Coccyx Pain

Etiology

Direct vertical trauma, repetitive microtrauma, and childbirth are common causes of coccyx pain. However, more serious underlying causes must be excluded, such as infections (including both soft tissue abscess and osteomyelitis) or malignancy (including chordoma, which has a high fatality rate).[1]

Also, coccydynia can be a referred pain due to lower gastrointestinal or urogenital disorders.[7] Neurological causes such as lumbar disc prolapse have been reported as a possible etiology in a limited number of cases.

The outcome of direct vertical trauma to the coccyx can vary from contusion to fracture-dislocation of the coccyx. Traumatic or non-traumatic compromise of the coccygeal ligaments can result in coccygeal dynamic instability (excessive movement of the coccyx during weight-bearing or while sitting). Abnormal mobility of the coccyx can result in coccygeal pain. Abnormally mobile coccyges can be either hypermobile (due to lax ligaments) or hypomobile (rigid). The coccyx may be subluxated anteriorly or posteriorly, unstable, or even dislocated.[8]

Coccyxes of certain shapes are more predisposed to coccydynia than others.[9] Abnormal coccygeal morphology or position predisposing to coccyx pain include abnormal scoliotic deformity (lateral deviation) or a coccyx that is excessively flexed or excessively extended.[1]

A distal coccyx bone spur (spicule) may cause pain when the skin is pinched beneath the spur during sitting.[10]

Idiopathic coccydynia is a 'diagnosis of exclusion' after careful screening for identifiable causes. 

Epidemiology

Factors related to the high risk of developing coccydynia are female sex and obesity, as body mass index may affect how a person sits or the amount of weight placed upon the coccyx.[7][11][7] Coccydynia is five times more common in females than in males.[5][8][12] Rapid weight loss has been reported to be a risk factor for coccydynia due to the loss of the cushioning effect of adipose in the buttock region. Other reported risk factors include osteoarthritis, osteomyelitis, and contact sports.

History and Physical

The typical presentation of coccydynia is pain localized to the coccyx. In traumatic coccydynia, there will be a preceding history of trauma followed by acute onset of pain. The pain will often have an insidious onset in idiopathic coccydynia without any obvious or specific precipitant. In coccydynia, due to other causes, a careful and thorough history will often suggest the possible etiology.

Coccydynia is typically worse while sitting and especially while sitting in a partly reclined (backward leaning) position.[1] The pain is usually exacerbated by prolonged sitting and cycling.[7] Standing up from the seated position may cause a temporary but severe increase in coccyx pain.[1] Other exacerbating factors may include standing for a long time, sexual intercourse, and defecation.[5]

Physical examination includes inspecting the overlying skin for any signs suggestive of infection or other differential diagnoses such as pilonidal sinus and hemorrhoids. 

"Foye's finger" for coccydynia: This is comparable to "Fortin's finger," where Dr. Fortin published on the usefulness of having patients with sacroiliac joint pain point to their site of pain, thus helping to distinguish this from lumbar pain generators.[13] Similarly, Dr. Foye recommends asking patients to point with one finger to their worst site of pain, which in coccydynia patients will be far more inferior than the more common causes of low back pain (located up in the lumbosacral spine), and more midline than buttock pain syndromes (such as sacroiliac pain and piriformis pain).[1]

External palpation usually reveals localized tenderness focally over the coccyx.

Per rectal examination may be useful in some patients to evaluate the degree of coccygeal mobility and will typically elicit pain when manipulating the coccyx.[11]

Beyond the evaluation of the coccyx itself, it is often helpful to assess for other sources of musculoskeletal pain by performing a physical examination of the sacroiliac joints, ischial bursae, and piriformis muscles.

Evaluation

Standard radiographs: AP radiographs can reveal coccyx scoliotic (lateral deviation) deformity. Lateral views are always indicated as coccyx curvature can be classified into four different types:[9]

• Type I: coccyx is slightly curved forward.
• Type II: coccyx is pointed straight forward.
• Type III: coccyx has a sharp forward angulation.
• Type IV: coccyx shows subluxation at the sacrococcygeal or the intercoccygeal joint.

From the lateral radiographs, the examiner can assess the intercoccygeal angle, which is the measured angle between the first and last segment of the coccyx, as proposed by Drs. Kim and Suk. It is used to assess the anterior angulation deformity of the coccyx. An increased intercoccygeal angle (increased forward angulation) has been reported as a possible etiology of coccydynia.[8]

Dynamic radiographs (sitting and standing): Dr. Maigne, in France, invented the idea of seated X-rays of the coccyx to see the coccyx position while the coccydynia patient was most symptomatic, which typically occurs while sitting. By comparing the coccyx position while sitting versus the position while standing, the clinician can objectively measure the amount of change. These coccygeal movements are measured as changes in the coccygeal angle (amount of flexion) and luxation (amount of listhesis at each of the coccygeal joints). These studies allow the classification of patients with coccydynia into groups based on coccygeal luxation and mobility (hypomobile, hypermobile, and normal mobility). The normal range of coccygeal mobility is between 5 and 20 degrees.[14][15] Thus, if sitting causes a change in the coccygeal angle of fewer than 5 degrees, this is hypomobility. Conversely, if sitting changes the coccygeal angle by 20 degrees or more, this is hypermobility.[14] 

The patients responding best to manual treatments are those with normal coccyx mobility, while those with immobile coccyxes had poor results with manual therapies.[16] In people without coccydynia, the change in luxation (listhesis) at the coccygeal joints is less than 25% of the anterior-posterior depth of the coccygeal vertebral body.[17] Seated radiographs of the coccyx often reveal abnormalities that were missed on non-seated radiographs.[18]

