Orthopaedics & Traumatology: Surgery & Research 105 (2019) S31–S42
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Orthopaedics & Traumatology: Surgery & Research
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Review article
The sacro-iliac joint: A potentially painful enigma. Update on the
diagnosis and treatment of pain from micro-trauma
Jean Charles Le Huec a,b,∗ , Andreas Tsoupras c , Amelie Leglise b , Paul Heraudet b ,
Gabriel Celarier b , Bengt Sturresson d
a
Polyclinqiue Bordeaux Nord Aquitaine, centre du dos, 15–30, rue Boucher, 33000 Bordeaux, France
DETERCA, departement Orthorachis 2, CHU Pellegrin Tripode, université de Bordeaux, place AR Leon, 33076 Bordeaux cedex, France
c
Département Orthopédie A Faundez, Hôpital La Tour, Meyrin, Switzerland
d
Orthopaedics Department, Angelholm Hospital, Sweden
b
a r t i c l e
i n f o
Article history:
Received 8 February 2018
Accepted 16 May 2018
Keywords:
Sacro-iliac joint dysfunction
Pelvic girdle pain
Spinal implant
Micro-traumatic lesion
Radiofrequency treatment
Sacro-iliac joint fusion
a b s t r a c t
The sacro-iliac joint (SIJ) located at the transition between the spine and the lower limbs is subjected to
major shear forces. Mobility at the SIJ is very limited but increases during pregnancy and the post-partum
period. Familiarity with the anatomy and physiology of the SIJ is important. The SIJ is a diarthrodial joint
that connects two variably undulating cartilage surfaces, contains synovial fluid, and is enclosed within
a capsule strengthened by several ligaments. This lecture does not discuss rheumatic or inflammatory
diseases of the SIJ, whose diagnosis relies on imaging studies and blood tests. Instead, it focuses on
micro-traumatic lesions. Micro-trauma causes chronic SIJ pain, which must be differentiated from hip
pain and spinal pain. The diagnosis rests on specific clinical provocation tests combined with a local
injection of anaesthetic. Findings are normal from radiographs and magnetic resonance imaging. Nonoperative treatment with exercise therapy and stretching aims primarily to strengthen the latissimus
dorsi, gluteus, and hamstring muscles to increase SIJ coaptation. Other physical treatments have not
been proven effective. Radiofrequency denervation of the dorsal sensory rami has shown some measure
of efficacy, although the effects tend to wane over time. Patients with refractory pain may benefit from
minimally invasive SIJ fusion by trans-articular implantation of screws or plugs, which has provided good
success rates.
© 2018 Elsevier Masson SAS. All rights reserved.
1. Introduction
The sacro-iliac joint (SIJ) is a diarthrodial joint that contains
synovial fluid and is enclosed within a capsule strengthened by
ligaments. It ensures the continuity of the pelvic ring, which bears
the weight of the upper body transferred to the S1 endplate at the
junction of the spine with the sacrum.
The SJI was seen in the early 20th century as a major contributor to low back pain. However, interest in this potential mechanism
was lost when Mixter and Barr described degenerative disc disease
and herniation in 1934 [1]. The advent of modern investigations
such as radiography, computed tomography (CT), and magnetic
resonance imaging (MRI) concentrated attention on the intervertebral discs and away from the SIJ. However, since the 1990s,
the huge increase in lumbar spine fusion surgery returned SIJ pain
∗ Corresponding author. Polyclinqiue Bordeaux Nord Aquitaine, centre du dos,
15–30, rue Boucher, 33000 Bordeaux, France
E-mail address: jclehuec1@aol.com (J.C. Le Huec).
https://doi.org/10.1016/j.otsr.2018.05.019
1877-0568/© 2018 Elsevier Masson SAS. All rights reserved.
to a prominent position. Concomitantly, several treatment options
were devised, whose efficacy deserves careful analysis.
The objective of this lecture is to discuss SIJ pain due to
micro-trauma, also known as idiopathic SIJ pain. In pain due to
micro-trauma, the blood tests are normal and the radiographs unremarkable. The mechanism is excessive tension of the ligaments
that ensure SIJ coaptation. Pain due to mechanical stress on the SIJ
capsule and ligaments can occur during pregnancy, due to sports
activities, or after a lumbo-sacral fusion procedure. Based on a literature review, this lecture discusses the answers to the five following
questions:
• What knowledge of anatomy and biomechanics is required to
understand sacro-iliac joint (SIJ) disorders?
• How can sacro-iliac joint (SIJ) disorders be diagnosed?
• What are the signs of sacro-iliac joint (SIJ) dysfunction due to
micro-trauma?
• What imaging studies are needed?
• How should idiopathic sacro-iliac joint (SIJ) pain be treated?
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2. What knowledge of anatomy and biomechanics is
required to understand sacro-iliac joint (SIJ) disorders?
Familiarity with the anatomy and biomechanics of the SIJ is
crucial to understand the sources of SIJ pain.
