Percutaneous techniques of stabilizing thoracic and lumbar compression fractures were first developed in France by Deramond in the late 1980s to treat pain from aggressive vertebral hemangiomas (88). Current techniques for these fractures now include vertebroplasty and kyphoplasty. Vertebroplasty is the minimally invasive internal fixation of a vertebral compression fracture (VCF) by the percutaneous injection of polymethylmethacrylate (PMMA) under high pressures into the involved vertebral body. However, this approach does not restore vertebral height. Kyphoplasty, developed more recently, addresses not only the fracture but also the resultant kyphotic spinal deformity. This technique employs a minimally invasive inflatable bone tamp to restore body height, leaving a cavity that is filled with PMMA, which is injected at lower pressures. Both kyphoplasty and vertebroplasty were developed specifically for pain reduction in patients with VCFs. This section reviews the techniques and expanding indications for the minimally invasive internal fixation and reduction of VCFs, focusing particularly on kyphoplasty.
Kyphoplasty procedures are commonly performed under local anesthesia but can also be performed under general anesthesia. In the lumbar spine, a transpedicular route is favored; an extrapedicular route is used in the thoracic spine. During kyphoplasty, the patient is positioned prone, and an 11-gage trocar with a cannula is introduced through the pedicle into the posterior aspect of the vertebral body using biplanar fluoroscopic guidance. In an attempt to restore the collapsed vertebra to a normal position, an inflatable balloon tamp is introduced through the cannula and inflated under controlled pressure. The balloon is typically inflated to a maximum of 250 psi with 1.5-6 mL of saline, creating a space within the vertebral body for the injection of PMMA cement. The balloon is then withdrawn, and PMMA mixed with barium is injected into the vertebral body under fluoroscopic control to ensure that the cement remains within the vertebral body (89-91) (Fig 9).
Vertebroplasty and kyphoplasty have been studied most extensively in the treatment of painful osteporotic VCFs and are now viable alternatives to conservative bracing or open surgical reduction and fixation. Patients with osteporotic VCFs have progressive kyphosis, chronic pain, and impaired ambulatory capacity, which can also lead to depression, malnutrition, and diminished pulmonary function (92). Osteoporotic VCFs are now the most common etiology of vertebral body fractures, with nearly 700,000 new VCFs sustained each year (93). Patients with these fractures rarely present with neurologic deficits, making percutaenous intervention feasible, provided the posterior elements and posterior cortical wall of the vertebral body are intact and no radiographic retropulsed bone in the spinal canal is evident.
One goal of these techniques is to reduce pain by stabilizing the fracture. Data from veretebroplasty have been encouraging, with more than 60% of patients reporting a significant improvement in pain and more than 50% of patients reporting improved ambulation (94-96). However, the relatively high rate of PMMA extravasation reported during vertebroplasty for a variety of indications is concerning. Epidural and foraminal extravasation of PMMA has been reported to occur in 26-70% of treated levels, whereas a recent study reported only a 2.7% incidence of such extravasation in kyphoplasty (89,97-99). The reduction of PMMA extravasation in kyphoplasty is probably related to
injection of cement at the lower pressures permitted by the creation of a bone cavity.
In kyphoplasty, goals of therapy include restoration of body height and sagittal spinal alignment as well as fracture stabilization and pain relief. Initial studies with short-term follow up reported that more than 90% of patients had improvement in symptoms following kyphoplasty with an average body height restoration of 35-40%, and longer term studies also noted substantial symptomatic improvements (89,90,95).
Nonsurgical treatment options for malignant spinal disease now include percutaneous fracture stabilization techniques along with traditional options like analgesia, radiotherapy, hormone therapy, bisphosphonates, cytotoxic drugs, embolization, and bracing. Multiple myeloma has received particular attention because 70-100% of cases have bony involvement in the form of painful compression fractures at multiple levels throughout the vertebral column. Although the disease remains incurable, advances in chemotherapeutic options have focused attention on reducing the attendant morbidity. Data on kyphoplasty for osteolytic metastatic disease from myeloma and other types of cancer have been encouraging, with authors reporting alleviation of pain and body height restoration of an average 35-45% (91,100).
Kyphoplasty is rapidly becoming an important therapeutic option for neurosurgeons treating vertebral compression fractures from osteoporosis and metastatic disease. Kyphoplasty's effectiveness for reducing pain, restoring vertebral body height, and on the improving functional outcome in patients warrant its practice by neurosurgeons. Future refinements will undoubtedly include clarification of the ideal time to perform kyphoplasty after a fracture, as well as the use of select bone substitutes rather than PMMA. Furthermore, bio-mechanical studies will help us to understand the effects of kyphoplasty on surrounding structures and could complement our existing knowledge of vertebroplasty mechanics. Lastly, we await data on the long-term efficacy of percutaneously fixed and restored vertebral bodies.
Kyphoplasty may also be performed during open surgery, offering a new adjunct to surgical treatment of those compression fractures that involve posterior cortical compromise and/or retropulsion of bone into the spinal canal with or without neurologic deficits. Currently, these fractures are contraindications to percutaneous kyphoplasty owing to the potential for causing or exacerbating neurologic injury and increased risk of epidural PMMA extravasation. Boszczyk et al. (101) reported good pain relief and kyphosis correction in 17 of 23 patients who underwent a microsurgical interlaminary kyphoplasty or vertebroplasty. Their approach lies between percutaneous augmentation and conventional open reconstruction on the treatment continuum (101). Boszczyk's results complement earlier work by Wenger and Markwalder, who are advocates of the benefits of open kyphoplasty, which helps with better visualization of vertebral body anatomy and the spinal canal during vertebral body stabilization by kyphoplasty (102).
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