Finger Orthoses for Rehabilitation―Part I: Biomedical Insights and Additive Manufacturing Innovations

Abstract

Background: Finger orthoses are essential for treating injuries, deformities, and disorders of the upper limbs by supporting, immobilizing, or correcting deformities. Recent advances in three-dimensional (3D) printing have significantly enhanced precision and customization compared to traditional fabrication methods such as thermoplastic molding, plaster or fiberglass casting, and the use of prefabricated splints. Methods: The present review was conducted using PubMed, Scopus, and other databases with keywords such as “hand therapy”, “additive manufacturing”, “finger and thumb”, and “orthosis”. Only English-language publications were considered, with a primary focus on articles published between 2010 and 2025. Key themes were identified and categorized into conditions necessitating finger orthoses, types and classifications, ergonomic design considerations, and advancements in additive manufacturing. Results: Finger orthoses address musculoskeletal injuries, inflammatory diseases, and neuromuscular disorders. Three-dimensional printing provides enhanced customization, reduced material waste, rapid prototyping, and the ability to create complex geometries, improving patient comfort and functionality. Conclusions: Finger orthoses effectively treat various conditions by supporting and stabilizing fingers. A thorough understanding of anatomy, biomechanics, and fabrication methods is crucial for achieving functional and comfortable designs. Three-dimensional printing offers a transformative approach to producing lightweight, customizable, and cost-effective orthoses, enabling innovative and personalized solutions. By bridging clinical needs and design strategies, this review may guide future innovations in patient-specific orthotic development.

1. Introduction

The upper limbs, consisting of the shoulder, arm, forearm, elbow, wrist, hand, and fingers, are essential parts of the body for daily activities. They enable a wide range of motion and different functions that help in performing various activities, ranging from basic lifting to more complex movements in sports and other physical activities. The biomechanics and anatomy of the upper limbs are significantly different from those of other body parts, having less soft tissue, lower force demands, faster movement, increased sensory needs, and higher precision in movement relative to other limb segments [1].

Injuries are more likely to occur in upper limbs due to their extensive use and complex structure. However, the location and frequency of injuries depend on several factors such as age, physical activity, occupation, trauma, and lifestyle, which can influence the vulnerability of different anatomical regions [2,3,4]. Fractures, dislocations, sprains, and strains are examples of injuries that occur in sports. Major trauma can also result from workplace accidents, traffic accidents, and home incidents. Therefore, addressing related injuries and disorders is essential. This ensures proper training techniques, protective gear, and prompt medication in times of injury.

Application of orthoses is one of the most efficient approaches toward management of upper limb injuries and deformities. Orthotics are medical devices used to treat various conditions such as musculoskeletal injuries, deformities, and functional impairments. As defined by the International Organization for Standardization of the International Society for Prosthetics and Orthotics (ISPO), “an orthosis is any externally applied device used to modify structural and functional characteristics of the neuromuscular skeletal system”. Upper limb orthotic applications follow three basic principles: protection, correction, and aid to function [5]. Protective orthoses provide stability to the limb and foster healing, whereas correctives deal with deformities of the joints and contractures. Functional orthoses compensate for deformities and muscle problems [1]. Orthotics are typically made of materials such as plastic, metal, and fabric, which are able to support, stabilize, align, or correct specific body parts [6].

The fingers and the thumb rank among the most important components of the upper limbs, since they are involved in many refined and complex movements of the human body. Nearly all functions of the upper limbs are carried out through the fingers and their important role in activities of daily living cannot be underestimated. The extent of injuries to the fingers varies in nature and can involve bones, tendons, and ligaments. Injuries that are not managed properly inevitably lead to permanent deformity and dysfunction. Common deficiencies include trigger finger, where the finger is locked in a flexed position, and mallet finger, where the tip of the finger can no longer straighten. Some other major deficiencies, such as Dupuytren’s contracture, which causes curling of the fingers toward the ventral surface, and Boutonnière deformity, causing flexion of the finger at the middle joint, also pose serious risks to the proper functioning of the hands. Those with injuries and deformities of the fingers tend to suffer great loss of dexterity and functionality, which hinders their ability to perform daily tasks and be independent. Individuals who lose the function of their fingers and thumbs may suffer from long-term pain and disability. Falling is the most common cause of injury among individuals over 65, accounting for 75–79% of trauma cases. In this age group, 29% of emergency department presentations involve injuries to the hand and wrist [7]. More broadly, hand injuries account for up to 30% of all cases seen in emergency care across all age groups [8]. Moreover, in sport-related injuries, approximately 25% involve the hand or wrist. Metacarpal and phalangeal fractures are common injuries which account for 10% of all fractures seen in the emergency department [9,10]. For instance, sport injuries typically result from falling, direct blows, or crushes relating to the active nature of sport, but stress fractures are rarely seen in people involved in racquet sports. This condition is most common in contact sports like football, lacrosse, and hockey [11]. Beyond sports injuries, upper limb injuries and bone disorders are also prevalent in elderly populations, where conditions such as osteoporosis and fragility fractures (especially of the distal radius) are common due to decreased bone density and increased fall risk [12,13]. In pediatric populations, injuries such as greenstick fractures and growth plate (physeal) injuries are frequent due to the developing skeleton and high levels of physical activity [14]. Moreover, injuries involving muscles, ligaments, and nerves, including tendon ruptures, ligament sprains, carpal tunnel syndrome, and brachial plexus injuries, can result in significant functional impairments such as reduced range of motion, decreased grip strength, chronic pain, and impaired hand dexterity [15,16]. These injuries require careful diagnosis and rehabilitation to restore normal function. To address these impairments effectively, appropriate treatment and supportive measures must follow. It is imperative to provide treatment and to support the fingers and thumb in the event of injury and disorder. Immobilization, correction, and stabilization by orthoses and other medical means are necessary for the restoration of function, pain reduction, and prevention of possible complications so that people with impaired limbs can perform daily activities better and improve their quality of life.

