Smith-Peterson Osteotomy and Ponte Osteotomy

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1 Smith-Peterson Osteotomy and Ponte Osteotomy 7 Kao-Wha Chang 7.1 Introduction Considerable discussion and confusion have circulated recently regarding the differences between, and the applicability of, two of simple and the most useful posterior osteotomy techniques that we currently have at our disposal. The Smith- Petersen and the Ponte osteotomy are similar but have certain differences that make them unique in both their application and their execution Smith-Petersen Osteotomy (SPO) The Smith-Petersen osteotomy (SPO) was described as a monosegmental chevron or V -shaped osteotomy for the lumbar spine in 1945 [ 1 ] (Fig. 7.1 ). This technique involved twoand three-level osteotomies through the L1, L2, and L3 articular processes. Correction of kyphotic deformity was achieved by forceful manual extension of the lumbar spine to close the posterior wedge osteotomies. This manipulation disrupted the anterior longitudinal ligament, creating an anterior monosegmental intervertebral opening wedge with elongation of the anterior column. K.-W. Chang, MD, PhD Orthopaedic Department, Taiwan Spine Center, Jen-Ai Hospital, Taichung, Taiwan, Republic of China admin_c@taiwanspinecenter.com.tw It is described as a posterior element resection with osteoclasis of the anterior and middle column for ankylosing spondylitis related kyphosis. The technique as it was originally described results in lengthening of the anterior column and shortening of the posterior column with the middle column functioning as a pivot point. Because of the sharp lordotic angle and elongation of the anterior column, this maneuver has been associated a number of severe complications including aortic rupture, cauda equina syndrome, paraplegia, and superior mesenteric artery syndrome [ 2 8 ]. Rupture of the aorta or its branches is associated with reduced elasticity of the aorta wall in older patients and with the sharp lordotic angle and elongation of the anterior column. Generally, accepted theories include stretch of calcific nondistensible and tethered vessels creating internal and media tears leading to rupture and aneurysms. Although this risk is small [ 6 8 ], many surgeons choose pedicle subtraction osteotomy (PSO) to avoid this complication. Vascular injury has been reported if the opening wedge was performed at L1-L2 or L2 L3 [ 6, 8, 9 ]. Reviewing these reports and postmortem findings reveals 2 cases of rheumatoid spondylitis treated before surgery with radiograph therapy, in which adherence between the aorta and the underlying anterior longitudinal ligament resulted in a complete transverse tear in the posterior wall of the aorta after manual osteoclasis and nonsurgical or surgical correction [ 8, 9 ]. Such preoperative therapy was not conducted Y. Wang et al. (eds.), Spinal Osteotomy, DOI / _7, Springer Science+Business Media Dordrecht

2 76 K.-W. Chang Fig. 7.1 Smith-Petersen osteotomy (Reproduced with permission from Wiggins GC et al. [ 26 ]) presently. We did not find any reference in the literature that the presently observed etiologies are linked to aortic- longitudinal ligament adherence. In the other 2 cases involving ankylosing spondylitis kyphotic patients with atheromatous calcification of their abdominal aorta [ 6 ], the vascular injuries involved SPO-related aortic wall tear and dissection of media. However, based on our observations of the absence of aortic injury in 354 patients treated with SPO including 101 patients with atheromatous calcification of abdominal aorta, apical lordosation osteotomy [ 11 ], or COWO [ 12 ] for correction of sagittal imbalance or kyphosis via an anterior open wedge and lengthening of the anterior column, the aorta can likely tolerate stretch and lengthening very well, even when complicated by atheromatous calcification [ 13 ]. Many series used SPO in which the spine is osteotomized through the posterior elements and corrected by direct pressure on the osteotomy site. The upper body and legs are extended to form a hollow cavity between the patient s ventral trunk and the surgical table, and the pressure causes the ossified anterior vertebral column to fracture. This often occurs with a sudden snap, which suddenly stretches the aorta opposite the anterior opening wedge and might injure the aorta. The osteoclasis created by this pressure might avulse a bone fragment from the vertebral body to form a spike, and the aorta may be tensed most at the spike while the anterior wedge is opened, which might lead to aortic damage. In our SPO patients, the osteoclasis usually occurred at the intervertebral disc at the level of osteotomy during performed posterior osteotomy by gravity on the patient s trunk or by light pressure on the osteotomy site after osteotomy. If the ossified anterior vertebral column was too hard to be fractured by light pressure, a fluoroscopically guided blunt ended osteotome was placed through the intervertebral disc at the level of the osteotomy. Then, osteoclasis was formed by gentle