Impact of spinopelvic alignment on decision making in deformity surgery in adults

A review

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Sagittal spinal misalignment (SSM) is an established cause of pain and disability. Treating physicians must be familiar with the radiographic findings consistent with SSM. Additionally, the restoration or maintenance of physiological sagittal spinal alignment after reconstructive spinal procedures is imperative to achieve good clinical outcomes. The C-7 plumb line (sagittal vertical axis) has traditionally been used to evaluate sagittal spinal alignment; however, recent data indicate that the measurement of spinopelvic parameters provides a more comprehensive assessment of sagittal spinal alignment. In this review the authors describe the proper analysis of spinopelvic alignment for surgical planning. Online videos supplement the text to better illustrate the key concepts.

Abbreviations used in this paper:CA = coronal alignment; CSVL = central sacral vertical line; HRQOL = health-related quality of life; LL = lumbar lordosis; PI = pelvic incidence; PSO = pedicle subtraction osteotomy; PT = pelvic tilt; SA = sagittal alignment; SPI = spinopelvic inclination; SS = sacral slope; SSM = sagittal spinal misalignment; SVA = sagittal vertical axis; TK = thoracic kyphosis; TLK = thoracolumbar kyphosis.

Article Information

Address correspondence to: Christopher P. Ames, M.D., Department of Neurosurgery, University of California, Medical Center, 400 Parnassus Avenue, A850, San Francisco, California 94143. email: amesc@neurosurg.ucsf.edu.

Please include this information when citing this paper: published online March 23, 2012; DOI: 10.3171/2012.2.SPINE11320.

© AANS, except where prohibited by US copyright law.

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Figures

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    Illustration depicting the Dubousset cone of economy. Normally when humans assume an erect posture, they stand within a certain zone of balance in which their torso remains within a certain distance from their pelvis. By doing this, energy expended by postural muscles is minimized. Beyond this zone, the cone of economy, energy expenditure rapidly increases and eventually spinal misalignment results. Printed with the permission of K. X. Probst/Xavier Studio, 2012. Also see online Videos 1 and 2.

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    Illustration showing the distance between the C-7 plumb line (C7PL) and the CSVL, which defines the amount of coronal plane decompensation in centimeters (indicated as –X). Printed with the permission of K. X. Probst/Xavier Studio, 2012.

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    Drawings showing measurement parameters for spinal SA. Left: The SVA is measured as the distance from the posterior superior corner of the sacrum to a vertical plumb line dropped from the C-7 centroid, here shown as +X°. Right: Spinopelvic inclination is a global angular measurement of SA. It is the angle formed by a line from the femoral heads to the T-1 or T-9 centroid and the vertical plumb line. Since this is an angle rather than a length measurement, it is not subject to magnification variability on radiographs. C7Pl = C-7 plumb line. Printed with the permission of K. X. Probst/Xavier Studio, 2012.

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    Left: Diagram showing the method for measuring TK. Typically, TK is measured from T-5 to T-12 given that the T-2 endplate is often difficult to visualize. Right: Diagram showing the method for measuring LL. Lumbar lordosis is generally measured from T-12 to S-1 (−X°) and thoracolumbar alignment from T-10 to L-2 (+X°). Printed with the permission of K. X. Probst/Xavier Studio, 2012.

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    Diagram showing the measurements of PI. Printed with the permission of K. X. Probst/Xavier Studio, 2012. Also see online Videos 3 and 4. a = center of sacral endplate; b = anterior superior point of sacral endplate.

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    Diagram showing the measurements of PT. Printed with the permission of K. X. Probst/Xavier Studio, 2012. Also see online Videos 3 and 4. VRL = vertical reference line.

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    Diagram showing the measurements of SS. Printed with the permission of K. X. Probst/Xavier Studio, 2012. Also see online Videos 3 and 4. HRL = horizontal reference line.

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    Diagrams depicting how an increase in PT (pelvic retroversion) contributes to the restoration of spinal SA. A: High SVA and low PT. B: Partial compensation of SVA with moderate PT. C: Full compensation of SVA with high PT. Printed with the permission of K. X. Probst/Xavier Studio, 2012.