Finger and thumb orthoses are also known as finger splints. However, finger splints are designed to immobilize or restrict movement in order to aid healing, while orthoses encompass various devices, including braces and supports, which serve purposes such as immobilization, correction, support, and enhancement of function [17]. In the present review, these two terms are used interchangeably. Depending on the diagnosis, finger problems may require orthotics that extend the hand and wrist, or they may be treated with smaller orthotics. Common types of finger orthoses are static splints, which fully immobilize the joints of the fingers, and dynamic splints, which allow controlled motion to assist mobility. For example, static splints are often used in the treatment of conditions like mallet finger, which involves a drooping fingertip due to extensor tendon injury and requires immobilization of the distal interphalangeal joint. On the other hand, dynamic splints might be used in conditions like Boutonnière deformity which is characterized by flexion of the proximal interphalangeal joint and hyperextension of the distal interphalangeal joint to gradually restore extension [18]. Other common finger conditions include swan neck deformity, which is characterized by excessive bending backward of the middle finger joint along with downward bending at the fingertip and is typically managed with ring splints [19]. Trigger finger causes painful locking or catching of the finger due to inflammation around the tendon sheath, and it may benefit from orthoses that limit movement at the base of the finger [20,21]. Jersey finger, which involves a torn tendon that normally bends the fingertip, is usually treated with splints that hold the injured finger in slight flexion during recovery after surgical repair [22]. Thumb spica splints are designed for the support or immobilization of the base joint and the knuckle joint of the thumb. They are also indicated for disorders like thumb fractures, ligamentous injuries, and osteoarthritis. The design and material depend on the nature of the injury or condition to be treated, ensuring optimal support and promoting effective recovery. This paper reviews finger orthoses, which may support, correct, immobilize, or improve the function of fingers by crossing one or more finger joints.

There are two major types of finger orthoses: prefabricated and custom-made. Prefabricated splints are mass-produced in standard sizes and designs, which allows them to be immediately used after injury. Custom-made orthoses are tailored specifically to accommodate a patient’s anatomy and injury [23]. Conventional customization methods can be time-consuming and costly, often requiring skilled labor and specialized materials. Such conventional techniques may offer limited customization and precision, leading to probable discomfort or improper fit. Additive manufacturing (AM), commonly known as 3D printing, is drastically changing the way finger orthoses are fabricated by producing highly accurate and customized splints based on detailed 3D scanning of the hand anatomy of the patient [24]. The method involves layer-by-layer deposition, thereby creating complex geometries and designs tailored to the patient’s anatomy. It provides better fit, enhanced comfort, and improved functionality [25]. In comparison with conventionally customized orthoses, 3D-printed orthotics have other advantages such as faster production time, better patient-specific customization, and possibilities for complex design that can enhance support along with mobility [26]. In addition to design flexibility, material selection plays a crucial role in determining the splint’s mechanical behavior, wearability, and patient comfort, which significantly influences the overall performance of 3D-printed orthoses [27].

The present review explores multiple aspects of finger splints, including the biomechanical and anatomical considerations of the fingers and thumb. In addition, the types and designs of finger orthoses and their specific functions in addressing finger injuries and deformities are discussed. Finally, the role of AM in the fabrication of finger orthoses is reviewed, highlighting the advantages of this innovative technology compared to conventional methods. With a primary focus on the design, classification, and fabrication of finger orthoses, this review does not cover clinical conditions, surgical procedures, or rehabilitation protocols.

2. Biomechanical and Anatomical Considerations of Fingers and Thumb

The human hand has a very complex anatomy, consisting of 27 bones, 29 joints, and at least 123 named ligaments. They are all working harmoniously to facilitate a wide range of precise and powerful movements, allowing us to grasp, touch, and manipulate objects effectively. Such complex structures can perform intricate movements while providing the required stability for daily tasks. Besides bones, joints, and ligaments, the hand includes tendons, muscles, nerves, blood vessels, and lymphatic vessels. Any impairment to the hand, whether due to injury, disease, or congenital condition, can significantly affect an individual’s ability to perform daily activities and maintain independence. Thus, a deep understanding of the anatomy and biomechanics of the fingers and thumb is crucial for the effective treatment of acute injuries and deformities by healthcare personnel who are involved in the fabrication and application of orthotics [1]. Understanding biomechanics helps to design effective and suitable orthoses that are tailored to the unique movements and load-bearing requirements of the hand’s intricate structures. This requires detailed knowledge of the forces exerted during various activities, the natural range of motion, and the interplay between different anatomical structures. Effective orthotic design not only enhances functional outcomes by providing stability and support but also minimizes discomfort and prevents further injury. This improves the quality of life for individuals with finger and thumb impairments.

The finger has a complex anatomical structure with several bones, joints, ligaments, and tendons. Figure 1 illustrates all joints in the hand. Except for the thumb, every finger consists of the distal interphalangeal (DIP), proximal interphalangeal (PIP), and metacarpophalangeal (MCP) joints, which are hinged, together with the proximal, middle, and distal phalanges. Volar plates, which are collateral ligaments affixed to strong fibrous connective tissue, support these joints [28]. Two lateral bands and a central slip that extends the DIP joint and the PIP joint, respectively, originate from the dorsal extensor tendon. The flexor digitorum profundus (FDP) and superficialis are two of the volar tendons. Flexing the PIP joint is the result of the flexor digitorum superficialis tendon attaching to the base of the middle phalanx and the FDP tendon attaching to the base of the distal phalanx. The schematic illustration in Figure 2 highlights the collateral ligaments, extensor tendons, and flexor tendons of the index finger.

The thumb contains two more joints in addition to the MCP joint: the interphalangeal (IP) joint and the carpometacarpal (CMC) joint, as shown in Figure 1. The CMC joint, also referred to as the trapeziometacarpal joint, is essential to the thumb’s extensive range of motion and connects the base of the thumb’s metacarpal bone to the trapezium bone in the wrist. Therefore, the thumb can be pronated and flexed approximately 80° with respect to the other metacarpals in the hand. The thumb is critical to hand function as it plays a major role in grasping and seizing objects. It makes up 40% of the total hand function in a healthy state [29]. There are three ways that the thumb’s MCP joint can move. The thumb moves like a ball-and-socket joint when it is straight. The side ligaments tighten, causing the thumb to move like a hinge as it bends. Thumb mobility and joint stability are provided by the internal muscles [29]. It is notable that single-digit amputations usually do not cause the loss of vital hand function. However, multiple finger amputations or severe injury/stiffness of the fingers present significant challenges. Most cases of a mutilated hand exhibit with multiple digital loss due to severely crushed and avulsed digits, precluding replantation [29]. In such circumstances, the thumb’s role becomes even more essential. Keeping the thumb and one finger allows some grasping ability. The thumb is capable of performing more than half of the effort required for hand tasks [30].

