Design Of Implants Research Articles

Influence of obesity on load-transfer mechanism, contact mechanics, and longevity of cemented acetabular cup

ObjectiveThis investigation aimed to assess the impact of obesity on the load-transfer mechanism, longevity, and contact mechanics of cemented acetabular cups. MethodsThree obesity scenarios were considered: obese case-I (100–110 kg), obese case-II (120–130 kg), and obese case-III (140–150 kg). Utilising six finite element models, the effects of different bodyweights on load transfer, contact mechanics, and cup longevity during normal walking conditions were assessed. Muscle forces and hip joint reaction forces were adjusted and linearly calibrated based on obesity cases. ResultsElevated stresses in cortical and cancellous bones, as well as the cement mantle, were observed in obese cases, suggesting a heightened risk of loosening and failure of the cemented fixation of the acetabular cup. Additionally, increased contact pressure and micromotion between articulating surfaces were noted in obese individuals, with a gradual escalation from obese case-I to obese case-III. ConclusionsThese findings highlight the significant negative impact of obesity on the performance of cemented acetabular cups, emphasizing the importance of considering bodyweight variations in the design and assessment of orthopaedic implants for optimal functionality and durability.

Evaluating the effect of functionally graded materials on bone remodeling around dental implants

ObjectivesThis study evaluates the potential for osseointegration and remodeling of customized dental implants made from Titanium-Hydroxyapatite Functionally Graded Material (Ti-HAP FGM) with optimized geometry, using the finite element method (FEM). MethodsThe study utilized CT scan images to model and assemble various geometrical designs of dental implants in a mandibular slice. The mechanical properties of Ti-HAP FGMs were computed by varying volume fractions (VF) of hydroxyapatite (0–20%), and a bone remodeling algorithm was used to evaluate the biomechanical characteristics of the ultimate bone configuration in the peri-implant tissue. ResultsThe findings of the FEA reveal that osseointegration improves with changes in the density and mechanical properties of the bone surrounding Ti-HAP implants, which are influenced by the varying VF of hydroxyapatite in the FGM. SignificanceIncreasing the hydroxyapatite fraction improves osseointegration, and appropriate length and diameter selection of Ti-HAP dental implants contribute to their stability and longevity.

The effect of different alignment strategies on trochlear orientation after total knee arthroplasty.

When planning and delivering total knee arthroplasty (TKA), there are multiple coronal alignment strategies such as functional alignment (FA), kinematic alignment (KA), mechanical and adjusted mechanical alignment (MA, aMA). Recent three-dimensional and robotic-assisted surgery (RAS) studies have demonstrated that KA potentially better restores the trochlear anatomy than MA. The purpose of this study was to compare the restoration of the native trochlear orientation in patients undergoing RAS TKA using fourdifferent alignment strategies. It was hypothesised that FA would result in the lowest number of outliers. This is a prospective study of 200 patients undergoing RAS-TKA with a single implant. All patients were analysed for MA and KA prebalancing, and 157 patients received aMA and 43 patients FA with intraoperative balancing. Preoperative transverse computed tomography scans were used to determine the posterior condylar axis (PCA), lateral trochlear inclination (LTI) angle, sulcus angle (SA) and anterior trochlear line (ATL) angle. Implant measurements were obtained using a photographic analysis. Intraoperative software data combined with implant data and preoperative measurements were used to calculate the differences. Outliers were defined as ≥3° of alteration. Trochlea dysplasia was defined as LTI < 12°. Native transepicondylar PCA had a median of 2°, LTI 18°, SA 137°, ATL 4°. LTI outliers were observed in 47%-60% of cases, with KA < FA < aMA < MA. For ATL, the range of outliers was 40.5%-85%, KA < FA < aMA < MA. SA produced 81% of outliers. Of all median angle values, only LTI when using KA was not significantly altered compared to the native knee. There is a significant alteration of trochlear orientation after TKA, regardless of the alignment strategy used. KA produced the lowest, but a substantial, number of outliers. The uniform design of implants causes the surgeon to compromise on balance in flexion versus trochlear position. The clinical relevance of this compromise requires further clinical investigations. Level II, prospective cohort study.

Electron beam powder bed fusion additive manufacturing of Ti6Al4V alloy lattice structures: orientation-dependent compressive strength and fracture behavior

High porosity level lattice structures made using electron beam powder bed fusion additive manufacturing (EBPBF) need to be sufficiently strong and the understanding of the mechanical anisotropy of the structures is important for the design of orthopedic implants. In this work, the combined effects of loading direction (LD), cell orientation, and strut irregularity associated with EBPBF of Ti6Al4V alloy lattices on the mechanical behavior of the lattices under compressive loading have been studied. Three groups of simple cubic unit cell lattices were EBPBF made, compressively tested, and examined. The three groups were [001]//LD lattices, [011]//LD lattices, and [111]//LD lattices. Simulation has also been conducted. Yield strength (σy-L) values of all lattices determined experimentally have been found to be comparable to the values predicted by simulation; thus, EBPBF surface defects do not affect σy-L. σy-L of [001]//LD lattices is 1.8–2.0 times higher than those of [011]//LD and [111]//LD lattices. The reason for this is shown to be due to the high stress concentrations in non-[001]//LD samples, causing yielding at low loading levels. Furthermore, plastic strain (εp) at ultimate compression strength of [001]//LD samples has been determined to be 4–6 times higher than the values of non-[001]//LD samples. Examining the tested samples has shown cracks more readily propagating from EBPBF micro-notches in non-[001]//LD samples, resulting in low εp.

Hip Implant Design using Stainless Steel 316L for Enhanced Stability and Patient Comfort

In a hip replacement procedure, the damaged bone and cartilage are removed and replaced with an artificial component known as prosthesis. Despite advancements in implant sterilization, design, fixation techniques, and the introduction of robotic surgery, a persistent challenge is to identify an optimal, patient-specific hip implant that meets individual criteria. The primary objective of the proposed study was to create a highly accurate patient-specific hip implant by standardizing the existing design. The secondary objective aimed to demonstrate the superiority of a customized design over a conventional one. Geometric measurements of the hip were extracted from CT scans using MIMICS 20.0 software, and the implant design was developed using SolidWorks. Finite Element Analysis (FEA) was employed for meshing and analyzing the planned implant. Comparative research through FEA analysis indicated that a customized implant made from SSL 13 material outperformed the standard implant, showcasing its suitability for the patients studied.

Personalized prediction of speech intelligibility for hearing-impaired listeners using a physiological model of the human ear

Due to the problems of occlusion effect, insufficient high-frequency gain, and acoustic feedback in conventional hearing aids, middle ear implants as a new type of hearing device have become an important compensatory tool for the treatment of patients with moderate to severe hearing loss. However, current speech intelligibility (SI) models are inadequate for predicting SI in hearing-impaired (HI) listeners after middle ear implants implantation. Moreover, the compensatory performance of middle ear implants before implantation remains unknown due to the invasive nature of the surgical procedure. Therefore, this study proposes a novel SI model that can predict the compensatory effects on SI after middle ear implants implantation. The model combines a physiologically nonlinear auditory preprocessing front-end with a short-term correlation analysis back-end. In normal-hearing (NH) listeners, the model accurately predicts speech reception thresholds (SRTs) and masking release under steady-state and fluctuating noise conditions. For HI listeners, the model modifies the parameters of outer hair cells and inner hair cells in the preprocessing front-end to simulate the patient’s audiogram, achieving excellent predictive capability for HI listeners’ test data. Overall, the proposed SI model can be used for the optimal design and algorithm fitting of middle ear implants tailored to patients with varying degrees of hearing loss, offering valuable insights for the clinical treatment of HI listeners.

