How Could FAIR Test Modify the H Reflex in Gastrocnemius Muscle in Patients with Piriformis Syndrome?

Piriformis syndrome (PS) is defined by a loose cluster of symptoms arising from entrapment of one or both divisions of the sciatic nerve as they pass the sciatic notch. This paper presents a method of using the H-reflex as an aid in the diagnosis of PS.

Forcible pressure from the piriformis muscle on the sciatic nerve can be induced by internal rotation of an affected limb in an adducted and flexed position (FAIR). This pressure is reflected in a delay of the H-reflex. The length of delay seen in 15 legs of 14 patients who met the criteria for PS is compared with that seen in 7 unaffected contralateral limbs.

Mean delay of H-reflex was 2.346 msec for affected legs and 0.368 msec for the combined control groups (p<0.01).

There were no Significant differences in delay latency between control group and amplitude between all groups (p>0.05).