Preoperative embolization minimizes blood loss, improves visualization
As cancer patients live longer, the incidence of spinal metastases is likely to increase. These lesions can be painful and are often hypervascular, making surgical treatment to control the pain or preserve function a challenge. Preoperative embolization has been effective in devascularizing spinal metastases and reducing bleeding complications during surgery by improving visualization.
To learn more, AAOS Now spoke with Eeric Truumees, MD, lead author of “Preoperative Embolization in the Treatment of Spinal Metastasis,” appearing in the August issue of the Journal of the AAOS (JAAOS).
AAOS Now: Why is preoperative angiographic assessment of spinal metastases so important?
Dr. Truumees: Preoperative angiographic assessment allows the treating physicians to estimate the degree and direction of a lesion’s blood supply and the degree to which that blood supply is shared by the spinal cord. For example, it allows physicians to understand whether the blood flow arises from the right or left vertebral artery in a cervical metastasis.
Almost two thirds of spinal metastases are hypervascular. To a point, tumor histology helps predict blood flow to the lesion. Cell lines particularly adept at recruiting neovascularization include renal, endocrine, and germ cell metastases. Rapidly growing lesions and those associated with pathologic fracture are also likely to be hypervascular.
Unfortunately, as some cancers metastasize, they de-differentiate into more rapidly growing and aggressive forms. Thus, we cannot use histology alone. At the time of surgery, these lesions may extend away from the bone and into soft-tissue regions where hemostasis is difficult to achieve. For example, lesions that extend to the vessels anteriorly or into the spinal canal restrict the use of modalities such as monopolar electrocautery and packing.
AAOS Now: What are the benefits and risks of preoperative embolization in the treatment of spinal metastases?
Dr. Truumees: Given that the vessels feeding the tumor often also supply the spinal cord, preoperative angiography allows the surgeon to determine risk to cord vascularity. Trial occlusion of the vessels may allow safe sacrifice of the vessel, for example. Locating the sources of the blood flow may affect the surgical approach. The vessels can be identified and ligated before marked bleeding begins. Embolization may decrease the risk for recurrence after surgical resection. Certainly, intraoperative visualization improves with better hemostasis.
The most important reason to consider preoperative embolization is to decrease life-threatening hemorrhage. Cancer patients often have clotting abnormalities. Minimizing intraoperative blood loss decreases surgical morbidity and mortality.
AAOS Now: When is preoperative embolization of hypervascular spinal lesions contraindicated?
Dr. Truumees: Preoperative embolization is never absolutely contraindicated. Relative contraindications are based on risk-benefit calculations for the individual patient. For example, in patients with renal impairment, use of contrast dye must be minimized, fluid status must be optimized, and normal blood pressure ensured. In patients with rapid neurologic decline, the potential benefits of embolization must be contrasted with the delay in cord decompression. During the angiogram phase, subsequent embolization may be contraindicated when the tumor feeder shares a vascular pedicle with the spinal cord.
AAOS Now: How important is it for the neuroradiologist and orthopaedic surgeon to work together?
Dr. Truumees: These are complex cases with multiple variables. As a result, clear communication with other care providers is critical. The orthopaedic surgeon should begin by understanding the patient’s overall prognosis, other sites of metastasis, and response to previous treatment. In that context, he or she should meet with the neuroradiologist to relate symptoms to the patient’s imaging findings and discuss the goals, timing, and techniques of the surgery being considered.
If preoperative angiography is selected, it is useful for the surgeon to attend or, at least, to review the films afterward. Often only partial embolization is possible, so the surgeon needs to know where the residual feeders are. Certainly, the surgeon must be aware of the patient’s neurologic response to any trial or permanent vessel occlusion.
AAOS Now: When is the best time to perform preoperative embolization to avoid revascularization?
Dr. Truumees: In general, the patient should be taken to surgery as soon after embolization as possible. The most vascular lesions also recanalize soonest. In some cases, a delay of up to 72 hours may be reasonable. For example, some patients will require dialysis after angiography. If the embolization requires a long procedure time, some surgeons prefer not to begin a major tumor resection and reconstruction procedure late in the day. Here, too, close communication with the neuroradiologist is important. Various embolic agents, from gelfoam to coils, can be used. Each offers different upsides and downsides. Often selection of the embolic agent reflects the intended timing of subsequent surgery.
AAOS Now: Is this treatment appropriate for patients of all ages?
Dr. Truumees: Yes; in fact, in some benign and slow growing lesions, embolization can be used in young children to delay surgery until they are older.
AAOS Now: In terms of patient education and informed consent, what issues need to be addressed?
Dr. Truumees: Treatment decisions in patients with spinal metastases are complex. The surgeon and patient have to consider current symptoms; risk to function (eg, cord compression); likelihood of success with nonsurgical management (pain control, response to chemotherapy, radiation therapy, and bracing); and overall prognosis. For example, if embolization and surgery will require 3 months of recovery time, and the patient has a 6-month life expectancy, nonsurgical measures may be preferable. If the patient is neurologically stable, this discussion would ideally take place over several days.
The goals of the surgery should be clearly stated. Typically, this type of spinal reconstruction will not affect the overall course of the disease but may help achieve local control. More often, surgery is indicated to protect the spinal cord and to control pain. The possibility of recurrence and the significant risks of surgery in this often fragile patient population must also be discussed.
AAOS Now: Are there instances when embolization is a stand-alone treatment?
Dr. Truumees: Embolization has reportedly definitively cured multifocal hemangiomas in children. In older patients, serial, palliative embolization has been used in lieu of surgery to control pain and decrease growth in large sacral giant cell and other lesions.
AAOS Now: What are some of the alternatives to preoperative embolization and what are the indications for their use?
Dr. Truumees: Alternatives to embolization focus on various pre- and intraoperative maneuvers to decrease lesion vascularity or achieve hemostasis. In some settings, neo-adjuvant radiation therapy (XRT) or chemotherapy may shrink spinal metastases and decrease the rate of cell division. With decreased metabolic activity in the tumor, vascularity may decrease. Historically, preoperative XRT is associated with a higher rate of postoperative wound complications.
At surgery, injection of polymethylmethacrylate (PMMA) into the vertebral body can decrease the vascularity of lesions contained within it. Additional hemostasis can be achieved by injecting small amounts of sterile alcohol directly into the lesion with a tuberculin syringe. A variety of prothrombotic materials (gelfoam, Surgicel [Ethicon Biosurgery, Somerville, N.J.]) should be readily available.
Disclosure information: Dr. Truumees—Cervical Spine Research Society; North American Spine Society; Stryker; Doctors Research Group
Maureen Leahy is assistant managing editor for AAOS Now. She can be reached at firstname.lastname@example.org