RESUMO
PURPOSE: Femorotibial angle (FTA) is a convenient measure of coronal knee alignment that can be extracted from a short knee radiograph, avoiding the additional radiation exposure and specialist equipment required for full-leg radiographs. While intra- and inter-reader reproducibility from the same image has been reported, the full scan-rescan reproducibility across images, as calculated in this study, has not. METHODS: In this study, 4589 FTA measurement pairs from 2586 subjects acquired a year apart were used to estimate FTA scan-rescan reproducibility using data from the Osteoarthritis Initiative. Subjects with radiographic progression of osteoarthritis or other conditions that may cause a change in coronal knee alignment were excluded. Measurement pairs were analysed using paired-samples t $t$ tests to detect differences and compared to symptomatic changes in Western Ontario and McMaster Universities Arthritis Index scores for joint pain, stiffness and physical function to detect correlations. RESULTS: The 95% limit of agreement and the paired-samples correlation were calculated with high precision to be [-1.76°, +1.78°] and 0.938, considerably worse than the corresponding figures for intra- and inter-reader reproducibility, without relation to symptomatic or radiographic changes in knee condition. This error will weakly attenuate R 2 ${R}^{2}$ and r $r$ values from their true values in correlative studies involving FTA. The realistic maximum value for R 2 ${R}^{2}$ is 87% and for Pearson's r $r$ is 93%. CONCLUSION: The scan-rescan reproducibility in FTA is almost double the intra- and inter-reader reliability from a single scan. At almost ±2° accuracy, FTA is inappropriate for surgical use, but it is sufficiently reproducible to produce good correlations in studies predicting disease incidence and progression. LEVEL OF EVIDENCE: Level II, retrospective study.
RESUMO
Aseptic loosening is the dominant failure mechanism in contemporary knee replacement surgery, but diagnostic techniques are poorly sensitive to the early stages of loosening and poorly specific in delineating aseptic cases from infections. Smart implants have been proposed as a solution, but incorporating components for sensing, powering, processing, and communication increases device cost, size, and risk; hence, minimising onboard instrumentation is desirable. In this study, two wireless, battery-free smart implants were developed that used passive biotelemetry to measure fixation at the implant-cement interface of the tibial components. The sensing system comprised of a piezoelectric transducer and coil, with the transducer affixed to the superior surface of the tibial trays of both partial (PKR) and total knee replacement (TKR) systems. Fixation was measured via pulse-echo responses elicited via a three-coil inductive link. The instrumented systems could detect loss of fixation when the implants were partially debonded (+7.1% PKA, +32.6% TKA, both p < 0.001) and fully debonded in situ (+6.3% PKA, +32.5% TKA, both p < 0.001). Measurements were robust to variations in positioning of the external reader, soft tissue, and the femoral component. With low cost and small form factor, the smart implant concept could be adopted for clinical use, particularly for generating an understanding of uncertain aseptic loosening mechanisms.
Assuntos
Artroplastia do Joelho , Prótese do Joelho , Humanos , Falha de Prótese , Reoperação/métodos , Tíbia/cirurgia , Articulação do Joelho/cirurgia , Desenho de PróteseRESUMO
