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Review

Stapes Prostheses in Otosclerosis Surgery: Materials, Design Innovations, and Future Perspectives

by
Luana-Maria Gherasie
1,2,
Viorel Zainea
1,2,*,
Razvan Hainarosie
1,2,
Andreea Rusescu
1,2,
Irina-Gabriela Ionita
1,2,
Ruxandra-Oana Alius
1,2 and
Catalina Voiosu
1,2
1
General Medicine, “Carol Davila” University of Medicine and Pharmacy, 050474 Bucharest, Romania
2
”Prof. Dr. D. Hociota” Institute of Phonoaudiology and Functional ENT Surgery, 050751 Bucharest, Romania
*
Author to whom correspondence should be addressed.
Actuators 2025, 14(10), 502; https://doi.org/10.3390/act14100502
Submission received: 31 August 2025 / Revised: 8 October 2025 / Accepted: 14 October 2025 / Published: 17 October 2025
(This article belongs to the Section Actuators for Medical Instruments)
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Abstract

Background: Stapes prostheses represent one of the earliest and most widely applied “biomedical actuators” designed to restore hearing in patients with otosclerosis. Unlike conventional actuators, which convert energy into motion, stapes prostheses function as passive or smart micro-actuators, transmitting and modulating acoustic energy through the ossicular chain. Objective: This paper provides a comprehensive analysis of stapes prostheses from an engineering and biomedical perspective, emphasizing design principles, materials science, and recent innovations in smart actuators based on shape-memory alloys combined with surgical applicability. Methods: A narrative review of the evolution of stapes prostheses was consolidated by institutional surgical experience. Comparative evaluation focused on materials (Teflon, Fluoroplastic, Titanium, Nitinol) and design solutions (manual crimping, clip-on, heat-activated prostheses). Special attention was given to endoscopic stapes surgery, which highlights the ergonomic and functional requirements of new device designs. Results: Traditional fluoroplastic and titanium pistons provide reliable sound conduction but require manual crimping, with a higher risk of incus necrosis and displacement. Innovative prostheses, particularly those manufactured from nitinol, act as self-crimping actuators activated by heat, improving coupling precision and reducing surgical trauma. Emerging designs, including bucket-handle and malleus pistons, expand applicability to complex or revision cases. Advances in additive manufacturing and middle ear cement fixation offer opportunities for customized, patient-specific actuators. Conclusions: Stapes prostheses have evolved from simple passive pistons to innovative biomedical actuators exploiting shape-memory and biocompatible materials. Future developments in stapes prosthesis design are closely linked to 3D printing technologies. These developments have the potential to enhance acoustic performance, durability, and patient outcomes, thereby bridging the gap between otologic surgery and biomedical engineering.

1. Introduction

1.1. Background and Pathophysiology

Otosclerosis is a localized bone disorder of the otic capsule characterized by abnormal remodeling of endochondral bone that leads to stapes fixation and progressive hearing loss [1]. Pathologically, the disease progresses in two phases: an active otospongiosis phase of bone resorption and vascular proliferation, followed by a sclerosis phase of new bone formation and fibrosis [2]. Over time, the fixated stapes impedes sound transmission to the inner ear, causing a chronic conductive hearing impairment [3]. If left untreated, otosclerosis can advance to severe hearing disability (often bilateral), with profound effects on communication and quality of life [4]. Epidemiologically, otosclerosis has a prevalence of roughly 0.04–1% in White populations (with lower rates in Asians) and shows a marked female predominance (~2:1 female-to-male) [5]. The condition typically manifests in early to mid-adulthood, most often presenting in the third or fourth decade of life, and tends to worsen gradually over subsequent years [6].

1.2. Clinical Presentation and Diagnosis

Patients with otosclerosis usually present with insidious, progressive hearing loss as the cardinal symptom [7]. In the majority of cases, this is a conductive hearing loss, although sensorineural or mixed components may develop in advanced stages when cochlear involvement occurs [8]. Tinnitus is also a common accompanying complaint, reported in approximately 60–70% of patients preoperatively [9,10]. Otoscopic examination is typically normal, but in active otospongiotic lesions, a reddish blush on the promontory (Schwartze’s sign) may be observed, reflecting hypervascular bone resorption [11]. A definitive diagnosis relies on both audiological and radiologic assessments. Pure-tone audiometry classically reveals a Carhart notch—a depression in bone conduction thresholds around 2 kHz—along with an air–bone gap (ABG) indicative of conductive loss. Stapedial reflexes are usually absent on the affected side due to stapes fixation. High-resolution Computer Tomography (HR-CT) imaging can identify characteristic demineralized foci in the otic capsule and is useful for confirmation, staging, and surgical planning [12]. However, CT is not always required for classic cases; many patients with a typical history proceed to surgery without radiographic evaluation. The earliest and most characteristic radiological finding is demineralization at the fissula antefenestram, a fibrocartilaginous cleft located just anterior to the oval window. On HR-CT, this region appears as a hypodense, radiolucent focus at the anterior margin of the stapes footplate, often described as the initial site of fenestral otosclerosis [13]. Imaging is more often employed in atypical cases or to distinguish otosclerosis from other rare causes of otic capsule demineralization (e.g., Paget’s disease or osteogenesis imperfecta) [14].
The tympanic membrane transmits acoustic vibrations to the malleus, which articulates with the incus. The incus connects to the stapes through the incudostapedial joint, forming the ossicular chain that conveys sound energy to the oval window of the cochlea (Figure 1).
The middle ear is a small, air-filled cavity that plays a crucial role in sound transmission from the external to the inner ear. It houses the auditory ossicles—the malleus, incus, and stapes—which form a mechanical chain that amplifies and conveys vibrations from the tympanic membrane to the oval window of the cochlea. The malleus is attached to the tympanic membrane, transmitting sound energy to the incus, which in turn articulates with the stapes. The stapes, the smallest bone in the human body, interfaces with the oval window, acting as the final link in the chain. At the junction between the incus and the stapes lies the incudostapedial joint, which ensures efficient energy transfer [15].
The tympanic membrane transfers sound vibrations through the ossicular chain (malleus and incus) to the prosthesis piston, which replaces the stapes and transmits mechanical energy to the oval window (ossicular coupling, black arrows). Additionally, part of the sound energy is transmitted acoustically through the middle ear cavity to the round window (indicated by red arrows), which compensates for pressure variations between the oval and round windows, enabling fluid displacement and effective cochlear vibration. Otosclerosis-induced fixation alters the impedance balance of the ossicular chain, motivating the development of prosthetic actuator solutions for efficient energy coupling.

1.3. Evolution of Otosclerosis Management

The surgical management of otosclerosis has a long and storied history spanning over a century. The first stapes surgery is credited to Kessel in 1876, who removed the immobilized stapes in an attempt to improve hearing [16]. Earlier descriptions of stapes fixation (by Valsalva in 1703) and rudimentary mobilization (by Ménière in 1842) had been noted. Still, Kessel’s procedure marked the true beginning of stapes surgery as a therapeutic approach [17]. These early efforts met with limited success and significant risks; indeed, in 1899 an international otology congress condemned stapes operations due to frequent infection and inner ear damage in the pre-antibiotic era. In 1952, Rosen reintroduced stapes mobilization, and a few years later (1956), John Shea performed the first stapedectomy using a Teflon prosthetic stapes replacement, stabilized with a vein graft [18]. Shea’s innovation achieved substantial hearing restoration and ushered in the modern era of otologic microsurgery. Refinements soon followed, including the transition from full stapedectomy to small-fenestra stapedotomy techniques that minimize trauma [19,20]. Modern stapedotomy is typically performed via a transcanal approach under magnification, wherein a ~0.7 mm opening is created in the stapes footplate (often using a microdrill or laser) and a piston prosthesis is inserted to reconnect the ossicular chain to the inner ear. Today, stapedotomy is considered the gold-standard treatment for otosclerosis, offering durable hearing improvement in the vast majority of cases [21]. Large surgical series consistently report closure of the ABG to within 10–15 dB in over 90% of primary cases [22].
In the hands of experienced surgeons, the procedure is safe. Complications can occur in a small minority of patients, including sensorineural hearing loss (estimated at a risk of profound deafness of ~0.5–1%), incudo-malleolar joint disruption or necrosis, tympanic membrane perforation, vestibular disturbance, facial nerve injury, or dysgeusia resulting from chorda tympani traction. Nonetheless, the overall benefit-risk profile is strongly favorable, and successful stapes surgery yields significant improvement in quality of life for those with otosclerosis. Notably, from a health-economic perspective, timely stapes surgery is cost-effective, as progressive otosclerosis otherwise leads to greater disability and rehabilitative costs if left untreated [9].
In recent years, the introduction of endoscopic ear surgery (EES) has further refined the surgical approach to otosclerosis. Endoscopic stapedotomy techniques allow a minimally invasive transcanal surgery with no external incision, resulting in reduced trauma to surrounding tissue and faster recovery for patients [23]. The endoscope provides enhanced visualization of the middle ear, permitting the surgeon to view hard-to-reach structures (such as the oval window niche, facial nerve recess, and sinus tympani). Clinical studies have shown that purely endoscopic stapes surgery can achieve audiologic outcomes and complication rates comparable to those of the traditional microscopic approach. However, endoscopic surgery also introduces new ergonomic challenges: the surgeon must operate essentially one-handed (as one hand holds the endoscope), and depth perception is limited. This has important implications for prosthesis selection and design, as discussed below [24,25]. Advances from early Teflon to titanium pistons primarily aimed to optimize coupling stiffness and reduce acoustic losses, guiding current actuator-based design.

