Chapter 47 Pain Originating from the Buttock: Sacroiliac Joint Syndrome and Piriformis Syndrome

Question 1

The sacroiliac joint complex frequently classified as an

Answer 1

auricular-shaped diarthrodial joint because at various junctures it contains a fibrous joint capsule containing
thick synovial fluid, cartilaginous surfaces, and an intricate set of ligamentous connections

Question 2

The SI joint is supported by a

Answer 2

network of myofascial
structures that help promote movement, support, and stability.
These structures include the gluteus maximus and
medius, biceps femoris, piriformis, the latissimus dorsi via the thoracolumbar fascia, and the erector spinae

Question 3

The sacroiliac joint primarily designed for

Answer 3

stability and weight-bearing, though small degrees of rotation (<2 mm) occur

Question 4

The nerve supply of the SI joint complex

Answer 4

the posterior joint and the surrounding ligaments appear to receive
innervation from the S1-S3 dorsal rami, with most studies noting a contribution from L5

Question 5

innervation of the ventral SI joint

Answer 5

nerve filaments stemming from the ventral rami of L4–S2,7 other experts
cite contributions from levels as cephalad as L2

Question 6

The mechanism of injury to the SI joint complex

Answer 6

a combination of axial loading and abrupt rotation

Question 7

On an anatomic level, pathologic changes affecting myriad structures comprising the SI joint can lead to nociception. These include

Answer 7

capsular or synovial disruption, ligamentous injury, myofascial pain, hypo- or hyper-mobility, extraneous compression or shearing forces, cysts, abnormal joint mechanics, micro- or macro-fractures, chondromalacia, and inflammation.

Question 8

etiologies for SI joint pain these causes can be divided into

Answer 8

intra- and extra-articular sources.

Question 9

examples of intra-articular causes of SI joint pain.

Answer 9

Arthritis and infection
Spondyloarthropathy
Trauma
Cystic disease

Question 10

Extra-articular sources

Answer 10

enthesopathy,

fractures, ligamentous injury and myofascial pain, Pregnancy, Cystic disease

Question 11

In contrast to intra-articular

pathology, extra-articular pain is more likely to be

Answer 11

unilateral, occur in younger individuals, present with more prominent tenderness, and be associated with a specific inciting event or biomechanical etiologies

Question 12

Risk factors can predispose to the insidious

development of SI joint pain.

Answer 12

Risk factors that operate
by increasing the stress borne by the SI joints include obesity, leg length discrepancy, gait abnormalities, persistent
strain or low-grade trauma (e.g., jogging), scoliosis, pregnancy, and surgery, especially fusion to the sacrum

Question 13

Spine surgery may cause post-procedural SI joint pain

by

Answer 13

increasing load bearing, weakening the surrounding

ligaments, iatrogenic violation of the SI joint complex, and postsurgical hypermobility

Question 14

Pregnancy predisposes

women to SI joint pain via the

Answer 14

combination of increased

weight gain, exaggerated lordotic posture, the mechanical trauma of parturition, and hormone-induced ligamental laxity

Question 15

diagnose of SI joint

Answer 15

Sacroiliac joint pain can be difficult to distinguish from

other sources of LBP. no single historical or physical examination sign can reliably diagnose a painful SI joint

Question 16

the more common findings used to select candidates for SI joint blocks are

Answer 16

pain predominantly localized below L5, pain exacerbated by rising from a sitting
position, and tenderness overlying the joint. SI joint pain is more likely to be unilateral and follow a specific inciting event

Question 17

pain referral

patterns from SI joints.

Answer 17

The pain may radiate from the buttock to the ipsilateral thigh, groin, lumbar region or
posterior thigh and leg, but there is no pathognomonic
radiation pattern for pain from the SI joint

Question 18

the gold standards for detecting SI joint involvement in patients with seronegative spondylarthropathy.

