Intercalated and osseointegrated prosthesis for finger and thumb amputation

Abstract

This invention presents a modular, osseointegrated prosthesis for restoring finger and thumb functionality after amputation. The prosthesis includes single-joint and dual-joint components, designed for the thumb's MCP joint and the PIP and DIP joints of other fingers. It integrates with the residual bone through intramedullary fixation, enabling seamless movement and restoring up to 180 degrees of extension in the MCP joint and precise motion in the PIP and DIP joints. Made from biocompatible materials like titanium with a hydroxyapatite coating, the prosthesis features mechanisms for optimal tendon movement and joint stabilization. It also incorporates distraction osteogenesis to lengthen the bone before implantation, ensuring functional and aesthetic outcomes. This solution offers significant advancements over current prosthetic technologies by combining functional restoration and aesthetic appeal, making it suitable for all finger amputations and enhancing the ability to regain full hand function with long-term stability and comfort.

Description

[0001] INTERCALATED AND OSSEOINTEGRATED PROSTHESIS FOR FINGER AND THUMB AMPUTATION

[0002] TECHNICAL FIELD

[0003] The present disclosure generally relates to medical devices, specifically in the field of orthopedics, and more particularly to prostheses for replacing amputated fingers. Finger amputation, a common upper extremity injury, often leads to significant functional and psychological impairments.

[0004] BACKGROUND

[0005] Finger prostheses are typically designed as single-joint or double-joint devices made from materials like silicone or plastic, providing limited natural movement and flexibility. These prostheses are used in cases of finger amputation, but often fail to fully restore finger functionality or provide the necessary natural extension for performing daily tasks. Finger amputations at the proximal phalanx level present significant challenges in reconstructing both the aesthetic appearance and functional capabilities of the digit. Current treatment approaches often rely on either distraction osteogenesis for lengthening the residual finger or prosthetic replacement to restore functionality. However, each method has inherent limitations.

[0006] • Distraction osteogenesis, while effective in preserving the natural appearance of the finger, often fails to restore adequate joint functionality, resulting in limited range of motion and compromised hand dexterity.

[0007] • Prosthetic joint replacement, on the other hand, can provide functional articulation but sacrifices the natural length and appearance of the finger, reducing patient satisfaction.

[0008] To address these limitations, an innovative method combining distraction osteogenesis and osseo integrated prosthetic joint replacement has been developed. This approach leverages the advantages of both techniques, ensuring the restoration of both natural appearance and functional movement in amputated digits.

[0009] The present invention offers a prosthesis that combines modular components, allowing for personalized adjustments and enhanced movement. Additionally, the prosthesis utilizes biocompatible materials like titanium with a hydroxyapatite coating to improve integration with bone, while incorporating bone-lengthening techniques to restore full finger function. This design ensures a more natural, fluid range of motion, particularly for individuals with amputated fingers.

[0010] SUMMARY

[0011] According to this invention, there is provided a modular and self-regenerative prosthesis for finger joints that integrates seamlessly with the residual bone of amputated fingers and is applicable in orthopedics. This prosthesis addresses the issues of inadequate finger functionality due to the absence of PIP and DIP joints in distraction osteogenesis alone, as well as the unsatisfactory appearance of the fingers when only artificial prosthetics are used.

[0012] The invention provides a solution where, following distraction osteogenesis for bone elongation, a specialized prosthesis is designed and implemented. This prosthesis includes double-joint components for PIP and DIP joints and a single-joint component for the MCP joint of the thumb, restoring appropriate finger functionality. It is inserted intramedullary, ensuring proper integration with the bone.

[0013] In the design of this prosthesis, mechanisms are incorporated to transfer force from adjacent structures to the joints, enabling natural and coordinated finger joint functionality. Additionally, artificial pulleys are used to facilitate optimal tendon movement. Made from biocompatible materials such as titanium with a hydroxyapatite coating, the prosthesis promotes natural finger movements, enabling up to 180-degree extension and restoring complete functionality in cases of finger amputation.

[0014] This invention is applicable to all fingers and provides individuals with amputated fingers a functional, aesthetically pleasing solution that enhances their ability to regain full hand use.

[0015] BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawing Figures depict one or more implementations in accord with the present teachings, by way of example only, not by way of limitation. In the Figures, like reference numerals refer to the same or similar elements.

[0017] FIG. 1: Illustrates a general view of the component with the male part, shown from the side perspective. The distal stem body (101) of the MCP joint prosthesis within the proximal phalanx bone of the thumb. The distal component includes a joint cavity consisting of a cavity base (102) and lateral cavity walls (103). Two male projections (104) extend from the cavity base (102) toward the lateral cavity walls (103). Grooves (108) on the distal stem body (101).

