Chapter 35: Miscellaneous Tips by the Masters of Vertebral Augmentation
35.1 If You Aim at Height Restoration, Mind the Access!
Some of the original intended advantages of balloon kyphoplasty (BKP) were to achieve height restoration and spinal realignment in patients with vertebral fractures, but BKP has inconsistently shown to be able to obtain significant fracture reduction. 1 Up to one-third of BKP-treated cases show no appreciable height restoration, either because the balloons expand in trajectories that produce inefficient internal fracture distraction or due to the loss of previously restored height and kyphotic realignment after balloon deflation. 2
Newer percutaneous devices have been introduced to achieve fracture reduction and kyphosis correction and are used along with vertebral cement augmentation. Two of these systems, vertebral body stents (VBS; DePuy Synthes-Johnson & Johnson) and SpineJack (Vexim-Stryker), offer the possibility to perform a kyphoplasty with an internal framework that consists of rigid devices that produce internal vertebral body distraction. The devices expand in a different manner than balloons that expand spherically and centrifugally. These devices expand in a predictable manner and in a way that exerts a strong predetermined craniocaudal distraction force perpendicular to the major fracture axis. 3 – 7
In order to allow the device to perform its craniocaudal distraction force and obtain the most efficient fracture reduction and height restoration, the axis of insertion of the device in the vertebral body is of paramount, yet sometimes underestimated, importance.
While the transpedicular access used to perform vertebroplasty and BKP aims at the safe zones at and around the pedicle to stay as far as possible from the medial pedicular cortical boundaries, in kyphoplasty with structural implants the pedicular access should be adapted in order to obtain a device placement inside the vertebral body along an axis parallel to the anticipated alignment of the original prefracture end plates (▶Fig. 35.1). When only one end plate is fractured and deformed, the axis of device insertion can be parallel to the intact end plate. The distraction performed perpendicular to this axis approximates the original prefracture shape of the vertebral body and allows the device to achieve maximum expansion and fracture reduction (▶Fig. 35.2 and ▶Fig. 35.3). A different axis of insertion of the device causes the distraction force to be incident with an angle that is nonperpendicular to one or both end plates, thereby resulting in less efficient fracture reduction and increases the risk of iatrogenic end plate disruption that can limit the device expansion to a lesser degree of height restoration than is optimal.
It is not always easy to obtain insertion of the device along the desired axis. The most frequently injured portion of the vertebral body in compression fractures is the superior end plate, often creating an unfavorable access angle between pedicles and superior end plate. In such cases, the transpedicular access is performed through the most caudal aspect of the pedicle and then advanced just tangentially underneath the superior end plate (▶Fig. 35.1).
Accessing the caudal part of the pedicle poses some technical challenges:
During the trocar docking into the cortex of the posterior elements, the trocar tends to slide caudally and poses the risk of inadvertently entering the neural foramen.
The caudal aspect of the pedicle is often smaller than the cranial part; attention should be made not to violate the medial pedicular cortex that protects the central canal, and the inferior cortex that protects the neural foramen (▶Fig. 35.1).
We suggest the use of a beveled tip low-profile (12- to 14-gauge) trocar to perform the initial access so as to be able to dock and steer along the optimal access path. This will provide the maximum control and precision placement of the trocar, especially while sliding under a fractured end plate. The initial access is then followed by insertion of larger access trocar via using k-wire exchange. The larger trocar is then able to accommodate the placement of the distraction devices (▶Fig. 35.2).
When the access is correct, the expansion of the distraction device can occur in an optimally craniocaudal orientation within the vertebral body, thereby maximizing the chances of full vertebral body height restoration and kyphosis correction (▶Fig. 35.2 and ▶Fig. 35.3).
If you are aiming at fracture reduction, to restore the prefracture vertebral body height in order to optimize pain relief, physiological biomechanics, and to prevent more fractures of adjacent and distant vertebral bodies, mind the access!