Answer 18

MRI and CT scanning

Question 19

Differences between MRI and CT scanning

Answer 19

Whereas MRI may be
more sensitive for detecting inflammation and the accompanying
structural changes, CT remains the reference
standard for disease states in which bone destruction or
ossification can occur

Question 20

the most accurate means to diagnose a painful SI joint complex

Answer 20

an analgesic response to an SI joint injection

Question 21

How much to inject into SI joint?

Answer 21

response to low volume (, 2 ml) SI joint blocks have

generally been used as the reference standard

Question 22

The conservative treatment of SI joint pain should ideally address the underlying etiology.

Answer 22

True and functional leg
length discrepancies can be treated with shoe lifts and
physical therapy, respectively. True leg length discrepancies result in increased stress and abnormal force vectors
on the ipsilateral lower extremity.

Question 23

Functional leg length discrepancies usually occur as a result of

Answer 23

muscle weakness or inflexibility at the pelvis or
ankle. Specific causes include pelvic obliquity, adduction, or flexion contractures of the hip, and genu valgum andvarum.

Question 24

The treatment of apparent leg length discrepancies

entails

Answer 24

aggressive physical therapy that targets the underlying etiology. If malalignment is suspected, osteopathic
or chiropractic manipulation has been reported to be of value

Question 25

conservative treatment for patients with spondyloarthropathies

Answer 25

immunomodulating
agents such as cytokine inhibitors and
methotrexate may reduce disease progression, alleviate pain, and improve function.

Question 26

Practice guidelines have found exercise to be beneficial

for

Answer 26

nonspecific chronic low back pain, but it may be

particularly beneficial in patients with SI joint pain

Question 27

have become the treatment of choice for patients in

whom conservative treatments fail to provide long-term symptom palliation

Answer 27

Neuroablative techniques, especially radiofrequency denervation

Question 28

in conventional RF

techniques, the typical lesion diameter ranges between

Answer 28

3 mm and 4 mm in a single plane

Question 29

in conventional RF techniques have been adapted to enhance

lesion size and overcome obstacle of small lesion size

Answer 29

bipolar lesioning, internally cooled electrodes, and replacing RF electrodes with cryoprobes

Question 30

Radiofrequency denervation may not benefit everyone
with SI joint pain. Targeting the posterior nerve supply
does not address

Answer 30

pain emanating from the ventral aspect of the joint

Question 31

Sacroiliac joint arthrodesis has been previously employed to treat

Answer 31

fractures, instability/dislocations, and pain secondary to degenerative changes

Question 32

Piriformis syndrome

Answer 32

cause of buttock and leg pain

Question 33

The piriformis muscle originates from the

Answer 33

anterior surface
of the S2–S4 sacral vertebrae, the capsule of the sacroiliac
joint, and the gluteal surface of the ilium near the posterior
surface of the iliac spine

Question 34

piriformis muscle travels

Answer 34

It runs laterally through the
greater sciatic foramen, becomes tendinous, and inserts
into the piriformis fossa at the medial aspect of the greater
trochanter of the femur.

Question 35

piriformis muscle is innervated by

Answer 35

branches of the ventral rami of the L5, S1, and S2 spinal nerves.

Question 36

structures that travel below the piriformis muscle

Answer 36

sciatic nerve, posterior femoral cutaneous nerve, gluteal nerves, and the gluteal vessels

Question 37

Six possible anatomic relationships occur between the

sciatic nerve and the piriformis muscle

Answer 37

an undivided sciatic nerve passing below (most common) or above the piriformis
muscle, an undivided nerve passing through the piriformis, a divided nerve passing through and below the
muscle or through and above the muscle, and a divided nerve passing above and below the muscle.

Question 38

Anomalies of the piriformis muscle and the sciatic nerve can cause sciatica. The compression usually
occurs between the

Answer 38

tendinous portion of the muscle and the bony pelvis.

