Improved stability with intramedullary stem after anterior femoral notching in total knee arthroplasty.

PURPOSE: It has been hypothesized that femoral notching in total knee arthroplasties weakens the cortex of the femur, which can predispose to femoral fractures in the postoperative period. Some authors suggest that patients who sustain inadvertent notching should have additional protection in the postoperative period, and consideration should be given to the use of prophylactic femoral stems. In this case, a question can be raised: Is the use of femoral stem in an anterior femoral notching an effective way to reduce the fracture risk? We hypothesized that for a larger notch, the use of a femoral stem does not decrease considerably the stress-riser at the notch edge, and the use of stem is not enough to reduce the risk of fracture. METHODS: In the present in vitro study, twelve synthetic femurs were selected and used for the experiments under two load scenarios. Femoral components with and without femoral stems were implanted in femurs with different notch sizes to predict experimentally the strain levels at the notch edge with the use of fiber Bragg gratings and at notch region with strain gauges. RESULTS: Despite the global strain reduction in stemmed condition, at the notch edge, the strain behavior was dissimilar for the different notch depths. For notch depths lower than 5 mm, the use of stem reduces the strain level at the notch edge to values below the intact femur condition, while for depths greater or equal to 5 mm, the strain levels at the notch edge were higher than the intact femur condition with values ranging from +10 to +189%. CONCLUSIONS: The present study suggests the use of a prophylactic stem for notch depths greater than 5 mm. For notch depths below 5 mm, the fracture risk due to strain increase at the notch edge seems to be low in the stemless condition.

The use of Taguchi technique to optimize the compression moulding cycle to process acetabular cup components.

Taguchi technique is a powerful method of solving engineering problems in order to improve the performance of a process and to enhance the productivity. The methodology for the design of the experiment is proposed in order to find the best parameters for better experimental results with less number of experiments as possible. In this study, Taguchi technique was applied to optimize the compression moulding cycle for processing the Acetabular cup prototype. For the design of the experiments, three main factors such as processing temperature, pressure and the time of compaction were identified which directly influence the quality of the final product. For each factor three levels were considered and an orthogonal array L9 was associated. With the L9 orthogonal array, a total of 9 trial experiments have been performed and the optimum parameters were identified. An experimental test was performed in order to validate the founded conditions. The optimized conditions encountered were: processing temperature of 160 degrees C, processing pressure of 1000 psi and the compaction time of 90 s. With these optimized parameters, the acetabular cup prototypes were processed for nanocomposites having ultra-high molecular weight (UHMWPE) reinforced with different volume fractions of carbon nanotubes (CNTs) in the range of 0.2 to 2.0 vol.%.

Biomechanical analysis comparing natural and alloplastic temporomandibular joint replacement using a finite element model.

PURPOSE: Prosthetic materials and bone present quite different mechanical properties. Consequently, mandible reconstruction with metallic materials (or a mandible condyle implant) modifies the physiologic behavior of the mandible (stress, strain patterns, and condyle displacements). The changing of bone strain distribution results in an adaptation of the temporomandibular joint, including articular contacts. MATERIALS AND METHODS: Using a validated finite element model, the natural mandible strains and condyle displacements were evaluated. Modifications of strains and displacements were then assessed for 2 different temporomandibular joint implants. Because materials and geometry play important key roles, mechanical properties of cortical bone were taken into account in models used in finite element analysis. RESULTS: The finite element model allowed verification of the worst loading configuration of the mandibular condyle. Replacing the natural condyle by 1 of the 2 tested implants, the results also show the importance of the implant geometry concerning biomechanical mandibular behavior. The implant geometry and stiffness influenced mainly strain distribution. CONCLUSION: The different forces applied to the mandible by the elevator muscles, teeth, and joint loads indicate that the finite element model is a relevant tool to optimize implant geometry or, in a subsequent study, to choose a more suitable distribution of the screws. Bone screws (number and position) have a significant influence on mandibular behavior and on implant stress pattern. Stress concentration and implant fracture must be avoided.

