33 Cementoplasty Outside the Spine
Summary
Metastatic disease to the skeletal system is a common occurrence that can be very painful and very debilitating. The metastatic tumors can weaken the bone leading to fracture or directly invade the bone and surrounding soft tissues. In addition to the conventional treatments for symptomatic metastases such as chemotherapy and radiation, percutaneous techniques such as tumor ablation and cementoplasty may be used to ameliorate symptoms produced by the metastases. While surgery may be appropriate for controlling symptoms produced by local invasion of tumor, patients who are significantly debilitated or those with a very short life expectancy may benefit from less invasive options such as percutaneous treatment. There are disadvantages to some of the conventional therapy including lack of structural stability after chemotherapy and radiation. Radiation is well known to cause regional osteoporosis and increase the risk of fracture in weight bearing bones. Cementoplasty also does not preclude the use of any of the other neoplastic treatments and can help provide structural stability to the axial and appendicular skeleton. Cementoplasty and the various ablative therapies can be effectively used alone or in combination with the conventional therapies for optimal local control of symptomatic metastatic disease. When utilizing the percutaneous therapies it is important to keep in mind the goals of providing adequate stabilization, ablating the interface between the tumor and normal bone, ablating the soft tissue component of the lesion that impinges on surrounding structures, and being mindful to not injure critical surrounding structures. When performing extraspinal cementoplasty and ablative therapies it is important to have adequate information prior to performing the procedure including adequate pre-procedure imaging and knowledge of the patient’s most debilitating symptoms. Clear treatment goals should be established prior to the procedure and multiple sessions may be necessary to adequately treat the full extent of the tumor without putting the patient at undue risk. Computed tomography and fluoroscopy are the most commonly used imaging modalities to guide the treatment. The location of percutaneous treatments most often involves the pelvis and acetabulum and reinforcement of the acetabulum often produces profound pain relief by stabilizing this area of prominent weight bearing. In addition to bone cement, some interventionalists may also use percutaneous screws to supplement the strength of the construct especially when large metastases are treated. Although care should be taken to avoid cement extravasation into the normal anatomy surrounding the metastasis, small amounts of extravasation are surprisingly well tolerated even into such important structures such as weight bearing joints. Other axial and appendicular osseous areas are also responsive to cementoplasty including the inferior pubic ramus, pubis, ilium, and long bones of the upper and lower extremities. When using cement in any osseous structure it should be kept in mind that although bone cement offers excellent support and resistance to compression, it tends to break with tensile or rotational forces so its use in long bones and other areas undergoing these forces should be in combination with other supporting devices such as nails, screws, or wires. There have also been reports of cementoplasty in more unusual locations such as the sternum, scapula, and clavicle. Complications associated with cementoplasty are rare but care should be taken to avoid cement extravasation and large volume cement injections causing displacement of a large amount of bone marrow especially in patients with compromised pulmonary function. It is not known whether cement injection into metastases causes spread of the malignancy but the use of ablative treatments could serve to limit the potential tumor spread. A combination of ablative techniques and cementoplasty could also ablate the tumor all the way out to its margins and reduce the tumor volume thereby making the injection of cement into the tumor easier. Cryoablation can impede the inflow of cement and complete thawing of the ablation zone is necessary to adequately inject cement into the area previously ablated. There has been considerable experience demonstrating that cementoplasty of the pelvis is an important technique for improving patient’s pain and quality of life in those patients suffering from painful pelvic metastases. Additional cementoplasty of metastatic disease outside the pelvis is limited but appears equally promising. The use of a combination of ablative treatments and cementoplasty can be a very effective way to manage patient with symptomatic metastases and should be considered in the appropriate clinical scenarios.
33.1 Introduction
Metastatic bone disease is common in patients with certain types of neoplasms, and patients that die with metastatic disease often have metastatic bone deposits. 1 , 2 These can be intensely symptomatic, and significantly degrade the quality of their life. Successfully treating symptomatic bone disease can be challenging, often requiring coordinated multidisciplinary efforts. Bone pain can make even simple things such as patient transfer or rolling over in bed an excruciatingly painful ordeal.
Symptoms from metastatic bone deposits arise from a variety of different mechanisms. Weakening of the bone may result in a pathologic fracture. In addition, tumor can invade the periosteum, which is richly innervated, producing severe pain or cause bleeding and subsequent elevation of the periosteum. Even without a pathologic fracture, weakened bone placed under stress, as with weight bearing, can be painful, therefore inhibiting ambulation or use of an extremity. Tumors can also produce nociceptive factors that cause inflammation or that can be irritating to nerve fibers and thus result in pain. Associated soft tissue masses arising from the metastasis can cause compression of adjacent structures, such as neurovascular bundles and other organs (e.g., bowel or bladder).
