Fibrocartilage in tendons and ligaments--an adaptation to compressive load.
Where tendons and ligaments are subject to compression, they are frequently fibrocartilaginous. This occurs at 2 principal sites: where tendons (and sometimes ligaments) wrap around bony or fibrous pulleys, and in the region where they attach to bone, i.e. at their entheses. Wrap-around tendons are most characteristic of the limbs and are commonly wider at their point of bony contact so that the pressure is reduced. The most fibrocartilaginous tendons are heavily loaded and permanently bent around their pulleys. There is often pronounced interweaving of collagen fibres that prevents the tendons from splaying apart under compression. The fibrocartilage can be located within fascicles, or in endo- or epitenon (where it may protect blood vessels from compression or allow fascicles to slide). Fibrocartilage cells are commonly packed with intermediate filaments which could be involved in transducing mechanical load. The ECM often contains aggrecan which allows the tendon to imbibe water and withstand compression. Type II collagen may also be present, particularly in tendons that are heavily loaded. Fibrocartilage is a dynamic tissue that disappears when the tendons are rerouted surgically and can be maintained in vitro when discs of tendon are compressed. Finite element analyses provide a good correlation between its distribution and levels of compressive stress, but at some locations fibrocartilage is a sign of pathology. Enthesis fibrocartilage is most typical of tendons or ligaments that attach to the epiphyses of long bones where it may also be accompanied by sesamoid and periosteal fibrocartilages. It is characteristic of sites where the angle of attachment changes throughout the range of joint movement and it reduces wear and tear by dissipating stress concentration at the bony interface. There is a good correlation between the distribution of fibrocartilage within an enthesis and the levels of compressive stress. The complex interlocking between calcified fibrocartilage and bone contributes to the mechanical strength of the enthesis and cartilage-like molecules (e.g. aggrecan and type II collagen) in the ECM contribute to its ability to withstand compression. Pathological changes are common and are known as enthesopathies. (+info)
Extensive post-traumatic ossification of the patellar tendon. A report of two cases.
Two men, aged 21 and 50 years, were seen with ossification of the patellar tendon after injury to the knee in adolescence. They complained of pain and had patella alta. Large bony masses were excised from below the affected patellae. The patellar tendon was then reconstructed using a Leeds-Keio ligament. The results at six and ten years, respectively, were good, with neither patient having pain or an extension lag. (+info)
Fertility after laparoscopic management of deep endometriosis infiltrating the uterosacral ligaments.
The aim of this study was to evaluate fertility outcome after laparoscopic management of deep endometriosis infiltrating the uterosacral ligaments (USL). From January 1993 to December 1996, 30 patients who presented with no other infertility factors were treated using laparoscopic surgery. The overall rate of intrauterine pregnancy (IUP) was 50.0% (15 patients). Only one of these 15 pregnancies was obtained using in-vitro fertilization techniques (IVF). The cumulative IUP rate for the 14 pregnancies which occurred spontaneously was 48.5% at 12 months (95% confidence interval 28.3-68.7). The rate of spontaneous pregnancies was not significantly correlated with the revised American Fertility Society (rAFS) classification. The rate of IUP was 47.0% (eight cases) for patients with stage I or II endometriosis and 46.1% (six cases) for the patients presenting stage III or IV endometriosis (not significant). These encouraging preliminary results show that in a context of infertility it is reasonable to associate classic treatment for endometriosis (e.g. lysis, i.p. cystectomy, biopolar coagulation of superficial peritoneal endometriotic lesions) with resection of deep endometriotic lesions infiltrating the USL. Apart from the benefit with respect to the pain symptoms from which these patients suffer, it is possible to use laparoscopic surgery with substantial retroperitoneal dissection and enable half of the patients to become pregnant. These results also raise the question of the influence of deep endometriotic lesions on infertility. (+info)
Plantar aponeurosis and internal architecture of the ball of the foot.
On the basis of its internal structure, the ball of the foot can be divided into three transverse areas, each with a different mechanical function: (1) an area proximal to the heads of the metatarsals in which the retinacula cutis are developed into a series of transverse bands, and in which the deep fibres of the plantar aponeurosis form ten sagittal septa connected to the deep transverse metatarsal ligament and through this the proximal phalanges of the toes, (2) an area below the heads of the metatarsals in which vertical fibres from the joint capsules and the sides of the fibrous flexor sheaths form a cushion below each metatarsal head, and in which fat bodies cover the digital nerves and vessels in their passage between the cushions, and (3) a distal area which comprises the interdigital web. The superficial fibres of the plantar aponeurosis are inserted into the skin of this distal area, and deep to them the plantar interdigital ligament forms a series of transverse lamellae connected to the proximal phalanges by a mooring ligament which arches from one fibrous flexor sheath to the next. When the metatarsophalangeal joints are extended, the fibres of the three areas are tensed and the skin is anchored firmly to the skeleton. The direction of the fibres in the distal and proximal area promotes the transfer of forces exerted on the skin during push-off and braking respectively, while the intermediate area is adapted to bear the weight of the body. A concentration of Pacinian corpuscles is found along the digital nerves in the weight-bearing area below the transverse metatarsal ligament. The nerves for the second, and especially for the third, interstice are close to or in contact with the sharp proximal edges of the sagittal septa. (+info)
Effect of androgens on the cranial suspensory ligament and ovarian position.
