Surgical cut validation tool and method

A method of manufacturing a surgical cut validation tool is discussed. A digital bone representation representing a bone is received including a virtual bone outer surface. At least one cutting plane is positioned intersecting the virtual bone outer surface. A digital tool representation representing the tool is created, including a virtual planar surface corresponding to each cutting plane and a virtual tool outer surface with a virtual border surface portion. The virtual border surface portion extends from a junction between the virtual tool outer surface and each virtual planar surface. At least part of the virtual border surface portion is defined from a corresponding portion of the virtual bone outer surface such as to represent a corresponding portion of the bone outer surface. The tool body is manufactured using the digital tool representation. A tool and a method of validating a cut in a bone are also provided.

TECHNICAL FIELD

The application relates generally to orthopedic instruments and, more particularly, to a validation tool for use during orthopedic surgery.

BACKGROUND OF THE ART

In joint replacement surgeries, sections of bones are removed and replaced by corresponding prosthesis. Typically, the surgeon selects a prosthesis size proportional to the bone size of the patient, and cuts the bone in order to match the size of the prosthesis, using cutting guides corresponding to the particular prosthesis being put in place. Validation blocks, which are typically prismatic, are inserted in the bone cut to validate that the bone has been cut to the proper size; if the block cannot be inserted, additional bone is cut until it can. Cement may also be used to compensate for poor cuts or uneven bones.

SUMMARY

In one aspect, there is provided a method of manufacturing a surgical cut validation tool, the method comprising: receiving a digital bone representation representing a bone, the digital bone representation including a virtual bone outer surface representing an outer surface of the bone at least for and around a section to be cut; positioning at least one cutting plane intersecting the virtual bone outer surface in the digital bone representation, each cutting plane representing a cut surface of the section to be cut; creating a digital tool representation representing the cut validation tool, including creating a virtual planar surface along each cutting plane, and creating a virtual tool outer surface including a virtual border surface portion, the virtual border surface portion extending from a junction between the virtual tool outer surface and each virtual planar surface, at least part of the virtual border surface portion being defined from a corresponding portion of the virtual bone outer surface such as to represent a corresponding portion of the outer surface of the bone; and manufacturing a body of the cut validation tool using the digital tool representation, including manufacturing a planar surface corresponding to each virtual planar surface and an outer surface corresponding to the virtual tool outer surface.

In another aspect, there is provided a surgical cut validation tool for validating a cut in a bone, the tool comprising: a body having at least one planar surface, and an outer surface extending from the at least one planar surface, the outer surface including a border surface portion extending from a junction between the outer surface and each planar surface; wherein each planar surface corresponds to a predetermined cut surface of a nominal section to be removed from the bone; and at least part of the border surface portion has a shape corresponding to that of part of an outer surface of the nominal section, the at least part of the border surface portion having a same relative position with respect to each planar surface than the part of the outer surface of the nominal section with respect to the each predetermined cut surface.

In a further aspect, there is provided a method of validating a cut in a bone, the method comprising: a) inserting a body of a tool into a cut section of the bone defined by at least one cut surface, the body having a planar surface in contact with each of the at least one cut surface; b) moving the body in the cut section until an outer surface of the body and an outer surface of the bone adjacent each of the at least one cut surface are at a closest alignment with one another; c) determining if a reference portion of the outer surface of the tool adjacent the cut surface protrudes beyond a corresponding portion of the outer surface of the bone; and d) if the reference portion of the outer surface of the tool protrudes beyond the corresponding portion of the outer surface of the bone, removing the body from the cut section, increasing a size of the cut section, and repeating steps a) to c).

DETAILED DESCRIPTION

In the present specification, including claims, “planar surface” includes smooth surfaces (e.g. extending completely within a plane) and textured surfaces (e.g. the contact points thereof being located within a plane) such as for example a surface including a series of spaced apart ridges or protrusions extending therefrom.

Referring toFIGS. 1-2, a surgical cut validation tool10is shown. The tool10includes a body having at least one planar surface; in the embodiment shown, the body12includes two intersecting planar surfaces14(FIG. 2). The body12also includes an outer surface16extending from the planar surfaces14. The tool10is designed to validate a cut in a bone and/or the fit between a custom or patient-specific prosthesis adapted to fit the patient's unique anatomy and designed to replace the cut section of the bone and an adjacent bone or prosthesis, as will be further detailed below.

