STUDY DESIGN: Biomechanical study. OBJECTIVE: To compare the relative rigidity of C2 transpedicular versus intralaminar fixation with and without offset connectors in C2-C6 subaxial constructs. SUMMARY OF BACKGROUND DATA: Insufficient biomechanical data exists on C2 laminar fixation in subaxial constructs, and no study has considered C2-C6 subaxial constructs or the use of offset connectors. METHODS: Six fresh-frozen cadaveric cervical spines underwent rigidity testing in the intact condition and after a destabilizing C3-C6 laminectomy. Specimens were instrumented with 20 mm pedicle and 20 mm intralaminar screws at C2, and with 14 mm lateral mass screws from C3-C6. In random order, three conditions (C2 pedicle screws, C2 laminar screws, and C2 laminar screws with offset connectors) were tested in flexion-extension, axial rotation, and lateral bending. RESULTS: Laminar screws in C2-C6 constructs were equivalent to transpedicular fixation in flexion-extension (P = 0.985), were significantly more rigid than pedicle screws in axial rotation (P = 0.002), and were significantly less rigid than pedicle screws in lateral bending (P = 0.002). Laminar screw constructs were more rigid than the intact condition in all planes.
STUDY DESIGN: Biomechanical study. OBJECTIVE: To compare the relative rigidity of C2 transpedicular versus intralaminar fixation with and without offset connectors in C2-C6 subaxial constructs. SUMMARY OF BACKGROUND DATA: Insufficient biomechanical data exists on C2 laminar fixation in subaxial constructs, and no study has considered C2-C6 subaxial constructs or the use of offset connectors. METHODS: Six fresh-frozen cadaveric cervical spines underwent rigidity testing in the intact condition and after a destabilizing C3-C6 laminectomy. Specimens were instrumented with 20 mm pedicle and 20 mm intralaminar screws at C2, and with 14 mm lateral mass screws from C3-C6. In random order, three conditions (C2 pedicle screws, C2 laminar screws, and C2 laminar screws with offset connectors) were tested in flexion-extension, axial rotation, and lateral bending. RESULTS: Laminar screws in C2-C6 constructs were equivalent to transpedicular fixation in flexion-extension (P = 0.985), were significantly more rigid than pedicle screws in axial rotation (P = 0.002), and were significantly less rigid than pedicle screws in lateral bending (P = 0.002). Laminar screw constructs were more rigid than the intact condition in all planes.
Authors: Peter G Passias; Cole A Bortz; Frank Segreto; Samantha Horn; Katherine E Pierce; Haddy Alas; Avery E Brown; Renaud Lafage; Virginie Lafage; Justin S Smith; Breton Line; Robert Eastlack; Daniel M Sciubba; Eric O Klineberg; Alexandra Soroceanu; Douglas C Burton; Frank J Schwab; Shay Bess; Christopher I Shaffrey; Christopher P Ames Journal: J Spine Surg Date: 2019-06