- Email: [email protected]
Approach options in adult spinal deformity surgery
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Available online at www.sciencedirect.com
www.elsevier.com/locate/semss
Approach options in adult spinal deformity surgery Amandeep Bhalla, MDa,n, Reginald Fayssoux, MDb, and Kris E. Radcliff, MDc a
Department of Orthopaedic Surgery, Harbor-UCLA Medical Center, 1000 W, Carson, Torrance, CA 90509 Desert Orthopaedic Center, Rancho Mirage, CA c Thomas Jefferson University, Egg harbor, NJ b
abstra ct Key objectives in adult spinal deformity surgery include sagittal and coronal alignment correction, bony fusion, alleviation of pain, and improved patient function. There are a variety of options for surgical approach and timing. Spinal deformity surgery can be approached anteriorly, posteriorly, and in a combined manner, with or without staging. Considerations in selecting an optimal surgical approach include the patient's sagittal alignment, bone quality, nutritional status, need for fusion across the lumbosacral junction, anterior column mobility, and the surgical team's technical expertise. & 2015 Elsevier Inc. All rights reserved.
1.
Paper
The goals of surgical treatment of adult spinal deformity include restoration of global sagittal and coronal balance, achieving fusion, alleviating pain, and improving function. There are a variety of different ways to achieve these objectives. From a surgical approach standpoint, spinal reconstruction can be performed via anterior, posterior, and combined approaches, with or without staging of the procedures. The optimal method must take into consideration the patient's sagittal alignment, bone quality, nutritional status, need for fusion across the lumbosacral junction, anterior column mobility, and the surgeon's and ancillary surgeon's technical expertise. The posterior approach is the workhorse approach for the treatment of spinal deformity. In its original form as a treatment for adolescent scoliosis surgery, it involved an uninstrumented fusion with a postoperative stabilizing turnbuckle cast, which was sufficient for stabilizing a progressive curve but of course did not allow for correction of the deformity. The advent of nonsegmental Harrington rod distraction techniques revolutionized spinal surgery and allowed for improved correction of these flexible adolescent curves at the expense of sagittal alignment, especially when n
Corresponding author. E-mail address: [email protected] (A. Bhalla).
http://dx.doi.org/10.1053/j.semss.2015.03.016 1040-7383/& 2015 Elsevier Inc. All rights reserved.
used in the lumbar spine. The evolution to segmental Cotrel– Dubousset instrumentation allowed these corrective instrumentation techniques to be applied to stiffer adult scoliotic curves but was still limited in terms of the correction of the sagittal plane. This limitation was mitigated by the development of the anterior approach, which allowed for anterior release of stiff spinal deformities and, when combined with segmental posterior fixation, ushered in the modern era of surgical treatment of adult spinal deformity. The introduction of transpedicular fixation, posterior osteotomy techniques, and posterior interbody fusion allowed for the development of the current iteration of posterior-only treatment of spinal deformity. Posterior-only approaches for the correction of spinal deformity have become increasingly more common. Threecolumn segmental transpedicular instrumentation, and the development of posterior osteotomy techniques enable greater curve correction without the need for anterior apical releases.1 Posterior-based osteotomies, including posterior column osteotomies (e.g., Ponte osteotomies), pedicle subtraction osteotomies, and vertebral column resections, allow for significant coronal and sagittal deformity correction from the posterior approach, though these can be technically challenging procedures to perform. Posterior column
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osteotomies typically allow 101 of sagittal correction per level, or about 11 of correction for every millimeter of bone resected.2 The pedicle subtraction osteotomy, which is a Vshaped wedge resection of the vertebral body including both pedicles and posterior elements, can achieve a correction of between 301 and 401 at a single level.3 Vertebral column resection can deliver much greater coronal and sagittal plane correction. The degree of correction afforded by posteriorbased osteotomies varies by region of the spine. Kim et al.4 analyzed the radiographic and functional outcomes after posterior segmental spinal instrumentation and fusion with and without anterior apical release of the lumbar curve in adult scoliosis patients. Of note, the surgeons involved have one of the largest experiences with treatment of adult spinal deformity and posterior-only procedures using these technically challenging posterior osteotomy techniques and thus their results may not be applicable to all. Regardless, the study showed superior clinical outcome scores (SRS) and subscales in self-image and function in the group with posterior-only surgery as compared to the group with the combined approach, without a difference in radiographic parameters. Perioperative morbidity and complications