manipulation. The osteoclasis thus formed occurs at anterior disc space. Correction should not be started without assured osteoclasis and is accomplished by a slow and finely controlled closure of the osteotomy. As the posterior wedge is closed, correction occurs in the anterior vertebral column by opening of the anterior disc space with smooth edges (Fig. 7.2 ). All these managements for SPO were to minimize the risks of vascular complications and seemed effective because none of our SPO patients had a vascular injury [ 14 ]. This maneuver also results in an anterior column defect occasionally requiring reconstruction with anterior column support. In some cases, if substantial correction is achieved with an SPO, it may be necessary to graft the disc space anteriorly. In most cases, if a moderate correction is

3 7 Smith-Peterson Osteotomy and Ponte Osteotomy 77 Preop Postop a b Fig. 7.2 ( a ) Preoperative lateral radiograph shows a 31-year-old male with ankylosing spondylitis related fl exion deformity. Postoperative lateral radiograph shows correction of the deformity with SPO at L2 L3. The edge of the opening wedge is smooth. ( b ) Preoperative and postoperative clinical appearance achieved at each level and the posterior column is closed bone-on-bone centrally and laterally, the SPO is likely to heal and anterior grafting and reconstruction is not needed. The technique is executed by resecting a V -shaped portion of the posterior elements (lamina and spinous process) and fusion mass between adjacent pedicles and correction is achieved by posterior column closing wedge and anterior column opening wedge. The effectiveness of this technique is much improved when it is applied to those patients who do not have an anterior column fusion (Fig. 7.3 ) Ponte Osteotomy (PO) The Ponte osteotomy (PO), described by Alberto Ponte in 1987 [ 15, 16 ], was described as a multilevel thoracic procedure to treat flexible thoracic kyphosis (Fig. 7.4 ). It is executed by undertaking an aggressive resection of the unfused facet joints, lamina, intraspinous ligaments, and ligamentum flavum at each level. Since the osteotomy is applied to the unfused spine, it could be argued that it is not an osteotomy in the true sense of the term. However, since it does require significant and specific osseous resection to be effective, the fused versus unfused status of the spinal segment is probably irrelevant. The PO resection can be narrow, amounting to an aggressive facetectomy or as radical as a complete resection of the posterior elements from pedicle to pedicle at each level. Since the technique is performed on the unfused spine, there is a mobile disc at each level, which may at times be difficult to discern. If there is no bony bridge anteriorly, then it is feasible. If there is a fine bony bridge, it can potentially be broken with closed osteoclasis and a PO turns into a SPO. Another difference between the SPO and the PO is that it is performed at multiple levels. This spreads the

4 78 K.-W. Chang a b Preop Postop Fig. 7.3 ( a ) Lateral view of a 43-year-old female suffering a degenerative thoracolumbar kyphosis. Postoperative lateral radiograph shows correction of the deformity with SPO at L1 L2 where do not have an anterior column fusion. Posteriorly weakening the disc and anterior longitudinal ligament with a blunt-ended osteotome can facilitate osteoclasis. ( b ) Preoperative and postoperative clinical appearance angular correction and anterior column translation, if any, over multiple levels. When using this technique, it results in an overall closing wedge effect. The anterior column remains supported by its undisturbed physiologic structures (discs and ligaments), leaving a stable spine after posterior column reconstruction. Additional anterior column procedures are unnecessary. This differs from the SPO s anterior column opening wedge and posterior column closing wedge effect. The middle column functioning as a pivot point during correction of sagittal imbalance or kyphotic deformity with SPO or PO results in the least change of length and risk of injury of neural tissue comparing with PSO and vertebral column resection (VCR). Multiple osteotomies will be required to achieve significant correction since a PO may only provide a few degrees of correction per level (Fig. 7.5 ). In addition, the technique requires a mobile anterior and middle column to be useful. It may at times be difficult to discern. If there is no bony bridge anteriorly, then it is feasible. If there is a fine bony bridge, it can potentially be broken with closed osteoclasis. If there is a thick, solid bony bridge, it will not budge without release. While working best on long flexible kyphosis, even relatively stiff curves may be effectively treated with this technique. The PO may also be useful when performed above and below more aggressive osteotomies to provide a harmonious transition between areas of maximum and minimum kyphosis. PO can also be added as an afterthought to add a few more degrees of correction above or below a major deformity correction (Fig. 7.6 ).

