title: A mechanical comparison and review of transverse, step-cut, and sigmoid osteotomies.
abstract: Successful incorporation of massive allografts for the treatment of bone deficiency demands maximizing biologic and mechanical factors. These factors have yet to be mastered, as evidenced by the 8% to 17% nonunion and the 5% to 20% fracture rate. The current study addresses the allograft incorporation process by examining the three construct geometries: transverse, step-cut, and sigmoid. Specimens were plated and mounted on a mechanical testing machine. A rotational displacement was applied, and torsional stiffness (N-m/ degrees ), maximum torque (N-m), and maximum displacement ( degrees ) were calculated. The sigmoid osteotomies had a torsional stiffness of 1.90 +/- 0.68 N-m/ degrees and maximum torque of 18.85 +/- 6.63 N-m versus 0.99 +/- N-m/ degrees and 14.48 +/- 2.15 N-m for the transverse osteotomies; and a maximum angular displacement of 11.60 degrees +/- 1.78 degrees versus 5.73 degrees +/- 1.6 degrees for the step-cut osteotomies. The step-cut osteotomies consistently failed at the step-cut corners, which acted as stress risers. Computer-aided solid modeling of the contact surfaces showed that the step and sigmoid osteotomy areas were 74% and 44%, respectively, larger than the transverse osteotomy. The sigmoid osteotomy, created with a template and pneumatic drill, seems to offer a mechanical advantage over the transverse and step-cut osteotomies by increasing stability and contact surface area relative to the transverse osteotomy but reducing the stress-riser effect of the step-cut osteotomy.
authors.affiliation: Department of Orthopaedic Surgery, Louisiana State University School of Medicine, New Orleans, LA, USA. bmcascio@msn.com
authors.forename: Brett M
authors.initials: BM
authors.lastname: Cascio
authors.forename: Kevin A
authors.initials: KA
authors.lastname: Thomas
authors.forename: Scott C
authors.initials: SC
authors.lastname: Wilson
mesh_terms: D001696:Biomechanical Phenomena; D016025:Bone Transplantation; D002102:Cadaver; D005269:Femur / Q000502:physiology / Q000601:surgery*; D006801:Humans; D010027:Osteotomy / Q000379:methods*; D013314:Stress, Mechanical; D019415:Torque; D014182:Transplantation, Autologous; D014945:Wound Healing / Q000502:physiology