Update on Assessment of Normal Sagittal Spinal Alignment

Transcription

1 3 rd Annual International Spinal Deformity Symposium November 3-4, 2017 Update on Assessment of Normal Sagittal Spinal Alignment Justin S. Smith, MD, PhD Harrison Distinguished Professor Department of Neurosurgery University of Virginia

2 Disclosures Zimmer Biomet: consultant, honoraria, royalties Nuvasive: consultant, honoraria K2M: consultant, honoraria AlloSource: consultant Cerapedics: consultant DePuy: research study group support NREF: fellowship funding AO: research support, fellowship funding

3 352 patients with (+) sagittal balance reviewed Severity of symptoms increase in a linear fashion with progressive positive sagittal balance All health-related quality of life (HRQOL) measures worsen as C7 plumbline (C7PL) deviates more Relative kyphosis is very poorly tolerated in lumbar spine

4 Correlation of HRQOL with C7-S1 Sagittal Vertical Axis (SVA)

5 Compensatory Mechanisms Pelvic retroversion - acetabulum more anterior Hip Extension - for mild pelvic retroversion Hip flexion/ Knee flexion - in severe/fixed deformity Courtesy of Dr. Frank Schwab

6 Pelvic Parameters SDSG Radiographic Measurement Manual

7 Pelvic Parameters (a lot of information with only 3 simple lines) PT PI 1. Perpendicular line from center of sacral endplate. 2. Line from center of sacral endplate to center of femoral head. 3. Vertical reference line straight upward from femoral head. Compensatory PT: Source of pain/disability Masks true magnitude of global sagittal malalignment PI: Indicator of ideal LL Pathologic PI-LL mismatch is source of pain/disability PI - LL

8 Which Radiographic Parameters Really Matter? 125 ASD, Single site; Surgical / Non-operative SpineView 300 parameters HRQOL Instruments ODI SF-12 SRS Correlations? Pelvic tilt and truncal inclination: two key radiographic parameters in the setting of adults with spinal deformity. Lafage V, Schwab F, Patel A, Hawkinson N, Farcy JP. Spine (Phila Pa 1976) Aug 1;34(17):E

9 3 most highly correlated parameters 1 PI - LL 2 SVA Linear Regression for Disability Thresholds (Oswestry Disability Index > 40) 3 Pelvic Tilt SVA = 4.7 cm PT = 22 0 PI-LL = 11 0

10 Alignment Objectives C7 T1 SVA T1 Tilt PT <5cm <0 0 <25 0 Proportional: LL=PI +/- 10 0

11 But is Normal Sagittal Spino-Pelvic Alignment that Simple?

12 Mean sagittal vertical axis fell 3.2 +/- 3.2 cm behind the front of the sacrum Increasing age correlated to a more forward sagittal vertical axis with loss of distal lumbar lordosis Loss of distal lumbar lordosis is most responsible for sagittal imbalance in those individuals who do not maintain sagittal alignment

13 Assessed normal spino-pelvic alignment in an asymptomatic volunteer population 55 volunteers from New York City, mean age 45 years (range years) No history of chronic LBP or spine surgery

14 PI LL TK CL Ames CP, et al. Spine. 2013;38:S149-S160.

15 Assessed normal spino-pelvic alignment in an asymptomatic volunteer population 260 volunteers from Chinese Han population, mean age 38 years (range years) No history of chronic LBP, spinal pathology, deformity, or hip/pelvic/lower limb disorder

16 LL significantly greater in women No significant differences based on sex for other parameters (C7 tilt, TK, PI, SS, PT) Zhu Z, et al. Spine. 2013;39:E1-E6.

17 Compared with a similarly aged Caucasian population, Chinese volunteers had lower PI (45 o vs 53 o ) and lower SS (40 o vs 33 o ) Zhu Z, et al. Spine. 2013;39:E1-E6.

18 Assessed normal spino-pelvic alignment in an asymptomatic volunteer population 1,461 volunteers from Japanese population, mean age 66 years (range years), BMI=23 Population-based cohort Asai Y, et al. Plos One. June, 2017.

19 SVA and TK significantly increased with age LL significantly decreased with age Women had significantly less TK and significantly greater LL than men, but mean differences were small. Asai Y, et al. Plos One. June, 2017.

20 PT significantly increased with age for both men and women PI did not significantly change with age Women had significantly greater PT and PI than men. PT: 19.5 o v 15.8 o PI: 51.2 o v 47.7 o Asai Y, et al. Plos One. June, 2017.