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    Diagrams showing the relative location of the gravity line (GL), heel line, pelvis, and femoral head (FH) for 3 age groups of patients. As patients age, the GL remains fixed with respect to the heels and lies anterior to the spine. Pelvic retroversion adjusts the GL–heel relationship as the plumb line shifts with age due to lumbar flattening and increased TK. Pelvic tilt and SVA normative values increase with age. Older patients may not require as low an SVA as younger patients. Printed with the permission of K. X. Probst/Xavier Studio, 2012.

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    Smith-Peterson osteotomies over multiple levels combined with lordotic cages can be used to produce excellent sagittal realignment and correction of PT. Preoperative (A) and postoperative (B and C) radiographs demonstrating a change in PT. Arrow indicates C-7 plumb line.

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    Using vertebral column resection and PSO to correct fixed multiplanar deformity. Preoperative anteroposterior (A) and lateral (B) radiographs showing high PT and fixed sagittal and coronal misalignment. Drawings showing coronal misalignment corrected with vertebral column resection (C) and sagittal misalignment corrected with PSO (D). Printed with the permission of K. X. Probst/Xavier Studio, 2012.

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    Postoperative anteroposterior (A) and lateral (B) radiographs from the case represented in Fig. 11 showing excellent SA and CA. Postoperative clinical photograph (C) showing the patient's standing posture.

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    Case representative of a patient with good correction for SVA and PT. Preoperative lateral radiograph (left) showing an SVA of 119.73 mm, LL of 28°, SS of 30°, PT of 22°, and PI of 52°. Postoperative lateral radiograph (right) showing an SVA of 30.14 mm, LL of 60°, SS of 38°, PT of 9°, and PI of 47°.

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    Case representative of high postoperative PT and poor correction of the SVA. Preoperative lateral radiograph (left) showing an SVA of 254.13 mm, LL of 32°, SS of 38°, PT of 40°, and PI of 78°. Postoperative lateral radiograph (right) showing an SVA of 150.42 mm, LL of 57°, SS of 40°, PT of 36°, and PI of 76°.

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    Case representative of high postoperative PT with good correction of the SVA. Preoperative lateral radiograph (left) showing an SVA of 142.38 mm, LL of 20°, SS of 16°, PT of 40°, and PI of 56°. Postoperative lateral radiograph (right) showing an SVA of 24.79 mm, LL of 54°, SS of 26°, PT of 30°, and PI of 56°.

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    Case representative of unfavorable thoracic reciprocal change; there was an increase in TK after fusion to T-10. Preoperative lateral radiograph (left) showing an SVA of 158.02 mm, LL of 14°, SS of 32°, PT of 27°, and PI of 59°. Postoperative lateral radiograph (right) showing an SVA of 128.59 mm, LL of 39°, SS of 35°, PT of 26°, and PI of 61°. Lumbar correction in this patient was insufficient.

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    Case representative of significant sagittal balance, degenerative flat back with primary extensor muscle weakness, and low preoperative PT. Despite improved postoperative lordosis of 37°, the patient had similar persistent stooping. The patient did not have hip flexion contracture. Low preoperative PT despite sagittal imbalance is a significant finding, as patients should retrovert the pelvis to partially rebalance. This finding can be indicative of poor extensor muscle strength or hip flexion contracture. Both hip flexion contracture and primary extensor muscle weakness will impair surgical correction and outcome. Preoperative lateral radiograph (left) displaying marked sagittal imbalance, flat-back deformity with 5° of lordosis, and 11° of PT. Postoperative radiograph (right) displaying continued sagittal imbalance despite 37° of lumbar correction, 42° of LL, 15° of PT, and 56° of PI.

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    The lower an osteotomy of a given size is placed in the spine, the greater the theoretical sagittal correction achieved. Stated a different way, for the same amount of angular correction, an osteotomy placed more superiorly in the spine would need to be larger. In practice, this additional angular correction achieved by more inferiorly placed osteotomies (for example, L-5 PSO vs L-3 PSO) may manifest as better PT correction. Preoperative radiograph (left) showing assessment of location for PSO. Blue line represents the C-7 plumb line; white vertical line, approximate corrected location of C-7 plumb line; and thick angled white line, the patient's spine. The angle subtended between the patient's spine and the planned C-7 plumb line (thinner white lines) represents the angle of correction needed given that the PSO was at that level. Thus, as the PSO moves more caudal, the angles become smaller. Postoperative radiograph (right) showing an L-3 PSO and adequate correction of the C-7 plumb line.

