Incidence of genetic polymorphisms involved in lipid metabolism among Chinese patients with osteonecrosis of the femoral head

Bone Remodeling and Bone Structural Genes in Legg-Calvé-Perthes Disease: The OPG rs2073618 and IL-6 rs1800795 Are Associated with High Risk in Mexican Patients

Legg-Calve-Perthes disease (LCPD) is an idiopathic avascular necrosis of the pediatric femoral head. Bone remodeling and bone structural genes have the potential to contribute to the progression of LCPD when there is disequilibrium between bone resorption and bone formation. A case-control study was performed to search for associations of several common polymorphisms in the genes Receptor Activator for Nuclear Factor κappa B (RANK), Receptor Activator for Nuclear Factor κappa B Ligand (RANKL), osteoprotegerin (OPG), interleukin (IL)-6, and type 1 collagen (COL1A1) with LCPD susceptibility in Mexican children. A total of 23 children with LCPD and 46 healthy controls were genotyped for seven polymorphisms (rs3018362, rs12585014, rs2073618, rs1800795, rs1800796, rs1800012, and rs2586498) in the RANK, RANKL, OPG, IL-6, and COL1A1 genes by real-time polymerase chain reaction with TaqMan probes. The variant allele (C) of IL-6 rs1800795 was associated with increased risk of LCPD (odds ratio [OR]: 3.8, 95% confidence interval [CI]: [1.08-13.54], p = 0.033), adjusting data by body mass index (BMI) and coagulation factor V (FV), the association with increased risk remained (OR: 4.9, 95% CI: [1.14-21.04], p = 0.025). The OPG polymorphism rs2073618, specifically GC-GG carriers, was associated with a more than fourfold increased risk of developing LCPD (OR: 4.34, 95% CI: [1.04-18.12], p = 0.033) when data were adjusted by BMI-FV. There was no significant association between RANK rs3018362, RANKL rs12585014, IL-6 rs1800796, COL1A1 rs1800012, and rs2586498 polymorphisms and LCPD in a sample of Mexican children. The rs1800975 and rs2037618 polymorphisms in the IL-6 and OPG genes, respectively, are informative markers of increased risk of LCPD in Mexican children.

Etiology of Femoral Head Avascular Necrosis in Patients: A Cross-Sectional Study

Background

Avascular necrosis (AVN), known as osteonecrosis, aseptic necrosis, or ischemic bone necrosis, results in the destruction of bone cells. In the present study, we aimed to report the most common causes of AVN in in patients referred to Isfahan educational and medical centers.

Materials and Methods

This study is a cross-sectional study that was performed on all patients with AVN in medical educational centers in Isfahan during 2019 and 2020. We included all patients diagnosed with AVN. Patients' information including age, sex, cause of femoral head necrosis, medical history, and drug usage were collected. Finally, reliable data from 99 patients were recorded.

Results

We collected data of 99 patients in this study. The most prevalent cause of ANV was corticosteroids use (32.3%), and it was more prevalent among women (51.4%); the second prevalent cause of AVN in our study sample was trauma (28.28%), and it was more prevalent among men (32.8%).

Conclusion

The most common cause of AVN was corticosteroids, which was consistent with previous studies. Other main causes of AVN were traumatic or idiopathic issues.

Association of ABCB1 and CYP450 Gene Polymorphisms and their DNA Methylation Status with Steroid-Induced Osteonecrosis of the Femoral Head in the Chinese Population