Androgens have been postulated to have a major role in testicular descent via regression of the cranial suspensory ligament, which in normal rodents anchors the ovary to the retroperitoneum near the lower pole of the kidney. This study aimed to quantitate the degree of descent of the foetal ovary in androgen-treated female mice to determine the role of androgens in regression of the cranial suspensory ligament and descent of the testis. Time-pregnant mice were injected with testosterone propionate or methyl testosterone (2.5-3.0 mg) in vehicle on day 13 or 14. Control animals received vehicle only. Newborn mice were anaesthetised and dissected for macroscopic anatomy of the ovary, which was quantified by measuring the vertical distance from the lower pole of the kidney to the lower pole of the ovary. Histological analysis was also performed. The external genitalia were masculinised in all females exposed to prenatal androgens. The ovaries of treated animals were mobile, with no cranial suspensory ligament, and located slightly caudal to the kidney. Wolffian duct structures were identifiable, but the gubernaculum was qualitatively unchanged compared with control females. The ovary was displaced caudally (P< 0.001), but only 15-25% of the distance to the lower abdomen. Exogenous androgens induce regression of the cranial suspensory ligament, causing the ovary to be more mobile and lower in the abdominal cavity. However, since the testicular position at birth is at or below the bladder neck, androgen-mediated regression of the cranial suspensory ligament is only an adjunct to the control of transabdominal testicular descent. (+info)
The glass point of elastin.
Elastin undergoes a glass transition in a temperature range depends on its water content. This behavior is similar to that of amorphous polymers swollen with solvent and, therefore, is additional evidence for the random network model proposed for the structure of elastin. (+info)
Development of the human elbow joint.
Many studies have been published on the development of the human elbow joint, but authors disagree on its morphogenetic timetable. Most discrepancies center on the cavitation of the elbow joint (including the humeroradial, humeroulnar, and superior radioulnar joints), and the organization of the tunnel of the ulnar nerve. We summarize our observations on the development of the elbow joint in 49 serially sectioned human embryonic (n = 28) and fetal (n = 21) upper limbs. During week 12, ossification begins in the epiphyses of the elements comprising the elbow joint. At the end of the embryonic period, the shallow groove between the posterior aspect of the medial epicondyle and the olecranon process, begins to be visible. The elbow joint cavity appears in O'Rahilly stage 21 (51 days) at the level of the humeroulnar and humeroradial interzones. Formation of the cavity begins at the medialmost portion of the humeroradial interzone and the lateralmost portion of the humeroulnar interzone. The annular ligament begins to develop in O'Rahilly stage 21 (51 days), and the superior radioulnar joint cavity appears between this ligament and the lateral aspect of the head of the radius during O'Rahilly stage 23 (56 days). We established the morphogenetic timetable of the human elbow joint. (+info)
Cirri of the stalked crinoid Metacrinus rotundus: neural elements and the effect of cholinergic agonists on mechanical properties.
Sea lilies are enigmatic animals due to their scarcity and their biology is comparatively neglected. Cirri, arranged in whorls of five along the sea lily stalk, anchor and support the animal. They consist of ossicles interconnected by collagenous ligaments and by a central canal. Cirri have a well-developed nervous system but lack muscular cells. A light and electron microscopic study was performed to clarify the morphology of the nervous system of the cirri. Two cellular networks were found, one of neuron-like cells and one of cells filled with bullet-shaped organelles. Both networks ramify throughout the cirral ossicles up to the interossicle ligaments. Mechanical tests were performed to analyse the influence of cholinergic agonists on the mechanical properties of these ligaments. In the tests, the cirral ligaments softened after the application of acetylcholine, muscarinic agonists and nicotinic agonists. The reaction time to muscarinic agonists was much slower than to acetylcholine and nicotinic agonists. At low concentrations, muscarinic agonists caused active development of force. No reaction to stimuli was observed in anaesthetized cirri. The data clearly establish the existence of catch connective tissue which can change its mechanical properties under nervous control mediated via nerves with cholinergic receptors. The possible sources of the observed force production are discussed and it is concluded that active contraction of collagenous ligaments causes movement of cirri. (+info)