As such, each planar surface14corresponds to a predetermined cut surface of a particular nominal removed bone section (i.e. the bone section which is required to be removed for replacement with a given prosthesis), and thus shaped to be received against a respective cut surface of the remaining bone. The outer surface16includes a border surface portion16′ (FIG. 1) extending from the junction of the outer surface16and each planar surface14. At least part of this border portion16′ has a shape corresponding to that of a corresponding portion of the outer surface of the nominal removed bone section, i.e. to the portion of the nominal removed bone section's outer surface having the same relative position with respect to each predetermined cut surface than the relative position of this part of the border surface portion with respect to each planar surface. In a particular embodiment, this part of the border portion16′ is defined along an entirety of the junction with one of the planar surfaces14. In another particular embodiment, the entirety of the border portion16′, i.e. the section of the outer surface16extending adjacent both planar surfaces14, has a shape corresponding to that of the outer surface of the nominal removed bone section adjacent the cut surfaces.

In a particular embodiment, which may be used to validate the cut in the bone, the outer surface16completely corresponds to the outer surface of the removed bone section. In another particular embodiment, which may be used to validate the cut in the bone and the fit between the corresponding prosthesis and an adjacent prosthesis or bone, the remainder of the outer surface16(i.e., the outer surface16with the exception of the part of the border portion16′ corresponding to the outer surface of the nominal removed bone section) corresponds to the outer surface of the prosthesis. In a further embodiment, the remainder of the outer surface16has a generic shape, for example ovoid, planar, or defined as two or more intersecting planar surface sections. The shape of the outer surface16is patient-specific at least along the part of the border portion16′ corresponding to the outer surface of the nominal removed bone section, as will be further detailed below.

In a particular embodiment and as shown inFIG. 2, each planar surface14has a textured surface pattern, for example formed by a series of spaced apart ridges18extending therefrom. The textured surface pattern is configured such that the planar surface14can be used as a filing tool against the remaining bone, and the material of the body12is selected to have sufficient resistance to be usable to file a bone. Alternately, the textured surface pattern may be provided on only one of the planar surfaces14.

In the embodiment shown, the tool10further includes a handle20extending from the body12. In a particular embodiment, the handle20is detachably connected to the body12. This may allow for identical handles to be manufactured in series to be used with different bodies, thus potentially minimizing manufacturing costs and/or time. In a particular embodiment, the handle20includes a tenon22which is snuggly received in a complementary mortise24defined in the body12and retained therein through friction. In the embodiment shown, the tenon22and mortise24have a cross-shaped cross-section, but other cross-sectional shapes may also be used. Other types of attachment are also possible. Alternately, the handle20and body12may be monolithic, i.e. manufactured together as a single piece.

The handle20may be made of the same material as that of the body12or alternately be made of a different material.

In a particular embodiment, the body12is manufactured from a digital bone representation30, an exemplary schematic illustration (e.g., screen shot of a CAD model) of which being illustrated inFIG. 4. In a particular embodiment, the body12is manufactured following the method60illustrated inFIG. 3. First, the digital bone representation30representing the bone to be cut for replacement by a prosthesis is received in a suitable processing system, as shown in step62. The three-dimensional shape of the digital bone representation30is patient-specific and is created from the actual configuration of the bone of the patient. In a particular embodiment, the bone is a tibia and the prosthesis forms part of a knee joint. However, it should be understood that the method60may apply to other articular joints, such as an elbow, shoulder, wrist, or hip and to other types of bone-replacement prosthesis.

The digital bone representation30may be created from images of the bone and surrounding region obtained from scans generated using Magnetic Resonance Imaging (MRI), Computed Tomography (CT), ultrasound, x-ray technology, optical coherence tomography, or the like. Such images may be provided by a user, such as a medical technician, a surgeon, or a treating physician, via a suitable communication means to a computer system adapted to process the method60. For this purpose, the user may electronically provide the scans of the patient's anatomy to the computer system via electronic mail, a Picture Archiving and Communication System (PACS) server, a website, or the like. The captured images may further be provided in various known formats, such as Digital Imaging and Communications in Medicine (DICOM), for handling, storing, printing, and transmitting information via PACS. Other exemplary formats are GE SIGNA Horizon LX, Siemens Magnatom Vision, SMIS MRD/SUR, and GE MR SIGNA 3/5 formats.

The images of the patient's bone and surrounding region may be processed and segmented. As images may be acquired along one or more planes throughout the body part, such as sagittal, coronal, and transverse, as well as multiple orientations, the data may be combined or merged during processing. The digital bone representation30may then be created from the segmented images.

