In-situ Audiometry Compared to Conventional Audiometry for Hearing Aid Fitting.

The use of in-situ audiometry for hearing aid fitting is appealing due to its reduced resource and equipment requirements compared to standard approaches employing conventional audiometry alongside real-ear measures. However, its validity has been a subject of debate, as previous studies noted differences between hearing thresholds measured using conventional and in-situ audiometry. The differences were particularly notable for open-fit hearing aids, attributed to low-frequency leakage caused by the vent. Here, in-situ audiometry was investigated for six receiver-in-canal hearing aids from different manufacturers through three experiments. In Experiment I, the hearing aid gain was measured to investigate whether corrections were implemented to the prescribed target gain. In Experiment II, the in-situ stimuli were recorded to investigate if corrections were directly incorporated to the delivered in-situ stimulus. Finally, in Experiment III, hearing thresholds using in-situ and conventional audiometry were measured with real patients wearing open-fit hearing aids. Results indicated that (1) the hearing aid gain remained unaffected when measured with in-situ or conventional audiometry for all open-fit measurements, (2) the in-situ stimuli were adjusted for up to 30 dB at frequencies below 1000 Hz for all open-fit hearing aids except one, which also recommends the use of closed domes for all in-situ measurements, and (3) the mean interparticipant threshold difference fell within 5 dB for frequencies between 250 and 6000 Hz. The results clearly indicated that modern measured in-situ thresholds align (within 5 dB) with conventional thresholds measured, indicating the potential of in-situ audiometry for remote hearing care.

[Comparative analysis of clinical and functional parameters in patients with stable stage II-III keratoconus after implantation of corneal segments and fitting of scleral rigid contact lenses]. / Sravnitel'nyi analiz kliniko-funktsional'nykh pokazatelei u patsientov so stabil'nym keratokonusom II­III stadii posle implantatsii rogovichnykh segmentov i podbora skleral'nykh zhestkikh kontaktnykh linz.

The modern treatment strategy for keratoconus (KC) involves sequential application of medical technologies aimed at stabilizing pathological changes in the cornea and restoring visual acuity. PURPOSE: This study compares the effect of implantation of intrastromal corneal ring segment (ICRS) and fitting of individual scleral rigid contact lenses (RCLs) on visual functions in patients with stage II-III KC after previously performed corneal collagen cross-linking. MATERIAL AND METHODS: The Helmholtz National Medical Research Center of Eye Diseases examined and treated 34 patients (69 eyes) aged 18 to 33 years with stage II-III KC. The study included patients who had previously undergone standard corneal collagen cross-linking. Depending on the type of optical correction, the patients were divided into two groups: patients in group 1 underwent ICRS implantation using a femtosecond laser; patients in group 2 were fitted with individual scleral RCLs. RESULTS: Improvement in clinical and functional parameters was observed in both groups. A higher clinical and functional result was achieved in group 2. CONCLUSION: For patients with stable stage II-III KC, it is advisable to recommend fitting of individual scleral RCLs for visual rehabilitation.

An adaptive prosthetic socket for people with transtibial amputation.

It is essential that people with limb amputation maintain proper prosthetic socket fit to prevent injury. Monitoring and adjusting socket fit, for example by removing the prosthesis to add prosthetic socks, is burdensome and can adversely affect users' function and quality-of-life. This study presents results from take-home testing of a motor-driven adaptive socket that automatically adjusted socket size during walking. A socket fit metric was calculated from inductive sensor measurements of the distance between the elastomeric liner surrounding the residual limb and the socket's inner surface. A proportional-integral controller was implemented to adjust socket size. When tested on 12 participants with transtibial amputation, the controller was active a mean of 68% of the walking time. In general, participants who walked more than 20 min/day demonstrated greater activity, less doff time, and fewer manual socket size adjustments for the adaptive socket compared with a locked non-adjustable socket and a motor-driven socket that participants adjusted with a smartphone application. Nine of 12 participants reported that they would use a motor-driven adjustable socket if it were available as it would limit their socket fit issues. The size and weight of the adaptive socket were considered the most important variables to improve.