5 7 Smith-Peterson Osteotomy and Ponte Osteotomy Indications for SPO and PO Fig. 7.4 Ponte osteotomy (Reproduced with the permission of Harry L. Shuftlebarger, MD) a PO and SPO, which are the simplest surgical technique of osteotomies, should always be considered to be applied to achieve a balanced spine. A long, rounded, smooth kyphosis, such as senile or Scheuermann s kyphosis with a mobile disc anteriorly, is often an ideal candidate for multiple POs (Fig. 7.5 ). For ankylosing spondylitis related thoracolumbar kyphosis, it can be treated with a PSO at L2 or L3. Sometimes a single PSO will not afford enough correction; therein, one might consider coupling this with 1 SPO or 2 3 POs at T10-L1. The other consideration is to perform a large SPO at L2-L3, making an effort to achieve a large amount of correction at 1 segment (Fig. 7.2 ). For ankylosing spondylitis related thoracic kyphosis, it is best treated with 1 or 2 SPOs at or around the apex and multiple POs above and below the apex (Fig. 7.7 ). Within the cord territory, the middle column functioning as a pivot point during b Preop Postop Fig. 7.5 ( a ) Lateral view of a 70-year-old female suffering senile kyphosis. Postoperative lateral radiograph of spine showing correction of deformity with multiple POs. ( b ) Preoperative and postoperative clinical appearance

6 80 K.-W. Chang a b Preop Postop Fig. 7.6 ( a ) Lateral radiograph of a 33-year-old male suffering ankylosing spondylitis related kyphosis. Postoperative lateral radiograph showing correction of the deformity with SPOs at T11 L3 and multiple POs at T5 T11. ( b ) Preoperative and postoperative clinical appearance correction of kyphotic deformity with SPO or PO and results in the least change of the length and risk of injury of neural tissue comparing with PSO and VCR. It is generally believed that an angular kyphosis, such as seen with posttraumatic kyphosis, is more amenable to a PSO or VCR. However, sometimes performing SPO and creating open wedges at and around the apex can obtained satisfactory correction with less neurological risk with the middle column functioning as the pivot point comparing with PSO or VCR (Fig. 7.8 ). Sagittal imbalance in a patient who has had a prior fusion to L4 with subsequent degeneration of L4 L5 and L5 S1 varies quite a bit from patient to patient. If osteotomy can be performed through the prior lumbar fusion segments, this is best treated with a PSO. On the other hand, if osteotomy cannot be performed through the prior lumbar fusion segments for any reason, then treat this by SPO and structural graft placement at L4 L5 and extension to the pelvis for structural support (Fig. 7.9 ). 7.3 Assessment of Patients for Correction When evaluating kyphotic deformities, it is important to understand both the radiographic investigations and the clinic examination. The clinical examination of a patient with sagittal malalignment begins with visual assessment of the coronal and the sagittal alignment of the patient s occiput over the pelvis. This is followed by an assessment of the range of motion and flexibility of the cervical, thoracic, lumbar spine and hip joint. Each region of the spine is assessed for its contribution to either the fixed or the flexible sagittal plane malalignment. Radiographic assessment of the curve is the next most important step in planning surgery. The

7 7 Smith-Peterson Osteotomy and Ponte Osteotomy 81 Preop Postop a b Fig. 7.7 ( a ) Lateral view of a 27-year-old male suffering ankylosing spondylitis related thoracic kyphosis. Postoperative lateral radiograph of spine showing radiographic investigation of patients with kyphosis begins with standing AP and lateral in. radiographs. These films should detail the position of the occiput in relation to the pelvis, hips, and proximal femurs. The radiographs should be taken with the patient in a natural position without knee flexion or hip hyperextension. This position will exacerbate the positive sagittal balance of fixed global sagittal