Coccydynia

Pain in and around the coccyx (tailbone), felt most when sitting, rising from sitting, and with pressure over the coccyx. The coccyx consists of 3 to 5 fused segments that serve as an attachment for the pelvic floor muscles (levator ani, coccygeus), the gluteus maximus and the anococcygeal ligament, and it bears weight when sitting leaning back.

• Causes:
  • Trauma: a fall onto the buttocks, childbirth (especially instrumental delivery and a large baby), repetitive microtrauma (cycling and rowing).
  • Abnormal coccyx mobility: hypermobility or subluxation (in about 50% of cases), or a posterior spiked coccyx. Obesity increases the posterior tilt of the pelvis and compression, and thin patients have less cushioning and an anterior prominence.
  • Pelvic floor muscle spasm, piriformis and levator ani myofascial pain.
  • Referred pain from lumbar disc disease and sacroiliac joint dysfunction, and pain from the rectum or anal canal (proctalgia, fissure, abscess, pilonidal disease).
  • Rare: infection, tumour (chordoma, metastasis, giant cell tumour), fracture, and sacral stress fracture.
• It is five times more common in women, and the incidence is highest in the 30s to 50s. Obesity is the strongest risk factor.
• About 90% improve with conservative care within 6 to 12 months, and the remainder have chronic pain.

• Localised pain and tenderness at the tailbone that is worse with sitting (especially on hard surfaces and leaning back), rising from a seated position, prolonged sitting, standing up, intercourse, defaecation and sometimes menses, and relieved by standing or leaning forward.
• Examination: tenderness on direct pressure over the coccyx, pain on moving the coccyx between the finger and thumb (rectal examination with the thumb externally on the coccyx), abnormal mobility (hypermobility, flexion above 25 degrees on sitting; subluxation or posterior displacement; or immobility), levator ani tenderness, and a normal neurological examination.
• Differential diagnosis: lumbar and sacroiliac referred pain, pelvic floor myofascial pain (levator ani syndrome), proctalgia fugax, anal fissure or abscess, pilonidal sinus, piriformis syndrome, pudendal neuralgia, sacral stress fracture, pelvic inflammatory disease, endometriosis, prostatitis, tumour and infection.
• Red flags: fever, a mass, progressive pain with weight loss or a history of cancer, saddle anaesthesia, bladder or bowel dysfunction, severe trauma, rectal bleeding, and constant night pain.
• Complications: chronic pain, difficulty sitting, work and social disability, and psychological distress.

• Clinical, with external palpation, digital rectal and vaginal examination of the coccyx and pelvic floor, and neurological assessment.
• Dynamic (sitting and standing) lateral X-rays of the coccyx show hypermobility (flexion above 25 degrees on sitting compared with standing), subluxation (posterior displacement of the coccyx on sitting), a posterior spicule, and exclude fracture or tumour. MRI shows bone oedema, fracture and soft tissue disease, and is used when X-ray is non-diagnostic or red flags exist.
• A diagnostic injection of local anaesthetic into the coccyx (or the ganglion impar block) that relieves pain supports the diagnosis.
• Exclude other causes: lumbar spine imaging if radicular features, pelvic imaging, blood tests (CRP, ESR) and proctoscopy as needed.

• Education and sitting modification: a wedge or ring (donut) cushion with a coccyx cut out to offload the tailbone, leaning forward when sitting, avoiding prolonged sitting on hard surfaces (change position every 20 to 30 minutes), and avoiding cycling and rowing until settled.
• Analgesia: paracetamol 1 g orally 6 hourly. Ibuprofen 400 mg orally 8 hourly with food (or naproxen 500 mg 12 hourly, or diclofenac 50 mg 8 hourly) for 1 to 2 weeks, with gastroprotection where needed. Topical diclofenac 1% gel 2 to 4 g 3 to 4 times daily (to the coccyx region, avoiding mucosa). Heat or ice.
• Bowel care: stool softeners or an osmotic laxative (macrogol 1 to 2 sachets daily, or lactulose 15 mL twice daily) to avoid straining, because defaecation aggravates the pain.
• Neuropathic or chronic pain: amitriptyline 10 mg at night increasing to 25 to 50 mg, gabapentin 300 mg at night titrated to 900 to 1800 mg daily, pregabalin 75 mg 12 hourly increasing to 150 mg 12 hourly, or duloxetine 30 to 60 mg daily. A short course of tramadol 50 mg 6 to 8 hourly (maximum 400 mg daily) only for severe pain.
• Physiotherapy: pelvic floor and levator ani relaxation (biofeedback, trigger point release, stretching), and manual coccygeal manipulation (external or intrarectal) with about 25 to 85% reported benefit over several sessions in selected patients.
• Injections for pain persisting beyond 4 to 6 weeks:
  • Coccygeal (intrameniscal or pericoccygeal) injection: triamcinolone acetonide 20 to 40 mg (or methylprednisolone acetate 40 mg) with lidocaine 1% 3 to 5 mL or bupivacaine 0.25% 3 to 5 mL, under fluoroscopy or ultrasound guidance, with relief in about 50 to 85% and a repeat injection after 4 to 6 weeks if effective (up to 2 or 3 injections).
  • Ganglion impar (sacrococcygeal) block: local anaesthetic with or without steroid, for sympathetically mediated pain, with radiofrequency ablation or neurolysis for recurrences.
  • Complications: infection, rectal puncture, and skin atrophy.
• Extracorporeal shock wave therapy (weekly for 3 sessions) and other physical therapies have limited evidence.
• Surgery: partial or total coccygectomy for chronic pain with documented subluxation or instability after at least 6 to 12 months of failed non-operative care and a positive diagnostic injection, with good or excellent results in about 60 to 90% of selected patients. Complications: wound infection (about 10 to 20%, because of the proximity to the anus), delayed healing, and persistent pain, so use careful skin preparation and prophylaxis (cefazolin 2 g IV with metronidazole 500 mg IV). Smokers, obese patients and those with psychological comorbidity have poorer outcomes.
• Special groups:
  • Postpartum: usually settles within 3 to 6 months with a cushion and analgesia. Paracetamol is first line in pregnancy and breastfeeding, and ibuprofen is also compatible with breastfeeding.
  • Pregnancy: cushions, physiotherapy, paracetamol and support. Avoid NSAIDs after 20 weeks.
  • Children and adolescents: usually trauma related, so look for fracture and refer if severe.
  • Elderly: check for fracture (osteoporotic), and exclude tumour.
  • Diabetes: monitor glucose after steroid injection (3 to 5 days).
  • Renal impairment: avoid NSAIDs and reduce gabapentin and pregabalin doses.
• Follow up: review at 4 to 6 weeks and 3 months. Refer to pain medicine or spinal surgery for failure after 3 to 6 months, suspected instability for consideration of injection, coccygectomy, or any red flag.