Finite element modelling and experimental validation of a total implanted shoulder joint.

Background Replicating a total shoulder arthroplasty in laboratory is a difficult task due to complex geometry of the structures and degrees of freedom of the joint. Implanted joint shoulders have been investigated using numerical tools, but models developed lack of experimental validation. The objective of this study was to develop a finite element model that replicated correctly an experimental simulator of an implanted joint shoulder based on the comparison of measured and calculated strains. The methods used include a non-cemented Anatomical Comprehensive© Total Shoulder System that was implanted in 4th generation composite bones. The finite element model designed replicates adequately the experimental model. Both models included the most important muscles of shoulder abduction and the same boundary conditions (loads, fixation, and interface conditions). Strain gauge rosettes were used to measure strain responses on the shoulder in 90° abduction. The results of linear regression analysis between numerical and experimental results present a high correlation coefficient of 0.945 and a root-mean-square-error of 35 µÎµ, suggesting adequate agreement between the experimental and the numerical models. Small strains were obtained and changes in load distribution from posterior to anterior region were observed. As conclusion we can say that the experiments allowed good replication of the finite element model, and the use of strain gauges is suitable for numerical-experimental validation of bone joints.

Strain shielding in proximal tibia of stemmed knee prosthesis: experimental study.

Theoretical concerns about the use of cemented or press-fit stems in revision total knee arthroplasty (TKA) include stress shielding with adverse effects on prosthesis fixation. Revision TKA components are commonly stemmed to protect the limited autogenous bone stock remaining. Revision procedures with the use of stems can place abnormal stresses through even normal bone by their constrained design, type of materials and fixation method and may contribute for bone loss. Experimental quantification of strain shielding in the proximal synthetic tibia following TKA is the main purpose of the present study. In this study, cortical bone strains were measured experimentally with tri-axial strain gauges in synthetic tibias before and after in vitro knee surgery. Three tibias were implanted with cemented and press-fit stem augments and solely with a tibial tray (short monobloc stem) of the P.F.C. Sigma Modular Knee System. The difference between principal strains of the implanted and the intact tibia was calculated for each strain gauge position. The results demonstrated a pronounced strain-shielding effect in the proximal level, close to tibial tray with the cemented stem augment. The press-fit stem presented a minor effect of strain shielding but was more extensively throughout the stem. An increase of strains closely to the distal tip of the cemented and the press-fit stem augment was observed. This suggests for a physiological condition, a potential effect of bone resorption at the proximal region for the cemented stem augment. The localized increase of strains in stems tip can be related with the clinical finding of the pain, at the end of stem after revision TKA.

The influence of different tibial stem designs in load sharing and stability at the cement-bone interface in revision TKA.

Total Knee Arthroplasty (TKA) changes mechanical loading of the knee joint. Bone loss in the tibia is commonly encountered at the time of the revision TKA. Restoration of lost bone support and joint stability are the primary challenges in revision TKA. Normally, these defects are treated with non-living structures like metallic augments or bone grafts (autografts or allografts). Alone, neither of these structures can provide the initial support and stability for revision implants. In the latter, the use of intramedullary stems can provide the necessary load sharing and protect the remaining host bone and graft from excessive stress, increasing component stability. The purpose of this study was to evaluate comparatively load sharing (cortical rim, cancellous bone and stem) and stability at the cement-bone interface under the tibial tray induced by the use of cemented and press-fit tibial component stem extensions. Furthermore the study of the desirable option in cases where the bone defect is cavitary (cancellous bone defect contained by an intact cortical rim) or uncontained bone defect (bone loss involving the supporting cortical rim) was carried out. Because in vitro evaluation of these biomechanical parameters is difficult we used finite element (FE) models to overcome this. The biomechanical results suggest an identical behaviour in case of cavitary defects for both types of stems assessed. In the case of uncontained defect treated with bulk allografts the cemented stem may be a prudent clinical option.

Hereditary angioedema with C1 inhibitor (C1-INH) deficit: the strength of recognition (51 cases).

