Technical field of invention:

Present invention in general relates to an artificial temporal bone and method for fabrication of the same with maximum internal and external anatomical details using 3D printing technique and in particular to develop accurate geometric model of temporal bone.

Prior art:

Temporal bone is one of the most complex neurovascular structures within the body. Otolaryngologist need to have sound anatomical knowledge during surgeries. Insufficient knowledge or lack of practice may lead to complication during surgeries. Thus for practicing purpose temporal bone laboratories are setup at various places. Researcher has tried to fabricate artificial temporal bone for practicing purpose. But none have succeeded in achieving complete internal and external anatomical structures, thus cadaver bones are used for training purpose. Cadaver Bones are having following drawback.

> Because of complex neurovascular structure of temporal bone, otolaryngologist need lot of practice before performing any surgeries

> Because of strict legislation in many countries regarding organ donation, availability of cadaver bone is very limited

> Harvesting cadaver temporal bone is also challenging task and it also carries many infectious agents such as hepatitis B and C virus, HIV virus etc.

> Dissecting cadaver bone is prohibited in many countries due to moral/ethical and religious ground moreover cost of cadaver bone is also very high

> Till now no one have achieved complete anatomical geometry of temporal bone.

US 20040175686 Al discloses process for producing an artificial bone model and an artificial bone model produced by the process. A process for producing an artificial bone model in accordance with the selective laser sintering process which comprises extending a powder material for sintering comprising 30 to 90 parts by weight of powder of a synthetic resin and 10 to 70% by weight of an inorganic filler to form a thin layer and irradiating a portion of the thin layer having the shape formed based on tomographic information of a natural bone with laser light so that the irradiated portion of the thin layer is sintered. The extension of the powder material for sintering to form the thin layer and the irradiation of the thin layer with laser light for sintering is conducted repeatedly. The artificial bone model can three-dimensionally reproduce steric shapes of natural bones such as bones in the human body precisely and accurately and exhibits the property for cutting closely similar to that of natural bones. The artificial bone model can be used for educational training or for studying a plan for curing before a surgical operation.

EP 2014315 Al discloses method of constructing artificial bone. The method comprises: extracting a part corresponding to a cancellous bone and/or a cortical bone from digitalized three-dimensional image data of a living bone, followed by setting a center line on the part; drawing a beam or a wall having a uniform diameter or thickness along the center line to form artificial bone image data; and stacking a sintered layer by laser-sintering a powder of titanium and the like based on the artificial bone image data. The precursor is suitable for an artificial bone having excellent osteoconductivity and osteoinductivity.

US 20160067375 Al discloses 3D biomimetic, bi-phasic key featured scaffold for osteochondral repair. This invention describes methods for the creation of 3D biologically inspired tissue engineered scaffolds with both excellent interfacial mechanical properties, and biocompatibility and products created using such methods. In some cases, a combination of nanomaterials, nano/microfabrication methods and 3D printing can be employed to create structures that promote tissue reconstruction and/or production. In other embodiments, electro spinning techniques can be used to create structures made of polymers and nanotubes. CN 104473705 A discloses head maxillofacial bone implant and a method for quickly molding the same. The method is particularly a processing method for prosthesis for defects of the facial bones of human bodies, and the prosthesis is obtained by the aid of a processing technology for quickly polymerizing and molding powder. The method includes constructing maxillofacial post-traumatic models of patients according to image data of the bones of the patients; manufacturing three-dimensional models according to treatment repair requirements of clinical doctors by means of symmetric mirroring, curve design, database matching and the like. The image data of the bones of the patients are acquired by the aid of image diagnostic techniques such as CT (computed tomography) or MRI (magnetic resonance imaging). The three-dimensional models are matched with the traumatic positions of the patients. The head maxillofacial bone implant and the method have the advantages that the prosthesis models can be molded by the aid of the processing method for quickly molding the implant, and accordingly the prosthesis can be manufactured; the prosthesis which is processed in a personalized manner can be designed and processed for the patients with the maxillofacial defects and particularly patients with complicated defect structures, and the prosthesis with an anatomical repair effect and an effect of recovering functions of the maxillofacial organs of the patients can be manufactured.

