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Complications of Sacroplasty

Harold Cordner MD, FIPP

Florida State University School of Medicine, Vero Beach, FL, USA

Introduction

Percutaneous sacroplasty has become a preferred treatment modality for sacral insufficiency fractures. Sacral insufficiency fractures are typically the result of undue stress on osteoporotic bones in the elderly population, however, they can also happen as a result of trauma. Patients may have debilitating symptoms as a result, ranging from low back pain to thigh and hip discomfort [1]. Treatment of sacral insufficiency fractures may be conservative, interventional or surgical. Unstable fractures usually require surgical open reduction and fixation and have a higher risk of complications and infection compared with percutaneous reduction.

Conservative treatment has mainly been bedrest, oral analgesics, partial weight-bearing, sacral bracing or corsets and physical therapy. Prolonged bed rest and immobility is associated with the development of DVT, pneumonia, pulmonary embolism, muscle atrophy, skin breakdown and pressure ulcers, constipation and fecal impaction and depression [1, 2]. Fifty percent of patients will not return to their prior level of function and the overall 1-year mortality rate is 14.3% [3]. Although most fractures will heal, resolution of symptoms may take 9–12 months, more aggressive treatment such as percutaneous sacroplasty will benefit patients who are incapacitated. Further, sacroplasty offers the potential of earlier return to activities of daily living, decreased pain and less opioid utilization [2–4].

Sacroplasty, first described by Dehdashti in 2000, for treatment of metastatic sacral lesions was developed as an extension of vertebroplasty by injecting polymethylmethacrylate (PMMA) into the sacrum to provide support and relief of pain [5]. Over the last two decades, its use has become more commonplace with similar goals of earlier symptom resolution and return to pre-injury function [2].

Diagnosis

The diagnosis of sacral insufficiency fracture is suspected when the patient presents with lower back, sacral or buttock pain, which can radiate to the thighs. Diagnosis is usually made with radiologic imaging to confirm sacral fractures. Frequently, conventional X-rays will not be adequate to visualize sacral fractures and may even be missed on CT imaging. The gold standard which yields the highest specificity and sensitivity is magnetic resonance imaging (MRI). Traditionally ordered lumbar MRI may not have enough field of view to see the sacrum adequately, so a dedicated sacral MRI is the best study to order. Coronal views with fat-suppressed T2 and STIR sequences are the best imaging to see sacral fractures. If a patient cannot undergo MRI scanning, CT and bone scan can be performed, however, a bone scan may be positive for up to one year after fracture, so it is the most sensitive, but least specific study (Figures 56.1a,b ).

**Figure 56.1** (a) Coronal MRI-STIR image showing bilateral sacral insufficiency fractures. (b) Coronal T2-MRI image showing bilateral sacral insufficiency fractures.

Anatomy

The sacrum is composed of five fused sacral segments and weight can be transferred through these segments which causes a unique appearance of sacral fractures. The sacrum is responsible for transmitting forces that occur along the spinal axis and functions as a structure through which forces from the upper body and lower extremities are transmitted and dissipated to enhance stability of the pelvic girdle. Insufficiency fractures due to osteoporosis extend in a cranial-caudal direction in parallel with the vector of force transmission through the sacral ala. Alhough various classification systems have been developed for sacral fractures, the Denis classification system is the most widely used and divides fractures into three zones. Zone 1 fractures lateral to the sacral foramina, Zone 2 fractures occur through the foramina but do not involve the central canal and Zone 3 injuries occur medial to the foramina and involve the spinal canal. The most common are classified as Zone 1, fractures extending from the sacral ala inferiorly. Transverse fractures across the sacral body can also commonly be seen with Zone 1 fractures, and are visualized as the classic H or “Honda sign” on bone scan (Figure 56.2a,b).

**Figures 56.2** **(a)** and **(b)** Bone scan images showing classic “H” or Honda sign.

It is important to be able to identify and visualize the appropriate anatomy for performing sacroplasty. These structures are the posterior, anterior and superior borders of the sacrum, the sacral foramen, the sacroiliac joint and sacral canal. Proper needle placement is critical and care must be taken to ensure the needle stays in the body of the sacrum. Some advocate use of CT and fluoroscopy to aid in correct placement. However, with proper identification of these structures, sacroplasty has been safely performed with fluoroscopy alone in most cases (Figure 56.3).

**Figure 56.3** Denis classification of Zones 1, 2 and 3 sacral fractures.

Indications

Acute or Sub-acute sacral fractures (benign or pathologic).

Contraindications

Unstable fractures or acute neurologic deficits related to the fracture
Infection, either local or systemic
Uncontrolled coagulopathy or bleeding disorder
Displaced sacral fractures
Compromise of the sacral foramina
Patient refusal.

Concerns for Sacroplasty Procedure

Metastatic lesions and extension into the sacrum
Coagulopathy or bleeding disorder
Immunocompromised or high risk of infection
Transverse fractures or fractures extending to the sacral foramen
Poor visualization of anatomy.

Technique

The patient is placed in the prone position on the fluoroscopy table and sterile prep and drapes are applied. Strict sterile technique is used. Sacroplasty is performed either by fluoroscopic guidance, computed tomography (CT) guidance or a combination of both. When visualizing the sacrum under CT guidance, the choice of the entry site depends on the fracture lines. For H-shaped fractures, one may choose fixation of the horizontal component by accessing the needle puncture posterolaterally through the sacroiliac joint. Other alternative sites are punctures over the sacral ala with angulation of the needle between the spinal canal and the ipsilateral sacral foramen. The lateral fractures can be accessed by placing the trocars more medially and advancing the trocar slightly laterally avoiding the sacral foramen and parallel to the fracture line (Figure 56.4a,b).

**Figure 56.4** (a) AP fluoroscoopy image of spinal needles in sacral foramen and sacroplasty trocars placed lateral to the foramen bilaterally. (b) Lateral fluoroscopy image of spinal needles in sacral foramen and sacroplasty trocars placed lateral to the foramen bilaterally.

For the fluoroscopic technique, needles may be placed in the lateral aspect of the sacral foramen to help aid visualization of the foramen during the procedure.

Cordner describes a variation of the short-axis technique using fluoroscopic visualization [6

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