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
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
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)
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
Methods 1
 190 adult deformity patients
: Retrospective review
 Long construct instrumentation
: > 6 levels with iliac screws
 Clinical and Radiographic data
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)
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)
Methods 4
 Combined anterior and posterior fusion grading (L4S1) (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
Methods 5
 Failure rate
: Major F & minor F
 Risk factors for failure of pelvic fixation
: Major F Vs. N-F
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)
Results 2 (Major F Vs. N-F)
Major (M) Failure
Avg ± SE
Non Failure (N-F)
Avg ± SE
P value (T-test,
*Fisher's exact test)
66.98 ± 3.1
30.11 ± 2.6
4 ± 0.27
0
9 ± 1.5
65.72 ± 1.5
28.93 ± 1.1
3.3 ± 0.22
2
8.32 ± 0.50
0.723
0.684
0.061
*1.000
0.668
6
14
*0.043
Pelvic Incidence (PI)
72.1 ± 3.4
62.7 ±1.3
0.015
Preop Pelvic Tilt (PT)
Postop PT
PT Change
Preop Sacral Slope (SS)
Postop SS
Preop Sagittal Balance
34.9 ± 4.7
34.5 ± 5.4
-0.4 ± 3.8
37.3 ± 3.8
37.63 ± 2.9
136 28.1 ± 50
28.1 ±1.2
26.9 ± 1.1
-1.22 ± 1.0
34.59 ± 1.3
37.63 ± 2.9
101 28.1 ± 101
0.106
0.106
0.838
0.529
0.588
0.557
Clinical Data
Age
Body Mass Index (BMI)
Comorbidity Number
Smoker
Numbar of Levels Fused
Revision Surgeries
Radiographic Data
70.3 ± 7.1
49.6 ± 6.8
0.05
Preop CSVL (absolute value)
Postop CSVL (absolute value)
Change in CSVL (absolute value)
Preop Lordosis
Postop Saggital Balance
49.1 ± 10
26.6 ± 12
33.4 ± 7.7
-27.0 ± 8.3
24.8 ± 3.0
27.4 ± 3.3
18.4 ± 2.6
-34.8 ± 3.2
0.057
0.951
0.106
0.404
Postop Lordosis
-46 ± 2.5
-53.08 ± 1.6
0.033
Change in Lordosis
Posterior Lateral Fusion
Interbody Fusion
Total Fusion
-19 ± 7.1
-18.3 ± 2.6
Major (M) Failure
Non Failure (N-F)
% Radiographic Fusion % Radiographic Fusion
63%
73%
50%
51%
75%
89%
0.927
P Value (*Fisher's
exact test)
*0.672
*1.000
*0.286
Result 3
 Anterior Column Support (ALIF or TLIF)
Major F group - 87.5% of patients
Non Failure (N-F) - 84.1%
Major F
Major F
Bilateral rods breakage at L5-S1 level which is considered Major
failure because it needed a revision surgery due to psuedarthrosis.
Minor F
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.
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
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.
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