Sacroiliac Joint Flashcards
1
Q
What is the orientation of the SIJ in the transverse plane?
A
Anterolaterally
2
Q
What are the functions of the SIJ?
A
Transmit forces from lumbar spine to: - Femur (when standing) - Ischial tuberosities (when sitting) Relieves stress: - Point of max. torsional strain in pelvis
3
Q
Why could the SIJ be classed as a diarthrodial joint?
A
2 articular surfaces
Separated by synovial fluid-filled cavity
Surrounded by joint capsule
4
Q
Why is the SIJ an atypical diarthrodial joint?
A
Also has fibrocartilage
Posterior capsule absent
Articular surfaces not smooth
5
Q
How could the joint be described in regards to the type?
A
Synovial in anterior 1/3
Fibrous in posterior 2/3
6
Q
Describe the inner layer of the SIJ capsule?
A
Synovial membrane (intima) 2-3 cellular layers Contains synovial villi which extend into joint
7
Q
What does the connective tissue of the outer fibrous layer of the SIJ capsule contain?
A
Fibroblasts
Blood vessels
Collagen fibres
8
Q
How does the joint capsule change with age?
A
Becomes more fibrous
9
Q
One part of the SIJ capsule is rudimentary/absent and the other is thin. Which is which?
A
Rudimentary/absent = Posterior capsule Thin = Anterior capsule
10
Q
What does the study by Sakomoto et al., (2013) say about the SIJ capsule?
A
90% of mechanosensitive units are found in the joint capsule
Nerve fibres in joint capsule:
- Joint disturbance = Pain
11
Q
What are useful references for overview of the SIJ and the joint capsule?
A
Bogduk, 2005
Cohen, 2005
Forst et al., 2017
12
Q
What is the general shape of the articular surfaces of the SIJ?
A
L or C shaped
13
Q
Describe the ‘undulating’ surfaces of the SIJ? What is its purpose?
A
Complementary depressions and elevations
- Increases stability by interlocking
- Protects from vertical shear force
14
Q
Describe the cranial limb of the articular surfaces of the SIJ?
A
Shorter
More horizontal
15
Q
Describe the caudal limb of the articular surfaces of the SIJ?
A
Longer
More vertical
16
Q
How do the articular surfaces vary between the sexes?
A
Sacral surface is smaller in females:
- Only covers S1-S2 (vs S1-S3 in males)
17
Q
What does the high coefficient of friction of the SIJ infer?
A
High stability
18
Q
Describe the articular cartilage of the sacral surface of the SIJ?
A
Typical hyaline cartilage
White, glossy and smooth
1-3mm thick (2-3x thicker than iliac)
Doesn’t change much throughout life
19
Q
How does Paquin, (1983) describe the iliac articular cartilage of the SIJ?
A
Special hyaline
20
Q
How does Kampen and Tillmann, (1998) describe the iliac articular cartilage of the SIJ?
A
Fibrocartilage in childhood
Hyaline as it matures
21
Q
How does Tuite, (2008) describe the iliac articular cartilage of the SIJ?
A
Both surfaces are hyaline inferiorly
Cartilage thinner on iliac surface (<1mm):
22
Q
What reasons does Tuite, (2008) suggest may be why the iliac articular cartilage is thinner than the sacral cartilage of the SIJ?
A
It only absorbs forces (vs the sacral surfaces transmitting them)
Only stressed by vertical shear
23
Q
How does the sacral articular surface appear histologically?
A
Thick
Similar to hyaline cartilage in limb joints
24
Q
How does the iliac articular surface appear histologically?
A
Thin
Rich in perpendicular and oblique collagen fibre bundles
25
Where is an accessory SIJ found?
Posterior to true SIJ between:
- Medial aspect of PSIS and
- Transverse tuberosity lateral to 2nd sacral foramen
26
What is the incidence of accessory SIJ in CT scans and cadavers? (Reference?)
13/100 CT scans
9/56 cadavers
(Ehara et al., 1998)
27
In what populations are accessory SIJs more common? (Reference?)
Elderly
Obese patients
(Prassopoulos et al., 1999)
28
What variations of the SIJ are more common in women?
Iliosacral complex
Bipartite iliac bony plate
Crescent-like iliac bony plate
29
What are the two less common SIJ variations?
Semicircular defects on both surfaces of SIJ
| Ossification centres
30
What are the prevalence rates of the 6 variations of the SIJ according to Prassopoulos et al., (1999)?
```
Accessory SIJ = 19.1%
Iliosacral complex = 5.8%
Bipartite iliac bony plate = 4.1%
Crescent-like iliac bony plate = 3.7%
Semicircular defects on both surfaces of SIJ = 3%
Ossification centres = 0.6%
```
31
What is the course of the anterior sacroiliac ligament?
