WO2013017647A1

WO2013017647A1 - Additive manufacturing of openings with reduced dimensions

Info

Publication number: WO2013017647A1
Application number: PCT/EP2012/065092
Authority: WO
Inventors: Karim CHELLAOUI
Original assignee: Materialise Nv
Priority date: 2011-08-02
Filing date: 2012-08-02
Publication date: 2013-02-07

Abstract

The invention relates to methods for manufacturing objects comprising openings with reduced dimensions using additive manufacturing.

Description

ADDITIVE MANUFACTURING OF OPENINGS

WITH REDUCED DIMENSIONS

FIELD OF THE INVENTION

BACKGROUND

Additive manufacturing is a process of making three dimensional solid objects from a digital model. This process finds use in a variety of fields including dental and medical tools and implants, civil engineering, engineering and construction (AEC), automotive and aerospace industries, industrial design, architecture, jewellery, footwear, and many others.

Stereolithography (SLA) and Selective Laser Sintering (SLS) are the most commonly used additive manufacturing technologies. However, these additive manufacturing technologies may not always provide a satisfactory result when the object being manufactured contains functional openings of reduced size. Indeed, when small openings are provided in an object made by an additive manufacturing technique, the openings often become congested by powder or resin leading to openings filled with the manufacturing material. This material is hard to remove and requires manual handing and time consuming post-processing of the manufactured parts.

Often, objects made by additive manufacturing include small functional openings, For example, patient-specific medical guides typically have openings that are used to accurately place pins, guide bone cuts or insert implants during orthopaedic procedures. The guides are made from a pre-operative plan formed from an MRI or CT scan of the patient and rely on the matching of a subcutaneous anatomic feature for correct positioning. These types of guides are often used in surgery of the spine, hip, knee or radius, but also other types of surgery are available. The main function of these guides is to guide inserted surgical instruments in a position that is planned pre-operatively. Each of these guides has custom design to implement the planning and to make the other surgical instruments fit in.

Potentially any kind of surgical instrument can be guided by such a guide, but the most commonly used surgical instruments are saw blades, drill bits, wires and metal guides. These surgical instruments have typical small dimensions of for instance 0.4 mm for a saw blade and for instance a diameter of 1 .5 mm for a metal guide. In order to maximize the accuracy of the guidance, two constraints have to be filled for the openings in which the instruments are inserted: the surgical instruments must have a close contact with the guide

there must be enough contact surface between the instruments and the guides

Examples of such guidance openings are rectangular slots 0.5mm thick, 15mm long and 10mm deep (for saw blades) or cylindrical slots of diameter 1 mm and 10mm deep (for drill bits and wires).

Additive manufacturing is the default choice for manufacturing patient-specific guides as it allows both the production of patient-specific surfaces for an accurate fit and the incorporation of functional features based on a pre-operative plan. However, as for other applications, the challenge for additive manufacturing techniques remains to generate openings of reduced size which are not congested with the manufacturing material.

SUMMARY OF THE INVENTION

Methods are provided herein for manufacturing objects with an opening of a reduced size by additive manufacturing technologies, whereby clogging of the opening is prevented. More particularly the methods of the invention comprise generating an opening with one or more recesses, whereby the required dimension of the opening is maintained.

In particular embodiments, methods are provided for manufacturing an object with at least one opening by additive manufacturing, comprising the steps of:

a) Determining the required dimensions of the opening, whereby the required

dimensions correspond to the functional properties of the opening;

b) Providing, in the design of said opening of said object, one or more recesses in said opening, whereby said recesses maintain said required dimensions of the opening; and

c) Manufacturing said object with said opening comprising said recess according to the design of step (b).

In particular embodiments of these methods, the total volume of the opening comprising the recess is at least 15% larger than the volume of the opening without the recess. More particularly, in at least one transversal section of the opening, the circumference of the opening comprising the recess is at least 15% larger than the circumference of the opening without the recess. In particular embodiments, in any given transversal section, the circumference of the opening comprising the recess is at least 15% larger than the circumference of the opening without the recess.

Typically, in methods for manufacturing envisaged herein, the opening extends as a shaft into the object. In particular embodiments the recess is designed in the opening such that it forms a groove extending over the over the length of the inner surface of said shaft. Additionally or alternatively, the recess is designed to form a groove transversely to the orientation of the shaft in the object.

In the methods envisaged herein, the recess provided on the opening can have an irregular shape, a crenated shape, a serrated shape, a jagged shape, a sinusoidal shape, a toothed shape, a parabolic shape, a notched shape, a scalloped shape, a denticulated shape or a combination thereof.

In particular embodiments of the methods envisaged herein, the opening concerned is an opening for insertion of an object and the required dimensions of the opening to be identified in step (a) are determined by the dimensions of said object

In particular applications of the methods envisaged herein, the object is a surgical guide and said opening is a guiding opening in the body of said surgical guide for guiding a surgical tool. In particular embodiments, methods for manufacturing a guide for a cutting or drilling tool or a fastening tool are provided, the guide being provided with a body comprising at least one shaft with a guiding opening. In particular embodiments the method comprises the steps of:

a) designing the guide body;

b) determining the required dimension of the guiding opening and shaft extending within said body, whereby said required dimensions correspond to the minimal shaft;

c) designing an improved shaft by providing recesses on the surface of said minimal shaft thereby maintaining the required dimensions of the guiding opening; and;

d) manufacturing said guide body with said improved shaft by additive manufacturing.

