Coccyx
Description
Alternative Names
- Tailbone
- Os coccygis
- Coccygeal bone
- Coccygeal segment
- Caudal vertebrae
General
- More commonly referred to as the tailbone
- Triangular shaped bone consisting of 3 to 5 segments
- Sits at the caudal end of the spine
- Does not contain vertebral canal, neural foramina, superior/inferior articular process
Anterior Surface
- 3 Transverse grooves indicate the fusion of segments[4]
Posterior surface
- Posterior sacral foramen
- Characterized by the presence of 2 coccygeal cornua
- These articulate with the cornua of the sacrum
- This foramen accommodates the posterior division of the fifth sacral nerve
- Fifth anterior sacral foramen
- Transverse process first coccygeal bone
- Articulates with transverse process of fifth sacral vertebra
- Houses the anterior division of the fifth sacral nerve
Sacrococcygeal joint
- Also called the sacrococcygeal symphysis
- Articulation between the fifth sacral and first coccygeal vertebral bodies[5]
- Also the articulation between the sacral and coccygeal cornua
- Allow for movement of the coccyx, particularly flexion during weight bearing
Intercoccygeal joints
- Needs to be updated
Anatomic variants of joints
- Historically, literature stated that all the intercoccygeal and sacrococcygeal disc spaces are fused[6]
- Variations: intact discs, discs with clefts or fibrofatty changes, replacement with synovial joints
- Shams et al study of 120 patients with idiopathic Coccydynia[6]
- 44 (37%) patients had an unfused sacrococcygeal joint
- 54 (45%) patients had no fusion of their intercoccygeal joint
Embryology
- Arises as the skeletal remnant of the caudal eminence
- Eminence regresses, coccyx remains
- Initially, four coccygeal vertebrae are separate but can fuse throughout life
- Significant variation between individuals, can have 5 or 3 vertebrae
Ligamentous Attachments
- Anterior sacrococcygeal ligament
- Continuation of the anterior longitudinal ligament
- Deep posterior sacrococcygeal ligament
- Continuation of the posterior longitudinal ligament
- Superficial posterior sacrococcygeal ligament
- Lateral sacrococcygeal ligaments
- Interarticular ligaments
- Spinosacral ligaments
- Sacrotuberous ligament
Muscle attachments
- Gluteus maximus
- Coccygeus
- Levator ani group (iliococcygeus, pubococcygeal, puborectalis)
Role in sitting
- Works in tandem with bilateral ischial tuberosity
- Forms a tripod by acting as the third leg
- Supports the weight of the body when an individual sits
Vascular Supply
- Median sacral artery
- Lateral sacral arteries (branches of the internal iliac artery)
- Inferior gluteal artery
- Small pelvic and perineal branches
Innervation
- Walther ganglion[7]
- Also termed ganglion impar
- Sympathetic ganglion directly anterior to coccyx
- Relay nociception and sympathetic innervation of the perineal region
- Can be blocked for pain control
- Somatic nerves
Clinical Significance
See Also
References
- ↑ White, Tim D., Michael T. Black, and Pieter A. Folkens. Human osteology. Academic press, 2011.
- ↑ 2.0 2.1 Daily, Drayton, et al. "Coccydynia: A Review of Anatomy, Causes, Diagnosis, and Treatment." JBJS reviews 12.5 (2024): e24.
- ↑ Image courtesy of teachmeanatomy.info, "coccyx"
- ↑ Nathan ST, Fisher BE, Roberts CS. Coccydynia: a review of pathoanatomy, aetiology,treatment and outcome. J Bone Joint Surg Br. 2010;92(12):1622–7.
- ↑ Foye PM. Coccydynia: tailbone pain. Phys Med Rehabil Clin N Am. 2017;28(3):539-49.
- ↑ 6.0 6.1 Shams A, Gamal O, Mesregah MK. Sacrococcygeal morphologic and morphometric risk factors for idiopathic coccydynia: a magnetic resonance imaging study. Glob Spine J. 2023;13(1):140-8.
- ↑ Gunduz OH, Sencan S, Kenis-Coskun O. Pain relief due to transsacrococcygeal ganglion impar block in chronic coccygodynia: a pilot study. Pain Med. 2015;16(7):1278-81.