Prediction of Cochlear Implant Fitting by Machine Learning Techniques.

OBJECTIVE: This study aimed to evaluate the differences in electrically evoked compound action potential (ECAP) thresholds and postoperative mapping current (T) levels between electrode types after cochlear implantation, the correlation between ECAP thresholds and T levels, and the performance of machine learning techniques in predicting postoperative T levels. STUDY DESIGN: Retrospective case review. SETTING: Tertiary hospital. PATIENTS: We reviewed the charts of 124 ears of children with severe-to-profound hearing loss who had undergone cochlear implantation. INTERVENTIONS: We compared ECAP thresholds and T levels from different electrodes, calculated correlations between ECAP thresholds and T levels, and created five prediction models of T levels at switch-on and 6 months after surgery. MAIN OUTCOME MEASURES: The accuracy of prediction in postoperative mapping current (T) levels. RESULTS: The ECAP thresholds of the slim modiolar electrodes were significantly lower than those of the straight electrodes on the apical side. However, there was no significant difference in the neural response telemetry thresholds between the two electrodes on the basal side. Lasso regression achieved the most accurate prediction of T levels at switch-on, and the random forest algorithm achieved the most accurate prediction of T levels 6 months after surgery in this dataset. CONCLUSION: Machine learning techniques could be useful for accurately predicting postoperative T levels after cochlear implantation in children.

The accuracy of digital templating in the preoperative planning of total knee arthroplasties: A systematic review and meta-analysis.

AIMS: Accurately predicting the implant size in total knee arthroplasties could increase the efficiency of the operation, decrease the costs associated with the procedure and result in improved patient outcomes. To substantiate its continued use, digital templating must demonstrate itself to be an accurate tool in predicting component size in order for surgeons to confidently use it to optimize the procedure. METHODS: A systematic literature review was performed and identified 16 studies within the Pubmed, Ebsco and Ovid-Embase databases, with 1189 TKR prostheses included for analysis. A quality of evidence assessment was performed on each study depending on the study design. A random effects meta-analysis model was used to pool overall implant accuracy and the reported inter-rater agreement when performing digital templating and displayed in a forest plot. Meta-regression was used analyze potential factors that may affect the accuracy of digital templating. RESULTS: The pooled proportion of accurate templates with 0 margin of error was found to be 56% (52-61, 95CI), which increases to 96% (0.94-0.98, 95CI) when allowing for a 1 size margin of error. Subgroup analysis between femoral and tibial components concluded no statistically significant difference. CONCLUSIONS: This study supports the continued use of digital templating for planning total knee arthroplasties and recommends further subgroup analysis of patient age, body mass index and sex against accuracy. This review was registered in the International Prospective Register of Systematic Reviews Database under ID: CRD420222367461. No funding was provided for the completion of this systematic review. BACKGROUND: Templating in the preoperative planning of total knee arthroplasties is a vital step in ensuring maximum operative efficiency. A method that can accurately predict the required implant size within 1 size could improve theatre turnover, decrease costs and benefit patient outcomes. The current literature on the accuracy of digital templating in total knee arthroplasties lacks a systematic review calculating the overall accuracy of the process, this study aims to address this gap.

Estudio in vitro del ajuste de supraestructuras pasivadas sobre implantes múltiples / In vitro study of the adjustment of passivated suprastructures on multiple implants

