The Otto Aufranc Award: Identification of a 4 Mb region on chromosome 17q21 linked to developmental dysplasia of the hip in one 18-member, multigeneration family

Molecular mechanisms and genetic factors contributing to the developmental dysplasia of the hip

The most prevalent hip disease in neonates is developmental dysplasia of the hip (DDH). A timely and accurate diagnosis is required to provide the most effective treatment for pediatric patients with DDH. Heredity and gene variation have been the subject of increased attention and research worldwide as one of the factors contributing to the pathogenesis of DDH. Genome-wide association studies (GWAS), genome-wide linkage analyses (GWLA), and exome sequencing (ES) have identified variants in numerous genes and single-nucleotide polymorphisms (SNPs) as being associated with susceptibility to DDH in sporadic and DDH family patients. Furthermore, the DDH phenotype can be observed in animal models that exhibit susceptibility genes or loci, including variants in CX3CR1, KANSL1, and GDF5. The dentification of noncoding RNAs and de novo gene variants in patients with DDH-related syndrome has enhanced our understanding of the genes implicated in DDH. This article reviews the most recent molecular mechanisms and genetic factors that contribute to DDH.

Deciphering the pathogenic role of rare RAF1 heterozygous missense mutation in the late-presenting DDH

Background

Developmental Dysplasia of the Hip (DDH) is a skeletal disorder where late-presenting forms often escape early diagnosis, leading to limb and pain in adults. The genetic basis of DDH is not fully understood despite known genetic predispositions.

Methods

We employed Whole Genome Sequencing (WGS) to explore the genetic factors in late-presenting DDH in two unrelated families, supported by phenotypic analyses and in vitro validation.

Results

In both cases, a novel de novo heterozygous missense mutation in RAF1 (c.193A>G [p.Lys65Glu]) was identified. This mutation impacted RAF1 protein structure and function, altering downstream signaling in the Ras/ERK pathway, as demonstrated by bioinformatics, molecular dynamics simulations, and in vitro validations.

Conclusion

This study contributes to our understanding of the genetic factors involved in DDH by identifying a novel mutation in RAF1. The identification of the RAF1 mutation suggests a possible involvement of the Ras/ERK pathway in the pathogenesis of late-presenting DDH, indicating its potential role in skeletal development.

Ultrasonographic screening for developmental dysplasia of the hip: the Graf method revisited

Until the 1980s, the diagnosis of developmental dysplasia of the hip (DDH) was based on clinical examination and radiographic imaging. In 1980, Reinhard Graf developed his own ultrasonographic method for the examination of the infant hip joint. Graf's method evaluates the osseous and cartilaginous coverage of the femoral head by the acetabulum in the infantile hip joint by measuring the angles α and β. The validity of Graf method is that with these measurements the hip joint is further classified by Graf classification into types I to IV that guide treatment. Currently, Graf method is considered the gold standard examination for the diagnosis of DDH in many European countries. This review article aims to discuss the incidence, risk factors and pathophysiology of DDH, and to emphasize on the Graf method for the evaluation, classification, prevention and further management of this entity.

Genome-Wide Association Study and Transcriptome of Japanese Patients with Developmental Dysplasia of the Hip Demonstrates an Association with the Ferroptosis Signaling Pathway

This study examined the association between developmental dysplasia of the hip (DDH) and disease-associated loci in a Japanese cohort. A genome-wide association study (GWAS) of 238 Japanese patients with DDH and 2044 healthy individuals was performed. As a replicate, GWAS was also conducted on the UK Biobank data with 3315 cases and matched 74,038 controls. Gene set enrichment analyses (GSEAs) of both the genetics and transcriptome of DDH were performed. Transcriptome analysis of cartilage specimens from DDH-associated osteoarthritis and femoral neck fractures was performed as a control. Most of the lead variants were very low-frequency ones in the UK, and variants in the Japanese GWAS could not be replicated with the UK GWAS. We assigned DDH-related candidate variants to 42 and 81 genes from the Japanese and UK GWASs, respectively, using functional mapping and annotation. GSEA of gene ontology, disease ontology, and canonical pathways identified the most enriched pathway to be the ferroptosis signaling pathway, both in the Japanese gene set as well as the Japanese and UK merged set. Transcriptome GSEA also identified significant downregulation of genes in the ferroptosis signaling pathway. Thus, the ferroptosis signaling pathway may be associated with the pathogenic mechanism of DDH.

Developmental dysplasia of the hip: A systematic review of susceptibility genes and epigenetics

BACKGROUND

Developmental dysplasia of the hip (DDH) is a complex developmental deformity whose pathogenesis and susceptibility-related genes have yet to be elucidated. This systematic review summarizes the current literature on DDH-related gene mutations, animal model experiments, and epigenetic changes in DDH.

METHODS

We performed a comprehensive search of relevant documents in the Medline, Scopus, Cochrane, and ScienceDirect databases covering the period from October 1991 to October 2021. We analyzed basic information on the included studies and summarized the DDH-related mutation sites, animal model experiments, and epigenetic changes associated with DDH.

RESULTS

A total of 63 studies were included in the analysis, of which 54 dealt with the detection of gene mutations, 7 presented details of animal experiments, and 6 were epigenetic studies. No genetic mutations were clearly related to the pathogenesis of DDH, including the most frequently studied genes on chromosomes 1, 17, and 20. Most gene-related studies were performed in Han Chinese or North American populations, and the quality of these studies was medium or low. GDF5 was examined in the greatest number of studies, and mutation sites with odds ratios > 10 were located on chromosomes 3, 9, and 13. Six mutations were found in animal experiments (i.e., CX3CR1, GDF5, PAPPA2, TENM3, UFSP2, and WISP3). Epigenetics research on DDH has focused on GDF5 promoter methylation, three microRNAs (miRNAs), and long noncoding RNAs. In addition, there was also a genetic test for miRNA and mRNA sequencing.

CONCLUSIONS

DDH is a complex joint deformity with a considerable genetic component whose early diagnosis is significant for preventing disease. At present, no genes clearly involved in the pathogenesis of DDH have been identified. Research on mutations associated with this condition is progressing in the direction of in vivo experiments in animal models to identify DDH susceptibility genes and epigenetics analyses to provide novel insights into its pathogenesis. In the future, genetic profiling may improve matters.

WNT1 expression influences the development of dysplasia of the hip via regulating RBPMS2/NOG-BMP2/4-GDF5- WISP2 pathway

OBJECTIVE

To explore the role of WNT family member 1 (WNT1) in the development of dysplasia of the hip (DDH) and the molecular mechanism involved in this process. Methods: Si-WNT1, pcDNA3.1-WNT1 or corresponding negative controls were transfected into human osteoblast hFOB1.19 and human chondrocyte C28/I2, respectively. The proliferation of cells was measured by EdU assay. The relative expressions of human noggin gene (NOG), growth differentiating factor 5 (GDF5), WNT1, and WNT1-inducible-signaling pathway protein 2 (WISP2) were determined by immunofluorescence analysis. The protein expressions of RNA-binding protein of multiple splice forms 2 (RBPMS2), NOG, bone morphogenetic protein 2 (BMP2), BMP4, WNT1 and WISP2 were determined by western blot. Animal experiment was also performed and the morphological development of hip joint was observed. Results: Overexpression of WNT1 promoted osteoblast proliferation and inhibited chondrocyte proliferation, while knockdown of WNT1 inhibited osteoblast proliferation. In chondrocytes, knockdown of WNT1 upregulated NOG expression, while overexpression of WNT1 downregulated its expression. In osteoblasts and chondrocytes, overexpression of WNT1 increased BMP2, BMP4, WNT1, and WISP2 expression. RBPMS2 and NOG were slightly expressed in each group. Conclusion: Overexpression of WNT1 promoted osteoblast proliferation, inhibited chondrocyte proliferation, and increased the expressions of BMP2, BMP4, WNT1, and WISP2. Therefore, WNT1 may be a new therapeutic target for DDH.

