Managing large type 2a bone defects from osteoporotic tibial plateau fractures : a finite element analysis

This computational study evaluated the biomechanical performance of asymmetric metaphyseal cones in managing large type 2a bone defects from osteoporotic tibial plateau fractures.

Using a pre-existing finite element model of a synthetic medium-sized tibia, six defect patterns with 50 mm cemented stems were analyzed under walking (WA) and stair descending (SD) loads. Models varied in cone unsupported ratios (R_u = 0%, 16%, 32%) and four bone quality levels (stiffness at 100%, 80%, 60%, and 40% of normal values). Gap healing thresholds (0 to 50 μm) were evaluated to assess bone-implant contact areas. Additional long-stem configurations (100 mm) were analyzed for severe osteoporotic conditions.

At 50 μm gap healing threshold, severe defects (R_u = 32%) achieved maximum geometrically possible contact area of 55%, while no-defect bone (R_u = 0%) reached 100%. Maximum micromotion (89 μm) remained below the critical osseointegration threshold of 150 μm, but interface area experiencing elevated micromotion (50 to 90 μm) increased markedly with deteriorating bone quality. High-strain regions formed at the inferior cone surface and stem base, with up to 16% of cancellous bone exceeding yield thresholds in severe osteoporotic models during SD. Long-stem configurations reduced supraphysiological strain volume by 47% compared to the short stem, but induced strain concentrations at the stem terminus. Medial defects generated higher strains than lateral configurations but exhibited more uniform strain distribution patterns.

Metaphyseal cones provide adequate biomechanical stability for tibial plateau fractures in osteoporotic bone. The findings suggest that gap healing enables maximal bone-implant contact within geometrical constraints, supporting the clinical use of these implants with appropriate patient selection and postoperative management.