|Year : 2016 | Volume
| Issue : 1 | Page : 61-66
MRI in Coccydynia
Pain Clinic in Charge- Jupiter, Bethany Hospitals, Thane, Program Committee Chairperson- AMC, Mumbai, Maharashtra, India
|Date of Web Publication||7-Jan-2016|
Dr. Kritika Doshi
104, Rohini, Tarangan-II, Behind Korum Mall, Thane - 400 606, Mumbai, Maharashtra
Source of Support: None, Conflict of Interest: None
Patients who are diagnosed clinically as Coccygodynia often do not get satisfactory relief. The clinical diagnosis is based on various hypotheses that have been proposed to explain the pain of coccydynia - including coccygeal spicules, pain from the pericoccygeal soft tissues, pelvic floor muscle spasm, referred pain from lumbar pathology, arachnoiditis of the lower sacral nerve roots, local posttraumatic lesions, somatization, etc. The diagnosis is difficult and the pathophysiology is poorly understood. Till recently, use of dynamic X-rays and MRI imaging was not considered to diagnose this condition. The author would like to report three patients who presented to the pain clinic with refractory coccygeal pain and underwent dynamic coccyx X-rays and MRI as part of their evaluation. All these patients had positive findings on MRI. These patients were treated satisfactorily as a result of the added diagnostic value of MRI.
Keywords: Coccydynia, coccyx pain, dynamic x-ray, intervention, MRI
|How to cite this article:|
Doshi K. MRI in Coccydynia. Indian J Pain 2016;30:61-6
| Introduction|| |
Coccydynia is a condition that refers to symptoms of pain around the tailbone from varying etiology. The neuro-anatomy and innervations of the pelvis which holds the sacrum, coccyx and pelvic structures is complex and also, it is extensively interconnected intrinsically and extrinsically to the spinal cord and muscles responsible for hip movement. Due to these complex innervations, patients continue to suffer from pain as objective evidence of the cause of pain cannot be documented. Referred pain from the spine and muscles can also present with symptoms of coccygeal area pain. 
As the symptoms become chronic, patients find their daily activities becoming painful. Many patients are labeled as having somatization or "functional"  pain and are not taken seriously. Also, in Indian traditional medicine the pelvis is regarded as the area where emotional and physical stress is buried- muladhar chakra. For various reasons (personal, cultural) this part of the body is associated with vulnerability and self-protection. Most patients give a history of fall or trauma preceding the symptoms but sensitivity to touch near "private area" means that physical examination by doctors is cursory and preventive care in the form of massage or manipulation is usually not sought by patients. This also means that issues of pelvic or gluteal pain are sometimes not addressed until quite severe. Thus, coccydynia is a painful condition that causes social embarrassment, is associated with psychological behavior changes and affects the quality of life of the person suffering.
While investigating patients, plain radiographs of the sacrum and coccyx alone are unable to identify the etiologic cause. Though expensive, MRI imaging of the sacrum and coccyx is a valuable tool to identify etiologic factors. Many patients undergo MRI of lumbar spine where the scan missed the lower sacrum and coccygeal joints completely.
The following patients were referred to the Pain Clinic as "refractory Coccydynia" patients.
| Case Reports|| |
A 56 y, female patient with no contributory medical or surgical history presented with pain on sitting since 5 years. There was no history of trauma. The onset of pain was gradual and had worsened in the past one year. There was no pain on ambulation or standing. She was diagnosed clinically as coccydynia and she received 2 injections of Depot steroid locally as a blind injection 1 year and 6 months previously. She had partial relief for one month after the injections. She was referred to the pain clinic in view of persistent pain.
She used to practice regular yoga before the pain started. Her examination findings included a localized diffuse bogginess/swelling over the sacrococcygeal area which was non tender [Figure 1].
Her CBC and CRP were within normal limits. All baseline hematologic investigations were within normal limits. X-Ray of LS Spine did not reveal any bony abnormality. (No dynamic Xrays were done). An MRI of saccrococcygeal region showed mild synovial thickening with joint effusion of the first intercoccygeal joint [Figure 2] and [Figure 3].
|Figure 2: MRI showing joint effusion and thickening at 1 st intercoccygeal joint |
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|Figure 3: MRI: Joint effusion and thickening at 1 st intercoccygeal joint |
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A 37 y male presented with a history of fall 8 months earlier with trauma to sacral region. The X-ray showed presence of ? post trauma fracture [Figure 4] and MRI confirmed presence of traumatic marrow edema and fluid collection [Figure 5] and [Figure 6]. Despite adequate analgesics, physiotherapy and use of cushions for more than 6 months, patient had increasing discomfort on sitting. He complained of gradually increasing pain on sitting since 3-4 months (almost 1 year after the trauma). He was unable to sit in office for more than 5 to 10 min and travelling to office by local train was painful as he could not sit on the hard seat.