malalignments. There are five main components to this evaluation: curve magnitude, location, type, shape, and flexibility. Curve magnitude is the most obvious parameter when assessing kyphotic deformities and sometimes the most clinically apparent. There is often a positive linear correlation with increasing stiffness as curve magnitude increases. Curve location may carry with it some implications for surgery treatment. The critical point is whether the pathology is in spinal thoracic spine/ correction of deformity with 2 SPOs at apex (T9 T12) and multiple POs above and below the apex. ( b ) Preoperative and postoperative clinical appearance spinal cord or lumbar spine/cauda equina territory. In assessing patients for possible correction, it is important to recognize the primary site of the deformity. We may occasionally compensate for deformity in one area by correction carried out in an area slightly removed from it. However, if any major correction is to be obtained, it must be performed in the area of main deformity. Typically, spinal deformity surgeons attempt to correct the most rigid and deformed portion of the curve to allow for continues flexibility and more normal motion in the unfused portions. The patient should be carefully assessed, and the main area or areas of deformity should be identified. The type of kyphosis is important in assessing surgical treatment options. There are two types, global or regional versus focal or segmental. Global or regional curves will require extensive mobilization and instrumentation to

8 82 provide balanced correction. These deformities require significant surgeries and are often associated with perioperative and postoperative morbidity. Focal or segmental kyphosis resulting from posttraumatic malalignment or congenital conditions often requires shorter, more focused surgeries. Another important feature is whether the kyphosis is more of a rounded, long sweeping kyphosis or a short, angular one. A long sweeping kyphosis, such as senile or Scheuermann s kyphosis, is more amenable to multiple SPOs or POs in part because of its multisegmental nature. A short, angular kyphosis, such as seen with posttraumatic kyphosis, is more amenable to a PSO or VCR. The last and perhaps most important radiographic assessment to be made is that of spinal flexibility through the kyphotic region. The flexibility of the deformity will define the surgical techniques that are most appropriate for correction. Flexible curves, such as those found in Scheuermann s kyphosis, can be treated without any osteotomy procedures. Rigid curves will require osteotomies to achieve correction. It is also important to assess the neurologic status in patients with kyphosis. Patients with sharp angular kyphosis or large magnitude kyphosis may have associated neurologic compression resulting in either myelopathy or radiculopathy or both. When CT scans are combined with MRIs, a detailed understanding of the neural anatomy in relation to the osseous anatomy can be achieved. This is very important when considering more aggressive surgical interventions such as osteotomies. 7.4 Principle of Spinopelvic Realignment K.-W. Chang In the domain of spinal surgery, it is useful to recall important concepts that can serve as a foundation to understanding and treating deformity. Therefore, it is important to consider that ideal spinal alignment allows an individual to assume standing posture with minimal muscular energy expenditure. Physiologic curvatures of a Fig. 7.8 It is generally believed that an angular kyphosis, such as seen with posttraumatic kyphosis is more amenable to a PSO or VCR. However, sometimes performing SPO and creating open wedges at and around the apex can obtained satisfactory correction with less neurological risk with the middle column functioning as the pivot point comparing with PSO or VCR. ( a ) Lateral view of a 50-year-old female suffering posttraumatic angular kyphosis. Postoperative lateral radiograph showing correction of the deformity with SPO at and around the apex (T10 T11 and T11 T12). ( b ) Preoperative and postoperative clinical appearance

