STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not Applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to methods for the optimization of joint arthroplasty component design and shoulder arthroplasty components such as stemless components and fracture stems for joint arthroplasty.

2. Description of the Related Art

Various prostheses for the replacement of the shoulder joint are known. In one example shoulder prosthesis, the upper portion of the humerus is replaced by a humeral component including (i) a stem, or cleat, that extends into a bore formed within the humerus and (ii) a generally hemispherical head portion that is connected to the stem. The hemispherical head of the humeral component articulates with a complementary concave section of a glenoid component mounted within the glenoid cavity of the scapula. This type of shoulder prosthesis may be called a “primary” or “total” prosthesis. In another example shoulder prosthesis, often called a hemiarthroplasty, a hemispherical head of the humeral component articulates with the native glenoid. In another example shoulder prosthesis, often called a “reverse” or “inverted” prosthesis, the glenoid component includes a convex section that articulates with a complementary concave proximal section of the head of the humeral component.

There is a breadth of complications in shoulder surgery associated with devices that are not anatomically correct. This includes fracturing the humerus when trying to implant a device that is not in the shape of the humeral anatomy, catastrophic early component loosening when contact with native bone is not optimized, as well as lack of long term bone ingrowth. In addition, a high rate of stress shielding with associated bone resorption has been reported in the literature due to a lack of uniform stress distribution. In the fracture setting, tuberosity resorption remains a significant problem and has a substantial negative impact on patient outcomes.

Thus, there exists a need for improved stemless components and fracture stems for joint arthroplasty, such as shoulder arthroplasty.

SUMMARY OF THE INVENTION

The present invention provides a methodology that improves the understanding of proximal humeral anatomy through the use of CT scan data and 3D modeling. This methodology describes the interaction of anatomical features of the proximal humerus and how these features change based on the specific location in the proximal humerus. Additionally, the methodology has demonstrated that the shape of the proximal humeral region is side specific. Therefore, having right and left specific devices with an anatomic shape in a true population based distribution further facilitates and improves joint prosthetic component design. The methodology can optimize loading and fit at the bone-device interface. Furthermore, models were created to test the methodology and the interaction of the anatomic features and their interdependence on each other. The results of the biomechanical testing validated the methodology demonstrating significantly improved initial fixation compared to currently available standard circular prosthetic component designs. The methodology has also resulted in improved stemless components and fracture stems for joint arthroplasty. The fracture stems include specific features for an improved anatomic fracture fixation device with optimal shape and size of fins to maximize tuberosity healing. Furthermore, cadaveric validation was performed of both the stemless components and fracture stems.

In one aspect, the invention provides a prosthesis comprising a central body having a longitudinal axis normal to a reference plane that extends through the central body; and a plurality of fins extending laterally from an outer surface of the central body, the plurality of fins being spaced apart around the outer surface of the central body, wherein spacing of the plurality of fins is asymmetric in the reference plane. The prosthesis can be a stemless prosthetic component, e.g., a stemless humeral prosthetic component. In some aspects, a first fin of the plurality of fins has a first fin length, the first fin length defined by a first distance from the central body to an outermost radial edge of the first fin, a second fin of the plurality of fins has a second fin length, the second fin length defined by a second distance from the central body to an outermost radial edge of the second fin. The second fin length can be less than the first fin length. In some aspects, each of the plurality of fins has a proximal fin edge having a proximal edge length and a distal fin edge having a distal edge length.

In some aspects, the proximal edge length of at least one of the plurality of fins is greater than the distal edge length of the at least one of the plurality of fins. In some aspects, the proximal edge length of at least one of the plurality of fins is equal to the distal edge length of the at least one of the plurality of fins. In some aspects, each of the plurality of fins has a lateral fin edge, and at least one of the plurality of fins has a lateral fin edge sloped at an oblique angle with respect to the reference plane.

In some aspects, at least one of the plurality of fins is substantially trapezoidal. In some aspects, at least one of the plurality of fins has rounded fin edges. In some aspects, the central body has a first opening and a second opening, the first opening corresponding to a proximal side of the central body and the second opening corresponding to a distal side of the central body. In some aspects, at least one of the plurality of fins is modular and removeably coupled to the central body. In some aspects, the prosthesis comprises four fins, or five fins, or six fins.

In some aspects, the first opening has a first diameter and the second opening has a second diameter, the first diameter being greater than the second diameter. The central body and the plurality of fins can be dimensioned for implantation into a humerus of a subject. The central body and the plurality of fins can be dimensioned for implantation into a femur of a subject.