The MCP joint is important for finger mobility. The middle and tip joints of the finger are bent forward when the MCP joint is flexed excessively backward. This occurs by the pull from the muscles that bend the fingers and the necessity to keep balance between the muscles that straighten and bend the fingers [1]. The MCP joints probably represent the most important joints for hand function. They contribute 77% of the total arc of finger flexion [31]. The PIP joint, with up to 120° arc of motion, has the largest range among the three joints in each digit of the hand. It produces 85% of intrinsic digital flexion and accounts for 85% of the total motion required to grasp an object. Although the PIP joint contributes only 20% to the overall arc of finger motion, its impairment can adversely affect the total functioning of the hand. A full range of PIP joint motion is, however, not essential to the overall functioning of the hand [29,32,33]. Nevertheless, the PIP joint is prone to injury and stiffness after trauma or immobilization [34]. The MCP and PIP joints rest in mild flexion when the hand is relaxed. The DIP joint produces 15% of intrinsic digital flexion but contributes only 3% to the overall flexion arc of the finger [35]. Moreover, there is a small amount of flexion in the DIP joints, usually between 5° and 10°. The hand is turned to a comfortable angle between 30° and 60°.

Generally, the thumb is relaxed and straight, retaining its natural alignment without any resistance or abduction. This position results from the natural resting tension in the flexor and extensor muscles, which preserves a balanced condition that reduces joint stress and muscular strain. The other fingers, including the little, ring, middle, and index fingers, appear slightly bent and follow a gentle curvature. The anatomy of a hand at rest is shown in Figure 3. The dorsal side of a hand lying on a surface is shown in Figure 3a. The tendons are running along the back of the hand toward the fingers and the hand appears relaxed, with the fingers slightly extended. Figure 3b shows the palmar (palm) aspect of the hand. The thumb appears relaxed and straight in this resting posture, keeping its natural alignment without any notable opposition or abduction. Compared to the ring and little fingers, the index and middle fingers have less flexibility at the MCP joints, resulting in a minor bend. The reason behind the greater degree of bending of the ring and little fingers in a relaxed state lies in variations in tendon and muscle tension. Flexor tendons exert different degrees of pull. Furthermore, each finger has a different anatomical structure and ligament flexibility, which determines the angles of their rest. The natural curvature of the hand, known as the palmar arch, also accounts for the greater flexion of the ring and little fingers with regard to effective gripping.

In addition to bones, joints, ligaments, and tendons, the hand’s function is critically dependent on its intrinsic and extrinsic muscles, as well as its intricate nerve supply [36,37]. The intrinsic muscles, located within the hand, allow fine motor control and precise finger movements, while the extrinsic muscles, originating from the forearm, provide strength for grasping and flexion/extension of the digits. The median, ulnar, and radial nerves are responsible for both motor innervation and sensory feedback in the hand [38]. Injury to these nerves, or to the associated muscles, can result in significant functional impairments such as ulnar claw hand, ape hand, or wrist drop, many of which may require splinting or orthotic intervention to restore function, prevent deformity, or maintain joint positioning during recovery [39].

3. Finger Orthosis Classifications and Types

Finger orthoses are classified based on various factors, including their function, the specific joints they target, the materials used in their construction, the conditions they are designed to treat, and their overall configuration. Understanding these classifications is essential not only for organizing the wide variety of splint types but also for supporting clinical decision-making. Each type of classification helps clinicians better understand the purpose of a splint and choose the one that best fits the patient’s condition, treatment goals, and physical needs. By matching the splint type to the patient’s requirements and comfort, these classifications help create more effective and personalized treatment plans and ultimately lead to better outcomes.

Functional classification is one of the most important ways to categorize finger splints, as it dictates how the splint interacts with the finger. Splints can be broadly classified into immobilization, mobilization, resting, and correctional splints. Immobilization splints, also referred to as static splints, such as stack splints, gutter splints, buddy tape, and ring splints, are designed to keep the finger joints in a fixed position, preventing movement and allowing for healing after fractures or soft-tissue injuries. Ring splints, also known as silver ring splints, are particularly useful for positioning the PIP joint, combining function with an esthetic design that resembles jewelry [40]. Figure 4 illustrates various designs of silver ring splints specifically crafted to immobilize single or multiple joints. These splints can immobilize one or more joints simultaneously, with variations that mechanically couple adjacent fingers in order to improve hand function and appearance. They are lightweight, well-ventilated, easy to don, and well tolerated by patients [41]. These immobilization splints can restrict the movement of one or more digital joints from the MCP through to the DIP joint and are often made from prefabricated materials like moldable soft metals with foam interfaces, rigid foams, or thin thermoplastics [42]. Splints that are made from sterling silver provide antibacterial properties while maintaining the necessary strength to prevent unwanted finger movement. The ring splints shown in Figure 4 were initially printed in wax using MultiJet Printing (MJP) technology, then cast in sterling (925) silver, and finally finished by hand. This process ensures a strong yet antibacterial final product, as sterling silver provides greater durability than pure silver, which is too soft for orthotic use. Direct 3D printing of silver has not been explored in this context, as it may result in parts that are too brittle for functional splinting. The splints are available in different sizes, with typical widths ranging from 3.5 to 5 mm, depending on joint location and therapeutic need. Some immobilization splints can be used for acute injuries or temporary immobilization and can be secured with hook-and-loop materials, Coban wrap, or medical adhesives, making them removable and replaceable for maintenance and hygiene. Another example in the classification is adhesive finger splints. These are innovative static splints designed to immobilize finger joints with minimal bulk. They use a wire wrapped in double-sided adhesive tape attached to an adhesive skin dressing, providing a lightweight, low-profile, and flexible option [43].

