Coccydynia

Coccydynia refers to pain in and among the area of the coccyx. It is characterized by coccygeal pain which is typically provocated by pressure. It may remain unclear in origin owing to the unpredictability of the source of pain ¹.

Epidemiology

No accurate data about the frequency of coccydynia is reported, but one study found that coccydynia accounted for 2.7% of all backache cases presenting to the hospital ⁸. It is approximately five times more common in females than males. 

Risk factors

• osteoporosis and other degenerative bone diseases

• osteomyelitis

• contact sports

Associations

• inflammatory bowel disease

• obesity

Clinical presentation

As the name suggests, pain is considered to be the primary symptom of coccydynia. However, pain is extremely varied and may be related to sitting, bowel movements, radiculopathic or generalized coccygeal pain. The coccyx may be tender on examination. 

Pathology 

Etiology

 Coccydynia can be classified into:

• idiopathic (most common)

• secondary coccygeal pain

  • abnormal mobility of the tailbone:

    • hypermobility  

    • rigid coccyx with abnormal features at its tip

    • anterior and posterior subluxation of the coccyx ⁷   

    • unstable or dislocating coccyx

  • morphological abnormality of the coccyx:

    • coccyx scoliotic deformity

    • increased intercoccygeal angle

  • trauma

    • post falls

    • childbirth

    • partial dislocation of the sacrococcygeal synchondrosis

  • tumor, e.g. chordomas, chondrosarcoma

  • inflammation/infection of the coccyx (rarely)

Radiographic features

Coccydynia is essentially a clinical diagnosis, but imaging modalities are helpful in assessment and possible identification of the etiology.

Plain radiography

Considered the first line of imaging of painful coccyx ¹⁰. Two types of radiographs:

• standard radiograph

  • coccyx scoliotic deformity (AP and lateral)

    • number and morphology of coccygeal segments

    • intercoccygeal angle ( between the first and last segment of the coccyx)

    • in idiopathic coccydynia was greater than that of traumatic

    • useful radiological assessment to evaluate the anterior angulation of the coccyx and its deformity

    • normal pivot of the coccyx lies between 5 and 25°

      • <5° this means immobility or better say rigid mobility.

      • >25° this means hypermobility ⁷

• dynamic stress films or weight bearing radiograph

  • sitting and standing positions.

  • superior than standard radiograph because it can detect measurement of the sagittal rotation of the pelvis and the coccygeal angle of incidence

MRI

Described features include ¹¹:

• rigid coccyx with a spicule or spur at its tip

• bursa along the dorsal surface of the coccyx

• presence of fluid collection within the sacrococcygeal synchondrosis

• large draining vein on the ventral coccyx

• any inflammation or soft tissue abnormalities around the coccyx

Treatment and prognosis

Conservative treatment includes rest, coccygeal cushion, physiotherapy and massage. In traumatic coccydynia the joint may heal spontaneously over weeks or months

Interventions include:

• injections of local anesthetic and steroid

• radiofrequency ablation of coccygeal discs and ganglion impar

• removal of the coccyx by surgery either partial or total (coccygectomy) in refractory cases

  • limited coccygectomy may to resect a mobile segment ⁵

History and etymology 

The word coccyx originates from the Greek word "cuckoo" (kokkyx), on the basis of resemblance to the structure a cuckoo's beak. The term was used in practice for the first time by Simpson in 1859, although was described as early as 1600s. It is also called the "tailbone" because it is located anatomically at the end of the vertebral column below the sacrum.

Differential diagnosis

Causes of pain in the coccygeal region include:

• pilonidal sinus/abscess

• sciatica

• sacroiliitis

• infection including shingles of the buttocks

• hemorrhoids

• paraganglioma of the coccyx

• piriformis syndrome ⁵