were higher in the group of patients treated with combined anterior and posterior surgery. Notably, the authors acknowledge that BMP was used in a greater number of patients treated with the posterior-only surgery, than in those treated with a combined approach, which confounds the study results. One challenge in treating patients with a posterior-only approach is the risk for pseudarthrosis. Kim et al.5 reported a 17% incidence (nearly 1 in 5) of pseudarthrosis after long primary arthrodesis with the use of modern segmental spinal instrumentation for the treatment of adult idiopathic scoliosis. Some authors contend that risk for pseudathrosis in the posterior-only approach can be mitigated with rhBMP-2. Luhmann et al.6 have reported a high rate of fusion for both anterior-only (96%) and posterior-only (93%) surgery with the use of rhBHP-2 for adult spinal deformity. Subsequent longterm follow-up study on the same patients showed significant fusion rate for anterior (91%), posterior (97%), and highdose posterior (100%) spinal fusion.7 These high-dose fusion groups used up to 40 mg of BMP per level, which may be cost prohibitive for some institutions. It is worth noting that in a recent prospective multicenter study,8 patients who received BMP to aid in spinal fusion had a greater total complication rate and a greater minor complication rate than patients who did not receive BMP, but they had similar wound, neurological, superficial, and deep infection rates. Research is needed to assess the long-term fusion rates and safety profile of higher doses of rh-BMP2. The development of posterior-based interbody-fusion techniques offers the advantage of circumferential fusion from a single incision and is helpful to augment fusion, especially helpful at the lumbosacral junction where the risk of pseudarthrosis is reportedly as high as 60%.9 Another option for increasing fusion rates across the lumbosacral junction in posteriorly approached patients is the transsacral interbody approach (i.e., AxiaLif), which provides anterior column support for long posterior fusions to the sacrum, though longterm results for this technique are not available.9
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Anterior surgery to treat adult thoracolumbar scoliosis was originally described by Dwyer et al. in 1969.10 These anterioronly reconstructions were typically utilized for thoracolumbar curvature, and they were able to achieve effective correction, especially in the sagittal plane because of the release of the anterior longitudinal ligament. Distal lumbar motion segments were often able to spared, a distinct advantage in comparison to the posterior approach options. In addition, anterior-only correction maintains the integrity of the posterior ligamentous complex. The major disadvantage of anterior approaches to the spine is the morbidity of the dissection, with risks to the lung, diaphragm, sympathetic chain, and major vascular structures in the thoracic and thoracolumbar spine, as well as the genitofemoral nerve, kidney and ureter, and the peritoneal contents in the lumbar spine. The main anterior approach options to the thoracic and lumbar spine include the transthoracic approach, thoracoabdominal approach, anterior retroperitoneal and transperitoneal approaches, and lateral retroperitoneal approach. Risks associated with the transthoracic approach include damage to the intercostal vessels during rib resection or exposure of the vertebrae as well as injury to the lungs. The thoracoabdominal approach enables access to the anterior spine at the thoracolumbar junction, but it carries the risks of entry into the thorax and the retroperitoneum as well as of pseudohernias from abdominal wall paralysis. Dangers of the retroperitoneal approach to the lumbar spine include injury to the sympathetic chain, the genitofemoral nerve, the segmental lumbar vessels, as well the aorta or the vena cava. The paramedian retroperitoneal approach is often utilized as it is substantially less morbid than the transperitoneal and thoracoabdominal approaches. Horton et al.11 have described less pain and functional disturbance in patients who have a paramedian retroperitoneal approach as compared to a thoracoabdominal approach. A significantly higher rate of retrograde ejaculation with the transperitoneal approach was noted as compared to the retroperitoneal approach.12 Anterior-only surgery (via the thoracoabdominal approach) is still utilized for relatively flexible thoracolumbar structural curves. Outside of this indication anterior-only surgery is uncommonly used. For elderly patients, without significant sagittal imbalance, consideration could be given to minimally invasive lateral transpsoas approach for stand-alone (i.e., uninstrumented) anterior interbody fusion. Relative stability is achieved with cages that span the apophyseal ring. Excellent coronal correction is typically achievable. The sagittal correction is less robust since the anterior longitudinal ligament remains intact. This approach to treatment has been shown to yield acceptable radiographic and clinical outcomes in short- and mid-term follow-up, with acceptable morbidity, though long-term results are lacking.13 Because of these limitations with anterior-only reconstruction, surgeons began to combine the anterior and posterior approaches in an effort to more effectively address complex spinal deformity. Through the anterior approach, surgeons are able to “release” stiff spinal deformities resulting from degenerative disk collapse via discectomy and release of the anterior longitudinal ligament, allowing for significant correction of
