Defining Pelvic Factors in Sphincter-Preservation of Low Rectal Cancer with a Three-Dimensional Digital Model of Pelvis

PurposeSurgeons often can contribute failure of sphincter-preserving procedure to a limitation of pelvis anatomy; however, they cannot determine definitely which anatomic diameter or spatial factor actually affected the success of the procedure.MethodsColorectal surgeons, radiologists, and research fellows collaborated closely to establish a three-dimensional digital model of the pelvis with spiral computerized tomography scanning data of patients with rectal cancer. Retrospective analysis on data of 97 patients with low rectal cancer was performed with this model to identify geometric factors that might affect a successful sphincter preservation procedure for low rectal cancer.ResultsA digital pelvic model was established. Multivariate analysis demonstrated that distance from the anal verge, body mass index, and pelvic factors affected the success of sphincter preservation. Sphincter preservation was more likely to succeed when the distance from anal verge was ≥5 cm and body mass index was <25 kg/m2. Shorter diameter from the upper pubis to the sacrococcyx, distance of sacrococcyx, and excessive curvature of the sacrum predicted failure of sphincter preservation in certain cases.ConclusionsPelvic diameters could affect the success of sphincter preservation for low rectal cancer patients besides the distance from anal verge and body mass index.