Design improvements and clinical evaluation of an adjustable clubfoot splint

Abstract

Clubfoot, a congenital deformity affecting 1 to 10 per 1000 live births in India, remains challenging to manage due to high relapse rates following Ponseti method treatment. Conventional foot abduction braces, though essential, often lead to poor compliance because of discomfort and restricted mobility. To address this, a lightweight adjustable clubfoot splint (ACS) is developed for infants up to six months, using a design-for-additive-manufacturing (DFAM) approach to reduce weight, enhance adjustability, and lower cost. The splint allows controlled foot positioning while permitting natural movement, aiming to improve comfort and adherence. Clinical evaluation in 33 infants, supported by computational modeling and simulations, demonstrated a 94% compliance rate and reduced relapse compared with standard braces. While adjustable splints are already available, many remain rigid, costly, and less accessible in resource-limited settings. The present work contributes a DFAM-based, low-cost, clinically validated splint, offering a practical alternative to improve treatment outcomes and long-term management of clubfoot.

Introduction

Congenital clubfoot, or congenital talipes equinovarus (CTEV), is a common musculoskeletal birth defect affecting approximately 1 to 10 per 1,000 live births, with higher prevalence in males^1,2. The deformity is characterized by inward turning of the heel, downward pointing of the foot, and inward twisting of the forefoot, leading to impaired mobility if untreated^3,4. Early intervention is critical to restore normal foot alignment and function, with the Ponseti method, a series of manipulations and serial casting, being the globally accepted gold standard⁵. Despite high initial correction rates, relapse is common, necessitating prolonged use of foot abduction braces (FABs) to maintain correction⁶.

CTEV is often bilateral, affecting both feet in up to 40% of cases, which can complicate treatment due to asymmetric foot growth and differing severity between limbs⁷. If untreated, the condition can lead to lifelong deformity, chronic pain, and functional limitations affecting mobility and quality of life⁸. Early diagnosis and intervention are therefore essential to prevent long-term musculoskeletal complications⁹. The severity of deformity can vary widely, requiring tailored treatment strategies to address individual anatomical differences. Moreover, effective bracing during the post-casting phase is crucial not only to maintain correction but also to support normal developmental milestones, such as crawling and walking, in infants¹⁰.

Traditional FABs, including Denis Browne splints and ankle-foot orthoses, are typically static, meaning they hold the foot in a fixed position without allowing controlled movement^11,12. This rigidity often leads to discomfort, skin irritation, pressure sores, and difficulties accommodating shoe size changes, contributing to poor parental compliance^13,14. Dynamic braces, on the other hand, are designed to allow controlled movement within prescribed ranges, theoretically supporting gradual correction while maintaining adjustability¹⁵. However, most commercially available dynamic braces are costly, lack precise angle adjustments, or are unsuitable for accommodating infant growth, limiting their widespread use, especially in low-resource settings^16,17. In addition, many dynamic devices require complex fittings or frequent professional adjustments, which can be inconvenient for families. The lack of modularity and adaptability in current designs further restricts their use across different stages of infant growth, underscoring the need for innovative solutions that combine affordability, comfort, and functional adjustability^18,19. It is therefore important to clarify that the present design should not be categorized as a dynamic splint, as it does not permit continuous motion during wear²⁰. Instead, it is more accurately defined as an adjustable clubfoot splint (ACS), which permits precise pre-setting of angles across multiple planes (abduction, adduction, dorsiflexion, and plantarflexion) before application and then maintains a fixed corrective position.

To address these limitations, an ACS was designed. Unlike traditional static FABs, the splint allows setting the foot at precise angles of abduction (up to 70°), adduction (up to 50°), dorsiflexion (up to 25°), and plantarflexion (up to 25°). It is important to clarify that while these ranges are adjustable before application, the splint remains fixed at the selected angles during wear; it does not allow continuous motion while the infant is wearing it. This controlled fixation ensures that the corrective positioning is maintained consistently, preventing unintended movements that could compromise the correction process. The splint also features length adjustment (140–220 mm) to accommodate growth, modular PLA-aluminum construction for reduced weight (< 152 g), and flexible cotton shoes secured with Velcro for enhanced comfort. The modular components of the ACS, including the shoe mountings and connector joints, were fabricated using Fused Deposition Modeling (FDM) 3D printing with polylactic acid (PLA), while the structural links were made from laser-cut aluminum alloy 5052-H32. This hybrid design-for-additive-manufacturing (DFAM) approach combines the lightweight, customizable advantages of 3D-printed polymer parts with the strength and durability of metal supports. These design features collectively improve usability, reduce complications, and promote parental compliance, while offering a cost-effective and adjustable solution suitable for low-resource healthcare settings.