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segmental sagittal malalignment. This is particularly useful in reestablishing lordosis of the lumbar spine. Correction achieved through anterior column reconstruction, obviates the need for more aggressive posterior-based osteotomies. Anterior approaches also allow for placement of bone graft within the anterior column, an excellent fusion environment due to the compressive loads experienced here and the large bony surface area available for fusion. Especially at the lumbosacral junction, interbody fusion is important to mitigate the risk of pseudarthrosis.14 Interbody support with structural grafts in the anterior column decreases stress on sacral screws. Interbody support also allows indirect decompression of up–down foraminal stenosis. However, placing structural grafts does lengthen the spine, which tends to have more risk to the neurologic elements via a stretch mechanism of injury when compared with posterior shortening (i.e., osteotomy) techniques. Furthermore, the morbidity of the approach needs to be weighed against its potential benefits. However, this calculus may be changing as lateral interbody fusion techniques offer minimally invasive options for anterior surgery, which may be coupled with an open, limited anterior approach for interbody fusion at the lumbosacral
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junction in an effort to reduce approach related morbidity. A more recent innovation involves release of the ALL via the minimally invasive lateral approach, allowing for significant segmental correction (in some cases approaching 301) in an effort to avoid having to perform the more morbid pedicle subtraction osteotomy (Fig. 1). It is worth noting that the role of minimally invasive anterior spine surgery for adult spinal deformity through the direct lateral approach, as a component of the combined surgery, is still being defined. There has been evidence to support the use of MIS techniques in adult spinal deformity surgery, particularly in symptomatic elderly patients without significant sagittal imbalance.15 Open surgery to date remains the gold standard for correction of spinal deformity. Berven et al.,16 in studying the outcomes of combined anterior and posterior surgery for the management of fixed sagittal plane deformity, noted that patient satisfaction with surgery, and overall clinical outcomes were best in cases that resulted in an increase in lumbar lordosis. Patients with preoperative regional hypolordosis (4 301) had the most reliable improvement of health status, and they had better clinical outcomes than those with lumbar lordosis in the physiologic range. The authors noted that 40% of patients in
Fig. 1 – Image on the left shows standing lateral radiograph of a 71-year-old woman who had undergone L2-5 interbody fusion with dynamic stabilization, with proximal junctional kyphosis at L1-2 level, contributing to positive sagittal balance. The image on the right shows postoperative standing lateral showing restoration of sagittal balance after less invasive lateral interbody fusion with transpsoas anterior longitudinal ligament release, and fusion extension to T10. (Adapted with permission from Deukmedjian et al. Anterior longitudinal release using the minimally invasive lateral retroperitoneal transpsoas approach: a cadaveric feasibility study and a report of 4 clinical cases. J Neurosurg Spine. 2012;17:530–539).
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the study had major complications, including pneumonia, dural tears, wound infection, and pseudarthrosis. Relative indications for combined anterior and posterior fusion include planned arthrodesis across the lumbosacral junction, lumbar pseudarthrosis, correction of a fixed lumbosacral obliquity, lumbar hypolordosis, posterior-element deficiency, and osteoporosis (Fig. 2).
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Pateder et al.17 compared the radiographic lumbar curve correction between posterior-only and combined anterior– posterior approach in patients with adult spinal deformity. The two groups were not significantly different in correcting adult lumbar scoliosis curves measuring between 401 and 701. While the posterior-only group and same-day anteriorand posterior-surgery group had similar major complication
Fig. 2 – (A) Anteroposterior, bending, and lateral radiographs of two patients with similar curve patterns and flexibility before surgical treatment. (B) Anteroposterior and lateral radiographs of the patients at follow-up, after one was treated with anterior and posterior combined approach, and the other was treated with a posterior-only surgery. (Adapted with permission from Good et al. Can posteiror-only surgery provide similar radiographic and clinical results as combined anterior (thoracotomy/ thoracoabdominal)/posterior approaches for adult scoliosis? Spine. 2010;35(2):210–218).
