Objective  To evaluate the effects of individual extralevator abdominoperineal excision(ELAPE)of rectal neoplasms in thelow posterior wall on the pelvic floor by finite element analysis.

  Methods  MIMICS 10.01, Geo Magic Studio 12, and ANSYS Workbench14.0 were used to analyze the magnetic resonance data obtained from the pelvic region of 27 healthy nulliparous volunteers.Threetypes of finite element models(intact model, ELAPE model, and individual ELAPE model)were developed.The maximal stress on nonlevator ani tissues were analyzed using the three models, while the maximal stress on levator ani tissues were analyzed using the intact model and the individual ELAPE model.Their stress distributions under the same pressure were analyzed and compared.

  Results  The maximal stress on non levator ani tissues obtained using the intact model, ELAPE model, and individual ELAPE model were(1.963±0.061), (5.127±0.070), and(3.667±0.126)MPa, respectively, with P < 0.01.High-stress zones were obtained at the joints with pelvicwalls on both sides using the three models, while the maximal stresses were obtained at the joints with pubis on both sides.The maximal stress on levator ani tissues obtained using the intact model and individual ELAPE model were(0.812±0.042)MPa and(1.437±0.043)MPa, respectively.Thus, the individual ELAPE model yielded higher values of maximal stress compared to the intact model.Both models generated high-stress zones at the joints with tendinous arch of levator ani tissues on both sides, and maximum stressesat the joints with pubis on both sides.

  Conclusion  Individual ELAPE decreases the stress on non levator ani tissues.This suggests thatthe risk of postoperative pelvic floor hernia is relatively reduced.