Clinical assessment of clubfoot treatment traditionally relies on scoring systems such as Pirani and Dimeglio scores, supplemented by biomechanical analyses of foot motion and pressure distribution^6,21. Studies indicate that noncompliance with braces is a major contributor to relapse, underscoring the need for patient-friendly, adjustable devices^22,23. ACSs with multiple degrees of freedom and ergonomic design have the potential to maintain correction while improving adherence, but few solutions combine affordability, precise adjustability, and biomechanical optimization^24,25. Also, many existing devices fail to account for infant growth, changing shoe sizes, or the need for lightweight construction, all of which influence comfort and long-term compliance²⁶. By integrating modular materials, scale markings for precise adjustments, and flexible attachment mechanisms, innovative splint designs can address these gaps and enhance treatment effectiveness across diverse patient populations^27,28.

The present study introduces and evaluates the developed ACS designed to overcome the limitations of both static and commercial dynamic braces. The primary objective is to demonstrate that the splint can maintain effective foot correction while addressing key issues of patient comfort, usability, and parental compliance. Secondary objectives include assessing the splint’s biomechanical functionality, adaptability to infant growth, and ability to reduce complications such as skin irritation, pressure sores, and improper shoe fit. Clinical trials were conducted on thirty-three infants with varying degrees of congenital clubfoot deformities, focusing on correction outcomes, practical ease of use, and overall safety. Furthermore, the study aims to establish the splint as a cost-effective, patient-centric alternative suitable for low-resource healthcare settings, thereby broadening accessibility to effective clubfoot management while ensuring high-quality care and long-term adherence.

Materials and methods

Methodology

Previous splint designs have limited capability to correct deformities along the X-, Y-, and Z-axes during the maintenance phase of clubfoot treatment. This study addresses these limitations through a systematic methodology, summarized in Fig. 1.

Fig. 1.

Research methodology for ACS development.

The process begins with a survey of existing static and ACSs. Most ACSs allow modifications in abduction angle, dorsiflexion angle, and splint length, whereas static splints are fixed and do not accommodate variations in patient anatomy. For example, static splints commonly provide an abduction angle of 70° and dorsiflexion angle of 10° but lack adjustability. Furthermore, splint lengths recommended for Indian patients are generally shorter than standard Steenbeek foot abduction brace (SFAB) guidelines. Based on these findings, the proposed ACS has a length range of 140–220 mm, allowing patient-specific adaptation.

The development process follows a structured workflow shown in Fig. 1. Initially, a Computer Aided Design (CAD) model of the splint is designed, and Finite Element Analysis (FEA) is performed to assess structural robustness and adjustability. Feedback from orthopaedic experts is then incorporated, and iterative CAD and FEA cycles are conducted as needed. Once approved by experts, the splint is fabricated using DFAM principles, optimizing weight, cost, and sturdiness. Finally, clinical trials assess patient compliance, correction efficiency, comfort, and long-term durability, providing feedback for future design improvements.

In addition to the 33 infants treated with the ACS, a separate comparative cohort of 25 infants managed with static FABs during the same period was included for compliance and complication analysis. Compliance was assessed through parental daily logbooks and verified at follow-up visits. Skin-related complications, including rash, blistering, and pressure sores, were noted at each visit. Importantly, no crossover occurred between groups; infants assigned to the ACS group did not previously use FABs as part of this study.

For systematic compliance tracking, each parent or primary caregiver was provided with a standardized daily logbook designed to record the number of hours the splint was worn, any interruptions in use, and reasons for removal. The logbooks also included sections to note the child’s comfort level and any visible skin irritation. These entries were reviewed weekly by the attending orthopaedic specialist during follow-up visits to verify consistency and accuracy. Where discrepancies were found, caregivers were interviewed directly to clarify usage details. At the end of the three-month observation period, average daily compliance was calculated as the ratio of the recorded wearing duration to the prescribed 23 h per day.