410 Improving Patient Outcomes through Design of Biodegradable Implants for Long Bone Fractures

OBJECTIVES/GOALS: Current long bone fracture standard of care uses inert metal intramedullary nails (IMN), 10x stiffer than femur cortex. Consequent “stress-shielding” bone loss sees &gt;5% of patients needing revision surgery. To improve nonunion healing, we develop automated design optimization methods for biodegradable Mg alloy IMNs to control local reloading. METHODS/STUDY POPULATION: Finite element analysis (FEA) is performed on 3D bone-IMN representations to establish this study’s baseline strain states for existing inert IMN geometries within QCT-informed femoral models under simulated biomechanical loading. FEA with Mg alloy properties for same IMN designs simulate transient IMN material loss through discrete time-step models with experimental in vivo Mg corrosion rates and strain-based bone density evolution using remodeling algorithms from literature. Transient stability and strength metrics, fracture zone stress profiles under gradual reloading and manufacturing constraints are formulated through gradient-based sensitivity analysis into a topology optimization framework (TOF) incorporating a reaction-diffusion degradation model to generate IMN topologies. RESULTS/ANTICIPATED RESULTS: TOF designs for Mg alloy IMNs with transient allowable strength constraints, using safety factors to prevent IMN failure, demonstrate higher compliance than standard inert IMNs with mechanical properties closer to native cortical bone. The biodegradation model within the TOF, informed by corrosion behavior from bone-IMN FEA study, predicts how potential design evolutions affect transient strain states of the system. Thus, local fracture region stress states are controlled by the algorithm optimizing for desirable transient stiffness profiles based on a minimum variance objective of fracture zone stress compared to a target bone stress profile. Optimized IMNs with porous, high surface area features achieve 50% decrease in IMN stiffness over 6 months recovery time and complete in vivo degradation in 24 months. DISCUSSION/SIGNIFICANCE: Our TOF reduces “stress-shielding” effects via design for controlled IMN biodegradation to gradually increase fracture zone loading, stimulating remodeling and reducing current risk of post-operative fracture and surgical removal in ~15k cases/yr. in the U.S. In vitro mechanical and in vivo clinical testing is required to validate design results.

Tibial Slope Is Not Associated With Implant Migration Following Cemented Total Knee Arthroplasty With a Single Implant Design

BackgroundThe influence of tibial slope on tibial component migration following total knee arthroplasty has not been widely studied, although excessive posterior slope has been implicated in some failures. As implant micromotion measured with radiostereometric analysis can indicate successful fixation, the purpose of this study was to determine the associations between tibial slope, tibial component migration, and inducible displacement. MethodsRadiostereometric analyses at 6 visits over 2 years quantified implant migration for 200 cemented total knee arthroplasties. Longitudinal data analysis examined the influence of postoperative tibial slope on implant migration (overall maximum total point motion (MTPM) migration and anterior–posterior tilt migration), accounting for age, sex, and body mass index. The correlations of tibial slope with 1-year migration, continuous migration, and inducible displacements were also examined. Additionally, the amount of change in slope was compared to migration. ResultsThe mean posterior tibial slope was 8.0° (standard deviation [SD] 3.8°) preoperatively and 3.8° (SD 3.1°) postoperatively, with a mean reduction in slope of 4.2° (SD 4.7°). Postoperative tibial slope (range 14.0° posterior slope to 3.4° anterior slope) was not associated with longitudinal overall migration (P = .671) or anterior–posterior tilt migration (P = .704). There was no association between postoperative tibial slope and migration at 1 year postoperatively (P = .441 for MTPM migration, P = .570 for tilt migration), change in migration from 1 to 2 years (P = .951), or inducible displacement (P = .970 MTPM, P = .730 tilt). The amount of change in tibial slope was also not associated with migration or inducible displacement. ConclusionsResidual and change in postoperative tibial slope were not associated with implant migration into tilt or overall migration, or inducible displacement for a single implant design. These findings support positioning tibial implants in a range of slopes, which may support patient-specific approaches to implant alignment.

Characterization of Pig Vertebrae under Axial Compression Integrating Radiomic Techniques and Finite Element Analysis

The study of pig bones, due to their similarity with human tissues, has facilitated the development of technological tools that help in the diagnosis of diseases and injuries affecting the skeletal system. Radiomic techniques involving medical image segmentation, along with finite element analysis, enable the detailed study of bone damage, loss of density, and mechanical functionality, which is a significant advancement in personalized medicine. This study involves conducting experimental tests on L3–L6 pig vertebrae under axial loading conditions. The mechanical properties of these vertebrae are analyzed, and the maximum loads they can sustain within the elastic range are determined. Additionally, three-dimensional models are generated by segmenting computerized axial tomography (CAT) scans of the vertebrae. Digital shadows of the vertebrae are constructed by assigning an anisotropic material model to the segmented geometries. Then, finite element analysis is performed to evaluate the elastic characteristics, stress, and displacement. The findings from the experimental data are then compared to the numerical model, revealing a strong correlation with differences of less than 0.8% in elastic modulus and 1.53% in displacement. The proposed methodology offers valuable support in achieving more accurate medical outcomes, employing models that serve as a diagnostic reference. Moreover, accurate bone modeling using finite element analysis provides valuable information to understand how implants interact with the surrounding bone tissue. This information is useful in guiding the design and optimization of implants, enabling the creation of safer, more durable, and biocompatible medical devices that promote optimal osseointegration and healing in the patient.

