The Quantitative Anatomical Study Of Percutaneous Cannulated Screw Fixation For Symphysis Pubis Diastasis

Background With the development of social economy, transportation, and construction industry, traumatic symphysis pubis diastasis increased year by year,because of the attention to symphysis pubis diastasis. Surgical operation with reconstruction plate, locking plate is the main treatment. They can recover the pelvic integrity and stability.But it may damage blood vessels, bladder, spermatic cord and so on. Beyond that, rectus abdominis is peeled on a large scale,and it leads to recover slowly.In recent years with the development of intraoperative C arm and navigation technology, percutaneous cannulated screw fixation for symphysis pubis diastasis was gradually carried out. The advantages of the operation are little trauma and less complication.But local detailed quantitative anatomical study and screw placement for specimen experiment are reported rarely.Objective By local dissecting the pelvis specimen of human corpse, the entry angle and length, safe entry and exit points, distances to the important structures in the periphery had been confirmed in the cannulated-screw technology for percutaneous-fixation, thus providing theoretical basis for clinical application of the technology.Methods Experiment materials:15adult preservative cadaver specimens (8men,7women),use part from the4th/5th lumbar level to upper1/3thighs. To rule out bone tumor, fracture and malformations.Important nervus vascularis and spematic funicle (or round ligament of uterus) were exposed layer by layer, in the periphery of pubic symphysis on15pelvis specimens of embalmed corpses of adults.Thickness of pubic symphysis and the distance between the outer edge of pubic tubercle and spematic funicle (or round ligament of uterus) were measured respectively.By applying the three-dimensional navigation technology, the best entry and exit points of the screw nail was determined.The distances were measured respectively from entry and exit points to the above-mentioned structures in the direction of guide pin. The entry depth and angles of guide pin with the coronal plane and cross section of the human body were measured. The surgery on two specimens that had not experienced anatomy were simulated to prove the surgery effect through post-surgery filming and CT.Results The thickness of symphysis pubis was gradually reduced from up to down. The pubic tubercle part was the most thick and it could accommodate1pieces of7.3mm cannulated-screw.The entry and exit points of cannulated-screw were in certain distances with the important nervus vascularis and spematic funicle (or round ligament of uterus) in the periphery, which were invulnerable to damages in the process of surgery. The proper lengthes of the hollow screw were:male (73.6±1.3) mm and female (72.4±1.7) mm. The threaded part was completely embedded in the side of the pubic tubercle. The angles of guide pin with coronal plane and cross section of human body were:male7.3°±1.1°and6.4°±1.0°,female6.9°±1.5°and6.1°±0.6°. The filming and CT examination of specimens in simulated surgery had proved all the pin tracks were in the bone substances with angle and length of screws staying within the scope of experiment.Conclution It was viable and safe to use the technology of percutaneous cannulated screw fixation for symphysis pubis diastasis.