EP 2384775 A2 describes method for producing an artificial bone and artificial bone produced by the method. A method for producing an artificial bone is provided wherein electromagnetic waves or electron beams are irradiated to a layer of one or more types of powder selected from metal biomaterials, ceramics for an artificial bone and plastic resins for an artificial bone based on image data corresponding to a shape of the artificial bone, thereby effecting sintering or melting, and wherein the thus sintered layer or the thus melted and solidified layer is laminated, and wherein a surface finish step is adopted in which inner faces and/or outer faces of both ends and their vicinities configuring a joined part to a human bone part are polished by a rotating tool based on the image data, and wherein further the irradiation of electromagnetic waves or electron beams at both ends and their vicinities configuring the joined parts is increased as compared to other regions. Further, an artificial bone is provided which is produced by the method.

CN 105125325 A discloses a manufacturing method for customizing a femoral head necrosis repair module by applying a three-dimensional printing technology. The method comprises the following steps: performing computerized tomography reconstruction on a femoral head of a patient, and manufacturing a femoral head prosthesis model on a computer solid figure so as to simulate conditions of the femoral head of the patient on the femoral head prosthesis model; excising necrosis and collapse parts in the femoral head prosthesis model; manufacturing femoral head repair modules for filling up the necrosis and collapse parts of the patient according to a skeletal three-dimensional image and a bone border of the femoral head of the patient, which are obtained after excising the necrosis and collapse parts; and printing out the repair modules by using a three-dimensional printer, wherein the material for preparing the repair modules can be a titanium alloy material or a polyethylene material. A femoral head prosthesis and a use method thereof are provided by the invention, and the femoral head prosthesis has good wear resistance, biocompatibility and stability; and a femoral head prosthesis highly matching the patient can be customized.

Therefore to overcome the drawbacks of the conventional method and techniques there is need to develop and design a novel technique for producing an artificial temporal bone. Hence the present invention provide design for fabrication of artificial temporal bone using 3D printing technique: a dissection training tool that can be used as dissection training tool for various ENT operational techniques. Object:

1. Primary object of the present invention is to provide design for fabrication of artificial temporal bone using 3D printing technique.

2. Another object of the present invention is to provide a design for fabrication of artificial temporal bone showing maximum internal and external anatomical features.

3. Yet another object of the present invention is to develop accurate geometric model of temporal bone.

4. Yet another object of the present invention is to use as dissection training tool for various ENT techniques.

5. Yet another object of the present invention is to provide 3D printing of temporal bone with close tolerances.

6. Yet another object of the present invention is to improve mechanical properties of 3D printed part of temporal bone.

7. Yet another object of the present invention is to validate the propose work through haptic feedback.

8. Yet another object of the present invention is to design a modal useful for explaining the intricate anatomical details of temporal bone externally as well as internally.

9. Yet another object of the present invention is to design bone that holds hearing as well as balance apparatuses of the body along with many other important nerves and blood vessels compactly arrange in small space.

Other objects, features and advantages will become apparent from detail description and appended claims to those skilled in art. STATEMENT:

Accordingly following invention provides a design for fabrication of artificial temporal bone using 3D printing technique and method of manufacturing the same. The invention describes the designing virtual model for artificial temporal bone and validating the design by fabricating artificial temporal bone using 3D printed technique. CT scan of normal human is used for designing virtual model. This scan is then imported to Materialise Mimics Software for creating accurate geometric model, where bony structure is selected and geometric model of skull is created. Temporal bone is then separated through suture line from other bones. Geometric model of temporal bone with all intricate internal and external anatomical details is obtained. This model is then converted to STL file for 3D Printing. Further post processing is carried out to remove errors from STL file and cleaned STL file is obtained for 3D printing. This STL file is then imported to 3D printing Software and is printed using FDM technique. Once the model is printed, it is validated through 2 different stages. In the first stage, once again geometric model using this CT scan data is created for further validation, sliced at slice thickness of 0.625 mm and all the features are virtually identified. In second stage, haptic feedback is recorded while dissecting temporal bone using EMG technique. This artificial temporal bone shows closeness of 89.88% to cadaveric temporal bone in terms of drill response.