Question 39

In patients in which the piriformis muscle is anterior to the sciatic nerve, the compression
of the nerve occurs between

Answer 39

the superior border of the piriformis and the superior margin of the greater sciatic
foramen

Question 40

Etiologies and predisposing factors of the piriformis syndrome include

Answer 40

trauma to the pelvis or buttock, hypertrophy or spasm of the piriformis and/ or adjacent gemelli muscles, female gender, pregnancy, anatomic abnormalities of the piriformis muscle or the sciatic nerve, leg-length discrepancies (a
minimum of half an inch difference in leg lengths), obesity,
cerebral palsy secondary to hypertonicity, lumbar hyperlordosis, and infection

Question 41

Trauma to the buttock leads to

Answer 41

inflammation and
spasm of the piriformis muscle. Inflammatory substances such as prostaglandins,
histamine, bradykinin, and serotonin are released from the inflamed muscle and may irritate the sciatic nerve resulting in a pain–spasm–inflammation–irritation–pain vicious cycle.The stretched, spastic, and inflamed piriformis
muscle may compress the sciatic nerve between the muscle and the pelvis.

Question 42

piriformis syndrome is consider to be

a form of myofascial pain syndrome

Answer 42

Isolated involvement
of the piriformis muscle is uncommon and usually occurs
as a part of soft tissue injuries resulting from rotation and/
or flexion movements of the hip and torso

Question 43

the tendinous portion
of the piriformis muscle, which is often the major site of pathology (e.g., enthesopathy) combines with the tendons
of the

Answer 43

obturator and gemelli muscles before their

insertion on the greater trochanter.

Question 44

Piriformis syndrome

may occur after what surgeries?

Answer 44

total hip replacement surgery or laminectomy. The scar tissue after laminectomy impinges on the nerve roots and “shortens” the sciatic nerve, rendering it
prone to repeated tension and trauma by the piriformis muscle.

Question 45

The differential diagnoses of piriformis syndrome include

Answer 45

the myriad causes of low back pain and sciatica

Question 46

patients with piriformis syndrome, however, usually do not

have neurologic deficits unless there is

Answer 46

compression or

irritation of the sciatic nerve.

Question 47

differential diagnoses of piriformis syndrome

Answer 47

Facet syndrome, sacroiliac joint dysfunction, trochanteric and ischial bursitis, myofascial
pain syndrome, pelvic tumor, endometriosis, and conditions
irritating the sciatic nerve

Question 48

diagnoses of piriformis syndrome

Answer 48

diagnosis of piriformis syndrome

is usually arrived at only after exclusion of differentials

Question 49

cardinal features of the piriformis syndrome

Answer 49

l History of trauma to the sacroiliac and gluteal regions
l Pain in the buttock that radiates to the ipsilateral hip or
down the ipsilateral leg
l Pain with maneuvers that stretch the piriformis muscle
(Lasegue and Freiberg tests)

Question 50

Patients with piriformis syndrome usually complain of

Answer 50

buttock pain with or without radiation to the ipsilateral leg.The buttock pain usually extends from the sacrum to the
greater trochanter since the muscle inserts into the medial
aspect of the greater trochanter. Some patients may
have paralumbar pain. Gluteal pain radiating to the ipsilateral
leg is usually present if the piriformis muscle irritates the
sciatic nerve

Question 51

piriformis syndrome pain is generally aggravated by

Answer 51

prolonged sitting, as in driving or biking, or when getting up from a sitting position. Pain occurs with bowel movements due to the proximity of the piriformis muscle to the
lateral pelvic wall, and is worse after sitting on hard surfaces.
Female patients may complain of dyspareunia.

Question 52

piriformis syndrome Physical examination of the patient may reveal

Answer 52

a pelvic tilt or tenderness in the buttock from the medial edge of
the greater sciatic foramen to the greater trochanter. A spindle-shaped mass may be felt in the buttock and there may be piriformis tenderness on rectal and pelvic examinations

Question 53

piriformis syndrome pain

Answer 53

The pain is aggravated by hip flexion, adduction,

and internal rotation

Question 54

piriformis syndrome neurologic signs

Answer 54

Neurologic signs are usually absent, although there maybe numbness in the lower leg or foot from compression of the sciatic nerve by the piriformis muscle. The straight leg raising test may be normal or
limited, with numbness occurring when the sciatic nerve is irritated.