2. Stapes Prostheses

2.1. From Passive Pistons to “Innovative Actuators”

From an engineering standpoint, the stapes prosthesis can be viewed as a tiny biomechanical actuator tasked with transmitting acoustic vibrations from the incus to the inner ear fluids, effectively replacing the function of the ankylosed stapes. For decades, the standard prosthetic design has been the straight piston (commonly fashioned from Teflon or fluoroplastic), which attaches to the incus and extends through the stapedotomy into the vestibule. These passive prostheses rely on static mechanical coupling and typically require the surgeon to manually crimp or bend a wire loop around the incus to secure the piston in place [26]. Manual crimping, however, carries a risk of exerting excessive force on the incus and can be technically demanding, especially under endoscopic conditions where only one hand is free. To address these issues, newer “smart” prosthesis designs made from SMA (most notably nitinol) have been developed. Nitinol (a nickel-titanium alloy) can undergo a thermally induced shape transformation, allowing such pistons to self-crimp tightly onto the incus when heated (for example, by laser or body temperature). Heat-activated nitinol prostheses thus eliminate the need for manual crimping, which not only simplifies the procedure but also yields a more consistent and gentle coupling force. For instance, flat ribbon nitinol pistons expand and close around the incus in a controlled manner upon activation, their wide ribbon loops distributing pressure and minimizing risk of focal trauma to the incus [27]. Clinical experience indicates that these self-crimping implants achieve stable attachment with less manipulation of the ossicles, an especially valuable property when operating endoscopically [28]. It should be noted that nitinol prostheses can undergo slight length changes during activation and may require precise sizing or minor adjustment to ensure optimal length after crimping. In parallel, other innovative coupling mechanisms have been introduced—for example, clip-on pistons with a pre-formed loop can simply snap onto the incus without any crimping—all aiming to facilitate secure, one-handed placement and reduce the instrumentation needed in the tight confines of the middle ear [29,30].

2.2. State-of-the-Art Developments

Advances in materials science and fabrication technology are continually influencing stapes prosthesis design [31]. Titanium has emerged as a popular prosthetic material, offering high strength and excellent sound transmission despite its very light weight. Many surgeons now favor titanium or titanium-based pistons due to their superior handling characteristics and durability. Another significant development is the emergence of patient-specific prostheses, facilitated by computer-aided design and additive manufacturing (3D printing). For complex revision cases or extensive ossicular chain damage, novel reconstruction strategies have also been explored. For example, the K-Helix (endohelix) titanium prosthesis can be combined with bioactive middle ear cement (e.g., glass-ionomer cement) to create an “endoskeletal” ossicular replacement, essentially cementing the prosthesis to remnant ossicular structures for stability. Similarly, specialized malleus-attachment pistons are available to bypass a missing or eroded incus, expanding the surgical options for complex anatomies [32].
Looking forward, the interface of microengineering and otology may yield “active” stapes prostheses that not only passively transmit sound, but actively modulate it. Research into micro-electro-mechanical systems (MEMS) is opening the door for implantable middle-ear transducers with integrated sensors or actuators [33]. In principle, a MEMS-enhanced stapes implant could dynamically adjust its stiffness or displacement in response to sound input, or provide feedback control to optimize hearing outcomes in real time. For instance, embedded electronics may help limit the force transmitted to the inner ear at high sound intensities, thereby protecting against potential damage [34]. Although such technologies remain experimental, the concept underscores the broader trend of convergence between otologic surgery and biomedical engineering. In summary, the modern stapes prosthesis is the product of both surgical innovation and high-tech design [35].

3. Surgical Treatment

3.1. Surgical Technique

Modern stapedotomy is most often performed via a transcanal approach. This requires removal of a portion of the scutum to visualize the incudo-stapedial joint, pyramidal eminence, and tympanic segment of the facial nerve. Under microscopic or endoscopic visualization, the posterior crus of the stapes is weakened, the tendon of the stapedius muscle is divided, and the stapes superstructure is down-fractured. A fenestration of approximately 0.7 mm is then created in the footplate, using either a micro-drill or laser [36].
In our institutional experience at the Prof. Dr. D. Hociotă Institute of Phonoaudiology and Functional ENT Surgery, the majority of procedures are performed under general anesthesia [37,38]. Fluoroplastic and Titanium pistons remain the most frequently used prosthesis type, valued for their inertness and handling characteristics. Nonetheless, potential limitations exist, including the risk of prosthesis displacement, malposition, or long-term loosening if fixation is not carefully achieved.
Complications, although relatively infrequent, must be recognized. In a landmark prospective series of 3050 stapedotomies, Vincent et al. reported that closure of the ABG was achieved within 10 dB in 94.2% of patients. Notably, many surgical failures were attributed to prosthesis malposition or inappropriate length [9].
The Skarżyński Piston is a titanium stapes prosthesis with an ultra-thin angled loop for precise incus attachment and a rounded tip to reduce inner ear trauma. Clinical data from the World Hearing Center in Poland demonstrate excellent outcomes, with ABG ≤ 10 dB in over 95% of patients and mean hearing gains of 25–30 dB, along with notable tinnitus improvement. Its lightweight, high-rigidity design enhances high-frequency transmission and surgical handling, exemplifying how engineering refinement and clinical expertise can jointly optimize stapedotomy outcomes [39].
Prosthesis selection is therefore a critical determinant of long-term success. Comparative studies, such as that of Faramarzi et al., have shown that classical devices (e.g., Schuknecht, Richards, and Causse pistons) achieve broadly similar audiologic outcomes in terms of ABG closure. The choice of material and coupling mechanism is increasingly guided by surgeon preference, surgical approach (microscopic vs. endoscopic), and patient-specific anatomy [40].

3.2. Advances in Stapes Surgery Technique

From an engineering perspective, current stapes prostheses can be broadly divided into two categories:
  • Manual-crimping prostheses, where the surgeon physically crimps the piston loop around the long process of the incus.
  • Non-crimping or self-crimping prostheses, which use advanced coupling mechanisms or SMA to achieve fixation without manual deformation [21].
The introduction of nitinol—a nickel-titanium SMA—has been particularly transformative. Nitinol pistons are heat-activated: when exposed to thermal energy (e.g., from a laser or body heat), the alloy undergoes a controlled shape transformation that secures the loop gently and uniformly around the incus. This innovation reduces dependence on the surgeon’s crimping technique, minimizes mechanical trauma to the ossicles, and improves reproducibility, especially under endoscopic conditions where single-handed operation is necessary. Flat-ribbon Nitinol pistons further distribute the contact pressure, protecting against focal necrosis of the incus [41].
Other novel designs include clip-on pistons with pre-formed loops that snap onto the incus without crimping, as well as malleus-anchored pistons that bypass the incus entirely in cases of incus erosion. Together, these developments reflect the ongoing convergence of otologic surgery and biomedical engineering, where prosthesis design is increasingly optimized not only for acoustic function but also for surgical ergonomics and long-term biocompatibility [42]. A comparative overview of the main ossicular replacement prostheses, highlighting their materials, coupling mechanisms, and design features, is presented in Table 1.
This table summarizes the properties, audiological outcomes, and practical considerations of the three most widely used stapes prosthesis materials: fluoroplastic (Teflon), titanium, and nitinol. Each material offers distinct mechanical and surgical handling characteristics. Fluoroplastic pistons have a long track record of biocompatibility but require manual crimping, with a small risk of incus dislocation over time. Titanium pistons are lightweight and radiologically inert, available in both manual loop and clip-on (Soft CliP) variants, with outcomes comparable to Teflon but offering surgical ergonomic advantages. Nitinol (nickel–titanium alloy) prostheses use shape-memory properties to achieve self-crimping fixation, simplifying coupling, providing consistent contact forces, and maintaining excellent long-term audiological stability. Across all materials, most studies report postoperative air–bone gap closure to within 10 dB in the majority of patients, highlighting the importance of coupling mechanism and surgical technique in optimizing outcomes [43,44]. A comparison of the mechanical and acoustic characteristics of fluoroplastic, titanium, and Nitinol, illustrating their influence on sound transmission efficiency, is provided in Table 2.
Quantitatively, titanium exhibits the highest stiffness-to-density ratio among modern prosthesis materials, providing superior vibrational fidelity and minimal damping (loss factor ≈ 0.005–0.01), which enhances energy transfer efficiency across the ossicular chain. Fluoroplastic, while lightweight, shows higher internal damping (≈0.03–0.05), reducing high-frequency transmission. Nitinol combines moderate stiffness (≈50 GPa in the austenitic phase) with intrinsic damping and shape-memory elasticity, enabling controlled compliance and self-crimping fixation that improve coupling stability and reduce mechanical stress. Experimental laser Doppler vibrometry and finite-element analyses indicate mean transmission efficiencies of 80–85% for Teflon, >90% for titanium, and ~88–92% for Nitinol-based pistons in the 0.5–4 kHz range, correlating with clinical hearing improvements of 25–30 dB and consistent ABG ≤ 10 dB in most cases [45,46].

4. Endoscopic Stapedotomy

In recent years, there has been a growing interest in endoscopic stapedotomy worldwide, and Balkan countries are also developing their experience with endoscopic ear surgery [47]. In a report published by Celik et al., it was concluded that endoscopic stapedotomy displayed similar audiological benefits, less invasive surgical procedures, and comparable complications compared to microscopic surgery [48].
The use of TES therefore offers surgeons many advantages, including the ability to expose hidden recesses, zoom into complex structures, and reduce the need for bone curettage [49,50]. It should be noted, however, that the endoscope does not meet all needs. The lack of depth perception, the need to operate with one hand, and the long learning curve make endoscopic technology less attractive [51]. Bartel et al. 2021 demonstrated that stapes surgery may be performed using an endoscope with an 0° angle and a 4 mm diameter [52].

5. Discussion

5.1. Prosthesis Materials and Acoustic Performance

Modern stapes prostheses exemplify the interplay between materials science and acoustic engineering in otologic surgery. Fluoroplastic pistons coupled with metal loops have a long track record of success, offering lightweight, inert construction and excellent biocompatibility. Titanium prostheses, introduced in the 1990s, leverage a high strength-to-weight ratio and low acoustic impedance. Titanium’s rigidity allows fabrication of thinner pistons that improve the surgeon’s view during placement, without compromising sound transmission. Nitinol (nickel–titanium alloy) brings shape-memory behavior, enabling “smart” self-crimping [53]. From an engineering standpoint, the middle ear can be conceptualized as a multi-stage energy transduction system that converts acoustic energy from the tympanic membrane into mechanical vibrations through the ossicular chain and subsequently into hydraulic motion within the cochlea. The prosthesis piston acts as a passive micro-actuator within this system, bridging the mechanical coupling between the incus and the oval window. The efficiency of energy transfer through this pathway depends primarily on the impedance matching between the prosthesis and the native ossicular elements, as well as on the geometric and material properties of the piston. A well-optimized actuator design minimizes mechanical losses at coupling interfaces, maintains linearity of motion across the speech frequency range, and prevents phase distortion during sound transmission.
The schematic of energy pathways (Figure 2) illustrates how vibrational energy is distributed along two principal transmission routes: the ossicular coupling pathway, which transfers mechanical motion via the prosthesis piston to the oval window, and the acoustic coupling pathway, which contributes to pressure modulation at the round window. This dual-path energy flow highlights the importance of actuator design in maintaining coherent energy transfer and pressure balance within the cochlea. From this perspective, future prosthesis development should integrate actuator design principles such as modal analysis, finite element simulation, and resonance tuning to enhance vibration amplitude while minimizing energy dissipation. Such an engineering-driven approach not only improves mechanical efficiency but also aligns the prosthesis functionally with the biomechanical environment of the middle ear.
Detailed comparative data on the material properties, design features, audiological outcomes, and clinical considerations of Teflon, titanium, and Nitinol stapes prostheses are presented in Table 3.
As seen above, audiological outcomes are generally excellent with all modern materials, with most studies reporting postoperative ABG closure within 10 dB in the majority of patients. This emphasizes other design aspects, particularly the prosthesis fixation method, as critical to optimizing sound conduction.
Recent advances in stapes prosthesis engineering have shifted focus from material biocompatibility toward actuator-like performance optimization. Titanium-based pistons, such as the TTP® and NiTiFLEX® models, exemplify this evolution by combining low mass and high stiffness to improve vibrational transmission and coupling precision within the ossicular chain. Their filigreed and self-retaining clip designs enhance surgical handling and ensure stable incus attachment while minimizing mechanical stress and damping losses. These actuator-oriented innovations aim to replicate the natural stapes motion through optimized impedance matching and controlled compliance at coupling interfaces, thereby improving energy transfer efficiency across the acoustic–mechanical–hydraulic pathway [45,46].

5.2. Fixation Techniques and Coupling Efficacy

Proper coupling of the prosthesis to the ossicular chain is essential for efficient vibration transmission. The traditional manual crimping technique, in which the surgeon wraps and presses a wire loop around the long process of the incus, is highly technique-dependent. If the crimp is too loose, microscopic slippage and “micro-motions” can occur at the incus interface, reducing displacement accuracy and leaving a residual ABG. Too tight a crimp, conversely, risks focal pressure on the incus blood supply or even a “strangulation” injury to the bone. This balancing act makes crimp quality a key variable—indeed, interindividual variability in post-operative hearing results has been partially attributed to inconsistent manual crimping. Huber et al. demonstrated that tighter fixation correlates with better sound transmission. In their series, prostheses with firm attachment yielded significantly better ABG outcomes (mean ABG ~ 3 dB lower and higher high-frequency gain) than looser attachments. They hypothesized and confirmed that improved mechanical coupling at the incus–prosthesis interface directly translates to enhanced acoustic output. This finding aligns with engineering principles of actuator coupling—minimizing interface compliance and energy losses leads to more faithful motion transfer [60].
To mitigate the limitations of manual crimping, two innovative fixation methods have gained popularity: self-crimping (thermal) pistons and spring clip pistons. Self-crimping Nitinol prostheses employ a loop of SMA that auto-tightens when heated by the surgeon’s laser or cautery. This yields a consistent, circumferential coupling force that is pre-calibrated by design. Early clinical trials and multi-center studies have indicated that these self-crimping pistons can “overcome the drawbacks” of manual crimping by reducing variability in outcomes. Rajan et al. reported significantly minor variations in residual ABG and more complete closure in the Nitinol group compared to manually crimped controls. Long-term follow-up confirms excellent stability: in a 12-year study, 96% of patients with Nitinol pistons maintained ABG ≤ 20 dB at the last follow-up (virtually identical to the early postoperative results), compared to 86% with conventional titanium loops. Notably, concerns that a very tight Nitinol loop might cause late incus erosion have not materialized—no adverse effect of the firm fixation was seen over >10 years [27]. These outcomes highlight how a self-adjusting actuator can provide reliable long-term performance and simplify the surgical procedure. By eliminating the need for pliers or manual deformation, Nitinol pistons also spare the incus from inadvertent intraoperative trauma (e.g., rocking or cracking during crimp attempts) [57].
Clip-on pistons represent another engineering solution to achieve secure yet atraumatic coupling. The titanium Soft CliP design (e.g., Kurz prosthesis) uses a spring-loaded C-shaped clip that snaps onto the incus, providing a standardized gentle pressure [53]. For the surgeon, this has tangible ergonomic benefits—no crimping step is required, which simplifies the workflow and reduces operative time by ~5 min on average. A’Wengen’s retrospective study of 120 cases showed that the clip piston “always holds firm and in the correct position”, yielding better hearing outcomes than earlier loop prostheses, with the most significant gains in speech discrimination scores. The firm, reliable attachment minimizes micro-movements, thereby maximizing sound energy transfer to the inner ear. At the same time, the clip’s spring mechanism avoids excessive force; unlike a crushed metal loop, it does not circumferentially compress the incus, virtually eliminating the risk of pressure-induced necrosis. These designs thus achieve an optimized balance of strong coupling (for acoustic efficiency) and controlled force (for safety)—a hallmark of good actuator design [56].
Clinical data confirm stable transmission efficiency and biocompatibility, validating the mechanical reliability of current piston geometries. It is worth noting that when comparing manual, self-crimping, and clip methods, most well-performed surgeries yield excellent and statistically similar hearing outcomes. A recent controlled study of 155 stapedotomies found no significant difference in ABG closure or bone-conduction changes between a manually crimped piston and a NiTi self-crimping piston at 6 weeks post-operative. This suggests that, under ideal conditions (experienced surgeon, proper technique), both fixation approaches are capable of achieving near-optimal sound conduction. The choice of fixation may then hinge on surgical context: for example, thermal self-crimping may be advantageous in narrow anatomy where crimping tools are awkward, whereas an unfavorably located chorda tympani might preclude use of a heat-activated prosthesis. Surgeon experience and comfort with a given device also play a significant role—with sufficient training, even manual crimping can be highly consistent. Nevertheless, the availability of self-crimping and clip-on options provides valuable flexibility. They not only streamline the procedure (especially for less experienced surgeons) but also add a safety margin against human error in coupling the “micro-actuator” to the ossicular lever arm [53,59].

5.3. Influence of Surgical Technique on Outcomes

Beyond prosthesis design, the method of stapedotomy creation can impact the functional outcomes and perioperative safety, linking surgical technology with actuator performance. The primary approaches to fenestrating the footplate are mechanical micro-drilling or the use of pick instruments (micro-perforators), versus laser stapedotomy, which utilizes laser energy (commonly KTP or CO2 lasers) to create the opening. Each technique affects how energy is delivered to the inner ear and the surrounding tissue, potentially causing trauma. In terms of hearing results, a meta-analysis encompassing 1614 cases concluded that laser stapedotomy yields slightly better postoperative hearing thresholds than non-laser techniques. Specifically, the probability of achieving a successful ABG closure was about 7% higher with lasers (risk ratio ~1.07, p = 0.005). This may be attributable to the laser’s ability to produce a precise, small fenestra with minimal ossicular disturbance, thereby optimizing the piston’s fit and reducing acoustic losses. Indeed, a well-formed 0.5–0.8 mm “cookie bite” hole maximizes the piston-footplate seal and maintains hydraulic transmission into the cochlea [61,62]. Mechanical drilling, by contrast, can transmit vibrational trauma or create an irregular fenestration, potentially compromising the piston’s sealing and requiring additional work on the footplate.
On the metric of patient safety and inner ear protection, lasers have mixed considerations. The meta-analysis found no significant difference in overall complication rates between laser and non-laser stapedotomies (combined RR 0.63, p = 0.23) [61]. In principle, avoiding drill contact should reduce the risk of acoustic trauma (noise-induced hearing loss) and oval window mechanical disturbance (which can cause vertigo or a “floating footplate”). Lasers also enable “no-touch” footplate fenestration, which may lower the incidence of perilymph gush or sensorineural hearing loss, as reported in some studies. However, laser use introduces thermal energy; if misused, there is a theoretical risk of thermal injury to cochlear structures or the stapedial annulus. In practice, modern laser parameters (pulsed delivery, low energy per pulse) and aiming techniques have made such complications exceedingly rare. Overall, both methods are considered very safe in experienced hands, with permanent sensorineural hearing loss rates typically <1–2% regardless of method. Many surgeons now adopt a hybrid approach, for example, thinning the footplate with a microdrill and then using a laser for the final perforation, combining the strengths of each method. The goal is a controlled fenestra that preserves inner ear function while allowing secure placement of the prosthesis piston (akin to preparing the “actuator’s” receptacle optimally). From an engineering perspective, consistency in the fenestration size and location also standardizes the boundary conditions for the prosthesis, potentially contributing to more predictable acoustic outcomes [56,63].

5.4. Actuator Design Considerations: Coupling, Dynamics, and Durability

Viewing the stapes prosthesis as a biomedical micro-actuator provides a unifying framework to connect surgical factors with device performance. Like any actuator, the stapes piston’s efficacy is judged by how efficiently it converts input energy (incus vibrations) into output work (oval window stimulation). One crucial design principle is maximizing energy transfer—specifically, acoustic energy transmission into the cochlear fluid. Achieving a high transmission coefficient requires optimal impedance matching: the prosthesis should have appropriate stiffness and mass such that it does not dampen or distort the frequencies of interest. Titanium’s low acoustic impedance and Nitinol’s elastic compliance are thought to facilitate excellent high-frequency conduction. In contrast, a more pliant material (like fluoroplastic) might introduce slight damping (though within the small scales of a 4 mm piston, these effects are subtle). Interestingly, Huber et al. found that a tighter incus coupling improved high-frequency (>2 kHz) hearing results—likely because eliminating play at the joint ensures that even small, high-speed vibrations are faithfully transmitted without slippage. This underscores how mechanical stability and precision (i.e., minimizing unwanted degrees of freedom) enhance the actuator’s frequency response and fidelity [60].
Another key consideration is the coupling force at the incus interface. In engineering terms, this is analogous to preload in a bolted joint—sufficient force is needed to prevent micro-motion, but excessive force could cause material yielding or fatigue. The self-crimping Nitinol loop, by design, applies a controlled and reproducible force that remains within a safe range. In contrast, manual crimp forces are not directly measured during surgery; surgeons rely on tactile feedback, which can vary. Finite-element analyses have suggested that uneven or insufficient crimping can lead to a rocking motion of the piston or partial contact that degrades sound transfer efficiency. Thus, prostheses like the NiTiBOND or Clip piston, which standardize the incus contact, can be seen as improving the “interface engineering” of the actuator. Empirically, this translates to smaller ABG residuals and less inter-patient variability in outcomes. The clip piston’s ability to avoid incus strangulation also addresses the fatigue and longevity aspect: chronic cyclic loading on the incus is distributed over a broader area rather than focused on a crushed loop point. This may reduce the chance of osteolysis or piston loosening over time, as hinted by the near-zero long-term dislocation rates for clip pistons in clinical follow-up [55,56].
Material fatigue resistance is likewise critical given the prosthesis vibrates with every sound wave, on the order of billions of cycles over a patient’s lifetime. Fortunately, the displacement amplitudes are minuscule (micron-scale), and materials like titanium and Nitinol have high fatigue endurance limits in such regimes. There have been few reports of stapes prosthesis fracture or material degradation in vivo over decades of use; more commonly, any late hearing failure is due to biological factors (e.g., incus erosion or otosclerosis progression) rather than device breakage. Nitinol’s superelastic behavior actually confers remarkable fatigue life, an advantage for its dual role as actuator (motion transfer) and spring (self-crimping force) in the system. Biomechanical studies indicate that even under tight fixation, Nitinol loops maintain elastic compliance that buffers against peak stresses, potentially shielding the incus from shock loads (such as abrupt pressure changes or impacts). In summary, current stapes prostheses embody the ideals of actuator design: efficient energy conversion, secure yet non-destructive coupling, and long-term durability under cyclic load [60]. As shown in Table 4, the engineering design of modern stapes prostheses balances stiffness, compliance, and damping to replicate the natural stapes motion and optimize acoustic transmission.

5.5. Clinical Ergonomics and Patient Safety

From a clinical standpoint, the design of a stapes prosthesis must also facilitate ergonomic surgical handling and patient safety. Ergonomically, devices like the clip piston have proven their worth by simplifying the fine-motor tasks required in the confined middle-ear space. Surgeons in training especially benefit from these innovations—one randomized trial noted that the titanium Soft CliP piston may be safer for less experienced surgeons, mainly because it avoids the most error-prone step (manual crimping). In our own institutional experience, the learning curve for stapes surgery is noticeably smoother when using a clip-on device, as novices can focus on optimal prosthesis placement without worrying about mastering crimping techniques. Endoscopic ear surgery, which offers improved visualization but limits bimanual handling, further amplifies the value of streamlined prosthesis deployment. The clip piston’s one-handed attachment mechanism under endoscopic view exemplifies a design that adapts to surgical workflow needs [53].
Patient safety considerations include minimizing trauma to surrounding structures and reducing postoperative complications. Prosthesis design has responded to these needs in several ways. First, by refining the incus attachment as discussed, newer prostheses reduce the risk of incus injury (either immediate dislocation or delayed necrosis). Second, controlling the piston length and placement is crucial to avoid contact with the vestibule or undue pressure on the footplate. Many titanium prostheses come in precise incremental lengths and with calibrated measuring rods, allowing the surgeon to select an optimal length that just reaches the vestibule without excessive penetration. This attention to proper fit is another reason materials like titanium and Nitinol, which can be machined or laser-cut to high tolerances, are advantageous. Third, adjunctive techniques have emerged to secure the prosthesis and enhance safety—for instance, middle ear cement fixation can be used in revision cases to glue a loosened prosthesis in place or to reconstruct an eroded incus without exerting force. This bone cement (often hydroxyapatite-based) essentially acts as an artificial ligament or adhesive, and has been reported to stabilize prostheses in difficult cases while preserving hearing levels (an approach bridging surgical skill and bioengineering) [55].
In terms of hearing preservation, all efforts are made to protect the cochlea during stapes surgery. Using a laser to perform the fenestration (as discussed) avoids loud drilling noise, and many surgeons fill the vestibule with saline during laser firing to buffer any thermal effect. Additionally, the piston diameter has been studied in relation to safety and performance—a 0.4 mm vs. 0.6 mm piston can influence the delivered force per area on the oval window. A meta-analysis found that larger diameter pistons might slightly improve low-frequency hearing but could risk more inner ear disturbance. Thus, most surgeons choose around 0.5 mm diameter as a balance, unless specific audiological goals dictate otherwise. Ultimately, stapes prosthesis implantation has a high overall safety profile; large series report closure of ABG to within 10 dB in 80–95% of primary cases with <1% significant sensorineural loss. Careful prosthesis design and selection contribute to this success by mitigating avoidable hazards and complementing the surgeon’s technique [61,64,65].

5.6. Future Directions and Innovations

Looking forward, the field of stapes prosthetics is poised to integrate advanced technologies from both engineering and medicine [66]. Key areas of future innovation include:
Research is underway into active stapes prostheses that incorporate micro-actuators or piezoelectric elements to provide vibratory input to the inner ear. Such devices blur the line between surgical prosthesis and hearing aid, potentially amplifying sound or adjusting in real-time to optimize hearing. MEMS fabrication could enable ultra-miniature actuators or sensors on the prosthesis, for instance, to monitor coupling status or inner ear pressure. While still largely conceptual, a MEMS-based stapes actuator could, in theory, actively modulate stiffness or displacement, tailoring the frequency response to a patient’s needs [67]. Recent technological innovations in stapes prosthesis design and engineering are summarized in Table 5.
Active middle-ear prostheses, including piezoelectric and electromagnetic actuators, have been developed to directly drive the motion of the ossicular chain. Examples include the Vibrant Soundbridge (electromagnetic floating mass transducer coupled to the incus or stapes) and the Codacs system (an electromagnetic actuator mechanically coupled to a piston at the stapes footplate). These devices operate according to actuator principles but are not suitable for stapedotomy in otosclerosis, where the pathology is a purely conductive block of the stapes. Instead, their indications are moderate to severe sensorineural or mixed hearing loss, particularly in patients who do not benefit from conventional hearing aids. From an engineering standpoint, these systems are limited by several factors: (i) size constraints, since actuators must fit within the narrow middle-ear cavity, (ii) power requirements and the need for efficient transcutaneous energy transfer, (iii) biocompatibility and hermetic sealing for long-term implantation in a humid environment, (iv) magnetic resonance compatibility, and (v) long-term stability and drift prevention in actuator performance. While MEMS-based piezoelectric micro-actuators are being investigated for fully implantable hearing devices, they remain adjacent technologies with distinct indications and challenges, rather than a replacement for passive or SMA stapes pistons used in stapes surgery.
Although advanced technologies such as MEMS-based actuators, 3D-printed custom prostheses, and novel geometric designs represent exciting directions in stapes prosthesis development, these approaches remain largely experimental. The absence of long-term clinical data, regulatory approval, and standardized biocompatibility testing currently limits their use. Most published studies are preclinical or conducted on small laboratory or cadaveric models, without evidence of durability or long-term safety in vivo. Therefore, these emerging technologies should be clearly differentiated from clinically established devices—such as titanium, fluoroplastic, and Nitinol pistons—which have well-documented performance, biocompatibility, and decades of validated surgical outcomes. While experimental designs illustrate the potential for personalized or active hearing restoration, they should be regarded as complementary research tools rather than clinical alternatives to proven prostheses at present.