Asymmetric Implant Design for Posterolateral Overhang of the Femoral Component in Total Knee Arthroplasty: A Retrospective Computed Tomography-Based Study.

Introduction During total knee arthroplasty (TKA), also referred to as total knee replacement (TKR), patients may experience pain in the posterolateral knee. One possible cause is the impingement between the popliteus tendon and the femoral components. The purpose of this study was to analyze the posterolateral overhang of the femoral component using 3D template software. Methods Preoperative CT scan images of 50 knees (11 males and 39 females) with osteoarthritis of grade 2 or lower according to the Kellgren-Lawrence classification were analyzed. The mean age of the subjects was 73.8±7.6 years (range 52-84 years). The Athena (Soft Cube Co., Ltd., Osaka, Japan) knee 3D image-matching software was used for the analysis. The positions of the two femoral components (symmetrical and asymmetrical) were simulated. In the coronal plane, the component overhang was measured between the resected lateral part of the posterior femur and its corresponding component size, and the two designs were compared in three zones (proximal, central, and distal). Results In the simulated femoral component, the asymmetric design had a significantly lower component overhang than the symmetric design in the proximal zone of the lateral posterior condyle (0.2±1.9 mm vs. 3.5±1.6 mm, p<0.01). In the proximal zone, significant overhang (>3 mm) was observed in 30 knees (60.0%) with the symmetric design, but only three knees (6.0%) had asymmetric designs (p<0.01). Conclusions The posterolateral overhang of the lateral posterior condyle occurs when a symmetrical prosthesis is used. The use of an asymmetric implant with a small, rounded proximal portion of the lateral posterior condyle improves this overhang and is expected to decrease problems such as impingement of the popliteus tendon and improve patient satisfaction.

Muscle and joint mechanics during maximum force biting following total temporomandibular joint replacement surgery

Total temporomandibular joint replacement (TMJR) surgery is the established treatment for severe temporomandibular joint disorders. While TMJR surgery is known to increase mouth-opening capacity, reduce pain and improve quality of life, little is known about post-surgical jaw function during activities of daily living such as biting and chewing. The aim of this study was to use subject-specific 3D bite force measurements to evaluate the magnitude and direction of joint loading in unilateral total TMJR patients and compare these data to those in healthy control subjects. An optoelectronic tracking system was used to measure jaw kinematics while biting a rubber sample for 5 unilateral total TMJR patients and 8 controls. Finite element simulations driven by the measured kinematics were employed to calculate the resultant bite force generated when compressing the rubber between teeth during biting tasks. Subject-specific musculoskeletal models were subsequently used to calculate muscle and TMJ loading. Unilateral total TMJR patients generated a bite force of 249.6 ± 24.4 N and 164.2 ± 62.3 N when biting on the contralateral and ipsilateral molars, respectively. In contrast, controls generated a bite force of 317.1 ± 206.6 N. Unilateral total TMJR patients biting on the contralateral molars had a significantly higher lateral TMJ force direction (median difference: 63.6°, p = 0.028) and a significantly lower ratio of working TMJ force to bite force (median difference: 0.17, p = 0.049) than controls. Results of this study may guide TMJ prosthesis design and evaluation of dental implants.