[0018] FIG. 2: Illustrates a general view of the component with the female part, shown from the side perspective. The proximal stem body (105) of the MCP joint prosthesis within the metacarpal of the thumb. The proximal component features a joint cavity with lateral cavity walls (106). Grooves (108) on the distal stem body (105).

[0019] FIG. 3: Illustrates the articulation mechanism between the distal male component (101) and the proximal female component (105).

[0020] FIG. 4: Illustrates the positioning of the prosthesis in the MCP joint of the thumb and its method of fixation.

[0021] FIG. 5: Illustrates the positioning of the prosthesis in the PIP and DIP joints and its method of fixation. FIG. 6: Illustrates the articulation mechanism between the distal male stem (101) and the proximal female stem (105) of the prosthesis (top view).

[0022] FIG. 7: Illustrates the articulation mechanism between the distal stem (101) and the proximal stem (105) of the prosthesis (side view).

[0023] FIG. 8: Illustrates the articulation mechanism between the distal stem (101) and the proximal stem (105) of the prosthesis (oblique view).

[0024] FIG. 9: Illustrates The articulation mechanism between the distal stem (101) and the proximal stem (105) of the prosthesis (two-dimensional view).

[0025] FIG. 10: Illustrates the distal stem includes a joint cavity consisting of a cavity base (102) and lateral cavity walls (103). Two male projections (104) extend from the cavity base (102) toward the lateral cavity walls (103). Grooves (108) on the distal stem body (101) (two-dimensional view).

[0026] FIG. 11: Illustrates the distal stem (101) includes a joint cavity consisting of a cavity base (102) and lateral cavity walls (103). Two male projections (104) extend from the cavity base (102) toward the lateral cavity walls (103). Grooves (108) on the distal stem body (101) (three- dimensional view).

[0027] FIG. 12: Illustrates the proximal stem (105) features a joint cavity with lateral cavity walls (106). Two small C-shaped female recesses (107) are located within the lateral cavity walls (106) of the joint cavity. Grooves (108) on the proximal stem body (105) (two-dimensional view).

[0028] DETAILED DESCRIPTION

[0029] Finger amputations present significant challenges in reconstructive surgery. These amputations compromise both the functionality and appearance of the hand, leading to reduced grip strength, dexterity, and aesthetic concerns. The thumb plays a unique role in hand function, enabling opposition, grasping, and pinching. Its MCP joint differs from the MCP joints of other fingers due to its greater range of motion and its ability to sustain higher forces. Consequently, prosthetic designs for the thumb require distinct considerations compared to other digits.

[0030] This invention addresses amputations involving the thumb’s MCP joint through a single-joint prosthesis and the PIP and DIP joints of fingers 2-5 using a dual-joint prosthesis to restore multi- articular movement. Both prostheses are designed to integrate seamlessly with the remaining bone structure using intramedullary fixation, restoring natural articulation and tendon dynamics to improve both form and function.

[0031] Each prosthesis consists of two primary components: a proximal stem and a distal stem. The proximal stem is implanted intramedullary in the bone proximal to the joint, while the distal stem is implanted intramedullary in the bone distal to the joint. These components work together as a functional unit, creating a secure and smooth articulation for the reconstructed joint.

[0032] The articulation mechanism employs a male-female interlocking design to mimic natural joint movements while maintaining stability. Male projections, located on the proximal stem, extend from the base of the cavity into the joint space. Female recesses, found on the distal stem, are designed as C-shaped grooves to securely receive the male projections. This mechanism enables a controlled range of motion, with the MCP prosthesis designed for a large range of motion (up to 180° extension) and the PIP and DIP prostheses tailored for finer motion ranges specific to interphalangeal joints. Additionally, the secure locking provided by this design prevents dislocation during movement.

[0033] Stabilization within the medullary canals is critical to ensure the prosthesis remains securely in place. To achieve this, longitudinal grooves on both proximal and distal stems increase surface area for bony integration, providing resistance to torsional forces and preventing rotation or loosening. The intramedullary design features stems that are tapered to match the shape of the medullary canals, enhancing fixation without excessive pressure. This design minimizes damage to the surrounding bone and soft tissue during implantation, ensuring a stable and durable integration with the patient’s anatomy.

[0034] Single-Joint Prosthesis (MCP Joint of the Thumb)

[0035] The single-joint prosthesis for reconstructing the MCP joint of the thumb consists of the following components:

[0036] 101 : Body of the distal stem.

[0037] 102: Base of the joint cavity on the distal stem.

[0038] 103: Lateral walls of the joint cavity on the distal stem.

[0039] 104: Male projections (spurs) of the distal stem.

[0040] 105: Body of the proximal stem.

[0041] 106: Lateral walls of the joint cavity on the proximal stem.