Referring toFIG. 4, the digital bone representation30is three dimensional and includes a virtual bone outer surface34which represents the outer surface of the bone at least for and around the region to be cut.

Referring back toFIG. 3, at step64, at least one virtual cutting plane32is defined and positioned in the digital bone representation30, with each virtual cutting plane32representing a cut surface of the bone. Each virtual cutting plane32thus intersects the virtual bone outer surface34. The position of the cutting plane(s)32is thus determined according to the physionomy of the particular bone, the type of prosthesis to be used, and/or any other appropriate parameter. In a particular embodiment where the section of the bone to be cut is a condyle, two intersecting cutting planes32are positioned.

In a particular embodiment, a digital prosthesis representation140,240is used; exemplary schematic illustrations (e.g., screen shot of a CAD model) of which are shown inFIGS. 6aand 7a. Referring back toFIG. 3, and with reference to step66, the digital prosthesis representation140,240is received. The digital prosthesis representation140,240is created from the digital bone representation30, and represents a custom, patient-specific prosthesis designed for replacing the cut section of the bone. As shown inFIGS. 6aand 7a, the digital prosthesis representation140,240includes a virtual contact surface142,242corresponding to each virtual cutting plane32and representing a contact surface of the prosthesis with the remaining bone, and a virtual prosthesis outer surface144,244extending from each virtual cutting plane, representing an outer surface of the prosthesis.

In another embodiment, the digital prosthesis representation140,240is not used in the creation of the digital tool representation, and step66is omitted.

At step68, the digital tool representation is then created, representing the body12of the tool10. Exemplary schematic illustrations (e.g., screen shot of a CAD model) for the digital tool representation50,150,250,350are shown inFIGS. 5, 6b,7band8. The digital tool representation50,150,250,350includes a virtual planar surface52,152,252,352corresponding to each virtual cutting plane32, each representing a contact surface of the body12with the remaining bone. The digital tool representation50,150,250,350also includes a virtual tool outer surface54,154,254,354, extending from each virtual planar surface52,152,252,352, and representing the outer surface of the body12. The virtual tool outer surface54,154,254,354includes a virtual border surface portion54′,154′,254′,354′ extending from the junction between the virtual tool outer surface54,154,254,354and each virtual planar surface52,152,252,352. At least part of the virtual border surface portion54′,154′,254′,354′ is defined from a corresponding portion of the virtual bone outer surface34, such as to define the corresponding part of the border portion16′ of the tool10which is configured to correspond to the outer surface of the nominal removed bone section. Accordingly, in a particular embodiment, the part of the virtual border surface portion54′,154′,254′,354′ defined from a corresponding portion of the virtual bone outer surface34extends along an entirety of the junction with one of the virtual tool outer surface54,154,254,354. In another particular embodiment, the entirety of the virtual border surface portion54′,154′,254′,354″, i.e. the section of the virtual tool outer surface54,154,254,354extending adjacent both virtual planar surface52,152,252,352, corresponds to the virtual bone outer surface34.

In a particular embodiment where the digital prosthesis representation is not used and step66is omitted, the virtual tool outer surface completely corresponds to the virtual bone outer surface34, such that the outer surface16of the body12of the tool10may represent a copy of the outer surface of the nominal removed bone section. An example of such a case is illustrated inFIG. 5. In this embodiment, the virtual tool outer surface54, including the virtual border surface portion54′, is defined to completely correspond to the virtual bone outer surface34of the digital bone representation30(FIG. 4). For instance, the virtual tool outer surface54may be defined by making a copy of the virtual bone outer surface34. In a particular embodiment, the virtual tool outer surface54and the virtual bone outer surface34are identical.

In another particular embodiment where the digital prosthesis representation is not used and step66is omitted, at least part of the virtual border surface portion is defined from the corresponding portion of the virtual bone outer surface34, and the remainder of the virtual tool outer surface has a generic shape, for example ovoid, planar, or defined as two or more intersecting planar surface sections. An example of such a case is illustrated inFIG. 8. In this embodiment, the part of the virtual border surface portion354′ extending a distance “A” from the lower virtual planar surface352along the entire junction of the virtual tool outer surface354with this virtual planar surface352is defined from the corresponding portion of the virtual bone outer surface34extending the distance “A” from the lower virtual cutting plane32along the entire junction of the virtual bone outer surface34with this virtual cutting plane32(FIG. 4). For instance, this part of the virtual border surface portion354′ may be defined by making a copy of the corresponding portion of the virtual bone outer surface34. In a particular embodiment, the corresponding parts of the virtual border surface portion354′ and the virtual bone outer surface34are identical. It is understood that in alternate embodiments, the part of the virtual border surface portion354′ defined from the corresponding portion of the virtual bone outer surface34may be defined along only part of the junction with the lower virtual planar surface352and/or along part or an entirety of the junction with the other virtual planar surface352.

