EP4287963A1

EP4287963A1 - Jaw surgical guide

Info

Publication number: EP4287963A1
Application number: EP22702322.3A
Authority: EP
Inventors: Sandro Moos; Enrico VEZZETTI; Andrea NOVARESIO; Guglielmo RAMIERI; Giovanni GERBINO; Emanuele ZAVATTERO; Claudia BORBON
Original assignee: Universita degli Studi di Torino; Politecnico di Torino
Current assignee: Universita degli Studi di Torino; Politecnico di Torino
Priority date: 2021-02-03
Filing date: 2022-02-02
Publication date: 2023-12-13
Also published as: IT202100002270A1; WO2022167942A1

Abstract

The invention relates to a cutting guide (15) of a mandible (20) comprising - a first shell (1) distal to the frontal plane, - a first cutting plane (2) fixed to the first shell (1), - a second shell (3) proximal to the frontal plane, - a second cutting plane (4) fixed to the second shell (3), - a connecting element (5) between the first shell (1) and the second shell (3), - a pair of reference elements (6) for positioning a prosthetic graft (30) in the mandible (20) to replace a pathological bone portion (40). The invention finds advantageous applications in the fields of maxillofacial surgery, otolaryngology (ENT) and plastic surgery, in particular for the treatment of bone tumour pathologies of the mandible.

Description

"Jaw surgical guide"

DESCRIPTION

TECHNICAL FIELD

The present invention relates to the surgery field and, in particular, to equipment and devices for surgical interventions on the mandible.

More particularly, the present invention relates to equipment and devices for replacing a pathological bone portion of the mandible with a graft, preferably coming from the patient's fibula.

The invention finds advantageous applications in the fields of maxillofacial surgery, otolaryngology (ENT) and plastic surgery, specifically for the treatment of bone tumour pathologies of the mandible.

STATE OF THE ART

Currently, industrially manufactured cutting guides are manufactured singly, without any connecting elements.

It is to be noted that, for the removal of the tumour from the tumour part, two resections must be performed in order to isolate the pathological bone portion.

The current cutting guides industrially produced have two shells, which have two cutting planes to support the blade of the resection tool, guiding the surgeon to perform the osteotomy; these two shells are two separate and distinct elements and there is no system that allows them to be united in a single object.

In some cases, due to the reduced bone contact, the anatomical adaptation ("fit") is not univocal.

The positioning of the residual abutments is solved only by using a pre-drilling system, by means of the cutting guide of the mandible, and a customized prosthesis. On the shells of the cutting guides there is a double series of holes; the first series is used to fix the guide to the bone and the second series is used to drill holes in the mandible where the customized prosthesis, for example a titanium plate, will be screwed. The set of holes on the graft flap, generally fibula, used for fixing the titanium plate are very difficult to see as the tissue that is left around the bone hides it.

Examples of known cutting guides are reported in patent documents CN107951538A, CN105852931B, CN105342702B and CN109219408A.

CN107951538A discloses mandible osteotomies performed with two separate cutting guides; the guides show the osteotomy plan.

However, the two cutting guides of the mandible are independent and a connecting element is not provided.

CN105852931B describes mandible osteotomies performed with two separate cutting guides; the guides show the osteotomy plan.

The graft flap, generally fibula, is taken with another cutting guide.

A third guide is used on the mandible to position the graft flaps in the receiving site, and this last guide also defines the position of the dental implants.

However, the two cutting guides of the mandible are independent and a connecting element is not provided; furthermore, the positioning of the fibula flaps occurs through a third guide anchored to the mandible.

CN105342702B describes a device to keep the healthy mandible portions in position following the resection and removal of the tumour area.

However, the device only allows keeping the mandible in position without defining the guide planes for performing osteotomies; furthermore, this device does not provide an aid for the positioning of the graft flap, generally fibula.

CN109219408A describes mandible osteotomies performed with two separate cutting guides shaped with a thin shell; the guides show the osteotomy plan.