Mobilization splints, also known as dynamic splints, facilitate controlled movement, aiding in rehabilitation by promoting flexibility and function while still providing necessary support. These splints are typically designed to counter progressive deformities or provide low-load stretching for flexion or extension contractures. Dynamic orthoses, which often incorporate elastic components, coils, or springs, allow movement of the patient’s joint(s) while wearing the orthosis. They may be indicated in postoperative treatment protocols, to assist with weak muscles, or to increase passive joint range of motion [44]. They are commonly used to manage conditions like rheumatoid arthritis (RA) and injuries such as mallet finger and jersey finger [42]. Correctional splints serve to correct deformities or prevent further progression of conditions, often used in cases like ulnar deviation or mallet finger [45]. To provide a clearer understanding of the differences and key features of immobilization and mobilization splints,

Table 1. Key aspects of immobilization and mobilization splints.

Aspect	Mobilization Splints (Dynamic)	Immobilization Splints (Static)
Purpose	Support and protect with limited movement	Fully immobilize to prevent any movement
Use cases	Minor sprains and strains Substitute for weak or absent muscle Provide resistance for exercise Increase passive joint range of motion Elongate soft-tissue contractures Post-surgery rehabilitation	Fractures Severe sprains Symptom relief Contracture management Improve and/or preserve joint alignment Post-surgical repair
Design characteristics	Allow controlled motion Stabilize without full immobilization	Rigid design Ensure no movement
Patient compliance	More willing to wear than rigid splints Better tolerated when finger movement is allowed Preferred when materials are light and flexible Preferred during rehab for comfort and mobility	Lower due to discomfort or bulkiness Often removed early if perceived as restrictive Adherence improves when healing benefits are clearly explained
Production cost	Moderate; may involve custom designs and more complex fabrication techniques (e.g., springs)	Typically lower; standardized forms are easy to mass-produce
Manufacturing cycle	Longer; dynamic features may require adjustments or patient-specific tuning	Shorter; can often be pre-fabricated or made quickly via thermoforming or 3D printing
Examples	Buddy tape Dynamic extension splints	Mallet finger splints Stack splints
Benefits	Reduce stiffness Maintain some muscle activity	Provide maximum support Promote proper healing

summarizes the main aspects of mobilization and immobilization splints, highlighting their functions, materials, and typical applications.

Joint involvement classification highlights the anatomical specificity of finger splints. Such devices can be tailored to support specific joints, such as DIP, PIP, MCP, or thumb joints. For example, DIP joint splints like stack splints are specifically designed to address injuries at the DIP joint, often used for conditions like mallet finger [46]. PIP and MCP joint splints, such as the ulnar gutter splint, provide stabilization for the PIP and MCP joints, respectively [47]. This classification underscores the precision required in splint design to address the unique needs of different finger joints, ensuring effective immobilization or mobilization where needed.

Material classification differentiates between rigid, soft, and custom-made splints. Rigid splints, constructed from materials like aluminum or thermoplastic, offer maximum stability and are often used in immobilization, as seen in ulnar gutter splints. Soft splints are made from flexible materials like neoprene and thermoplastic polyurethanes (TPU), providing gentle support while allowing some degree of movement, making them ideal for conditions requiring less aggressive intervention [48]. Custom-made splints are tailored to fit the patient’s anatomy, often using moldable materials that conform to the exact shape of the finger, providing a blend of comfort and effectiveness [49,50].

Condition classification focuses on the medical context in which splints are used. Such splints are designed to address specific conditions, whether traumatic injuries, chronic conditions, or post-surgical recovery. For instance, ulnar gutter splints and buddy tape are frequently used for traumatic injuries such as fractures, sprains, and soft-tissue damage [48,51]. Chronic conditions like arthritis may require splints that provide long-term support and manage joint deformities, such as the silver ring splint. Post-surgical splints are used to protect and support the finger during the healing process, ensuring that surgical outcomes are maintained [52]. Age is an important factor in classifying conditions, as it can affect how finger orthoses are designed. Adults often experience slower healing and increased joint stiffness when using orthotic devices. In contrast, finger-based orthotic devices can be risky for children, as they may present choking hazards and are more likely to be removed or misplaced. To avoid these challenges, it is often better to use orthotic devices that support the forearm rather than only the finger when treating finger disorders in children [53].

Design classification distinguishes between prefabricated and custom-made splints. Prefabricated splints are available in standard sizes and are convenient for immediate use, making them ideal for acute injuries and temporary support [49]. Examples include ring splints, also known as oval-8 splints. Custom-made splints are designed and fabricated to fit an individual’s specific needs, often used in cases where standard sizes are inadequate or a higher degree of precision is required for effective treatment [54,55]. Further discussion of the advantages and considerations of prefabricated versus custom-made finger splints are provided in a subsequent section.

Various classifications of finger splints, including their subcategories and specific examples, are listed in

Table 2. Classification of finger splints with associated subcategories and examples.

Classification	Subcategory	Type of Splint	Examples
By functionality	Immobilization splints	Static finger splints	Stack splint; aluminum foam splint; buddy tape; ulnar gutter splint; ring splint; adhesive splint
	Mobilization splints	Dynamic finger splints	Dynamic extension splint
		Static finger splints	Ring splint
	Resting splints	Static finger splints	Static progressive splint; soft volar splint
	Correctional splints	Dynamic finger splints	Dynamic extension splint
		Static finger splints	Silver ring splint; ulnar deviation splint
By joint involvement	DIP joint splints		Stack splint; dip immobilizer
	PIP joint splints		Ring splint; gutter splint
	MCP joint splints		MCP blocking splint; ulnar deviation splint
	Thumb splints		Thumb spica splint; CMC splint
By material	Rigid splints		Aluminum foam splint; stack splint; ulnar gutter splint
	Soft splints		Buddy tape; soft volar splint
	Custom-made splints		Custom thermoplastic splint; custom molded splint
By condition	Traumatic injuries		Gutter splint; mallet finger splint; ulnar gutter splint
	Chronic conditions		Silver ring splint; ring splint
	Post-surgical splints		Dynamic extension splint, static progressive splint
By design	Prefabricated splints		Ring splint; silver ring splint
	Custom-made splints		Custom thermoplastic splint; custom molded splint

. As shown, some splints, such as silver ring splints, may appear under multiple classifications depending on their intended use, material, or joint involvement. Figure 5 illustrates the versatility of finger orthoses in providing targeted support. Depending on clinical need, they can be designed to support, immobilize, or correct a single finger, multiple fingers, or even the entire hand. The design features of these orthoses can vary in shape, material type, ventilation (solid or perforated), and whether they are adjustable or fixed.