A 33y male, with no medical or surgical contributory history presented with pain on sitting. He worked in a bank with prolonged sitting for more than 8 hours daily. He had no history of trauma or previous interventions. He had been on and off NSAIDs and other analgesics for more than 6 months. The pain was constant and affected his working. He was unable to sit for more than 2-3 minutes and also had trouble wearing his shoes and clothes in sitting position.
His dynamic X-ray [Figure 7] showed inflammatory changes and spicules at first intercoccygeal joint with subluxation.
MRI was confirmatory and showed - joint space reduction, articular margin erosions with periarticular osteophytes and subarticular sclerosis at first intercoccygeal joint suggestive of degenerative arthropathy - maybe due to subluxation of distal segment on sitting. MRI also showed an ossified loose body along L5-S1 facet joint [Figure 8].
|Figure 8: MRI: Joint space reduction, articular margin erosions with periarticular osteophytes and subarticular sclerosis at first intercoccygeal joint suggestive of degenerative arthropathy |
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Functional anatomy of the coccyx
The coccyx is a triangular bone that consists of 3 to 5 fused vertebral segments. The ventral surface is concave with grooves indicating lines of fusion. The dorsal aspect is convex and displays similar lines of fusion as well as multiple paired tubercles known as coccygeal articular processes.  The largest or first coccygeal segment articulates with the lowest sacral segment. The sacrococcygeal joint is a thin intervertebral disc of fibrocartilage also sometimes referred as interosseous ligament.  Occasionally, the intercoccygeal joints are synovial.
Despite its small size, the coccyx has several important functions:
- Important role in providing attachment to many muscles, ligaments and fascia. The muscles with attachment to the coccyx include the gluteus maximus, levator ani, sphincter ani, coccygeus. The coccyx is bordered anteriorly by the levator ani muscle and the sacrococcygeal ligament.
- The lateral edges serve as insertion sites for the coccygeal muscles, the sacrospinous ligament, the sacrotuberous ligament, and fibers of the gluteus maximus muscle.
- Inferiorly, the iliococcygeus muscle tendon inserts onto the tip of the coccyx.
These ligaments and muscles help support the pelvic floor and also contribute voluntary bowel control.
- Role in Weight bearing: The coccyx is involved in weight-bearing support to a person in the seated position- it serves as one leg of the tripod along with the ischial tuberosities as well as it functions to stabilize the person in a sitting position.
Most patients present with pain while sitting. Leaning back while in a seated position leads to increased pressure on the coccyx. In the sitting posture, flexion or extension of the coccyx may be encountered.
The physiologic movements at the coccyx are flexion and extension executed by pelvic floor muscle attachments.
- Flexion (forward movement) is an active movement performed by the levator ani and the sphincter ani externus muscles.
- Extension (backward movement) is a passive movement due to increased intra-abdominal pressure and relaxation of the levator ani and sphincter ani externus muscles which occurs during defecation and parturition. 
- Passive flexion is due to the direct pressure of the seat over the coccyx.
Imaging for coccydynia
Coccydynia has been a clinical diagnosis till now. But now, coccydynia is recognized as a symptom and not a diagnosis. Recently, dynamic Xrays and MRI have helped provide a possible etiological diagnosis for pain presenting around the coccygeal area.
- Routine radiograph is used to evaluate the anterior angulation of the coccyx- the normal pivot of the coccyx lies between 5 and 25 ° and depending on the angulation, it is classified as classified as type I, II, III or IV.  The angulation helps identify mobility of coccyx as an angle of less than 5 ° means immobility or rigid mobility and more than 25 ° means hypermobility  of the coccyx.
- The routine radiograph is also useful in cases of deformity or fractures.
- A dynamic X-Ray of the coccyx can help visualize the mobility,  the site of abnormal mobility (intercoccygeal joint or sacrococcygeal joint) as well as presence of enthesopathic spurs around the bones. A comparison of sitting and standing films will yield radiographic abnormalities in up to 70% of symptomatic coccydynia cases. 
In 40% of the cases, the dynamic X-rays fail to demonstrate a lesion and these cases with normal dynamic films represent the actual "idiopathic" coccydynia.
