Sacral Insufficiency Fracture

By admin Last updated Feb 27, 2024

Ovid: 5-Minute Orthopaedic Consult

Editors: Frassica, Frank J.; Sponseller, Paul D.; Wilckens, John H.

Title: 5-Minute Orthopaedic Consult, 2nd Edition

> Table of Contents > Sacral Insufficiency Fracture

Sacral Insufficiency Fracture

Matthew D. Waites AFRCS (Ed)

Simon C. Mears MD, PhD

Basics

Description

Sacral Insufficiency fractures occur in the sacral ala between the SI joints and the neural foramina (Denis Zone 1) (1).
- The fracture pattern adopts a characteristic H-shape, which is pathonemonic of the condition.
- It is postulated that the vertical limbs of the H occur 1st, followed by the transverse fracture line.
- In ~50% of cases, the fracture results from low-energy trauma such as a fall (2).
Sacral insufficiency fractures often are
associated with other insufficiency fractures around the pelvic girdle,
most commonly the pubic rami.

General Prevention

Maintenance of adequate bone mineral density in patients
with osteoporosis, including bone density monitoring and treatment with
calcium, vitamin D, and bisphosphonates

Epidemiology

>90% occur in postmenopausal females (3)
Predominantly Caucasian females (2)

Incidence

Currently, the true incidence is unknown,
but based on the fact that plain radiographs do not diagnose the
injury, they may be grossly underreported.
It is estimated that 1–2% of patients
attending a rheumatology clinic with lumbar pain have an insufficiency
fracture of the pelvic girdle (3).

Risk Factors

Osteoporosis
Inflammatory arthritis
Primary bone or metastatic neoplasms
Radiotherapy (4)
Metabolic bone disease
Corticosteroids
Total hip replacement (5–7)

Pathophysiology

The mechanism of injury has yet to be defined, but theoretically:
- During ambulation, load is transmitted from the spine through the sacrum around the pelvic rim to the lower limbs.
- In people with osteoporosis, the tilting
  and rotation of the pelvis during ambulation or sudden load
  transmission during a fall creates shear forces that generate
  microfractures vertically in the sacral ala.
- These fractures may be unilateral initially before progressing bilaterally.
- Continued tilting and rotation of the
  pelvis around 2 cross-axes lead to microfracture transversely between
  the 2 vertical fracture lines (2,8,9).
This theory explains the characteristic H
or butterfly appearance on bone scintigraphy and why, in some sacral
insufficiency fractures, only 1 or 2 vertical fractures are apparent,
depending on how far the fracture has propagated before the diagnosis
is made.

Etiology

Sometimes no antecedent trauma is apparent.
Low-energy fall in up to 50% (2)

Associated Conditions

Other insufficiency fractures around the pelvic girdle
Vertebral compression fractures
Osteoporosis

Diagnosis

Signs and Symptoms

No clear set of symptoms that pinpoints the diagnosis
Suspicion of a sacral insufficiency fracture should be raised in the presence of mechanical low back and buttock pain.
Pain is exacerbated by sitting or mobilizing.

History

Low back and buttock pain of gradual onset that is relieved by lying down.
Sometimes a fall is recalled on questioning.
Diagnosis of cancer
Recent radiotherapy
Previous or concurrent insufficiency fracture of the pelvic girdle
Corticosteroids

Physical Exam

Pain on palpation of sacrum
Pain with weightbearing

Tests

Lab

Alkaline phosphatase may be elevated.

Imaging

Plain radiographs are unhelpful (rarely show fracture).
Bone scintigraphy is the test of choice (shows characteristic H-shape).
CT can outline the fracture accurately.
MRI signs are sensitive but not specific:
- Band of low signal on T1-weighted images
- High-signal associated with edema on T2-weighted images

Diagnostic Procedures/Surgery

DEXA scan to determine bone density

Differential Diagnosis

Malignancy
Infection

P.363

Treatment

Initial Stabilization

Pain relief
Bed rest

General Measures

Activity

Sacral insufficiency fractures are stable.
Once pain is controlled, the patient should be mobilized to avoid complications associated with prolonged recumbency.
Early mobilization reduces additional bone demineralization.