References Beall D, Lorio MP, Yun BM, Runa MJ, Ong KL, Warner CB. Review of vertebral augmentation: an updated meta-analysis of the effectiveness. Int J Spine Surg 2018;12(3):295–321  Disch AC, Schmoelz W. Cement augmentation in a thoracolumbar fracture model: reduction and stability after balloon kyphoplasty versus vertebral body stenting. Spine 2014;39(19):E1147–E1153  Rotter R, Martin H, Fuerderer S, et al. Vertebral body stenting: a new method for vertebral augmentation versus kyphoplasty. Eur Spine J 2010;19(6):916–923  Diel P, Röder C, Perler G, et al. Radiographic and safety details of vertebral body stenting: results from a multicenter chart review. BMC Musculoskelet Disord 2013;14:233  Wang D, Zheng S, Liu A, et al. The role of minimally invasive vertebral body stent on reduction of the deflation effect after kyphoplasty: a biomechanical study. Spine 2018;43(6):E341–E347  Noriega D, Krüger A, Ardura F, et al. Clinical outcome after the use of a new craniocaudal expandable implant for vertebral compression fracture treatment: one year results from a prospective multicentric study. BioMed Res Int 2015;2015:927813  Noriega D, Maestretti G, Renaud C, et al. Clinical performance and safety of 108 SpineJack implantations: 1-year results of a prospective multicentre single-arm registry study. BioMed Res Int 2015; 2015:173872
35.2 Pearls of Vertebroplasty and Kyphoplasty
There are several important pearls in accomplishing an accurate needle placement and an optimal fill, and good post-op outcomes when performing kyphoplasty or vertebroplasty. These techniques include using last image hold, utilizing a bevel needle for maximum needle steering capability when driving the access needle, magnifying the image if visualization is difficult, and dressing the wound site with steri-strips, which can be left on for 5 days.
The fluoroscopic last-minute hold allows the provider to save the last image on the screen (▶Fig. 35.4). For example, if you save the anteroposterior (AP) view as you reach the medial cortex, then rotate to the lateral view and it shows the access needle is not in the vertebral body, the AP image information displayed can be used to determine if there is enough room medial to the pedicle to advance. Additionally, the last image hold can display the lateral view before injecting cement to see densities already present prior to cement injection, for example, a calcified aorta or a radiopaque material within the colon will be visually documented prior to injection so as not to confuse these densities with cement extravasation. Collimation of the X-ray beam will decrease scatter by decreasing the number of electrons passing through the X-ray tube and will also improve the image (▶Fig. 35.5, ▶Fig. 35.6, and ▶Fig. 35.7).
When high-grade fractures require precise trajectories, use a bevel needle to drive the access to the vertebral body. The bevel point up will drive the needle tip upward, bevel point down will drive the needle tip downward, bevel point medial will drive the needle tip toward the center, and bevel point lateral will drive the needle tip lateral (▶Fig. 35.8 and ▶Fig. 35.9). This is especially helpful when you need room to pass by the medial wall of the pedicle if you are close to the medial cortex.
Leaving a transparent film dressing on the wound will allow the patient’s caretaker to monitor for bleeding, swelling, and infection while maintaining a sterile environment under the transparent film dressing (▶Fig. 35.10).
35.3 Excellence is a Habit
“We are what we repeatedly do. Excellence, then, is not an act, but a habit.”
We have the privilege of offering a treatment to patients that nearly immediately alleviates the agony they are experiencing and simultaneously restores the functionality lost secondary to their ailment. We must remember to put the patient first. Time and again, patients are not offered interventional treatment for vertebral fractures given that many fractures do not require treatment. This is true. There are many vertebral fractures that are not terribly painful and do not limit a patient’s function. The question concerning whether a fracture requires treatment is centered on one question. How much pain is the patient in? If the patient is in severe pain, their functionality is sure to be diminished. Waiting to see if your patient will either spontaneously “heal” or remain bedbound in a back brace, potentially developing pneumonia in the next 4 to 6 weeks, should not be contemplated. The benefits of the treatment far outweigh the risks.