Hereditary angioedema (HAE) is a rare autosomal dominant disease due to C1 esterase inhibitor deficiency (C1-INH). The disease is characterized by subcutaneous and submucosal edema in the absence of urticaria due to the accumulation of bradykinin. This descriptive study aimed to evaluate the clinical characteristics of patients with a confirmed diagnosis of HAE referred to our Outpatient Clinic between December 2009 and November 2017. Fifty-one patients (38 F, 13 M) with a mean age of 32 years (range: 7-70 y) were included. Family history of HAE was reported in 70% (36/51) of the cases; 33/46 patients became symptomatic by 18 years of age. The median time between onset of symptoms and diagnosis was 13 years (3 mo-50 y). The most frequent triggering factors for attacks were stress (74.4%), trauma (56.4%), and hormonal variations (56%). The main symptoms were subcutaneous edema in 93.5% (43/46) of patients, gastrointestinal symptoms in 84.8% (39/46), and obstruction in the upper airways in 34.8% (16/46). Hospitalization occurred in 65.2%, of whom 13.3% had to be transferred to the Intensive Care Unit. Prophylactic treatment was instituted in 87% (40/46) of patients, and 56.5% (26/46) required additional treatment to control attacks. Owing to our data collection over a period of 8 years, a significant number of patients were identified by this HAE reference center. Despite early recognition and prophylactic treatment, a high percentage of patients were hospitalized. HAE is still diagnosed late, reinforcing the need for more reference centers specialized in diagnosis and educational projects for health professionals.

A New Light Trap Model as an Alternative for Controlling Pests in Eucalyptus Plantations.

Eucalyptus plantations can be affected by species of defoliating caterpillars. The integrated management of this group primarily involves a monitoring system, natural enemies, and biological products. Alternative control methods, including the use of conventional light traps, have not been adopted, mostly because of their low efficiency. Therefore, a more efficient light trap model was developed. The new model allowed the capture of 3.6 times as many insects as the conventional model, with a 261% gain in control efficiency. The use of this new model represents another integrated management alternative for lepidopteran pests of eucalyptus plantations and other cultured plants.

Experimental validation of intact and implanted distal femur finite element models.

Four finite element (FE) models of intact and distal femur of knee replacements were validated relative to measured bone strains. FE models of linear tetrahedrons were used. Femoral replacements with cemented stemless, cemented and noncemented femoral stems of the PFC Sigma Modular Knee System were analyzed. Bone strains were recorded at ten locations on the cortex. The magnitude of the FE bone strains corresponded to the mean measured strains, with an overall agreement of 10%. Linear regression between the FE and mean experimental strains produced slopes between 0.94 and 1.06 and R(2) values between 0.92 and 0.99. RSME values were less than 12%. The FE models were able to adequately replicate the mechanical behavior of distal femur reconstructions.

Beef palatability and its relationship with protein degradation and muscle fibre type profile in longissimus thoracis in Alentejana breed from divergent growth pathways.

The traditional beef production in the South of Portugal is based on a discontinuous growth (DG) system that requires lower external inputs and could enhance meat quality and financial returns to cattle producers. This system allows farmers to take advantage of the bull's compensatory growth when the pasture is abundant and finishes the cattle on concentrates for 2 to 3 months before slaughter. The fast gain rate before slaughter could be a valuable strategy to improve tenderness and to reduce its inconsistency in beef production. Therefore, the aim of this study was to evaluate the effects of production system (continuous growth (CG) v. DG) on longissimus thoracis muscle properties from Alentejana bulls. In total, 40 Alentejana male calves were allocated to two distinct feeding regimes: in the CG system, animals were fed concentrate plus hay and slaughtered at 18 months of age, whereas in the DG system, animals were fed on hay until 15 months of age and then fed the same diet provided to the CG group until 24 months of age. The DG system had a positive impact on meat tenderness (P<0.001) and global acceptability (P<0.001). DG bulls had greater fibre cross-sectional area (CSA) of glycolytic fibres (P<0.05) and relative area of the muscle (RA) occupied by type IIX fibres (P<0.01) and greater levels of α-actinin (P<0.05) and myosin light chain 2 (P<0.01) proteins, and pH24h (P<0.01) than CG bulls. The latter had greater CSA of type I (P<0.05) and type IIA (P<0.01) and greater RA of type IIA (P<0.05) and oxidative (P<0.05) than CG bulls. The compensatory growth production system had a positive impact on meat tenderness and global acceptability, overcoming the negative effects of slaughter of the bulls at a later age. The DG beef system could be a worthwhile strategy of beef production in Mediterranean areas due to the low-quality pasture in summer.

