US-12616485-B2 - Drill bit, drill kit and method for drilling a cavity or a recess into a skull

US12616485B2US 12616485 B2US12616485 B2US 12616485B2US-12616485-B2

Abstract

A drill bit for drilling a cavity or a recess into a skull, wherein the cavity or the recess is configured to receive an implantable fixture screw unit of a hearing aid system, is disclosed. The drill bit includes a first part including a drill tip with a first drill diameter, wherein the drill tip comprises a tip angle of between 137 degrees to 143 degrees along a longitudinal axis of the drill bit and wherein the drill tip comprises a back rake angle of between −1 degree and +1 degree, in particular a back rake angle of substantially 0 degrees, a second part including a plurality of flute blades with a second drill diameter, wherein the second drill diameter is greater that the first drill diameter, and a transition part which is arranged between the first part and the second part and along the longitudinal axis, wherein the transition part includes a body clearance.

Inventors

Hanna PETERS
Emelie LAGER
Anton Hedström
Martin Johansson
Thomas Eriksson

Assignees

OTICON MEDICAL A/S

Dates

Publication Date: 20260505
Application Date: 20240221
Priority Date: 20200708

Claims (19)

1 . A method for drilling a cavity or a recess into a skull, wherein the cavity or the recess is configured to receive an implantable fixture screw unit of a hearing aid system, wherein the method comprises: applying an incision hole to a bone layer of the skull by using a first tool; cleaning the incision hole by using a cleaning tool; arranging a guiding tool into the cleaned incision hole, wherein the guiding tool includes a hollow tube; and applying a drill bit into the hollow tube and drilling the cavity or the recess in a single step, wherein the drill bit comprises: a first part including a drill tip with a first drill diameter, wherein the drill tip comprises a tip angle of between 137 degrees to 143 degrees along a longitudinal axis of the drill bit and wherein the drill tip comprises a back rake angle of between-1 degree and +1 degree, a second part including a plurality of flute blades with a second drill diameter, wherein the second drill diameter is greater than the first drill diameter and a transition part which is arranged between the first part and the second part and along the longitudinal axis, wherein the transition part includes a body clearance, and wherein a diameter of the hollow tube is greater than the second drill diameter.
2 . The method according to claim 1 , wherein each of the plurality of flute blades of the second part comprises at least one land, and wherein the second part comprises parabolic or essentially parallel opposing surfaces extending between the lands of the plurality of flute blades.
3 . The method according to claim 2 , wherein the plurality of flute blades comprises a cutting edge with a thickness of between 0.10 mm to 0.40 mm.
4 . The method according to claim 2 , wherein drill flutes are arranged between adjacent flute blades of the plurality of flute blades and wherein a thickness of the drill flutes varies along the drill bit and/or wherein the thickness of the drill flutes is between 0.8 mm and 1.2 mm.
5 . The method according to claim 2 , wherein the second part or the transition part includes a back-rake angle which is either positive or negative and/or wherein a back rake angle of the flute blades is within an angle range of between −3 degrees to +3 degrees not including 0 degrees.
6 . The method according to claim 1 , wherein the plurality of flute blades comprises a cutting edge with a thickness of between 0.10 mm to 0.40 mm.
7 . The method according to claim 6 , wherein drill flutes are arranged between adjacent flute blades of the plurality of flute blades and wherein a thickness of the drill flutes varies along the drill bit and/or wherein the thickness of the drill flutes is between 0.8 mm and 1.2 mm.
8 . The method according to claim 6 , wherein the second part or the transition part includes a back-rake angle which is either positive or negative and/or wherein a back rake angle of the flute blades is within an angle range of between −3 degrees to +3 degrees not including 0 degrees.
9 . The method according to claim 1 , wherein drill flutes are arranged between adjacent flute blades of the plurality of flute blades and wherein a thickness of the drill flutes varies along the drill bit and/or wherein the thickness of the drill flutes is between 0.8 mm and 1.2 mm.
10 . The method according to claim 9 , wherein the second part or the transition part includes a back-rake angle which is either positive or negative and/or wherein a back rake angle of the flute blades is within an angle range of between −3 degrees to +3 degrees not including 0 degrees.
11 . The method according to claim 1 , wherein the second part or the transition part includes a back-rake angle which is either positive or negative and/or wherein a back rake angle of the flute blades is within an angle range of between −3 degrees to +3 degrees not including 0 degrees.
12 . The method according to claim 1 , wherein the second part includes a helix angle between the longitudinal axis and a direction of the flute blades of between 20 degrees and 30 degrees.
13 . The method according to claim 12 , wherein the helix angle is between 24 degrees to 26 degrees.
14 . The method according to claim 1 , wherein the transition part includes a region with an essentially constant diameter along the longitudinal axis and/or wherein a length of the region with an essentially constant diameter along the longitudinal axis is between 1.05 mm and 1.55 mm and/or wherein the region with an essentially constant diameter does not have a cutting edge.
15 . The method according to claim 1 , wherein the body clearance includes a minimum diameter equal to a minimum diameter of the first part and a maximum diameter equal to a diameter of the second part.
16 . The method according to claim 1 , wherein the body clearance includes a transition angle of 7 degrees to 13 degrees along the longitudinal axis and between a minimum diameter and a maximum diameter of the transition part.
17 . The method according to claim 1 , wherein a length along the longitudinal axis and between an end of the drill tip and a maximum diameter of the transition part is between 4.65 mm and 4.75 mm.
18 . The method according to claim 1 , wherein the drill tip has a first drill diameter of between 3.78 mm to 3.82 mm and/or wherein the drill tip comprises a cutting edge angle of between 7 degrees to 13 degrees.
19 . The method according to claim 1 , wherein the back rake angle is substantially 0 degrees.