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Fig. 2 – Continued. rates of 24% and 23%, respectively, patients who underwent staged anterior and posterior surgery had a major complication rate of 45%.17 This study was limited by the small cohort, the statistically significant difference in the preoperative scoliosis measurements between the two groups, and the surgeons' selection bias in choosing the surgical approach.
When a decision for a combined approach for treatment of spinal deformity has been made, the options of doing the anterior and posterior surgery on the same day versus on two separate days must be considered. Staged procedures are well tolerated by many patients, but they may be associated with a higher risk of infection and
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blood transfusion.14 For fused, rigid deformities, patients may be served better with a three-stage surgery with two periods of anesthesia. During the first anesthetic, posterior osteotomies are performed along with the preparation of pedicle screw sites, but without placement of implants. At the next stage anterior release and osteotomies are done, followed by deformity correction and posterior instrumentation. There is evidence that staged procedures result in significantly longer hospital stays, and are at higher risk of infection and wound complications if done too close together. This may be attributed to inadequate time to recover from postoperative malnutrition, which develops to an appreciable extent in adults undergoing spinal deformity surgery.18 The order in which the staged procedures are done must also be considered. In a patient with a mobile anterior column, a posterior–anterior order can be utilized if acceptable sagittal correction can be achieved first via posterior column osteotomies and segmental transpedicular fixation. A staged anterior procedure 4–6 weeks after the initial posterior surgery can then be performed to provide anterior column support and aid in achieving a circumferential fusion. This allows ample time to recover from the first surgery before undergoing the second. Naturally a posterior–anterior staged procedure would not be feasible in correcting sagittal malalignment in patients who have a fused anterior column, or a stiff anterior column secondary to degenerative disease that requires an anterior release. In these situations, an anterior release would precede the posterior reconstruction, or a posterior-only approach with osteotomies would need to be considered. Achieving the goals of coronal and sagittal alignment correction, bony fusion, alleviation of pain, and improved patient function is paramount to success. Although spinal deformity surgical patients have a complex reconstructive problem, these objectives may be achieved in part by careful consideration of the factors that weigh in the selection of the surgical approach.
r e f e r e n c e s
1. Dorward IG, Lenke LG. Osteotomies in the posterior-only treatment of complex adult spinal deformity: a comparative review. Neurosurg Focus. 2010;28(3):E4. 2. Dorward I, Lenke L, Stoker G, Woojin C, Koester L, Sides B. Radiographic and clinical outcomes of posterior column osteotomies in spinal deformity correction. Spine. 2014;39 (11):870–880. 3. Cho K, Bridwell K, Lenke L, Berra A, Baldus C. Comparison of Smith–Petersen versus pedicle substraction osteotomy for the correctino of fixed sagittal imbalance. Spine. 2005;30 (18):2030–2037.
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4. Kim Y, Lenke L, Kim Y, Kim Y, Bridwell K, Stobbs G. Surgical treatment of adult scoliosis: is anterior apical release and fusion necessary for the lumbar curve? Spine. 2008;33(10):1125–1132. 5. Kim YJ, Bridwell KH, Lenke LG, et al. Pseudarthrosis in primary fusions for adult idiopathic scoliosis: incidence, risk factors, and outcome– analysis. Spine. 2005;30(4):468–474. 6. Luhmann SJ, Bridwell KH, Cheng I, et al. Use of bone morphogenetic protein-2 for adult spinal deformity. Spine. 2005;30:S110–S117. 7. Mulconrey DS, Bridwell KH, Flynn J, et al. Bone morphogenetic protein (RHBMP-2) as a substitute for iliac crest bone graft in multi-level adult spinal deformity surgery: minimum twoyear evaluation of fusion. Spine. 2008;33:2153–2159. 8. Shay Bess, Breton G Line, Virginie Lafage. Does recombinant human bone morphogenetic protein-2 use in adult spinal deformity increase complications and are complications associated with the location of rhBMP-2 Use? A prospective multicenter study of 279 patients. Spine. 2004;39(3):233–242. 