In further particular embodiments, the present invention relates to a method for manufacturing a guide for a cutting or drilling tool or a fastening tool. In further particular embodiments said guide is for guiding such a tool into an object of interest along a desired path. In particular embodiments, the guide is designed for positioning on an object of interest by positioning elements. More particularly said method comprises the steps of:

a) determining the desired body structure of said guide such that it contains the required positioning elements for positioning said guide on said object of interest; b) determining the required dimension of the guiding opening extending within said body, whereby said required dimensions correspond to the minimal shaft; c) designing an improved shaft by providing recesses on the surface of said minimal shaft thereby maintaining the required dimensions of the guiding opening; and;

In particular embodiments, methods are provided wherein the surface of said improved shaft is at least 15% larger than the surface of said minimal shaft. In particular embodiments, the present invention provides in a method wherein said recesses form grooves extending over the length of the surface of said shaft. In particular embodiments, the present invention provides in a method wherein said recesses form grooves extending transversally to the direction of the guiding opening. In particular embodiments, the present invention provides in a method wherein said surface of said improved shaft has an irregular shape corresponding to a crenated shape, a serrated shape, a jagged shape, a sinusoidal shape, a toothed shape, a parabolic shape, a notched shape, a scalloped shape, a denticulated shape or a combination thereof. In particular embodiments, the present invention provides in a method wherein said guide is a surgical guide and said guiding opening is an opening for guiding a surgical tool. In particular embodiments, the present invention provides in a method wherein said surgical tool is chosen from a drilling tool, a cutting tool, a sawing tool or a screwing tool. In particular embodiments, the present invention provides in a method wherein said guide opening is for a fastening means, such as a pin.

Also provided herein are objects made by additive manufacturing comprising at least one opening of a reduced size, whereby the opening is provided with a recess, which recess does not affect the functional dimension of the opening. More particularly, objects are provided which are made by additive manufacturing and comprise at least one opening with a recess as described herein, which objects are obtainable by the methods described herein.

For particular applications, guides are provided which are obtainable by the methods according to the present invention. In particular embodiments, the guides comprise a guiding opening whereby the functional opening is formed by the crests of square or trapezoidal waves formed by the surface of the improved shaft. In particular embodiments, the guides are provided wherein the cross-section of the minimal shaft is an oblong and the surface of the shaft extending along the longer sides of the oblong are recessed. In particular embodiments, the guides are provided wherein the surface of the shaft forms a trefoil around the guiding opening. BRIEF DESCRIPTION OF THE DRAWINGS

The following description of the figures of specific embodiments of the invention is merely exemplary in nature and is not intended to limit the present teachings, their application or uses. Throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

Figure 1 Illustration of a conventional opening (A) for inserting an object with a rectangular cross-section, such as a saw blade (1 ) and an opening comprising recesses (B) which can serve as an improved guiding opening according to a particular embodiment of the methods and devices described herein .

Figure 2 Example of an opening (4) and the same opening provided with recesses (3) according to a particular embodiments of the invention. Such an opening can for instance be used as an opening for a saw blade guide.

Figure 3 Illustration of an alternative embodiment of a conventional opening (A) for inserting a longitudinal object, such as a pin or a saw blade (1 ) and an opening comprising recesses (B) which can serve as an improved guiding opening .

Figure 4 Example of an opening (4) and the same opening provided with recesses (3) according to a particular embodiments of the invention. Such an opening can for instance be used as an opening for guiding a saw blade.

Figure 5 Illustration of a conventional opening (A), e.g. for inserting a drilling tool and an opening comprising recesses (B) which can serve as an improved guiding opening according to particular embodiments of the methods and objects described herein.

Figure 6 Example of an opening (4) and the same opening provided with recesses (3) according to a particular embodiments of the invention. Such openings comprising recesses can be used to guide a drill according to particular embodiments of the methods and objects described herein.

Figure 7 Plunging view in an opening provided with recesses forming a sine wave according to particular embodiments of the methods and tools of the invention. This opening can be used as a saw blade guide opening.

Figure 8 Plunging view in an opening provided with recesses forming a square wave according to particular embodiments of the methods and tools of the invention. This opening can be used as a saw blade guide opening. DETAILED DESCRIPTION

The present invention will be described with respect to particular embodiments but the invention is not limited thereto but only by the claims. Any reference signs in the claims shall not be construed as limiting the scope thereof.

As used herein, the singular forms "a", "an", and "the" include both singular and plural referents unless the context clearly dictates otherwise.

The terms "comprising", "comprises" and "comprised of" as used herein are synonymous with "including", "includes" or "containing", "contains", and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps. The terms "comprising", "comprises" and "comprised of" when referring to recited members, elements or method steps also include embodiments which "consist of" said recited members, elements or method steps.

Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order, unless specified. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

The term "about" as used herein when referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of +/-10% or less, preferably +/-5% or less, more preferably or less, and still more preferably +/-0.1 % or less of and from the specified value, insofar such variations are appropriate to perform in the disclosed invention. It is to be understood that the value to which the modifier "about" refers is itself also specifically, and preferably, disclosed.

The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within the respective ranges, as well as the recited endpoints.

All documents cited in the present specification are hereby incorporated by reference in their entirety.

Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, definitions for the terms used in the description are included to better appreciate the teaching of the present invention. The terms or definitions used herein are provided solely to aid in the understanding of the invention.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments. Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

The application provides methods for manufacturing objects with an opening of a reduced size by additive manufacturing technologies.

The problems with the manufacture of small openings in additive manufacturing arises when two surfaces facing each other are too close to provide in an easy removal of the particles/resin used as building materials for these technologies.

Thus, in particular embodiments, at least the following constraints can be fulfilled by an improved design:

- Adequate contact surface to fulfill the required function, e.g. to accurately guide an inserted object; and;

Acceptable surface-to-surface distance to permit an easy the removal of unused particles/resin.

The advantages of such designs include:

- The avoidance of congestion issues when manufacturing small openings in additive manufacturing;

The possibility of manufacturing smaller openings than what was possible with conventional methods, down to the maximum accuracy of the manufacturing technology;

- The possibility of manufacturing openings that can be much deeper than what was possible with conventional methods; and;

A better air or liquid flow around the inserted instrument leading to better cooling of the heating occurring when using instruments with much friction.

Applications covered by this invention are not restricted to medical applications (orthopaedic surgery, dental surgery) and can occur in any context.

More particularly the methods of the invention are of interest for the manufacturing of objects which are to comprise one or more openings, whereby the dimension of the opening is important. Typically such openings are functional openings, i.e. they serve for the introduction of another object or part. The introduction of an object or part envisaged for this opening can be temporary (i.e. passage or guidance of objects) or for permanent fixation (e.g. in the context of an assembly of different objects). In light of the envisaged function of the opening, while the total volume of the opening is not important, the functional dimension of the opening is typically important, e.g. to ensure accurate guiding or stable fixation.

The methods of the present invention involve the creation of one or more recesses on the opening of interest, which recess is such that it does not affect the functional dimensions of the opening. In particular embodiments, methods are thus provided for the manufacturing of objects which comprise generating an opening with one or more recesses, whereby the required dimension of the opening is maintained.

In more particular embodiments, methods are provided for manufacturing an object with at least one opening by additive manufacturing, comprising the steps of:

a) Determining the required dimensions of the opening, whereby the required

dimensions correspond to the functional properties of the opening;

As detailed above, the required dimensions of the opening are typically dependent on and determined by the envisaged function of the opening. For instance, where the opening is required for introducing a cylindrical object, such as pin, the required dimension will be determined by the diameter of the cylinder.

Typically, in methods for manufacturing envisaged herein, the opening extends as a shaft into the object. In particular embodiments this shaft extends in a direction which is perpendicular to the surface of the object, but this need not be the case. It is thus envisaged that the one or more recesses provided on the opening can be provided all or part of the surface of the opening (corresponding to the inner wall of the shaft). For instance, in particular embodiments, a recess provided in the opening forms a groove extending over the over the length of the inner surface of said shaft. In particular embodiments, two or more grooves extend radially from the central axis of the opening.

Additionally or alternatively, a recess can be provided which forms a groove transverse to the orientation of the shaft of the opening in the object. Typically, in the methods and objects provided herein, the recesses are provided such that the internal surface or wall of the opening has an irregular shape provided with recessed openings and inward facing contact surfaces, said contact surfaces ensuring the functional properties of the opening.

In particular embodiments of the methods and objects envisaged herein, the surface or wall of the opening or shaft in the objects is at least 15% larger than the surface of the opening based on its required dimensions. More particularly, the surface of the recessed opening is at least 20%, 25%, 30%, 40%, 50%, 60%, 70% or 80% larger than the surface of the opening based on its required dimensions. By ensuring that the opening a surface area of 25% or larger, the manufacturing of the opening can be ensured to occur without any of the mentioned drawbacks. Typically, the excess surface area (i.e. recesses) is (are) spread regularly over the surface of the opening or shaft, while maintaining the required dimensions of the opening. More particularly this implies that the recesses do not extend over the entire surface of the opening, more particularly do not extend over the entire circumference of the opening in any cross-section of the shaft of the opening. In further particular embodiments, the recesses extend over between 10-90%, more particularly between 20-80% of the surface of the opening or shaft.

In the methods envisaged herein, the required dimensions of the opening are maintained by ensuring a minimal area of the opening corresponding to the required dimensions. Such areas are also referred to herein as "contact areas", as the function of the opening will typically require contact of an object with these areas. Methods for determining the minimal required contact areas for a functional opening are known to the skilled person. Typically for guidance of an object through a shaft, the opening should comprise at least three contact areas at different cross-sections of the shaft jointly corresponding to the required dimensions, which the object will contact simultaneously when passing through the shaft. The size of the contact areas is not critical (may be reduced to contact points) but will be determined by the envisaged function of the opening. Where the opening is required to guide a larger object in a predetermined direction, the distance between the different contact areas can often be increased. Typically however it will be of interest to provide a larger number of smaller recesses rather than a limited number of large recesses. In particular embodiments the recesses increase in volume extending away from the opening. In particular embodiments, the one or more recesses extend in a direction which is not parallel to the orientation of shaft of the opening. In further embodiments, the recesses extend in a direction to perpendicular to the orientation of the shaft (and/or perpendicular to the surface of the object comprising the opening). In further particular embodiments, the opening is provided with one or more recesses which each extend in more than one different orientations. In particular embodiments, where the surface of the shaft is significantly larger in one direction than in another (e.g. a rectangular opening such as for guiding a blade), the excess surface area can be provided primarily or only on the larger surface area. It will be understood that in particular embodiments, the surface of the opening can be increased to such an extent, that it reaches the outer surface of the objects, resulting in one or more additional openings on the surface of the object, other than the functional opening. Such openings may further improve the air or liquid flow through the opening. It will be understood that such openings are only of interest if they do not compromise the general stability or robustness of the object and do not interfere with other functions of the object. In particular embodiments, the one or more recesses do not extend to the outer surface of the object.

