WO2019076422A1

WO2019076422A1 - Method and device for patient specific templates of total shoulder replacement

Info

Publication number: WO2019076422A1
Application number: PCT/EG2018/000023
Authority: WO
Inventors: Mahmoud Alm El Din HAFEZ
Original assignee: Hafez Mahmoud Alm El Din
Priority date: 2017-10-22
Filing date: 2018-10-22
Publication date: 2019-04-25
Also published as: WO2019076422A4

Abstract

This invention relates to a method of determining the optimal positioning of the glenoid and humeral component. The method is a preplanned surgery on a specific software design an electronic model of patient specific instruments perform the correct and accurate position of the glenoid and humeral component for the patient going to total shoulder replacement surgery. This method identifies in a clear manner the center of the glenoid component; that gives the surgeons an easy way to orientate the glenoid component in the correct location over the densest area of bone and relative to a medial point of the patient's scapula and aligned with the coracoid bone level. Another goal of this method is to identify the retroversion and the location and slope of cutting level over the humeral head with a specific angle according to the diagnosis of the case based on the CT-Scan. The 3D printing technologies will carry out producing of these patient specific templates.

Description

A Method and a Patient-Specific Template for Total Shoulder Arthroplasty

This application claims the benefit of Egyptian Provisional application No. 26/2017 filed on October 22, 2017 and Egyptian Patent Application No. 655/2018 on April 22, 2018

Technical Field

The present invention relates to a method and a patient-specific device (template) for fixing an artificial shoulder joint, with both humeral and glenoid parts, for patients undergoing a shoulder joint replacement surgery. The device consists of two separate pieces: one for the humeral bone, while the other for the glenoid cavity bone. The first piece comes in two designs to suit different cases and conditions of the humeral bone, whether a fracture, stiffness, bone sliding or tumors. The second piece comes in four designs to suit different cases and conditions of patients under surgery, whether a fracture, corrosion or stiffness. The device is designed to match the anatomical structure of the shoulder joint and the anatomical markers on the bone surface on which it would be fixed. Guided by the patient's CT scan pictures, the surgeon would be able to fix the joint in its right place. The inventive device is printed by 3D printer; it is made from the nylon material approved by American Food and Drug Administration (FDA).

Disadvantages of Prior Art

Traditional medical tools are used for total shoulder arthroplasty (TSA) surgery are numerous. They should be handled by highly skilled and experienced surgeons to complete the surgical procedures. In total shoulder arthroplasty surgery, the shoulder joint-with both the glenoid cavity and the humeral bones-is replaced. The surgeon uses traditional tools for determining the place, alignment and partial size of the joint. The surgeon thus should be skillful in using such tools for the new artificial joint to fit into the place of the natural one.

Total shoulder arthroplasy (also known as total shoulder replacement) is a very difficult type of surgery. This is due to the special anatomical morphology of the shoulder joint and its complicated function and movement unlike other joints, such as knee, foot and pelvic joints. It should be done by long-experienced skillful surgeons, which makes it a difficult surgery with moderate outcomes. It is a surgery that depends on the surgeon's skill rather than advanced machinery. It has no standards.

Another difficulty of the surgery lies in the fact that the shoulder joint, with its both parts: the humeral and glenoid ones, is not protruding by nature. In addition, one of the vital nerves of the human body passes through the anatomical morphology of the shoulder joint, making the surgical opening small; unlike other joints, such as the knee joint, characterized with surgical conditions comfortable for the surgeon.

During surgery, the shoulder joint consisting of two pieces: one for the glenoid cavity and the other for the humeral bone is replaced.

The surgeon uses traditional tools of multi-step surgical technique for specifying the place, alignment and partial joint size. He should use such tools skillfully for the artificial joint to fit into the place of the natural one. Determining the joint size depends, especially in the glenoid part, on bone mass and density; the surgeon has no easy and obvious mechanism for determining the bone mass and thickness before surgery. Hence, it is a challenge to choose the right size and alignment for the joint in fixing artificial shoulder joint surgeries.

Another difficulty is that the use of two-dimensional X-rays makes the surgeon unable to deal with medical and surgical difficulties, such as shoulder birth defects and previous fractures. The surgeon, in these cases, would not be able to determine the dimension, location and depth of the fracture, thus threatening the success of artificial shoulder joint fixation surgeries. If the shoulder contains pre-fixation metal discs, the surgeon would be unable to determine the disc's right place through the use of X-rays, CT scan and two-dimensional resonance.

There are different types of artificial shoulder joint fixation, such as complete joint fixation, a half joint fixation or a reverse joint fixation. Hence, there is a need to an accurate technique for choosing the appropriate surgery type and requirements, such as specifying the position, size and alignment of the joint. The surgeon should be of high skill and long experience to be able to efficiently perform the different surgery types.

In view of the above mentioned, it becomes clear that there is a dire need to find a new method and surgical approach to overcome the current difficulties. Hence, the present invention provides a patient-specific device for determining the position, alignment and size of both parts of the joint: the humeral and glenoid parts. The inventive device also provides an easier surgical technique for complete joint, a half joint or a reverse joint fixation.

Detailed Description of the Invention

The present invention relates to a method and a patient-specific device for fixing artificial shoulder surgical pre-planning. It provides a patient-specific device for single use only. The inventive device is applicable to different medical cases, such as fractures, stiffness or bone sliding.

The device consists of two separate pieces: one for the humeral bone, while the other for the glenoid cavity bone. The first piece comes in two designs to suit different cases and conditions of the humeral bone, whether a fracture, stiffness, bone sliding or tumors. The second piece comes in four designs to suit different cases and conditions of patients under surgery, whether a fracture, corrosion or stiffness. All designs depend on the anatomical structure and markers of the shoulder joint with its humeral and glenoid parties, especially the external edge of the humeral bone head and the two head grooves of the shoulder bone (figure 1), as well as the glenoid cavity of the shoulder bone (figure 10).

Depending on the patient's two-dimensional X-ray or three-dimensional CT scan, the device is designed as a three-dimensional model for the shoulder joint bone with both parts: the humeral and glenoid ones, using a special computer program. Surgery pre-planning is performed by a computer program to accurately determine the position, alignment and size of both parts of the artificial shoulder joint: the humeral and glenoid ones. The CT scan creates a model that matches the patient's bone topology.

Surgical planning depends on the anatomical axis of the shoulder bone, allowing the surgeon to determine the amount of bone to be cut from the humeral bone head and the quality and thickness of the glenoid cavity bone. Accordingly, surgeons will be able to determine the size and alignment of the joint in a more accurate way in comparison to traditional surgical tools.

Unlike other joints, the anatomy of the shoulder joint allows a wide range of motion such as rotation for more than 180°. It is connected to the elbow joint, characterized also with a wide-range motion, through the humeralis. However, the elbow joint is deep inside the body, making it difficult to broaden and crave the glenoid cavity bone for making fixation openings for the shoulder artificial joint. These openings are made using the keel in the glenoid part of the shoulder joint. Cases of the shoulder joint, such as stiffness, tumors, fractures and bone sliding, make it difficult for surgeons of ordinary skill to perform this type of surgery. The present inventive two-part device of various designs helps surgeons to fix artificial knee joint with high accuracy. The humeral part of the shoulder joint, according to the present invention, comes in two designs to suit the different cases of stiffness, fracture, tumor or bone sliding. The designs are called the crescent and the shaft designs.

The crescent design for the humeral part of the shoulder joint appears in figures 2, 3, 4, 5 and 6. It is used if the humeral bone head is intact and there is no fracture or tumors in the humeral bone. The crescent design consists of a plane surface taking the shape of a crescent for making a cut in the head of the humeral bone according to the required inclination angle and the amount of bone to be cut, as predetermined during computer-assisted surgical pre-planning. It contains three openings for fixing the device in its proper position in the humeral bone by the aid of the computer-assisted surgical pre-planning and the patient's CT scan. The crescent design also includes a fixing hook to prevent the device displacement, allowing the surgeon to fix it in its proper position on the bone. Being a patient specific-device, it is designed to suit the anatomical morphology of the patient's bone recognized by CT scan.

The second design, called the shaft design for the humeral part of the shoulder joint, appears in figures 7, 8, and 9. It is used if the head of the humeral bone is broken, if there are f actures or tumors in the humeral bone or if it contains prefixed metal discs. The present invention aims at resolving the difficulties related to performing fixing artificial shoulder surgeries in such cases.

The shaft design is a vertical structure with an inclined surface at its end. It is used for making cuts in the humeral bone head, in accordance to the required inclination angle and the amount of bone to be cut as pre-determined during the computer- assisted surgical pre-planning. Moreover, the shaft includes two openings for fixing the machine on its proper position as pre-determined by the surgeon according to the computer-assisted surgical pre-planning and the patient's CT scan. The design also includes a fixation arm to prevent the displacement of the device, allowing the surgeon to accurately fix it in its proper position on the bone, as previously mentioned about the crescent design.

The second part of the device, related to designing the glenoid cavity for the shoulder joint, has four different designs according to the different cases of stiffness, tumor or bone sliding (figure 10). The designs depend on the quality, thickness and density of the glenoid cavity bone, which are the fundamentals of fixing an artificial shoulder joint surgery.

The first design for the glenoid part is called the two-foot design (figures 11 and 12). It is fixed on the glenoid cavity using these two feet, one above the cavity and one below the cavity, to prevent device displacement. The design also contains three openings for making paths for inserting the keel (in the glenoid part of the shoulder joint). Opening a path for the keel using conventional methods is very difficult, for it necessitates inserting a bone block in the glenoid cavity to prevent its breakage during surgery. Unlike traditional surgical techniques, there is no need to broaden or crave the glenoid cavity, keeping it safe from breakage during surgery.

This design is used when the glenoid cavity bone is weak or of low quality. The presence of two fixation feet in the cavity ends prevents the surgeon from contacting low-density parts in the middle of the cavity, thus keeping it safe. The design contains three openings for making paths for inserting the keel in the glenoid cavity of the shoulder joint.

The second design for the glenoid part of the shoulder joint is called the arm and leg design (see figures 13andl 4). This part is fixed on the glenoid cavity using the feet at the bottom and the arm at one side to prevent movements in the anteroposterior direction. This design is used if there are previous fractures in the glenoid cavity, as it prevents movement in two directions. The second design for the glenoid cavity of the shoulder joint is called the two-arm design (see figures 15 and 16). This part is fixed on the glenoid cavity using two arms in both directions. This design is used in cases of atrophy and low thickness of the glenoid cavity in both superior and inferior directions because it guarantees fixation in both directions. It is the most important design, as it is difficult in most surgeries of fixing the shoulder joint to broaden and crave the glenoid cavity in both superior and inferior directions in case of its atrophy or erosion. This is due to lack of obvious reference fixation points for the traditional tools used in broadening and craving before the process of opening joint fixation paths. This design makes the invention unique; the patient-specific device is designed to fit the eroded bone with the aid of the patient's CT scan showing the bone topology. The appropriate place, size and alignment for the device are determined by the computer program and the device is manufactured accordingly.

The fourth design for the glenoid part of the shoulder joint is called a wing-foot design (see figures 17 and 18). The foot is used for fixation at the bottom side, while the wing is used for fixation above the shoulder cavity from the posterior side. This design is used in case of erosion or weakness of the coracoid bone.

All previously-mentioned designs of the glenoid and humeral parts are made by a computer-assisted surgical planning. Data of the patient's CT scan is inputted into the program for performing surgery preplanning. The CT scan gives a vivid image of the bone alone without cartilages or soft tissues. In addition, CT scan gives the same image for patient unlike resonance that gives different images by time due to the change of cartilage status and its erosion percent. Data inputted is converted into a three-dimensional model for both the glenoid and humeral bones. Surgery pre-planning is then performed as above mentioned depending on the anatomical axes and markers for the shoulder joint. The inventive device is fixed in its proper place due to the matching between its internal surface topology and the external surface topology of the bone. It thus fits only the place pre-determined in surgery preplanning on the bone surface during surgery. It is designed and usable for one patient only due to differences in bone surface topology.