9 7 Smith-Peterson Osteotomy and Ponte Osteotomy 83 Fig. 7.8 (continued) Preop Postop b a b c Preop Postop Preop Postop Fig. 7.9 A 67-year-old female suffering postinstrumentation kyphoscoliosis. Osteotomy cannot be performed through the prior lumbar fusion segments. ( a ) Preoperative radiograph and CT showing T4 T12 kyphosis = 45, T12 S1 lordosis = 9, PI = 36, PT = 40, and SVA = 14 cm ( b ) Postoperative radiograph and CT showing correction of deformity with SPO at L4 L5 and POs at T9 T11, T4 T12 kyphosis = 13, T12 S1 lordosis = 35, PI = 36, PT = 20, and SVA = 1.7 cm. ( c ) Preoperative and postoperative clinical appearance

10 84 the spine in the sagittal plane, the straight spine in the coronal plane, balanced tension of the spinal ligaments, and activation of intrinsic anterior and posterior musculature should permit extended pain-free erect position. Spinal malalignment in spinal deformity challenges balance mechanisms used for maintenance of an upright posture to achieve the basic human needs of preserving level visual gaze and retaining the head over the pelvis. Progressive severity in skeletal malalignment might result in greater recruitment in muscular effort and greater energy expenditure to maintain the erect posture as well as use of compensatory mechanisms. Spinal malalignment to the extremes of the Cone of Economy leads to extreme muscular demand, fatigue, and significant pain as well as disability. Once a spinal deformity has reached the level of marked loss in function and quality of life, surgical intervention is often recommended and requested. Spinal deformities can range from a simple biplanar and segmental deformity to more complex three-dimensional global deformities with significant loss of coronal and sagittal alignment. When evaluating reconstructing sagittal balance for sagittal imbalance, the C7 plumb line (i.e., sagittal vertical axis, SVA) should fall through the posterior superior corner of S1 or between the posterior-superior corner of S1 and the hip joints. This assumes the patient is standing in a natural position without knee flexion or hip hyperextension. Correction of deformity should attempt to obtain a postoperative SVA < 50 mm. Restoration of SVA < 50 mm brings the SVA behind the femoral head to achieve a physiologic standing posture and relieve the complaint of falling forward and facilitates level gaze Clinically, this threshold has been met with better quality of life [ 17 ]. This narrow range of acceptability for the alignment of the SVA still allows for an infinite combination of cervical and lumbar lordosis and thoracic kyphosis to achieve balance. The normal range for thoracic kyphosis is and the normal range for lumbar lordosis is Since the work by Vidal and Marnay [ 18, 19 ], several authors have enhanced the understanding of global alignment by including the pelvis, which has been described as a regulator of sagittal K.-W. Chang plane alignment. Numerous studies have been conducted to understand the relationship between pelvic parameters and spinal alignment. This has led to the recognition that pelvic incidence (PI, concerning with pelvic morphology) and pelvic tilt (PT, concerning with pelvic position) are essential components of standing alignment [ ]. PI is a morphological constant and decides the lumbar lordosis. Pelvic tilt (PT) is the positional parameter of pelvis as a compensatory mechanism to maintain spinopelvic alignment. 