BRIEF DESCRIPTION OF DRAWING:

This invention is described by way of example with reference to the following drawing where,

Figure 1 of sheet 1 shows axial view of artificially designed temporal bone

Figure 2 of sheet 1 shows slicer view of artificially designed temporal bone

In order that the manner in which the above-cited and other advantages and objects of the invention are obtained, a more particular description of the invention briefly described above will be referred, which are illustrated in the appended drawing. Understanding that these drawing depict only typical embodiment of the invention and therefore not to be considered limiting on its scope, the invention will be described with additional specificity and details through the use of the accompanying drawing.

Detailed description:

Present invention describes the designing virtual model for artificial temporal bone and validating the design by fabricating artificial temporal bone using 3D printed technique. CT scan of normal human was used for designing virtual model. After selecting proper thresholding, virtual temporal bone model was extracted from other bony structure. Virtual model was then validated for internal and external anatomical features slice by slice. Once all the features are ensured in virtual model it was then tessellated and saved in STL file and then fabricated using 3D printing (FDM) technique.

It was observed that while slicing the STL model for 3D printing, some tiny features are skipped because of dimensional inaccuracy. Hence to validate the said tiny internal anatomical features, CT scan of artificial temporal bone was taken and all the internal features were validated in DICOM file. Again virtual model was developed using this DICOM files and external anatomical features were validated. Further validation was carried out by performing basic mastoidectomy, thus exploring various internal anatomical features.

For strength validation, haptic feedback was taken while dissecting on artificial temporal bone and was compared with cadaver temporal bone. Resisting drill force (drill response) was measured using EMG technique. 89.88 % of closeness in terms of drill response was observed as compare to cadaver temporal bone. Methodology :-

In this work detailed geometric/ virtual model of artificial temporal bone is created using CT scan data. CT scan of three volunteers (one female and two male of age group 20-30 yrs) was acquired from Galaxy City Scan, Nagpur. DICOM files of each and every scan were closely examined to ensure error free file for modeling i.e. all the important features were verified in original CT scan. CT scan of female volunteer was having maximum features; hence it was selected for further processing.

This scan was then imported to Materialize Mimics Software for creating accurate geometric model, where bony structure was selected and geometric model of skull was created. Temporal bone was then separated through suture line from other bones. Geometric model of temporal bone with all intricate internal and external anatomical details was obtained. This model was then converted to STL file for 3D Printing. Further post processing was carried out to remove errors from STL file and cleaned STL file was obtained for 3D printing. This STL file was then imported to 3D printing Software and was printed using FDM technique. Once the model was printed, it was validated through 2 different stages.

Stage 1 - In this stage, CT scan Artificial Temporal Bone was acquired from Galaxy City Scan, Nagpur. Each and every slice of CT scan in all views i.e. axial, coronal and sagittal view was closely examined. All the features present in original CT scan of female volunteer were identified in CT scan of Artificial Temporal Bone. Once again geometric model using this CT scan data was created for further validation. Geometric model was again sliced at slice thickness of 0.625 mm and all the features were virtually identified. This technique helped us in ensuring maximum features in geometric model.

Stage 2 - In this stage, haptic feedback was recorded while dissecting temporal bone using EMG technique. Initially sensors were placed at wrist, thumb finger and index finger to obtained maximum signals (feedback). It was observed that index finger was giving maximum feedback as compared to other. During dissection, sensor was placed at index finger and drill response was captured while dissecting cadaveric temporal bone as well as artificial temporal bone. Drill response was captured in terms of maximum muscle force (in newton's) exerted during dissection. Maximum drill response while dissecting cadaver was 725.018N and while dissecting artificial bone was 651.714N as shown in below table.

