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Vertebral Refracture after Unipedicular Kyphoplasty Resulting in Lateralized Cement Distribution
1906
’
Letters to the Editor
embolic agent that may be used for embolization of AMLs (3). EVOH is theoretically advantageous in this setting because of its penetrating ability and the formation of an intravascular cast extending from the smaller, distal tumor vasculature to the proximal, larger blood supply, as well as its predictability and controllability. A limited amount of literature exists describing the use of EVOH in AMLs (3) with no long-term followup (4). The patient described here had a large, tortuous, aneurysmal angiogenic component, as seen on preembolization angiography, which was the cause of bleeding. It was treated with EVOH (Onyx 34; Micro Therapeutics), with a good immediate result, but the EVOH did not penetrate to the distal small arteries of the tumor (Fig 1c), so recurrence was predictable. The tumor steadily grew on follow-up examinations, and recurrence of a rich, although different, angiogenic component was demonstrated on angiography at 59 months. The patient remained asymptomatic. EVOH creates an intravascular barrier with the ability to extend from the distal arterioles to the most proximal artery, which supplies the AML. Therefore, the extent of distribution in vessels of smaller diameter depends on the viscosity of the embolizing agent. The presence of a continuous cast, extending throughout the selected vasculature, might improve the long-term results by obliterating the blood supply and physically preventing angiogenesis. In the present case, the recurrent angiogenic component was composed of small vessels and did not show recurrence of the dysplastic, tortuous, aneurysmal arteries. As Onyx 34 is more viscous than Onyx 18, the latter should theoretically be preferred to achieve a more distal and extensive occlusion of the vascular component because of its relative fluidity and better penetration (3,4). Perhaps the deeper penetration ability may be associated with a better long-term result. However, considering the fact that EVOH is an expensive embolic material, our preferred embolic material for renal AML is ethanol, with its high solubility, distal penetration, and low cost.
REFERENCES 1. Ramon J, Rimon U, Garniek A, et al. Renal angiomyolipoma: long-term results following selective arterial embolization. Eur Urol 2009; 55: 1155–1162. 2. Bissler J, Kingswood J. Renal angiomyolipomata. Kidney Int 2004; 66: 924–934. 3. Katsanos K, Sabharwal T, Ahmad F, Dourado R, Adam A. Onyx embolization of sporadic angiomyolipoma. Cardiovasc Intervent Radiol 2009; 32: 1291–1295. 4. Vanninen RL, Manninen I. Onyx, a new liquid embolic material for peripheral interventions: preliminary experience in aneurysm, pseudoaneurysm, and pulmonary arteriovenous malformation embolization. Cardiovasc Intervent Radiol 2007; 30:196–200.
Frankl and Hennemeyer
’
JVIR
Vertebral Refracture after Unipedicular Kyphoplasty Resulting in Lateralized Cement Distribution From: Joseph Frankl, BS Charles Hennemeyer, MD Department of Medical Imaging (C.H.) University of Arizona College of Medicine (J.F.) 1501 N. Campbell Avenue Tucson, AZ 85724
Editor: A unipedicular approach for kyphoplasty and vertebroplasty has several theoretical advantages compared with a bipedicular approach, including lower risk, shorter operating time, less radiation exposure, and reduced cost compared with a bipedicular approach (1). However, biomechanical models show that right-sided or left-sided cement distribution, as occasionally occurs with unipedicular approaches, results in unequal vertebral loading under pressure (2). We present a case of vertebral refracture shortly after unipedicular kyphoplasty that was likely due to asymmetric cement distribution in the vertebral body. Institutional review board approval was not required for this case report. A 68-year-old white woman was seen for a vertebral compression fracture (VCF). She had fractured L1 in the past and obtained complete relief after kyphoplasty at an outside institution. Her past medical history included osteoporosis, low vitamin D level, chronic obstructive pulmonary disease, smoking 1– 1.5 packs per day, and bilateral breast cancer. She had failed conservative medical treatment for lower back pain (tramadol 100 mg daily, ibuprofen 200 mg when necessary), and thoracic and lumbar radiographs showed compression of T8 and T10. Osteopenia and cement present in the old fracture of L1 were also noted, but no known or demonstrated findings suggested metastases. A single-photon emission computed tomography/computed tomography (SPECT-CT) bone scan showed mild radiotracer activity at T8 indicating chronicity and intense activity at T10 indicating acuity. T12 was intact and normal at the time of the SPECT-CT scan. We decided to perform kyphoplasty at T10 but not T8 because of the chronic nature of the T8 VCF. During initial procedural fluoroscopy, we identified a new VCF at T12 (Fig a). The new fracture was deemed contributory to the patient’s severe back pain, and it was decided to augment this level in addition to the planned T10 fracture. We addressed T10 first via a rightsided unipedicular approach and then accessed T12 via a left-sided unipedicular approach in a similar fashion (Fig b). Next, polymethylmethacrylate (PMMA) was Neither of the authors has identified a conflict of interest. http://dx.doi.org/10.1016/j.jvir.2015.09.006
