Biomechanical Optimization Study of Posterior Tilt Extension Stems in the Repair of Tibial Plateau Bone Defects

Yong Wang^1,2Ruihu Hao³Lin Guo^1*Xiaoyu Zhou^1*

• ¹Affiliated Zhongshan Hospital of Dalian University, Dalian, China
• ²Dalian Medical University, Dalian, China
• ³Dalian Jiaotong University, Dalian, China

Abstract Background : Tibial plateau bone defect represents a pivotal challenge in revision knee arthroplasty, where suboptimal extension stem design predisposes to stress concentration and subsequent prosthesis loosening. Physiological posterior tibial slope (5°–7°) optimizes knee biomechanics, yet bone defects disrupt proximal tibial anatomy, rendering traditional stems biomechanically incompatible. The synergistic optimization of "defect severity-stem length-posterior tilt angle" remains underexplored. Methods : A finite element model was constructed incorporating 3 defect areas (20%, 40%, 60%), 2 stem lengths (40mm, 80mm), and 5 posterior tilt angles (0°–10°), yielding 30 experimental cohorts. Under 2450N axial loading, stress distribution (cortical/cancellous bone, prosthesis, sleeve) and bone-prosthesis micromotion were quantitatively evaluated. Results : All micromotion magnitudes remained below the 150μm osseointegration threshold. In 20% defects, 40mm stems with ≤7° tilt mitigated cortical stress concentration; 80mm stems showed lower micromotion but excessive cancellous stress at 10° tilt. In 40%/60% defects, increasing tilt reduced micromotion (37.3%/45.3% reduction), with 80mm stems exhibiting superior stability. Extreme tilt (10°) in long stems exacerbated cortical stress and prosthesis load. Conclusion : Based on the finite element analysis results, this study provides a hypothetical reference for the selection of posterior tilt angles of extension stems in the repair of tibial plateau defects: a posterior tilt angle of ≤7° is suggested for 20% defects when using a 40mm stem; 7°–10° for 40% defects when using an 80mm stem; and 5°–7° for 60% defects when using an 80mm stem. This preliminary biomechanical finding offers a basis for exploring personalized implant design, while the realization of precision-based repair and improved prosthesis longevity requires further validation by multi-center clinical data, diverse patient anatomical models (e.g., differences in tibial size and medullary canal morphology), and in vitro experiments.These data need to be verified through multi-center clinical data and in vitro artificial bone experiments.