Coccydynia

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Coccydynia is also known as coccygodynia or tailbone pain. This pain condition normally resolves with supportive care but can occasionally become persistent. The effects on quality of life can be dramatic.

Anatomy

The coccyx has between three to five vertebrae. A Turkish MRI based anatomy study found significant variation in asymptomatic people. They found having four segments was the most common, followed by five, then three. They also found a significant rate of intercoccygeal joint fusions, which was most prominent in the most caudal joint. Fusion of the whole structure into one segment was uncommon. The authors found the intercoccygeal angle to be 135° ± 1.15°, with a higher angle in those with a single segment.

Epidemiology and Risk Factors

The overall prevalence is unknown. The female to male ratio is 5:1. The coccyx is more posteriorly located in women, which is thought to be a risk factor for trauma. It is also more common in obese individuals.

Aetiology

• Falling backwards into a sitting position - The most common cause which can cause bruising, fracture, or dislocation.
• Repetitive microtrauma - such as from prolonged sitting on certain surfaces.
• Instability - sacrococcygeal joint hyper- or hypomobility, or coccygeal joint dynamic hypermobility on sitting and standing radiographic comparisons.
• Labour and delivery or instrumented birth.
• Posterior bone spicule - found on the dorsal aspect of the tip of the coccyx.
• Osteoarthritis.
• Rare causes - CRPS, infection, metastatic malignancy, CPPD, Chordomas, Benign notochordal cell tumours, avascular necrosis, sacral nerve arachnoiditis, glomus tumour, precoccygeal dermoid cyst.

Clinical Features

The patient generally can generally pin point the area of pain, which is much more caudal than the normal areas of low back pain. Sitting is normally painful but this may be reduced upon leaning forward and taking the pain off the coccyx. Transitional movements from sitting to standing can sometimes provoke pain. Sexual intercourse and passing bowel motions can also be painful. There may be radiation to the pelvic floor. Red flag symptoms should be evaluated.

On examination there is normally a well localised area of tenderness externally. Per rectal examination can be performed to evaluate the coccyx internally. The index finger is inserted per rectum while the thumb holds the external surface of the coccyx. The coccyx can be moved and pain can be evaluated and compared to surrounding structures.