As will be illustrated with particular examples herein below, in particular embodiments of the methods and objects envisaged herein, the circumference of the opening comprising the recess taken at a given cross-section is at least 15% larger than the circumference of the opening would be without the recess, based on its required dimensions. In particular embodiments, the cross-section of the opening at the surface of the object is at least 15% larger than the circumference of the opening In the methods and objects envisaged herein, the recess provided on the opening can have an irregular shape, a crenated shape, a serrated shape, a jagged shape, a sinusoidal shape, a toothed shape, a parabolic shape, a notched shape, a scalloped shape, a denticulated shape or a combination thereof. Similarly, the resulting shape of the opening comprising the recess or a cross-section thereof in any direction can be sinusoidal, jagged, parabolic, toothed, or crenated. In particular embodiments, the cross-section of the opening or shaft taken perpendicularly to its orientation in the object or the cross-section taken in a direction which is parallel to the orientation of the opening in the object is sinusoidal, parabolic, toothed, or another regular symmetrical shape. In further particular embodiments, where more than one recess is provided, the size of the different recesses is regular, more particularly identical.

In particular embodiments of the methods envisaged herein, the opening concerned is an opening for insertion of an object and the required dimensions of the opening to be identified in step (a) are determined by the dimensions of said object. In particular embodiments, the length of the object can also be taken into account, to ensure the required dimension of the depth of the opening.

The methods described herein are widely applicable in the field of additive manufacturing and the nature of the object is not critical to the invention. However, the described methods can be particularly suitable for applications in the field of surgical instruments. Thus, in particular applications of the methods envisaged herein, the object is a surgical guide and said opening is a guiding opening in the body of said surgical guide for guiding a surgical tool. This embodiment will be discussed in detail below, the features envisaged for the recesses of the openings of the guides described herein are similarly applicable to other objects.

In particular embodiments, the application envisages methods for manufacturing a guide comprising slots or holes for use with a cutting or drilling tool wherein the slots or holes are designed and manufactured such that the slot or hole guiding the cutting or drilling tool is provided with recesses, whereby the slot or hole maintains the required dimensions of the guiding opening while the recesses provide in an enlarged surface opening of the slot or hole, thereby enabling it to be made using additive manufacturing techniques.

Additional methods for manufacturing guides comprising holes or openings are provided where the distance between two opposing surfaces is dictated by the material properties and not only by the dimensions of the inserted instrument. The openings guide the inserted device with a number of guidance surfaces which limits the freedom of movement of the inserted device. The inserted device is cornered by the guidance surfaces with the use of contact points, lines, surfaces or any other type of contact surface that constrains the movement of the inserted device in a desired way. Example of such guidance surface can be made of crests, bumps or squares or any type of uneven surfaces that can ensure enough guidance on the inserted device. In some embodiments these guidance surfaces are placed at regular intervals, but the present invention cannot be limited to such design. In some embodiments the same features are repeated a number of times on the guidance surfaces but the present invention encompass also designs in which different features are disposed irregularly. Thus particular methods are provided for manufacturing a guide for a cutting or drilling tool or a fastening tool, for guiding said tool into an object of interest along a desired path, the guide being provided with a body comprising at least one shaft with a guiding opening. In more particular embodiments the methods comprise the steps of:

a) designing the guide body; b) determining the required dimension of the guiding opening and shaft extending within said body, whereby said required dimensions correspond to the minimal shaft;

In further embodiments, methods are provided for manufacturing a guide for a cutting or drilling tool or a fastening tool, for guiding said tool into an object of interest along a desired path, the guide being provided with a body comprising at least one shaft with a guiding opening, wherein the guide is designed for positioning on an object of interest by positioning elements. More particularly said method comprises the steps of:

a) determining the desired body structure such that it contains the required positioning elements for positioning said guide on said object of interest;

b) determining the required dimension of the guiding opening extending within said body, whereby said required dimensions correspond to the minimal shaft;

In particular embodiments, the envisaged methods are used in the context of providing a guiding opening for an object, and said methods comprise the steps of: i) determining the required dimensions of said guiding opening based on the size, shape and desired trajectory of said object through said guide;

ii) providing, in the design of said guiding opening of said guide, one or more recesses thereby maintaining the required dimensions of said guiding opening; and; iii) manufacturing said guide with said opening comprising said recess according to said design.

In these methods, the trajectory can be any envisaged trajectory, including but not limited to, a linear trajectory.

As used throughout the application, the term "guide" refers to an object which contains a body and a, opening for a cutting or drilling tool or a fastening tool, for guiding said tool into an object of interest along a desired path. In particular embodiments, the guide according to the invention is a reference structure providing a reference position ensuring the correct axis for applying a tool, also referred to as a reference guide. More in particular the present invention relates to surgical guides for use in determining an axis relative to a body part. A surgical guide can be used during a surgical procedure to help ensure that an instrument or tool is applied to a body part by a practitioner at a particular location and/or with a particular orientation. A guide can have mechanisms providing various degrees of freedom so that the guide can be adjusted in use. In further particular embodiments the "guide" is a model or a prosthesis. Thus, in particular embodiments, the invention provides methods for manufacturing reference guides and prostheses.

