Orthopaedic Surgery - Sacral Insufficiency Fracture

Basics

Sacral insufficiency fractures are a type of:

Fragility fracture

that develop when normal physiologic loads are applied to:

Structurally weakened sacral bone.

They most commonly occur in the:

Sacral ala

between the:

Sacroiliac joint

and

Sacral neural foramina.

This corresponds primarily to:

Denis Zone I.

Characteristic Fracture Pattern

The classic fracture pattern is:

H-shaped.

It consists of:

Vertical fractures through one or both sacral alae

connected by a:

Transverse fracture line.

This characteristic appearance may be seen particularly well on:

Bone scintigraphy

and is often called the:

Honda sign

or

H-sign.

Development of the H-Pattern

The vertical components are thought to develop first as a result of:

Shearing forces through the sacral alae.

Continued pelvic loading and rotation can then produce a:

Transverse fracture

connecting the two vertical components.

Not all patients have a complete H-shaped configuration at diagnosis.

Mechanism of Injury

Sacral insufficiency fractures may occur:

Without a recognized traumatic event.

In approximately:

50% of historical cases

the patient recalls a:

Low-energy fall.

Associated Pelvic Fractures

These fractures frequently occur with other:

Pelvic insufficiency fractures.

The most common associated fractures involve the:

Pubic rami.

Prevention

Prevention is directed toward maintaining or improving:

Bone mineral density.

Measures may include:

Osteoporosis screening

Calcium supplementation when indicated

Adequate vitamin D

Appropriate anti-osteoporosis medication

Fall prevention

Epidemiology

Sacral insufficiency fractures occur primarily in:

Older adults with osteoporosis.

More than:

90% of cases in older series

occurred in:

Postmenopausal women.

Population Distribution

Historical reports described a predominance among:

Caucasian women.

This likely reflects, at least in part, differences in:

Osteoporosis prevalence

and studied populations.

Incidence

The true incidence remains:

Uncertain.

Sacral insufficiency fractures are probably substantially:

Underdiagnosed

because routine radiographs often fail to show the fracture.

Estimated Frequency

Older reports suggested that approximately:

1–2% of patients presenting to rheumatology clinics with lumbar pain

may have an insufficiency fracture involving the:

Pelvic ring.

Risk Factors

Important risk factors include:

Osteoporosis

Inflammatory arthritis

Metabolic bone disease

Chronic corticosteroid use

Pelvic radiotherapy

Primary bone tumor

Metastatic bone disease

Previous fragility fracture

Total Hip Arthroplasty

Sacral insufficiency fractures have also been reported following:

Total hip replacement.

Underlying osteoporosis and changes in:

Pelvic load transmission

may contribute.

Pathophysiology

During standing and walking, force is transferred from the:

Spine

through the:

Sacrum

and then around the:

Pelvic ring

toward the lower extremities.

Osteoporotic Bone

In patients with poor bone quality, repeated:

Pelvic rotation

Tilting

and

Axial loading

can generate sufficient shear forces to create:

Microfractures within the sacral alae.

Vertical Fracture Formation

The initial microfractures may be:

Unilateral

and later progress to:

Bilateral vertical fractures.

Transverse Component

Continued motion around different pelvic axes can eventually generate a:

Horizontal or transverse fracture line

between the vertical fractures.

Imaging Correlation

This proposed mechanism explains why bone scans may demonstrate:

One vertical limb

Two vertical limbs

or the complete:

H-shaped pattern

depending on how far the fracture has progressed before diagnosis.

Etiology

Many cases occur without:

Antecedent trauma.

Others follow a:

Minor fall

or another low-energy event.

The underlying cause is usually:

Reduced bone strength.

Associated Conditions

Common associated conditions include:

Osteoporosis

Pubic ramus insufficiency fractures

Other pelvic fragility fractures

Vertebral compression fractures

Diagnosis

Diagnosis can be difficult because there is no single symptom or examination finding that is:

Pathognomonic.

A high index of suspicion is required.

Signs and Symptoms

The most common clinical presentation is:

Low-back pain

Sacral pain

or

Buttock pain.

Mechanical Pain

Pain is usually aggravated by:

Sitting

Standing

Walking

Weight bearing

and other forms of mobilization.

Relief With Rest

Symptoms often improve when the patient:

Lies down

or reduces weight-bearing activity.