The Genetic Epidemiology of Joint Shape and the Development of Osteoarthritis

Congruent, low-friction relative movement between the articulating elements of a synovial joint is an essential pre-requisite for sustained, efficient, function. Where disorders of joint formation or maintenance exist, mechanical overloading and osteoarthritis (OA) follow. The heritable component of OA accounts for ~ 50% of susceptible risk. Although almost 100 genetic risk loci for OA have now been identified, and the epidemiological relationship between joint development, joint shape and osteoarthritis is well established, we still have only a limited understanding of the contribution that genetic variation makes to joint shape and how this modulates OA risk. In this article, a brief overview of synovial joint development and its genetic regulation is followed by a review of current knowledge on the genetic epidemiology of established joint shape disorders and common shape variation. A summary of current genetic epidemiology of OA is also given, together with current evidence on the genetic overlap between shape variation and OA. Finally, the established genetic risk loci for both joint shape and osteoarthritis are discussed.

Current Evidence about Developmental Dysplasia of the Hip in Pregnancy

In adults, developmental dysplasia of the hip (DDH) represents a spectrum of disorders. It is commonly found in women in routine orthopedic practice. Hip dysplasia is a leading precursor of joint laxity; when untreated, it can contribute to chronic modifications, such as thickening of the pulvinar and ligamentum teres (which can also elongate), hypertrophy of the transverse acetabular ligament, and osteoarthritis. DDH is presumed to be associated with alterations in pelvic morphology that may affect vaginal birth by the reduction in the transverse diameter of the pelvic inlet or outlet. Here, we provide an overview of the current knowledge of pregnancy-associated DDH. We primarily focused on how a surgical DDH treatment might influence the pelvic shape and size and the effects on the mechanism of birth. We presented the female pelvis from the standpoint of bone and ligament morphology relative to a pelvic osteotomy. Then, we described whether the pregnancy was impacted by previous surgical DDH treatments, performed from infancy to adulthood. In conclusion, hip dysplasia is not associated with high-risk complications during pregnancy or with increased difficulty in vaginal delivery.

Computer-Aided System Application Value for Assessing Hip Development

Purpose

A computer-aided system was used to semiautomatically measure Tönnis angle, Sharp angle, and center-edge (CE) angle using contours of the hip bones to establish an auxiliary measurement model for developmental screening or diagnosis of hip joint disorders.

Methods

We retrospectively analyzed bilateral hip x-rays for 124 patients (41 men and 83 women aged 20-70 years) who presented at the Affiliated Zhongshan Hospital of Dalian University in 2017 and 2018. All images were imported into a computer-aided detection system. After manually outlining hip bone contours, Tönnis angle, Sharp angle, and CE angle marker lines were automatically extracted, and the angles were measured and recorded. An imaging physician also manually measured all angles and recorded hip development, and Pearson correlation coefficients were used to compare computer-aided system measurements with imaging physician measurements. Accuracy for different angles was calculated, and the area under the receiver operating characteristic (AUROC) curve was used to represent the diagnostic efficiency of the computer-aided system.

Results

For Tönnis angle, Sharp angle, and CE angle, correlation coefficients were 0.902, 0.887, and 0.902, respectively; the accuracies of the computer-aided detection system were 89.1, 93.1, and 82.3%; and the AUROC curve values were 0.940, 0.956, and 0.948.

Conclusion

The measurements of Tönnis angle, Sharp angle, and CE angle using the semiautomatic system were highly correlated with the measurements of the imaging physician and can be used to assess hip joint development with high accuracy and diagnostic efficiency.

Genetics of developmental dysplasia of the hip

In the last decade, the advances in the molecular analyses and sequencing techniques allowed researchers to study developmental dysplasia of the hip (DDH) more thoroughly. Certain chromosomes, genes, loci and polymorphisms are being associated with variable severity of this disorder. The wide range of signs and symptoms is dependent either on isolated or systemic manifestation. Phenotypes of isolated cases range from only a mild ligamental laxity, through subluxation, to a complete dislocation of the femoral head. Systemic manifestation is connected to various forms of skeletal dysplasia and other malformations characterized by significant genetic aberrations. To reveal the background of DDH heredity, multiple studies focused on large sample sizes with an emphasis on the correlation between genotype, phenotype and continuous clinical examination. Etiological risk factors that have been observed and documented in patients include genetic, environmental, and mechanical factors, which significantly contribute to the familial or nonfamilial occurrence and phenotypic variability of this disorder. Still, the multifactorial etiology and pathogenesis of DDH are not yet sufficiently clarified, explained, or understood. Formation of connective tissue, osteogenesis, chondrogenesis, and all other affected pathways and variations in the function of their individual elements contribute to the creation of the pathology in a developing human body. This review article presents an up-to-date list of known DDH associated genes, their products, and functional characteristics.

Developmental Dysplasia of the Hip: A Review of Etiopathogenesis, Risk Factors, and Genetic Aspects

As one of the most frequent skeletal anomalies, developmental dysplasia of the hip (DDH) is characterized by a considerable range of pathology, from minor laxity of ligaments in the hip joint to complete luxation. Multifactorial etiology, of which the candidate genes have been studied the most, poses a challenge in understanding this disorder. Candidate gene association studies (CGASs) along with genome-wide association studies (GWASs) and genome-wide linkage analyses (GWLAs) have found numerous genes and loci with susceptible DDH association. Studies put major importance on candidate genes associated with the formation of connective tissue (COL1A1), osteogenesis (PAPPA2, GDF5), chondrogenesis (UQCC1, ASPN) and cell growth, proliferation and differentiation (TGFB1). Recent studies show that epigenetic factors, such as DNA methylation affect gene expression and therefore could play an important role in DDH pathogenesis. This paper reviews all existing risk factors affecting DDH incidence, along with candidate genes associated with genetic or epigenetic etiology of DDH in various studies.