4. Ergonomic and Functional Design Factors

When designing and fabricating finger splints, several critical parameters must be considered to ensure the effectiveness and comfort of the orthosis. These parameters, collectively referred to as the ergonomic and functional design factors [56]. Key considerations include the interaction of the splint with the patient’s skin, the appropriate thickness of the splint, the introduction of porosity or perforation to enhance breathability and heat dissipation, and the secure fixation of the splint to prevent it from falling off. By carefully addressing these factors, designers can create finger splints that are not only functional and durable, but also comfortable and safe for long-term use.

When designing finger splints, one of the foremost considerations must be the interaction between the orthosis and the patient’s skin, particularly in managing conditions like edema and preventing skin irritation [57]. Effective edema control is instrumental in treating various finger problems and this can often be integrated into the design of the orthosis [58]. For example, incorporating a self-adherent compressive wrap beneath the splint not only helps in managing swelling, but also ensures that the splint stays securely in place [59]. In cases where continuous orthotic application is required—such as 24 h wear—it may be necessary to fabricate multiple splints to accommodate different activities [60]. Additionally, the use of adhesive-based splints presents challenges such as potential skin irritation during removal and decline in adhesive effectiveness with repeated use, which can necessitate frequent reapplication. Furthermore, the adhesives used in these splints, particularly if they are non-medical grade, may pose risks of allergic reactions [43]. Therefore, careful consideration of skin-friendly materials and designs that minimize irritation and maximize comfort is essential in the fabrication of finger splints. This approach not only enhances the therapeutic effect of the splint, but also ensures that it can be worn consistently without compromising the patient’s skin health.

The thickness of a finger splint is an indispensable design parameter that directly influences its comfort, effectiveness, and overall usability. Typically, low-temperature thermoplastic materials with a thickness of 1.6 mm (1/16 inch) or thinner are preferred for finger splints due to their balance of strength and minimal bulk [42,60]. These thinner materials are ideal for digits, providing sufficient support and protection while maintaining a slim profile that does not hinder the user’s daily activities. However, the choice of thickness can vary depending on the individual’s hand size and strength. For instance, in cases involving stronger individuals or those with larger hands, a slightly thicker material, such as 2.38 mm (3/32 inch), may be more appropriate [60]. However, it is essential to avoid making the splint too thick, as this can lead to discomfort, reduced mobility, and difficulty in wearing the splint for extended periods [61]. Conversely, if the splint is too thin, it may lack the necessary rigidity, compromising its ability to provide adequate support and protection. Therefore, selecting the appropriate thickness is a delicate balance that must consider both the physical requirements of the patient and the functional demands of the splint for everyday use.

The introduction of perforation or porosity in finger splints is a design consideration that can significantly impact both the functionality and comfort of the orthosis. Perforations can enhance breathability, allowing for better air circulation and reducing the risk of moisture buildup, which is particularly beneficial in preventing skin irritation and maintaining overall skin health during prolonged use [62]. This feature is especially important in warm or humid conditions, where trapped moisture or heat can lead to discomfort or even skin breakdown. Moreover, perforations can make the splint lighter and more flexible, contributing to greater comfort and ease of movement for the patient. Beyond functionality, strategically placed perforations can also add an esthetic element to the splint, enhancing its visual appeal depending on the design and where the perforations are introduced. Malloum et al. [63] developed a composite material of polylactic acid (PLA) and polyvinyl alcohol (PVA) to create porous 3D-printed medical splints, improving breathability and comfort compared to traditional thermoplastic splints. The PVA was dissolved after printing to leave voids in the PLA, enhancing the splints’ suitability for extended wear and patient compliance. However, the decision to use perforated versus non-perforated materials must be made carefully. While perforations offer several advantages, they can also introduce challenges, such as rougher edges that may cause skin irritation or uneven pressure distribution, especially in the presence of edema [60]. The size and pattern of the perforations play key roles in mitigating these issues. For example, microperforations, which are smaller and more evenly distributed, can minimize the risk of irritation and pressure points while still providing the benefits of enhanced breathability. On the other hand, in some cases, particularly where maximum support and rigidity are required or where the skin is highly sensitive, non-perforated materials may be preferable.

Ensuring secure and comfortable fixation of finger splints is essential for their effectiveness and the patient’s overall comfort. Due to their small size, finger orthoses may slip off during sleep or daily activities, which can significantly reduce their therapeutic benefits. To prevent this, it is often necessary to supplement the primary attachment, such as Velcro straps, with additional securing methods like taping [43,64]. However, it is imperative to apply these additional fixations carefully to prevent complications. For instance, taping the splint too tightly around the finger can create a tourniquet effect, restricting blood flow and potentially causing discomfort, swelling, or even tissue damage [65]. Conversely, if the fixation is too loose, the splint may shift out of place, compromising its support and protection. A balanced approach involves using long Velcro straps to anchor the orthosis more securely around the hand or wrist, providing a stable yet adjustable fit that maintains the splint’s position without causing undue pressure [60]. Collectively, these ergonomic and functional design considerations directly impact clinical outcomes. Splints that are comfortable, breathable, and securely fitted are more likely to be worn consistently, thereby enhancing patient compliance and contributing to the long-term success of treatment. Figure 6 illustrates the four key design factors, including fixation method, porosity for breathability, skin contact, and material thickness, that influence the performance and comfort of finger orthoses.

5. Additive Manufacturing of Finger and Thumb Orthoses

AM, commonly known as 3D printing, is a transformative manufacturing technique that builds objects layer by layer from digital models. This method contrasts sharply with traditional subtractive manufacturing, where material is removed to create the final product. AM processes vary widely, each with distinct characteristics that influence part precision, material properties, post-processing requirements, and overall costs. Initially, AM technologies were limited to polymeric materials, waxes, and paper laminates, but advancements have since expanded their scope to include composites, metals, ceramics, and biocompatible materials, broadening its application in various industrial and healthcare sectors.