Question 55

physical examination signs may be

helpful in confirming the presence of piriformis syndrome

Answer 55

l Pace sign: pain and weakness on resisted abduction of the
hip while the patient is seated, (i.e. the hip is flexed).
l Lasegue sign: pain on voluntary flexion, adduction, and
internal rotation of the hip.
l Freiberg sign: pain on forced internal rotation of the extended thigh. This is due to stretching of the piriformis
muscle and pressure on the sciatic nerve at the sacrospinous ligament.

Question 56

function of the piriformis muscle

Answer 56

it is an adductor of the flexed thigh and an external rotator of
the extended hip.

Question 57

diagnosis of piriformis syndrome using studies

Answer 57

electromyography
(EMG), computed tomography (CT), and magnetic resonance
imaging (MRI) may show abnormalities.

Question 58

EMG diagnosis of piriformis syndrome

Answer 58

EMG may detect myopathic and neuropathic changes including a delay in the H-reflex with the affected leg in a flexed,
adducted, and internally rotated (FAIR) position as compared with the same H-reflex in the normal anatomic position. A three–standard-deviation prolongation of the
H-reflex has recently been recommended as the physiologic
criterion for piriformis syndrome.

Question 59

CT and MRI diagnosis of piriformis syndrome

Answer 59

CT and MRI
of the soft tissues of the pelvis often show an enlarged
piriformis muscle,84 whereas bone scan may demonstrate
increased radioactive uptake.

Question 60

treatment of piriformis syndrome includes

Answer 60

physical
therapy combined with the use of anti-inflammatory drugs,
analgesics, and muscle relaxants to reduce inflammation,
spasm, and pain

Question 61

Physical therapy for piriformis syndrome

Answer 61

involves stretching
of the piriformis muscle with flexion, adduction, and internal rotation of the hip followed by pressure applied to the piriformis muscle. Abnormal biomechanics caused by posture, pelvic obliquities, and leg length inequalities
should be corrected.

Question 62

Patients of piriformis syndrome do not

respond to conservative therapy are candidates for

Answer 62

local anesthetic and steroid injections. Most injections are into
the piriformis muscle with or without perisciatic nerve
injections. Caudal steroid and local anesthetic injections
have been anecdotally reported to be effective, presumably
because the injected solution diffuses along the nerve root sleeves to the proximal part of the sciatic nerve and blocks the nerves that innervate the piriformis muscle

Question 63

TECHNIQUES OF PIRIFORMIS MUSCLE

AND PERISCIATIC NERVE INJECTIONS

Answer 63

The sciatic nerve is located with a nerve stimulator, the needle is withdrawn a few centimeters, and 40 mg methylprednisolone in 5- to 10-ml dilute
local anesthetic is injected. Newer techniques involve identification of the piriformis muscle with a muscle EMG or with the use of CT guidance. fluoroscopy, and EMG are used to identify the
piriformis muscle. Correct needle placement is confirmed
with muscle EMG and injection of contrast media. The steroid is then injected into the piriformis muscle.

Question 64

TECHNIQUES OF PIRIFORMIS MUSCLE

AND PERISCIATIC NERVE INJECTIONS: CT-guided approach

Answer 64

the muscle is identified
and insertion of the needle is guided radiologically. Local
anesthetic (2 ml 0.5% bupivacaine) with steroid is injected
into the muscle, which may replaced by the injection of 100 units of botulinum toxin type A (BTX-A) if spasm or
hypertrophy is noted. One advantage of this approach is that it may better facilitate injections targeting the tendinous insertions of the external rotators of the hip (e.g., piriformis, gemelli, obturator internus muscles).

