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Application of full-balance-integrated technique in asymmetrical pedicle subtraction osteotomy for treating fixed degenerative lumbar kyphoscoliosis
Formosan Journal of Surgery (2015) 48, 110e115
Available online at www.sciencedirect.com
ScienceDirect journal homepage: www.e-fjs.com
CASE REPORT
Application of full-balance-integrated technique in asymmetrical pedicle subtraction osteotomy for treating fixed degenerative lumbar kyphoscoliosis Hsien-Ta Hsu a, Ming-Hsueh Lee b, Kuo-Feng Huang a,c,* a Division of Neurosurgery, Department of Surgery, Taipei Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Taipei, Taiwan b Department of Neurosurgery, Chang Gung Memorial Hospital, Chia-Yi Center, Chiayi, Taiwan c School of Medicine, Tzu Chi University, Hualien 97004, Taiwan
Received 29 October 2014; received in revised form 27 December 2014; accepted 23 January 2015
Available online 23 May 2015
KEYWORDS full-balanceintegrated technique; kyphoscoliosis; pedicle subtraction osteotomy; sagittal balance
Summary A 56-year-old female patient experienced mild back pain, which radiated to her legs, as well as intermittent claudication for 5 years. The symptoms became more pronounced on sitting and walking, and conservative therapy was ineffective in relieving pain. Preoperative whole-spine X-ray scans revealed degenerative lumbar kyphoscoliosis. Asymmetrical pedicle subtraction osteotomy was performed and a convex-sided posterolateral wedge osteotomy was applied to correct the scoliosis and restore sagittal balance. Pre- and postoperative sagittal balance was measured using a C7 plumb line for both scans, and the difference was calculated. Lumbar scoliosis was measured using the Cobb angle. The degree of correction required to restore sagittal alignment was 25 , which was determined on the basis of the full-balance-integrated technique. The operative time and blood loss were 365 minutes and 1620 mL, respectively. Postoperatively, the lumbar scoliosis decreased from 10.2 to 2.0 , and the sagittal vertical axis decreased from 7.6 cm to 3.3 cm. The visual analog scale and Oswestry disability index scores indicated that the patient was relieved of the symptoms after the surgery. No complications were observed during the follow-up period. Copyright ª 2015, Taiwan Surgical Association. Published by Elsevier Taiwan LLC. All rights reserved.
Conflicts of interest: No funds were received in support of this work. No benefits in any form were received from a commercial party related directly or indirectly to the subject of this study. * Corresponding author. Division of Neurosurgery, Department of Surgery, Taipei Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, 289 Jianguo Road, Xindian, New Taipei City 23143, Taiwan. E-mail address: [email protected] (K.-F. Huang). http://dx.doi.org/10.1016/j.fjs.2015.01.004 1682-606X/Copyright ª 2015, Taiwan Surgical Association. Published by Elsevier Taiwan LLC. All rights reserved.
Asymmetrical pedicle subtraction osteotomy
1. Introduction Degenerative sagittal imbalance is either flexible or fixed.1 An anterior release and posterior instrumentation can be used to correct the deformity of patients with flexible degenerative sagittal imbalance, whereas pedicle subtraction osteotomy (PSO), commonly applied for treating
Figure 1 Anteroposterior view of the whole spine revealing a lumbar scoliosis of 10.2 calculated using Cobb angles between the upper end plate of L1 (yellow line) and the lower end plate of L5 (yellow line).
111 ankylosing spondylitis,2,3 iatrogenic flat-back deformity,4 and posttraumatic kyphosis,5,6 is used for correcting the sagittal alignment of patients with fixed degenerative sagittal imbalance. PSO is theoretically performed on L4, which is always the apex of lumbar lordosis, in a normal population.7 However, most spine surgeons prefer L3 as the osteotomy site, because wedge resection is easier to perform on L3
Figure 2 Lateral view of the whole spine revealing the C7 plumb line (red line) falling 7.6 cm (yellow line) anterior to the posterosuperior corner of the S1 plateau.