Volume 26
’
Number 12
’
December
’
2015
1907
Figure. (a) Lateral intraoperative fluoroscopic image with the patient prone showing a compression fracture at T12 (arrows). Kyphoplasty was performed on L1 at another institution. (b) Posterior-anterior prone intraoperative fluoroscopic image showing cannula in T12 (arrow). Note the relatively lateral position of the cannula at this level (midline at dashed line). (c) Posterior-anterior prone intraoperative fluoroscopic image of the final cement distribution showing lateralization at T12 and extravasation into a paravertebral vein (arrows). (d) SPECT/CT bone scan showing a new right-lateral VCF with intense technetium 99m uptake in T12 (in oval), which received a left lateralized kyphoplasty. (e) Posterior-anterior prone intraoperative fluoroscopic image showing an even cement distribution in T12 that was achieved after right-sided unipedicular kyphoplasty (arrows).
injected under fluoroscopic guidance into T10, resulting in adequate crossing of the vertebral body midline. However, we terminated injection of T12 before the polymethylmethacrylate could adequately cross the vertebral body midline because of extravasation into a left paravertebral vein (Fig c). The patient reported immediate pain relief after the procedure, which lasted approximately 1.5 months. She subsequently began experiencing pain in the same distribution as before with pain and tenderness on palpation localized to T12. We considered refracture of T12 or an adjacent level and performed a SPECT/CT bone scan, which showed a right-lateral VCF of T12 with intense technetium 99m uptake in the noncemented portion of the vertebral body consistent with a new fracture (Fig d). As a consequence of repeat pain and imaging evidence, we elected to retreat T12 with a rightsided unipedicular approach (Fig e). Pain relief after the second kyphoplasty was immediate and continued
through the time of the patient’s most recent follow-up appointment approximately 2.5 months later. Serious adverse events are rare with kyphoplasty and the similar procedure vertebroplasty, although there may be a risk for adjacent-level VCFs (3). Care is taken by operators to limit cement leakage and prevent embolization that can cause spinal cord and nerve root compression, pulmonary embolism, and possibly death. Unipedicular kyphoplasty has similar rates of cement leakage and pain-reducing efficacy compared with bipedicular kyphoplasty (4). However, this case highlights the risk that must be balanced when considering unipedicular versus bipedicular kyphoplasty/vertebroplasty. Cement extravasation accounts for most clinically relevant adverse events in vertebroplasty and kyphoplasty but is often asymptomatic. It may be appropriate when encountering incomplete cement distribution from a unipedicular approach to consider either adding a second bipedicular probe or attempting to use alternative
1908
’
Letters to the Editor
maneuvers to increase cement flow because asymmetric cement distribution may predispose to repeat fractures through induced mechanical effects. Failure of cement to distribute across the vertebral midline creates unequal load sharing between opposing sides of the vertebral body and may increase the risk of internal refracture on the noncemented side (2).
ACKNOWLEDGMENT No outside financial support was received for this work. The authors thank the patient for allowing this case to be presented. They also thank the clinical staff and
Frankl and Hennemeyer
’
JVIR
nurses within the Department of Medical Imaging for their assistance in treating the patient.
REFERENCES 1. Steinmann J, Tingey CT, Cruz G, Dai Q. Biomechanical comparison of unipedicular versus bipedicular kyphoplasty. Spine (Phila Pa 1976) 2005; 30: 201–205. 2. Liebschner MA, Rosenberg WS, Keaveny TM. Effects of bone cement volume and distribution on vertebral stiffness after vertebroplasty. Spine (Phila Pa 1976) 2001; 26:1547–1554. 3. Liu W-G, He S-C, Deng G, et al. Risk factors for new vertebral fractures after percutaneous vertebroplasty in patients with osteoporosis: a prospective study. J Vasc Interv Radiol 2012; 23:1143–1149. 4. Chen L, Yang H, Tang T. Unilateral versus bilateral balloon kyphoplasty for multilevel osteoporotic vertebral compression fractures: a prospective study. Spine (Phila Pa 1976) 2011; 36:534–540.