Mapping of developmental dysplasia of the hip to two novel regions at 8q23-q24 and 12p12

Developmental dysplasia of the hip (DDH), previously known as congenital hip dislocation, is a frequently disabling condition characterized by premature arthritis later in life. Genetic factors play a key role in the aetiology of DDH. In the present study, a genome-wide linkage scan with the Affymetrix 10K GeneChip was performed on a four-generation Chinese family, which included 19 healthy members and 5 patients. Parametric and non-parametric multipoint linkage analyses were carried out with Genespring GT v.2.0 software, and the logarithm of odds (LOD) score and nonparametric linkage (NPL) score were calculated. Parametric linkage analysis was performed, assuming an autosomal recessive trait with full penetrance and Affymetrix 'Asian' allele frequencies. The strongest evidence for linkage was found on chromosome 8q23-24, with a peak LOD score of 2.658 (θ=0), covering 2.377 Mb from single nucleotide polymorphisms (SNPs) rs724717 to rs720132. This interval included nine additional successive SNPs: rs1566071, rs1902121, rs756404, rs702768, rs777813, rs2033995, rs147959, rs2884367 and rs1898287. The same region also yielded the highest NPL score of 2.883 (P=0.0156) from the non-parametric multipoint linkage analysis. Additionally, the second highest NPL score of 2.727 (P=0.0156) and LOD score of 2.528 (θ=0) were obtained on chromosome 12p12 for three consecutive markers (rs1919980, rs763853 and rs725124). This region overlapped a narrow distance of 0.642 Mb. Notably, in addition to these two regions; no significant linkage was identified for other chromosomal regions (with LOD and NPL scores >2.0). For the first time, at least for this pedigree, the evidence in the present study showed that DDH is mapped to two novel regions at 8q23-q24 and 12p12.

Genetic Predisposition to Developmental Dysplasia of the Hip

BACKGROUND

The etiopathogenesis of developmental dysplasia of the hip (DDH) has not been clarified. This systematic review evaluated current literature concerning all known chromosomes, loci, genes, and their polymorphisms that have been associated or not with the prevalence and severity of DDH.

METHODS

Following the established methodology of Meta-analysis of Observational Studies in Epidemiology guidelines, MEDLINE, EMBASE, and Cochrane Register of Controlled Trials were systematically searched from inception to January 2019.

RESULTS

Forty-five studies were finally included. The majority of genetic studies were candidate gene association studies assessing Chinese populations with moderate methodological quality. Among the most frequently studied are the first, third, 12th,17th, and 20th chromosomes. No gene was firmly associated with DDH phenotype. Studies from different populations often report conflicting results on the same single-nucleotide polymorphism (SNP). The SNP rs143384 of GDF5 gene on chromosome 20 demonstrated the most robust relationship with DDH phenotype in association studies. The highest odds of coinheritance in linkage studies have been reported for regions of chromosome 3 and 13. Five SNPs have been associated with the severity of DDH. Animal model studies validating previous human findings provided suggestive evidence of an inducing role of mutations of the GDF5, CX3CR1, and TENM3 genes in DDH etiopathogenesis.

CONCLUSION

DDH is a complex disorder with environmental and genetic causes. However, no firm correlation between genotype and DDH phenotype currently exists. Systematic genome evaluation in studies with larger sample size, better methodological quality, and assessment of DDH patients is necessary to clarify the DDH heredity. The role of next-generation sequencing techniques is promising.

Developmental dysplasia of the hip: a systematic literature review of the genes related with its occurrence

Developmental dysplasia of the hip (DDH) is one of the most prevalent congenital malformations. It has a wide spectrum of anatomical abnormalities of the hip joint and is characterized by mild or incomplete formation of the acetabulum leading to laxity of the joint capsule, secondary deformity of the proximal femur and irreducible hip dislocation. It is the leading cause of early hip osteoarthritis in young individuals.

Both genetic and environmental factors have been proposed to play an important role in the pathogenesis of DDH. A high prevalence is present in Asian, Caucasian, Mediterranean and American populations, with females being more frequently affected. We evaluated a variety of genetic studies indexed in the PubMed database.

Several susceptive genes, including WISP3, PAPPA2, HOXB9, HOXD9, GDF5, TGF Beta 1, CX3CR1, UQCC, COL1A1, TbX4 and ASPN have been identified as being associated with the development of DDH. Moreover, genetic association has also been reported between hip dysplasia and other comorbidities. Even though genetic components are a crucial part in the aetiology of DDH, several DDH susceptibility genes need further investigation.

The purpose of this review is to present current literature evidence regarding genes responsible for DDH development.

Cite this article: EFORT Open Rev 2019;4:595-601. DOI: 10.1302/2058-5241.4.190006

Developmental Dysplasia of Hip: Perspectives in Genetic Screening

Development dysplasia of the hip (DDH) is a complex developmental disorder despite being a relatively common condition mainly caused by incompatibility of the femoral head and the abnormal joint socket. Development dysplasia of the hip describes a wide spectrum of disorders ranging from minor acetabular dysplasia to irreducible dislocation of the hip. Modern medicine still suffers from lack of information about screening and precise genetic examination. Genome wide linkage and association studies have brought significant progress to DDH diagnosis. Association studies managed to identify many candidate (susceptible) genes, such as PAPPA2, COL2A1, HOXD9, GDF-5, and TGFB1, which play a considerable role in the pathogenesis of DDH. Early detection of DDH has a big chance to help in preventing further disability and improve the psychological health and quality of life in those children. This emphasizes the importance to establish a universal screening program along with the genetic counseling.

Ten- and 20-year Survivorship of the Hip After Periacetabular Osteotomy for Acetabular Dysplasia

INTRODUCTION

Acetabular dysplasia is a multifactorial condition characterized by a shallow hip socket with predisposition to osteoarthritis of the hip. The Bernese periacetabular osteotomy (PAO), developed by Reinhold Ganz in 1984, reorients the dysplastic hip joint to provide more uniform coverage of the femoral head and to extend the longevity of the native hip. Since 1987, the senior author performed the Bernese PAO on more than 430 patients. We performed a cross-sectional retrospective study on this cohort of patients to determine the 10- and 20-year survivorship after PAO in addition to assessing functional outcomes and radiographic parameters.

METHODS

Four hundred thirty-four patients were treated for acetabular dysplasia with PAO by the senior surgeon from 1987 to 2014. Data were obtained for 302 hips in 258 patients in a retrospective fashion from medical records and/or mail-in/phone questionnaires. Functional outcome data consisted of postoperative Hip Osteoarthritis Outcome Score and University of California-Los Angeles Activity Score. Pre- and postoperative radiographs were used to determine lateral center-edge angle, anterior center-edge angle, Tönnis angle/grade, and head-to-ilioischial line distance. Survivorship of the native hip was determined by Kaplan-Meier analysis.

RESULTS

Of the 302 hips analyzed, 248 were still surviving native hips and 54 had gone on to a total hip arthroplasty (THA) at the time of data acquisition. The average age of patients in the entire cohort at PAO was 32.7 years (range, 13 to 63 years). Of the 258 patients, 215 were female patients (83.3%) and 43 male patients (16.8%). The average age of patients in the surviving group at PAO was 32.3 years, and the average age of patients in the THA group was 36.6 years (P < 0.01). At the time of data acquisition, follow-up ranged from 2 to 27 years (average, 11.2 years). Hip Osteoarthritis Outcome Score and University of California-Los Angeles Activity Score are reported for the surviving native hips after PAO. Radiographic analyses for surviving and failed hips are described, with pre- and postoperative Tönnis grade being statistically significant predictors for conversion to THA (P < 0.01). Survivorship of the native hip was 86% at 10 years and 60% at 20 years in the surviving cohort. Survivorship stratified by age at the time of PAO demonstrated a 10-year survivorship of 93.3%, 90.1%, 81.6%, and 63.2% at ages 20, 30, 40, and 50 years, respectively. No notable difference exists in survivorship between male and female patients; however, male patients had a trend toward lower survivorship compared with female patients at 15 years.