Description

This application is a Divisional of copending application Ser. No. 17/369,312, filed on Jul. 7, 2021, which claims priority under 35 U.S.C. § 119(a) to Application No. 20184691.2, filed in Europe on Jul. 8, 2020, all of which are hereby expressly incorporated by reference into the present application. FIELD OF THE DISCLOSURE The present disclosure relates to the field of drill bits, drill kits and methods for drilling. More particularly, the disclosure relates to a drill bit, a drill kit and a method for drilling a cavity or a recess into a skull, wherein the cavity or the recess is configured to receive an implantable fixture screw unit of a hearing aid system. BACKGROUND Medical implants such as bone anchored hearing aid systems are applied for the rehabilitation of patients suffering from hearing losses for which traditional hearing aids are insufficient. A typical bone anchored hearing aid system comprises an external hearing aid provided with a vibrating transducer connected to a skin-penetrating abutment through a coupling. The abutment may have an interconnection to an implantable fixture screw unit anchored in the skull bone. The implantable fixture is typically made of titanium and may be provided with a flange to prevent the fixture from being pushed through the skull bone when exposed to a sudden accidental impact. The abutment penetrates the skin and the subcutaneous tissue in order to establish a direct coupling (direct bone conduction) from a hearing aid processor to the skull bone. The methods for installing bone anchored hearing aid implant systems are moving towards minimally invasive methods that can be performed quickly in order to minimize intra- and post-operative problems, to achieve a predictable outcome, and to achieve better cosmetic results. However, the existing incision techniques are rather complicated and require a flap area to be provided by making an incision. Typically, a scalpel is used to make an incision down to the periosteum along a marking of the incision area and to separate the tissue from the underlying periosteum. Further, all subcutaneous tissue in the graft area is separated from the periosteum. Additionally, the subcutaneous tissue needs to be carefully separated from the skin graft, and all hair follicles need to be removed. Furthermore, some level of manual skin thinning typically is required to be performed. Some attempts have been made to avoid the linear incision techniques to install implants for bone anchored hearing aids. Some of these attempts include punch techniques. The techniques apply a standard biopsy punch that is used to provide a circular incision of 5-12 mm. These techniques are associated with a number of drawbacks. These drawbacks include the risk of damaging the tissue due to friction, heat and tearing caused by the action of the drill. The punching techniques apply punching holes larger than 5 mm in order to allow for introducing irrigation fluid (to cool the bone tissue) during the drilling process and also for providing sufficient visibility. These large punch diameters are not optimal for the soft tissue abutment interface. A large circular incision will prolong the healing time and introduce the risk of granulation tissue formation and subsequent infection. Moreover, the skin thickness needs to be determined pre- and/or intra-operatively. Additionally, it is known to use a minimally invasive Ponto surgery technique in order to install implants for bone anchored hearing aids. Hereby, an incision hole is made by using a biopsy punch. Afterwards the periosteum and soft tissue are removed from the transplantation site. The drilling procedure comprises two different drilling steps. A first drill is used in order to generate a first cavity or recess. Afterwards, a widening drill is used in order to widen the first cavity or recess and to prepare the cavity or recess for the implant for bone anchored hearing aids. By using different drills, the operation surgery time is prolonged and the switching, restarting and realigning of the widening drill may cause adverse consequences for the cavity or recess to be drilled. Therefore, there is a need to provide a solution that addresses at least some of the above-mentioned problems. SUMMARY According to a first exemplary aspect a drill bit for drilling a cavity or a recess into a skull is disclosed. The drill bit may comprise a first part including a drill tip with a first drill diameter, wherein the drill tip comprises a tip angle of between 137 degrees to 143 degrees along a longitudinal axis of the drill bit. A tip angle of between 137 degrees to 143 degrees is advantageous for drilling into the relatively hard skull material. The tip angle of between 137 degrees and 143 degrees enables a sufficient engagement of the cutting lips of the drill tip with the skull material. The first part of the drill bit is the part of the drill bit which is closest to the bone during drilling. The drill tip may incl