Conventional splints are often made using labor-intensive methods. These splints are typically expensive and rely on approximations that can lead to a lack of precision. Since they are custom-molded onto the patient, their effectiveness heavily depends on the skill of the professional, often resulting in inconsistencies in fit, comfort, and overall patient satisfaction [54,66]. Occupational therapists and healthcare professionals traditionally craft upper limb orthoses by manually shaping thermoplastic materials. This process involves placing the patient’s hand and wrist on a thermoplastic sheet, tracing the contours, and then cutting and heating the material through hot-water immersion or using a thermal blower to make it malleable. Because precise joint positioning is essential, skilled professionals are required. Compared to traditional materials like plaster of Paris, which can be bulky and uncomfortable, thermoplastics provide a lighter, more durable, and customizable option, significantly improving patient comfort and fit [67]. Nevertheless, AM offers significant advantages over all the conventional methods mentioned for fabricating finger orthoses [68]. Choi et al. [69] compared 3D-printed lattice casts with traditional plaster of Paris casts for mallet finger treatment. The 3D-printed casts were lighter and more customizable, and offered better ventilation and hygiene, resulting in higher patient satisfaction. In contrast, traditional plaster casts, although easier to apply, were linked to complications like skin necrosis, edema, and discomfort. Portnoy et al. [70] conducted a study with 36 occupational therapy students, comparing finger orthoses made through conventional and AM methods. Participants expressed higher satisfaction with the additively manufactured orthoses, reporting better fit and esthetics, and reduced weight compared to those made by conventional techniques. Güven and Suner-Keklik [49] compared custom-made and prefabricated splints for stabilizing finger flexion, focusing on the DIP and PIP joints. The study found custom-made splints more effective in limiting joint motion, offering better stabilization for cases requiring restricted movement for healing. Moreover, traditional splints often suffer from poor mechanical properties, uncomfortable pressure points, and difficulties in cleaning, which can reduce their usability and effectiveness [71]. In contrast, AM allows production of highly customized splints that precisely match the patient’s anatomy, significantly enhancing comfort, functionality, and patient compliance. Cronin et al. [46] investigated the clinical benefits and acceptance of a 3D-printed splint for treating mallet finger injuries and compared the results with conventional generic stack splints, finding 70% of patients reported excellent or good outcomes with the 3D-printed splints. The splints were effective in immobilizing the DIP joint while allowing movement of the PIP joint. In total, 90% of patients preferred the 3D-printed splint over the generic stack splint, citing improved fit, comfort, and ease of use.

The fabrication process of a 3D-printed finger orthosis involves several essential steps, illustrated in a flow chart in Figure 7. First, the problem is defined to identify the specific requirements and constraints for the orthosis. The second step involves the customization of the finger splint, which typically includes scanning the patient’s finger to ensure a precise fit. Next, the design is modeled and subjected to finite element analysis (FEA) to evaluate the distribution of load and deformation, ensuring that the orthosis functions as intended under various conditions. Finally, the design is optimized based on the FEA results to confirm that the deformation and load distribution are appropriate and safe for intended use.

One of the primary reasons for preferring AM in the production of finger splints is the ability to create lightweight, breathable, and easy-to-clean designs. These characteristics directly address common issues associated with traditional splints, such as discomfort, hygiene concerns, and reduced functionality during daily activities [69,72]. Additionally, the customization capabilities of AM enable the creation of splints that cater to individual needs, making them more comfortable and supportive. In a study by Kadioglu et al. [73], 25 patients with upper extremity trauma received 3D-printed splints, which were evaluated for cost, patient comfort, and support efficiency. They found that 3D-printed splints were cost-effective, with complete recovery and all patients returned to daily activities after three weeks. The splints were comfortable and facilitated effective treatment without causing radiological artifacts. AM also allows for the incorporation of complex geometries and design features, such as perforations for breathability and ergonomic contours, which is difficult or impossible to achieve with conventional methods [74]. In a study by Irani et al. [75], it was noted that patients not only valued the functional aspects of 3D-printed finger splints, but also appreciated the ability of AM to produce splints in various colors.

The versatility of AM is further reflected in the wide range of materials that can be used to produce finger splints. In recent years, thermoplastic polymers have become widely used in orthosis production due to their ability to soften when heated and harden at room temperature. This property makes them ideal for creating orthoses that fit the patient’s anatomy and improve comfort. Thermoplastics have also transformed the nonsurgical treatment of upper limb fractures by preserving limb function, supporting fractures from large stress, and preventing joint deformities [76,77]. One of the most commonly used materials in manufacturing orthoses is PLA, favored for its biocompatibility, biodegradability, ease of printing, and suitable mechanical properties [73]. Other materials include acrylonitrile butadiene styrene (ABS), known for its durability; TPUs and thermoplastic elastomers, which offer flexibility and comfort; and polyamide (PA), particularly PA11 and PA12, which are highly valued for producing orthoses due to their strong mechanical properties, durability, and biocompatibility. PA11 and PA12 are especially important in orthotic applications because they offer a balance of strength, flexibility, and resistance to wear, making them ideal for creating robust and long-lasting splints [77,78]. For a comprehensive overview, readers are encouraged to refer to our previous work on materials and manufacturing for ankle–foot orthoses (AFOs), where a detailed list of common materials and AM technologies is presented [27]. Many of these materials are equally applicable for manufacturing both finger splints and AFOs.

Additional polymers with niche or emerging potential include polyethylene (PE) and polypropylene (PP), which are valued for their light weight and biocompatibility but are less commonly used in fused deposition modeling (FDM) printing due to warping, shrinkage, and poor layer adhesion [79,80,81]. Polycarbonate (PC) offers high impact resistance and strength but requires elevated printing temperatures and controlled environments [82,83]. Polyether ether ketone (PEEK), a high-performance thermoplastic with exceptional mechanical and thermal properties, is primarily used in high-load orthopedic or implantable applications and is typically considered over-engineered for finger splints [84,85].

Table 3. Comparison of key 3D-printable polymers, including commonly used and emerging materials relevant to finger orthosis design.

