One in two women and one in five men older than 50 years will experience an osteoporotic fracture, which can result in substantial pain, morbidity, and health care utilization. A new osteoporotic vertebral fracture occurs every 22 seconds; 1.4 million occur worldwide every year. The majority are asymptomatic or result in tolerable symptoms, with only a third of patients with a new fracture seeking medical attention. In the vast majority, the acute back pain symptoms subside over a period of 6 to 8 weeks as the fracture heals.
Vertebroplasty and kyphoplasty are minimally invasive, image-guided procedures that involve the injection of cement into a fractured vertebral body ( Figs. 67.1 and 67.2 ). The majority of these vertebral augmentation procedures are performed in a small subset of patients with symptomatic osteoporotic compression fractures that fail conservative medical therapy. Failure of medical therapy is variably defined but can be considered if the pain persists at a level that severely compromises mobility or activities of daily living despite analgesic therapy or if unacceptable side effects such as confusion, sedation, or constipation occur as a result of the doses of medication required to reduce the pain to tolerable levels. Notably, the first report of augmentation (published in 1987) was for neoplastic disease. As survival rates in cancer patients continue to improve, symptomatic neoplastic vertebral fractures and neoplastic vertebral tumors have increased in prevalence. A selected subgroup of these patients, in particular, those with symptomatic fractures from multiple myeloma and metastasis that fail to respond to conservative therapy, also benefit from vertebral augmentation. The primary goal of augmentation is pain relief and enhanced functional status with the secondary goal of vertebral body stabilization in cases of fracture. Key points, indications for, and contraindications to vertebral augmentation are summarized at the end of the chapter.
Conservative Medical Therapy for Vertebral Compression Fractures
The goals of conservative therapy are pain reduction (with analgesics, bed rest, or both), improvement in functional status (with orthotic devices and physical therapy), and prevention of future fractures (with vitamin D and calcium supplementation and bisphosphonate therapy).
Although conservative management of those with mild pain and no limitation of function is appropriate, conservative treatment of those with more severe pain or limitation of function is not benign. In this cohort, conservative therapy often involves a period of bed rest, which may lead to undesirable side effects such as loss of bone mass and muscle strength, decubitus ulceration, and venous thromboembolic disease, all of which can prolong the recovery period and result in loss of independence. Bone loss occurs at a rate of approximately 2% per week, muscle strength is reduced by 10% to 15%, and infectious complications can lead to septicemia and osteomyelitis. Moreover, the presence of fracture or malignancy combined with bed rest elevates the risk for venous thromboembolic disease in this cohort. Overall, the complications of prolonged bed rest, combined with opioid analgesic use and its associated side effects, can result in a vicious cycle of physical deconditioning, poor nutrition, and subsequent increased risk for vertebral insufficiency.
Technical Aspects of Vertebral Augmentation
Evaluation of patients for vertebral augmentation should identify those likely to benefit from vertebral augmentation, as well as screen for contraindications. The decision to proceed with treatment must be based on a good history, physical examination, appropriate laboratory evaluation, and imaging, as summarized in Boxes 67.1 and 67.2 .
Indications
- 1.
Treatment of symptomatic osteoporotic vertebral body fractures that are refractory to conservative medical therapy
- 2.
Treatment of symptomatic vertebral bodies weakened or fractured because of neoplasia that are refractory to medical therapy
Absolute Contraindications
- 1.
Active systemic infection, in particular, spinal infection
- 2.
Uncorrectable bleeding diathesis
- 3.
Insufficient cardiopulmonary health to safely tolerate sedation or general anesthesia
- 4.
Myelopathy resulting from fracture retropulsion or epidural tumoral extension
- 5.
Known allergy to bone cement
Relative Contraindications (Should Be Treated Only by Experienced Practitioners)
- 1.
Marked loss of vertebral body height (greater than 75% loss of height), which makes the procedure more difficult since there may be little space for placement of a cannula.
- 2.
Vertebroplasty above T5 , which is challenging because of the small size of the vertebral bodies and pedicles. The shoulders often limit fluoroscopic imaging at these levels.
- 3.
Severe osteopenia resulting in poor visualization of osseous structures on fluoroscopy , which increases the risk for improper needle placement and cement leakage. This can be overcome with guidance by computed tomography.
- 4.
Disruption of the posterior cortex , which increases the risk for posterior cement leakage and therefore the risk for spinal cord or nerve root compression. This is frequently seen with burst fractures and neoplasm. The integrity of the posterior cortex is best evaluated with computed tomography.
- 5.