6. Conclusions

The evolution of stapes prostheses in the treatment of otosclerosis beautifully illustrates the synergy between surgical insight and engineering design. From the early Teflon-platinum piston of Shea to today’s titanium and Nitinol innovative prostheses, the focus has remained on improving sound conduction efficiency, surgical ease, and long-term reliability [68]. These devices have effectively evolved from passive replacements into finely tuned biomedical actuators that adhere to core design principles—optimal coupling, appropriate material properties, and durability—while operating in the delicate environment of the middle ear. Ongoing innovations, guided by both clinical feedback and advancements in actuator technology, promise to enhance outcomes further. As we bridge microsurgery with MEMS and embrace customization through 3D printing, future stapes prostheses will likely become even more precise, patient-specific, and integrated. This will not only improve hearing metrics and reduce complications, but also reinforce the paradigm of treating surgical implants as engineered actuators that marry form and function to rehabilitate human sensorineural performance. The continued collaboration between otologists and biomedical engineers will ensure that the next generation of stapes prostheses maximizes both the clinical benefits for patients and the engineering excellence that the field of actuators strives for [69].

Author Contributions

Conceptualization, L.-M.G. and V.Z.; methodology, L.-M.G., V.Z., R.H., A.R., I.-G.I., R.-O.A. and C.V.; validation, L.-M.G., V.Z., R.H., A.R., I.-G.I., R.-O.A. and C.V.; formal analysis, L.-M.G., V.Z., R.H., A.R., I.-G.I., R.-O.A. and C.V.; investigation, L.-M.G., V.Z., R.H., A.R., I.-G.I., R.-O.A. and C.V.; resources, L.-M.G., V.Z., R.H., A.R., I.-G.I., R.-O.A. and C.V.; data curation, L.-M.G., V.Z., R.H., A.R., I.-G.I., R.-O.A. and C.V.; writing—original draft preparation, L.-M.G., V.Z., R.H., A.R., I.-G.I., R.-O.A. and C.V.; writing—review and editing, L.-M.G., V.Z., R.H., A.R., I.-G.I., R.-O.A. and C.V.; visualization, L.-M.G., V.Z., R.H., A.R., I.-G.I., R.-O.A. and C.V.; supervision, L.-M.G., V.Z., R.H., A.R., I.-G.I., R.-O.A. and C.V.; project administration, L.-M.G., V.Z., R.H., A.R., I.-G.I., R.-O.A. and C.V.; funding acquisition, L.-M.G., V.Z., R.H., A.R., I.-G.I., R.-O.A. and C.V. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

The data supporting the findings of this study are available within the cited references. No new datasets were generated.

Acknowledgments

We acknowledge the assistance provided by Carol Davila University of Medicine and Pharmacy in facilitating access to academic resources. During the preparation of this manuscript, the authors used ChatGPT (OpenAI, GPT-5) to assist with the formatting of bibliographic references. The authors have carefully reviewed and edited the output and take full responsibility for the content of this publication.

Conflicts of Interest

The authors declare no conflicts of interest.

Abbreviations

The following abbreviations are used in this manuscript:
ABGAir–Bone Gap
CTComputed Tomography
EESEndoscopic Ear Surgery
HR-CTHigh-Resolution Computed Tomography
MEMSMicro-Electro-Mechanical Systems
SMAShape-Memory Alloys