Objective: Osteonecrosis of the femoral head (ONFH) is a severe pathological state with multiple etiologies. Steroid hormone metabolism-related genes play an important role in ONFH. The aim of this study was to investigate the relationships between polymorphisms of the drug-metabolizing enzyme gene, cytochrome P450 (CYP450), and the drug transporter gene, ATP-binding cassette subfamily B member 1 (ABCB1), as well as their DNA methylation status with the pathogenesis of steroid-induced ONFH. Methods: In this case-control study, we evaluated five single nucleotide polymorphisms (SNPs) in two genes in a Han Chinese population, including 79 patients with steroid-induced ONFH and 114 persons who took steroids but did not develop steroid-induced ONFH. SNPs were genotyped by the improved multiplex ligation detection reaction. MethylTarget technology was used to ascertain the methylation status at two CpG islands in the ABCB1 gene for statistical analysis. Finally, interactions between the SNPs and the CpG site's methylation levels were statistically analyzed by methylation quantitative trait locus. Results: We found that the T allele of the CYP450 rs2242480 locus was associated with steroid-induced ONFH risk reduction (odds ratio [OR] = 0.598, 95% confidence interval [CI]: 0.360-0.992, p = 0.046). In the genetic model analysis, the T allele of the rs2032582 locus in the ABCB1 gene was associated with a reduced risk of steroid-induced ONFH under the dominant model (OR = 0.465, 95% CI: 0.223-0.972, p = 0.042). The CpG sites with significant differences (p < 0.05) in methylation levels between the cases and controls were ABCB1_1_192…ABCB1_2_43. A total of 14 pairs of linear regression tests between SNPs and methylation sites demonstrated statistical significance (p < 0.05). Conclusions: This study provides evidence for two steroid-induced ONFH susceptibility genes (ABCB1, CYP450) in the Han Chinese population.

Association between genetic polymorphisms and osteonecrosis in steroid treatment populations: a detailed stratified and dose-response meta-analysis

Steroid treatment has become recognized as an important risk factor for avascular osteonecrosis of the femoral head. However, not all patients who receive long-term, high-dose steroids develop osteonecrosis, indicating that there are individual differences in occurrence.We explored the relationship between polymorphisms and steroid-induced osteonecrosis of the femoral head (SONFH) incidence with variables. We used a multilevel mixed-effects logistic regression model, which is an expansion of logistic regression, for each type of steroid, primary disease, drug dose, applied duration, and single-nucleotide polymorphism (SNP). We also conducted a dose-response meta-analysis to analyze the cumulative dosage and SONFH risk in mutation carriers. There were significant correlations between the ABCB1 rs1045642 mutant and SONFH in the prednisone-use and methylprednisolone/prednisone-use populations. The ABCB1 rs2032582 mutant homozygote had a protective effect in the methylprednisolone/prednisolone renal transplant population. For ApoB rs693, mutation increased the incidence of SONFH in prednisone-use and methylprednisolone/prednisolone-use populations and renal transplant patients. For ApoB rs1042031, mutation increased the risk of SONFH in the prednisone-use population. The PAI-1 rs1799768 mutation had a protective effect on the SONFH risk prednisone-use and renal transplant populations. ABCB1 rs1045642 mutations have a protective effect against SONFH, and ApoB rs693 and rs1042031 increase the SONFH risk. Cumulative dosage and treatment duration had little effect on the results. In addition, there was a dose-effect correlation in ABCB1 rs1045642 and rs2032582 mutation carriers.

MMP-14 single-nucleotide polymorphisms are related to steroid-induced osteonecrosis of the femoral head in the population of northern China

BACKGROUND

Osteonecrosis of the femoral head (ONFH) is a refractory disease which frequently occurs in young and middle-aged people. Recent studies indicated that MMP-14 played an important role in the development of chondrocytes, metabolism of osteoblasts as well as fate decision of hypertrophic chondrocytes. The aim of this study was to investigate the association between polymorphisms of MMP-14 and steroid-induced osteonecrosis of the femoral head in the Chinese population.

METHODS

We selected 7 SNPs (rs3751488, rs1003349, rs1042703, rs2236302, rs1042704, rs2236303, and rs2236304) on gene MMP-14. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using the chi-squared test, genetic model analysis, haplotype analysis, and stratification analysis.

RESULTS

We discovered that the genotype "G/G" of rs2236302 was associated with ONFH risk in the MMP-14 in the codominant model (OR = 8.62, 95% CI = 1.07-69.46, p = 0.038) and recessive model (OR = 8.86, 95% CI = 1.10-71.31, p = 0.013).

CONCLUSIONS

We have confirmed that the susceptive SNPs (rs2236302) of MMP-14 from the MMPs/TIMPs system exhibit a significant association with increased risk of steroid-induced ONFH in the population of northern China.