PURPOSE: Medial bicompartmental arthroplasty, the combination of ipsilateral medial unicompartmental and patellofemoral arthroplasty, is an alternative to total knee arthroplasty for patients with medial tibiofemoral and severe patellofemoral arthritis, when the lateral tibiofemoral compartment and anterior cruciate ligament are intact. This study reports the gait and subjective outcomes following medial bicompartmental arthroplasty. METHODS: Fifty-five subjects were measured on the instrumented treadmill at top walking speeds, using standard metrics of gait. Modular, single-stage, medial bicompartmental arthroplasty subjects (n = 16) were compared to age, body mass index, height- and sex-matched healthy (n = 19) and total knee arthroplasty (n = 20) subjects. Total knee arthroplasty subjects with pre-operative evidence of tricompartmental osteoarthritis or anterior cruciate ligament dysfunction were excluded. The vertical component of ground reaction force and temporospatial measurements were compared using Kruskal-Wallis, then Mann-Whitney test with Bonferroni correction (α = 0.05). Oxford Knee and EuroQoL EQ-5D scores were compared. RESULTS: Objectively, the medial bicompartmental arthroplasty top walking speed of 6.7 ± 0.8 km/h was 0.5 km/h (7%) slower than that of healthy controls (p = 0.2), but 1.3 km/h (24%) faster than that of total knee arthroplasty subjects (5.4 ± 0.6 km/h, p < 0.001). Medial bicompartmental arthroplasty recorded more normal maximum weight acceptance (p < 0.001) and mid-stance forces (p = 0.03) than total knee arthroplasty subjects, with 11 cm (15%) longer steps (p < 0.001) and 21 cm (14%) longer strides (p = 0.006). Subjectively, medial bicompartmental arthroplasty subjects reported Oxford Knee Scores of median 41 (interquartile range 38.8-45.5) compared to total knee arthroplasty Oxford Knee Scores of 38 (interquartile range 30.5-41, p < 0.02). Medial bicompartmental arthroplasty subjects reported EQ-5D median 0.88 (interquartile range 0.84-0.94) compared to total knee arthroplasty median 0.81 (interquartile range 0.73-0.89, p < 0.02.) CONCLUSION: This study finds that, in the treatment of medial tibiofemoral osteoarthritis with severe patellofemoral arthritis, medial bicompartmental arthroplasty results in nearer-normal gait and improved patient-reported outcomes compared to total knee arthroplasty. LEVEL OF EVIDENCE: III.
Assuntos
Artroplastia do Joelho , Prótese do Joelho , Osteoartrite do Joelho , Humanos , Artroplastia do Joelho/métodos , Osteoartrite do Joelho/cirurgia , Satisfação do Paciente , Articulação do Joelho/cirurgia , Marcha , Resultado do TratamentoRESUMO
PURPOSE: This study investigated the gait and patient reported outcome measures of subjects converted from a partial knee arthroplasty to combined partial knee arthroplasty, using a compartmental approach. Healthy subjects and primary total knee arthroplasty patients were used as control groups. METHODS: Twenty-three patients converted from partial to combined partial knee arthroplasty were measured on the instrumented treadmill at top walking speeds, using standard gait metrics. Data were compared to healthy controls (n = 22) and primary posterior cruciate-retaining total knee arthroplasty subjects (n = 23) where surgery were performed for one or two-compartment osteoarthritis. Groups were matched for age, sex and body mass index. At the time of gait analysis, combined partial knee arthroplasty subjects were median 17 months post-revision surgery (range 4-81 months) while the total knee arthroplasty group was median 16 months post-surgery (range 6-150 months). Oxford Knee Scores and EuroQol-5D 5L scores were recorded at the time of treadmill assessment, and results analysed by question and domain. RESULTS: Subjects revised from partial to combined partial knee arthroplasty walked 16% faster than total knee arthroplasty (mean top walking speed 6.4 ± 0.8 km/h, vs. 5.5 ± 0.7 km/h p = 0.003), demonstrating nearer-normal weight-acceptance rate (p < 0.001), maximum weight-acceptance force (p < 0.006), mid-stance force (p < 0.03), contact time (p < 0.02), double support time (p < 0.009), step length (p = 0.003) and stride length (p = 0.051) compared to primary total knee arthroplasty. Combined partial knee arthroplasty subjects had a median Oxford Knee Score of 43 (interquartile range 39-47) vs. 38 (interquartile range 32-41, p < 0.02) and reported a median EQ-5D 0.94 (interquartile range 0.87-1.0) vs. 0.84 (interquartile range 0.80-0.89, p = 0.006). CONCLUSION: This study finds that a compartmental approach to native compartment degeneration following partial knee arthroplasty results in nearer-normal gait and improved patient satisfaction compared to total knee arthroplasty. LEVEL OF EVIDENCE: III.