This artificial temporal bone shows closeness of 89.88% to cadaveric temporal bone in terms of drill response.

In this way the proposed work is validated in two different stages. In stage 2, various internal anatomical features were also explored through mock surgery, thus visual validation was also performed. Dissection of cadaveric as well as artificial temporal bone was performed by Dr. Prashant M. Naik (MS ENT) at Naik's Hospital Nagpur.

Best method of performance of the invention:

The sole purpose of this project was to develop accurate geometric model of artificial temporal bone with maximum internal and external anatomical features that can be fabricated and handed over to PG Students and practicing otolaryngologist in physical form. Said design was fabricated using 3D Printing (FDM) technique which can replace conventional method of dissecting cadaver bones. In initial 3D printed model, many internal features were absent. Proper orientation was chosen to 3D Print of further bones to ensure all features are presented in physical model. While dissecting cadaver temporal bone, maximum drill responsive force exerted was 725.018N, whereas while dissecting artificial temporal bone maximum drill responsive force exerted was 651.714N i.e. closeness of 89.88% was achieved.

Application:

An artificial temporal bone model using 3D printing technique is having capabilities to be used as teaching aids to medical students and practicing otolaryngologist. Various surgical techniques can be simulated using this model such as:

i. Mastoidectomy

ii. Facial Nerve Surgery

iii. Translabyrinthine approaches to Internal Acoustic Canal

iv. Cochleostomy

v. Endolymphatic SAC Surgery

vi. Lateral Sinus Decompression etc. Anatomical features:

While performing mock surgery on artificial temporal bone following features were encountered.

i. This bone shows squamous part, tympanic part, styloid process, and petromastoid part.

ii. Lateral surface has external acoustic canal, glenoid fossa, zygomatic process, Glaserian fissure with anterior tympanic and chorda tympani foramina, tympanic plate, tympanomastoid and tympanosquamous sutures, mastoid emissary foramen, mastoid process, and middle ear structures as malleus and incus long processes, promontory, oval and round window, eustachian and tensor tympani canals, and aditus ad antrum.

iii. Anterior surface shows Meckel's cave, facial hiatus and foramen for greater superficial petrosal nerve, groove for middle meningeal artery, upper opening of internal carotid canal, and medial to it the tensor tympani canal as well as eustachian tube.

iv. The inferior surface shows lower opening of internal carotid canal, jugular fossa, vascular crest and foramen for Jacobson's nerve, styloid process and stylomastoid foramen, and digastric as well as occipital grooves.

v. The posterior surface shows sigmoid sulcus, superior petrosal sulcus, vestibular aqueduct, arcuate eminence, subarcuate foramen, internal acoustic canal, and cochlear canaliculus for aqueduct. The fundus of the internal acoustic canal shows falciform crest, Bill's bar and other openings in its relation.

vi. The various canals and foramina described above can be threaded and by pulling on the threads integrity of these openings can be verified. vii. During mock surgery on this bone, for example simple mastoid surgery, following structures can be easily delineated: sinus plate, dural plate, sinodural angle, digastric ridge, aditus ad antrum, fossa incudis and incus, and the bulging of the lateral semicircular canal. viii. As facial canal can be threaded almost up to first genu of facial, this bone is useful to practice the facial nerve decompression surgery as well as the facial recess approach. Also, as lateral semicircular canal bulge is very well demarcated, endolymphatic sac surgery can be learnt on this bone.

The cochlear canal in this bone is formed for up to 1cm. Hence, cochleostomy and cochlear implant simulation can very well be practiced on this bone.

Additional advantages and modification will readily occur to those skilled in art. Therefore, the invention in its broader aspect is not limited to specific details and representative embodiments shown and described herein. Accordingly various modifications may be made without departing from the spirit or scope of the general invention concept as defined by the appended claims and their equivalents.