CONCLUSION

The 10- and 20-year survivorship of the native hip after PAO is approximately 86% and 60%, respectively, in our cohort of 302 hips. Older age at the time of PAO and higher Tönnis grade are negative prognostic factors for joint survival after PAO. Surviving hips after PAO have good functional outcomes even up to 20 years after surgery. This survivorship analysis represents one of the largest and longest survival studies of patients after PAO, and our results are consistent with other published studies.

LEVEL OF EVIDENCE

Level III.

Novel mutation in Teneurin 3 found to co-segregate in all affecteds in a multi-generation family with developmental dysplasia of the hip

DDH is a debilitating condition characterized by incomplete formation of the acetabulum leading to dislocation of the hip, suboptimal joint function and accelerated wear of the articular cartilage resulting in early onset crippling arthritis of the hip in 20-40 year olds. Current diagnostic tests in newborns using physical manipulation of the femur or ultrasound either under or over-diagnose this condition. Developing an accurate, cost effective diagnostic test is a goal of this study. To better understand the biologic pathways involved in acetabular development, DNA from severely affected individuals in a four generation family that showed inter-generational transmission of the disorder was isolated and whole exome sequenced. A novel A to C transversion at position 183721398 on human chromosome four was found to co-segregate with the affected phenotype in this family. This mutation encodes a glutamine to proline change at position 2665 in the Teneurin 3 (TENM3) gene and was judged damaging by four prediction programs. Eight week old knock-in mutant mice show delayed development of the left acetabulum and the left glenoid fossa as shown by the presence of more Alcian blue staining on the socket rims of both the hip and the shoulder. We hypothesize that mutated TENM3 will slow chondrogenesis. MMP13 has been shown to impair extracellular matrix remodeling and suppress differentiation. Bone marrow cells from the knock-in mouse were found to overexpress MMP13 with or without BMP2 stimulation. This variant may elucidate pathways responsible for normal hip development and become part of an accurate test for DDH. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Poorer radiological outcome after delayed diagnosis and treatment in human position in Fettweis plaster cast in 93 unstable hip joints type D, III and IV according to Graf

PURPOSE

In this study the course of unstable hips after successful treatment with Fettweis plaster of Paris (POP) is examined. Special focus will be given to age at beginning of treatment and initial hip type.

METHODS

The development of 93 unstable hips treated between November 2001 and April 2015 was examined. Inclusion criteria were: 1) unstable hips with successful treatment with Fettweis POP; 2) presence of two pelvic radiographs (12 to 24 months and 24 to 48 months). We analyzed: 1) the initial ultrasound hip type according to Graf; 2) the average age at first and second radiograph; 3) the Tönnis classification: normal findings (< 1 SD), slightly (1 SD to 2 SD) and severely dysplastic hips (> 2 SD).

RESULTS

In all, there were 14 hips type D, 41 hips type III and 38 hips type IV. Mean age of the first radiograph was 13.9 months and of the second 28.5 months. The first radiograph showed: (< 1 SD): 36, (1 SD to 2 SD): 34, (> 2 SD): 23 hips, the second radiograph: (< 1 SD): 33, (1 SD to 2 SD): 19, (> 2 SD): 30 hips. With subdivision at the start of treatment at age eight or fewer weeks 2/16 hips (12.5%) and with initiation of the treatment more than eight weeks 22/77 (26.0%) deteriorated. During the course between first and second radiograph a total of 35.7% of initial hip type D, 19.5% of type III and 23.7% of type IV deteriorated.

CONCLUSION

Radiograph controls after treatment with Fettweis POP show poorer outcome after delaying the start of treatment more than 8 weeks. These findings were independent of the initial ultrasound hip type. Regular radiograph controls of all hip types treated for unstable hips are justified to detect residual dysplasia.

LEVEL OF EVIDENCE

IV.

Genome-wide association study of developmental dysplasia of the hip identifies an association with GDF5

Developmental dysplasia of the hip (DDH) is the most common skeletal developmental disease. However, its genetic architecture is poorly understood. We conduct the largest DDH genome-wide association study to date and replicate our findings in independent cohorts. We find the heritable component of DDH attributable to common genetic variants to be 55% and distributed equally across the autosomal and X-chromosomes. We identify replicating evidence for association between GDF5 promoter variation and DDH (rs143384, effect allele A, odds ratio 1.44, 95% confidence interval 1.34–1.56, P = 3.55 × 10⁻²²). Gene-based analysis implicates GDF5 (P = 9.24 × 10⁻¹²), UQCC1 (P = 1.86 × 10⁻¹⁰), MMP24 (P = 3.18 × 10⁻⁹), RETSAT (P = 3.70 × 10⁻⁸) and PDRG1 (P = 1.06 × 10⁻⁷) in DDH susceptibility. We find shared genetic architecture between DDH and hip osteoarthritis, but no predictive power of osteoarthritis polygenic risk score on DDH status, underscoring the complex nature of the two traits. We report a scalable, time-efficient recruitment strategy and establish for the first time to our knowledge a robust DDH genetic association locus at GDF5.

Konstantinos Hatzikotoulas et al. report the largest genome-wide association study to date for developmental dysplasia of the hip using national clinical audit data from the UK. They find a significant association with the GDF5 locus and evidence for shared genetic architecture with hip osteoarthritis.

Whole genome sequencing of pairwise human subjects reveals DNA mutations specific to developmental dysplasia of the hip

Developmental dysplasia of the hip (DDH) is a common congenital malformation characterized by mismatch in shape between the femoral head and acetabulum, and leads to hip dysplasia. To date, the pathogenesis of DDH is poorly understood and may involve multiple factors, including genetic predisposition. However, comprehensive genetic analysis has not been applied to investigate a genetic component of DDH. In the present study, 10 pairs of healthy fathers and DDH daughters were enrolled to identify genetic hallmarks of DDH using high throughput whole genome sequencing. The DDH-specific DNA mutations were found in each patient. Overall 1344 genes contained DDH-specific mutations. Functional enrichment analysis showed that these genes played important roles in the cytoskeleton, microtubule cytoskeleton, sarcoplasm and microtubule associated complex. These functions affected osteoblast and osteoclast development. Therefore, we proposed that the DDH-specific mutations might affect bone development, and caused DDH. Our pairwise high throughput sequencing results comprehensively delineated genetic hallmarks of DDH. Further research into the biological impact of these mutations may inform the development of DDH diagnostic tools and allow neonatal gene screening.

