[Applied anatomy study of posterior approach via sacrectomy for reaching the deep intrapelvic sacral plexus]

Objective: To observe the possibility of posterior approach via sacrectomy for reaching intrapelvic sacral plexus and expose the deep intrapelvic origin of sciatic nerve from sacral plexus in order to perform nerve graft. Methods: Five adult cadaver specimens were used in the study with prone position in May 2012. Cut off the gluteus maximus along the origins and lift to the lateral side, the piriformis was lay beneath. The sciatic nerve and the inferior gluteal nerve pierced from the infrapiriformis foramen in the operative field. Excise the origin of the piriformis via sacrectomy with osteotome and the length and width of the insertion on sacrum were measured. The piriformis was resected and then the sacral nerve roots beneath were exposed. The S2-S4 sacral nerve roots and the deep intrapelvic origin of sciatic nerve from sacral plexus were revealed after carefully dissecting. From July 2012 to June 2016, nine patients with lumbosacral plexus injury were performed surgery through the posterior approach in Department of Hand Surgery, Beijing Jishuitan Hospital.There were 6 male and 3 female patients, with a mean age of 29 years. All patients were diagnosed as upper and lower sacral plexus injury, in one of them combing with contralateral lower sacral plexus injury. The average time from injury to operation was 8.3 months. Results: The length and width of the piriformis insertion on sacrum were (3.44±0.15) cm and (2.42±0.11) cm, respectively. The deep intrapelvic origin of sciatic nerve from sacral plexus in all nine patients can be revealed clearly and there was enough operative space that nerve transfer or graft can be performed through the posterior approach via sacrectomy. The total blood loss during operation was (1 822±1 523) ml. Conclusion: The piriformis and part of sacrum it attached can be resected safely through the posterior approach and the deep intrapelvic sacral plexus and the origin of sciatic nerve can be well exposed.