When the digital prosthesis representation is used as per step66, the outer surface of the prosthesis may be defined to mimic the outer surface of the cut section of the bone adjacent one or more cut surface(s). Accordingly, and as shown for example inFIGS. 6A-6B, the virtual tool outer surface154may completely correspond to the virtual prosthesis outer surface144. For instance, the virtual tool outer surface154may be defined by making a copy of the virtual prosthesis outer surface144. In the example shown, the prosthesis is retained in the remaining bone through retaining features extending from one of the contact surfaces of the prosthesis and penetrating into the bone, represented in the digital prosthesis representation140(FIG. 6a) by virtual retaining features146extending from the lower virtual contact surface142, with the outer surface of the prosthesis being free of any retaining features. Accordingly, the body12of the tool10is defined to represents a copy of the visible/exposed portion of the prosthesis when engaged to the remaining bone.

In this embodiment, the part of the virtual prosthesis outer surface144extending a distance “A” from the lower virtual contact surface142along the entire junction of the virtual prosthesis outer surface144with this virtual contact surface142(FIG. 6a) is defined from the corresponding portion of the virtual bone outer surface34extending the distance “A” from the lower virtual cutting plane32along the entire junction of the virtual bone outer surface34with this virtual cutting plane32(FIG. 4). Accordingly, having the virtual tool outer surface154completely corresponding to the virtual prosthesis outer surface144results in the part of the virtual border surface portion154′ extending the distance “A” from the lower virtual planar surface152along the entire junction of the virtual tool outer surface154with this virtual planar surface152(FIG. 6b) also being defined from the corresponding portion of the virtual bone outer surface34extending the distance “A” from the lower virtual cutting plane32along the entire junction of the virtual bone outer surface34with this virtual cutting plane32(FIG. 4). In a particular embodiment, the corresponding parts of the virtual border surface portion154′ and the virtual bone outer surface34are identical. Depending on the configuration of the prosthesis and accordingly of the virtual prosthesis outer surface144, in alternate embodiments, the part of the virtual border surface portion154′ defined from the corresponding portion of the virtual bone outer surface34may be defined along only part of the junction with the lower virtual planar surface152and/or along part or an entirety of the junction with the other virtual planar surface152.

Another embodiment where the digital prosthesis representation is used but where the virtual prosthesis outer surface and the virtual bone outer surface adjacent the cutting planes differ from one another is shown inFIGS. 7a-7b. The prosthesis may include retaining features as part of and/or extending from its outer surface to engage the outer surface of the remaining bone. In the example shown, the prosthesis includes a rim overlapping the outer surface of the bone and other overlapping retaining members, which are represented by virtual retaining features246in the digital prosthesis representation240ofFIG. 7a, with all virtual retaining features246being located adjacent the lower virtual planar surface152. The part of the virtual border surface portion254′ extending the distance “A” from the lower virtual planar surface252along the entire junction of the virtual tool outer surface254with this virtual planar surface252(FIG. 7b) is defined from the corresponding portion of the virtual bone outer surface34extending the distance “A” from the lower virtual cutting plane32along the entire junction of the virtual bone outer surface34with this virtual cutting plane32(FIG. 4), and the remainder of the virtual tool outer surface254is defined from the corresponding portion B of the virtual prosthesis outer surface244. For instance, this part of the virtual border surface portion254′ may be defined by making a copy of the corresponding portion of the virtual bone outer surface34. In a particular embodiment, the corresponding parts of the virtual border surface portion254′ and the virtual bone outer surface34are identical. It is understood that in alternate embodiments, the part of the virtual border surface portion254′ defined from the corresponding portion of the virtual bone outer surface34may be defined along only part of the junction with the lower virtual planar surface252and/or along part or an entirety of the junction with the other virtual planar surface252. The connection between the two profiles for the virtual tool outer surface254is preferably made in a seamless manner. The body12of the tool10thus represents a copy of the bone near the cut surface(s) and of the visible/exposed portion of the prosthesis elsewhere, such that the body12is free of the outer surface retaining features of the prosthesis.