Objetivo: Comparar dos procedimientos de soldadura convencionales empleando una aleación de Cr-Co, para co- nectar barras coladas seccionadas a ser fijadas sobre implantes. Materiales y métodos: A partir de un modelo maes- tro que representa un maxilar desdentado con cuatro implan- tes, se confeccionaron veinte (n=20) probetas seccionadas en tres partes. Se conformaron dos grupos, cada uno con diez (n=10) ejemplares. Una vez acondicionadas, fueron atornilla- das al modelo maestro. Su desajuste inicial se analizó utili- zando una lupa estereoscópica, con una cámara incorporada y un software. Las partes fueron soldadas empleando un pro- cedimiento diferente para cada grupo. Las correspondientes al Grupo I se invistieron en un block refractario a base de sílico-fosfato. Las del Grupo II se montaron en una estructu- ra metálica Clever Spider. El desajuste fue mensurado y los resultados procesados estadísticamente. El nivel de significa- ción fue establecido en p<0,05. Resultados: El Grupo I tuvo un desajuste inicial de 97,30±13,81µm y el Grupo II de 98,53±11,24µm. Luego de la soldadura, el Grupo I registró 98,53±17,17µm, 1,23µm mayor respecto al inicial. En el Grupo II se observó 103,13±17,61µm, 4,60µm por encima del original. Se analizaron mediante prue- ba t de Student; en ambos casos el resultado fue de p>0,05. Al comparar entre sí los grupos I y II, por medio de la prueba t y de comprobación no paramétrica de Mann-Whitney, se ob- servaron diferencias no significativas, p=0,41 y p=0,38 res- pectivamente (AU)

Aim: Compare two conventional welding procedures us- ing a Cr-Co alloy, to connect sectioned cast bars to be fixed on implants. Materials and methods: From a master model representing a toothless jaw with four implants, twenty (n=20) specimens sectioned into three parts were made. Two groups were formed, each with ten (n=10) specimens. Once conditioned, they were screwed to the master mod- el. Its initial mismatch was analyzed using a stereoscop- ic magnifier, with a built-in camera and a software. The parts were welded using a different procedure for each group. Those corresponding to Group I were invested in a refractory block based on silyl-phosphate. Those of Group II were mounted on a Clever Spider metal structure. The mismatch was measured, and the results processed statisti- cally. The level of significance was established at p<0.05. Results: Group I had an initial mismatch of 97.30 ±13.81µm, and Group II of 98.53±11.24µm. After welding, Group I registered 98.53±17.17µm, 1.23µm higher than the initial one. In Group II, 103.13±17.61µm was observed, 4.60µm above the original. They were analyzed using Stu- dent's t test; in both cases the result was p>0.05. When com- paring groups I and II, using the t-test and the Mann-Whitney nonparametric verification, non-significant differences were observed, p=0.41 and p=0.38 respectively. Conclusions: Under the conditions of this study, it was ob- served that the two welding methods analyzed were reliable for joining metallic superstructures without affecting their final fit (AU)

Short partial doffs of release/relock sockets may effectively stabilize limb fluid volume in prosthesis users with transtibial amputation.

BACKGROUND: A challenge often faced by people with lower extremity amputation is management of prosthetic socket fit due to changes in fluid volume within their residual limb. Prior research suggests that intermittently doffing the prosthetic socket may help stabilize daily residual limb fluid volume. METHODS: To assess the effects of partial doff duration on residual limb fluid volume retention, participants with transtibial amputation were tested by walking on a treadmill in a controlled, laboratory setting under three conditions. An automated system to release the locking pin and enlarge the socket was used to produce the partial doffing. Percent limb fluid volume changes after partial doffing for 4 min (Short Rest) and for 10 min (Long Rest) were compared with no partial doffing (No Release). Limb fluid volume was monitored using bioimpedance analysis. FINDINGS: Mean percent fluid volume changes in the posterior region were  -1.2% for No Release, 2.7% for Short Rest, and 1.0% for Long Rest. Short and Long Rests had larger increases than No Release (P = 0.005 and 0.03, respectively); Short and Long Rests were not statistically different (P = 0.10). Eight of the thirteen participants experienced a higher percent fluid volume gain for both release protocols while four experienced a higher percent fluid volume gain for only one release protocol. INTERPRETATION: A partial doff duration as short as 4 min may be an effective strategy to stabilize limb fluid volume in prosthesis users with transtibial amputation. Trials in at-home settings should be pursued.

Feasibility testing of a novel prosthetic socket sensor system.