Examples of known cutting guides are also reported in the following scientific publications:

- M. Mottini, S. M. Seyed Jafari, M. Shafighi, and B. Schaller, "New approach for virtual surgical planning and mandibular reconstruction using a fibula free flap", Oral Oncol., Vol. 59, pp. e6 - e9, Aug. 2016;

- Y. Y. Wang et al., "Mandibular reconstruction with the vascularized fibula flap: comparison of virtual planning surgery and conventional surgery", Int. J. Oral Maxillofac. Surg., Vol. 45, no. 11, pp. 1400-1405, Nov. 2016;

- F. Wilde, C.-P. Cornelius, and A. Schramm, "Computer-Assisted Mandibular Reconstruction using a Patient-Specific Reconstruction Plate Fabricated with Computer-Aided Design and Manufacturing Techniques", Craniomaxillofacial Trauma Reconstr., Vol. 7, no. 2, pp. 158-166, June 2014;

- R. Bose et al., «Mandibular reconstruction after cancer: an in-house approach to manufacturing cutting guides», Int. J. Oral Maxillofac. Surg., Vol. 46, no. 1, pp. 24-31, Jen. 2017;

- G. Succo et al., "Step-by-step surgical technique for mandibular reconstruction with fibular free flap: application of digital technology in virtual surgical planning", Eur. Arch. Otorhinolaryngol., Vol. 272, no. 6, pp. 1491-1501, June 2015;

- L. Ganry, J. Quilichini, C. M. Bandini, P. Leyder, B. Hersant, and J.P. Meningaud, "Three-dimensional surgical modeling with an open-source software protocol: study of precision and reproducibility in mandibular reconstruction with the fibula free flap», Int. J. Oral Maxillofac. Surg., Vol. 46, no. 8, pp. 946-957, Aug. 2017.

However, none of the aforesaid scientific publications describes or suggests a cutting guide equipped with a connecting element useful for positioning the graft in the receiving site and the synergistic use of the mandible cutting guide and the bone graft cutting guide.

Furthermore, all the solutions known up to now and reported above have numerous drawbacks.

In particular, in the guides currently available, the parts of the mandible remaining following the removal of the tumour remain free from each other and, therefore, can lose alignment; the fibula graft and the healthy portions of the mandible must be manually positioned by the surgeon during insertion and must be fixed with screws of the titanium plate; the orientation of the flap - to be understood as rotation of the graft around its axis - must be estimated by eye by the surgeon so the operation is possible but the quality of its success exclusively depends on the skills (albeit exceptional) of the surgeon; the precision of the operation is poor and the duration of the operation increases due to the considerable laboriousness of the procedure for aligning and fixing the flap in the receiving site.

A cutting guide able to identify the plans for performing osteotomies for the removal of the pathological bone during the demolition phase of the surgical intervention, to correctly position the prosthesis in the receiving site during the mandibular reconstructive surgical phase and to set the initial position of the residual mandibular abutments would satisfy the needs of numerous surgical applications, for example for the treatment of bone pathologies such as mandible tumours.

The present invention, which relates to such a cutting guide equipped with a connecting element, intends to meet the above requirements.

In particular, the present invention intends to solve the technical problem of having a cutting guide for the blade of the cutting tool during osteotomy.

Furthermore, the present invention intends to solve the technical problem of how to keep the remaining parts of the healthy mandible in position following the removal of the pathological bone.

Furthermore, the present invention intends to solve the technical problem of guaranteeing a univocal positioning of the cutting guide even for cases in which the supporting surface has limited dimensions.

Finally, the present invention intends to solve the technical problem of positioning the replacement element (graft or implant or flap) in the receiving site as decided during the preoperative planning virtual phase.

In summary, therefore, up to the present time, to the knowledge of the Applicants, there are no known solutions that allow the plans for performing osteotomies for the removal of the pathological bone to be uniquely identified in every circumstance during the demolition phase of the surgical intervention, to correctly position the prosthesis in the receiving site during the mandibular reconstructive surgical phase and to set the initial position of the residual mandibular abutments, specifically in surgical applications for the treatment of bone pathologies such as mandible tumours. Therefore the Applicants, with the cutting guide equipped with a connecting element according to the present invention, intend to remedy this lack.

OBJECTS AND SUMMARY OF THE INVENTION

It is the object of the present invention to overcome the drawbacks of the known prior art related to the difficulty of identifying the plans for performing osteotomies for the removal of pathological bone portions during the demolition phase of a surgical intervention.

Furthermore, it is an object of the present invention to overcome the drawbacks of the known prior art related to the difficulty of correctly positioning the prosthesis in the receiving site during the mandibular reconstructive surgical phase.

Furthermore, it is an object of the present invention to overcome the drawbacks of the known prior art related to the difficulty of setting the initial position of the residual mandibular abutments.