A novel iterative mixed model to remap three complex orthopedic traits in dogs

Hip dysplasia (HD), elbow dysplasia (ED), and rupture of the cranial (anterior) cruciate ligament (RCCL) are the most common complex orthopedic traits of dogs and all result in debilitating osteoarthritis. We reanalyzed previously reported data: the Norberg angle (a quantitative measure of HD) in 921 dogs, ED in 113 cases and 633 controls, and RCCL in 271 cases and 399 controls and their genotypes at ~185,000 single nucleotide polymorphisms. A novel fixed and random model with a circulating probability unification (FarmCPU) function, with marker-based principal components and a kinship matrix to correct for population stratification, was used. A Bonferroni correction at p<0.01 resulted in a P< 6.96 ×10-8. Six loci were identified; three for HD and three for RCCL. An associated locus at CFA28:34,369,342 for HD was described previously in the same dogs using a conventional mixed model. No loci were identified for RCCL in the previous report but the two loci for ED in the previous report did not reach genome-wide significance using the FarmCPU model. These results were supported by simulation which demonstrated that the FarmCPU held no power advantage over the linear mixed model for the ED sample but provided additional power for the HD and RCCL samples. Candidate genes for HD and RCCL are discussed. When using FarmCPU software, we recommend a resampling test, that a positive control be used to determine the optimum pseudo quantitative trait nucleotide-based covariate structure of the model, and a negative control be used consisting of permutation testing and the identical resampling test as for the non-permuted phenotypes.

Exome sequencing identified rare variants in genes HSPG2 and ATP2B4 in a family segregating developmental dysplasia of the hip

Background

Developmental dysplasia of the hip (DDH) is a common pathological condition of the musculoskeletal system in infants which results in a congenital and developmental malformation of the hip joint. DDH is a spectrum of pathologies affecting the infant hip ranging from asymptomatic subtle radiographic signs through mild instability to frank dislocations with acetabular dysplasia. A Saudi family with three affected individuals with DDH was identified and genetic analysis was performed to detect the possible genetic defect(s) underlying DDH in the affected members of the family.

Methods

We performed whole genome genotyping using Illumina HumanOmni 2.5 M array and whole exome sequencing (WES) using Nextera Rapid capture kit and Illumina NextSeq500 instrument in four individuals of a family with DDH.

Results

SNP data analysis did not identify any runs of homozygosity and copy number variations. Identity-by-descent (IBD) analysis on whole genome genotyping data identified a shared haplotypes on chromosome 1 in affected individuals. An analysis of the WES data identified rare heterozygous variants in HSPG2 and ATP2B4 genes in the affected individuals. Multiple prediction software predicted that the variants identified are damaging. Moreover, in silico analysis showed that HSPG2 regulates ATP2B4 expression using a variety of transcription factors.

Conclusion

Our results indicate that there might be a functional epistatic interaction between HSPG2 and ATP2B4, and DDH in the family studied is due to a combined effect of both variants. These variants are also present in the asymptomatic mother suggesting that the variants in HSPG2 and ATP2B4 are incompletely penetrant. This study provides the first evidence of digenic inheritance of DDH in a family and extends the spectrum of genetic heterogeneity in this human disorder.

Electronic supplementary material

The online version of this article (doi:10.1186/s12881-017-0393-8) contains supplementary material, which is available to authorized users.

A recurrent mutation in bone morphogenetic proteins-2-inducible kinase gene is associated with developmental dysplasia of the hip

Developmental dysplasia of the hip (DDH) is a complex disorder of the hip joint affecting 1-5‰ of newborns. While genetic influence on DDH has been long known, DDH has not been ascribed to any specific genetic event. The present study reported on variants contributing to DDH susceptibility in a family with four individuals affected across three generations. Whole-exome sequencing was performed in three affected and two unaffected individuals of a pedigree with DDH. Candidate variants were confirmed by Sanger sequencing and then validated in available family members and 37 sporadic DDH patients. Two novel heterozygous, inframe mutations causing multi-nucleotide substitution polymorphisms (c.1432_1440delCAGCAGCAG corresponding with p.Gln478_480del and c.1440_1441insCAG corresponding with p.Gln480ins) in exon 11 of chromosome 4 in bone morphogenetic proteins-2-inducible kinase (BMP2K) were identified; these were found in members of the pedigree affected by DDH and in the unaffected grandmother of the proband, who was deemed to be the carrier of potential mutations, but not in the unaffected normal control saunt of the proband. These two variants shared the same genomic coordinate but with different types of mutation in BMP2K. BMP2K is known to be associated with bone and cartridge development and heterozygous mutations were found to be present in 4/4 (100%) of the affected family members, 4/15 (26.7%) of the unaffected family members and 0/7 (0%) of the unaffected unrelated family members. Genotyping of 37 unrelated, sporadic DDH patients showed that three cases were positive for the BMP2K c.1432_1440delCAGCAGCAG variants (8.12%). These findings provided strong evidence for the role of BMP2K variants in causing DDH and demonstrated that the combination of pedigree information and next-generation sequencing is an effective method for identifying pathogenic sites associated with DDH.

Severe cartilage degeneration in patients with developmental dysplasia of the hip

Developmental dysplasia of the hip (DDH) is a developmental disorder that has long-term chronic pain and limited hip joint mobility as major pathological characteristics. This study aims to access the association between the development of DDH and cartilage metabolic disorders. Cartilage tissue samples were acquired from patients with DDH, osteoarthritis (OA) and femoral neck fracture. The proteoglycan level was evaluated by safranin O-fast green, toluidine blue and hematoxylin-eosin (HE) staining. The levels of collagen-II (Col-II), collagen-X (Col-X) and metal matrix proteinase-13 (MMP-13) were evaluated by immunohistochemistry (IHC) and Western blotting analysis. The morphologic evaluation of cartilage was conducted by transmission electron microscopy (TEM). Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to detect the mRNA level of aggrecan, Col-II, Col-X and MMP-13. The aggrecan level in the cartilage matrix was significantly decreased in DDH patients by safranin O-fast green and toluidine blue staining in comparison with that in the OA and control groups. In contrast with the OA group, the Col-II expression was reduced while the MMP-13 expression increased in DDH patients, as shown by IHC and Western blotting analysis. The collagenous fibrils in cartilage of DDH patients appeared significantly sparse and disordered in the TEM analysis. In DDH patients, the mRNA expression levels of Col-II and aggrecan were markedly reduced, while the mRNA expression of Col-X was markedly increased, compared with the OA patients. There is severe articular cartilage degeneration in DDH patients. This observation provides us with new insight into cartilage metabolic regulation in DDH. © 2017 IUBMB Life, 69(3):179-187, 2017.

Emerging insights into the genetic basis of canine hip dysplasia

Canine hip dysplasia (CHD) is the most common inherited polygenic orthopedic trait in dogs with the phenotype influenced also by environmental factors. This trait was described in the dog in 1935 and leads to a debilitating secondary hip osteoarthritis. The diagnosis is confirmed radiographically by evaluating signs of degenerative joint disease, incongruence, and/or passive hip joint laxity. There is no ideal medical or surgical treatment so prevention based on controlled breeding is the optimal approach. The definitive CHD diagnosis based on radiographic examination involves the exposure to ionizing radiation under general anesthesia or heavy sedation but the image does not reveal the underlying genetic quality of the dog. Phenotypic expression of CHD is modified by environmental factors and dogs with a normal phenotype can be carriers of some mutations and transmit these genes to their offspring. Programs based on selection of dogs with better individual phenotypes for breeding are effective when strictly applied but remain inferior to the selection of dogs based on estimation of breeding values. Molecular studies for dissecting the genetic basis of CHD are ongoing, but progress has been slow. In the future, the recommended method to improve hip quality in controlled breeding schemes, which will allow higher selection pressure, would be based on the estimation of the genomic breeding value. Since 2012, a commercial DNA test has been available for Labrador Retrievers using a blood sample and provides a probability for development of CHD but we await evidence that this test reduces the incidence or severity of CHD.