The program searches for the appropriate electronic form for the device, according to the software-determined size, position and alignment of the artificial joint. The internal surfaces of the device, of both the glenoid and humeral parts, are identical to the bone's external surface, thus guaranteeing accurate fixation.

The electronic file of the device is sent to a 3D printer for being manufactured and applied in surgeries. Each piece of the device contains, on its surface, engraved information about joint size, orientation and the patient's name to avoid template mingling.

The device is characterized by ease of sterilization, carrying and handling for its light weight. The template's weight does not exceed 100 gram, unlike traditional devices that exceed 35 kilograms in weight and consist of many boxes making them difficult to sterilize and carry. The inventive method and device are used for fixing an artificial shoulder joint, with both the glenoid and humeral parts, for patient undergoing a shoulder joint replacement surgery. The device consists of two different pieces: one for the humeral bone in two designs and the other for the glenoid cavity in four designs.

The device is designed by a computer program for surgery pre-planning, by the aid of the patient's CT scan, and printed by a 3D printer.

Surgeons use this template for fixing a shoulder artificial joint according to a computer-assisted surgical planning.

Description of the Figures Figure 1 represents a three-dimensional perspective for the humeral bone showing some anatomical markers for the bone, such as the two head groove (1) and the external edge of the humeral bone head (2).

Figure 2 represents a three-dimensional perspective and a two-dimensional front view for the humeral part's crescent design. It is part of a device specific for a patient undergoing an artificial shoulder joint fixation surgery. Piece (3), the fixing hook (4) and fixation openings (5) appear in the figure.

Figure 3 represents a two-dimensional front view for the humeral part's crescent design while being fixed on the humeral bone (7). It is part of a device specific for a patient undergoing an artificial shoulder joint fixation surgery (6).

Figure 4 represents a two-dimensional elevation for the humeral part's crescent design while being fixed on the humeral bone (7). It is part of a device specific for a patient undergoing an artificial shoulder joint fixation surgery (6).

Figure 5 represents a two-dimensional side elevation for the humeral part's crescent design while being fixed on the humeral bone (7). It is part of a device specific for a patient undergoing an artificial shoulder joint fixation surgery (6).

Figure 6 represents a three-dimensional perspective for the humeral part's crescent design. It is part of a device specific for a patient undergoing an artificial shoulder joint surgery fixation. The internal surface topology appears in Figure (8).

Figure 7 represents a side elevation and a two-dimensional front view for the humeral part's shaft design. It is part of a device specific for a patient undergoing an artificial shoulder joint fixation surgery. The cutting surface (11), the fixation shaft (10) and the fixation openings (9) appear in the figure.

Figure 8 represents a side elevation and a two-dimensional front elevation for the humeral part's crescent design, while being fixed on the humeral bone (7). It is part of a device specific for a patient undergoing an artificial shoulder joint fixation surgery (12). Figure 9 represents a three-dimensional perspective for the humeral part's shaft design. It is part of a device specific for a patient undergoing an artificial shoulder joint fixation surgery; the design shows the internal surface topology (13).

Figure 10 represents a three-dimensional perspective for the shoulder bone with some anatomical markers such as the glenoid cavity (14)

Figure 11 represents three-dimensional front and back views for the two-foot design for the inventive device's glenoid part. Openings for making internal paths (15), the fixation feet (16) and the internal surface topology appear in the figure (17).

Figure 12 represents a two-dimensional side view for the glenoid part's two-foot design while being fixed on the glenoid cavity bone (19). It is part of a device specific for a patient undergoing an artificial shoulder joint fixation surgery (18). Figure 13 represents three-dimensional front and back views for the glenoid part's foot-arm design. It is part of a device specific for a patient undergoing an artificial shoulder joint fixation surgery (18). Openings for making internal paths (20), the fixation feet (21), the fixation arm (22) and the internal surface topology appear (23) in the figure.