The guides according to the present invention are provided with a body structure comprising at least one shaft with a guiding opening. The shaft with the guiding opening provides the location for insertion and guidance of the tool. The body structure of the guide provides in mechanical strength and may also comprise other suitable features useful when working with the guide. These additional features may comprise, but are not limited to, reference surfaces including patient- or object- specific surfaces, clamping tools or other tools for attachment of the guide to the working area, reference structures for ensuring the correct position of the guide, and many other useful tools.

It is noted that, as indicated above, the methods are described herein by referring to different steps as "first" and "second" or "further" steps. It will be clear to the skilled person that this is mainly for purposes of clarity but does not imply that the order of the steps can not be changed and/or that different steps can be performed simultaneously.

Typically, in a first step according to the methods of the invention the desired body structure of the guide is determined or designed. The desired body structure will mainly be determined by the envisaged function of the guide. This function may include not only the guiding function ensured by the opening but this latter function may be combined with other functions which can be the same (e.g. other openings) or different (e.g. handling features).

In particular embodiments, the guides according to the present invention can used for positioning on an object of interest (including e.g. a human body part) and comprise positioning elements for (accurate) positioning on said object of interest. Accordingly, in these embodiments, the methods of the invention involve determining or designing the desired body structure of the guide so as to provide thereon the required positioning elements for positioning the guide on the object of interest. These positioning elements may be any sort of features enabling the positioning of the guide onto the object of interest, and can for instance include a patient- or object- specific surface, clamping tools or other tools enabling the attachment of the guide onto the object of interest. Where the guide is a patient-specific guiding tool, the step of designing the body may include obtaining a three dimensional image of the body part on which the guide is to be positioned, determining the surface structure of the body part on which the guide is to be positioned and designing the body structure based thereon.

In a further step of the methods of the invention the size, position and orientation of the guiding opening is determined or designed onto the body structure of the guide. As will be apparent, the guiding openings envisaged according to the invention include all openings which can be required for introducing (either permanently or temporarily) an object, typically a tool. In particular embodiments the function of the shaft is the guiding of a cutting or drilling tool along a desired path. In further embodiments, the function of the shaft is the positioning of a fastening tool, such as a pin or screw (i.e. an independent tool) or a part of another object (i.e. for assembly). The position of the guiding opening corresponds to the location where the cutting, drilling or fastening tool is required to perform its function. The dimensions of the guiding opening are determined or designed such that the cutting, drilling or fastening tool can be inserted into and guided through the guiding opening. The size and dimensions of this provided guiding opening are further referred herein to as the minimal shaft.

In a further step, based on the minimal shaft, an improved shaft is determined or designed. This is done by providing recesses on the surface of said minimal shaft while still maintaining the required dimensions of the guiding opening. Accordingly, an improved shaft is provided, this improved shaft being provided with recesses extending over the surface area of the guiding opening, while the guiding dimension and guiding properties of the original minimal shaft are maintained in the improved shaft. Accordingly, the improved shaft allows the insertion and guidance of a tool through the guiding opening, having the guiding properties of the minimal shaft, and combines this property with an enlarged surface area, which has several advantages, including allowing a better air or liquid flow around the tool, and ensuring better clearance of the openings when made through additive manufacturing techniques. Details of the technical nature of the improved shaft are provided herein below.

Optionally, during the step wherein the improved shaft is determined, other aspects, including functional aspects of the tool may be included in the design as well. Accordingly, said improved shaft may be further provided with additional features such as for instance providing a screw thread or thread on said improved shaft. Finally, in a further step, the guide body with said improved shaft is manufactured. In particular embodiments, this is done using additive manufacturing techniques.

Additive Manufacturing (AM) techniques are used for manufacturing the guides according to the invention. As an example, the manufacturing of medical-image- based patient-specific surgical instruments via AM is described in US patent 5,768,134 (Swaelens et al).

In particular embodiments, the present invention provides methods for manufacturing guides, and more particularly surgical guides, provided with at least one guiding slot, wherein the method comprises the steps of:

a) designing a surgical guide body;

b) designing on said surgical guide body a minimal guiding slot extending through said surgical guide body, wherein said minimal guiding slot is designed such that a surgical tool can be inserted and guided through said guiding slot; In particular embodiments, this step involves pre-operative planning, which will determine the desired position and orientation of the guiding slot.

c) designing an improved guiding slot by providing on the surface of said minimal guiding slot recessed openings, thereby providing the surface of said improved guiding slot with an irregular shape, while still maintaining the guiding properties of the guiding slot for said surgical tool; and

d) manufacturing said surgical guide provided with said improved guiding slot.

In particular embodiments, the envisaged methods for providing a surgical guide comprise the steps of:

i) determining the required dimensions of said guiding opening for guiding a surgical tool based on the size, shape and desired trajectory of said surgical tool; ii) providing, in the design of said guiding opening of the surgical guide, one or more recesses thereby maintaining the required dimensions of said guiding opening; and;

iii) manufacturing said guide with said opening comprising said recess according to the design of step (ii).

