The coccyx (pronounced: cox-ix) is a small, triangular-shaped, bony structure located at the base of the spinal column. Most of us give no thought to it until we inadvertently fall on it. Normally exhibiting little movement, the coccyx is composed of three to five coccygeal vertebrae (four being the most common) that may be fused into one structure, or into segments of two or more vertebrae. Unlike the higher spinal vertebrae, the coccyx has no hole in the middle to allow passage of the spinal cord, nor is it assigned an abbreviation or number as is the case with the other spinal vertebrae (e.g., seven cervical vertebrae numbered C1 to C7, twelve thoracic vertebrae numbered T1 to T12, five lumbar vertebrae numbered L1 to L5, and the five sacral vertebrae numbered S1 to S5).
The length of the coccyx is varies by individual, with a range of roughly one to four inches. It usually curves gently from the end of the spine into the pelvis. The coccyx is larger at the inverted base (where it connects with the lowest vertebrae of the sacrum (L5) forming the sacrococcygeal joint), then tapers downward to a rounded or cleft (bifid) point at the distal tip (apex). Since it gave the appearance of an animal’s tail, in the past it was widely referred to as a tailbone.
Until the 1970s, the coccyx was considered to be a vestigial remnant that served no function other than to remind us of our evolution from apes to man. We now know that the coccyx is an integral part of a complex system of support (the pelvic diaphragm) for our internal organs. Among the nine muscles attached to the coccyx are the gluteus maximus, the levator ani, the sphincter ani externis and the coccygeus. These muscles play a vital role in pelvic floor support and our ability to stand and maintain bowel control.
Of the 31 pairs of nerves that emanate from the spinal cord, the coccygeal nerve is the 31st and lowest nerve pair. The coccygeal plexus (collection of nerve fibers) located in the pelvic cavity arises from the S4 and S5 vertebrae. Its function is to transmit sensory information to the brain from the skin overlying the coccyx.
When pain (coccydynia) occurs at or near the coccyx it can be mild to severe and will often compromise an individual’s quality of life. The pain can be caused by sprains, chips, bruises, cracks, pulled ligaments, dislocations or fractures (a rare but painful occurrence) of the coccyx. These conditions may have been the result of falls (e.g., slipping on ice, ice-skating, etc.), repetitive friction from rowing, cycling or horseback riding, and sports-related blunt trauma (gymnastics, football, etc.). Coccydynia can occur at any age in both males and females. It is said to occur more often in women than men due to the shape of the female pelvis. Racial predisposition has not been reported.
Coccydynia can also be caused by a cyst at or near the tip of the coccyx (e.g., pilonidal cyst), infections, and, in rare cases, malignant tumors (either primary or metastatic). Women sometimes experience painful coccyx bruising when the baby descends through the pelvis during childbirth. The sensation of pain at the coccyx may also be idiopathic (cause unknown), and in some cases, psychosomatic (in the head). The pain, irrespective of cause, is generally more intense when the individual is sitting on a hard surface, stands for long periods of time, engages in sexual intercourse, becomes constipated, or has bowel movement. In some instances, coccyx pain may not be felt at the site of the coccyx itself, but is instead referred to the back, hips, thighs or legs. The wide variety of coccyx pain causes emphasizes the need for a thorough case history and examination by a back and neck specialist to determine the best treatment alternative.
The symptoms of coccydynia include (1) pain that worsens when the coccyx is palpated (touched); (2) non-specific pain around the hips, pelvis or lower back; (3) the inability to stand in place or sit still for periods of time; (4) pain that worsens with constipation and feels better after a bowel movement; (5) pain during sex; and, (6) visible bruising if injury is due to trauma.
The treatment of coccydynia is most often conservative with the application of compresses, bed rest, non-steroidal anti-inflammatory drugs (NSAIDs) to reduce inflammation, and stool softeners to prevent constipation. Depending on the severity of the pain and its impact on daily activities, the back and neck specialist may recommend prescription pain medications, physical therapy, ultrasound or fluoroscopically guided injections of local anesthetics or corticosteroids into the collection of nerve cells (the ganglion impar) located at the sacrococcygeal junction. Immediate pain abatement usually follows the injection into the ganglion impar and can, in some cases, last indefinitely.
In those cases where extensive conservative treatment fails to provide pain relief the surgical removal of the coccyx (coccygectomy) may be undertaken. The removal of the coccyx has the same risks as other surgeries, e.g., wound healing problems, infection, and the possibility that the surgery will not result in pain relief.
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