9. Anand N, Kahwaty S, Daroudi S, Baron E, Boachie-Adjei O. Multicenter minimally invasive Axialif L5-S1 interbody fusion for anterior column support at the end of a long segment construct: feasibility, safety, complications, early and late 3 year outcomes. Spine. 2011 [poster presented at a Spine affiliated meeting in 2011]. 10. Dwyer AF, Newton NC, Sherwood AA. An anterior approach to scoliosis. A preliminary report. Clin Orthop Relat Res. 1969;62:192–202. 11. Horton WC, Bridwell KH, Glassman SD, et al. The Morbidity of Anterior Exposure for Spinal Deformity in Adults: An Analysis of Patient-based Outcomes and Complications in 112 Consecutive Cases. Paper 32, Presented at Scoliosis Research Society 40th Annual Meeting, Miami, FL; October 2005. 12. Sasso RC, Kenneth J, LeHuec JC. Retrigrade ejaculation after anterior lumbar interbody fusion: transperitoneal versus retroperitoneal exposure. Spine. 2003;28:1023–1026. 13. Anand N, Baron EM, Thaiyananthan G, Khalsa K, Goldstein TB. Minimally invasive multilevel percutaneous correction and fusion for adult lumbar degenerative scoliosis: a technique and feasibility study. J Spinal Disord Tech. 2008;21:459–467. 14. Rothman-Simeone. 5th ed, vol II. The Spine. Saunders Elsevier, Philadelphia, 2006. 15. Haque RM, Mundis GM, Ahmed Y, International Spine Study Group. Comparison of radiographic results after minimally invasive, hybrid, and open surgery for adult spinal deformity: a multicenter study of 184 patients. Neurosurg Focus. 2014;36 (5):E13. 16. Berven S, Diveren V, Smith J, Hu S, Bradford D. Management of fixed sagittal plane deformity: outcome of combined anterior and posterior surgery. Spine. 2003;28(15):1710–1776. 17. Pateder Dhruv B, Kebaish Khaled M, Cascio Brett M, Neubaeur Phillip, Matusz David M, Kostuik John P. Posterior only versus combined anterior and posterior approaches to lumbar scoliosis in adults: a radiographic analysis. Spine. 2007;32(14):1551–1554. 18. Dick J, Boachie-Adiei O, Wilson M. One-stage versus twostage anterior and posterior spinal reconstruction in adults: comparison of outcomes including nutritional status, complication rates, hospital costs, and other factors. Spine. 1992; 17(suppl 85):310–316.
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Available online at www.sciencedirect.com
www.elsevier.com/locate/semss
Approach options in adult spinal deformity surgery Amandeep Bhalla, MDa,n, Reginald Fayssoux, MDb, and Kris E. Radcliff, MDc a
Department of Orthopaedic Surgery, Harbor-UCLA Medical Center, 1000 W, Carson, Torrance, CA 90509 Desert Orthopaedic Center, Rancho Mirage, CA c Thomas Jefferson University, Egg harbor, NJ b
abstra ct Key objectives in adult spinal deformity surgery include sagittal and coronal alignment correction, bony fusion, alleviation of pain, and improved patient function. There are a variety of options for surgical approach and timing. Spinal deformity surgery can be approached anteriorly, posteriorly, and in a combined manner, with or without staging. Considerations in selecting an optimal surgical approach include the patient's sagittal alignment, bone quality, nutritional status, need for fusion across the lumbosacral junction, anterior column mobility, and the surgical team's technical expertise. & 2015 Elsevier Inc. All rights reserved.
1.
Paper
The goals of surgical treatment of adult spinal deformity include restoration of global sagittal and coronal balance, achieving fusion, alleviating pain, and improving function. There are a variety of different ways to achieve these objectives. From a surgical approach standpoint, spinal reconstruction can be performed via anterior, posterior, and combined approaches, with or without staging of the procedures. The optimal method must take into consideration the patient's sagittal alignment, bone quality, nutritional status, need for fusion across the lumbosacral junction, anterior column mobility, and the surgeon's and ancillary surgeon's technical expertise. The posterior approach is the workhorse approach for the treatment of spinal deformity. In its original form as a treatment for adolescent scoliosis surgery, it involved an uninstrumented fusion with a postoperative stabilizing turnbuckle cast, which was sufficient for stabilizing a progressive curve but of course did not allow for correction of the deformity. The advent of nonsegmental Harrington rod distraction techniques revolutionized spinal surgery and allowed for improved correction of these flexible adolescent curves at the expense of sagittal alignment, especially when n
Corresponding author. E-mail address: [email protected] (A. Bhalla).
