Quantifying the tolerance of chick hip joint development to temporary paralysis and the potential for recovery.

BACKGROUND: Abnormal fetal movements are implicated in joint pathologies such as arthrogryposis and developmental dysplasia of the hip (DDH). Experimentally induced paralysis disrupts joint cavitation and morphogenesis leading to postnatal abnormalities. However, the developmental window(s) most sensitive to immobility-and therefore the best time for intervention-have never been identified. Here, we systematically vary the timing and duration of paralysis during early chick hip joint development. We then test whether external manipulation of immobilized limbs can mitigate the effects of immobility. RESULTS: Timing of paralysis affected the level of disruption to joints, with paralysis periods between embryonic days 4 and 7 most detrimental. Longer paralysis periods produced greater disruption in terms of failed cavitation and abnormal femoral and acetabular geometry. External manipulation of an immobilized limb led to more normal morphogenesis and cavitation compared to un-manipulated limbs. CONCLUSIONS: Temporary paralysis is detrimental to joint development, particularly during days 4 to 7. Developmental processes in the very early stages of joint development may be critical to DDH, arthrogryposis, and other joint pathologies. The developing limb has the potential to recover from periods of immobility, and external manipulation provides an innovative avenue for prevention and treatment of developmental joint pathologies.

Effects of normal and abnormal loading conditions on morphogenesis of the prenatal hip joint: application to hip dysplasia.

Joint morphogenesis is an important phase of prenatal joint development during which the opposing cartilaginous rudiments acquire their reciprocal and interlocking shapes. At an early stage of development, the prenatal hip joint is formed of a deep acetabular cavity that almost totally encloses the head. By the time of birth, the acetabulum has become shallower and the femoral head has lost substantial sphericity, reducing joint coverage and stability. In this study, we use a dynamic mechanobiological simulation to explore the effects of normal (symmetric), reduced and abnormal (asymmetric) prenatal movements on hip joint shape, to understand their importance for postnatal skeletal malformations such as developmental dysplasia of the hip (DDH). We successfully predict the physiological trends of decreasing sphericity and acetabular coverage of the femoral head during fetal development. We show that a full range of symmetric movements helps to maintain some of the acetabular depth and femoral head sphericity, while reduced or absent movements can lead to decreased sphericity and acetabular coverage of the femoral head. When an abnormal movement pattern was applied, a deformed joint shape was predicted, with an opened asymmetric acetabulum and the onset of a malformed femoral head. This study provides evidence for the importance of fetal movements in the prevention and manifestation of congenital musculoskeletal disorders such as DDH.

Immobilized chicks as a model system for early-onset developmental dysplasia of the hip.

We have almost no understanding of how our joints take on their range of distinctive shapes, despite the clinical relevance of joint morphogenesis to postnatal skeletal malformations such as developmental dysplasia of the hip (DDH). In this study, we investigate the role of spontaneous prenatal movements in joint morphogenesis using pharmacological immobilization of developing chicks, and assess the system as a suitable model for early-onset hip dysplasia. We show that, prior to joint cavitation, the lack of dynamic muscle contractions has little impact on the shape of the hip joint. However, after the timepoint at which cavitation occurs, a dramatic effect on hip joint morphogenesis was observed. Effects in the immobilized chicks included flattening of the proximal femur, abnormal orientation of the pelvis relative to the femur and abnormal placement and coverage of the acetabulum. Although many clinical case studies have identified reduced or restricted movement as a risk factor for DDH, this study provides the first experimental evidence of the role of prenatal movements in early hip joint development. We propose that the immobilized chick embryo serves as a suitable model system for the type of early-onset DDH which arises due to neuromuscular conditions such as spinal muscular atrophy.

Morphometric and ultrasonographic study of the human fetal hip joint during intrauterine development.

