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Copyright (c) 2022 Slovenian Medical Journal. This work is licensed under a
Creative Commons Attribution-NonCommercial 4.0 International License.
Methods of internal sacroiliac fixation – Literature review 
and case series analysis of iliac screw fixation
Metode notranjega fiksiranja križnice na črevnico – Pregled literature in analiza serije 
primerov fiksiranja z iliakalnim vijakom
Janez Mohar
Abstract
In order to achieve bone fusion between the mobile lumbar spine and the immobile sacrum, surgical techniques have 
been developed along with the development of instrumentation systems for internal fixation of the thoracolumbar spine 
that allows the extension and fixation of such systems to the structural elements of the pelvis. The term sacroiliac fixa-
tion encompasses all instrumentation systems and surgical techniques for fixation of the lumbosacral spine to the ilium. 
Nowadays, prevention of pseudarthrosis of the bone fusion at the lumbosacral region, the border between two different 
structures (mobile lumbar spine and static pelvic ring), is one of the main challenges of surgical treatment of adult lumbar 
spine deformities. Biomechanically, the lumbosacral junction represents an axis of rotation extending in the lateral plane 
through the posterior longitudinal ligament at the height of the intervertebral disc of the moving segment L5-S1. The 
flexion torque arm’s size depends on the number of instrumented movable spine segments. Counter-torque is required 
for system stability, which, due to the short lever arm, depends mainly on the implant’s attachment strength to the pelvic 
ring’s bony elements. Sacroiliac fixation systems prevent the formation of pseudoarthrosis of the bone fusion of the lum-
bosacral junction. Its occurrence, with the exclusion of biological causes (i.e., infection), depends solely on the strength of 
the instrumentation system (the brittleness of the material) and the quality of attachment of the instrumentation to the 
pelvic ring (loss of fixation at the bone-implant interface).
Indications for sacroiliac fixation are lumbosacral fusion above the third lumbar vertebra, osteotomies of the lumbar verte-
bra, fractures of the sacrum with spinopelvic dissociation, partial or complete sacrectomy, lumbosacral fusion in the face 
of osteoporotic bone, spondylolisthesis grade III or more of Meyerding classification, correction of kyphotic or scoliotic 
deformity of the lumbar spine and pelvic obliquity in the frontal plane in neuromuscular deformities of the lumbar spine.
This review article aims to describe the spinopelvic junction’s biomechanics, present the developmental history of im-
plants and surgical techniques, and describe the modern sacroiliac fixation methods.
Valdoltra Orthopaedic Hospital, Ankaran, Slovenia
Correspondence / Korespondenca: Janez Mohar, e: janez.mohar@ob-valdoltra.si
Key words: spine deformity; pseudoarthrosis; lumbosacral junction; iliac screw; S2-alar-iliac screw
Ključne besede: deformacija hrbtenice; psevdoartroza; ledveno-križnični prehod; iliakalni vijak; S2-alarni iliakalni
Received / Prispelo: 26. 1. 2021 | Accepted / Sprejeto: 16. 4. 2021
Cite as / Citirajte kot: Mohar J. Methods of internal sacroiliac fixation – Literature review and case series analysis of iliac screw fixation. 
Zdrav Vestn. 2022;91(9–10):382–92. DOI: https://doi.org/10.6016/ZdravVestn.3222
eng slo element
en article-lang
10.6016/ZdravVestn.3222 doi
26.1.2021 date-received
16.4.2021 date-accepted
Surgery, orthopaedics, traumatology Kirurgija, ortopedija, travmatologija discipline
Review article Pregledni znanstveni članek article-type
Methods of internal sacroiliac fixation – Liter-
ature review and case series analysis of iliac 
screw fixation
Metode notranjega fiksiranja križnice na črevni-
co – Pregled literature in analiza serije primerov 
fiksiranja z iliakalnim vijakom
article-title
Methods of internal sacroiliac fixation Metode notranjega fiksiranja križnice na črevnico alt-title
spine deformity, pseudoarthrosis, lumbosacral 
junction, iliac screw, S2-alar-iliac screw
deformacija hrbtenice, psevdoartroza, ledve-
no-križnični prehod, iliakalni vijak, S2-alarni 
iliakalni vijak
kwd-group
The authors declare that there are no conflicts 
of interest present.