35.4 Osteonecrosis of the Spine (Kümmel–Verneuil Disease)
Osteonecrosis (ON), vascular necrosis, pseudarthrosis, and Kümmel’s spondylitis 1 – 12 are descriptions of severe complications of a vertebral osteoporotic fracture (VOF). It has been discussed that disruption of anterior perforating vessels results in pseudarthrosis of the vertebra; hence, ON is mostly located at the anterior aspect of the vertebra (▶Fig. 35.11). In addition to a VOF, malignancy, infection, radiation therapy, liver cirrhosis, alcoholism, steroid treatments, sarcoidosis, hemoglobinopathies such as sickle cell anemia, Cushing’s syndrome, Gaucher’s syndrome, and dysbarism after diving accidents can also lead to ON. 1 , 4 , 10 – 12 Nevertheless, osteoporosis and a fracture are by far the main causes for developing ON. This pathology bears typical changes on X-ray and MR imaging. 13 – 17 On X-ray or CT, we typically find an intravertebral cleft, also described as a “gas sign” demonstrating fluid and/or gas in the vertebral body. 14 , 17 On MRI, we find fluid or gas in the vertebral body, which can be seen as a dark or bright zones on T1 and T2/short tau inversion recovery (STIR) depending on what is present within the cleft. 6 , 8 , 14 , 17
In typical cases of ON, no bone healing occurs, and the risk of severe kyphosis and compression of the dorsal neural structures increases massively. This disease may be missed if only standing X-rays are performed; therefore, it is indicated to perform a prone or supine X-ray, which can help in making the appropriate diagnosis.
Nonsurgical treatment is not indicated to avoid plegic complications. In the past, vertebroplasty and balloon kyphoplasty (BKP) have been performed. Both techniques have led to severe bone resorption, collapse, and cement dislocation with ON, but this is seen more commonly with BKP (▶Fig. 35.12). It is known that cement filling after BKP and all other bone displacement vertebral augmentation procedures lead to stress shielding of the vertebra and increased resorption in the portions of the vertebral body not affected by the fracture, so it is thought that BKP and other procedures like it should be avoided in ON. 18 – 21 Stress-shielding phenomena have not been found in vertebroplasty. 18 , 19
In order to achieve a good cement fill and interdigitation, vertebroplasty in cases of ON should be performed by experienced practitioners. New bone-preserving kyphoplasty procedures using implants such as the Kiva implant or the SpineJack have, so far, not resulted in cement dislocation and might be indicated to achieve good stabilization of the vertebral body without increased stress shielding and an increased risk of cement dislocation (▶Fig. 35.13).
References Chou LH, Knight RQ. Idiopathic avascular necrosis of a vertebral body. Case report and literature review. Spine 1997;22(16):1928–1932  Hasegawa K, Homma T, Uchiyama S, Takahashi H. Vertebral pseudarthrosis in the osteoporotic spine. Spine 1998;23(20):2201–2206  Huy MD, Jensen ME, Marx WF, Kallmes DF. Percutaneous vertebroplasty in vertebral osteonecrosis (Kümmell’s spondylitis). Neurosurg Focus 1999;7(1):e2  Ito M, Motomiya M, Abumi K, et al. Vertebral osteonecrosis associated with sarcoidosis. Case report. J Neurosurg Spine 2005;2(2):222–225  Jang JS, Kim DY, Lee SH. Efficacy of percutaneous vertebroplasty in the treatment of intravertebral pseudarthrosis associated with noninfected avascular necrosis of the vertebral body. Spine 2003;28(14):1588–1592  Maheshwari PR, Nagar AM, Prasad SS, Shah JR, Patkar DP. Avascular necrosis of spine: a rare appearance. Spine 2004;29(6):E119–E122  Murakami H, Kawahara N, Gabata T, Nambu K, Tomita K. Vertebral body osteonecrosis without vertebral collapse. Spine 2003;28(16):E323–E328  Van Eenenaam DP, el-Khoury GY. Delayed post-traumatic vertebral collapse (Kummell’s disease): case report with serial radiographs, computed tomographic scans, and bone scans. Spine 1993;18(9):1236–1241  Young WF, Brown D, Kendler A, Clements D. Delayed post-traumatic osteonecrosis of a vertebral body (Kummell’s disease). Acta Orthop Belg 2002;68(1):13–19  Allen BL Jr, Jinkins WJ III. Vertebral osteonecrosis associated with pancreatitis in a child. A case report. J Bone Joint Surg Am 1978;60(7):985–987  Brower AC, Downey EF Jr. Kümmell disease: report of a case with serial radiographs. Radiology 1981;141(2):363–364  Hutter CD. Dysbaric osteonecrosis: a reassessment and hypothesis. Med Hypotheses 2000;54(4):585–590  Lieberman IH, Dudeney S, Reinhardt MK, Bell G. Initial outcome and efficacy of “kyphoplasty” in the treatment of painful osteoporotic vertebral compression fractures. Spine 2001;26(14):1631–1638  Maldague BE, Noel HM, Malghem JJ. The intravertebral vacuum cleft: a sign of ischemic vertebral collapse. Radiology 1978;129(1):23–29  Van