Effects of heterogeneous surface characteristics on hemocompatibility and cytocompatibility of bacterial nanocellulose

The surface properties of cardiovascular biomaterials play a critical role in their biological responses. Although bacterial nanocellulose (BNC) materials have exhibited potential applications in cardiovascular implants, the impact of their surface characteristics on biocompatibility has rarely been studied. This study investigated the mechanism for the biocompatibility induced by the physicochemical properties of both sides of BNC. With greater wettability and smoothness, the upper BNC surface reduced protein adsorption by 25 % compared with the lower surface. This prolonged the plasma re-calcification time by 14 % in venous blood. Further, compared with the lower BNC surface, the upper BNC surface prolonged the activated partial thromboplastin time by 5 % and 4 % in arterial and venous blood, respectively. Moreover, the lower BNC surface with lesser rigidity, higher roughness, and sparser fiber structure promoted cell adhesion. The lower BNC surface enhanced the proliferation rate of L929 and HUVECs cells by 15 % and 13 %, respectively, compared with the upper BNC surface. With lesser stiffness, the lower BNC surface upregulated the expressions of CD31 and eNOS while down-regulating the ICAM-1 expression - This promoted the proliferation of HUVECs. The findings of this study will provide valuable insights into the design of blood contact materials and cardiovascular implants.

A statistical analysis of human talar shape and bone density distribution.

The shape of the talus, its internal structure, and its mechanical properties are important in determining talar behavior during loading, which may be significant for the design of surgical tools and implants. Although recent studies using statistical shape modeling have described quantitative talar external shape variation, no similar quantitative study exists to describe the density distribution of internal talar structure. The goal of this study is to quantify statistical variation in talar shape and density to benefit the design of talar implants. To this end, weight-bearing computed tomography (CT) scans of the ankle were collected in neutral, bilateral standing posture, and three-dimensional models were generated for each talus. Local density derived from the Hounsfield unit of each CT voxel was extracted. A weighted spherical harmonic analysis was performed to quantify the talar external shape. One hundred and seventy-nine volumes of interest were placed in the same relative position within each talus to quantify the talar density. Additionally, a finite element analysis (FEA) was conducted on a talus with both heterogeneous and homogeneous material properties to observe the effect of these properties on the stress and strain response. Significant differences were found in the talar density in sex and age, as well as in the stress and strain response between homogeneous and heterogeneous FEA. These differences show the importance of considering heterogeneity when examining the load response of tarsal bones.

Surface slicing and toolpath planning for in-situ bioprinting of skin implants

Bioprinting has emerged as a successful method for fabricating engineered tissue implants, offering great potential for wound healing applications. This study focuses on an advanced surface-based slicing approach aimed at designing a skin implant specifically for in-situ bioprinting. The slicing step plays a crucial role in determining the layering arrangement of the tissue during printing. By utilizing surface slicing, a significant shift from planar fabrication methods is achieved. The developed methodology involves the utilization of a customized robotic printer to deliver biomaterials. A multilayer slicing and toolpath generation procedure is presented, enabling the fabrication of skin implants that incorporate the epidermal, dermal, and hypodermal layers. One notable advantage of using the approximate representation of the native wound site surface as the slicing surface is the avoidance of planar printing effects such as staircasing. This surface slicing method allows for the design of non-planar and ultra-thin skin implants, ensuring a higher degree of geometric match between the implant and the wound interface. Furthermore, the proposed methodology demonstrates superior surface quality of the in-situ bio-printed implant on a hand model, validating its ability to create toolpaths on implants with complex surfaces.

One-piece versus two-piece ceramic dental implants

In this narrative review, a structured comparison between one-piece and two-piece zirconia dental implants is highlighted. Ceramic dental implants have long ceased to be hype; on the contrary, they can offer a significant addition to the daily dental implant practice. Not only do their favourable aesthetics play a significant role, but their ability to work completely metal-free is of added value, particularly for patients with a proven allergy for Grade 5 titanium. Furthermore, the fact that peri-implantitis seems to appear only incidentally is an important supporting argument for their use as well. Whereas the original design of zirconia implants was formerly always of a one-piece/one-phase structure (the monobloc design), nowadays, two-piece/two-phase designs (the so-called hybrid concept) are also widely utilised to restore missing teeth. Both concepts have advantages and disadvantages, scientifically as well as clinically.For this paper, relevant articles from the recent scientific literature were selected from PubMed. The aim was to identify and summarise what has previously been published on one-piece versus two-piece ceramic implants. This article will compare the benefits and drawbacks of one-piece versus two-piece ceramic implants based on clinical- (design, different sizes, surgical protocol, prosthetics), scientific- (loading and eventual complications) and patient-related (costs and long-time perspectives) criteria.