7.5 Pragmatic Approach to Spinopelvic Realignment In clinical practice, radiographic reference values help identify regional angulations and linear displacements that can be considered as within the normal alignment range for a given patient. However, because of the large range considered normal, regional values alone are insufficient in assessing patient-specific harmonious alignment and the optimal values to strive for in realigning a deformity. It is thus important to consider the idea of spinopelvic harmony, which relates to the proportionality of one given regional parameter to another and in practical terms the global spinopelvic alignment of the individual. When pathology, such as kyphotic deformity, perturbs regional alignment, it leads to a chain of modifications along the standing axis. In severe cases, the consequence is a large sagittal vertical axis and pelvic tilt, lost lumbar lordosis resulting in spinopelvic mismatch and sagittal imbalance. Based on the idea of spinopelvic harmony and believing that by a chain of interconnected parameters [ 20, 24, 25 ], spinopelvic harmony can be reconstructed according to and in proportion to pelvic morphology. We developed a method to determine the lumbosacral curve which theoretically would bring sagittal balance to an ideal state by calculation and simulation for each patient preoperatively and made template rods of the curve and a blueprint accordingly for operative procedures to follow [ 26 ]. It is a pragmatic approach for optional spinopelvic realignment to a given individual on the basis of their respective

11 7 Smith-Peterson Osteotomy and Ponte Osteotomy 85 a b c Preop Postop Preop Postop Fig A 65-year-old female with degenerative kyphoscoliosis. ( a ) Preoperative radiograph and MRI showing, T4 T12 lordosis = 35, T12 S1 kyphosis = 59, SVA = 21 cm, PI = 34, and PT = 42. ( b ) Postoperative radiograph and CT showing corrective of the deformity with SPOs from L2 to S1, T4 T12 kyphosis = 30, T12 S1 lordosis = 54, SVA = 1.5 cm, PI = 33, and PT = 11. ( c ) Preoperative and postoperative clinical appearance pelvic morphology. As a pragmatic tool for clinical application, spinopelvic realignment objectives involve utilizing the key pelvic parameters that are constant for each given patient. (The codes of each patient for optimizing reconstructed sagittal balance.) We found quality control of the reconstructed sagittal balance for sagittal imbalance is possible. Correctly orienting the pelvis, reconstructed by the restoration of enough L1 S1 lordosis with adequate distribution at L4 S1 segments, is a matter of critical importance for optimizing reconstructed sagittal balance. The correctly oriented pelvis can be determined before surgery. However, for optimal clinical outcomes, treatment should be adapted to a given individual on the basis of their respective realignment needs. In a simplified manner, for a given subject, a ground rule of harmonious alignment consist of a lumbar lordosis proportional to PI and the thoracic kyphosis proportional to the lumbar lordosis, PT < 20 and SVA < 5 cm [ 18 ]. The method of realignment, whether PO, SPO, PSO, VCR, or intervertebral spacer, is of secondary importance to the primary goal of obtaining surgical realignment objectives Clinical Application of SPO and PO for Pragmatic Approach to Spinopelvic Realignment The following subsection is organized around case presentations and aims to provide an overview on how the principles outlined previously can be applied in clinical practice when planning operative spinopelvic realignment procedures utilizing SPOs and POs Instrumentation to the Low Lumbar Spine with Junctional Failure (Fig. 7.9 ) Radiographs in Fig. 7.9 reveal a common postinstrumentation flat-back deformity and junctional failure resulting in both sagittal and coronal imbalance. The patient is shifted forward and to the right with significant pelvic retroversion, high SVA, PT, and mismatch between PI and lumbar lordosis. Surgical realignment includes an SPO and asymmetrical PLIF (for coronal imbalance) at L4-5, extension to the pelvis for structural support, and POs at T9 T11 to rebalance the spine in sagittal and coronal plane. Alignment objectives were obtained with this patient with a satisfactory overall global alignment Degenerative Kyphoscoliosis with Degenerative Disc Disease (Fig ) Radiographs in Fig. 7.8 demonstrate a kyphotic lumbar spine, high SVA, PT (severe pelvic retroversion), and coronal imbalance. The goals in realignment need to focus on regional establishment of proper lumbar lordosis, which in turn can reset the pelvis to normal revision and rebalance the spine in sagittal plane and equalization of the length of convex and concave side of lumbar spine, which is turn can rebalance the spine in