Avtorji so izjavili, da ne obstajajo nobeni 
konkurenčni interesi. conflict
year volume first month last month first page last page
2022 91 9 10 382 392
name surname aff email
Janez Mohar 1 janez.mohar@ob-valdoltra.si
name surname aff
eng slo aff-id
Valdoltra Orthopaedic Hospital, 
Ankaran, Slovenia
Ortopedska bolnišnica Valdoltra, 
Ankaran, Slovenija 1
Slovenian Medical Journallovenian Medical Journal
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Methods of internal sacroiliac fixation
1 Introduction
Surgical treatment of complex pathology of the 
thoracolumbar spine is based on the internal fixation 
of the bone structures involved in the disease pro-
cess with the aim of preventing progression, and at 
the same time, stabilizing the corrected position of 
the deformed spinal column. Such an “internal fix-
ator” is actually a multi-level instrumentation con-
struct consisting of pedicle screws, fixated bilaterally 
to the vertebrae, and rods connecting the heads of the 
pedicle screws to one another. The instrumentation 
construct thereby turns the mobile segments of the 
thoracolumbar spine into an immobile structure of 
interconnected vertebrae, which is a prerequisite for 
early mobilization of the patient after surgery. By sta-
bilizing the vertebrae, the instrumentation construct 
allows the bone graft placed on the decorticated bone 
structures to connect over time into a static bone 
fusion mass, which permanently fuses the mobile 
segments included in the construct. Biomechanical-
ly, the lumbosacral region is a junction between the 
mobile lumbar spine and the static pelvic ring. The 
axis of rotation between these two structures in the 
lateral plane passes through the posterior longitudi-
nal ligament at the height of the intervertebral disc 
of the L5-S1 moving segment. This anatomical region 
is therefore the area where both static and dynamic 
Izvleček
Da bi dosegli zatrditev med gibljivo ledveno hrbtenico in negibljivo križnico, so se ob razvoju instrumentacijskih siste-
mov za notranje fiksiranje prsno-ledvene hrbtenice razvijale kirurške tehnike, ki omogočajo podaljšati take sisteme na 
kostne elemente medenice. Izraz sakroiliakalno (SI) fiksiranje zajema vse instrumentacijske sisteme in kirurške tehnike za 
notranjo učvrstitev ledveno-križničnega predela hrbtenice na črevnico. Preprečevanje psevdoartroze kostne fuzije ledve-
no-križničnega prehoda, ki nastane na meji med dvema različnima strukturama (gibljivo ledveno hrbtenico in statičnim 
medeničnim obročem), je dandanes eden glavnih izzivov kirurškega zdravljenja deformacij ledvene hrbtenice pri odraslih. 
Ledveno-križnični prehod je biomehansko os vrtenja, ki v stranski ravnini poteka skozi posteriorni longitudinalni ligament 
v višini medvretenčne ploščice gibljivega segmenta L5-S1. Velikost ročice fleksijskega navora je odvisna od števila instru-
mentiranih ravni gibljive prsno-ledvene hrbtenice, za stabilnost sistema pa je potreben nasprotni navor, ki je zaradi kratke 
ročice odvisen predvsem od pričvrstitvene moči vsadka na kostne elemente medeničnega obroča. Sistemi SI-fiksiranja 
preprečujejo nastanek psevdoartroze kostne fuzije ledveno-križničnega prehoda, njen pojav pa je ob odsotnosti bioloških 
vzrokov (npr. okužba) odvisen izključno od trdnosti instrumentacijskega sistema (lomljivost materiala) in kakovosti fiksira-
nja instrumentarija na medenični obroč (omajanje na stiku med vsadkom in kostjo).