Clinical assessment protocol

A total of 33 infants (24 males and 9 females; mean age: 35 days) diagnosed with congenital clubfoot were recruited for the study following completion of manipulations and serial casting using the Ponseti method. Of these, 31 cases presented with bilateral deformity and 2 with unilateral deformity. Infants with prior surgical intervention or comorbid musculoskeletal conditions were excluded. All parents provided informed consent, and ethical approval was obtained from the institutional committee. The ACS was introduced immediately after the final cast removal. Splints were fitted under the supervision of an orthopaedic specialist and worn continuously for three months, except during bathing. The severity of deformity was assessed weekly using the Pirani scoring system (score range 0–6). The initial Pirani scores recorded in this study correspond to the measurements taken immediately before pre-casting. Additional data collected included the number of casts required for correction, age at Achilles tenotomy, parental compliance, and any complications (e.g., skin irritation, sores, ulcers). A control group of infants treated with conventional FABs was used for comparison of compliance and correction outcomes.

CAD model design and FEA analysis

The ACS was modeled using Autodesk Fusion 360 (Version v.2.0.16985, Autodesk Inc., USA) design software. The mechanism was developed with provisions to adjust multiple alignment angles, including abduction up to 70°, dorsiflexion up to 25°, plantar flexion up to 25°, and adduction up to 50°. The shoe foot plate was dimensioned to accommodate the foot size of infants up to six months of age. Figure 2a shows the isometric view of the splint, while Fig. 2b illustrates the maximum abduction angle adjustment. Length adjustment is another key feature of the design, allowing the splint to be set to a minimum of 140 mm to match the shoulder width of the patient. Figure 2c demonstrates the dorsiflexion setting in the CAD model, adjustable up to 25°.

Fig. 2.

(a) Isometric view, (b) 70° abduction and 50° adduction angle, (c) Dorsiflexion angle adjustment, (d) FEA Analysis of ACS.

FEA was conducted using ANSYS Workbench 2023 R1 (Ansys Inc., USA) to evaluate the structural safety of the ACS under representative infant loading conditions (Fig. 2d). A linear static structural analysis was performed to estimate deformation and stress distribution within the splint components. The CAD model was discretized using tetrahedral SOLID187 elements with an average element size of 1.5 mm, achieving mesh convergence and reliable numerical accuracy.

The heel region of each footplate was defined as a fixed support to simulate its attachment to the connecting bar, while a uniformly distributed vertical load, normal to the shoe’s inner surface, was applied to represent half of the infant’s body weight on each foot. Based on Indian Council of Medical Research (ICMR) data, the total weight range of infants up to six months is 6.4–9.7 kg, corresponding to an applied load of approximately 31–48 N per footplate.

All materials were assumed to behave in a linear elastic manner. The 3D-printed PLA components were modeled with a Young’s modulus of 3.5 GPa and a Poisson’s ratio of 0.36, whereas the aluminum alloy 5052-H32 components were assigned a Young’s modulus of 70 GPa and a Poisson’s ratio of 0.33. These values were obtained from standard material data sheets and corroborated with published literature on 3D-printed PLA and 5052-H32 aluminum.

The FEA results indicated a maximum deflection of 0.89173 mm at the distal end of the footplate under the conservative upper-load condition of 9.7 kg. This maximum deflection represents less than 0.65% of the total splint length (140–220 mm) and therefore falls within the 2–3% deformation threshold commonly accepted for orthotic and prosthetic components as per ISO 22523:2006 (External limb orthoses) and ISO 10328:2016 (Structural testing of lower-limb prostheses). Comparable studies on pediatric ankle–foot orthoses have reported deflections below 1–2 mm under similar loads, validating this range as clinically acceptable for maintaining alignment without compromising rigidity²⁹. As the simulated deformation occurred primarily in non-contact structural regions and not at the foot–shoe interface, it is unlikely to influence corrective positioning during clinical use.