Bockel SR, Mindelzun RE. Gas in the psoas muscle secondary to an intravertebral vacuum cleft: CT characteristics. J Comput Assist Tomogr 1987;11(5): 913–915  Bhalla S, Reinus WR. The linear intravertebral vacuum: a sign of benign vertebral collapse. AJR Am J Roentgenol 1998;170(6):1563–1569  McKiernan F, Faciszewski T. Intravertebral clefts in osteoporotic vertebral compression fractures. Arthritis Rheum 2003;48(5):1414–1419  Becker S. The impact of cement stiffness, bone density and filling volume after balloon kyphoplasty and the risk of stress shielding on adjacent vertebral fractures. Osteoporos Int 2010;21(Suppl 1):118–119  Dabirrahmani D, Becker S, Hogg M, Appleyard R, Baroud G, Gillies M. Mechanical variables affecting balloon kyphoplasty outcome: a finite element study. Comput Methods Biomech Biomed Engin 2012;15(3):211–220  Krüger A, Oberkircher L, Kratz M, Baroud G, Becker S, Ruchholtz S. Cement interdigitation and bone-cement interface after augmenting fractured vertebrae: a cadaveric study. Int J Spine Surg 2012;6(1):115–123  Rohlmann A, Boustani HN, Bergmann G, Zander T. A probabilistic finite element analysis of the stresses in the augmented vertebral body after vertebroplasty. Eur Spine J 2010;19(9):1585–1595
35.5 Cement Augmentation
Percutaneous vertebroplasty (PVP) is widely used in the management of osteoporotic vertebral compression fractures (VCFs), but there are reported cases where a patient’s symptoms show partial response with change in the nature of pain. Upon referral to our institution, we revisited the imaging on such cases and found in some cases to have either too little cement deposition or, more frequently, uneven cement distribution only on one side of the treated vertebrae.
The author has found in his practice that a salvage procedure after failure of an improperly used technique can be quite beneficial to some patients and can help prevent open surgical intervention. Proper patient selection using both clinical and imaging findings is critical and it should be remembered that all patients may not be suited for repeat vertebroplasty.
PVP may be done using a unipedicular or bipedicular approach for cement injection with straight or curved needles. Regardless of needle type, the cement should be placed in the midline with adequate and uniform cement deposition. In certain cases with improperly performed techniques, we do see patients with uneven cement distribution or a small amount of cement within the vertebral body. Injection using a bipedicular technique tends to deliver a more uniform cement distribution more so than a unipedicular technique. When such vertebroplasty cases are deemed failure of treatment, performing repeat salvage cement augmentation can be considered the first choice prior to open surgery, especially for patients in whom the unipedicular approach was initially used.
Bone cement is introduced via the pedicle on the side of the vertebral body with the least amount of cement for cement delivery into the nonfilled portion of the previously partially filled vertebral body. This will give rise to a more uniform cement distribution and will help in filling any previously unfilled fracture clefts. For patients in whom a bipedicular approach was initially used, repeat vertebroplasty is technically more difficult, but usually the pedicle size is sufficient enough so a repeat augmentation can still be performed. At times, a small pedicle may necessitate the use of a small gauge access cannula and delivery port in order to properly access the vertebral body. At higher levels in the spine, especially in the thoracic spine, a parapedicular approach can be used.
The author’s clinical practice is primarily focused around treatment of pathological osteolytic compression fractures with all types of cases including metastatic disease with a complete breach of the vertebral cortices including the posterior vertebral body wall.
Cement filling of pathologically fractured vertebral body is very different from filling an osteoporotic VCF as benign fractures usually have a fill pattern that is homogeneous where a cement ball is seen to form at the point of injection, which grows in size as more cement is injected and is ultimately seen to fill the anterior and middle portions of the vertebral body as the injection is observed under constant fluoroscopic imaging. In severe osteolytic pathologically fractured vertebra, the initial cement injection shows cement spreading toward channels of least resistance and can be seen darting toward the breached posterior cortex. If this happens, the operator may have to stop the injection as extravasation into the spinal canal can lead to neurologic injury and the result of limiting the amount of cement can sometimes produce inadequate stabilization of the vertebral body.