http://dx.doi.org/10.1053/j.semss.2015.03.016 1040-7383/& 2015 Elsevier Inc. All rights reserved.
used in the lumbar spine. The evolution to segmental Cotrel– Dubousset instrumentation allowed these corrective instrumentation techniques to be applied to stiffer adult scoliotic curves but was still limited in terms of the correction of the sagittal plane. This limitation was mitigated by the development of the anterior approach, which allowed for anterior release of stiff spinal deformities and, when combined with segmental posterior fixation, ushered in the modern era of surgical treatment of adult spinal deformity. The introduction of transpedicular fixation, posterior osteotomy techniques, and posterior interbody fusion allowed for the development of the current iteration of posterior-only treatment of spinal deformity. Posterior-only approaches for the correction of spinal deformity have become increasingly more common. Threecolumn segmental transpedicular instrumentation, and the development of posterior osteotomy techniques enable greater curve correction without the need for anterior apical releases.1 Posterior-based osteotomies, including posterior column osteotomies (e.g., Ponte osteotomies), pedicle subtraction osteotomies, and vertebral column resections, allow for significant coronal and sagittal deformity correction from the posterior approach, though these can be technically challenging procedures to perform. Posterior column
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osteotomies typically allow 101 of sagittal correction per level, or about 11 of correction for every millimeter of bone resected.2 The pedicle subtraction osteotomy, which is a Vshaped wedge resection of the vertebral body including both pedicles and posterior elements, can achieve a correction of between 301 and 401 at a single level.3 Vertebral column resection can deliver much greater coronal and sagittal plane correction. The degree of correction afforded by posteriorbased osteotomies varies by region of the spine. Kim et al.4 analyzed the radiographic and functional outcomes after posterior segmental spinal instrumentation and fusion with and without anterior apical release of the lumbar curve in adult scoliosis patients. Of note, the surgeons involved have one of the largest experiences with treatment of adult spinal deformity and posterior-only procedures using these technically challenging posterior osteotomy techniques and thus their results may not be applicable to all. Regardless, the study showed superior clinical outcome scores (SRS) and subscales in self-image and function in the group with posterior-only surgery as compared to the group with the combined approach, without a difference in radiographic parameters. Perioperative morbidity and complications were higher in the group of patients treated with combined anterior and posterior surgery. Notably, the authors acknowledge that BMP was used in a greater number of patients treated with the posterior-only surgery, than in those treated with a combined approach, which confounds the study results. One challenge in treating patients with a posterior-only approach is the risk for pseudarthrosis. Kim et al.5 reported a 17% incidence (nearly 1 in 5) of pseudarthrosis after long primary arthrodesis with the use of modern segmental spinal instrumentation for the treatment of adult idiopathic scoliosis. Some authors contend that risk for pseudathrosis in the posterior-only approach can be mitigated with rhBMP-2. Luhmann et al.6 have reported a high rate of fusion for both anterior-only (96%) and posterior-only (93%) surgery with the use of rhBHP-2 for adult spinal deformity. Subsequent longterm follow-up study on the same patients showed significant fusion rate for anterior (91%), posterior (97%), and highdose posterior (100%) spinal fusion.7 These high-dose fusion groups used up to 40 mg of BMP per level, which may be cost prohibitive for some institutions. It is worth noting that in a recent prospective multicenter study,8 patients who received BMP to aid in spinal fusion had a greater total complication rate and a greater minor complication rate than patients who did not receive BMP, but they had similar wound, neurological, superficial, and deep infection rates. Research is needed to assess the long-term fusion rates and safety profile of higher doses of rh-BMP2. The development of posterior-based interbody-fusion techniques offers the advantage of circumferential fusion from a single incision and is helpful to augment fusion, especially helpful at the lumbosacral junction where the risk of pseudarthrosis is reportedly as high as 60%.9 Another option for increasing fusion rates across the lumbosacral junction in posteriorly approached patients is the transsacral interbody approach (i.e., AxiaLif), which provides anterior column support for long posterior fusions to the sacrum, though longterm results for this technique are not available.9
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Anterior surgery to treat adult thoracolumbar scoliosis was originally described by Dwyer et al. in 1969.10 These anterioronly reconstructions were typically utilized for thoracolumbar curvature, and they were able to achieve effective correction, especially in the sagittal plane because of the release of the anterior longitudinal ligament. Distal lumbar motion segments were often able to spared, a distinct advantage in comparison to the posterior approach options. In addition, anterior-only correction maintains the integrity of the posterior ligamentous complex. The major disadvantage of anterior approaches to the spine is the morbidity of the dissection, with risks to the lung, diaphragm, sympathetic chain, and major vascular structures in the thoracic and thoracolumbar spine, as well as the genitofemoral nerve, kidney and ureter, and the peritoneal contents in the lumbar spine. The main anterior approach