’
Letters to the Editor
embolic agent that may be used for embolization of AMLs (3). EVOH is theoretically advantageous in this setting because of its penetrating ability and the formation of an intravascular cast extending from the smaller, distal tumor vasculature to the proximal, larger blood supply, as well as its predictability and controllability. A limited amount of literature exists describing the use of EVOH in AMLs (3) with no long-term followup (4). The patient described here had a large, tortuous, aneurysmal angiogenic component, as seen on preembolization angiography, which was the cause of bleeding. It was treated with EVOH (Onyx 34; Micro Therapeutics), with a good immediate result, but the EVOH did not penetrate to the distal small arteries of the tumor (Fig 1c), so recurrence was predictable. The tumor steadily grew on follow-up examinations, and recurrence of a rich, although different, angiogenic component was demonstrated on angiography at 59 months. The patient remained asymptomatic. EVOH creates an intravascular barrier with the ability to extend from the distal arterioles to the most proximal artery, which supplies the AML. Therefore, the extent of distribution in vessels of smaller diameter depends on the viscosity of the embolizing agent. The presence of a continuous cast, extending throughout the selected vasculature, might improve the long-term results by obliterating the blood supply and physically preventing angiogenesis. In the present case, the recurrent angiogenic component was composed of small vessels and did not show recurrence of the dysplastic, tortuous, aneurysmal arteries. As Onyx 34 is more viscous than Onyx 18, the latter should theoretically be preferred to achieve a more distal and extensive occlusion of the vascular component because of its relative fluidity and better penetration (3,4). Perhaps the deeper penetration ability may be associated with a better long-term result. However, considering the fact that EVOH is an expensive embolic material, our preferred embolic material for renal AML is ethanol, with its high solubility, distal penetration, and low cost.
REFERENCES 1. Ramon J, Rimon U, Garniek A, et al. Renal angiomyolipoma: long-term results following selective arterial embolization. Eur Urol 2009; 55: 1155–1162. 2. Bissler J, Kingswood J. Renal angiomyolipomata. Kidney Int 2004; 66: 924–934. 3. Katsanos K, Sabharwal T, Ahmad F, Dourado R, Adam A. Onyx embolization of sporadic angiomyolipoma. Cardiovasc Intervent Radiol 2009; 32: 1291–1295. 4. Vanninen RL, Manninen I. Onyx, a new liquid embolic material for peripheral interventions: preliminary experience in aneurysm, pseudoaneurysm, and pulmonary arteriovenous malformation embolization. Cardiovasc Intervent Radiol 2007; 30:196–200.
Frankl and Hennemeyer
’
JVIR
Vertebral Refracture after Unipedicular Kyphoplasty Resulting in Lateralized Cement Distribution From: Joseph Frankl, BS Charles Hennemeyer, MD Department of Medical Imaging (C.H.) University of Arizona College of Medicine (J.F.) 1501 N. Campbell Avenue Tucson, AZ 85724
Editor: A unipedicular approach for kyphoplasty and vertebroplasty has several theoretical advantages compared with a bipedicular approach, including lower risk, shorter operating time, less radiation exposure, and reduced cost compared with a bipedicular approach (1). However, biomechanical models show that right-sided or left-sided cement distribution, as occasionally occurs with unipedicular approaches, results in unequal vertebral loading under pressure (2). We present a case of vertebral refracture shortly after unipedicular kyphoplasty that was likely due to asymmetric cement distribution in the vertebral body. Institutional review board approval was not required for this case report. A 68-year-old white woman was seen for a vertebral compression fracture (VCF). She had fractured L1 in the past and obtained complete relief after kyphoplasty at an outside institution. Her past medical history included osteoporosis, low vitamin D level, chronic obstructive pulmonary disease, smoking 1– 1.5 packs per day, and bilateral breast cancer. She had failed conservative medical treatment for lower back pain (tramadol 100 mg daily, ibuprofen 200 mg when necessary), and thoracic and lumbar radiographs showed compression of T8 and T10. Osteopenia and cement present in the old fracture of L1 were also noted, but no known or demonstrated findings suggested metastases. A single-photon emission computed tomography/computed tomography (SPECT-CT) bone scan showed mild radiotracer activity at T8 indicating chronicity and intense activity at T10 indicating acuity. T12 was intact and normal at the time of the SPECT-CT scan. We decided to perform kyphoplasty at T10 but not T8 because of the chronic nature of the T8 VCF. During initial procedural fluoroscopy, we identified a new VCF at T12 (Fig a). The new fracture was deemed contributory to the patient’s severe back pain, and it was decided to augment this level in addition to the planned T10 fracture. We addressed T10 first via a rightsided unipedicular approach and then accessed T12 via a left-sided unipedicular approach in a similar fashion (Fig b). Next, polymethylmethacrylate (PMMA) was Neither of the authors has identified a conflict of interest. http://dx.doi.org/10.1016/j.jvir.2015.09.006
Volume 26
’
Number 12
’
December
’
2015
1907
Figure. (a) Lateral intraoperative fluoroscopic image with the patient prone showing a compression fracture at T12 (arrows). Kyphoplasty was performed on L1 at another institution. (b) Posterior-anterior prone intraoperative fluoroscopic image showing cannula in T12 (arrow). Note the relatively lateral position of the cannula at this level (midline at dashed line). (c) Posterior-anterior prone intraoperative fluoroscopic image of the final cement distribution showing lateralization at T12 and extravasation into a paravertebral vein (arrows). (d) SPECT/CT bone scan showing a new right-lateral VCF with intense technetium 99m uptake in T12 (in oval), which received a left lateralized kyphoplasty. (e) Posterior-anterior prone intraoperative fluoroscopic image showing an even cement distribution in T12 that was achieved after right-sided unipedicular kyphoplasty (arrows).