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    Photograph showing hip flexion contracture that will prevent successful sagittal realignment surgery and should be identified preoperatively.

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    Drawings showing the method for measuring pelvic obliquity. Printed with the permission of K. X. Probst/Xavier Studio, 2012.

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    Preoperative (A) and postoperative (B) radiographs demonstrating that a failure to note a leg length discrepancy can lead to further coronal decompensation with correction of the scoliosis. Further decompensation to the right was noted after curve correction. Postoperative radiograph (C) obtained following a second surgery, showing that some of the curve correction was removed and the instrumentation was extended to the pelvis. Note that the pelvic obliquity due to leg length discrepancy was not significantly changed.

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    Pelvic obliquity may also be compensatory in severe curves, resulting from an attempt to maintain balance. In these cases, correction of the scoliosis results in rebalancing of the spine and spontaneous reciprocal decrease in the pelvic obliquity. Preoperative radiograph (left) displaying severe scoliosis and high pelvic obliquity. Postoperative radiograph (right) showing coronal correction and a decrease in pelvic obliquity.

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    Patients with pelvic obliquity on standing radiography should be assessed for leg length discrepancy, and the radiography studies should be repeated with a shoe lift approximating the leg discrepancy to assess the effect on the spinal curve. Photograph (A) obtained during clinical assessment, showing leg length discrepancy. Standing anteroposterior radiograph (B) showing spinal misalignment without the shoe lift. Standing anteroposterior radiograph (C) obtained after the addition of a shoe lift to the side with the short leg, showing partial correction of the scoliosis. Coronal alignment shifted back slightly to the left of neutral. Despite the curve correction with the shoe lift, the patient's back pain continued and she elected to undergo surgery for her symptoms.

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    Drawing of general algorithm for the treatment of patients with scoliosis, coronal misalignment, and pelvic obliquity. In patients with pelvic obliquity in which the spine is flexible and aligned, full correction of the curve may lead to significant coronal decompensation, as the scoliotic curve may be compensatory. In some of these patients, the addition of a shoe lift will allow the flexible spine to relax and may improve alignment and deformity-related symptoms. If the spine is rigid, as is more common in adults, a shoe lift may be poorly tolerated and may not be effective in rebalancing the spine. Patients in such cases may require incomplete curve corrections and sometimes a shoe lift as well depending on the final standing alignment. PO = pelvic obliquity. Printed with the permission of K. X. Probst/Xavier Studio, 2012.

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    Drawings of complex curve patterns in which the coronal correction strategy must take into account the patients probable alignment shift when standing to determine how much curve correction is possible in each direction. Often this may involve shifting the patient's coronal plumb slightly off to the side opposite the short leg. Printed with the permission of K. X. Probst/Xavier Studio, 2012.

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    Preoperative standing anteroposterior radiograph (A) showing the C-7 plumb line initially off to the left, which was the side of the short leg. Radiograph (B) showing an intraoperative correction strategy designed to shift the intraoperative plumb line a few centimeters to the right. Radiograph (C) showing the return of pelvic obliquity upon standing, resulting in a well-aligned spine in the coronal plane. White line indicates the C-7 plumb line; black line, the CSVL.

References

  • 1

    Barrey CJund JNoseda ORoussouly P: Sagittal balance of the pelvis-spine complex and lumbar degenerative diseases. A comparative study about 85 cases. Eur Spine J 16:145914672007

    • Search Google Scholar
    • Export Citation
  • 2

    Boulay CTardieu CHecquet JBenaim CMouilleseaux BMarty C: Sagittal alignment of spine and pelvis regulated by pelvic incidence: standard values and prediction of lordosis. Eur Spine J 15:4154222006

    • Search Google Scholar
    • Export Citation
  • 3

    Dubousset JImportance de la vertèbre pelvienne dans l'équilibre rachidien. Application à la chirurgie de la colonne vertébrale chez l'enfant et l'adolescent. Villeneuve P: Pied Équilibre et Rachis ParisFrison-Roche1998. 141149

