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.

Purpose of the study: One of the most frequent complications of medial meniscal suture is injury to the saphenous nerve or its branches. The purpose of this study was to ascertain the relations of the medial meniscus with the infrapatellar branches of the saphenous nerve.

Material and methods: Twenty lower limbs were dissected to study the pathways of the saphenous nerve and its branches in relation to different landmarks of the medial meniscus and palpable bony zones. Sixteen measurements were made on each knee held in extension.

Results: The infrapatellar trunk of the saphenous nerve exhibited two terminal branches in all knees dissected. Level of the bifurcation in relation to the joint space varied. Similarly the position of the branches varied greatly in relation to different landmarks. The most frequent configuration was a main trunk situated 8 mm anteriorly to the tubercle of the great adductor and 60 mm from the mid point of the medial border of the patella. The bifurcation into two branches was situated 23 mm above the joint space. The two branches ran obliquely anteriorly and inferiorly forming an angle of 55° on average with a vertical line. The superior branch ran 24 mm behind the anterior meniscal point and 55 mm from the posterior meniscal point; the inferior branch ran 42.6 mm and 38 mm from these two points.

Discussion: Injury to the saphenous nerve or its branches is mainly observed for suturing techniques done medially to laterally. Incidence has reached 38% in certain series. This incidence has declined with the increasingly widespread use of arthroscopy, but saphenous injury still occurs for meniscal repairs using a posteromedial approach. The risk is similar for medially to laterally or laterally to medially sutures. Since there is no safety zone, it would be advisable to prefer an «all medially» technique.

Conclusion: Measurements made on dissection specimens enabled us to delimit three zones of increasing risk for nerve injury. The zone with the highest risk measures 20 mm wide. Its anterior limit is situated behind the most anterior meniscal point and its posterior limit is situated 28 mm from the posterior meniscal point.