History

Patients may report:

Gradual onset of low-back or buttock pain

with no obvious trauma.

A minor fall may only be identified after:

Detailed questioning.

Important Historical Features

Ask about:

Known osteoporosis

Previous pelvic insufficiency fracture

Vertebral compression fracture

Chronic corticosteroid therapy

History of malignancy

Recent pelvic radiotherapy

Physical Examination

Physical findings are often:

Nonspecific.

Sacral Tenderness

There may be:

Pain with direct palpation of the sacrum.

Weight-Bearing Pain

Standing or walking may reproduce:

Sacral or buttock pain.

Neurologic Examination

A neurologic examination should be performed to exclude:

Lumbar radiculopathy

Spinal stenosis

Malignancy

and other neurologic causes.

Neurologic deficits are uncommon in uncomplicated sacral insufficiency fractures.

Laboratory Tests

Laboratory tests do not establish the diagnosis.

Alkaline Phosphatase

Serum:

Alkaline phosphatase

may be mildly elevated because of:

Bone healing activity.

Metabolic Bone Workup

Patients with fragility fractures may require evaluation of:

Calcium

Phosphate

Vitamin D

Renal function

Parathyroid hormone

and other tests when secondary osteoporosis is suspected.

Imaging

Plain Radiographs

Plain radiographs are frequently:

Normal or nondiagnostic.

They have relatively poor sensitivity for sacral insufficiency fractures.

Radiographic Findings

When abnormalities are visible, they may include:

Sclerosis

Fracture lucency

Cortical irregularity

or associated:

Pubic ramus fractures.

Bone Scintigraphy

Bone scintigraphy is:

Highly sensitive.

The classic finding is an:

H-shaped or butterfly pattern of increased uptake.

Honda Sign

The characteristic H-shaped uptake pattern is commonly known as the:

Honda sign.

Although strongly suggestive, the complete pattern is:

Not present in every patient.

CT

CT can accurately demonstrate:

Fracture lines

Cortical disruption

Sclerosis

and the overall:

Fracture configuration.

It is particularly useful when distinguishing fracture from:

Tumor or other destructive bone disease.

MRI

MRI is highly sensitive and often demonstrates the fracture before it becomes visible on:

Plain radiographs.

MRI Findings

Typical findings include:

Low signal intensity on T1-weighted images

and

High signal intensity on T2-weighted or fluid-sensitive sequences

because of:

Bone marrow edema.

A low-signal fracture line may also be visible.

MRI H-Pattern

When the complete fracture is present, MRI may reproduce the characteristic:

H-shaped configuration.

Bone Density Assessment

A:

DEXA scan

should be considered to evaluate:

Bone mineral density

and identify osteoporosis requiring treatment.

Differential Diagnosis

Important alternatives include:

Malignancy

Infection

Lumbar degenerative disease

Sacroiliac joint pathology

Vertebral compression fracture

Hip pathology

Malignancy

Sacral insufficiency fracture may mimic:

Metastatic bone disease

especially in patients with a history of:

Cancer

or

Radiotherapy.

Advanced imaging can help distinguish these disorders.

Infection

Sacral osteomyelitis should be considered when the clinical picture includes:

Fever

Systemic illness

Marked inflammatory marker elevation

or imaging findings atypical for a fragility fracture.

Treatment

Initial Stabilization

Initial treatment focuses on:

Pain relief

and short-term reduction of painful activity.

Bed Rest

A brief period of:

Relative bed rest

may be required when pain is severe.

However, prolonged bed rest should be avoided whenever possible.

General Measures

Sacral insufficiency fractures are usually:

Mechanically stable.

Once pain is reasonably controlled, the patient should begin:

Mobilization as tolerated.

Early Mobilization

Early mobilization helps prevent complications associated with prolonged recumbency, including:

Muscle wasting

Further bone demineralization

Venous thromboembolism

Pressure ulcers

Pulmonary complications

Assistive Devices

Temporary use of:

Walker

Cane

or other ambulatory support may reduce pain while allowing continued movement.

Nursing Care

Patients with limited mobility should be monitored for:

Pressure injuries

Constipation

Deconditioning

and other complications of prolonged inactivity.

Opioid-Related Care

Patients requiring opioid analgesia should generally receive an appropriate:

Bowel regimen

to reduce constipation.

