Abstract: Objective To evaluate the effects of individual extralevator abdominalperineal excision(ELAPE) for Rectal Neoplasms below levator hiatus on pelvic floor by finite element analysis. Method MIMICS 10.01, GeoMagic Studio 12 and ANSYS Workbench 14 were used to deal with magnetic resonance data of 27 healthy nulliparous volunteers’ pelvic, and then three types of finite element models were developed: intact models, ELAPE models and individual ELAPE models. Non-levator ani tissue’s maximal stresses of three types of models, and levator ani’s maximal stresses of intact models and individual ELAPE models, and their stress distributions under the same pressure were analyzed and compared. Results In intact models, ELAPE models and individual ELAPE models, non-levator ani tissue’s maximal stresses were respectively (1.963±0.061), (5.127±0.070) and (4.703±0.110) MPa. Those in individual ELAPE models were lower than in ELAPE models, but higher than in intact models(P<0.01). The high-stress zone of intact models and ELAPE models showed at the joints with surrounding structures on both sides; the high-stress zone of individual ELAPE models showed in front of the joints with surrounding structures on both sides; and, the maximal stresses of three types of models showed in front of both sides. In intact models and individual ELAPE models, levator ani’s maximal stresses were respectively （0.812±0.042）and（0.719±0.027）MPa. The latter were lower than the former. The high-stress zone of both showed in front of the joints on both sides. The former maximum stressed showed at ventral ends on both sides, and the latter showed higher than the former on both sides. Conclusion This individual ELAPE is able to decrease the stress of non-levator ani tissue, which suggests that the risk of postoperative pelvic floor hernia is relatively reduced.

Key words: ectal neoplasms, Pelvic Floor, Biomechanics, Finite element analysis