These objects are achieved with the cutting guide according to the present invention that, advantageously and thanks to the presence of a connecting element, allows to improve the efficacy and efficiency of surgical interventions on the mandible, in particular the replacement of a pathological bone portion of the mandible with a graft, preferably coming from the patient's fibula.

The cutting guide equipped with a connecting element according to the present invention has, as advantages, the possibility of

- having a greater personalization of the guide depending on the clinical case,

- having a greater possibility of adjustments of the positions or setting during surgery depending on the clinical situation,

- quickly positioning and univocally orienting the cutting device on the patient's mandible thanks to the anatomical "fit" of the cutting guide shells and of the connecting arm,

- keeping the parts of the healthy mandible in position following the removal of the pathological bone,

- ensuring a better positioning of the prosthesis during the reconstructive phase compared to traditional methods, in particular for cases in which several bone fragments are used by adopting an innovative closure and positioning system implemented on the cutting guide used for the removal of the flap,

- reducing the times in the theatre for the patient's benefit and also the costs related to the stay in the theatre.

Specifically, the aforesaid and other objects and advantages of the invention, which will emerge from the following description, are achieved with the cutting guide according to claim 1.

Preferred embodiments and variants of the cutting guide according to the present invention are the subject of the dependent claims.

It is understood that all the appended claims form an integral part of the present description and that each of the technical features claimed therein is possibly independent and can be autonomously used with respect to the other aspects of the invention.

It will be immediately evident that innumerable changes (for example relevant to shape, sizes, arrangements and parts with equivalent functionality) can be made to what described without departing from the scope of the invention as claimed in the appended claims.

Further advantageous features will become more evident from the following description of preferred but not exclusive embodiments, merely given by way of nonlimiting example.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described hereinafter by means of some preferred embodiments, given by way of non-limiting example, with reference to the attached drawings. These drawings illustrate different aspects and examples of the present invention and, where appropriate, similar structures, components, materials and/or elements in different figures are denoted by similar reference numbers. FIG. 1 is a perspective view of the cutting guide according to the present invention;

FIG. 2 is a perspective view of the cutting guide according to the present invention applied to the mandible of a patient who has a bone affected by a tumour;

FIG. 3A is a perspective view of the mandible of a patient in which the bone affected by a tumour requires a critical proximal osteotomy;

FIG. 3B is a perspective view of the mandible of a patient in which the bone affected by a tumour requires a critical proximal osteotomy, mandible to which the cutting guide according to the present invention is applied;

FIG. 4 is a perspective view of the cutting guide according to the present invention that, through the connecting element, keeps the parts of the healthy mandible in position after having removed the tumour;

FIG. 5 is a perspective view of the mandible of a patient to which the cutting guide according to the present invention is applied and the bone graft replacing the removed pathological portion;

FIG. 6 is a perspective view of a detail of the cutting guide according to the present invention;

FIG. 7, illustrating Example 1 - CASE 1 Simulation, is a perspective view of the cutting guide according to the present invention positioned on the mandible, performing osteotomies and reposition of the tumour;

FIG. 8 is the colorimetric map of the absolute distance between the model created during Example 1 - CASE 1 Simulation and the CAD model;

FIG. 9, illustrating Example 1 - CASE 2 Simulation, is a perspective view of the positioning of cutting shells without the connecting element and performing osteotomies; the critical positioning of the cutting shell proximal to the frontal plane is noted;

FIG. 10 is the colorimetric map of the absolute distance between the model created during Example 1 - CASE 2 Simulation and the CAD model;

FIG. 11, illustrating Example 2 - CASE 1 Simulation, is a perspective view of the cutting guide according to the present invention positioned on the mandible, performing osteotomies and reposition of the tumour;

FIG. 12 is the colorimetric map of the absolute distance between the model created during Example 2 - CASE 1 Simulation and the CAD model;

FIG. 13, illustrating Example 2 - CASE 2 Simulation, is a perspective view of the positioning of cutting shells without the connecting element and performing osteotomies; the critical positioning of the cutting shell distal to the frontal plane is noted;

FIG. 14 is the colorimetric map of the absolute distance between the model created during Example 2 - CASE 2 Simulation and the CAD model;

FIG. 15, illustrating Example 3 - CASE 1 Simulation, is a perspective view of the cutting guide according to the present invention positioned on the mandible, performing osteotomies and illustrative reposition of the tumour;

FIG. 16 is the colorimetric map of the absolute distance between the model created during Example 3 - CASE 1 Simulation and the CAD model;

FIG. 17, illustrating Example 3 - CASE 2 Simulation, is a perspective view of the positioning of cutting shells without the connecting element and performing osteotomies; the critical positioning for both shells is noted;

FIG. 18 is the colorimetric map of the absolute distance between the model created during Example 3 - CASE 2 Simulation and the CAD model.