PURPOSE: Poorly fitting prosthetic sockets contribute to decreased quality of life, health, and well-being for persons with amputations. Therefore, improved socket fit is a high clinical priority. METHODS: In this study, we describe the design and testing of a novel sensor system that can be incorporated into a prosthetic socket to measure distal end weight bearing in the socket and can alert a prosthesis user if poor socket fit is suspected. We present the results of testing this device with three Veterans who were new prosthesis users and three Veterans who were experienced prosthesis users. RESULTS AND CONCLUSIONS: We collected sensor data during walking trials while participants wore varying numbers of sock plies and qualitative feedback on the design of the socket fit sensor system. For analysis, peak sensor measurements during walking cycles were identified and combined with socket fit data (i.e., a clinician-determined level of "good," "too tight," or "too loose" and the number of sock ply worn each trial). We found consistent relationships between peak sensor measurements and socket fit in our sample. Also, all users expressed an interest in the device, highlighting its potential benefits during early prosthesis training.Implications for RehabilitationEnsuring socket fit is challenging for many prosthesis users.A novel wearable sensor system can be used to identify socket fit issues for some prosthesis users.This type of system could be most helpful for new prosthesis users and those with sensory and cognitive challenges.

Corneal RGP Contact Lens Fitting Software for Keratoconus Built-In Anterior Segment Optical Coherence Tomography.

OBJECTIVE: To assess the performance of the contact lens fitting software built into anterior segment optical coherence tomography (AS-OCT). METHODS: This retrospective study enrolled patients with keratoconus prescribed with spherical corneal rigid gas-permeable contact lenses based on a contact lens fitting software. Subjects were classified into four subgroups based on corneal morphology: nipple, oval, globus, and marginal type. Software performance was evaluated according to the correlation between the back optical zone radius (BOZR) calculated by the contact lens fitting program and the BOZR of the lens prescribed, and the number of trial lens replacements required.Results:A total of 340 eyes of 254 patients with a mean age of 40.4 ± 13.6 years were included. The oval type was the most common (61.8%), followed by the nipple type (26.2%). Linear regression analysis revealed a significant correlation between the prescribed and the calculated BOZR in all subgroups (R 2 = 0.92, P < 0.01 for the nipple type; R 2 = 0.76, P < 0.01 for the oval type; R 2 = 0.93, P < 0.01 for the globus type; and R 2 = 0.79, P < 0.01 for the marginal type). Furthermore, the globus type had the highest proportion of cases requiring at least one trial lens replacement (36.3%), followed by the nipple group (27.0%). There were no significant differences among the subgroups ( P = 0.14). CONCLUSIONS: In conclusion, our findings reveal that the contact lens fitting software built into AS-OCT may be useful for accurate contact lens prescription for any corneal shape.

The Acoustics of Instant Ear Tips and Their Implications for Hearing-Aid Fitting.

OBJECTIVES: Today, approximately 70 to 80% of hearing aid fittings are made with silicone instant ear tips rather than custom earmolds. Nevertheless, little is known about the impact of instant ear tips on the acoustic coupling between the hearing aid receiver and the individual ear canal, even though it can have a major impact on the overall sound of the hearing aids. This study aimed to investigate the acoustic properties of different instant ear tip types and their across-subject variability, the within-subject reliability of those properties, and the influence of the users' level of experience with ear-tip insertion on the acoustics. Furthermore, subjective ratings of occlusion produced by the ear tips were considered. DESIGN: Five types of instant ear tips (Open, Tulip, Round [2-vent], Round [1-vent], Double Domes) provided by the hearing aid manufacturer Widex were considered in this study. Probe-microphone measurements were performed at the eardrums of 30 participants (60 ears). In the first experiment, the real ear occluded insertion gain and the vent effect (VE) were measured, and the listeners rated the subjective occlusion experienced with each ear tip. In the second experiment, the same measurements were repeated six times per participant. The within-subject variability of the acoustic ear tip properties was investigated as well as the impact of the degree of users' experience with ear tip insertion on the resulting real ear measurements. RESULTS: All tested ear tips were, on average, acoustically transparent up to 1 kHz except Double Domes, which were only transparent up to 600 Hz. Distinct VE profiles were found for each ear tip type, but a large across-subject variability was observed for both real ear occluded insertion gain and VE. However, the within-subject reliability was high. The measured VE was highly correlated with the perceived occlusion. Finally, no significant effect of the level of experience in ear tip insertion on the acoustic properties of the ear tips was found, but the within-subject variability was larger in the less experienced group. CONCLUSIONS: These results suggest that the acoustic properties of instant ear tips and their coupling to the individual ear canal impact the resulting hearing aid fitting and should be considered by the hearing care professionals and reflected in the fitting software. The high within-subject reliability indicates that the ear tip acoustics remain stable for the individual in daily use. Finally, real ear measurements should be considered an essential part of the hearing aid fitting process in clinical practice to ensure an optimal fit for the individual hearing aid user.

