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A telltale sign of fracture in a 74-year-old woman

Christopher Davis, MPAS, PA-C, RT; William Jacoby, MD; Asim Khwaja, MD

The authors practice at Associated Radiologists LTD, Banner Baywood Medical Center, Mesa, Arizona. They have indicated no relationships to disclose relating to the content of this article.

CASE

A 74-year-old woman presented to the emergency department with a 3- to 4-day history of intractable lower back pain. The pain had intensified until the patient could no longer walk pain-free. Eventually, any movement of her lower extremities or lower back produced excruciating pain.

The patient had been experiencing chronic back pain for the past 6 years as a result of a motor vehicle accident. Past treatments for the pain included vertebroplasty at the L5 level, epidural and sacroiliac joint steroid injections, spinal stimulation, pain medications, and muscle relaxants.

On physical examination, the patient was alert and oriented. Vital signs and pertinent laboratory data were normal. Cranial nerves II to XII revealed no focal deficits, and motor and sensory examinations were essentially normal, except for a decreased vibratory sense of the ankles and toes. Pain was elicited with any movement of the left lower extremity and localized on palpation to the left sacral region. Deep tendon reflexes were 2+ and Babinski signs were absent. Diagnostic imaging tests included nuclear medicine bone scintigraphy (Figure 1) and CT of the pelvis without contrast (Figure 2). What do these images reveal?

DISCUSSION

Figure 1 reveals abnormal activity within both sacral ala as well as in the midline of the sacrum. The pattern is consistent with a sacral insufficiency fracture. Although no clear fracture lines are seen on CT (Figure 2), the scintigraphic findings strongly suggest a diagnosis of sacral insufficiency. Activity within the axial and appendicular skeleton was otherwise normal. Evaluation for subtle fractures was limited because of pronounced osteopenia within the sacrum. Iliac wings appeared intact. The hips were unremarkable, as was the remainder of the pelvis.

Bilateral percutaneous sacroplasty was performed in an attempt to stabilize the sacral insufficiency fractures, provide pain relief, and hopefully restore mobility. The patient was placed in the prone position on the CT table, and a preliminary axial scan of the sacrum was obtained. The patient’s overlying skin was prepped and draped in a sterile fashion for a posterior bilateral paramedian approach. The right sacrum was treated first. The 21-gauge coaxial needle was advanced to the periosteum and a local anesthetic administered. Subsequently, an 11-gauge trocar needle was advanced into the right sacrum under CT guidance. Polymethyl methacrylate (PMMA) cement mixed with barium tracer was then injected into the sacrum, with progressive withdrawal of the cannula in a stepwise fashion. CT was used to monitor disbursement of the cement material. On completion of the right sacroplasty, CT confirmed that the cement was contained in the right sacrum without extension into the adjacent neural foramina or sacroiliac joint (see Figure 3). The procedure was repeated on the left sacrum, including CT confirmation that the PMMA cement did not extend into the adjacent neural foramina or sacroiliac joint.

Sacral insufficiency can render a patient immobile. This underdiagnosed condition is especially prevalent in patients with osteoporosis, rheumatoid arthritis, or chronic corticosteroid use. These fractures occur when abnormal bone is placed under normal stresses.¹ Symptoms of sacral insufficiency include low back pain below the lumbar region on physical examination, sacroiliac joint pain, and tenderness to palpation in the sacral region. The patient may have experienced a recent trauma; however, this is not always the case.

Diagnostic imaging is required to confirm sacral insufficiency. General radiographs of the pelvis are usually not helpful in diagnosing sacral insufficiency but may reveal other causes of low back pain. CT of the pelvis is often useful but, as was the case in this patient, may only suggest sacral insufficiency. Clear fracture lines are not always evident. The imaging modality of choice is a nuclear medicine bone scintigraphy. A positive finding is indicated by the presence of the Honda sign.² The sign appears as the affected bone takes up the radioactive tracer in the telltale pattern of an “H” in the sacrum. Occasionally, only one side of the sacrum may be “hot,” or have increased uptake, but this is still positive for sacral insufficiency.

Conservative treatment historically consisted of bed rest and analgesics.³ However, early ambulation has its merits because immobility in an elderly patient is associated with increased risk of deep venous thrombosis, pulmonary embolism, decreased pulmonary compliance, and decubitus ulcers. Until recently, no active treatment for this debilitating injury could be offered.⁴

Sacroplasty derives from the technique of vertebroplasty, a procedure in which PMMA is injected into the vertebral body to stabilize the bone and decrease the pain of vertebral compression fractures. The theory is that if vertebroplasty is beneficial for vertebral compression fractures, then sacroplasty may be beneficial for patients suffering from sacral insufficiency because these disease processes are similar in nature.

Technical differences between sacroplasty and vertebroplasty are important to consider. As the sacral nerve roots pass through the sacral foramina, injection of PMMA must be accurately visualized in order to assure a safe distribution; however, the sacrum is difficult to visualize under cross table fluoroscopic guidance in the standard angiography suite. CT guidance provides the opportunity to visualize the placement of the introducer needles in an axial plane before administering the cement; therefore, CT is the imaging modality of choice for performing sacroplasty. Potential risks that are specific to sacroplasty include inadvertent placement of PMMA in the sacral foramen and the sacroiliac joints. Risks common to both vertebroplasty and sacroplasty include infection, excessive bleeding, and failure to relieve the patient’s pain.

Following the procedure, the patient was returned to her room to recover. Twelve hours after CT-guided sacroplasty, the patient described feeling significantly better. Her pain level had decreased to about 1 on a scale of 1 to 10. The next day the patient was discharged to a skilled nursing facility to continue her recovery. In a telephone interview from home 2 weeks after the procedure, the patient reported still feeling low back pain; however, she was ambulatory with a walker and required significantly less pain medication. Follow-up in the interventional radiology clinic will continue.

Julie Vajnar, PA-C, RT, department editor

REFERENCES

	1.	Dasgupta B, Shah N, Brown H, et al. Sacral insufficiency fractures: an unsuspected cause of low back pain. Br J Rheumatol. 1998;37(7):789-793.
	2.	Shearman CM, El-Khoury GY. Pitfalls in the radiologic evaluation of extremity trauma: part II. The lower extremity. Am Fam Physician. 1998;57(6):1314-1322.
	3.	Garant M. Sacroplasty: A new treatment for sacral insufficiency fracture. J Vasc Interv Radiol. 2002;13(12):1265-1267.
	4.	Pommersheim W, Huang-Hellinger F, Baker M, Morris P. Sacroplasty: a treatment for sacral insufficiency fractures. AJNR Am J Neuroradiol. 2003;24(5):1003-1007.