DETAILED DESCRIPTION OF THE INVENTION

While the invention is susceptible to various modifications and alternative constructions, some preferred embodiments are shown in the drawings and will be described in detail hereinbelow.

It is to be understood, however, that there is no intention of limiting the invention to the specific illustrated embodiments, but, on the contrary, the invention is intended to cover all modifications, alternative constructions and equivalents that fall within the scope of the invention as defined in the claims.

In the following description, therefore, the use of "for example", "etc.", "or" denotes non-exclusive alternatives without any limitation, unless otherwise indicated; the use of "also" means "including, but not limited to", unless otherwise indicated; the use of "includes / comprises" means "includes / comprises, but not limited to", unless otherwise indicated.

The cutting guide of the present invention is based on the innovative concept of combining a connecting element between two shells, one of which is equipped with suitable reference elements.

The Inventors have in fact surprisingly observed and unexpectedly discovered that such a cutting guide is able to allow the univocal positioning of the cutting guide even in the presence of small shells; in many cases the positioning, sought exclusively with the anatomical "fit", is not very precise and not univocal.

In the present description, the term "guide" means a sufficiently rigid element that is positioned on the mandible; the shape of the guide element shows the orientation of the osteotomies identified by the cutting planes.

In the present description, the term "cut" means the bone resection operation aimed at removing the mandibular tumour.

In the present description, the term "mandible" means the lower maxillary bone of the skull, mobile and articulated, consisting of a central body, on whose upper edge there is the lower dental arch, and two lateral parts that connect it to the skull.

In the present description, the term "shell" means a sufficiently rigid element integral with the first cutting plane element or the second cutting plane element to guide the blade of the cutting tool; the shape of the inner part of the shell, the one in contact with the bone, replicates the mandible's anatomy in correspondence with the contact region and this facilitates the positioning of the guide on the bone by researching the anatomical "fit".

In the present description, the term "cutting plane" means a sufficiently rigid element, integral with the first shell or the second shell, and useful for identifying the orientation of the osteotomies and for guiding the surgeon during the bone resection phase.

In the present description, the term "connecting element" means a sufficiently rigid element integral with the first shell and the second shell and useful for univocally identifying the mutual position of the two shells.

In the present description, the term "reference element(s)" means a sufficiently rigid element integral with the connecting element and useful for correctly positioning the cutting guide of the fibula for inserting the flap inside the mandible as a replacement of the tumour mandibular part.

In the present description, the term "reference foot(feet)" means a rigid element integral with the first portion and the second portion of the cutting guide of a bone graft; these reference feet must be used in synergy with the cutting guide of a mandible and allow to identify the correct position of the cutting guide of a bone graft inside the mandible.

In the present description, the term "graft" means the autologous tissues, bone tissues and soft tissues, taken from a part of the body, the fibula.

In the present description, the term "pathological bone portion" means the mandible volumetric part compromised by the tumour or another degenerative cause, for which surgical removal is required.

In the present description, the term "healthy bone portion" means the mandible remaining part that, following the removal by osteotomy of the pathological part, is divided into two parts and requires an autologous bone prosthesis to recompose the lower maxillary bone.

In the present description, the term "segment" means a portion of bone taken from the fibula.

In the present description, the term "flap" means the autologous graft, consisting of one or more vascularized bone segments, taken from the fibula and used to restore the normal aesthetic and functional characteristics of the mandible, in replacement of the pathological bone portion.

In the present description, the term "frontal (or coronal) plane" means an imaginary plane passing through the human body. This plane is vertical, parallel to the forehead and perpendicular to the median plane. The frontal (or coronal) plane divides the human body into anterior and posterior part. The median plane is vertical and passing through the centre of the body dividing it into two equal halves (right side and left side).

With reference to FIGS. 1, 2, 4, 5 and 6 it is observed that the cutting guide 15 of a mandible 20 according to the present invention comprises a first shell 1 distal to the frontal plane, a first cutting plane 2 fixed to the first shell 1, a second shell 3 proximal to the frontal plane, a second cutting plane 4 fixed to the second shell 3, a connecting element 5 between the first shell 1 and the second shell 3 comprising, in turn, a pair of reference elements 6, a pair of reference feet 7 integral with the cutting guide 10 that, together with the pair of reference elements 6, are suitable for positioning a graft 30 in the mandible 20 to replace a pathological bone portion 40.