To swaddle, or not to swaddle? Paleoepidemiology of developmental dysplasia of the hip and the swaddling dilemma among the indigenous populations of North America

OBJECTIVES

Clinical prevalence of developmental dysplasia of the hip (DDH) is high among modern indigenous populations of North America, yet no systematic study of the paleoepidemiology of this group exists. This study discusses the skeletal criteria, epidemiology, pathophysiology, and risk factors of DDH. A range of cases of DDH from an archaeological Native American population are described and the clinical and prehistoric prevalence of DDH among indigenous populations of North America are calculated and discussed within a biocultural perspective.

METHODS

Pelves of 390 adults from the Late Prehistoric (1490 B.P. ± 70) Buffalo site, West Virginia, were examined for DDH. Morphology of true and false acetabula was classified and other changes of the pelvis, lower limb, and spine were noted along with cranial deformation, providing evidence of infant restriction. Prevalence of DDH among living and archaeological indigenous peoples of North America were calculated and compared. Cranial deformation was assessed as evidence for swaddling.

RESULTS

DDH was identified in 18 adults from Buffalo, resulting in a minimum prevalence of 46.15 per 1,000, within the range reported in modern indigenous groups in North America. Most, but not all, of the DDH cases were associated with cranial deformation, but not all cases of cranial deformation were associated with DDH.

CONCLUSIONS

The etiology of DDH suggests that components of both genetic predisposition and swaddling practices have combined to create a high-risk environment for the development of DDH, contributing to high prevalence within archaeological populations, like Buffalo, and modern Indigenous groups of North America.

Linkage mapping and whole exome sequencing identify a shared variant in CX3CR1 in a large multi-generation family

Developmental dysplasia of the hip (DDH) is a crippling condition that affects children and adults, with an average incidence of 1-1.5 cases per 1000 live births. It results in disabling arthritis of the hip in up to 60% patients in the 20-40 year age group. There is no accurate diagnostic test available for newborns. The purpose of our study is to develop a sensitive and specific genetic test for DDH by identifying causative mutations. Linkage analysis and whole exome sequencing of 4 severely affected individuals of a 4 generation 71 member family was performed. The damaging rs3732378 variant in the CX3CR1 chemokine receptor was shared by all affected family members and by 15% of 28 sporadic dysplastics.

Two single-nucleotide polymorphisms in the DKK1 gene are associated with developmental dysplasia of the hip in the Chinese Han female population

AIMS

Developmental dysplasia of the hip (DDH) is a common congenital or acquired skeletal disease characterized by subluxation, dislocation, or dysplasia of the hip joint. This study aimed to explore the potential impact of Dickkopf-1 (DKK1) gene polymorphisms on embryonic hip joint development and the course of DDH.

METHODS

One hundred ninety-two unrelated Chinese Han female DDH patients and 191 unrelated, healthy, ethnically matched female controls were recruited and genotyped for two tag single-nucleotide polymorphisms (SNPs) of DKK1 using the Sequenom method.

RESULTS

One of the two DKK1 tag SNPs, rs11001560, was not shown to be significantly statistically different in allele frequency between DDH patients and control groups (χ(2)=0.898, df=1, p=0.343). However, a significant difference in genotype distribution was observed (χ(2)=21.987, df=2, p<0.0001). For SNP rs1569198, significant differences were observed in both allele frequency and genotype distribution between the DDH group and control group (χ(2)=31.484, df=1, p<0.0001 and χ(2)=30.323, df=2, p<0.0001). The A allele frequency of rs1569198 has a significant association to increased risk of DDH development (odds ratio [OR]=3.032, 95% confidence interval [95% CI]: 2.034-4.519).

CONCLUSION

In conclusion, the association between two tag SNPs of the DKK1 gene and DDH development reached statistical significance in our study population; the results of our genetic association analysis indicated that DKK1 may be a good candidate responsible for DDH development in the Chinese Han female population.

Association of a single nucleotide polymorphism in HOXB9 with developmental dysplasia of the hip: a case-control study

Developmental dysplasia of the hip (DDH) is one of the most common skeletal disorders. It comprises a spectrum of abnormalities, including shallow acetabulum and decreased coverage of the femoral head. Genetic component plays a considerable role in the aetiology of DDH. HOXB9 may be involved in the aetiology and pathogenesis of DDH, as it plays an important role in the development of the limbs. Our objective was to evaluate whether single nucleotide polymorphisms (SNPs) of HOXB9 (rs2303486 and rs8844) were associated with DDH in Chinese population. The HOXB9 tag SNPs were genotyped in 460 DDH cases and 562 control subjects by Taqman assay, and their association was examined. rs8844 was not associated with DDH. rs2303486 was associated with DDH in the dominant genetic model (p = 0.037; odds ratio (OR) = 1.32; 95% confidence interval (CI) = 1.02–1.71). After stratification by sex, significant association of the dominant genetic model still existed in the female subjects (p = 0.015; OR = 1.46; 95% CI = 1.08–1.98),but not in the male subjects. After stratification by severity, we discovered an association with hip dislocation in the dominant model(p=0.042; OR = 1.35; 95% CI = 1.01–1.80), but not with subluxation or instability. HOXB9 is associated with DDH in Chinese.

Developmental dysplasia of the hip: linkage mapping and whole exome sequencing identify a shared variant in CX3CR1 in all affected members of a large multigeneration family

Developmental dysplasia of the hip (DDH) is a debilitating condition characterized by incomplete formation of the acetabulum leading to dislocation of the femur, suboptimal joint function, and accelerated wear of the articular cartilage resulting in arthritis. DDH affects 1 in 1000 newborns in the United States; there are well-defined "pockets" of high prevalence in Japan, and in Italy and other Mediterranean countries. Although reasonably accurate for detecting gross forms of hip dysplasia, existing techniques fail to find milder forms of dysplasia. Undetected hip dysplasia is the leading cause of osteoarthritis of the hip in young individuals, causing over 40% of cases in this age group. A sensitive and specific test for DDH has remained a desirable yet elusive goal in orthopedics for a long time. A 72-member, four-generation affected family has been recruited, and DNA from its members retrieved. Genomewide linkage analysis revealed a 2.61-Mb candidate region (38.7-41.31 Mb from the p term of chromosome 3) co-inherited by all affected members with a maximum logarithm (base 10) of odds (LOD) score of 3.31. Whole exome sequencing and analysis of this candidate region in four severely affected family members revealed one shared variant, rs3732378, that causes a threonine (polar) to methionine (non-polar) alteration at position 280 in the transmembrane domain of CX3CR1. This mutation is predicted to have a deleterious effect on its encoded protein, which functions as a receptor for the ligand fractalkine. By Sanger sequencing this variant was found to be present in the DNA of all affected individuals and obligate heterozygotes. CX3CR1 mediates cellular adhesive and migratory functions and is known to be expressed in mesenchymal stem cells destined to become chondrocytes. A genetic risk factor that might be among the etiologic factors for the family in this study has been identified, along with other possible aggravating mutations shared by four severely affected family members. These findings might illuminate the molecular pathways affecting chondrocyte maturation and bone formation.