Assuntos
Artroplastia do Joelho , Osteoartrite do Joelho , Humanos , Artroplastia do Joelho/métodos , Articulação do Joelho/cirurgia , Amplitude de Movimento Articular , Marcha , Osteoartrite do Joelho/cirurgiaRESUMO
BACKGROUND: Little is known regarding anterior-posterior stability after anterior cruciate ligament-preserving partial (PKA) and combined partial knee arthroplasty (CPKA) compared to standard posterior cruciate-retaining total knee arthroplasty (TKA). METHODS: The anterior-posterior tibial translation of twenty-four cadaveric knees was measured, with optical tracking, while under 90N drawer with the knee flexed 0-90°. Knees were tested before and after PKA, CPKA (medial and lateral bicompartmental and bi-unicondylar), and then posterior cruciate-retaining TKA. The anterior-posterior tibial translations of the arthroplasty states, at each flexion angle, were compared to the native knee and each other with repeated measures analyses of variance and post-hoc t-tests. RESULTS: Unicompartmental and bicompartmental arthroplasty states had similar laxities to the native knee and to each other, with ≤1-mm differences throughout the flexion range (P ≥ .199). Bi-unicondylar arthroplasty resulted in 6- to 8-mm increase of anterior tibial translation at high flexion angles compared to the native knee (P ≤ .023 at 80-90°). Meanwhile, TKA exhibited increased laxity across all flexion angles, with increased anterior tibial translation of up to 18 ± 6 mm (P < .001) and increased posterior translation of up to 4 ± 2 mm (P < .001). CONCLUSIONS: In a cadaveric study, anterior-posterior tibial translation did not differ from native laxity after PKA and CPKA. Posterior cruciate ligament-preserving TKA demonstrated increased laxity, particularly in anterior tibial translation.
Assuntos
Artroplastia do Joelho , Ligamento Cruzado Posterior , Ligamento Cruzado Anterior/cirurgia , Fenômenos Biomecânicos , Humanos , Articulação do Joelho/diagnóstico por imagem , Articulação do Joelho/cirurgia , Ligamento Cruzado Posterior/cirurgiaRESUMO
The study "Contribution of the Pubofemoral Ligament to Hip Stability: A Biomechanical Study" by Martin, Khoury, Schröder, Johnson, Gómez-Hoyos, Campos, and Palmer found that cutting the hip capsular ligament allowed a large increase in femoral internal rotation, particularly in the flexed hip, causing subluxation to occur. In addition to providing new data on the role of the pubofemoral ligament, it raises the question of whether hip joint surgeons should repair the capsule-what are the likely consequences?-and whether any beneficial effects persist in long-term clinical follow-ups. For now, hip capsular repair seems a sound adjunct to hip arthroscopic surgery.
Assuntos
Artroscopia , Articulação do Quadril/cirurgia , Humanos , Ligamentos Articulares/cirurgia , Amplitude de Movimento Articular , RotaçãoRESUMO
Achieving osseointegration is a fundamental requirement for many orthopaedic, oral, and craniofacial implants. Osseointegration typically takes three to 6 months, during which time implants are at risk of loosening. The aim of this study was to investigate whether osseointegration could be actively enhanced by delivering controllable electromechanical stimuli to the periprosthetic bone. First, the osteoconductivity of the implant surface was confirmed using an in vitro culture with murine preosteoblasts. The effects of active treatment on osseointegration were then investigated in a 21-day ex vivo model with freshly harvested cancellous bone cylinders (n = 24; Ø10 mm × 5 mm) from distal porcine femora, with comparisons to specimens treated by a distant ultrasound source and static controls. Cell viability, proliferation and distribution was evident throughout culture. Superior ongrowth of tissue onto the titanium discs during culture was observed in the actively stimulated specimens, with evidence of ten-times increased mineralisation after 7 and 14 days of culture (p < 0.05) and 2.5 times increased expression of osteopontin (p < 0.005), an adhesive protein, at 21 days. Moreover, histological analyses revealed increased bone remodelling at the implant-bone interface in the actively stimulated specimens compared to the passive controls. Active osseointegration is an exciting new approach for accelerating bone growth into and around implants.