2.1. Anatomy [2]
The SIJ is a diarthrodial joint that connects two variably undulating surfaces, contains synovial fluid, and is enclosed within a
capsule strengthened by ligaments. A distinctive feature of the
SIJ is the presence not only of hyaline cartilage, but also of fibrocartilage. The combination of an irregular surface and presence of
fibro-cartilage contributes to stabilise the joint.
On the iliac bone, the joint surface is on the medial auricular aspect of the iliac wing, behind the iliac fossa and above the
greater sciatic notch. Overall, the appearance is that of a prominent
C-shaped ridge.
The sacral auricular surface is at the upper part of the lateral
border of the sacrum, which is chiefly composed of the first two
sacral vertebrae and upper part of the third sacral vertebra. It is
directed downwards, posteriorly, and laterally. Overall, it appears
as an L-shaped groove.
The joint surfaces are not smooth but instead exhibit a number of
irregular ridges and depressions (Fig. 1). They are covered by a deep
Fig. 2. Anterior ligaments. 1. Anterior longitudinal ligament. 2. Ilio-lumbar ligament.
3. Anterior sacro-iliac ligament. 4. Antero-superior iliac spine. 5. Inguinal ligament.
6. Sacro-tuberous ligament. 7. Sacro-spinous ligament. 8. Ischial spine. 9. Coccyx.
10. Pubic symphysis. © Cyrille Martinet.
Fig. 1. Anatomy of the sacro-iliac joint: anterior view. 1. Body of the pubic bone.
2. Auricular surface of the sacrum. 3. Sacrum. 4. Antero-superior iliac spine. 5.
Iliac tuberosity. 6. Auricular surface of the ilium. 7. Anterior sacro-iliac ligament.
8. Postero-superior iliac spine. 9. Coccyx. © Cyrille Martinet.
layer of hyaline cartilage and a superficial layer of fibro-cartilage.
These two layers together are thicker on the sacrum (3 mm) than
on the ilium (0.5 mm).
The two surfaces interlock with each other.
The joint is enclosed in a very compact, short, fibrous capsule
that is strengthened by powerful ligaments. Four ligaments can be
individualised.
The anterior sacro-iliac ligament, composed of two bands (cranial and caudal), is located at the inferior and anterior part of the
joint. The cranial band counteracts downwards displacement of the
sacral promontory, whereas the caudal band counteracts upwards
displacement of the coccyx during ventral tilting of the sacrum.
The inter-osseous sacro-iliac ligament is an extremely strong
structure that attaches immediately above and behind the SIJ on
the sacrum and ilium.
The posterior sacro-iliac ligament is oriented in such a way that
it blocks the SIJ when it is put under tension. The superficial plane of
the ligament is composed of four bands: the ilio-transverse-sacral
ligament; the axillary ligament, which is the strongest of the four
bands and runs parallel to the axis of nutation; the ligament of
Zaaglas; the sacro-spinous ligament of Bichat (Fig. 2).
The deep plane is composed of the inter-osseous ligament,
which is the strongest of the structures stabilising the SIJ (Fig. 3).
The ilio-lumbar ligament stabilises L5 on the sacrum. It has two
bands, cranial and caudal, which also contribute to lock the SIJ
(Fig. 4).
At a distance from this extremely powerful ligament complex,
the sacro-tuberous and sacro-spinous ligaments are ancillary structures with no major role in stabilising the SIJ. Severing these
ligaments during surgical release of the pudendal nerve does not
significantly worsen SIJ pain.
Muscles also contribute to stabilise the SIJ. Three muscles are
actively involved: the latissimus dorsi via the thoraco-lumbar fascia, the gluteus maximus, and the piriformis (Fig. 5).
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Nakagawa TA [4] added further information by describing nerve
fibres arising from the anterior rami of the L4 and L5 nerve roots;
superior gluteal nerve; and dorsal rami from the L5, S1, and S2 nerve
roots. The distribution of the nerve supply to the capsule occurred
at the level of each of the involved nerve roots.
Grob KR et al. [5] argued that the SIJ was chiefly innervated by
the dorsal sacral rami, based on their finding that all the nerve fibres
identified by foetal dissection came from the dorsal mesenchyme.
Studies by Fortin JD et al. [6] supported this hypothesis. However,
firm evidence now exists that the capsule receives a nerve supply
from anterior rami [7].
Histological examination of the nervous structures in the SIJ
capsule shows both myelinated and unmyelinated fibres, encapsulated Pacini mechanoreceptors, and non-Pacini mechanoreceptors.
These findings strongly suggest that pain signals and proprioceptive signals can arise from the SIJ [8].
2.2. Biomechanics of the sacro-iliac joint (SIJ)
Fig. 3. Posterior ligaments. 1. Ilio-lumbar ligament. 2. Postero-superior iliac spine.
3. Inter-osseous sacro-iliac ligaments. 4. Posterior sacro-iliac ligaments. 5. Sacrospinous ligament. 6. Ischial spine. 7. Coccyx. 8. Sacro-tuberous ligament. 9. Ischial
tuberosity. © Cyrille Martinet.
