Biomedical subjects

M Barink

Publications and source records attributed to M Barink.

11 recordsLinked to original sources

PubMed2006

Functional evaluation of the TKA patient using the coordination and variability of rising.

A kinematic analysis of the knee function is important for the evaluation of total knee arthroplasties (TKA). We used the coordination and variability of rising from a chair as functional knee parameters. Twelve knee patients were measured prior to surgery (=pre-TKA group) and one year after surgery (=post-TKA group). A group of 15 healthy, age-matched subjects was selected as control group. The WOMAC questionnaire, frequently used by orthopaedic surgeons, was administered prior to the test. The test consisted of 10 times rising from a low chair and 10 times from a high chair. Knee and hip angles and angular velocities were measured with electrogoniometers. The relative phase (=MRP) between hip and knee was a measure for the coordination of rising and the standard deviation of the relative phase of the 10 trials (=SRP) was a measure for the variability. The coordination and variability of rising of the TKA patients were compared to the control group, and the relationship with the WOMAC questionnaire was calculated. The coordination of rising from a high chair and the variability of rising from both chair heights were significantly different for the pre-TKA group compared to the control group (p<0.05). The post-TKA group showed no significant differences with the control group, which indicates a functional recovery after TKA implantation. The functional parameters correlated adequately with the subjective WOMAC questionnaire. This study showed that our method is an objective measure of functionality and it will be worthwhile to use it as an additional evaluation tool.

Aged↗

PubMed2005

The difference in trochlear orientation between the natural knee and current prosthetic knee designs; towards a truly physiological prosthetic groove orientation.

The patella groove of total knee replacements has evolved from a groove with a neutral orientation to a groove with a lateral (also referred to as valgus) orientation. In this study the authors questioned whether femoral components with a lateral groove orientation more closely approximate the configuration in the natural knee. The groove orientations of an implanted CKS femoral component, available in different sizes and with different groove orientations, were determined and compared with formerly published measurements of the natural trochlear orientation. It was found that the prosthetic groove orientations differed considerably from human anatomy, up to a maximum deviation of 6.4 degrees. The orientations of the prosthetic grooves were all equal within the area of the natural trochlea. The area of the natural trochlea guides the patella between about 30 degrees and 120 degrees of knee flexion. The orientations of the prosthetic grooves were different in the area of the supracondylar pouch/proximal anterior flange. This area guides the patella between about 0 degrees and 30 degrees of knee flexion. As this study showed a considerable deviation between natural and prosthetic groove orientation, an optimal prosthetic groove orientation, matching the average orientation in the natural knee, was mathematically determined.

Arthroplasty, Replacement, Knee↗

PubMed2005

Can internal stresses explain the fracture resistance of cusp-replacing composite restorations?

The aim of this study was to explore and compare the results of occlusal load application to cusp-replacing composite restorations, studied by means of finite element (FE) analysis and in vitro load tests. A three-dimensional (3D) FE model was created with a set up similar to an in vitro load test that assessed the fatigue resistance of upper premolars with buccal cusp-replacing resin composite restorations. Occlusal load was applied to two geometries (with and without palatal cuspal coverage), and the tooth-restoration interface and composite material stresses were calculated. Subsequently, safety factors were calculated by dividing the material strength values by the obtained stresses. The highest safety factors were observed for the restorations with cuspal coverage. This was consistent with the load test, in which cuspal coverage led to higher fracture resistance. Furthermore, the FE analysis predicted that failure of the tooth-restoration interface is more likely than failure of the composite material. Correspondingly, the load test showed predominantly adhesive failures of the restorations. Although the described test methods did not lead to a complete understanding of the failure mechanism, it can be concluded that the FE analysis provides additional information with regard to the differences in fracture behaviour of these types of restorations.

Adhesiveness↗

PubMed2005

A three-dimensional dynamic finite element model of the prosthetic knee joint: simulation of joint laxity and kinematics.