Joined at the hip? A paleoepidemiological study of developmental dysplasia of the hip and its relation to swaddling practices among indigenous peoples of North America

OBJECTIVES

Clinical prevalence of developmental dysplasia of the hip (DDH) is the highest among modern indigenous populations of North America, yet no systematic study of the paleoepidemiology of this group exists. This study discusses the skeletal criteria, epidemiology, pathophysiology, and risk factors for DDH. A range of cases of DDH from an archaeological Native American population are described, and the clinical and prehistoric prevalence of DDH among indigenous populations of North America are calculated and discussed within a biocultural perspective.

METHODS

Pelves of 390 adults from the Late Prehistoric (1490 BP ± 70) Buffalo site, West Virginia were examined for DDH. Morphology of true and false acetabula was classified and other changes of the pelvis, lower limb, and spine were noted along with cranial deformation, providing evidence of infant restriction. Prevalence of DDH among living and archaeological indigenous peoples of North America were calculated and compared.

RESULTS

DDH was identified in eighteen adults from Buffalo, resulting in a prevalence of 46.15, within the range reported in modern indigenous groups in North America. However, there is a significant difference between the DDH prevalence in prehistory and today in the target population.

CONCLUSIONS

Indigenous peoples of North America have the highest reported global prevalence of DDH today and in prehistory. The etiology of DDH suggests that components of both genetic predisposition and swaddling practices have combined to create a high-risk environment for the development of DDH, contributing to its high prevalence within archaeological populations, like Buffalo, and modern Native American/Aboriginal groups within North America.

Variations of the COL1A1 gene promoter and the relation to developmental dysplasia of the hip

AIM

Developmental dysplasia of the hip (DDH) is one of the most common hip deformities in children. Since the COL1A1 gene is located in the DDH relating region, we investigated the COL1A1 promoter variations in the development of DDH.

RESULTS

We collected 154 unrelated female patients and 180 matched healthy female children, and then sequenced the COL1A1 gene promoter for detection of variations. Three variations in the COL1A1 gene promoter were detected in ten patients (T-139C, C-106T, and C-35T [rs113647555]), but none of the 180 health controls. The chi-square test showed that the rate of total variations in COL1A1 gene contributed to DDH (p=0.0016).

CONCLUSION

We detected three variations in the COL1A1 gene promoter in patients and first demonstrated that the higher rate of total variations of COL1A1 gene contributed to DDH in Chinese female children; thus, the COL1A1 gene is a new candidate gene for DDH disease.

Heritability and sibling recurrent risk of developmental dysplasia of the hip in Chinese population

BACKGROUND

Previous familial segregation studies supported that developmental dysplasia of the hip (DDH) is a multifactorial genetic disease. However, the exact extent of genetic effects has not been fully evaluated, especially in Asian population. The aim of this study is to estimate the sibling recurrent risk and heritability of DDH in a large Chinese cohort.

MATERIALS AND METHODS

Four hundred and twenty-nine DDH probands and 534 matched normal controls were recruited from a screening programme for DDH, including 628 siblings in families of probands and 889 siblings in those of controls, respectively. The detailed information of family history was obtained, and the prevalence of DDH among siblings of probands, as well as controls, was determined. The sibling recurrent risk and heritability was estimated using classical liability threshold model.

RESULTS

Eighty-seven siblings (13.85%) in families of proband and 14 siblings (1.57%) in normal control families were diagnosed as DDH. The recurrent risk in siblings of probands was at least tenfolds that in siblings of controls. Compared with the normal controls, the sibling recurrent risk was about 12-fold increase in male sib, and 9-fold increase in female sib. Overall, a high heritability of 83.59 ± 4.90% (h(2) ± SE) was observed. When stratified by genders, it was even higher for female siblings (91.02 ± 7.25%).

CONCLUSION

This study for the first time exhibits a high sibling recurrent risk and heritability for DDH in Asian population. It also shows there is a high probability to identify the underlying predisposition genes in future genetic study.

Demographic differences in adolescent-diagnosed and adult-diagnosed acetabular dysplasia compared with infantile developmental dysplasia of the hip

BACKGROUND

Acetabular dysplasia is a common cause of hip pain that can lead to premature osteoarthritis. This study explores whether demographic characteristics of patients diagnosed with acetabular dysplasia in adolescence and adulthood [adult-diagnosed dysplasia (AD)] differ from those who are diagnosed with developmental dysplasia of the hip (DDH) in infancy.

METHODS

Database review identified 633 patients undergoing periacetabular osteotomy for dysplasia from August 1991 to January 2008. Excluding patients with syndromal conditions and 80 lacking contact information, 421 patients received a questionnaire regarding birth and family history; 324 (70.3%) completed the survey. Thirteen were excluded because of unrelated hip conditions, leaving 311 patients for analysis.

RESULTS

Respondents were divided into 2 groups according to whether they had a history of DDH in infancy (102 patients) or were diagnosed in adolescence/adulthood (209 patients). Statistically significant differences (P < 0.05) were found in sex distribution (female: DDH = 98.0%, AD = 88.0%), affected limb (left hip: DDH = 33.3%, AD = 19.1%), bilaterality (DDH = 45.1%, AD = 61.2%), and breech presentation (DDH = 25.3%, AD = 9.4%). Over 50% of all the respondents had a family history of hip disease; over 40% were first-order relatives. First-order family members of patients with AD had a higher incidence of hip replacement by the age of 65 (50.0% vs. 22.7%). Patients with DDH were more likely to have first-order family members with DDH (59.0% vs. 15.8%).

CONCLUSIONS

This study confirms demographic differences between patients diagnosed with hip dysplasia in infancy versus adolescence/adulthood and supports the hypothesis that these represent distinct forms of dysplasia. In both, there is a familial tendency toward hip disease with a higher incidence of arthroplasty in the AD group's family members and higher frequency of infantile dysplasia in the DDH group's family members.

CLINICAL RELEVANCE

Infantile DDH is diagnosed with neonatal examination and patients are routinely followed into adolescence. Adolescent/adult AD is not detected until symptoms develop. Further study is needed to determine whether younger family members of patients with hip osteoarthritis should be screened to detect potentially at-risk hips.

Genetic study on developmental dysplasia of the hip

BACKGROUND

Developmental dysplasia of the hip (DDH) is a developmental disorder of the hip joint that results in an abnormal socket of the femoral head, ranging from instability, subluxation and complete dislocation of the hip joint. DDH has a considerable genetic component.

DESIGN

We reviewed the recent progress on genetic study of DDH.

RESULTS

By linkage and case-control association studies, DDH loci have been identified with several susceptibility genes that involve in bone and joint biology; however, no unequivocal genes with global significance have been detected. The current problem of the association study in DDH is discussed.

CONCLUSIONS

By advanced technologies and international collaboration, we need to find more susceptibility genes and bridge the gap between genetic evidence and molecular mechanisms.