Nursing

Patients at rest should be monitored carefully for decubitus ulcers.
Patients on narcotics should be given stool softeners.

Special Therapy

Physical Therapy

Therapy may help in strengthening after the fracture is healed.

Medication

First Line

Acetaminophen
Oral narcotic analgesics

Second Line

Calcium
Vitamin D
Calcitonin
Diphosphonates

Surgery

In cases of prolonged and persistent pain resistant to analgesics, sacroplasty may be considered (8,10,11).
- Percutaneous injection of small aliquots of bone cement into the fracture site to prevent micromotion at the fracture
- Performed under regional or general anesthetic using CT guidance
- The use of bone cement in this manner is not FDA approved.
Operative internal fixation can improve pain in patients with established nonunion of the sacrum (12).

Follow-up

Patients should be monitored with radiographs of the pelvis at 6–8-week intervals until pain free.

Disposition

Issues for Referral

Awareness of these insufficiency fractures is key.
Patients whose fractures do not heal should be referred to an orthopaedist.
Patients with severe osteoporosis may need referral to an osteoporosis specialist for metabolic workup.

Prognosis

Most reported cases treated nonoperatively heal in 3–4 months (3).

Complications

Nonoperative treatment:
- Delayed union
- Recurrent Insufficiency fracture
Operative treatment:
- Damage to iliac vessels
- Damage to lumbosacral nerve roots
- Chronic pain

References

1. Denis F, Davis S, Comfort T. Sacral fractures: An important problem. Retrospective analysis of 236 cases. Clin Orthop Relat Res 1988;227:67–81.

2. Leroux JL, Denat B, Thomas E, et al. Sacral insufficiency fractures presenting AS acute low-back pain. Biomechanical aspects. Spine 1993;18:2502–2506.

3. Weber M, Hasler P, Gerber H. Insufficiency fractures of the sacrum. Twenty cases and review of the literature. Spine 1993;18:2507–2512.

4. Baxter NN, Habermann EB, Tepper JE, et al. Risk of pelvic fractures in older females following pelvic irradiation. JAMA 2005;294:2587–2593.

5. Carter SR. Stress fracture of the sacrum: brief report. J Bone Joint Surg 1987;69B:843–844.

6. Davies AM. Stress lesions of bone. Current Imag 1990;2:209–216.

7. Launder WJ, Hungerford DS. Stress fracture of the pubis after total hip arthroplasty. Clin Orthop Relat Res 1981;159:183–185.

8. Cooper KL, Beabout JW, Swee RG. Insufficiency fractures of the sacrum. Radiology 1985;156: 15–20.

9. Ries T. Detection of osteoporotic sacral fractures with radionuclides. Radiology 1983;146: 783–785.

10. Garant M. Sacroplasty: a new treatment for sacral insufficiency fracture. J Vasc Interv Radiol 2002;13:1265–1267.

11. Pommersheim W, Huang-Hellinger F, Baker M, et al. Sacroplasty: A treatment for sacral insufficiency fractures. Am J Neuroradiol 2003;24:1003–1007.

12. Mears DC, Velyvis JH. In situ fixation of pelvic nonunions following pathologic and insufficiency fractures. J Bone Joint Surg 2002;84A:721–728.

Miscellaneous

Codes

ICD9-CM

805.6 Fracture sacrum, closed
808.2 Fracture pubis, closed
808.43 Multiple pelvic fractures, closed

Patient Teaching

Activity

Activity should be restricted to a level that does not cause pain.
Assistive devices, such as a walker or a cane, should be used during healing.

Prevention

Maintain mobility.
Adequate daily calcium in diet
Osteoporosis prevention and treatment

FAQ

Q: How are sacral insufficiency fractures treated?

A: With activity modification, ambulatory aids, and oral pain medicines. Osteoporosis should be treated.