Figure 14 represents a two-dimensional side view for the glenoid part's foot-arm design, while being fixed on the glenoid cavity bone (19). It is part of a device specific for a patient undergoing an artificial shoulder joint fixation surgery (24). Figure 15 represents front and back views for the two-arm design for the inventive device's glenoid part (25). The fixation arms (25) and the internal surface topology appear in the figure (26).

Figure 16 represents a three-dimensional side view for the glenoid part's two-arm design, while being fixed on the glenoid cavity bone (19). It is part of a device specific for a patient undergoing an artificial shoulder joint fixation surgery (27). Figure 17 represents a three-dimensional front and back perspectives for the glenoid part's wing-foot design. It is part of a device specific for a patient undergoing an artificial shoulder joint fixation surgery. The figure shows fixing wing (29), fixation foot (28) and internal surface topology (30).

Figure 18 represents a two-dimensional view for the wing-foot design for the glenoid part of the inventive device (31), whereas it appears fixed to the glenoid cavity bone (19). It is part of a device specific for a patient undergoing an artificial shoulder joint fixation surgery (31).

Claims

1- A method and a patient-specific device for fixing an artificial shoulder joint, with both humeral and glenoid parts, for patients undergoing a shoulder joint replacement surgery. The device consists of two separate pieces: one for the humeral bone, while the other for the glenoid cavity bone. The first piece comes in two designs to suit different cases and conditions of the humeral bone, whether a fracture, stiffness, bone sliding or tumors. The second piece comes in four designs to suit different cases and conditions of patients under surgery, whether a fracture, corrosion or stiffness. The device design depends on the anatomical structure of the shoulder joint and the anatomical markers on the bone surface on which it would be fixed, with the aid of the patient's CT scan pictures. The said device makes it easier for the surgeon to determine the position of the middle opening of the glenoid cavity joint along with the middle line of the bone. It guides the surgeon to the desired cutting angle and the cut thickness for the humeral bone head, using the two head groove as a surface guide for fixation.

2- A device according to claim no. 1, whereas the humeral part comes in two designs; the first of which is called the crescent design. It is characterized with a plane surface taking the shape of a crescent for making a cut in the humeral bone head. The design has three openings through which it is fixed on the humeral bone. It has an upper fixing hook for being mounted at the top of the humeral bone.

3- A device according to claim no. 2, whereas the second design of the humeral part is called the shaft design. It is characterized with a shaft ending with an inclined surface for making a cut in the humeral bone head. It has two opening for fixation on the humeral bone. It has a bottom arm for being mounted on the humeral bone.

4- A device according to claim no. 1, whereas the glenoid part comes in four designs. The glenoid part's first design is called the two-foot design; it has two feet-an upper foot and a bottom one-for its fixation on the glenoid cavity. The design includes also three selecting openings in place of the middle opening of the glenoid cavity joint.

5- A device according to claim no. 1 , whereas the second design of the glenoid part is called an arm and leg design. It has a foot at its bottom and an arm at its side for its fixation fixed on the glenoid cavity. It has three selection openings in place of the middle opening of the glenoid cavity joint.

6- A device according to claim no. 5, whereas the third design of the glenoid part is called a two arm design. It has two arms at each side for its fixation on the glenoid cavity. It has three openings in place of the middle opening of the glenoid cavity joint.

7- A device according to claim no. 5, whereas the fourth design of the glenoid part is called a wing-foot design. It has a bottom foot and an upper wing from inside for its fixation on the glenoid cavity. It has three openings in place of the middle opening of the glenoid cavity joint.

8- A device according to claim no. 1 , whereas it has an internal surface that matches the bone surface at its fixation place.

9- A device according to claim no. 1 , whereas the template's internal surface is designed to match the bone's external surface by the aid of the anatomical structure and the anatomical markers of the bone, such as the two head groove, the external edge of the humeral bone and internal glenoid cavity.

10- A device according to claim no. 1, whereas surgery pre-planning depends on the CT scan of the patient undergoing a surgery for fixing an artificial shoulder joint.

1 1- A device according to claim no. 1, whereas it is made from nylon to be light and sterizable. Nylon is a medical material certified by American Food and Drug Administration (FDA).