RESUMO
Introduction: Arthroplasty-associated bone loss remains a clinical problem: stiff metallic implants disrupt load transfer to bone and, hence, its remodeling stimulus. The aim of this research was to analyze how load transfer to bone is affected by different forms of knee arthroplasty: isolated partial knee arthroplasty (PKA), compartmental arthroplasty [combined partial knee arthroplasty (CPKA), two or more PKAs in the same knee], and total knee arthroplasty (TKA). Methods: An experimentally validated subject-specific finite element model was analyzed native and with medial unicondylar, lateral unicondylar, patellofemoral, bi-unicondylar, medial bicompartmental, lateral bicompartmental, tricompartmental, and total knee arthroplasty. Three load cases were simulated for each: gait, stair ascent, and sit-to-stand. Strain shielding and overstraining were calculated from the differences between the native and implanted states. Results: For gait, the TKA femoral component led to mean strain shielding (30%) more than three times higher than that of PKA (4%-7%) and CPKA (5%-8%). Overstraining was predicted in the proximal tibia (TKA 21%; PKA/CPKA 0%-6%). The variance in the distribution for TKA was an order of magnitude greater than for PKA/CPKA, indicating less physiological load transfer. Only the TKA-implanted femur was sensitive to the load case: for stair ascent and gait, almost the entire distal femur was strain-shielded, whereas during sit-to-stand, the posterior femoral condyles were overstrained. Discussion: TKA requires more bone resection than PKA and CPKA. These finite element analyses suggest that a longer-term benefit for bone is probable as partial and multi-compartmental knee procedures lead to more natural load transfer compared to TKA. High-flexion activity following TKA may be protective of posterior condyle bone resorption, which may help explain why bone loss affects some patients more than others. The male and female bone models used for this research are provided open access to facilitate future research elsewhere.
RESUMO
Periprosthetic infection is one of the most devastating complications following orthopaedic surgery. Rapid detection of an infection can change the treatment pathway and improve outcomes for the patient. In here, we propose a miniaturized lactate biosensor developed on a flexible substrate and integrated on a small-form bone implant to detect infection. The methods for lactate biosensor fabrication and integration on a bone implant are fully described within this study. The system performance was comprehensively electrochemically characterised, including with L-lactate solutions prepared in phosphate-buffered saline and culture medium, and interferents such as acetaminophen and ascorbic acid. A proof-of-concept demonstration was then conducted with ex vivo ovine femoral heads incubated with and without exposure to Staphylococcus epidermidis. The sensitivity, current density and limit-of-detection levels achieved by the biosensor were 1.25 µA mM-1, 1.51 µA.M-1.mm-2 and 66 µM, respectively. The system was insensitive to acetaminophen, while sensitivity to ascorbic acid was half that of the sensitivity to L-lactate. In the ex vivo bone model, S. epidermidis infection was detected within 5 h of implantation, while the control sample led to no change in the sensor readings. This pioneering work demonstrates a pathway to improving orthopaedic outcomes by enabling early infection diagnosis.
Assuntos
Técnicas Biossensoriais , Ácido Láctico , Infecções Estafilocócicas , Staphylococcus epidermidis , Infecção da Ferida Cirúrgica , Técnicas Biossensoriais/métodos , Animais , Staphylococcus epidermidis/isolamento & purificação , Ovinos , Infecções Estafilocócicas/diagnóstico , Infecção da Ferida Cirúrgica/diagnóstico , Ácido Láctico/análise , Ácido Láctico/química , Humanos , Tecnologia sem Fio , Próteses e Implantes , Desenho de Equipamento , Infecções Relacionadas à Prótese , Enzimas Imobilizadas/química , Ortopedia , Oxigenases de Função MistaRESUMO
OBJECTIVE: The aim of this study is to understand stakeholder experiences of diagnosis of cardiovascular disease (CVD) to support the development of technological solutions that meet current needs. Specifically, we aimed to identify challenges in the process of diagnosing CVD, to identify discrepancies between patient and clinician experiences of CVD diagnosis, and to identify the requirements of future health technology solutions intended to improve CVD diagnosis. DESIGN: Semistructured focus groups and one-to-one interviews to generate qualitative data that were subjected to thematic analysis. PARTICIPANTS: UK-based individuals (N=32) with lived experience of diagnosis of CVD (n=23) and clinicians with experience in diagnosing CVD (n=9). RESULTS: We identified four key themes related to delayed or inaccurate diagnosis of CVD: symptom interpretation, patient characteristics, patient-clinician interactions and systemic challenges. Subthemes from each are discussed in depth. Challenges related to time and communication were greatest for both stakeholder groups; however, there were differences in other areas, for example, patient experiences highlighted difficulties with the psychological aspects of diagnosis and interpreting ambiguous symptoms, while clinicians emphasised the role of individual patient differences and the lack of rapport in contributing to delays or inaccurate diagnosis. CONCLUSIONS: Our findings highlight key considerations when developing digital technologies that seek to improve the efficiency and accuracy of diagnosis of CVD.
