double deep gluteal muscles

During routine dissections on a 65-year-old male cadaver, we encountered double piriformis, double gemelli superior and inferior, double quadratus femoris muscles in the left gluteal region. The sciatic nerve passed between the lower piriformis and the upper superior gemelli muscles [infrapiriform foramen] as usual. No other variation was found in the region. This rare variation may be of importance in the radiology and surgery of this region