What is the initial workup and management for a patient presenting with a suspected injured coccyx (tailbone)?

Initial Workup and Management of Suspected Coccyx Injury

Begin with dynamic radiography of the coccyx in both standing and sitting positions to evaluate for fracture, hypermobility, and morphologic abnormalities that correlate with pain. 1

Initial Clinical Assessment

Key History Elements

• Mechanism of injury: Direct trauma from falls or childbirth is the most common cause, though one-third of cases are idiopathic 2, 1
• Pain characteristics: Worsening with sitting, particularly on hard surfaces, and relief with standing 3
• Risk factors: Female gender and obesity significantly increase risk 2

Physical Examination Findings

• Palpation: Direct tenderness over the coccyx region 2
• Rectal examination: May reveal coccygeal mobility or tenderness (though often deferred initially)
• Weight-bearing assessment: Pain reproduction with sitting versus standing

Imaging Protocol

First-Line Imaging: Dynamic Radiography

Dynamic X-rays in standing AND sitting positions are the essential first step, as they reveal both morphologic parameters and pathologic hypermobility that static films miss 1. This is superior to standard radiographs alone.

Key radiographic findings to identify:

• Hypermobility: >25% posterior subluxation or >25° flexion while sitting (>35° is considered significant hypermobility) 1
• Fracture classification: Type 1 (flexion), Type 2 (compression), or Type 3 (extension) 1
• Morphology: Type II coccyx morphology correlates with increased pain 1
• Subluxation: Intercoccygeal joint displacement 1
• Bony spicules: Sharp projections that can cause soft tissue irritation 1

Advanced Imaging: MRI Indications

Order MRI when dynamic radiography shows normal or only slightly increased mobility, or when the coccyx is rigid without visible spicules 4. MRI should NOT be the initial study but is valuable for unexplained pain.

MRI reveals pathology missed by radiographs:

• Disc abnormalities (seen in 70/172 patients): Intradiscal effusion or Modic 1-type endplate changes 4
• Soft tissue pathology at coccyx tip (seen in 41/172 patients): Venous dilatations, inflammation 4
• Bone marrow edema: Indicates acute injury 4
• Pattern correlation: Mobile coccyx typically shows disc abnormalities (63/105 cases), while rigid coccyx shows tip abnormalities (37/67 cases) 4

CT Imaging

CT is NOT routinely indicated for isolated coccyx injury unless there is concern for complex pelvic trauma requiring evaluation of other structures 5. The ACR guidelines for spine trauma do not specifically recommend CT for isolated coccyx injuries.

Initial Management Algorithm

Conservative Treatment (First-Line for 90% of Cases)

Conservative management succeeds in 90% of patients and should be attempted for at least 2-3 months before considering interventional options 2.

Specific conservative measures:

• Ergonomic modifications: Donut cushions or wedge cushions to offload the coccyx when sitting 2
• NSAIDs: For anti-inflammatory effect 2
• Physical therapy: Pelvic floor rehabilitation and manual manipulation 2
• Activity modification: Avoid prolonged sitting on hard surfaces 2

Interventional Treatment (For Refractory Cases)

If conservative treatment fails after 2-3 months, ganglion impar block provides dramatic pain relief and should be the next step 3.

Ganglion impar block technique:

• Approach: Trans-sacrococcygeal joint or intra-coccygeal joint approach under fluoroscopy 3
• Efficacy: Complete pain relief (NRS 0 from baseline 7.5) in all patients in recent case series, with sustained relief at one-year follow-up 3
• Advantage: Single injection often sufficient, avoiding repeat procedures 3

Alternative interventional options if ganglion impar block fails:

• Local steroid injections at the coccyx 2
• Radiofrequency ablation 1
• Transcutaneous electrical nerve stimulation 2

Surgical Treatment (Last Resort)

Total coccygectomy is reserved for post-traumatic instability unresponsive to all conservative and interventional measures 6.

Surgical considerations:

• Total versus partial: Total coccygectomy yields superior results; partial resection associated with poor outcomes 6
• Success rate: 19/28 patients achieved complete pain relief, with 21/28 satisfied 6
• Patient selection: Critical for success; best results in post-traumatic instability with documented hypermobility or subluxation 6

Critical Pitfalls to Avoid

• Do not order static radiographs alone: Dynamic views are essential to detect hypermobility, which is missed on standard films 1
• Do not rush to MRI: Dynamic radiographs should be performed first; MRI is reserved for cases where radiographs are equivocal 4
• Do not perform partial coccygectomy: If surgery is indicated, total resection provides better outcomes 6
• Do not overlook idiopathic cases: One-third of coccydynia has no trauma history and still responds to the same treatment algorithm 2, 1
• Do not skip ganglion impar block: This intervention provides excellent pain relief before considering surgery 3