Assuntos
Doenças Cardiovasculares , Diagnóstico Tardio , Grupos Focais , Pesquisa Qualitativa , Humanos , Doenças Cardiovasculares/diagnóstico , Reino Unido , Feminino , Masculino , Pessoa de Meia-Idade , Adulto , Diagnóstico Tardio/prevenção & controle , Idoso , Tecnologia Digital , Relações Médico-Paciente , Tecnologia Biomédica , Entrevistas como Assunto , Comunicação , Erros de Diagnóstico/prevenção & controle , Participação dos Interessados , Saúde DigitalRESUMO
OBJECTIVE: Ultrasound speckle tracking enables in vivo measurement of soft tissue deformation or strain, providing a non-invasive diagnostic tool to quantify tissue health. However, adoption into new fields is challenging since algorithms need to be tuned with gold-standard reference data that are expensive or impractical to acquire. Here, we present a novel optimization approach that only requires repeated measurements, which can be acquired for new applications where reference data might not be readily available or difficult to get hold of. METHODS: Soft tissue motion was captured using ultrasound for the medial collateral ligament (MCL) of three quasi-statically loaded porcine stifle joints, and medial ligamentous structures of a dynamically loaded human cadaveric knee joint. Using a training subset, custom speckle tracking algorithms were created for the porcine and human ligaments using surrogate optimization, which aimed to maximize repeatability by minimizing the normalized standard deviation of calculated strain maps for repeat measurements. An unseen test subset was then used to validate the tuned algorithms by comparing the ultrasound strains to digital image correlation (DIC) surface strains (porcine specimens) and length change values of the optically tracked ligament attachments (human specimens). RESULTS: After 1500 iterations, the optimization routine based on the porcine and human training data converged to similar values of normalized standard deviations of repeat strain maps (porcine: 0.19, human: 0.26). Ultrasound strains calculated for the independent test sets using the tuned algorithms closely matched the DIC measurements for the porcine quasi-static measurements (R > 0.99, RMSE < 0.59%) and the length change between the tracked ligament attachments for the dynamic human dataset (RMSE < 6.28%). Furthermore, strains in the medial ligamentous structures of the human specimen during flexion showed a strong correlation with anterior/posterior position on the ligaments (R > 0.91). CONCLUSION: Adjusting ultrasound speckle tracking algorithms using an optimization routine based on repeatability led to robust and reliable results with low RMSE for the medial ligamentous structures of the knee. This tool may be equally beneficial in other soft-tissue displacement or strain measurement applications and can assist in the development of novel ultrasonic diagnostic tools to assess soft tissue biomechanics.
Assuntos
Algoritmos , Ultrassonografia , Suínos , Humanos , Animais , Ultrassonografia/métodos , Reprodutibilidade dos Testes , Cadáver , Articulação do Joelho/diagnóstico por imagem , Joelho de Quadrúpedes/diagnóstico por imagemRESUMO
BACKGROUND: Knee alignment affects the development and surgical treatment of knee osteoarthritis. Automating femorotibial angle (FTA) and hip-knee-ankle angle (HKA) measurement from radiographs could improve reliability and save time. Further, if HKA could be predicted from knee-only radiographs then radiation exposure could be reduced and the need for specialist equipment and personnel avoided. The aim of this research was to assess if deep learning methods could predict FTA and HKA angle from posteroanterior (PA) knee radiographs. METHODS: Convolutional neural networks with densely connected final layers were trained to analyse PA knee radiographs from the Osteoarthritis Initiative (OAI) database. The FTA dataset with 6149 radiographs and HKA dataset with 2351 radiographs were split into training, validation, and test datasets in a 70:15:15 ratio. Separate models were developed for the prediction of FTA and HKA and their accuracy was quantified using mean squared error as loss function. Heat maps were used to identify the anatomical features within each image that most contributed to the predicted angles. RESULTS: High accuracy was achieved for both FTA (mean absolute error 0.8°) and HKA (mean absolute error 1.7°). Heat maps for both models were concentrated on the knee anatomy and could prove a valuable tool for assessing prediction reliability in clinical application. CONCLUSION: Deep learning techniques enable fast, reliable and accurate predictions of both FTA and HKA from plain knee radiographs and could lead to cost savings for healthcare providers and reduced radiation exposure for patients.