Lipid Transporter Activity-Related Genetic Polymorphisms Are Associated With Steroid-Induced Osteonecrosis of the Femoral Head: An Updated Meta-Analysis Based on the GRADE Guidelines

Aims: The purpose of this study was to assess the relationship between genetic variants and steroid-induced osteonecrosis of the femoral head (SONFH) in steroid use populations. Methods: We searched the public databases up to April 15, 2018. This study analyzed only the single-nucleotide polymorphisms (SNPs) that have appeared in more than three studies and assessed the level of evidence by classifying the outcomes according to the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. Results: The ABCB1 rs1045642 C>T mutation had a protective effect against SONFH in the allelic model (I ² = 50.2%; OR: 0.74; 95% CI: 0.55-1.00; p = 0.046). The rs2032582 mutation in the ABCB1 gene showed no relationship to SONFH (allelic model: I ² = 63.4%; OR: 0.85; 95% CI: 0.58-1.23; p = 0.382). In ApoB rs693, four models showed that mutations can increase SONFH risk, but the allelic model did not. The ApoB rs1042031 mutation increased SONFH risk in the dominant model (I ² = 50.3%; OR: 2.90; 95% CI: 1.49-5.66; p = 0.002). Conclusion: An allelic model of ABCB1 rs1045642 showed that mutations have a protective effect against SONFH at a very low level of evidence. The mutations in ApoB rs693 and rs1042031 increase the SONFH risk with moderate levels of evidence.

Correlation Between Steroid-Induced Osteonecrosis of The Femoral Head and Hepatic CYP3A Activity: A Systematic Review and Meta-Analysis

BACKGROUND

Steroid-induced osteonecrosis of the femoral head (ONFH) in young adults is a challenging disorder that can impairs the quality of life of a patient. The disease also leads to frequent occurrences of collapse of the femoral head and resultant dysfunction of the hip joint. In recent years, some scholars have studied steroid-induced lipid metabolism disorder and achieved the effect of steroid-induced ONFH treatment. This study aims to review the investigations on the hepatic CYP3A (cytochrome P4503A enzyme) genetic polymorphisms in steroid-induced ONFH patients. We then further explore its activity correlation with the development of steroid-induced ONFH in a rabbit model.

METHODS

A systematic literature search of articles was conducted in PubMed, Web of Science, Google Scholar, Springerlink, and the Chinese National Knowledge Infrastructure database up to February 2017. Twelve relevant articles were retrieved. The odds ratios, standard mean difference, and 95% confidence intervals were calculated to assess the effect of hepatic CYP3A activity on the rabbit model with steroid-induced ONFH. Fixed-effects and random-effects models were used to analyze the heterogeneity. Begg's funnel plot was used to assess publication bias.

RESULTS

High hepatic CYP3A activity significantly decreased the risk for steroid-induced ONFH in the rabbit model (p <. 05). The CYP3A gene may be potentially associated with increased risk of steroid-induced ONFH in the human allele model.

CONCLUSION

The study suggests that high hepatic CYP3A activity decreases the risk of steroid-induced ONFH.

Substrain-specific differences in bone parameters, alpha-2-macroglobulin circulating levels, and osteonecrosis incidence in a rat model

Osteonecrosis of the femoral head (ONFH) is a potentially devastating complication that occurs in up to 40% of young adults receiving chronic glucocorticoid (GC) therapy. Through a validated GC therapy rat model, we have previously shown that Wistar Kyoto (WK) rats exhibit a genetic susceptibility to GC-induced ONFH compared to Sasco Fischer (F344) rats. We have undertaken this study in order to investigate differences between these two strains for their bone parameters, alpha-2-macroglobulin (A2M) circulating levels and incidence of GC-induced osteonecrosis of the femoral head. WK and F344 rats were treated either with 1.5 mg/kg/day of prednisone or placebo for 6 months. Blood was taken every month. The femoral heads were harvested for histological examination to detect ONFH and analyzed with micro-computed tomography. After 3 months of GC-therapy, plasma A2M was elevated in treated rats only. GC-treated WK rats exhibited histological evidence of early ONFH through higher rates of cellular apoptosis and empty osteocyte lacunae in the subchondral bone compared to placebos and to F344 rats. Furthermore, micro-CT analysis exhibited femoral head collapse only in GC-treated WK rats. Interestingly, GC-treated F344 rats exhibited significant micro-CT changes, but such changes were less concentrated in the articular region and were accompanied histologically with increased marrow fat. These µCT and histological findings suggest that elevated A2M serum level is not predictive and suitable as an indicative biomarker for early GC-induced ONFH in rodents. Elevated A2M levels observed during GC treatment suggests that it plays role in the host reparative response to GC-associated effects. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1183-1194, 2017.