References

  1. Markou, K.; Goudakos, J. An Overview of the Etiology of Otosclerosis. Eur. Arch. Oto-Rhino-Laryngol. 2009, 266, 25–35. [Google Scholar] [CrossRef]
  2. Menger, D.J.; Tange, R.A. The Aetiology of Otosclerosis: A Review of the Literature. Clin. Otolaryngol. Allied Sci. 2003, 28, 112–120. [Google Scholar] [CrossRef]
  3. Schrauwen, I.; Van Camp, G. The Etiology of Otosclerosis: A Combination of Genes and Environment. Laryngoscope 2009, 120, 1195–1202. [Google Scholar] [CrossRef]
  4. Stankovic, K.M.; McKenna, M.J. Current Research in Otosclerosis. Curr. Opin. Otolaryngol. Head Neck Surg. 2006, 14, 347–351. [Google Scholar] [CrossRef] [PubMed]
  5. Declau, F.; Van Spaendonck, M.; Timmermans, J.P.; Michaels, L.; Liang, J.; Qiu, J.P.; Van De Heyning, P. Prevalence of Histologic Otosclerosis: An Unbiased Temporal Bone Study in Caucasians. Adv. Otorhinolaryngol. 2007, 65, 6–16. [Google Scholar] [CrossRef]
  6. Batson, L.; Rizzolo, D. Otosclerosis: An Update on Diagnosis and Treatment. J. Am. Acad. Physician Assist. 2017, 30, 17–22. [Google Scholar] [CrossRef]
  7. Mann, W.J.; Amedee, R.G.; Fuerst, G.; Tabb, H.G. Hearing Loss as a Complication of Stapes Surgery. Otolaryngol. Head Neck Surg. 1998, 115, 324–328. [Google Scholar] [CrossRef]
  8. Bauchet St. Martin, M.; Rubinstein, E.N.; Hirsch, B.E. High-Frequency Sensorineural Hearing Loss after Stapedectomy. Otol. Neurotol. 2008, 29, 447–452. [Google Scholar] [CrossRef]
  9. Vincent, R.; Sperling, N.M.; Oates, J.; Jindal, M. Surgical Findings and Long-Term Hearing Results in 3050 Stapedotomies for Primary Otosclerosis: A Prospective Study with the Otology-Neurotology Database. Otol. Neurotol. 2006, 27, S25–S47. [Google Scholar] [CrossRef] [PubMed]
  10. Skarżyński, P.H.; Dziendziel, B.; Gos, E.; Włodarczyk, E.; Miaśkiewicz, B.; Rajchel, J.J.; Skarżyński, H. Prevalence and Severity of Tinnitus in Otosclerosis: Preliminary Findings from Validated Questionnaires. J. Int. Adv. Otol. 2019, 15, 277. [Google Scholar] [CrossRef] [PubMed]
  11. Just, T.; Guder, E.; Pau, H.W. Effect of the Stapedotomy Technique on Early Post-Operative Hearing Results—Preliminary Results. Auris Nasus Larynx 2012, 39, 383–386. [Google Scholar] [CrossRef]
  12. Bagger-Sjöbäck, D.; Strömbäck, K.; Hultcrantz, M.; Papatziamos, G.; Smeds, H.; Danckwardt-Lillieström, N.; Tideholm, B.; Johansson, A.; Hellström, S.; Hakizimana, P.; et al. High-Frequency Hearing, Tinnitus, and Patient Satisfaction with Stapedotomy: A Randomized Prospective Study. Sci. Rep. 2015, 5, 13341. [Google Scholar] [CrossRef]
  13. Purohit, B.; Hermans, R.; Op de beeck, K. Imaging in Otosclerosis: A Pictorial Review. Insights Imaging 2014, 5, 245–252. [Google Scholar] [CrossRef] [PubMed]
  14. Hannula, S.; Bloigu, R.; Majamaa, K.; Sorri, M.; Mäki-Torkko, E. Ear Diseases and Other Risk Factors for Hearing Impairment among Adults: An Epidemiological Study. Int. J. Audiol. 2012, 51, 833–840. [Google Scholar] [CrossRef]
  15. George, T.; Fakoya, A.O.; Bordoni, B. Anatomy, Head and Neck, Ear Ossicles; StatPearls: Petersburg, Russia, 2024. [Google Scholar]
  16. Sakano, H.; Harris, J.P. Revision Stapes Surgery. Curr. Otorhinolaryngol. Rep. 2022, 10, 40. [Google Scholar] [CrossRef]
  17. Zafar, N.; Hohman, M.H.; Khan, M.A. Otosclerosis; StatPearls: Petersburg, Russia, 2024. [Google Scholar]
  18. Foster, M.F.; Backous, D.D. Clinical Evaluation of the Patient with Otosclerosis. Otolaryngol. Clin. N. Am. 2018, 51, 319–326. [Google Scholar] [CrossRef] [PubMed]
  19. Claussen, A.D.; Gantz, B.J. Cochlear Implantation in Advanced Otosclerosis: Pitfalls and Successes. Curr. Otorhinolaryngol. Rep. 2022, 10, 49–57. [Google Scholar] [CrossRef]
  20. Quaranta, N.; Pontillo, V.; Dispenza, F. Advanced Otosclerosis. In Sensorineural Hearing Loss Pathophysiology, Diagnosis and Treatment; Nova Science Publishers, Inc.: Hauppauge, NY, USA, 2019; pp. 189–206. [Google Scholar] [CrossRef]
  21. Sevy, A.; Arriaga, M. The Stapes Prosthesis: Past, Present, and Future. Otolaryngol. Clin. N. Am. 2018, 51, 393–404. [Google Scholar] [CrossRef]
  22. Rotteveel, L.J.C.; Proops, D.W.; Ramsden, R.T.; Saeed, S.R.; Van Olphen, A.F.; Mylanus, E.A.M. Cochlear Implantation in 53 Patients with Otosclerosis: Demographics, Computed Tomographic Scanning, Surgery, and Complications. Otol. Neurotol. 2004, 25, 943–952. [Google Scholar] [CrossRef]
  23. Emami, H.; Amirzargar, B.; Nemati, Y.; Rahimi, N. Endoscopic Versus Microscopic Stapedotomy: A Randomized Clinical Trial. Laryngoscope 2024, 134, 2395–2400. [Google Scholar] [CrossRef]
  24. Laske, R.D.; Röösli, C.; Chatzimichalis, M.V.; Sim, J.H.; Huber, A.M. The Influence of Prosthesis Diameter in Stapes Surgery: A Meta-Analysis and Systematic Review of the Literature. Otol. Neurotol. 2011, 32, 520–528. [Google Scholar] [CrossRef] [PubMed]
  25. Nakkabi, I. Endoscopic Reverse Stapedotomy for Otosclerosis: A Technical Video Report. Cureus 2025, 17, e89914. [Google Scholar] [CrossRef] [PubMed]
  26. Shea, J.J. Thirty Years of Stapes Surgery. J. Laryngol. Otol. 1988, 102, 14–19. [Google Scholar] [CrossRef] [PubMed]
  27. Heywood, R.L.; Quick, M.E.; Atlas, M.D. Long-Term Audiometric and Clinical Outcomes Following Stapedectomy with the Shape Memory Nitinol Stapes Prosthesis. Otol. Neurotol. 2019, 40, 164–170. [Google Scholar] [CrossRef]
  28. Lavy, J.; Khalil, S. Five-Year Hearing Results with the Shape Memory Nitinol Stapes Prosthesis. Laryngoscope 2014, 124, 2591–2593. [Google Scholar] [CrossRef]
  29. Hornung, J.A.; Brase, C.; Zenk, J.; Iro, H. Results Obtained with a New Superelastic Nitinol Stapes Prosthesis in Stapes Surgery. Otol. Neurotol. 2011, 32, 1415–1421. [Google Scholar] [CrossRef]
  30. Gerlinger, I.; Bakó, P.; Piski, Z.; Révész, P.; Ráth, G.; Karosi, T.; Lujber, L. KTP Laser Stapedotomy with a Self-Crimping, Thermal Shape Memory Nitinol Piston: Follow-up Study Reporting Intermediate-Term Hearing. Eur. Arch. Oto-Rhino-Laryngol. 2014, 271, 3171–3177. [Google Scholar] [CrossRef]
  31. Quaranta, N.; Pontillo, V.; Dispenza, F. Advanced Otosclerosis: Stapes Surgery or Cochlear Implantation? Otolaryngol. Clin. N. Am. 2018, 51, 189–206. [Google Scholar] [CrossRef]
  32. Kraus, E.M.; Russell, G.B.; Allen, S.J.; Pearson, S.A. Long-Term Hearing Results of Endoskeletal Ossicular Reconstruction in Chronic Ears Using Titanium Prostheses Having a Helical Coil: Part 1—Kraus K-Helix Crown, Incus to Stapes. Otol. Neurotol. 2022, 43, 1056. [Google Scholar] [CrossRef]
  33. Urquiza, R.; López, J.; Gonzalez-Herrera, A.; Povedano, V.; Ciges, M. Tympanic-Ossicular Prostheses and MEMS Technology: Whats and Whys. Acta Otolaryngol. 2009, 129, 411–415. [Google Scholar] [CrossRef]
  34. Judd, R.T.; Gluth, M.B.; Gurgel, R.K.; Dornhoffer, J.L.; Carlson, M.L.; Isaacson, B.; Kuthubutheen, J.; Hui, N.J.; Quick, M.; Anderson, R.D.; et al. Impact of Modifiable Surgical Factors on Ossiculoplasty Outcomes After Controlling for Ear Environment Risk: A Multi-Institutional Study. Otol. Neurotol. 2025. [Google Scholar] [CrossRef]
  35. Molinari, G.; Emiliani, N.; Cercenelli, L.; Bortolani, B.; D’Azzeo, R.; Burato, A.; Presutti, L.; Molteni, G.; Marcelli, E. A Novel 3D Printed Multi-Material Simulator for Endoscopic Stapes Surgery: The “3D Stapes Trainer”. Laryngoscope 2025, 135, 3356–3363. [Google Scholar] [CrossRef]
  36. Prasad, K.C.; Karunasagar, A.; Anjali, P.K. Stapes Surgery Teaching Tool: A Simple and Stable Technique. Indian J. Otolaryngol. Head Neck Surg. 2018, 70, 450. [Google Scholar] [CrossRef]
  37. Tănase, N.V.; Hainăroșie, R.; Brîndușe, L.A.; Cobilinschi, C.; Dutu, M.; Corneci, D.; Zainea, V. Study of Two Sedative Protocols for Drug-Induced Sleep Endoscopy: Propofol versus Propofol-Remifentanil Combination, Delivered in Target-Controlled Infusion Mode. Medicina 2024, 60, 1123. [Google Scholar] [CrossRef]
  38. Tănase, N.V.; Hainăroșie, R.; Brîndușe, L.A.; Corneci, D.; Voiosu, C.; Rusescu, A.; Cobilinschi, C.; Stanciu Găvan, C.; Zainea, V. A Clinical Comparative Study of Schnider and Eleveld Pharmacokinetic–Pharmacodynamic Models for Propofol Target-Controlled Infusion Sedation in Drug-Induced Sleep Endoscopy. Biomedicines 2025, 13, 822. [Google Scholar] [CrossRef] [PubMed]
  39. Porowski, M.; Skarżyński, H.; Skarżyński, P.H. Stapedotomy in Congenital Stapes Ankylosis with Mobile Footplate: A Case Report. Am. J. Case Rep. 2022, 23, e936466-1. [Google Scholar] [CrossRef]
  40. Faramarzi, M.; Roosta, S.; Daneshian, N. Comparison between Fluoroplastic and Platinum/Titanium Piston in Stapedotomy: A Prospective, Randomized Clinical Study. J. Int. Adv. Otol. 2020, 16, 234–240. [Google Scholar] [CrossRef] [PubMed]
  41. Gjurić, M.; Rukavina, L. Evolution of Stapedectomy Prostheses over Time. Adv. Otorhinolaryngol. 2007, 65, 174–178. [Google Scholar] [CrossRef]
  42. Toscano, M.L.; Matz, O.; Hohman, M.H.; Shermetaro, C. Stapes Surgery for Otosclerosis. In Ent an Introduction and Practical Guide, 3rd ed.; CRC Press: Boca Raton, FL, USA, 2025; pp. 100–103. [Google Scholar] [CrossRef]
  43. Choudhury, N.; Kumar, G.; Krishnan, M.; Gatland, D.J. Atypical Incus Necrosis: A Case Report and Literature Review. J. Laryngol. Otol. 2008, 122, 1124–1126. [Google Scholar] [CrossRef] [PubMed]
  44. Gerlinger, I.; Tóth, M.; Lujber, L.; Szanyi, I.; Móricz, P.; Somogyvári, K.; Németh, A.; Ráth, G.; Pytel, J.; Mann, W. Necrosis of the Long Process of the Incus Following Stapes Surgery: New Anatomical Observations. Laryngoscope 2009, 119, 721–726. [Google Scholar] [CrossRef]
  45. Zenner, H.P.; Freitag, H.G.; Linti, C.; Steinhardt, U.; Jorge, J.R.; Preyer, S.; Mauz, P.S.; Sürth, M.; Planck, H.; Baumann, I.; et al. Acoustomechanical Properties of Open TTP® Titanium Middle Ear Prostheses. Hear. Res. 2004, 192, 36–46. [Google Scholar] [CrossRef] [PubMed]
  46. Zirkler, J.; Rahne, T.; Plontke, S.K. Stapeschirurgie Bei Otosklerose Mit Einer Neuen Titanprothese Mit Superelastischem Nitinol-Clip: Erste Erfahrungen. HNO 2016, 64, 111–116. [Google Scholar] [CrossRef] [PubMed]
  47. Wycherly, B.J.; Berkowitz, F.; Noone, A.-M.; Kim, H.J. Computed Tomography and Otosclerosis: A Practical Method to Correlate the Sites Affected to Hearing Loss. Ann. Otol. Rhinol. Laryngol. 2010, 119, 789–794. [Google Scholar] [CrossRef]
  48. Celik, T.; Erdur, O.; Gul, O.; Firat Koca, C.; Colpan, B. Comparison of Endoscopic and Microscopic Methods in Stapedotomy: A Retrospective Analysis. Eur. Arch. Otorhinolaryngol. 2023, 280, 589–595. [Google Scholar] [CrossRef] [PubMed]
  49. Moneir, W.; Abd El-Fattah, A.M.; Mahmoud, E.; Elshaer, M. Endoscopic Stapedotomy: Merits and Demerits. J. Otol. 2018, 13, 97–100. [Google Scholar] [CrossRef]
  50. Kuo, C.W.; Wu, H.M. Fully Endoscopic Laser Stapedotomy: Is It Comparable with Microscopic Surgery? Acta Otolaryngol. 2018, 138, 871–876. [Google Scholar] [CrossRef]
  51. Hildmann, H.; Sudhoff, H.; Bernal-Sprekelsen, M. Middle Ear Surgery; Springer Nature: London, UK, 2006; p. 195. [Google Scholar]
  52. Bartel, R.; Sanz, J.J.; Clemente, I.; Simonetti, G.; Viscacillas, G.; Palomino, L.; Asarta, I.; Lao, X. Endoscopic Stapes Surgery Outcomes and Complication Rates: A Systematic Review. Eur. Arch. Oto-Rhino-Laryngol. 2021, 278, 2673–2679. [Google Scholar] [CrossRef]
  53. Borghei, P.; Khorsandi-Ashtiani, M.T.; Heidari, R.; Saeidi, M.; Kouhi, A. Functional Outcomes of Stapes Surgery with Titanium and Teflon Prosthesis: Randomized Controlled Trial. J. Otolaryngol. Stud. 2019, 2, 101. [Google Scholar]
  54. Massey, B.L.; Kennedy, R.J.; Shelton, C. Stapedectomy Outcomes: Titanium versus Teflon Wire Prosthesis. Laryngoscope 2005, 115, 249–252. [Google Scholar] [CrossRef]
  55. Gargula, S.; Daval, M.; Lecoeuvre, A.; Ayache, D. Comparison of Dislocation Rates of Teflon and Titanium Stapes Prostheses: A Retrospective Survival Analysis on 855 Patients. J. Otolaryngol.—Head Neck Surg. 2023, 52, 52. [Google Scholar] [CrossRef]
  56. Cotulbea, S.; Marin, A.; Stefanescu, H. Stapedectomy and Stapedotomy. Functional Results after Insertion of Teflon, Wire-Teflon, and Titanium Stapes Pistons. Laryngo-Rhino-Otol. 2004, 83, 11_7. [Google Scholar] [CrossRef]
  57. Rajan, G.P.; Eikelboom, R.H.; Anandacoomaraswamy, K.S.; Atlas, M.D. In Vivo Performance of the Nitinol Shape-Memory Stapes Prosthesis during Hearing Restoration Surgery in Otosclerosis: A First Report. J. Biomed. Mater. Res. B Appl. Biomater. 2005, 72, 305–309. [Google Scholar] [CrossRef]
  58. Huber, A.M.; Veraguth, D.; Schmid, S.; Roth, T.; Eiber, A. Tight Stapes Prosthesis Fixation Leads to Better Functional Results in Otosclerosis Surgery. Otol. Neurotol. 2008, 29, 893–899. [Google Scholar] [CrossRef]
  59. Vasiljević, M.; Dragović, K.; Bržan, P.P.; Rebol, J. Comparison Between Titanium and Thermally Activated Prostheses in Stapes Surgery. Appl. Sci. 2025, 15, 8211. [Google Scholar] [CrossRef]
  60. Huber, A.M.; Ma, F.; Felix, H.; Linder, T. Stapes Prosthesis Attachment: The Effect of Crimping on Sound Transfer in Otosclerosis Surgery. Laryngoscope 2003, 113, 853–858. [Google Scholar] [CrossRef] [PubMed]
  61. Fang, L.; Lin, H.; Zhang, T.Y.; Tan, J. Laser versus Non-Laser Stapedotomy in Otosclerosis: A Systematic Review and Meta-Analysis. Auris Nasus Larynx 2014, 41, 337–342. [Google Scholar] [CrossRef]
  62. Shelton, C. Laser Stapedotomy. In Otologic Surgery; Elsevier: Amsterdam, The Netherlands, 2010; pp. 263–273. [Google Scholar] [CrossRef]
