title: Effect of soft tissue thickness over the posterior border of the vertebral body and disc space on cage placement during posterior lumbar interbody fusion: a cadaveric study.
abstract: In the present study, we investigated whether there is a difference between visual depth (VD) and radiological image depth (RD) of cages (i.e., structural interbody support devices) placed in disc spaces during posterior lumbar interbody fusion and whether soft tissues covering the posterior border of the vertebral body and associated disc space are the cause of any observed differences. Using digital calipers, cages were inserted at a depth of 5 mm from the soft tissues covering the posterior border of the vertebral body and disc space under direct vision; this depth was defined as VD. After insertion, RD was measured in triplicate. The reliability of RD measurements was evaluated using an intraclass coefficient test. To identify the cause of differences between VD and RD, the thicknesses of soft tissues were measured microscopically. A total of 40 lumbar intervertebral disc spaces with cages were evaluated. The mean RD of cages was 3.12 mm, while the mean difference between the VD and RD of cages (DVRD) was 1.91 mm. On histological examination, the mean thickness of the soft tissue was 2.02 mm. Comparative analysis between histological values and DVRD showed no statistical difference (P = 1.14, 1.55, 0.06). There was a significant difference between VD and RD during cage placement, and soft tissue structure appeared to be responsible for the DVRD of inserted cages. Therefore, cages should be inserted deeper to account for differences between visual and radiological image depths.
authors.affiliation: Department of Orthopedics, Scoliosis Research Institute, Korea University Guro Hospital, Seoul, Korea.
authors.forename: Jae Hyuk
authors.initials: JH
authors.lastname: Yang
authors.forename: Niraj Sharad
authors.initials: NS
authors.lastname: Kasat
authors.forename: Jin Ho
authors.initials: JH
authors.lastname: Whang
authors.forename: Min Keun
authors.initials: MK
authors.lastname: Kim
authors.forename: Kyueng-Whan
authors.initials: KW
authors.lastname: Min
authors.forename: Jae Young
authors.initials: JY
authors.lastname: Hong
authors.forename: Hitesh N
authors.initials: HN
authors.lastname: Modi
authors.forename: Seung Woo
authors.initials: SW
authors.lastname: Suh
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D002102:Cadaver; D005260:Female; D006801:Humans; D016268:Internal Fixators; D007403:Intervertebral Disc / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000601:surgery; D008159:Lumbar Vertebrae / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000601:surgery; D008297:Male; D008875:Middle Aged; D009141:Musculoskeletal System / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000601:surgery; D015588:Observer Variation; D011859:Radiography; D015203:Reproducibility of Results; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods*