Thesacrococcygealsymphysis(sacrococcygeal articulation,articulation of the sacrum and coccyx) is anamphiarthrodialjoint, formed between the oval surface at the apex of thesacrum,and the base of thecoccyx.
| Sacrococcygeal symphysis | |
|---|---|
 Articulations ofpelvis.Posterior view. | |
 Anterior view. | |
| Details | |
| Identifiers | |
| Latin | articulatio sacrococcygea, symphysis sacrococcygea |
| TA98 | A03.2.08.001 |
| TA2 | 1688 |
| FMA | 16210 |
| Anatomical terminology | |
It is a slightly moveable joint[1]which is frequently, partially or completely, obliterated in old age,[2]homologouswith the joints between the bodies of thevertebrae.
Structure
editArticular disc
editThesacrococcygeal discorinterosseus ligament[3]is similar to theintervertebral discs[2]but thinner, thicker in front and behind than at the sides, and with a firmer texture. The articular surfaces are elliptical with longer transversal axes. The surface on the sacrum is convex and that on the coccyx concave.[2]Occasionally the coccyx is freely movable on the sacrum, most notably duringpregnancy;in such cases asynovial membraneis present.
Ligaments
editThe joint is strengthened by a series of ligaments:
- Theventraloranterior sacrococcygeal ligamentis an extension of theanterior longitudinal ligament(ALL) that runs down along the spine on the anterior sides of thebodies of the vertebrae.It consists of a few irregular fibers that attach to the anterior sides of the sacrum and coccyx and blend with theperiosteum.[1]
- Thedorsalorposterior sacrococcygeal ligamenthas a deep and a superficial part:
- Thedeep dorsal ligamentis a flat band which corresponds to theposterior longitudinal ligament(PLL) that run down inside thevertebral canalon the posterior surfaces of the bodies of the vertebrae. From the posterior side of the fifth sacral body inside the sacral canal, the dorsal ligament stretches to the posterior side of the coccyx, to attach deep to the superficial dorsal ligament.[1]
- Thesuperficial dorsal ligamentcorresponds to theligamenta flavaand closes the posterior aspect of the distal end of the vertebral canal.[1]It stretches frommedian sacral crest[3]and the free margin of thesacral hiatus[1]to the dorsal surface of the coccyx.[1]
- Thelateral sacrococcygeal ligamentsrun from the lower lateral angles of the sacrum to thetransverse processesof the first coccygeal vertebra to complete theforaminafor thelast sacral nerve.[1]Three lateral ligaments have been reported on either side.[3]
- Theinterarticularorintercornual sacrococcygeal ligamentsstretches from thecornuof the sacrum to the cornu of the coccyx.[1]
Function
editMovements in the joint are restricted toflexionandextension.These essentially passive movements occurs duringdefecationandlabour.When movements in the sacrum increase the anteroposterior diameter of thepelvic outlet,movements in the sacrococcygeal joint can further increase this diameter.[2]
Clinical significance
editThe joint ispalpabledeep within thenatal cleft,and can be felt as a horizontal groove. With the palpating finger on the dorsal surface of the coccyx, a degree of rotation can be produced with an applied forward pressure.[2]
See also
edit- Anococcygeal raphé
- Coccydynia(coccyx pain, tailbone pain)
- Ganglion impar
- Rump (croup)
Notes
editReferences
edit
This article incorporates text in thepublic domainfrompage 309of the 20th edition ofGray's Anatomy(1918)
- Morris, Craig E. (2005).Low Back Syndromes: Integrated Clinical Management.McGraw-Hill.ISBN0-07-137472-8.
- Huijbregts, Peter A. (2001). "In: Current Concepts of Orthopaedic Physical Therapy".Lumbopelvic region: Anatomy and biomechanics(PDF).APTA.
- Masquelet, Alain C.; Christopher J. McCullough; Ian S. Fyfe; Raoul Tubiana (1993).An Atlas of Surgical Exposures of the Lower Extremity.Taylor & Francis.ISBN1-85317-003-8.(A good illustration of the posterior and lateral ligaments.)
- Palastanga, Nigel; Field, Derek; Soames, Roger (2006).Anatomy and Human Movement: Structure and Function.Elsevier Health Sciences.ISBN0-7506-8814-9.