Preferably the first shell 1 and the second shell 3 are joined by the connecting element 5; preferably the first shell 1 has a complex shape with a preferably constant thickness whose part in contact with the mandible reproduces the anatomical shape of the bone and the second shell 3 has a complex shape with a preferably constant thickness whose part in contact with the mandible reproduces the anatomical shape of the bone.

Preferably the first cutting plane 2 is integral with the first shell 1 and the second cutting plane 4 is integral with the second shell 3.

Preferably the connecting element 5, equipped with a pair of reference elements 6, has a shape with uniform section, preferably square, developed along a rectilinear profile in the central part and curvilinear at the ends.

Preferably the pair of reference elements 6 is used to correctly position the cutting guide 10 equipped with the reference feet 7; the correct position of the guide 10 involves the correct positioning of the fibula flap, that is to say of the graft 30, inside the mandible, this positioning being achieved by aligning the reference feet 7 with the reference elements 6. Preferably the pair of reference elements 6 has a cubic shape of a size congruent with the side of the section of the connecting element 5.

Preferably the pair of feet 7 is integral with the cutting guide 10 and each foot corresponds to a corresponding reference element 6, in order to determine the correct position of the fibula flap inside the mandible.

Preferably the pair of feet 7 has a preferably square sectional shape of a size congruent with that of the connecting element 5, developed along a profile consisting of two straight segments.

Preferably the cutting guide 15 is made of a biocompatible and sterilisable plastic material, more preferably it is made of methacrylic photoreactive resins for applications compatible with the additive manufacturing.

Preferably, the cutting guide 15 has a thickness ranging between 2.0 mm and 7.0 mm and, in any case, has a thickness not lower than 2.0 mm.

Preferably the graft 30 is taken from an autologous bone portion selected from fibula and iliac crest; more preferably the graft 30 is taken from the fibula 50.

Preferably the cutting guide 15 is suitable for the treatment of bone pathologies such as mandible tumours.

With particular reference to FIG. 1, it is observed that the positioning of the cutting guide 15 on the bone of the mandible 20 is ensured by the shells 1 and 3, the internal surface of these elements follows the shape of the bone of the mandible 20.

The anatomical "fit" of shells 1 and 3 allows to quickly position and orient the cutting guide 15 on the bone in a univocally way.

Subsequently, the cutting guide 15 is fixed to the bone by screws using the holes on the two shells 1 and 3.

With reference to FIG. 2, it is observed that the cutting guide 15 is positioned on the mandible 20.

Elements 2 and 4 identify the corresponding cutting planes, which direct the blade of the cutting tool to perform the two osteotomies.

Once the two cuts have been completed, the portion of bone affected by the tumour 40 has been confined and can therefore be removed from the mandible 20 and replaced with a bone segment, or graft, 30, preferably taken from the patient's fibula himself.

With reference to FIGS. 3 A and 3B, it is observed that the connecting element 5 performs the following tasks.

In certain clinical cases, the osteotomy proximal to the frontal plane, the one defined by the cutting plane 4, falls in correspondence with the condyle neck.

In this circumstance, or more generally when the anatomical "fit" is not sufficient to determine the programmed positioning, the support bone surface for the shell 3 has limited dimensions, with the consequent impossibility of correctly positioning the shell 3 on the mandible 20.

A non-univocal positioning of the cutting guide 15 involves the execution of a different osteotomy than the one planned before the surgical intervention, compromising the accuracy of the reconstruction of the mandible 20.

Always with reference to FIGS. 3A and 3B, it is illustrated, by way of example, a case of proximal resection in which the problem just described is present (FIG. 3A) and how it has been solved (FIG. 3B).

In fact, to overcome the aforesaid critical issue, the connecting element 5 between the shell 1 and the shell 3 was introduced.

The lower shell 1, thanks to the internal conformation, guarantees an immediate and univocal positioning and, consequently, the connecting element 5 allows to position without errors also the shell 3.

The connecting element 5 has been designed so that it is sufficiently rigid to avoid elastic deformations during the anchoring operation of the cutting guide 15 on the mandible 20.

On the contrary, the known commercial cutting guides do not have the connecting element and, therefore, the correct positioning of the two guides must be ensured exclusively by researching the anatomical "fit".

