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.