Biomechanical characteristics of Sanders type II and III calcaneal fractures fixed by open reduction and internal fixation and percutaneous minimally invasive fixation

BackgroundThis work investigated the differences in the biomechanical properties of open reduction and internal fixation (ORIF) and percutaneous minimally invasive fixation (PMIF) for the fixation of calcaneal fractures (Sanders type II and III calcaneal fractures as examples) through finite element analysis.MethodsBased on CT images of the human foot and ankle, according to the principle of three-point fixation, namely the sustentaculum tali, the anterior process and the calcaneal tuberosity were fixed. Three-dimensional finite element models of Sanders type II and III calcaneal fractures fixed by ORIF and PMIF were established. The proximal surfaces of the tibia, fibula and soft tissue were constrained, and ground reaction force and Achilles tendon force loads were added to simulate balanced standing.ResultsThe maximum stress was 80.54, 211.59 and 113.88 MPa for the calcaneus, screws and plates in the ORIF group and 70.02 and 209.46 MPa for the calcaneus and screws in the PMIF group, respectively; the maximum displacement was 0.26, 0.21 and 0.12 mm for the calcaneus, screws and plates in the ORIF group and 0.20 and 0.14 mm for the calcaneus and screws in the PMIF group, respectively. The values obtained from the simulation were within the permissible stress and elastic deformation range of the materials used in the model, and there was no significant stress concentration. The maximum stress and displacement of the calcaneus and implants were slightly lower in the PMIF group than in the ORIF group when fixing Sanders type II and III calcaneal fractures.ConclusionsThis study may provide a reference for optimising the design of implants, the development of individualised preoperative plans and the choice of clinical surgical approach.

Effect of Surgical Technique, Implant Design, and Time of Examination on Contact Kinematics: A Study of Bicruciate-Stabilized and Posterior-Stabilized Total Knee Arthroplasty

BackgroundBicruciate-stabilized (BCS) total knee arthroplasty (TKA) designs attempt to approximate natural knee mechanics. Multiple surgical techniques, including gap balancing (GB) and measured resection (MR), have been developed to provide optimal implant positioning and soft-tissue balance. The goal of this study was to determine the effect of surgical technique on BCS TKA contact kinematics. Secondary goals included investigating the change of kinematics over time and comparing BCS TKA kinematics to a posterior-stabilized (PS) design. MethodsThe study included the BCS-GB, BCS-MR, and PS-MR groups. The BCS-GB and BCS-MR groups underwent weight-bearing radiostereometric analysis for multiple knee flexion angles at 3 months and 1 year postoperatively, whereas the PS-MR group was imaged at 1 year postoperatively. The medial and lateral contact kinematics were determined from implant poses. ResultsThere were no differences in BCS TKA kinematics between the GB and MR techniques. There were differences in the mid-flexion ranges when comparing the 3-month and 1-year kinematics of the BCS design; however, they were less than 1.5 mm. Differences existed between the kinematics of the BCS and PS designs at all flexion angles for the medial condyle (P < .0006) and at 0° of flexion on the lateral condyle (P < .0001). ConclusionsContact kinematics for a BCS design were similar for both surgical techniques, suggesting both are appropriate for this design. Small, likely clinically insignificant differences were found between 3-month and 1-year kinematics. The BCS TKA kinematics differed from the PS design; however, it is unclear whether these differences improve clinical outcomes.

Exploring tribology and material contact science in spine surgery: implications for implant design.

Tribology, an interdisciplinary field concerned with the science of interactions between surfaces in contact and their relative motion, plays a well-established role in the design of orthopedic implants, such as knee and hip replacements. However, its applications in spine surgery have received comparatively less attention in the literature. Understanding tribology is pivotal in elucidating the intricate interactions between metal, polymer, and ceramic components, as well as their interplay with the native human bone. Numerous studies have demonstrated that optimizing tribological factors is key to enhancing the longevity of joints and implants while simultaneously reducing complications and the need for revision surgeries in both arthroplasty and spinal fusion procedures. With an ever-growing and diverse array of spinal implant devices hitting the market for static and dynamic stabilization of the spine, it is important to consider how each of these devices optimizes these parameters and what factors may be inadequately addressed by currently available technology and methods. In this comprehensive review, the authors' objectives were twofold: 1) delineate the unique challenges encountered in spine surgery that could be addressed through optimization of tribological parameters; and 2) summarize current innovations and products within spine surgery that look to optimize tribological parameters and highlight new avenues for implant design and research.

