Answer to the Letter to the Editor of Wang Kai et al. concerning "Radiographic evaluation of indirect decompression of mini-open anterior retroperitoneal lumbar interbody fusion: oblique lateral interbody fusion for degenerated lumbar spondylolisthesis" by Jun Sato et al. Eur Spine J (2017) 26:671-678. - Sato J; Ohtori S; Orita S; Yamauchi K; Eguchi Y; Ochiai N; Kuniyoshi K; Aoki Y; Nakamura J; Miyagi M; Suzuki M; Kubota G; et al. (European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society, 2018)