What Is a Sacral Fracture and How Is It Treated?

A sacral fracture is a break in the sacrum, the large triangular bone at the base of your spine that connects to the pelvis on each side. These fractures range from hairline cracks caused by repetitive stress or weakened bone to severe, displaced breaks from high-energy trauma like car crashes. Treatment depends heavily on the type: some heal with rest and pain management, while others require surgery to stabilize the pelvis and protect the nerves that run through the sacrum. What makes sacral fractures particularly tricky is that they are frequently missed on initial imaging, sometimes for weeks, which can delay the right treatment and lead to lasting problems.

How Sacral Fractures Happen

Sacral fractures fall into three broad categories based on what caused them, and understanding the cause matters because it shapes everything from the severity of the injury to the treatment plan.

High-energy traumatic fractures happen in younger people after events like motorcycle crashes, car accidents, and falls from significant height.¹ These injuries tend to be severe, often involving displacement of bone fragments and disruption of the pelvic ring. Because the pelvis is a ring-shaped structure, a break in the sacrum frequently means damage elsewhere in the ring too. One case report describes an 18-year-old motorcyclist who sustained a transverse sacral fracture at the S2 level with posterior displacement and immediate neurological deficits including loss of sphincter control.² That kind of injury almost always requires surgical intervention.

Insufficiency fractures are the opposite end of the spectrum. They develop in older adults, primarily postmenopausal women, whose bones have weakened from osteoporosis or other metabolic bone conditions. There is often no obvious trauma at all, or the triggering event is something as minor as stepping off a curb.³ Biopsy studies of bone from patients with sacral insufficiency fractures show a distinct pattern: not just the loss of trabecular structure you would expect with osteoporosis, but also pronounced under-mineralization of the bone that remains, with evidence of chronic micro-damage trying to heal.⁴ Radiation therapy for pelvic cancers also weakens the sacrum and can cause insufficiency fractures. A meta-analysis of over 11,000 female patients found that pelvic insufficiency fracture rates after definitive radiation were around 25%, and that modern techniques like IMRT reduced the rate compared to older methods.⁵

Stress fractures in athletes are the third category. These develop from repetitive loading rather than a single impact or bone weakness. Long-distance runners are the classic group affected, though any high-mileage endurance sport can be the culprit. Some research suggests that among athletes with pelvic stress injuries, the incidence of sacral stress fractures may be as high as 20%.⁶ These fractures are distinct from both traumatic and insufficiency fractures because the bone itself is healthy; it simply could not keep up with the repetitive stress placed on it.

Symptoms and When Nerves Are Involved

The most common complaint is pain in the low back, buttocks, or sacral region. In athletes with stress fractures, the onset is usually gradual and worsens with activity, and the presentation can look a lot like a disc problem or sacroiliac joint dysfunction.⁷ In older adults with insufficiency fractures, the pain often seems to come out of nowhere and is severe enough to limit walking or even sitting. Many patients with insufficiency fractures present to the emergency department complaining of nonspecific low back pain, which is part of why these fractures are so frequently misdiagnosed.⁸

What sets sacral fractures apart from many other pelvic injuries is the neurological risk. The sacrum houses the sacral nerve roots, which control bladder and bowel function, sexual function, and sensation in the saddle area and parts of the legs. When a fracture displaces bone into the sacral canal or foramina, these nerves can be compressed or damaged. Symptoms range from numbness and weakness in a foot to full-blown cauda equina syndrome with loss of bladder and bowel control. In one reported case of a severe pelvic ring injury, the patient had nerve deficits at multiple levels and still had residual weakness and needed a leg brace a year after surgery.⁹ When sacral fractures go unrecognized for weeks, patients can present late with incontinence and numbness as their primary complaints, a scenario that carries a worse prognosis.¹⁰

Why These Fractures Are So Often Missed

Sacral fractures have a reputation in emergency medicine and orthopedics as being under-recognized, and the numbers back that up. A study of geriatric U-type sacral fractures found that more than a third were missed on initial evaluation. Of those missed fractures, over half were never caught during the patient’s episode of care at all.¹¹ The problem is not just carelessness. Plain X-rays are genuinely poor at showing sacral fractures because the sacrum is overlaid by bowel gas, the pelvic bones, and other soft tissues that obscure fracture lines.

How much better are advanced imaging methods? A study comparing the three main modalities found that plain X-rays detected only about 29% of sacral insufficiency fractures. CT raised that to about 94%. MRI caught every fracture in the study and also showed details that CT missed, including bone marrow swelling and the extent of surrounding tissue involvement.¹² For athletes with suspected stress fractures, MRI is the imaging method of choice because it can pick up the bone marrow edema that precedes a visible fracture line. On MRI, a sacral stress fracture typically appears as an area of abnormal signal running parallel to the sacroiliac joint.⁷

Even CT can miss certain fracture patterns, particularly the horizontal component of U-shaped fractures in older patients. The sacrum curves, and standard axial CT slices can fail to capture a transverse fracture that runs along the curve. Radiologists have to actively look for these patterns, and when they do not, the fracture goes unreported. If you are an older adult with new, unexplained low back or sacral pain and a negative X-ray, pushing for an MRI is a reasonable step.

Non-Surgical Treatment

Most sacral insufficiency fractures and stress fractures are treated without surgery. The approach centers on pain control, activity modification, and a gradual return to weight-bearing. For insufficiency fractures, conservative management is typically reserved for fractures that are not displaced and where pain can be adequately managed within about a week so that the patient can begin mobilizing.¹³ Prolonged bed rest is avoided because it accelerates bone loss and deconditioning, exactly what an already-osteoporotic patient does not need.

For athletic stress fractures, treatment means stopping the offending activity. Most patients in a case series of 13 athletes with sacral stress fractures had been running or jogging when symptoms began.¹⁴ Recovery typically involves a period of non-weight-bearing or reduced activity followed by a slow, structured return. Cross-training with low-impact activities like swimming or cycling is usually introduced early to maintain cardiovascular fitness while the bone heals. Runners are understandably anxious to get back to training, but returning too soon risks re-injury or progression to a complete fracture.

Sacroplasty for Persistent Pain

When an insufficiency fracture does not respond well to conservative treatment, or when pain is severe enough that the patient cannot mobilize at all, sacroplasty is an option. The procedure is essentially the sacral equivalent of vertebroplasty: a needle is guided into the fracture site under imaging, and bone cement is injected to stabilize the break and reduce pain. It can be performed through several different technical approaches depending on the fracture’s location.¹⁵

The results from a prospective registry of the first 102 patients treated with sacroplasty are striking. Average pain scores dropped from about 7.8 out of 10 before the procedure to under 1 at six months. Functional scores improved by a similar margin. Cement leakage occurred in roughly 18% of cases, but only one patient experienced a new neurological deficit from the leakage.¹⁶ Sacroplasty is not a first-line treatment for everyone with an insufficiency fracture, but for patients who remain in severe pain and cannot participate in rehabilitation, it can be a reliable way to get them moving again.

Surgical Fixation for Unstable Fractures

When a sacral fracture is displaced or the pelvic ring is unstable, surgery is usually needed. The goal is to restore the normal alignment of the pelvis, hold the fragments in place while they heal, and protect the nerves running through the sacrum. Several fixation methods exist, and the choice depends on the fracture pattern, the patient’s anatomy, and the surgeon’s experience.¹⁷

The main hardware options include iliosacral screws that cross from the ilium into the sacral body, trans-sacral screws that pass all the way across the sacrum, and lumbopelvic (spinopelvic) fixation that connects the lumbar spine to the pelvis with rods and screws. Finite element analysis of fragility fractures has shown that trans-sacral screws can provide stability similar to more complex constructs like bilateral triangular fixation, with less invasiveness, when the patient’s anatomy allows safe screw placement.¹⁸ Intraoperative navigation and 3D imaging have become increasingly important in these procedures because the anatomy is complex and there is very little room for error when placing screws near the sacral nerve roots.

Biomechanical studies also compare these fixation strategies across different fracture locations within the sacrum. The fracture’s position relative to the sacral foramina matters: a fracture running through the lateral ala behaves differently under loading than one running through the central canal, and the optimal hardware may differ accordingly.¹⁹ The trend in the field is toward less invasive, percutaneous techniques when the fracture pattern and patient allow, reserving open surgery for the most complex injuries.