Many studies have focused on the nerve supply to the SIJ with
the goal of explaining the occurrence of SIJ pain (Fig. 6).
Solonen KA [3] reported one of the first descriptions of the
lumbo-sacral plexus branches arising from the superior gluteal
nerve, dorsal rami of the first two sacral nerve roots (S1 and S2),
and obturator nerve.
The sacrum is wedged between the two iliac bones, where it
is maintained by the SIJs, characterised by limited and irregular
mobility, and by the fan-shaped posterior ligament system that
divides the forces communicated by the spine to the sacral plateau,
transferring them in turn to the two hemi-pelvises and hips (Fig. 7).
In the coronal plane, the SIJ facets are directed obliquely downwards and medially. Consequently, the greater the weight applied
to the sacral plateau, the more the sacrum descends between the
two iliac wings, thereby increasing the tension placed on the ligaments (Fig. 8). In the horizontal plane, the sacrum tends to slip
forwards to compensate for the downwards displacement, but due
to the interlocking of its joint surfaces with those of the iliac wings
at the pelvic inlet, it forms a posterior-based wedge.
During movements, the SIJ surfaces glide on each other to absorb
and withstand the mechanical loads. Mobility at the SIJ is very
small and usually barely perceptible. Movements occur in all three
planes and include linear and angular displacements, which may
be symmetrical or asymmetrical (Fig. 9). The sacrum is mobile
between the two fixed iliac bones and can rotate in either direction
around its transverse axis. These movements are known as nutation and counter-nutation. Farabeuf convincingly identified the
Fig. 4. Ilio-lumbar ligament. © Cyrille Martinet.
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anterior displacement of the distal end of the sacrum and is facilitated by hip extension. The gliding distance has been measured
at 4 to 8 mm [7,8]. However, the most widely recognised data are
those obtained by Sturesson et al. [10] using a stereotactic method
with hip flexion on one side and hip extension on the other. When
the sacrum is fixed, the iliac bone can tilt anteriorly or posteriorly.
The nutation/counter-nutation movement described in Fig. 5 is the
usual movement. Its amplitude as measured with great accuracy
by Sturesson et al. is 2.
In the coronal plane in the bipedal stance position, the weight of
the body applied to the sacrum is theoretically divided in two, with
one half being transferred to each SIJ then to each femoral head.
The weight of the body tends to push the sacrum downwards and
forwards. The resulting nutcracker effect locks the SIJs, as discussed
above.
This model is only theoretical, however, as the loads on the
sacrum are not divided equally between the two sides. The angle
formed by the contacting auricular surfaces is about 12 in the coronal plane. Thus, the SIJs transfer 80% of the loads transversally to
the acetabula, leaving 20% that are transferred vertically. Thus, the
SIJs fragment the weight of the body.
Studies of the relationships between the spine in its entirety
and the pelvis have highlighted the key role played by the SIJs.
Roussouly et al. [11] have devised a classification of sagittal spinal
alignment that helps to analyse the variations in the role of the
SIJs according to body habitus. Thus, joint surface angulation varies
with body habitus.
Movement amplitude at the SIJ is 40% less in males than in
females [10]. During pregnancy, the high hormone levels considerably increase the flexibility of the ligaments. The ligaments may
also be slack in very elderly individuals.
In sum
• the SIJs receive continuous stress due to nutation and
counter-nutation movements during standing and walking;
• the SIJs are stabilised by strong anterior and posterior capsular and ligamentous structures, which receive an abundant
nerve supply;
• further stabilisation is provided by the latissimus dorsi, gluteus maximus, and piriformis muscles.
3. How can sacro-iliac joint (SIJ) disorders be diagnosed?
3.1. Pain non related to SIJ
Fig. 5. A. Muscles that stabilise the sacro-iliac joint: latissimus dorsi via the thoracolumbar fascia, gluteus maximus, and piriformis (Robert R et al. [7]). B. Mobility at
the sacro-iliac joint and relative movements of the iliac wings. © Cyrille Martinet.
axis of nutation/counter-nutation as running horizontally through
the body of the inter-osseous ligament (i.e., posterior to the SIJs).
Bonnaire described an axis running through the centres of the
sacral auricular surfaces and Weisel two axes, one anterior to the
SIJ surface for rotation and the other at a distance for translation.
However, there is no evidence that these other axes are relevant
[9].
Nutation of the SIJ consists in posterior displacement of the distal end of the sacrum when the sacral groove moves along the iliac
ridge. Hip flexion facilitates nutation. Counter-nutation consists in
Referred pain must be differentiated from specific SIJ pain. To
this end, the many conditions unrelated to the SIJs must be ruled
out.
3.1.1. Pain due to spinal conditions
Maigne et al. have argued that pain ascribed to the SIJs is usually
due to disorders of the thoracic and lumbar spine [12], based on
the fact that the cutaneous and subcutaneous tissues at the upper
buttocks and retro-sacral area (including the sacro-iliac region) are
innervated by dorsal branches of the spinal nerves emerging at the
thoraco-lumbar junction. According to these authors, low back pain
attributed to a locked SIJ may often have its source at T12-L1, with
a tender point at the iliac crest and tenderness of the buttock soft
tissues. Pain arising from the ilio-lumbar ligaments is more difficult
to identify, particularly as it frequently co-exists with pain from the
SIJ.