Association of ABCB1 C3435T polymorphism with the susceptibility to osteonecrosis of the femoral head: A meta-analysis

BACKGROUND AND OBJECTIVE

The exploration for the etiology of osteonecrosis of the femoral head (ONFH) has got some promising findings, but the morbidity of ONFH is still not under control. The C3435T polymorphism of ATP-binding cassette subfamily B member 1 (ABCB1) gene has been reported to possess significant influence on ONFH onset, but relevant outcomes remain conflicting rather than conclusive. Therefore, a meta-analysis was useful to pool these results together for a more reliable conclusion.

METHODS

The association of ABCB1 C3435T polymorphism with ONFH susceptibility was estimated through calculated odds ratios (ORs) with their 95% confidence intervals (95% CIs). The Q-test was applied for detecting inter-study heterogeneity, whereas sensitivity analysis for identifying any study owning substantial influence on pooled results. Begg's funnel plot and Egger's test were employed to examine publication bias across included studies.

RESULTS

ABCB1 C3435T polymorphism significantly decreased the risk of ONFH under TT vs CC (OR = 0.26, 95% CI = 0.13-0.50), TT+CT vs CC (OR = 0.72, 95% CI = 0.52-0.99), TT vs CC+CT (OR = 0.28, 95% CI = 0.15-0.52), and T vs C (OR = 0.64, 95% CI = 0.50-0.81) contrasts.

CONCLUSION

The variant C3435T in the ABCB1 gene may offer protection against the attack of ONFH, and more studies with larger sample sizes should be conducted to certify this issue.

Association between genetic polymorphisms of MMP8 and the risk of steroid-induced osteonecrosis of the femoral head in the population of northern China

BACKGROUND

Steroid-induced osteonecrosis of the femoral head (ONFH) is the most common clinical nontraumatic ONFH. Once ONFH occurs, it seriously reduces patients' quality of life. The matrix metalloproteinase/tissue inhibitor of metalloproteinase (MMP/TIMP) system was found to play a significant role in the development of ONFH. The aim of this study was to identify the associations between 7 genes selected from the MMP/TIMP system and steroid-induced ONFH.

METHODS

We genotyped 34 single-nucleotide polymorphisms (SNPs) of 7 genes selected from the MMP/TIMP system in a case-control study with 285 cases of steroid-induced ONFH and 308 healthy controls. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using the chi-squared test, genetic model analysis, haplotype analysis, and stratification analysis.

RESULTS

We found that the minor alleles of rs1940475 and rs11225395 in MMP8 were associated with a 1.32-fold increased risk of steroid-induced ONFH in the allelic model analysis (P = 0.021 and 0.022, respectively). In the genetic model analysis, we found that rs3740938, rs2012390, rs1940475, and rs11225395 were associated with an increased risk of steroid-induced ONFH. In further stratification analysis, rs3740938 and rs2012390 displayed a significantly increased risk of steroid-induced ONFH in females under the dominant (rs3740938, OR = 2.69, 95% CI: 1.50-4.83, P = 0.001; rs2012390, OR = 2.30, 95% CI: 1.31-4.03, P = 0.012) and additive (rs3740938, OR = 2.02, 95% CI: 1.24-3.29, P = 0.010; rs2012390, OR = 1.77, 95% CI: 1.12-2.80, P = 0.047) models. In addition, haplotype "AGTCA" of MMP8 was found to be associated with a 1.40-fold increased risk of steroid-induced ONFH (95% CI: 1.04-1.88, P = 0.025).

CONCLUSION

Our results verify that genetic variants of MMP8 contribute to steroid-induced ONFH susceptibility in the population of northern China. In addition, we found that gender differences might interact with MMP8 polymorphisms to contribute to the overall susceptibility to steroid-induced ONFH.

Comparative study of serum proteomes in Legg-Calve-Perthes disease

Background

Legg-Calve-Perthes Disease (LCPD) is an idiopathic osteonecrosis of the developing femoral head complicated by pain and disability of the hip joint. To date, the pathological mechanisms of LCPD are not well-known. This study screened the changes in serum protein expression in patients with LCPD.