112 than on L4. The procedure involves resecting the vertebral wedge from the spine, widening from the anterior cortex of the vertebral body through the pedicles and toward the posterior elements of the spine.8 The degree of correction should be measured preoperatively to avoid inadequate sagittal-balance restoration after osteotomy. Among the various methods9e12 used for calculating the degree of correction, the full-balanceintegrated (FBI) technique9 is relatively simple and effective. In this technique, the projected C7 plumb line falling on the S1 plateau is evaluated preoperatively to determine the degree of correction. Sagittal imbalance is sometimes accompanied with coronal imbalance. For the concurrent restoration of sagittal balance and correction of coronal imbalance, an asymmetrical PSO can be used.8 Coronal imbalance can be corrected during wedge closure through the removal of a large portion of the wedge-shaped bone on the convex side and a small portion of the vertebral body on the concave side.
2. Case report The patient was a 56-year-old female who experienced mild back pain, which radiated to her legs, as well as intermittent claudication for 5 years. The symptoms became more pronounced on sitting and walking, and conservative therapy was ineffective in relieving pain. Preoperative whole-spine X-ray scans revealed lumbar kyphoscoliosis (Cobb angle: 10.2 ) and positive sagittal balance [sagittal vertical axis (SVA): 7.6 cm] (Figs. 1 and 2). A magnetic resonance imaging scan of the lumbar spine revealed hypertrophy of the facet joints and the ligamentum flavum, as well as disk herniations at L3eL4 and L4eL5 (Fig. 3). Asymmetrical PSO was performed and convex-sided posterolateral wedge osteotomy was applied to correct the kyphoscoliosis and to restore sagittal balance. Before performing the asymmetrical PSO, the angle for correcting lumbar kyphosis was calculated according to the FBI technique.9 First, a new projected C7 plumb line should pass through the S1 plateau. A 15 angle (angle of C7 translation) was obtained by measuring the angle between a line connecting the center of L4 with the center of C7, and another line connecting the center of L4 with a projected C7 plumb line that fell vertically on the S1 plateau. Second, the angle of
H.-T. Hsu et al. femur obliquity was calculated to be 5 by measuring the inclination of the femoral axis to the vertical. Third, the pelvic-tilt compensation angle was 5 because the patient’s pelvic tilt was 23.5 (between 15 and 25 ) (Fig. 4). Hence, the summation of the correction angle was 25 , which lies within the range of the degree of correction provided by the PSO. Before osteotomy was performed, pedicle screws were placed cephalad and caudad to L3 to stabilize the spine during the procedure. The spinous process and lamina of L3 were removed. Osteotomy was performed circumferentially by including the lateral walls of the vertebral body without breaching its ventral side. The bone was removed using an osteotome and a curette, while safeguarding the nerve roots and thecal sac with a protector. By resecting a large wedge-shaped bone on the convex side and a small portion on the concave side with the remaining vertebral body being equivalent on both sides, the correction of the coronal plane was attained during the closure of the bony defect. The osteotomy site was closed by hyperextending the chest and legs with the operating table. When rods were being positioned and locked, the thecal sac and roots were carefully inspected to exclude any impingement. Intraoperative neuromonitoring was performed to avoid neurological complications during the corrective procedure. The operative time and blood loss were 365 minutes and 1620 mL, respectively. One month postoperatively, the lumbar scoliosis decreased from 10.2 to 2.0 , and the SVA decreased from 7.6 cm to 3.3 cm (Figs. 5 and 6). During the follow-up period at 3 months, 6 months, and 2 years postoperatively, the patient’s back pain improved, and the scores decreased from 7 to 4, 2, 2 on the visual analog scale, and from 22 to 18, 14, and 14 on the Oswestry disability index, respectively. No postoperative complications were observed during the 2-year follow-up period.
3. Discussion The surgical outcomes of our patient who underwent asymmetric PSO were satisfactory according to the visual analog scale and Oswestry disability index scores. Regarding kyphoscoliosis correction, the coronal plane improved considerably and the sagittal balance was restored to normal. Using the FBI technique, we accurately evaluated the degree of correction, and determined the most suitable
Figure 3 (A) Sagittal view of a magnetic resonance imaging (MRI) scan of the lumbar spine revealing disk herniations (yellow arrows) and ligamentum flavum hypertrophy (red arrows) at L3eL4 and L4eL5; (B) axial view of the MRI scan of the lumbar spine revealing hypertrophy of the ligamentum flavum and facet joints (yellow arrows) at L3eL4; (C) axial view of the MRI scan of the lumbar spine exhibiting hypertrophy of the ligamentum flavum and facet joints (yellow arrows) at L4eL5.