For testing purposes of prostheses at a preclinical stage, it is very valuable to have a generic modelling tool, which can be used to optimize implant features and to avoid poor designs being launched on to the market. The modelling tool should be fast, efficient, and multi-purpose in nature; a finite element model is well suited to the purpose. The question posed in this study was whether it was possible to develop a mathematically fast and stable dynamic finite element model of a knee joint after total knee arthroplasty that would predict data comparable with published data in terms of (a) laxities and ligament behaviour, and (b) joint kinematics. The soft tissue structures were modelled using a relatively simple, but very stable, composite model consisting of a band reinforced with fibres. Ligament recruitment and balancing was tested with laxity simulations. The tibial and patellar kinematics were simulated during flexion-extension. An implicit mathematical formulation was used. Joint kinematics, joint laxities, and ligament recruitment patterns were predicted realistically. The kinematics were very reproducible and stable during consecutive flexion-extension cycles. Hence, the model is suitable for the evaluation of prosthesis design, prosthesis alignment, ligament behaviour, and surgical parameters with respect to the biomechanical behaviour of the knee.

Arthroplasty, Replacement, Knee↗

PubMed2004

[Research methods in dentistry 5. The finite element method].

The finite element method is a commonly applied experimental research technique. The method comprises computer simulation of constructions under load and of internal mechanical processes, which enables the study of effects of geometrical and material variations. The analysis shows internal stresses and, consequently, predictions can be made of possible failure. In dentistry, the method is applied in disciplines, such as orthodontics, oral and maxillofacial surgery, implantology en restorative dentistry.

Computer Simulation↗

PubMed2003

A three-dimensional finite element model of the polymerization process in dental restorations.

Restoration of dental restorations with resin composite is hampered by shrinkage of the material during the polymerization process. In this study, we simulated the polymerization process in a detailed three-dimensional finite element model of a human upper premolar with a cusp-replacing restoration. It was analyzed how the stress patterns changed during polymerization and it was assessed whether immediate failure of the restoration is likely to occur and if so, which locations within the restoration are at highest risk and what the clinical implications of these findings are for clinical practice. It was found that the stresses increased rapidly during polymerization and decreased again in the post-polymerization phase. At the interface, tensile stresses relaxed to a higher degree than the shear stresses. Stress values in the composite material and at the interface with the tooth tissue were lower than the reported strength values suggesting that immediate failure is unlikely. The safety factor against mechanical failure of the interface, however, was relatively low indicating that the interface between the composite material and the tooth tissue is at a higher risk for failure than the bulk of the restoration. Stress relaxation was less effective in areas where the interface surface was irregular. In common practice, irregular interface surfaces are used to increase the retention of the restoration. This study indicates that the increased retention may be compromised to some extent by higher shrinkage stresses. The fact that stresses considerably decreased during the post-polymerization period suggests that mechanical loading should be limited during the first few hours after restoration.

Bicuspid↗

PubMed2003

The trochlea is bilinear and oriented medially.

Malfunctioning of total knee replacements often is related to patellofemoral problems. Because the trochlea guides the patella during flexion and extension, its geometry has a major influence in patellofemoral problems. There is controversy in the literature: relative to the mechanical axis, some authors have found a laterally oriented trochlea and others have found a medially oriented trochlea. The groove of implanted prosthetic femoral components always has lateral or neutral orientations. The objectives of the current study were to clarify the controversy found in the literature, to determine whether the trochlear orientation is truly linear, and to determine whether the orientation depends on the size of the femur. The trochleae of 100 human femurs were measured using a three-dimensional measurement system. Detailed analysis of the results indicated that the trochlea is best described as bilinear, with the distal half oriented 0.2 degrees +/- 2.8 degrees laterally and the proximal half oriented 4.2 degrees +/- 3.2 degrees medially. Trochlear orientation was not dependent on bone size.

Cadaver↗

PubMed2003

Does layering minimize shrinkage stresses in composite restorations?