With reference to FIG. 4, it is observed that, following the removal of the pathological bone 40, the remaining parts of the healthy mandible are no longer connected to each other and are therefore free to move relative to each other; the connecting element 5 avoids losing the exact reciprocal position in the space of the two healthy bone portions by connecting them rigidly.

With reference to FIGS. 5 and 6, it is observed that, finally, the reference elements 6, integral with the connecting element 5, aligned with the reference feet 7 present on the cutting guide 10, allow to correctly position the cutting guide 10 and therefore to correctly position the bone fragment, or graft, 30, preferably taken from the patient's fibula.

To perform an adequate mandibular reconstruction, the inclination of the extreme faces of the graft fragment 30 must coincide with the spatial orientation of the planes of the osteotomies performed on the mandible 20.

The cutting guide 10 of the graft 30 shows the geometric information of the length of the bone fragment and the orientation of the planes of the osteotomies.

On the cutting guide 10 of the graft 30 there are two reference feet 7; to identify the correct position of the graft flap 30 inside the mandible 20 it is necessary:

- to lay the reference feet 7 of the cutting guide 10 of the graft 30 on the connecting element 5, as shown in FIG. 5, and

- to align the front face of the reference feet 7 with the front face of the support references 6, as shown in FIG. 6.

For mandibular reconstructions that involve the use of a single fibula segment, a pair of reference feet 7 will be present on the cutting guide 10.

For mandibular reconstructions that involve the use of two or more fibula segments, a series of reference feet 7 and a closure system 100' or 100" will be present on the cutting guide 10.

The cutting guide 15 of a mandible 20 according to the present invention is described in greater detail hereinafter by means of experimental data, which are intended as illustrative but not limitative of the present invention.

In order to experimentally evaluate the effectiveness of the cutting guide 15 of a mandible 20, two simulations were performed for each of the three examples reported below:

- CASE 1: simulation of execution of mandibular osteotomies using the cutting guide 15 of a mandible 20 equipped with a connecting element 5 between the first shell 1 and the second shell 3 according to the present invention; and

- CASE 2: simulation of execution of mandibular osteotomies with traditional cutting guides, therefore without a connecting element 5.

The simulations were performed on two models, made of plastic material, of anatomical replicas corresponding to the mandible.

To quantify the correct execution of mandibular osteotomies, the two simulations models were compared with the preoperative planning CAD model. An osteotomy is considered correct if the position and the orientation of the latter coincide with the cutting plane defined in the preoperative phase on the CAD model.

The cutting guide carries out the task of reproducing in the theatre the position and the orientation of the definitive cutting planes on the CAD model, therefore it is essential to univocally identify, during the surgical intervention, the correct positioning of the cutting guide 15 of a mandible 20 on the patient's bone anatomy. Once the osteotomies were completed, the shape of the two plastic material models was acquired using a structured light 3D scanner and then aligned to the CAD model in correspondence of the bone parts that remain invariant following the surgical intervention.

The three examples below reported concern, respectively:

Example 1: the removal of the body and the right mandibular ramus. The positioning of the proximal shell to the frontal plane is critical. The positioning is defined as critical when the positioning of the shell through the research for the anatomical "fit" is not sufficiently univocal and immediate.

Example 2: the removal of the left body of the mandible. The positioning of the distal shell to the frontal plane is critical.

Example 3: the removal of the left body of the mandible. The positioning of both shells, proximal and distal to the frontal plane, is critical. CASE 1 Simulation

In FIG. 7 it is observed that, following the positioning of the cutting guide 15 on the mandible 20, the osteotomies were performed and then the tumour bone portion was removed.

In FIG. 8 it is observed that the model created was acquired with the 3D scanner, aligned to the CAD model and then a colorimetric map was defined to quantify the distance between the two objects.

The maximum absolute distance at the proximal osteotomy with respect to the frontal plane is 1.90 mm, at the distal osteotomy it is 1.25 mm.

CASE 2 Simulation

In FIG. 9 it is observed that the positioning of the distal shell 1 with respect to the frontal plane was easy and univocal, vice versa the position of the proximal shell 3 was not identifiable at all due to the small size of the shell. The research for the correct position exclusively through the anatomical "fit" between guide and mandible is not sufficient to univocally and immediately position the aid device for performing the osteotomy.

In FIG. 10 it is observed that the model created was acquired with the 3D scanner, aligned with the CAD model and then a colorimetric map was defined to quantify the distance between the two objects.