- MRI can help visualize a rigid coccyx with a spicule  or spur at its tip, presence of bursa along the dorsal surface of the coccyx or presence of fluid collection within the sacrococcygeal synchondrosis. It is also useful to identify engorged veins on the ventral coccyx and any inflammation or soft tissue abnormalities around the coccyx.
| Discussion|| |
Coccydynia is poorly understood because of the multifactorial nature of coccygeal pain. Hence, it is now recognized as a symptom and not a diagnosis. Coccydynia, or coccygodynia, is term used to describe pain in the region of the coccyx. Simpson first introduced the term in 1859  but accounts of coccygeal pain date back to the 16th century. ,
Despite the identification of chronic coccygeal pain hundreds of years ago, the inability to diagnose the causative factors makes its treatment difficult. Many physiologic and psychological factors contribute to its etiology. The complex innervations of structures associated means that referred pain from spine, myofascial components, lax ligaments, abnormal pelvic tilts etc can all present as pain around the coccyx. The risk factors for developing coccydynia include presence of osteoporosis, degenerative bone diseases, osteomyelitis, playing of contact sports. It is also associated with obesity and IBD.
| Management of coccydynia|| |
Initial treatment is conservative and a multidisciplinary approach beginning with physical therapy and ergonomic adaptations is used.
Physical therapy includes mobilization, deep transverse friction of ligaments, manipulation with intra-rectal approach, massage of levator ani and coccygeus muscles, pelvic floor exercises to relax pelvic floor with biofeedback. Electromodality is useful in some patients. 
Ergonomic adaptations include specially designed gel-filled cushions, posture changes where patient is asked to lean forward and rest their arms in front to help take pressure off the coccyx.
Analgesics include Nonsteroidal anti-inflammatory drugs, analgesics, and anticonvulsants to manage pain in patients with coccydynia.
Most cases of coccydynia resolve within weeks to months with conservative treatment, but for a few patients, the pain can become chronic and debilitating. If patient has no relief with pain-medications, image guided injections can be performed.
When conservative, measures fail surgical option of coccygectomy has been reported to be successful. ,
This patient had no relief with conservative treatment. She was given an intra-articular injection at Coccyx 1-2 after visualizing the disc under image guidance [Figure 9] with complete resolution of symptoms. She was advised to do continue with corrective exercises for pelvic floor and continue yoga.
|Figure 9: Image guided injection with coccygeal discogram and dye leaking outside |
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Discussion: This patient probably had age related degenerative changes and the vigorous yoga exercises may have aggravated the symptoms. The local steroid injections did not help as they were not directed at the intercoccygeal synovial inflammation. A fluoroscopy guided and targeted injection of anti-inflammatory medication probably gave the patient longer relief.
This patient complained of pain only on sitting on hard surfaces. He probably had post traumatic pelvic floor muscle stiffness that aggravated the passive flexion of the coccyx on sitting. This anterior movement of the coccyx occurring as the result of the muscular tension in the pelvic floor may have been the cause of his pain. He underwent dry needling of gluteus maximus and pyriformis muscles.
Discussion: The trauma was severe enough to have caused marrow edema and may have also caused bruising of muscles associated. This may have caused shortening of the muscles with fibrosis leading to formation of trigger points in those muscles, causing pain. Dry needling addressed this component and relaxation therapy helped maintain the length of the pelvic floor muscles.
Patient was posted in rural location and unable to complete conservative treatment regime. He was given an injection under fluoroscopy of Local anesthetic with depot steroid (1 ml 0.75% Ropivacaine + 40 mg Depomedrol) between coccyx 1 and 2 with good relief of pain on sitting. His symptoms reduced and he was advised to begin physiotherapy and continued exercises at home. He was also advised to change his position frequently and avoid prolonged sitting.
Discussion: The prolonged sitting job caused this patient to remain in a slumped posture which resulted in the uneven distribution of weight posteriorly. Also, the constant pressure of sitting with the resultant constant pressure on the pelvic floor muscles leads them to became fibrotic, painful and highly pain-sensitive with perpetual 'coccyx-guarding spasm'. Due to constant abnormal pull from the shortened muscles, he developed enthesopathic changes like osteophytes and spicules. The local injection was aimed at giving pain relief to pursue physiotherapy.
| Conclusion|| |
Coccydynia was for long considered as a "psychological" or somatization pain. Now, it is an accepted symptom arising from various etiologic structures and can cause significant compromise to the person's ability to perform or endure various activities.
Coccydynia is related to coccygeal instability in almost half of the cases and these can be documented by dynamic X-rays of Coccyx. Plain X-Rays are of less diagnostic utility.
The diagnosis should be documented with dynamic X-ray films to look for evidence of luxations and hypermobility. If the dynamic X-rays are normal, the cause of pain may be intradiscal inflammation, bursitis due to rigid coccyx or pain could be located at the sacral insertion of the sacrotuberous ligament - here as MRI is an invaluable imaging technique and should be used. MRI can diagnose an inflammatory reaction around a disc or the peri-coccygeal soft tissue or bone oedema.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9]