12 86 coronal plane. Surgical realignment includes SPOs and asymmetrical PLIF with different size of intervertebral spacer at L2-S1. Postoperative SVA and PT were substantially reduced along with an increase in lumbar lordosis. Conclusion There are many options including PO, SPO, PSO, and VCR available for the surgical treatment of kyphotic deformities. They run the gamut from simple to complex. All procedures are technically demanding and have inherent risks. The more substantial the resection, the greater the risk of blood loss, neurologic deficit, and complications. While the less technically demanding osteotomy/resection techniques seem simple, significant realignment of the vertebral column may pose neurologic risks irregardless of the complexity of the surgical technique. The more aggressive resection techniques are accompanied by high blood loss and the potential for catastrophic neurologic complications. For this reason, it is mandatory that the surgical technique chosen should match the requirements of the pathology and patients metabolic capacities. When two different techniques may provide similar results, the less involved technique should always be used. In this way, PO and SPO, which are the simplest surgical technique of osteotomies, should always be considered to be applied to achieve a balanced spine. However, it is important to acknowledge that performing inadequate surgery may ultimately cause more harm to the patient than doing nothing. In its simplest form, the two primary tenets of spinal deformity surgery are (1) appropriate release or resection of the deformity to provide adequate mobilization and (2) providing sufficient fixation to stabilize the spine and protect the spinal cord intraoperatively and ultimately to fix the vertebral column in the reduced position while fusion is occurring. Appropriate exposure to and experience with these techniques will allow the surgeon to treat a variety of simple and K.-W. Chang complex deformities. However, even in the hands of experienced surgeons, these techniques may result in significant complications. Both the surgeon and the patient are well advised to consider their options carefully before surgery. It is evident that the goals of ideal spinopelvic alignment cannot be obtained in all cases. Limitations on the basis of patient factors (e.g., Comorbidities), surgeon factors (experience), operative parameters (e.g., hemodynamic instability and loss of monitoring potentials), and constraints of the healthcare environment (ability to properly care for patients after complex reconstruction) all need heavy consideration in ambitious operative planning. Key Points SPO and PO are the simplest and most useful posterior-column-only wedge osteotomy techniques. The similarity between SPO and PO is both result in closing wedge of posterior column. The difference between SPO and PO is SPO s anterior column opening wedge vs PO s anterior column intact during closing wedge of posterior column by both techniques. The middle column functioning as a pivot point during correction of sagittal imbalance or kyphotic deformity with SPO or PO results in the least change of the length and risk of injury of neural tissue comparing with PSO and VCR. Vascular injury due to open wedge of anterior column by SPO is very rare. Pragmatic approach to spinopelvic realignment is considering the idea of spinopelvic harmony instead of normal regional values and to reconstruct lumbar lordosis proportional to PI, PT <20 and SVA <5 cm, a standing posture with minimal muscular energy expenditure. PO and SPO which are the simplest surgical technique of osteotomy should always be considered to be applied to achieve a balance spine.