The maximum absolute distance at the proximal osteotomy with respect to the frontal plane is 6.15 mm, at the distal osteotomy it is 1.35 mm.

As the colorimetric maps (FIG. 8 and FIG. 10) show, the osteotomies performed during the first simulation are more accurate, the position and the orientation of the cutting plane corresponding to the osteotomy reflects much more those planned in the preoperative phase on the CAD model.

During the second simulation, the most critical positioning corresponds to the proximal shell: the absolute distance of the osteotomy performed with respect to the virtual one is 6.15 mm, which is reduced to 1.9 mm by adopting the connecting element 5 between the first shell 1 and the second shell 3.

CASE 1 Simulation

In FIG. 11 it is observed that, following the positioning of the cutting guide 15 on the mandible 20, the osteotomies were performed and then the tumour bone portion was removed.

In FIG. 12 it is observed that the model created was acquired with the 3D scanner, aligned to the CAD model and then a colorimetric map was defined to quantify the distance between the two objects.

The maximum absolute distance at the proximal osteotomy with respect to the frontal plane is 0.55 mm, at the distal osteotomy it is 0.98 mm.

CASE 2 Simulation

In FIG. 13 it is observed that the positioning of the proximal shell 3 with respect to the frontal plane was easy and univocal, vice versa the positioning of the distal shell 1 was not univocal due to the insufficient anatomical "fit" between the internal part of the shell and the shape of the mandible. For clinical reasons it was not possible to increase the size of the shell 1. The research for the correct position exclusively through the anatomical "fit" between guide and mandible is not sufficient to univocally and immediately position the aid device for the execution of the osteotomy.

In FIG. 14 it is observed that the model created was acquired with the 3D scanner, aligned to the CAD model and then a colorimetric map was defined to quantify the distance between the two objects.

The maximum absolute distance at the proximal osteotomy with respect to the frontal plane is 0.40 mm, at the distal osteotomy it is 3.00 mm.

As the colorimetric maps (FIG. 12 and FIG. 14) show, the osteotomies performed during the first simulation are more accurate, the position and the orientation of the cutting plane corresponding to the osteotomy reflects much more those planned in the preoperative phase on the CAD model.

During the second simulation, the most critical positioning corresponds to the distal shell: the absolute distance of the osteotomy performed with respect to the virtual one is 3.00 mm, which is reduced to 0.98 mm by adopting the connecting element 5 between the first shell 1 and the second shell 3. The position of the proximal shell is easily identifiable only by researching the anatomical "fit" as it is positioned in correspondence with the mandibular angle, which by intrinsic conformation guarantees a univocal and immediate positioning.

Example 3

CASE 1 Simulation

In FIG. 15 it is observed that, following the positioning of the cutting guide 15 on the mandible 20, the osteotomies were performed and then the tumour bone portion was removed.

In FIG. 16 it is observed that the model created was acquired with the 3D scanner, aligned with the CAD model and then a colorimetric map was defined to quantify the distance between the two objects.

The maximum absolute distance at the proximal osteotomy with respect to the frontal plane is 0.21 mm, at the distal osteotomy it is 1.20 mm.

CASE 2 Simulation

In FIG. 17 it is observed that the positioning of both shells was critical. The research for the correct position exclusively through the anatomical "fit" between guide and mandible is not sufficient to univocally and immediately position the aid device for performing the osteotomy.

In FIG. 18 it is observed that the model created was acquired with the 3D scanner, aligned with the CAD model and then a colorimetric map was defined to quantify the distance between the two objects.

The maximum absolute distance at the proximal osteotomy with respect to the frontal plane is 2.87 mm, at the distal osteotomy it is 3.15 mm.

As the colorimetric maps (FIG. 16 and FIG. 18) show, the osteotomies performed during the first simulation are more accurate, the position and the orientation of the cutting plane corresponding to the osteotomy reflects much more those planned in the preoperative phase on the CAD model. During the second simulation, both shells reported a critical positioning: the absolute distance of the proximal osteotomy performed compared to the virtual one is 2.87 mm, which is reduced to 0.21 mm by adopting the connecting element 5 between the first shell 1 and the second shell 3. Furthermore, the absolute distance of the distal osteotomy performed with respect to the virtual one is 3.15 mm, which is reduced to 1.20 by adopting the connecting element 5.