[0042] 107: Small C-shaped recesses on the proximal stem.

[0043] 108: Grooves on the proximal and distal stems.

[0044] 112: 1stMetacarpal

[0045] 113: 1stProximal phalanx

[0046] Distal Stem Design: The distal stem (FIG. 1-101) is intramedullary implanted into the first metacarpal bone. It features a joint cavity with a base (FIG. 1-102) and lateral walls (FIG. 1-103). Two male projections (FIG. 1-104) extend from the base of the joint cavity (FIG. 1-102) toward the lateral walls (FIG. 1-103). Grooves (FIG. 1-108) on the body of the proximal stem (FIG. 1-101) are designed to ensure secure fixation within the medullary canal of the first metacarpal.

[0047] • Proximal Stem Design:

[0048] The proximal stem (FIG. 2-105) is intramedullary implanted into the proximal phalanx of the thumb. It has a joint cavity with lateral walls (FIG. 2-106). Two small C-shaped recesses (FIG. 3- 107) are located within the lateral walls of the joint cavity (FIG. 2-106). Grooves (FIG. 2-108) on the body of the distal stem (FIG. 2-105) ensure secure fixation within the medullary canal of the proximal phalanx.

[0049] • Articulation Mechanism:

[0050] The articulation between the proximal stem (FIG. 3-101) and the distal stem (FIG. 3-105) is achieved by locking the two male projections (FIG. 3-104) of the proximal stem into the two small C-shaped recesses (FIG. 3-107) of the distal stem (FIG. 5). The design of the projections and recesses allows for a range of motion up to 180 degrees in extension. FIGs 7-10 provide two- dimensional and three-dimensional views of the prosthesis. The artificial pulley, as disclosed in Patent No US20220023029A1: https: / / patents.google.com / patent / US20220023Q29Al / en will be used to facilitate proper tendon movement in the dual-joint prosthesis of the fingers.

[0051] Dual-Joint Prosthesis (DIP and PIP Joints)

[0052] The dual-joint prosthesis for reconstructing the PIP and DIP joints of fingers 2 to 5 comprises the following components (FIG. 5):

[0053] 101 : Body of the distal stem.

[0054] 102: Base of the joint cavity on the distal stem.

[0055] 103: Lateral walls of the joint cavity on the distal stem.

[0056] 104: Male projections (spurs) of the distal stem.

[0057] 105: Body of the proximal stem.

[0058] 106: Lateral walls of the joint cavity on the proximal stem.

[0059] 107: Small C-shaped recesses on the proximal stem.

[0060] 108: Grooves on the proximal and distal stems.

[0061] 109: Proximal phalanx

[0062] 110: Middle phalanx Ill : Distal phalanx

[0063] The distal stem (Fig. 5- 101) and the proximal stem (Fig. 5-105) of the PIP joint prosthesis is designed for intramedullary placement within the proximal phalanx (Fig. 5-109) and the middle phalanx of the fingers (Fig. 5-110). Two male projections (Fig. 5-104) on the distal stem lock securely into two small C-shaped female recesses (Fig. 5-107) on the proximal stem. Grooves (Fig. 5-108) on the bodies of both the distal stem (Fig. 5-101) and the proximal stem (Fig. 5-105) are specifically designed to ensure firm fixation of the stems within the medullary canals of the respective bones. The distal stem (Fig. 5-101) and the proximal stem (Fig. 5-105) of the DIP joint prosthesis is designed for intramedullary placement within the middle phalanx (Fig. 5-110) and the distal phalanx of the fingers (Fig. 5-111). Two male projections (Fig. 5-104) on the distal stem lock securely into two small C-shaped female recesses (Fig. 5-107) on the proximal stem. Grooves (Fig. 5-108) on the bodies of both the distal stem (Fig. 5-101) and the proximal stem (Fig. 5-105) are specifically designed to ensure firm fixation of the stems within the medullary canals of the respective bones.

[0064] The method of the present invention for treating an amputated thumb involves osteotomizing the remaining bone of the proximal phalanx as the first step (1). Next, an external distractor is applied to facilitate osteogenesis distraction, with the proximal pins of the distractor inserted into the proximal segment of the proximal phalanx bone and the distal pins placed into the distal segment

[0065] (2). Distraction is then performed at a rate of 1 millimeter per day, leading to the formation of new bone (callus) between the two segments, which results in the lengthening of the proximal phalanx

[0066] (3). Finally, the external fixator is removed (4).

[0067] This novel approach involves a three-stage surgical process designed to reconstruct amputated fingers at the proximal phalanx level, achieving both aesthetic and functional restoration:

[0068] 1. Distraction Osteogenesis :

[0069] • The residual stump bone is osteotomized, and an external distractor is applied (FIG. 6-1 and 2).