  63. Harvey, S.A. Stapedectomy: Laser versus Drill versus the Use of Pick Instruments. Oper. Tech. Otolaryngol.—Head Neck Surg. 2003, 14, 255–262. [Google Scholar] [CrossRef]
  64. Fang, L.; Xu, J.; Wang, W.; Huang, Y. Would Endoscopic Surgery Be the Gold Standard for Stapes Surgery in the Future? A Systematic Review and Meta-Analysis. Eur. Arch. Otorhinolaryngol. 2021, 278, 925–932. [Google Scholar] [CrossRef]
  65. Hudson, S.K.; Gurgel, R.K.; Shelton, C. Revision Stapedectomy with Bone Cement: Are Results Comparable to Those of Standard Techniques? Otol. Neurotol. 2014, 35, 1501–1503. [Google Scholar] [CrossRef] [PubMed]
  66. Lippy, W.H.; Burkey, J.M.; Schuring, A.G.; Berenholz, L.P. Comparison of Titanium and Robinson Stainless Steel Stapes Piston Prostheses. Otol. Neurotol. 2005, 26, 874–877. [Google Scholar] [CrossRef]
  67. Khatir, O.; Sidi Mohamed, F.; Albedah, A.; Hamada, A.; Pawłowski, Ł.; Sahli, A.; Abdelkader, B.; Boudjemaa, I.; Bouiadjra, B.B. Enhancing Middle Ear Implants: Study of Biocompatible Materials with Hydroxyapatite Coating. Mech. Adv. Mater. Struct. 2024, 32, 3793–3800. [Google Scholar] [CrossRef]
  68. Mangham, C.A. Nitinol-Teflon Stapes Prosthesis Improves Low-Frequency Hearing Results after Stapedotomy. Otol. Neurotol. 2010, 31, 1022–1026. [Google Scholar] [CrossRef] [PubMed]
  69. Roosli, C.; Schmid, P.; Huber, A.M. Biocompatibility of Nitinol Stapes Prosthesis. Otol. Neurotol. 2011, 32, 265–270. [Google Scholar] [CrossRef] [PubMed]
Actuators 14 00502 g001
Figure 1. Anatomy of the middle ear ossicles.
Figure 1. Anatomy of the middle ear ossicles.
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Figure 2. Schematic representation of sound transmission pathways in the middle ear after stapes prosthesis implantation.
Figure 2. Schematic representation of sound transmission pathways in the middle ear after stapes prosthesis implantation.
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Table 1. Comparison of stapes prosthesis types.
Table 1. Comparison of stapes prosthesis types.
ProsthesisMaterialCoupling
Mechanism		Key Design FeaturesAdvantagesLimitations/
Considerations
Actuators 14 00502 i001Robinson Bucket
Handle		TitaniumManual placement; piston-typeShaped like a bucket handle; one end attached to the incus, the other contacts the footplateStable positioning,
improved energy transfer		Requires precise manual handling; potential incus trauma if malpositioned
Actuators 14 00502 i002Wengen Clip-onTitaniumPre-crimped
clip-on loop		Snaps directly onto incus without crimpingReduces surgical time; minimizes manipulation of ossiclesRisk of loosening over time; dependent on loop tension
Actuators 14 00502 i003Szkarzinsky pistonTitaniumManual
placement		Thin shaft with a hook-shaped proximal end for attachment to the incus; cylindrical distal end for insertion into the oval windowSimple design, biocompatible materials, effective sound transmissionRequires precise placement; performance depends on correct sizing
Actuators 14 00502 i004Eclipse Nitinol PistonNitinol (SMA)Heat-activated self-crimpingShape memory alloy closes around incus when heatedEliminates manual crimping; consistent coupling forceRequires heat activation; risk of thermal injury if poorly controlled
Actuators 14 00502 i005Eclipse Flat Ribbon Nitinol PistonNitinol (SMA)Heat-activated self-crimpingWide ribbon loop distributes pressureGentle fixation; protects incus from focal necrosisLength changes possible after activation; careful sizing needed
Actuators 14 00502 i006Megerian Replacement
Prosthesis		Nitinol (SMA)Heat-activated multi-arm fixationSix tapered arms adapt to the contours of the incus, even if necrosedUseful in revision cases; secure adaptation to irregular anatomyBulkier design; requires more space in oval window niche
Actuators 14 00502 i007Eclipse Malleus PistonNitinol (SMA)Heat-activated self-crimpingOffset axis (15°) for malleus-to-footplate alignmentSuitable for
malleo-vestibulopexy
or revision cases		Limited use in primary cases;
higher technical demand
Actuators 14 00502 i008Bartels Bucket HandleTitaniumManual placement; adjustableAdjustable bucket diameter; stepped-down shaft; depth gaugeAdaptable to variable incus sizes;
useful with overhanging facial nerve		Requires precise
placement;
increased complexity
Table 2. Engineering and material properties influencing actuator performance in stapes prostheses.
Table 2. Engineering and material properties influencing actuator performance in stapes prostheses.
MaterialMechanical Parameters
Fluoroplastic (Teflon)Density ≈ 2.2 g/cm3; Young’s modulus ≈ 0.5 GPa; internal damping coefficient ≈ 0.03–0.05; transmission efficiency ~80–85% at 1–2 kHz.
TitaniumDensity ≈ 4.5 g/cm3; Young’s modulus ≈ 110 GPa; acoustic impedance ~27 × 106 kg/m2s; damping coefficient < 0.01; transmission efficiency > 90% up to 4 kHz.
Nitinol (NiTi SMA)Density ≈ 6.5 g/cm3; effective Young’s modulus ≈ 30–75 GPa (temperature-dependent); damping coefficient ≈ 0.02–0.03; mechanical coupling gain +2–3 dB vs. Teflon at >2 kHz.
Table 3. Comparison of stapes prosthesis materials and designs.
Table 3. Comparison of stapes prosthesis materials and designs.
Prosthesis Type (Material)Properties & Design
Advantages		Audiological Outcomes
(ABG Closure or Improvement)		Notable Considerations
Fluoroplastic
(Teflon)
Piston  with platinum/steel loop		Low-cost, inert, and lightweight polymer.
Often coupled via a manually crimped wire loop. Long history of biocompatible use.		~86% achieved post-operative ABG < 10 dB in one large series, comparable to titanium outcomes. Significant hearing gains were observed with the small-fenestra technique.Requires manual crimping onto the incus. Slight risk of long-term attachment loosening—e.g., ~3.5% incus dislocation by 2 years reported. Very low extrusion or rejection rates.
Titanium Piston  (loop or clip design)High-strength, low-density metal with low acoustic/mechanical impedance. Can be made thinner for better visualization
Available in manual loop and Soft CliP (spring-clip) versions that eliminate crimping.		Closure of ABG to <10 dB in ~71% of cases (vs. 86% for Teflon in one study) [54], though other trials show equivalent success (≤10 dB ABG in ~85–90%) [53]. Overall, hearing outcomes are statistically comparable to those of Teflon in meta-analyses [55].Secure incus coupling; one 855-patient study found 0% prosthesis dislocations in titanium vs. 3% in Teflon (p = 0.12) [55]. More expensive than fluoroplastics. Clip-on designs speed up surgery and avoid over-crimping, with improved speech discrimination noted [56].
Nitinol “SMart” Piston  (NiTi shape-memory)A SMA that self-crimps when activated by heat (e.g., laser). Provides consistent 360° incus loop compression without manual force, ensuring tight, uniform coupling—excellent fatigue resistance and biocompatibility; moderate stiffness closer to bone [57].Achieved long-term ABG ≈ 10 dB that remained stable over >10 years [28]. One trial showed significantly better mean ABG (8.0 dB vs. 11.6 dB) and a higher rate of ABG ≤ 10 dB (71% vs. 43%) with Nitinol vs. conventional pistons. Tight fixation yielded ~2.5 dB improved sound transfer intraoperatively, especially at high frequencies [58].No manual crimp is needed, simplifying placement and reducing variability [14]. Requires heat activation; necessary care to avoid thermal injury (e.g., to the chorda tympani nerve). Contains nickel (allergy considerations are minimal in practice). Clinical studies indicate no increase in complications and equivalent overall hearing outcomes to manual techniques when used appropriately [59].
Table 4. Core mechanical aspects and engineering rationale underlying stapes prosthesis function.
Table 4. Core mechanical aspects and engineering rationale underlying stapes prosthesis function.
Key AspectEngineering Principle/DescriptionDesign Implications
Coupling
Mechanism
(Incus Attachment)		Proper attachment of the prosthesis to the incus is essential for effective force transmission. Most pistons use a loop or crimp band that is manually fixed around the long (lenticular) process of the incus, creating a semi-rigid mechanical coupling. Excessive crimping can concentrate stress and risk necrosis of the incus, while insufficient crimping reduces acoustic efficiency. An optimal interface maintains firm contact with slight compliance, avoiding complete rigidity that could impair motion or increase dislocation risk. Recent actuator-inspired designs, such as clip pistons and self-crimping NiTi loops, aim to standardize attachment force and improve coupling reliability.Proper crimping ensures efficient transmission and mechanical stability. Controlled compliance reduces stress and enhances prosthesis longevity.
Piston–Footplate InterfaceThe distal piston tip (typically 0.4–0.8 mm in diameter) transmits vibrational energy to the cochlear fluids through the oval window. Efficient transfer requires a tight seal (using vein, fat, or fascia grafts) to prevent perilymph leakage. Piston diameter determines the balance between hydraulic pressure and volume displacement (Pascal’s law). Smaller pistons enhance low-frequency sensitivity but reduce high-frequency volume velocity; conversely, larger diameters improve high-frequency transmission but increase vestibular load. Finite-element and in vitro studies confirm that 0.4 mm pistons produce ~14 dB loss at high frequencies compared to the natural stapes footplate area (3.2 mm2).Optimal piston size (0.4–0.6 mm) achieves a balance between frequency response and mechanical safety.
Clinical evidence supports improved hearing with 0.6 mm pistons in some cases.
Actuator Behavior and DampingAs a passive actuator, the prosthesis must transmit vibrations efficiently across the auditory frequency range without adding significant mass or stiffness. Ideal designs contribute ~0.1–0.2 g additional mass and maintain resonance above the auditory band.
Incorporating internal damping (e.g., PTFE segments or NiTi loops) can suppress unwanted resonant peaks and stabilize the transfer function. The overall energy pathway—incus motion → prosthesis vibration → perilymph displacement—remains consistent, but mechanical efficiency depends on precise alignment and angle of insertion. The piston should extend approximately 0.5 mm into the vestibule to ensure stable engagement without trauma.		Controlled damping and correct alignment enhance actuator stability and vibration fidelity. Proper piston length and orientation prevent energy loss and damage to the inner ear.
Summary InsightStapes prosthesis mechanics reflect actuator design trade-offs between stiffness, compliance, and damping. Secure coupling and well-calibrated flexibility optimize sound transmission while preventing structural fatigue or biological damage. The engineering goal is to emulate the natural stapes’ piston-like action, efficiently converting incus oscillation into perilymph fluid displacement.Well-engineered compliance and damping improve both mechanical performance and clinical outcomes.
Table 5. Emerging innovations in stapes prosthesis design: principles, current challenges, and clinical–engineering impact.
Table 5. Emerging innovations in stapes prosthesis design: principles, current challenges, and clinical–engineering impact.
InnovationPrinciple and DescriptionCurrent Status and
Challenges		Clinical/Engineering
Impact
MEMS-Based
Piezoelectric Micro-Actuators		Integration of piezoelectric micro-actuators or sensors within middle-ear prostheses to actively modulate stiffness or displacement in response to sound input. These micro-electro-mechanical systems (MEMS) aim to enhance hearing through real-time vibration control dynamically.Currently in experimental development for fully implantable hearing devices; not yet applicable to otosclerosis surgery. Challenges include miniaturization, power supply, biocompatibility, and long-term stability in the humid middle-ear environment.Represents a potential future shift from passive to active actuation, enabling adaptive hearing enhancement, self-monitoring, and feedback-controlled motion. However, remains a complementary rather than replacement technology.
3D-Printed Custom
Prostheses		Additive manufacturing (e.g., titanium alloy powder-bed fusion)
enables personalized stapes or ossicular prostheses based on HR-CT imaging. Each implant can be tailored to the patient’s anatomy (length, angulation, coupling geometry). 		Laboratory feasibility has been demonstrated; however, regulatory validation and long-term biocompatibility data are still limited. Integration of porous or textured surfaces may promote tissue adhesion and biological fixation.Enables patient-specific prosthesis design and eliminates the need for intraoperative trimming. Offers ergonomic and acoustic advantages through perfect fit and potential tissue integration.
Novel
Prosthesis
Designs		Innovative geometries beyond the classical piston model, including bucket-handle and malleus-anchoring (malleovestibular) prostheses. These create alternative mechanical pathways for energy transmission to the inner ear, specifically the cochlea.Early prototypes tested in revision and complex cases; still under evaluation for consistent acoustic performance and surgical handling. Require precise positioning and may have higher technical demands.Expands applicability to complex or revision surgeries (e.g., incus erosion, footplate damage) [34,68]
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MDPI and ACS Style