options to the thoracic and lumbar spine include the transthoracic approach, thoracoabdominal approach, anterior retroperitoneal and transperitoneal approaches, and lateral retroperitoneal approach. Risks associated with the transthoracic approach include damage to the intercostal vessels during rib resection or exposure of the vertebrae as well as injury to the lungs. The thoracoabdominal approach enables access to the anterior spine at the thoracolumbar junction, but it carries the risks of entry into the thorax and the retroperitoneum as well as of pseudohernias from abdominal wall paralysis. Dangers of the retroperitoneal approach to the lumbar spine include injury to the sympathetic chain, the genitofemoral nerve, the segmental lumbar vessels, as well the aorta or the vena cava. The paramedian retroperitoneal approach is often utilized as it is substantially less morbid than the transperitoneal and thoracoabdominal approaches. Horton et al.11 have described less pain and functional disturbance in patients who have a paramedian retroperitoneal approach as compared to a thoracoabdominal approach. A significantly higher rate of retrograde ejaculation with the transperitoneal approach was noted as compared to the retroperitoneal approach.12 Anterior-only surgery (via the thoracoabdominal approach) is still utilized for relatively flexible thoracolumbar structural curves. Outside of this indication anterior-only surgery is uncommonly used. For elderly patients, without significant sagittal imbalance, consideration could be given to minimally invasive lateral transpsoas approach for stand-alone (i.e., uninstrumented) anterior interbody fusion. Relative stability is achieved with cages that span the apophyseal ring. Excellent coronal correction is typically achievable. The sagittal correction is less robust since the anterior longitudinal ligament remains intact. This approach to treatment has been shown to yield acceptable radiographic and clinical outcomes in short- and mid-term follow-up, with acceptable morbidity, though long-term results are lacking.13 Because of these limitations with anterior-only reconstruction, surgeons began to combine the anterior and posterior approaches in an effort to more effectively address complex spinal deformity. Through the anterior approach, surgeons are able to “release” stiff spinal deformities resulting from degenerative disk collapse via discectomy and release of the anterior longitudinal ligament, allowing for significant correction of
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segmental sagittal malalignment. This is particularly useful in reestablishing lordosis of the lumbar spine. Correction achieved through anterior column reconstruction, obviates the need for more aggressive posterior-based osteotomies. Anterior approaches also allow for placement of bone graft within the anterior column, an excellent fusion environment due to the compressive loads experienced here and the large bony surface area available for fusion. Especially at the lumbosacral junction, interbody fusion is important to mitigate the risk of pseudarthrosis.14 Interbody support with structural grafts in the anterior column decreases stress on sacral screws. Interbody support also allows indirect decompression of up–down foraminal stenosis. However, placing structural grafts does lengthen the spine, which tends to have more risk to the neurologic elements via a stretch mechanism of injury when compared with posterior shortening (i.e., osteotomy) techniques. Furthermore, the morbidity of the approach needs to be weighed against its potential benefits. However, this calculus may be changing as lateral interbody fusion techniques offer minimally invasive options for anterior surgery, which may be coupled with an open, limited anterior approach for interbody fusion at the lumbosacral
27 (2015) 163–168
165
junction in an effort to reduce approach related morbidity. A more recent innovation involves release of the ALL via the minimally invasive lateral approach, allowing for significant segmental correction (in some cases approaching 301) in an effort to avoid having to perform the more morbid pedicle subtraction osteotomy (Fig. 1). It is worth noting that the role of minimally invasive anterior spine surgery for adult spinal deformity through the direct lateral approach, as a component of the combined surgery, is still being defined. There has been evidence to support the use of MIS techniques in adult spinal deformity surgery, particularly in symptomatic elderly patients without significant sagittal imbalance.15 Open surgery to date remains the gold standard for correction of spinal deformity. Berven et al.,16 in studying the outcomes of combined anterior and posterior surgery for the management of fixed sagittal plane deformity, noted that patient satisfaction with surgery, and overall clinical outcomes were best in cases that resulted in an increase in lumbar lordosis. Patients with preoperative regional hypolordosis (4 301) had the most reliable improvement of health status, and they had better clinical outcomes than those with lumbar lordosis in the physiologic range. The authors noted that 40% of patients in
Fig. 1 – Image on the left shows standing lateral radiograph of a 71-year-old woman who had undergone L2-5 interbody fusion with dynamic stabilization, with proximal junctional kyphosis at L1-2 level, contributing to positive sagittal balance. The image on the right shows postoperative standing lateral showing restoration of sagittal balance after less invasive lateral interbody fusion with transpsoas anterior longitudinal ligament release, and fusion extension to T10. (Adapted with permission from Deukmedjian et al. Anterior longitudinal release using the minimally invasive lateral retroperitoneal transpsoas approach: a cadaveric feasibility study and a report of 4 clinical cases. J Neurosurg Spine. 2012;17:530–539).
