The coccyx is a small triangular bone made up of 3 - 5 rudimentary vertebrae. These segments may or may not be fused together.
Rear View
Front View
Side View
It is joined to the lower part of the sacral bone by the synovial sacro-coccygeal joint.
It is supported by ligaments to the front (anterior sacro-coccygeal), side (lateral sacro-coccygeal) and back (posterior sacro-coccygeal).
It has a nerve supply from the sacral plexus and the coccygeal nerve.
The pelvic floor muscles attach to it's tip
Movements
It flexes forward during contraction of the pelvic floor muscles e.g. during sex
It extends backwards during labour and defaecation.
It can also bend to each side and rotate a little on it's long axis.
In many normal people the coccyx is angled forwards making it difficult to feel.
Causes of pain
Trauma
Direct blow to the coccyx - can be fractured and bruised - may lead to posterior subluxation - see later
Inflammation of the sacro-coccygeal joint.
Sacro-coccygeal ligament sprain.
Referred pain from other sources (common)
Lumbar spine facet joints and muscles
Pelvic Floor Muscles
Sacrospinous / Sacrotuberous Ligaments
Buttock Muscles (Gluteus Maximus)
Tumours
Secondary spread to the sacrum and coccyx bones.
Referred pain from lower rectal and anal tumours. If there is a history of altered bowel function or rectal bleeding, then this cause should be excluded before proceeding to any other treatments.
Investigations
Static tests
X-rays shortly after an injury can reveal coccyx fractures
Spinal MRI scans can help to rule out a disc prolapse as a cause of referred pain
Dynamic tests
Lateral x-rays in the standing and sitting position can reveal a posterior dislocation of the coccyx which only occurs when seated. (PIctures from www.coccyx.org)
Treatment
Coccygeal pain (coccydynia) is notoriously difficult to treat. Like any other painful condition, treatment should be directed to the source of the pain. However, the source can only be found after a thorough examination whilst considering all the possible local and referred causes. Focussing on where the patient says its painful will only result in failure. In this condition one has to literally think laterally.
Sacro-coccygeal Joint Injection
Injection of a small amounts of local anaesthetic and steroid into this joint can help when it is inflamed after an injury (e.g. fall onto the bottom).
To make this treatment less painful a small volume caudal epidural injection can be done first helping to numb the area.
The joint injection can also be combined with manipulation of the coccyx per rectum (see below).
In the very nervous the whole thing can be performed under intravenous sedation .
Manipulation of the coccyx via the rectum
After an injury the coccyx can get stuck in one position. This can be due to stiffness of the sacro-coccygeal joint and spasm of the surrounding pelvic muscles. In women this can make sexual intercourse very painful, as using the pelvic floor muscles causes the coccyx to flex forwards.
The coccyx can be held using a pincer grip between the doctor's index finger (placed in the patient's rectum) and the doctor's thumb on the outside. The coccyx can then be gently manipulated into flexion / extension, side bending and rotation. Moving the coccyx backwards into extension also stretches the pelvic floor muscles when they are in spasm.
Sometimes a small click is heard when the coccyx is manipulated. This emanates from the sacro-coccygeal joint as it releases.
Manipulation of the coccyx can be combined with a caudal epidural injection, sacro-coccygeal joint injection and intravenous sedation .
Trigger Point Injections
Trigger point injections to Gluteus Maximus and the Pelvic Floor Muscles (see pictures above) can be useful when these are the cause of referred pain to the coccyx. Botox injections may also be helpful in the longer term. Exercises for these specific muscles should be encouraged.
Prolotherapy
When the cause of the coccyx pain is due to a sprain of the sacrotuberous or sacrospinous ligaments, Prolotherapy may help repair the sprain. A diagnostic local anaesthetic / steroid injection should help to confirm the diagnosis before proceeding.
Spinal Manipulation
When the cause of the coccyx pain is due to referred pain from the lumbar paraspinal muscles (spinal dysfunction), spinal manipulation can be very helpful.
Removing the coccyx will fail to help if the coccyx is not the cause of the pain.
It is important that all the other causes of referred pain to the coccyx are explored / treated in the pain clinic before resorting to surgical excision.
Surgical excision may be helpful where a posterior disclocation has been demonstrated in the seated position.