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Fig. 6. Innervation. A. Innervation of the posterior aspect of the sacro-iliac joint. 1. Posterior branch of the second sacral root. B. Innervation of the anterior aspect of the
sacro-iliac joint. 1. Lateral cutaneous nerve of the thigh. 2. Femoral nerve. 3. Genito-femoral nerve. 4. Obturator nerve. 5. Gluteal nerve. 6. Ischiatic nerve. 7. Pudendal nerve.
© Cyrille Martinet.
to the SIJs. Piriformis syndrome can co-exist with an SIJ disorder
or exist in isolation; the pain is replicated by palpation, stretching,
and contraction of the piriformis during hip mobilisation.
3.1.5. Pain due to neurological conditions
Pudendal nerve irritation, although relatively common (1% to
2%), often goes unrecognised, leading to diagnostic wanderings
[14]. Most cases (65%) are due to entrapment of the nerve between
the sacro-tuberous and sacro-spinous ligaments. In 15% of cases,
the nerve is entrapped in Alcock’s canal by the fascia of the internal
obturator muscle. The pain, which may be excruciating, generally
manifests as burning or electrical-shock sensations. The pain develops during the day and is exacerbated by the seated position, so that
the patients often remain standing to obtain relief. The pudendal
nerve supplies the urinary tract, the anus and rectum, the perineum,
and the genitalia. The site of the pain due to pudendal nerve irritation varies across individuals. The definitive diagnosis requires an
electrophysiological study of the sacral reflexes at multiple levels,
as well as ultrasonography and Doppler imaging.
3.1.6. Bone pain
Osteoporosis may result in an H-shaped sacral fracture that may
cause pain at the postero-superior iliac spine. The diagnosis is provided by CT of the pelvis.
Fig. 7. Biomechanics: transmission of forces from the spine to the pelvi.
3.1.2. Pain due to hip disease
Hip disease is usually easy to recognise based on the clinical
and radiological findings. However, the diagnosis may be difficult
to rule out clinically, as many of the manoeuvres used to test the
SIJ also mobilise the hip.
3.1.3. Pain originating in the pelvic organs
Pain due to pelvic disorders may be referred to the SIJs.
3.1.4. Pain arising in the muscles
Simons and Travell [13] showed that pain from myofascial
trigger points at the gluteal, quadratus lumborum, ilio-psoas, multifidus, rectus abdominus, and piriformis muscles is often referred
3.2. Inflammatory diseases responsible for SIJ pain must be ruled
out
SIJ pain may be caused, not by micro-trauma, but by
inflammatory diseases, notably rheumatic diseases such as the
spondyloarthropathies. These diseases directly involve the joint,
where gradual destruction of the cartilage surfaces may eventually
result in complete joint fusion. The diagnosis relies both on blood
tests and on imaging studies including radiographs, CT and, in some
cases, MRI. Inflammatory diseases are not considered here. They are
managed nearly only by pharmacological means.
Other differential diagnoses that must be ruled out by appropriate investigations include infections (due to staphylococci, brucella,
or tuberculosis), tumours, and metabolic disorders.
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Fig. 8. Biomechanics: the sacro-iliac joints are squeezed between the sacrum and iliac bones. A. Direction of the forces that ensure the posterior cohesion of the sacro-iliac
joints. B. Direction of the forces that ensure the anterior cohesion of the sacro-iliac joints. C. Ground reaction forces that ensure cohesion of the sacro-iliac joints. © Cyrille
Martinet.
SIJ disorders related to spinal surgery have received growing interest due to the huge increase in the number of lumbar
and lumbo-sacral fusion procedures performed over the last two
decades. Ha et al. [16] found that 75% of patients managed with
lumbo-sacral fusion reported SIJ pain 5 years later compared to
only 38% of controls. Despite persistent controversy, many recent
studies support an adverse impact of spinal fusion on the SIJs. Further plausibility is provided by the fact that lumbo-sacral fusion
eliminates all adaptation capabilities at the L5-S1 junction, thereby
transferring the stresses to the SIJs. Additional stresses may arise
from the failure in many fusion procedures to restore the normal
lumbo-sacral lordosis, notably between L4 and S1. Insufficient lordosis is a recognised contributor to alterations at the proximal end
of the instrumentation, with proximal junctional kyphosis or failure [17]. Similarly, the SIJ, located distal to the fused segment, may
be subjected to major stresses. Thus, Charles et al. [18] described 2
patients in whom long spinal fusion was followed by SIJ dislocation
that was documented by imaging studies and required SIJ fusion.
In sum
Idiopathic SIJ pain occurs in three main groups of patients:
Fig. 9. Radiograph view used to assess the sacro-iliac joint. This test, in contrast, is
appropriate for investigating sacro-iliac joint mobility.