Indikacije za SI-fiksiranje so ledveno-križnična kostna fuzija (zatrditev) več kot treh ledvenih vretenc, razširjene korektivne 
osteotomije ledvenih vretenc, zlomi križnice s spinopelvično (SP) disociacijo, delna ali popolna sakrektomija, ledveno-
-križnična kostna fuzija pri osteoporotični kosti, spondilolisteza, ki je večja od II. stopnje po Meyerdingovi klasifikaciji, 
korekcija kifotične ali skoliotične deformacije ledvene hrbtenice in nagib medenice v čelni ravnini pri živčnomišičnih de-
formacijah ledvene hrbtenice.
Pregledni članek opisuje biomehaniko SP prehoda, predstavi zgodovino razvoja vsadkov ter kirurških tehnik in prikaže 
sodobne metode SI-fiksiranja.
load forces are concentrated. When the sacrum and 
multiple lumbar vertebrae are included in the instru-
mentation construct, biomechanical conditions are 
iatrogenically created that require balancing torques 
proximal and distal to the axis of rotation in the 
lumbosacral junction. The magnitude of the flexion 
torque proximal to the axis of rotation depends on 
the number of thoracolumbar vertebrae included in 
the instrumentation construct. The torque distal to 
the axis of rotation depends on the length of the distal 
lever arm and on the implant’s attachment strength 
to the bony elements of the pelvic ring. The prerequi-
site for flexion-extension stability is that the implants, 
which are fixed to the elements of the pelvic ring, run 
anterior to the axis of rotation. The term SP fixation 
broadly covers all instrumentation systems and sur-
gical techniques for fixation of the lumbar spine to 
the sacrum, the latter being the biomechanical part 
of the pelvic ring. Sacroiliac (SI) fixation encompasses 
all instrumentation systems and surgical techniques 
for fixation of the lumbosacral spine to the ilium. Pre-
venting the formation of pseudarthrosis of bone fu-
sion mass of the lumbosacral junction and thus the 
failure of the instrumentation construct is one of the 
main challenges of surgical treatment of lumbar spine 
deformities today (1,2).
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Figure 1: Posterior (A), superior (B), and lateral (C and D) 
views of the anatomical diagram of the pelvic ring with 
O’Brien zones marked (zone I = blue, zone II = yellow, zone 
III = grey) and with the iliac (arrow) and S2AI screws (arrow 
head) inserted.
Indications for SIJ fixation are lumbosacral fusion 
above the third lumbar vertebrae, extensive corrective 
osteotomies of the lower thoracic and lumbar verte-
brae, fractures of the sacrum with spinopelvic dissoci-
ation, partial or complete sacrectomy, lumbosacral fu-
sion in the face of osteoporotic bone, spondylolisthesis 
grades III, IV, and V, kyphotic or scoliotic deformity of 
the lumbar spine, and unstable sitting position due to 
pelvic obliquity in the frontal plane in neuromuscular 
deformities of the lumbar spine (3).
SP fixation techniques are divided according to the 
area of fixation in the sacropelvic region, which is de-
fined by O’Brien’s anatomic zones (Figure 1). The at-
tachment strength of the distal part of the instrumen-
tation construct increases depending on the number of 
zones included in the construct (4-6). O’Brien zone I 
consists of the S1 vertebral body and the cranial sacral 
alae, and SP fixation techniques in this anatomical area 
are the S1 pedicle screw, L5-S1 transfacet screw, and the 
Dunn-McCarthy technique. In the latter, the S-shaped 
rods are posteriorly fixated to the sacral ala. It is suit-
able for non-ambulatory children with neuromuscu-
lar scoliosis, in whom the pelvis is too small and the 
iliac cortices are too thin for classic iliac fixation (7). 