Polymerization shrinkage of resin composites may impair restoration longevity. It is hypothesized that layering, rather than bulk, techniques result in less stress in the tooth-restoration complex. The aim of this study was to compare shrinkage stresses for different restorative techniques used for cusp-replacing restorations with direct resin composite. In a 3-D FE model, the dynamic process of shrinkage during polymerization was simulated. Time-dependent parameters (shrinkage, apparent viscosity, Young's modulus, Poisson ratio, and resulting creep), which change during the polymerization process, were implemented. Six different restorative procedures were simulated: a chemically cured bulk technique, a light-cured bulk technique, and 4 light-cured layering techniques. When polymerization shrinkage is considered, a chemically cured composite shows the least resulting stress. The differences seen among various layering build-up techniques were smaller than expected. The results indicate that the stress-bearing locations are the interface and the cervical part of the remaining cusp.

Chemical Phenomena↗

PubMed2003

A different fixation of the femoral component in total knee arthroplasty may lead to preservation of femoral bone stock.

Good femoral bone stock is important for the stability of the femoral component in revision knee arthroplasty. However, the primary total knee replacement (TKR) may cause significant loss of bone stock in the distal anterior femur. Earlier stress-induced bone remodelling simulations have suggested that a completely debonded component may save bone stock in the distal anterior region. However, these simulations did not consider the fixation of a debonded implant and possible secondary effects of micromotions and osteolysis at the interface. The current study tries to combine the preservation of bone stock with adequate component fixation. Different bone remodelling simulations were performed around femoral knee components with different sizes of bonding area and different friction characteristics of the debonded area. The fixation of the femoral component with different bonding characteristics is quantified with calculated implant-bone interface stresses. The results show that a bonded femoral component with a debonded inner side of the anterior flange may significantly reduce bone resorption in the endangered distal anterior femur, without jeopardizing the fixation of the femoral implant. This effect may be obtained in vivo by using a femoral component with a highly polished inner side of the anterior flange.

Arthroplasty, Replacement, Knee↗

PubMed2003

[A finite element model of a cusp-replacing adhesive restoration].

This article describes the development of a three-dimensional finite element model of a premolar, based on a micro-scale computed tomographic data-acquisition technique. Using the model shrinkage stresses were analysed during and after the polymerisation process of resin composite. The stress patterns generated were three-dimensional. The results of this study indicate that failure of the interface is more probable than failure of the composite material. The described procedure is a relatively easy method to produce a highly detailed 3-D finite element model of a premolar with an adhesive cups-replacing restoration.

Bicuspid↗

PubMed2002

Do unloading periods affect migration characteristics of cemented femoral components? An in vitro evaluation with the Exeter stem.

Prosthetic migration has been identified as a marker for future revision of cemented total hip reconstructions. This could be tested at a pre-clinical stage with dynamic loading experiments. The purpose of this study was to assess the effects of resting periods, which are a considerable part of the daily activity cycle, on the migration characteristics of femoral cemented stems. Ten polished Exeter stems were implanted in composite femurs and loaded either with a continuous load or a discontinuous load. Continuous loading involved 345,600 loading cycles at 1 Hz, whereas the discontinuous loading involved loading at 1 Hz for 2.5 hours and a resting period of 21.5 hours for a period of four days. Hence, a total of 36,000 loading cycles were applied to these reconstructions. The subsidence patterns of the prostheses were considerably affected by the resting periods. The prostheses exhibited a step-wise migration pattern with migration steps of about 50 microns after every resting period, whereas the continuously loaded prostheses showed a more gradual migration pattern. The final subsidence of the specimens when loaded with resting periods was significantly less than the subsidence measured without resting periods. However, these specimens were loaded with fewer loading cycles. If this was taken into account, the discontinuously loaded specimens had a four fold higher average migration per loading cycle than the specimens that were loaded continuously. In conclusion, the resting periods had a considerable effect on the migration patterns, which should be realized when these stems are analyzed with pre-clinical tests.

Activities of Daily Living↗