Scoping review to evaluate existing measurement parameters and clinical outcomes of transtibial prosthetic alignment and socket fit.

INTRODUCTION: Fit and alignment are observable objectives of the prosthesis rendering process for individuals with lower limb amputation. Nevertheless, there is a dearth of validated measures to directly assess the quality of this clinical procedure. OBJECTIVES: The objectives of this scoping review are to evaluate existing measurement parameters and clinical outcomes used in investigations of transtibial socket fit or prosthetic alignment and to identify gaps in the literature regarding tools for evaluation of prosthetic fitting. STUDY DESIGN: Scoping literature review. METHODS: A comprehensive search was conducted in the following databases: MEDLINE (through PubMed), Embase (through Elsevier), Scopus (through Elsevier), and Engineering Village (through Elsevier), resulting in 6107 studies to be screened. RESULTS: Sixty-three studies were included in the review. When measuring fit, studies most frequently reported on patient-reported comfort (n = 22) and socket size compared with the residual limb volume (n = 9). Alignment was most frequently measured by the prosthetists' judgment and/or use of an alignment jig (n = 34). The measurement parameters used to determine alignment or fit varied greatly among the included studies. CONCLUSION: This review demonstrated that most measures of socket fit rely on a patient's self-report and may vary with biopsychosocial factors unrelated to the socket fitting process. Meanwhile, alignment is determined mostly by the prosthetist's judgment, paired with objective measurements, such as alignment jigs and gait analysis. Efforts to standardize and validate measures of these parameters of prosthetic fitting are vital to improving clinical practice and reporting outcomes.

A multi-parameter grading system for optimal fitting of scleral contact lenses.

Background: While scleral lens practise has improved over the years due to factors such as availability of lenses with better materials and designs as well as experience of practitioners, a lack of objectivity appears to remain in terms of assessment of scleral lens fitting. This prospective observational work aimed to achieve standardization on this front through proposing a grading system for scleral lens fitting. Methods: After application of prosthetic replacement of ocular surface ecosystem (PROSE) devices on the participants' eyes, four fundamental components for understanding scleral lens fitting such as central and limbal corneal clearance, mid-haptic compression, and alignment of lens edge over anterior sclera were assessed through a series of slit-lamp biomicroscopy imaging as well as with anterior segment optical coherence tomography. FitConnect® was used to modify the device parameters to simulate different grading patterns on the proposed scale. Serial imaging was done for all the different lenses to compose the grading scale. Results: A clinically relevant grading scale was constructed that pictorially demonstrated grades for the different aspect of scleral lens fitting. The grades were conveniently scaled within three categories: "optimal", "acceptable" and "not acceptable". Conclusion: The gradation of scleral lens fitting parameters would take a step towards objectifying the assessment patterns in practise. This will also help reducing the gap between a novice and an experienced practitioner in terms of understanding of scleral lens fitting.

Management of Keratoconus With Corneal Rigid Gas-Permeable Contact Lenses.