O’Brien zone II consists of the S2 vertebral body, cau-
dal sacrum, and coccyx. SP fixation techniques in this 
anatomical area are the S2 pedicle screw, sacro-alar iliac 
screw, sacral neural foramina hooks in the form of a jaw 
construct, and the Jackson technique with intrasacral 
rods (8). O’Brien zone III constitutes the ilia and the 
SP fixation techniques in this anatomical area are the 
Galveston technique, the iliac screw, and the Kostuik 
transilial bar technique. In order to achieve the greatest 
possible fixation strength on the pelvic ring, these tech-
niques are combined or implants are used that allow 
fixation through two O’Brien zones at the same time. 
These are the Chopin block, the Tacoma plate, the Col-
orado 2 iliosacral plate, the Warner and Fackler tech-
nique, the iliosacral screw, and the S2-alar-iliac screw 
(S2AI) (9).
Biomechanical stress on the fixation construct is 
significantly reduced with additional stabilization by 
inserting an intervertebral cage between the L4, L5, and 
S1 vertebral bodies (L4-L5 and L5-S1 mobile segments 
of the lumbosacral junction). This reduces micromove-
ments anterior to the axis of rotation in the lumbosa-
cral junction, the axis of rotation moves proximally, 
and the intervertebral cage thus provides support to 
the construct and “protects” it against failure (break-
age or loosening of the implants) (10). Biomechanical 
research has proven that SIJ fixation with iliac screws 
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Figure 2: SP fixation with the Luque-Galveston technique in 
a 13-year-old boy with scoliosis as part of spinal muscular 
atrophy; anteroposterior (A) and lateral (B) projection 
(source: Archives of the Department of Orthopaedic Surgery 
of the University Clinical Centre Ljubljana).
reduces the strain on the instrumentation construct 
more than the intervertebral cage alone (10,11). In-
tervertebral cage implantation between the vertebral 
bodies of the lumbosacral junction is therefore a pre-
requisite for all instrumented lumbosacral fusions. In 
the case of long thoracolumbar-sacral instrumentation 
constructs, the insertion of the intervertebral cage must 
always be combined with SIJ fixation.
2 Development of implants for Fixation in 
O’Brien zone III
The first example of an implant in O’Brien zone III 
was a transiliac rod connecting the iliac alae to which 
a lumbar instrumentation was attached. This concept 
was first described as early as 1962 in the form of the 
Harrington rod, a modification of which was later up-
graded by Kostuik with his own implant suitable for 
more modern and more rigid instrumentation systems 
(12,13).
In the 1970s, when fixing his multisegmental sys-
tem of rods and sublaminar wires to the pelvis, Luque 
curved the distal ends laterally and led them through 
the posterior alae of ilium. As the Luque L-rod is 
considered a weak SIJ fixation, it was not able to with-
stand physiological flexion and torsion forces (14,15).
In 1982, Allen and Ferguson of the University of Tex-
as Medical Branch at Galveston described a technique 
for pelvic fixation with Luque’s segmental instrumenta-
tion by inserting extended left and right L-shaped rods 
into the ilia (16). The Luque-Galveston technique of in-
trailiac rod stabilization (Figure 2) became the first bio-
mechanically and clinically successful form of fixation 
of long instrumentation constructs in O’Brien’s zone III. 
The technique involves the introduction of rod instru-
mentation with an entry point at the posterior superior 
iliac spine, the rod passing between the two cortices of 
the ilium. The degree of lumbosacral spinal fusion rate 
using this technique is described to be 88-90% (17,18). 