Inject contrast into the vertebral body before cement delivery to get a good idea about channels of least resistance. Based on what is seen on the injection of contrast, the tip of the delivery port can be extended more anteriorly or into another location within the vertebral body. If another appropriate location cannot be accessed with the initial straight needle, a curved needle can be used for delivery of cement to a different location.
After cement is seen extending into the posterior third of the vertebral body or noted to abut the breached cortex of any vertebral wall, the author usually waits for 2 to 3 minutes, which lets the cement to harden a bit and this hardened cement can serve as a barrier to unwanted cement extension. This technique can help more cement to be deposited into appropriate areas within the vertebral body.
35.6 Tips and Techniques of Vertebral Augmentation
35.6.1 Cementing Tips after Prior Vertebral Augmentation
During vertebroplasty or vertebral augmentation in patients with compression fractures, inadequate cement fill will lead to fracture extension, collapse, or result in nonunion clefts. Using slow and low-pressure cement injection with thick cement is key to a successful cement fill. The bone filling cannula needs to be placed in the middle of the cement ball and it is imperative to obtain stability of the vertebral fracture by adding cement to the fracture clefts and the load-bearing portion of the vertebral body between the pedicles.
When reaugmenting a previous vertebroplasty or vertebral augmentation, an en face view may be used to visualize the pedicle outline and the upper vertebral margins. A transpedicular or parapedicular approach can be utilized to reaccess the vertebral body. Kambin’s triangle offers access to the superior end plate in order to obtain a sufficiently medial trajectory of the cannula and to avoid the neural canal and the nerve root. The use of a smaller (10- to 11-gauge) cannula is recommended for revision augmentation. The operator needs to be certain that there are no new subjacent fractures and if there is no significant postprocedural pain relief, continued fracture due to an unfilled cleft, collapse of the vertebral body, or fracture around the cement needs to be suspected. Upright lateral X-rays can be used to visualize significant vertebral body collapse and any positional change of height. A computed tomography (CT) scan can also demonstrate vacuum clefts and fissures. Magnetic resonance (MR) imaging or bone scan can also be used to assess for postoperative complications if these are suspected. CT may also be used and can be used to assess the adequacy of the cement fill in regard to filling the fracture clefts and stabilizing the overall structure of the vertebral body.
35.6.2 Kyphoplasty and Revision of L3 Pedicle Screw after Posttraumatic Screw Displacement
A 78-year-old woman with past medical history of primary osteoporosis and frequent falls as well as loss of balance due to spinal stenosis and scoliosis had a L3–S1 spinal fusion 4 weeks priorto a fall (▶Fig. 35.14). The patient presented with new and increasing back pain different in nature from the surgical pain and proximal to the incision. A lateral radiograph demonstrated osteoporotic vertebral compression fractures of L2 and L3 with the left L3 pedicle screw dehiscent superiorly into the L2–L3 intervertebral disk (▶Fig. 35.15). Sagittal short tau inversion recovery (STIR) and postcontrast T1-weighted MR images demonstrated vertebral body linear signal abnormalities typical of that of a vertebral fracture of L2 and an end plate fracture of L3 (▶Fig. 35.16).
A decision was made to perform a balloon kyphoplasty of L2 to treat the vertebral compression fracture above the construct and at L3 to treat the vertebral fracture as well as to restabilize the dehiscent hardware (▶Fig. 35.17). A drill was directed through the left L3 pedicle away from the superior end plate and a balloon tamp was then placed in the center of the left side of the vertebral body (▶Fig. 35.18) The balloon tamp was inflated and a right-sided one-step introducer was also placed via a parapedicular approach (▶Fig. 35.19). A drill was then advanced through the introducer into the center of the vertebral body, adjacent to the inflated left-sided balloon (▶Fig. 35.20). Attention was then turned to the L2 vertebral body with bilateral transpedicular right and left balloon tamps placed and inflated. The right-sided L3 drill was placed without a balloon following the drill placement due to the risk of balloon rupture if it came in contact with the contralateral pedicle screw (▶Fig. 35.21). Polymethyl methacrylate injection was then performed at the L2 and L3 levels with cement filling the voids (▶Fig. 35.22). Final images demonstrated no leakage or extravasation of cement (▶Fig. 35.23).