Association analysis between HOXD9 genes and the development of developmental dysplasia of the hip in Chinese female Han population

Background

Developmental dysplasia of the hip (DDH) is a congenital or acquired deformation or misalignment of the hip joint which affects mainly females. We hypothesized that HOXD9 gene could be regulated in acetabular size or shape and related in DDH developing.

Methods

Two hundred and nine Chinese Han female DDH patients and 173 ethnic, age matched healthy female controls were genotyped for HOXD9 two tag SNPs using sequenom method.

Results

One of the two tag SNPs, rs711822, was not shown significantly differences in genotypic or allelic distribution between case and control group. Comparing the genotypic distribution of rs711819, there was significant differences between DDH patients group and control group (χ2 = 7.54, df =2, P =0.023), and the association to DDH developing reached significance (P =0.045, OR =1.79, 95 % CI: 1.01-3.17 by dominant mode).

Conclusion

In conclusion, the association between one tag SNP of HOXD9 gene and the development of DDH reach significant in our study population, this result indicate the positive correlation between HOXD9 gene and DDH developing. Further study in larger sample size and different population as well as functional studies will help to understand the pathogenesis of DDH.

Variable expression and incomplete penetrance of developmental dysplasia of the hip: clinical challenge in a 71-member multigeneration family

Developmental dysplasia of the hip is a crippling condition that affects children and adults. Identical twin studies support a strong causative genetic component. Although clinical tests for newborns can detect gross malformations, it is the subtle malformations that are often not detected, resulting in early onset osteoarthritis of the hip in adults. As a first step in identifying the causative mutation, we have recruited the largest documented affected family with 71 members spanning generations. Clinical and radiographic signs of developmental dysplasia of the hip are described, and the diagnostic challenge of identifying affected family members is discussed.Variable expression of disease allele is evident in several members of the family and greatly contributes to the diagnostic challenge facing clinicians.

Etiology of osteoarthritis: genetics and synovial joint development

Osteoarthritis (OA) has a considerable hereditary component and is considered to be a polygenic disease. Data derived from genetic analyses and genome-wide screening of individuals with this disease have revealed a surprising trend: genes associated with OA tend to be related to the process of synovial joint development. Mutations in these genes might directly cause OA. In addition, they could also determine the age at which OA becomes apparent, the joint sites involved, the severity of the disease and how rapidly it progresses. In this Review, I propose that genetic mutations associated with OA can be placed on a continuum. Early-onset OA is caused by mutations in matrix molecules often associated with chondrodysplasias, whereas less destructive structural abnormalities or mutations confer increased susceptibility to injury or malalignment that can result in middle-age onset. Finally, mutations in molecules that regulate subtle aspects of joint development and structure lead to late-onset OA. In this Review, I discuss the genetics of OA in general, but focus on the potential effect of genetic mutations associated with OA on joint structure, the role of joint structure in the development of OA--using hip abnormalities as a model--and how understanding the etiology of the disease could influence treatment.

The epidemiology and demographics of hip dysplasia

The etiology of developmental dysplasia of the hip (DDH) is unknown. There are many insights, however, from epidemiologic/demographic information. A systematic medical literature review regarding DDH was performed. There is a predominance of left-sided (64.0%) and unilateral disease (63.4%). The incidence per 1000 live births ranges from 0.06 in Africans in Africa to 76.1 in Native Americans. There is significant variability in incidence within each racial group by geographic location. The incidence of clinical neonatal hip instability at birth ranges from 0.4 in Africans to 61.7 in Polish Caucasians. Predictors of DDH are breech presentation, positive family history, and gender (female). Children born premature, with low birth weights, or to multifetal pregnancies are somewhat protected from DDH. Certain HLA A, B, and D types demonstrate an increase in DDH. Chromosome 17q21 is strongly associated with DDH. Ligamentous laxity and abnormalities in collagen metabolism, estrogen metabolism, and pregnancy-associated pelvic instability are well-described associations with DDH. Many studies demonstrate an increase of DDH in the winter, both in the northern and southern hemispheres. Swaddling is strongly associated with DDH. Amniocentesis, premature labor, and massive radiation exposure may increase the risk of DDH. Associated conditions are congenital muscular torticollis and congenital foot deformities. The opposite hip is frequently abnormal when using rigorous radiographic assessments. The role of acetabular dysplasia and adult hip osteoarthritis is complex. Archeological studies demonstrate that the epidemiology of DDH may be changing.

Association of interleukin-6 and transforming growth factor-β1 gene polymorphisms with developmental hip dysplasia and severe adult hip osteoarthritis: a preliminary study

Developmental hip dysplasia (DDH) greatly contributes to occurrence of severe hip osteoarthritis (OA) in adulthood, but the association between the two is not a perfect one. Both conditions are known to have a strong genetic component. Transforming growth factor β1 (TGF-β1) and interleukin-6 (IL-6) are two pro-inflammatory cytokines included in pathogenesis of OA, bone remodeling and development of bone and joint tissues. TGF-β1 gene has a polymorphic site in the signal sequence ((29)T→C) and "C allele carriage" is associated with higher circulating TGF-β1 levels. IL-6 gene has several polymorphic sites in the promoter region including -572T→C transition associated with higher circulating IL-6 levels. As a preliminary investigation on possible association between these polymorphisms and severe adult hip OA secondary to DDH, 28 consecutive patients and 20 healthy controls were genotyped at these loci. With adjustment for sex, "C allele carriage" in the TGF-β1 signal sequence and CC genotype ("transition homozygous") at locus -572 in the IL-6 promoter were each associated with severe OA secondary to DDH (OR=13.4, p=0.016 and OR=6.2, p=0.024, respectively). The combination of these genotypes was particularly strongly associated with the disease (OR=11.1, p<0.001). Data support feasibility of larger-scale studies on potential association between TGF-β1 signal sequence and IL-6 promoter polymorphisms and occurrence of DDH and (un)related severe OA.

Differential genetic regulation of canine hip dysplasia and osteoarthritis

BACKGROUND

Canine hip dysplasia (HD) is a common polygenic trait characterized by hip malformation that results in osteoarthritis (OA). The condition in dogs is very similar to developmental dysplasia of the human hip which also leads to OA.

METHODOLOGY/PRINCIPAL FINDINGS

A total of 721 dogs, including both an association and linkage population, were genotyped. The association population included 8 pure breeds (Labrador retriever, Greyhounds, German Shepherd, Newfoundland, Golden retriever, Rottweiler, Border Collie and Bernese Mountain Dog). The linkage population included Labrador retrievers, Greyhounds, and their crosses. Of these, 366 dogs were genotyped at ∼22,000 single nucleotide polymorphism (SNP) loci and a targeted screen across 8 chromosomes with ∼3,300 SNPs was performed on 551 dogs (196 dogs were common to both sets). A mixed linear model approach was used to perform an association study on this combined association and linkage population. The study identified 4 susceptibility SNPs associated with HD and 2 SNPs associated with hip OA.

CONCLUSION/SIGNIFICANCE

The identified SNPs included those near known genes (PTPRD, PARD3B, and COL15A1) reported to be associated with, or expressed in, OA in humans. This suggested that the canine model could provide a unique opportunity to identify genes underlying natural HD and hip OA, which are common and debilitating conditions in both dogs and humans.