From ala and pelvic surface of sacrum
| To adjoining margin of anterior surface of ilium
32
What is the anterior sacroiliac ligament an extension of?
Anterior joint capsule
33
What does the anterior sacroiliac ligament prevent?
Anterior diastasis of SIJ
34
What causes the greatest stress to the anterior sacroiliac ligament?
Axial loading
35
Where does the short posterior sacroiliac ligament lie?
Superiorly
36
Where does the long posterior sacroiliac ligament lie?
Inferiorly
37
What is the posterior sacroiliac ligament a continuation of?
Fibrous tissue (capsule)
38
How do the fibres of the posterior sacroiliac ligament compress the sacrum between the ilia?
FIbres run anterolaterally:
- Axial weight pulls ilia medially
- Compresses sacrum
- Locks congruent articular surfaces of SIJ
39
What is the course of the long posterior sacroiliac ligament?
Fibres run vertically:
- From PSIS
- To 3rd/4th transverse tubercles of sacrum
40
What is the function of the long posterior sacroiliac ligament?
Prevents excessive counternutation:
- Sacral promontory moving posterosuperiorly
- Ilia moving anteriorly on sacrum
41
What does the long posterior sacroiliac ligament work with to prevent SIJ separation?
Interosseous SIJ ligament
42
What is the course of the short posterior sacroiliac ligament?
Runs from 1st/2nd transverse tubercles
| TO iliac tuberosity
43
What is the function of the short posterior sacroiliac ligament?
Limits nutation:
- Forward movement of sacral promontory
Resists anterior displacement of SIJ
44
Where does the interosseous sacroiliac ligament lie?
In recess between sacrum and ilium dorsal to joint cavity
45
What is the function of the interosseous sacroiliac ligament?
Infers multi-directional stability
Very important in limiting movement:
- Severing it in cadavers increased joint movement
46
What is the deepest ligament of the SIJ?
Interosseous sacroiliac ligament
47
What is the course of the sacrotuberous ligament?
```
From:
- Posterior ilium
- Lateral sacrum
- Lateral coccyx
To ischial tuberosity
```
48
What is the function of the sacrotuberous ligament?
Anchors inferior sacrum to ischium:
| - Counterbalances rotation at superior sacrum
49
What is the course of the sacrospinous ligament?
From:
- Lateral sacrum
- Lateral coccyx
To ischial spine
50
What is the function of the sacrospinous ligament?
Perhaps acts as a fibrous part of coccygeus
51
Why are the sacrotuberous and sacrospinous ligaments important in high impact activities?
Superior sacrum receives great force via lumbar vertebrae
Weight transferred anterior to SIJ which would pull sacrum anteroinferiorly:
- Prevented by STL and SSL
52
What muscle, acting via the sacrotuberous ligament, stabilises the SIJ?
Long head of biceps femoris
53
What is the course of the iliolumbar ligament?
From tips of L4/L5 transverse processes
| To posterior iliac crest
54
What are the functions of the iliolumbar ligament?
Strengthens relationship between ilium and vertebral column
Prevents L5 from anterior displacement on S1
Opposes gliding movements between vertebrae
55
What is the reference for the iliolumbar ligament?
Palanstanga, 2013
56
When does the SIJ develop?
Initially thought to develop in week 10
| Recently suggested it develops in week 8
57
From what layers does the SIJ develop?
Three layers in pelvic mesenchyme:
1. Sacral cartilage
2. Iliac cartilage
3. Interposed zone of mesenchyme
58
In what zone of mesenchyme does the early articular cavity form?
Interposed zone of pelvic mesenchyme
59
When does the synovial membrane form and from what?
Shortly before birth
| Formed from mesenchyme surrounding edge of primordial central cavity
60
At what stage do bony ridges and bony grooves form on the bony surfaces of the SIJ?
Puberty
61
What is the arterial supply to the SIJ?
Anteriorly = Branches of iliolumbar artery
Posteriorly = Superior gluteal artery
Anteriorly and posteriorly = Lateral sacral arteries
62
Where do the venous draining the SIJ drain to?
Internal iliac vein
63
Where does lymph drain from the SIJ?
Internal iliac nodes
64
What is the anterior nervous supply to the SIJ?
L4-S2 ventral rami
65
What do earlier studies suggest give nervous supply to the anterior SIJ?
Obturator nerve
Superior gluteal nerve
Lumbosacral trunk
66
What is the posterior nervous supply to the SIJ?
Medial branches of L4-S3 dorsal rami
| Some studies also suggest contributions from L3 and S4
67
What do some studies also suggest about the nervous supply to the SIJ?
Anterior SIJ is devoid of nervous tissue
68
What 4 movements are possible at the SIJ?
Rotation
Translation
Nutation
Counternutation
69
What movements of the SIJ are possible in the x (transverse) axis?
