Morphometric study of the fetal development of the human hip joint: significance for congenital hip disease.

Hip joints (280) from 140 human fetuses, obtained from abortions and deaths in the perinatal period, were studied. The fetuses ranged from 8.7 to 40 cm in crown-rump length and are believed to be between 12 and 42 weeks in age. The joints were dissected, morphology inspected, and measurements taken of the depth and diameter of the acetabulum, the diameter of the femoral head, length and width of the ligament of the head, the neck-shaft, and torsion angles of the proximal femur. Regression models were fitted to determine which would best predict the growth pattern. Multivariate analysis of variance showed no significant differences between males and females or between the right and left sides. Acetabular depth was shown to be the slowest-growing hip variable, increasing less than fourfold in the period studied. Acetabular indices less than 50 percent indicate a shallow socket at term. Femoral head and acetabular diameter demonstrated a strong relationship (r = 0.860) and in many joints the femoral head diameter exceeded that of the acetabulum. Considerable variability was demonstrated in both femoral angles. The femoral angles showed only low correlation with the other hip variables. These observations indicate that soft tissue structures about the joint must play an important role in neonatal joint stability. The explanation of greater female and left side involvement in congenital hip disease must lie in factors other than growth changes of hip dimensions. Neither angle appears to be a useful indicator of normal joint development.     

Prenatal development of the human submandibular gland

The prenatal development of the human submandibular gland has been investigated in 26 fetuses from the 10th week of gestation to full term. At 10-12 weeks, the glandular elements (primitive ducts and acini) were immature and surrounded by a loose mesenchyme. The acinar cell population increased gradually till the age of 32 weeks, and the rate of increase was diminished thereafter. At 16 weeks, intercalated and striated ducts were distinguished and their number increased till the age of 32 weeks when their number seemed to be stabilized. The development of the granular convoluted tubule cells from the proximal segments of striated ducts occupied the later stages of development. They appeared around the age of 20 weeks and proceeded till full term. At birth, the gland appeared devoid of mucous acini and fat cells and the secretory end-pieces were of the serous type. During the second trimester, periodic acid-Schiff- and alcian blue-positive secretory materials appeared in the epithelial cells of both ducts and acini, and in their lumina. This secretory activity was transitory and disappeared around the age of 28 weeks. The possible function of these secretory products is discussed.     

The transmission of load through the human hip joint

This paper describes the results of loading experiments carried out on human hip joints. The unloaded surfaces of the femoral head and the acetabulum are slightly incongruous. The location and magnitude of the contact areas between the surfaces therefore depend on the magnitude and direction of the applied load. The contact areas were determined experimentally for a variety of loads typical of normal walking. Two distinct contact areas were found on the anterior and posterior aspects of the acetabulum at light loads, gradually merging with increasing load until, at a certain transition load, the dome of the acetabulum comes into contact and contact is then complete. The value of the transition load depends on the rate of loading, due to creep of the cartilage, and was found to vary from 50 per cent of body weight in young specimens to 25 per cent of body weight for elderly specimens for rates of loading typical of normal walking. Thus, the dome of the acetabulum is out of contact for a substantial portion of the swing phase of normal walking.

The analysis of a much simplified model of the hip joint is presented. The dependence of contact area on load is demonstrated, but also a method of determining the transition load for complete contact from the load/deflection relation for the hip is suggested. The values of the transition load quoted above were obtained by this method. The analysis further indicates that the distribution of pressure between the articular surfaces depends critically on the distribution of cartilage thickness throughout the joint. It is suggested that the distribution of cartilage thickness is such as to lead to a state of uniform pressure at the upper end of the physiological load range. Some experimental evidence is presented in support of this suggestion.

It is concluded that the function of joint incongruity is to allow the articular surfaces to come out of contact at light loads so that the cartilage may be exposed to synovial fluid for the purposes of nutrition and lubrication. At large loads, the distribution of cartilage thickness ensures that a state of hydrostatic pressure is achieved in order that cartilage, with a large fluid content, may transmit large pressures without flow and consequent loss of its integrity.     

Biomechanical construction principles of the human hip joint in frontal plane

The prognosis of hip joint function is only to determine unsatisfactory on the base of the knowledges of anatomy by means of inspection or angles and distances from X-rays as well as on the base of models known for the biomechanic of hip. The term "normal anatomical" hip structure is analysed with respect to functional biomechanical influences on its macroscopic design in frontal plane. It is shown to interpret the macroscopic hip design as result of an effective arrangement of centre of rotation and muscle forces which a minimum on energy needing for its function. A mathematical equation describes the skeleton-muscle-system hip biomechanically. This new connection between angles and distances as well as first easy consequences are proofed on a-p-hip radiographs of 53 normal adults.     

Prenatal development of the intrinsic nerves of the muscles of the human foot

Myelogenesis and blood supply of the intraorganic nerves have been studied in 4-6- and 7-9-month-old human fetuses. At first, the intramuscular nerves are presented as very thick fasciculi (the diameter is more than 90), thick (the diameter is from 50 up to 90) and single muddle neural fasciculi (the diameter is from 30 up to 50 mcm). The microcirculatory blood bed is formed at the expense of branches of the blood vessel-satellites and the blood vessels of the surrounding tissues and is carried out, without any interruption, along the whole extent. In 7-9-month-old fetuses the neural apparatus becomes more complex. The number of the middle neural fasciculi appear. On the background of fine neural fibers in the fasciculi a small part of the middle neural fibers appears, and in the musculus flexor digitorum brevis--single thick neural fibers. The intramuscular nerves have their own hemocirculatory bed presented by microvessels that are on the perineurium surface, in its bulck and among neural fibers.     

New aspects of the morphology and function of the human hip joint ligaments.