Assuntos
Aprendizado Profundo , Osteoartrite do Joelho , Humanos , Tornozelo , Reprodutibilidade dos Testes , Articulação do Joelho/cirurgia , Extremidade Inferior , Osteoartrite do Joelho/cirurgia , Estudos RetrospectivosRESUMO
INTRODUCTION: Cardiovascular diseases are highly prevalent among the UK population, and the quality of care is being reduced due to accessibility and resource issues. Increased implementation of digital technologies into the cardiovascular care pathway has enormous potential to lighten the load on the National Health Service (NHS), however, it is not possible to adopt this shift without embedding the perspectives of service users and clinicians. METHODS AND ANALYSIS: A series of qualitative studies will be carried out with the aim of developing a stakeholder-led perspective on the implementation of digital technologies to improve holistic diagnosis of heart disease. This will be a decentralised study with all data collection being carried out online with a nationwide cohort. Four focus groups, each with 5-6 participants, will be carried out with people with lived experience of heart disease, and 10 one-to-one interviews will be carried out with clinicians with experience of diagnosing heart diseases. The data will be analysed using an inductive thematic analysis approach. ETHICS AND DISSEMINATION: This study received ethical approval from the Sciences and Technology Cross Research Council at the University of Sussex (reference ER/FM409/1). Participants will be required to provide informed consent via a Qualtrics survey before being accepted into the online interview or focus group. The findings will be disseminated through conference presentations, peer-reviewed publications and to the study participants.
Assuntos
Cardiopatias , Medicina Estatal , Humanos , Tecnologia Digital , Pesquisa Qualitativa , Inquéritos e Questionários , Cardiopatias/diagnósticoRESUMO
Introduction: Preclinical assessment of bone remodelling onto, into or around novel implant technologies is underpinned by a large live animal testing burden. The aim of this study was to explore whether a lab-based bioreactor model could provide similar insight. Method: Twelve ex vivo trabecular bone cylinders were extracted from porcine femora and were implanted with additively manufactured stochastic porous titanium implants. Half were cultured dynamically, in a bioreactor with continuous fluid flow and daily cyclic loading, and half in static well plates. Tissue ongrowth, ingrowth and remodelling around the implants were evaluated with imaging and mechanical testing. Results: For both culture conditions, scanning electron microscopy (SEM) revealed bone ongrowth; widefield, backscatter SEM, micro computed tomography scanning, and histology revealed mineralisation inside the implant pores; and histology revealed woven bone formation and bone resorption around the implant. The imaging evidence of this tissue ongrowth, ingrowth and remodelling around the implant was greater for the dynamically cultured samples, and the mechanical testing revealed that the dynamically cultured samples had approximately three times greater push-through fixation strength (p < 0.05). Discussion: Ex vivo bone models enable the analysis of tissue remodelling onto, into and around porous implants in the lab. While static culture conditions exhibited some characteristics of bony adaptation to implantation, simulating physiological conditions with a bioreactor led to an accelerated response.
RESUMO
Smart implantable electronic medical devices are being developed to deliver healthcare that is more connected, personalised, and precise. Many of these implantables rely on piezoceramics for sensing, communication, energy autonomy, and biological stimulation, but the piezoceramics with the strongest piezoelectric coefficients are almost exclusively lead-based. In this article, we evaluate the electromechanical and biological characteristics of a lead-free alternative, 0.94Bi0.5Na0.5TiO3-0.06BaTiO3 (BNT-6BT), manufactured via two synthesis routes: the conventional solid-state method (PIC700) and tape casting (TC-BNT-6BT). The BNT-6BT materials exhibited soft piezoelectric properties, with d33 piezoelectric coefficients that were inferior to commonly used PZT (PIC700: 116 pC/N; TC-BNT-6BT: 121 pC/N; PZT-5A: 400 pC/N). The material may be viable as a lead-free substitute for soft PZT where moderate performance losses up to 10 dB are tolerable, such as pressure sensing and pulse-echo measurement. No short-term harmful biological effects of BNT-6BT were detected and the material was conducive to the proliferation of MC3T3-E1 murine preosteoblasts. BNT-6BT could therefore be a viable material for electroactive implants and implantable electronics without the need for hermetic sealing.