Asymmetrical pedicle subtraction osteotomy
113
Figure 5 Anteroposterior view of the whole spine revealing a lumbar scoliosis of 2.0 calculated using Cobb angles between the upper end plate of L1 (yellow line) and the lower end plate of L5 (yellow line). Figure 4 Angle of C7 translation (black curved arrow) is obtained by measuring the angle between a line connecting the center of L4 with the center of C7, and another line connecting the center of L4 with a projected C7 plumb line that falls vertically on the S1 plateau; angle of femur obliquity (red curved arrow) is obtained by calculating the inclination of the femoral axis to the vertical; the pelvic tilt is indicated by a yellow curved arrow; the green, yellow, red, and black oval dots refer to the center of C7, the center of L4, the center of the femoral head, and the center of the knee, respectively; the straight yellow and red lines represent the S1 plateau and the projected C7 plumb line, respectively.
osteotomy procedure for treating the patient. Additionally, no complications were observed during the follow-up, and the patient was satisfied with the treatment and expressed no reluctance in repeating the procedure. Degenerative lumbar sagittal imbalance is more common in Asian countries than in Western countries, probably because most Asian people assume a squatting position while performing sedentary work. It occurs in middle-aged and elderly people because of reduced disk space, osteoporotic vertebral compression fracture, and atrophy of the lumbar extensor muscles.1 Degenerative sagittal imbalance
114
Figure 6 Lateral view of the whole-spine film showing the C7 plumb line (red line) falling 3.3 cm (yellow line) anterior to the posterosuperior corner of the S1 plateau.
is flexible at the early stages; however, it becomes fixed over a long period, prohibiting patients from standing upright. Occasionally, patients sustain lumbar kyphoscoliosis, whereas sagittal imbalance is accompanied with coronal imbalance. According to Bridwell,8 sagittal imbalance can be classified into two types. Type I is a segmental problem, in which the patient is able to maintain sagittal balance by hyperextending segments above and below, allowing the C7 plumb line to fall over the sacrum on a standing
H.-T. Hsu et al. sagittal radiograph. In type II, the patient cannot maintain sagittal balance by hyperextending segments above and below. Therefore, the patient has a stooped posture because of the inability to stand upright, and the C7 plumb line is 6 cm or more in front of the posterosuperior corner of the S1 end plate. For type II patients, an osteotomy is necessary to correct the sagittal imbalance. The choice of osteotomy depends on the degree of correction required. The degree of correction per level is approximately 10 for SmithePetersen osteotomy (SPO),8 approximately 25e35 for PSO,8 and approximately 40e60 for vertebral column resection (VCR).13 In our case, PSO was adopted over SPO and transforaminal lumbar interbody fusion for correcting sagittal imbalance because the concurrent correction of the coronal imbalance by using asymmetrical resection cannot be performed using SPO, and transforaminal lumbar interbody fusion cannot completely restore sagittal alignment for fixed degenerative kyphoscoliosis. Le Huec et al9 developed the FBI technique for calculating the degree of correction before performing osteotomy. This technique enables surgeons to determine the type of osteotomy, such as SPO, PSO, or VCR, that is suitable for patients requiring small or large lordosis restoration. Using this technique, the degree of correction was measured to be approximately 25 , and PSO was considered more suitable for our case than multiple SPOs for simultaneously correcting kyphosis and scoliosis. Bridwell8 described the two types of coronal imbalance. In type I, the right shoulder is high with a low right pelvis. In type II, the right shoulder is low with a low right pelvis. Bridwell8 believed that type II coronal imbalance could be corrected only by using VCR, whereas type I coronal imbalance accompanied with type II sagittal imbalance could be corrected using asymmetric PSO. In our case, the patient sustained type I sagittal imbalance with a lumbar scoliosis that was unassociated with type II coronal imbalance. Therefore, an asymmetric PSO was adopted for treating her kyphoscoliosis. Toyone et al14 reported 14 cases of degenerative lumbar kyphoscoliosis in patients whose ages were between 45 and 76 years (average age: 67 years) who had undergone asymmetric PSO with a minimum follow-up period of 2 years. The average operative time was 310 minutes (range: 25e375 minutes), and the average blood loss was 1090 mL (range: 700e2900 mL). The mean lumbar scoliosis decreased from 40 to 12 , and the mean SVA decreased from 12 cm to 3 cm. There were four complications: one dural tear, two hook dislodgments at the cephalad side requiring instrument revision, and one rod breakage requiring no instrument revision. However, the degree of correction required was not mentioned for these 14 cases, and the method for measuring the required restoration preoperatively was not specified. PSO is a technically challenging technique that is potentially catastrophic for inexperienced surgeons. “First, do no harm” is the principle followed while performing a difficult technique on patients. Before attempting an asymmetrical PSO on patients with lumbar kyphoscoliosis, surgeons should familiarize themselves with the procedure by attending associated conferences and by practicing the technique on cadavers.
Asymmetrical pedicle subtraction osteotomy
115
References 1. Cho KJ, Kim KT, Kim WJ, et al. Pedicle subtraction osteotomy in elderly patients with degenerative sagittal imbalance. Spine J. 2013;38:E1561e1566. 2. Qian BP, Jiang J, Qiu Y, Wang B, Yu Y, Zhu ZZ. Radiographical predictors for postoperative sagittal imbalance in patients with thoracolumbar kyphosis secondary to ankylosing spondylitis after lumbar pedicle subtraction osteotomy. Spine J. 2013;38: E1669e1675. 3. Park YS, Kim HS, Baek SW. Spinal osteotomy in ankylosing spondylitis: radiological, clinical, and psychological results. Spine J. 2014;14:1921e1927. 4. Potter BK, Lenke LG, Kuklo TR. Prevention and management of iatrogenic flatback deformity. J Bone Joint Surg Am. 2004;86: 1793e1808. 5. Schnake KJ, Kandziora F. Correction of posttraumatic kyphosis of the thoracolumbar spine with modified pedicle subtraction osteotomy. Eur Spine J. 2010;19:2231e2232. 6. Heary RF, Bono CM. Pedicle subtraction osteotomy in the treatment of chronic, posttraumatic kyphotic deformity. J Neurosurg Spine. 2006;5:1e8. 7. Roussouly P, Gollogly S, Berthonnaud E, Dimnet J. Classification of the normal variation in the sagittal alignment of the human
8.
9.
10.
11.
12.
13.
14.
lumbar spine and pelvis in the standing position. Spine J. 2005; 30:346e353. Bridwell KH. Decision making regarding SmithePetersen vs. pedicle subtraction osteotomy vs. vertebral column resection for spinal deformity. Spine J. 2006;31:S171e178. Le Huec JC, Leijssen P, Duarte M, Aunoble S. Thoracolumbar imbalance analysis for osteotomy planification using a new method: FBI technique. Eur Spine J. 2011;20:S669e680. Aurouer N, Obied I, Gille O, Pointillart V, Vital JM. Computerized preoperative planning for correction of sagittal deformity of the spine. Surg Radiol Anat. 2009;31:781e792. Ondra SL, Marzouk S, Koski T, Silva F, Salehi S. Mathematical calculation of the pedicle subtraction osteotomy size to allow precision correction of fixed sagittal deformity. Spine J. 2006; 31:E973eE979. Yang BP, Chen LA, Ondra SL. A novel mathematical model of the sagittal spine: application to pedicle subtraction osteotomy for correction of fixed sagittal deformity. Spine J. 2008;8:359e366. Jeszenszky D, Haschtmann D, Kleinstuck FS, et al. Posterior vertebral column resection in early onset spinal deformities. Eur Spine J. 2014;23:198e208. Toyone T, Shiboi R, Ozawa T, et al. Asymmetrical pedicle subtraction osteotomy for rigid degenerative lumbar kyphoscoliosis. Spine J. 2012;37:1847e1852.
Available online at www.sciencedirect.com
ScienceDirect journal homepage: www.e-fjs.com
CASE REPORT
Application of full-balance-integrated technique in asymmetrical pedicle subtraction osteotomy for treating fixed degenerative lumbar kyphoscoliosis Hsien-Ta Hsu a, Ming-Hsueh Lee b, Kuo-Feng Huang a,c,* a Division of Neurosurgery, Department of Surgery, Taipei Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Taipei, Taiwan b Department of Neurosurgery, Chang Gung Memorial Hospital, Chia-Yi Center, Chiayi, Taiwan c School of Medicine, Tzu Chi University, Hualien 97004, Taiwan
Received 29 October 2014; received in revised form 27 December 2014; accepted 23 January 2015
Available online 23 May 2015
KEYWORDS full-balanceintegrated technique; kyphoscoliosis; pedicle subtraction osteotomy; sagittal balance
Summary A 56-year-old female patient experienced mild back pain, which radiated to her legs, as well as intermittent claudication for 5 years. The symptoms became more pronounced on sitting and walking, and conservative therapy was ineffective in relieving pain. Preoperative whole-spine X-ray scans revealed degenerative lumbar kyphoscoliosis. Asymmetrical pedicle subtraction osteotomy was performed and a convex-sided posterolateral wedge osteotomy was applied to correct the scoliosis and restore sagittal balance. Pre- and postoperative sagittal balance was measured using a C7 plumb line for both scans, and the difference was calculated. Lumbar scoliosis was measured using the Cobb angle. The degree of correction required to restore sagittal alignment was 25 , which was determined on the basis of the full-balance-integrated technique. The operative time and blood loss were 365 minutes and 1620 mL, respectively. Postoperatively, the lumbar scoliosis decreased from 10.2 to 2.0 , and the sagittal vertical axis decreased from 7.6 cm to 3.3 cm. The visual analog scale and Oswestry disability index scores indicated that the patient was relieved of the symptoms after the surgery. No complications were observed during the follow-up period. Copyright ª 2015, Taiwan Surgical Association. Published by Elsevier Taiwan LLC. All rights reserved.
Conflicts of interest: No funds were received in support of this work. No benefits in any form were received from a commercial party related directly or indirectly to the subject of this study. * Corresponding author. Division of Neurosurgery, Department of Surgery, Taipei Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, 289 Jianguo Road, Xindian, New Taipei City 23143, Taiwan. E-mail address: [email protected] (K.-F. Huang). http://dx.doi.org/10.1016/j.fjs.2015.01.004 1682-606X/Copyright ª 2015, Taiwan Surgical Association. Published by Elsevier Taiwan LLC. All rights reserved.
Asymmetrical pedicle subtraction osteotomy
1. Introduction Degenerative sagittal imbalance is either flexible or fixed.1 An anterior release and posterior instrumentation can be used to correct the deformity of patients with flexible degenerative sagittal imbalance, whereas pedicle subtraction osteotomy (PSO), commonly applied for treating
Figure 1 Anteroposterior view of the whole spine revealing a lumbar scoliosis of 10.2 calculated using Cobb angles between the upper end plate of L1 (yellow line) and the lower end plate of L5 (yellow line).
111 ankylosing spondylitis,2,3 iatrogenic flat-back deformity,4 and posttraumatic kyphosis,5,6 is used for correcting the sagittal alignment of patients with fixed degenerative sagittal imbalance. PSO is theoretically performed on L4, which is always the apex of lumbar lordosis, in a normal population.7 However, most spine surgeons prefer L3 as the osteotomy site, because wedge resection is easier to perform on L3
Figure 2 Lateral view of the whole spine revealing the C7 plumb line (red line) falling 7.6 cm (yellow line) anterior to the posterosuperior corner of the S1 plateau.
112 than on L4. The procedure involves resecting the vertebral wedge from the spine, widening from the anterior cortex of the vertebral body through the pedicles and toward the posterior elements of the spine.8 The degree of correction should be measured preoperatively to avoid inadequate sagittal-balance restoration after osteotomy. Among the various methods9e12 used for calculating the degree of correction, the full-balanceintegrated (FBI) technique9 is relatively simple and effective. In this technique, the projected C7 plumb line falling on the S1 plateau is evaluated preoperatively to determine the degree of correction. Sagittal imbalance is sometimes accompanied with coronal imbalance. For the concurrent restoration of sagittal balance and correction of coronal imbalance, an asymmetrical PSO can be used.8 Coronal imbalance can be corrected during wedge closure through the removal of a large portion of the wedge-shaped bone on the convex side and a small portion of the vertebral body on the concave side.
2. Case report The patient was a 56-year-old female who experienced mild back pain, which radiated to her legs, as well as intermittent claudication for 5 years. The symptoms became more pronounced on sitting and walking, and conservative therapy was ineffective in relieving pain. Preoperative whole-spine X-ray scans revealed lumbar kyphoscoliosis (Cobb angle: 10.2 ) and positive sagittal balance [sagittal vertical axis (SVA): 7.6 cm] (Figs. 1 and 2). A magnetic resonance imaging scan of the lumbar spine revealed hypertrophy of the facet joints and the ligamentum flavum, as well as disk herniations at L3eL4 and L4eL5 (Fig. 3). Asymmetrical PSO was performed and convex-sided posterolateral wedge osteotomy was applied to correct the kyphoscoliosis and to restore sagittal balance. Before performing the asymmetrical PSO, the angle for correcting lumbar kyphosis was calculated according to the FBI technique.9 First, a new projected C7 plumb line should pass through the S1 plateau. A 15 angle (angle of C7 translation) was obtained by measuring the angle between a line connecting the center of L4 with the center of C7, and another line connecting the center of L4 with a projected C7 plumb line that fell vertically on the S1 plateau. Second, the angle of
H.-T. Hsu et al. femur obliquity was calculated to be 5 by measuring the inclination of the femoral axis to the vertical. Third, the pelvic-tilt compensation angle was 5 because the patient’s pelvic tilt was 23.5 (between 15 and 25 ) (Fig. 4). Hence, the summation of the correction angle was 25 , which lies within the range of the degree of correction provided by the PSO. Before osteotomy was performed, pedicle screws were placed cephalad and caudad to L3 to stabilize the spine during the procedure. The spinous process and lamina of L3 were removed. Osteotomy was performed circumferentially by including the lateral walls of the vertebral body without breaching its ventral side. The bone was removed using an osteotome and a curette, while safeguarding the nerve roots and thecal sac with a protector. By resecting a large wedge-shaped bone on the convex side and a small portion on the concave side with the remaining vertebral body being equivalent on both sides, the correction of the coronal plane was attained during the closure of the bony defect. The osteotomy site was closed by hyperextending the chest and legs with the operating table. When rods were being positioned and locked, the thecal sac and roots were carefully inspected to exclude any impingement. Intraoperative neuromonitoring was performed to avoid neurological complications during the corrective procedure. The operative time and blood loss were 365 minutes and 1620 mL, respectively. One month postoperatively, the lumbar scoliosis decreased from 10.2 to 2.0 , and the SVA decreased from 7.6 cm to 3.3 cm (Figs. 5 and 6). During the follow-up period at 3 months, 6 months, and 2 years postoperatively, the patient’s back pain improved, and the scores decreased from 7 to 4, 2, 2 on the visual analog scale, and from 22 to 18, 14, and 14 on the Oswestry disability index, respectively. No postoperative complications were observed during the 2-year follow-up period.
3. Discussion The surgical outcomes of our patient who underwent asymmetric PSO were satisfactory according to the visual analog scale and Oswestry disability index scores. Regarding kyphoscoliosis correction, the coronal plane improved considerably and the sagittal balance was restored to normal. Using the FBI technique, we accurately evaluated the degree of correction, and determined the most suitable
Figure 3 (A) Sagittal view of a magnetic resonance imaging (MRI) scan of the lumbar spine revealing disk herniations (yellow arrows) and ligamentum flavum hypertrophy (red arrows) at L3eL4 and L4eL5; (B) axial view of the MRI scan of the lumbar spine revealing hypertrophy of the ligamentum flavum and facet joints (yellow arrows) at L3eL4; (C) axial view of the MRI scan of the lumbar spine exhibiting hypertrophy of the ligamentum flavum and facet joints (yellow arrows) at L4eL5.