Substantial canal narrowing (without neurologic dysfunction), which increases the risk that even a small amount of cement leakage will produce neurologic compromise.
- 6.
Retropulsion of fracture fragments , which increases the risk for further canal compromise with vertebral augmentation, particularly if the posterior vertebral body wall is unstable.
- 7.
Epidural extension of tumor , which in the setting of pathologic fractures results in significantly higher rates of spinal canal leakage than osteoporotic fractures do.
Identify patients who will probably benefit from vertebral augmentation.
Screen for absolute contraindications.
Document failure of conventional medical therapy.
Symptoms:
- •
Fractures possibly occurring with little or no trauma
- •
Deep pain with a sudden onset
- •
Midline location
- •
Exacerbation by axial mechanical loading (worsened with standing or weight bearing and often at least partially relieved by recumbency)
- •
Exacerbation with motion (especially flexion)
- •
Referred lateral radiation in a dermatomal pattern possibly present
- •
Signs:
- •
Point tenderness at the spinous process of the fractured vertebra. Local signs may be surprisingly absent. However, up to 30% of patients may have subjective off-midline pain or tenderness over nontarget vertebrae and still gain significant benefit.
- •
Localization to a specific level if possible is important in targeting treatment in patients who have multiple compression fractures, some of which may be healed and do not require treatment. In difficult cases, examination can be performed with fluoroscopic assistance to localize the pain to a specific anatomic level.
- •
Assess lower extremity neurologic function.
Laboratory evaluation:
- •
Screen for infection, coagulopathy, and metabolic abnormality.
- •
Additional tests such as urinalysis, electrocardiography, and/or chest radiography are left to the discretion of the practitioner.
- •
Imaging:
- •
Its role is to confirm the clinical diagnosis, identify and assess the acuity of the acute painful fracture, identify potential difficulties, and plan the procedure.
- •
MRI with STIR or T2-weighted sequences with fat saturation should be obtained in all patients if not contraindicated. These sequences identify marrow edema, which distinguishes acute from chronic fractures. MRI also distinguishes between benign osteoporotic and pathologic fractures and assesses the degree of fracture retropulsion, epidural tumor extension, spinal canal compromise, and compression of the spinal cord or nerve roots. Fracture clefts appear as a linear band of T1 hypointensity and T2 hypointensity or hyperintensity within the vertebral body.
- •
In patients who cannot undergo MRI, nuclear scintigraphic bone scanning or single-photon emission computed tomography in combination with CT are the tests of choice. Acute fractures will take up the injected 99m Tc-MDP tracer in much higher concentrations; CT evaluates bone integrity and the spinal contents. In patients with pathologic fractures, CT also helps define the extent of sclerosis and posterior wall osteolysis, which in turn predict increased technical challenges associated with the procedure.
- •
CT, computed tomography; MDP, methylene diphosphate (medronate); MRI, magnetic resonance imaging; STIR, short tau inversion recovery.
Sedation
Analgesia is typically necessary for vertebroplasty and kyphoplasty. In the majority of cases, it is achieved with a combination of local analgesics (e.g., lidocaine with bicarbonate or bupivacaine) and moderate sedation (intravenous midazolam and fentanyl). In some cases, general anesthesia is needed to provide adequate comfort and safety, particularly in patients at high risk for airway or respiratory complications with prone positioning or those with significant preprocedure narcotic analgesic requirements. However, having the patient awake is desirable because it allows feedback (e.g., increasing pain, neurologic dysfunction) that can alert the operator to potential complications. In all cases, continuous monitoring is performed with a minimum of electrocardiography, blood pressure measurements, and pulse oximetry. Sedation and monitoring are performed by anesthesiologists, nurse anesthetists, or certified nursing personnel. In patients with substantial preexisting respiratory or cardiac disease, an anesthesiologist can be asked to evaluate the patient and determine whether monitored anesthesia care is warranted. The patient should not eat or drink for at least 4 to 6 hours before the procedure.
Patient Positioning
Prone or oblique prone is the ideal patient position for thoracic and lumbar procedures. In practical terms, we allow patients an amount of freedom to place themselves in the prone oblique position should it promote greater comfort throughout the procedure. This can introduce 10 to 15 degrees of obliquity, depending on the patient’s position. In addition to the clear advantage of easy access, this position with proper cushion support under the upper part of the chest and lower part of the abdomen maximizes extension of the fractured segments, thereby promoting reduction of kyphosis. The patient’s arms should be placed sufficiently toward the head to keep them out of the path of the fluoroscope. Analgesia should be considered before placement on the table because this part of the procedure may be quite painful. Particular care must be taken when transferring patients who are aged or have osteoporosis or myelomatous infiltration since this may result in new rib or vertebral fractures.