    • Search Google Scholar
    • Export Citation
  • 4

    Dubousset J: Reflections of an orthopaedic surgeon on patient care and research into the condition of scoliosis. J Pediatr Orthop 31:1 SupplS1S82011

    • Search Google Scholar
    • Export Citation
  • 5

    Dubousset JThree-dimensional analysis of the scoliotic deformity. Weinstein SL: The Pediatric Spine: Principles and Practice New YorkRaven Press1994. 479496

    • Search Google Scholar
    • Export Citation
  • 6

    Duval KLam TSanderson D: The mechanical relationship between the rearfoot, pelvis and low-back. Gait Posture 32:6376402010

  • 7

    Gelb DELenke LGBridwell KHBlanke KMcEnery KW: An analysis of sagittal spinal alignment in 100 asymptomatic middle and older aged volunteers. Spine (Phila Pa 1976) 20:135113581995

    • Search Google Scholar
    • Export Citation
  • 8

    Glassman SDBerven SBridwell KHorton WDimar JR: Correlation of radiographic parameters and clinical symptoms in adult scoliosis. Spine (Phila Pa 1976) 30:6826882005

    • Search Google Scholar
    • Export Citation
  • 9

    Glassman SDBridwell KDimar JRHorton WBerven SSchwab F: The impact of positive sagittal balance in adult spinal deformity. Spine (Phila Pa 1976) 30:202420292005

    • Search Google Scholar
    • Export Citation
  • 10

    Gottfried ONDaubs MDPatel AADailey ATBrodke DS: Spinopelvic parameters in postfusion flatback deformity patients. Spine J 9:6396472009

    • Search Google Scholar
    • Export Citation
  • 11

    Hardacker JWShuford RFCapicotto PNPryor PW: Radiographic standing cervical segmental alignment in adult volunteers without neck symptoms. Spine (Phila Pa 1976) 22:147214801997

    • Search Google Scholar
    • Export Citation
  • 12

    Hori TKawaguchi YKimura T: How does the ossification area of the posterior longitudinal ligament progress after cervical laminoplasty?. Spine (Phila Pa 1976) 31:280728122006

    • Search Google Scholar
    • Export Citation
  • 13

    Hu SHRodriguez JPFarin AHseigh PO'Shaughnessy BAShaffrey CI: Restoration of Global Sagittal Balance with Thoracolumbar Osteotomy Results in Spontaneous Correction of Cervical Alignment in Patients who Maintain Horizontal Gaze. Presented at the 38th annual meeting of the Cervical Spine Research SocietyCharlotte, NC2010. (http://www.medicine.virginia.edu/clinical/departments/neurosurgery/residenttraining/lectures-presentations.html) [Accessed February 17 2012]

    • Search Google Scholar
    • Export Citation
  • 14

    Jackson RPPeterson MDMcManus ACHales C: Compensatory spinopelvic balance over the hip axis and better reliability in measuring lordosis to the pelvic radius on standing lateral radiographs of adult volunteers and patients. Spine (Phila Pa 1976) 23:175017671998

    • Search Google Scholar
    • Export Citation
  • 15

    Janssen MMDrevelle XHumbert LSkalli WCastelein RM: Differences in male and female spino-pelvic alignment in asymptomatic young adults: a three-dimensional analysis using upright low-dose digital biplanar x-rays. Spine (Phila Pa 1976) 34:E826E8322009

    • Search Google Scholar
    • Export Citation
  • 16

    Kim KTPark KJLee JH: Osteotomy of the spine to correct the spinal deformity. Asian Spine J 3:1131232009

  • 17

    Kim YJBridwell KHLenke LGRhim SCheh G: An analysis of sagittal spinal alignment following long adult lumbar instrumentation and fusion to L5 or S1: can we predict ideal lumbar lordosis?. Spine (Phila Pa 1976) 31:234323522006

    • Search Google Scholar
    • Export Citation
  • 18

    Labelle HRoussouly PBerthonnaud EDimnet JO'Brien M: The importance of spino-pelvic balance in L5–S1 developmental spondylolisthesis: a review of pertinent radiologic measurements. Spine (Phila Pa 1976) 30:S27S342005