Methods

Age- and sex-matched serum samples from 10 control subjects and 10 patients with LCPD were compared using the isobaric tags for relative and absolute quantification (iTRAQ) technique. Gene ontology analyses, KEGG pathway and functional network analyses were performed. Proteins of interest with large differences in expression, S100-A8, alpha-1-acid glycoprotein 1, haptoglobin and apolipoprotein E, were compared by western blotting.

Results

The disease/control ratios showed 26 proteins were significantly differentially expressed (all p < 0.05). Including higher abundances of complement factor H (1.44), complement C4-B (1.45), isocitrate dehydrogenase [NAD] subunit alpha (2.7) alpha-1-acid glycoprotein 1 (1.87), heptoglobin (1.53) and Ig lambda-2 chain C regions (1.46), and lower levels of apolipoprotein E (0.50), apolipoprotein F (0.60), apolipoprotein C-III (0.69), S100-A8 (0.73), S100-A9 (0.75) and prothrombin (0.77) in LCPD than in controls. The alpha-1-acid glycoprotein 1 and haptoglobin increases, and apolipoprotein E and S100-A8 decreases were confirmed by western blot. KEGG pathway analysis revealed these proteins were related to the complement and coagulation cascades, Staphylococcus aureus infection, PPAR signaling, fat digestion and absorption, and vitamin digestion and absorption. Functional network analysis suggested that the proteins were involved in lipid regulation.

Conclusions

The complement and coagulation cascades, and abnormal lipid metabolism may be involved in the pathogenesis of LCPD.

Osteonecrosis of the femoral head: diagnosis and classification systems

Osteonecrosis of femoral head is a rare but disabling condition that usually results in progressive femoral head collapse and secondary arthritis necessitating total hip arthroplasty if not treated appropriately in early stages. However, early diagnosis is challenging as the onset of disease is insidious and the symptoms and signs are usually minimal and nonspecific until it becomes advanced. Of several diagnostic modalities, magnetic resonance imaging (MRI) is considered the imaging method of choice with the highest sensitivity and specificity, while detection of potential risk factors is very important as well. Many investigators have developed several different classification systems; however, there still is controversy regarding the optimal classification system. Diagnostic methods and the evolution of different classification systems will be reviewed in this paper.

ABCB1 gene polymorphisms and glucocorticoid-induced avascular necrosis of the femoral head susceptibility: a meta-analysis

BACKGROUND

The results of studies on association between ABCB1 gene polymorphisms and glucocorticoid-induced avascular necrosis of the femoral head (GANFH) are controversial. This study aimed to assess the association of ABCB1 gene polymorphisms with the risk of GANFH by conducting a meta-analysis.

MATERIAL AND METHODS

The PubMed, Cochrane Library, and Embase databases were searched for papers that describe the association between ABCB1 polymorphisms and GANFH risk. Summary odds ratios and 95% confidence intervals (CI) were estimated based on a fixed-effects model or random-effects model, depending on the absence or presence of significant heterogeneity.

RESULTS

A total of 5 studies and 833 patients were included in the final analysis. Significant differences were found for rs1045642 polymorphism in the comparisons of CC vs. CT+TT (OR, 1.462; 95% CI, 1.066-2.007; P=0.019), and rs2032582 polymorphism in the comparisons of GG vs. G(TA)+(TA)(TA) (OR, 1.548; 95% CI,1.063-2.255; P=0.023).

CONCLUSIONS

The study demonstrated that the ABCB1 polymorphisms (rs1045642 and rs2032582) significantly reduced the risk of GANFH.

Maternal medication use, fetal 3435 C>T polymorphism of the ABCB1 gene, and risk of isolated septal defects in a Han Chinese population

