title: Biomechanical examination of the thoracic spine--the axial rotation moment and vertical loading capacity of the transverse process.
abstract: Our objective was to examine the load-bearing capacity of the transverse processes of human cadaveric thoracic vertebrae to vertical loads and axial rotation moments (i.e., moment applied in the transverse plane). A secondary objective was to examine the effect of the attached rib stumps. We wanted to demonstrate that the transverse process is durable enough to support the CAB hook--a complementary hook to the CD system--and can handle the vertical load or axial rotation moment during correction of scoliosis. We used 107 thoracic vertebrae removed from 10 cadavers. They were prepared in vertebral pairs, and were fixed into a material testing apparatus. Superoinferior vertical loads and axial rotation moments were applied to the transverse process using the CAB hooks at a rate of 30 mm/min and 8.5°/s respectively until it fractured. We recorded 142 measurements, 99 were for vertical load and 43 for axial rotation moment. The average ultimate vertical load was 338 (SD = 128) N and the average ultimate axial rotation moment was 14.4 (SD = 4.52) Nm. The ultimate axial rotation moment for specimens with rib stumps attached was significantly greater than for specimens without rib stumps 15.9 (SD = 4.1) Nm versus 12.5 (SD = 4.4) Nm. Our results showed that both the vertical and axial rotation loading capability of the transverse process are large enough to withstand significant correctional forces, without fracture, through the CAB hooks.
authors.affiliation: Department of Orthopaedics, University of Debrecen Medical Health and Science Center, Nagyerdei Krt. 98, Debrecen 4032, Hungary. csz@med.unideb.hu
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Csernátony
authors.forename: Szabolcs
authors.initials: S
authors.lastname: Molnár
authors.forename: Zsolt
authors.initials: Z
authors.lastname: Hunya
authors.forename: Sándor
authors.initials: S
authors.lastname: Manó
authors.forename: László
authors.initials: L
authors.lastname: Kiss
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena / Q000502:physiology; D002102:Cadaver; D019544:Equipment Failure Analysis; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular / Q000502:physiology*; D012272:Ribs / Q000502:physiology* / Q000601:surgery; D012399:Rotation; D012600:Scoliosis / Q000503:physiopathology* / Q000601:surgery; D013123:Spinal Fusion / Q000295:instrumentation; D013525:Surgical Instruments; D013904:Thoracic Vertebrae / Q000502:physiology* / Q000601:surgery; D019415:Torque; D016474:Weight-Bearing / Q000502:physiology*