Asymmetrical pedicle subtraction osteotomy
113
Figure 5 Anteroposterior view of the whole spine revealing a lumbar scoliosis of 2.0 calculated using Cobb angles between the upper end plate of L1 (yellow line) and the lower end plate of L5 (yellow line). Figure 4 Angle of C7 translation (black curved arrow) is obtained by measuring the angle between a line connecting the center of L4 with the center of C7, and another line connecting the center of L4 with a projected C7 plumb line that falls vertically on the S1 plateau; angle of femur obliquity (red curved arrow) is obtained by calculating the inclination of the femoral axis to the vertical; the pelvic tilt is indicated by a yellow curved arrow; the green, yellow, red, and black oval dots refer to the center of C7, the center of L4, the center of the femoral head, and the center of the knee, respectively; the straight yellow and red lines represent the S1 plateau and the projected C7 plumb line, respectively.
osteotomy procedure for treating the patient. Additionally, no complications were observed during the follow-up, and the patient was satisfied with the treatment and expressed no reluctance in repeating the procedure. Degenerative lumbar sagittal imbalance is more common in Asian countries than in Western countries, probably because most Asian people assume a squatting position while performing sedentary work. It occurs in middle-aged and elderly people because of reduced disk space, osteoporotic vertebral compression fracture, and atrophy of the lumbar extensor muscles.1 Degenerative sagittal imbalance
114
Figure 6 Lateral view of the whole-spine film showing the C7 plumb line (red line) falling 3.3 cm (yellow line) anterior to the posterosuperior corner of the S1 plateau.
is flexible at the early stages; however, it becomes fixed over a long period, prohibiting patients from standing upright. Occasionally, patients sustain lumbar kyphoscoliosis, whereas sagittal imbalance is accompanied with coronal imbalance. According to Bridwell,8 sagittal imbalance can be classified into two types. Type I is a segmental problem, in which the patient is able to maintain sagittal balance by hyperextending segments above and below, allowing the C7 plumb line to fall over the sacrum on a standing
H.-T. Hsu et al. sagittal radiograph. In type II, the patient cannot maintain sagittal balance by hyperextending segments above and below. Therefore, the patient has a stooped posture because of the inability to stand upright, and the C7 plumb line is 6 cm or more in front of the posterosuperior corner of the S1 end plate. For type II patients, an osteotomy is necessary to correct the sagittal imbalance. The choice of osteotomy depends on the degree of correction required. The degree of correction per level is approximately 10 for SmithePetersen osteotomy (SPO),8 approximately 25e35 for PSO,8 and approximately 40e60 for vertebral column resection (VCR).13 In our case, PSO was adopted over SPO and transforaminal lumbar interbody fusion for correcting sagittal imbalance because the concurrent correction of the coronal imbalance by using asymmetrical resection cannot be performed using SPO, and transforaminal lumbar interbody fusion cannot completely restore sagittal alignment for fixed degenerative kyphoscoliosis. Le Huec et al9 developed the FBI technique for calculating the degree of correction before performing osteotomy. This technique enables surgeons to determine the type of osteotomy, such as SPO, PSO, or VCR, that is suitable for patients requiring small or large lordosis restoration. Using this technique, the degree of correction was measured to be approximately 25 , and PSO was considered more suitable for our case than multiple SPOs for simultaneously correcting kyphosis and scoliosis. Bridwell8 described the two types of coronal imbalance. In type I, the right shoulder is high with a low right pelvis. In type II, the right shoulder is low with a low right pelvis. Bridwell8 believed that type II coronal imbalance could be corrected only by using VCR, whereas type I coronal imbalance accompanied with type II sagittal imbalance could be corrected using asymmetric PSO. In our case, the patient sustained type I sagittal imbalance with a lumbar scoliosis that was unassociated with type II coronal imbalance. Therefore, an asymmetric PSO was adopted for treating her kyphoscoliosis. Toyone et al14 reported 14 cases of degenerative lumbar kyphoscoliosis in patients whose ages were between 45 and 76 years (average age: 67 years) who had undergone asymmetric PSO with a minimum follow-up period of 2 years. The average operative time was 310 minutes (range: 25e375 minutes), and the average blood loss was 1090 mL (range: 700e2900 mL). The mean lumbar scoliosis decreased from 40 to 12 , and the mean SVA decreased from 12 cm to 3 cm. There were four complications: one dural tear, two hook dislodgments at the cephalad side requiring instrument revision, and one rod breakage requiring no instrument revision. However, the degree of correction required was not mentioned for these 14 cases, and the method for measuring the required restoration preoperatively was not specified. PSO is a technically challenging technique that is potentially catastrophic for inexperienced surgeons. “First, do no harm” is the principle followed while performing a difficult technique on patients. Before attempting an asymmetrical PSO on patients with lumbar kyphoscoliosis, surgeons should familiarize themselves with the procedure by attending associated conferences and by practicing the technique on cadavers.
