The anatomical and radiographic measurement in Chinese for the axial lumbosacral interbody fusion via retrorectal approach

English Keywords:Interbody fusion  Retrorectal space  Entry point of sacrum  Radiology  Anatomy

English Abstract:

  【Abstract】 Objective：To investigate the feasibility of the axial lumbosacral interbody fusion via retrorectal approach in Chinese.Method：80 lumbosacral lateral X-ray films from normal adults（40 males and 40 females） were selected，the entry point in sacrum was determined by measuring of the L5 inferior and the S1 anterior part from the lumbosacral lateral X-ray.The CT images of pelvic were obtained from these 80 patients without sacral fracture and pelvic tumor，the distance from the anterior edge of middle of the sacrum to the posterior edge of the rectum was measured at S3 and S4 plane，which was the safe distance for establishing working channel.40 dry and normal adult sacrum specimens were used to measure the distance between the medial edge of anterior sacral foramina on the planar of the sacral horizontal line，which was the safe distance on coronal plane.The working channel with the largest diameter of 1.2cm was established in two adult corpses（1 male and 1 female），based on the surgical protocol of AxiaLIF（axial lumbosacral interbody fusion），the lumbosacral region and rectal space were exposed through autopsy.The injury to the anatomical structure around working channel was observed.Results：The entry point in sacrum for normal male and female was（71.6±14.8）% and（66.9±18.6）% from the lumbosacral lateral X-ray film，the distance of retrorectal space was 9.9±4.7mm and 9.7±4.6mm for S3 and S4 planar respectively on CT scan of male pelvic，while was 6.0±2.6mm and 5.9±2.4mm respectively on CT scan of female pelvic，which showed significant sex-related difference（P＜0.05）.The distance between the bilateral medial edge of anterior sacral foramina on the planar of the sacral horizontal line（TS1、TS2、TS3、TS4）　was 3.1±0.3mm、2.9±0.2mm、2.7±0.2mm and 2.6±0.2mm respectively，which showed significant difference（P＜0.05）.The procedure of sham operation on the adult corpse went with no difficulty，the working channel with diameter of 1.2cm was established successfully with no injury to adjacent major structure.The distance between medial iliac vessels and the sacral entry point was 5.0cm and 5.6cm for male and female respectively.Conclusion：As for AxiaLIF approach in Chinese, the entry point lies in the lower half of S1 vertebral.It is safe and reliable for tapping and placing a working tube of a diameter of 1.2cm under this approach.