UNLABELLED: The main method for the early screening of the developmental dysplasia of the hip (DDH) is the ultrasound imaging. There are several studies about the ultrasound imaging of newborns' hips, but only a few studies include the prenatal period of life. Our aim was to examine the prenatal development of the hip joint through the evolution of the α angle seen on the ultrasound, described in the Graf R method, combined with anatomical dissection. MATERIALS AND METHODS: Thirty-one post-mortem fetal hips were analyzed trough anatomical dissection, in 25 cases trough ultrasound imaging, in which the α angle was measured. Based on the morphometric examination, we applied the sine rule and we calculated the α1 angle, which also represents the coverage of the femoral head. RESULTS: Based on the morphometric examination, not only the diameters of the femoral head and of the acetabulum, but also the joint cavity (X) showed an increase during development. Both of the α angles (measured α, calculated α1) showed a decrease as the fetus developed. CONCLUSIONS: The decrease of the angles (α, α1) and the increase of the joint cavity during development correspond to the findings of the main research papers: the hip joint is less stable in the perinatal life. The α angle can be accurately determined only after the ossification of the acetabulum had started, in our case after the fetus is older than 18 weeks.

Vascularity and histology of fetal labrum and chondrolabral junction: its relevance to chondrolabral detachment tears.

PURPOSE: Recently, acetabular labral tears were recognized as a source of hip pain. Most of these tears were found to be localized at the chondrolabral junction. The purpose of this study was to evaluate the chondrolabral junction in reference to its collagen fiber orientation and its vascularity, which might be used to explain the preponderance of labral tears. METHODS: Eighteen formalinized fetuses with a mean gestational age of 17 weeks (range: 11-24 weeks) were examined. The acetabuli were removed en bloc with the proximal femur for ease of orientation. The acetabuli were prepared and examined in four quadrants, namely, anterior, superior, posterior, and inferior. RESULTS: The staining pattern of the posteroinferior labrum was more dense than the anterosuperior labrum, due to its high collagen content. Collagen fibers in the posteroinferior quadrants were oriented perpendicularly to the chondrolabral junction, while those in the anterosuperior quadrants had a parallel oriented. Perpendicular collagen orientation and high collagen content may explain the stronger anchorage of the labrum to the bony acetabulum in posteroinferior quadrants. All of the vessels supplying the labrum originate from the capsular connective tissue and traverse the body of the labrum to reach the articular side. None of these vessels traverse the chondrolabral junction to reach the bony acetabulum. The total number of blood vessels was significantly higher in the capsular zone than in the articular zones. The number of blood vessels did not differ between the acetabular quadrants. CONCLUSIONS: In an effort to understand the chondrolabral junction tears, we can conclude that collagen content and fiber orientation may represent the histological basis for the predominance of tears at the anterosuperior region.

An approach to comparative anatomy of the acetabulum from amphibians to primates.

The objective of this study was to investigate the anatomy, both macroscopic and microscopic, of the soft tissue internal structures of the hip joint in animal species and in three human hips (an adult and two fetuses). We dissected the hip joints of 16 species and compared the anatomical features of the soft tissue from the respective acetabula. In addition, a histological study was made of the specimens studied. In amphibians, we found a meniscus in the acetabulum, which was not observed in any of the other species studied. The isolated round ligament is observed from birds onwards. In the group of mammals analysed, including the human specimens, we found a meniscoid structure in the acetabular hip joint. Furthermore, we found that the meniscoid structure forms an anatomo-functional unit with the round ligament and the transverse ligament of the coxofemoral joint. These discoveries suggest the participation of the soft tissue anatomy in adaptative changes of species.

The labro-acetabular complex.

The human hip is subjected to several hundred million loading cycles during a lifetime. Hip instability and femoro-acetabular impingement cause damage to the rim of the acetabulum. The acetabular rim is a highly specialized structure known as the labro-acetabular complex. A unidirectional flow of synovial fluid has been identified in this region. The synovial fluid circulation is driven by the bellows-like movement of the zona orbicularis and depends on hip flexion and extension. Surgical repair of the damaged labro-acetabular complex should satisfy two goals. First, the labrum should be preserved or reconstructed when possible. Second, the precipitating cause of the labro-acetabular damage must be addressed.

Embryology of the acetabular labral-chondral complex.

Damage to and repair of the acetabular labral-chondral complex are areas of clinical interest in the treatment of young adults with pain in the hip and in the prevention of degenerative arthritis of the hip. There are varying theories as to why most acetabular tears are located anterosuperiorly. We have studied the prenatal development of the human acetabular labral-chondral complex in 11 fetal hips, aged from eight weeks of gestation to term. There were consistent differences between the anterior and posterior acetabular labral-chondral complex throughout all ages of gestation. The anterior labrum had a somewhat marginal attachment to the acetabular cartilage with an intra-articular projection. The posterior labrum was attached and continuous with the acetabular cartilage. Anteriorly, the labral-chondral transition zone was sharp and abrupt, but posteriorly it was gradual and interdigitated. The collagen fibres of the anterior labrum were arranged parallel to the labral-chondral junction, but at the posterior labrum they were aligned perpendicular to the junction. We believe that in the anterior labrum the marginal attachment and the orientation of the collagen fibres parallel to the labral-chondral junction may render it more prone to damage than the posterior labrum in which the collagen fibres are anchored in the acetabular cartilage. The anterior intra-articular projection of the labrum should not be considered to be a pathological feature.

Measuring hip development using magnetic resonance imaging.

BACKGROUND: Abnormal hip development can have severe consequences if not detected and treated early. Previous studies have shown that if the abnormality is detected early, the outcome is good. Much is known about embryological hip development (weeks 1-10 after conception) from postmortem examination. For ethical reasons, information about hip development in the fetal stage of pregnancy (10 weeks to term) is less certain as it is largely gained from animal studies and from early radiograph studies. A few autopsy-based studies have been reported looking at hip development, but no one has shown, to our knowledge, that postmortem magnetic resonance is able to provide the same and possibly more information. The aim of this study was to assess the value of magnetic resonance imaging in providing information on fetal hip development. METHODS: Measurements of 30 patients (gestation, 17-42 weeks) were made regarding the width and depth of the acetabulum and the radius and diameter of the femoral head; volume and area were calculated. RESULTS: With the exception of the acetabular width, each dimension showed little development until week 20 when growth rose exponentially. The acetabular width showed a slow rate of growth, despite changes in the femoral head. Levels of observer agreement were high for all but depth (intraclass correlation coefficients, 0.90). CONCLUSIONS: The measurements were in line with previous postmortem studies. Magnetic resonance imaging is a valid alternative to postmortem in the assessment of hip development. Magnetic resonance imaging has the potential to alert clinicians to the possible abnormal development, allowing early intervention. STUDY DESIGN: Cross-sectional study with purposive sampling.

Growth and development of the child's hip.

The child's hip begins in intrauterine development as a condensation of mesoderm in the lower limb bud that rapidly differentiates to resemble the adult hip by eight weeks of life. The developmental instructions are transmitted through complicated cell signaling pathways. From eight weeks of development to adolescence, further growth of the hip is focused on differentiation and the establishment of the adult arterial supply. The postnatal growth of the child's hip is a product of concurrent acetabular and proximal femoral growth from their corresponding growth plates. Absence of appropriate contact between acetabulum and proximal femur yields an incongruent joint. Multiple disease processes may be understood in light of this growth process, including Legg-Calvé-Perthes disease and developmental dysplasia of the hip.

Prenatal development of the human pelvis and acetabulum.

The prenatal development of the human pelvic bone and acetabulum has been studied by means of classical histology and microradiography. The embryonic phase leads to a fully developed hip within 8 weeks of gestation. The fetal period is a growth phase, including the following main features: endochondral ossification of the ilium from the ninth week, asymmetrical development of the iliac shaft from the fifteenth week, "chondroid-like" tissue formation above the acetabulum from the twenty-sixth week and haversian bone remodelling from the twenty-eighth week. The fetal development of the pelvis and acetabulum seems to be highly related to mechanical stimuli, the most important being the gluteal muscular activity and the simultaneous pressure of the femoral head.

Anatomic study of the pre- and neonatal hip. Physiopathologic considerations on dysplasia and congenital dislocation of the hip.

Therapeutic success in dysplasia and congenital dislocation of the hip depends on an early diagnosis. The physiopathology remains very debatable and several concepts are propounded. For a better physiopathologic understanding, the authors have carried out a study of the morphology and development of 22 pre- and neonatal hips. At first, the acetabulum is cartilaginous and distorted by the moving femoral head; this acetabulum is histologically affected by the femoral pressure. The pathologic hip is characterized by defective posterior bony coverage of the femoral head by the acetabulum. The acetabulum ossifies during the 3 months following birth, forming a cup-like cavity under the pressure of the femoral head. Therefore, neonatal screening tests such as sonography must take place in the first weeks of life.