Material	Tensile Strength (MPa)	Elongation at Break (%)	Properties	Clinical Notes
PLA	50–70	4–10	Biodegradable, easy to print	Suitable for rigid splints, prototyping
ABS	30–50	10–50	Tough, slightly flexible	Better impact resistance than PLA
TPU	50–80	200–600	Elastic, shock-absorbing	Ideal for soft splints or inserts
PA11/PA12	40–60	250–400	Durable, wear-resistant	Excellent for functional, long-term splints
PETG	40–50	50–120	Transparent, good strength	Improved heat dissipation
CF-Nylon	60–110	1–15	Reinforced, high strength	Lightweight and strong splints
PP	30–40	100–600	Lightweight, biocompatible	Limited use due to printing challenges
PE	10–40	300–600	Soft, flexible	Rarely used due to adhesion issues
PC	55–75	100–150	High strength, heat resistant	Requires controlled printing environment
PEEK	90–110	40–50	Implant-grade, high-temp	Rare in splints due to high cost and complexity

presents a comparison of key 3D-printable polymers, highlighting both widely used and emerging materials relevant to finger orthosis design.

Emerging biodegradable and smart polymers are gaining attention in the fabrication of finger orthoses. For instance, Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a biodegradable copolymer belonging to the polyhydroxyalkanoates (PHAs) family. PHAs are composed of hydroxyalkanoic acid monomers and exhibit diverse mechanical and thermal properties depending on their monomer composition and fermentation conditions. Among them, PHB is well known but inherently brittle. To improve flexibility and processability, PHBV is synthesized by incorporating 3-hydroxyvalerate units, making it suitable for additive manufacturing of biomedical products, including customized orthopedic supports and potentially finger orthoses [86]. Owing to its biocompatibility, thermoplasticity, and sustainable degradation profile, PHBV is gaining traction as a promising material for use in 3D-printed devices, especially as a biodegradable alternative to petroleum-based polymers [87]. Moreover, shape memory polymers (SMPs) are another group of materials that open avenues for more responsive, patient-friendly orthotic designs. SMPs are smart materials capable of undergoing temporary deformation and returning to their original shape in response to an external stimulus [88,89]. Barmouz et al. [90] have employed SMPs in four-dimensional (4D) printing of hand orthosis to treat patients with cerebral palsy, and other studies have explored their potential to reduce the need for multiple 3D-printed iterations by allowing post-printing customization [91].

Kumar et al. [92] showed that finger splints made from materials like polyethylene terephthalate glycol-modified (PETG), PLA, ABS, and carbon fiber–reinforced nylon (CF-nylon) demonstrated 121.37% faster heat dissipation. This improved thermal property, along with significant weight reduction (30.52% lighter), made these splints highly effective at preventing overheating and promoting comfort during rehabilitation, especially in demanding environmental conditions. Figure 8 presents a variety of polymer ring splints made from PA12, fabricated using selective laser sintering (SLS) technology. These examples highlight the versatility of PA12 in producing durable, lightweight, and highly customizable orthotic devices. These splints are available in different colors and patterns, highlighting the esthetic and functional possibilities of PA12 in orthotic design.

Additionally, the use of biodegradable and sustainable materials in AM is gaining attention, particularly in the context of reducing the environmental impact of medical device production. These materials not only meet the functional requirements of finger splints, but also align with modern sustainability goals [93,94]. It is notable that 3D printing is a material-efficient method for producing finger splints. By using only the necessary amount of material, it significantly reduces waste compared to conventional manufacturing techniques. This efficiency not only leads to lighter and more comfortable splints, but also lowers production costs. Emzain et al. [95] used FEA to design and optimize a sleeve finger splint so as to reduce material usage while maintaining structural integrity. The lighter design improved comfort without compromising safety or functionality. Zolfagharian et al. [96] found that a 3D-printed splint with 28.87% mass reduction (retaining 71.13% of the original mass) provided the optimal balance between heat dissipation, structural strength, and light-weight design. They demonstrated that optimized material distribution can maintain performance while minimizing mass. Figure 9 depicts several advantages of using AM in the fabrication of finger orthoses.

Several AM techniques are commonly employed in the production of finger splints, each offering unique benefits. Fused deposition modeling (FDM), also known as fused filament fabrication (FFF), is one of the most widely used techniques due to its accessibility, cost-effectiveness, and ability to produce durable parts [61,96]. FDM works by extruding a thermoplastic filament through a heated nozzle, which deposits the material layer by layer to build the splint. SLS is another important technique, particularly valued for its ability to produce parts with complex geometries and excellent mechanical properties [97]. SLS uses a laser to sinter powdered material, layer by layer, into a solid structure and is especially useful for creating intricate designs without the need for support structures. Stereolithography (SLA) is a third key technique, known for producing parts with high precision and smooth surface finishes. SLA uses a laser to cure liquid resin into hardened plastic, layer by layer, making it ideal for producing detailed and esthetically pleasing splints [46]. Digital light processing (DLP) is a closely related technique to SLA, sharing many of the same advantages, such as high precision, superior surface finish, and the ability to produce fine details. However, DLP differs in that it uses a digital light projector instead of a laser. This projector flashes an entire layer’s pattern onto the resin at once, curing the layer in a single exposure rather than tracing it point by point. This makes DLP generally faster than SLA, especially for larger and more complex parts, while still maintaining the high quality and smooth surface finishes that are characteristic of photopolymer-based 3D printing. Figure 10 shows a 3D-printed finger orthosis designed to immobilize both the DIP and PIP joints of the middle finger. This orthosis is fabricated using Biores Red biocompatible resin utilizing DLP technology. Each of these techniques offers different advantages that can be leveraged depending on the specific requirements of the finger splint. For instance, FDM is often chosen for its affordability and ease of use, SLS for its strength and complexity, and SLA for its precision and finish [77]. To provide an overview of recent research on the application of AM in the production of finger and thumb orthoses, several studies are summarized in

Table 4. Recent studies on application of AM in the fabrication of finger and thumb splints.

