Biomedical subjects

Angelo Cappello

Publications and source records attributed to Angelo Cappello.

27 records · Page 2Linked to original sources

PubMed2003

A new method to compare planned and achieved position of an orthopaedic implant.

The present study describes an automatic method to evaluate the efficacy of a computer aided orthopaedic surgery system by comparing the position of the joint implant, as derived from post-operative computed tomography (CT) scans, to that planned by the surgeon before the operation. The method relies on two spatial registrations, one to align the post-operative femur with the pre-operative femur, the second to compute the planned versus achieved (PVA) accuracy as the roto-translation that registers the pre-operative implant position with the post-operative position. Two surface registration algorithms (a generic average distance minimisation and the specialised iterative closest point (ICP) method) were comparatively evaluated first on a set of test cases to measure the absolute accuracy and robustness with respect to peculiar situations such as a distant starting point. The average distance method failed the registration of one test case and showed peak errors of 0.97 degrees on the rotations and 3.09 mm on the translations. The ICP method was found much more efficient and was able to register all test cases. The peak error was 0.44 degrees on the rotations and 0.67 mm on the translations. The ICP method was then used to compute the PVA accuracy on six clinical cases treated with a CT-based planning system in combination with conventional surgical procedures. The method successfully processed all cases demonstrating the efficacy of the proposed procedure in the specific application.

Orthopedics↗

PubMed2003

Fluoroscopic and gait analysis of the functional performance in stair ascent of two total knee replacement designs.

Understanding total knee replacement mechanics and their influence on patient mobility requires accurate analysis of knee joint kinematics and traditional full body kinematics and kinetics. Three-dimensional fluoroscopic and gait analysis techniques were carried out on patients with either mobile bearing or posterior stabilized knee prostheses during stair ascent. Statistically significant correlation was found between knee flexion at foot strike and the position of the mid-condylar contact points, and between maximum knee adduction moment and corresponding lateral trunk tilt. A more complete and powerful assessment of the functional performances of different TKR designs can be performed in-vivo by combining gait and fluoroscopic analyses.

Aged↗

PubMed2003

Accuracy and repeatability of cementless total hip replacement surgery in patients with deformed anatomies.

The present study is aimed to assess the repeatability of orthopaedic surgeons in planning total hip replacement surgery, and the Planned-vs.-Achieved accuracy obtainable with a conventional unassisted surgical procedure. A CT-based surgical planning system called Hip-Op was used for pre-operative planning the pose of the cementless components. The study group included only patients affected by severe deformities of the hip joint. In the repeatability study three surgeons were asked to repetitively plan the same three cases in a blind way. There was agreement among surgeons and also consistency for each surgeon in planning the implant position, while the most expert surgeon was more repeatable in planning the implant orientation. For all patients of the study group, the Planned-vs.-Achieved accuracy was computed as the difference between the spatial position of both prosthetic components derived from the post-operative CT scans and that achieved by the surgeon in the pre-operative planning. The average differences for the stem were lower than 5 mm for the position, and lower than 5 degrees for the orientation. For the socket the average differences increased to 8 mm and 10 degrees. The study shows the need for a more informative planning environment and for intra-operative supports, especially when deformed anatomies are involved.

Anatomy↗

PubMed2003

A PC-based system for evaluating the efficacy of the NESS Handmaster orthosis.

Functional electrical stimulation (FES) is a viable alternative to conventional treatments aimed at restoring function and mobility following central nervous system (CNS) damage. Muscle contractions are converted into functional activity, thus, its wide range of clinical applications. Research efforts are currently focused on the development of programmable stimulators that enable the patient to perform tasks related to activities of daily living. Herein, we present a PC-based surface stimulator that enables the user to vary the stimulus waveform and the activation sequence of different muscle groups within a wide range of options. This instrumentation is not only a development platform for other, more sophisticated neuroprostheses, but an essential tool for evaluating the rehabilitative efficacy of the NESS Handmaster (NESS Ltd., Israel). Our PC-based stimulator reproduces Handmaster motor tasks by selectively activating the five muscle groups that control the hand, palmar, and lateral grasps. The stimulator is entirely controlled by the plegic patient with the push of a button. The ancillary software permits acquisition of up to sixteen analog channels, so that feedback signals for closed-loop control of the grasp function can be measured.

Equipment Design↗

PubMed2003

A global method based on thin-plate splines for correction of geometric distortion: an application to fluoroscopic images.

Quantitative analysis of biomedical images needs a careful correction of geometric distortion. To avoid the discontinuities of the local correction techniques and achieve good accuracy in the presence of global and local distortion, a novel global correction technique based on thin-plate splines is proposed. The technique approximates the grid points by a thin plate minimizing the weighted sum of the bending energy and the mean squared residual errors. The method proposed is compared with three traditional correction techniques: two local and one global. One local technique is linear and takes into account translation, rotation, and scaling, the other is nonlinear and includes skewing. The global technique is based on a two-dimensional polynomial model. Computer-based simulations and experimental tests on fluoroscopic images were carried out. The local techniques were sensitive to both sigmoidal and radial distortion. The polynomial and thin-plate splines global techniques were found sensitive only to sigmoidal distortion and to radial distortion, respectively. The two global techniques showed better performances with respect to any local on synthetic and real images. Where the distortion is predominantly radial or high computational efficiency is required, the polynomial global correction technique should be preferred. Where the distortion has a local nature or is predominantly sigmoidal, the thin-plate splines global correction technique should be chosen.