Antibiotic Prophylaxis and Skin Preparation
The risk for infection is minimized by following standard operating room guidelines for sterile preparation of the skin, draping, operator scrubbing, and use of sterile gowns, masks, and gloves. Few data support or oppose antibiotic administration, but there are reports of spine infections after these procedures, and the presence of polymethyl methacrylate (PMMA) makes these infections difficult to treat successfully. We routinely use antibiotic prophylaxis. Prophylaxis for these procedures comes in one of two forms. An intravenous antibiotic such as cefazolin (1 g) or clindamycin (600 mg with penicillin allergy) may be administered before skin incision. Alternatively, the PMMA may be mixed with an antibiotic, such as tobramycin (1.2 g), as the cement is being prepared; this practice has diminished in favor of intravenous antibiotics.
Needle Placement
The most important aspect of needle placement is to keep the needle trajectory lateral to the medial cortex and superior to the inferior cortex of the pedicle. This prevents entry of the needle into the spinal canal or neural foramen. The needle may be placed via a transpedicular or parapedicular approach. In the transpedicular approach, the needle is directed from the posterior surface of the pedicle, through the length of the pedicle, and into the vertebral body. The long intraosseous path protects the postganglionic nerve roots and other soft tissues. However, the pedicle configuration can limit one’s ability to achieve a final needle tip position near the midline. In the parapedicular approach, the needle is directed along the lateral surface of the pedicle, with the pedicle being penetrated along its path or the vertebral body at its junction with the pedicle. This approach may permit more medial tip placement, which can be useful during treatment of levels with anatomically small pedicles, in particular, in the thoracic spine.
For either of these approaches there are multiple potential image guidance strategies, including anteroposterior (AP) and end-on (“down the barrel”) views, with the latter technique involving ipsilateral oblique rotation of the image intensifier to place the fluoroscopy beam and needle track parallel to each other. The following description assumes the use of two perpendicular image intensifiers simultaneously (biplanar fluoroscopy):
- 1.
Rotate the image intensifier to a true AP position by aligning the spinous process midway between the pedicles ( Fig. 67.3 ).
Figure 67.3
Initial positioning of the needle for a transpedicular approach. A, Anteroposterior (AP) fluoroscopic image. The image intensifier is first rotated to a true AP position to align the spinous process midway between the pedicles (vertical dotted line). The craniocaudad angulation is changed to bring the pedicles to the midportion of the vertebral body (horizontal dotted lines). B, Lateral fluoroscopic image. The image intensifier is rotated to a true lateral position by overlapping the cortices of both pedicles and ensuring that the posterior margin of the vertebral body is aligned (dotted lines). Note that the entire needle trajectory within the vertebral body should be considered during initial transpedicular access for optimal final needle position (solid line). C, Near “end-on” projection during needle placement with preservation of the medial and inferior cortices of the pedicle. Note that a “T-grip” needle handle can obscure bony landmarks and slight rotation of the image intensifier may be required. D, Midline needle position obtained via a unilateral transpedicular approach, which can be achieved with larger target pedicles, typically in the lumbar vertebrae.
- 2.
Change the craniocaudad angulation by bringing the pedicles to the midportion of the vertebral body. Use the lateral fluoroscopic view to aid in determination of the correct craniocaudad adjustment required.
- a.
For the end-on view, rotate image intensifier approximately 20 degrees ipsilateral to the target pedicle so that the medial cortex of the pedicle is at the middle third of the vertebral body. The vertebra adopts the “Scotty dog” configuration. Place the needle so that it is “end on” to the image intensifier and appears as a dot.
- a.
- 3.
Plan the trocar trajectory. For the AP and partial ipsilateral oblique views, the trocar entry site should be at the 3-o’clock position of the right pedicle or the 9-o’clock position of the left pedicle for the transpedicular approach. In the end-on view, it is centered within the circle formed by the cortex of the pedicle. For parapedicular approaches an entry site just lateral to the 3- or 9-o’clock position of the pedicular cortex is best.
- 4.
Anesthetize the skin and periosteum by subcutaneous injection of lidocaine or bupivacaine via a 22-gauge needle along the planned trajectory. Use this smaller-gauge needle to assess and adjust the planned trajectory.
- 5.
Make a small vertical skin incision (allows easier craniocaudal needle angulation), and insert the 11- or 13-gauge diamond-tipped needle stylet (sheathed in a cannula).
- 6.
