidities in patients undergoing revision TKA can be a challenging problem. This study showed that the number of reported co-morbidities was the most significant predictor of poorer outcomes.

Introduction: Alcohol can induce adipogenesis by bone marrow stromal cells and may cause osteonecrosis of the femoral heads. Currently, there are no medications available to prevent alcohol-induced osteonecrosis. The purpose of this study was to evaluate the effects of puerarin on adipocytic differentiation of bone marrow stromal cells and on the prevention of alcohol-induced osteonecrosis.

Materials and Methods: In the in vitro study, bone marrow stromal cells were treated with ethanol as model groups, with ethanol and puerarin as experimental groups, and without ethanol or puerarin to serve as controls. In the in vivo study, model group mice received ethanol intragastrically and normal saline by intramuscular injection. The experimental group received the same dose of alcohol intragastrically and puerarin by intramuscular injection, and the control group received water intragastrically and normal saline by intramuscular injection daily, for 4, 6, 8, and 10 months, respectively.

Results: It was found that in the in vitro experimental group, the number of adipocytes, contents of triglycerides and levels of PPARγ mRNA expression were significantly decreased, and alkaline phosphatase activity, contents of osteocalcin and levels of osteocalcin mRNA expression were significantly increased compared with cells in model groups. In the in vivo experimental group, cholesterol, and triglyceride in serum were significantly decreased, and alkaline phosphatase activity was significantly higher, compared with the model group. Fat cell hypertrophy and proliferation, thinner and sparse trabeculae, diminished hematopoiesis, and increased empty osteocyte lacunae in the subchondral region of the femoral head were observed in the model groups. However, no significant changes were seen in femoral heads of the experimental and the control group.

Discussion: The results showed that puerarin can inhibit adipogenic differentiation by bone marrow stromal cells both in in vitro in cell culture and in vivo animal experiments. These findings indicate that puerarin can prevent alcohol-induced adipogenesis and osteonecrosis.

Introduction: The authors systematically reviewed the available literature in order to define the outcomes for avascular necrosis (AVN) and spontaneous osteonecrosis of the knee (SPONK) after unicompartmental knee arthroplasty (UKA) or total knee arthroplasty (TKA).

Materials and Methods: A literature review yielded seven reports with Hospital for Special Surgery (HSS) or Knee Society Score (KSS) outcomes for arthroplasty secondary to either AVN or SPONK. The mean pre-operative, post-operative, and difference in KSS or HSS scores plus the mean revision rates for the arthroplasties for each underlying disease (AVN and. SPONK) were tabulated and reported in this order. The reported means were weighted by the number of knees in each study.

Results: A total of 63 TKAs were performed for AVN and 85 TKAs were performed for SPONK. Additionally, 74 UKAs were performed for SPONK. TKAs performed secondary to AVN had mean KSS scores of 50.6, 90.2, and 39.4 points. The revision rate was 12.5% (SD=10.45). TKAs performed for SPONK had mean HSS scores of 55.6, 82.5, and 27 points. The revision rate was 5.9% (SD=2.79). UKAs performed for SPONK had mean HSS scores of 54, 83.1, and 29.1 points with a revision rate was 9.7% (SD=5.9).

Discussion: Although the KSS for TKAs performed for AVN match the KSS performed in osteoarthritic patient populations receiving TKAs, the revision rate is higher in the AVN group. The HSS scores for patients with SPONK receiving TKAs or UKAs are similar although the revision rate is higher for UKAs.

Introduction: Alcohol can induce osteoporosis and osteonecrosis. Studies have demonstrated that alcohol contributed to abnormal lipid metabolism in cells in bone marrow but the mechanisms have not been defined. The purpose of this study was to evaluate the effect of alcohol on the differentiation of pluripotential cells cloned from bone marrow.

Materials and Methods: The cells were maintained in culture and treated with either increasing concentrations of ethanol (0.09, 0.15, and 0.21 mol/L) or without alcohol to serve as controls. Morphologic features of the cells were monitored using a phase-contrast microscope. Alkaline phosphatase activity was determined using a colorimetric assay. Gene expression of adipogenesis [422 (aP2), PPAR y] and osteogenesis (osteocalcin) was evaluated using the Northern blot technique and reverse transcription-polymerase chain reaction (RT-PCR). ANOVA was used for statistical analysis.

Results: The cells treated with ethanol started to accumulate triglyceride vesicles at Day 7; the number of adipocytes and the percentage of the area that contained the cells with fat vesicles increased significantly; and the level of alkaline phosphatase activity diminished with longer durations of exposure and with higher concentrations of ethanol. Analysis of gene expression showed diminished expression of osteocalcin without a significant increase in the expression of the fat cell specific gene, 422 (aP2), and PPAR y, in cells treated with ethanol. This suggested that adipogenesis may occur at a point downstream in the fatty acid metabolism pathway.

