piriformis actions
- straight leg- external rotation at hip
- hip and knee flexed to 90- abduction of hip
what exits the piriformis
-sacral plexus branches
exits superior to piriformis
-superior gluteal vessels and n’s
exits inferior to piriformis
- inf gluteal vessels and n’s
- pudendal vessels and n
- post femoral cutaneous n
- n’s to short external rotators of femur
sciatic n- course thru piriformis
-inferior- 90% of population!
muscle spasm- pathophysiology
- m spindle- stretch R
- intrafusal fibers- sensory R’s- monitor length and rate of change in length of extrafusal fibers
- sensory innervation- group 1a afferents
- motor innervation- gamma motor neurons; alpha motor neurons
gamma reflex loop
- stretch/contraction of m- act gamma motor neuron- causes intrafusal fibers to contract- stretches m spindle- act group 1a afferents- innervates/excites alpha motor neuron- m contraction
- maintains our postural tone
gamma loop dysfxn- stretch reflex
- sudden stretch of m- stretching of m spindle- act of alpha motor neuron- m contraction- spasm
- sensory signals also go to higher centers of CNS- respond w gamma stim which maintains spasm
nociception- spinal cord
-nociceptive impulses ascend via contralateral spinothalamic tract
nociception- brain
- A delta fibers carry impulses to neothalamus and somatosensory cortex- localization/discrmination of pain type
- C fibers- behavior modification, memories
nociception- CNS
- symp stim- lowers pain threshold
- vasoconstrictoin- “
- NE may sensitize nociceptors- amplifies pain response
theory for facilitation
- impulse from spinal cord reaches the motor neuron- release of peptides in peripheral tissues- infl cascade
- results in lowering nociceptor thresholds
- infl agents irritate and inflame the epineurium and act nociceptive endings of nevi neuvorum- results in n distribution pain
pififormis syndrome
- peripheral neuritis of sciatic n caused by abnormal condition of piriformis m
- masquerades as other common SDs
epidemiologic considerations
- 4-5 decades, women- most common
- primary- anatomic cause
- secondary- precipitating cause
Anatomic cause
- split piriformis m
- split sciatic n
- anomalous sciatic n path
- <15% of pts
precipitating cause
- m adopts position of strain
- macrotrauma
- microtrauma
- ischemic mass effect
- lcoal ischemia
sx’s
- pain w sitting, standing, or lying longer than 15-20 min
- pain and/or paresthesia radiating from sacrum thru gluteal area and down post aspect of thigh
- pain improves w ambulation
- pain when rising from seated/squatting position
signs
- tenderness in region of SI joint
- tenderness over piriformis m
- palpable mass in ipsilateral buttock
PE
- hip external rotation SD
- sausage-shaped mass
- counterstrain tender points
- myofascial trigger points
- IT band tension (insertion at IT band orgination)
special tests
- Lasegue sign
- freiburg sign
- pace sign
lasegue sign
-pain when pressure is applied over piriformis m and its tendon, when hip is flexed to 90 and knee is extended
freiburg sign
-pain during passive internal rotation of hip
pace sign
-revealed with the FAIR test
treatment
- early conservative tx is most effective!!!
- pharmacological
- OMT
- home stretching exercises
- surgery and prevention
