Co-occurrence of a previously unreported double-headed accessory psoas major with an unusually positioned accessory...

The iliopsoas muscle complex traditionally consists of the iliacus muscle and psoas major, occasionally including the psoas minor. These elements were distinguished based on their shared function and common distal attachment. Although accessory structures have been previously reported within the complex, they are rare. This study reports an unusual observation of the co-occurrence of two additional muscles within the iliopsoas muscle complex during dissection: an accessory iliacus muscle and a four-headed accessory psoas major, the anatomical position and morphological features of which indicate a high possibility of femoral nerve compression.