21 773 patients analyzed Ideal spinopelvic values increased with age PT=10.9 0, PI-LL=10.5 0, and SVA=4.1mm for patients <35 years PT= degrees, PI-LL=16.7 0, and SVA=78.1mm for patients >75 years Realignment targets should account for age, with younger patients requiring more rigorous alignment objectives

22 Age-Adjusted Alignment Objectives P< for all age group comparisons ODI threshold of 40

23 76 y/o woman SVA = +22 cm PT = 44 LL = -5 PI-LL = 78 SVA = +6 cm PT = 26 LL = 55 PI-LL = 18

24 Ideal values for patients 75+ years are: PT=28.5 o, PI-LL=16.7 o, SVA=7.8 cm

25 343 surgically treated adult spinal deformity patients; 2-yr alignment measures compared with ageadjusted normal thresholds Only ~30% of patients achieved age-adjusted alignment thresholds Under-corrected patients had worse outcomes; no significant outcomes differences between matched and over-corrected (?PJK risk)

26 Study of the Roussouly classification of sagittal spinal alignment in an asymptomatic adult population 296 asymptomatic adults without spinal pathology, mean age 27 years (range: years)

27 Identified patients in each of the 4 Roussouly Types and identified a novel subgroup: Type 3 Anteverted Lauuissat F, et al. Eur Spine J. In press.

28 Type 1 Short, focal hyperlordosis in lower L-spine SS <35 o Mean of only 3 vertebra in lumbar curve L-spine has high backward tilt lumbar tilt angle Type 2 Relatively flat lumbar lordosis, SS <35 o Mean of 4 vertebra in lumbar curve L-spine has moderate backward tilt Type 3 Anteverted Low-grade PI (mean=48 o ), despite high SS (>35 o ) PT low or negative (mean=4 o ) Mean of 5 vertebra in lumbar curve Lauuissat F, et al. Eur Spine J. In press.

29 Type 3 35 o < SS < 45 o Mean PI 53 o Mean of 4.5 vertebra in lumbar curve Type 4 SS > 45 o Mean PI 62 o Hyperlordotic (mean=69 o ) Lumbar curve tilts forward Lauuissat F, et al. Eur Spine J. In press.

30 12% 22% 16% 30% 20% Type 3 anteverted: discordance between high LL and a low PI, caused by a high SS and confirms that LL is less correlated to PI than SS Suggests that theoretical LL value should be calculated from the SS (SS-LL mismatch) Lauuissat F, et al. Eur Spine J. In press.

31 C7 plumbline was located in front of the hip axis and center of the sacral endplate in 13% of this asymptomatic population More men than women had the C7 plumbline was located in front of the hip axis and center of the sacral endplate (22% vs 7%) Lauuissat F, et al. Eur Spine J. In press.

32 Mathematical modeling based on 75 adolescent patients to predict patient-specific normal sagittal alignment of the spine Patients were all free of any known spine disease; (mean age 14.5 yrs, 26M/49F)

33 Created 3-dimensional spine model with EOS images and stereos software. Multiple radiographic measures assessed Cidambi KR, et al. Spine Deformity. 2015;3:

34 Used multiple regression modeling to create a normal contour function Model allows an adolescent patient s PI to predict normal sagittal alignment to best match that patient s native curve characteristics Average difference between actual sagittal positions of each vertebra and those predicted by the model were less than 5 mm at each level Cidambi KR, et al. Spine Deformity. 2015;3:

35 Objective was to develop and characterize a novel simplified measure of sagittal deformity

36 T1 pelvic angle (TPA): angle subtended by line from center of T1 to femoral head and line from femoral head to center of sacral endplate TPA accounts for both SVA and pelvic tilt TPA correlates with HRQOL Severe deformity threshold is TPA of 20 o and MCID is 4.1 o Based on application to a large 3-column osteotomy database, proposed alignment goal of 10 o for TPA. Ryan DR, et al. Spine. 2014;39:

37 TPA is a measure of global spinopelvic alignment but may not be measurable on all intraoperative x-rays The lumbar pelvic angle (LPA) can be used as an intraoperative tool to gauge global correction

38 LPA correlates with TPA, PI-LL and HRQOL in adult deformity patients LPA predicts global alignment as it correlates with baseline and 2-yr TPA and SVA Goal correction is LPA <7 o Protopsaltis T, et al. Spine. In press.

39 Conclusions Sagittal spino-pelvic alignment correlates with HRQOL, but what constitutes normal alignment is complex. Basic sagittal alignment goals are useful but are highly simplified. Normal sagittal spino-pelvic alignment varies based on multiple factors: Age and sex Ethnicity Overall spino-pelvic morphology Further study is needed to better define normal sagittal alignment on an individual basis.

40 Thank You