Physical Therapy

Physical therapy may assist with:

Gait

Balance

Lower-extremity strengthening

Functional mobility

and

Fall prevention.

Medication

First-Line Analgesia

Pain may be treated with:

Acetaminophen

and, when needed,

Short-term opioid analgesia.

Osteoporosis Management

Treatment should also address the underlying abnormality in:

Bone strength.

Potential measures include:

Calcium

Vitamin D

and appropriate pharmacologic therapy for:

Osteoporosis.

Bisphosphonates

Bisphosphonates may be used as part of long-term osteoporosis management when:

Clinically indicated.

They are not primarily used as an acute analgesic treatment for the fracture.

Calcitonin

Calcitonin has historically been used for:

Osteoporosis

and fracture-related pain, although its role is now more limited.

Anabolic Therapy

Selected patients with severe osteoporosis or repeated fragility fractures may be candidates for:

Bone-forming anabolic therapy

under specialist supervision.

Sacroplasty

For persistent, severe pain that prevents mobilization despite appropriate nonoperative treatment:

Percutaneous sacroplasty

may be considered.

Sacroplasty Technique

Sacroplasty involves injection of small amounts of:

Bone cement

into the sacral fracture region.

The goal is to reduce:

Fracture micromotion

and improve:

Pain and mobility.

Image Guidance

Sacroplasty is performed using:

CT

or

Fluoroscopic guidance

under regional or general anesthesia depending on the technique and patient.

Sacroplasty Risks

Potential complications include:

Cement extravasation

Nerve injury

Vascular injury

and rare embolic complications.

Operative Fixation

Internal fixation is rarely necessary.

It may be considered in patients with:

Established painful nonunion

Persistent instability

or failure of other treatments.

Follow-Up

Patients should be monitored until they become:

Pain free

and regain functional:

Mobility.

Follow-Up Imaging

Older treatment protocols recommended pelvic radiographs at approximately:

6–8-week intervals.

Because radiographs may remain insensitive, repeat CT or MRI is generally reserved for:

Persistent symptoms

Concern for nonunion

or

Diagnostic uncertainty.

Referral

Orthopaedic referral is appropriate when there is:

Failure of fracture healing

Persistent disabling pain

Neurologic abnormalities

or concern regarding:

Instability or nonunion.

Osteoporosis Referral

Patients with severe osteoporosis or an unexplained fragility fracture may require evaluation by an:

Endocrinologist

Metabolic bone specialist

or dedicated:

Osteoporosis service.

Prognosis

Most uncomplicated fractures treated nonoperatively heal within approximately:

3–4 months.

Functional improvement may occur earlier as pain decreases.

Prognostic Factors

Recovery may be influenced by:

Age

Bone quality

Associated pelvic fractures

Mobility

Medical comorbidities.

Complications

Delayed Union

Severe osteoporosis and continued abnormal loading can contribute to:

Delayed fracture healing.

Recurrent Insufficiency Fracture

Patients remain at risk of additional:

Pelvic

Vertebral

and other fragility fractures if the underlying osteoporosis is not treated.

Nonunion

True sacral nonunion is uncommon but can cause:

Chronic pain

and persistent difficulty with:

Weight bearing.

Chronic Pain

Some patients continue to experience:

Low-back

Sacral

or

Buttock pain

after the expected healing period.

Operative Complications

Potential complications of interventional or surgical treatment include:

Injury to the iliac vessels

Lumbosacral nerve root injury

Cement leakage

Infection

Patient Monitoring

Follow-up should assess:

Pain

Walking ability

Weight-bearing tolerance

Neurologic status

Evidence of healing

Fall risk

and treatment of:

Underlying osteoporosis.

Key Principle

Sacral insufficiency fracture is a fragility fracture of the sacrum most commonly seen in older osteoporotic women, often after little or no trauma.

The classic configuration consists of:

Vertical sacral alar fractures joined by a transverse fracture, producing an H-shaped or Honda-sign pattern on bone scintigraphy.

Because plain radiographs frequently miss the diagnosis, persistent mechanical sacral or buttock pain in an at-risk patient should prompt consideration of:

MRI, CT, or bone scintigraphy.

Most fractures are treated successfully with:

Pain control, early mobilization, rehabilitation, and treatment of osteoporosis, while persistent disabling pain or nonunion may require:

Sacroplasty or operative stabilization.