1. Failure of Pelvic Fixation after Long Construct Fusions in Adult Deformity Patients; Clinical and Radiographic Risk Factors
Woojin Cho, MD, PhD; Jonathan R. Mason, MD; Adam S. Wilson, MD; Christopher I. Shaffrey, MD; Francis H. Shen, MD; Adam L. Shimer, MD; Wendy M. Novicoff, PhD; Kai-Ming Fu, MD, PhD; Joshua Heller, MD; Vincent Arlet, MD

2. Introduction Rigid internal fixation → higher fusion rates
Lumbosacral fusion
: L5-S1 fixation alone
: Pelvic fixation
long constructs,
high grade spondylolithesis
unstable sacral fractures,
sacral tumors - 2

3. Introduction
Various Pelvic Fixation Methods : Galveston technique, S2 screws, four rod technique, S2 alar iliac screws, and S1-Iliac screws
S1-Iliac Screw Constructs
: long term study with minimum 5 year follow up
5 nonunions out of 67 cases
23 removal of iliac screws
spondylolisthesis + long constructs
No reports of the risk factors for failure
(Tsuchiya K, Bridwell KH, Kuklo TR, et al. Spine 2006) 3

4. Purpose
To report the failure rate and risk factors for failure of pelvic fixation with S1-Iliac screws used at the base of long constructs in adult deformity patients 4

5. Methods 1 190 adult deformity patients : Retrospective review
Long construct instrumentation
: > 6 levels with iliac screws
Clinical and Radiographic data 5

6. Methods 2 Failure (F) and Non-Failure (N-F)
Major F: rod breakage between L4 and S1, failure of S1 screws (breakage, halo formation, or pullout), and prominent iliac screws requiring removal
Minor F: rod breakage between S1 and iliac screws and failure of iliac screws (not require revision surgery) 6

7. Methods 3 Major Failure (Major F) Vs. Non-Failure (N-F)
Clinical data: age, body mass index (BMI), number of comorbities, and previous revision surgery
Radiographic data (Preop, Postop, Change): pelvic incidence, pelvic tilt, sacral slope, sagittal balance, coronal balance, lordosis, and Fusion status (L4-S1) 7

8. Methods 4
Combined anterior and posterior fusion grading (L4-S1) (A modified Lenke’s fusion grading system)
Posterior Fusion (PF) : Grade A, B, C
Anterior Fusions (AF)
: a sentinel sign at both L4-5 and L5-S1
Combined Fusions : PF or AF 8

9. Methods 5 Failure rate : Major F & minor F
Risk factors for failure of pelvic fixation
: Major F Vs. N-F 9

10. Result 1 190 patients → 67 patients Overall Failure (F) rate: 34.3%
Major F: 8 Pts (11.9%) rod breakage between L4 and S1, failure of S1 screws (breakage, halo formation, or pullout), and prominent iliac screws requiring removal
Minor F: 15 Pts (22.4%) rod breakage between S1 and iliac screws and failure of iliac screws. (not require revision surgery) 10

11. Results 2 (Major F Vs. N-F)11

12. Result 3 Anterior Column Support (ALIF or TLIF)
Major F group % of patients
Non Failure (N-F) % 12

13. Major F 13

14. Major F
Bilateral rods breakage at L5-S1 level which is considered Major failure because it needed a revision surgery due to psuedarthrosis. 14

15. Minor F 15

16. Minor F
Unilateral rod breakage below the S1 level which is a Minor failure because it doesn’t need a revision surgery as it can occur due to continuous motion at the SI joint after solid fusion at L5-S1. 16

17. Conclusion
The incidence of overall failure after pelvic fixation in adult deformity surgery : 34.3%
Major failure : 11.9%
Minor failure : 22.4%
Risk factors for Major failures :
larger Pelvic Incidence,
Revision Surgery,
failure to restore Lumbar Lordosis
failure to restore Sagittal Balance 17

18. Discussion Proper sagittal alignment
↑pelvic incidence → ↑ postoperative lumbar lordosis
↓lumbar lordosis → ↓ optimal sagittal alignment → may predispose for more biomechanical stress on pelvic fixation → ↑ failure rate
Therefore, adult deformity surgeons who use pelvic fixation for long construct fusions should pay special attention to restoring optimal sagittal alignment to prevent pelvic fixation failure. 18

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