Biomechanically, the Luque-Galveston technique does 
not provide enough resistance to axial traction, which 
represents the force component during lumbar flexion, 
so micromovements in the sacroiliac joint can lead to 
erosive changes in the contact between the rod and the 
bone (windshield-wiper effect), which results in the loss 
of the fixation function of the implant. Erosive chang-
es do not always lead to clinically expressed pseudoar-
throsis, although it is more common in the presence of 
the “windshield-wiper effect” (18). The described rate 
of pseudoarthrosis of the lumbosacral junction when 
using the Luque-Galveston technique in adult spinal 
deformities varies between 36% and 41% (19,20). An 
additional weakness of the technique is the demanding, 
anatomy-adapted bending of the rods that are inserted 
into the ilium. The Luque-Galveston technique is still 
a relative indication in non-ambulatory patients with 
neuromuscular scoliosis, due to the low profile of the 
implant and the price of the commercially proximally 
pre-bent U-shaped rod (unit rod). The Luque-Galves-
ton intrailiac rod concept later led to the development 
of SIJ fixation with iliac screws (21).
The technique of fixing the lumbar instrumentation 
to the iliosacral screw was first described in 1973, but 
later developed in its improved form in the 1980s into 
the possibility of SIJ fixation with the first generation of 
hybrid segmental instrumentation with the Cotrel-Du-
bousset system (22,23). In this technique, a screw is in-
serted from the outer side of the ilium towards the body 
of the S1 vertebra. The screw provides strong tricortical 
bone graft (inner and outer cortices of the ilium and 
posterior cortex of the sacrum). The iliosacral screw 
as a stand-alone implant in SIJ fixation is connected to 
the rods of the lumbar instrumentation construct via 
a connecting element. In this technique, the S1 pedi-
cle screws are not used due to possible contact with the 
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iliosacral screws within the S1 vertebral body. The tech-
nique itself, however, allows considerable modularity 
in relation to anatomical conditions. Due to the exten-
sive dissection along the iliac edge and the possibility 
of damaging the posterior iliosacral ligament, which 
triggers sacroiliac joint instability and a high incidence 
of neurological injuries due to incorrect position of 
the screw, the use of this technique is currently limited 
mainly to revision cases (15,23).
3 Modern techniques of SIJ fixation
3.1 Iliac screw
Certain shortcomings of the Luque-Galveston tech-
nique were overcome by the technique of connecting 
iliac screws to the rod of the instrumentation construct 
with modular connectors (24). On the cadaver model, 
a three times stronger fixation of the iliac screws into 
the ilium is made possible compared to the Galveston 
intrailiac rod by the presence of threads and the great-
er thickness of the implant (25). The entry point of the 
iliac screw is at the level of the posterior superior iliac 
spine or just below it, and the direction (trajectory) of 
insertion is either towards the superior portion of the 
acetabula or towards the anterior inferior iliac spine. 
The latter direction allows the insertion of longer im-
plants, is safer regarding the possibility of piercing the 
acetabular floor and the fixation can be made stronger, 
since the screw is inserted through a greater narrowing 
between the cortices of the ilium in its course above the 
sciatic notch (26). Due to the longer iliac screw, there 
is a greater possibility for it to go outside the safety tra-
jectory and thus for more complications, however, the 
longer screw enables a stronger fixation to the ilium. 
Longer iliac screws have been proven to have a greater 
pull-out force, and under physiologic torsion, and com-
pressive loading conditions there should be no statisti-
cally significant differences in the mechanical stability 
of SIJ fixation between shorter and longer iliac screws, 
but on the condition that the shorter screw also runs 
anterolaterally of the sciatic notch (27). The gold stan-
dard for iliac screw insertion is therefore the thickest 
and longest possible implant, which runs in the direc-
tion of the anterior inferior iliac spine, namely antero-
laterally of the sciatic notch.
