Abstract:

Objective　Based on the anatomical study，position and variation of anatomical structure of the hypogastric abdominal wall and pelvic cavity were observed and the important neuroanatomical structure refinement measured. To perform an anatomical study on lateral-rectus to sacroiliac joint disruption complicated with lumbosacral plexus injury in an attempt to testify feasibility of the approach．Methods  Position and variation of anatomical structure of the hypogastric abdominal wall and pelvic cavity were observed in 10 cadaveric adults(20 sides), to expose the anterior rectus sheath, obliquus externus abdominis, inferior epigastric artery, arcuate line, the above superficial ring and the spermatic cord in male patients (or the round ligament in female patients) within the inguinal ligament. An adequate exposure included the pelvic ring from the quadrilateral plate to sacroiliac joints, quadrilateral plate, ala of ilium and most part of the medial side of the posterior column of acetabula is obtained by the lateral-rectus approach. Then horizontal distances between anterior branches of lumbar nerves 4，5，lumbosacral trunk(LST) and sacroiliac joint were measured with a caliper.    Results     According to the anatomical study and the anterior of sacroiliac joint, there was an operative window between femoral vessels, spermatic cord and the iliopsoas muscle to expose the sacroiliac joint, obturator nerve, umbosacral stem and internal iliac vessels while retracting abdominal muscles, iliac vessels and intraperitoneal tissues to the medial and iliopsoas to the lateral. The S1 vertebra was posterior to median sacral vessels and iliac vessels, which when retracted laterally can expose S1 and S2 foramen. The distance between the lumbar nerve 5 as it exits from the intervertebral foramen and the sacroiliac joint, the distance between anterior branches of lumbar nerve 4 branch and the sacroiliac joint at the level where the lumbar nerve 5 exits the intervertebral foramen, the distance between the beginning of the LST and the sacroiliac joint，the distance of the LST to the sacroiliac joint at the promontory, the proximity of the LST to the sacroiliac joint at the pelvic brim. There are no significant statistical difference between the left and right side(P＞0.05).    Conclusion    Based on the anatomical study， the author believes that there is enough space anterior to the sacroiliac joints for placement of internal fixation under the nerve root with minor effects on nerve. weconfirm that the lateral-rectus approach can be used for reduction and internal fixation of the sacroiliac joint fracture and dislocation. There exists security space of operation. what's more, the approach provides a new way for the treatment of nerve injury caused by sacroiliac joint damage.

Key words: Lateral-rectus approach, 　Pelvic fracture, 　Sacroiliac joint, 　Lumbosacral plexus