Methods for trephination and irrigation of the frontal sinus cavity

A method for providing fluid communication into a cavity covered by a bony surface under skin, comprising:

• a) inserting a guide tube distal end into an incision and proximate the bony surface;
• b) inserting a drill into the guide tube and placing the drill against the bony surface;
• c) drilling through the bony surface to provide a hole with access to the cavity;
• d) withdrawing the drill from the guide tube;
• e) placing a guide pin coaxially into the guide tube and into the hole;
• f) axially withdrawing the guide tube from the incision, while leaving the guide pin in the hole;
• g) coaxially inserting a cannula over the guide pin and approximating the cannula distal open end into the engagement with the hole to provide fluid communication between the cannula and the cavity;
• and
• h) withdrawing the guide pin.

A method of drilling into frontal sinus cavity having a depth defined between a posterior wall and a frontal wall having a thickness comprising the steps of

• providing a drill guide having a distal end for engaging the bone and a proximal end carrying an abutment surface with a predetermined distance between;
• providing a powered drill having a distal drilling tip and a proximal abutment surface with a predetermined distance therebetween greater than the predetermined distance of the drill guide to define an extension distance less than the depth of the sinus cavity plus the thickness of the frontal bone and greater than the thickness of the frontal bone;
• placing the distal end of the drill guide in engagement with the frontal bone;
• drilling a hole through the frontal bone by inserting the powered drill through the drill guide;
• and
• engaging the powered drill abutment surface with the drill guide abutment surface such that the distal drilling tip penetrates into the sinus cavity but is prevented from contacting the posterior wall.