injected under fluoroscopic guidance into T10, resulting in adequate crossing of the vertebral body midline. However, we terminated injection of T12 before the polymethylmethacrylate could adequately cross the vertebral body midline because of extravasation into a left paravertebral vein (Fig c). The patient reported immediate pain relief after the procedure, which lasted approximately 1.5 months. She subsequently began experiencing pain in the same distribution as before with pain and tenderness on palpation localized to T12. We considered refracture of T12 or an adjacent level and performed a SPECT/CT bone scan, which showed a right-lateral VCF of T12 with intense technetium 99m uptake in the noncemented portion of the vertebral body consistent with a new fracture (Fig d). As a consequence of repeat pain and imaging evidence, we elected to retreat T12 with a rightsided unipedicular approach (Fig e). Pain relief after the second kyphoplasty was immediate and continued
through the time of the patient’s most recent follow-up appointment approximately 2.5 months later. Serious adverse events are rare with kyphoplasty and the similar procedure vertebroplasty, although there may be a risk for adjacent-level VCFs (3). Care is taken by operators to limit cement leakage and prevent embolization that can cause spinal cord and nerve root compression, pulmonary embolism, and possibly death. Unipedicular kyphoplasty has similar rates of cement leakage and pain-reducing efficacy compared with bipedicular kyphoplasty (4). However, this case highlights the risk that must be balanced when considering unipedicular versus bipedicular kyphoplasty/vertebroplasty. Cement extravasation accounts for most clinically relevant adverse events in vertebroplasty and kyphoplasty but is often asymptomatic. It may be appropriate when encountering incomplete cement distribution from a unipedicular approach to consider either adding a second bipedicular probe or attempting to use alternative
1908
’
Letters to the Editor
maneuvers to increase cement flow because asymmetric cement distribution may predispose to repeat fractures through induced mechanical effects. Failure of cement to distribute across the vertebral midline creates unequal load sharing between opposing sides of the vertebral body and may increase the risk of internal refracture on the noncemented side (2).
ACKNOWLEDGMENT No outside financial support was received for this work. The authors thank the patient for allowing this case to be presented. They also thank the clinical staff and
Frankl and Hennemeyer
’
JVIR
nurses within the Department of Medical Imaging for their assistance in treating the patient.
REFERENCES 1. Steinmann J, Tingey CT, Cruz G, Dai Q. Biomechanical comparison of unipedicular versus bipedicular kyphoplasty. Spine (Phila Pa 1976) 2005; 30: 201–205. 2. Liebschner MA, Rosenberg WS, Keaveny TM. Effects of bone cement volume and distribution on vertebral stiffness after vertebroplasty. Spine (Phila Pa 1976) 2001; 26:1547–1554. 3. Liu W-G, He S-C, Deng G, et al. Risk factors for new vertebral fractures after percutaneous vertebroplasty in patients with osteoporosis: a prospective study. J Vasc Interv Radiol 2012; 23:1143–1149. 4. Chen L, Yang H, Tang T. Unilateral versus bilateral balloon kyphoplasty for multilevel osteoporotic vertebral compression fractures: a prospective study. Spine (Phila Pa 1976) 2011; 36:534–540.