Algorithms↗

PubMed2002

Computer-assisted preoperative planning of a novel design of total ankle replacement.

Computer-assisted preoperative planning are particularly sought for enhancing surgical implantation and improving clinical outcome of ankle joint replacement arthroplasty. A planning tool was designed to enhance the surgical implantation of a novel ligament-compatible three-component prosthesis. The tool includes a geometric and mechanical model of the ankle complex. The geometry of the articular surfaces and of main ligaments is defined from digitisation on a scanned lateral radiographs of the joint. From the expected movement arc and from component dimensions, a mechanical model of the ligaments is used to select the optimal size and the position the three prosthesis components. The planning is based on the minimisation of ligament change in length and of bone stock to be removed. The main output report is a detailed picture of the replaced ankle with indications of component locations and quantitative measure of bone cuts. An advanced report also superimposes the resulting prediction of prosthesis component kinematics at the replaced joint to the original radiographs.

Ankle↗

PubMed2002

Effect of display modality on spatial accuracy of orthopaedic surgery pre-operative planning applications.

Graphical representation of a patient's anatomy is fairly similar in the majority of orthopaedic surgery planning programs. The position of implantable devices is usually established using a three-pane window showing 2D cross sections of the CT data set taken on three user-selectable orthogonal planes. In some cases this orthogonal-plane representation is replaced or extended by interactive 3D visualization, obtained using surface rendering techniques. These ways to represent the CT data come naturally and easily to the programmer. However, the efficacy of these display strategies is questionable. The present study aims to assess if the display modality used to visualize CT data affects the inherent spatial accuracy achievable in a surgical planning application. A group of users was asked to perform repeatedly a specific planning task using various display interfaces to the same underlying software application. The planning task was designed to allow an assessment of the accuracy with which each user was able to position the prosthetic component. A specialized interface, called multimodal display, presented a peak error of 0.45 mm and 0.95 deg, significantly lower than the 2.4 mm and 4 deg for the othogonal slices interface, and the 3.8 mm and 16.7 deg for the 3D-rendering interface. The results of this study indicate an important effect of the type of visualization modality used to represent CT data on final accuracy of the planning operation.

Computer Graphics↗

PubMed2002

Prediction of hip fracture can be significantly improved by a single biomedical indicator.

Femoral neck fractures are a relevant clinical and social problem. The aim of this study was to improve the prediction of patients at-risk of femoral neck fracture with respect to the current densitometric-based methods. In particular, finite element models were used to assess the prediction accuracy obtained by combining together data from the bone density distribution, the proximal femur anatomy, and the fall-related loading conditions. Two-dimensional finite element models were developed based on dual energy x-ray absorptiometry data. A population of 93 elder Caucasian women (half of them reporting a femoral neck fracture) were retrospectively classified both using the standard clinical protocol and Bayes' linear classifiers. This study showed that the bone mineral density in the femoral neck region dominated the fracture event (65% accuracy). Adding the subject's height and the neck-shaft angle to the bone density increased the accuracy to 77%. The classification accuracy was further improved to 82% by including the peak principal tensile strain obtained from the finite element analyses. This research demonstrated that adding one single biomechanical indicator to the standard clinical measurements improves the identification of patients at-risk of femoral neck fracture.

Aged↗

PubMedDate not supplied

Stabilometric parameters are affected by anthropometry and foot placement.

OBJECTIVE: To recognize and quantify the influence of biomechanical factors, namely anthropometry and foot placement, on the more common measures of stabilometric performance, including new-generation stochastic parameters. DESIGN: Fifty normal-bodied young adults were selected in order to cover a sufficiently wide range of anthropometric properties. They were allowed to choose their preferred side-by-side foot position and their quiet stance was recorded with eyes open and closed by a force platform. BACKGROUND: biomechanical factors are known to influence postural stability but their impact on stabilometric parameters has not been extensively explored yet. METHODS: Principal component analysis was used for feature selection among several biomechanical factors. A collection of 55 stabilometric parameters from the literature was estimated from the center-of-pressure time series. Linear relations between stabilometric parameters and selected biomechanical factors were investigated by robust regression techniques. RESULTS: The feature selection process returned height, weight, maximum foot width, base-of-support area, and foot opening angle as the relevant biomechanical variables. Only eleven out of the 55 stabilometric parameters were completely immune from a linear dependence on these variables. The remaining parameters showed a moderate to high dependence that was strengthened upon eye closure. For these parameters, a normalization procedure was proposed, to remove what can well be considered, in clinical investigations, a spurious source of between-subject variability. CONCLUSION: Care should be taken when quantifying postural sway through stabilometric parameters. It is suggested as a good practice to include some anthropometric measurements in the experimental protocol, and to standardize or trace foot position. RELEVANCE: Although the role of anthropometry and foot placement has been investigated in specific studies, there are no studies in the literature that systematically explore the relationship between such BF and stabilometric parameters. This knowledge may contribute to better defining the experimental protocol and improving the functional evaluation of postural sway for clinical purposes, e.g. by removing through normalization the spurious effects of body properties and foot position on postural performance.

Adult↗