In these methods the envisaged trajectory of the surgical tool can be, but need not be a linear trajectory. The methods can be applied to a guiding opening for any type of trajectory envisaged.

The surgical guides, made by the methods of the invention, thus may contain a body structure comprising said guiding slot. The body structure is typically designed so as to be supported on an object of interest. In particular embodiments the object of interest is an animal or human body part. In further particular embodiments, the guide is patient-specific and the body structure contains an external patient-specific surface which fits specifically on a body part, which furthers the accuracy of the surgical intervention.

The nature of the improved shaft (e.g. guiding slot) envisaged in the methods of the present invention is as described herein above.

Typically, the internal surface of the improved shaft has an irregular shape provided with recessed openings and inward facing guiding surfaces, said guiding surfaces providing the guiding properties of the guiding opening.

In particular embodiments, the present invention provides methods wherein the surface of the improved shaft or guiding slot is at least 15% larger than the surface of the minimal shaft or guiding slot. More particularly, the surface of the improved shaft is at least 20%, 25%, 30%, 40%, 50%, 60%, 70% or 80% larger than the surface of the minimal shaft. It will be understood that according to the present invention the excess surface area is typically spread regularly over the surface of the shaft, while maintaining the minimal shaft dimensions for guiding. This further implies that typically, the recesses extend in a direction which is not parallel to the insertion orientation of the tool in the shaft (such as but not limited to perpendicular to the insertion orientation of the tool in the shaft), and typically (but not necessarily) extend in more than two different orientations. In particular embodiments, where the surface of the shaft is significantly larger in one direction than in another (e.g. a rectangular opening such as for guiding a blade), the excess surface area can be provided primarily or only on the larger surface area. It will be understood that in particular embodiments, the surface of the improved shaft can be increased to such an extent, that it reaches the outer surface of the guide body, resulting in one or more openings at the surface of the guide body (other than the guiding opening). Such openings may further improve the air or liquid flow around the tool. It will be understood that such openings are only of interest if they do not compromise the general stability or robustness of the guide body and do not interfere with other functions of the guide (including positioning of the guide on the object of interest, where applicable). In particular embodiments, the surface of the improved shaft does not extend to the wall of the guide body, i.e. the surface is not infinitely extended.

In a further particular embodiment methods are provided wherein the recesses form grooves extending over the length of the surface of said shaft. The recessed form of the improved shaft can according to a particular embodiment be maintained throughout the entire depth of the shaft. Accordingly, the irregular shape of said improved guiding slot is maintained throughout the depth of the improved guiding slot, ensuring that the manufacturing of the guides with improved guiding opening can be provided independent of the thickness of the guide.

According to a particular embodiment, methods are provided wherein the recesses form grooves extending transversally to the direction of the guiding opening (the insertion orientation of the tool in the shaft). Inventors have found that while the manufacturing and design is simplified when the recesses form grooves extending throughout the entire depth of the shaft, this does not seem to be a requirement. It is noted that as long as recesses are provided in the guiding slot on each additive manufacturing layer of the guide ensuring that for each additive manufacturing layer the guiding slot is provided with a surface area larger than the surface area of the minimal shaft, the guide can be made through additive manufacturing techniques without any congestion problems occurring in the guiding opening. In particular embodiments, the recesses provided in the guiding opening may also form grooves extending transversely to the direction of the guiding opening.

According to particular embodiments of the methods and tools provided herein the surface of the improved shaft has an irregular shape corresponding to a crenated shape, a serrated shape, a jagged shape, a sinusoidal shape, a toothed shape, a parabolic shape, a notched shape, a scalloped shape, a denticulated shape or a combination thereof. A multitude of different shapes and forms as well as combinations thereof can be provided each providing a contribution to the present invention. While certain shapes (e.g. jagged shape) provide a minimal guidance surface others such as a toothed shape show an enlarged guidance surface. Depending on the type of guidance required, the shape of the surface can be chosen. When guidance is absolutely critical and net even minor deviations can be tolerated the safe approach would be to maximize the guidance surface, whereas only a minor guidance surface would be required if a large number of contact points with the tool can be provided.

According to particular embodiments of the methods of the present invention, as indicated above, the guide is a surgical guide and the guiding opening is an opening for guiding a surgical tool. More in particularly, the surgical tool may be chosen from a drilling tool, a cutting tool, a sawing tool or a screwing tool. In particular embodiments, the tool is a saw blade.

According to particular embodiments of the methods of the present invention provides the guide opening is for a fastening means, such as a pin.

The methods described herein are of interest in the context of Additive manufacturing. Additive Manufacturing (AM) can be defined as a group of techniques used to fabricate a tangible model of an object typically using three-dimensional (3-D) computer aided design (CAD) data of the object. Currently, a multitude of Additive Manufacturing techniques is available, including stereolithography, Selective Laser Sintering, Fused Deposition Modeling, foil-based techniques, etc.

Selective laser sintering uses a high power laser or another focused heat source to sinter or weld small particles of plastic, metal, or ceramic powders into a mass representing the 3-dimensional object to be formed. Fused deposition modeling and related techniques make use of a temporary transition from a solid material to a liquid state, usually due to heating. The material is driven through an extrusion nozzle in a controlled way and deposited in the required place as described among others in U.S. Pat. No. 5.141.680. Foil-based techniques fix coats to one another by means of gluing or photo polymerization or other techniques and cut the object from these coats or polymerize the object. Such a technique is described in U.S. Pat. No. 5.192.539.