Anterior Segment Biometry During Accommodation After Posterior Chamber Phakic Implantable Collamer Lens Implantation.

To evaluate the dynamic changes in anterior segment parameters during accommodation following Implantable Collamer Lens (ICL) implantation with swept-source optical coherence tomography (SS-OCT). Under the accommodation of 0.00 diopters (D), 3.00 D, and maximum amplitude, SS-OCT was used to examine the anterior segment parameters, including ICL vault, ICL depth (the distance between the corneal endothelium and the posterior surface of ICL), crystalline lens thickness, anterior chamber depth, and various parameters of the anterior chamber angle, comprising angle opening distance, angle recess area, trabecular iris space area, and trabecular iris angle. During accommodation, the ICL vault showed a significant decrease from baseline (536 ± 278 μm) to 3.00 D (522 ± 281 μm), followed by an increase from 3.00 D to maximum amplitude (548 ± 306 μm) (analysis of variance [ANOVA], P < .001). Four eyes (2.61%) exhibited a decrease in ICL vault to less than 100 μm (47 ± 32 μm) at maximum accommodation. The ICL depth decreased significantly as accommodation increased (ANOVA, P < .001). Crystalline lens thickness increased, whereas anterior chamber depth decreased during accommodation (ANOVA, P < .001). The anterior chamber angle widened during 3.00 D of accommodation but narrowed at maximum accommodation, leading to significant changes in the angle opening distance, angle recess area, trabecular iris space area, and trabecular iris angle during accommodation (ANOVA, P < .001 for all). The anterior segment, including ICL vault and anterior chamber angle, undergo significant dynamic changes during accommodation. These accommodative changes may require careful monitoring for the surgery design of ICL implantation. [J Refract Surg. 2024;40(3):e164-e172.].

Impact of keratinized mucosa on implant-health related parameters: A 10-year prospective re-analysis study.

To investigate whether the lack of keratinized mucosa (KM) affects peri-implant health after 10 years of loading. Data from 74 patients with 148 implants from two randomized controlled studies comparing different implant systems were included and analyzed. Clinical parameters including bleeding on probing (BOP), probing depth (PD), plaque index,marginal bone loss (MBL), and KM width (KMW) at buccal sites were collected at baseline (time of the final prosthesis insertion), 5-year and 10 years postloading. Multivariable logistic and linear regression models by means of a generalized estimated equation (GEE) were used to evaluate the influence of buccal KM on peri-implant clinical parameters; BOP, MBL, PD, and adjusted for implant type (one-piece or two-piece) and compliance. A total of 35 (24.8%) implants were healthy, 67 (47.5%) had mucositis and 39 (27.6%) were affected by peri-implantitis. In absence of buccal KM (KM = 0 mm), 75% of the implants exhibited mucositis, while in the presence of KM (KMW >0 mm) 41.2% exhibited mucositis. Regarding peri-implantitis, the corresponding percentages were 20% (KM = 0 mm) and 26.7% (KM >0 mm). Unadjusted logistic regression showed that the presence of buccal KM tended to reduce the odds of showing BOP at buccal sites (OR: 0.28 [95% CI, 0.07 to 1.09], p = 0.06). The adjusted logistic regression model revealed that having buccal KM (OR: 0.21 [95% CI, 0.05 to 0.85], p = 0.02) and using two-piece implants (OR: 0.34 [95% CI, 0.15 to 0.75], p = 0.008) significantly reduced the odds of showing BOP. Adjusted linear regression by means of GEE showed that KM and two-piece implants were associated with reduced MBL and MBL changes (p < 0.05). The lack of buccal KM appears to be linked with peri-implant parameters such as BOP and MBL, but the association is weak. The design of one-piece implants may account for their increased odds of exhibiting BOP.