US Patent 7740598 Coaxial cannula provided with a sealing element

The invention relates to a coaxial cannula for extracting samples from tissue comprising a biopsy needle unit provided with a space for sample extraction and a sample separation unit which coaxially encompasses the biopsy needle on an external wall and is longitudinally movable. The inventive coaxial cannula comprises a sealing element which is arranged on the proximal end thereof and closes the space between the internal wall of the coaxial cannula and the external walls of the sample separation unit. The sealing element opens an air outlet when the biopsy needle unit is inserted, and prevents air intake when the biopsy needle unit is positioned and vacuum is produced in the internal chamber of the biopsy needle.