3.3. This lecture focuses only on SIJ pain due to micro-trauma
Micro-trauma can subject the SIJ to undue stress, thereby
causing pain, a condition often known as idiopathic SIJ pain. Macrotrauma can also cause SIJ pain, often in the setting of a pelvic
fracture, but is not considered here. However, this discussion does
include sports-related injuries responsible for pubic symphysis
instability, which frequently causes SIJ pain and can occur as part
of the complex syndrome known as pubalgia.
Idiopathic SIJ pain can also develop during pregnancy, which is
normally associated with pubic symphysis instability. Persistence
of this instability in middle-aged multiparous women may also
cause chronic SIJ pain [15].
• pregnant women, in whom the pain resolves within a few
months after delivery;
• athletes and manual workers who maintain an asymmetrical posture involuntarily, due to poor technique when
performing required gestures, or to compensate for another
abnormality (such as leg length discrepancy or scoliosis);
• patients with a history of lumbo-sacral fusion, which eliminates shock-absorption by the distal lumbar disks, thereby
increasing the stresses applied to the SIJs.
4. What are the signs of sacro-iliac joint (SIJ) dysfunction
due to micro-trauma?
4.1. Clinical assessment of the SIJs [19]
The SIJs can produce a wealth of clinical symptoms, which,
however, show considerable overlap with symptoms from
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Fig. 10. The clinical provocation tests. A. Posterior pelvic pain provocation test (P4 test) or Östgaard test: gentle compression along the axis of the femur with the hip flexed
at 90◦ . B. Flexion, abduction, and external rotation test (FABER test). C. Sacro-iliac compression test. D. Gaenslen test. E. Active straight leg-raising test (active Lasègue test).
F. Long dorsal ligament (LDL) test, or finger sign: exquisitely tender point over the sacro-iliac joint. G. Distraction test.
neighbouring structures. Thus, pain from the SIJs may be erroneously ascribed to other sources such as the entheses, given
the large number of neighbouring ligaments (e.g., the ilio-lumbar,
sacro-spinous, and sacro-tuberous ligaments). Other potential
sources of error include neurogenic pain, referred pain from pelvic
organs, and myo-fascial syndromes.
Nevertheless, several clinical manifestations have been well
described and can be identified. A diagnosis of SIJ pain requires
a positive result on at least three of the following six provocation
tests designed to trigger SIJ pain (Fig. 10).
Posterior pelvic pain provocation test (P4 test) or Östgaard test:
the patient is supine with the hip flexed to 90◦ and the knee flexed
while the examiner applies moderate pressure (about 5 kg) axially
along the femur towards the floor.
Flexion, abduction, and external rotation test (FABER test):
the patient is supine with the hip flexed and abducted, and the
examiner stabilises the pelvis by maintaining the iliac crest on the
opposite side while gradually applying pressure to the flexed knee
to externally rotate the thigh.
Sacro-iliac compression test: the patient lies on one side and the
examiner applies pressure to the iliac crest, thus moving the iliac
wings closer together.
Gaenslen test: the patient lies on one side with the hip straight
and the knee flexed while the examiner uses one hand to extend
the hip and the other to stabilise the iliac wing (this test is similar
to the Léry test).
Long dorsal ligament (LDL) test, also known as the finger sign,
first described by Vleeming et al. [20]: the examiner applies pressure to the LDL over the proximal portion of the SIJ.
Active straight leg-raising test (active Lasègue test): this functional test is performed by the patient, who lies supine and lifts the
lower limb while keeping the knee extended [21].
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Fig. 11. Test injection via the posterior approach using a fine epidural-type needle.
When at least three of these tests are positive, there is a strong
suspicion of idiopathic SIJ pain related to micro-trauma and a test
injection should be recommended [22].
4.2. Test injections are part of the diagnostic strategy
A positive response (pain relief) to repeated test injections correlates with treatment efficacy [23]. Flawless technique must be
applied. Local anaesthesia is administered and strict aseptic technique followed. With the patient prone, fluoroscopy is used to
locate the SIJ (with a slightly oblique X-ray beam), and a fine epidural needle is then inserted at the distal part of the joint (Fig. 11). A
contrast agent is injected to check that the needle is properly positioned. An anaesthetic is then injected, followed in some cases by
a corticosteroid. The total volume injected must not exceed 2 mL.
When the test is positive, the pain relief is dramatic [19]. Thus, a
patient who could not perform the active straight leg-raising test
becomes able to lift the leg without pain.
5.3. Magnetic resonance imaging (MRI)
MRI may show sclerosis of the edges of the SIJ in patients with
chronic inflammatory sacro-iliitis or post-traumatic sequelae. In
patients with SIJ pain due to microtrauma, however, the CT findings
remain within the normal range.
5.4. Scintigraphy
Scintigraphy is sensitive but lacks specificity and has not been
proven helpful [12].
5.5. Ultrasonography
Ultrasonography is not typically used for the SIJ. However, some
studies suggest that Doppler imaging of the vascular network about
the joint may provide the diagnosis of active sacro-iliitis.