The SIJ fixation construct with iliac screws fails in 
two ways: either by loosening which causes pseudar-
throsis, or by the implant breaking. Loosening of the 
iliac screw occurs during cyclic micromovements at the 
bone-implant interface. The phenomenon is common, 
but in most cases, it is clinically silent, except when the 
loosening leads to pseudarthrosis (2,28,29). Revision of 
loose iliac screws is necessary if pseudarthrosis devel-
ops, namely by inserting longer and thicker implants, 
reinforcing the contact between the implant and the 
bone with bone cement, or by stabilization using dual 
iliac screws (30-33). The latter technique, i.e. DIS (Du-
al Iliac Screw), is primarily suitable for resections and 
osteotomies of the sacrum and certain forms of sacrum 
fractures with dislocation of fragments (34).
Screw fracture is a rarer form of fixation failure with 
a reported rate of 5.3%, which more often affects the 
younger population with good bone quality and insuf-
ficient screw diameter (28). The indication and options 
for revision surgery are otherwise the same as in the 
case of loosening.
The SIJ instrumentation construct in the form of 
combined S1 pedicle screw and iliac screw has certain 
disadvantages:
• Insertion of the iliac screw requires an extensive lat-
eral soft tissue dissection along the iliac crest, thereby 
creating a surgical “dead space” (a prerequisite for lo-
cal infection).
• The iliac screw is connected to the rod of the con-
struct via a connector, which further reduces the 
stiffness of the construct and thus represents an ad-
ditional locus minoris resistentiae for its failure, while 
there are no biomechanical differences if the connec-
tor is fixed to the rod above or below the S1 pedicle 
screw (35). The described rate of pseudarthrosis in 
the lumbosacral junction when using instrumenta-
tion with iliac screws in adult spinal deformities var-
ies between 6.4% and 14% (19,36).
• The head of the iliac screw and the connector repre-
sent a significant implant prominence, which is a rel-
atively common cause of local pain and revisions (in-
cidence between 6% and 22%) (2,19,37). The results 
of recently published research show a significantly 
lower rate of this type of complication if the entry 
point of the iliac screw is below the posterior superi-
or iliac spine, or if the screw head is “sunk” deep into 
the iliac bone (38-40). Under favourable anatomical 
conditions, the “anatomical” or “subcrestal” entry 
point of the iliac screw, it is possible to fix the rod on 
the screw head without using connectors (41).
3.2 S2AI screw
The instrumentation construct with the S2AI screw 
is the latest SIJ fixation technique, which enables sta-
bility without the necessary use of connectors, with a 
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less prominent screw head, and with less extensive lat-
eral soft tissue dissection (42-44). In this technique, a 
polyaxial screw is inserted through a starting point on 
the sacrum that is 2–4 mm lateral and 4–8 mm distal to 
the S1 dorsal foramen (lateral to the midline connect-
ing the S1 and S2 foramen), and the trajectory passes 
through the sacrum, sacroiliac joint and into the ilium 
in the direction towards the anterior inferior iliac spine 
(1,21,44). S2AI screw enables a tricortical fixation (pos-
terior cortex of the sacrum and both cortices of the sac-
roiliac joint) and is suitable for both children and adults 
(45-48). Insertion of the S2AI screw through the carti-
laginous tissue of the sacroiliac joint may increase local 
postoperative pain and accelerate degenerative changes 
in the joint (49,50). Additional potential complications 
are screw misalignment and, rarely, screw head prom-
inence in lean subjects with pain over the sacral area. 
Incorrect position of the S2AI screw with posterior illi-
ac wall perforation leads to its reduced fixation streng-
ht and thus to reduced stability of the construct, while 
anterior or inferior prominence of the ilium endangers 
vital structures in the pelvis and sciatic notch (superior 
gluteal artery and sciatic nerve) (3,44).