Conventional methods for treating symptomatic metastases in the pelvis and extremities include surgery, radiation therapy, and chemotherapy. More recently, percutaneous techniques such as cementoplasty and ablative methods (e.g., radiofrequency ablation, microwave ablation, and cryoablation) have been introduced. Surgery can be highly efficacious, particularly in the treatment of pathologic fractures in long bones of the extremities. At times, excision of a metastasis can also be performed and, if surgery is successful, this can provide excellent and durable pain relief. Evaluation and management of acetabular metastases comparing patients treated with surgery versus those managed with percutaneous cementoplasty has been studied. 3 – 5 Surgical treatment may have some advantages in patients that are candidates for this type of surgery, in that symptom control and mobility may be better than with cementoplasty alone. There are several disadvantages inherent to surgery, including the fact that patients are often in such debilitated condition that they are poor surgical candidates for anesthesia and major resection. Prolonged period of convalescence may be required after surgery, which may be undesirable in an individual with a restricted lifespan. These debilitated patients are often difficult to rehabilitate. It has been argued that percutaneous imaging-guided cement injections may provide a less invasive, less expensive, but still highly effective treatment that decreases pain, and improves mobility and quality of life and stabilizes the skeletal area of interest particularly in those with limited projected survival. 3 , 4 , 6
Radiation is an extremely useful tool and extensive experience with this modality exists. This technique is noninvasive and often provides excellent pain control but, unfortunately, up to 30% of patients do not receive satisfactory improvement in their symptoms. 6 In addition, although radiation is useful in treatment of tumor, it does not provide mechanical reinforcement of bone so patients with symptoms on weight bearing may find that their symptom improvement after radiation is limited. 7 Partial reconstitution of bone with healing can sometimes occur but may take months and the previously applied radiation may promote regional osteoporosis, thereby further increasing the risk of fracture. 6 , 8 Chemotherapy can be a useful adjunct but a significant portion of patients may show incomplete or no response. Chemotherapy toxicity can be significant. Often the appropriate treatment approach uses multiple modalities, making multidisciplinary treatment decisions crucial. It is important to remember that cementoplasty does not preclude use of other treatment modalities. Subsequent radiotherapy can be performed in the presence of cement, and indeed may allow radiation to be held in reserve for future use if needed.
33.2 Anatomic Sites
This chapter will focus principally on cementoplasty within the pelvis, exclusive of the sacrum as this is covered elsewhere in this textbook. Pelvic cementoplasty procedures were first performed in the mid-1990s but have gained considerable popularity in the last 10 years. 9 – 11 This technique is still not uniformly available, even in major medical centers, but is gaining in acceptance. More recently, some experience with cementoplasty of long bones and other sites have also been reported. 1
33.2.1 Pelvic Cementoplasty
The pelvis is a large osseous structure that contains a substantial amount of cancellous bone and is an extremely common site of metastatic bone disease. Considerable force is transmitted through the pelvic ring, particularly in the upright position and on ambulation. Force is transmitted through the spine through the sacroiliac joints toward the acetabular roof and superior pubic ramus or from the lower extremity in the upright position (▶Fig. 33.1). Destruction of osseous integrity along this pathway can produce symptoms, particularly on ambulation and/or weight bearing. 6
Regrettably patients may present with large metastatic deposits. Large lesions can be challenging to treat, as it may not be practical or reasonable to treat the entirety of the tumor particularly if a considerable soft tissue component is present. In this situation it is helpful to devise a plan of treatment whereby the areas most likely to provide symptom relief are targeted. Several principles should be considered in choosing the regions of the tumor to treat:
Reinforcement of weight- or stress-bearing bone with cement or other stabilizing material.
Cementation +/− ablation or ablation alone of the interface between tumor and normal bone.
Ablation of soft tissue components of the lesion which impinge on adjacent structures.
It is important to be aware of adjacent important structures, such as neurovascular bundles, bowel, bladder, and joints to minimize the possibility of leakage into the surrounding structures.
At present these procedures are relatively uncommon with only modest experience having been accrued. Both patients and referring doctors may know very little about them. Before embarking on a cementoplasty procedure in the pelvis, it is important to have clear goals as to what is hoped to be achieved. Moreover, it is crucial that the patient be aware of the potential risks and benefits and be involved in the decision making regarding the treatment goals and potential outcomes. Recent imaging (computed tomography [CT] and/or magnetic resonance imaging [MRI]) should be available and a thorough understanding of the patient’s symptoms is mandatory if a procedure is to be undertaken. It is important to know as precisely as possible where the patient’s most debilitating pain is, and what worsens or elicits the patient’s pain (e.g., weight bearing, sitting, etc.). As patients may have extensive metastatic disease, those most symptomatic areas should be treated first, with other regions being addressed later if required. Unnecessarily treating more extensive areas can put the patient at risk for more complications and potentially turn an effective palliative procedure into one that may worsen the patient’s condition.
33.2.2 Technique of Cementoplasty
The exact technique utilized varies considerably from one operator to another, as does the equipment used. A wide variety of different needles, cements, and ablation equipment have been reported in the literature with successful outcomes. Most operators performing cementoplasty already have considerable experience with vertebroplasty and can readily translate these skills to sites outside the spine.
For planning purposes reasonably contemporaneous cross-sectional imaging is required. Ideally, patients should not be coagulopathic and should not have platelet counts below 50,000 in order to minimize bleeding complications. Treatment while the patient has an active infection should also be, whenever possible, avoided. The use of prophylactic antibiotics in many procedures is common and should be employed in cementoplasty in order to minimize the possibility of infection. These procedures can at times be lengthy and uncomfortable for patients. Moreover, comorbidities and narcotic-tolerance can make analgesia difficult. Many operators utilize anesthesiology in order to safely ensure that patients are comfortable, and optimally monitored during the procedure.
Prior to undertaking the procedure, clear goals and reasonable expectations should be established. Areas of greatest stress or weight bearing should be selected to be buttressed and reinforced. Satisfactory outcomes can be achieved without complete filling of the entirety of large lesions, provided the key areas are treated. If cement can also be placed near the interface between tumor and bone, or the interface can be treated with ablation techniques, this can contribute to a good symptomatic outcome. Cementing of undisplaced or minimally displaced fracture sites can provide dramatic improvement in pain.
Although fluoroscopic guidance alone can be utilized with good success, some operators feel more comfortable with CT or cone beam CT guidance. The complex three-dimensional anatomy of the pelvis can make purely fluoroscopic guidance challenging. Combined fluoroscopy with cone beam CT facilitates confirmation of needle placement and also permits real-time evaluation of cement distribution. 3 , 4 , 9 , 10 , 12
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