In sum
In sum
The clinical diagnosis of idiopathic SIJ pain due to microtrauma is strongly suspected based on a positive response to
three or four of six provocation tests described above and is
then confirmed by a positive fluoroscopy-guided local injection of anaesthetic, defined as reversion to negative of the
provocation tests.
• Few investigations are capable of confirming a diagnosis of
idiopathic SIJ pain due to micro-trauma;
• Findings are normal from radiographs and MRI, which serve
chiefly to rule out other diagnoses;
• Single-photon emission CT has not been proven effective in
establishing the diagnosis.
6. How should idiopathic sacro-iliac joint (SIJ) pain be
treated?
5. What imaging studies are needed?
6.1. Available treatment options
5.1. The standard imaging study is an antero-posterior
radiograph of the pelvis
CT may be needed also in patients with subacute or chronic pain.
MRI may be indicated in patients with recent-onset pain and in
young patients.
The main goal is to rule out a rheumatic disease responsible
for erosions, subchondral hyperostosis, or trans-articular fusion,
whose location is suggestive.
5.2. Computed tomography (CT) and scintigraphy
CT provides an accurate evaluation of erosions, as well as a map
of the mechanical and inflammatory lesions. However, CT makes
no contribution to the diagnosis of chronic idiopathic lesions.
6.1.1. Non-operative treatments, physiotherapy
Non-operative treatments are rarely used. The physiotherapy
methods are described as designed to increase SIJ coaptation and
stability. They have been used chiefly during pregnancy and postpartum period. Treatment with pelvic belts has been reported [24].
In pregnant women with SIJ pain, Nilsson-Wikmar et al. [25]
evaluated three physical therapy treatments, a non-elastic sacroiliac belt, the same belt plus daily home exercises, and the same
belt plus an in-clinic exercise programme. No significant differences were found among the three groups. In all three groups,
the pain abated between gestation week 38 and 12 months postpartum. The authors concluded that exercises were not effective.
Stuge et al. [26] reported similar findings and emphasised the need
for adjusting the physical therapy programme to each individual
patient, confirming the absence of a well-defined protocol.
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Fig. 12. Techniques for achieving posterior denervation of the sacro-iliac joint. A. Denervation of the sacro-iliac joint using the SimplicityTM probe: principle shown on a
cadaver specimen. B. Denervation of the sacro-iliac joint using a water-cooled electrode: temperature declines as distance from the electrode tip increases but the active
surface area is nearly 1 cm2 .
Many studies have evaluated manual therapies applied by
osteopaths or chiropractors [27]. However, they used a variety
of techniques with no clearly defined protocol, precluding definitive conclusions about efficacy. In the only well-designed study,
manipulation failed to significantly alleviate SIJ pain [28]. Using a
stereophotogrammetric technique, Tullberg et al. [29] showed that
neither manipulation nor local injections altered SIJ position while
standing.
Thus, whether manual therapies can provide benefits is vigorously debated. The only validated point is that sufficiently
well-developed quadriceps, abdominal, and hamstring muscles are
needed to ensure coaptation and stability of the SIJ, which they
control actively.
Another non-operative option is prolotherapy, in which a nonpharmacological substance such as dextrose or platelet-rich plasma
is injected into or about the joint. The rationale is that the injections might strengthen the SIJ connective tissues, thereby inducing
pain relief. Many studies providing low-level evidence have been
published, as well as a single randomised controlled trial (RCT)
of dextrose vs. local corticosteroid therapy [30]. In the trial, the
two groups showed similar improvements 2 weeks after the injection, whereas after 15 months a significantly higher proportion of
patients had at least 50% pain relief in the dextrose group (58.7%
vs. 10.2% in the corticosteroid group). A Cochrane review by Dagenais et al. [31] of prolotherapy for low back pain showed that the
absence of control groups and poor quality of most studies precluded conclusions about efficacy.
6.1.2. Local corticosteroid injections
Local corticosteroid injections into or around the SIJ are widely
used. The injection into the joint of a corticosteroid combined with
a local anaesthetic serves to confirm the diagnosis of pain from
the SIJ. As a therapeutic intervention, local corticosteroid injection has chiefly been used to treat inflammatory diseases in small
groups of patients. The results varied widely and were not sustained
over time. Only two RCTs of local corticosteroid injections to treat
idiopathic SIJ pain are available [32,33].
In one of the RCTs, 24 patients without spondyloarthropathy
were allocated at random to a peri-articular injection of either a
corticosteroid and lidocaine or saline and lidocaine, in a volume of
3 mL. After 2 months, efficacy as assessed based on SIJ provocation
tests was better in the corticosteroid group.
The other RCT included 20 patients with seronegative spondyloarthropathy, who were also randomised to a local anaesthetic
with or without a corticosteroid. At the 2-month assessment, pain
relief was significantly greater in the corticosteroid group.
The other published studies discussed by Luukkainen et al.
[32,33] used a retrospective or other non-randomised design and
did not provide proof of efficacy.
6.1.3. Radiofrequency denervation
Radiofrequency denervation was first advocated by Shealy [34].
