The risk of direct peroneal nerve injury using the Ranawat "inside-out" lateral release technique in valgus total knee arthroplasty.

The purposes of our study are to define a "danger zone" and a "safe zone" to avoid common peroneal nerve direct injury performing the "inside-out" release technique of posterior-lateral corner during total knee arthroplasty and to identify anatomic landmarks to localize the nerve before the soft-tissues release. Twenty cadaver dissections were used for testing. The distance from the nerve to the posterior-lateral corner of the tibia and to the posterior border of the iliotibial band averaged, respectively, 13.5 and 35.8 mm. The nerve is at risk during the release of the posterior-lateral capsule, in the triangle defined by the popliteus tendon, the tibial cut surface, and the most posterior fibers of iliotibial band (danger zone), but not during pie-crusting of the iliotibial band (safe zone).