Assuntos
Comércio , Próteses e Implantes , Animais , Camundongos , Íons , Comunicação , EletrônicaRESUMO
Modern orthopaedic implants use lattice structures that act as 3D scaffolds to enhance bone growth into and around implants. Stochastic scaffolds are of particular interest as they mimic the architecture of trabecular bone and can combine isotropic properties and adjustable structure. The existing research mainly concentrates on controlling the mechanical and biological performance of periodic lattices by adjusting pore size and shape. Still, less is known on how we can control the performance of stochastic lattices through their design parameters: nodal connectivity, strut density and strut thickness. To elucidate this, four lattice structures were evaluated with varied strut densities and connectivity, hence different local geometry and mechanical properties: low apparent modulus, high apparent modulus, and two with near-identical modulus. Pre-osteoblast murine cells were seeded on scaffolds and cultured in vitro for 28 days. Cell adhesion, proliferation and differentiation were evaluated. Additionally, the expression levels of key osteogenic biomarkers were used to assess the effect of each design parameter on the quality of newly formed tissue. The main finding was that increasing connectivity increased the rate of osteoblast maturation, tissue formation and mineralisation. In detail, doubling the connectivity, over fixed strut density, increased collagen type-I by 140%, increased osteopontin by 130% and osteocalcin by 110%. This was attributed to the increased number of acute angles formed by the numerous connected struts, which facilitated the organization of cells and accelerated the cell cycle. Overall, increasing connectivity and adjusting strut density is a novel technique to design stochastic structures which combine a broad range of biomimetic properties and rapid ossification.
RESUMO
The mechanical advantage of the knee extensor mechanism depends heavily on the patellar tendon moment arm (PTMA). Understanding which factors contribute to its variation may help improve functional outcomes following arthroplasty. This study optimized PTMA measurement, allowing us to quantify the contribution of different variables. The PTMA was calculated about the instantaneous helical axis of tibiofemoral rotation from optical tracked kinematics. A fabricated knee model facilitated calculation optimization, comparing four data smoothing techniques (raw, Butterworth filtering, generalized cross-validated cubic spline-interpolation and combined filtering/interpolation). The PTMA was then measured for 24 fresh-frozen cadaveric knees, under physiologically based loading and extension rates. Combined filtering/interpolation enabled sub-mm PTMA calculation accuracy throughout the range of motion (root-mean-squared error 0.2 mm, max error 0.4 mm), whereas large errors were measured for raw, filtered-only and interpolated-only techniques at terminal flexion/extension. Before scaling, the mean PTMA was 46 mm; PTMA magnitude was consistently larger in males (mean differences: 5 to 10 mm, p < .05) and was strongly related to knee size: larger knees have a larger PTMA. However, while scaling eliminated sex differences in PTMA magnitude, the peak PTMA occurred closer to terminal extension in females (female 15°, male 29°, p = .01). Knee size accounted for two-thirds of the variation in PTMA magnitude, but not the flexion angle where peak PTMA occurred. This substantial variation in angle of peak PTMA has implications for the design of musculoskeletal models and morphotype-specific arthroplasty. The developed calculation framework is applicable both in vivo and vitro for accurate PTMA measurement.