This deformation is negligible and well within acceptable safety limits. The maximum equivalent (von Mises) stress recorded was far below the yield strengths of both materials (PLA ≈ 60 MPa, aluminum ≈ 193 MPa), confirming that the splint can safely withstand all anticipated static loads. Although infants under six months do not bear full standing weight, using this conservative “worst-case” load scenario ensures an adequate safety margin and validates that the ACS remains structurally secure even under forces generated during typical infant kicking or crawling activity.

In addition to deflection, the stress distribution within the splint was analyzed to ensure material safety under load. The results indicated that the maximum von Mises stress developed at the junction of the aluminum C-link and footplate interface, with a peak value of approximately 45 MPa under the 9.7 kg loading condition. This value is significantly below the yield strengths of both materials, approximately 193 MPa for aluminum alloy 5052-H32 and 60 MPa for 3D-printed PLA, confirming purely elastic behavior without risk of permanent deformation. The stress contours were uniformly distributed across the load-bearing components, and no localized stress concentrations were observed. These results confirm that the ACS maintains sufficient mechanical integrity under typical and worst-case loading scenarios, ensuring safe clinical use.

Analytical verification and FEA correlation

For preliminary estimation, basic analytical methods were initially considered to approximate bending behavior in the splint components. However, since the ACS consists of complex, non-uniform geometries rather than a uniform beam structure, these simplified equations could not accurately represent the real load distribution. Therefore, FEA was used as the principal validation tool to quantify deformation and stress under realistic loading conditions. The FEA model captured the combined effects of the modular aluminum and 3D-printed PLA components, providing a more reliable prediction of the splint’s mechanical response. The results confirmed that deflection and stress values remained well within the safe elastic limits of both materials.

Figure 3 presents a comparison of the deformation results in the splint. It shows the deflection in the foot plate under UDL conditions, as calculated using the theoretical method, alongside the deflection results obtained from ANSYS Workbench. This figure demonstrates the correlation between theoretical calculations and simulation outcomes, providing a clear comparison for validating the splint’s design and ensuring its structural integrity under real-world conditions.

Fig. 3.

Comparison of deformation results in splint.

To account for potential asymmetric loading between the two feet, an additional simulation was performed to assess the torsional response of the connecting shaft. During use, each shoe may experience slightly different abduction or adduction angles, generating small torsional moments along the central bar. To evaluate this, a torsional load of 10 N·mm was applied at one footplate while the opposite side remained fixed. The resulting maximum angular twist (< 1°) and von Mises stress (< 35 MPa) confirmed that the connecting structure provides adequate torsional stiffness and remains safely within the elastic range of both materials. Although a full dynamic multi-axial analysis was beyond the scope of this study, these findings indicate that the ACS design maintains sufficient rigidity to resist twisting under normal clinical conditions.

Fabrication of the developed ACS

The fabrication of the developed ACS involved the integration of various components, each designed and manufactured with specific materials and processes to achieve the desired functionality. The design of the splint was based on a 3D model created using Autodesk Fusion 360 design software, and the major components include the length adjustment links, footplate, C-link, and shoe mounting. Also, accessories such as Allen screws, nuts, bolts, washers, Velcro straps, and thrust bearings were incorporated into the assembly. The shoe mounting, manufactured using a 3D printing process with polylactic acid (PLA), provides significant advantages due to its high strength-to-weight ratio and cost-effectiveness, serving as an alternative to aluminum to reduce weight. The choice of PLA as the primary 3D printing material was guided by its biocompatibility, availability, and mechanical suitability for pediatric orthotic applications. PLA exhibits a tensile strength of approximately 60 MPa and a Young’s modulus of about 3.5 GPa, providing adequate stiffness for maintaining corrective alignment in infants while keeping the structure lightweight. It is also biodegradable, non-toxic, and FDA-approved for limited biomedical applications, making it safe for components that come into prolonged contact with infant skin. While materials such as PETG, ABS, or nylon can offer marginally higher toughness, they typically require higher printing temperatures, emit volatile compounds, and lack the same level of biocompatibility. Therefore, PLA was chosen as a clinically safe, low-cost, and easily processable option that satisfies both the mechanical and manufacturing requirements of the ACS. Future work will consider advanced bio-based composites and fiber-reinforced filaments to further enhance durability and long-term wear performance.

