S1. 772 facet joint angles (386 lower lumbar levels of 136 patients) were measured on coronal CT scans by transverse interfacet-joint angle (TIFA).

• 共观察136例患者386个下腰椎间隙的CT影像，采用横切关节面角度（TIFA）测量法，测量了772个下腰椎小关节角度。