When Nerve Decompression Is Needed

Deciding whether to surgically decompress the sacral nerves is one of the more nuanced decisions in sacral fracture management. An expert consensus statement laid out the thinking in detail: not every neurological deficit requires a laminectomy. An isolated, incomplete nerve deficit after a displaced sacral fracture from high-energy trauma is not, by itself, an indication for decompression surgery after the fracture has been reduced. But if the deficit is worsening or progressive, decompression becomes indicated.²⁰

The reasoning behind this conservative approach gets support from outcome data. A study comparing patients who underwent direct decompression (laminectomy to physically relieve pressure on the nerves) with those who had only indirect decompression (fracture reduction and stabilization without opening the spinal canal) found similar functional outcomes and neurological recovery in both groups. Restoring the alignment of the pelvis and stabilizing the fracture seem to be the key factors, and the nerves often recover on their own once the bone is back in position and the fracture is stable.²¹ That said, a complete nerve deficit with clear evidence of root compression on MRI, particularly in a lower-energy injury, shifts the balance toward decompression.²⁰

Bone-Building Medication for Insufficiency Fractures

Because sacral insufficiency fractures are fundamentally a bone quality problem, treating the underlying bone disease is at least as important as treating the fracture itself. Teriparatide, a synthetic form of parathyroid hormone that stimulates new bone formation, has shown promising results specifically in sacral insufficiency fractures. A controlled trial in elderly patients found that the median time to visible callus formation was about 10.6 weeks in the teriparatide group versus 13.6 weeks in controls. At the eight-week mark, every fracture in the treatment group had healed compared to only 10% in the control group.²²

A separate study comparing teriparatide directly against sacroplasty in postmenopausal women with sacral insufficiency fractures found that the drug group actually healed better at one month than those who received cement augmentation.²³ A smaller observational study of seven elderly women treated with teriparatide for at least six months found that average pain scores dropped from about 87 out of 100 to about 13, and CT imaging showed bone union or sclerotic healing changes at the fracture sites in all patients.²⁴ These are small studies, but the consistency of the results across different research groups makes a reasonable case that anabolic bone therapy deserves a role in managing these fractures, not just standard osteoporosis medications that slow bone loss.

Nonunion and Chronic Pain

Most sacral fractures heal, but nonunion does happen. It is rare, and it tends to occur when fractures are missed initially or managed inadequately.²⁵ When it does occur, the consequences are significant: chronic pain in the lower back and buttocks, discomfort while sitting, and major limitations in daily activity.²⁶ Surgical treatment of sacral nonunion typically involves bone grafting and fixation, but it is a more complex procedure than treating a fresh fracture, and outcomes are less predictable. The best prevention is getting the diagnosis right the first time and treating the fracture appropriately from the start.

Sacral Fractures During Pregnancy and in Children

Pregnancy-related sacral fractures are an uncommon but real phenomenon. In a series of 23 cases, about a quarter of patients developed pain during the final trimester, while the remaining three-quarters reported symptoms in the postpartum period.²⁷ The combination of hormonal changes that loosen ligaments, increased body weight, and altered gait mechanics during pregnancy can place enough stress on the sacrum to cause a fracture, even in women with no prior bone disease. These are stress fractures rather than traumatic ones, and they are generally managed conservatively with rest and gradual return to activity. The key challenge is recognition: low back and pelvic pain are so common in late pregnancy and postpartum that a fracture may not be considered until the pain fails to resolve.

In children, sacral fractures are rare. A review of nearly 4,900 pediatric trauma cases at a children’s hospital identified only eight sacral fractures over seven years. Most were lateral fractures that did not involve the nerves and healed without surgery. Only one child, who had a fracture through the central canal with a significant nerve injury, needed an operation.²⁸ Children’s bones are more flexible and heal faster, so the threshold for surgical intervention is higher, and outcomes are generally good. The main concern, as with adults, is making sure the fracture is identified in the first place rather than being attributed to a soft-tissue injury.