Typically AM techniques start from a digital representation of the 3-D object to be formed. Generally, the digital representation is sliced into a series of cross-sectional layers which can be overlaid to form the object as a whole. The AM apparatus uses this data for building the object on a layer-by-layer basis. The cross-sectional data representing the layer data of the 3-D object may be generated using a computer system and computer aided design and manufacturing (CAD/CAM) software.

The objects according to the present invention may be manufactured in different materials, provided they are compatible with the envisaged additive manufacturing technology. Typically, for the manufacturing of surgical tools such as surgical guides only materials that are biocompatible (e.g. USP class VI compatible) with the animal or human body are taken into account. Preferably the guides are formed from a heat- tolerable material allowing it to tolerate high-temperature sterilization. In the case selective laser sintering is used as an AM technique, the guides may be fabricated from a polyamide such as PA 2200 as supplied by EOS, Munich, Germany or any other material known by those skilled in the art may also be used.

In particular embodiments, the invention provides surgical instruments at least partially manufactured by additive manufacturing and obtainable with any of the methods according to the present invention, comprising at least one improved guiding slot made by additive manufacturing for guiding a tool in a surgical procedure, wherein the surface of said improved guiding slot is an irregular surface providing recessed openings. In particular embodiments, the irregular shape of said improved guiding slot is provided with recessed openings and inward facing guiding surfaces, said guiding surfaces providing the guiding properties of the guiding slot.

In further particular embodiments, the invention provides a guide part manufactured by additive manufacturing comprising an opening for guiding an instrument through a shaft. The guide part has a shaft for guiding a tool in or through a shaft having the features resulting from the methods as described herein above. In particular embodiments, the guiding feature is characterized in that:

- the contact surface of at least part of the wall of the shaft is interrupted such that it consists of three or more contact areas forming a guide path which ensures the correct guidance of the instrument and

- the open areas located between the contact areas of the shaft are interconnected and together are at least 50% larger in volume than the volume of the instrument to be guided through the shaft.

Typically the guide contains a body structure comprising the shaft. The body structure is typically designed so as to be supported on an object of interest. In particular embodiments the object of interest is an animal or human body part. Thus, in particular embodiments, the body structure of the guide is designed so as to fit onto a body part and comprises positioning features which are specific for said body part. In further particular embodiments the object of interest is a device, such as an implant and the body structure is designed so as to fit onto said device. In particular embodiments, the guide body is patient-specific and the method comprises designing said body structure based on a three-dimensional image of said object of interest on which the guide is to be positioned. More particularly the body is designed such as to contain patient-specific surfaces allowing exact and reliable positioning of said guide on said patient-specific body part or device.

In particular embodiments, the three or more contact areas alternate along the length of the shaft. In further particular embodiments, only the parts of the wall of the shaft extending along the longer sides are interrupted.

According to another particular embodiment, the present invention provides in a guide wherein the guiding opening is formed by the crests of square or trapezoidal waves formed by the surface of the improved shaft.

According to another particular embodiment, the present invention provides in a guide wherein the cross-section of the minimal shaft is an oblong and the surface of the shaft extending along the longer sides of the oblong are recessed. In particular embodiments, the cross section of the instrument is an oblong and the parts of the wall of the shaft extending along the longer sides are interrupted. According to another particular embodiment, the present invention provides in a guide wherein the surface of the shaft forms a trefoil around the guiding opening. In particular embodiments, the open areas of the shaft form a trefoil around the guide path in any transverse section of the shaft.

In particular embodiments, the contact surfaces are formed by the crests of sine waves formed by the wall of the shaft.

The present invention will be illustrated by the following non-limiting embodiments. EXAMPLES

Example 1 : Saw blade guide (Figures 1 and 2)

Figures 1 and 2 provide exemplary embodiments of an opening, such as could be used as a saw blade guide. As shown in figures 1 and 2 the contact surfaces are provided as a set of crests when seen from above the direction in which the instrument is inserted. In the present example the tool that is inserted can be a reciprocating saw blade.

Figure 1 a shows a conventional opening for inserting a saw blade (in grey) provided based on the required dimensions for guiding the saw blade, while figure 1 b provides an opening comprising recesses according to an embodiment of the methods and objects described herein. Such an opening comprising recesses can serve as an improved guiding opening. The distance between the surfaces of the opening is increased in the recesses, while still maintaining guidance of the tool. The grooves of the improved guiding opening extend over the length of the surface of the shaft. Figure 2 shows a picture of an embodiment of the methods and objects envisaged herein. The model has 2 types of openings: conventional openings (4) made based on the required dimensions and the new type comprising recesses (3). When making such structures using additive manufacturing techniques it can be noticed that the conventional openings (4) are congested while the openings comprising recesses according to the methods described herein are not congested while still maintaining the same functional properties.

Example 2: Saw blade guide (Figures 3 and 4)

Figures 3 and 4 provide exemplary embodiments of an opening which can be used as a saw blade guide or part thereof. As shown in figures 3 and 4 the contact surfaces of the opening which remain upon introduction of the recesses are provided as a set of crests when seen in a cross-section of the opening transversal to the orientation of the opening.. Figure 3a shows a conventional opening which can be used for inserting a saw blade (in grey) without recesses, while figure 3b provides an opening comprising recesses corresponding to an "improved guiding opening". The distance between the surfaces of the opening is increased in the areas of the recesses while still maintaining the functional dimensions of the opening required for guidance of the tool. The grooves of the improved guiding opening extend transversally to the direction of the guiding opening. The black arrow indicates the direction of insertion of the tool.