ABSTRACT: Vision correction using a corneal rigid gas-permeable contact lens, which is relatively safe, easy to replace, and economical, is still the basis of the management for keratoconus. For eyes with keratoconus, two fitting strategies have traditionally been used in Japan: apical touch fitting with spherical lenses and parallel fitting with multicurve lenses. These two techniques have different success rates depending on the type and severity of keratoconus. Therefore, it is important to classify eyes with keratoconus into four types according to the shape of the cornea and select the prescription techniques according to this classification. If the corneal GPs prescribed by these fitting methods cannot be used because of mechanical irritation to the corneal epithelium, the "piggyback lens system" is an effective option. Furthermore, proper lens care must be instructed to patients to prevent contact lens-related complications and maintain visual function. If these fittings and introductions can be performed properly, corneal GPs can safely provide effective and comfortable vision for many patients with keratoconus, even for those with severe keratoconus.

Echocardiography-guided Cardiac Implantable Electronic Device Implantation to Reduce Device Related Tricuspid Regurgitation: A Prospective Controlled Study.

BACKGROUND: Endocardial leads of permanent pacemakers (PPM) and implantable defibrillators (ICD) across the tricuspid valve (TV) can lead to tricuspid regurgitation (TR) or can worsen existing TR with subsequent severe morbidity and mortality. OBJECTIVES: To evaluate prospectively the efficacy of intraprocedural 2-dimentional-transthoracic echocardiography (2DTTE) in reducing/preventing lead-associated TR. METHODS: We conducted a prospective randomized controlled study comparing echocardiographic results in patients undergoing de-novo PPM/ICD implantation with intraprocedural echo-guided right ventricular (RV) lead placement (Group 1, n=56) versus non-echo guided implantation (Group 2, n=55). Lead position was changed if TR grade was more than baseline in Group 1. Cohort patients underwent 2DTTE at baseline and 3 and/or 6 months after implantation. Excluded were patients with baseline TR > moderate or baseline ≥ moderate RV dysfunction. RESULTS: The study comprised 111 patients (74.14 ± 11 years of age, 58.6% male, 19% ICD, 42% active leads). In 98 patients there was at least one follow-up echo. Two patients from Group 1 (3.6%) needed intraprocedural RV electrode repositioning. Four patients (3.5%, 2 from each group, all dual chamber PPM, 3 atrial fibrillation, 2 RV pacing > 40%, none with intraprocedural reposition) had TR deterioration during 6 months follow-up. One patient from Group 2 with baseline mild-moderate aortic regurgitation (AR) had worsening TR and AR within 3 months and underwent aortic valve replacement and TV repair. CONCLUSIONS: The rate of mechanically induced lead-associated TR is low; thus, a routine intraprocedural 2DTTE does not have a significant role in reducing/preventing it.

Comparison of Cup Setting Angle Accuracy between Computed Tomography-Based and Computed Tomography-Free Navigation in the Same Patients with Crowe's Classification I or II Hip Dysplasia.

BACKGROUD: In total hip arthroplasty, the cup setting angle may affect the postoperative results. In recent years, both computed tomography-based navigation and computed tomography-free (imageless) navigation have been reported to produce high accuracy in cup installation; however, no direct comparison between these two methods has been performed. The present study aimed to directly compare the cup installation angle accuracy between computed tomography-based navigation and computed tomography-free navigation in patients with Crowe's classification stage I or II dysplastic osteoarthritis and to examine the factors affecting the cup installation accuracy. METHODS: Using both navigation systems for the same technique, primary total hip arthroplasty was performed by the same surgeon in 36 patients. A cup was installed using computed tomography-based navigation, and the installed cup was measured again using computed tomography-free navigation. We compared the error between the target angle and the intraoperative installation angle for each navigation method by performing statistical analyses. RESULTS: For computed tomography-based navigation, errors in the inclination and the anteversion angles compared to the target angle were 3.14° ± 1.55° and 1.47° ± 0.99°, respectively. For computed tomography-free navigation, the inclination and anteversion angle errors were significantly larger, i.e., 6.84° ± 4.78° and 5.43° ± 5.22°, respectively (p < 0.01). The inclination and anteversion angles of computed tomography-free navigation were correlated, and there were no significant factors influencing the error. CONCLUSIONS: Computed tomography-based navigation is more accurate for cup installation than computed tomography-free navigation. When using computed tomography-free navigation, it is necessary to add technical schemes before and during surgery to improve the cup installation accuracy.