Viscoelastic behaviour and failure of bovine cancellous bone under constant strain rate.

A programme has been established to characterize the long-term behaviour of cancellous bone. Fresh bovine cancellous specimens of dimensions 10 x 10 x 10 mm3 and 10 x 40 x 3.6 mm3 were manufactured and used within the testing programme. Results published in the literature indicate that the long-term behaviour of cancellous bone is well described by a power law, which is a very similar response of typical polymers. So far, dynamic mechanical tests (DMA) in three-point bending, under frequencies between 0.01 and 100 Hz at room temperature, confirmed the published results in a qualitative way. Nevertheless, the measured dimensionless damping, tan delta, was slightly higher than the values reported in the literature for the compact bone. The relaxation curves were obtained from dynamic tests and confirmed that bone relaxation modulus can be described by a power law function of time. Tests under constant compression strain rate were performed at four different strain rates: 0.15/s, 0.015/s, 0.0015/s and 0.00015/s and strain rate dependent behaviour was observed. An average elastic bending modulus of 300 MPa was obtained.

Clinical diagnosis of bacterial vaginosis.

OBJECTIVE: To evaluate the accuracy of Amsel's criteria individually or in combinations of two for the clinical diagnosis of bacterial vaginosis. METHODS: This cross-sectional study enrolled 135 women at UNICAMP, and evaluated Amsel's four clinical criteria. Sensitivity, specificity, positive and negative predictive values were calculated for each criterion individually, in combinations of two, and for the classic test with at least three criteria present. The Nugent method was used as gold standard. RESULTS: The most sensitive individual criteria were pH and vaginal discharge (97%), the latter having lowest specificity (26%). The criterion with highest specificity was the presence of clue cells (86%). The combination of two criteria showed sensitivity of 83% to 93%, and specificity of 82% to 94%. CONCLUSION: The accuracy of Amsel's clinical criteria individually or in combinations of two was as accurate as the presence of at least three criteria for the diagnosis of bacterial vaginosis.

Tetrahedral versus hexahedral finite elements in numerical modelling of the proximal femur.

The objective of this study was to evaluate and compare tetrahedral and hexahedral finite element meshes of simplified and realistic proximal intact femur geometries. Theoretical expressions of stresses and strains were derived for the simplified model of the femur. For the analysis of the realistic geometry of the proximal femur, a CAD model of the third generation composite femur (Pacific Research Labs, Vashion Island, WA) was used and simulations were performed with Hyperworks (Altair Engineering, Inc., Troy, MI) finite element analysis software. Convergence tests with hexahedral (8- and 20-node brick-elements) and tetrahedral (4- and 10-node tetrahedrons) elements were analysed by comparing the periosteal von Mises stresses and principal strains at a selected point of the femur. The numerical periosteal strains were also compared with experimental ones to determine the accuracy of the finite elements. Overall, we concluded, for the simplified femur, that tetrahedral linear element allowed results more closely to theoretical ones, but hexahedral quadratic elements seem to be more stable and less influenced to the degree of refinement (NDOF) of the mesh. It was not possible to correlate these findings with those observed for the realistic proximal femur simulations where no significant differences were seen using refined meshes, with more than NDOF=20,000 for hexahedral elements.

Application of a vibration measuring technique to evaluate the dynamic stiffness of porcine periodontal ligament.

