The weight of the spine coupled with gravity forces the sacrum to wedge snugly between the two innominates.
This phenomenon along with other passive anatomical features that provide stability are called form closure .
“ Refers to a stable situation with closely fitting joint surfaces, where no extra forces are needed to maintain the state (stability) of the system”
Stabilization of the pelvis via ligamentous structures
SI Joint Surfaces:
Sacrum: The articular surface, called auricular, is concave, covered in thick hyaline cartilage and is shaped like a plane propeller - wider P-A in the upper aspect and wider A-P in the lower aspect .
Ilium: Controversy exists as to if the iliac side is fibrocartilage or hyaline. Either way, its convex surface is irregular (rough).
Shape of the SIJ effectively resists flexion.
Ligaments - designed to limit the mobility of the SI joint.
The ligaments must oppose strong forces for long periods of time.
Simonian noted the strength of the ligaments by cutting through the pubic symphysis and the iliac wings only flared out slightly.
Iliolumbar Ligament: limits axial rotation and anterior glide of L5 on the sacrum.
Sacrotuberous Ligament: resists sacral movement into nutation, (tightens the ligament). It also has as an important connection to the long head of the biceps femoris.
Sacrospinal Ligament: see #2
Dorsal Sacral Iliac Ligament: this large ligament tightens in counter-nutation. It makes up 2/3 of the posterior SI connections and blends with #2, erector spinae and thoracolumbar fascia.
1 2 4 4 3
Anterior Sacroiliac Ligament: opposes axial translation of the sacrum and separation of the SI joints.
Interosseous Ligament (not shown): fills in the irregular spaces posterior and superior to the joint; resists joint separation.
Sacroiliac Joint - Capsule
Superior portion is a caudal extension of the iliolumbar ligament
Anterior portion is dense connective tissue and caudally blends with the sacrospinous ligament
Posterior portion is made up of multiple interwoven bands (interosseous ligaments)
Sacroiliac Joint - Innervation
Anterior superior joint receives info. from spinal nerves L4 & 5
Anterior inferior joint supplied by S1 & 2 and other sacral nerves
Muscles: The major muscles and fascia that are involved in the SI joint are the gluteus maximus and medius, psoas, piriformis multifidus , latissimus dorsi, abdominal obliques, transversus abdominus , biceps femoris , l atissimus dorsi , pelvic floor & diaphragm and thoracolumbar fascia.
The forces created by the muscles acting on SI joint to provide stability is called Fo rce Closure.
“ Force closure refers to a system whereby additional forces are necessary to maintain the joint in place.”
Second Interdisciplinary Word Congress on Low Back Pain – San Diego 1995
Extends spine and pelvis
Contraction creates sacral nutation (locking) thus ligaments tighten and SI joint locks
Tendon pass above interosseous ligament and inserts into sacrum, iliac crest, and sacrotuberous ligament
Contraction facilitates nutation
Directly compresses SI joint due to fiber orientation
Fibers blend with sacrotuberous ligament and thoracolumbar fascia
Extends, abducts, and medially rotate humerus
Deep fibers: lower T/S spinous processes and iliac crest
Superficial fibers: oblique caudal fibers blend with thoracolumbar fascia and then contralateral gluteal muscles
Long head crosses over the ischeal tuberosity & blends into sacrotuberous ligament
Contraction increases sacrotuberous tension
Externally rotates femur
Crosses SI joint perpendicular & compresses the joint
The Transverse Abdominals wrap around the spine and goes all the way to the front and when activated it stabilizes the spine and pelvis
Clinical of importance in surgery, it blends with the deep cervical fascia which forms a plane for infection to travel
Deepest of the 3 layers
Perhaps the most functional for core stabilization, spinal stabilization
If joint is compressed this will result in restriction
If joint is not compressed enough this will result in instability or hypermobility
If joint does not function in a smooth & efficient manner this can result in abnormal firing patterns
The Panjabi Model as modified by Vleeming & Lee
Joint function requires normal function of the joint & of the muscles
Joint restriction can be due to muscular and ligamentous elements
Local stabilizers vs. Global stabilizers & global maximizers
The Tranversus Abdominus
The rest of the inner unit
Shut off after 3 minutes in slumped posture
Atrophy occurs in most of modern (sitting) society
Mass is replaced by fatty infiltration
Damaged by childbirth – a normal vaginal delivery
Is affected by the other inner unit muscles not functioning
Puborectalis – a muscle of the pelvic floor can be overactive as a consequence of rectus over-activity which is itself a product of Tranversus Abdominus weakness
3 Phases to LBP Rehabilitation
Phase I: Acute Phase
Physiatrist and treatment team focus on making a diagnosis, developing an appropriate treatment plan, and implementing the treatment regimen to reduce the initial low back pain and source of inflammation.
This may include any/all of the items listed above and/or the utilization of ultrasound, electrical stimulation, or specialized injections.
3 Phases to LBP Rehabilitation
Phase II: Recovery Phase
Once the initial pain and inflammation are better managed, the rehabilitation team then focuses on helping the patient to restore working function of the body.
This includes returning the patient to normal daily activities while implementing a specialized exercise program that is designed to help the individual regain flexibility and strength.
3 Phases to LBP Rehabilitation
Phase III: Maintenance Phase
The goal of this phase of low back pain rehabilitation is two-fold:
Educating the individual on ways to prevent further injury and strain to the back
Helping the individual to maintain an appropriate level of physical fitness to help further increase strength and endurance.
Disc Lesions with/out Radiculopathy
98% of Disc lesions occur at L4-5 & L5-S1
Overuse, strenuous activity, or improper use (i.e., repetitive or heavy lifting, exposure to vibration for prolonged periods of time)
Degeneration of vertebrae (often caused by stresses on the muscles and ligaments that support the spine, or the effects of instability.