A computed tomography scan (CT) of a normal adult coccyx shows variability in the fusion of the sacrococcygeal and intercoccygeal joints. Female coccyges are more often shorter, straighter, and more retroverted.[19]. However, these anatomic findings should be interpreted in correlation with a thorough history and detailed clinical examination before determining whether the findings are (or are not) the cause of the patient's pain.[20] 

Magnetic resonance imaging (MRI) can be used to assess the anterior curvature of the coccyx, the fusion of the sacrococcygeal and intercoccygeal joints, as well as the presence of a distal coccyx bone spicule (spur).[21] These anatomical findings can either be a precipitant or a consequence of coccydynia.[21] Overall, MRI can be a helpful diagnostic test for patients with coccydynia.[22] MRI can also assist in screening for local malignant and non-malignant tumors.[1]

Coccygeal discogram: This involves injecting contrast and local anesthetic into the sacrococcygeal region to determine the specific site of pain.[14] It can serve as a diagnostic and therapeutic procedure. 

Nuclear medicine bone scan: This is typically only used in patients with coccydynia in whom a search for malignancy or infection (e.g., osteomyelitis) is warranted.[1] 

Routine blood tests: These studies may help in rare cases, such as when suspected etiologies include infection, malignancy, gastrointestinal or urogenital problems.

Treatment / Management

Many patients with coccydynia experience relief of symptoms within weeks or months of onset, whether or not they receive medical treatment. The success of conservative treatment has been reported to be 90%.[5] The following modalities can be offered in acute and chronic cases:(B3)

Acute Coccydynia

• Oral or topical nonsteroidal anti-inflammatory drugs (NSAIDs) can be helpful acutely to decrease both pain and inflammation.
• Cushions on the patient's chair can make sitting more comfortable. A cushion with a wedge-shaped cut-out beneath the coccyx can result in the coccyx hovering over the empty area, thus resulting in less coccygeal weight-bearing and less coccygeal pain. Other cushion options include U-shaped cushions and circular (donut) cushions.[1]
• Pelvic floor physical therapy may be particularly helpful for patients who have substantial muscular pain within the adjacent para-coccygeal muscles.[1] Correct sitting posture can also be assessed and improved.
• Modalities: cold or hot compresses may be helpful in some patients. However, be cautious to avoid injury to the skin by causing skin temperatures resulting in either freezing or burning injuries.
• Fluoroscopy-guided steroid injections: These anti-inflammatory injections can be especially helpful in patients with coccydynia that has been present for less than six months.[23]
(B2)

Chronic and Refractory Coccydynia

• Manipulation under anesthesia, with or without injection of local anesthetic and corticosteroid: Manipulation may help relieve ligamentous pain or pain due to muscular spasms. Different manual treatments have been reported in the literature, including levator ani massage, levator ani stretch, and joint mobilization.[16] The levator ani massage and stretch have been reported to yield better outcomes than the joint mobilization modality.[16]
• Ganglion impar sympathetic nerve block with local anesthetic (even without corticosteroid) can provide some patients with complete and sustained resolution of symptoms.[24] Some patients may require repeat injections. The addition of corticosteroids may give additional relief. There are a variety of techniques for performing ganglion impar injection.[25][26][27][28]
• Pelvic floor physical therapy can be helpful for coccydynia, including in patients who have persistent pain despite coccygectomy.[29]
• Transcutaneous electrical nerve stimulation (external using two cutaneous probes or internal using one cutaneous probe and one intrapelvic probe) may be used.[5] 
• Spinal cord stimulation may be worth considering for some coccydynia patients.[5]
• Surgical intervention. Coccygectomy involves amputation (removal) of the coccyx. This treatment is usually reserved for the small percentage of patients who fail to get adequate relief from non-surgical care.[1] Partial or total coccygectomy has reportedly been beneficial in cases of both traumatic and idiopathic coccydynia after all conservative measures were unsuccessful.[9][30][31] Post-operative complications after coccygectomy include local infection, pelvic floor prolapse (sagging), retained coccygeal fragments, and ongoing pain despite the surgery.[1] 
• Psychotherapy can be helpful when non-organic etiology is suspected.[12] However, note that the psychological profile in patients with coccydynia is similar to other groups of patients, so it is important not to assume that coccydynia is due to psychological causes.[2][32]
(B2)

Differential Diagnosis

The following conditions can result in pain in the coccyx region that should be differentiated from coccydynia:

• Sacroiliac joint pain or inflammation
• Pilonidal cyst with abscess or sinus
• Sciatica
• Hemorrhoids
• Shingles of the buttocks or other forms of infection
• Piriformis syndrome.
• Malignancy, e.g., chordoma or chondrosarcoma
• Pelvic floor muscle pain

Prognosis

The prognosis for patients with coccydynia is variable. While most patients' symptoms improve or resolve with conservative (non-surgical) care, other patients have notoriously persistent, even lifelong, coccyx pain. The severity of the pain and the functional impairment (the limited ability to sit) can be disabling. Coccygectomy has a relatively high postoperative infection rate, and even after tailbone removal, many patients have some degree of persistent pain.

Complications

One complication of coccydynia is that it may become a chronic pain syndrome. Early and thorough medical attention may help patients avoid delays in diagnosis and treatment. The hope is that this will help decrease the chances of the pain becoming persistent and disabling.