Advance the needle to the bone surface while making small corrections in craniocaudad angulation on the true lateral view (care is needed to angle the image intensifier so that a true lateral view is obtained). For the parapedicular approach, the position at which bone is encountered (i.e., at the junction of the pedicle and vertebral body) is more anterior on the lateral view.
- 7.
Once in the bone, advance the needle either with a drilling motion and controlled forward pressure or by carefully tapping the needle handle with an orthopedic mallet.
- 8.
Maintain a true AP view of the image intensifier for advancement of the needle unless using the end-on view, in which case the needle is kept as a dot during initial placement through the pedicle. The needle must remain lateral to the medial cortex of the pedicle until it has traversed the entire pedicle on the lateral view.
- 9.
Once the needle has traversed the pedicle, one can replace the diamond-tipped needle with a straight bevel-tipped needle or curved needle for better maneuverability ( Fig. 67.4 ). Advance the needle further via the lateral view to the anterior third to quarter of the vertebral body.
Figure 67.4
Photographs of typical vertebroplasty needles. A, Typical coaxial vertebroplasty needle—the inner stylet locks into the outer cannula. Note the large handles to facilitate insertion and removal from the bone. Manufacturers may use different colored or marked handles to indicate the type of needle tip (magnified in B ). A needle with a beveled tip can be used to facilitate directing the needle along the desired trajectory.
Additional Steps for Kyphoplasty
For vertebroplasty, the PMMA is delivered through the cannula after placement of the needle as just described. Kyphoplasty involves the additional steps of balloon tamp insertion and inflation to create a cavity within the bone ( Fig. 67.5 ). For kyphoplasty, pull the cannula back to the posterior aspect of the vertebral body to allow the insertion of the balloon tamp. After the needle stylet is removed, insert the balloon tamp through the cannula and slowly inflate with iodinated contrast medium. The balloon is attached to a locking syringe with a digital manometer ( Fig. 67.6 ). Monitor the inflation with both the pressure transducer and intermittent fluoroscopy. Continue inflation until one of two conditions is met: the system reaches significant pressure or maximum balloon volume or further inflation results in patient discomfort. Balloon placement can be either unipedicular or bipedicular. Deflate and then remove the balloon.
Cement Placement
The consistency of the cement, when ready for injection, is similar to that of toothpaste. Wong and Mathis recommend a drip test, in which the cement should ball up at the end of the needle and not drip downward, which will result in a cement consistency that is slightly more viscous than toothpaste. Working time varies from 10 to 20 minutes, depending on temperature and the specific PMMA formulation being used. A variety of delivery systems are available for the cement. These systems vary from a few 1-mL syringes with a spatula and a mixing bowl to self-contained delivery devices. A screw-syringe injector with long, flexible delivery tubing has the advantage of minimizing exposure of the operator to radiation.
Vertebroplasty
- •
After removing the needle stylet, fill the cannula with saline to prevent pressurized injection of air and air embolism. Connect the delivery system to the cannula and inject the cement slowly.
- •
Monitor carefully with fluoroscopic imaging to ensure that the cement remains within the vertebra. Posterior or posterolateral leakage could result in irritation of or damage to the spinal cord or nerve roots and should be avoided. New pain with a different character should prompt an immediate pause in the procedure and additional views.
- •
End points for cement injection include passage of cement beyond the marrow space or cement reaching the posterior quarter of the vertebral body on the lateral projection. In the case of cement leakage, one may wait 1 to 2 minutes to allow the cement to harden and then reinject to see whether the cement is redirected within the vertebral body. Ideally, the cement will extend across the midline to the opposite pedicle by the end of the injection. The optimal volume of cement remains a matter of controversy.
- •
The final portion of cement may be delivered by inserting the needle stylet. Alternatively, the cement may be allowed to harden and the needle removed with a gentle rocking motion to ensure that the cement within the cannula separates at the tip of the cannula.
Kyphoplasty
- •
The cavity created by the balloon tamp allows injection of cement that is more viscous than that typically used for vertebroplasty. The cavity and more viscous cement theoretically minimize the risk for extravasation of cement. Sufficient time is allowed for the cement to reach a doughy consistency, with loss of the “sheen” of the initially mixed cement.
- •
Many practitioners use manual bone filler devices to inject cement, although one can use injector systems. The delivery system is connected to the cannula and the cement is injected slowly under fluoroscopic guidance. The cavity is filled with cement from anterior to posterior until it matches or slightly exceeds the volume of the inflated balloon tamp.
