Odontoid screw plate fixation system, designation and its anatomical analysis

English Keywords:Anterior plate fixation  Odontoid fracture  Anatomy  Hangman fracture  Mimics

English Abstract:

  【Abstract】 Objectives: To offer the anatomical data and feasibility of self-designed odontoid screw plate fixation system(OSPFS). Methods: 40 healthy volunteers′[20 of each gender, age 22-32 years(mean 26 years)] CT data of cervical spine were collected and imported into Mimics software, the data included: dens height, dens anteroposterior diameter, dens width, C2 vertebral anterior height, C2 vertebral posterior height, C2 vertebral body diameter, C2 vertebral body width, C2 anterior inferior lip height, C2 anterior inferior lip width, the angle between C2 inferior end plate and the line of C2 anterior lip and the highest point of C2 vertebral posterior marginal, the angle between coronal plane and the axis of odontoid, the angle of C2 vertebral body which was measured in the plane with C2 vertebral body width, the angle between C2 sagittal plane front edge and C2-C3 vertebral anterior edge sagittal plane tangent line, C3 vertebral body diameter, C3 vertebral body width, C3 vertebral anterior height, C3 vertebral posterior height, C3 anterior inferior lip height, C2/3 anterior intervertebral disk thickness, C2/3 middle intervertebral disk thickness, C2/3 posterior intervertebral disk thickness, the angle between C3 superior end plate and the line of C3 vertebral sagittal highest point of the leading edge and the lowest point of vertebral posterior marginal, the angle between C3 superior end plate and C2-C3 vertebral anterior edge sagittal plane tangent line, the angle between dens′ ideal screw channel and C2-C3 vertebral anterior edge sagittal plane tangent line. All these data were analyzed by SPSS software to work out relevant parameter range to OSPFS, the design and manufacture of odontoid screw plate fixation system are on the basis of these data, and simulated surgery in Mimics software and on cadavers． After simulated surgery, the accuracy of screw channel position were detected by the transparent function of Mimics and undergoing CT scanning and three-dimensional reconstruction. Results: The OSPFS was designed based on the C2, C3 and C2/3 related anatomical measurements completely. OSPFS consisted of screw fixing plate, C2/3 disc fusion device and related accessories, which used medical titanium alloy material(Ti-6Al-4V) manufacturing. The complex included dens fixation parts, vertebral body anchoring parts and locking parts. The simulated surgery in Mimics software and on cadavers was successfully carried out which demonstrated the placement of OSPFS was feasible. The screw channel position of odontoid screw plate were accurate which detected by the transparent function of Mimics and undergoing CT scanning and three-dimensional reconstruction. Conclusions: The placement of self-designed OSPFS in C2-3 complex is feasible anatomically.