A radiofrequency device is applied percutaneously to disrupt the
dorsal lateral branches of the S2, S3, and S4 nerve roots, which supply the SIJ. However, only the dorsal sensory fibres are accessible to
the radiofrequency waves and the treatment therefore has no effect
on the sensory nerve fibres supplying the anterior part of the joint.
Dreyfuss et al. conducted a double-blind RCT in 20 healthy volunteers to assess the effects of injecting a local anaesthetic around
the dorsal lateral nerve branches supplying the SIJ [35]. The results
suggest that radiofrequency neurotomy of the lateral branches to
the SIJ may be more effective than intra-articular injections. This
study therefore supports the use of radiofrequency to denervate
the SIJ ligaments.
However, part of the nerve supply to the SIJ comes from the L4,
L5, and S1 nerve roots. This diversity in the sources of SIJ innervation
may substantially limit the efficacy of radiofrequency denervation,
which chiefly disrupts the dorsal branches of the S1, S2, and S3
nerve roots.
The relative success of radiofrequency denervation has encouraged the development of new techniques. Sophisticated electrodes
have thus been devised to locate the nerve branches relative to
bony landmarks (posterior sacral foramina).
Water-cooled radiofrequency systems use water to cool the
electrode, thus allowing thermolysis of a larger volume without
inducing unwanted tissue damage.
The SimplicityTM probe (Abbott, Chicago, IL, USA) creates a
continuous strip lesion via three active electrodes, each of which
targets one of three consecutive sacral foramina on the same side
(Fig. 12).
Cohen et al. [36] conducted an RCT comparing water-cooled
radiofrequency denervation versus a sham procedure in 28
patients. After 3 and 6 months, a 3-fold greater pain decrease was
noted in the radiofrequency group compared to the sham group.
Although these techniques seem promising, multicentre RCTs
are needed to confirm the good preliminary findings, since the
therapeutic effects seem to deteriorate in the medium term.
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J.C. Le Huec et al. / Orthopaedics & Traumatology: Surgery & Research 105 (2019) S31–S42
Fig. 13. Treatment by an external fixation frame.
6.1.4. Surgery
Although several techniques have been reported, few of them
have been evaluated in well-designed studies, particularly RCTs.
Most studies involved screw fixation in patients with posttraumatic lesions. Nevertheless, several small studies focused on
arthrodesis to treat SIJ pain due to micro-trauma [37,38] and refractory to non-operative and minimally invasive treatments.
Three small studies published before 2006 assessed SIJ arthrodesis by screw fixation and bone grafting through a direct and fairly
aggressive surgical approach [37–39]. The outcomes were rather
disappointing, with success rates ranging from 50% to 70%. In the
study by Schutz and Grob [39], 82% of patients were dissatisfied
and 65% required revision surgery.
A 1999 report by Sturesson et al. [40] describes the effects
of external frame fixation on the SIJs (Fig. 13). The frame was
used initially to confirm its effectiveness in alleviating the pain
and subsequently for immobilisation after SIJ arthrodesis using
Gaenslen’s technique via the trans-iliac approach. The outcome
was excellent in 24 patients and fair in 13 patients, with the
remaining 3 patients having no improvement. Half the patients
returned to work. Despite the discomfort induced by the frame,
which had to be worn until complete healing was achieved, the
results were extremely encouraging. Nevertheless, infection of
the fixator pin sites was common. With a modified arthrodesis
technique involving percutaneous trans-ilio-sacral screw fixation
®
under fluoroscopic guidance, the success rate was similar and the
risk of pin-site infection was eliminated.
In 2010, a new and minimally invasive technique was described
at the 7th World Congress of low back pain held in Los Angeles (unpublished data). Three cross-sectionally triangular porous
metal implants are implanted percutaneously under fluoroscopic
guidance or, more recently, intra-operative navigation (Fig. 14).
This minimally invasive procedure is performed under general
anaesthesia with the patient in the prone position. The SIJ is located
either by fluoroscopy using two projections, inlet and outlet, which
clearly delineate the SIJ contours; or by intra-operative navigation
after pre-operative CT. A 3-cm incision is made laterally along the
projection on the skin of the plane of the SIJ. Two or three 2-mm
guidewires are inserted through the iliac bone, across the SIJ, and
finally into the sacrum, taking care to avoid the foramina. Each
guide wire is advanced into the sacrum to the midline as seen on
an antero-posterior view. A drill is then used to increase the diameter until an impactor can be inserted to prepare the trajectory of
the implant. The final implant is then inserted over the guide wire
and forcefully press-fit in place. The end of the porous titanium
implant should be flush with the lateral cortex of the iliac bone.
The procedure can be performed on a day-care basis, with immediate post-operative weight bearing and use of a walker for the first
3 weeks.
Three multicentre prospective studies have been performed
using this implant (iFuse, SI-Bone, San Jose, CA, USA).
A multicentre prospective study done in the USA showed good
2-year outcomes with significant pain relief by about 50% after 1
year and improvements in quality-of-life scores [41].