Technical Aspects of Vertebral Augmentation
Evaluation of patients for vertebral augmentation should identify those likely to benefit from vertebral augmentation, as well as screen for contraindications. The decision to proceed with treatment must be based on a good history, physical examination, appropriate laboratory evaluation, and imaging, as summarized in Boxes 67.1 and 67.2 .
Indications
- 1.
Treatment of symptomatic osteoporotic vertebral body fractures that are refractory to conservative medical therapy
- 2.
Treatment of symptomatic vertebral bodies weakened or fractured because of neoplasia that are refractory to medical therapy
Absolute Contraindications
- 1.
Active systemic infection, in particular, spinal infection
- 2.
Uncorrectable bleeding diathesis
- 3.
Insufficient cardiopulmonary health to safely tolerate sedation or general anesthesia
- 4.
Myelopathy resulting from fracture retropulsion or epidural tumoral extension
- 5.
Known allergy to bone cement
Relative Contraindications (Should Be Treated Only by Experienced Practitioners)
- 1.
Marked loss of vertebral body height (greater than 75% loss of height), which makes the procedure more difficult since there may be little space for placement of a cannula.
- 2.
Vertebroplasty above T5 , which is challenging because of the small size of the vertebral bodies and pedicles. The shoulders often limit fluoroscopic imaging at these levels.
- 3.
Severe osteopenia resulting in poor visualization of osseous structures on fluoroscopy , which increases the risk for improper needle placement and cement leakage. This can be overcome with guidance by computed tomography.
- 4.
Disruption of the posterior cortex , which increases the risk for posterior cement leakage and therefore the risk for spinal cord or nerve root compression. This is frequently seen with burst fractures and neoplasm. The integrity of the posterior cortex is best evaluated with computed tomography.
- 5.
Substantial canal narrowing (without neurologic dysfunction), which increases the risk that even a small amount of cement leakage will produce neurologic compromise.
- 6.
Retropulsion of fracture fragments , which increases the risk for further canal compromise with vertebral augmentation, particularly if the posterior vertebral body wall is unstable.
- 7.
Epidural extension of tumor , which in the setting of pathologic fractures results in significantly higher rates of spinal canal leakage than osteoporotic fractures do.
Identify patients who will probably benefit from vertebral augmentation.
Screen for absolute contraindications.
Document failure of conventional medical therapy.
Symptoms:
- •
Fractures possibly occurring with little or no trauma
- •
Deep pain with a sudden onset
- •
Midline location
- •
Exacerbation by axial mechanical loading (worsened with standing or weight bearing and often at least partially relieved by recumbency)
- •
Exacerbation with motion (especially flexion)
- •
Referred lateral radiation in a dermatomal pattern possibly present
- •
Signs:
- •
Point tenderness at the spinous process of the fractured vertebra. Local signs may be surprisingly absent. However, up to 30% of patients may have subjective off-midline pain or tenderness over nontarget vertebrae and still gain significant benefit.
- •
Localization to a specific level if possible is important in targeting treatment in patients who have multiple compression fractures, some of which may be healed and do not require treatment. In difficult cases, examination can be performed with fluoroscopic assistance to localize the pain to a specific anatomic level.
- •
Assess lower extremity neurologic function.
Laboratory evaluation:
- •
Screen for infection, coagulopathy, and metabolic abnormality.
- •
Additional tests such as urinalysis, electrocardiography, and/or chest radiography are left to the discretion of the practitioner.
- •
Imaging:
- •
Its role is to confirm the clinical diagnosis, identify and assess the acuity of the acute painful fracture, identify potential difficulties, and plan the procedure.
- •
MRI with STIR or T2-weighted sequences with fat saturation should be obtained in all patients if not contraindicated. These sequences identify marrow edema, which distinguishes acute from chronic fractures. MRI also distinguishes between benign osteoporotic and pathologic fractures and assesses the degree of fracture retropulsion, epidural tumor extension, spinal canal compromise, and compression of the spinal cord or nerve roots. Fracture clefts appear as a linear band of T1 hypointensity and T2 hypointensity or hyperintensity within the vertebral body.
- •
In patients who cannot undergo MRI, nuclear scintigraphic bone scanning or single-photon emission computed tomography in combination with CT are the tests of choice. Acute fractures will take up the injected 99m Tc-MDP tracer in much higher concentrations; CT evaluates bone integrity and the spinal contents. In patients with pathologic fractures, CT also helps define the extent of sclerosis and posterior wall osteolysis, which in turn predict increased technical challenges associated with the procedure.
- •
CT, computed tomography; MDP, methylene diphosphate (medronate); MRI, magnetic resonance imaging; STIR, short tau inversion recovery.
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