Assuntos
Prótese do Joelho , Ligamento Patelar , Fenômenos Biomecânicos , Feminino , Humanos , Joelho , Articulação do Joelho/fisiologia , Masculino , Ligamento Patelar/fisiologia , Amplitude de Movimento Articular/fisiologiaRESUMO
AIMS: The aim of this study was to determine the risk of tibial eminence avulsion intraoperatively for bi-unicondylar knee arthroplasty (Bi-UKA), with consideration of the effect of implant positioning, overstuffing, and sex, compared to the risk for isolated medial unicondylar knee arthroplasty (UKA-M) and bicruciate-retaining total knee arthroplasty (BCR-TKA). METHODS: Two experimentally validated finite element models of tibia were implanted with UKA-M, Bi-UKA, and BCR-TKA. Intraoperative loads were applied through the condyles, anterior cruciate ligament (ACL), medial collateral ligament (MCL), and lateral collateral ligament (LCL), and the risk of fracture (ROF) was evaluated in the spine as the ratio of the 95th percentile maximum principal elastic strains over the tensile yield strain of proximal tibial bone. RESULTS: Peak tensile strains occurred on the anterior portion of the medial sagittal cut in all simulations. Lateral translation of the medial implant in Bi-UKA had the largest increase in ROF of any of the implant positions (43%). Overstuffing the joint by 2 mm had a much larger effect, resulting in a six-fold increase in ROF. Bi-UKA had ~10% increased ROF compared to UKA-M for both the male and female models, although the smaller, less dense female model had a 1.4 times greater ROF compared to the male model. Removal of anterior bone akin to BCR-TKA doubled ROF compared to Bi-UKA. CONCLUSION: Tibial eminence avulsion fracture has a similar risk associated with Bi-UKA to UKA-M. The risk is higher for smaller and less dense tibiae. To minimize risk, it is most important to avoid overstuffing the joint, followed by correctly positioning the medial implant, taking care not to narrow the bone island anteriorly.Cite this article: Bone Joint Res 2022;11(8):575-584.
RESUMO
The frequency of surgeries involving the use of metal implants in orthopedic medicine to replace degenerative or fractured joints is increasing, and it is therefore important to optimize the lifespan and quality of these implants. Advances in additive manufacturing (AM), or 3D printing, are creating new opportunities to personalize implants in ways that reduce mechanical stress at the joint implant interface and improve bone ingrowth and implant stability; however, it is not well understood if and to what degree the AM process alters the corrosion behavior of the materials it produces. In this study, six Ti6Al4V prints manufactured via a selective laser melting (SLM) method were examined regarding their corrosion behavior in both saline and bovine calf serum (BCS) solutions. Ecorr and Icorr values were comparable between the CM-Ti6Al4V control and SLM-EDM surfaces; however, SLM surfaces were found to have more narrow passivation behavior evidenced by significant decreases in Epass values relative to CM-Ti6Al4V. We believe this is a consequence of microstructural differences between CM-Ti6Al4V and SLM-Ti6Al4V. Specifically, the SLM-Ti6Al4V demonstrated a dominant α' martensitic microstructure and decreased vanadium-rich ß-phase. BCS solution had a detrimental effect on potential parameters, Ecorr and OCP, decreasing these values relative to their saline counterparts. Increased surface roughness of the SLM-printed surface seemed to amplify the effects of the BCS solution. Furthermore, modest decreases in Epass and Ipass were observed in BCS solution, suggesting that the presence of protein may also interfere with passivation behavior. These findings have implications for how SLM-Ti6Al4V implants will perform in vivo and could possibly influence implant longevity and performance.
RESUMO
Stiff total hip arthroplasty implants can lead to strain shielding, bone loss and complex revision surgery. The aim of this study was to develop topology optimisation techniques for more compliant hip implant design. The Solid Isotropic Material with Penalisation (SIMP) method was adapted, and two hip stems were designed and additive manufactured: (1) a stem based on a stochastic porous structure, and (2) a selectively hollowed approach. Finite element analyses and experimental measurements were conducted to measure stem stiffness and predict the reduction in stress shielding. The selectively hollowed implant increased peri-implanted femur surface strains by up to 25 percentage points compared to a solid implant without compromising predicted strength. Despite the stark differences in design, the experimentally measured stiffness results were near identical for the two optimised stems, with 39% and 40% reductions in the equivalent stiffness for the porous and selectively hollowed implants, respectively, compared to the solid implant. The selectively hollowed implant's internal structure had a striking resemblance to the trabecular bone structures found in the femur, hinting at intrinsic congruency between nature's design process and topology optimisation. The developed topology optimisation process enables compliant hip implant design for more natural load transfer, reduced strain shielding and improved implant survivorship.