87. ANATOMIC STUDY OF EXTRAPELVIC INNERVATION OF THE PIRIFORM MUSCLE: FEASIBILITY OF SELECTIVE NEUROTOMY FOR THE TREATMENT OF PIRIFORM SYNDROME

Abstract

Purpose of the study: The piriform syndrome is treated medically: functional rehabilitation and injections. If the medical treatment fails, tenotomy of the piriform muscle can be proposed. Published studies report good outcome in 66 to 87% Of patients. The purpose of this study was to examine the extrapelvic innervations of this muscle in order to assess the feasibility of neurotomy of he piriform muscle.

Material and method: Twenty gluteal regions were dissected. We studied first the relations between the piriform muscle and the ischiatic nerve. Then the innervations branches of the piriform muscle were localized in three landmarks.

Results: We found the of the six types of relation between the ischiatic nerve and the piriform muscle described by Beaton, with frequencies comparable to reports in the literature. Innervation of the piriform muscle does not follow a standard pattern, even though the innervations generally comes from the ischiatic nerve; the nerve branches come from the superior and inferior gluteal pedicles. In addition, these nerve branches penetrate the deep aspect of the muscle in random fashion. In addition, accessibility to the deep aspect of the piriform muscle cannot be achieved easily but requires prior section of its insertion on the greater trochanter.

Discussion: In our opinion, these results suggest that isolated neurotomy of the piriform muscle is not clinically feasible; it might be possible to improve function results of isolated tenotomy by performing a neurotomy of the nerve branches visible during the tenotomy procedure. A greater benefit might be expected in forms where the ischiatic nerve crosses the piriform muscle.