Abnormal growth (tumor)
Obesity (often caused by increased weight on the spine and pressure on the discs)
– a term that encapsulates all the possible causes of joint changes
– implies some holding element that restricts movement
- possible candidates : muscle, ligament or capsular change due to some past trauma to the tissue
Joint Fixation or Restriction
a. Capsular & Ligamentous Changes following trauma & the inflammatory cascade Clinical Orthopedics, 1987, Akeson, Amiel, Abel, Garfin & Woo (for an overview see the Aging Body by Morgenthal & Boughie – Chapter 3
b. Trigger Points / Myofascial Changes Travell & Simons – Myofascial Pain & Dysfunction – the Trigger Point Manual Volume 1 & 2
c. Muscle Imbalances Janda
d. Alterations in the Arthrokinetic Reflex Cassidy / Mooney
Movement Dysfunction Causes:
Cassidy / Mooney
Based on Hilton’s law, the nerves that innervate a joint innervate the muscles around the joint. If there's a problem within the joint the surrounding muscles will be weakened or shut off. This has been proposed as a primary mechanism of dysfunction in all areas of the spine.
1.) SI joint dysfunction and glute inhibition, (Bernard and Cassidy 91)
2.) Lumbar joint dysfunction and multifidus inhibition, (Hides 96)
3.) Cervical spine and L. coli (longissimus coli muscle) inhibition, (Wright, Jull 2001)
Directional Instability Nutation vs. Counternutation Dominance
Sacrotuberus ligament Checks Nutation
Long & Short Sacroiliac ligaments Checks Counternutation
Nutation Counternutation Nutation Counternutation
Functionally putting the puzzle together:
We need to be able to assess the complaints through functional testing.
Orthopedic (Functional) Exams/Assessments
Acute Vs. Chronic
Determine if the problem is an acute vs.
Gillet’s Test Performed knee to chest while standing: Pull knees alternately to chest. The PSIS that moves down the furthest in relation to the opposite one is the unblocked side. The blocked side will come very little or appear to move cephalically. Recruitment is from the bottom up. Hip flexion must be at least 90 degrees.
Piedallu’s Sign : The movement of the posterior superior iliac spines upon forward flexion. A positive Piedallu’s sign is asymetrical movement.
Gaelen’s Test: The patient lies on the side with the upper leg (test leg) hyperextended at the hip (1st photo). The patient holds the lower leg flexed against the chest. The examiner stabilizes the pelvis while extending the hip of the uppermost leg. The test can also be performed supine (2nd) but this position may limit the amount of hyperextension. Position patient so the test hip extends beyond the edge pf the table. Then draw up both legs onto the chest then slowly lower the test leg into extension. Pain in the sacroiliac joints indicates a positive test.
How can we incorporate static anatomy into functional anatomy?
Gait – Heel Strike
Prior to heel strike, heel strike becomes active
Which increases tension of sacrotuberous ligament
Thus compresses SI joint
Forces transmitted across SI joint into spine
Gait – Stance Phase
Innominates begin anterior rotation
Loose SI joint. locking
Long Dorsal SI ligament tension increases
Need to stabilize SI joint
Gluteus maximus activates and replaces Biceps femoris
Contralateral lats dorsi activates
Gait – Swing Phase
No weight in SI joint. It is suspended.
Ligamentous control of SI joint
With Each Phase of Gait
Opposite arm and “wringing of spine”
(it occurs like taking a rubber band and
twisting it, when you let go, it “springs”)
Ligaments, discs, and spinal curves maximize yielding energy storage
Elastic Energy is released in the next cycle —followed by muscular energy
Treatment should be inclusive to include all the tissues that can affect movement. Each treatment should be tailor made to fit the patients dysfunction, manipulation, mobilization, rehabilitation, stretching & diet/nutrition should a part of every doctor’s practice regiment.
Physical rehabilitation and/or therapy
Weight loss (if overweight)
INTEGRATED METHOD OF TREATMENT
Following a prevention program (as directed by your physician)
Assistive devices (i.e., mechanical back supports)
Application With all our knowledge in anatomy we need to learn how to apply it to the patient who is having pain after all the treatments they’ve had.
Extensive connections of sacrotuberous ligaments
SI joint is located in the middle of considerable force streams
Dysfunctional of Form/Force Closure can have significant effects locally at the SI joint and far into the lower/upper limbs or cervical spine.
Loss of bracing
Shifting of loads into the lumbar/sacral area
Often these connections are incomplete, unilateral or asymetrical
I.E. - Unilateral shorten biceps
Could these differences cause symptoms in the patient? The answer is YES!
Our goal is to find these differences
Decrease muscle length
These imbalances will change the function of the SI joints and L/S as a UNIT
FAILED SELF BRACING
“ Abnormal movement of the sacrum in the SI joints may lead to abnormal stress loads transmitted into the L/S thus abnormal stress on the intervertebral discs and joints.”
Failed Self Bracing
Weak erector spinae leads to insufficient nutation
Weak gluteus maximus leads to insufficient SI compression
Weak Lats leads to insufficient SI compression
Decreased SI joint. compression & poor nutation leads to dysfunction and pain syndromes
Failed Self Bracing
Sustained counter-nutation leads to:
Absent SI compression therefore increasing joint shear forces
Lordosis is lost
Load is transferred to L/S and discs…increasing shear
Failed Self Bracing
Irritation of the SI joint inhibits the gluteus maximus
Inhibition = weakness
Hamstring will attempt to increase hip extension and help increase SI joint compression
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