[0070] • Controlled distraction at a rate of 1 millimeter per day gradually lengthens the finger until the desired length is achieved .

[0071] • This stage preserves the natural soft tissue structure and restores the digit's appearance .

[0072] 2. Arthroplasty with Osseointegrated Prosthetic Joint

[0073] • A custom-designed prosthetic joint is implanted intramedullary to replace missing articulations (FIG. 4).

[0074] • For non-thumb digits, a dual-joint prosthesis reconstructs the PIP and DIP joints. For thumbs, a single-joint prosthesis reconstructs the MCP joint (FIG. 5).

[0075] • This ensures functional articulation and allows the patient to perform precise movements.

[0076] 3. Tendon Transfer and Artificial Pulley Placement, as disclosed in Patent No US20220023029A1 : htps: / / patents.google.com / patent / US20220023Q29Al / en • Tendons from adjacent fingers are transferred to restore active control of the reconstructed joints.

[0077] • Artificial pulleys are positioned to guide tendon movement, ensuring smooth and efficient joint function.

[0078] By integrating distraction osteogenesis for lengthening with osseointegrated prosthetic joint replacement and tendon reconstruction, this method addresses the limitations of traditional approaches. It offers a groundbreaking solution that restores the natural appearance and full functionality of the finger, significantly improving patient outcomes.

Claims

ClaimsWhat is claimed is:

1. A prosthesis for reconstructing an amputated finger or thumb, comprising:• A proximal stem for intramedullary fixation within the proximal bone, providing secure stabilization;• A distal stem for intramedullary fixation within the distal bone, configured to prevent loosening;• An articulation mechanism comprising: o Male projections extending from a cavity base on one of the stems, o C-shaped female recesses within the lateral walls of a cavity on the other stem;• A joint cavity within the distal stem, including lateral walls and a cavity base for engaging the male projections• A modular design, wherein the prosthesis is configurable as either a single-joint design for reconstructing a single joint or a dual -joint design for reconstructing two adjacent joints.

2. The prosthesis of claim 1, wherein the male projections and female recesses allow a range of motion up to 180 degrees in the MCP joint of the thumb.

3. The prosthesis of claim 1, wherein the proximal and distal stems incorporate grooves that increase contact surface area for enhanced osseointegration and long-term stability.

4. The prosthesis of claim 1 , wherein the proximal and distal stems are tapered to match the shape of the medullary canal, ensuring a secure and anatomically aligned fixation.

5. The prosthesis of claim 1, wherein the dual-joint design is configured for reconstructing PIP and DIP joints, with the distal stem fitting within the middle phalanx and the proximal stem within the proximal phalanx for PIP, and the distal stem fitting within the distal phalanx and the proximal stem within the middle phalanx for DIP, enabling reconstruction of articulated finger movements.

6. The prosthesis of claim 1, wherein the single-joint design is optimized for MCP joint reconstruction, particularly for the thumb.

7. The dual -joint design of claim 5 restores multi-articular movements, with tailored ranges of motion for interphalangeal joints to enable functional dexterity.

8. The prosthesis of claim 5, wherein the dual-joint design enables a range of motion tailored to the reconstruction of articulated finger movements, with a specific focus on restoring PIP and DIP joint functionality.

9. The method of claim 8, wherein distraction osteogenesis preserves the integrity of natural soft tissue structures, contributing to the restoration of the finger's appearance and function.

10. The prosthesis of claim 1, wherein the joint cavity of the distal stem includes lateral walls and a cavity base designed for secure engagement with the male projections, ensuring stable joint motion.

11. The prosthesis of claim 1 , wherein the stems are constructed from biocompatible materials such as titanium or hydroxyapatite-coated materials to promote osseointegration and compatibility with human tissue.

12. The prosthesis of claim 5, wherein the dual-joint design enables the restoration of coordinated multi-articular movements in amputated fingers 2-5, specifically enhancing the functionality of the PIP and DIP joints.

13. The prosthesis of claim 1, wherein a torsion-resistance mechanism is incorporated to mitigate rotational forces and prevent loosening of the implant during use.

14. The distal stem of the prosthesis of claim 1 includes dual male projections extending from the cavity base to the lateral cavity walls, forming a secure locking interface with the proximal stem.

15. The prosthesis of claim 5, wherein the dual-joint design restores natural articulation and enhances tendon dynamics, improving biomechanical functionality of the reconstructed finger.

16. The method of claim 8, wherein the custom-designed prosthesis ensures a precise fit and accommodates patient-specific anatomical variations to optimize performance.

17. The prosthesis of claim 1 is engineered to minimize soft tissue and bone trauma during implantation.

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