Cranial perforator-Introducer (Complete specification)
Specifications:
This invention relates to a device for surgical treatment of a chronic subdural hematoma which occurs after a head injury.
The human brain is covered by 3 membranes- dura, arachnoid and pia, and over these is the skull. After a head injury, blood may collect beneath the dura (sub-dural space) and if this does not resolve spontaneously then it enters a chronic phase. This occurs after an interval of 3-6 weeks and results in a gradually expanding liquefied clot in the sub dural space. If this is not evacuated in time then the pressure of this fluid on the brain can cause death of the patient.
Conventional surgical evacuation is done by 1) removing a large piece of the bone {upto 80mm diameter} overlying the hematoma followed by evacuation; 2) making large holes in the brain {about 20mm each} and then washing out the hematoma; or 3} making a tiny twist drill hole {about 3-5 mm} in the bone to wash out the hematoma.
The small incision twist drill method is the easiest successful method but involves a cumbersome and heavy drill machine. Also insertion of a drain is a technically difficult method because of the small size of the hole and the overlying scalp tissues which need to be retracted manually.
The present invention is designed to overcome these problems of the twist drill technique by using a small light weight hand held cranial perforator to make a suitable hole in the bone. This is replaced by a funnel shaped introducer through which a drain tubing can be easily guided into the sub dural cavity.
Description of the drawing:
Figure 1: the cranial perforator which is about 6 inches long and can be easily held in the hand.
Figure 2: the introducer which replaces the perforator for introducing the drain cum lavage catheter.
Figure 3: showing the method of washing out the hematoma through the introducer after the hole in the bone has been made using the perforator.
Detailed description:
From figure 1 it can be seen that the perforator consists of 3 parts-
a. Handle (1)
b. perforating piece consisting of a shaft (2) and a sharp perforating tip (3) and
a posterior threaded part (4)
c. depth locking system (5)
The handle is made of ebonite, wood or steel. It is about 8 to 10 cm in length with a width of around 2 cm. The tip is bulbous in nature and rounded to easily and comfortably fit into the palm of the operator without any discomfort.
The perforating piece is a steel rod firmly fixed to the handle. The exposed part is around 5-6 cm in length and has a maximum diameter of 4-4.5 mm. The tip is sharp and tapered for easy drilling of the skull bone which will be done by alternate clockwise-anticlockwise rotations of the handle while applying firm downward pressure. The tapering tip shall be around 5-7 mm long. This is followed by a smooth part of around 8-12 mm length to compensate for bone thickness. Behind this will be a threaded part for holding the depth locking nut system.
The depth locking nut is a 2-piece system of nuts which run over the threaded part of the perforating piece and can lock at any one point by apposition. The nut toward the sharp tip will overhang the smooth part of the rod so that the length of the exposed part of the rod can be adjusted according to the depth of the bone.
From figure 2 it is seen that the introducer is a hollow funnel or conical piece, with the lower part being threaded (1) for about 5-7 mm and having an outer diameter of 4-4.5 mm and an inner diameter of 2.5 - 3 mm. Above this is a smooth hollow conical part (2) which widens over a length of about 3-4 cm to accommodate an inner diameter of around 5-6 mm. The upper rim (3) is widened and serrated or scored for better grip during introduction.
Figure 3 is a schematic diagram showing the method of hematoma evacuation after the bone has been drilled with the perforator. Shown here is a cross-section of skull bone with underlying dura (1), hematoma fluid (2) and the brain underneath (3). The tapered threaded tip (4) is seen screwed into the bone and a soft catheter (6) is passed easily through the wider conical part of the introducer (5). Two such holes are made in to the hematoma cavity and then sterile saline is pushed through the catheter (7) to gradually wash out the hematoma cavity and replace it with saline solution.

Statement of claim
I/We claim,
1. A cranial perforator and introducer consisting of two individual parts, the first part being the perforator which has a sharp tip to pierce bone and a shaft on which is mounted a depth locking nut system and where the shaft is attached to a handle, all in a total length of less than 20 cm so as to be easily fit into the operators grasp; and the second part being the introducer which is essentially a funnel shaped hollow metal piece which can be screwed into the bone after the perforator is removed and through which a tubing of around 2-3 mm diameter can be introduced.
2. The device as claimed in claim 1 wherein the perforator handle is made of ebonite, wood, steel or any other suitable material and of a size that can easily and firmly fit into the operators hand.
3. The device as claimed in claim 1 wherein the perforator has a shaft diameter of around 5 mm so as to provide easy passage of a soft tubing of around 3 mm diameter.
4. The device as claimed in claim 1 wherein the introducer is a hollow funnel shaped piece with the lesser diameter equal to that of the perforator shaft and which has threads to affix to the bone and allow smooth passage to a soft tubing of around 3 mm diameter.
5. The device as claimed in claim 1 wherein the introducer may be made of metal or hard plastic and may optionally have an obturator for easier introduction through the bone.
6. A cranial perforator and introducer system substantially as herein described and illustrated in the figures of the accompanying drawings.