    • Search Google Scholar
    • Export Citation
  • 19

    Labelle HRoussouly PChopin DBerthonnaud EHresko TO'Brien M: Spino-pelvic alignment after surgical correction for developmental spondylolisthesis. Eur Spine J 17:117011762008

    • Search Google Scholar
    • Export Citation
  • 20

    Lafage VAmes CSchwab FKlineberg EAkbarnia BSmith J: Changes in thoracic kyphosis negatively impact sagittal alignment following lumbar pedicle subtraction osteotomy: a comprehensive radiographic analysis. Spine (Phila Pa 1976) 37:E180E1872012

    • Search Google Scholar
    • Export Citation
  • 21

    Lafage VBharucha NJSchwab FHart RABurton DBoachie-Adjei O: Multicenter validation of a formula predicting postoperative spinopelvic alignment. Clinical article. J Neurosurg Spine 16:15212012

    • Search Google Scholar
    • Export Citation
  • 22

    Lafage VSchwab FPatel AHawkinson NFarcy J: A validated formula for predicting post operative sagittal balance in the setting of adult spinal deformity. Scoliosis Research Society 43rd Annual MeetingSalt Lake City, UT2008

    • Search Google Scholar
    • Export Citation
  • 23

    Lafage VSchwab FPatel AHawkinson NFarcy JP: Pelvic tilt and truncal inclination: two key radiographic parameters in the setting of adults with spinal deformity. Spine (Phila Pa 1976) 34:E599E6062009

    • Search Google Scholar
    • Export Citation
  • 24

    Lafage VSchwab FSkalli WHawkinson NGagey PMOndra S: Standing balance and sagittal plane spinal deformity: analysis of spinopelvic and gravity line parameters. Spine (Phila Pa 1976) 33:157215782008

    • Search Google Scholar
    • Export Citation
  • 25

    Lafage VSchwab FVira SHart RBurton DSmith JS: Does vertebral level of pedicle subtraction osteotomy correlate with degree of spinopelvic parameter correction? Clinical article. J Neurosurg Spine 14:1841912011

    • Search Google Scholar
    • Export Citation
  • 26

    Lafage VSchwab FVira SPatel AUngar BFarcy JP: Spino-pelvic parameters following surgery can be predicted: a preliminary formula and validation of standing alignment. Spine (Phila Pa 1976) 36:103710452011

    • Search Google Scholar
    • Export Citation
  • 27

    Lazennec JYRamaré SArafati NLaudet CGGorin MRoger B: Sagittal alignment in lumbosacral fusion: relations between radiological parameters and pain. Eur Spine J 9:47552000

    • Search Google Scholar
    • Export Citation
  • 28

    Lee CSLee CKKim YTHong YMYoo JH: Dynamic sagittal imbalance of the spine in degenerative flat back: significance of pelvic tilt in surgical treatment. Spine (Phila Pa 1976) 26:202920352001

    • Search Google Scholar
    • Export Citation
  • 29

    Legaye JDuval-Beaupère GHecquet JMarty C: Pelvic incidence: a fundamental pelvic parameter for three-dimensional regulation of spinal sagittal curves. Eur Spine J 7:991031998

    • Search Google Scholar
    • Export Citation
  • 30

    Legaye JHecquet JMarty CDuval-Beaupere G: Equilibre sagittal du rachis. Relations entre bassin et courbures rachidiennes sagittales en position debout. Rachis 5:2152261993

    • Search Google Scholar
    • Export Citation
  • 31

    Mac-Thiong JMLabelle HBerthonnaud EBetz RRRoussouly P: Sagittal spinopelvic balance in normal children and adolescents. Eur Spine J 16:2272342007

    • Search Google Scholar
    • Export Citation
  • 32

    O'Brien MFKuklo TRBlanke KMLenke LG: Spinal Deformity Study Group Radiographic Measurement Manual Memphis, TNMedtronic Sofamor Danek2004

    • Search Google Scholar
    • Export Citation
  • 33

    Ondra SLMarzouk SKoski TSilva FSalehi S: Mathematical calculation of pedicle subtraction osteotomy size to allow precision correction of fixed sagittal deformity. Spine (Phila Pa 1976) 31:E973E9792006

    • Search Google Scholar
    • Export Citation
  • 34

    Rajnics PTemplier ASkalli WLavaste FIlles T: The importance of spinopelvic parameters in patients with lumbar disc lesions. Int Orthop 26:1041082002