Objective	Method	Materials	Description	Ref.
To support and correct finger deformities due to RA	FDM	ABS; PLA	Custom-fit splints for RA finger deformities. They are lightweight, comfortable, and easy to clean.	[61]
To provide a patient-specific splint for mild to high-grade mallet finger fracture	─	PLA	Patient-specific splint with improved ergonomics, material efficiency, breathability, and hygiene.	[98]
To manage finger deformities caused by RA	FDM	PLA	A cost-effective, customized 3D-printed splint improving finger alignment, dexterity, and comfort, tested on 20 patients.	[54]
For conservative upper limb finger treatment	FDM	PLA	A custom 3D-printed PLA orthosis that is ergonomic, easy to clean, and supportive for finger deformities.	[71]
To rectify discomfort and improper fit caused by conventional splints for mallet finger injuries	SLA	Black resin	Custom 3D-printed splints for mallet finger, improving fit, comfort, and functionality with high patient satisfaction.	[46]
To address excess material, poor fit, and discomfort caused by conventional splints	FDM	ABS	An optimized conical sleeve splint, reducing mass by 42.18% while maintaining structural integrity.	[95]
To resolve discomfort, poor fit, and hygiene issues associated with conventional splints	FDM	PLA	Customizable 3D-printed PLA splints with better fit, comfort, functionality, and thermoformable adjustments.	[72]
To lower costs and improve customization, addressing poor fit in conventional orthoses	FDM	PLA	Comparison of 3D-printed orthoses to SilverRing™ showing similar fit, comfort, and esthetics with better affordability.	[75]
Hand and finger splint for trauma	FDM	PLA	Personalized splints for 25 patients showing full recovery, cost-effectiveness, improved comfort, no radiological artifacts, and easy return to daily activities.	[73]
Mallet finger splint for tendon injuries	FDM	PLA; PETG; ABS; CF-Nylon	Customized splints showing improved strength, weight reduction, comfort, and heat dissipation, ideal for mallet finger rehabilitation.	[92]
Porous finger splint	FDM	PLA; PVA	Breathable, comfortable splints with a 70/30 PLA/PVA ratio for increased porosity.	[63]
Thumb splint for musculoskeletal conditions	FDM	ABS	Customized splints offering better ergonomics, esthetics, comfort, and moisture release than traditional splints.	[99]
Finger splints for hand-burn patients	FDM	TPU; PLA	Customized, breathable, cost-effective splints that improve patient compliance and were easily adjustable.	[100]
Finger support	PolyJet	Rubber and elastomer	Flexible, resizable support for finger deformities, validated by FEA and testing for strength and reliability.	[101]
Mallet finger splint	FDM	PLA	Custom-fit, low-cost, radiolucent splints for mallet finger, offering ease of production, better fit, and improved compliance.	[55]
To minimize or prevent progress of deformities in children with cerebral palsy	FDM	PLA	Lightweight, esthetically pleasing orthoses developed through an 8-step process, using low-cost materials.	[102]
Swan neck deformity treatment	FDM	ABS	Software for patient-specific orthosis models for 3D printing, offering lighter, better-fitting, and more esthetic orthoses with higher satisfaction but longer preparation time.	[70]
Finger splint for mallet finger injury	FDM	PLA	Reducing mass and improving mechanical properties and heat dissipation, with the splint retaining 71.13% of its original mass performing best.	[96]

“—” indicates printing method not reported in the study.

. This table highlights the versatility of 3D printing for orthotic applications, with FDM and PLA being the most commonly used method and material. The table outlines the objective of each study, the printing method, the materials used, and a brief description of the findings or outcomes.

Despite the advantages of AM for producing finger splints, there are some notable disadvantages compared to conventional methods. Two major shortcomings are the initial cost and technical expertise required for 3D printing, including the need for specific software and hardware which may not be readily available in all clinical settings [103]. Furthermore, the process of designing and printing custom splints can be time-consuming, potentially delaying treatment. In comparison, prefabricated splints are much cheaper and readily available, offering a quick, low-cost solution in cases where immediate treatment is required and customization is not a priority. However, 3D printing can still be cost-effective when compared to traditional hand-molded or manually customized orthoses, which require significant labor and time for shaping, adjusting, and fitting. While the initial investment in 3D-printing technology can be high, it becomes more economical for frequent or mass production of custom splints due to reduced material waste and faster production once the system is in place [104].

Another common disadvantage associated with 3D printing is the inherent weakness in the layer-by-layer construction process, which can lead to reduced structural integrity [105,106]. This weakness is more of a concern in applications where higher loads are applied, such as in knee or spinal orthoses, where strength and durability are paramount. Nonetheless, for finger splints, the mechanical loads are relatively low, and the strength requirements are not as high. Thus, even though 3D-printed splints may not match the mechanical robustness of higher-quality splints, they still provide adequate support for finger immobilization. Biomechanical assessments indicate that the flexor tendons in finger joints generate forces in the range of 8.15 N for full flexion, which is significantly lower than forces acting on joints like the knee or ankle [107]. Furthermore, studies of finger splinting options show that the requirements for stabilizing finger joints are less mechanically demanding, making even lighter materials or less structurally robust designs suitable for immobilizing fingers [54,108].

6. Conclusions

The present review provides a comprehensive study of finger orthoses, including biomechanical and anatomical considerations, classification systems, design strategies, and the growing role of 3D-printing technologies. Finger orthoses serve to support, correct, immobilize, or improve finger function by addressing one or more joints. Their effective use depends on a solid understanding of finger anatomy, biomechanics, and natural motion patterns.

Different splint types, including immobilization and mobilization, were examined along with factors such as materials, joint involvement, thickness, perforation, skin interaction, and fixation methods that influence comfort and functionality. Recent advances in 3D printing have enabled the development of customized, lightweight, and cost-effective finger splints. Its ability to rapidly produce patient-specific designs with complex geometries has made it an invaluable tool in both clinical and research settings. However, limitations such as poor surface finish, limited responsiveness to movement, and printing speed remain. These challenges have drawn attention to emerging technologies like 4D printing, where time-responsive smart materials are used to create orthoses that dynamically adapt to the user’s movement and environment, allowing for more personalized care and potentially better clinical outcomes.

Interdisciplinary collaboration between clinicians, engineers, and researchers remains essential to advancing orthotic design. Further studies on long-term patient outcomes, material biocompatibility, and patient-focused assessment will play a key role in improving finger orthoses for clinical use.