3.3 Comparison between the iliac screw and 
the S2AI screw
Research on biomechanical studies between the iliac 
screw and the S2AI screw showed statistical comparabil-
ity in the strength of the two constructs under different 
types of strain on cadaver models (51-53). Meta-analy-
ses of clinical comparisons between the iliac screw and 
the S2AI screw published so far have demonstrated a 
statistically significant reduction in the risk of revision 
Patient 
number
Gender Age (years) Indication for surgery Levels of 
instrumentation 
placement 
Follow-up time after 
surgery (months)
1 female 72 iatrogenic deformation T11-ilium 66
2 male 62 iatrogenic deformation T11-ilium 59
3 female 43 adult idiopathic scoliosis T8-ilium 49
4 male 54 iatrogenic deformation T12-ilium 45
5 female 60 sagittal imbalance L2-ilium 44
6 female 48 iatrogenic deformation L3-ilium 44
7 male 64 sagittal imbalance T11-ilium 44
8 female 58 adult idiopathic scoliosis T10-ilium 42
9 female 64 adult idiopathic scoliosis T3-ilium 39
10 female 57 adult idiopathic scoliosis T10-ilium 38
11 female 52 adult idiopathic scoliosis T11-ilium 38
12 male 61 degenerative scoliosis T11-ilium 34
13 female 49 sagittal imbalance L2-ilium 26
14 female 39 congenital deformity L3-ilium 25
15 female 46 syndromic scoliosis T6-ilium 24
16 female 58 adult idiopathic scoliosis T2-ilium 21
17 female 69 degenerative scoliosis T11-ilium 16
18 male 63 degenerative scoliosis T12-ilium 16
19 male 72 iatrogenic deformation T11-ilium 11
20 female 50 adult idiopathic scoliosis T9-ilium 7
Table 1: Patient cohort characteristics.
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Sample characteristics Number
Number of patients 20
Gender 6 men / 14 women
Age (years) 57 ± 9 (39–72)
Number of levels of 
instrumentation placement 9 (5–18)
Follow-up time (months) 34 ± 16 (7–66)
Table 2: Descriptive cohort statistics.
surgery, wound infection, or implant prominence with 
local pain after surgery when using the S2AI screw in 
both adults and children, while the use of an iliac screw 
increased the risk of the fixation construct loosening 
or breaking threefold (54-56). Despite the more chal-
lenging technique of inserting the S2AI screw through 
the sacrum and pelvis, and despite concerns about the 
long-term effect on sacroiliac joint degeneration, for 
which there is no clinical evidence yet, there is now suf-
ficient evidence that SIJ fixation with the S2AI screw is 
superior to SIJ fixation with an iliac screw (57-65).
Figure 3: Revision Case No. 1: Anteroposterior radiographs of the patient’s spine before (A) and after surgery (B). C – the 
condition after the breakage of the left and right fixation rods (arrowheads) and the breakage of the left iliac screw (circled). 
D – connection of the broken rods with a connecting link (arrowheads), removal of the proximal part of the iliac screw and 
fixation of the distal part of the left rod into the sacrum with a sacral-alar screw (arrow).
4 Case series analysis of sacroiliac screw 
fixation
Between July 2015 and June 2020, 20 bilateral SIJ 
fixations with an iliac screw were performed at the Val-
doltra Orthopaedic Hospital, representing the author’s 
initial series of consecutive cases using this technique 
(Table 1 and 2). All iliac screws were inserted using the 
free-hand technique and their position was checked 
with an X-ray image intensifier during the operation. 
Due to the expected complexity, three procedures 
(patients 9, 15 and 16) were performed in two stages 
during the same hospitalization (in the first stage, the 
placement of the implants, and in the second stage, de-
formity correction). In 15 cases it was a primary op-
eration with a predominant idiopathic aetiology, and 
in five cases it was a revision procedure as part of an 
iatrogenic deformity, either kyphosis or kyphoscolio-
sis. In two patients (number 3 and 16), three revision 
procedures were performed due to the indication in 
the area of SIJ fixation (fracture of the iliac screw, local 
infection, and iliac screw prominence). The retrospec-
tive analysis of the case series was approved by the Eth-
ics Committee of the Valdoltra Orthopaedic Hospital, 
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Figure 4: Revision Case No. 2: X-ray image of the patient’s spine, anteroposterior (A) and lateral (B) before the surgery and 
anteroposterior (C) and lateral (D) after the surgery.