The 3D-printed components were produced using FDM technology (0.2-mm layer height, 100% infill) to achieve precise dimensional control and strength while maintaining low weight. Additive manufacturing enabled iterative optimization of the footplate geometry, hinge housings, and scale markings directly from the CAD model, avoiding the need for molds or machining. This capability allows the ACS to be customized for individual infant sizes at low cost and rapid turnaround, distinguishing it from conventional braces fabricated through molding or metal casting.

It allows for adjustable abduction (0°–70°) and adduction angles (0°–50°) and includes an in-built scale for precise adjustments, which is an improvement over traditional clubfoot splint. The foot plate, made of 2 mm thick aluminum, enables dorsiflexion and plantar flexion angles (0°–25°) with engraved angle markings for easy adjustments. The connection between the foot plate and the C-link incorporates a pivot-lock connector, allowing the clinician to temporarily adjust the angle of dorsiflexion or plantarflexion during fitting. Once the desired position is set, the joint is secured using an Allen screw, rendering the splint static and rigid during wear. This feature facilitates precise pre-setting in the ACS and allows provision for crawling motion. It was fabricated using laser cutting, bending, drilling, and fillet processes, with two inserts added for secure connection with the C-link.

The C-link, also made of aluminum and manufactured via laser cutting, connects the foot plate and supports crawling motion during use. The length adjustment links are essential to accommodate splint lengths ranging from 140 mm to 220 mm, catering to shoulder-to-shoulder distances of patients as they grow. The links are designed with bent corners to prevent slippage or buckling, and they are manufactured from corrosion-resistant, lightweight aluminum alloy 5052-H32. The links are connected to the C-links using thrust bearings to enhance stability and enable crawling motion. Also, a scale on the links facilitates precise length adjustment, a feature unavailable in traditional splints. The assembly of the splint allows for complete customization of abduction, adduction, dorsiflexion, and plantar flexion angles, ensuring adaptability as the child grows. Soft cotton shoes, which can be easily secured with velcro straps, are used in conjunction with the shoe mounting, offering comfort and allowing the shoes to be replaced as needed without replacing the entire splint.

Figure 4 shows the fully assembled splint, demonstrating its integrated structure, designed for optimal support, adjustability, and patient comfort.

Fig. 4.

Assembly of ACS.

Unlike conventional braces that employ rigid plastic shoes, the ACS uses customized cotton shoes secured to the footplates with Velcro straps. This design improves comfort and reduces skin irritation, while the snug fit of the cotton shoes, together with secure fastening, prevents excessive twisting or displacement of the foot within the brace. Clinical observation during follow-up confirmed that corrective positioning was maintained without evidence of shoe slippage.

Results and discussion

A total of 33 infants were treated using the developed ACS following Ponseti serial casting. Of these, 31 cases were bilateral and 2 were unilateral, giving a total of 64 feet treated. The average number of casts required to achieve initial correction was 4.24 (range: 3–8). All patients underwent percutaneous achilles tenotomy before splint application to ensure complete dorsiflexion correction.

Statistical analysis was descriptive, involving calculation of means, ranges, and percentages for variables such as pirani scores, number of casts, and compliance rates. Given the sample size and observational study design, no inferential statistical tests were performed.

At the initiation of ponseti casting (immediately prior to the pre-casting application), the mean Pirani scores were 5.36 for the left foot and 5.30 for the right foot. Following three months of continuous ACS application, pirani scores remained near zero, confirming that correction achieved through the ponseti casting phase was successfully maintained, with no evidence of relapse during the bracing period³⁰. Table 1 summarizes the clinical outcomes of 33 infants treated with the ACS. The results are grouped by deformity type and sex for clarity. The mean number of casts required for initial correction was 4.2 ± 1.1, and the mean initial pirani scores were 5.36 for the left foot and 5.30 for the right foot. After three months of continuous splint use, mean final pirani scores approached zero, indicating near-complete correction. Importantly, no cases of skin rash, pressure sores, dehydration, or ulceration were reported, and all infants maintained good overall health with no discontinuation of treatment. Parental compliance remained high (94%), attributed to the splint’s comfort, lightweight design, and easy adjustability.

Table 1.

Summary of clinical outcomes for 33 infants treated with the ACS.

