Multicenter validation of a formula predicting postoperative spinopelvic alignment

Clinical article

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Object

Sagittal spinopelvic imbalance is a major contributor to pain and disability for patients with adult spinal deformity (ASD). Preoperative planning is essential for pedicle subtraction osteotomy (PSO) candidates; however, current methods are often inaccurate because no formula to date predicts both postoperative sagittal balance and pelvic alignment. The authors of this study aimed to evaluate the accuracy of 2 novel formulas in predicting postoperative spinopelvic alignment after PSO.

Methods

This study is a multicenter retrospective consecutive PSO case series. Adults with spinal deformity (> 21 years old) who were treated with a single-level lumbar PSO for sagittal imbalance were evaluated. All patients underwent preoperative and a minimum of 6-month postoperative radiography. Two novel formulas were used to predict the postoperative spinopelvic alignment. The results predicted by the formulas were then compared with the actual postoperative radiographic values, and the formulas' ability to identify successful (sagittal vertical axis [SVA] ≤ 50 mm and pelvic tilt [PT] ≤ 25°) and unsuccessful (SVA > 50 mm or PT > 25°) outcomes was evaluated.

Results

Ninety-nine patients met inclusion criteria. The median absolute error between the predicted and actual PT was 4.1° (interquartile range 2.0°–6.4°). The median absolute error between the predicted and actual SVA was 27 mm (interquartile range 11–47 mm). Forty-one of 54 patients with a formula that predicted a successful outcome had a successful outcome as shown by radiography (positive predictive value = 0.76). Forty-four of 45 patients with a formula that predicted an unsuccessful outcome had an unsuccessful outcome as shown by radiography (negative predictive value = 0.98).

Conclusions

The spinopelvic alignment formulas were accurate when predicting unsuccessful outcomes but less reliable when predicting successful outcomes. The preoperative surgical plan should be altered if an unsuccessful result is predicted. However, even after obtaining a predicted successful outcome, surgeons should ensure that the predicted values are not too close to unsuccessful values and should identify other variables that may affect alignment. In the near future, it is anticipated that the use of these formulas will lead to better surgical planning and improved outcomes for patients with complex ASD.

Abbreviations used in this paper: ASD = adult spinal deformity; HRQOL = health-related quality-of-life; IQR = interquartile range; NPV = negative predictive value; PI = pelvic incidence; PPV = positive predictive value; PSO = pedicle subtraction osteotomy; PT = pelvic tilt; SVA = sagittal vertical axis.

Article Information

Address correspondence to: Virginie Lafage, Ph.D., 306 East 15th Street, Suite 1F, New York, New York 10003. email: virginie.lafage@gmail.com.

Please include this information when citing this paper: published online September 23, 2011; DOI: 10.3171/2011.8.SPINE11272.

© AANS, except where prohibited by US copyright law.

Headings

Figures

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    Sagittal spinal radiological parameters. Positive values for sagittal curvatures denote a lordotic alignment, while negative values denote a kyphotic alignment.

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    Pelvic radiological parameters.

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    Population pyramid illustrating the age (in years) and sex distribution of the 99 study patients.

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    Histogram of PSO levels illustrating the number of PSO resections performed at each lumbar vertebral level.

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    Case 1. Preoperative (left) and postoperative (right) radiographs obtained in a patient who underwent sagittal realignment surgery, showing a successful realignment surgery.

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    Case 2. Preoperative (left) and postoperative (right) radiographs obtained in a patient who underwent sagittal realignment surgery, showing an unsuccessful realignment surgery.

References

  • 1

    Berven SDeviren VDemir-Deviren SHu SSBradford DS: Studies in the modified Scoliosis Research Society Outcomes Instrument in adults: validation, reliability, and discriminatory capacity. Spine (Phila Pa 1976) 28:216421692003

  • 2

    Booth KCBridwell KHLenke LGBaldus CRBlanke KM: Complications and predictive factors for the successful treatment of flatback deformity (fixed sagittal imbalance). Spine (Phila Pa 1976) 24:171217201999

  • 3

    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

  • 4

    Buchowski JMBridwell KHLenke LGKuhns CALehman RA JrKim YJ: Neurologic complications of lumbar pedicle subtraction osteotomy: a 10-year assessment. Spine (Phila Pa 1976) 32:224522522007

  • 5

    El Fegoun ABSchwab FGamez LChampain NSkalli WFarcy JP: Center of gravity and radiographic posture analysis: a preliminary review of adult volunteers and adult patients affected by scoliosis. Spine (Phila Pa 1976) 30:153515402005

  • 6

    Farcy JPSchwab FJ: Management of flatback and related kyphotic decompensation syndromes. Spine (Phila Pa 1976) 22:245224571997

  • 7

    Gertzbein SDHarris MB: Wedge osteotomy for the correction of post-traumatic kyphosis. A new technique and a report of three cases. Spine (Phila Pa 1976) 17:3743791992

  • 8

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

  • 9

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

  • 10

    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 lordosis?. Spine (Phila Pa 1976) 31:234323522006

  • 11

    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

  • 12

    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

  • 13

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

  • 14

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

  • 15

    Legaye JDuval-Beaupère G: Sagittal plane alignment of the spine and gravity: a radiological and clinical evaluation. Acta Orthop Belg 71:2132202005

  • 16

    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

  • 17

    Mac-Thiong JMTransfeldt EEMehbod AAPerra JHDenis FGarvey TA: Can c7 plumbline and gravity line predict health related quality of life in adult scoliosis?. Spine (Phila Pa 1976) 34:E519E5272009

  • 18

    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

  • 19

    Rillardon LLevassor NGuigui PWodecki PCardinne LTemplier A: [Validation of a tool to measure pelvic and spinal parameters of sagittal balance.]. Rev Chir Orthop Repar Appar Mot 89:2182272003. (Fr)

  • 20

    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

  • 21

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

  • 22

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

  • 23

    Thomasen E: Vertebral osteotomy for correction of kyphosis in ankylosing spondylitis. Clin Orthop Relat Res 194:1421521985

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