| Pubic symphysis | |
|---|---|
| Symphysis pubis exposed by a coronal section. (Pubic symphysis visible at center left.) | |
| #5 is Pubic symphysis | |
| Latin | symphysis pubica, symphysis pubis |
| Gray's | subject #80 310 |
The pubic symphysis or symphysis pubis is the midline cartilaginous joint (secondary cartilaginous) uniting the superior rami of the left and right pubic bones. It is located anterior to the urinary bladder and superior to the external genitalia; for females it is above the vulva and for males it is above the penis. In males, the suspensory ligament of the penis attaches to the pubic symphysis. In females, the pubic symphysis is intimately close to the clitoris. In normal adults it can be moved roughly 2 mm and with 1 degree rotation. This increases for women at the time of child birth.[1]
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Symphysis pubis is a nonsynovial amphiarthrodial joint, and comes from the Greek word "symphysis", meaning growing together. The anterior width of the symphysis pubis is 3-5 mm greater than its intrapelvic posterior width. This joint is connected by fibrocartilage and may contain a fluid filled cavity; the center is avascular, possibly due to the nature of the compressive forces passing through this joint, which may lead to harmful vascular disease.[2] The ends of both pubic bones are covered by a thin layer of hyaline cartilage attached to the fibrocartilage. The fibrocartilaginous disk is reinforced by a series of ligaments. These ligaments cling to the fibrocartilaginous disk to the point that fibers intermix with it.
Two such ligaments are the superior and inferior, these being the ligaments that provide the most stability; the posterior and anterior ligaments are weaker. The strong and thicker superior ligament is reinforced by the tendons of the rectus abdominis, obliques externus, gracilis and thigh adductors muscles. The inferior ligament in the pubic arch is known as the arcuate pubic ligament.
Fibrocartilage
Fibrocartilage is composed of small chained bundles of thick, clearly defined, type I collagenfibers. This fibrous connective tissue bundles have cartilage cells between them; these cells to a certain extent resemble tendon cells. The collagenous fibers are usually placed in an orderly arrangement parallel to tension on the tissue. It has a low content of glycosaminoglycans (2% of dry weight). Glycosaminoglycans are long, unbranched polysaccharides (relatively complex carbohydrates) consisting of repeating disaccharide units. Fibrocartilage does not have a surrounding perichondrium. Perichondrium surrounds the cartilage of developing bone; it has a layer of dense irregular connective tissue and functions in the growth and repair of cartilage.
Hyaline cartilage
Hyaline cartilage is the white, shiny gristle at the end of long bones. This cartilage has very poor healing potential, and efforts to induce it to repair itself frequently end up with a similar, but poorer fibrocartilage.
Analysis of the pelvis shows the skinny regions function as arches, transferring the weight of the upright trunk from the sacrum to the hips. The symphysis pubis connects these two weight-bearing arches, and the ligaments that surround this pelvic region maintain the mechanical integrity.
The main motions of the symphysis pubis are superior/inferior glide and separation/compression. The functions of the joint are to absorb shock during walking and allow delivery of a baby.
In the newborn, the symphysis pubis is 9-10 mm in width, with thick cartilaginous end-plates. By mid-adolescence the adult size is achieved. During adulthood the end-plates decrease in width to a thinner layer. Degeneration of the symphysis pubis accompanies aging and postpartum. Women have a greater thickness of this pubic disc which allows more mobility of the pelvic bones, hence providing a greater diameter of pelvic cavity during childbirth.
During pregnancy in the human, hormones such as relaxin remodel this ligamentous capsule allowing the pelvic bones to be more flexible for delivery. The non-pregnant gap of the symphysis pubis is 4-5 mm but in pregnancy there will be an increase of at least 2-3 mm, therefore, it is considered that a total width of up to 9 mm between the two bones is normal for a pregnant woman. The symphysis pubis separates to some degree during the birthing process. In some women this separation can become a diastasis of the symphysis pubis. The diastasis could be the result of a rapid birth[3] or a forceps delivery[4] or maybe even be prenatal.[5] A diastasis of the symphysis pubis is a symptom of pelvic girdle pain (PGP). Overall, about 45% of all pregnant women and 25% of all women postpartum suffer from PGP.[6]
Before the Caesarean section technique was available, if labor failed to progress because the head of the fetus was too large, the mother's symphysis pubis was cut and the skull of the fetus was crushed. The Caesarean section has allowed the largely safe delivery of such infants.[7]
In remote, isolated areas, women presenting with a large baby and a small pelvis must travel great distances for medical help; a symphysiotomy has been suggested.[8] This practice was carried out in Europe before the introduction of the Caesarean section.
Metabolic disease, such as renal osteodystrophy, produces widening, while ochronosis results in calcific deposits in the symphysis. Inflammatory disease, such as ankylosing spondylitis, results in bony fusion of the symphysis. Osteitis pubis, the most common inflammatory disease in this area, is treated with anti-inflammatory medication and rest. Degenerative joint disease of the symphysis, which can cause groin pain, results from instability or from abnormal pelvic mechanics.[9]
The pubic symphysis widens slightly whenever the legs are stretched far apart. In sports where these movements are often performed, the risk of a pubic symphysis blockage is high, in which case, after completion of the movement, the bones at the symphysis do not realign correctly and can get jammed in a dislocated position. The resulting pain can be quite severe, especially on further strain put upon the affected joint. In most cases, the joint can only be successfully reduced into its normal position by a trained medical professional.
Pubic symphyses have importance in the field of forensic anthropology, as they can be used to estimate the age of adult skeletons. Throughout life, the surfaces are worn at a more or less predictable rate. By examining the wear of the pubic symphysis, it is possible to estimate the age of the person at death.[10]
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