In order to demonstrate the effectiveness of the cutting guide according to the present invention, experimental tests and a comparison with the traditional cutting guides were carried out. The results of the tests carried out are shown in the tables below:

New cutting guides

Example 1 Example 2 Example 3

Average distance 0.19 0.27 0.23

Mean square deviation 0.20 0.23 0.37

Proximal osteotomy maximum distance 1.90 0.55 0.21

Distal osteotomy maximum distance 1.25 0.98 1.20

Conventional cutting guides

Example 1 Example 2 Example 3

Average distance 0.30 0.30 0.37

Mean square deviation 0.47 0.29 0.48

Proximal osteotomy maximum distance 6.15 0.40 2.87

Distal osteotomy maximum distance 1.35 3.00 3.15

As it is visible from the above results, the cutting guide equipped with a connecting element according to the invention is better than the traditional cutting guides since the average distance value obtained during the first simulation is lower than that of the second simulation for all the examples examined. Observing the mean square deviation values, higher for the second simulation in all the examples, it is deduced that by adopting a cutting guide 15 of a mandible 20 equipped with a connecting element 5 it is possible to reproduce in the theatre with greater precision the position and the orientation of the virtual osteotomies compared to the use of the traditional cutting guides.

As it is deduced from what set out above, the innovative technical solution herein described has the following advantageous characteristics:

- possibility of greater personalization of the guide depending on the clinical case,

- possibility of making changes during surgery depending on the clinical situation,

- fast positioning and univocal orientation of the cutting device on the patient's mandible thanks to the anatomical "fit" of the cutting guide shells and the connecting arm,

- maintaining the healthy mandible parts in position following the removal of the pathological bone,

- ensuring a better positioning of the prosthesis during the reconstructive phase compared to the traditional methods, in particular for cases where more bone fragments are used, synergistic use of the cutting guide (15) of a mandible (20) and of the cutting guide (10) of a graft (30) for the positioning of the flap to replace the tumour mandibular part, reducing time in the theatre for the patient⁷ s benefit and also the costs related to the stay in the theatre.

From the above description it is evident, therefore, how the cutting guide according to the present invention allows to achieve the proposed objects.

It is equally clear, to a person skilled in the art, that it is possible to make changes and further variations to the solution described with reference to the attached figures, without thereby departing from the teaching of the present invention and from the scope as defined by the appended claims.

Claims

1. A cutting guide (15) of a mandible (20) comprising a first shell (1) distal to the frontal plane,

- a first cutting plane (2) fixed to the first shell (1), a second shell (3) proximal to the frontal plane,

- a second cutting plane (4) fixed to the second shell (3), a connecting element (5) between said first shell (1) and said second shell (3) comprising, in turn, a pair of reference elements (6), a pair of reference feet (7) that, together with the pair of reference elements (6), are suitable for positioning a graft (30) in said mandible (20) to replace a pathological bone portion (40).

2. A cutting guide (15) according to claim 1, wherein said first shell (1) has a complex shape with preferably constant thickness whose part in contact with the mandible reproduces the anatomical shape of the bone and wherein said second shell (3) has a complex shape with preferably constant thickness whose part in contact with the mandible reproduces the anatomical shape of the bone.

3. A cutting guide (15) according to claim 1 or 2, wherein said first cutting plane (2) is integral with said first shell (1) and said second cutting plane (4) is integral with said second shell (3).

4. A cutting guide (15) according to any of the preceding claims, wherein said connecting element (5), equipped with a pair of reference elements (6), has a shape with a uniform section, preferably square, developed along a straight profile in the central part and curvilinear at the ends.

5. A cutting guide (15) according to any of the preceding claims, wherein said pair of reference elements (6) has a cubic shape of a size congruent with the side of the square section of the connecting element (5).

6. A cutting guide (15) according to any of the preceding claims, wherein said pair of feet (7) has a preferably square cross-sectional shape of a size congruent with that of the connecting element (5), developed along a profile consisting of two rectilinear segments.

7. A cutting guide (15) according to any of the preceding claims, made of a biocompatible and sterilisable plastic material, preferably made of methacrylic photoreactive resins for applications compatible with the additive manufacturing.

8. A cutting guide (15) according to any of the preceding claims, having a thickness ranging between 2.0 mm and 7.0 mm and, in any case, having a thickness not lower than 2.0 mm.

9. A cutting guide (15) according to any of the preceding claims, wherein said graft (30) is taken from an autologous bone portion selected between fibula and iliac crest; more preferably said graft (30) is taken from the fibula (50).

10. A cutting guide (15) according to any of the preceding claims, for the treatment of bone pathologies such as tumours of the mandible.