Chapter 47 Pain Originating from the Buttock: Sacroiliac Joint Syndrome and Piriformis Syndrome Flashcards
KEY POINTS 1. Sacroiliac joint pain can be caused by intra- and extraarticular causes. 2. Several tests confirm the diagnosis of SI joint syndrome. An analgesic response to an SI joint injection is the most accurate means to diagnose a painful SI joint complex. 3. Corticosteroid injections may provide short or intermediate-term relief in well-selected patients but evidence for long-term benefit is mainly anecdotal. 4. There is moderate evidence supporting RF denervation to treat pain arising
The sacroiliac joint complex frequently classified as an
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
The SI joint is supported by a
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
The sacroiliac joint primarily designed for
stability and weight-bearing, though small degrees of rotation (<2 mm) occur
The nerve supply of the SI joint complex
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
innervation of the ventral SI joint
nerve filaments stemming from the ventral rami of L4–S2,7 other experts
cite contributions from levels as cephalad as L2
The mechanism of injury to the SI joint complex
a combination of axial loading and abrupt rotation
On an anatomic level, pathologic changes affecting myriad structures comprising the SI joint can lead to nociception. These include
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.
etiologies for SI joint pain these causes can be divided into
intra- and extra-articular sources.
examples of intra-articular causes of SI joint pain.
Arthritis and infection
Spondyloarthropathy
Trauma
Cystic disease
Extra-articular sources
enthesopathy,
fractures, ligamentous injury and myofascial pain, Pregnancy, Cystic disease
In contrast to intra-articular
pathology, extra-articular pain is more likely to be
unilateral, occur in younger individuals, present with more prominent tenderness, and be associated with a specific inciting event or biomechanical etiologies
Risk factors can predispose to the insidious
development of SI joint pain.
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
Spine surgery may cause post-procedural SI joint pain
by
increasing load bearing, weakening the surrounding
ligaments, iatrogenic violation of the SI joint complex, and postsurgical hypermobility
Pregnancy predisposes
women to SI joint pain via the
combination of increased
weight gain, exaggerated lordotic posture, the mechanical trauma of parturition, and hormone-induced ligamental laxity
diagnose of SI joint
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
the more common findings used to select candidates for SI joint blocks are
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
pain referral
patterns from SI joints.
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
the gold standards for detecting SI joint involvement in patients with seronegative spondylarthropathy.
MRI and CT scanning
Differences between MRI and CT scanning
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
the most accurate means to diagnose a painful SI joint complex
an analgesic response to an SI joint injection
How much to inject into SI joint?
response to low volume (, 2 ml) SI joint blocks have
generally been used as the reference standard
The conservative treatment of SI joint pain should ideally address the underlying etiology.
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.
Functional leg length discrepancies usually occur as a result of
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.
The treatment of apparent leg length discrepancies
entails
aggressive physical therapy that targets the underlying etiology. If malalignment is suspected, osteopathic
or chiropractic manipulation has been reported to be of value
conservative treatment for patients with spondyloarthropathies
immunomodulating
agents such as cytokine inhibitors and
methotrexate may reduce disease progression, alleviate pain, and improve function.
Practice guidelines have found exercise to be beneficial
for
nonspecific chronic low back pain, but it may be
particularly beneficial in patients with SI joint pain
have become the treatment of choice for patients in
whom conservative treatments fail to provide long-term symptom palliation
Neuroablative techniques, especially radiofrequency denervation
in conventional RF
techniques, the typical lesion diameter ranges between
3 mm and 4 mm in a single plane
in conventional RF techniques have been adapted to enhance
lesion size and overcome obstacle of small lesion size
bipolar lesioning, internally cooled electrodes, and replacing RF electrodes with cryoprobes
Radiofrequency denervation may not benefit everyone
with SI joint pain. Targeting the posterior nerve supply
does not address
pain emanating from the ventral aspect of the joint
Sacroiliac joint arthrodesis has been previously employed to treat
fractures, instability/dislocations, and pain secondary to degenerative changes
Piriformis syndrome
cause of buttock and leg pain
The piriformis muscle originates from the
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
piriformis muscle travels
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.
piriformis muscle is innervated by
branches of the ventral rami of the L5, S1, and S2 spinal nerves.
structures that travel below the piriformis muscle
sciatic nerve, posterior femoral cutaneous nerve, gluteal nerves, and the gluteal vessels
Six possible anatomic relationships occur between the
sciatic nerve and the piriformis muscle
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.