In another aspect, the invention provides a prosthesis comprising a central body; and a plurality of fins extending laterally from an outer surface of the central body, the plurality of fins being spaced apart around the outer surface of the central body, wherein at least one of the plurality of fins has an inner perimeter and an outer perimeter, the inner perimeter and the central body defining a window. The prosthesis can be a fracture stem, e.g., a humeral fracture stem. In some aspects, at least one of the fins having the at least one window includes one or more throughholes in a wall defined by the inner perimeter and the outer perimeter of the fin having the at least one window. Each throughhole can be configured to receive a suture. The central body can have a first opening, a second opening, and a hollow region extending between the first opening and the second opening. At least one of the plurality of fins can be modular and removeably coupled to the central body.

In some aspects, the prosthesis can further comprise a bone graft positioned in the at least one window. The prosthesis may further comprise a stem dimensioned to be received by a distal opening in the central body. The prosthesis may further comprise a proximal section having a first articular surface dimensioned to articulate with a second articular surface of a native bone or a prosthetic component, and a stem connected to the central body, the stem being dimensioned to be received by an opening in the central body. In some aspects, the first articular surface can be convex. In other aspects, the first articular surface can be concave. In some aspects, the prosthesis can be a monoblock prosthesis or a modular prosthesis. The central body and the plurality of fins can be dimensioned for implantation into a humerus of a subject.

In some aspects, the prosthesis comprises a first fin and a second fin, the first fin and the second fin being spaced apart around the outer surface of the central body such that the first fin aligns with a greater tuberosity of the humerus and the second fin aligns with a lesser tuberosity of the humerus when the prosthesis is implanted in the humerus. The first fin can have a first perimeter of a first length, and the second fin can have a second perimeter of a second length, and the first length can be greater than the second length. The central body and the plurality of fins can be dimensioned for implantation into a femur of a subject.

In another aspect, the invention provides a prosthesis comprising a central body having a first section and a second section; and a plurality of fins extending laterally from an outer surface of the central body, the plurality of fins being spaced apart around the outer surface of the central body, wherein the first section has a first longitudinal axis and the second section has second longitudinal axis angled with respect to the first longitudinal axis. The prosthesis can be a fracture stem, e.g., a humeral fracture stem. The second section can be removeably coupled to the first section. At least one of the plurality of fins can comprise at least one throughhole. The central body can have a first opening, a second opening, and a hollow region extending between the first opening and the second opening. At least one of the plurality of fins can be modular and removeably coupled to the central body. At least one of the plurality of fins can be configured to align a first fin segment with the first longitudinal axis and align a second fin segment with the second longitudinal axis.

In some aspects, the prosthesis may further comprise a stem dimensioned to be received by a distal opening in the central body. The prosthesis may further comprise a proximal section having a first articular surface dimensioned to articulate with a second articular surface of a native bone or a prosthetic component, and a stem connected to the central body, the stem being dimensioned to be received an opening in the central body. In some aspects, the first articular surface can be convex. In other aspects, the first articular surface can be concave. In some aspects, the prosthesis can be a monoblock prosthesis or a modular prosthesis. The central body and the plurality of fins can be dimensioned for implantation into a humerus of a subject.

In another aspect, the invention provides a kit for implanting a joint component into a bone of a joint wherein the joint component comprises a central body and a plurality of fins extending laterally from an outer surface of the central body. The kit may comprise a trial template having (i) a central ring having a longitudinal axis normal to a reference plane that extends through the central ring, and (ii) a plurality of arms extending laterally from an outer surface of the central ring. The plurality of arms can be spaced apart around the outer surface of the central ring, wherein spacing of the plurality of arms is asymmetric in the reference plane.

In some aspects, the central ring can have a central aperture defined by an inner aperture of the central ring, the central ring can have a wall defined by the inner perimeter and an outer perimeter of the central ring, and the wall includes a passageway for receiving a locator pin. The kit may further comprise a locator tool having a handle connected to the locator pin.

In another aspect, the invention provides a kit for implanting a joint component into a bone of a joint wherein, the joint component comprises a central body and a plurality of fins extending laterally from an outer surface of the central body. The kit can comprise a preparation tool having (i) a central hollow cylinder having a longitudinal axis normal to a reference plane that extends through the central hollow cylinder, and (ii) a plurality of arms extending laterally from an outer surface of the central hollow cylinder. The plurality of arms can be spaced apart around the outer surface of the central hollow cylinder, wherein spacing of the plurality of arms is asymmetric in the reference plane.

In some aspects, spacing of the plurality of arms of the preparation tool corresponds to spacing of the plurality of fins of the joint component, and each of the arms of the preparation tool has a lesser thickness than its corresponding fin of the joint component. The kit may further comprise a cannulated instrument for impacting the preparation tool into the bone.