Sacral rotation in sagittal plane:
- Nutation
- Counternutation
70
What movements of the SIJ are possible in the y (longitudinal) axis?
Sacral rotation in the horizontal plane
71
What movements of the SIJ are possible in the z (sagittal) axis?
Sacral rotation in the coronal plane
72
How much does SIJ movement decrease with age?
~40-50% in males
| ~50% in females
73
How is the amount of movement of the SIJ measured?
Roentgen stereophotogrammetric motion analysis (RSA)
74
How much rotation is possible at the SIJ?
Maximum is 4 degrees (mean is 2.5)
75
How much translation is possible at the SIJ?
Maximum is 1.6mm (mean is 0.7mm)
76
What IV joints do nutation and counternutation affect?
Mainly L5-S1 (but also those superior to it)
77
What ligaments resist nutation?
Sacrotuberous ligament
| Sacrospinous ligament
78
What ligament resist counternutation?
Long posterior sacroiliac ligament
79
How can pain at the SIJ arise with age?
Increased joint laxity with age
| Therefore increased counternutation = Pain
80
What is the combined range of counternutation in individuals older than 72?
4 degrees (normal is <2 degrees)
81
What is force closure?
Anticipation for SIJ loading
| Ligaments of SIJ tighten = Nutation
82
What induces force closure?
Sacral connections of erector spinae induce nutation by pulling ilia together
83
What is the course of the first pelvic trabecular system?
Arises from inferior auricular surface
| Runs in an arc shape toward superior surface of acetabulum
84
What does the first pelvic trabecular system align with?
Vertical trabeculae bundle:
| - Supports head and neck of femur
85
What is the course of the second pelvic trabecular system?
Begins at superior auricular surface
Runs to:
- Posterior border of greater sciatic notch
- Inferior border of acetabulum
86
What does the second pelvic trabecular system align with?
Arcuate bundle in femur
87
In what motion are the first and second pelvic trabecular systems important?
Bidepal motion
88
Why are there different pelvic trabecular system patterns in apes?
Different weight distribution
89
What is the alternate name for the third pelvic trabecular system?
Sacroischial trabeculae
90
What is the course of the third pelvic trabecular system?
Begins at auricular surface
| Extends to ischium
91
When is the third pelvic trabecular system important?
When sitting:
| - ischium supporting weight of body
92
At birth, the structure of the SIJ in humans is similar to that of quadrupeds. Why does it change with age?
Locomotion
93
How do the bony surfaces of the SIJ change after puberty?
Become rough
| Fibrous plaques form in some areas
94
What age related changes of the SIJ are seen in a person's 20s?
Fusion of sacral vertebrae
95
What age related changes of the SIJ are seen in a person's 30s and 40s?
More grooves
| Bony ridges on articular surface of ilium to increase stability
96
What age related changes of the SIJ are seen in a person's 50s?
Degeneration begins:
- Synovial articular surfaces erode
- Synovial cleft narrows to 1-2mm
97
What age related changes of the SIJ are seen in a person's 60s?
Capsule becomes more collaginous
98
What age related changes of the SIJ are seen in a person's 70s?
Synovial cleft only 0-1mm
| Ankylosis often present
99
What age related changes of the SIJ are seen in a person's 80s?
Erosions and plaques:
- Inevitable
- Pervasive
100
When does SIJ pain arise in pregnancy?
Week 18 of gestation
101
What causes SIJ pain in pregnancy?
Increased oestrogen and relaxin:
- Relaxation of ligaments
- Less SIJ interlocking
- Increased pelvic rotation
- Increased lordosis
102
What does SIJ ligament relaxation allow?
Increased SIJ diameter by 10-15% for passage of baby
103
In what women are SIJ changes during pregnancy more prominent?
Multiparous women
104
How does a sacroiliac belt reduce pain? (Reference?)
Reduces SIJ mobility
| Mens et al., 2006
105
What can cause a lateral compression injury to the SIJ?
RTAs
Fall from height (>15 feet)
Sports injuries
Crush injuries
106
What is the most common mechanism of injury to the SIJ?
Lateral compression
107
What does the mortality of a SIJ fracture depend on?
Severity of bleeding
| Presence of thoracic/abdominal injures
108
In what individuals are low energy stress fractures more common in?
Females
109
In what individuals are high energy fractures (lateral compression, AP compression or vertical shear) more common in?
Males
110
What conditions are SIJ fractures related to?
Osteoarthritis
| Ankylosing spondylitis
111
What are the three types of lateral compression and anterior pelvic rami fracture?
Type I = Ipsilateral sacral fracture
Type II = Ipsilateral crescent fracture
Type III = Ipsilateral Type I/II and contralateral open-book fracture
112
What are the three types of AP compression and symphysis diastasis injuries?
Type I = Minor opening of symphysis and anterior SIJ
Type II = Anterior SIJ opening but intact posterior ligs.