The fundamental etiology of the majority of nonsyndromic congenital heart defects is commonly believed to involve the interaction of multiple environmental and genetic factors. This study aimed to explore the joint effects of fetal 3435 C>T polymorphism in the ABCB1 gene and maternal medication use on the risk of septal defects in a Han Chinese population. An age- and gender-matched case-control study involving 265 pairs was conducted from March 2012 to September 2013. Information on maternal periconceptional medication use was obtained through questionnaires. The genotyping of 3435 C>T polymorphism was performed by sequencing. Logistic regression analysis was performed to assess the joint effects of ABCB1 gene 3435 C>T polymorphism and maternal medication use on the risk of septal defects. Use of maternal medication periconceptionally was significantly associated with an increased risk of septal defects [adjusted odds ratio (OR) 2.133; 95 % confidence interval (CI) 1.361-3.444; P = 0.001)]. The genotype distributions of 3435 C>T polymorphism differed significantly between cases and control subjects (P < 0.001). Meanwhile, more patients were carriers of the ABCB1 CC/CT genotypes, which were significantly associated with an increased risk of septal defects (OR 2.414; 95 % CI 1.418-4.110; P = 0.001). Children who carry the CC/CT genotype and have been exposed periconceptionally to medication have an almost fourfold increased risk of having septal defects than nonexposed children with the TT genotype (adjusted OR 3.932; 95 % CI 1.708-9.051), particularly perimembranous ventricular septal defects (VSD) (adjusted OR 4.070; 95 % CI 1.570-10.552). In conclusion, fetal 3435 C>T polymorphism in the ABCB1 gene increases the risk for isolated septal defects in the presence of maternal medication use periconceptionally, particularly for perimembranous VSD.

Coagulation abnormalities in osteonecrosis and bone marrow edema syndrome

The aim of this review was to provide information about the variety of thrombophilic and hypofibrinolytic markers that are possible risk factors for the development of osteonecrosis and bone marrow edema syndrome. A total of 48 parameters were identified in 45 studies that included 2163 patients. The most frequently reported laboratory findings included altered serum concentrations of lipoproteins, decreased concentration and function of fibrinolytic agents, increased levels of thrombophilic markers, and several single nucleotide polymorphisms. Despite inhomogeneities in reported parameters, results, patients' collectives, and treatment strategies, these data suggest that coagulation abnormalities may play an important role in the emergence of osteonecrosis and bone marrow edema syndrome.

Genetic risk factors for glucocorticoid-induced osteonecrosis: a meta-analysis

Glucocorticoid-induced osteonecrosis is a common and severe adverse event. We conducted a meta-analysis to investigate whether polymorphisms in target genes were associated with the risk of corticosteroid-induced osteonecrosis. Published literature from PubMed and EMBASE were searched for eligible publications. Pooled odds ratio (OR) and 95% confidence interval (CI) were calculated using a fixed- or random-effects model. There were 23 articles with 35 genes described the relationship between polymorphisms and glucocorticoid-induced osteonecrosis. Meta-analyses were carried out for those SNPs with three or more eligible studies, which included four SNPs located in three genes (PAI-1, MTHFR, ABCB1). The meta-analysis revealed that the PAI-1 4G allele was associated with an increased risk of osteonecrosis compared with the 5G allele (combined studies: OR=1.932, 95% CI=1.145-3.261). The OR for the 4G/4G vs. 5G/5G genotype of PAI-1 was 3.217 (95% CI 1.667-6.209 with combined studies), The relative risk of osteonecrosis was increased in the 4G allele vs. 5G/5G and 4G/4G genotype vs. 5G allele, with odds ratios of 2.304 (95% CI=1.235-4.299) and 2.307 (95% CI=1.527-3.485) in combined studies, respectively. The ABCB1 C3435T genotype distributions available confirmed that the C allele increased osteonecrosis risk compared with the T allele (OR 1.668, 95% CI=1.214-2.293) and TT genotype (OR 2.946, 95% CI=1.422-6.101). There was no evidence for significant association between MTHFR C677T and ABCB1 G2677T/A polymorphisms and risk of osteonecrosis. Results of this meta-analysis indicate that the PAI-1 4G/5G and ABCB1 C3435T polymorphisms may be risk factors for osteonecrosis.

The pathogenesis of nontraumatic osteonecrosis

Nontraumatic osteonecrosis continues to be a challenging problem causing debilitating major joint diseases. The etiology is multifactorial, but steroid- and alcohol-induced osteonecrosis contribute to more than two thirds of all cases with genetic risk factors playing an important role in many other cases, especially when they contribute to hypercoagulable states. While the exact mechanisms remain elusive, many new insights have emerged from research in the last decade that have given us a clearer picture of the pathogenesis of nontraumatic osteonecrosis of the femoral head. Progression to end stage osteonecrosis of the femoral head appears to be related to four main factors: interactions involving the differentiation pathway of osteoprogenitor cells that promote adipogenesis, decreased angiogenesis, direct suppression of osteogenic gene expression and proliferation of bone marrow stem cells, and genetic anomalies or other diseases that promote hypercoagulable states.