In another aspect, the invention provides a method for manufacturing a prosthetic component for replacing a part of a bone of a joint in a subject. The method comprises forming the prosthetic component to include a vertical length and a horizontal length. The vertical length and the horizontal length of the prosthetic component can be determined by: (a) creating a three dimensional model from one or more scans of the bone of the joint; (b) positioning on the model a bone cut reference plane that extends to an outer surface of the model; (c) orienting on an image including the bone cut reference plane a first reference line that extends from a first border of a head of the bone to an opposite second border of the head of the bone; (d) orienting on the image a second reference line that extends from a third border of the head of the bone to an opposite fourth border of the head of the bone; (e) determining the vertical length of the prosthetic component from a first length of the first reference line; and (f) determining the horizontal length of the prosthetic component from a second length of the second reference line.

In some aspects, step (a) comprises creating a three dimensional model using multiple scans from a single subject or multiple scans from more than one subject. Manufacturing a prosthetic component may include using additive manufacturing. The prosthetic component can be a stemless prosthetic component or a fracture stem. The image can be processed to remove cortical bone in the bone cut reference plane before orienting the first reference line and the second reference line on the image of the cancellous bone.

In another aspect, the method for manufacturing a prosthetic component may additionally include determining a maximum depth for a prosthetic. The maximum depth of the prosthetic component can be determined by finding an intersection point of the first reference line and the second reference line on the image, or by determining the midpoint of first reference line. After selecting the midpoint or the intersection point, then the depth may be determined by orienting on an image of the model a third reference line that extends from the intersection point to fifth border of the head of the bone and determining the maximum depth of the prosthetic component from the length of the third reference line.

In some aspects, the method may further comprise forming the prosthetic component to include an inclination angle, the inclination angle of the prosthetic component having been determined by (j) orienting on the image of the model an axial reference line; and (k) determining the inclination angle of the prosthetic component from a reference angle between the axial reference line and the bone cut reference plane. In some aspects, step (b) may comprise positioning on the model an anatomic cut reference plane and selecting the anatomic cut reference plane to be the bone cut reference plane. Step (b) may comprise (i) positioning on the model an anatomic cut reference plane, (ii) positioning on the model a second reference plane spaced from the anatomic cut reference plane, and (iii) selecting the second reference plane to be the bone cut reference plane.

In some aspects, the second reference plane can be spaced to be parallel to the anatomic cut reference plane. The second reference plane can be spaced about two to ten millimeters from the anatomic cut reference plane. The second reference plane can be spaced about five millimeters from the anatomic cut reference plane.

In some aspects, the method may further comprise forming the prosthetic component to include a protruding section having a length, the length of the protruding section having been determined by (l) orienting on the image a fourth reference line from the first reference line to a surface of a tuberosity; and (m) determining the length of the protruding section from a fourth length of the fourth reference line. The protruding section can be a fin of a prosthetic component comprising at least one of a stemless prosthetic or a fracture stem.

In some aspects, the method may further comprise forming the prosthetic component to include a protruding section having a length, the length of the protruding section having been determined by (l) orienting on the image a fourth reference line from the midpoint of the first reference line to a surface of a tuberosity; and (m) determining the length of the protruding section from a fourth length of the fourth reference line. The protruding section can be a fin of a prosthetic component consisting of at least one of a stemless prosthetic or a fracture stem.

In some aspects, the method may further comprise forming the prosthetic component to include a protruding section having a length, the length of the protruding section having been determined by (l) determining an intersection point of the first reference line and the second reference line on the image (m) orienting on the image a fourth reference line from the intersection point to a surface of a tuberosity; and (n) determining the length of the protruding section from a fourth length of the fourth reference line. The protruding section can be a fin of a prosthetic component consisting of at least one of a stemless prosthetic or a fracture stem. The prosthetic component can comprise at least one of cobalt chrome, titanium, stainless steel, plastic, and ceramic. The prosthetic component can comprise multiple materials, and one or more additive manufacturing systems may be used to manufacture different parts of the prosthetic component that are assembled for implantation into the patient.

In some aspects, the joint is selected from elbow, wrist, hand, spine, hip, knee, ankle, and foot. When the joint is the elbow, the bone is selected from the ulna, radius and humerus, when the joint is the wrist, the bone is selected from the radius, ulna and carpal bones, when the joint is the hand, the bone is selected from phalanges, metacarpals, and carpals, when the joint is the spine, the bone is a vertebrae, when the joint is the hip, the bone is selected from the femur and the pelvis, when the joint is the knee, the bone is selected from the femur, tibia, and patella, when the joint is the ankle, the bone is selected from the talus, the tibia and the fibula, and when the joint is the foot, the bone is selected from phalanges, tarsals, and metatarsals

These and other features, aspects, and advantages of the present invention will become better understood upon consideration of the following detailed description, drawings, and appended claims.

