Sacral Fracture (Broken Sacrum)

What is the sacrum?

The sacrum is a shield-shaped bone formed by five fused vertebrae. It sits below the lumbar spine and wedges between the two hip bones at the sacroiliac joints, forming the back of the pelvic ring. Nerves that control the bladder, bowel, sexual function and parts of the legs pass through openings (foramina) in the sacrum.

Types of sacral fracture

Doctors also describe traumatic fractures by location (the Denis zones). Zone 1 is outside the nerve openings and rarely causes nerve damage. Zone 2 runs through the openings. Zone 3 involves the central canal and carries the highest risk of nerve damage to bladder and bowel.

Note that the tailbone below the sacrum is a separate bone; see coccyx fracture.

Symptoms

• Deep pain in the low back, buttock, hip or groin
• Pain worse when standing, walking or climbing stairs, and eased by lying down
• Tenderness over the sacrum
• Bruising and swelling after trauma
• Nerve symptoms: numbness, tingling or pain down the back of the leg, foot weakness, bladder or bowel changes, or reduced sensation in the saddle area

Insufficiency fractures often start without a clear injury and are frequently mistaken for arthritis, sciatica or a disc problem, which delays diagnosis.

Diagnosis

• Examination: tenderness, pain with movement of the pelvis, and a nerve exam including the saddle area and anal tone
• X-rays: often normal, because bowel gas and the sacrum's shape hide the break
• CT scan: shows the fracture pattern in detail and is standard after major trauma
• MRI: the most sensitive test for insufficiency and stress fractures, showing bone swelling before the fracture line is visible
• Bone scan: may show an "H-shaped" (Honda sign) pattern typical of sacral insufficiency fractures
• Bone density (DEXA) scan and blood tests for calcium, vitamin D and other causes of bone weakness after a low-energy fracture

Treatment

Stable fractures (most insufficiency and many traumatic fractures)

• Early walking: weight-bearing as pain allows, often with a walker or crutches. Long bed rest is avoided because of clots, muscle loss and pneumonia, especially in older adults.
• Pain relief: acetaminophen (paracetamol) first; short-term stronger medicines if needed. Use NSAIDs with caution in older adults, those with kidney or stomach problems or on blood thinners.
• Prevent constipation, which is common with pain medicines and makes straining painful.
• Physical therapy to regain strength and walking confidence.
• Blood clot prevention when mobility is limited.

Surgery

Surgery is used for:

• Unstable fractures, often with other pelvic ring injuries
• Fractures displaced into the nerve canal, with nerve symptoms (decompression)
• Insufficiency fractures with severe pain that prevents walking despite good pain control

Options include iliosacral screws placed through small incisions under X-ray guidance, rods and plates (lumbopelvic fixation) for complex fractures, and sacroplasty, an injection of bone cement into the fracture, used in some centers for painful insufficiency fractures.

Treating bone fragility

Any fracture from a low-energy injury is a sign of osteoporosis until proven otherwise. Treatment may include calcium and vitamin D, bone-strengthening medicines and fall prevention.

Healing time

Complications

• Chronic low back or buttock pain
• Nerve damage causing leg weakness, numbness, bladder, bowel or sexual problems
• Complications of immobility in older adults: blood clots, pneumonia, pressure sores and loss of independence
• Nonunion (failure to heal), which is uncommon

Frequently asked questions

What are the symptoms of a sacral fracture?

The main symptom is deep pain in the low back, buttock, hip or groin that gets worse when standing or walking and eases when lying down. There may be tenderness over the sacrum. Numbness in the groin or buttocks, leg weakness, or bladder or bowel changes suggest nerve involvement and need urgent assessment.

How long does a sacral fracture take to heal?

Most stable sacral fractures heal in about 8 to 12 weeks. Pain usually improves noticeably within 6 weeks, though full recovery, especially for older adults with insufficiency fractures, can take 3 to 6 months. Fractures with nerve damage or needing surgery take longer.

What is a sacral insufficiency fracture?

It is a break in the sacrum caused by normal everyday stress on bone that has been weakened, usually by osteoporosis, pelvic radiation or long-term steroids. It often occurs without a fall. It mainly affects women over 60 and is frequently mistaken for arthritis or sciatica.

Can you walk with a fractured sacrum?

Usually yes, for stable fractures. Doctors encourage walking as soon as pain allows, often with a walker or crutches, because early movement prevents blood clots, muscle loss and pneumonia. Unstable fractures may need surgery before weight-bearing. Follow your surgeon's weight-bearing instructions.

Does a broken sacrum need surgery?

Most do not. Stable fractures, including most insufficiency fractures, heal with pain relief and early walking. Surgery is needed for unstable fractures, fractures pressing on nerves, and some insufficiency fractures with pain that prevents walking despite good treatment.