A multicentre RCT compared iFuse implantation to nonoperative therapy [42]. After 2-years, outcomes with the implant
were significantly better regarding pain relief and the SF-36
quality-of-life score.
A European multicentre RCT also compared iFuse implantation
to non-operative therapy [43]. Preliminary results recorded after 1
year are consistent with those of the two earlier studies.
Other groups applied the same principle with technical variations designed to improve stability and fusion rates.
Rappoport et al. [44] reported a prospective 1-year study in 32
patients who underwent SIJ fusion by the percutaneous insertion
of a hydroxyapatite-coated screw. Outcomes were satisfactory with
all pre-operatively employed patients returning to work within 3
months.
®
Fuchs and Ruhl [45] used the Diana implant (Signus, Medizintechnik GmbH, Alzenau, Germany), which resembles a hollow,
cylindrical, inter-body cage. The implant is fixed using screws
between the two surfaces of the SIJ. The fusion rate was only 31%
after 2 years, although 73% of patients reported pain relief and 49%
decreased their intake of analgesics. There would not seem to be
a satisfactory mechanical rationale for using joint distraction at a
joint subjected to shear forces.
Fig. 14. Treatment by percutaneous insertion of an Si-Bone implant under computed tomography guidance. A. Coronal computed tomography view showing the three
porous metal implants. B. Sagittal computed tomography view indicating that the implants are properly positioned.
J.C. Le Huec et al. / Orthopaedics & Traumatology: Surgery & Research 105 (2019) S31–S42
The current brisk increase in the use of implants to treat patients
with SIJ pain is somewhat alarming. Well-designed RCTs are needed
to validate the various suggested techniques, some of which seem
devoid of a biomechanical rationale.
6.2. Therapeutic management algorithm
An algorithm for managing idiopathic SIJ pain due to microtrauma would appear helpful.
Although some patients have a history of trivial trauma, such
as a fall on the buttocks or lifting a heavy weight, most report no
previous trauma. Referred pain and pain from inflammatory disease
must be ruled out. Lumbo-sacral fusion is a source of micro-trauma
that can cause idiopathic SIJ pain.
The physical examination should eliminate disorders of the hip
and lumbar spine. The clinical provocation tests help to orient the
diagnosis towards a disorder of the SIJ. In patients with at least
three positive provocation tests, a diagnostic test injection of local
anaesthetic into the joint and surrounding ligaments should be
performed to confirm the diagnosis.
An antero-posterior radiograph or CT scan should be obtained
to rule out an inflammatory disease and EOS imaging to evaluate
sagittal balance. In doubtful cases, MRI is the best investigation
for identifying inflammatory disease and determining which blood
tests and other imaging studies are appropriate.
The diagnostic test injection of a local anaesthetic in and about
the joint is positive if it provides complete pain relief, particularly
during the active straight leg-raising test.
Physical therapy should consist only in stretching exercises and
in strengthening the latissimus dorsi, gluteus medius, and hamstring muscles.
Radiofrequency denervation of the dorsal rami has been proven
effective, particularly with the larger active surfaces of lastgeneration probes.
Finally, in patients with refractory pain, SIJ fusion can be performed. Minimally invasive techniques involving trans-sacro-iliac
fixation deserve preference, as they seem to have provided the best
results in recent RCTs.
7. Conclusion take-home messages
The SJI connects the spine to the lower limbs and is subjected
to major shear forces. In clinical practice, three situations may be
encountered.
The very limited mobility of the SIJ increases during pregnancy
and the post-partum period, often causing pain, which resolves
within a few months after delivery.
Activities during sports or work may result in micro-trauma due
to repetitive, ill-designed, and often asymmetrical movements that
place excessive strain on the SIJ capsule and ligaments. The resulting chronic SIJ pain must be differentiated from pain arising from
the hip or lumbar spine. Local test injections assist in the diagnosis and provide transient pain relief. Lasting pain relief can then be
obtained by radiofrequency denervation of the dorsal sacral rami.
Lumbo-sacral fusion also increases the stresses placed on the
SIJs, particularly when good sagittal balance is not restored.
The diagnosis of idiopathic SIJ pain rests on clinical provocation
tests followed, when positive, by a test injection of local anaesthetic, which relieves the pain.
Non-operative treatment combining physical therapy and
stretching seeks primarily to strengthen the latissimus dorsi,
gluteal, and hamstring muscles. Radiofrequency denervation of the
dorsal sensory rami has provided some measure of efficacy, which
may diminish over time. In refractory SIJ pain, minimally invasive
S41
trans-ilio-sacral fusion techniques are now available and produce
good success rates.
Disclosure of interest
Dr. Le Huec reports grants from medtronic, personal fees from
safeorthopaedics, non-financial support from tornier, outside the
submitted work. The other authors declare that they have no competing interest.
Funding
None.
Contributions of each author
J.C. Le Huec and A. Leglise wrote the article.
A. Tsoupras, P. Heraudet, and A. Celarier performed the literature
review.
B. Sturesson supervised the translation to English and contributed his clinical expertise.
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