Type III = Complete SIJ disruption
113
What pelvic injury can a vertical shear force result in?
Displacement of hemipelvis
114
What is the classification system of pelvic fractures called?
Young-Burgess Classification
115
What is a crescent fracture?
Combination of:
- Vertical iliac fracture
- SIJ dislocation
116
What is a crescent fracture characterised by?
SIJ disruption:
| - Extended proximally as a fracture of posterior iliac wing
117
What are the three types of crescent fractures?
Type I = Less than or equal to 1/3 of SIJ dislocated
Type II = 1/3-2/3 of SIJ dislocated
Type III = More than or equal to 1/3 of SIJ dislocated
118
How long would a pelvic injury take to recover?
8-12 weeks
119
What are the benefits of ORIF for a pelvic fracture?
High success rate
120
How can the pelvis be stabilised prior to ORIF?
External fixation via pins in ilia
121
When might external fixation be enough in pelvic fractures?
If minimal displacement
122
What are the downsides of ORIF?
```
Long recovery
Risk of re-displacement
Surgical risks:
- Haemorrhage
- Infection
- Nerve damage
```
123
How is ORIF carried out in SIJ disruptions?
Plates
124
How is ORIF carried out in crescent fractures?
Screws
125
How is ORIF carried out in sacral fractures?
Screws
126
What can improve outcomes in pelvic injuries?
Early stabilisation of pelvic ring
127
What injury has a worse prognosis; SIJ injuries of iliac wing fractures?
SIJ injuries
128
What can pelvic injuries predispose the patient to?
SIJ dysfunction syndrome
129
What did Borg, (2011) find regarding the prognosis of pelvic injuries?
30% satisfied with QoL post-surgery:
- 20% less than those who did not require surgery
10% unsatisifed
130
In pelvic fractures, what injuries can the strong ligaments cause?
Avulsion fractures
131
What SIJ ligaments are most likely to be ruptured with pelvic fractures? What ligaments require a severe fracture to be disrupted
Anterior sacroiliac ligaments
| Posterior sacroiliac ligaments
132
Why are NSAIDs prescribed in pelvic fractures?
Ligament damage results in inflammation
Inflammation results in pain
NSAIDs reduce inflammation
133
What percentage of lower back pain cases are due to SIJ dysfunction?
15-25%
134
What injury mechanism tends to result in SIJ dysfunction?
Combination of:
- Axial loading and
- Abrupt rotation
135
What are some intra-articular causes of SIJ dysfunction?
Arthritis
| Inflammatory conditions
136
What are some extra-articular causes of SIJ dysfunction?
Enthesopathy
Fracture
Ligamentous damage
137
What factors can predispose to SIJ dysfunction?
```
Leg length discrepancy
Gait abnormalities
Prolonged vigorous exercise
Scoliosis
Spinal fusion to sacrum
Lumbar spine surgery
Pregnancy
```
138
What are the SIJ pain criteria?
1. Pain in region of SIJ
2. Stressing SIJs in clinical tests reproduces pain
3. Selectively infiltrating SIJ relieves pain
139
Where does SIJ pain radiate?
```
Buttocks (94%)
Thigh
Leg
Ankle/Foot
Groin
Abdomen
```
140
Why is SIJ dysfunction difficult to diagnose?
Cannot be diagnosed by:
- Examination
- Osteopathic or chiropractic techniques
- Imaging
141
What physical exam tests can be used to attempt to diagnose SIJ dysfunction?
Compression test
| Bilateral internal hip rotation test
142
How sensitive and specific is radionucleotide bone scanning for SIJ dysfunction?
13% sensitive
| 100% specific
143
Why can CT be useful in SIJ dysfunction?
Can find other potential pathologies
144
What does Bogduk, (2005) suggest is the only reliable way to diagnose SIJ dysfunction?
Analgesic response to small-volume local anaesthetic block
145
What is the basis of management of SIJ pain?
Target underlying pathology and alleviate symptoms
146
What conservative therapies can be used for SIJ dysfunction?
```
Shoe insoles if:
- Leg length discrepancies
- Gait abnormalities
Physiotherapy/Chiropractic techniques
Mobilisation-stabilisation
Pelvic belt
```
147
When is radiofrequency ablation used to treat SIJ pain?
If positive response to diagnostiv block
148
When might radiofrequency ablation not be successful in relieving pain?
If pain is from ventral SIJ
149
How else can SIJ pain be relieved?
Intra-articular hyaluronic acid injections
| Surgical arthrodesis
150
Why is the SIJ the 1st joint affected in ankylosing spondylitis?
Clefts in iliac cartilage allow osteophyte invasion
151
What is the most common SIJ disorder (especially if 40 years old +)? Is it usually unilateral or bilateral?
Osteoarthritis
| Unilateral