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the study had major complications, including pneumonia, dural tears, wound infection, and pseudarthrosis. Relative indications for combined anterior and posterior fusion include planned arthrodesis across the lumbosacral junction, lumbar pseudarthrosis, correction of a fixed lumbosacral obliquity, lumbar hypolordosis, posterior-element deficiency, and osteoporosis (Fig. 2).
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Pateder et al.17 compared the radiographic lumbar curve correction between posterior-only and combined anterior– posterior approach in patients with adult spinal deformity. The two groups were not significantly different in correcting adult lumbar scoliosis curves measuring between 401 and 701. While the posterior-only group and same-day anteriorand posterior-surgery group had similar major complication
Fig. 2 – (A) Anteroposterior, bending, and lateral radiographs of two patients with similar curve patterns and flexibility before surgical treatment. (B) Anteroposterior and lateral radiographs of the patients at follow-up, after one was treated with anterior and posterior combined approach, and the other was treated with a posterior-only surgery. (Adapted with permission from Good et al. Can posteiror-only surgery provide similar radiographic and clinical results as combined anterior (thoracotomy/ thoracoabdominal)/posterior approaches for adult scoliosis? Spine. 2010;35(2):210–218).
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Fig. 2 – Continued. rates of 24% and 23%, respectively, patients who underwent staged anterior and posterior surgery had a major complication rate of 45%.17 This study was limited by the small cohort, the statistically significant difference in the preoperative scoliosis measurements between the two groups, and the surgeons' selection bias in choosing the surgical approach.
When a decision for a combined approach for treatment of spinal deformity has been made, the options of doing the anterior and posterior surgery on the same day versus on two separate days must be considered. Staged procedures are well tolerated by many patients, but they may be associated with a higher risk of infection and
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blood transfusion.14 For fused, rigid deformities, patients may be served better with a three-stage surgery with two periods of anesthesia. During the first anesthetic, posterior osteotomies are performed along with the preparation of pedicle screw sites, but without placement of implants. At the next stage anterior release and osteotomies are done, followed by deformity correction and posterior instrumentation. There is evidence that staged procedures result in significantly longer hospital stays, and are at higher risk of infection and wound complications if done too close together. This may be attributed to inadequate time to recover from postoperative malnutrition, which develops to an appreciable extent in adults undergoing spinal deformity surgery.18 The order in which the staged procedures are done must also be considered. In a patient with a mobile anterior column, a posterior–anterior order can be utilized if acceptable sagittal correction can be achieved first via posterior column osteotomies and segmental transpedicular fixation. A staged anterior procedure 4–6 weeks after the initial posterior surgery can then be performed to provide anterior column support and aid in achieving a circumferential fusion. This allows ample time to recover from the first surgery before undergoing the second. Naturally a posterior–anterior staged procedure would not be feasible in correcting sagittal malalignment in patients who have a fused anterior column, or a stiff anterior column secondary to degenerative disease that requires an anterior release. In these situations, an anterior release would precede the posterior reconstruction, or a posterior-only approach with osteotomies would need to be considered. Achieving the goals of coronal and sagittal alignment correction, bony fusion, alleviation of pain, and improved patient function is paramount to success. Although spinal deformity surgical patients have a complex reconstructive problem, these objectives may be achieved in part by careful consideration of the factors that weigh in the selection of the surgical approach.
r e f e r e n c e s
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