Figure 4 shows a picture of an embodiment of the methods and tools described herein. The model has 2 types of openings: conventional, without recesses, based on the required dimensions of the opening (4) and the opening provided with recesses as described herein (3). When making such structures using additive manufacturing techniques it can be noticed that the conventional openings (4) are congested while the recessed openings are not congested while still maintaining the same functional (e.g. guidance) properties (especially visible for the three (guiding) openings central in the image).

Example 3: Drilling guide (Figures 5 and 6)

Figures 5 and 6 provide exemplary embodiments of an opening which can be used as a drilling guide or part thereof. As shown in figures 5 and 6 the contact surfaces which remain after introduction of the recesses are provided as a set of crests when seen in a transverse section of the opening or shaft (i.e. the direction in which the instrument is to be inserted).

Figure 5a shows a conventional guiding opening e.g. for inserting a drilling tool (in grey) without recesses, based on the required dimensions of the opening, while figure 5b provides a recessed opening according to an embodiment of the methods described herein. In the improved guiding opening, the distance between the surfaces of the opening is increased at the recesses, while still maintaining the functional dimension of the opening for guidance of the tool. In this embodiment, the grooves of the improved guiding opening extend over the length of the surface of the shaft.

Figure 6 shows a picture of an embodiment of the methods and tools provided herein. The model has 2 types of openings: conventional openings based on the required dimensions (4) and the recessed openings according to a particular embodiment of the methods described herein (3). When making such structures using additive manufacturing techniques it can be noticed that the conventional openings (4) are congested while the recessed openings (3) are not congested while still maintaining the same guidance properties. Example 4: Saw blade guide (Figure 7)

Figure 7 provides an exemplary embodiment of an opening which can be used as a sawing guide or part thereof. As shown in figure 7 the contact surfaces which remain upon providing the opening with recesses are provided as a set of crests when seen in a cross-section of the opening ( transversal to the direction in which the instrument is to be inserted). In the present embodiment, the device that is inserted can be an oscillating saw blade.

The guidance of the device is ensured by the contacts which are retained to ensure the required dimension of the opening. In this embodiment, the contact is made by the extrusion of 2 sine waves in phase. The period of the sine wave is designed so that at least 3 sine crests ensure the required dimensions and thus are always in contact with the inserted saw blade. Example 5: Saw blade guide (Figure 8)

Figure 8 provides an exemplary embodiment of an opening which can be used as a sawing guide or part thereof. As shown in figure 8 the contact surfaces which remain upon providing the opening with recesses, are provided as a set of crests when seen in a cross-section of the opening (i.e. transversal to the direction in which the instrument is to be inserted). In the present embodiment, the device that is inserted can be an oscillating saw blade.

The guidance of the device is ensured by contacts made of the extrusion of 2 square waves. The period of the square wave is designed so that at least 3 crests are always in contact with the inserted saw blade.

Claims

1 . A method for manufacturing an object with at least one opening by additive

manufacturing, comprising the steps of:

a) Determining the required dimensions of the opening, whereby the required dimensions correspond to the functional properties of the opening;

2. The method according to claim 1 , wherein the circumference of said opening comprising said recess is at least 15% larger than the circumference of said opening without said recess.

3. The method according to claims 1 or 2, wherein said opening extends as a shaft into the object and said recess forms a groove extending over the over the length of the inner surface of said shaft.

4. The method according to claims 1 or 2 wherein said opening extends as a shaft into the object and said and said recess forms a groove transversally to the orientation of the shaft in the object.

5. The method according to any of claims 1 to 4, wherein said recess has an irregular shape a crenated shape, a serrated shape, a jagged shape, a sinusoidal shape, a toothed shape, a parabolic shape, a notched shape, a scalloped shape, a denticulated shape or a combination thereof.

6. The method according to any one of claims 1 to 5, wherein said opening is an opening for insertion of an object and said required dimensions of the opening are determined by the dimensions of said object

7. The method according to claims 1 to 5, wherein said object is a surgical guide and said opening is a guiding opening in the body of said surgical guide for guiding a surgical tool.

8. The method according to claim 7, wherein said surgical tool is chosen from a drilling tool, a cutting tool, a sawing tool or a screwing tool.

9. The method according to any one of claims 1 to 6, wherein said opening is for introduction of a fastening means, such as a pin.

10. The method according to any one of claims 1 to 9, wherein said opening is for guiding another object along a desired path in said object comprising said opening.

11. The method of claim 7, wherein the method comprises the steps of: a) determining the required dimensions of said guiding opening for guiding said surgical tool based on the size, shape and desired trajectory of said surgical tool; b) providing, in the design of said guiding opening of said surgical guide, one or more recesses thereby maintaining the required dimensions of said guiding opening; and;

c) manufacturing said surgical guide with said opening comprising said recess according to the design of step (b).

12. An object comprising an opening, obtainable by the method according to any one of claims 1 to 11 .

13. The object of claim 12, wherein said object is a guide for a cutting or drilling tool or a fastening tool.