Total meniscectomies are commonly thought to cause progressive degenerative arthrosis pathology in articular cartilage in a period of a few years because of alteration of the biomechanical environment including increased joint instability. This concern has lead to a preference for partial meniscectomies, although lateral partial meniscectomies sometimes lead to catastrophic results. We performed a three-dimensional finite element model of the human tibiofemoral joint to examine the effect of lateral meniscectomy on knee biomechanics. The results were compared to those from modeling a medial meniscectomy. Under axial femoral compressive loads, the peak contact stress and maximum shear stress in the articular cartilage increased 200% more after a lateral than a medial meniscectomy. These increased stresses could partly explain the higher cartilage degeneration observed after a lateral meniscectomy. ß

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The Finite Element Method (FEM) can be used to analyze very complex geometries, such as the pelvis, and complicated constitutive behaviors, such as the heterogeneous, nonlinear, and anisotropic behavior of bone tissue or the noncompression, nonbending character of ligaments. Here, FEM was used to simulate the mechanical ability of several external and internal fixations that stabilize pelvic ring disruptions. A customized pelvic fracture analysis was performed by computer simulation to determine the best fixation method for each individual treatment. The stability of open-book fractures with external fixations at either the iliac crests or the pelvic equator was similar, and increased greatly when they were used in combination. However, external fixations did not effectively stabilize rotationally and vertically unstable fractures. Adequate stabilization was only achieved using an internal pubis fixation with two sacroiliac screws.

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