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

History

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.

Examination

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.

Diagnosis and Imaging

The diagnosis is generally made clinically with corroborating features of history and examination. In those with mild symptoms without significant trauma imaging is not required. ref name="uptodate"/>

Obtain coccygeal imaging in those with with severe pain and significant trauma, or persistent pain. Red flag symptoms should be evaluated with imaging or other further investigations as appropriate, which is normally MRI.ref name="uptodate"/>

XR Imaging

AP and lateral xrays can be helpful in evaluating for fracture, dislocation, hypermobility, bone spurts, and osteoarthritis.ref name="uptodate"/>

Dynamic XR Imaging (coccygeal stress views)

This is used to assess for dynamic coccygeal hypermobility where lateral radiographs are compared to sitting and lying (or standing) radiographs. The patient should sit in the most painful position. Normal xrays do should some coccygeal flexion on sitting but this should be by 20 degrees or less. Any listhesis (subluxation) should be less than 25 percent of the coccygeal vertebral body while sitting in the non-hypermobile coccyx.ref name="uptodate"/>

Coned down lateral views (bone spurs)

Coned down views can be used to image for bone spurs. A collimator is used to improve image quality.ref name="uptodate"/>

MRI Imaging

This should include T1 and T2 sagittal sequences, as well as a STIR image to show oedema.ref name="uptodate"/>

Differential Diagnosis

• Coccygeal disorders: fracture or dislocation, sacrococcygeal joint hyper or hypomobility, coccygeal joint hypermobility, bone spicule
• Referred spinal pain
• Pelvic floor or pelvic organ disease: endometriosis, prostatitis, PID, levator ani syndrome, etc.
• Pilonidal sinus
• Proctalgia fugax
• Rare causes - CRPS, infection, metastatic malignancy, CPPD, Chordomas, Benign notochordal cell tumours, avascular necrosis, sacral nerve arachnoiditis, glomus tumour, precoccygeal dermoid cyst.

Prognosis

90% of cases resolve with conservative management or without medical input. Pain is less likely to resolve in those when it has developed without an initial traumatic event.ref name="uptodate"/>

Management

Conservative Management

Initial management should include protection and analgesia, and this should be pursued for at least two months. Wedge or donut cushions can be used to offset the pressure away from the coccyx. The wedge cushion has a wedge shape cut out of the back of the cushion. Donut cushions have a hole in the centre. A DIY solution can be done by cutting out a wedge from 5-10cm foam rubber.

Injection Treatment

Injections with local anaesthetic with or without a corticosteroid may be helpful, especially in those with instability or bone spurs. The injections should be directed to an anatomic problem where possible, such as the individual coccygeal joints, sacrococcygeal junction, bone spur, ganglion impair, or the caudal epidural space. Injection under fluoroscopy may be required.

The ganglion impair is a midline sympathetic ganglion anterior to the upper coccyx, and injection has some promising results.

Prolotherapy can be considered.

Pelvic Floor Physiotherapy

This may be indicated in those with significant pelvic floor myofascial pain, such as with pain more anterior and inferior to the coccyx, rather than on the coccyx itself.

Manipulation

Manipulation can worsen symptoms in those with hypermobility, fractures, and bone spurs. Manipulation is done via the rectum and can include levator ani massage.

Surgery

Surgery generally involves either complete coccygectomy with excision proximal to the sacrococcygeal junction, or partial coccygectomy leaving the upper coccygeal vertebra.