A new description of the lumbar erector spinae muscle in man.

A study of the attachments of the musculotendinous fibres of the lumbar erector spinae muscle shows that it is made of two parts: a superficial or costal part, and a deep or vertebral part. The superficial part arises by small fleshy slips from the posterior (superficial) surface as well as the rostral and lateral margins of the erector spinae aponeurosis. It inserts by slender flattened tendons into the lower ten ribs. The deep part arises by large fleshy laminae from the deep surface of the erector spinae aponeurosis. It inserts through musculotendinous fibres mainly into the upper four lumbar and lower eight thoracic vertebrae. The superficial part corresponds to the iliocostalis lumborum and upper part of the longissimus thoracis. The deep part corresponds to the lower part of the longissimus thoracis. The functional significance of the present findings is discussed.