[Ultrasound anatomy of the fetal hip joint with special reference to the blood supply]. / Sonoanatomie des fetalen Hüftgelenks unter besonderer Berücksichtigung der Blutversorgung.

AIM: Study of the anatomy of the fetal hip joint in 115 pregnancies between 13. to 40.th weeks of gestation by ultrasound. METHOD: Sonoanatomy was studied by high resolution ultrasound (Acuson 128). For investigation of vascular supply of the fetal hip, colour-coded Doppler sonography was performed. In-vivo studies on vascular supply were correlated with histological sections of 34 fetal hip specimens, according to the conceptional age of 13-35 weeks. RESULTS: Vascular studies of the proximal end of the human femur showed a supply by the lateral and medial femoral circumflex arteries branched from the femoral artery or the deep femoral artery. After 22 weeks of gestation the acetabular artery supplied by the obturator artery was visible by means of Doppler sonography. At the end of pregnancy, large numbers of intraosseous blood vessels are demonstrable within the femoral head and neck. CONCLUSION: The basic arterial pattern of the hip joint is established at birth. Proximal end of the growing femur, acetabulum, os ilium and labrum acetabulare are clearly visible by ultrasound.

The acetabular notch in hip dysplasia.

In the first few months of life, a notch may be seen on radiographs of the superolateral margin of the infant hip. It may be associated with a steeply inclined acetabular roof and may be an indicator of persistent neonatal instability or displacement of the femoral head.

The fetal acetabulum. A histomorphometric study of acetabular anteversion and femoral head coverage.

To study the development of the acetabulum in the early fetal period, 39 embryologic specimens were reviewed in detail. Histologic serial sections were made through 47 hips in the transverse plane. Measurements of acetabular anteversion and femoral head coverage revealed that both parameters depend on the exact level of sectioning. However, when measured at the level of the maximum diameter of the femoral head, they did not show significant variation through the embryonic and early fetal stages (six to 20 weeks). This is in contradistinction to the late fetal period. The hip does remain covered during this early fetal period. Congenital dislocation of the hip is not an early developmental condition. This accounts for the absence of any reports of hip dislocations in the first half of gestation.

Arterial supply of the acetabulum in the fetus: application to periacetabular surgery in childhood.

The need to perform triple osteotomies of the pelvis passing very close to the articular surface leads to the isolation of bony fragments whose vascularisation may be precarious. To assess the risks of such surgery, we undertook an anatomic study of the vascularisation of the acetabulum in the fetus. 53 specimens were injected to study the vessels to the acetabulum and their distribution within the osteocartilaginous specimen. The acetabular a., a branch of the obturator a., gives a central pedicle distributed to the acetabular fossa, the triradiate cartilage and ending in the three primary bony components. The superior gluteal, inferior gluteal, internal pudendal and obturator aa. form a periacetabular vascular circle. The abundant vascularity of the acetabulum makes massive necrosis improbable in the child. However, there is a zone of precarious anastomosis at the anterior portion of the acetabulum.

[Aging process of the acetabular labrum--an electron-microscopic study].

We have studied the aging process of the labrum of the hip using scanning and transmission electron-microscopes. The materials consisted of 22 human hip joint acetabula. Disruption and irregular ridges were evident on the uppermost superficial layer and the superficial layer of the labrum in their fifties of age. Collagen fibers composing the labrum increased in density and sectional area in the specimens of subjects up to their twenties, but decreased in those of subjects in their thirties. At the joint of the labrum and articular cartilage, a bundle of fibers approximately 20 microns in diameter was observed to extend from the labrum to the cartilage, reinforcing the bond of these components. Disruption of this area starting on the acetabular side and leaving fibers of the labrum of about 400 to 500 microns on the cartilage side was more frequent in the specimens of subjects in their fifties of age. The changes with aging in the collagen fibers along with concentration of the stress of weight bearing at the point where the labrum meets the cartilage, may have some effect on the well-fitting of the acetabulum and femoral head.