Introduction

Iliolumbar fixation is an important adjunctive technique that may be beneficial for the operative management of multiple conditions affecting the aging spine, including untreated idiopathic or degenerative scoliosis, sagittal plane deformities such as kyphosis or flat-back syndrome, high-grade spondylolisthesis, sacral fractures, tumors or infections requiring sacrectomy, and stenotic lesions distal to a multilevel lumbar arthrodesis. It has been well established that the biomechanical and biological conditions unique to this region make it more difficult to achieve a successful fusion. Therefore, the incorporation of instrumentation into the pelvis is extremely valuable in many situations, because it helps to restore spinal balance and confers greater stability to the lumbosacral junction. The increasing rigidity of these constructs may also serve to enhance bone formation in complex reconstructive cases that may otherwise be prone to the development of a nonunion.

Reliable fixation to the pelvis was first achieved in the 1970s with Luque instrumentation which utilized a bar with a curved distal end that could be advanced into the iliac crest. A decade later, the Galveston method was introduced, which provided even greater fixation because it allowed for the application of contoured rods, which were inserted though the posterior superior iliac spine, in between the inner and outer tables of the pelvis, toward the sciatic notch. Nevertheless, these early systems were still found to give rise to an relatively high incidence of pseudarthrosis, ranging from 6% to 41%.¹

Iliac screws improve on these initial approaches by taking advantage of innovations in implant design and modularity. These constructs are not only more rigid; their pull-out strength has been shown to be three times greater than that of a standard Galveston rod.² Given their superior biomechanical properties, it is anticipated that the use of iliac screws may reduce the risk of pseudarthrosis compared to other types of lumbosacral constructs. However, the proper placement of this instrumentation requires an intricate knowledge of pelvic anatomy in order to avoid cortical breaches through the ileum or penetration into the acetabulum.³ Furthermore, the surgeon must also take into account the position of the screws for the purpose of contouring the rod and ensure adequate soft tissue coverage to ensure the heads will not be too prominent, which could contribute to patient discomfort.⁴

Case Studies

Clinical Case #1—Degenerative Scoliosis

A 69-year-old woman presents with complaints of severe axial low back pain that radiates into her anterior thighs in conjunction with a curvature of her thoracolumbar spine. The patient had previously been treated in a Milwaukee brace for a diagnosis of adolescent idiopathic scoliosis until skeletal maturity but had never undergone a previous spinal procedure. She feels as if her symptoms and her deformity have been worsening despite multiple conservative treatments, including physical therapy, pain medications, and a series of spinal injections. Her past medical history is notable for osteoporosis and a 30 pack-year history of smoking.

Physical examination findings include obvious thoracic and lumbar prominences upon forward flexion with some tenderness to palpation at the apices of the curves. However, her shoulders and pelvis are essentially level. She exhibits normal motor and sensory function with no long tract signs. She also has no tension signs in her lower extremities.

Posteroanterior and lateral scoliosis x-rays display a right thoracic curve from T5 to T11 and a left lumbar curve from T11 to L4, measuring 58 degrees and 67 degrees, respectively (Figure 62-1). However, her overall coronal and sagittal alignment appears to be reasonably balanced. These films demonstrate clear progression compared to previous radiographs acquired several years ago. Aside from her deformity, an MRI study of her entire spine reveals no intraspinal abnormalities or significant compression of the neural elements.

FIGURE 62-1 Posteroanterior scoliosis x-ray reveals thoracic and lumbar curves measuring 58 degrees and 67 degrees, respectively.

Clinical Case #2—Pathologic Fracture

A 59-year-old man who initially presented with a 1-month history of axial low back pain with occasional lower extremity symptoms consistent with neurogenic claudication. The patient has a known diagnosis of colorectal cancer that was treated with multiple abdominal operations and chemotherapy. The patient is currently requiring high-dose narcotics for his pain, which is increasing in severity. His past medical history is otherwise unremarkable except for mild hypertension.

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