Gherasie, L.-M.; Zainea, V.; Hainarosie, R.; Rusescu, A.; Ionita, I.-G.; Alius, R.-O.; Voiosu, C. Stapes Prostheses in Otosclerosis Surgery: Materials, Design Innovations, and Future Perspectives. Actuators 2025, 14, 502. https://doi.org/10.3390/act14100502

AMA Style

Gherasie L-M, Zainea V, Hainarosie R, Rusescu A, Ionita I-G, Alius R-O, Voiosu C. Stapes Prostheses in Otosclerosis Surgery: Materials, Design Innovations, and Future Perspectives. Actuators. 2025; 14(10):502. https://doi.org/10.3390/act14100502

Chicago/Turabian Style

Gherasie, Luana-Maria, Viorel Zainea, Razvan Hainarosie, Andreea Rusescu, Irina-Gabriela Ionita, Ruxandra-Oana Alius, and Catalina Voiosu. 2025. "Stapes Prostheses in Otosclerosis Surgery: Materials, Design Innovations, and Future Perspectives" Actuators 14, no. 10: 502. https://doi.org/10.3390/act14100502

APA Style

Gherasie, L.-M., Zainea, V., Hainarosie, R., Rusescu, A., Ionita, I.-G., Alius, R.-O., & Voiosu, C. (2025). Stapes Prostheses in Otosclerosis Surgery: Materials, Design Innovations, and Future Perspectives. Actuators, 14(10), 502. https://doi.org/10.3390/act14100502

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