Anomalies of the piriformis muscle and the sciatic nerve can cause sciatica. The compression usually
occurs between the
tendinous portion of the muscle and the bony pelvis.
In patients in which the piriformis muscle is anterior to the sciatic nerve, the compression
of the nerve occurs between
the superior border of the piriformis and the superior margin of the greater sciatic
foramen
Etiologies and predisposing factors of the piriformis syndrome include
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
Trauma to the buttock leads to
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.
piriformis syndrome is consider to be
a form of myofascial pain syndrome
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
the tendinous portion
of the piriformis muscle, which is often the major site of pathology (e.g., enthesopathy) combines with the tendons
of the
obturator and gemelli muscles before their
insertion on the greater trochanter.
Piriformis syndrome
may occur after what surgeries?
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.
The differential diagnoses of piriformis syndrome include
the myriad causes of low back pain and sciatica
patients with piriformis syndrome, however, usually do not
have neurologic deficits unless there is
compression or
irritation of the sciatic nerve.
differential diagnoses of piriformis syndrome
Facet syndrome, sacroiliac joint dysfunction, trochanteric and ischial bursitis, myofascial
pain syndrome, pelvic tumor, endometriosis, and conditions
irritating the sciatic nerve
diagnoses of piriformis syndrome
diagnosis of piriformis syndrome
is usually arrived at only after exclusion of differentials
cardinal features of the piriformis syndrome
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)
Patients with piriformis syndrome usually complain of
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
piriformis syndrome pain is generally aggravated by
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.
piriformis syndrome Physical examination of the patient may reveal
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
piriformis syndrome pain
The pain is aggravated by hip flexion, adduction,
and internal rotation
piriformis syndrome neurologic signs
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.
physical examination signs may be
helpful in confirming the presence of piriformis syndrome
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.
function of the piriformis muscle
it is an adductor of the flexed thigh and an external rotator of
the extended hip.
diagnosis of piriformis syndrome using studies
electromyography
(EMG), computed tomography (CT), and magnetic resonance
imaging (MRI) may show abnormalities.
EMG diagnosis of piriformis syndrome
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.
CT and MRI diagnosis of piriformis syndrome
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.
treatment of piriformis syndrome includes
physical
therapy combined with the use of anti-inflammatory drugs,
analgesics, and muscle relaxants to reduce inflammation,
spasm, and pain
Physical therapy for piriformis syndrome
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.
Patients of piriformis syndrome do not
respond to conservative therapy are candidates for
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
TECHNIQUES OF PIRIFORMIS MUSCLE
AND PERISCIATIC NERVE INJECTIONS
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.
TECHNIQUES OF PIRIFORMIS MUSCLE
AND PERISCIATIC NERVE INJECTIONS: CT-guided approach
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).
TECHNIQUES OF PIRIFORMIS MUSCLE
AND PERISCIATIC NERVE INJECTIONS
uses the lower border of the sacroiliac
joint as the landmark.
Landmarks
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.
TECHNIQUES OF PIRIFORMIS MUSCLE
AND PERISCIATIC NERVE INJECTIONS
uses the lower border of the sacroiliac
joint as the landmark.
Needle placement
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.
TECHNIQUES OF PIRIFORMIS MUSCLE
AND PERISCIATIC NERVE INJECTIONS
uses the lower border of the sacroiliac
joint as the landmark.
Evoked motor response
The evoked motor response of the foot can be inversion, eversion, dorsiflexion, or plantar flexion.
TECHNIQUES OF PIRIFORMIS MUSCLE
AND PERISCIATIC NERVE INJECTIONS
uses the lower border of the sacroiliac
joint as the landmark.
Needle movement
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.
TECHNIQUES OF PIRIFORMIS MUSCLE
AND PERISCIATIC NERVE INJECTIONS
uses the lower border of the sacroiliac
joint as the landmark.
Injection of steroid
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.
TECHNIQUES OF PIRIFORMIS MUSCLE
AND PERISCIATIC NERVE INJECTIONS
uses the lower border of the sacroiliac
joint as the landmark.
injectant
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
Botulinum toxin
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
Botulinum toxin Recovery
depends on neuromuscular sprouting and reinnervation of the muscle, which generally takes several weeks to months.
The typical doses of botulinum toxin employed
100 mouse units for BTX-A (Botox) and 5000 to 10,000 units for botulinum toxin type B (Myobloc).
Complications of botulinum toxin
plexopathy, polyradiculoneuritis,
and local psoriasiform dermatitis
Surgical management of piriformis syndrome
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
Surgical management of piriformis syndrome complications
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