The performance of a tooth replacement by using a dental implant relies on the mechanical and biological capability of the anatomical substitute to restore lost physiological functions. The design of an implant device able to properly replace the physiological tooth requires the study of the load transfer mechanism at the implant-bone interface and the understanding of the relevance of the periodontal ligament (PDL) in this mechanism. The PDL is a connective soft tissue that provides the fixation of the tooth in its bone-socket and the attenuation of occlusal loads. It also provides the ground cells that are involved in the remodelling process, induced by a change in the stress-strain pattern of the alveolar bone and also in the cementum of the tooth root. The purpose of this study was to determine the PDL effects on the dynamic load transfer mechanism, from the tooth to the alveolar bone, evaluating the equivalent dynamic stiffness of the ligament structure. A porcine fresh mandible with a tooth was used within the study, applying an experimental procedure to identify the dynamic transmissibility of the entire system. The transmissibility function provided information about the stiffness and damping of the PDL, information that can assist the design of an improved dental implant system.

Trends in diabetes incidence from 1992 to 2015 and projections for 2024: A Portuguese General Practitioner's Network study.

BACKGROUND: Diabetes is known as a major cause of morbidity and mortality worldwide. Portugal is known as the European country with the highest prevalence of this disease. While diabetes prevalence data is updated annually in Portugal, the General Practitioner's (GP) Sentinel Network represents the only data source on diabetes incidence. This study describes the trends in Diabetes incidence, between 1992 and 2015, and estimate projections for the future incidence rates in Portugal until 2024. METHODS: An ecological time-series study was conducted using data from GP Sentinel Network between 1992 and 2015. Family doctors reported all new cases of Diabetes in their patients' lists. Annual trends were estimated through Poisson regression models as well as the future incidence rates (until 2024), sex and age group stratified. Incidence rate projections were adjusted to the distribution of the resident Portuguese population given Statistics Portugal projections. RESULTS: The average increase in Diabetes incidence rate was in total 4.29% (CI95% 3.80-4.80) per year under study. Until 1998-2000, the annual incidence rate was higher in women, and from 1998-2000 to 2013-2015 turn out to be higher in men. The incidence rate projected for 2022-2024 was 972.77/10(5) inhabitants in total, and 846.74/10(5) and 1114.42/10(5), respectively, in women and men. CONCLUSIONS: This is the first study in Portugal to estimate diabetes incidence rate projections. The disturbing reported projections seem realistic if things continue as in the past. Actually, effective public health policies will need to be undertaken to minimize this alarming future scenario.

Selection of muscles as indicators of tenderness after seven days of ageing.

The selection of a muscle that could be used as an index muscle for beef tenderness was performed using nine commercially important muscles. A total of 50 bulls, Charolais×Alentejano (n=9), Simmental×Alentejano (n=9) and Alentejano (n=32), were slaughtered at two different commercial live weights: crossbred animals (sample A) between 500 and 600 kg (carcass weight between 310 and 370 kg) and purebred Alentejano (sample B) between 350 and 450 kg (carcass weight between 185 and 295 kg). Slaughter ages varied between 16 and 24 months in both groups. The shear force of nine muscles (Mm. biceps femoris, gastrocnemius, longissimus thoracis, longissimus lumborum, quadriceps femoris, semimembranosus, semitendinosus, supraspinatus and triceps brachii caput longum) was assessed seven days post-mortem. In both samples, the comparison between different muscle means and the combined mean of all muscles and the respective correlations showed that the Mm. biceps femoris and semimembranosus could be used as index muscles. However, the biceps femoris is preferred, because it showed greater stability in terms of the coefficient of variation.

The importance of femur/acetabulum cartilage in the biomechanics of the intact hip: experimental and numerical assessment.