13 7 Smith-Peterson Osteotomy and Ponte Osteotomy References 1. Smith-Petersen MN, Larson CB, Aufranc OE. Osteotomy of the spine for correction of fixation deformity in rheumatoid arthritis. J Bone Joint Surg. 1945;27: Adams JC. Technique, dangers and safeguards in osteotomy of the spine. J Bone Joint Surg Br. 1952;34: Simmons EH. Kyphotic deformity of the spine in ankylosing spondylitis. Clin Orthop. 1977;128: Law WA. Osteotomy of the spine. Clin Orthop. 1969;66: Styblo K, Bossers GT, Slot GH. Osteotomy for kyphosis in ankylosing spondylitis. Acta Orthop Scand. 1985;56: Klems VH, Friedebold G. Ruptur der Aorta abdominalis nach Aufrichtungsoperation bei Spondylitis ankylopoetica. Z Orthop. 1971;108: Weatherley C, Jaffary D, Terry A. Vascular complications associated with osteotomy in ankylosing spondylitis: a report of two cases. Spine. 1988;13: Lichtblau PO, Wilson PD. Possible mechanism of aorta rupture in orthopaedic correction of rheumatoid spondylitis. J Bone Joint Surg Am. 1956;38: Booth KC, Bridwell KH, Lenke LG, et al. Complications and predictive factors for the successful treatment of flatback deformity (fixed sagittal imbalance). Spine. 1999;24: Chang KW, Chen YY, Lin CC, et al. Apical lordosating osteotomy and minimal segment fixation for the treatment of thoracic or thoracolumbar osteoporotic kyphosis. Spine. 2005;30: Chang KW, Cheng CW, Chen HC, et al. Closingopening wedge osteotomy for the treatment of sagittal imbalance. Spine. 2008;33: Chen TC, Tu MY, Wu CM, et al. Risk of aorta injury in patients treated by accomplishing an anterior open wedge and lengthening of anterior column. J Orthop Surg Taiwan. 2008;25: Chang KW, Chen YY, Lin CC, et al. Closing wedge osteotomy versus opening wedge osteotomy in ankylosing spondylitis with thoracolumbar kyphotic deformity. Spine. 2005;30: Ponte A, Sicciard GL. Surgical treatment of Scheuermann s hyperkyphosis. Orthop Trans. 1985;9: Ponte A. Posterior column shortening for Scheuermann s kyphosis. An innovative one-stage technique. In: Haher TR, Merola AA, editors. Surgical techniques for the spine. New York: Thieme; p Schwab F, Patel A, Ungar B, et al. Adult spinal deformity postoperative standing imbalance: how much can you tolerate? An overview of key parameters in assessing alignment and planning corrective surgery. Spine. 2010;35: Vidal J, Marnay T. Morphology and anteroposterior body equilibrium in spondylolisthesis L5 S1 [in French]. Rev Chir Orthop Reparatrice Appar Mot. 1983;69: Vidal J, Marnay T. Sagittal deviations of the spine, and trial of classification as a function of the pelvic balance [in French]. Rev Chir Orthop Reparatrice Appar Mot. 1984;70 Suppl 2: Schwab F, Lafage V, Boyce R, et al. Gravity line analysis in adult volunteers: age-related correlation with spinal parameters, pelvic parameters, and foot position. Spine. 2006;31:E Duval-Beaupere G, Marty C, Barthel F, et al. Sagittal profile of the spine prominent part of the pelvis. Stud Health Technol Inform. 2002;88: Legaye J, Duval-Beaupere G, Hecquet J, et al. Pelvic incidence: a fundamental pelvic parameter for threedimensional regulation of spinal sagittal curves. Eur Spine J. 1998;7: Roussouly P, Gollogly S, Berthonnaud E, et al. Classification of the normal variation in the sagittal alignment of the human lumbar spine and pelvis in the standing position. Spine. 2005;30: Vialle R, Levassor N, Rillardon L, et al. Radiographic analysis of the sagittal alignment and balance of the spine in asymptomatic subjects. J Bone Joint Surg Am. 2005;87: Berthonnaud E, Dimnet J, Roussouly P, et al. Analysis of the sagittal balance of the spine and pelvis using shape and orientation parameters. J Spinal Disord Tech. 2005;18: Chang KW, Leng X, Zhao W, et al. Quality control of reconstructed sagittal balance for sagittal imbalance. Spine. 2011;36:E Wiggins GC, Ondra SL, Shaffrey CI. Management of iatrogenic flat-back syndrome. Neurosurg Focus. 2003;15(3):E8.

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