Asymmetrical pedicle subtraction osteotomy
115
References 1. Cho KJ, Kim KT, Kim WJ, et al. Pedicle subtraction osteotomy in elderly patients with degenerative sagittal imbalance. Spine J. 2013;38:E1561e1566. 2. Qian BP, Jiang J, Qiu Y, Wang B, Yu Y, Zhu ZZ. Radiographical predictors for postoperative sagittal imbalance in patients with thoracolumbar kyphosis secondary to ankylosing spondylitis after lumbar pedicle subtraction osteotomy. Spine J. 2013;38: E1669e1675. 3. Park YS, Kim HS, Baek SW. Spinal osteotomy in ankylosing spondylitis: radiological, clinical, and psychological results. Spine J. 2014;14:1921e1927. 4. Potter BK, Lenke LG, Kuklo TR. Prevention and management of iatrogenic flatback deformity. J Bone Joint Surg Am. 2004;86: 1793e1808. 5. Schnake KJ, Kandziora F. Correction of posttraumatic kyphosis of the thoracolumbar spine with modified pedicle subtraction osteotomy. Eur Spine J. 2010;19:2231e2232. 6. Heary RF, Bono CM. Pedicle subtraction osteotomy in the treatment of chronic, posttraumatic kyphotic deformity. J Neurosurg Spine. 2006;5:1e8. 7. Roussouly P, Gollogly S, Berthonnaud E, Dimnet J. Classification of the normal variation in the sagittal alignment of the human
8.
9.
10.
11.
12.
13.
14.
lumbar spine and pelvis in the standing position. Spine J. 2005; 30:346e353. Bridwell KH. Decision making regarding SmithePetersen vs. pedicle subtraction osteotomy vs. vertebral column resection for spinal deformity. Spine J. 2006;31:S171e178. Le Huec JC, Leijssen P, Duarte M, Aunoble S. Thoracolumbar imbalance analysis for osteotomy planification using a new method: FBI technique. Eur Spine J. 2011;20:S669e680. Aurouer N, Obied I, Gille O, Pointillart V, Vital JM. Computerized preoperative planning for correction of sagittal deformity of the spine. Surg Radiol Anat. 2009;31:781e792. Ondra SL, Marzouk S, Koski T, Silva F, Salehi S. Mathematical calculation of the pedicle subtraction osteotomy size to allow precision correction of fixed sagittal deformity. Spine J. 2006; 31:E973eE979. Yang BP, Chen LA, Ondra SL. A novel mathematical model of the sagittal spine: application to pedicle subtraction osteotomy for correction of fixed sagittal deformity. Spine J. 2008;8:359e366. Jeszenszky D, Haschtmann D, Kleinstuck FS, et al. Posterior vertebral column resection in early onset spinal deformities. Eur Spine J. 2014;23:198e208. Toyone T, Shiboi R, Ozawa T, et al. Asymmetrical pedicle subtraction osteotomy for rigid degenerative lumbar kyphoscoliosis. Spine J. 2012;37:1847e1852.