Parameter	Bilateral (n = 31)	Unilateral (n = 2)	Total (n = 33)
Sex (M/F)	22/9	2/0	24/9
Mean age at start of bracing (days)	35 ± 5	33 ± 6	35 ± 5
Mean number of casts for correction	4.2 ± 1.1 (3–8)	4.0 ± 1.0 (3–5)	4.2 ± 1.1 (3–8)
Initial pirani score (L)	5.36 ± 0.47 (4.0–6.0)	6.0	5.36 ± 0.47
Initial pirani score (R)	5.30 ± 0.50 (4.0–6.0)	6.0	5.30 ± 0.50
Final pirani score (L)	0.03 ± 0.09 (0–0.5)	0	0.02 ± 0.08
Final pirani score (R)	0.02 ± 0.08 (0–0.5)	0	0.02 ± 0.08
Skin complications	None	None	None
Compliance rate	−	−	94%

The findings of this clinical evaluation demonstrate that the ACS is both effective and safe for maintaining correction following ponseti casting. The significant reduction in Pirani scores, with nearly all feet achieving complete correction after three months, highlights its clinical efficacy. Importantly, no skin-related complications such as rashes, sores, or ulcers were reported, underscoring the safety of the device—an essential consideration in infant orthotic use. While dynamic bracing in clubfoot management is not new, the ACS introduces specific design innovations that address limitations of both static FABs and high-cost commercial dynamic splints. The lightweight PLA–aluminum construction minimizes bulk while maintaining durability, modular angle adjustments with engraved scales allow precise and individualized correction, and customized cotton shoes improve comfort while reducing the risk of skin irritation. These refinements collectively enhanced usability and led to high parental compliance, a critical determinant of long-term success in preventing relapse.

Compared to static FABs, which frequently show limited compliance due to discomfort, rigidity, and restricted mobility, the ACS demonstrated superior adaptability and comfort, contributing to a markedly higher adherence rate. As summarized in Table 2, infants using the ACS exhibited an average daily wearing time of 21–23 h per day, corresponding to a 94% compliance rate, while previous reports on static FABs have documented adherence levels of only 60–70%. Parental feedback also indicated that the lighter weight, adjustable range of motion, and soft cotton shoes significantly improved ease of use and reduced irritation. These design refinements enhanced comfort without compromising the splint’s corrective stability, supporting the conclusion that the ACS offers a more user-friendly and clinically effective alternative to traditional static braces.

Table 2.

Comparison of compliance (average wearing time/day) between infants using static FABs and the developed ACS.

Time of Evaluation	Static FAB (n = 25)	ACS (n = 33)
1 st Month	17.55 h	18.97 h
2nd Month	18.25 h	22.68 h
3rd Month	17.37 h	23.15 h

Unlike many dynamic commercial braces, the ACS also offers affordability, making it suitable for resource-limited healthcare settings. Taken together, these results support the ACS as a cost-effective, patient-centered alternative that combines clinical efficacy, safety, and accessibility, with strong potential for widespread adoption in diverse clinical contexts.

Comparison with traditional foot abduction braces

A comparative evaluation was conducted between infants treated with the designed ACS and those using static FABs such as the SFAB. A total of 58 infants were included in the study, with 25 assigned to the static FAB group and 33 to the ACS group. Compliance rates and average daily wearing durations were monitored over three consecutive months. The results are summarized in Table 2.

The findings indicate that infants in the ACS group demonstrated consistently higher compliance, with mean daily wearing times consistently exceeding those of the static FAB group across all evaluation points. Parental feedback suggested that the primary reasons for lower compliance in the static FAB group included discomfort, restricted movement, device weight, and difficulties in accommodating shoe size changes. In contrast, the ACS effectively addressed these concerns through its lightweight construction, adjustable sizing, and controlled pre-set alignment capability, which allows clinicians to fine-tune correction angles before use while maintaining stability during wear. Compliance was calculated as the ratio of the average recorded daily wearing duration to the prescribed 23 h per day recommended by the ponseti protocol. The ACS group achieved a mean compliance rate of 94%, corresponding to an average daily use of approximately 21.6 h. This is markedly higher than the 60–70% compliance rates typically reported for static FABs in previous studies³¹.

Biomechanical advantages of the developed ACS

The novel design of the developed ACS incorporates key biomechanical features that optimize both function and patient comfort. The splint is designed for adjustability, allowing clinicians to pre-set specific angles of abduction (up to 70°), adduction (up to 50°), dorsiflexion, and plantarflexion (each up to 25°) before application. Once these angles are set, the splint remains static during wear, maintaining the corrective position and only allows crawling motion. This controlled pre-set alignment ensures positional accuracy while providing customization for individual anatomy and growth. The design thus improves comfort and usability without compromising stability. The splint also offers length adjustability from 140 mm to 220 mm to accommodate infant growth. These angles are adjusted and locked prior to use, ensuring that the splint remains static during application. The adjustability thus refers to customization of corrective positioning, not continuous dynamic motion. These adjustable ranges are comparable to, and in some aspects exceed, those of conventional and commercial braces. For example, the Steenbeek Foot Abduction Brace (SFAB) typically provides a fixed abduction angle of 70° and dorsiflexion of 10–15°, with no provision for adduction or continuous length adjustment. The Dobbs dynamic brace allows up to 60° of abduction and 15–20° of dorsiflexion but lacks modular length expansion and is significantly heavier. In contrast, the developed ACS offers a broader range of angle adjustments, up to 70° abduction, 50° adduction, and 25° dorsiflexion/plantarflexion, while maintaining a lightweight design (< 152 g).

This feature accommodates infant growth and eliminates the need for frequent replacements. Another significant advantage is weight optimization. The developed ACS weighs less than 152 g, making it significantly lighter than traditional splints, which enhances comfort and improves compliance. Quantitatively, this weight reduction is substantial compared with conventional designs. The Steenbeek Foot Abduction Brace (SFAB), widely used in low-cost clubfoot management, weighs approximately 250–300 g depending on size and configuration²⁹, while the Dobbs dynamic brace and Mitchell-Ponseti brace typically range from 350 to 450 g. In comparison, the developed ACS weighs only 152 g, representing a 40–60% reduction in total weight³². This reduction contributes directly to improved comfort, ease of handling, and higher compliance during prolonged wear in infants. The use of lightweight 3D-printed PLA components and aluminum alloy 5052-H32 structural elements effectively balances durability with minimal mass.

The materials used in its construction further contribute to its biomechanical efficiency. The splint is fabricated using PLA for footplates, which ensures lightweight and biocompatible properties, while aluminium alloy 5052-H32 is used for structural support, providing both durability and reduced weight. The design follows the DFAM approach, which allows precise fabrication, cost efficiency, and adaptability to specific patient requirements.

Clinical benefits and cost analysis

Traditional FABs have been associated with various complications, including skin blistering, pressure sores, and discomfort due to improper shoe fit and rigid bar structures. The developed ACS effectively addresses these issues by allowing customized cotton shoes, which are securely fastened using velcro straps. This ensures a snug yet comfortable fit, reducing friction and minimizing the risk of blister formation. The splint incorporates an adjustable bar mechanism with pivot-lock connectors, which permit controlled angular adjustments during fitting only and are securely locked before use to maintain corrective positioning throughout wear. This design reduces excessive pressure on the feet compared to rigid bar structures, thereby improving comfort without compromising correction. The developed ACS is estimated to cost approximately ₹2,100 (~ USD 25) per unit, based on its material and fabrication costs. This estimate includes PLA filament (145 g; ₹450/USD 5), aluminum components (₹800/USD 9), Velcro fasteners, cotton shoes, and accessories (₹400/USD 5), and energy and finishing expenses (~₹450/USD 5). The average 3D printing time for one complete pair of splints is 5.5–6 h using an FDM printer operating at 0.2 mm layer height and 100% infill density. Assembly and fitting require approximately 20–25 min. These parameters make the ACS suitable for decentralized or small-scale manufacturing in clinical or rehabilitation centers equipped with 3D printing facilities. The cost comparison with other braces—such as the Dobbs brace (~ USD 1,200), Mitchell brace (~ USD 350), and DB brace (~ USD 70)—is indicative rather than directly equivalent, as these commercial devices incorporate differing production scales, material compositions, and distribution costs. The purpose of this comparison is to emphasize affordability and accessibility rather than to imply identical manufacturing frameworks. Within the scope of this study, the ACS demonstrates that additive manufacturing enables cost-effective, patient-specific production, particularly in resource-limited healthcare environments.