Referring back toFIG. 3, once the digital tool representation50,150,250,350is created, the body12of the tool10is manufactured in step70. In embodiments where the tool handle20is manufactured in one piece with the tool body12, a digital handle body is added to the digital tool representation50,150,250,350before the tool is manufactured. Manufacturing of the body12of the tool10includes creating each planar surface14of the body12in correspondence with the respective virtual planar surface52,152,252,352of the digital tool representation50,150,250,350and creating the outer surface16of the body12in correspondence with the virtual tool outer surface54,154,254,354of the digital tool representation50,150,250,350. The handle20may be manufactured at the same time, or manufactured separately. In a particular embodiment, the body12of the tool10is manufactured using a rapid prototyping method with the digital tool representation50,150,250,350(e.g. CAD model) used directly as input or transformed as required before being input into an appropriate application of a rapid prototyping system, and made from plastic (e.g. polyamide) or metal material. Alternately, the body12of the tool10(optionally together with the handle20) may be machined, for example from solid metal, using computer-aided machining (CAM), and machining parameters related for example to the tool material, cutting tools, and cutting operations, may be defined. A machining trajectory used for producing the tool body12(optionally together with the handle20) may then be generated from the digital tool representation50,150,250,350, and an appropriate computer numerical control (CNC) code specifying the tool paths as well as any additional required information may then be generated and sent to the machining tool over a suitable communication link.

In an embodiment where the planar surface(s)14of the body12include a textured pattern to be used as a filing tool, the planar surface(s)14may be manufactured directly with the textured pattern thereon. Alternately, the textured pattern may be created in a subsequent manufacturing step. In these embodiments, the material used is selected such as to be more resistant than bone such as to be able to use the tool for filing. Examples of suitable materials include, but are not limited to, titanium, stainless steel, and cobalt-chrome.

The tool10may be used to validate a cut in a bone in accordance with the method80and with reference to the diagram ofFIG. 7and the schematic illustration ofFIG. 8. First, at step82, the body12of the tool10is inserted into the cut section of the bone, with each outer surface14of the body12in contact with the respective cut surface15of the bone. In a particular embodiment, the handle20facilitates manipulation of the body12for proper placement thereof into the cut section.

At step84, the body12is moved until the outer surfaces16,17of the body12and of the remaining bone are as close to alignment as possible at the junction therebetween. At least part of the border portion16′ of the outer surface16of the tool is configured to correspond to the outer surface of the nominal removed bone section adjacent the corresponding junction with the cut surface(s)15. Accordingly, this part of the border portion16′ defines a reference portion of the outer surface16of the tool.

This reference portion and the outer surface of the bone17should be continuous or substantially continuous with one another at the junction between the two if the cut section of the bone corresponds to the nominal cut section of the bone. The junction between the reference portion of the outer surface16of the tool and the bone outer surface17is thus examined at step86, to determine if the outer surfaces16,17are continuous or substantially continuous along that junction. If the reference portion of the tool12protrudes beyond the corresponding outer surface17of the bone, the body12is removed from the cut and the size of the cut section is increased, as illustrated in step88, and steps82to86are repeated until the outer surfaces16,17are continuous or substantially continuous along the junction. In a particular embodiment, the size of the cut section is increased by filing at least one of the cut surfaces15with the corresponding planar surface14of the body12which defines a filing tool through an appropriate textured pattern.

If the corresponding outer surface17of the bone protrudes beyond the reference portion of the tool12, shimming material and/or cement and/or any adequate filler may be required to position the prosthesis. Preferably, the bone is initially cut to obtain a cut section smaller than the nominal cut section, and progressively enlarged while verifying the size of the cut section with the tool12between each step, such as to reduce the risks of requiring such additional materials.

In a particular embodiment where the body12of the tool10represents the custom prosthesis at least away from the cut surface(s)15, once the reference portion of the tool outer surface16and the bone surface17are continuous or substantially continuous, the body12of the tool10is further used to verify a fit between the custom prosthesis and an adjacent bone or prosthesis. At step90, the articulation is moved throughout its range of motion with the body12in place in the cut section, and the fit is verified. In a particular embodiment, such verification includes verifying that a tension in the ligaments of the articulation is adequate. The tool10may thus allow confirming of the dynamic interaction of the corresponding prosthesis within the articulation before the prosthesis is installed.