Question 65

TECHNIQUES OF PIRIFORMIS MUSCLE
AND PERISCIATIC NERVE INJECTIONS
uses the lower border of the sacroiliac
joint as the landmark.

Landmarks

Answer 65

The patient is placed prone and the lower border of the sacroiliac joint, greater sciatic foramen, and the head of the femur are identified by fluoroscopy.

Question 66

TECHNIQUES OF PIRIFORMIS MUSCLE
AND PERISCIATIC NERVE INJECTIONS
uses the lower border of the sacroiliac
joint as the landmark.

Needle placement

Answer 66

A 15-cm insulated needle connected to a nerve stimulator is inserted 1 to 2 cm lateral and 1 to 2 cm caudal to the lower border of the sacroiliac joint. The needle is advanced perpendicularly until a motor-evoked
response of the sciatic nerve is obtained at a depth between
7 and 10 cm.

Question 67

TECHNIQUES OF PIRIFORMIS MUSCLE
AND PERISCIATIC NERVE INJECTIONS
uses the lower border of the sacroiliac
joint as the landmark.

Evoked motor response

Answer 67

The evoked motor response of the foot can be inversion, eversion, dorsiflexion, or plantar flexion.

Question 68

TECHNIQUES OF PIRIFORMIS MUSCLE
AND PERISCIATIC NERVE INJECTIONS
uses the lower border of the sacroiliac
joint as the landmark.

Needle movement

Answer 68

The needle is pulled back 0.3 to 0.5 cm, to avoid intraneural injection, and corticosteroid (40 mg) mixed with saline is
injected to avoid sciatic nerve block.

Question 69

TECHNIQUES OF PIRIFORMIS MUSCLE
AND PERISCIATIC NERVE INJECTIONS
uses the lower border of the sacroiliac
joint as the landmark.

Injection of steroid

Answer 69

Injection of steroid
perisciatically is recommended even in the absence of signs
of sciatic nerve entrapment, because nerve inflammation is
common in this condition. The needle is then pulled back an additional 1.0 cm so that the tip of the needle lies in the belly of the piriformis muscle.

Question 70

TECHNIQUES OF PIRIFORMIS MUSCLE
AND PERISCIATIC NERVE INJECTIONS
uses the lower border of the sacroiliac
joint as the landmark.

injectant

Answer 70

A small volume of radiopaque contrast is injected (some use air to outline the muscle especially in the presence of contrast allergy) to confirm needle position before more steroid (40 mg), this time mixed with local anesthetic, is injected to reduce muscle swelling and/or spasm. Methylprednisolone
(40 mg) (or 40 mg triamcinolone) in 6 to 8 ml local anesthetic, is injected into the muscle to reduce the swelling
and/or spasm

Question 71

Botulinum toxin

Answer 71

may be injected into the muscle if the
patient has a transient response to steroid and local anesthetic.
Botulinum toxin blocks the release of acetylcholine
at the neuromuscular junction, resulting in prolonged relaxation

Question 72

Botulinum toxin Recovery

Answer 72

depends on neuromuscular sprouting and reinnervation of the muscle, which generally takes several weeks to months.

Question 73

The typical doses of botulinum toxin employed

Answer 73

100 mouse units for BTX-A (Botox) and 5000 to 10,000 units for botulinum toxin type B (Myobloc).

Question 74

Complications of botulinum toxin

Answer 74

plexopathy, polyradiculoneuritis,

and local psoriasiform dermatitis

Question 75

Surgical management of piriformis syndrome

Answer 75

Surgery may be entertained in recalcitrant cases or
when there is a documented anatomic abnormality of the
piriformis muscle. The muscle may be excised, divided,
or thinned

Question 76

Surgical management of piriformis syndrome complications

Answer 76

The obturator internus, gemelli, and quadratus
femoris muscles share common functions with the piriformis muscle and can compensate for the loss of piriformis muscle function