Also, by effectively maintaining correction, the splint reduces recurrence rates, eliminating the need for repeat casting and surgical interventions such as tenotomies. This leads to further cost savings for both healthcare providers and families.

Limitations of the study

While the designed ACS demonstrated significant clinical benefits, several limitations must be acknowledged. One major limitation is the short follow-up period of three months, which restricts the ability to assess long-term recurrence rates and sustained correction outcomes. A more extended follow-up, ideally spanning two to four years, is necessary to determine the long-term efficacy of the splint and its impact on preventing relapses. Another limitation is the reliance on parental self-reports for compliance monitoring, which may introduce reporting bias. Also, because participants and caregivers were aware of their involvement in a monitored clinical study, compliance behavior may have been positively influenced by observation (a potential Hawthorne effect). Although this effect is common in early clinical device evaluations, future studies incorporating sensor-based usage tracking and non-observed follow-ups could help quantify and reduce this bias, providing a more objective assessment of long-term adherence. The absence of sensor-based tracking prevents objective measurement of brace usage, making it difficult to accurately evaluate patient adherence. Also, while the study confirmed the safety and effectiveness of splints within a controlled clinical setting, broader studies across diverse populations and healthcare environments are required to validate its applicability on a larger scale. The ethical considerations limited the inclusion of patient photographs, which could have provided visual documentation of treatment progress, further strengthening the findings of study. Future research incorporating digital tracking, larger sample sizes, and extended follow-up periods will be essential to address these limitations and provide a more comprehensive assessment of the splint’s long-term benefits.

A potential limitation of the ACS is that the use of Velcro-fastened cotton shoes, while improving comfort and compliance, may not provide the same level of rigidity as conventional hard shoes. Although no positional compromise was observed in this study, further long-term evaluation is required to fully validate this feature under prolonged use. One limitation of the present analysis is that dynamic impulse forces generated by infant kicking were not modeled. While static loading ensured conservative safety validation, future studies should incorporate dynamic simulations for a more realistic assessment of in-use forces.

Conclusion

The designed ACS demonstrated substantial clinical efficacy in maintaining foot correction and improving compliance among pediatric patients with congenital clubfoot deformities. In a study involving 33 infants, the mean pirani scores dropped from 5.36 (left foot) and 5.30 (right foot) at baseline to near 0 after three months of continuous splint use, indicating effective correction maintenance. The lightweight, adjustable, and biomechanically optimized design significantly enhanced patient comfort, resulting in a 94% adherence rate, a marked improvement over the traditional rigid brace. The splint’s-controlled range of motion ensured optimal foot alignment while allowing controlled pre-set adjustability prior to wear, addressing key limitations of static braces. Additionally, no adverse effects such as skin irritation or pressure sores were reported, supporting its safety for prolonged use. Despite these promising outcomes, certain limitations must be acknowledged, including the short follow-up period and reliance on parental compliance reports, which could introduce reporting bias. Future research should incorporate sensor-based monitoring to obtain objective compliance data and longitudinal studies to assess long-term effectiveness and recurrence rates. The ACS represents a viable, cost-effective, and patient-centered alternative to conventional braces, with strong potential for adoption in both routine clinical care and resource-limited healthcare systems.

Author contributions

Mahavir K Beldar conducted the investigation, performed data curation, and prepared the original draft. Kashinath Sahoo and Nagesh K Chougule provided supervision and conceptualized the study. Bharatkumar B Ahuja supported data curation and software analysis. Dadaso D Mohite contributed to data curation, software analysis, and manuscript review and editing. All authors reviewed the manuscript.

Data availability

Data is provided within the manuscript.

Declarations

Competing interests

The authors declare no competing interests.

Ethics approval

This study was performed in line with the principles of the Declaration of Helsinki. Approval was granted by the Ethics Committee of College of Engineering, Pune (Date: 11/01/2023, No. 2429).

Informed consent

Informed consent was obtained from the parents or legal guardians of all individual participants included in the study.

Informed consent for Publication

Informed consent was obtained from the parents or legal guardians of all participants for both participation in the study and for the publication of any potentially identifying information or images in an online open-access publication.