No. 1/2021, on January 20, 2021. The author confirms 
that he received written consent from both patients 
for the anonymized medical data and image material 
publication.
4.1 Revision case No. 1
A 43-year-old patient (No. 3, Table 1) with a rigid, 
right-sided idiopathic scoliotic curvature of the lum-
bar spine between the T12 and L4 vertebrae and the 
apex of the L2 vertebra underwent a one-stage correc-
tion, a posterior instrumented bone fusion between 
the T8 vertebra and the sacrum, and SIJ fixation (Fig-
ures 3A in 3B). Four months after the operation, she 
was involved in a traffic accident when another vehicle 
hit hers from behind. On the basis of imaging tests, 
skeletal damage or a change in the position of the im-
plants were ruled out, but chronic pain appeared in the 
lumbosacral region. Three years after the operation, 
she sensed a crack in the lumbosacral junction and 
felt a severe localized pain. Imaging tests showed the 
failure of the instrumentation construct with fixation 
rod breakage between the L4 and L5 vertebrae and the 
left iliac screw breakage (Figure 3C). During the revi-
sion procedure, the distal part of the instrumentation 
was repaired and an intervertebral cage was inserted 
through the foramen to allow additional intracorpo-
real bone fusion (Figure 3D). The explanation for the 
instrumentation construct failure is the cyclic load-
ing on the material and its stress fracture, the cause of 
which is pseudoarthrosis of the posterior bone fusion 
between the fourth and fifth lumbar vertebrae (discov-
ered during surgery). The occurrence of pseudoarthro-
sis was most likely caused by insufficient stabilization 
of the lumbosacral junction during the first operation, 
since the intervertebral cage was not inserted at the 
L5-S1 segment.
4.2 Revision case No. 2
In a 58-year-old patient (no. 16, Table 1) with dou-
ble adult idiopathic scoliotic curvature, a two-stage 
correction, an instrumented bone fusion between the 
T2 vertebra and the sacrum, and SIJ fixation were per-
formed due to the progression of the deformity and 
persistent pain despite conservative measures (Figure 
4). After the surgery, the patient lost some weight, 
but due to the reduction of subcutaneous fat over the 
posterior superior iliac spine area, the heads of the 
iliac screws and both connectors protruded, which 
390
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Zdrav Vestn | September – October 2022 | Volume 91 | https://doi.org/10.6016/ZdravVestn.3222
Figure 5: Revision Case No. 3: image of the patient before 
the removal of the second iliac screw. The scar after the 
posterior approach to the spine (arrowhead), the scar after 
excision of the purulent fistula and removal of the right iliac 
screw (black arrow) and the prominence of the head of the 
left iliac screw (white arrow) are visible.
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irritated the patient locally. Five months after the pro-
cedure, there was a perforation of the skin envelope 
and a fistula with pus discharge above the right illiac 
screw prominence with systemic and laboratory signs 
of inflammation. The patient underwent emergency 
surgery with excision of the fistula, explantation of 
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Nine months after the primary procedure, the left iliac 
screw was also electively removed due to pronounced 
localized pain with the patient signing that she is 
aware of possible later complications related to the loss 
of strength of the lumbosacral instrumentation con-
struct (Figure 5).
5 Conclusion
Modern SIJ fixation techniques, such as internal 
fixation with the iliac and S2AI screws, improve the 
bone fusion rate after transplantation of a free bone 
graft into the lumbosacral region. This creates the 
prerequisites for sustainable clinical and health-eco-
nomic justification of corrective interventions for 
thoracolumbar spine deformities in adult patients. 
Due to the aging of the population, the demands for a 
better quality of life, and the ever-increasing physical 
activity of the elderly population, the number of such 
operations is increasing in the developed world.
Conflict of interest
None declared.
391
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