Discussion: Alcohol induces bone marrow fatty changes in patients and in animal models contributing to osteoporosis and osteonecrosis. This study demonstrated that alcohol treatment decreased osteogenesis while enhancing adipogenesis by bone marrow stromal cells, which may be one of the mechanisms leading to osteoporosis and osteonecrosis. Inhibition of adipogenesis may lead to the prevention of the disease.

Clinical relevance: This is a novel finding that alcohol induces adipogenesis in a cloned bone marrow stromal cell. The results explain the clinical observation that there is increased adipogenesis in alcohol-induced osteoporosis and osteonecrosis.

Introduction: Treatment of osteonecrosis continues to be a challenging problem in orthopedic practice. Arthroplasty is generally successful but long-term results are inferior especially in young adults. Alternative treatments such as core decompression and trap-door procedures provide only temporary benefits and need much improvement. The replacement of necrotic bone to promote osteogenesis and angiogenesis and healing subchondral bone are future approaches. Autogenous cancellous bone is the preferred graft material but its supply is limited. Allografts are useful but not as desirable as autografts. Substitutes for bone grafts have been actively researched but few are available currently. In this study, we have attempted to use genetically engineered bone marrow stem cells in order to enhance the healing of a bone defect in a mouse model.

Materials and Methods: A bone marrow stem cell was cloned from Balb/c mice and transfected with LacZ and neomycin resistance genes. The cells were cultured for 7 to 10 days and both the osteoblastic and angiogenic properties of the cells were examined using Northern blots to detect osteocalcin and VEGF gene expression. The cells were also analyzed for alkaline phosphatase activity to demonstrate the osteoblastic phenotype of the cells. A suspension containing 2 x 10⁷ cells/ml phosphate buffered solution was prepared for cell transplantation. A total of forty-eight, 8-week old Balb/c mice were used in this study. A 1.2 mm defect was created bilaterally with an electric drill in the femurs of 24 mice to mimic the core decompression and trap-door procedures. 2 x 10⁶ cells were transplanted into each defect of the right femur while the left femur served as a control trap-door defect which was injected with PBS but without cells. An equal number of cells were injected either at subcutaneous sites, in the hindquarter muscles, or into the renal capsule (8 mice in each site) to evaluate ossification at ectopic sites. Animals were sacrificed at 2, 4, 6 and 8 weeks. Defect repair was evaluated radiographically and the contribution to osteogenesis by transplanted cells was studied histomorphometrically using tissue sections stained with X-gal as well as biochemically on DNA extracts using primers for the neomycin resistance gene.

Results: Radiopaque tissue appeared two weeks after the cells were transplanted into bone defects, muscle, subcutaneous sites, and the renal capsule. Histological analysis demonstrated that these tissues consist of newly formed bone from transplanted cells that stained positively with X-gal and contained neo DNA. The repair tissue did not contain cartilaginous areas indicating that ossification surrounding the D1-BAG cells was not through the endochondral process. At four weeks, 4 of 6 femora showed a defect that was filled with new bone. At 6 weeks, all of the defects (6 of 6) contained fully restored bone. However, in the control side that was injected with PBS (no cells) only 2 of 6 at 4 weeks, 3 of 6 at 6 weeks, and 5 of 6 at 8 weeks showed complete repair. All histological sections of bone defects (n = 24) were examined histomorphometrically using a computerized image analysis system. Transplantation of marrow stem cells into bone defects produced more bone at an earlier time point than controls and, the process of enhanced ossification continued throughout the healing process.

Discussion: The cloned bone marrow stem cell can directly form bone after transplantation into bone defects and into ectopic sites, indicating that the in vitro expanded bone marrow stem cells can serve as a grafting material to enhance healing of bone defects and the treatment of osteonecrosis. In addition, this study demonstrates that genetic labelling is a useful tool in studies of cell differentiation in vivo and that bone marrow stem cells may be useful as a carrier of genetically-engineered factors in the treatment of skeletal diseases.

Introduction: Osteonecrosis continues to be a challenging problem in orthopaedic practice. Etiology is multi-factorial but steroid- and alcohol-associated osteonecrosis contributed to more than two thirds of all the cases. While the pathogenesis of the disease is still unknown, many new insights have emerged from research in the last decade. Studies have demonstrated that both steroids and alcohol promote adipogenesis and inhibit osteogenesis, in vitro and in vivo, leading to osteonecrosis and osteoporosis. It has been found that Dexamethasone can turn on adipogenic transcription factor PPARy2 but suppress osteogenic transcription factor Cbfa1/Runx2. Steroids also decrease VEGF production resulting in inhibition of angiogenesis by osteoprogenitor cells. However, alcohol produces adipogenesis through a different mechanism at a point downstream in the fatty acid metabolism pathway, but it does inhibit osteogenesis by decreasing osteocalcin gene expression. Increased adipogenesis and osteoporosis, together with decreased osteogenesis and angiogenesis, will eventually lead to the final pathway of osteonecrosis.