Experimental studies have been made to study and validate the biomechanics of the pair femur/acetabulum considering both structures without the presence of cartilage. The main goal of this study was to validate a numerical model of the intact hip. Numerical and experimental models of the hip joint were developed with respect to the anatomical restrictions. Both iliac and femur bones were replicated based on composite replicas. Additionally, a thin layer of silicon rubber was used for the cartilage. A three-dimensional finite element model was developed and the boundary conditions of the models were applied according to the natural physiological constrains of the joint. The loads used in both models were used just for comparison purposes. The biomechanical behaviour of the models was assessed considering the maximum and minimum principal bone strains and von Mises stress. We analysed specific biomechanical parameters in the interior of the acetabular cavity and on femur's surface head to determine the role of the cartilage of the hip joint within the load transfer mechanism. The results of the study show that the stress observed in acetabular cavity was 8.3 to 9.2 MPa. When the cartilage is considered in the joint model, the absolute values of the maximum and minimum peak strains on the femur's head surface decrease simultaneously, and the strains are more uniformly distributed on both femur and iliac surfaces. With cartilage, the cortex strains increase in the medial side of the femur. We prove that finite element models of the intact hip joint can faithfully reproduce experimental models with a small difference of 7%.

Repercussions of growth path on carcass characteristics, meat colour and shear force in Alentejana bulls.

The aim of this study was to evaluate the carcass and meat characteristics of eight muscles from bulls with distinct growth paths. A total of 40 Alentejana male calves were allocated to two distinct feeding regimes. In the continuous growth (CG) system, the animals were fed concentrates plus hay and were slaughtered at 18 months of age. On the other hand, in the discontinuous growth (DG) system, the animals were fed hay until 15 months of age; the cattle were then fed the same diet provided to the CG group from 15 to 24 months of age. The DG reduced hot carcass weight, fatness and dressing %, but the proportions of fat, bone and muscle tissues in the leg were not affected. In contrast, there was a positive impact of compensatory growth on supraspinatus, triceps brachii, semitendinosus, biceps femoris muscle tenderness, overcoming the negative effects of age at slaughter. The reasons for such improvement in meat tenderness were not related to intra-muscular fat content or myofibrillar protein degradation values. An association between tenderness and muscle collagen properties was not established. The results indicate that the compensatory growth has a muscle-dependent effect.

Influence of head constraint and muscle forces on the strain distribution within the intact femur.

The aim of this study was to analyse the influence of muscle action and a horizontally constrained femoral head on the strain distribution within the intact femur. The strain distribution was measured for three loading configurations: joint reaction force only, joint reaction force plus abductors, and joint reaction force plus the abductors, vastus lateralis and iliopsoas. In each case the strains were recorded from 20 uniaxial strain gauges placed on the medial, lateral, anterior and posterior aspects of the proximal femur. Application of the abductor muscle force produced a marginal decrease in the strain levels on all aspects of the femur as compared with the joint reaction force alone. This is in contrast with previous studies which have simulated an unconstrained femoral head. The inclusion of vastus lateralis and iliopsoas further reduced the strain levels. A horizontally constrained femoral head produces smaller variation in the strain levels when muscle forces are applied. In vivo data, demonstrating negligible movement of the femoral head in one-legged stance, support the results of this study and suggest that in the absence of comprehensive muscle force data, a constrained femoral head may provide a more physiologically relevant loading condition.

A note on the muscle, fat and bone contents of Portuguese light lamb carcasses.

A total of 72 lambs weighing between 10.1-13.0 kg (category C of the European Union grading for light lambs) from the Bragançano, Campaniço, Merino Branco, Merino Preto e Serra da Estrela breeds were studied. These breeds represent 66.8% of the Portuguese sheep population. Evaluations were made at the same subcutaneous fat contents in the carcass (88.5 g kg(-1)). Small, significant (p < 0.05) differences in the range of muscle and bone contents were found; the ranges being 30 and 25 g kg(-1), respectively. These variations led to significant diferences in the muscle:bone ratios, the highest value being 3.30 and the lowest 2.73. Significant differences were also found in the content of higher-priced joints (leg + chump, loin + ribs and anterior ribs) and in the proportion of kkcf (9 g kg(-1)). No significant differences were found in the content of total fat [subcutaneous, intermuscular and kidney knob and channel fat (kkcf)] and in the muscle: total fat ratios.