    • Search Google Scholar
    • Export Citation
  • 35

    Rose PSBridwell KHLenke LGCronen GAMulconrey DSBuchowski JM: Role of pelvic incidence, thoracic kyphosis, and patient factors on sagittal plane correction following pedicle subtraction osteotomy. Spine (Phila Pa 1976) 34:7857912009

    • Search Google Scholar
    • Export Citation
  • 36

    Roussouly PGollogly SBerthonnaud EDimnet J: Classification of the normal variation in the sagittal alignment of the human lumbar spine and pelvis in the standing position. Spine (Phila Pa 1976) 30:3463532005

    • Search Google Scholar
    • Export Citation
  • 37

    Roussouly PNnadi C: Sagittal plane deformity: an overview of interpretation and management. Eur Spine J 19:182418362010

  • 38

    Sarwahi VBoachie-Adjei OBackus SITaira G: Characterization of gait function in patients with postsurgical sagittal (flatback) deformity: a prospective study of 21 patients. Spine (Phila Pa 1976) 27:232823372002

    • Search Google Scholar
    • Export Citation
  • 39

    Schwab FFarcy JPBridwell KBerven SGlassman SHarrast J: A clinical impact classification of scoliosis in the adult. Spine (Phila Pa 1976) 31:210921142006

    • Search Google Scholar
    • Export Citation
  • 40

    Schwab FLafage VBoyce RSkalli WFarcy JP: Gravity line analysis in adult volunteers: age-related correlation with spinal parameters, pelvic parameters, and foot position. Spine (Phila Pa 1976) 31:E959E9672006

    • Search Google Scholar
    • Export Citation
  • 41

    Schwab FLafage VPatel AFarcy JP: Sagittal plane considerations and the pelvis in the adult patient. Spine (Phila Pa 1976) 34:182818332009

    • Search Google Scholar
    • Export Citation
  • 42

    Schwab FLafage VShaffrey CIFarcy JPBoachie-Adjei OShelekov A: Pre-operative pelvic parameters must be considered to achieve adequate sagittal balance after lumbar osteotomy. Presented at the 18th International Meeting on Advanced Spine Techniques, Scoliosis Research SocietyCopenhagen, Denmark2011. (http://www.srs.org/imast/2011/) [Accessed February 17 2012]

    • Search Google Scholar
    • Export Citation
  • 43

    Schwab FPatel AUngar BFarcy JPLafage V: Adult spinal deformity-postoperative standing imbalance: how much can you tolerate? An overview of key parameters in assessing alignment and planning corrective surgery. Spine (Phila Pa 1976) 35:222422312010

    • Search Google Scholar
    • Export Citation
  • 44

    Schwab FJPatel AShaffrey CISmith JSFarcy JPBoachie-Adjei O: Sagittal realignment failures following pedicle subtraction osteotomy surgery: are we doing enough? Clinical article. J Neurosurg Spine [in press]2012

    • Search Google Scholar
    • Export Citation
  • 45

    Smith JSBess SShaffrey CIBurton DCHart RAHostin R: Dynamic changes of the pelvis and spine are key to predicting postoperative sagittal alignment following pedicle subtraction osteotomy: a critical analysis of preoperative planning techniques. Spine (Phila Pa 1976) [epub ahead of print]2011

    • Search Google Scholar
    • Export Citation
  • 46

    Smith JSShaffrey CIBerven SGlassman SHamill CHorton W: Improvement of back pain with operative and nonoperative treatment in adults with scoliosis. Neurosurgery 65:86942009

    • Search Google Scholar
    • Export Citation
  • 47

    Tanguay FMac-Thiong JMde Guise JALabelle H: Relation between the sagittal pelvic and lumbar spine geometries following surgical correction of adolescent idiopathic scoliosis: a preliminary study. Stud Health Technol Inform 123:2993022006

    • Search Google Scholar
    • Export Citation
  • 48

    Vedantam RLenke LGKeeney JABridwell KH: Comparison of standing sagittal spinal alignment in asymptomatic adolescents and adults. Spine (Phila Pa 1976) 23:2112151998

    • Search Google Scholar
    • Export Citation

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