3 research outputs found
Study of a constrained finite element elbow prosthesis: the influence of the implant placement
BackgroundThe functional results of total elbow arthroplasty (TEA) are controversial and the medium- to long-term revision rates are relatively high. The aim of the present study was to analyze the stresses of TEA in its classic configuration, identify the areas of greatest stress in the prosthesis-bone-cement interface, and evaluate the most wearing working conditions.Materials and methodsBy means of a reverse engineering process and using a 3D laser scanner, CAD (computer-aided drafting) models of a constrained elbow prosthesis were acquired. These CAD models were developed and their elastic properties, resistance, and stresses were studied through finite element analysis (finite element method-FEM). The obtained 3D elbow-prosthesis model was then evaluated in cyclic flexion-extension movements (> 10 million cycles). We highlighted the configuration of the angle at which the highest stresses and the areas most at risk of implant mobilization develop. Finally, we performed a quantitative study of the stress state after varying the positioning of the stem of the ulnar component in the sagittal plane by +/- 3 degrees.ResultsThe greatest von Mises stress state in the bone component for the 90 degrees working configuration was 3.1635 MPa, which occurred in the most proximal portion of the humeral blade and in the proximal middle third of the shaft. At the ulnar level, peaks of 4.1763 MPa were recorded at the proximal coronoid/metaepiphysis level. The minimum elastic resistance and therefore the greatest stress states were recorded in the bone region at the apex of the ulnar stem (0.001967 MPa). The results of the analysis for the working configurations at 0 degrees and 145 degrees showed significant reductions in the stress states for both prosthetic components; similarly, varying the positioning of the ulnar component at 90 degrees (- 3 degrees in the sagittal plane, 0 degrees in the frontal plane) resulted in better working conditions with a greater resulting developed force and a lower stress peak in the ulnar cement.ConclusionThe areas of greatest stress occur in specific regions of the ulnar and humeral components at the bone-cement-prosthesis interface. The heaviest configuration in terms of stresses was when the elbow was flexed at 90 degrees. Variations in the positioning in the sagittal plane can mechanically affect the movement, possibly resulting in longer survival of the implant.Level of evidence:
Biomechanical Analysis of a New Elbow Prosthesis
Total elbow arthroplasty (TEA) is an effective and frequently used
treatment for patients with debilitating elbow pathology. Total elbow prostheses
have lagged behind those of the knee, hip and shoulder for different reasons,
such as the high failure rate of the early designs. Concern remains regarding the
longevity of TEA implants, especially in younger patients. The main cause of
revision of the implant is usually related to the phenomenon of aseptic loosening
mainly due to the cement-bone interface failure.
Aim of this work is the biomechanical analysis of a new elbow prosthesis to
investigate the mechanical behaviour at the cement-bone interface. For this
reason, a musculoskeletal model has been developed by modelling the forces of
the muscles and after FEM analyses have been performed.
Obtained results confirm the validity of the implemented model and can
provide guidelines for surgeons regarding the implant configurations with the
aim to reduce the aseptic loosening