Scanning Electron Microscopic Assessment of Stent Coating Integrity in Jailed Wire Technique for Bifurcation Treatment.

OBJECTIVES: To assess the impact of different guidewires on stent coating integrity in jailed wire technique (JWT) for bifurcation treatment. BACKGROUND: JWT is commonly adopted to protect side branch in provisional one-stent strategy for coronary bifurcation lesions. However, this technique may cause defects in stent coatings. The degree of coating damage caused by different types of jailed wires remains unknown. METHODS: A fluid model with a bifurcation was established to mimic the condition in vivo. One-stent strategy was performed with three types of guidewire (nonpolymer-jacketed wire, intermediate polymer-jacketed wire, and full polymer-jacketed wire) tested for JWT. Scanning electron microscopy (SEM) was used to evaluate stent coating integrity and wire structure. The degrees of coating defects were recorded as no, slight, moderate, and severe defects. RESULTS: A total of 27 samples were tested. Analyses of SEM images showed a significant difference in the degree of coating damage among the three types of wire after the procedure of JWT (P < 0.001). Nonpolymer-jacketed wire could inevitably cause a severe defect in stent coatings, while full polymer-jacketed wire caused the least coating damages. Besides, there were varying degrees of coil deformation in nonpolymer-jacketed wires, while no surface damage or jacket shearing was observed in full polymer-jacketed wires. CONCLUSIONS: Although nonpolymer-jacketed wire has long been recommended for JWT, our bench-side study suggests that full polymer-jacketed wire may be a better choice. Further clinical studies are needed to confirm our findings.

Impact of Tibial Component Coronal Alignment on Knee Joint Biomechanics Following Fixed-bearing Unicompartmental Knee Arthroplasty: A Finite Element Analysis.

OBJECTIVE: Unicompartmental knee arthroplasty (UKA) has indicated a higher rate of revision than total knee arthroplasty (TKA). The success of UKA depends on UKA component alignment, fixation, and soft tissue integrity. The purpose of this study was to investigate the effects of different tibial component alignments in the coronal plane on the stress distribution in UKA. It was hypothesized that the stress distribution would approach native knee when the tibial component was neutrally positioned. METHODS: The left legs from two healthy volunteers were considered to represent the geometric native knee models. All bones within the knee joint were extracted from the three-dimensional (3D) computed tomography (CT). MRI was used to generate cartilage, menisci, and four major ligaments. The UKA components were virtually implanted in the medial compartment of the knee model using MIMICS. A total of five different configurations of UKA tibial obliquity in the coronal plane (neutral, 3° varus, 6° varus, 3° valgus, and 6° valgus) were adopted and investigated. Subject-specific inhomogeneous material properties of bones were used in the finite element analysis (FEA) model. The von Mises stress in the tibia platform and proximal tibia, and the load distribution between the medial and lateral compartments were extracted and compared among the five different configurations. RESULTS: The inhomogeneous material properties of the trabecular bone were closer to real physics than traditional homogeneous methods. Neutral and 3° varus alignments of the tibial component in the coronal plane have better stress distribution between medial and lateral compartment as healthy knee models, and less stress-shielding effects than other UKA configurations. The stress pathway under the medial tibia platform in neutral and 3° varus UKA configurations was similar and more obvious than the other three UKA configurations. Notably, the stress of the medial tibia platform in the 3° varus UKA models was more homogenous than the neutral UKA configuration. The 6° varus, 3° valgus, and 6° valgus UKA models had higher stress at the location of anterolateral and posterolateral tibia platform than other UKA configurations. CONCLUSION: Neutral or 3° varus positioned in the coronal plane for the tibial component could be the optimal alignment for UKA. Excessive varus or valgus obliquity in the coronal plane lead to significant differences in bone stress transfer and load distribution in the knee, and increase the risk of UKA failure.