The capsular ligaments of the human hip joint were submitted to exact morphological analysis, and they proved to be multiple and numerous. We have described various ligamentous systems and their interconnections, and have suggested new terminologies and systematics. The ligaments were subjected to functional analysis by means of measuring strips to determine the positions in which the ligaments are taut. The ligament systems were all found to serve a restrictive function, and various parts of the apparatus restricted all possible movements in the hip joint. Extension is restricted by the medial iliofemoral complex, abduction by the pubofemoral ligament, and adduction by the posterior coxal ligaments and by the superior ischiofemoral ligament. Flexion is restricted by the inferior ischiofemoral ligaments, inward rotation by the superior ischiofemoral ligament, and outward rotation by the lateral iliofemoral complex. Only the ligament of the femoral head is unable to exert a restricting function, despite reaching a state of tension in extreme adduction.     

Prenatal human cranial development evaluated on coronal plane radiographs

The purpose of the present investigation has been to analyse prenatal cranial base development in the coronal plane and to combine the findings with results in former reports on cranial base maturation estimated in the horizontal and sagittal planes. The study is based upon cranial bases of 26 human fetuses from the first half of the prenatal period. Fetal coronal plane cranial base tissue blocks were dissected, radiographed, and sectioned for microscopic examination. Five stages in cranial base development are defined and related to general parameters for fetal size and fetal maturation. Two different maturation patterns were recognized in the sphenoid corpus. Canal structures, remnants of the craniopharyngeal canal, were observed in specimens showing bilateral centers of ossification in the sphenoid corpus. The radiographic method used is easy to record and recommended for diagnosing prenatal and neonatal cranial malformations.     

Prenatal development of the human nucleus ambiguus during the embryonic and early fetal periods

The ontogenetic development of the nucleus ambiguus was studied in a series of human embryos and fetuses ranging from 3 to 12.5 weeks of menstrual age (4 to 66 mm crown-rump length). They were prepared by Nissl and silver methods. Nucleus ambiguus neuroblasts, whose neurites extend towards and into the IXth and rostral Xth nerve roots, appear in the medial motor column of 4-6-week-old embryos (4.25-11 mm). These cells then migrate laterally (6.5 weeks, 14 mm) to a position near the dorsal motor nucleus of X. At 7 weeks (15 mm), nucleus ambiguus cells begin their migration, which progresses rostrocaudally, into their definitive ventrolateral position. The basic pattern of organization of the nucleus is established in its rostral region at 8 weeks (22.2-24 mm) and extends into its caudal region by 9 weeks (32 mm), when its nearly adult organization is evident. Cells having the characteristics of mature neurons first appear rostrally in the nucleus during the 8.5-9-week period (24.5-32 mm), gradually increase in number, and constitute the entire nucleus at 12.5 weeks (65.5 mm). Definitive neuronal subgroups first appear at 10 weeks (37.5 mm) in the large rostral nuclear region. These features suggest that the human nucleus ambiguus develops along a rostrocaudal temporospatial gradient. Evidence indicates that function of nucleus ambiguus neurons, manifested by fetal reflex swallowing, occurs after the cells migrate into their definitive position, establish the definitive nuclear pattern, and exhibit mature characteristics.     

The thixotropic effect of the synovial fluid in squeeze-film lubrication of the human hip joint.

The thixotropic (shear-thinning) effect of the synovial fluid in squeeze-film lubrication of the human hip joint is evaluated, taking into account filtration of the squeezed synovial film by biphasic articular cartilage. A porous, homogeneous, elastic cartilage matrix filled with the interstitial ideal fluid, with the intact superficial zone (of lower permeability and stiffness in compression) already disrupted or worn away, models an early stage of arthritis. Due to a high viscosity of the normal synovial fluid at very low shear rates, the squeezed synovial film at a fixed time after the application of a steady load is found to be much thicker in a small central part of the lubricated contact area. In the remaining part, the film is thin as it corresponds to the Newtonian fluid with the same high-shear-rate viscosity. Filtration is lower for the normal cartilage with the intact superficial zone due to its lower permeability and compression stiffness. But even in the fictitious case of zero filtration, calculations show that the effect of thixotropy on the increase of the minimum synovial film thickness would manifest itself as late as after several tens of seconds since the physiologic load application. At that time, this thickness would be as low as about 0.3 microm. It follows that thixotropy of the normal synovial fluid (and so much more of the inflammatory fluid) is irrelevant in squeeze-film lubrication of both the normal and arthritic human hip joints.     

A morphological and functional analysis of the extent of cartilage coverage in the human hip joint

The extension and the shape of the cartilage surface of 30 human femora and acetabula were measured. The results were considered and discussed as the response of the articular cartilage to the specific stress on this joint. 3 kinds of cartilage distribution were found on the femoral head; these shapes were understood as the consequence of the position and the dwelling time of the actual cartilage stimulating area. The largest extention of the cartilage was found in the ventrolateral direction and the smallest in medial direction. The cartilage margin of the "A" type was regulary curved. The "B" type has an inlet towards the fovea capitis. This inlet reaches in the "C" type to the fovea as an area free of cartilage. The acetabula could not be divided into types with different cartilage distribution because of the great similarity in shape. Therefore we computed an average acetabulum. The largest extension of the facies lunata was found 15 degrees in front of the roof of the acetabulas as seen in x-ray pictures. The cornu anterius is always narrower than the cornu posterius. The outer margin of the osseous acetabulum does not reach the equator, it lies on a latitude of 11.5 degrees. The incisura acetabuli is inclined against the vertical line with 18.3 degrees. The width of the facies lunata can be considered as a result of mechanical stress. The different extensions of the cartilage of both joint components in ventro-lateral direction seems to be the consequence of different extensions of movement. The area of movement of the caput femoris is larger than the area of the acetabulum.